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Color removal from kraft mill effluents by a coagulation-flotation process Wood, Arnaldo Hugo 1974

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COLOR REMOVAL FROM KRAFT HILL EFFLUENTS BY A COAGULATION-FLOTATION PROCESS by ARNALDO HUGO WOOD B . A . S c . , U n i v e r s i d a d d e O r i e n t e , 1 9 6 3 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER APPLIED SCIENCE i n t h e D e p a r t m e n t o f C H E M I C A L E N G I N E E R I N G We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA S e p t e m b e r , 1 9 7 1 * In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f C H E M I C A L E N G I N E E R I N G The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8 . C a n a d a D a t e S E P T E M B E R I 9 7 ^ A B S T R A C T T h e t e c h n i q u e o f c o a g u l a t i o n - f l o t a t i o n h a s b e e n e v a l u a t e d f o r t h e r e m o v a l o f c o l o r b o d i e s f r o m k r a f t m i l l e f f l u e n t s . T h e p r o c e s s w a s b a s e d u p o n c o a g u l a t i o n o f t h e c o l l o i d a l c h r o m o p h o r e s u s i n g a c a t i o n i c s u r f a c t a n t ( d i d o d e c y l d i m e t h y l a m m o n i u r n b r o m i d e ) a s a c o a g u l a n t a n d f l o -t a t i o n a g e n t . S e v e r a l s e t s o f b a t c h e x p e r i m e n t s w e r e d e s i g n e d a n d c a r r i e d o u t i n a f l o t a t i o n c e l l . T h e e f f e c t s o f pH o v e r t h e r a n g e 3 . 6 - 5 . 6 a n d o f s u r f a c t a n t c o n c e n t r a t i o n s f r o m • 1 0 0 - 2 0 0 ppm w e r e i n v e s t i g a t e d . A n i n t e r a c t i o n w a s s h o w n t o e x i s t b e t w e e n t h e s e t w o f a c t o r s . T h e b e s t r e s u l t s w e r e o b t a i n e d a t pH 3 . 6 a n d 1 0 0 ppm o f s u r f a c t a n t . S i n c e t h e p e r c e n t a g e o f c o l o r r e m o v e d w a s p r o v e n n o t t o b e r e l i a b l e i n e x p r e s s i n g t h e p r o c e s s r e s u l t , a n o t h e r a p p r o a c h h a d t o b e d e v e l o p e d . O t h e r s t u d i e s e m b r a c e d : a ) t h e f 1 o a . t a b r l i t y o f t h e s u r f a c t a n t i n a q u e o u s s o l u t i o n a t d i f f e r e n t p H s a n d i n i t i a l c o n c e n t r a t i o n s ; b ) t h e b e h a v i o u r o f t h e k r a f t m i l l w a s t e d u r i n g s e v e r a l a c i d i f i c a t i o n - a l k a l i z a t i o n s e q u e n c e s ; c ) t h e e f f e c t o f s t o r a g e o n t h e c o l o r a n d s o l i d s c o n t e n t o f t h e e f f l u e n t . V a r i a b l e s s u c h a s p r e m i x i n g t i m e , s t i r r e r s p e e d , i i a i r f l o w r a t e , s p a r g e r s i z e , i n t r o d u c t i o n o f the s u r f a c t a n t and t e m p e r a t u r e were b r i e f l y i n s p e c t e d . L a b o r a t o r y s c a l e c o n t i n u o u s equipment was assembled and run at the optimum ba t c h c o n d i t i o n s . The p r e s e n c e of a p r e m i x i n g s t a g e t u r n e d out to be e s s e n t i a l f o r the p r o c e s s . The r e s u l t s were comparable to those p r e v i o u s l y o b t a i n e d i n batch and hence the p o s s i b i l i t y o f d e v e l o p i n g a c o n t i n u o u s c o a g u l a t i o n - f l o t a t i o n p r o c e s s was e s t a b l i s h e d . i i i TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES v i i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS x INTRODUCTION 1 . Chapter 1 BACKGROUND INFORMATION 4 1.1 The C o l o r Bodies i n K r a f t M i l l E f f l u e n t s : A P o t e n t i a l P o l l u t a n t 4 1.2 Removal o f C o l o r from K r a f t M i l l E f f l u e n t s 10 1.3 E s s e n t i a l s o f A d s o r p t i v e Bubble S e p a r a t i o n Techniques (22) 14 1.4 M i c e l l e Formation and C r i t i c a l M i c e l l e C o n c e n t r a t i o n i n Aqueous S o l u t i o n s of S u r f a c t a n t s 17 1.5 A Word of C a u t i o n C o n c e r n i n g the Design and A n a l y s i s o f F l o t a t i o n E x p eriments (46) 20 i v Chapter Page 2 OBJECTIVES OF THIS WORK 22 2.1 Batch Experiments 23 2.2 Continuous Experiments 24 3 EXPERIMENTAL 25 3.1 Batch S t u d i e s 25 3.2 Continuous S t u d i e s 31 4 RESULTS AND DISCUSSION 36 4.1 S t u d i e s on the F l o a t a b i l i t y o f Pure S u r f a c t a n t 36 4.2 S t u d i e s of the F l o t a t i o n P r o c e s s A p p l i e d to K r a f t M i l l Waste 44 4.3 S t u d i e s on the I n f l u e n c e of pH Adjustment and Time E l a p s e d on the K r a f t M i l l Waste 61 4.4 S t u d i e s on the B e h a v i o r o f K r a f t M i l l Waste i n V a r i o u s A c i d i f i c a t i o n -A l k a l i z a t i o n Sequences 66 4.5 Other V a r i a b l e s of I n t e r e s t 72 5 CONCLUSIONS 74 5.1 From the S t u d i e s on the F l o a t a b i l i t y of the S u r f a c t a n t 74 5.2 From the S t u d i e s on the F l o t a t i o n P r o c e s s 75 5.3 From the S t u d i e s on the E f f l u e n t B e h a v i o r 77 6 FURTHER WORK 79 REFERENCES 81 v Appendices Page A A n a l y s i s of V a r i a n c e of the Designed Set of Batch Experiments 87 B R e g r e s s i o n A n a l y s i s A p p l i e d to the Data O b t a i n e d a t pH 3.6 108 C A n a l y t i c a l Techniques and C l e a n i n g P r o c e d u r e 127 D F l o t a t i o n of K r a f t M i l l E f f l u e n t . T a b u l a t e d Batch E x p e r i m e n t a l R e s u l t s 133 E B i b l i o g r a p h i c Survey on Proposed Methods f o r Removing C o l o r From K r a f t M i l l E f f l u e n t s 136 v i LIST OF TABLES Tab! e Page 1' T h e o r e t i c a l E s t i m a t i o n s of P e r c e n t a g e of L i g h t T r a n s m i s s i o n a t V a r i o u s Depths of Water w i t h V a r i o u s C o n c e n t r a t i o n s o f C o l o r , 580 mu 8 2 Schematic C l a s s i f i c a t i o n of the A d s o r p t i v e Bubble S e p a r a t i o n Techniques 15 3 E x p e r i m e n t a l R e s u l t s from the F a c t o r i a l E x p eriments 27 4 E x p e r i m e n t a l R e s u l t s O b t a i n e d f o r Di d o d e c y l d i m e t h y l ammoni urn Bromi de at pH 4.6 and 25°C 42 5 Continuous Experiment R e s u l t s O b t a i n e d a t pH 3.6, 100 ppm o f S u r f a c t a n t and V a r i o u s R e t e n t i o n Times 60 v i i LIST OF FIGURES F i g u r e Page 1 Absorbance v e r s u s w a v e l e n g t h f o r v a r i o u s c o n c e n t r a t i o n s of f i r s t c a u s t i c e x t r a c -t i o n s t a g e e f f l u e n t 7 2 Schematic diagram o f the a p p a r a t u s used i n the b a t c h e x p e r i m e n t s 28 3 Schematic diagram o f the f l o t a t i o n a p p a r a t u s used i n the c o n t i n u o u s e x p e r i m e n t s . 32 4 F l o t a t i o n of s u r f a c t a n t i n water 37 5 F l o t a t i o n of s u r f a c t a n t i n w a t e r . . . . . . . . . 40 6 F l o t a t i o n o f s u r f a c t a n t i n k r a f t m i l l e f f l u e n t 47 7 R a t i o of s o l i d s f l o a t e d to s u r f a c t a n t f l o a t e d i n k r a f t m i l l e f f l u e n t . 48 8 F l o t a t i o n o f s o l i d s from k r a f t m i l l e f f l u e n t 49 9 F l o t a t i o n o f s o l i d s from k r a f t m i l l e f f l u e n t 49 10 C o l o r v e r s u s pH f o r t o t a l m i l l e f f l u e n t 56 v i i i F i g u r e Page 11 E f f e c t o f s t o r a g e time and pH on s o l i d s c o n t e n t of k r a f t m i l l e f f l u e n t 62 12 E f f e c t of s t o r a g e time and pH on c o l o r o f k r a f t m i l l e f f l u e n t 63 13 E f f e c t of s t o r a g e on absorbance ( a t pH 7.6) of u n t r e a t e d waste 64 14 C o l o r removal from k r a f t m i l l e f f l u e n t as a f u n c t i o n of amount of s u r f a c t a n t added and pH 67 15 B e h a v i o u r of k r a f t m i l l e f f l u e n t i n the sequence acidification«alkalization* a c i d i f i c a t i o n 69 16 B e h a v i o u r of k r a f t m i l l e f f l u e n t i n the sequence a l k a l i z a t i o n - a c i d i f i c a t i o n • alkalization«acidification 70 17 A c i d i f i c a t i o n o f k r a f t c a u s t i c e x t r a c t i o n e f f l u e n t w i t h 98% HaSO., 71 i x ACKNOWLEDGEMENTS ' : T h e a u t h o r w i s h e s t o t h a n k D r . R i c h a r d M . B r a n i o n f o r h i s s u p p o r t a n d a d v i c e i n t h i s r e s e a r c h , a n d e s p e c i a l l y f o r r e m a i n i n g a t r u e f r i e n d a t t i m e s w h e n e v e r y b o d y e l s e f a i l e d . T h e i n t e r e s t s h o w n b y o t h e r m e m b e r s o f t h e F a c u l t y o f t h e U . B . C . C h e m i c a l E n g i n e e r i n g D e p a r t m e n t r e g a r d i n g t h i s p r o j e c t i s s i n c e r e l y a c k n o w l e d g e d , p a r t i c u l a r l y t o D r . K . L . P i n d e r . M a n y v a l u a b l e d i s c u s s i o n s w e r e h e l d w i t h D r . J a n L e j a f r o m t h e M i n e r a l E n g i n e e r i n g D e p a r t m e n t a n d D r . J u l i e n D e m a e r s c h a l k f r o m t h e F a c u l t y o f F o r e s t r y . H i g h l y a p p r e c i a t e d i s t h e a s s i s t a n c e o f f e r e d a n d t h e w o r k p e r f o r m e d b y t h e s t a f f o f t h e w o r k s h o p o f t h e s a m e d e p a r t m e n t . T h e a u t h o r f e e l s i n d e b t e d t o h i s f e l l o w g r a d u a t e s t u d e n t s f o r t h e i r m o s t h e l p f u l s u g g e s t i o n s r e c e i v e d d u r i n g d u l l h o u r s . T h a n k s a r e a l s o d u e t o E n g . D o n H e r s c h m i l l e r f o r h i s c o n c e r n a n d c o o p e r a t i o n d u r i n g t h e e x p e r i m e n t a l w o r k . F i n a l l y , g r a t i t u d e i s e x p r e s s e d t o my w i f e , M i r i a m f o r s h a r i n g w i t h me e v e r y s t e p o f t h e w a y . x I N T R O D U C T I O N In r e c e n t y e a r s the c o l o r o f e f f l u e n t s d i s c h a r g e d i n t o r e c e i v i n g waters has emerged as an i m p o r t a n t e n v i r o n -mental problem. In a d d i t i o n to the a e s t h e t i c a s p e c t s , i t has been suggested t h a t the c o l o r i n t r o d u c e d i n t o t h e s e waters may be p a r t l y r e s p o n s i b l e f o r the d e t e r i o r a t i o n o f the s t r u c t u r e o f marine b i o l o g i c a l communities (1) because the development of p h y t o p l a n k t o n i c organisms i s i n h i b i t e d by the reduced p e n e t r a t i o n o f s u n l i g h t . K r a f t pulp m i l l e f f l u e n t s are complex m i x t u r e s of the b y - p r o d u c t s o f the p u l p i n g and b l e a c h i n g p r o c e s s e s . The p o l l u t a n t s i n k r a f t m i l l waste water are p r i m a r i l y wood e x t r a c t i v e s , and l i g n i n and c e l l u l o s e d e g r a d a t i o n p r o d u c t s . I t i s b e l i e v e d t h a t the c o l o r e d m a t e r i a l s o r g i n a t e from l i g n i n and l i g n i n fragments which have a quinone t y p e s t r u c -t u r e ( 2 ) . These compounds i m p a r t a brown c o l o r to the e f f l u e n t c a u s i n g the r e c e i v i n g waters to t u r n the c o l o r o f dark t e a . P r e s e n t t r e a t m e n t p r o c e s s e s f o r k r a f t m i l l wastes are p r i m a r i l y devoted to the removal o f BOD. These p r o c e s s e s 1 2 such as the a c t i v a t e d s l u d g e p r o c e s s o r a e r a t e d lagoons do not have much e f f e c t on c o l o r , p r o b a b l y because c o l o r i s a s s o c i a t e d w i t h l i g n i n l i k e m a t e r i a l s which are r e s i s t a n t to m i c r o b i o l o g i c a l d e g r a d a t i o n . A v a r i e t y o f p r o c e s s e s have been been proposed f o r c o l o r removal from k r a f t m i l l waste w a t e r s . These i n c l u d e t r e a t m e n t w i t h l i m e , a d s o r p t i o n on c a l c i u m c a r b o n a t e or a c t i v a t e d c a r b o n , r e v e r s e o s m o s i s , f i l t r a t i o n , l i q u i d - l i q u i d e x t r a c t i o n , and f l o t a t i o n . The l i m e t r e a t m e n t p r o c e s s a t p r e s e n t seems to be the one f a v o r e d by i n d u s t r y . The f l o t a t i o n p r o c e s s has been used i n water t r e a t m e n t p r o c e s s e s and i n the t r e a t m e n t o f paper m i l l wastes i n South A f r i c a and Sweden but has been l i t t l e used i n North America ( 3 ) . An i o n f l o t a t i o n p r o c e s s s p e c i f i c f o r c o l o r removal from k r a f t m i l l waste water was devel o p e d by H e r s c h m i l l e r ( 4 ) . T h i s p r o c e s s i s based on the c o a g u l a t i o n of t h e nega-t i v e l y charged s o l u b l e or c o l l o i d a l chromophores ( t h e colligend) u s i n g a c a t i o n i c s u r f a c e a c t i v e agent ( t h e c o l l e c t o r ) . The pr o d u c t of the c o a g u l a t i o n r e a c t i o n , a s u r f a c e a c t i v e complex c a l l e d sublate i s f l o a t e d to the s u r f a c e by the i n t r o d u c t i o n of a i r b u b b l e s . At the s u r f a c e a f r o t h c o n t a i n i n g most of the c o l o r i s formed and can be e a s i l y removed. The r e s u l t s o b t a i n e d showed the f e a s i b i l i t y of the p r o c e s s a t l e a s t on a b a t c h , l a b o r a t o r y s c a l e . 3 The purpose of the p r e s e n t i n v e s t i g a t i o n was to expand upon the r e s u l t s of H e r s c h m i l l e r i n terms of the e f f e c t s o f c e r t a i n v a r i a b l e s on c o l o r r e m o v a l , to see i f t h e r e were any i n t e r a c t i o n e f f e c t s between v a r i a b l e s i n a s t a t i s t i c a l s e n s e , t o d e v e l o p a b e t t e r c r i t e r i o n f o r e v a l u a t i n g t h e e f f e c -t i v e n e s s of the p r o c e s s , and to attempt to t r y out the p r o c e s s on a c o n t i n u o u s b a s i s . The i n f o r m a t i o n thus made a v a i l a b l e s h o u l d be u s e f u l i n o p t i m i z i n g the p r o c e s s and i n d e t e r m i n i n g i t s economic s u i t a b i l i t y . Chapter 1 BACKGROUND INFORMATION 1.1 The C o l o r Bodies i n K r a f t M i l l E f f l u e n t s :  A P o t e n t i a l P o l l u t a n t The c o l o r o f the k r a f t m i l l wastes r e s u l t s from the p resence of s o l u b l e or c o l l o i d a l components of wood as m o d i f i e d by the p u l p i n g and b l e a c h i n g o p e r a t i o n s . During the c h l o r i n a -t i o n s t a g e of a c o n v e n t i o n a l k r a f t p u l p b l e a c h i n g sequence, the c o l o r - p r o d u c i n g compounds are r e n d e r e d s o l u b l e and a r e m o s t l y removed i n the subsequent c a u s t i c e x t r a c t i o n s t a g e . The waste water from the p u l p washers of the c a u s t i c e x t r a c -t i o n s t a g e c o n s t i t u t e s the g r e a t e s t s o u r c e of c o l o r i n the e f f l u e n t ( 5 ) . L i g n i n and/or i t s d e g r a d a t i o n p r o d u c t s a r e r e s p o n s i b l e f o r most of the c o l o r of the e f f l u e n t ( 2 ) . D e s p i t e the con-s i d e r a b l e amount of work which has been performed w i t h the i n t e n t i o n of i d e n t i f y i n g the s p e c i f i c c h romophoric groups r e s p o n s i b l e f o r c o l o r , the m a t t e r has not y e t been c o m p l e t e l y r e s o l v e d . A c c o r d i n g to Hayes and Munroe ( 3 ) , 4 5 . . . t h e dark c o l o r in k r a f t m i l l e f f l u e n t o r i g i n a t e s in double bonds con juga ted with a romat i c r i n g s , c h a l c o n e s , q u i n o i d s t r u c t u r e s , f r e e r a d i c a l s , m e t a l l i c complexes ( 6 ) , a l k a l i n e deg rada t i on p roduc ts of sugar and c h l o r i n a t e d l i g n i n d e r i v a t i v e s ( 7 ) . Much of the c o l o r is in the form of c o l l o i d a l pa r t i cIe s (8 ) . Known t o x i c i m p u r i t i e s are a l s o p resen t in the e f f l u e n t : r e s i n a c i d s , f a t t y a c i d s , i n o r g a n i c and o r g a n i c s u l f i d e s , t e t r a c h I o r o -o-benzoqu inone and 4 - p - t o I y I - I-pentanoI ( 9 ) . C e r t a i n of these compounds, e . g . r e s i n a c i d s , f a t t y a c i d s and l i g n i n are s u r f a c e a c t i v e , hence p a r t l y r e s p o n s i b l e f o r the g e n e r a t i o n o f foam. A l l t h e p u b l i s h e d m a t e r i a l on t h e s u b j e c t agrees t h a t "a l a r g e p o r t i o n o f the p o l l u t a n t s behave as s t r o n g l y h y d r o p h i l i c , n e g a t i v e l y charged c o l l o i d s " (3,4,10,11,12,13). The m a j o r i t y o f the t e c h n i q u e s suggested f o r removal of the c o l o r f r a c t i o n from the e f f l u e n t s a r e based on t h a t f e a t u r e (Appendix E ) . The 1 i g n i n - r e l a t e d components of the was t e , which as mentioned p r o v i d e most of the c o l o r , a re l a r g e l y u n a f f e c t e d by b i o - o x i d a t i o n . These compounds have not been found t o x i c to any a q u a t i c s p e c i e s y e t obser v e d - a t l e a s t , a t normal e f f l u e n t c o n c e n t r a t i o n s . B u t , a l t h o u g h no c o n c l u s i v e reasons have been g i v e n a g a i n s t dumping h i g h l y c o l o r e d e f f l u e n t s i n t o r e c e i v i n g w a t e r s , the c o l o r of e f f l u e n t i s meeting i n c r e a s e d c r i t i c i s m on the f o l l o w i n g grounds: 1. B y r e d u c i n g s u n l i g h t p e n e t r a t i o n , t h e c o l o r m i g h t : a ) i n h i b i t t h e p h o t o -s y n t h e t i c a c t i v i t i e s o f a q u a t i c p l a n t s a n d m i c r o o r g a n i s m s t h e r e b y c a u s i n g a n 6 u p s e t i n t h e e c o l o g y o f t h a t p a r t i c u l a r body o f w a t e r ( 1 ^ , 1 5 ) ; b) a f f e c t t h e g r a z i n g h a b i t s o f z o o p l a n k t o n and o t h e r m a r i n e o r g a n i s m s w h i c h depend upon s i g h t f o r d i s c r i m i n a t o r y f e e d i n g ( 1 6 ) . 2. The c o l o r e d c o m p o n e n t s m i g h t be t o x i c t o some o f t h e l o w e r s c a l e o f o r g a n i s m s i n t h e a q u a t i c e c o - s y s t e m . 3. A t some d o w n s t r e a m p o i n t , t h e c o l o r e d w a t e r may become p a r t o f a m u n i c i p a l w a t e r s u p p l y , w h e r e c o l o r r e m o v a l m i g h t be t r o u b 1 e s o m e . k. E s t h e t i c a 1 1 y , s t r o n g c o l o r i s i n c o n s i s t e n t w i t h p r e s e n t p u b l i c a t t i t u d e s . S e v e r a l a t t e m p t s have been made to e s t i m a t e l i g h t a b s o r p t i o n v a l u e s o f k r a f t m i l l e f f l u e n t s , t h e s e have not y e t been f u l l y s u c c e s s f u l specifically because o f the l a c k of a s t a n d a r d method more d i r e c t l y a p p l i c a b l e to the e f f l u e n t s . Herschmi11er (4) s t u d i e d the changes i n absorbance o f f i r s t c a u s t i c e x t r a c t i o n s t a g e e f f l u e n t a t d i f f e r e n t c o n c e n t r a t i o n s and wavelengths ( F i g u r e 1 ) . B.C. Research (15) has p u b l i s h e d h i g h l y i n t e r e s t i n g r e s u l t s c o n c e r n i n g t h e o r e t i c a l e s t i m a t e s of l i g h t d e p l e t i o n due t o d i f f e r e n t c o l o r c o n c e n t r a t i o n s i n k r a f t m i l l e f f l u e n t s ( T a b l e 1 ) . From t h e i r r e s u l t s i t i s o b v i o u s t h a t d i f f e r e n c e s i n c o l o r v a l u e s as s m a l l as 10 u n i t s can d r a m a t i c a l l y reduce the p e n e t r a t i o n of l i g h t . S i n c e p h o t o s y n t h e t i c a c t i v i t i e s depend e n t i r e l y on v i s i b l e r a d i a t i o n , the e x t i n c t i o n of l i g h t would c o r r e s p o n d to e l i m i n a t i o n of p r i m a r y p r o d u c t i o n and c o n s e q u e n t l y , of a l l the dependent a q u a t i c l i f e . 7 f i g u r e 1. A B S O R B A N C E VERSUS WAVELENGTH FOR VARIOUS CONCENTRAT IONS OF FIRST CAUST IC EXTRACT ION STAGE EFFLUENT w a v e l e n g t h ( n a n o m e t e r s ) T a b l e 1 T h e o r e t i c a l E s t i m a t i o n s o f P e r c e n t a g e c f L i g h t T r a n s m i s s i o n a t V a r i o u s Depths of Water w i t h V a r i o u s C o n c e n t r a t i o n s o f C o l o r , 580 mu Depths On) PERCENT TRANSMISSION AT VARIOUS COLOR UNITS 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 1 97.1 94 .2 91 .4 88.7 86.1 83.6 81.1 78.7 76.4 74.2 63.8 55.0 47.3 40.8 35.1 30.2 26.0 22.4 2 94.2 83.7 83.6 78.7 74.2 69.9 65.8 61 .9 58.4 55.0 40.8 30.2 22.4 16.6 12.4 9.1 6.8 5.0 3 91.4 83.5 76.4 69.9 63.8 53.4 53.3 48.7 44.6 40.8 26.0 16.6 10.6 6.8 4.3 2.8 1 .8 1.1 ** 88.7 78.7 69.9 61 .9 55.0 43. 7 43.2 38.4 34.1 30.2 16.6 9.1 5.0 2.8 1.5 5 S S . l 74.2 63.9 55.0 47.3 40.8 35.1 30.2 26.0 22.4 10.6 5.0 2.4 1.1 6 83.5 69.9 58.4 48.7 40.8 34.1 28.5 23.8 19.9 16.6 6.8 2.8 1.1 7 81 .1 65.8 ' 53.3 43.2 35.1 28.5 23.1 18.7 15.2 12.4 4.3 1.5 3 73.7 61.9 43.7 38.4 30.2 23.8 18.7 14.7 11.5 9.1 2.8 9 76.4 58.4 44.6 34.1 26.0 19.9 15.2 11.5 8.9 6.8 1 .8 10 74.2 55.0 40.8 30.2 22.4 16.6 12.4 9.1 6.8 5.0 1.1 11 71 .9 58.8 37.3 26.8 19.3 13.9 10.0 7.2 5.2 3.7 12 59.8 43.7 34.1 23.8 16.6 11.5 8.1 5.7 3.9 2.8 13 67.8 45.9 31 .1 21.1 14.3 9.7 6.6 4.5 3.0 2.1 14 55.8 43.2 28.5 18.7 12.4 8.1 5.3 3.5 2.3 1.5 15 63.3 40.8 26.0 16.6 10.6 6.8 4.3 2.8 1 .8 1.1 15 52.0 33.4 23.8 14.7 9.1 5.7 3.5 2.2 1 .3 17 60.1 36.2 21 .7 13.1 7.9 4.7 2.8 1.7 1 .0 18 53.4 34.1 19.9 11.5 6.8 3.9 2.3 1.3 19 55.6 32.1 18.1 10.3 5.8 3.3 1.9 1.0 20 55.0 30.2 16.6 9.1 5.0 2.8 1 .5 21 53.4 28.5 15.1 8.1 4.3 2.3 22 51.8 25.8 12.0 7.2 3.7 1 .9 CONTINUED 23 50.2 25.2 12.6 6.4 3.2 1.6 T a b l e 1 ( C o n t i n u e d ) Depth (m) PERCENT TRANSMISSION AT VARIOUS COLOR UNITS 1 2 3 4 5 5 7 | 8 9 10 15 20 25 30 35 40 45 50 24 43.8 23.8 11.5 5.7 2.8 1.3 25 47.3 22.4 10.6 5.0 2.4 1.1 30 40.8 16.6 6.8 2.8 1.1 35 35.1 12.4 4.3 1.5 40 30. 2 9.1 2.8 45 25.0 6.8- 1 .8 50 22.4 5.0 1.1 60 16.6 2.8 70 12.4 1.5 80 9.1 90 6.8 100 5.0 110 3.7 120 2.8 130 2.1 1 0 1.2 Removal of C o l o r from K r a f t M i l l E f f l u e n t s There have been numerous t e c h n i q u e s proposed f o r c o l o r removal from pulp and paper m i l l e f f l u e n t s . Of t h e s e methods the b e s t p r o s p e c t s f o r a c o m m e r c i a l l y v i a b l e p r o c e s s a r e : a) l i m e c o a g u l a t i o n , b) a d s o r p t i o n on a c t i v a t e d c a r b o n , c) f l o t a t i o n t e c h n i q u e s , and more r e c e n t l y u l t r a f i l t r a t i o n . The b u l k o f a l l the p u b l i s h e d m a t e r i a l r e l a t e d to c o l o r removal from k r a f t m i l l waste waters i s summarized i n Appendix E. The p r e s e n t d i s c u s s i o n i s concerned o n l y w i t h p r e v i o u s work d i r e c t e d toward removal of the c o l o r of the wastes by a p p l y i n g f l o t a t i o n t e c h n i q u e s . The main f e a t u r e s o f t h e s e f l o t a t i o n t e c h n i q u e s w i l l be o u t l i n e d i n the next s e c t i o n . F i r s t H u t c h i n s o n (17) i n 1958, f o l l o w e d by Waldichuk (18) and s e v e r a l o t h e r a u t h o r s ( 1 9 , 2 0 ) , p o i n t e d out v e r y i n t e r e s t i n g developments i n which advantage was being taken of the n a t u r a l foaming tendency of k r a f t m i l l e f f l u e n t s to remove c e r t a i n u n d e s i r a b l e c o n s t i t u t e n t s from the w a s t e s . The e x p e r i m e n t a l work performed by Warner and M i l l e r (21) i n d i c a t e d t h a t i t i s p o s s i b l e to remove 18 to 37% of the l i g n i n d i s p e r s e d i n water by means of foam thus removing a c o n s i d e r a b l e amount of the c o l o r p r e s e n t i n the k r a f t e f f l u e n t . Of s p e c i a l i n t e r e s t i s a paper p u b l i s h e d by W i l s o n and Wang (12) i n 1970. T h e i r work compared the p e r c e n t a g e of c o l o r removed, i n terms of l i g n i n c o n c e n t r a t i o n , a c h i e v e d 11 b y t w o d i f f e r e n t f l o t a t i o n t e c h n i q u e s : f o a m f r a c t i o n a t i o n a n d i o n f l o t a t i o n . T h e e f f e c t s o f d i f f e r e n t f a c t o r s ' , s u c h a s p H , s u r f a c t a n t d o s a g e , d i s s o l v e d a n d s u s p e n d e d s o l i d s c o n c e n -t r a t i o n w e r e a l s o s t u d i e d . T h e i r m o s t s t r i k i n g r e s u l t w a s t o p r o v e t h e i n e f f e c t i v e n e s s o f f o a m f r a c t i o n a t i o n a s a m e t h o d f o r c o l o r r e m o v a l a s o p p o s e d t o i o n f l o t a t i o n . R e c e n t l y D a s ( 1 1 ) e x p l o r e d t h e p o s s i b i l i t i e s o f a p r e c i p i t a t i o n - f l o t a t i o n p r o c e s s . F i r s t , m u l t i v a l e n t c a t i o n s , i . e . C a , Mg , A l w e r e a d d e d t o t h e k r a f t e f f l u e n t a t a pH b e l o w - t h e l e v e l o f t h e i r h y d r o x i d e p r e c i p i t a t i o n . T h e c a t i o n s r e a c t e d w i t h t h e s t r o n g l y n e g a t i v e l y c h a r g e d c h r o m o p h o r i c c o l l o i d s f o r m i n g a n i n s o l u b l e , h y d r o p h i l i c , g e l a t i n o u s p r e c i p i t a t e . N e x t , s u f f i c i e n t c a t i o n i c a m i n e w a s a d d e d t o r e n d e r t h e p r e c i p i t a t e h y d r o p h o b i c a n d h e n c e t o r e m o v e i t a s a d r y s c u m b y f l o t a t i o n . N e v e r t h e l e s s , t h e o b j e c t i v e - t o f l o a t t h e p r e c i p i t a t e ( d i s p e r s e d a i r f l o t a t i o n ) b y t r e a t i n g w i t h a m i n e , e v e n up t o 5 0 0 ppm d o s a g e , w a s n o t s u c c e s s f u l . I n s t e a d , i t w a s n o t e d t h a t t h e c a t i o n i c a m i n e a l o n e , a t s u b -s t a n t i a l l y l o w e r d o s a g e , w a s c a p a b l e o f r e a c t i n g , w i t h t h e c o l o r b o d i e s a t p H s b e t w e e n 3 a n d 4 f o r m i n g a h y d r o p h o b i c p r e c i p i t a t e w h i c h f l o a t e d w i t h o u t a n y a e r a t i o n . T h e r e s u l t s i n d i c a t e d t h a t a t a n o p t i m u m a m i n e d o s a g e o f 3 0 0 p p m , ^ p o l l u t i o n r e d u c t i o n t o t h e e x t e n t o f 8 8 % c o l o r , 67% COD ( c h e m i c a l o x y g e n d e m a n d ) , 70% T 0 C ( t o t a l o r g a n i c c a r b o n ) , 4 2 % BOD ( b i o c h e m i c a l o x y g e n d e m a n d a n d 1 0 0 % t u r b i d i t y c o u l d b e o b t a i n e d . 