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Foam separation of kraft mill effluents. Herchmiller, Donald Wayne 1972

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FOAM SEPARATION OF KRAFT MILL EFFLUENTS by  DONALD WAYNE HERSCHMILLER B.A.Sc., U n i v e r s i t y  of B r i t i s h  C o l u m b i a , 1969  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS  FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  in  t h e Department of  CHEMICAL ENGINEERING  We a c c e p t required  this  thesis  as c o n f o r m i n g  to  standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 19 72  the  In p r e s e n t i n g of the  this  requirements f o r an  thesis  that  Library  study.  granted by  his r e p r e s e n t a t i v e s .  copying or p u b l i c a t i o n not  be  be  of t h i s  allowed without my  the  make i t agree for Depart-  that  for financial  written  Department of Chemical E n g i n e e r i n g The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, -Canada  1972  thesis  Head of my  gain  permission.  D.W.  January  shall  It i s understood thesis  University  I further  permission f o r e x t e n s i v e copying of t h i s  ment or by  shall  the  a v a i l a b l e f o r r e f e r e n c e and  s c h o l a r l y purposes may  fulfilment  advanced degree of the  of B r i t i s h Columbia, I agree that freely  in p a r t i a l  Herschmiller  ABSTRACT  A processes, ents  laboratory as  applied  is described.  flotation  on  the  most  because  of  foam  Substantial  ion  the  problems  that  efflu-  f r a c t i o n a t i o n and  ion"'  concentrated because  primarily  this  property  lent  a v a i l a b l e a n a l y t i c a l methods,  removal  colour  shown  presents facing  the  one  of  the  industry  the  mechanism o f  removal  and  greatest today.  not  r e m o v a l s were o b t a i n e d ,  r e s u l t s were o b t a i n e d  process  conditions,  corresponding  excess  bleaching  success-  but  it  was  was  really  flotation.  flotation  optimum  and  separation  f r a c t i o n a t i o n t e c h n i q u e was  Positive ion  developed  the  foam  laboratory.  e f f l u e n t colour  treatment  subsequently an  i n the  r e a d i l y to  The ful.  m e t h o d s , foam  effluent colour  waste water  k r a f t pulping  procedures  removal  itself  to  Two  were t e s t e d The  investigation into  of  95  per  for  the  recovery  removal cent.  removal  of  of of  with  of  use  effluent colour. flotable  effluent colour  Variation  the  material were  surfactant  in  dosage  of At and  the  showed that below a c r i t i c a l As. c o n c e n t r a t i o n s  value the amount of  r a p i d l y , reaching  value.  The  found to be s i g n i f i c a n t l y the sparger  a high  removal  flotation  cell  Optimum pH was  r a t e of f l o t a t i o n  recovery  a f f e c t e d by the a i r sparge rate  available for adsorption.  solution  had  The  c l e a r l y d e f i n e d as 5.1.  oxygen demand d a t a , while  strate  a significant  of  effluent. The  of  reduction  the  system.  apparent.  not e x t e n s i v e , demon-  in the bio-degradable  for industrial  de-  Removal of m a t e r i a l  p o s s i b l e f u t u r e development of the  a v i a b l e candidate  pH  a marked e f f e c t on the  other than j u s t the chromophoric f r a c t i o n was Biological  was  pore s i z e , both parameters which would  termine the area  the  removed.  beyond which i n c r e a s e s i n s u r f a c t a n t c o n c e n t r a t i o n  were of l i t t l e  and  no c o l o u r was  i n c r e a s e d above t h i s  c o l o u r removed i n c r e a s e d level  level  application  portion  process  into  is discussed.  TABLE OF CONTENTS  Page ABSTRACT. .  i i  LIST OF TABLES  ix  LIST OF FIGURES  x  ACKNOWLEDGEMENTS  xiii  Chapter 1  INTRODUCTION  .  2  BASIC BACKGROUND KNOWLEDGE OF THE PULPING, BLEACHING, AND EFFLUENT SYSTEMS  1 4  General  4  Kraft Pulping  4  L i g n i n , the Colour Producer  5  Chromophores Derived from the Pulping Process  6  Chromophores Derived from the B l e a c h i n g Process  7  P r o p e r t i e s of the Various Chromophores. . . . 12 Summary 3  14  MILL EFFLUENT COLOUR REMOVAL TECHNOLOGY The R e l a t i v e Dominance of Hydrated  iv  15  Lime . . . 15  Chapter  Page Other A l t e r n a t i v e s Activated  16  Carbon  16  Aluminium and Iron S a l t s  17  The Grenoble Process  18  Summary 4  19  ABSORPTIVE BUBBLE SEPARATION METHODS General  21  The C l a s s i f i c a t i o n System  21  Foam F r a c t i o n a t i o n  24  Froth  26  Fl o t a t i on  Ore  Flotation  26  Low Gas-flow-rate Methods Ion  Flotation  Precipitate  5  21  26 27  Flotation  27  Other Froth F l o t a t i o n Methods  28  Reported S e p a r a t i o n s  28  Summary  30  ION FLOTATION  31  Introduction  31  Surface A c t i v i t y . . . .  32  Micelles  34  Other Parameters A f f e c t i n g Stability  Ion F l o t a t i o n . . .  of the Froth  The C o l l e c t o r - C o l l igend Ratio  v  35 35 36  Chapter  Page I n t r o d u c t i o n of S u r f a c t a n t  37  Choice of C o l l e c t o r  37  Bubble S i z e  38  Air  6  and C h a r a c t e r i s t i c s  Sparge Rate  38  pH . . •  39  Ionic S t r e n g t h  40  Concentration of Colligend  40  Temperature  41  The K i n e t i c s of Ion F l o t a t i o n  41  Summary  42  EXPERIMENTAL APPARATUS Foam F r a c t i o n a t i o n  43 Apparatus  43  Ion F l o t a t i o n Apparatus 7  46  EXPERIMENTAL PROCEDURE  48  Foam F r a c t i o n a t i o n  - Batch Operation  Foam F r a c t i o n a t i o n  - Continuous  Operation  48 . .  49  Ion F l o t a t i o n - General  51  Analytical  53  Tests and Procedures  Colour Determination  53  Biological  53  Oxygen Demand  pH, Measurement and C a l i b r a t i o n  53  S t i r r e r Speed C a l i b r a t i o n  54  Flotable Solids  54  vi  Determination  Chapter  Page C l e a n i n g Procedures Electrophoretic  55  Mobility  Zeta P o t e n t i a l  and/or  Measurement  55  Rotameter C a l i b r a t i o n 8  56  RESULTS AND DISCUSSION General  57  - the E f f l u e n t  57  Foam F r a c t i o n a t i o n  (Batch) Results  Foam F r a c t i o n a t i o n  (Continuous) Results  Ion F l o t a t i o n  60 . . .  Results  67  General The  67 Col l e c t o r - C o l 1igend Ratio  Collector Micelle  Formation  74 75  Bubble S i z e  80  Collector  Rate  .  81  Pre-mix Time  85  B0D5 Removal Kinetics The  of the F l o t a t i o n  .  88  . .  92  Process. . .  95  Recovery.  Ion F l o t a t i o n System as Part  of an I n d u s t r i a l  10  70  pH  Ai r Sparge  9  63  Treatment  CONCLUSIONS  99  RECOMMENDATIONS FOR FURTHER STUDY  101  REFERENCES  104  NOMENCLATURE  109  vii  APPENDICES  Page  A  The M o d i f i e d Colour Test  B  Summary of Ion F l o t a t i o n  C  Flotation  Ill Data  Recovery Results  vi i i  119 122  LIST OF TABLES  Table 1  2  3  Page Typical Data  Batch O p e r a t i o n Foam  Fractionation 61  T y p i c a l Continuous O p e r a t i o n Foam F r a c t i o n a t i o n Data  64  Biological  90  Oxygen Demand Removal Data  ix  LIST OF FIGURES  Figure 1  2  3  4  5  6  Page General Types of Chromophoric S t r u c t u r e s Present i n K r a f t P u l p i n g Wastes  8  P o s s i b l e S i t e s of Degradative Attack by C102andCl2onLignin  10  Formation of o-Benzoquinonoid Chlorination  11  G e n e r a l i z e d Formation Pul p Bl each i ng  Unit d u r i n g  of o-Quinone d u r i n g . .  11  Schematic Diagram of the Grenoble Process f o r P u r i f i c a t i o n of K r a f t Pulp M i l l E f f l u e n t s . .  20  C l a s s i f i c a t i o n Scheme f o r the Various A d s o r p t i v e Bubble S e p a r a t i o n Methods  22  7  Four Modes f o r Continuous  8  Schematic Diagram o f the Foam F r a c t i o n a t i o n Experimental Apparatus  44  Schematic Diagram of the Ion F l o t a t i o n Experimental Apparatus  47  Colour versus pH f o r F i r s t C a u s t i c E x t r a c t i o n Stage E f f l u e n t  58  Colour versus pH f o r T o t a l  59  9  10  11  x  Foam F r a c t i o n a t i o n  Mill  Effluent  . .  . . . .  25  Fi gure  Page  12  Schematic  13  Percent Colour Removal versus S u r f a c t a n t Dosage  14  Drawing o f Scum Formation.  Percent F l o t a t i o n  69  71  Recovery versus  S u r f a c t a n t Dosage  73  15  Percent Colour Removal versus pH  76  16  Percent F l o t a t i o n Recovery at Various pH Values Zeta P o t e n t i a l versus pH f o r F l o t a t i o n Cell Effluent  78 79  Percent F l o t a t i o n Recovery at pH 5.1 f o r Two Sparger P o r o s i t i e s  82  Percent F l o t a t i o n Recovery at pH 4.5 f o r Two Sparger P o r o s i t i e s  83  17  18  19  20  Percent F l o t a t i o n Air  Recovery at Various  Sparge Rates  84  21  Foam Volume versus A i r Sparge Rate  86  22  Foam Volume versus S u r f a c t a n t Dosage  87  23  Absorbance versus Wavelength f o r Run 3  91  24  P l o t o f Mln([M-R]/M) versus Time f o r Runs 16 and 20 P l o t of log(M-R) versus Log(time) f o r Runs 16 and 20 . . . .  25  26  Proposed Ion F l o t a t i o n Process f o r P u r i f i c a t i o n of Pulp M i l l E f f l u e n t s  xi  93 94  96  Fi gure Al  A2  A3  A4  Page Absorbance versus Wavelength f o r Various 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 Stage E f f l u e n t  112  Absorbance versus C o n c e n t r a t i o n of F i r s t C a u s t i c E x t r a c t i o n Stage Effluent  113  Absorbance versus Wavelength f o r Various Strengths of the Pt-Co Standard S o l u t i o n Absorbance versus  Colour C o n c e n t r a t i o n  xi i  . . . .  