12 The work r e p o r t e d by Hayes and Munroe (3) r e p r e s e n t e d a new approach to the g e n e r a l t r e n d f o l l o w e d i n i o n f l o t a t i o n e x p e r i m e n t s . They e v a l u a t e d the removal of c o l o r b o d i e s from k r a f t m i l l e f f l u e n t s by a d d i n g , to a f i x e d amount of alum, v a r i o u s c o n c e n t r a t i o n s of s e l e c t e d c a t i o n i c , s y n t h e t i c , h i g h m o l e c u l a r w e i ght p o l y e l e c t r o l y t e s a t d i f f e r e n t pHs. The dosage of each f l o c c u l a n t - a i d ranged from 0.5 to 3 ppm and the pH v a l u e s from 5.5 to 10.0. The presence of i n t e r a c t i o n between pH and f l o c c u l a n t c o n c e n t r a t i o n became e v i d e n t from the r e s u l t i n g p l o t s , a l t h o u g h the a u t h o r s made no a t t e m p t to e x p l a i n i t . I t was a l s o e s t a b l i s h e d t h a t the f l o t a t i o n time d e c r e a s e d as the dosage of f l o c c u l a n t - a i d was i n c r e a s e d . The h i g h e s t v a l u e o b t a i n e d was 5-6 minutes w i t h calgo'n WT-2600. A l l the e x p e r i m e n t s were performed w i t h a d i s p e r s e d a i r f l o t a t i o n system because of the f a s t e r f o r m a t i o n and s e p a r a t i o n of the f l o e . In t h e i r m i n i p l a n t s t u d i e s i t was c l a i m e d t h a t a d e c r e a s e of 90% i n c o l o r , 50% i n BOD and 66% i n COD o c c u r r e d . The most e x t e n s i v e work done on the s u b j e c t was c a r r i e d out by H e r s c h m i l l e r i n h i s M.A. Sc. t h e s i s ( 4 ) . He performed a s e r i e s of batch runs i n a r a t h e r s i m p l e f l o t a t i o n c e l l . The waste water used was Canadian F o r e s t P r o d u c t s L i m i t e d , P o r t M e l l o n D i v i s i o n , combined e f f l u e n t . The t e m p e r a t u r e of the e f f l u e n t was a d j u s t e d to 22°C, and the amount of waste used was 2.5 l i t e r i n each r u n . The c o l l e c t o r used was didodecyldimethylammoniurn bromide. The per cent of c o l o r 13 removed and of s o l i d s f l o a t e d were e v a l u a t e d under d i f f e r e n t v a l u e s of the f o l l o w i n g p a r a m e t e r s : i ) s u r f a c t a n t or c o l l e c t o r dosage, i i ) pH, i i i ) s p a r g e r p o r o s i t y and hence, i n d i r e c t l y , bubble s i z e , i v ) s u r f a c t a n t premix t i m e , v) a i r sparge r a t e , v i ) c o l l i g e n d - c o l 1 e c t o r r a t i o . However, the p o s s i b i l i t y o f any i n t e r a c t i o n between such f a c t o r s , was not i n v e s t i g a t e d . In h i s batch r e s u l t s , f l o t a t i o n r e c o v e r y and c o l o r removal were found i n excess of 95% at optimum c o n d i t i o n s ; a l s o p r e c i p i t a t e f l o t a t i o n of the t h i r d type was p o i n t e d out as the p r i n c i p a l mechanism of the p r o c e s s . F u r t h e r r e s e a r c h based on Herschmi11er 1 s t h e s i s was c a r r i e d out by Chan et al. (10) i n a n o t h e r s e t o f b a t c h e x p e r i m e n t s . They s c r e e n e d a wide v a r i e t y o f s u r f a c t a n t s and found t h a t q u a t e r n a r y ammonium s a l t s worked b e s t . The most e f f e c t i v e commercial one found was A l i q u a t 221 ( d i m e t h y l d i c o c o ammonium c h l o r i d e m anufactured by General M i l l s C h e m i c a l s I n c . , Kanakee, I l l i n o i s ) . They a l s o n o t i c e d t h a t t h e r e was an optimum dosage of s u r f a c t a n t (500 ppm). I f t h i s optimum was exceeded the t r e a t e d e f f l u e n t became c l o u d y o r t u r b i d . The b e s t pH range was found to be 3.0 to 5.0. A t o t a l d e c r e a s e of 95% i n c o l o r and 80% i n f l o a t a b l e s o l i d s was c l a i m e d . Up to the p r e s e n t the i o n f l o t a t i o n p r o c e s s has not been a p p l i e d c o m m e r c i a l l y to the removal of c o l o r from k r a f t m i l l w a s t e s . 14 1 .3 E s s e n t i a l s of A d s o r p t i v e Bubble S e p a r a t i o n Techniques (22) A d s o r p t i v e bubble s e p a r a t i o n t e c h n i q u e s a r e based on d i f f e r e n c e s i n s u r f a c e a c t i v i t y . M a t e r i a l , which may be m o l e c u l a r , c o l l o i d a l , or m a c r o p a r t i c u l a t e i n s i z e , i s s e l e c -t i v e l y adsorbed or a t t a c h e d a t the s u r f a c e s of bubbles r i s i n g t hrough a l i q u i d , and i s t h e r e b y c o n c e n t r a t e d o r s e p a r a t e d . A s u b s t a n c e which i s not s u r f a c e a c t i v e i t s e l f can o f t e n be made e f f e c t i v e l y s u r f a c e a c t i v e through union w i t h or adherence to a s u r f a c e a c t i v e collector. The s u b s t a n c e so removed i s termed a oolligend ( 2 3 ) . There are a number of i n d i v i d u a l a d s o r p t i v e bubble s e p a r a t i o n t e c h n i q u e s . T a b l e 2 shows the scheme of c l a s s i f i -c a t i o n proposed by Karger et al. ( 2 4 ) . These t e c h n i q u e s ( o r methods) are d i v i d e d u n e q u a l l y i n t o two main g r o u p s : the l a r g e r , c a l l e d foam s e p a r a t i o n , r e q u i r e s the g e n e r a t i o n of a foam or f r o t h to c a r r y o f f m a t e r i a l . The smaller, which i s termed nonfoaming a d s o r p t i v e bubble s e p a r a t i o n , does n o t . T h i s s m a l l e r d i v i s i o n i s f u r t h e r d i v i d e d . Bubble f r a c t i o n a t i o n (25) i s the t r a n s f e r o f m a t e r i a l w i t h i n a l i q u i d by bubble adsorption or a t t a c h m e n t , f o l l o w e d by d e p o s i t i o n at the top of the l i q u i d as the bubbles e x i t . Solvent s u b l a t i o n (23) i s the s i m i l a r t r a n s f e r t o , or to e i t h e r i n t e r f a c e o f , an immiscible l i q u i d p l a c e d on top of the main l i q u i d . The l a r g e r d i v i s i o n i s a l s o s u b d i v i d e d . Foam f r a c t i o n a t i o n i s the foaming o f f of d i s s o l v e d m a t e r i a l from a s o l u t i o n v i a T a b l e 2 Schematic C l a s s i f i c a t i o n of the A d s o r p t i v e Bubble S e p a r a t i o n Techniques A d s o r p t i v e bubble s e p a r a t i o n methods Foam S e p a r a t i on Foam f r a c t i o n a t i o n ( f r o t h ) F l o t a t i o n Non-foaming a d s o r p t i v e bubble s e p a r a t i o n S o l v e n t s u b l a t i o n Bubble f r a c t i o n a t i on 1 Ore Macro- Mi c r o - Pr e c pi t a t e 1 Ion M o l e c u l a r A d s o r b i n g f l o t a t i < tn 1 6 a d s o r p t i o n a t t h e b u b b l e s u r f a c e s . F r o t h f l o t a t i o n , o r s i m p l y f l o t a t i o n ( 2 6 ) , i s t h e r e m o v a l o f p a r t i c u l a t e m a t e r i a l b y f r o t h i n g ( f o a m i n g ) . F r o t h f l o t a t i o n , i n t u r n , h a s m a n y s u b d i v i s i o n s . O r e f l o t a t i o n ( 2 6 ) i s t h e s e p a r a t i o n o f m i n e r a l s . M a c r o f l o t a -t i o n i s t h e s e p a r a t i o n o f m a c r o s c o p i c p a r t i c l e s . M i c r o f 1 o t a t i o n ( 2 7 ) i s t h e s e p a r a t i o n o f m i c r o s c o p i c p a r t i c l e s , e s p e c i a l l y c o l l o i d s o r m i c r o o r g a n i s m s ( u n d e r c e r t a i n c o n d i t i o n s , t h e s e p a r a t i o n o f c o l l o i d s may s o m e t i m e s b e t e r m e d c o l l o i d f l o t a t i o n ) . M o l e c u l a r f l o t a t i o n i s t h e s e p a r a t i o n o f s u r f a c e i n a c t i v e m o l e c u l e s b y f o a m i n g w i t h a c o l l e c t o r w h i c h g i v e s a n i n s o l u b l e p r o d u c t . A d s o r b i n g c o l l o i d f l o t a t i o n i s t h e s e p a r a t i o n o f a s o l u t e t h r o u g h a d s o r p t i o n o n c o l l o i d a l p a r t i c l e s w h i c h a r e t h e n r e m o v e d b y f l o t a t i o n . T h e o r e t i c a l l y i o n a n d p r e c i p i t a t e f l o t a t i o n d i f f e r f r o m o n e a n o t h e r i n t h a t w i t h t h e l a t t e r p r o c e s s t h e c o m p o n e n t t o b e r e m o v e d i s p r e c i p i t a t e d b e f o r e t h e a d d i t i o n o f c o l l e c t o r . S t i l l , L e m l i c h ( 2 2 ) d e f i n e s t h r e e t y p e s o f p r e c i p i t a t e f l o t a t i o n : a) P r e c i p i t a t e f l o t a t i o n o f t h e f i r s t k i n d i n v o l v e s t h e f l o t a t i o n o f p r e c i p i t a t e d p a r t i c l e s by a s u r f a c e - a c t i v e s p e c i e s ; t h e l a t t e r i s n o t a c h e m i c a l c o n s t i t u e n t o f t h e p r e c i p i t a t e s u b s t a n c e and o c c u r s o n l y on t h e s u r f a c e o f t h e p a r t i c l e s . b) P r e c i p i t a t e f l o t a t i o n o f t h e s e c o n d k i n d uses no s u r f a c t a n t t o f l o a t t h e p a r t i c l e s b u t two h y d r o p h i l i c i o n s p r e c i p i t a t e t o f o r m a s o l i d w i t h h y d r o p h o b i c s u r f a c e . 1 7 c) P r e c i p i t a t e f l o t a t i o n of the t h i r d type is a form of ion f l o t a t i o n , in which ions are . p r e c i p i ta ted by s u r f a c t a n t s , and the . r e s u l t i n g p a r t i c l e s are f l o a t e d . A c c o r d i n g t o R u b i n a n d J o h n s o n ( 2 8 ) , w h i l e i o n f l o -t a t i o n r e q u i r e s s t o i c h i o m e t r i c o r g r e a t e r c o n c e n t r a t i o n s o f c o l l e c t o r , p r e c i p i t a t e f l o t a t i o n i s e f f e c t i v e i n s o m e s y s t e m s i n w h i c h t h e c o l l i g e n d i o n c o n c e n t r a t i o n i s 1 0 0 t i m e s t h a t o f t h e c o l l e c t o r . I n a d d i t i o n , i o n f l o t a t i o n i s v e r y s e n s i t i v e t o g a s f l o w r a t e w h i c h a f f e c t s t h e r a t e o f r e m o v a l ; t o c o l l e c t o r c o n c e n t r a t i o n w h i c h d e t e r m i n e s t h e a m o u n t r e m o v e d b u t n o t t h e r a t e ; a n d t o i o n i c s t r e n g t h w h i c h a f f e c t s b o t h t h e r a t e a n d t o t a l r e m o v a l . P r e c i p i t a t e f l o t a t i o n o n t h e o t h e r h a n d i s r e l a t i v e l y i n s e n s i t i v e t o g a s f l o w r a t e a n d c o l l e c t o r c o n c e n -t r a t i o n a n d c o m p l e t e l y i n d e p e n d e n t o f i o n i c s t r e n g t h . S i n c e t h e d i f f e r e n c e b e t w e e n a n y t w o o f t h e s e p r o c e s s e s i s v e r y s u b t l e a n d m o s t o f t h e t i m e t h e r e i s a n o v e r l a p i n t h e d e f i n i -t i o n , t h e r e a d e r i s r e f e r r e d t o t h e e x c e l l e n t t r e a t i s e o f L e m l i c h ( 2 2 ) f o r m o r e d e t a i l s o n e a c h s p e c i f i c m e t h o d . 1 . 4 M i c e l l e F o r m a t i o n a n d C r i t i c a l M i c e l l e C o n c e n t r a t i o n  i n A q u e o u s S o l u t i o n s o f S u r f a c t a n t s A d i s t i n c t i v e f e a t u r e o f s u r f a c e a c t i v e i o n s a n d m o l e c u l e s i s t h e i r t e n d e n c y t o f o r m , i n t h e i n t e r i o r o f t h e i r s o l u t i o n s , a g g r e g a t e s k n o w n a s m i e e l l e s , w i t h r e s u l t a n t a n o m a l i e s i n t h e p h y s i c a l a n d e l e c t r i c a l p r o p e r t i e s o f t h e i r s o l u t i o n s . M i c e l l e f o r m a t i o n t a k e s p l a c e a b o v e a c e r t a i n 18 t e m p e r a t u r e [Krafft point) and a c e r t a i n c o n c e n t r a t i o n [ C r i t i c a l M i c e l l e Concentration). The a g g r e g a t e s a r r a n g e themselves i n such a way t h a t the hydrocarbon c h a i n s are c l o s e t o g e t h e r and d i r e c t e d away from the w a t e r , and the charged h y d r o p h i l i c ends are i n c o n t a c t w i t h the water ( 2 3 ) . T h i s s t r u c t u r e g i v e s the m i c e l l e s a t h e r m o d y n a m i c a l l y more s t a b l e s t a t e . The p r e s e n c e of a h y d r o p h o b i c p a r t i n the a m p h i p a t h i c monomer c o n f e r s on the m o l e c u l e i t s s u r f a c e a c t i v e p r o p e r t i e s but i t s m i c e l l e f o r m i n g c a p a b i l i t y as w e l l . T h e r e f o r e , i n s t r i k i n g c o n t r a s t to monomers, the m i c e l l e s which have a h y d r o p h i l i c e x t e r i o r , are not s u r f a c e a c t i v e ( 2 9 ) . The Krafft point (20) i s c h a r a c t e r i z e d by a sudden i n c r e a s e i n the s u r f a c t a n t s o l u b i l i t y , r e ached a t a c e r t a i n t e m p e r a t u r e , below which the s o l u b i l i t y of the s u r f a c t a n t i s n e g l i g i b l e . Above the Krafft point the m i c e l l e i s t h e t h e r m o d y n a m i c a l l y p r e f e r r e d form ( 3 1 ) . For t h a t r e a s o n o n l y the m i c e l l e and not the s o l i d agent e x i s t s ( 3 2 ) . At t h i s p o i n t the s a t u r a t i o n c o n c e n t r a t i o n s t a y s a l m o s t c o n s t a n t and i s c a l l e d C r i t i c a l M i c e l l e Concentration (33,34,35,36,37). In the i n t e r e s t s o f s t r i c t a c c u r a c y (38) i t i s i m p o r t a n t to emphasize t h a t the f o r m a t i o n o f m i c e l l e s from the c o n s t i t u e n t monomers i n v o l v e s a r a p i d , dynamic, a s s o c i a -t i o n - d i s s o c i a t i o n e q u i l i b r i u m . E x p e r i m e n t a l l y i t i s found t h a t m i c e l l e s become d e t e c t a b l e over a narrow range of con-c e n t r a t i o n s as the t o t a l c o n c e n t r a t i o n of s o l u t e i s i n c r e a s e d . 1 9 As such, the concentrat ion dependence of the degree of m i c e l l i -zat ion changes gradua l l y . A t ru l y abrupt, discontinuous t r ans i t i on is excluded (32,39,40). Besides there is not a unique number of monomers which can form a mice l le but a range with r e l a t i v e l y wide l i m i t s . Hence mice l les are polydisperse (41). This is in agreement with the fact that the average mice l l a r s ize varies continuously with condit ions such as temperature, concentration of sur fac tant , concentrat ion of counterions or other add i t i v es , nature of counter ion, chain length and s t ruc ture . It fol lows that in the C r i t i c a l Mice l le Concentration region not one kind of m i ce l l e , but many kinds appear, each with a s l i g h t l y d i f f e ren t ion ic dependence and most l i k e l y d i f f e r en t charges or even none at a l l (35). The concentration at which mice l les become f i r s t detectable depends on the s e n s i t i v i t y of the experimental probe used. Because the C r i t i c a l Mice l le Concentration is not a sharply defined point above which some propert ies are qua l i t a t i v e l y d i f f e ren t from those below i t , a l l propert ies of a so lut ion in th is region are expected, to vary, in. a continuous manner. There i s , nevertheless, a r e l a t i v e l y narrow region of concentrations in which those changes are most marked. Opera t iona l l y , the C r i t i c a l M ice l le Concentrat ion, is usual ly obtained by p lo t t ing some so lut ion property against surfactant concentration and taking i t to be the f i r s t evident deviat ion from monomeric behavior (37). 20 Well above the C r i t i c a l M i c e l l e C o n c e n t r a t i o n , i n aqueous media, t h e r e o c c u r e x t e n s i v e i n t e r a c t i o n s between m i c e l l e s , which a re o f t e n d i f f i c u l t to u n r a v e l , p a r t i c u l a r l y i f the m i c e l l e s a re i o n i c . In such c o n c e n t r a t e d s o l u t i o n s , many p h y s i c a l p r o p e r t i e s o f s o l u t i o n s e x h i b i t b reaks or k i n k s somewhat s i m i l a r to the ones t h a t t a k e p l a c e a t the C r i t i c a l M i c e l l e C o n c e n t r a t i o n where m i c e l l e s f i r s t form. The c o n c e n t r a -t i o n s where such breaks o r k i n k s happen a r e f r e q u e n t l y d e s c r i b e d as "the second C r i t i c a l M i c e l l e C o n c e n t r a t i o n " ( 4 2 , 4 3 ) . T h i s phenomena i s not w e l l u n d e r s t o o d but i t c l e a r l y i n v o l v e s changes i n i n t e r - m i e e l 1ar i n t e r a c t i o n s as a l s o monomer-micelle i n t e r a c t i o n s . The p r e c e d i n g i n f o r m a t i o n has been e x c l u s i v e l y concerned w i t h t h o s e f a c t s t h a t w i l l be proven i m p o r t a n t i n d i s c u s s i n g the r e s u l t s o f the p r e s e n t work. For a complete d i s c u s s i o n o f m i c e l l e s , i n g e n e r a l , any one o f a number of e x c e l l e n t t e x t s on s u r f a c t a n t s or s u r f a c e a c t i v i t y c o u l d be c o n s u l t e d ( 3 5 , 36,37,44,45). 1 .5 A Word of C a u t i o n C o n c e r n i n g the Design and A n a l y s i s o f  F l o t a t i o n E x periments (46) A p r o p e r l y des igned exper imenta l i n v e s t i g a t i o n of the e f f e c t s of changes in f l o t a t i o n v a r i a b l e s w i l l p rov ide f o r measurement of the e f f e c t s of i n t e r a c t i o n s among the v a r i a b l e s . Yet many f l o t a t i o n expe r imen te r s 21 are v i c t i m s of e r roneous ideas as to how expe r imen ta t i on should p roceed . They a t t a c k i n v e s t i g a t i o n of s eve ra l p rocess v a r i a b l e s by ho ld ing a l l cons t an t except one , v a r y i ng i t over a range u n t i l an appa ren t l y optimum leve l f o r best r e s u l t s i s o b t a i n e d . They then hold t h i s v a r i a b l e cons tan t at i t s optimum l e v e l , v a r y i ng a second v a r i a b l e u n t i l i t s optimum leve l is f ound . Ho ld ing the f i r s t two cons tan t at t h e i r supposed optimums, they proceed in s i m i l a r f a s h i o n f o r the t h i r d v a r i a b l e . F i n a l l y , they end up with what they c o n s i d e r to be an optimum combina t ion of l e v e l s of the v a r i a b l e s . I m p l i c i t in such a p rocedure is the assumpt ion tha t the e f f e c t s of each v a r i a b l e are independent of the l e v e l s of a l l o t h e r s ; the re are no i n t e r a c t i o n s . In f l o t a t i o n t h i s is seldom the c a s e , nor is the combina t ion so a r r i v e d at n e c e s s a r i l y the op t i mum. No one has any rea l unders tand ing of any f l o -t a t i o n o p e r a t i o n un less he unders tands the nature of the s i g n i f i c a n t i n t e r a c t i o n s among the important p rocess v a r i a b l e s . Such unde r -s t and ing can seldom be deduced from t h e o r e t i c a l knowledge, and, in f a c t , most apparent d i s -c r e p a n c i e s between expected behav iour based on theory and ac tua l behav iour of f l o t a t i o n systems are p robab ly s imply m a n i f e s t a t i o n s of such i n t e r a c t i o n s . Only by i n c l u d i n g s t u d i e s of the e f f e c t s of s e ve r a l v a r i a b l e s in the same group of exper iments can such i n t e r a c t i o n s be p r o p e r l y d e l i n e a t e d , and t h i s is but one more reason f o r p roceed ing by groups of t e s t s in any exper imenta l program. Chapter 2 OBJECTIVES OF THIS WORK The e f f i c i e n c y o f the f l o t a t i o n p r o c e s s i n removing the c o l o r f r a c t i o n from k r a f t m i l l e f f l u e n t i s g e n e r a l l y d e f i n e d i n terms o f the p e r c e n t a g e o f c o l o r removed. A s t a n d a r d c o l o r t e c h n i q u e i s a p p l i e d to t h i s purpose. In h i s t h e s i s work Herschmi 11 e r (4) i n t r o d u c e d the concept o f f l o a t a b l e s o l i d s under c e r t a i n assumptions and s u g g e s t e d an a n a l y t i c a l t e c h n i q u e to d e t e r m i n e them (see Appendix C ) . A f t e r p r e l i m i n a r y e x p e r i -ments i t was found t h a t n e i t h e r p r o c e d u r e was a c c u r a t e i n e x p r e s s i n g the f l o t a t i o n e f f i c i e n c y . The r e s u l t s of both t e c h n i q u e s are a f f e c t e d by the r e q u i r e d f i l t r a t i o n s t a g e and can even be h i g h l y m i s l e a d i n g , as i t w i l l be proven l a t e r i n t h i s e s s a y . For t h a t r e a s o n , the f i r s t o b j e c t i v e i n mind was to develop a method of e x p r e s s i n g the p r o c e s s r e s u l t . The amount of f l o a t a b l e s o l i d s was d e t e r m i n e d w i t h a c o m p l e t e l y d i f f e r e n t approach (see Appendix C ) . Through t h i s , i t was f e a s i b l e to e x p r e s s the response o f the p r o c e s s i n t h r e e complementary ways: a) % s u r f a c t a n t f l o a t e d , b) r a t i o o f s o l i d s f l o a t e d / s u r f a c t a n t f l o a t e d , c) % s o l i d s f l o a t e d . 22 2 3 Once the p r i m a r y d i f f i c u l t y was s o l v e d , i t was p o s s i b l e to l a y out the e x p e r i m e n t a l o b j e c t i v e s as f o l l o w s : 1. Studies on the floatability of the pure surfactant. The main o b j e c t i v e of these e x p e r i m e n t s was to i n v e s t i g a t e the b e h a v i o r o f an aqueous s o l u t i o n o f the s u r f a c t a n t : i ) a t d i f f e r e n t pHs i i ) a t d i f f e r e n t s u r f a c t a n t dosages 2. Studies on the f l o t a t i o n process applied to kraft  m i l l waste water. The e f f e c t s o f pH and s u r f a c t a n t dosage on each of the re s p o n s e s was i n v e s t i g a t e d i n o r d e r to d i s c l o s e any s i g n i f i c a n t i n t e r a c t i o n among them. Depending on the r e s u l t s , a g e n e r a l r e g r e s s i o n model f o r the e f f e c t s o f the s t u d i e d f a c t o r s or the optimum s e t o f c o n d i t i o n s was to be e s t a b l i s h e d and a p p l i e d t o a c o n t i n u o u s p r o c e s s . The o u t l i n e o f the e x p e r i m e n t s was: 2.1 Batch Experiments i ) i n t e r r e l a t i o n between % s u r f a c t a n t f l o a t e d , pH and amount of s u r f a c t a n t added, i i ) i n t e r r e l a t i o n between r a t i o o f s o l i d s f l o a t e d / s u r f a c t a n t f l o a t e d , pH and amount of s u r f a c t a n t added, i i i ) i n t e r r e l a t i o n between % s o l i d s f l o a t e d , pH and amount of s u r f a c t a n t added. 24 2 . 2 Continuous Experiments S i n c e most p r e v i o u s work had been done on a ba t c h b a s i s , and s i n c e the p r o c e s s , i f i t were ever to be used i n d u s t r i a l l y , would.have to o p e r a t e c o n t i n u o u s l y , e x p e r i m e n t s , u s i n g the b e s t c o n d i t i o n s o b s e r v e d i n batc h r u n s , were done on a c o n t i n u o u s o p e r a t i o n b a s i s . 3. Studies of the influence of the pH adjustment  and elapsed time on kraft mill waste water. A c a r e f u l r e c o r d was kept o f the obser v e d changes i n c o l o r v a l u e s and t o t a l s o l i d s c o n t e n t o f the agein g e f f l u e n t a f t e r i t s pH a d j u s t -ment, i n comparison t o the o r i g i n a l sample. The r e l a t i v e f i l t e r a b i 1 i t y o f the e f f l u e n t was a l s o n o t i c e d but i n a r a t h e r q u a l i t a t i v e manner. 