115 118  A C K N O W L E D G E M E N T S  I wish to thank Dr. R.M.R. Branion and  guidance throughout the course  of t h i s  I would a l s o l i k e to express faculty  and  Pinder, for their  students, p a r t i c u l a r l y  to thank my  the  f o r the f i r s t  t i m e , f o r b e a r i n g with  f o r funding  the  Dr.  Bloedel  ideas  me. L t d . and  L t d . f o r t h e i r assistance in o b t a i n -  e f f l u e n t samples and Federal  to  f e l l o w graduate  D. Bass upon whom most of my  Canadian F o r e s t Products  and  Engineering  Columbia, p a r t i c u l a r l y  A l s o acknowledged are MacMillan  ing m i l l  thanks to the  support.  I would a l s o l i k e  were a i r e d  study.  s t a f f of the Department of Chemical  of the U n i v e r s i t y of B r i t i s h K.L.  my  f o r h i s support  the National  Research  Department of Energy, Mines, and  Council  Resources  program.  Thanks are a l s o due  to my  w i f e , I n g r i d , f o r pro-  v i d i n g encouragement i n the d i f f i c u l t e a r l y days of r e s e a r c h , to H. A. MacLean f o r e d i t i n g to Shari H a l l e r f o r the f i n a l  typed  xiii  the f i r s t  copy.  this  draft,  and  CHAPTER  1  INTRODUCTION  Pulp  and  form, i n v o l v e s the stabilization mill  and  duced and have now  The  methodology f o r removing the  f o r reducing  the b i o l o g i c a l l y  of the  settleable  available  organics  been developed to a s u b s t a n t i a l degree.  treatment scheme; a t e r t i a r y  stage  of the  certain  underlines  conventional  to remove, or  remove, the c o l o u r c o n t a i n i n g , r e l a t i v e l y  Biological  affect  This f a c t  the need f o r at l e a s t a t h i r d step i n the  partially  non-biodegradable  effluent.  Historically  i t was  the  d i s p o s i n g of the voluminous sludge which i s pro-  p r o p e r t i e s such as e f f l u e n t c o l o u r .  to be  and  organic f r a c t i o n  treatment does n o t , however, s i g n i f i c a n t l y  portion  in i t s present  removal of s e t t l e a b l e s o l i d s  of the biodegradable  effluents.  solids  paper wastewater t r e a t m e n t ,  relatively  [ 1 ] , this  fraction  has  innocuous to a q u a t i c l i f e .  argued, i s u s u a l l y c o l o u r e d and  is usually s u f f i c i e n t l y  been  considered  Natural  t u r b i d and  water,  dilution  high t h a t the added m a t e r i a l would  1  2  not  a l t e r the  work [2] has  natural  state appreciably.  shown that  a l t e r e d spectrum of the certain  d e p t h , may The  the  However, r e c e n t  reduced p e n e t r a t i o n  and  the  l i g h t , which does penetrate to a  a f f e c t aquatic  growth.  non-biodegradable p o r t i o n  of the  pulp  mill  e f f l u e n t i s comprised p r i m a r i l y of wood e x t r a c t i v e s  and  lignin  the  degradation products which are  pulping  and  bleaching  stages.  material  i s chromophoric.  relative  complexities  i n v o l v e d , the  A l a r g e p o r t i o n of  Because of the  of the  purification  formed during  l i m i t a t i o n s and  range of a n a l y t i c a l  compounds and  aqueous s o l u t i o n by The  removal of  this  portion.  Foam f r a c t i o n a t i o n has organic  procedures  techniques u l t i m a t e l y employed  were, f o r the most p a r t , r e l a t e d to j u s t the chromophoric  this  been used to remove s o l u b l e  i n d i v i d u a l cations  and  anions from  complex formation with s u r f a c t a n t s  technique makes use  of the  surface-active  [3].  properties,  induced or n a t u r a l , of the  s o l u t e which cause i t to accumulate  at g a s - l i q u i d i n t e r f a c e s .  The  to the be  surface  by  introducing  material gas  can  then be  bubbles and  c o l l e c t e d i n a more c o n c e n t r a t e d form by  can  raised  subsequently  drainage of  the  foam. Although k r a f t p u l p i n g surface  wastes contain  a c t i v e components [ 3 0 ] , these were not  some n a t u r a l thought to  3  be  related  to the bulk  of the chromophoric s u b s t a n c e s .  Thus,  removal of the s u r f a c e a c t i v e components would not n e c e s s a r i l y remove the Available  chromophoric substances to any information  are l a r g e l y quinonoid  lignin  [4] i n d i c a t e s that the  d e r i v e d and  with  the  as a pH  i n d i c a t o r , leads  under a l k a l i n e  in the degradation  to the  This  c o n c l u s i o n t h a t , at  possesses a negative research  foam f r a c t i o n a t i o n foundation  technique  with  the  and  ion f l o t a t i o n  a cationic  factant. this  This technique  presented  tigate  a few  technique t i o n s , the  again  build.  e f f o r t should  be  In  as p o s s i b l e ?  shifted suritself,  Would i t be b e t t e r to i n v e s -  s p e c i f i c a r e a s , i n d e p t h , or to e x p l o r e  as widely  system  and  using a c a t i o n i c  proved to be s u c c e s s f u l .  another problem.  sur-  foam f r a c t i o n a t i o n  research  technique,  Based on  undertaken,  r e v e a l e d that the presumed mechanisms were i n v a l i d f u r t h e r i n d i c a t e d that the  the  charge.  study was  upon which to  Experimentation  to an  fact,  least  c o n d i t i o n s , a s u b s t a n t i a l p o r t i o n of  c o n c l u s i o n the present  f a c t a n t as the  processes  f a c t that the e f f l u e n t behaves, i n a s e n s e ,  chromophoric m a t e r i a l  using the  degree.  chromophores  type compounds are u s u a l l y i n v o l v e d .  coupled  this  appreciable  the  In a review of a l l c o n s i d e r a -  l a t t e r course of a c t i o n was  chosen.  CHAPTER 2  BASIC BACKGROUND KNOWLEDGE OF THE PULPING, BLEACHING, AND EFFLUENT SYSTEMS  General In order to attempt  to understand  the mechanics  of any separation i t i s necessary to have as much information as possible about the chemical and physical nature of the component which i s to be removed and about the chemical and physical nature of the environment from which i t i s to be separated.  For the chromophoric agents  (colour producing  bodies) of the kraft pulping and bleaching processes, this task i s extremely  complicated.  Kraft Pulping No discussion of the kraft pulping and bleaching wastes can develop  without some attention to the basic char-  a c t e r i s t i c s of the pulping process.  The kraft pulping process  normally employs a strongly alkaline sodium hydroxide and  4  5  sodium s u l f i d e hydroxide  cooking s o l u t i o n  or " l i q u o r . "  The sodium  a t t a c k s a l l components of the wood, i n c l u d i n g  c e l l u l o s e , to v a r y i n g degrees.  The sodium s u l f i d e i n c r e a s e s  the rate of a t t a c k on the l i g n i n , while b u f f e r i n g of  the sodium hydroxide  Hagglund [ 6 ] , l i g n i n  on the c e l l u l o s e  first  the e f f e c t  [ 5 ] . A c c o r d i n g to  takes up s u l f u r i n the s o l i d  phase, f o l l o w e d by molecular s p l i t t i n g which forms f r e e hydroxyl fragments.  groups, thereby producing  Sulfidization  l i g n i n molecule  reduces  m e r i z e , thus promoting  or prevents  the tendency to r e p o l y -  and r e t a i n i n g s o l u b i l i t y . reaction  Because  ( i . e . proceeding  s u c c e s s i v e steps i n d i f f e r e n t areas of the wood  the innermost is  lignin  of the r e a c t i v e groups i n the  k r a f t p u l p i n g i s a topochemical in  soluble  l a y e r o f l i g n i n , the l i g n i n  a t t a c k e d l a s t and very s l o w l y .  fore, yields  additional  substance)  of the c e l l  The t e c h n i c a l  wall  cook, t h e r e -  i n a s o l u b l e form, l i g n i n which has undergone  a degree of degradation ranging from a l i t t l e  L i g n i n , the Colour Lignin  to a great  deal.  Producer  i s , t h e n , the major c o n s t i t u e n t o f the wood  which the process transforms  into a soluble  v a r y i n g amounts of carbohydrates  and other  L i g n i n and/or i t s degradation products  form, along with extractives.  are r e s p o n s i b l e f o r  5  sodium s u l f i d e hydroxide  cooking s o l u t i o n  or " l i q u o r . "  The sodium  attacks a l l components of the wood, i n c l u d i n g  c e l l u l o s e , to v a r y i n g degrees.  The sodium s u l f i d e i n c r e a s e s  the rate of a t t a c k on the l i g n i n , while b u f f e r i n g of  the sodium hydroxide  Hagglund [ 6 ] , l i g n i n  [ 5 ] , A c c o r d i n g to  on the c e l l u l o s e  first  the e f f e c t  takes up s u l f u r i n the s o l i d  phase, f o l l o w e d by molecular s p l i t t i n g which forms f r e e hydroxyl fragments. lignin  groups, thereby  Sulfidization  molecule  m e r i z e , thus  reduces  promoting  producing  or prevents  the tendency to r e p o l y -  and r e t a i n i n g s o l u b i l i t y . reaction  Because  ( i . e . proceeding  s u c c e s s i v e steps i n d i f f e r e n t areas of the wood  the innermost is  lignin  of the r e a c t i v e groups i n the  k r a f t p u l p i n g i s a topochemical in  soluble  l a y e r of l i g n i n , the l i g n i n  a t t a c k e d l a s t and very s l o w l y .  fore, yields  additional  substance)  of the c e l l  The t e c h n i c a l  wall  cook, t h e r e -  i n a s o l u b l e form, l i g n i n which has undergone  a degree of degradation ranging from a l i t t l e  L i g n i n , the Colour Lignin which the process  to a great d e a l .  