4. Studies on the behavior of the kraft mill waste in the following sequences: i ) a c i d i f i c a t i o n - a 1 k a l i z a t i o n -a c i d i f i c a t i o n ; i i ) a l k a l i z a t i o n - a c i d i f i c a t i o n - a l k a l i z a t i o n -a c i d i f i c a t i o n. / Chapter 3 EXPERIMENTAL 3.1 Batch S t u d i e s 3.1.1 Design of Experiments As m e n t i o n e d , the main o b j e c t i v e s of the s e t of ba t c h e x p e r i m e n t s were: a) to d e t e r m i n e i f the two f a c t o r s , pH and amount o f s u r f a c t a n t added, had an i n f l u e n c e on t h e r e s p o n s e s ; b) to d i s c l o s e whether t h e r e was a s i g n i f i c a n t i n t e r a c t i o n between the f a c t o r s and i f s o , to e s t a b l i s h the optimum c o n d i -t i o n s f o r the p r o c e s s . For the s e purposes a s e t o f 3 2 f a c t o r i a l e x p e r i m e n t s was d e s i g n e d . The s e t was chosen w i t h one r e p l i c a t i o n per c e l l , w i t h e v e n l y spaced v a l u e s o f the f i x e d v a r i a b l e s {Model I) and e x e c u t e d i n a c o m p l e t e l y randomized o r d e r . The s e l e c t e d d e s i g n had the f o l l o w i n g a d v a n t a g e s : i ) Any i n t e r a c t i o n between the f a c t o r s was d e t e c t a b l e ; i i ) A g e n e r a l r e g r e s s i o n model f o r the e f f e c t of the main f a c t o r s on the response c o u l d have been e a s i l y computed i n the event t h a t no i n t e r -a c t i o n had been p r e s e n t . i i i ) Any e f f e c t due to agein g o f the e f f l u e n t w i t h i n one s e t o f 25 26 e x p e r i m e n t s or any v a r i a t i o n i n the q u a l i t y of the e f f l u e n t from s e t to s e t would have been c o u n t e r a c t e d by the r a n d o m i z a t i o n o f the e x p e r i m e n t a l o r d e r . To c o l l e c t the r e q u i r e d data f o r the e i g h t e e n i n t e n d e d e x p e r i -ments i t was n e c e s s a r y to c a r r y out a t o t a l of 27 b a t c h e x p e r i m e n t s , grouped i n t h r e e d i f f e r e n t s e t s ; see Appendix D. The e i g h t e e n s e l e c t e d e x p e r i m e n t s a r e summarized i n T a b l e 3. 3.1.2 Apparatus F i g u r e 2 shows a s c h e m a t i c o f the a p p a r a t u s used i n t h i s work. L a b o r a t o r y a i r was passed to the f l o t a t i o n c e l l t hrough a p r e s s u r e r e g u l a t o r and i t s f l o w was measured and a d j u s t e d w i t h a r o t a m e t e r . The r o t a m e t e r was c a l i b r a t e d a t the w o rking p r e s s u r e o f 10 p s i g w i t h a bubble meter. A l l gas f l o w s are r e p o r t e d i n ml/sec a t 10 p s i g and room t e m p e r a t u r e . The f l o t a t i o n c e l l c o n s i s t e d of a l a r g e pyrex g l a s s b o t t l e from which the bottom had been removed. The c e l l was about 16 cms i n d i a m e t e r a t the top and h e l d a volume of 2.5 l i t e r s , w i t h room f o r a two and o n e - h a l f c e n t i m e t e r f r o t h bed. The d i f f u s e r c o n s i s t e d of a 5.4 cm d i a m e t e r f r i t t e d g l a s s s p a r g e r ( C o r n i n g G l a s s Works). The nominal-maximum pore s i z e was of 4-5.5 m i c r o n s . The d i f f u s e r was p o s i t i o n e d T a b l e 3 E x p e r i m e n t a l R e s u l t s from the F a c t o r i a l Experiments PH ppm of S u r f a c t a n t Set Days A f t e r % S u r f a c t a n t S o l i d s F l o a t e d % S o l i d s Added Sampii ng F l o a t e d S u r f a c t a n t F l o a t e d F l o a t e d 3.6 100 2 5 90.38 1 .67 20.49 3.6 1 00 3 7 90.0 1 .47 24.26 3.6 1 50 2 4 . 87.33 1 .34 20.80 3.6 1 50 3 3 80.33 0.875 21 .65 3.6 200 2 12 81 .25 0.97 20.08 3.6 200 2 19 81 . 0.802 19.11 4.6 100 2 17 30.0 0.80 3.41 4.6 100 3 5 17.0 1 .24 4.0 4.6 1 50 2 7 67.66 1 .36 1 5.66 4.6 1 50 2 13 70.66 1 .25 17.25 4.6 200. 2 16 75.0 0.94 18.23 4.6 200 3 6 • 51 .0 0.64 13.23 5.6 100 1 14 24.5 0.53 1 .78 5.6 100 2 8 27.0 0.185 0.581 5.6 1 50 2 6 24.66 0.16 0.71 5.6 1 50 3 1 6.66 .53 0.819 5.6 200 3 2 25.0 1 .78 17.52 5.6 200 3 20 32.0 0.88 11 .27 28 f i g u r e 2. S C H E M A T I C D I A G R A M O F T H E A P P A R A T U S U S E D I N T H E B A T C H E X P E R I M E N T S S t i r r e r S p e e d C o n t r o l l e r L a b . A i r V a l v e X P r e s s u r e R e g u l a t o r p H M e t e r s c u m F L O T A T I O N C E L L D i f f u s e r Y R u b b e r B u n g R o t a m e t e r V a l v e M a n o m e t e r G a u g e 29 11.5 cms from the top of the v e s s e l by means o f a rubber bung, which a l s o s e a l e d the bottom o f the c e l l . The f r o t h was removed m a n u a l l y w i t h a s m a l l scoop. A d i g i t a l pH meter was used f o r measuring the pH. The c o l o r t e s t r e a d i n g s were taken i n a Unicam SP.800B s c a n n i n g s p e c t r o p h o t o m e t e r and the s u r f a c t a n t c o n c e n t r a t i o n s were determined c o l o r i m e t r i c a l l y u s i n g a Bausch and Lomb S p e c t r o n i c 20. P r o v i s i o n s f o r i n i t i a l s t i r r i n g of the s u r f a c t a n t were a v a i l a b l e i n the form o f a l a b s t i r r e r w i t h speed c o n t r o l . 3.1.3 M a t e r i a l s The waste waters used were d i f f e r e n t samples from Crown Z e l l e r b a c h ( E l k F a l l s D i v i s i o n ) e f f l u e n t . The waste was s h i p p e d from the m i l l in f i v e - g a l l o n c o n t a i n e r s ; upon a r r i v a l some was s t o r e d a t a t e m p e r a t u r e o f 4°C and the r e s t f r o z e n . As the time and t e m p e r a t u r e of s t o r a g e of the waste water c o u l d have a marked i n f l u e n c e on the e x p e r i m e n t a l r e s u l t s , i t was n e c e s s a r y to keep a c a r e f u l r e c o r d o f the sample's h i s t o r y . The c o l l e c t o r s o l u t i o n was p r e p a r e d by d i s s o l v i n g a weighed q u a n t i t y o f didodecyldimethylammoniurn bromide ( o b t a i n e d from Eastman Kodak) i n 10 ml o f low water c o n t e n t (0.10%) methanol. The r e q u i r e d amount o f methanol and the s t i r r e r speed were de t e r m i n e d i n e a r l i e r e x p e r i m e n t a l r u n s . 3 0 3.1 .4 Proc e d u r e One and a h a l f l i t e r s of the s t o r e d waste water were poured i n t o a one g a l l o n b a t t e r y j a r and mixed w i t h an equal volume of d i s t i l l e d w a t e r . D i l u t e sodium h y d r o x i d e , or h y d r o c h l o r i c a c i d was added to a d j u s t the pH o f the e f f l u e n t to a v a l u e r e q u i r e d f o r the p a r t i c u l a r t e s t . The tem p e r a t u r e o f the s o l u t i o n was r e c o r d e d , then two l i t e r s were t r a n s f e r r e d to the f l o t a t i o n c e l l and the r e s t saved f o r c o l o r and t o t a l s o l i d s a n a l y s i s . In the t h i r d s e t o f exp e r i m e n t s the same a n a l y s e s were a l s o performed on samples of the d i l u t e d s o l u t i o n t a k e n p r e v i o u s l y to i t s pH a d j u s t m e n t . The s t i r r e r was p l a c e d i n the e f f l u e n t and s t a r t e d a t 950 RPM. At t h i s p o i n t the c o l l e c t o r s o l u t i o n was added by means o f a hypodermic s y r i n g e a t an ap p r o x i m a t e r a t e of 0.2 c c / s e c . The s t i r r i n g was c o n t i n u e d f o r f i v e a d d i t i o n a l m i n u t es a t the same speed. Next the s t i r r e r was removed from the f l o -t a t i o n c e l l and the a i r f l o w s t a r t e d and a d j u s t e d to 1.66 c c / s e c . The a i r was a l l o w e d t o bubble f o r f i f t e e n m i n u t e s , r e g a r d i n g z e r o t i m e as the moment when the bub b l e s f i r s t emerged through the d i f f u s e r . Once the s e t time had e l a p s e d the a i r f l o w was stopped and sample of the r e m a i n i n g s o l u -t i o n were taken to a n a l y s e f o r c o l o r , t o t a l s o l i d s and r e s i d u a l s u r f a c t a n t . The e x p e r i m e n t s performed w i t h d i s t i l l e d w a ter to study the s u r f a c t a n t b e h a v i o r were c a r r i e d out w i t h the 31 same g e n e r a l procedure. Herschmi11er 1 s m o d i f i e d c o l o r t e s t (4) was used u n a l t e r e d to de t e r m i n e the c o l o r o f the samples. The method o f van S t e v e n i n c k and Maas f o r q u a t e r n a r y ammonium d e t e r g e n t s was adapted f o r d e t e r m i n i n g the concen-t r a t i o n of r e s i d u a l s u r f a c t a n t (see Appendix C ) . At f i r s t t he d e t e r m i n a t i o n of f l o a t a b l e s o l i d s was done a f t e r H e rschmi11er' s s u g g e s t i o n but l a t e r on t h i s was found to be not s a t i s f a c t o r y f o r the e x p e r i m e n t a l work i n t e n d e d and t h e r e a f t e r a d i f f e r e n t approach was dev e l o p e d (see Appendix C ) . 3.2 Con t i n u o u s S t u d i e s 3.2.1 Ap p a r a t u s The c o n t i n u o u s a p p a r a t u s assembled i s shown s c h e -m a t i c a l l y i n F i g u r e 3. I t can be d i v i d e d i n t o t h r e e f u n c t i o n a l component groups: the e f f l u e n t and s u r f a c t a n t f e e d i n g s y s t e m , the p r e m i x i n g tank and the f l o t a t i o n column. The e f f l u e n t f e e d i n g system c o n s i s t e d o f a 13 g a l l o n , p o l y e t h y l e n e tank w i t h an i n l e t f o r r e g u l a t e d l a b o r a t o r y a i r on top and w i t h i t s bottom connected v i a a r o t a m e t e r to the m i x i n g t a n k . A c a r t r i d g e f i l t e r was p l a c e d i n - l i n e b e f o r e the r o t a m e t e r to p r e v e n t i t from c l o g g i n g . C a l i b r a t i o n o f the r o t a m e t e r was undertaken but no s e n s i b l e d e p a r t u r e was found from t h e m a n u f a c t u r e r s c a l i b r a t i o n c u r v e . The s u r f a c t a n t s o l u t i o n 32 f i g u r e 3. SCHEMAT IC DIAGRAM OF THE FLOTATION A P P A R A T U S USED IN THE C O N T I N U O U S E X P E R I M E N T S S y r i n g e P u m p w i t h S u r f a c t a n t S C U , U U B ^ C O L U M N i b b e r B u n g F L O T A T I O N O p e n • C h a n n e l M a n o m e t e r 33 was p r e p a r e d i n a s e p a r a t e c o n t a i n e r and then added through a s y r i n g e pump. Both streams d i s c h a r g e d i n t o the top of the p r e m i x i n g t a n k . A g l a s s b o t t l e , w i t h i t s bottom removed, s e r v e d as the p r e m i x i n g t a n k . I t was c o n v e n i e n t l y s i z e d t o g i v e the r e q u i r e d r e t e n t i o n t i m e . A rubb e r bung was used to s e a l the c o n t a i n e r and a s h o r t o u t l e t p l a c e d i n i t . The s t i r r e r used i n the b a t c h experiments p r o v i d e d the n e c e s s a r y m i x i n g . A pe r i s t a l t i c pump c o u p l e d to a v a r i a b l e speed d r i v e t r a n s f e r r e d the m i x t u r e to the f l o t a t i o n column. Tygon t u b i n g 1/4 O.D. was employed f o r a l l the d i f f e r e n t l i q u i d c a r r y i n g c o n d u i t s . The r e q u i r e d s e t t i n g s f o r the d i f f e r e n t d e l i v e r y r a t e s used had to be p r e v i o u s l y d e t e r m i n e d f o r both pumps. The p l a s t i c f l o t a t i o n column was t h r e e i n c h e s i n i n s i d e d i a m e t e r and f o u r f e e t h i g h . Three o n e - i n c h d i a m e t e r f r o t h removal p o r t s were p r o v i d e d 15, 27 and 39 i n c h e s from the bottom f l a n g e o f the column. Two l i q u i d f e e d p o s i t i o n s were l o c a t e d o p p o s i t e to the f i r s t two p o r t s and one was p l a c e d f o u r i n c h e s from the column bottom. The system was q u i t e v e r s a t i l e a l l o w i n g a wide v a r i a t i o n i n l i q u i d h e i g h t and f e e d p o s i t i o n i n the column, enhanced by the v a r i a b l e speed pump. The d i f f u s e r from the bat c h e x p e r i m e n t s was f i t t e d to the bottom of the column. The same i n s t r u m e n t s p r e v i o u s l y d e s c r i b e d were used f o r a n a l y s i s and pH a d j u s t m e n t . 34 3.2.2 M a t e r i a l s These were the same as those used i n the b a t c h s t u d i e s . 3.2.3 P r o c e d u r e The raw e f f l u e n t was d i l u t e d w i t h an equal amount of d i s t i l l e d water and i t s pH a d j u s t e d to 3.6. These two s t e p s took p l a c e i n an open g l a s s c o n t a i n e r which f a c i l i t a t e d both o p e r a t i o n s . The s o l u t i o n was poured i n t o the e f f l u e n t tank and i t s t e m p e r a t u r e r e c o r d e d . Samples were saved f o r c o l o r and t o t a l s o l i d s a n a l y s i s . The weighed s u r f a c t a n t was d i s s o l v e d i n methanol up to a c o n c e n t r a t i o n o f 10 mg/cc and t r a n s f e r r e d to the s y r i n g e pump. R e g u l a t e d l a b o r a t o r y a i r was a l l o w e d i n t o the waste tank and the p r e s s u r i z e d e f f l u e n t d e l i v e r e d to the m i x i n g t a n k . The f l o w was a d j u s t e d to the d e s i r e d r a t e . A f t e r two or t h r e e minutes the s t i r r e r and the s y r i n g e pump were s t a r t e d . The s t i r r e r speed was s e t a t 950 RPM. The s u r f a c t a n t was added so as to keep the r a t i o 100 mg of s u r f a c t a n t / 1 i t e r of e f f l u e n t . The r e t e n t i o n time i n the p r e m i x i n g tank was f i v e m i n u t e s . During the f i r s t e i g h t minutes the e f f l u e n t from the tank was d i s c a r d e d . Next, the a e r a t i o n of the column was commenced; the a i r f l o w r a t e was a d j u s t e d to 1.66 c c / s e c ( a t 10 p s i g ) and the s u r f a c t a n t - w a s t e m i x t u r e was connected to the l o w e s t l i q u i d i n l e t o f the column. The l i q u i d l e v e l was allowed to r i s e to 35 the r e q u i r e d h e i g h t , and kept c o n s t a n t t h e r e a f t e r . Once the p r o c e s s was r u n n i n g under t h e s e c o n d i t i o n s f o r two hold-up times and f i f t e e n e x t r a m i n u t e s , the f i r s t sample was drawn. The second sample was taken f i f t e e n minutes l a t e r . A l l the samples withdrawn were a n a l y s e d f o r r e s i d u a l s u r f a c t a n t and t o t a l s o l i d s . I t must be emphasized, t h a t any attempt made to run the p r o c e s s c o n t i n u o u s l y o m i t t i n g the s t i r r i n g d u r i n g the p r e m i x i n g s t a g e or the e n t i r e s t a g e c o m p l e t e l y d i d not s u c c e e d . On the o t h e r hand, one q u a l i t a t i v e c o n t i n u o u s run i n which the a i r e n t r a i n e d d u r i n g the s t i r r i n g s t a g e was the o n l y s o u r c e o f a e r a t i o n ; was h i g h l y s a t i s f a c t o r y . Chapter 4 RESULTS AND DISCUSSION 4.1 S t u d i e s on the F l o a t a b i l i t y of Pure S u r f a c t a n t Two s e r i e s of b a t c h e x p e r i m e n t s were c a r r i e d out to e s t a b l i s h the e f f e c t s of h y d r o g e n - i o n c o n c e n t r a t i o n and of s u r f a c t a n t dosage on the amount of s u r f a c t a n t r e c o v e r e d by f l o t a t i o n . As mentioned b e f o r e , the same g e n e r a l e x p e r i m e n t a l p r o c e d u r e was a p p l i e d i n a l l r u n s . The t e m p e r a t u r e was kept c o n s t a n t a t 25°C. 4.1.1 E f f e c t o f pH A l l e x p e r i m e n t s i n v o l v e d i n i t i a l s o l u t i o n s of c o n c e n t r a t i o n 150 ppm i n s u r f a c t a n t . The chosen amount was the m i d p o i n t of the e x p l o r a t o r y range i n t e n d e d to be used l a t e r , w i t h the k r a f t m i l l e f f l u e n t . The e f f e c t s o f the hyd r o g e n - i o n c o n c e n t r a t i o n were d e t e r m i n e d a t pH v a l u e s o f 2.6, 3.6, 4.6 and 5.6 as i n d i c a t e d i n F i g u r e 4„ I t i s e v i d e n t from F i g u r e 4 t h a t the maximum r e c o v e r y of s u r f a c t a n t i s c o n s t a n t over the range pH 3.6-4.6. A t lower 36 f i g u r e 4. F L O T A T I O N O F S U R F A C T A N T IN W A T E R s u r f a c t a n t c o n c e n t r a t i o n 1 5 0 p p m j 2 . 6 3 . 6 4 . 6 PH 5 . 6 3 8 o r h i g h e r pH v a l u e s t h e p e r c e n t a g e o f s u r f a c t a n t f l o a t e d d r o p s t o a l m o s t h a l f i t s m a x i m u m . Q u a t e r n a r y a m m o n i u m s a l t s a r e g e n e r a l l y c o n s i d e r e d t o b e a l m o s t c o m p l e t e l y i o n i z e d i n s o l u t i o n ( 4 7 ) a n d t h e r e f o r e t o f u n c t i o n a s o r d i n a r y s t r o n g e l e c t r o l y t e s ( 4 8 ) . N e v e r t h e l e s s M c B a i n ( 4 9 ) h a s h e l d t h a t a s s o c i a t e d i o n s a r e p r e s e n t e v e n i n v e r y d i l u t e s o l u t i o n s . M o r e o v e r R a l s t o n et al. ( 5 0 , 5 1 ) h a v e e s t a b l i s h e d t h e p r e s e n c e o f i o n i c a g g r e g a t e s f o r h i g h e r d i a l k y l q u a t e r n a r y a m m o n i u m c h l o r i d e s ( d i d o d e c y l d i m e t h y l a m m o n i u r n c h l o r i d e a m o n g t h e m ) i n t h e v i c i n i t y o f t h e i r C M C . S i n c e t h e p r o p e r t y o f f o a m i n g d e p e n d s o n s i n g l e i o n s ( 2 3 ) r a t h e r t h a n o n i o n i c a g g r e g a t e s , i t s e e m s p l a u s i b l e t o c o n c l u d e t h a t t h e o v e r a l l e l e c t r o s t a t i c e q u i l i b r i u m b e t w e e n i o n s a n d i o n i c a g g r e g a t e s i s g r e a t l y a f f e c t e d b y p H . F o r t h a t r e a s o n , t h e p e r c e n t a g e o f s u r f a c t a n t f l o a t e d c o u l d b e i n d i c a t i v e o f t h e r e l a t i v e a m o u n t o f u n -a s s o c i a t e d s p e c i e s i n s o l u t i o n . F r o m t h e d a t a o b t a i n e d i n F i g u r e 4 , t h e f o l l o w i n g c o n c l u s i o n c a n b e i n f e r r e d f o r t h e pH v a l u e s s t u d i e d : At 1 5 0 ppm of s u r f a c t a n t and 2 5 ° C , the range of pH 3 . 6 - 4 . 6 forms a p l a t eau o u t s i d e of which the c o n c e n t r a t i o n of ions in s o l u t i o n is g r e a t l y d i m i n i s h e d . 4 . 1 . 2 E f f e c t o f S u r f a c t a n t D o s a g e T h e s e c o n d s e r i e s o f e x p e r i m e n t s w a s p e r f o r m e d w i t h t h e pH a d j u s t e d t o 4 . 6 , i t s m o s t p r o m i s i n g v a l u e f o r a n 39 i o n f l o t a t i o n p r o c e s s . The e f f e c t of the s u r f a c t a n t c o n c e n t r a -t i o n was d e t e r m i n e d over the range 5.41 x 1 0 ~ 5 , to 4.2 x IO"*1* (25-200 ppm) as i n d i c a t e d i n F i g u r e 5. Very s c a r c e i n f o r m a t i o n has been p u b l i s h e d d e a l i n g w i t h the expected Krafft p o i n t f o r the h i g h e r d i a l k y l q u a t e r n a r y ammonium compounds. A l l the work done i n t h i s f i e l d has been l i m i t e d to e s t a b l i s h i n g the C r i t i c a l M i c e l l e C o n c e n t r a t i o n of a c e r t a i n s u r f a c t a n t a t a c e r t a i n t e m p e r a t u r e , r e g a r d l e s s of how f a r above the Krafft p o i n t the t e m p e r a t u r e i s . The main reason f o r t h i s p a r t i c u l a r a t t i t u d e seems to l i e i n the f a c t t h a t . . . a l t h o u g h t h e s o l u b i l i t y o f a m p h i p a t h i c e l e c t r o l y t e s c h a n g e s v e r y r a p i d l y i n a s m a l l t e m p e r a t u r e i n t e r v a l w h e n t h e C r i t i c a l M i c e l l e C o n c e n t r a t i o n h a s b e e n r e a c h e d , t h e C r i t i c a l M i c e l l e C o n c e n t r a t i o n i s n o t i t s e l f m a r k e d l y i n f l u e n c e d by t e m p e r a t u r e . (35) R a l s t o n et al. (50,51) p o i n t e d out the dependence of C r i t i c a l M i c e l l e C o n c e n t r a t i o n on t e m p e r a t u r e . From t h e i r e x p e r i m e n t s i t can be seen t h a t as the t e m p e r a t u r e i s i n c r e a s e d , the s l o p e of the p r e c r i t i c a l range becomes s t e e p e r but the c r i t i c a l p o i n t i t s e l f o c c u r s a t almost the same c o n c e n t r a t i o n f o r t e m p e r a t u r e s r a n g i n g from 20° to 60°C. H u t c h i n s o n and Winston (33) found no s i g n i f i c a n t d i f f e r e n c e i n the C r i t i c a l M i c e l l e C o n c e n t r a t i o n of dodecylammoniurn c h l o r i d e i n a t e m p e r a t u r e i n c r e a s e o f 10°C. Adam and P a n k h u r s t (52) e s t a b l i s h e d 20°C as the Krafft p o i n t f o r hexadecyl ( c e t y l ) 40 f igure 5, FLOTATION OF SURFACTANT IN WATER 100 90 o "• ° \ 80 m 70 o Z 60 \ . 1 50 # 30 o 20 o exper imenta l value 10 — theoret i ca l value . pH 4.6 0 i i i i 50 100 15© 200 ppm ©f surfactant added 41 trimethylammonium bromide. The C r i t i c a l M i c e l l e C o n c e n t r a t i o n f o r didodecy1dimethylammonium c h l o r i d e i s g i v e n as 1 .8 x 10 _ l f m o l e s / l i t e r (75 ppm) by Shinoda ( 3 6 ) . The o r i g i n a l paper (34) mentioned 30°C as the te m p e r a t u r e a t which the e x p e r i -ment was c a r r i e d o u t , but no r e f e r e n c e i s made c o n c e r n i n g the expected K r a f f t p o i n t . A nother i m p o r t a n t p i e c e of i n f o r m a t i o n i s t h a t the C r i t i c a l M i c e l l e C o n c e n t r a t i o n f o r an a l k y l q u a t e r n a r y bromide i s equal o r s l i g h t l y l e s s than i t s c o r r e s p o n d i n g c h l o r i d e ( 3 6 ) . Thus, b e a r i n g i n mind a l l t h e s e f a c t s , i t w i l l be assumed: a) The C r i t i c a l M i c e l l e C o n c e n t r a t i o n o f d i dodecy1d ime thy1ammon iu rn b r o m i d e i s i n t he v i c i n i t y o f 75 ppm. (36) b) The t e m p e r a t u r e a t w h i c h t he e x p e r i -m e n t a l work was done ( 2 5 ° C ) i s above t h e Kraff t p o i n t o f t he r e f e r r e d s u r f a c t a n t . A q u i c k i n s p e c t i o n of the e x p e r i m e n t a l r e s u l t s ( T a b l e 4) i n d i c a t e s t h a t any i n c r e a s e of s u r f a c t a n t c o n c e n t r a t i o n above a c e r t a i n c r i t i c a l p o i n t causes a marked d e p r e s s i o n i n the pe r c e n t a g e r e c o v e r e d by f l o t a t i o n . A d d i t i o n a l l y , below t h i s c r i t i c a l c o n c e n t r a t i o n , the p e r c e n t a g e of s u r f a c t a n t f l o a t e d l e v e l s out a t a d e f i n i t e c o n s t a n t v a l u e . T h i s c r i t i c a l p o i n t i s r e g a r d e d by most a u t h o r s (32,33,39,53,54,55,56,57,58,59,60) a s , T a b l e 4 E x p e r i m e n t a l R e s u l t s O b t a i n e d f o r Didodecyldimethylammonium Bromide a t pH 4.6 and 25°C C o n c e n t r a t i o n i n ppm % F l o a t e d ± 3% Amount not F l o a t e d , i n ppm Amount F l o a t e d , i n ppm T h e o r e t i c a l Amount to be f l o a t e d , i n ppm 25 93.12 1 .72 23.28 22.5 50 87.50 6.25 43.75 45.0 100 72.5 27.50 72.5 72.5 150 53.33 70.0 80.0 72.5 200 32.50 135.0 65.0 72.5 43 . . . a s a t u r a t i o n po in t f o r s i n g l e s u r -f a c t a n t i o n s ; above t h i s c o n c e n t r a t i o n m i c e l l e s fo rm, and any s u r f a c t a n t in excess of t h i s c o n c e n t r a t i o n which is added to the s o l u t i o n is e n t i r e l y in the form of m i ceI Ies . I t was a l r e a d y mentioned t h a t h i g h e r d i a l k y l q u a t e r n a r y ammonium compounds a s s o c i a t e f i r s t , a t low c o n c e n t r a t i o n s , i n t o i o n i c a g g r e g a t e s ; f o l l o w e d by the f o r m a t i o n o f m i c e l l e s once the C r i t i c a l M i c e l l e C o n c e n t r a t i o n i s r e a c h e d . The m i c e l l e s a r e a t t r i b u t e d to the i n c o r p o r a t i o n o f u n d i s s o c i a t e d m o l e c u l e s i n t o the i o n i c a g g r e g a t e s ( 3 4 ) . Taking i n t o account a l l t h e s e f a c t s i t i s p o s s i b l e to c o n c l u d e from the o b t a i n e d d a t a : a) The C r i t i c a l M i c e l l e C o n c e n t r a t i o n f o r d idodecy1d imethy1ammon iu rn b r o m i d e a t pH 4.6 and 25 ° C i s 72.5 ± 3%. No t e t h e c l o s e a g r e e m e n t o f t h i s v a l u e w i t h t h e f i g u r e r e p o r t e d by S h i n o d a (36) f o r the c h l o r i d e . b) Be low t h e C r i t i c a l M i c e l l e C o n -c e n t r a t i o n o n l y 90% o f t h e s u r -f a c t a n t was f o u n d t o be i n t he i o n i c f o r m and hence r e c o v e r a b l e by f l o t a t i o n . P r e s u m a b l y , a g e i n g o f the s t o r e d s u r f a c t a n t i s p a r t i a l l y r e s p o n s i b l e f o r s u c h b e h a v i o r . c) A b o v e t h e C r i t i c a l M i c e l l e C o n -c e n t r a t i o n o n l y 72.5 ppm o f the s u r -f a c t a n t i s r e c o v e r e d by f l o t a t i o n . The r e m a i n i n g amount i s a s s o c i a t e d e i t h e r i n the f o r m o f l a r g e i o n i c a g g r e g a t e s , i o n i c m i c e l l e s o r n e u t r a l m i c e l l e s . In any c a s e the a s s o c i a t i o n r e n d e r e d the c o l l o i d a l p a r t i c u l a t e s un-f l o a t a b l e . 