Producer  i s , t h e n , the major c o n s t i t u e n t of the wood transforms  into a soluble  v a r y i n g amounts of carbohydrates  and other  L i g n i n and/or i t s degradation products  form, along with extractives.  are r e s p o n s i b l e f o r  6  most o f the c o l o u r i n the p u l p i n g  and b l e a c h i n g  e f f l u e n t s [7].,  L i g n i n i s a h i g h l y branched or c r o s s - l i n k e d , h i g h l y r e a c t i v e , polymer with 840.  a s u b u n i t o f a m o l e c u l a r weight o f approximately  Two o f the r e a c t i o n s which l i g n i n w i l l  t i o n s which are p a r t i c u l a r l y pulping  important with r e s p e c t  to the  process i t s e l f , s u l f o n a t i o n and h y d r o l y s i s , have  been d i s c u s s e d . in b l e a c h i n g  Other r e a c t i o n s i n c l u d e those important  and, u l t i m a t e l y , i n the f i n a l  of the c h a r a c t e r i s t i c s and  undergo, r e a c -  oxidation.  •*  determination  of the e f f l u e n t s , namely  halogenation  A l l these r e a c t i o n s , t h e n , are the means by  which the s t r u c t u r a l u n i t s which determine the e f f l u e n t c o l o u r are produced.  Despite  the c o n s i d e r a b l e  amount of  work which has been performed with 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  chromophoric groups r e s p o n s i b l e f o r  c o l o u r , the matter has not y e t been completely  resolved.  For.the most p a r t , i r r e s p e c t i v e of l i q u o r o r i g i n ing or the various  bleach  stages), structures  ( i . e . pulp-  producing  c o l o u r c o n s i s t of aromatic and quinonoid n u c l e i and and  carbonyl  e t h y l e n i c groups [ 5 ] .  Chromophores Derived from the Pulping H a r t l e r e t al.  [7] l i s t  a number of l i g n i n  chromophores which have been i s o l a t e d pulping  operation.  These  Process  include,  derived  from e f f l u e n t s of the  7  . . . a l i p h a t i c d o u b l e bonds conjugated . with the aromatic ring, quinonemethides> quinones, chalcone structures, and h e a v y metal complexes with catechol structures.  The structures shown in Figure 1 are i l l u s t r a t i v e of these types.  These structures, i t must be noted, could be present  in the forms shown or as components of larger structures.  Chromophores Derived from the Bleaching Process When pulp is bleached the l i g n i n or i t s degradation products are further degraded, but under conditions which are much less harsh than those of the pulping operation. Therefore, the colour imparted to bleach plant effluents i s a combination of pre-existing chromophores and perhaps  d i f f e r e n t , chromophoric  in the bleaching process  groups which have been created  itself.  Studies [8] conducted New  additional,  at the State University of  York College of Forestry indicate that the colour of  chlorination stage effluents can be traced to the formation of o-benzoquinoid  units, probably as intermediaries. Studies  [8] with model compounds have shown that the condensation product of such an intermediary i s the corresponding catechol ( 1 , 2-dihydroxybenzene) d e r i v a t i v e .  Other reactions, in  addition to a condensation, are possible.  In fact,some  DIHYDROXYSTILBENE TYPE HC 11 CH  OCHOH \  or  R= /C=0 -CH=CHOCHOH QUINONEMETHIDE TYPE C =f  I! O  OCH  CH 0 3  OH  OCHII  STILBENEQUINONE TYPE  HC I  HC II  ll O  OCH-  FIGURE 1 General Types of Chromophoric Structures Present in Kraft Pulping Wastes  9  oxidations  r e s u l t i n g in rupture of the  be expected to y i e l d fragments  low  quinone r i n g would  molecular w e i g h t , c o l o u r l e s s  [9,10]. A l a r g e body of evidence [11,12,13,14] i n d i c a t e s  t h a t what i s probably true of the t r u e , i n g e n e r a l , of the  c h l o r i n a t i o n stage i s a l s o  other bleach  [ 1 1 , 1 2 ] , i n a two-part study, suggested that and  sodium c h l o r i t e  Sarkanen e t  stages.  in t h e i r oxidative  chlorine  reactions  dioxide  with  guaiacyl  type compounds cause, (a) some r i n g o p e n i n g , and  also  formation of p-benzoquinone s t r u c t u r e s .  (b)  not  i d e n t i f i e d , oxidative  The  formation of the  in bleach  p-benzoquinone d e r i v a t i v e s was  a wide v a r i e t y of s i d e c h a i n s , l e a d i n g  clusion  that Figure  attack  by  C10 2  an e x t r a p o l a t i o n 2 details and  the  C l 2 on  to l i g n i n  itself  possible sites  lignin.  Figure  of  the  that chain  alternate reaction.  Bailey  and  a l k a l i n e hydrogen peroxide o x i d i z e s substituents  of l i g n i n  to the could  con-  be  degradative  Dence [13] the  the  chlorination report  various  side  very a c t i v e l y , r e s u l t i n g i n  formation of methoxyhydroquinone and qui none .  observed  3 illustrates  formation of an o-benzoquinonoid u n i t during and  occur.  of l i g n i n model compounds con-  taining  made.  Other,  r e a c t i o n s were a l s o s a i d to  liquor reactions  al.  subsequently  the  p-benzo-  10  C—  Electrophilic displacement  ^  (ci ) 2  _ O  Quinone formation (ClOg)  /—Demethylation (CI0 , c i ) 2  2  ^-Ring opening(CI0 ) 2  Dealkylation (CIO ,CI ) 2  2  E1GURE_2 Possible Sites of Degradative Attack by CI0 and Cl on Lignin 2  2  11  ^ Coloured material of ^c£&*s1 u n k n o w n structure  Cl x "  CP**-  Cl -H 0 2  2  ICK  o  -o  Colourless aliphatic o-Benzoquinonoid unit (non-cyclic) fragments (Coloured)  Softwood lignin Unit Cl  x  denotes c h l o r i n e substituents at u n s p e c i f i e d p o s i t i o n s  F I G U R E 3 F o r m a t i o n of o - B e n z o q u i n o n o i d U n i t s D u r i n g Chlorination  l ^ C o n a ^ V / Ox.  > If  j—(  O  OH  Coloured  O -  .  (Red)  .Colourless degradation p  r  o  d  u  c  t  s  F I G U R E 4 G e n e r a l i z e d F o r m a t i o n of o - Q u i n o n e D u r i n g B l e a c h i n g  12  In summary, the chemicals been shown to convert l i g n i n tures which can then is  to o- or p-quinonoid  undergo f u r t h e r r e a c t i o n s .  a g e n e r a l i z e d p i c t u r e of t h i s  previously  used i n b l e a c h i n g have  procedure.  noted  produced  of the above  c o u l d be present i n the forms shown or i n c o r p o r a t e d  into l a r g e r molecular  Properties  fragments.  of the Various Chromophores The  regarded  A g a i n , as  products  struc-  Figure 4  f o r the case of the chromophoric groups  during the p u l p i n g o p e r a t i o n , the end reactions  type  c o l o u r producing  fragments were once commonly  as being i n the c o l l o d i a l  data f o r the c h l o r i n a t i o n caustic extraction  state.  Recently, published  stage e f f l u e n t [8] and  effluent  [4] have tended  f o r the  to d i s p u t e t h i s  s u p p o s i t i o n , proposing i n s t e a d t h a t the fragments are composed of m a t e r i a l of a very wide range of m o l e c u l a r but are completely s o l u b l e .  The  f o r m a t e r i a l i n the c h l o r i n a t i o n to be  about 1500  [8].  The  average m o l e c u l a r weight e f f l u e n t has  effluent  t h i r d , by weight) i s roughly one-tenth  found  two  residue.  principal  been r e p o r t e d  m o l e c u l a r weight of the ether  extractable material in this  f o r the t o t a l  weight,  Loras  (approximately  of the value given  [ 1 6 ] , i n gel permeation  f r a c t i o n s with  one-  average m o l e c u l a r  studies, weights  13  g r e a t e r and s m a l l e r than 5000. black  for acidified  l i q u o r y i e l d e d average molecular weights of 1600 [ 4 , 8 ] .  Reported r e s u l t s again  The r e s u l t s  [ 4 ] f o r c a u s t i c e x t r a c t i o n stage e f f l u e n t  showed two f r a c t i o n s ; the f i r s t  an average m o l e c u l a r  weight of 500, the second an average of 200. Clarke  and Davis [ 1 5 ] , i n t h e i r c o a g u l a t i o n  studies  of c h l o r i n a t i o n stage w a s t e s , i n d i c a t e t h a t some c o l l o i d s are i n v o l v e d . colloidal  Although the d i s p u t e  materials  could well  as to whether or not  are present i s not f u l l y  resolved, i t  be d e r i v e d from a d i f f e r e n c e i n c l a s s i f i c a t i o n .  Some of the l a r g e r macromolecules could well  have a m o l e c u l a r  weight o f 50,000, f o r which Rezanowich, Yean, and Goring [17] o  have c a l c u l a t e d a diameter of 50 A, been a f f o r d e d some experimental t h i s s i z e would be v i s i b l e is  an estimate  verification.  which has  A p a r t i c l e of  under an e l e c t r o n microscope and  c l a s s i f i e d by some i n v e s t i g a t o r s as c o l l o i d a l [ 4 1 ] . The  chromophores, or at l e a s t a s i g n i f i c a n t  portion  of them, show a markedly d i f f e r e n t absorbance i n d i f f e r e n t hydrogen i o n c o n c e n t r a t i o n s . i n c r e a s e s with  i n c r e a s i n g pH, a not too s u r p r i s i n g r e s u l t  c o n s i d e r i n g the e x i s t e n c e quinone-methide t y p e . that n e g a t i v e l y alkaline  The absorbance o f the e f f l u e n t  of s t r u c t u r a l  This  f a c t a l s o leads  charged s i t e s  conditions.  fragments of the to the c o n c l u s i o n  e x i s t , at the very  l e a s t , under  14  Summary In summary, the chromophoric f r a c t i o n mill  e f f l u e n t c o n s i s t s of a complex mixture of s o l u b l e  d e r i v e d fragments with s t r u c t u r e s previously carry  of the t o t a l  s i m i l a r to those d e t a i l e d  and w h i c h , at l e a s t under r e s t r i c t e d  a negative c h a r g e .  lignin-  pH c o n d i t i o n s ,  CHAPTER 3  MILL EFFLUENT COLOUR REMOVAL TECHNOLOGY  The R e l a t i v e Dominance of Hydrated Lime Most e a r l y e f f o r t s mill  wastes were simply  successful National  adaptations  Council  l a t e d to these  of the Paper Industry  The  f o r A i r and Stream  a l a r g e q u a n t i t y of m a t e r i a l r e -  investigations.  adsorbents were s c r e e n e d .  In a l l more than 30 The National  Council  mined that hydrated lime o f f e r e d the best prospect commercially  kraft  of methods known to be  i n removing c o l o u r from n a t u r a l w a t e r s .  Improvement has p u b l i s h e d  and  at removing c o l o u r from  v i a b l e process  f o r three  reasons  coagulants deterfor a  [18,19]:  1.  I t was r e a d i l y a v a i l a b l e and r e l a t i v e l y cheap.  2.  Recovery techniques were h i g h l y developed, i n f a c t , they were a v a i l a b l e a t v i r t u a l l y every m i l l .  3.  K r a f t m i l l o p e r a t i n g p e r s o n n e l possessed the background and knowledge necessary to operate the o v e r a l l p r o c e s s .  15  16  A v a r i e t y of problems have plagued lime processes  and  i n dewatering  produced by the a hydrated of  not w i l l i n g  Early d i f f i c u l t i e s  countered  filter  to accept  hydrated [1,4,8]  i t as the  only  [18,19] i n v o l v e d problems  the g e l a t i n o u s , l i m e - o r g a n i c  "minimum dose" p r o c e s s .  An  lime precoat on a vacuum f i l t e r precoat  of the  d e s p i t e some c o n s i d e r a b l e progress  the i n d u s t r y i s s t i l l answer.  adaption  c r a c k i n g problems  ensludge  attempt at using failed  [22,23].  The  because use of a  massive dose of lime to reduce the i n f l u e n c e of o r g a n i c matter on sludge the sludge  d e w a t e r a b i 1 i t y , coupled with  remains r e a c t i v e as an a l k a l i n e  the f a c t  reagent  scheme f o r i n c o r p o r a t i n g the c o l o u r removal process the r e c a u s t i c i z i n g studies to  and  mill  be f a v o u r a b l e  were  stage of l i q u o r r e c o v e r y .  p i l o t plant t r i a l s  that  l e d to a into  Laboratory  have proven, g e n e r a l l y ,  [ 2 4 ] ; c o l o u r removals of about 90 per  cent  obtained.  Other A l t e r n a t i v e s Activated  Carbon  Research and tinuing  p i l o t plant e f f o r t s  are p r e s e n t l y con-  i n the v a r i o u s adaptati ons of the lime p r o c e s s , as well  as i n other a r e a s . decolourization  has  The  a t t r a c t i v e n e s s of a c t i v a t e d  carbon  been enhanced by improved r e g e n e r a t i o n  17  techniques  and  by the development of markets f o r by-products  [25].  Aluminium and  Iron  Although e f f o r t s wastes using  Salts  to remove c o l o u r from pulp  alum as the primary coagulant have been  [2,18] to be non-competitive f o r commercial there has  been renewed i n t e r e s t  Davis [15] have r e p o r t e d and  ferric  and  total  liquors. and  on  organic  pH must be  rigidly  Clarke  recent work i n which  carbon from c h l o r i n a t i o n  reported  application,  area.  s a l t s were i n v e s t i g a t e d f o r the  They p o i n t out  and  aluminium  removal of c o l o u r stage  waste  that f o r optimum removal, dosage  controlled.  e l e c t r o l y t e a d d i t i v e s were not e f f e c t on  in t h i s  mill  removal, although  Silica  and  organic  found to have any  poly-  significant  they tended to promote b e t t e r  flocculation. Smith and and  ferric  Christman  [20] have i n v e s t i g a t e d alum  c h l o r i d e c o a g u l a t i o n of u n s p e c i f i e d k r a f t  sulfite  mill  results  of sedimentation  were r e p o r t e d  wastes.  In a d d i t i o n to pH  dosage d a t a , the  s t u d i e s , at optimum c o n d i t i o n s ,  f o r both the alum and  wastewater systems.  and  and  ferric  chioride-kraft  18  T e j e r a and of aluminium and and t o t a l wastes.  Davis  [21] have i n v e s t i g a t e d  ferric salts  o r g a n i c carbon They noted  from k r a f t m i l l coagulants  caustic  [15].  extraction  are about twelve  f o r t h i s waste than f o r the  wastes s t u d i e d e a r l i e r  use  f o r the removal of c o l o u r  that both  times more e f f e c t i v e  the  chlorination  In the three cases c i t e d  above,  the sludge r e s u l t i n g from the c o a g u l a t i o n process has been listed  as voluminous and, i n some c a s e s , s l o w - s e t t l i n g .  More work i s d e f i n i t e l y  needed i n order to determine  e f f i c i e n t means of circumventing t h i s  The  Grenoble  problem.  Process  R e c e n t l y , the Pulp and has  an  Paper I n s t i t u t e of Canada  p u b l i s h e d i n f o r m a t i o n [26] concerning t h e i r progress i n  developing the French  "Grenoble"  mercially viable a l t e r n a t i v e . weight amines are d i s s o l v e d octane, paraffin  oil,  process [42] i n t o a com-  In t h i s p r o c e s s , high  molecular  i n an o r g a n i c s o l v e n t ( e . g . i s o -  or kerosene) and  the  colour-bearing e f f l u e n t .  The  the c o l o u r e x t r a c t stream  i s regenerated with a s t r o n g l y  alkaline solution. of 90 to 99% and  COD,  The  two  a g i t a t e d with  phases are separated  method has been shown to be  removal of c o l o u r and  in a single stage.  30 to 75%  capable  removal of  The major problem  and  BOD  encountered  19  has been the formation of r e l a t i v e l y s t a b l e d i l u t e of the amine-solvent phase i n the p u r i f i e d resulting is  emulsions  aqueous u n d e r f l o w ,  i n many c a s e s , i n high chemical l o s s e s .  Figure 5  a schematic r e p r e s e n t a t i o n of the p r o c e s s .  Summary Despite the promise shown by the v a r i o u s  available  methods, no one method can be s a i d to have achieved a l e v e l of performance which  p r e c l u d e s research  Each method has advantages  economics  is likely  In f a c t , the p o s s i b i l i t y the bleach cycling  importance of i n d i v i d u a l  to leave scope f o r new methods.  of process change, e s p e c i a l l y i n  sequence, and the d e s i r a b i l i t y  of process waters  of increased r e -  to cut down on the o v e r a l l  of e f f l u e n t treatment ensure the maintenance assumption.  others.  and disadvantages and even with  f u r t h e r development the o v e r - r i d i n g situation  e f f o r t into  of this  cost  Acidified caustic extraction effluent PURSH CATION STAGE  Aqueous phase  REGENERATION _STAGE  Aqueous phase  Amine & Solvent  NaOH Solution Purified effluent to recycle o r sewer  Dark NaOH solution to pulp mill liquor cycle  FIGURE 5 Schematic Diagram of i h e Grenoble Process for Purification of Kraft Pulp M i l l Effluents  o  CHAPTER 4  ADSORPTIVE BUBBLE SEPARATION METHODS  General I n t e r e s t i n bubble s e p a r a t i o n techniques the body of l i t e r a t u r e on the s u b j e c t , has grown in the l a s t 10 to 15 y e a r s .  a n d , hence  tremendously  I t was not u n t i l r e c e n t l y ,  however, t h a t an e f f o r t was made to s t a n d a r d i z e the r a t h e r chaotic p r o l i f e r a t i o n rather d i f f e r e n t considered  of terminology  [27].  Because two  and o f t e n misnamed techniques  are to be  i n t h i s work, b r i e f coverage of the methods and  the nomenclature  i s necessary.  The C l a s s i f i c a t i o n  System  The proposed system of c l a s s i f i c a t i o n [28] i s outlined  i n Figure 6.  Adsorptive  Bubble S e p a r a t i o n  the g e n e r i c name given f o r a l l the t e c h n i q u e s . which  i n v o l v e a foam or a f r o t h  s e p a r a t i o n methods.  are r e f e r r e d  Methods i s Those methods  to as foam  Those methods which, i n the absence of  21  ADSORPTIVE SEPARATION  BUBBLE METHODS  •Monfoaming Adsorp. Bubble Separation  Foam Separation  Bubble Fractionation  Solvent Sublation  (Froth)  Ore Flotation  Flotation  Micro-  Macro-  Precipitate  Ion  Flotation  Flotation  Flotation  Flotation  Molecular Flotation  Adsorbing Colloid Flotation  FIGURE 6 Classification Scheme for the Various Adsorptive Bubble Separation Methods  „  23  foam, achieve a s e p a r a t i o n of the c o n s t i t u e n t s foaming a d s o r p t i v e separation  by v i r t u e of the s u r f a c e  are termed, q u i t e a p p r o p r i a t e l y , nonbubble s e p a r a t i o n  methods.  J u s t as a l l  techniques are based on d i f f e r e n c e s  so a l s o are the bubble s e p a r a t i o n the  activity  d i f f e r e n c e i s surface  methods.  activity.  In t h i s  a c t i v i t y has  a d d i t i v e , can be separated  from s o l u t i o n , or from one a n o t h e r , on t h i s The c o l l e c t i o n  case,  Thus s u r f a c e - a c t i v e ,  or s u r f a c e - i n a c t i v e substances where s u r f a c e been induced by an a p p r o p r i a t e  in properties,  of a s o l u t e  basis.  at the g a s - l i q u i d  f a c e , under e q u i l i b r i u m c o n d i t i o n s , can be d e s c r i b e d  inter-  by the  Gibbs equation [ 2 9 ] .  