4 4 F i g u r e 5 compares the t h e o r e t i c a l b e h a v i o r a g a i n s t the a c t u a l v a l u e s . The agreement i s q u i t e good and i n most cases w i t h i n the p e r c e n t a g e o f e r r o r a t t r i b u t e d to the a n a l y t i c a l t e c h n i q u e s used f o r d e t e r m i n i n g the s u r f a c t a n t c o n c e n t r a t i o n . The t h e o r e t i c a l p o i n t s were c a l c u l a t e d on the f o l l o w i n g b a s i s : a) Below the C r i t i c a l M i c e l l e Concen-t r a t i o n 90% o f the s u r f a c t a n t i s r e c o v e r a b l e by f l o t a t i o n , b) Once the CMC r e g i o n i s passed o n l y 72.5 ppm of the s u r -f a c t a n t are r e c o v e r a b l e by f l o t a t i o n . Because no o t h e r type o f i n t e r a c t i o n i s p r e s e n t , i t i s most p r o b a b l e t h a t the tendency d i s p l a y e d i n F i g u r e 5 w i l l be f o l l o w e d a t o t h e r pH v a l u e s . The main p r e d i c t a b l e d i f f e r e n c e would be a s h i f t i n the C r i t i c a l M i c e l l e Concen-t r a t i o n from 72.5 ppm a t a pH 3.6-4.6 to a much lower v a l u e a t ranges 2.6-3.6, 4.6-5.6. S i n c e the pH v a l u e s o u t s i d e the 3.6-4.6 range l a c k e d any p r a c t i c a l i n t e r e s t f o r the work i n t e n d e d , t h i s assumption was not c o n f i r m e d . 4.2 S t u d i e s o f the F l o t a t i o n P r o c e s s A p p l i e d t o K r a f t  M i l l Waste 4.2.1 Batch Experiments The d e s i g n o f the s e t o f b a t c h e x p e r i m e n t s has a l r e a been d e s c r i b e d . P r e l i m i n a r y e x p e r i m e n t s i n d i c a t e d t h a t the most i n s t r u c t i v e r e s u l t s about the f l o t a t i o n p r o c e s s would be o b t a i n e d , a t i n i t i a l s u r f a c t a n t c o n c e n t r a t i o n s r a n g i n g 45 from 100-200 ppm and pH v a l u e s v a r y i n g from 3.6 to 5.6. The temperature of the e f f l u e n t was kept m o s t l y between 25° and 35°C, a l t h o u g h no attempt was made to f i x i t to a c e r t a i n p a r t i c u l a r v a l u e . I t i s i m p o r t a n t to s t r e s s t h a t the c o m p o s i t i o n of k r a f t m i l l e f f l u e n t i s not always the same. The amount of each component p r e s e n t v a r i e s w i t h i n c e r t a i n l i m i t s de-pending on the type of wood and p r o c e s s c o n d i t i o n s . Each s e t of batch e x p e r i m e n t s was performed w i t h d i f f e r e n t samples from the same m i l l . F i g u r e s 6, 7, and 8 show the t y p i c a l average be-h a v i o r s o f each response a t the chosen l e v e l s of each f a c t o r . In each c a s e , the presence o f i n t e r a c t i o n s can be i n f e r r e d by j u s t i n s p e c t i n g the p l o t s . T h i s was c o n f i r m e d beyond any doubt i n the A n a l y s i s o f V a r i a n c e performed on the s e t of data (Appendix A ) . At t h i s p o i n t , i t becomes q u i t e o b v i o u s t h a t the t r e n d s i n the data s h o u l d be a n a l y z e d o b s e r v i n g the i n f l u e n c e of each f a c t o r a t f i x e d l e v e l s o f t h e o t h e r . Any e f f o r t to draw g e n e r a l i n f e r e n c e s on the main e f f e c t s caused by the s t u d i e d f a c t o r s would be m e a n i n g l e s s . S t i l l , i t i s p o s s i b l e to s e l e c t pH 3.6 and 100 ppm o f s u r f a c -t a n t as the b e s t parameters f o r the p r o c e s s , w i t h i n t h e s t u d i e d r a n g e s . S i n c e each response has a d e f i n i t e meaning i n the p r o c e s s , i . e . 46 i ) % s u r f a c t a n t f l o a t e d d e t e r m i n e s the amount o f s u r f a c t a n t consumed d u r i n g the f l o t a t i o n p r o c e s s , i r r e s p e c t i v e o f w h e t h e r any c o l o r body i s b e i n g a t t a c h e d t o i t , i i ) r a t i o o f s o l i d s f l o a t e d / s u r f a c t a n t f l o a t e d m e a s u r e s a s o r t o f e f f i c i e n c y o f t he f l o t a t i o n p r o c e s s , i i i ) % s o l i d s f l o a t e d g i v e s an i d e a o f t h e p o s s i b l e amount o f f l o a t a b l e s o l i d s t h a t c o u l d be removed f r o m the e f f l u e n t a t c e r t a i n f i x e d c o n d i t i o n s , i t i s mandatory to d i s c u s s t h e i r t e n d e n c i e s t o g e t h e r . F i g u r e 9 w i l l a l s o be h e l p f u l i n the f o l l o w i n g d i s c u s s i o n . 4.2.1.1 pH 3.6 I t has been r e p e a t e d l y p o i n t e d out t h a t the removal of c o l o r from k r a f t m i l l wastes by a d d i t i o n o f c a t i o n i c s u r f a c t a n t s i s more s u c c e s s f u l a t low pHs (10,11,12,61). T h i s i s i n agreement w i t h the b e h a v i o r d i s p l a y e d by the p r o c e s s i n graphs 6, 7, 8. The changes t h a t the f l o t a t i o n p r o c e s s undergoes as the i n i t i a l dosage o f s u r f a c t a n t i s i n c r e a s e d a r e r e m a r k a b l y i n t e r e s t i n g . A t 100' ppm, a dark t h i c k scum i s formed on top o f the s o l u t i o n , d u r i n g the f i r s t two or t h r e e minutes t h a t b u b b l i n g a i r i s passed through the f l o t a -t i o n c e l l . T h e r e a f t e r n e i t h e r scum nor foam i s formed and the c l e a r s o l u t i o n remains u n a l t e r e d . I f the s u r f a c t a n t dosage i s r a i s e d to 150 and 200 ppm, s t i l l t he scum would be 47 f i g u r e 6 . F L O T A T I O N O F S U R F A C T A N T I N K R A F T M I L L E F F L U E N T 48 f i g u r e 7 . R A T I O O F S O L I D S F L O A T E D T O S U R F A C T A N T F L O A T E D I N K R A F T M I L L E F F L U E N T 2 . 0 •o 1 .8 0 8 1 .6 £ 1-4 (0 S 1-2 (0 5 1-0 h T3 0 o (0 "D • MM o 0) . 8 -. 6 -.4 -.2 -0 p H 0 3 . 6 A 4 . 6 • 5 . 6 i_ • _L 5 0 1 0 0 1 5 0 p p m o f s u r f a c t a n t a d d e d 0 2 0 0 49 f i g u r e 8 . F L O T A T I O N O F S O L I D S F R O M K R A F T M I L L E F F L U E N T 50 f i g u r e 9 F L O T A T I O N O F S O L I D S F R O M K R A F T M I L L E F F L U E N T 51 formed w i t h i n the f i r s t few m i n u t e s , but f o l l o w e d by an i n c r e a s i n g amount of a heavy compact, w h i t e foam. The f o l l o w -i n g c o n c l u s i o n s can be made based on the b e h a v i o r f o l l o w e d by the p r o c e s s i n the s t u d i e d r a n g e s : 1. The m a j o r i t y o f t he n e g a t i v e l y c h a r g e d c o l l o i d s p r e s e n t i n t he e f f l u e n t a r e c h r o m o p h o r e s . Most o f t h e s e c h r o m o p h o r e s a r e no t a s s o c i a t e d w i t h any o t h e r c h e m i c a l s p e c i e s i n t he s o l u t i o n . 2. An i n s t a n t a n e o u s c o a g u l a t i o n r e a c t i o n t a k e s p l a c e be tween the n e g a t i v e l y c h a r g e d c h r o m o p h o r e s and the h y d r o p h o b i c c a t i o n o f t h e s u r f a c t a n t . The c o m p l e x ( s u b l a t e ) i s i n s o l u b l e , h y d r o p h o b i c and e a s i l y s e p a r a b l e by f l o t a t i o n . 3. The f o a m i n g p r o c e s s d e v e l o p e d a t h i g h e r s u r f a c t a n t c o n c e n t r a t i o n s must be c a u s e d by t h e e x c e s s o f s u r f a c t a n t i o n s i n s o l u t i o n . T h i s c o n c l u s i o n i s b a s e d on the s i m i 1 a r i t y o f the t y p e o f foam f o r m e d w i t h t he one p r o d u c e d i n a q u e o u s s o l u t i o n o f t he s u r f a c t a n t a t the same p H . k. T h e r e m i g h t a l s o be o t h e r c h r o m o p h o r i c s p e c i e s p r e s e n t i n the s o l u t i o n b u t , most l i k e l y , i n the f o r m o f n e u t r a l , i n s o l u b l e , c o l l o i d a l a g g r e g a t e s w h i c h t h e r e f o r e w o u l d not i n t e r f e r e w i t h t h e e l e c t r o s t a t i c p r o c e s s d e s c r i b e d in ( 2 ) . N e v e r t h e l e s s , t h e y a r e removed f rom t h e s o l u t i o n d u r i n g the coagu1 a t i o n - f 1 o t a t i o n p r o c e s s . A c c o r d i n g t o F i g u r e 8 the p e r c e n t a g e of s o l i d s f l o a t e d from the e f f l u e n t i s the same f o r the t h r e e s u r f a c t a n t dosages used. T h i s t r e n d i s s u p p o r t e d by the l i n e a r r e g r e s s i o n a n a l y s i s of the da t a (Appendix B ) . In terms of F i g u r e 9 t h i s means t h a t the amount of s o l i d s t h a t c o u l d be p o s s i b l y 52 f l o a t e d i s c o n s t a n t and ranges from 130 to 160 ppm. There-f o r e , any s u r f a c t a n t used i n excess of 100 ppm would be wasted. F i g u r e 7 c o n f i r m s this c o n c l u s i o n s i n c e the " e f f i c i e n c y " of the p r o c e s s i s h i g h l y d e c r e a s e d a t s u r f a c t a n t dosages over 100 ppm. These r e s u l t s v e r i f y the e a r l i e r c o n c l u s i o n s made. At the b e g i n n i n g o f the p r o c e s s , the p r i m a r y mechanism i s a c o a g u l a t i o n r e a c t i o n between chromophores and c a t i o n i c s u r -f a c t a n t which i s not i n t e r f e r e d w i t h by any o t h e r c h e m i c a l s p e c i e s p r e s e n t i n the s o l u t i o n . S i n c e the r e a c t i o n i s i n s t a n t a n e o u s and the s u b l a t e i s i m m e d i a t e l y f l o a t e d , t h e r e i s no i n t e r a c t i o n w i t h the s u r f a c t a n t i n e x c e s s , a t l e a s t i n the range under s t u d y . F i g u r e 6 i m p l i e s t h a t , a t 100 ppm, 90% o f the s u r f a c t a n t i s i n i t s i o n i c form and t h e r e f o r e f r e e to r e a c t w i t h the chromophores. T h i s v a l u e s u g g e s t s t h a t the i o n i c a g g r e g a t e s do not form so r e a d i l y i n the k r a f t e f f l u e n t as they do i n aqueous s o l u t i o n s . Most l i k e l y because o f the presence o f o t h e r c o m p e t i t i v e s p e c i e s i n the waste. At c o n c e n t r a t i o n s h i g h e r than 100 ppm, the % o f s u r f a c t a n t f l o a t e d does not s t a y c o n s t a n t a t 90%; i n s t e a d i t be g i n s to decrease i n a l i n e a r r e l a t i o n s h i p (Appendix B ) . The r e a s o n i s presumably the development of Van der Waal bonds by the long c h a i n hydrocarbons weaving around c o l l o i d a l p a r t i c l e s s t i l l i n s o l u t i o n r a t h e r than any i n t e r a c t i o n between the s u r f a c t a n t i o n s among t h e m s e l v e s . In any event 53 the aggregates are not s u r f a c e a c t i v e and c o n s e q u e n t l y not removable by f l o t a t i o n . 4.2.1.2 pH 4.6 The f l o t a t i o n p r o c e s s under study d i s p l a y s i t s most d r a m a t i c changes at pH 4.6. T h e r e f o r e , i t i s e s p e c i a l l y i m p o r t a n t to u n d e r s t a n d the n a t u r e of those changes s i n c e they r e p r e s e n t the b e s t s o u r c e of i n f o r m a t i o n r e g a r d i n g the mechanisms i n v o l v e d i n the p r o c e s s . At 100 ppm, t h e p r o c e s s f a i l s c o m p l e t e l y to produce any scum; o n l y an i n c i p i e n t , l i g h t brown f r o t h i s formed. I n c r e a s i n g the s u r f a c t a n t dosage to 150 ppm produces s p e c t a c u l a r m o d i f i c a t i o n s i n the p r o c e s s . I m m e d i a t e l y , a dark t h i c k scum i s formed s u p p o r t e d by a heavy, s t a b l e , c o l o r l a d e n f r o t h . No f u r t h e r d e v e l o p -ment of e i t h e r f r o t h o r scum i s o b s e r v e d i n the s o l u t i o n . In g e n e r a l , t h i s b e h a v i o r resembles v e r y much the one e x h i b i t e d by t h e p r o c e s s a t pH 3.6, 100 ppm. N e v e r t h e l e s s , the t u r b i d i t y o f the r e a m i n i n g s o l u t i o n i s c o n s i d e r a b l y h i g h e r a t pH 4.6. A s u r f a c t a n t dosage of 200 ppm p r o d u c e s , d u r i n g the f i r s t few seconds of the p r o c e s s , a c h o c o l a t e - c o l o r e d f r o t h w i t h a c r e a m - c o l o r e d r i n g underneath i t . Next the r i n g becomes b i g g e r and p a l e r , f i n a l l y a c q u i r i n g the c h a r a c t e r i s t i c s o f the heavy w h i t e foam produced by an excess o f f r e e s u r f a c t a n t i o n s i n s o l u t i o n . The i n c r e a s e i n the t u r b i d i t y of the 54 r e m a i n i n g s o l u t i o n becomes q u i t e n o t i c e a b l e . At t h i s p o i n t , i t seems l o g i c a l to c o n c l u d e f o r t h e pH under s t u d y t h a t : 1. A l t h o u g h the l a r g e r p e r c e n t a g e o f t he n e g a t i v e l y c h a r g e d c h r o m o p h o r e s a r e no t a s s o c i a t e d , s t i l l a c e r t a i n f r a c t i o n o f them i s a t t a c h e d to o t h e r c h e m i c a l s p e c i e s i n the s o l u t i o n . 2. The a t t a c h e d m o i e t y o f t h e c h r o m o p h o r e s c o m p e t e s p r e f e r e n t i a l l y f o r t he h y d r o p h o b i c c a t i o n , p r o b a b l y b e c a u s e o f the p r e s e n c e o f s e v e r a l n u c l e o p h i l i c g r o u p s in t he a g g r e g a t e , i . e . a h i g h e r i n t e n s i t y o f n e g a t i v e c h a r g e s . The c o m p l e x f o r m e d e i t h e r i s no t s u r f a c e a c t i v e o r i t i s t o o s t r o n g l y bound to t h e b u l k o f t he s o l u t i o n to be s e p a r a b l e by f l o t a t i o n . F o r t h a t r e a s o n , an a l m o s t e n t i r e l a c k o f f r o t h i s o b s e r v e d , as i s an i n c r e a s e i n t h e t u r b i d i t y o f t h e s o l u t i o n . 3. Once the c o n c e n t r a t i o n o f s u r f a c t a n t i s i n c r e a s e d to an op t imum v a l u e where t he i n t e r f e r i n g s p e c i e s a r e e l e c t r o s t a t i c a l l y s a t i s f i e d , the c o a g u l a t i o n r e a c t i o n be tween the u n a t t a c h e d c h r o m o p h o r e s and the h y d r o p h o b i c c a t i o n t a k e s p l a c e . The s u b l a t e i s s u r f a c e a c t i v e and i s removed by f l o a t i o n i n the f o r m o f a f r o t h w i t h a c o a g u l a t e d scum on t o p . k. I f t he c o n c e n t r a t i o n o f s u r f a c t a n t e x c e e d s the op t imum v a l u e , the h y d r o c a r b o n c h a i n s o f t h e s u b l a t e b e g i n to a s s o c i a t e , a phenomenon a k i n t o t he f o r m a t i o n o f m i c e l l e s in a q u e o u s s o l u t i o n s and c a l l e d h e m i m i c e l l e s by G a u d i n and F u e r s t e n a u ( 6 2 ) . The h e m i -m i c e l l e s a r e not s u r f a c e a c t i v e . As t he amount o f c o l l e c t o r i s i n c r e a s e d , t he p e r -c e n t a g e o f f r e e i o n s a l s o i n c r e a s e s and c o n s e q u e n t l y the f o a m i n g p r o c e s s . The most i m p o r t a n t of the p r e v i o u s c o n c l u s i o n s (number one) i s based on a r e c e n t p u b l i c a t i o n by Swanson 55 et al. ( 1 3 ) . These a u t h o r s have p o i n t e d to the presence of a m i x t u r e of chromophores i n the waste water samples. S i n c e the c o l o r o f the e f f l u e n t changes w i t h pH, they s u g g e s t e d , as a p l a u s i b l e e x p l a n a t i o n , t h a t "the degree of i o n i z a t i o n o f each chromophore i s d i f f e r e n t a t d i f f e r e n t pH v a l u e s " (see F i g u r e 10, taken from r e f e r e n c e 4 ) . F u r t h e r m o r e , the c o l o r b o d i e s were d i v i d e d i n t o a c i d - s o l u b l e and a c i d - i n s o l u b l e g r o u p s . Regarding the former i t i s remarked t h a t "they have low m o l e c u l a r w e i g h t , hi g h u n conjugated C00H g r o u p s , l i g n i n l i k e c h a r a c t e r , and seem a s s o c i a t e d w i t h c o l o r l e s s carbon compounds." I t can be observed through F i g u r e s 6 and 8 t h a t the p e r c e n t a g e of s u r f a c t a n t and s o l i d s f l o a t e d i s minimum at 100 ppm and, as i s of c o u r s e , the amount of s o l i d s f l o a t e d ( F i g u r e 9 ) . S t i l l , the r e c o v e r y o f some s u r f a c t a n t by f l o t a t i o n a t t h i s s p e c i f i c dosage i s p r o b a b l y a c h i e v e d by t h e presence of some n a t u r a l s u r f a c e a c t i v e s p e c i e s i n the e f f l u e n t and because the c o a g u l a t i o n r e a c t i o n i s not c o m p l e t e l y s u p p r e s s e d . Y e t , t h e r e are no f r e e s u r f a c t a n t i o n s i n s o l u t i o n as e v i d e n c e d by the l a c k of foam. 150 ppm r e p r e s e n t s the optimum dosage f o r a l l the p r o c e s s r e s p o n s e s . The p r o c e s s i s more " e f f i c i e n t " ( F i g u r e 7) and the amount of s o l i d s removed by f l o -t a t i o n f a l l s w i t h i n the range of "the amount o f p o s s i b l y f l o a t a b l e s o l i d s " (130-160 ppm). At 200 ppm the p e r c e n t a g e of s u r f a c t a n t f l o a t e d remains c o n s t a n t . I t seems t h a t the f r a c t i o n not f l o a t e d because of Van der Waal i n t e r a c t i o n s i s f u l l y r e p l a c e d by the amount f l o a t e d as f r e e i o n s . However, the 56 f i g u r e 1 0 . C O L O R V E R S U S p H F O R T O T A L M I L L E F F L U E N T 3 0 0 0 ^ 2 5 0 0 0) c 3 O O » 2 0 0 0 o o ° 1 5 0 0 1 0 0 0 ' I I I L 2 4 6 8 p H 1 0 1 2 57 p r o c e s s " e f f i c i e n c y " s u f f e r s a marked d e c r e a s e . T h i s i s q u i t e u n d e r s t a n d a b l e s i n c e the amount of s o l i d s f l o a t e d ( t h e numerator i n the " e f f i c i e n c y " term) i s h i g h l y a f f e c t e d by the f o r m a t i o n of hemimieel 1es. The d r a s t i c change i s more e a s i l y a p p r e c i a t e d i n F i g u r e 9 than i n F i g u r e 8. I t must be p o i n t e d out t h a t the p e c u l i a r c h a r a c -t e r i s t i c s e x h i b i t e d by the p r o c e s s a t t h i s pH c o r r e s p o n d s q u i t e c l o s e l y t o the ones obse r v e d and d e s c r i b e d by H e r s c h m i l l e r (4) i n d i f f e r e n t a s p e c t s of h i s work. Y e t , t h e e f f l u e n t u s e d , t h e s e t o f c o n d i t i o n s f i x e d and the p r o c e s s r e s p o n s e s were not the same i n h i s work; a l s o the r e s u l t s o b t a i n e d were e x p l a i n e d u s i n g a d i f f e r e n t a p proach. 4.2.1.3 pH 5.6 The b e h a v i o r o f the f l o t a t i o n p r o c e s s a t pH 5.6 i s o n l y a d r a m a t i z a t i o n of what happened a t pH 4.6. The same c o n c l u s i o n s made b e f o r e w i l l h o l d i n t h i s case w i t h o n l y one m o d i f i c a t i o n ; the p e r c e n t a g e o f a t t a c h e d chromophores i s a t i t s h i g h e s t . Moreover the e x p e c t a b l e f r a c t i o n o f s u r -f a c t a n t i n i o n i c form i s c o n s i d e r a b l y l e s s a t this pH ( F i g u r e 4 ) . At dosages of 100 and 150 ppm the p r o c e s s o n l y produces a s p a r s e , a l m o s t i n s i g n i f i c a n t , l i g h t - b r o w n f r o t h . The p e r -c entage o f s u r f a c t a n t f l o a t e d i n c r e a s e s v e r y l i t t l e ( F i g u r e 6 ) , the p r o c e s s " e f f i c i e n c y " and the p e r c e n t a g e of s o l i d s 58 f l o a t e d remain almost c o n s t a n t . On the o t h e r hand, a t 200 ppm, a dark brown f r o t h i s formed on top of a cream r i n g , w h i c h , a g a i n , becomes b i g g e r and p a l e r and f i n a l l y r e p r e s e n t s the w e l l known foaming p r o c e s s due to f r e e s u r f a c t a n t i o n s . I t f o l l o w s t h a t , a l t h o u g h an i n c r e a s e i n s o l i d s f l o a t e d and p r o c e s s " e f f i c i e n c y " has been s u d d e n l y a c h i e v e d ; t h i s w i l l p r o b a b l y be the optimum c o n d i t i o n s f o r t h e c o a g u l a t i o n p r o c e s s s i n c e the r e s t of the chromophores are a t t a c h e d t o the n o n f l o a t a b l e complex. Any i n c r e a s e i n the s u r f a c t a n t dosage w i l l cause a deleterious e f f e c t on the amount of s o l i d s removed by f l o t a t i o n . .As a r u l e , the s o l u t i o n becomes more t u r b i d w i t h each i n c r e a s e i n the amount of s u r f a c t a n t and t h e r e i s not a marked improvement a t the s o - c a l l e d optimum dosage. 4.2.2 Continuous E x p e r i m e n t s The b a t c h e x p e r i m e n t s r e s u l t s made i t p o s s i b l e t o s e l e c t pH 3.6 and 100 ppm o f s u r f a c t a n t as b e i n g p r o b a b l y t h e b e s t parameters f o r the p r o c e s s . F u r t h e r b a t c h e x p e r i m e n t s aimed a t d i m i n i s h i n g the amount o f s u r f a c t a n t per l i t e r of k r a f t e f f l u e n t were c o m p l e t e l y u n s u c c e s s f u l (see Appendix D). S e v e r a l p r e l i m i n a r y t r i a l s were n e c e s s a r y b e f o r e any p o s i t i v e r e s u l t c o u l d be a c h i e v e d i n the c o n t i n u o u s r u n s . D i f f e r e n t methods f o r m i x i n g the s u r f a c t a n t and the e f f l u e n t were t r i e d : i ) to f e e d both streams s e p a r a t e l y i n t o the 59 f l o t a t i o n column, i i ) to add the s u r f a c t a n t to the e f f l u e n t s t r e a m , and t h e n , the m i x t u r e , to the f l o t a t i o n column, i i i ) to s e t a s t i r r e d p r e m i x i n g s t a g e f o r both streams b e f o r e they e n t e r e d to the f l o t a t i o n column. P r a c t i c a l l y , no r e s u l t s were o b t a i n e d w i t h the f i r s t two p r o c e d u r e s . I t was a l s o i m p o r t a n t to keep the a i r f l o w r a t e s low s i n c e the d e v e l o p -ment of t u r b u l e n c e , a t h i g h e r v a l u e s , t o t a l l y o b v i a t e d the c o a g u l a t i o n - f l o t a t i o n p r o c e s s by r e d i s p e r s i n g the s u b l a t e . Once the c o n t i n u o u s equipment was p e r f e c t e d , i t was run u s i n g the b e s t b a t c h parameters but v a r i o u s r e t e n t i o n times i n the column. The r e s u l t s ( T a b l e 5) are c o m p a r a b l e , i n g e n e r a l , to t h o s e o b t a i n e d i n the b a t c h r u n s . The p r o c e s s behaved e x a c t l y the same as the c o r r e s p o n d i n g b a t c h e x p e r i -ment. No foam or f r o t h was d e v e l o p e d , o n l y a t h i c k dark scum. The t r e a t e d e f f l u e n t was v i r t u a l l y c o l o r l e s s . I t i s c l e a r l y n o t i c e a b l e t h a t i n c r e a s i n g the f l o t a t i o n time over 15 minutes has a d e l e t e r i o u s e f f e c t on the p r o c e s s , p r o b a b l y due to r e d i s s o l u t i o n o f the p r e c i p i t a t e . The p e r c e n t a g e o f s u r f a c t a n t f l o a t e d was h i g h e r i n the c o n t i n u o u s r u n , p o s s i b l y because a f r e s h b o t t l e of the r e a g e n t was used and, con-s e q u e n t l y , a g e i n g was not i n v o l v e d . T a b l e 5 Continuous Experiment R e s u l t s Obtained a t pH 3.6, 100 ppm of S u r f a c t a n t and V a r i o u s R e t e n t i o n Times F l o t a t i o n Time (mi n utes) % S u r f a c t a n t F l o a t e d % S o l i d s F l o a t e d S o l i d s F l o a t e d S u r f a c t a n t F l o a t e d S o l i d s F l o a t e d (ppm) Temp. °C 8 98 6 15 06 1 .12 110 25° 8 95 0 18 1 .42 133 26° 15 98 6 15 06 1 .12 n o 25° 15 94 8 17 5 1 .35 128 26° 30 94 48 12 62 0 .94 93 25° 30 94 5 15 1 .17 111 26° 45 98 22 11 57 0 .86 85 25° 45 94 3 12 0 0 .94 89 26° CT) o 61 4.3 S t u d i e s on the I n f l u e n c e of pH Adjustment and Time  E l a p s e d on the K r a f t M i l l Waste 4.3.1 T o t a l S o l i d s Content N e i t h e r the samples w i t h t h e i r pHs p r e v i o u s l y a d j u s t e d to a c e r t a i n v a l u e , nor the o r i g i n a l e f f l u e n t showed any marked d i f f e r e n c e i n t h e i r s o l i d s c o n t e n t w i t h t i m e , i . e . w i t h i n the same b a t c h , s i n c e the t o t a l amount of s o l i d s p r e s e n t c o u l d change from b a t c h to b a t c h (Figures 11-A,B,C,D). 