dy, = -RT I r . d ( l n a.)  where is  y-j i s the s u r f a c e  tension  of the i  (1)  t  h  component;  i t s a c t i v i t y ; R i s the gas c o n s t a n t ; T i s the  temperature; and compound  i  r..  i s the s u r f a c e  a|  absolute  excess c o n c e n t r a t i o n  of  at the i n t e r f a c e , i n u n i t s of mass per u n i t  area. The rendering face  of a s u r f a c e - i n a c t i v e component  a c t i v e , by a d d i t i o n of a s u i t a b l e c h e m i c a l , can be  sur-  24  achieved  i n a number o f ways  bonding,  and by v a r i o u s  ionic  attraction,  [ 3 0 ] : by c h e l a t i o n ,  physical  attractions,  electrostatic  attraction,  by  hydrogen  including  and  physical  adsorption.  Foam  Fractionation Foam  sorption which on  through  t o p o f t h e main  head  richer  foam  dissolved  illustrates general  liquid in and  i n the simple  Theoretical  distillation  In  The p r o c e s s  feed  usual  modes  the p r o c e s s ,  feed  o f the over-  them by  of delib-  batchwise or  mode o r i n a number o f h i g h e r  f o r continuous  i s analagous [28,31,32].  to the Figure  foam  fractionation.  i s affected  by t h e g a s - t o -  time  o f t h e foam  t h e amount o f r e f l u x  i t sposition,  a foam  is rela-  o r by r e l e a s e  to produce  can be d e v e l o p e d  residence  form  o f the components.  can be o p e r a t e d  [ 3 0 ] , the o p e r a t i o n ratio,  then  removal  by a g i t a t i o n  ad-  o f gas b u b b l e s  t h e foam  separation  t r e a t m e n t , which  methods, four  Since  material,  in a partial  gas b u t i t i s more  sparging.  The b u b b l e s  of l i q u i d .  can be p r o d u c e d  continuously, modes.  body  on t h e s e l e c t i v e  on t h e s u r f a c e  a solution.  i n the adsorbed  results  bubbles  erate  i s based  o f one o r more s o l u t e s  rise  tively  The  fractionation  position,  (internal  bubble  size,  7  and t h e l i q u i d and and  external) temperature.  25  Overflow-  " oo o o  o  0  Pool o o © o  0 0  Bottoms Gas SIMPLE  STRIPPER  o ° o aLO o o o o o o  Feed_  ENR1CHER  COMBINED  FIGURE 7 Four Modes for Continuous Foam Fractionation  26  Froth  Flotation Ore  Flotation  Froth f l o t a t i o n , as shown i n Figure 6 i n v o l v e s a l a r g e number of s u b d i v i s i o n s . separation. through [34].  Ore p a r t i c l e s  is a solid-solid  are separated from gangue  s e l e c t i v e attachment at the s u r f a c e of r i s i n g A very well developed  ture e x i s t s . still,  Ore f l o t a t i o n  bubble's  and s p e c i a l i z e d body of l i t e r a -  In f a c t , t h i s branch  of the technology i s  p r o b a b l y , much ahead of the other t e c h n i q u e s .  Low Gas-flow-rate  Methods  More i m p o r t a n t , f o r t h i s separation  s.tudy, are the new  c o n t r a s t [35] to these methods  ore f l o t a t i o n  utilize  lower  of the continuous  the g a s - l i q u i d  and foam  phase.  fractionation,  tall  columns or v i o l e n t  agita-  The s e p a r a t i o n occurs only at  i n t e r f a c e and not i n the foam phase.  and p r e c i p i t a t e  In  rates of gas flow and produce  s m a l l e r volumes of foam without  flotation  foam  techniques f o r removal of low c o n c e n t r a t i o n s of  s u r f a c e i n a c t i v e m a t e r i a l s from aqueous d i s p e r s i o n s .  tion  particles  flotation  are two such  Ion  techniques.  27  Ion  Flotation Sebba i n t r o d u c e d the f i r s t of the low  foam s e p a r a t i o n tion which  techniques i n 1959  [36].  Sebba's ion f l o t a -  i s based, i n p a r t , on work by Langmuir d e s c r i b e d the a d s o r p t i o n of metal  monolayer  of s t e a r i c a c i d .  gas-f1ow-rate  and S c h a e f e r [37]  ions onto an  In ion f l o t a t i o n  insoluble  a surfactant  i o n , or c o l l e c t o r , of o p p o s i t e charge to the ion to be r e moved i s added to the l a t t e r i n s t o i c h i o m e t r i c amounts and in such a way  that i t e x i s t s  micelle.  c o l l e c t o r r e a c t s with the i n o r g a n i c  organic  The  as a simple ion and not as a  [38] ion to form an i n s o l u b l e soap, which  to the s u r f a c e to form a f r o t h which insoluble  collapses  [36] or is raised  i n t o an  scum.  Precipitate  Flotation  Baarson and Ray were among the e a r l i e s t to r e p o r t on the p r e c i p i t a t e technique i n v o l v e s  flotation  precipitating  investigators  technique [ 3 9 ] .  the m a t e r i a l  removed before a d d i t i o n of the c o l l e c t o r .  which  This  i s to be  While t h i s i s  u s u a l l y accomplished by pH adjustment, the process i s not so restricted.  (Other techniques have been used, i n c l u d i n g  use of two h y d r o p h i l i c ions which s o l i d with a hydrophobic s u r f a c e  precipitate [42].)  the  to form a  Since the  condensed  28  phase i s a f l o c c u l e n t m a t e r i a l , the o v e r a l l material  charge on the  to be removed i s r e d u c e d , thereby r e q u i r i n g  tant to r e a c t only with ions on the outermost duce the hydrophobic s u r f a c e . less  l a y e r to p r o -  The net r e s u l t i s t h a t much  than the s t o i c h i o m e t r i c amounts of c o l l e c t o r  A d e t a i l e d s t u d y , i n which ion and p r e c i p i t a t e  several  flotation  l i s h e d by Rubin et al. [ 3 5 ] . available  surfac-  are r e q u i r e d .  of the v a r i a b l e s  of both  are compared, has been pubAdditional  information i s  in a l a t e r publication [40].  Other Froth  Flotation  Methods  Other s u b d i v i s i o n s m a c r o f 1 o t a t i o n , the removal f l o t a t i o n , the removal micro-organisms  of f r o t h  flotation  [28] i n c l u d e  of macroscopic p a r t i c l e s ; micro-  of m i c r o s c o p i c p a r t i c l e s ,  especially  or c o l l o i d s ; m o l e c u l a r f l o t a t i o n , the  removal  of s u r f a c e i n a c t i v e molecules through the use of a s u r f a c t a n t which y i e l d s  an i n s o l u b l e product and adsorbing c o l l o i d  f l o t a t i o n , the removal adsorbed on c o l l o i d a l  of d i s s o l v e d substances that are  first  particles.  Reported S e p a r a t i o n s A wide d i v e r s i t y of systems a d s o r p t i v e bubble methods.  In 1962  are s e p a r a b l e by the  Rubin and Gaden [3]  29  compiled a l i s t which a n i o n s , 21 f a t t y  i n c l u d e d 18 m e t a l s , 14 d y e s , 4 organic  acids and d e t e r g e n t s ,  enzymes, and some miscellaneous stances.  In 1968 Lemlich  which were reported pilation. in  i n o r g a n i c and organic  [28] compiled a l i s t  sub-  of a p p l i c a t i o n s  i n the time between h i s and Rubin's com-  A partial  summary of the types of systems d e t a i l e d  Lemlich's paper would  of various  22 p r o t e i n s and  include:  the s e p a r a t i o n  s u r f a c t a n t s ; the removal of various  from water  inorganic  ions such as orthophosphate, f 1 u o r o z i r c o n a t e , dichromate e t c . ; the removal the  of phenol and various  removal of v a r i o u s  other  phenolic  compounds;  pH i n d i c a t o r s and dyes; the removal  and, i n some c a s e s , s e p a r a t i o n s  of various  trace r a d i o a c t i v e  metal c a t i o n s , such as C s + , S r 2 + , Ce 2 ± ; the removal of a wide v a r i e t y of other metals from s o l u t i o n , e.g. f e r r o u s iron, ferric  i r o n , s i l v e r , lead and copper; the s e p a r a t i o n  of a v a r i e t y of heavy metal i o n s ; the a n a l y t i c t e s t s developed by u t i l i z i n g  the various  techniques;  the removal o f v a r i o u s  p r o t e i n s from s o l u t i o n ; the s e p a r a t i o n enzymes; the c o n c e n t r a t i o n removal of various  and removal  of various microorganisms; the  inorganic colloids  such as f e r r i c  s t a n n i c o x i d e , k a o l i n c l a y , and f e r r o c y a n i d e removal  of detergents  from municipal  of a wide v a r i e t y of organic industrial k r a f t black  oxide,  complexes; the  wastewater;  the removal  and m e t a l l i c p o l l u t a n t s from  wastewater; and the removal of t a l l liquor.  of v a r i o u s  o i l from  30  Summary That the foam s e p a r a t i o n methods o f f e r removal, p a r t i c u l a r l y liquid  i s very  evident  f o r small  promise f o r  amounts, of m a t e r i a l  from the f o r e g o i n g .  from  The methods, i n  such i n s t a n c e s , o f t e n provide  a means of s e p a r a t i o n which  might be i m p o s s i b l y  by the more c o n v e n t i o n a l  niques.  tech-  In any c a s e , the a d s o r p t i v e bubble s e p a r a t i o n  methods have gained neglected  difficult  enough s t a t u r e to prevent t h e i r  i n the s o l u t i o n  or p u r i f i c a t i o n  problems.  being  of most s e p a r a t i o n , c o n c e n t r a t i o n ,  CHAPTER 5  ION FLOTATION  I n t r o d u c t i on Despite the  f a c t that the  technique which was  ulti-  mately used i n t h i s work i s more c o r r e c t l y a s p e c i a l i z e d of p r e c i p i t a t e f l o t a t i o n , i t i s usual to i n c l u d e the  ion  really  flotation classification quite  publication  arbitrary  and  [42].  although P i n f o l d  would seem to p r e f e r  to c a l l  nique p r e c i p i t a t e f l o t a t i o n of the c o n s i s t e n t with the As  form, the tant ion  Sebba i n 1959  and  of o p p o s i t e charge to the  is possible  and  to attach  f o r the  itself  co-ordination.)  