4.3.2 C o l o r While the c o l o r of the r e f r i g e r a t e d , o r i g i n a l e f f l u e n t remained u n a l t e r e d d u r i n g the chosen p e r i o d o f time ( F i g u r e 12D), the samples w i t h p r e v i o u s l y a d j u s t e d pH d i s p l a y e d two types o f b e h a v i o r s . A l l o w i n g f o r the e x p e c t a b l e c o l o r d i f f e r e n c e s between each b a t c h , i t c o u l d be s a i d t h a t , a t pH 3.6, the c o l o r v a l u e remained p r a c t i c a l l y c o n s t a n t ( F i g u r e 12A) b u t , on the o t h e r hand, a t pHs o f 4.6 and 5.6 t h e r e seemed to be a d e f i n i t e d e c r e a s e o f c o l o r a f t e r the s e v e n t h day ( F i g u r e 12 B,C). Swanson et al. (13) r e p o r t e d the a b s o r p t i o n s p e c t r a of k r a f t e f f l u e n t s , a t pH 7.6, a f t e r s t o r i n g the samples f o r 1, 3, 6 and 24 days a t room t e m p e r a t u r e ( F i g u r e 1 3 ) . A marked d e c r e a s e i n c o l o r i s e v i d e n t between t h r e e and s i x days of s t o r a g e . 62 f i g u r e 1 1 . E F F E C T O F S T O R A G E T L V i E A N D p H C M S O L ! D S C O N T E N T O F K R A F T MILL E F F L U E N T A 0 , d , 0 d i f f e r e n t b a t c h e s 0 ^ A - O ( d e f r o z e n o n ! 2 t h d a y ) i O p : * ° O ^ A A 5 0 oo o 1 0 1 5 A 20 o o c o o o B. 1 0 r D H 4 , 5 o h 0 o o o c. 1 0 r p H 5 . 6 F ° 0 1 0 0 o o A A A 1 5 0 o D. l O r n o p H a d j u s t m e n t 0 r o ° o o o o o o o 5 1 0 1 5 c l a y s a f t e r s a m p l i n g O 2 0 63 f i g u r e 12. E F F E C T O F S T O R A G E T I M E A N D p H O N C O L O R O F K R A F T M I L L E F F L U E N T A. 0 , D , 0 different batches F i l t e r e d a t : A = O (defrozen on 12th day) 1 5 r P H 3.6 o 101- O A ^ A • . • 10 15 2 0 o B' 0 1 5 r P H 4 . 6 1 1 0 h 1 5« o o o o I +- 15 Q . C. r p H 5.6 v . 1 0 h o 5 • • o o • • _ J o ° o ° 10 10 15 A O 15 2 0 • 2 0 D. 1 5 p n o p H a d j u s t m e n t 1 0 h ° ° o o 0 0 o ° 0 5 10 15 d a y s a f t e r s a m p l i n g o 2 0 64 f i g u r e 1 3 . E F F E C T O F S T O R A G E O N A B S O R B A N C E ( a t p H 7 . 6 ) O F U N T R E A T E D W A S T E 4 0 3 0 0) 75 2 0 > O C CO € 4 O CO n (0 •A-2 5 4 n m 2 8 0 n m 4 2 0 n m •o 1 1 1 0 1 5 t i m e , d a y s 2 0 2 5 65 4.3.4 F i l t e r a b i l i t y The f i l t r a t i o n r a t e o f the e f f l u e n t , which i s q u i t e high i n a l k a l i n e medium becomes much s l o w e r a t low pH v a l u e s , e s p e c i a l l y a t 3.6. The p o s s i b i l i t y of the p r e s e n c e of n e u t r a l , i n s o l u b l e , chromophoric a g g r e g a t e s a t t h i s pH has been men-t i o n e d a l r e a d y and c o u l d p r o b a b l y be the cause f o r the marked change i n the f i l t r a t i o n r a t e . Moggio (63) o b s e r v e d t h a t "the c o l o r b o d i e s become i n c r e a s i n g l y i n s o l u b l e a t low pHs." Brown (64) has a l s o d e s c r i b e d a s i m i l a r phenomenon i n h i s e x p e r i m e n t a l work. The c o l o r r e a d i n g s , as a r u l e , a re always lower i n those samples i n which the pH has been a d j u s t e d a t i t s l o w e s t v a l u e . T h e r e f o r e , a l t h o u g h the c o l o r r e a d i n g s are t a k e n a t the same pH v a l u e f o r a l l samples, i t i s a f a c t t h a t some c o l o r has been l e f t behind d u r i n g the r e q u i r e d f i l t r a t i o n s t a g e . I t i s a l s o n o t e w o r t h y t h a t , once the f l o t a t i o n p r o c e s s has been a c c o m p l i s h e d , the f a s t e s t f i l t r a t i o n r a t e f o r the r e m a i n i n g s o l u t i o n i s o b t a i n e d a t pH 3.6. T h i s means t h a t most o f the c o l l o i d s and c o l l o i d a g g r e g a t e s p r e s e n t ( c h r o m o p h o r i c o r not) have been removed from the s o l u t i o n d u r i n g the f l o t a t i o n p r o c e s s . Undoubtedly t h i s i s i n a g r e e -ment w i t h the q u a l i t y of the r e s u l t a n t s o l u t i o n . In g e n e r a l , f o r pH 4.6 and 5.6, the h i g h e r the i n i t i a l amount of s u r f a c t a n t the more t u r b i d the f i n a l s o l u t i o n t u r n s . The t u r b i d i t y of the s o l u t i o n and most of i t s c o l o r i s removed d u r i n g the f i l t r a t i o n s t age p r e c e d i n g the c o l o r t e s t . For t h a t r e a s o n , 66 i t i s o b v i o u s t h a t s u r f a c t a n t and c o l o r b o d i e s are bound i n a complex, n o n - f l o a t a b l e a g g r e g a t e , b i g enough to be removed by f i l t r a t i o n . F i g u r e 14 shows how d e c e i v i n g the c o l o r t e s t can be, i f taken as a measure of the p r o c e s s r e s p o n s e . A c c o r d i n g to i t the amount of c o l o r removed i n c r e a s e s as the dosage of s u r f a c t a n t i s r a i s e d , r e g a r d l e s s o f the pH o f the e f f l u e n t . I t f o l l o w s t h a t the p r e s ence of i n t e r a c t i o n i s not d i s c l o s e d . Moreover, the c o n c l u s i o n reached i s o p e n l y d e n i e d by the p r o c e s s b e h a v i o r s i n c e the "worst l o o k i n g " e f f l u e n t i s o b t a i n e d when the f l o t a t i o n parameters a r e s e t a t pH 5.6 and 200 ppm o f s u r f a c t a n t . 4.4 S t u d i e s on the B e h a v i o r of K r a f t M i l l Waste i n V a r i o u s  A c i d i f i c a t i o n - A ! k a l i z a t i o n Sequences i ) a c i d i f i c a t i o n - a l k a l i z a t i o n - a c i d i f i c a t i o n i i ) a l k a l i z a t i o n - a c i d i f i c a t i o n - a l k a l i z a t i o n - a c i d i f i c a t i o n A sample from E l k F a l l s t o t a l m i l l e f f l u e n t was used i n t h e s e s t u d i e s . T h i s t o t a l m i l l e f f l u e n t was o b t a i n e d by m i x i n g p r o p o r t i o n a l amounts of the f o u r main o u t l e t s from the m i l l . The pH of the mixed e f f l u e n t was seven and hence t h i s was the s t a r t i n g p o i n t . C o n c e n t r a t e d h y d r o c h l o r i c a c i d and c o n c e n t r a t e d sodium h y d r o x i d e were the a c i d and a l k a l i used (see Appendix C ) . 67 f i g u r e 1 4 . C O L O R R E M O V A L F R O M K R A F T M I L L E F F L U E N T A S A F U N C T I O N O F A M O U N T O F S U R F A C T A N T A D D E D A N D p H 1 0 0 9 0 8 0 -a 70 > | 6 0 0) 0 s 5 0 h 8 4 0 3 0 2 0 1 0 P H 0 3 . 6 A 4 . 6 • 5 . 6 5 0 1 0 0 1 5 0 p p m o f s u r f a c t a n t a d d e d 2 0 0 68 F i g u r e s 15 and 16 show the b e h a v i o r d i s p l a y e d by the e f f l u e n t i n the two a f o r e m e n t i o n e d sequences r e s p e c t i v e l y . A l t h o u g h f o r a d i f f e r e n t p urpose, Prahacs et al. (61) i n v e s -t i g a t e d the t r e n d s f o l l o w e d d u r i n g the a c i d i f i c a t i o n o f k r a f t m i l l c a u s t i c e x t r a c t i o n s t a g e e f f l u e n t . They d i d not perform a back n e u t r a l i z a t i o n . The agreement between both r e s u l t s i s r e a l l y r e m a r k a b l e . T h e i r r e s u l t s a r e p a r t i a l l y r e p roduced i n F i g u r e 17. S i n c e the main o b j e c t i v e s of t h e s e s t u d i e s were to g a i n some knowledge of the b e h a v i o r o f the waste a t the pHs under s t u d y , t h e d i s c u s s i o n w i l l be f o c u s s e d i n t h a t d i r e c t i o n . The most s t r i k i n g f e a t u r e i n both F i g u r e s , 15 and 1 6 , i s t h a t once the e f f l u e n t has been brought to a v e r y low pH, the o r i g i n a l p a t t e r n ( i . e . c u r v e AB) i s never re p r o d u c e d d u r i n g any f u r t h e r a l k a l i z a t i o n - a c i d i f i c a t i o n sequences. From t h a t p o i n t on, the t y p i c a l s t r o n g base-s t r o n g a c i d n e u t r a l i z a t i o n c u r v e i s always o b t a i n e d . G a t h e r i n g a l l the i n f o r m a t i o n t o g e t h e r , i t can be s a i d t h a t i ) D u r i n g the f i r s t a c i d i f i c a t i o n o f the e f f l u e n t from pH 7 to 3, c e r t a i n c h e m i c a l s p e c i e or s p e c i e s are i r r e v e r s i b l y t r a n s f o r m e d , i i ) No n o t i c e a b l e p r e c i p i t a t e o r gas e v o l u t i o n i s o b s e r v e d , i i i ) The c o l o r of the s o l u t i o n i s l e f t u n a f f e c t e d by the change s i n c e back a l k a l i z a t i o n r e s t o r e s the c o l o r , r e a d i n g to i t s f u l l i n i t i a l v a l u e . 69 f i g u r e 1 5 . B E H A V I O U R O F K R A F T M I L L E F F L U E N T IN T H E S E Q U E N C E A C I D I F I C A T I O N • A L K A L I Z -A T I O N - A C I D I F I C A T I O N 1 2 r A-B m l HCI — C - A - A 'm l NaOH A'-A-C m l HCI — 2.5 2.0 1.5 1.0 .5 A-B I i i 1 I i I i I C - A - A ' - ^ 0 .2 .4 .6 .8 1.0 1.2 ± 2.5 2.0 1.5 1.0 0 -*-ALA-C 70 — { f i g u r e 1 6 . B E H A V I O U R O F K R A F T M I L L E F F L U E N T IN T H E S E Q U E N C E A L K A L I Z A T I O N • A C I D I F I C -A T I O N • A L K A L I Z A T I O N - A C I D I F I C A T I O N 71 f i g u r e 1 7 , A C I D I F I C A T I O N O F K R A F T C A U S T I C -E X T R A C T I O N E F F L U E N T W I T H 9 6 % H 2 SO4 O s o f t w o o d 0.2 OA 0 .6 0 .8 1.0 1.2 1.4 v o l u m e of H 2 S 0 4 r e q u i r e d , ' , m l / l i t e r of e f f l u e n t 72 I t has been suggested t h a t some types of sugars are o r i g i n a l l y a t t a c h e d to the c o l o r b o d i e s and r e l e a s e d , a f t e r w a r d s , i n p o l y m e r i c form a t c e r t a i n pH v a l u e s ( 1 3 ) . Tak i n g i n t o account how complex the c o m p o s i t i o n of the e f f l u e n t i s and how many p o s s i b l e i n t e r a c t i o n s can be developed between a l l the d i f f e r e n t s p e c i e s p r e s e n t , i t would be presumptuous to name the f a c t o r r e s p o n s i b l e f o r such a p e c u l i a r b e h a v i o r . In agreement w i t h the d i s c u s s e d r e s u l t s , i t i s p o s s i b l e t h a t an i n c r e a s i n g c o n c e n t r a t i o n o f hydronium i o n a s s i s t s i n b r e a k i n g the bonds t h a t h o l d the a c i d s o l u b l e chromophores to t h e i r a s s o c i a t e s and, from t h a t moment, they remain i n s o l u t i o n as i n d i v i d u a l species,. 4.5 Other V a r i a b l e s o f I n t e r e s t B e f o r e c l o s i n g t h i s d i s c u s s i o n , i t must be p o i n t e d out t h a t the i n f l u e n c e of c e r t a i n v a r i a b l e s was d e t e r m i n e d d u r i n g s e v e r a l s e t s of t e n t a t i v e b a t c h e x p e r i m e n t s . P r e v i o u s work c a r r i e d out by Herschmi11er (4) i n r e l a t i o n t o t h e s e s p e c i f i c v a r i a b l e s was ta k e n as a good s t a r t i n g p o i n t . For t h a t reason t h o s e v a r i a b l e s were f i x e d a t d e f i n i t e v a l u e s d u r i n g the e x p e r i m e n t a l work. T h i s was done w i t h the i n t e n -t i o n o f n a r r o w i n g the b a s i c s t u d y t o the most i m p o r t a n t v a r i a b l e s . They s h a l l be mentioned b r i e f l y : 73 Air flow rate and sparger s i z e - I t was found t h a t the f l o t a t i o n p r o c e s s performed a t i t s b e s t at low gas f l o w r a t e (1.66 c c / s e c ) and u s i n g a f i n e p o r o s i t y d i s p e r s e r ( 4 , 6 5 ) . Introduction of the surfactant - The b e s t r e s u l t s were o b t a i n e d d i s s o l v i n g the s u r f a c t a n t i n 10 cc methanol and i n t r o d u c i n g i t a t v e r y slow r a t e s by a s y r i n g e . Any attempt to i n t r o d u c e the s u r f a c t a n t i n a s i n g l e dose or i n a powder form r e s u l t e d i n v e r y poor r e s u l t s ( 1 0 ) . Premixing time and s t i r r e r speed - The p r e m i x i n g time and the s t i r r e r speed appeared to have a marked e f f e c t on the f o r m a t i o n o f the p r e c i p i t a t e . Five minutes o f p r e -m i x i n g time and a s t i r r e r speed o f 950 RPM seemed to make a good c o m b i n a t i o n o f both p a r a m e t e r s . Temperature - Rubin and Johnson (65) o b s e r v e d t h a t t e m p e r a t u r e s i n the range from 15° t o 34°C do not a f f e c t the i o n f l o t a t i o n p r o c e s s . Prahacs and Wong (61) found no s e n s i b l e change i n the p e r c e n t a g e o f c o l o r removed from k r a f t c a u s t i c e x t r a c t i o n e f f l u e n t a t t e m p e r a t u r e s v a r y i n g from 20 to 58°C. The e x p e r i m e n t s d i s c u s s e d were c a r r i e d out always w i t h an e f f l u e n t t e m p e r a t u r e w i t h i n 25-35°C. The r e s u l t s o b t a i n e d d i d not show any s i g n i f i c a n t tempera-t u r e dependence. Chapter 5 CONCLUSIONS 5.1 From the S t u d i e s on the F l o a t a b i l i t y o f the S u r f a c t a n t 1 . The p e r c e n t a g e o f s u r f a c t a n t r e c o v e r e d by f l o t a t i o n i s an optimum a t pH v a l u e s v a r y i n g from 3.6 to 4.6. O u t s i d e t h i s r a n g e , the tendency o f the s u r f a c t a n t i o n s to a s s o c i a t e i s maximum. 2. A t optimum pH v a l u e s and i n aqueous s o l u t i o n , the p r e s ence o f a g g r e g a t e s becomes e v i d e n t a t c o n c e n t r a t i o n s g r e a t e r than 72.5 ppm. N e v e r t h e l e s s , the i n t e r a c t i o n o f the s u r f a c t a n t i o n s among them s e l v e s i s not a c r i t i c a l f a c t o r i n the c o l o r c o a g u l a t i o n p r o c e s s . 3. Under the b e s t c o n d i t i o n s , 90% of the s u r f a c t a n t i n s o l u t i o n i s i n i o n i c form. The r e s t i s p r o b a b l y aggre-gates t h a t might be r e a d i l y formed i n s o l u t i o n o r , more l i k e l y , due to a g e i n g o f the s u r f a c t a n t . 74 75 4. I t i s p o s s i b l e to use the p e r c e n t a g e o f s u r -f a c t a n t r e c o v e r e d by f l o t a t i o n as a means to d e t e r m i n e the presence of i t s a g g r e g a t e s i n aqueous s o l u t i o n . T h i s t e c h -nique s t i l l needs f u r t h e r improvement. 5.2 From the S t u d i e s on the F l o t a t i o n P r o c e s s 5.2.1 Batch Experiments 1. I t has been d i s c l o s e d the p r e s e n c e of s i g n i f i -c a n t i n t e r a c t i o n between the pH o f the waste and the amount of s u r f a c t a n t added. C o n s e q u e n t l y , the b e h a v i o r o f the f l o t a t i o n p r o c e s s depends e n t i r e l y on the combined v a l u e s assumed by t h e s e v a r i a b l e s . 2. I t i s p o s s i b l e t o s e l e c t pH 3.6 and 100 ppm of s u r f a c t a n t as the b e s t parameters f o r the p r o c e s s w i t h i n the s t u d i e d r a n g e s . At t h e s e c o n d i t i o n s i t was o b s e r v e d t h a t : a) the amount of s o l i d s t h a t c o u l d be p o s s i b l y f l o a t e d v a r i e d from 130-160 ppm, b) the p r o c e s s r e s p o n s e s were a t t h e i r b e s t v a l u e s , i . e . 90% s u r f a c t a n t f l o a t e d , 1.57 r a t i o of s o l i d s f l o a t e d to s u r f a c t a n t f l o a t e d and 21.5 o f t o t a l s o l i d s f l o a t e d , c) the r e p r o d u c i b i l i t y o f the r e s u l t s was h i g h l y s a t i s f a c t o r y , 76 d) two s i m u l t a n e o u s p r o c e s s e s seemed to take p l a c e : i ) a g g r e g a t i o n o f the a c i d i n s o l u b l e chromophores, i i ) an i n s t a n t a n e o u s c o a g u l a t i o n r e a c t i o n between the a c i d - s o l u b l e , n e g a t i v e l y charged chromophores and the c a t i o n i c s u r f a c t a n t i o n e) the complex s p e c i e s formed by the d e s c r i b e d p r o c e s s e s were i m m e d i a t e l y removed by f l o t a t i o n i n t h e form o f a d a r k , t h i c k scum. N e i t h e r f r o t h nor foam was p r e s e n t . In g e n e r a l both appeared to be r e l a t e d w i t h an i n e f f i c i e n t performance o f the p r o c e s s . 3. The f l o t a t i o n p r o c e s s was found t o be s e n s i t i v e to a i r f l o w r a t e , s p a r g e r s i z e , means of i n t r o d u c i n g the s u r f a c t a n t , s t i r r e r speed and p r e m i x i n g t i m e . However, no s i g n i f i c a n t t emperature dependence was found i n the range o f 25 to 35°C. 5.2.2 Continuous Experiments 1. The p o s s i b i l i t y o f r u n n i n g the c o a g u l a t i o n -f l o a t i o n p r o c e s s c o n t i n u o u s l y has been f u l l y d e m o n s t r a t e d . 2. The p r o c e s s b e h a v i o r and r e s u l t s of the c o n t i n u o u s runs are comparable to t h o s e o b t a i n e d a t the c o r r e s p o n d i n g b a t c h e x p e r i m e n t s . 77 3. The m i x i n g of the s u r f a c t a n t and e f f l u e n t r e q u i r e s a s e p a r a t e s t i r r e d p r e m i x i n g s t a g e i n o r d e r to a c h i e v e p o s i t i v e r e s u l t s . 4. The development of t u r b u l e n c e a t h i g h a i r f l o w r a t e s o b v i a t e s the f l o t a t i o n - c o a g u l a t i o n p r o c e s s by r e d i s p e r s -i n g the s u b l a t e . 5. An i n c r e a s e o f the f l o t a t i o n time above f i f t e e n minutes has a d e l e t e r i o u s e f f e c t on the p r o c e s s , presumably because of r e d i s s o l u t i o n o f the p r e c i p i t a t e . 5.3 From the S t u d i e s on the E f f l u e n t B e h a v i o r 1. D u r i n g the s t o r a g e o f the r e f r i g e r a t e d o r i g i n a l sample, no s e n s i b l e change i n c o l o r has been d e t e c t e d . Y e t , i f the c o l o r t e s t i s preceded by a pH a d j u s t m e n t , the f i n a l c o l o r r e a d i n g s are b e i n g a f f e c t e d v i a the f i l t r a t i o n s t a g e . There i s a l s o some e v i d e n c e of time e f f e c t s a t pHs 4.6 and 5.6. For t h a t r e a s o n , i t has been proven the i n a c c u r a c y of the c o l o r t e s t f o r e x p r e s s i n g f l o t a t i o n r e s u l t s . Regard-in g the t o t a l s o l i d s c o n t e n t no marked d i f f e r e n c e was i n t r o -duced by s t o r a g e or pH a d j u s t m e n t , b e s i d e s the normal i n c r e a s e s due to the c h e m i c a l s added. 78 2. During the a c i d i f i c a t i o n of the e f f l u e n t from pH 7 to 3 c e r t a i n c h e m i c a l s p e c i e or s p e c i e s are i r r e v e r s i b l y t r a n s f o r m e d . The t r u e mechanism i n v o l v e d i s not known. I t i s suggested the r e l e a s i n g of the a c i d s o l u b l e chromophores from t h e i r a s s o c i a t e s as p a r t i a l l y r e s p o n s i b l e f o r such b e h a v i o r . Chapter 6 FURTHER WORK The p r e s e n t work has proven t h e f e a s i b i l i t y o f a c o n t i n u o u s c o a g u l a t i o n - f l o a t i o n p r o c e s s f o r removing the c o l o r b o d i e s from k r a f t m i l l e f f l u e n t s . Yet the p r o c e s s , a t i t s p r e s e n t s t a g e , i s not c o m m e r c i a l l y c o m p e t i t i v e w i t h o t h e r proposed t e c h n i q u e s due to the h i g h c o s t o f the s u r -f a c t a n t . T h e r e f o r e , f u r t h e r s t u d i e s are r e q u i r e d r e g a r d i n g i t s i n d u s t r i a l p o s s i b i l i t i e s . I t i s suggested t h a t any f u t u r e work undertaken i n t h i s p r o c e s s s h o u l d have the f o l l o w i n g aims: 1 . To m o d i f y t h e p r o c e s s u s i n g d i s p e r s e d o r e n t r a i n e d a i r as the a e r a t i o n s o u r c e . T h i s would e l i m i n a t e the use of f i n e s p a r g e r n o z z l e s and i t s c o n s e q u e n t l y p l u g g i n g . 2. E i t h e r to f i n d a cheaper and/or more e f f i c i e n t s u r f a c t a n t o r to develop a s u r f a c t a n t r e c o v e r y p r o c e s s f o r i t s r e c y c l e . A suggested r e c o v e r y p r o c e s s would be to 79 80 d i s s o l v e the c o l o r e d s u b l a t e i n a c a u s t i c s o l u t i o n . T h i s s h o u l d break up the s u r f a c t a n t - c h r o m o p h o r e complex l e a v i n g a q u a t e r n a r y ammonium h y d r o x i d e and a s o l u b l e c o l o r compound. The q u a t e r n a r y ammonium h y d r o x i d e c o u l d be s o l v e n t e x t r a c t e d from t h i s a l k a l i n e s o l u t i o n . A c i d i f i c a t i o n o f the e x t r a c t and removal of the s o l v e n t would complete the system. How-e v e r , the d e s c r i b e d r e c o v e r y p r o c e s s i s p u r e l y i n t h e re a l m of educated s p e c u l a t i o n . 3. To det e r m i n e the t o x i c i t y of the c l e a r e f f l u e n t s i n c e i t i s not known how the r e m a i n i n g s u r f a c t a n t c o n t r i b u t e s to i t . 4. To c h a r a c t e r i z e the k r a f t e f f l u e n t c o l o r b o d i e s b e f o r e and a f t e r the t r e a t m e n t i n o r d e r to g a i n a b e t t e r u n d e r s t a n d i n g of the i n v o l v e d mechanisms. REFERENCES H a r g e r , J.R.E. et al. 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APPENDIX A ANALYSIS OF VARIANCE OF THE DESIGNED SET OF BATCH EXPERIMENTS A . l G e n e r a l Review (66,67) A.1.1 T w o - f a c t o r E x p e r i m e n t s To p r e s e n t g e n e r a l f o r m u l a s f o r the a n a l y s i s o f v a r i a n c e o f a t w o - f a c t o r e x p e r i m e n t u s i n g r e p e a t e d o b s e r v a -t i o n s , the case of n r e p l i c a t i o n s of the t r e a t m e n t combina-t i o n s d e t e r m i n e d by a l e v e l s of f a c t o r A and b l e v e l s o f f a c t o r B w i l l be c o n s i d e r e d . The o b s e r v a t i o n s may be c l a s s i f i e d by means of a r e c t a n g u l a r a r r a y i n which the rows r e p r e s e n t the l e v e l s o f f a c t o r A and the columns r e p r e s e n t the l e v e l s o f f a c t o r B. Each t r e a t m e n t c o m b i n a t i o n d e f i n e s a c e l l i n the a r r a y . Thus t h e r e a r e ab c e l l s , each c e l l c o n t a i n i n g n o b s e r v a t i o n s . Denoting the k t h o b s e r v a t i o n taken a t the i t h l e v e l o f f a c t o r A and the j t h l e v e l of f a c t o r B by y^^^, the abn a r e shown i n the f o l l o w i n g t a b l e . The o b s e r v a t i o n s i n the ( i j ) t h c e l l c o n s t i t u t e a random sample of s i z e n from a p o p u l a t i o n t h a t i s assumed 87 8 8 Table Al Two-Factor Experiment with n Repl icat ions B A 1 2 • • • 0 b Total Mean 1 y l 1 1 y l 2 1 • o 9 y l b l T i - -y l 1 2 • • y 1 22 • • • • 9 y l b2 a • ^1 In • y l 2n • y i bn 2 y 2 1 1 y 22 1 e 9 y 2 b l T 2 - . y 2 • • y 2 1 2 • y 2 2 2 • • • 9 y 2 b 2 9 • • • • y 2 1 n • • • y 2 2 n • • 9 9 y 2 b n 9 9 • • a • • y a l l • • y a 2 1 • • 9 9 9 y a b l T a • • y J a • ° y a l 2 • y a 2 2 • • • 9 y a b 2 • • y a l n • y a 2 n • 9 • y a b n Total T - l . T - 2 . • • 9 T . • b • . T 9 9 9 Mean y . 2 . • • 9 y. b. to be n o r m a l l y d i s t r i b u t e d w i t h mean y . . and v a r i a n c e a 2 . A l l db p o p u l a t i o n s are assumed to have the same v a r i a n c e 90 where: T.. = sum of the o b s e r v a t i o n s i n the 1 J * ( i j ) t h c e l l T. = sum of the o b s e r v a t i o n s f o r the i t h l e v e l of f a c t o r A T >. = sum o f the o b s e r v a t i o n s f o r the j t h * J* l e v e l o f f a c t o r B sum of a l l abn o b s e r v a t i o n s v.. = mean o f the o b s e r v a t i o n s i n the ( i j ) t h 1 J * c e l l mean of t h e o b s e r v a t i o n s f o r the i t h l e v e l o f f a c t o r A y . = mean of the o b s e r v a t i o n s f o r t h e j t h * J * 1evel o f f a c t o r B y = mean o f a l l a Z m o b s e r v a t i o n s A.l.2 Two-Factor A n a l y s i s o f V a r i a n c e The g e n e r a l model f o r a t w o - f a c t o r e x p e r i m e n t i s y i j k = u + a i + 6 j + ( a 3 ) i j + e i j k where: e i i k m e a s u r e s the d e v i a t i o n s of the obser v e d y i j k v a ^ u e s i n t n e ("i J ) t h c e l l from the p o p u l a t i o n mean u--. ( c * 3 ) . . denote the i n t e r a c t i o n e f f e c t o f the 1 J i t h l e v e l of f a c t o r A and the j t h l e v e l of f a c t o r B a.j the e f f e c t o f the i t h l e v e l of f a c t o r A 3 . the e f f e c t o f the j t h l e v e l o f f a c t o r B u o v e r a l l mean The f o l l o w i n g r e s t r i c t i o n s a re imposed on the g e n e r a l model f a. = 0 , I 3 , = 0 , f ( a 6 ) . . = 0 , J ( a 3 ) . . = 0 i = l 1 j = l J i = l J j = l J The t h r e e hypotheses to be t e s t e d a r e : i ) H ^ : a 1 = a 2 = , * * a A = 0 H | : a t l e a s t one of the ct.'s i s not equal to z e r o i i ) H ' ' : 3 X = 3 2 = • . . 3. = 0 a t l e a s t one of the B.'s i s not equal to z e r o 92 i i i ) H 0 : ( a B ) n = H x : at l e a s t not equal ( a 3 ) 1 2 = . . . ( a3 ) = 0 a D one of the (a6) . . 's i s to z e r o J T a b l e A2 A n a l y s i s o f V a r i a n c e f o r the Two-Factor Experiment w i t h n R e p l i c a t i o n s Source o f V a r i a t i o n Sum of Squares Degrees o f Freedom Mean Square Computed f a = T a b u l a t e d F l e v e l of s i g n i f i c a n c e Main E f f e c t s A SSA (a-1) „ 2 SSA S> " (a-1) 2 f - S i f l " F = a = [ ( a - 1 ) , a b ( n - l j ] B SSB (b-1) -2 SSB S 2 - (b-1) 2 f _ s 2  f 2 " F 2 " F = a • [ ( b - 1 ) , a b ( n - l ) ] I n t e r a c t i o n AB SS(AB) ( a - D ( b - l ) „ 2 _ SS(AB) s 3 " ( a - l ) ( b - l ) 2 F = a = [ ( a - l ) ( b - l ) , a b ( n - l ) E r r o r SSE a b ( n - l ) „2 _ SSE s " a b ( n - l ) TOTAL SST abn-1 CO 94 The sum of squares a r e u s u a l l y o b t a i n e d by con-s t r u c t i n g the f o l l o w i n g t a b l e of t o t a l s . T a b l e A3 T o t a l f o r the Sum of the O b s e r v a t i o n s B A 1 2 • • • b T o t a l 1 T l l . T ! 