surfactant  to the The  i n a recent  present  f l o t a t i o n was  involves,  techremains  through the  the  ion  surfacconcen-  solution.  ( c o l l e c t o r ) to be  f r o t h formed by  first  in i t s simplest  amounts, of a  surface-inactive  31  [42],  ion that i s to be  subsequent passage of gas  (It  specification is  [28].  ion  a d d i t i o n , in s t o i c h i o m e t r i c  t r a t e d , and  by  [35]  the  i t under  " t h i r d " t y p e , he  e a r l i e r convention  mentioned p r e v i o u s l y ,  i n t r o d u c e d by  The  case  uncharged  (colligend)  passage of  gas  32  subsequently c o l l a p s e s collected  to produce a scum which contains the  i o n i n a c o n c e n t r a t e d form.  product i s known as a s u b l a t e .  This  c o l l e c t o r - c o l 1igend  N o r m a l l y , the f l o t a t i o n i s  performed i n very d i l u t e s o l u t i o n s  (as low as 10" 5 moles per  liter  Rising  i n c o l l e c t o r or c o l l i g e n d ) .  concentrations  can, however, lead to p r e c i p i t a t i o n o f the s u b l a t e the  before  passage of gas through the s o l u t i o n ; and, hence, to the  overlap  of nomenclature with p r e c i p i t a t e f l o t a t i o n .  ion f l o t a t i o n separation  p r o c e s s , indeed a l l the a d s o r p t i v e  bubble  methods, depends on that property of a molecule  known as s u r f a c e  Surface  The  activity.  Activity Ion  flotation  with the l i q u i d a highly  involves  of p r i n c i p a l  the l i q u i d - g a s i n t e r f a c e ,  i n t e r e s t being water.  p o l a r s u b s t a n c e , i s an e x c e p t i o n a l l y  for a s a l t - l i k e  or p o l a r s o l u t e .  molecule such as d o d e c a n o l ,  good  When a s u r f a c e  C12H25OH,  Water, solvent  active  which i s i n s o l u b l e or  hydrophobic at one end, but p o l a r or h y d r o p h i l i c at the other is  placed  i n water i t tends to o r i e n t i t s e l f so as to be  more s t a b l e for this  thermodynamically.  condition  One of the two p o s s i b i l i t i e s  i s f o r the h y d r o p h i l i c group to be accepted  i n t o the water and the hydrophobic group to be squeezed o u t , i n t o the a i r .  In f a c t , t h i s  property i s shown by a f a i r l y  33  extensive  group of substances and the a b i l i t y  at the a i r - w a t e r i n t e r f a c e  to concentrate  i s the b a s i s f o r what i s r e -  f e r r e d to as "surface a c t i v i t y . " the molecule i s u s u a l l y an a l k y l  The non-polar part o f or a l k y l a r y l  chain.  It  need not be so r e s t r i c t e d , however, and f1uorocarbons or other s u b s t i t u t e d hydrocarbons could a l s o form part of the non-polar s t r u c t u r e . it  I t must be of s u f f i c i e n t s i z e so t h a t  cannot be drawn i n t o and accommodated by the water  structure.  The p o l a r part of the molecule can be d e r i v e d  from a wide range of groups; the more common ones are hydroxyl; c a r b o x y l i c , sulphonic, phosphoric, groups; the t h i o l or t e r t i a r y  or other  acid  or mercaptan group; p r i m a r y , s e c o n d a r y ,  amines; and the  quaternary ammonium i o n .  For a complete d i s c u s s i o n of s u r f a c e a c t i v i t y any one  of a number o f e x c e l l e n t t e x t s on s u r f a c e  could be c o n s u l t e d terminated and  with  Schaefer  based.  [43,44].  mention of the o r i g i n a l  of  of aluminium i o n s .  of copper or 2 x IO" 8 moles per  Upon compressing the monolayers  s u r f a c t a n t between f l o a t i n g  barriers,  characteristic  The r e s u l t i n g  c o n t a i n the heavy metal s a l t .  tively  f i n d i n g s o f Langmuir  S t e a r i c a c i d was spread on water c o n t a i n i n g as l i t t l e  "crumple p a t t e r n s " developed. to  d i s c u s s i o n w i l l be  [ 3 7 ] , upon which i o n f l o t a t i o n was, i n p a r t ,  as 5 x 10" 8 moles per l i t e r liter  The present  chemistry  scum was shown  This property  of the r e l a -  f i x e d monolayer of s u r f a c t a n t to a t t r a c t o p p o s i t e l y  34  charged i o n s , or c o u n t e r i o n s , was r e p o r t e d with i t was not u n t i l  over twenty years  o b s e r v a t i o n was converted a workable  i n t e r e s t , but  had passed before the  from a l a b o r a t o r y c u r i o s i t y  into  process.  Mi eel 1es The  second way i n which s u r f a c t a n t ions can a t t a i n  a thermodynamically more s t a b l e s t a t e , p r o v i d i n g the concentration  is sufficiently  h i g h , i s by grouping t o g e t h e r so  t h a t the hydrocarbon chains  are c l o s e together  and thus  d i r e c t e d away from the water and the charged h y d r o p h i l i c ends are  i n contact with  i t . Such a grouping i s c a l l e d  a micelle.  A fundamental and d e t a i l e d treatment of the s u b j e c t can be obtained  by r e f e r r i n g  to the work of Shinoda [ 4 5 ] .  Sebba r e p e a t e d l y detrimental  s t a t e s [46] that m i c e l l e s have a  e f f e c t on i o n f l o t a t i o n  because s i n g l e  ions of  s u r f a c t a n t are r e q u i r e d i n order t h a t the amphipathic nature of the i o n can be u t i l i z e d . single  In a d d i t i o n , he s t a t e s  ions are needed to produce a f r o t h  stability.  of the r e q u i r e d  R e c e n t l y , Rubin et al. [35] have  Sebba's s t r e s s on the absence of m i c e l l e s .  questioned They have noted  that aged c o l l e c t o r s o l u t i o n s , which contained  m i c e l l e s , gave  the same removals as others which had been f r e s h l y Pinfold  that  prepared.  [42] has suggested t h a t the only d e l e t e r i o u s e f f e c t  of m i c e l l e s i s an i n c r e a s e d requirement f o r c o l l e c t o r .  35  The at which  the  specific  data  key  are  of  [42]  have shown  the  the  micelles  rate  These  to  r e s u l t s of  are  that  micelles  prove  the  to  that ion  the  to  flotation solvent;  ethyl  or  Because  have been  tion  can  take  removed  the  will,  at  ion  object the  their  one  [46] slow  rates  Although  few  suggests  that  process.  the  Others  very  rapidly.  some i m p o r t a n c e  present  to  the  of  dispute  considered  absence.  in  prepare material  the  lower  the  rapid  [46]  the  discussing  the  in a  such.as  to  take  suggests for  slightly —methyl,  acetone.  surfactant  before  impor-  surfactant  alcohols  the  surface  on  prudent  Sebba  i n ketones  i s very to  dispersed.  relative  ions  micelle  forma-  place.  Affecting  Stability  and  the  dissolve as  the  work.  a l c o h o l , or  Parameters  In  of  i n which  flotation  will  Other  such  propyl ion  way  i s to  polar  or  disintegrate  i t is s t i l l  ensure  simplest  be  present  of m i c e l l e s ,  precautions  formed  is a r e l a t i v e l y  Notwithstanding tance  i s probably  a v a i l a b l e , Sebba  formation  facts will  matter  of  of  the  flotation, the  same t i m e  Ion  Flotation  Froth persistent froths  technique  i s to  provide  support  produce f o r the  are  a  handicap,  a froth sublate  that and  36  break r e l a t i v e l y e a s i l y . of f r o t h  stability  references [43 ,44]. stability  are:  A detailed  treatment of the s u b j e c t  can be gained by c o n s u l t i n g Some of the f a c t o r s  the general  which a f f e c t  froth  the type of c o l l e c t o r ; the c o n c e n t r a t i o n  of the c o l l e c t o r and the s u b l a t e ; temperature; f l o t a t i o n characteristics;  The  and the pH of the s o l u t i o n .  Col 1 e c t o r - C o l 1 i g e n d  Although ratio  collector-col1igend  i s i m p o s s i b l e f o r the present work because of lack o f and m o l e c u l a r w e i g h t , or r a t h e r ,  d i s t r i b u t i o n o f m o l e c u l a r weights o f the c o l l i g e n d ,  factor in  Ratio  the e s t a b l i s h m e n t of the  knowledge of the composition the  i s worth n o t i n g .  G e n e r a l l y , s i n c e the s u b l a t e  i o n f l o t a t i o n i s a chemical  and  cell  colligend  must be at l e a s t  this  formed  compound, the r a t i o of c o l l e c t o r a s t o i c h i o m e t r i c one.  In a  c o n c e n t r a t e d system such as the one s t u d i e d i n t h i s work, in which the c o l l i g e n d this  is precipitated  before f l o t a t i o n ,  r a t i o can be expected to be c l o s e l y  adhered t o . I f ,  f o r a more d i l u t e system, the mode of c o l l e c t i o n depends on the  s u r f a c t a n t and c o l l i g e n d  ions meeting at a bubble  f a c e , the r e s i d e n c e time must be s u f f i c i e n t to allow In p r a c t i c e , excess c o l l e c t o r w i l l  surthis.  probably be needed.  37  I n t r o d u c t i o n of The  introduction  can  be  made i n one  the  course of the  r e p o r t e d f o r the [47]  to  results  Surfactant of  the  dose or by  a series  experiment.  Various  results  i n the  probably compatible because f o r two improved s t o i c h i o m e t r i c e f f i c i e n c y  sibility  i n s u f f i c i e n t froth  sion  of the  have been  s u b l a t e could be  production  change  flotation.  systems the of  system  of small doses during  two.methods, ranging from l i t t l e  a marked improvement [48] are  s u r f a c t a n t to the  and  expected to be  The  different and  the  hence  of  pos-  redisper-  different  magni t u d e s .  Choice of The  a  Collector  choice of c o l l e c t o r i s one  c u l t problems i n v o l v e d i n the because of the  ion  i n the  solution.  chosen a c c o r d i n g to the  most  to the  exact nature  G e n e r a l l y the following  of  collector  guidelines:  (i)  the c o l l e c t o r must, u s u a l l y , be o f o p p o s i t e charge t o the c o l l i g e n d i o n ;  (ii)  the f i n a l s u b l a t e should be i n s o l u b l e or only s l i g h t l y s o l u b l e i n water;  (iii)  diffi-  f l o t a t i o n technique, usually  i n s u f f i c i e n t knowledge as  colligend  should be  ion  of the  because of the u n d e s i r a b i l i t y o f the presence o f m i c e l l e s , the s h o r t e s t c h a i n c o l l e c t o r should be p r e f e r r e d ;  38  (iv)  the c o l l e c t o r must be i n e x p e n s i v e or at l e a s t compatible w i t h a recovery stage i f the process i s t o be a commercial application;  (v)  s i n c e the c o l l e c t o r w i l l be wasted from the p r o c e s s , i n at l e a s t s m a l l c o n c e n t r a t i o n s , the e f f l u e n t concent r a t i o n should have no d e l e t e r i o u s e f f e c t s on the environment.  Bubble S i z e and  Characteristics  There i s l i t t l e useful in  the  literature.  i n f o r m a t i o n on  this  It i s c l e a r however, that the  parameter  smallest  bubble s i z e i s d e s i r a b l e ,  and  thus a sparger of the  finest  porosity  The  practical  of  is  the  actual  should be  used.  work r e q u i r e d to produce the bubble s i z e i s r e l a t e d  s m a l l e r bubble.  to the  d i f f u s e r , other c o m p l i c a t i n g f a c t o r s tion  of bubble a r e a s .  Two  constraint,  such parameters are  the  d i f f u s e r contains a d i s t r i b u t i o n of pore s i z e s  the  solution  which w i l l  to be  a f f e c t s u r f a c e t e n s i o n and  of moderate  Air  calcula-  and  that that  contains a number of components, a f a c t  Photographic techniques are is  the  fact  the  usually  Although  pore diameter of prevent d i r e c t  course,  required  hence the [42]  i f the  bubble s i z e . correlation  sophistication.  Sparge Rate  In g e n e r a l , the technique i s d i v i d e d  p u b l i s h e d work on  i n t o two  the  ion f l o t a t i o n  schools of thought; Sebba et a l .  39  have used very small bubbles, slow gas flow r a t e s , and have produced small volumes of foam; Grieves et al. have used coarser bubbles, higher flow r a t e s , and have produced correspondingly greater volumes of foam.  While the larger  volume of foam would have the advantage of supporting the sublate more e f f e c t i v e l y and preventing redispersion, the separation would not be as good, nor the power or other operating costs as a t t r a c t i v e .  "*  The determining f a c t o r , of  course, would be the re-entry of the sublate into the bulk of the s o l u t i o n .  The optimum r a t e , therefore, would seem  to be that rate at which the bubbles just break through the  surface q u i e t l y , reducing re-entry to a minimum. It  would also be logical to assume that this c r i t e r i o n would be better met by Sebba's regime.  £H The nature of both the c o l l e c t o r and the colligend can  change markedly with pH.  Therefore, this parameter would  seem to be one of the most important ones that must be controlled.  Sebba [46] l i s t s a number of effects which might  occur due to a change in pH: (i)  t h e charge o f the c o l l i g e n d i o n , o r f o r t h a t m a t t e r , the s u r f a c t a n t i o n might be a l t e r e d ;  40  (ii)  the nature o f the p r o c e s s , and hence the s t o i c h i o m e t r i c e f f i c i e n c y , might be changed;  (iii)  the s t a b i l i t y o f the f r o t h , which supports the s u b l a t e , might be changed;  (iv)  the adjustment o f pH to extreme v a l u e s and, hence, the l a r g e a l t e r a t i o n of the i o n i c s t r e n g t h might suppress f l o t a t i o n ; and  (v)  Sebba [46]  the s o l u b i l i t y o f the s u b l a t e might be a f f e c t e d .  concludes that c o n t r o l  range than i s the  normal p r a c t i c e  of pH  w i t h i n a narrower  in i n d u s t r y  is  often  requi r e d .  Ionic The in  Strength  presence of neutral  a number of ways; they can  c o n c e n t r a t i o n ; they can with the  colligend  for  colligend  ion f l o t a t i o n  to 10" 3  moles per  has  they can  available  C o n c e n t r a t i o n of The  lower the  r e s u l t in the  i o n ; and  with competition f o r the  salts affects critical  process  micelle  formation of complexes provide the  colligend  collector.  Colligend  concentration  been reported  liter.  the  range most e f f e c t i v e  [42]  This range has  to be  about  10~ 5  been suggested  as  41  an area of p r a c t i c a l  application  per l i t e r the s o l u t i o n  because below 10~ 5 moles  i s so d i l u t e  that a s t a b l e foam might  not develop and above 10" 3 moles per l i t e r the amount of s u b l a t e to be handled and the p o s s i b i l i t y of complexes forming if  may make o p e r a t i o n d i f f i c u l t . flotation  tion  i s not proceeding  that a d i l u t i o n  well  Sebba [46] suggests  that  i n a concentrated  solu-  can o f t e n have a b e n e f i c i a l  effect.  Temperature Temperature e f f e c t s ignored  i n the l i t e r a t u r e .  have been almost  Although study  i s probably  w a r r a n t e d , no attempt w i l l  the present  work.  The  of t h i s  parameter  be made to do so i n  K i n e t i c s of Ion F l o t a t i o n K i n e t i c s t u d i e s of the process  neglected. of  completely  Grieves  the k i n e t i c s  have been  et al. [48] have p u b l i s h e d the r e s u l t s  of the f l o t a t i o n , i n a c e l l  p o r o s i t y f r i t , of  largely  with  a coarse-  F e F e ( C N ) 6 2 " " i o n s , using a c a t i o n i c  collector. Rubin et al. [35] found t h a t the foam tion  of C u 2 +  ions, in a cell  with  fractiona-  a fine-porosity  frit  using  42  sodium as  dodecylsulfate  a reversible f i r s t  as  a c o l l e c t o r could be  represented  order r e a c t i o n , v i z .  (2)  where  R'  and  time t and  M'  are  f r a c t i o n s of c o l l i g e n d removed at  under steady s t a t e Rubin [ 5 3 ] has  conditions,  used the  respectively.  equation,  log(M-R) = logA - mlogt  where tions the  m  and  A  are  constants and  removed at time  t  and  R  (3)  and  M  are  the  frac-  u l t i m a t e l y , r e s p e c t i v e l y , in  k i n e t i c study of a p r e c i p i t a t e f l o t a t i o n  system.  Summary Ion and  the  research  most of the derived  flotation  systems are  e f f o r t can  available  h a r d l y be  theoretical  from r e l a t i v e l y  few  relatively  classed  can  be  expected to y i e l d  novel  large; have been  However, a number  important and  process i s proceeding i n t o a stage where  activity  as  considerations  individuals.  of aspects have been i d e n t i f i e d as the  still  a workable  gradually  increasing technology.  CHAPTER 6  EXPERIMENTAL APPARATUS  Foam F r a c t i o n a t i o n Apparatus The a plastic  foam f r a c t i o n a t i o n  three inch (ID)  trials  four f o o t high  as shown s c h e m a t i c a l l y i n Figure 8. for  use  ation.  in a l l modes, batch The  liquid  and  l e v e l was  h y d r o s t a t i c head, overflow  39  liquid two  inches  The  system was  maintained  column.  designed fraction-  by means of a  Three one-inch  at 15 i n c h e s , 27  feed p o s i t i o n s were l o c a t e d opposite  the column bottom. i n t o two  column,  one  was  inches,  to the  streams; the f i r s t stream provided s u r f a c t a n t storage  stream passed through a rotameter and was column through a s p a r g e r .  The  ably c o n s t r u c t e d f i n e  mesh) s c r e e n .  (200  43  Two first  placed f o u r inches  Regulated l a b o r a t o r y a i r was  on top of the waste and  simple  diameter  from the bottom f l a n g e of the column.  foam removal ports and  split  cylindrical  c o n t i n u o u s , of foam  foam removal ports were provided and  were conducted i n  sparger  from  dried  and  pressure  tanks; the introduced  second to the  c o n s i s t e d of a s u i t The  pressurized  Head Tank  Rotameter]  Level Controller  M  -J  Valve  Filter  MXH>S  L—|XI—^  A  Waste  Surf. Tank  Tank  Vacuum  Gauge (^) Lab.air. Regulator  Drier  K7  J  Tank Manometer t  •  FIGURE 8 Schematic Diagram of the Foam Fractionation Experimental Apparatus  45  waste and s u r f a c t a n t tanks d e l i v e r e d t h e i r contents v i a rotameters to a mix-tank - head tank and subsequently to the column. filter  A d d i t i o n a l l y , the waste l i n e  upstream of the The  i n c l u d e d an  inline  rotameter.  foam removal  system  c o n s i s t e d of a s q u i r r e l  cage fan a i r blower which drew the foam from the column with a vacuum a s s i s t .  C o l l a p s e d foam flowed i n t o a seven  diameter c y l i n d r i c a l  v e s s e l , from which a DCL-Micro Pump  boosted i t to a head tank. lapsed foam flowed through liquid  inch  The  r e f l u x p o r t i o n of the  a rotameter to a three pronged  d i s t r i b u t o r atop the column.  