2 . • • • T l b - T... 2 • • T 2 , . • • • • • • T 2 b -o 9 T 2 - . o o • 9 a • o T a l -• 9 Ta2» • • o 9 a T . ab • o « T a • • T o t a l T - l . T - 2 . 9 • 9 T . • b • T 9 9 9 and u s i n g the f o l l o w i n g c o m p u t a t i o n a l f o r m u l a s : a b n T S S T = y y y v * - - v n . L , . L , , L , " i j k abn i = l j = 1 k=1 95 a 2 2 I T j • _ i 1 *' SSA = — bn abn SSB = -L^ I T 2. T 2 an abn y y i.. I T . y T . T2 SS(AB) = l i L ^ J i ^ J 1=J + bn an abn SSE = SST - SSA - SSB - SS(AB) A. 2 T a b u l a t e d A n a l y s i s o f V a r i a n c e and Sample C a l c u l a t i o n s A. 2 . 1 A n a l y s i s o f V a r i a n c e f o r % S u r f a c t a n t F l o a t e d ,  pH and Amount of S u r f a c t a n t Added A . 2 . 1 . 1 T a b u l a t e d Data 96 T a b l e A4 T a b u l a t e d Data f o r % S u r f a c t a n t F l o a t e d , pH and Amount of S u r f a c t a n t Added pH Amount o f S u r f a c t a n t 3.6 ( b i ) 4.6 ( b 2 ) 5.6 ( b 3 ) Added, ppm (ax) 100 90. 30. 27. 90.38 17. 24.5 ( a a ) 150 80.33 67.66 24.66 87.33 70.66 6.66 ( a , ) 200 81.25 75. 25. 81. 51 . 32. 97 A.2.1.2 T a b l e o f T o t a l s T a b l e A5 T o t a l f o r the Sum o f the O b s e r v a t i o n s f o r % S u r f a c t a n t F l o a t e d , pH and Amount o f S u r f a c t a n t Added pH Amount o f S u r f a c t a n t Added, ppm 3.6 ( b i ) 4.6 ( b 2 ) 5.6 ( b 3 ) T o t a l 100 180.38 47. 51.5 278.88 ( a 2 ) 150 167.66 138.32 31.32 337.30 ( a , ) 200 162.25 126. 57.00 345.25 TOTAL 510.29 311.32 139.82 961.43 98 A.2.1.3 A n a l y s i s o f V a r i a n c e T a b l e A6 A n a l y s i s o f V a r i a n c e f o r % S u r f a c t a n t F l o a t e d , pH and Amount of S u r f a c t a n t Added Source of V a r i a t i o n Sum o f Squares Degrees o f Freedom Mean Square Computed f T a b u l a t e d F a = l e v e l o f s i g n i f i c a n c e Main Effects Amount o f S u r f a c t a n t Added 437.83 2 218.92 s 2 = 3.449 F(2,9,.95) = 4. 26 pH 1 1 ,458.29 2 5729.14 s* = 90.26 F(2,9,.99) = 8. 02 I n t e r a c t i o n 2,286.97 4 571 .74 s 2 = 9.00 F(4,9,.99) = 6. 42 E r r o r 571.21 9 63.47 TOTAL 14,754.30 17 9 9 A.2.2 A n a l y s i s of V a r i a n c e f o r R a t i o of S o l i d s F l o a t e d /  S u r f a c t a n t F l o a t e d , pH and Amount o f  S u r f a c t a n t Added A.2.2.1 T a b u l a t e d Data . T a b l e A7 T a b u l a t e d Data f o r R a t i o o f S o l i d s F l o a t e d , pH and Amount of S u r f a c t a n t Added PH Amount o f S u r f a c t a n t Added, ppm 3.6 ( b i ) 4.6 ( b 2 ) 5.6 ( b 3 ) U i ) 100 1 .47 1 .67 0.80 1 .24 0.185 0.53 (a 2) 150 0.875 1 .34 1 .36 1 .25 0.16 0.53 (a 3) 200 0.97 0.802 0.64 0.94 0.88 1 .78 100 A.2.2.2 T a b l e o f T o t a l s T a b l e A8 T o t a l f o r the Sum o f the O b s e r v a t i o n s f o r R a t i o o f S o l i d s F l o a t e d / S u r f a c t a n t F l o a t e d , pH & Amount of S u r f a c t a n t Added pH Amount o f S u r f a c t a n t Added, ppm 3.6 ( b i ) 4.6 ( b 2 ) 5.6 ( b 3 ) T o t a l ( a i ) 100 3.14 2.04 0.715 5.895 ( a * ) 150 2.21 2.61 0.69 5.51 ( a . ) 200 1 .77 1 .58 2.66 6.01 TOTAL 7.12 6.23 4.065 17.415 101 A.2.2.3 A n a l y s i s o f V a r i a n c e T a b l e A9 A n a l y s i s of V a r i a n c e f o r % S o l i d s F l o a t e d , pH and Amount o f S u r f a c t a n t Added Source of V a r i a t i o n Sum of Squares Degrees of Freedom Mean Square Computed f T a b u l a t e d F a = l e v e l o f s i g n i f i c a n c e Main Effects Amount o f S u r f a c t a n t Added 0.02 2 0.01 s\ = 0.117 F(2,9,.95) = 4. 26 pH 0.82 2 0.41 s\ = 4.82 F(2,9,.95) = 4. 26 I n t e r a c t i o n 2.08 4 0.52 S 3 = 6.12 F(4,9,.95) = 3. F(4,9,.99) = 6. 63 42 E r r o r 0.766 9 0.085 TOTAL 3.686 17 1 0 2 A.2.3 A n a l y s i s o f V a r i a n c e f o r % S o l i d s F l o a t e d , pH and  Amount of S u r f a c t a n t Added A.2.3.1 T a b u l a t e d Data T a b l e A10 T a b u l a t e d Data f o r % S o l i d s F l o a t e d , pH and Amount of S u r f a c t a n t Added pH Amount of S u r f a c t a n t Added, ppm 3.6 ( b i ) 4.6 ( b 2 ) 5.6 ( b 3 ) (ax) 100 24.26 20.49 3.41 4.0 0.58 1 .78 (a 2) ~}i : 150 21 .65 20.80 15.66 17.25 0.71 0.819 (a 3) 200 20.08 19:11 13.23 18.23 17.52 11.27 103 A.2.3.2 T a b l e of T o t a l s T a b l e A l l T o t a l f o r the Sum o f the O b s e r v a t i o n s f o r % S u r f a c t a n t F l o a t e d , pH and Amount o f S u r f a c t a n t Added pH Amount o f S u r f a c t a n t Added, ppm 3.6 (b-i) 4.6 ( b 2 ) 5.6 ( b 3 ) T o t a l ( a i ) 100 44.75 7.41 2.36 54.52 ( a 2 ) 150 42.45 32.91 1 .53 76.89 (a.) 200 39.19 31.46 28.79 99.44 TOTAL 126.39 71 .78 32.68 230.85 1 04 A.2.3.3 A n a l y s i s o f V a r i a n c e T a b l e A12 A n a l y s i s o f V a r i a n c e f o r % S o l i d s F l o a t e d , pH and Amount o f S u r f a c t a n t Added Source of V a r i a t i o n Sum o f Squares Degrees of Freedom Mean Square Computed f T a b u l a t e d F a = l e v e l o f s i g n i f i c a n c e Main Effects Amount o f S u r f a c t a n t Added 168.15 2 84.07 s\ = 17.96 F(2,9,.99) = 8.02 pH 738.48 2 369.24 szz = 78.89 F(2,9,.99) = 8.02 I n t e r a c t i o n 285.17 4 71 .29 s23 = 15.23 F(2,9,.99) = 6.42 E r r o r 42.12 9 4.68 TOTAL 1233.92 17 105 A.2.4 Sample C a l c u l a t i o n The r e q u i r e d c a l c u l a t i o n s s h a l l be i l l u s t r a t e d by u s i n g the data o b t a i n e d from % s o l i d s f l o a t e d , pH and amount of s u r f a c t a n t added. SST = 24 . 2 6 2 + 20.49 2 + 21.65 2 + 20.802 + 20.082+19.112 + 3 . 4 1 2 + 4 2 + 1 5.66 2 + 1 7.2 5 2 + 1 3 . 2 3 2 + 18.23 2 + 0.58 2 + 1 .78 2 + 0. 71 2 + 0.81.92 + 17 .52 2 + 1 1 .27 2 - ( 2 3 0 ^ 8 5 ) 2 C C A - 54.52 2 + 76.89 2 + 99.44 2 ( 2 3 0 . 8 5 ) 2 SSA = 3128.80 - 2960.65 = 168.15 CCR _ 126.39 2 + 71.78 2 + 32.68 2 ( 2 3 0 . 8 5 ) 2 SSB g 18 SSB = 3699.13 - 2960.65 =738.48 _ 44.75 2+42.45 2+39.1 9 2 + 7.41 2 +32.91 2 +31 .46 2+2. 36 2+1 .53 +28.79* 2 - 3128.80 - 3699.13 + 2960.65 SSAB = 4152.45 - 3128.80 - 3699.13 + 2960.65 = 285 SSE = 1233.92 - 168.15 - 738.48 - 285.17 = 42.07 MSA = 1 6 8 : 1 5 = 84.07 MSB = 7 3 8 A 4 8 = 369.24 MSAB = 2 8 5 J 7 . = 7 U 2 g MSE = 4 2 ; 1 2 = 4.68 2 _ 84.07 _ , 7 Q f i  S i " " O S . - , 1 7 - 9 6 2 _ 369.24 _ ? f t R q  S 2 4768 " 7 8 ' 8 9 S s " 4.68 " 107 A.2.5 C o n c l u s i o n s S i n c e i n the t h r e e s e t s o f d a t a s t u d i e d the i n t e r -a c t i o n between the two f a c t o r s , i . e . pH and amount of s u r -f a c t a n t added, i s h i g h l y s i g n i f i c a n t , i t i s not s e n s i b l e to attempt to draw i n f e r e n c e s on the main e f f e c t s f o r the p r e s e n c e of i n t e r a c t i o n c o u l d mask them. I n s t e a d , the data s h o u l d be a n a l y z e d o b s e r v i n g the i n f l u e n c e of each f a c t o r a t f i x e d l e v e l s o f the o t h e r . APPENDIX B REGRESSION A N A L Y S I S A P P L I E D TO THE DATA OBTAINED AT PH 3.6 B . l General Review (68) B . l . l L i n e a r R e g r e s s i o n The method of l e a s t squares was a p p l i e d to the data i n an attempt to o b t a i n a s t r a i g h t - l i n e r e l a t i o n s h i p between the v a r i a b l e s p r e s e n t l y under s t u d y . The f o r m u l a e used f o r a r e g r e s s i o n model o f the t y p e y = 3o + S i * + e, were the f o l l o w i n g : 1) y = b 0 + b i x p r e d i c t i v e model 2 ) b . - i i m (S x . ) ( Z y.) Z x 3) b 0 = y - b i x 108 S S T O T A L = I A -(z y f ) 2 n S 3 f l « , > t - ^ ^ ) REGRESSION = ^ x j 2 S S T O T A L = S S R E G R E S S I O N + S S R E S I D U A L 2 S S R E S I DUAL s " (n -2) p _ S S R E G R E S S ION  h " S 2 R 2 = S S R E G R E S S I O N S S TOTAL 110 where: y = dependent or random v a r i a b l e x = independent or f i x e d v a r i a b l e So> 3 i = parameters of the r e g r e s s i o n model y = p r e d i c t e d value of y f o r a given x b 0 , b i = estimates of 30» 3 i based on the observations e = y - y = r e s i d u a l d i f f e r e n c e between the a c t u a l observation f o r a given x and the corresponding f i t t e d value obtained by use of the f i t t e d r e g r e s s i o n equation n = number of observations S S T n T / i | = Sum of squares about the mean R E G R E S S I O N = Sum of squares due to r e g r e s s i o n ^ R E S I D U A L = ^ u m °^ s c l u a r e s about r e g r e s s i o n s 2 = mean square about r e g r e s s i o n , i t provides an estimate based on n - 2 degrees of freedom of the variance about the r e g r e s s i o n , 6 2 R 2 = c o e f f i c i e n t of d e t e r m i n a t i o n , i t represents the percentage of the v a r i a t i o n i n the data which i s explained by the r e g r e s s i o n equation. SE = / s 7 = standard e r r o r of estimate, i t means that the band around^the r e g r e s s i o n surface computed as y. ± SE E a p p r o x i -mately includes 68% of the observation used to estimate the r e g r e s s i o n c o e f f i c i e n t s ( b 0 , b i ) I l l B.l.2 Examining the R e g r e s s i o n E q u a t i o n B.l.2.1 Lack of F i t and Pure E r r o r The sum of squares r e s i d u a l can be broken i n t o the amount due to the v a r i a t i o n between the v a l u e o f y w i t h i n g i v e n v a l u e s o f x, and a n o t h e r component which i s n o r m a l l y c a l l e d the l a c k o f f i t c o n t r i b u t i o n . The f i r s t component, c a l c u l a t e d from r e p e a t e d p o i n t s , r e f l e c t s mere random v a r i a -t i o n o r pure e x p e r i m e n t a l e r r o r ; w h i l e the second component i s a measure of the s y s t e m a t i c v a r i a t i o n brought about by h i g h e r o r d e r terms. The c o m p u t a t i o n s r e q u i r e d f o r t e s t i n g hypotheses i n a r e g r e s s i o n problem w i t h r e p e a t e d measure-ments on the response may be summarized as shown i n t h e t a b l e . The computed f v a l u e s a r e compared w i t h t h e 100 (1 - a) % p o i n t o f the t a b u l a t e d F ( 1 , n - 2) o r F(k - 2, n - k ) d i s t r i b u t i o n r e s p e c t i v e l y , i n o r d e r to d e t e r m i n e the r e l a t i v e s i g n i f i c a n c e o f the r a t i o t e s t e d . B - l .2.2 P l o t o f R e s i d u a l s In p e r f o r m i n g the r e g r e s s i o n a n a l y s i s c e r t a i n assump-t i o n s about the e r r o r s are made, i . e . the e r r o r s a r e i n d e p e n -d e n t , have zero mean, a c o n s t a n t v a r i a n c e , a 2 , and f o l l o w a normal d i s t r i b u t i o n . Thus i f the f i t t e d model i s c o r r e c t , the r e s i d u a l s s h o u l d e x h i b i t t e n d e n c i e s t h a t tend to c o n f i r m T a b l e Bl A n a l y s i s o f V a r i a n c e f o r Repeated Measurements on the Response Source of V a r i a t i o n Sum o f Squares Degrees o f Freedom Mean Square Computed f R e g r e s s i o n Re s i dual Lack of f i t Pure e r r o r ^ R E G R E S S I O N SSS ^ R E S I D U A L S S R E S I D U A L ~ S S P U R E E R R O R -4- S S P U R E E R R O R 1 n - 2 k - 2 n - k S S R E G R E S S 1 0 N S S R E S I D U A L n - 2 S S R E S I D U A L " S S P U R E E R R O R S S R E G R E S S I O N S* S S R E S 1 D U A L " S S P U R E ERROR k - 2 _ 2 S S P U R E E R R O R s e n - k s e 2 ( k - 2) TOTAL SS T O T A L n - 1 where n = number o f o b s e r v a t i o n s u s i n g k d i s t i n c t v a l u e s o f x. 113 the assumptions made, or a t l e a s t , s h o u l d not e x h i b i t a d e n i a l of the a s s u m p t i o n s . The b e s t and e a s i e s t way to examine the r e s i d u a l s i s g r a p h i c a l . In p r a c t i c a l r e g r e s s i o n s i t u a t i o n s a d e t a i l e d e x a m i n a t i o n of the c o r r e s p o n d i n g r e s i d u a l p l o t s i s u s u a l l y f a r more i n f o r m a t i v e , and the p l o t s w i l l a l m o s t c e r t a i n l y r e v e a l any v i o l a t i o n s o f a ssumptions s e r i o u s enough to r e q u i r e c o r r e c t i v e a c t i o n . The most common p l o t s o f r e s i d u a l s a r e : i ) In time sequence, i f t h e o r d e r i s known. T h i s w i l l i n d i c a t e whether a l o n g - t e r m time e f f e c t i s i n f l u e n c i n g the d a t a . i i ) A g a i n s t the independent v a r i a b l e s . T h i s w i l l r e v e a l : a) the c o n s t a n c y of the v a r i a n c e , b) e r r o r i n c a l c u l a t i o n , i . e . l i n e a r e f f e c t o f x not removed, : r v c) need f o r e x t r a t e r m s , f o r example a q u a d r a t i c term i n x i n the model. . i i i ) A g a i n s t the a c t u a l v a l u e of y. T h i s w i l l t e s t the a c c u r a c y of the p r e d i c t i v e model. Care must be t a k e n t o a v o i d the use of the p r e d i c t i v e model o u t s i d e the e x p l o r e d x r a n g e , i . e . f o r e x t r a p o l a t i n g p u r p o s e s . Regarding the independence of the e r r o r s , i t has been s t a t e d t h a t i n g e n e r a l r e g r e s s i o n s i t u a t i o n s the e f f e c t o f 114 c o r r e l a t i o n between r e s i d u a l s need not be c o n s i d e r e d when p l o t s are made, e x c e p t when the r a t i o number of degrees o f freedom i n r e s i d u a l s / n u m b e r of r e s i d u a l s i s q u i t e s m a l l . B.2 T a b u l a t e d A n a l y s i s o f V a r i a n c e , Sample C a l c u l a t i o n and  P l o t o f R e s i d u a l s B.2.1 A n a l y s i s o f V a r i a n c e f o r % S u r f a c t a n t F l o a t e d  vs Amount of S u r f a c t a n t Added at pH 3.6 T a b l e B2 A n a l y s i s o f V a r i a n c e f o r % S u r f a c t a n t F l o a t e d vs Amount of S u r f a c t a n t Added a t pH 3.6 Source o f V a r i a t i o n Sum of Squares Degrees of Freedom Mean Square Computed f T a b u l a t e d F R e g r e s s i o n R e s i d u a l Lack o f f i t Pure e r r o r 120.50 33.60 [ 6.5 [27.1 1 5 1 4 120.5 33.6 r -in 5 ~ 6 - 7 2 ^ = 6 . 5 I f ^ f = 17.93 6.77(3-2) ° * 9 6 F(1,5.99) = 16.26 F ( l , 4 , . 9 9 ) = 21.20 TOTAL 154.1 6 115 B.2.2 A n a l y s i s of V a r i a n c e f o r R a t i o o f S o l i d s F l o a t e d /  S u r f a c t a n t F l o a t e d vs Amount o f S u r f a c t a n t  Added a t pH 3.6 T a b l e B3 A n a l y s i s of V a r i a n c e f o r R a t i o of S o l i d s F l o a t e d / S u r f a c t a n t F l o a t e d vs Amount o f S u r f a c t a n t Added a t pH 3.6 Source o f V a r i a t i o n Sum o f Squares Degrees o f Freedom Mean Square Computed f Tabu!ated F R e g r e s s i o n 0.69 R e s i d u a l 0.20 Lack o f f i t Pure e r r o r TOTAL 0.03 0.17 0.89 0.69 0.69 0.04 = 17.25 F ( l , 5 . 9 9 ) = 16.26 0.02 = 0.04 0.03 1 = 0.03 0.03 _ n i n r 0 . 0 4 2 ( 3 - 2 ) - a 7 D 5 F ( l , 4 , . 9 9 ) = 21.20 0.17 = 0.042 116 B.2.3 A n a l y s i s o f V a r i a n c e f o r % S o l i d s F l o a t e d vs  Amount of S u r f a c t a n t Added a t pH 3.6 T a b l e B4 A n a l y s i s o f V a r i a n c e f o r % S o l i d s F l o a t e d vs Amount of S u r f a c t a n t Added a t pH 3.6 Source o f V a r i a t i o n Sum of Squares Degrees o f Freedom Mean Square Computed f T a b u l a t e d F R e g r e s s i o n R e s i d u a l 6.37 11 .93 1 5 6.37 11 93 ' ' * =2.39 2.39 " 2 - 6 6 F ( l ,5.99) = 16.26 TOTAL 18.30 6 B.2.4 Sample C a l c u l a t i o n s The r e q u i r e d c a l c u l a t i o n s s h a l l be i l l u s t r a t e d by u s i n g the data o b t a i n e d from the r e l a t i o n r a t i o of s o l i d s f l o a t e d / s u r f a c t a n t f l o a t e d vs amount of s u r f a c t a n t added a t pH 3.6. B.2.4.1 C a l c u l a t i o n s Concerned w i t h the  R e g r e s s i o n E q u a t i o n T a b l e B5 C a l c u l a t i o n s Concerned w i t h the R e g r e s s i o n E q u a t i o n Amount of S u r f a c t a n t S o l i d s f l o a t e d Days A f t e r Added i n ppm S u r f a c t a n t f l o a t e d Samp!i ng X y xy X 2 y 2 X y y y - y (e) 100 1.47 147. 10,000 2.16 1 .56 -0.09 7 100 1 .67 167. 10,000 2.79 1 .56 0.11 5 100 1 .72 172. 10,000 2.96 1 .56 0.16 15 150 0.87 130.5 22,500 0.76 1 .21 -0.34 3 150 1 .34 201 . 22,500 1 .80 1 .21 0.13 4 200 0.97 194. 40,000 0.94 0.86 0.11 1 2 200 0.80 160. 40,000 0.64 0.86 -0.06 19 • E1000 28.84 E l 171 .5 E l 55,000 1 2.05 142.9 1 .26 E0.02 118 1171.5 - I000_|__8^i b l = n w s w ~ = " ° - 0 7 ( 2 ) 1 55,000 - u u " u ; 1 .26 - (-0.007 x 142.9) = 2.26 (3) y = 2.26 - 0.007x (1 ) SS TOTAL 1 2.05 (8.84) 7 = 0.89 (6) S S REGRESS I ON 1171.5 - 1000 x 8.84 155,000 TToobTr 7 = 0.69 ( 7 ) S SRESIDUAL = ° ' 8 9 " ° ' 6 9 = ° - 2 0 (8) 119 (9) s = 0.2 R 2 O!89 " 7 7 - 5 3 (11) (10) B.2.4.2 C a l c u l a t i o n s Concerned w i t h the " l a c k of f i t " T e s t T a b l e B6 C a l c u l a t i o n s Concerned w i t h the " l a c k of f i t " T e s t Amount of S u r f a c t a n t S o l i d s f l o a t e d 2 y y Number of Degrees of _2 2 2 _2 Added i n ppm X S u r f a c t a n t f l o a t e d y R e p e t i t i ons <V Freedom <n R - 1) y nR y y i " H y 100 1 .47 2.16 1 .62 3 2 2.62 7.87 0.04 100 1.67 2.79 100 1.72 2.96 150 24.86 0.87 27.91 0.76 1 .10 2 1 1 .22 2.44 0.12 150 1 .34 1 .80 200 22.21 0.97 22.56 0.94 0 .885 2 1 0.783 1 .566 0.014 200 0.80 0.64 E l . 7 7 21 .58 24 20.17 degree o f freedom f o r pure e r r o r s - n - k = 7 - 3 = 4 S S P U R E ERROR = lZ A " ^ = 0 ' 1 7 SS = SS - SS = 0 20 - 0 LACK OF F IT ^ R E S I D U A L ° ° P U R E ERROR U * ^ U 2 S S P U R E ERROR 0.17 n n A O t . S e = = - ^ = 0.0425 n . + n A * S S R E S I D U A L " S S P U R E ERROR _ 0.03 computed f = s e * (k - 2) 0.0425(3-2) t a b u l a t e d F ( 1 , 4, .99) = 21.20 B.2.4.3 P l o t o f R e s i d u a l s 1 2 2 CO 3 W 0) I > f i g u r e B 1 . R E S I D U A L S O F T H E R E G R E S S I O N M O D E L O B T A I N E D F O R T H E % O F S U R F A C T A N T F L O A T E D • I 2 0 - o o o o u -o 1 1 1 1 I I 2 r 5u • • • I I I 2 r - 5 10 15 d a y s a f t e r s a m p l i n g A A I 8 £ 5 0 1 0 0 1 5 0 p p m of s u r f a c t a n t a d d e d • 8 $ 8 5 9 0 9 5 1 0 0 a c t u a l p e r c e n t a g e o f s u r f a c t a n t 6  2 0 2 0 0 f l o a t e d 123 f i g u r e B 2 . R E S I D U A L S O F T H E R E G R E S S I O N M O D E L O B T A I N E D F O R T H E R A T I O O F S O L I D S F L O A T E D T O S U R F A C T A N T F L O A T E D I 0 . 2 (0 3 "3 0) 0 . 2 h 0 . 4 II 0 . 2 r 0 0 . 2 h 0 . 4 u • • • I I I 0 . 2 r - 0 . 2 - 0 . 4 o 0 I I i 5 10 15 d a y s a f t e r s a m p l i n g 5 0 1 0 0 1 5 0 p p m of s u r f a c t a n t a d d e d • • c P • • i 2 0 2 0 0 0 0 .5 1.0 1.5 2 .0 a c t u a l r a t i o o f s o l i d s f l o a t e d t o s u r f a c t a n t f l o a t e d 124 B.3 Cone!u s i o n s B.3.1 % S u r f a c t a n t F l o a t e d vs Amount o f S u r f a c t a n t Added i ) The p r e d i c t i v e model i s y = 100.247 - 0.099x i i ) 78% o f the v a r i a t i o n i n the data i s e x p l a i n e d by the r e g r e s s i o n e q u a t i o n i i i ) The h y p o t h e s i s t h a t a l i n e a r r e g r e s s i o n does not e x i s t can be r e j e c t e d r u n n i n g a r i s k o f l e s s than 1% o f b e i n g wrong i v ) The^band around the r e g r e s s i o n s u r f a c e computed as y j ± 2.59 a p p r o x i m a t e l y i n c l u d e s 68% o f the o b s e r v a t i o n s used to e s t i m a t e the r e g r e s s i o n c o e f f i c i e n t s v) A c c o r d i n g to the l a c k o f f i t t e s t the model i s a p l a u s i b l e one which has not been found i n a d e q u a t e by the da t a v i ) The mean o f the e r r o r s i s z e r o v i i ) The p l o t s o f r e s i d u a l s r e v e a l n e i t h e r a time dependence nor any v i o l a t i o n s o f the assump-t i o n s made, n e v e r t h e l e s s the y v a l u e s a r e s l i g h t l y u n d e r p r e d i c t e d . by the model (y < y ) 125 B.3.2 R a t i o o f S o l i d s F l o a t e d / S u r f a c t a n t F l o a t e d vs Amount of S u r f a c t a n t Added i ) The p r e d i c t i v e model i s y = 2.26 - 0.007x i i ) 77% of the v a r i a t i o n i n the data i s e x p l a i n e d by the r e g r e s s i o n e q u a t i o n i i i ) The h y p o t h e s i s t h a t a l i n e a r r e g r e s s i o n does not e x i s t can be r e j e c t e d r u n n i n g a r i s k o f l e s s than 1% of b e i n g wrong. i v ) The^band around the r e g r e s s i o n s u r f a c e computed as y-j ± 0.2 a p p r o x i m a t e l y i n c l u d e s 63% of the o b s e r v a t i o n s used to e s t i m a t e the r e g r e s s i o n c o e f f i c i e n t s v) A c c o r d i n g to the l a c k of f i t t e s t the model i s a p l a u s i b l e one which has not been found ina d e q u a t e by the data v i ) The mean o f the e r r o r s i s zero v i i ) The p l o t o f r e s i d u a l s r e v e a l e d n e i t h e r a time dependence nor any v i o l a t i o n s o f the assump-t i o n s made 126 B.3.3 % S o l i d s F l o a t e d v e r s u s amount o f s u r f a c t a n t added i ) The h y p o t h e s i s t h a t a l i n e a r r e g r e s s i o n does not e x i s t cannot be r e j e c t e d , t h e r e f o r e i t i s not a d v i s a b l e to assume a l i n e a r a s s o c i a t i o n between the dependent and independent v a r i a b l e s APPENDIX C ANALYTICAL TECHNIQUES AND CLEANING PROCEDURE C.1 C o l o r D e t e r m i n a t i o n As mentioned, Herschmi11er's m o d i f i e d c o l o u r t e s t (4) was used w i t h o u t m o d i f i c a t i o n ; so i t w i l l not be r e p o r t e d here. C.2 R e s i d u a l S u r f a c t a n t D e t e r m i n a t i o n A f a i r l y e x t e n s i v e amount of l i t e r a t u r e was s u r -veyed on the d i f f e r e n t t e c h n i q u e s proposed f o r d e t e r m i n i n g the c o n c e n t r a t i o n of c a t i o n i c s u r f a c e - a c t i v e agents i n aqueous s o l u t i o n s (69,70,71,72,73). The method suggested by Van S t e v e n i n c k and Mass appeared to be the most p r o m i s i n g ; t h e r e f o r e i t was t r i e d on s e v e r a l t e n t a t i v e f l o t a t i o n runs u s i n g the m i l l e f f l u e n t and m o d i f i e d a c c o r d i n g l y . An adequate volume of the r e m a i n i n g e f f l u e n t was d i l u t e d to 50 ml. Then, i n s u c c e s s i o n , were added 5 ml o f 10% sodium c a r b o n a t e , two drops of c o n c e n t r a t e d sodium 1 27 1 28 h y d r o x i d e ( p r e p a r e d by d i s s o l v i n g 50 g of C P . sodium h y d r o x i d e i n 50 ml o f d i s t i l l e d w a t e r ) , 1 ml o f bromophenol b l u e ( f r e s h l y p r e p a r e d d a i l y by d i s s o l v i n g 40 mg o f dye i n 100 ml o f 0.001N NaOH) and 10 ml of 1 , 2 - d i c h i o r o e t h a n e ( s p e c t r o p h o t o m e t r i c g r a d e ) . The m i x t u r e was hand-shaken f o r t h r e e minutes i n a s t o p p e r e d 125 cc t e f l o n s e p a r a t o r y f u n n e l and a l l o w e d to s e t t l e f o r 20 e x t r a m i n u t e s . S i n c e the o p t i c a l d e n s i t y of the o r g a n i c phase changed w i t h t i m e , a l l the r e a d i n g s were taken e x a c t l y at 50-55 seconds a f t e r the s e t t l i n g time was o v e r , a t 600 my. For the same r e a s o n , d i s t i l l e d water was used as a blank i n s t e a d of the e x t r a c t i o n s o l v e n t and s p e c i a l care was taken to submit a l l samples to the same timed p r o c e d u r e . The c o n c e n t r a t i o n o f the c a t i o n i c s u r f a c t a n t was determined by means of a c a l i b r a t i o n g r a p h , p r e v i o u s l y p r e p a r e d from s o l u t i o n s w i t h known' c o n c e n t r a t i o n s o f s u r -f a c t i o n ( F i g u r e C l ) . The d e v i a t i o n from Beer's law became app a r e n t a t c o n c e n t r a t i o n s above 1.7 ppm. The a c c u r a c y of the t e c h n i q u e was e s t a b l i s h e d by r e p e a t i n g the e x p e r i m e n t a l r u n s , w i t h d i s t i l l e d water i n s t e a d o f the m i l l e f f l u e n t . T o t a l s o l i d s were det e r m i n e d b e f o r e and a f t e r f l o t a t i o n and, hence, the amount of s u r f a c t a n t f l o a t e d c o u l d be e s t i m a t e d and compared w i t h the r e s u l t s o f the c o l o r i m e t r i c t e c h n i q u e . On the average both methods agreed w i t h i n a 3. % of d i f f e r e n c e . 1 2 9 f i g u r e C1„ C A L I B R A T I O N G R A P H F O R V A R I O U S C O N C E N T R A T I O N S O F S U R F A C T A N T 130 C. 3 F l o a t a b l e S o 1 i d s D e t e rm i n a t i on The f i r s t a n a l y t i c a l method (4) a p p l i e d f o r de-t e r m i n i n g the amount o f f l o a t a b l e s o l i d s i n the m i l l e f f l u e n t , had t h e f o l l o w i n g q u e s t i o n a b l e a s s u m p t i o n s : i ) A l l the s u r f a c t a n t p r e s e n t i n the s o l u t i o n was f l o a t e d o r removed by f i 1 t r a t i on i i ) A s t r i c t l y s t o i c h i o m e t r i c r e a c t i o n took p l a c e between t h e s u r f a c t a n t and t h e p o t e n t i a l l y f l o a t a b l e s o l i d s p r e s e n t i n the e f f l u e n t i i i ) The f i l t r a t i o n s t a g e d i d not e x e r t any i n f l u e n c e upon the amount o f p o t e n t i a l l y f l o t a b l e s o l i d s s t i l l p r e s e n t i n the e f f l u e n t a t t h a t moment In o r d e r to de v e l o p a second a p p r o a c h , i t was n e c e s s a r y to determi ne: a) t o t a l amount o f s o l i d s p r e s e n t i n t h e i n i t i a l s o l u t i o n a f t e r i t s pH a d j u s t -ment and b e f o r e the a d d i t i o n o f the s u r f a c t a n t b) t o t a l amount o f s o l i d s p r e s e n t i n t h e r e m a i n i n g e f f l u e n t a f t e r the e x p e r i -ment was completed a) r e s i d u a l amount of s u r f a c t a n t p r e s e n t i n the r e m a i n i n g e f f l u e n t a f t e r the exp e r i m e n t was completed Then: 131 1 . a + amount of s u r f a c t a n t added -b = d, t o t a l amount of s o l i d s f l o a t e d 2. amount of s u r f a c t a n t added - c = e , amount of s u r f a c t a n t a c t u a l l y f l o a t e d 3. d - e = amount o f s o l i d s f l o a t e d from the e f f l u e n t , a t a f i x e d pH and w i t h a c e r t a i n i n i t i a l amount of s u r f a c t a n t No f i l t r a t i o n s t a g e was r e q u i r e d . The s o l i d s a n a l y s e s were done a c c o r d i n g to t h e s t a n d a r d t e s t f o r "Residue on E v a p o r a t i o n " ( 7 4 ) . T e s t s were performed w i t h 100 cc a l i q u o t s o f s o l u t i o n and run i n d u p l i c a t e . The samples were l e f t i n the oven a t 103°C, f o r 12 h o u r s ; a l l o w e d to c o o l f o r two hours i n a d e s i c c a t o r and weighed. For t h a t purpose a M e t t l e r H10T b a l a n c e was used. The w e i g h t s were a c c u r a t e to the n e a r e s t 0.1 mg. P o s s i b l e d e c o m p o s i t i o n of the q u a t e r n a r y ammonium s u r f a c t a n t d u r i n g the h e a t i n g p e r i o d was a l s o t e s t e d f o r . No o b s e r v a b l e d e c o m p o s i t i o n o c c u r r e d . C.4 C l e a n i n g P r o c e d u r e A f t e r each experiment the f l o t a t i o n equipment was t h o r o u g l y s c o u r e d w i t h a brush and r e c o v e r e d m e t h a n o l . Next the p r o c e d u r e was r e p e a t e d but t h i s time w i t h a soap-water s o l u t i o n . F i n a l l y the equipment was r i n s e d t w i c e , one w i t h tap water and s e c o n d l y w i t h f r e s h m e t h a n o l . 132 P i p e t s , e v a p o r a t i n g d i s h e s and o t h e r l a b o r a t o r y g l a s s w a r e were soaked i n a warm chromic a c i d - s u l f u r i c a c i d s o l u t i o n , f o l l o w e d by r i n s i n g w i t h l a r g e volumes o f tap wa t e r . The e v a p o r a t i n g d i s h e s were a d d i t i o n a l l y p l a c e d i n the oven, a t 103°C f o r two h o u r s , then a l l o w e d t o c o o l i n a d e s s i c a t o r . The d i f f u s e r was c l e a n e d w i t h a s o f t t o o t h b rush and a m i l d d e t e r g e n t s o l u t i o n . A f t e r w a r d s i t was r i n s e d w i t h d i s t i l l e d water and backwashed w i t h f r e s h m e t h a n o l . B e f o r e u s i n g any new f r i t t e d f i l t e r , i t was washed by s u c t i o n w i t h hot h y d r o c h l o r i c a c i d and r i n s e d w i t h d i s t i l l e d w a t e r . T h i s t r e a t m e n t removed l o o s e p a r t i c l e s o f f o r e i g n m a t t e r such as d u s t . L a t e r , the g e n e r a l p r o c e d u r e f o l l o w e d to a v o i d permanent s t a i n of the f r i t was to c l e a n i t w i t h hot c o n c e n t r a t e d s u l f u r i c a c i d p l u s a few drops o f sodium n i t r i t e . Then hot d i s t i l l e d water was passed t h r o u g h the f r i t u n t i l the pH of the wash w a s t e r remained n e u t r a l . APPENDIX D F l o t a t i o n o f K r a f t M i l l E f f l u e n t . T a b u l a t e d Batch E x p e r i m e n t a l R e s u l t s F i r s t S e t pH Amount of S u r f a c t a n t Added, ppm Days A f t e r Sampli ng Temp. °C % S u r f . F l o a t e d I n i t i a l C o l o r (Pt-Co U n i t s ) F i nal C o l o r (Pt-Co U n i t s ) % C o l o r Removed I n i t i a l S o l i d s , ppm Sol i d s F l o a t e d , ppm % Sol i d s Fl o a t e d S o l i d s f l o a t e d S u r f , f l o a t e d 5.6 200 5 35 60.5 1320 400 69.7 NA NA NA NA 4.6 200 6 35 78 1330 30 97.7 NA ' NA NA NA 5.6 150 7 35 43 1340 180 86.6 NA NA NA NA 4.6 200 9 32 80 1175 15 98.7 NA NA NA NA 4.6 100 10 26 51 1075 120 88.8 NA NA NA NA 5.6 150 11 28 25.3 1040 NA NA NA NA NA NA 6.6 150 12 28 6.66 1213 370 69.5 NA NA NA NA 6.6 200 13 28 13 1100 220 80 NA NA NA NA 5.6 100 14 25 24.5 920 225 75.5 728 13 1 .78 .53 CO co Second Set pH Amount of S u r f a c t a n t Added, ppm Days A f t e r Sampl1ng Temp. °C % S u r f . F l o a t e d I n i t i a l C o l o r (Pt-Co U n i t s ) F i nal C o l o r (Pt-Co U n i t s ) % C o l o r Removed I n i t i a l Sol i d s , ppm Sol i d s F l o a t e d , ppm % Sol i d s Fl o a t e d S o l i d s f l o a t e d S u r f , f l o a t e d 3.6 150 4 30 87.3 960 140 85.4 846 176 20.80 1 .34 3.6 100 5 25 90.4 1250 140 88 732 150 20.5 1 .67 5.6 150 6 29 24.7 1460 225 84.6 848 6 0.71 0.16 4.6 150 7 28 67.7 1360 115 91 .5 881 138 15.7 1 .36 5.6 100 8 25 27 1410 285 79.8 860 5 0.58 0.18 3.6 200 12 25 81 .25 940 35 96.4 784 158 20.1 0.97 4.6 150 13 29 70.7 1050 105 90 771 133 17.25 1 .25 5.6 200 14 35 10 1260 105 91 .7 819 36 4.39 1 .80 3.6 100 15 25 92.1 850 120 86 747 160 21 .3 1 .72 4.6 200 16 25 75 1070 40 96.4 735 134 18.23 0.94 4.6 100 17 26 30 1050 220 79 703 24 3.41 0.80 3.6 200 19 28 81 870 35 96 680 130 19.11 0.80 co T h i r d S e t pH A m o u n t o f S u r f a c t a n t A d d e d , ppm D a y s A f t e r S a m p l i n g T e m p . °C % S u r f . I n i t i a l C o l o r F i n a l C o l o r % C o l o r R e m o v e d I n i t i a l S o l i d s , ppm S o l i d s F l o a t e d , ppm % S o l i d s F l o a t e d S o l i d s f l o a t e d F l o a t e d ( P t - C o Urn* t s ) ( P t - C o U n i t s ) S u r f , f l o a t e d 5.6 5.6 5.6 3.6 4 .6 4 .6 3 .6 5.6 too 150 200 150 100 200 100 200 1 1 2 3 5 6 7 20 25 25 25 25 25 25 25 25 0 6 .66 25 8 0 . 3 17 51 90 32 820 820 940 680 765 785 71 5 880 NA NA NA 25 105 15 40 50 NA ' NA NA 96 .4 8 6 . 3 98 .2 9 4 . 5 94 .3 647 647 508 485 525 499 544 497 0 5.3 89 105 21 66 132 56 0 .82 17.52 21 .65 4 13 .23 24 .26 11 .27 NA .53 , 1.78 .87 1 ..24 .64 1.47 0 .88 F o u r t h S e t 3.6 3.6* 50 100 8 9 25 27 26 50 NA NA NA NA NA NA 681 1 558 0 •1 26 0 8.08 o 2 .52 ' ( s a m p l e n o t d i l u t e d ) APPENDIX E BIBLIOGRAPHIC SURVEY ON PROPOSED METHODS FOR REMOVING COLOR FROM KRAFT MILL EFFLUENTS .\tocoio, W. A- Color removal from kraft mill effluents. Proc. • 0.C jnd Waste Conf., Purdue Univ. Eng. Bull., Extension Scr. nc'S7:465-76 (1955). r i c problem of color removal from kraft mill effluents has not kept pace ."•'li the progress made in the biological stabilization of these effluents, prin-• '<IW because the color-imparting substances exert little or no biological I!;cii demand; hence the soiuticn of biological stabilization was considered — <rc pressing. However, color removal is important, because the- presence of "\;r is evidence to the public that the stream contains such, cftlucnts and, ...,agh it does not create stream pollution, may lead to unwarranted an.l • -••jst accusations. Tl:e color bodies in kraft effluents are primarily iiguin :'i:pounds whose color increases with increasing pH values; at pl l values o:» • t aciii side, they become increasingly insoluble. The removal can he accorn-•:-!;cJ by either biological, physical, or chemical means; the use of hydratcd x offered the greatest promise of eventual success from economic and .coition standpoints (.cf. B.l .P.C. 23: 5S3-4). In all-previous attempts for ;• !-jr removal from kraft-mill effluents, the matter of sludge handling has !..<-n the uiisumiotmtable obstacle; hence, hydrated-limc sludge conditioning "vilsorls received first consideration. Two multistage methods were developed; V'.li involve the carbonation of the sludge, and one involves further treatment the carbonated calcium-organic sludge with black liquor, with the result th.it economical dewaterir.g in standard equipment and recovery of the cal-cium content of the sludge in re-usable form become possible. Details of the two procedures a:e given. The development of a satisfactory sludge-handling method does not signify that the complete solution to the color proi/icm hi'.s ttcn found; other factors still require extensive investigation. 3 tables, 4 fig-ures, and 3 references. E.S. 2 4 3 0 . Colour and methods for colour removal. N E M E R O W , N . L . Proc. II th Industr. Waste Conf., Purdue Univ. Engng Exin Scr. No. 91. 1956. 584-594. The removal of colour from waste waters is important from an aesthetic point of view, and the author discusses various aspects of the removal of colour.' Methods for measuring the intensity of colour are indicated briefly, and the concent of reflected light from a river water and the need for an instrument to measure it. arc discussed. The cxocriencv.s of various investigators in the removal of colour from waste w.-.tcrs are reviewed. These show that colour can be removed by many methods, with '.arious degrees of efficiency. The chemical and physical structural characteristics of coloured compounds which effect colour removal are shown in a table. A bibliography of 29 references is appended. 136 Y/IN'CET, RUSSELL L . The pulp and paper industry- pollution abatement program in the United States. Pulp Paper Mag. Can. 57, no. 3: 224-6, 230 (Convention issue, 1956). The function, research activities, problems, ar.cl achievements of the N'a-l tional Council for Stream Improvement are described. Major problems center around solids removal, sludge dewatcring and disposal, C.O.D. reduction,i toxicity, and color removal. Over the past decade, U. S. pulp and paper in-' ciustry pollution/ton of product has been decreased by over 50%. C.L.B. 372. NKMEROW, NELSON L . Color and methods for color removal. Proc. 11th Ind. Waste Conf., Purdue Univ. Eng. Bull., E x -tension Ser. no. 91: 5S4-94 (June, 1957). Because of complaints from the public, the removal of color from waste waters is often more important than the removal of B.O.D. For the measure-ment of color intensity and quality the s(>cctrophotometcr, the filterphoto-mcter, or a color comparator (such as the Hellige comparator) may he used. Both transmitted and reflected light may he measured in sewage and waste waters. The first is useful in determining the efficiency of color removal, whereas the second is measured because it is the light seen by an ohserver; A review of the literature pertaining to methods used for the removal of color from waste waters is given. 1'ast experience indicates that color may he removed hy many methods with varied degrees of efficiency. The chemical structure of the colored com|>ouud< is an important factor ii* "'"c choice of. the method of removal, i tables and 20 references. J.S. 1034. MCIXN-IS, J- S.. MILLS, K . II.. and COLLINS, T . T . , JR. Color and sulphide problems in water treatment at Hudson Pulp & Paper Corp. Paper Trade J . 142, no. 27: 32-5. 38; no. 29: 26-34 (July 7, 21, 195S). iJevelopmcnts of the water-treating facilities and procedures at ihc Htidsoil Pulp and l'apcr Corp. plant at Palatka. Fla. arc discussed. Practical aspects involved in the removal of color and sulfide from water for use in the manu-facture of bleached pulp and in drinking-water systems arc described. Methods for the removal of organic colorants in water include coagulation, destruction by chlorination and other oxidizing agents, decoloration by ad-sorption on charcoal and other surface-active materials, filtration, and elec-trolysis. The most practical of these procedures is coagulation of the nega-tively charged color bodies with sufficient alum at optimum pH using clay as a weighting agent and a proper coagulant aid. Recent years have seen the development of several excellent coagulant aids which help materially in the reduction of color by broadening the pH range at which tloc formation occurs and improving the settling and filtering characteristic of the color floes formed. The effectiveness of some of these materials (activated silica and Separan) has been shown by mill 'lata. Pilot-plant studies on sulfide removal indicated the important role of sulfur bacteria, in conjunction with aeration, for the removal of sulfide atal reduction of chlorine demand. These considerations are important where the water is to undergo a subse-«|ucnt softening operation followed by chlorination before use in the mill process. The second section of the article includes a detailed literature sum-mary on the subjects of color and sulfide removal in water treatment. 2 tables. 1 figure, and 103 references. • R . A . S . 6781. EK.KCKR, HF.KBK.RT F., and BROWN", R I C H A R D 1. 'Hie s u r f a c e reaction method f o r c o l o r removal from kraft blcachery effluents. Tappi 4 2 , no. 3 : 2 -15 -S ( M a r c h , 1 9 5 9 ) . Previews research by tlie National Council tor Stream Improvement anil by several kraft mills lias shown that color can he removed successfully front combined kraft and bleach cfilncnts by precipitation with lime. The resulting sludge, however, has been extremely difficult to dewater to a dryness suitable for rcburning in the kiln. The authors describe laboratory and bench-scale pilot plant experiment-; in which caustic extract from a bleached kraft mill is treatnl by application to a prccoat of hydratcd lime on a rotary vacuum filter. The limc-liguin reaction takes place at the surface of the prccoat, form-ing a film which iv.ay be continually doctored oft exposing a fresh reactive surface. The ltmc-nrganic film is dry enouch to be fed IQ the kiln along with lime mtvl and culor removal is in excess of 95%. A larger scale pilot plant lias hcni set up at a southern bleached kraft mill by an equipment m a i m - \ faclurcr. and the process• »•» now under evaluation.-(> figure*. — K.A.S. 1232. New approaches lo pulp and paper mill waste Ircalnicnl. C l l l M . IF. \V. ftufuUr." Wastes, 1959,4, 2UO-204. The author reports on and discusses rescue!) and clcwlop-ncnt work in progress to improve the treatment of pulp •uul paper mill ctllucnls. The three baste problems bciny studied arc the ilcwatcrinp ami disposal of sludges obtained from sedimentation processes, reduction of colour in bleaching waste waters, and reduction of R.O.O. Developments in the methods employed for dewatering sludge arc outlined (sec Wat. Pollut. Abstr., 1959. 32. Abstr. No. 2103). Studies show thai addition of fly ash to the influent of the sedimentation tank improves sedimenta-tion and increases the rate of dewatering of the sludge; the possibility of applying fly J;h as a preliminary coating on tillers is being investigated arid preliminary tests have given good results. Preliminary pilot tests on an aerobic thermophilic process for •the digestion of sludge indicate that substantial quantities of volatile matter can be destroyed in a relatively short time by this method. l:\pIoration of all suggested methods for reducing colour has revealed that the most promising is the lime treatment technique; it was recently discovered that caustic extract from kraft bleaching could be almost completely decolorized by vacuum filtration through a bed of hydratcd lintc. Previous work carried out to increase the efficiency of B.O.D. removal from tne waste waters produced by the paper industry is reviewed. It has been found that aeration and recirculation in stabilization tanks greatly improves oxygen transfer, hence increasing the degree of oxidation occurring per unit of storage time. Graphs i't included to illustrate the results obtained. 1149 BfjJCFs Herbert F . Chemical treatment and water reclamation. Pulp Paper Mac. Can. 65, no. 6: T260 :2 (June, 1961). A chem. process tor the redn. of both color and B . O . D . from kraft pulp-ing and bleaching diluents has been devd. It involves slaking lime from the kiln with part of the diluent to be trd. and adding it to the remaining c-filn-cnt. Org . cpds., inch color bodies, are adsorbed on the lime, which is then sepd. from the effluent in a thickener anddewatcred on a vacuum filt-r or centrifuge. The supernatant from the thickener, together with the filtrate from the vacuum filter, is then carbonated with lime-kiln gas at controlled p H in a reactor to reclaim lime in soln. and further decolorize the diluent. •CaCGY from the reactor is "reclaimed on the mud filter in the causticizing svstcm. Tt'.c filter cake from the lime trmt. contains the added lime still as C a ( O I I ) : ™d is used tocausticizc the green liquor. The liquor dissolves the org. cpds. from the lime and they appear in the white liquor produced. After the digester, they end up in the black liquor sent to the recovery furnace, where they are burned together with org. matter dissolved out of the d i -gested wood. This process gave a better than 909c color removal a:.d a B . O . D . redn. of 40-6070. W i t h some modifications (elimination of the first elarifier), it was found applicable to the trmt. of X S S C diluent as well, though at added expense (need for a lime kiln and slaker). The residual color (300-SGO units) of the linie-trd. cftlucnt is gen. acceptable for discharge into streams, but is loo high for water re-use in some processes. Two meth-ods for addnl. color removal were investigated, one based on activated car-bon and the other on foam fractionation. The latter required use of an ex-ternal surfactant to produce a suitable foam and gave uneconomical enrich-ment ratios for color removal, but might he suitable for B . O . D . redn. and addnl. tall oil recovery from diluents rich in tall oil soaps. The activaicd-C process, at decreased p H and elevated temp., gave nearly total color removal from efi'.uctiis of ail kraft bleach plant stages, but the economics of the trmt. require further large-scale study and improvement. Total cost of h.ig'a-degree kraft diluent trmts. for nearly closed water recirculation l iucl . hiol. trmt., lime decolorization, C adsorption, and desalination hy clectroilialvsi-) is still too high, viz., 50 cents per 1000 gal. S ref. C . h i B . 5649. '. M C K I ' H Y , Xelson F . , antl GISECOKY, Dale R. Removal of color f r o m iulfatc pulp wadi liquors. Proc. 19th Ind. Waste Conf. i h r g . B u l l . Purdue Univ. 4'.'. no. 1; Eng. Kxtensicm Ser. no. 117;; 59-7!> (May , 195-1 ;publ. J a n , 1965). Studies concerning the effectiveness of a high-pressure (600 to 3200 p.si.g.)/l::gh-ten:p. (254 to 4 C 0 C . ) trmt. (using a Parr Pressure Reaction App.) in the removal of color from the diluent resulting from the caustic extn. stage of a kraft 'pulp blenching process show that under basic con-ditions ( p l l 7.5 or 9.3), essentially complete diluent vaporization is necessary for effective decolorization to occur. However, under acidic conditions ( p H 3.5 or 5.5), effluent light transmittancc of up to 50% (compared to distilled water) was attained with effluent vaporization of only 357?- A transmittance of up to 937i< was attained at 100;o diluent vaporization. The mechanisms of the decolorization reactions are unknown. Holding time under steady-state conditions had only a small' effect on decolorization. Tests indicate that the sludge obtained as a result of decolorization can be removed by filtration. About 3,COO ga!. of dark-colored waste arc produced/t._of_ pulp bleached. 10 ref. L . G . S . //S54. Davis. C. I... Jr. T E R T I A R Y T R E A T M E N T 01 K R A F T MILL E F F L U E N T INCLUDING C H E M I C A L C O A G U L A T I O N FOR C O L O R R E M O V A L . Tappi 5 2, no. 11: 2132-4 (Nov.. 1969). To protect estuary waters, the Ga. State Water Quality Control Board required clarification, chem. trim., and biochem. stabilization ol krat't linerbourad mill waste prior to discharge. The decree of chem. trim, is defined in terms of A PI color units and is lumteJ to 30 ppm with a ma\. waste discharge of 10 million gal., Jay. The 5-day BOD is limited to S00 lb. day, and suspended solids are limited to ID ppm. A tnnt. system to meet these specs, was put into operation in March, I96ts at the Rieeboro. Ga. mill of Interstate Paper Corp. In sequence, it involves waste tlocculation with lime i 37 L/day caled. as 90:c CaO). removal of lime sludge and settleaMe solids, natural stabilization in an oxidn. basin satd. with Ca hydroxide at pll ca. 12.0. mech. aeration, and controlled discharge. The mill's rated capacity is 400 t./day of unbleached kraft Iincrboard. Process water requirements texcl. cooling) are I 2.500 {al./t. only about half the ind. av. A prelim, rept. cf operating experience and costs is given. Total capital investment for waste Umt. is cstd. at $2,500,000 U0"c of mill cost), of which nvarly $500,000 went into the color-removal system. Total first-year cost for operation and admin, of the system (incl. 5269,000 tor chemicals) was SbS3,700. or S3.19 per t. of prodn. (assuming 10-yr. linear depreciation). The color-removal installation was supported partly by a $467,000 grant from the Fed. Water Pollution Control Admin. C U B . SS53, Marton, J . ; Stern, A . M . ; Marton, T . D E C O L O R I Z A T I O N O F K R A F T 13LACK LIQUOR WITH POL YPOR US VERSICOLOR, A WHITE-ROT F U N G U S . Tappi 52, no. 10:1975-81 (Oct., 1969). A strain of the white rot fungus, Polypoms versicolor, which had been previously adapted to kraft lignin. significantly reduced the color of dild. pine kraft black liquor. The mechanism of the color removal was studied by using 3 kinds of lignin (spruce MWL, pine Indulin A T , and pine black liquor) and several lignin model substances. Lignin was not sufficient as the sole carbon source to support cell propagation: cell growth required an easily metabo-lizable sugar and other nutrient suppls. The intensity of cell growth and, simult., the degree of dccolorization were higher under aerobic than under anaerobic conditions. The acrobically grown ceils adsorbed lignin on their surfaces: hence phys. adsorption plays a major role in removing color, rendering the process less attractive from a technol. point of view. Part of the lignin was metabolized and chem. degraded. Under anaerobic conditions, where the rate of dccolorization was much lower, phys. adsorption also became less significant. Adsorption did not play an important role for the phenolic lignin models; most of them could be metabolized caiily. The reaction prods, were studied by means ol" differential spec:ry. .and thin-layer ch.oniat. The main steps involved in the aerobic U T U . arc of an oxidative nature, in line with a phenol oxidase mechanism advanced recently by Kirk, Harkin, £ Cowling. The formation of quinoid intermediates was demonstrated. The reactions of the phenolic models and their potential relations to the behavior of lignin chromophores are discussed. 16 ref. C.L.B.. 10561. Luncr. P.: Deuce. C\: P.enneit. D.: Kune. F. -L. MECHANISMS OF COLOR R E M O V A L IN T i l l : T R E A T -MENT OF PULPING A N D B L E A C H I N G El 1 LIT N IS WITH LIME. I. T R E A T M E N T 01 C A U S r i C EXTRACTION STAGE. B L E A C H I N G E F F L U E N T . NCASI Tech. Hull. no. 239: 52 p. (July, 1970). Commercial spent liquor from the N.iOII estn. stage ni'.a softwood kraft bleaching sequence was sepd. into precipitahlc and nonprecipi-table fractions by trim, with lime (CaO) or slaked lime (C"J hydroxide). The solid; comprising each fraction were suhjcvVd '.•> elemental and function.;! group anal, and mol.wl. detns. as a me:::!* of clarifying the mechanism of the lime pptn. process 'or color removal. Results showed that removal of color from the spent NaOII e \ ln . liquor with lime is a chemical rather than u phy». process and that it is dep. on the presence of ciiolie and phenolic O i l groups and on the mol.wt. of the solids contained in the liquor. Enolic and phenolic OH groups on structures contg. chromophoric pjoups react with lime and other Ca cpds. under alk. conditions forming insol. Ca salts which ppl. In spent NaOH oxtn. liquors the phenolic O i l content is low, and pptn. results primarily from interaction of lime with enolic O i l groups. The mol.wt. of the solids is a determinant factor in the lime pptn. process as it affects the soly. of the resulting Ca salts. 32 ref. WAV. 10562. Luncr, P.: Donee. C : Bennett. D.:Ota. M . MECHANISMS OF COLOR R E M O V A L IN TIIF. T R E A T -MENT OF' PULPING A N D B L E A C H I N G E F F L U E N T S WITH LIME. II. T R E A T M E N T OF C l l l .ORINATION STAGE Ii L E A C H I N G E F F L U E N T S . NCASI Tech. Bull. no. 242: 24 p. (Dec., 1970);cf. A B I F C 41: abstr. 10561. As in the case of the previous work on NaOH extm stage bleaching effluent, these studies demonstrated that removal of colored erg. matter from spent chlorination stage blenching cftlucnt by lime involved Ca salt pptn. which was dep. on (1) the presence of weakly acidic cnoiic and, lo a lesser degree, phenolic O H groups, and (2) on the mol.wt. of the dissolved solids present as a determinant of soly. of the resultant Ca salts. It is possible as well, that during lime neuln. of chlorination stage effluent, hydrolysis of chloro substitu-ents causes further formation of weakly acidic O i l groups which react with lime forming insol. Ca salts. 18 ref. W.W. 9227. Sameslmna, K. ; Kondo. T . STUDY ON T i l l : COLOR OF PULP INDUSTRY W \ S U ; LIQUORS. I. RELATIONSHIP BETWEEN I HE ( O l OR OF WASTE LIQUOR FROM K R A F T PI LP ML LTTST U'.F B L E A C H I N G A N D EIIE ISOLATED (IILOR1NF-OXYLIGNTN. J. Japan Wood Res. Soc. iMoku/ai GakkaUhi) 16. no. 7: 347-52 (Nov.. 1970). [Jap.: Engl. sum.| Pine and birch kraft pulps were subjected to multistage bleaching by the Cl:!!!:!) sequence, and the color-causing substance in the spent bleach liquors was isolated by acidification to pl l 1.0 lid. by ccntrifugation and dialysis. This substance, tentatively called CT-oxyliguin, contributed ca. 80^ to the total color and ca. 45'. ; to the COD of the effluent. It contained only ca. 1.6"- carbohydrates las xylose), showed a shoulder on the UV absorption curve at ca. 2S5 nm., and gave an IR spectrum charac. of lignin. In comparison with other lignin prepns., it displayed marked light absorption in the visible spectrum but no charac. absorption max. Its mol.wt. was rel. high, comparable to that of pine dioxane 'Jgnin. The dark cotaf may derive largely from reactions assocd. with lignin rfcni.'ihylalion. in which the I'll and CO groups act as chromophores and the COOH f.roup as auxochromc. 18 re 1". • C.L.B. 1602. Mohanrao. G. J.; Subrahmanyam, P. V. R. STREAM A N D A I R POLLUTION P R O B L E M S RELATED T O D I S P O S A L or E F F L U E N T S F R O M P U L P A N D P A P E R INDUSTRY. IpptaS, no. 3: 155-63 (July-Sept., 1971). [Engl.) This is mainly a rev. regarding stream pollutants. The main water pollutants are high pll, H O D . C O D , suspended solids, and coloring matter. U O D and solids may be reduced to reasonable limits by means of activated sludge ttnu. and by anaerobic lagoons. The latter ire less expensive. Color and C O D are difficult to remove. Suspended solids that emanate mainly from machine waters can be reduced initially by ituraplant techniques involving savealls, and later by coagulation and sedimentation. Possibly it would be well to reduce B O D and to correct the pll of pulp mill effluents by means of anaerobic lagooning. flic anaerobic effluent can be subjected to Eand disposal or treated by aerated lasooning before discharging into a stream. Ail pollutants from kraft mills are also considered briefly. They consist mainly of hydrogen sulfide, methyl mcrcaptan, dimcthvl sulfide, and "particulate pollutants". Their sources are outlined. 30 ref. L.E.W. 1558. Basu, S. STUDIES ON CARBONATION OF BLACK LIQUOR TOR LIGNIN PRECIPITATION AND ITS SUBSEQUENT SEPA-RATION. Ippta 8, no. 4: 207-14 (Oct./Dec., 1971). [Engl.] A study was made concerning the feasibility of removing "ligno-oiganic" components from black liquor by "carbonation" in rendering the liquor suitable for causticization of Na cpds. to NaOH. The process parameters during carbonation included the degree of turbulence, temp., pressure, time, and final pH. All of these were studied, and the optimum conditions were detd. Pressure carbona-tion at 4.5 kg./sq.cm. fid. by trmt. with acetone to insure coacervation-flocculation had a pronounced effect on removal of the ligno-organic components, obtained as a lyophilic colloid. Carbonation at atm. pressure was carried out on a small scale. Pressure carbonation was done in an elec. heated 18-liter autoclave provided with arrangements for recirculating the liquor through a heat exchanger. The response of the black liquor to coagulation-coacervation flocculation as a means of lignin removal was found to be correlated with the props, of the original ccllulosic raw matl. with respect to lignin content and distribution. 21 ref. L.E.W. 10S67. Davis, C L . COLOR R E M O V A L FROM K R A F T PULPING E F F L U E N T HY LIME ADDITION. Water Poll. Control Res. S-'r. (EPA) no. 1204CEN<~ 12/71 : 72 p. (Dee. I, 1971). [Avail, from NTIS; PI121S306] cf. AB1PC 40: abstr. 6S54 and ABIPC 42: abstr. 2729. 1589. Interstate Pancr Corp. COLOR R E M O V A L I-ROM K R A F T PULPING E F F L U E N T BY LIME ADDITION. Water Pol). Control Res. Scr. (U.S. EPA) 12040 ENC: 117 p. (Dec. 1, 1971). [Supt. Dee., GPO, Washington, D.C. 20402; S1.25] A prototype color removal sv slim using slaked lime was designed, constructed, and operated as m integral part of a tertiary trmt. system tor total process effhunt from a kraft lincrboard mill (Interstate Paper Corp.) at Ricehnro, Ga. The lime pptn. process was combined witli primary clurificiiion (Id. by natural biochem. lake stabilization and meeh. aeration. Results showed that the system can operate under widely varying conditions to yield a rel. const, effluent color of ca. 125 ppm APHA color units by dosage of the original effluent (1200 ± 200 p.jm color units) with 1000 ± 5 0 ppm of Ca hydroxide. Assuming a price of S15.35/t. of 90Sc CaO lime, this trmt. level costs S53.73 per million gal. of effluent. Equipment evaln. indicated substantial savings in capital cost for future installations, since performance is directly related to control of lime feed. The Ca was recovered continuously under mill conditions, using a statist, designed prorram which is described. The total tertiary trmt. system achieved an overall 5-day BOD redn. of 98%; the final discharge averaged 6 ppm BOD. 19 ref. C .L .B. 569. Dalpkc, H.-L. STUDIES DEALING WITH E F F L U E N T T R E A T M E N T B Y THE USE OF A C T I V A T E D C A R B O N . Papier 26, no. 1: 4-10 (Jan., 1972). [Gcr.; Engl. & Fr. sum.) The removal of biologically harmful substances (characd. by 5-day UOD dclns.) from mill effluents is known to be essential in preserving (or restoring) waterways. Besides biol. purification, a no. of chem. and phys. purification processes have been suggested for redg. 5-day BOD. One of these involves the adsorptive action of activated C. The author gives cxptl. data obtained in a scries of 4-slagc lab. cxpts. involving effluent trmt. in 4 C-contg. cylinders, and covers the thcotct. basis, for van dcr Waals adsorption. Apparently, the effluent studied could be decolorized completely at a specific flow rate of 1.5 liter/hr./kg. C. Such trmt. also removed the residual fibers completely, and lowered the 5-day BOD level to r.ot over 25 mg. O/litcr. The technique is shown in appropriate illustrations. 2 ref. • L.E.W. '.855. Subrahmanynm, P. V . R.; Sadian, P. C ; Mohanrao, G. J. ASPECTS 01 COLOR R E M O V A L I'ROM PULP AND PAPER MILL I I I I . I T NTS. Ippta y, no. 1: 20-3 (Jan./March, 1972). I Engl.) Lignin is described as an "aesthetic pollutant", and its "nonbio-dcgradabilir." is discussed. I-'or the removal from effluents of color due to lignin, chemical methods like massive lime trmt., hiol. methods like activated sludge trmt. and the utilization of various fungi, and phys. methods like adsorption by activated carbon or soils have been suggested. Lab. studies by the present authors, using 8 different soils, are described in detail, it is .shown that color redn. is directly proportional to soil cation-exchange capacity. The requirement of land for trg. pulp-mili effluents is also caled., assuming a steady rate of percolation and a given rate of evapn. 12 ref. L.E.W. 4 1 5 4 . Lcszezvnski. C . D E C O L O R I Z A T I O N Oi- K R A F T M I L L E F F L U E N T S . Przeglad Papier. 28, no. 3: 8S-9 (March, 1972). (Pot.J Colored substances in the effluents from kraft mills, consisting mainly of lignin derivs. and tannins, are not degraded in the activated sludge purification process. Although these substances are not toxic to aquatic organisms in conens. presently found in waters, they are harmful by inhibiting the penetration of sunlight into the water, increase the costs of trmt. of water, and prevent the use of the waters for recreational purposes. For these reasons, many methods have been proposed for decolorization of effluents prior to their disposal into natural waters, inch ppm. with metal salts, adsorption on activated C, reverse osmosis, etc. Among these methods only trmt. with lime was found suitable for ind. purposes The process, devd. and patented in the USA, consists essentially in mixing the effluents with lime, scpg. the ppt. contg. the colored substances by sedimentation, dewatering it to a dryness of 40-60C£, and using it in the causticization plant. The process has been introduced in three U.S. mills, notably the Riceboro (Ga.) mill of the Interstate Paper Corp.. the Georgia-Pacific Corp. mill in Woodland (Maine), and the Continental Can Co. mill in Hodge (La.). The decolorization procedures and their efficiency at the three mills are described. Also mentioned are pilot plant studies carried out by the International Paper Co. and the American Can Co. on lime decoloration of bleaching effluents, and on modifications of kraft pulp bleaching processes to reduce the load of colored substances in effluents. 13 tef. J.S, 'i';\S. Dytncrskii, Yu. I.; Svittsov, A. A.; Romanenko, Yu. K.; Zhilin, Yu. N.; Semenov, V. P.; Trupchaninova. O. V. USE OF R E V E R S E OSMOSIS AND U L T R A F I L T R A T I O N FOR Til l - PURIFICATION OF E F F L U E N T S . Bumazh. Prom. no. 7: 22-4 (July, 1972). [Russ.] Purification of mill effluents by the methods of reverse osmosis and ultrafiltration was studied in the lab. of the Baikal .pulp mill. Some results are repotted of cxpts. carried out on efilueuts which have been purified chem. and Idol., on nonpuriiicd effluents, and on black liquor evapn. condensates. In both purification methods CA membranes of domestic prudn. were used. The results of these preliminary cxpts. indicate tlial purification is more effective compared to the presently used methods, and that the purified effluents can be used as recycle process water. The advantage of ultrafiltration over reverse osmosis is a high efficiency at rel. low pressures (3-10 kg./sq.cm.). On the other hand, reverse osmosis removes dissolved mineral cpds.; until now such removal has been the most complex problem in effluent purification. J.S. 453(U). Lavrinenko, I. K.; Soivanik, P. A . ; Vilenskii, V. I. PURIFICATION OF PAPFR MILL E F F L U E N T S BY MICROITLTRATION. VodosnabzJi. Kanaliz. Cidrotckli. Sooruzh., Resp. Mezhved. Nauch.-Tekh. Sb. no. 15: 40-4 (1972). [Russ.] It was shown that it is possible to use microfiltcrs for the purification of paper mill effluents and of process water used by such mills. From: Ref. Zh., Kliim. no. 24: abstr. 1557 (Dec, 25, 1972). D . M . C 9719(R). Tyler, M. A. ; Fitzgerald, A . D. A REVIEW O F C O L O R REDUCTION T E C H N O L O G Y IN PULP A N D PAPER MILL E F F L U E N T S . CPPA Tech. Sect. Proc. 1972: D l 16-23; discn.: D123-5. Over 60 lit. repts. on effluent trmts. for color removal were studied to assess the status of ind. practices. Lime trmt. is the most established method, achieving 65% color removal from bleached kraft effluent at a capital cost of S1-1-5 million and operating costs of S 1.0-1.5 per ton of pulp. Coagulation with alum gives similar results at similar costs, but requires improved systems for handling the difficultly dewatcring sludge. Adsorption on activated C accomplishes complete color removal, but at high operating costs. Switching from CI to oxygen bleaching of kraft pulp would reduce effluent color by 60-65% and save ca. 52 per ton of pulp in chem. consumption. Capital costs for such a conversion arc cstd. at S2 million. 8 ref. C . L . B . 3028(M). Gould. m. NEW LIME PROCESS EOR R E M O V A L OF COLOR F R O M K R A F T MILL E F F L U E N T A T GEORGIA-PACIFIC ICORP.'S) WOODLAND, MAINE, MILL. TAPPI Envir. Conf. 1972: 141-7. The paid, effluent-decoloring process described involves trmt. of alk. extn. waste from a kraft bleach plant with ca. 2000 ppm. of lime before entering a solids-contact clarificr. Reaction of lime with color bodies precipitates a scttlcablc sludge which is continuously removed from the clarificr. The lime sludge underflow is then mixed with prefiltcrcd lime mud and dewatered on a conventional belt filter. The dewatered sludge is fed directly into the lime kiln where (lie color bodies arc burnt off and the lime is recovered. The full-scale trmt. plant (installed after pilot-plant trials) removes ca. 907o of the color and ca. 45% of the BOD from the effluent of the alk. extn. stage, and recovers ca. 80% of the lime used. Mill experiences, inch process parameters, costs, and maintenance, after the 1st yr. of operation are indicated. C . L . B . 1613. Oswalt, J. L . ; Land, J. G„ Jr. f£r?£JVr M 0 V A L F R 0 M K R A F T P U L P M ' L L E F F L U -ENTS BY MASSIVE LIME T R E A T M E N T . Envir. Protection Techjiol. Ser. EPA-R2-73-086: 109 p (Feb., 1973). r A demonstration plant was installed and operated to determine whether trmt. with 20,000 ppm lime could effectively and economically decolor kraft pulp mill effluents, notably the black effluent from the alk. extn. stage of the bleach plant, and the reddish-brown effluent from the final unbleached pulp washing stage. The impact of massive lime trmt. on a hypothetical 1000 t./'day bleached kraft integrated mill is described. Using all the lime normally available in such a mill would allow trmt. of 4 million of the 29 million gal. of toral effluent. This would remove 72% of the total effluent's color, reducing the residual color to ca. 740 API IA units at an cstd. cost of $1.80/t. ol" pulp, incl. depreciation, insurance, and taxes. 10 ref. C .L .B . 1630. Swanson, J. W.; Dugal, 11. S.; Buchanan. M. A.; Dickey, E. IC. K R A F T E F F L U E N T COLOR C H A R A C T E R I Z A T I O N B E F O R E AND A F T E R STOICHIOMETRIC LIME T R E A T -MENT. Envir. Protection Technol. Ser. EPA-R2-73-14 1: 75 p. (Feb., 1973). [GPO, Supt. Doc, Washington, D.C. 20402; SI.00j The NCASI lime trmt. process was round to remove an av. ot" ca. 86% of the color, 57% of the total org. C, and 17% of total sugars from unbleached kraft mill effluents collected at Rieeboio, Ga., over a 15-month period and processed at Appleton, Wis. No appreciable change in chloride content was noted. The wt.-av. mol.wis. of the untrd. jcid-insol. fractions varied from less than 400 to ca. 30,000: the mol.wts. of the untrd. acid-sol., lime-trd. acid-insoL, and lime-trd. acid-sol. fractions varied from below 400 to ca. 5000. The study showed that color bodies having an apparent mol.wt. below 400 are not removed, but those having mol.wts. above 5000 are completely removed. In the 400-5000 mol.wt. range, partial removal takes place. Based on IR spectry., the acid-insol. color bodies of high mol.wt. seem to contain a high proportion of CO groups, probably conjugated with an aromatic ring, while the low mol. acid-sol. fractions seem to contain noneonjugatcd COOH groups assocd. with carbohydrates. Color bodies are aromatic cpds., partly degraded lignin, having a neg. charge and existing primarily as sol. Na salts in aq. solus. The color bodies which are not removed by lime trmt. have low mol.wt., high unconjugated COOH groups, lisminlikc character, and seem assocd. with colorless C cpds. 18 ref. " C .L .B . 11801. Gould, M. COLOR R E M O V A L FROM K R A F T MILL E F F L U E N T B Y AN IMPROVED LIME PROCESS. Tappi 56, no. 3: 79-82 (March, 1973); cf. AB1PC 41: abstr. 10544; 43: abstr. 3028, 8487. 1626. Spruill, E . L . COLOR R E M O V A L A N D S L U D G E R E C O V E R Y F R O M T O T A L MILL E F F L U E N T . Tappi 56, no. 4: 98-100 (April, 1973). A lime trmt. color removal system, with recovery of lime and fibrous sludge integrated into the kraft lime processing system, has been constructed for trmt. of total mill effluent at the unbleached kraft mill of Continental Can Co., Hodge, La. With about 1000 ppm of lime, color redn. of 80-90% has been achieved in kraft effluent, with lower effectiveness on neutral sulfite chem. wastes. Good centrifugal dewatering and lime kiln incineration of sludges have been recorded. Settling and thickening of color sludge have been excellent, but carbonation-stage settling has been more variable. 8 ref. " C .L .B . 1G32(M). Tinipo. W. C ; Lanrt. 1". \V. A C T I V A T E D CARl .ON 'I R E A T M E N T 01" U N B L E A C H E D K R A I T E F F L U E N T FOR REUSE: PILOT P L A N T RESULTS. TAI'Pl Envir. Conf. (San Francisco), May 1973: 203-1S. An earlier lab. study at St. Regis Paper Co.'s R&D Div. (Pensacola, Fla.) established the degree of effluent trmt. achievable with activated C alone and combined with other method*. It also helped to pick the best of 24 activated C prepns., and ascertained tiiat McOH and other low-niol. org. cpds. are not removable by activated C. The. present rept. gives cxptl. and operating data tor a 30 gal./min. pilot plant in which 3 different pretrmts. (clarification, clarification plus lime trmt., and biooxidn. plus clarification) preceded the adsorptive removal of effluent components in 2 different systems. One system utilized 4 std. downtlow granular C columns, the other involved multistage countercurretit agitation ( F A C E T system, short for "line activated carbon effluent trmt."). The lime/C sequence achieved color removals to below 100 APHA color units and TOC removals to less than 100 mg./liter. It was the most econ. of the 3 sequences studied. Optimum chem. dosaaes were 320-600 mg. of CaO/liter plus 2.5 lb. of C/1000 gal. For successful trmt. with activated C, tiic unbieached kraft effluents must contain ca. 80 mg. of Ca/liter. The other 2 sequences yielded rel. low adsorption rates, probably due to coagulation of colloidal color bodies on the C surface. The F A C E T system was found to be tech. sound and capable of further devt. to provide trmt. at lower capital cost than with conventional C columns. 17 ref. C .L .B . 1640(M). Wright, R. S. C O L O R R E M O V A L F R O M K R A F T PULP MILL E F F L U -ENTS HY MASSIVE LIME T R E A T M E N T . TAPP1 Envir. Conf. (San Francisco), May 1973: 229-35. Massive lime trmt. by the NCASI-dcvd. process will remove over 90% of color bodies from eflluents of the final unbleached kraft pulp washing stage and of the alk. extn. stage in bleach plants. These 2 effluents contain 65-75% of the total coior load produced in the mfr. of bleached kraft pulp. Using all the lime normally available in a typical bleached kraft mill, ca. 14%. of the total effluent can be trd. Dy trg. the most highly colored eflluents, 72% of the mill's total color load can be removed. The introduction of massive lime into the mill's liquor causticizing operation will dil. the white liquor and lower its concn. by ca. 15%. Hence the total liquor vol. handled throughout the mill will inciease and require increased capacity of chem. prepn. and recovery equipment. For a given pulp prodn., lime kiln fuel requirements inciease 6.4%. Moreover, the carryover of org. cpds. by the massive lime sludge into the cooking liquor system can intensify foam problems. Buildups of CI and other matls. have no apparent effect on the chem. recovery cycle. A typical 1000 t./day kraft mill may spend ca. Sl.SO/t. of bleached pulp for massive lime trmt. of 4,000,000 gal. effluent, without adverse effect on pulp bleachability or final prod, quality. C . L . B . 5110. Sanks. R. L. ION-l-:XCllANGL; COLOR AND MINERAL REMOVAL PROM KRAFT HLEACH WASTES. U.S. EPA, Envir. Prot. Technol. EPA-R2-73-25S: 201 p. (May, 1973). [Supt. Doc, GPO, Washington, D.C. 20402; S2.35) Laboratory evalns. of 20 ion-exchange resins and 7 carbons for removing color and minerals from kraft bleach plant effluent showed that the resins were equal !•> carbon for decoloring the combined waste. With few exceptions, resins were unsuited for decoioring wastes from each stage separately. Except for success in the use of weak wash to regenerate Amberlite XAD-8 resin, utilization ofmill liquors for regeneration was unsuccessful. Sulfuric acid, NaOH, and ammonia were good regenerants, but lime was poor. Single stage ion-exchange produced water adequate for unbleached pulping while two-stage desalination produced water adequate for bleached pulping. The costs for desalination incl. amortization over a 10 yr. period are wtd. to vary from SI.38/1000 gal. (for the nonoptimized lab. process) to S0.42/1000 gal. (with estd. 90% cation regeneration efficiency, 85% anion regeneration efficiency, and 87% prod, recovery). 63 ref. W.W. (See also abstr. no. 5615, 5642) 5649. Croom, H. C.;Owens-Illinois Inc. SYSTEM EOR REMOVING COLOR FROM PAPER MILL LIQUID WASTE. U.S. pat. 3,736,254. issued May 29, 1973. 7 claims. Liquid pulping effluent is mixed with an aq. slurry of lime and lime mud composed principally of calcium carbonate, under alk. condi-tions. The mixt. is subjected to clarification sepn. of formed precipitanls. The liquid effluent overflow is carbonated by bubbling carbon dioxide gas through it to ppt. calcium carbonate and residual color-imparting entities and to effect adjustment of the.pH to approx. neutral. The decolorized liquid is ready for discharge. F J . L . 8534. Pulp & Paper International. COLOR REMOVAL PROCESS. Pulp Paper Intern. 15, no.5: 69 (May, 1973). PPR1C has successfully tested a new method for decolorizing pulp mill effluents which was originally developed and patented at the Centre Technique of France. The principal color-earn ing effluent streams from a pulp mill are contacted with high molecular weight amines dissolved in a water immiscible solvent. The nroccss is said to remove 90-98%. of the color, 45-85% of the COD, and 30-70% of the liOD from the effluents. The amines can be regenerated and recirculated to the process. Small scale tests in a kraft mill gave results as good as laboratory trials. Assuming economic feasibility studies civc favorable results, the process will be relesled on a larger scale. " P.IU1. 15901V t. J o h n s o n , J . S., Jr.: Minium. R. E.: Moore. G. I:'. HYPKRFILTRATION .'REVERSE OSMOSIS) Oh KRAFT PULP MILL AND ULEACI! PLANT WASTES. TAPPI Envir. Com". (Sat:f raneisco), May 1973: 23743. Kraft mill eflluents ( b r o w n s t o c k wash water, decker and screen room wastes, and bleach jlar.t effluents') were subjeeicd to high-pressure In perfiliration f!.0.) through dynamic membranes of polyacrylate o n a hydrous Zn'JV) oxide subs'rate: to moderate-pres-sure ultrafiltration using low-talt-rejection membranes comprising single layers of hydrous ZrtlVfoxide or of neut. org. polymers; a n d to low-pressure filtration. Devatering of weak black liquor was also attempted. Compared to conwntional detachable CA membranes, f.uxes were considerably h h i i e t , and decontamination seemed adequate for reuse of many Curates. Moreover, filtration could he conducted at the temp, of the process, and the membranes could be regenerated or removed and B a n n e d in situ. 24 ref. C.L.B. 10265. Kemmer, F. N.; Nalco Chemical Co. COLOR REMOVAL PROCESS. Can. pat. 929,712. Issued July 10, 1973. 4 claims. This process for decolorizing paper mill waste with lime is similar to that described previously in U.S. pat. 3,578,587; cf. ABIPC 42: abstr. 4034. F.J.L. 7911. Fremont, H. A.; United States Plywood-Champion Papers Inc. COLOR REMOVAL FROM KRAFT MILL AQUEOUS EFFLUENTS. U.S. pat. 3,758,405. Issued Sept. 11, 1973. 10 claims. A system is provided for removing color bodies from aq. effluents from kraft pulp mfr. such as first stage caustic extn. filtrate. The system involves adjusting the pll of the effluent to about 9, subjecting the effluent to ultrafiltration to form an aq. permeate and a rctcntatc contg. all the color bodies in a solids concn. of at least 15%, and thermally oxidg. the rctcntatc to oxidize the color bodies to colorless inorg. salts and gases which can be safely disposed of. F.J.L. 

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