All liquid  streams  were measured by r o t a m e t e r s , as mentioned; p r o v i s i o n e x i s t e d f o r timed sample The system was  col-  also  collection. q u i t e v e r s a t i l e with a wide a d j u s t -  ment of l i q u i d h e i g h t , foam h e i g h t , and hence r e t e n t i o n w i t h i n the l i m i t s  of the four f o o t column.  were ranged so that gas f l u x rates 3.4  scfm/sqft and  1.5  gpm/sqft were a t t a i n a b l e .  liquid  liquid  flow r a t i o s  retention  from 0.2  f l u x rates from 0.2  from 0.13  The  rotameters  s c f m / s q f t to gpm/sqft to  These values allowed gas-toto 17.0  times up to 120 minutes  scf/gal  and  to be s t u d i e d .  liquid According  to Rose and Sebald [31] these l e v e l s would cover the of p r a c t i c a l  value.  time,  range  46  Ion F l o t a t i o n  Apparatus  The  flotation  system, shown s c h e m a t i c a l l y i n F i g u r e  9, c o n s i s t e d of a s u i t a b l y air  stream  cell  connected  to a f l o t a t i o n  c o n s i s t e d of a l a r g e pyrex  bottom had been removed. in  r e g u l a t e d , d r i e d and measured  diameter  cell.  The f l o t a t i o n  glass b o t t l e from which the  The c e l l  was about 16 centimeters  at.the top and held a volume of 2.5  liters,  with room f o r a two and o n e - h a l f centimeter f r o t h bed. The bung.  d i f f u s e r was h e l d i n place by means of a rubber  The d i f f u s e r c o n s i s t e d of a 5.4 centimeter  Corning f r i t t e d  glass f i l t e r  of known pore s i z e .  diameter Two  dif-  f e r e n t d i f f u s e r s were a v a i l a b l e ; one with a nominal-maximum p o r o s i t y of 10-15 m i c r o n s , the other with a nominal-maximum p o r o s i t y of 4 - 5.5 microns.  The d i f f u s e r was  11.5 centimeters from the top of the v e s s e l . from 0.5 to 20 ml/sec of a i r were The ment.  excess  Provision  positioned Gas r a t e s o f  attainable.  foam was removed with a vacuum  for initial  stirring  pH-adjustment c h e m i c a l s , was a v a i l a b l e  o f the s u r f a c t a n t , or i n the form o f a  G.K. H e l l e r Co. Laboratory s t i r r e r  and c o n t r o l l e r .  for  A l l experiments  pH measurement was a l s o made.  a batch n a t u r e , using an experimental  arrange-  volume of 2.5  Provision were o f liters.  Speed  Controller  Vacuum  pH  Train  Meter  FLOTATION CELL  Lab. air  Diffuser Pressure Regulator  Gauge  Rubber  Bung  a  FIGURE 9 Schematic Diagram of the Ion Flotation Experimental Apparatus  48  CHAPTER 7  EXPERIMENTAL PROCEDURES  Foam F r a c t i o n a t i o n The  the  foam  c o n s t r u c t i o n of  taken.  Experiments  Products  a continuous  Mellon  as  a feed  amines  as  the s u r f a c t a n t .  and is  the  solution  An  out w i t h poured held was  raw  into  back not  to  adjusted.  s y s t e m was  using  Canadian  caustic  the  property  colour test  account  an  of t h i s  Forest  [ 4 9 ] was modified  stage  long  chain  of  prime  investigated test  procedure  A.  experimental Two  liters  run, of  the  raw  A p o r t i o n of the  colour test. The  under-  extraction  c o l o u r removal-was  column.  f o r the  feasible  o f two  effluent. the  and  flow  evaluate  was  one  i n c l u d e d i n Appendix Prior  first  process  to  either  standard  modified.  o p e r a t i o n was  fractionation  liquor  Because  batch  were p e r f o r m e d  Ltd. - Port  interest,  Operation  o b j e c t o f the  w h e t h e r o r not before  - Batch  resulting  The  pH  liquid  of  column was  effluent  were  raw  effluent  the  batch  h e i g h t was  washed then was  runs simply  49  r e c o r d e d , and of  12 inches was  a i r was was  remained the same f o r a l l r u n s . selected  and was  a l s o held c o n s t a n t .  adjusted to a pre-determined  injected.  This event was  A foam h e i g h t  r a t e and  The  the s u r f a c t a n t  r e c o g n i z e d as time z e r o .  F o l l o w i n g the b u i l d u p of the 12 inch head of foam, the a i r was  adjusted to a value which produced a reasonably  foam, with minimal i n t e r n a l was  coalescence.  removed from the s o l u t i o n  i n order to maintain  apparatus  was  the s u r f a c t a n t  the a i r f l o w r a t e was  the r e q u i r e d head of foam.  the foamate were c o l l e c t e d p e r i o d i c a l l y The  As  dry  increased  Samples of  for colour analyses.  shut down when a maximum a i r r a t e would  produce no f u r t h e r foam.  Samples of the r e s i d u a l  liquid  were then withdrawn. Colour analyses were performed and r e d u c t i o n , based on the bottoms or r e s i d u a l  per cent c o l o u r liquid,  was  computed.  Foam F r a c t i o n a t i o n  - Continuous  Operation  Following c o n s t r u c t i o n and flow system, a study was establishing  two  commenced with  the e f f e c t of the primary  r a t e , a i r flow r a t e , and first  t e s t i n g of the  continuous  an o b j e c t i v e of variables; liquid  foam height on c o l o u r removal.  experiments were performed using the  caustic  flow The  50  e x t r a c t i o n stage l i q u o r used i n the p r e v i o u s l y runs.  Subsequently i t was  combined or t o t a l  mill  from MacMi11an-Bloedel of the p o s s i b i l i t y  described  decided to s h i f t emphasis  e f f l u e n t and a sample was  obtained  Limited's Harmac D i v i s i o n .  of biological  to the  Because  a c t i o n , the e f f l u e n t  was  s t o r e d at a temperature of 4° c e n t i g r a d e . S u r f a c t a n t s o l u t i o n was  prepared to the r e q u i r e d  c o n c e n t r a t i o n by d i s s o l v i n g weighed q u a n t i t i e s of the s u r f a c t a n t i n d i s t i l l e d water.  Rotameter  to the p r e - s e l e c t e d v a l u e s , l i q u i d  s e t t i n g s were a d j u s t e d  height was  drawoff port (and hence foam h e i g h t ) was system was  s t a r t e d up.  The system was  s e t , the foam  s e l e c t e d , and the  allowed about s i x  r e s i d e n c e times to come to a steady s t a t e before the set of samples was  taken from the raw  f l o w , and the foamate  streams.  e f f l u e n t , the under-  A l l flows were checked by  timing a measured volume and a l i q u i d A second s e t of samples was  first  balance was  performed.  taken and the system was  shut  down. Colour analyses were performed and changes were expressed as enrichment, X /X_ , concentration  r e d u c t i o n , X^/X^ B  and as bottoms  . The f r a c t i o n a l  c o l o u r re-  F  moval from the feed stream was  [1 - B/F  • X_/X_] . D  meaning of the symbols  concentration  is outlined  i n the  F  The  Nomenclature.  51  Ion  Flotation  - General  All  ion f l o t a t i o n experiments were performed as  batch runs i n the simple apparatus d e t a i l e d The wastewater Canadian  used, i n a l l but the f i r s t  erated room which was centigrade.  Two  The waste was  l o t s of about 100 l i t e r s  flotation rpm  cell.  liters  The s t i r r e r was  prepared by d i s s o l v i n g  cyldimethylammonium Co.)  bromide  experi-  adjusted  were poured i n t o the  controlled  at a speed of made.  (unless otherwise s t a t e d )  a weighed q u a n t i t y of didode(obtained from Eastman Kodak  i n 50 ml of low water content (0.10%) methanol.  c o l l e c t o r s o l u t i o n was Mixing was the  P r i o r to each  and pH adjustment, i f n e c e s s a r y , was The c o l l e c t o r s o l u t i o n  was  were used over  r u n , the temperature of the e f f l u e n t was  to 22° c e n t i g r a d e , then 2.45  200  stored in a r e f r i g -  maintained at a temperature of 4 °  course of the four month s t u d y .  mental  three r u n s , was  Forest Products L i m i t e d - Port Mellon D i v i s i o n  combined m i l l e f f l u e n t .  the  i n Chapter 6.  added, s l o w l y , to the s t i r r e d  The effluent.  continued f o r a predetermined length of t i m e ,  e x p i r y of which  signalled  the removal  of the s t i r r e r , the  r e l e a s e of f l o t a t i o n a i r i n t o the c e l l , and time z e r o . A series  of 29 f l o t a t i o n runs was  order to e v a l u a t e both f i l t e r e d  performed i n  c o l o u r removal  and t o t a l  52  f l o a t a b l e s o l i ds  recovery  Parameters s t u d i e d (i) (11) (iii) (iv) (v) (vi)  under a wide v a r i e t y of  included:  surfactant  or collector  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 , s u r f a c t a n t premix time, a i r sparge r a t e , and i o n i c s t r e n g t h and c o l l e c t o r charge.  These  (vii) (viii) (ix) (x)  Time and  dosage,  pH,  In a d d i t i o n , a number of other surveyed.  conditions.  colligend-  areas of i n t e r e s t were b r i e f l y  included:  biological foam  oxygen  demand r e m o v a l ,  volume,  collector micelle the effect  formation,  o f methanol,  (xi)  effluent  a g i n g , and t h e  (xii)  kinetics  of the f l o t a t i o n recovery.  scope of the  p r o j e c t d i d not  following: (i) (ii) (iii)  temperature  effects,  choice of collector, or froth  stability.  permit study of  the  53  Analytical  Tests and Procedures Colour Determination As mentioned, the m o d i f i e d c o l o u r procedure i s  fully  covered i n Appendix A, so i t need not be r e p o r t e d h e r e .  Biological  Oxygen Demand  The B0D5 t e s t s were performed Columbia  Research  Council  without m o d i f i c a t i o n .  at the B r i t i s h  and t h e i r t e s t procedure was  used,  The C o u n c i l ' s procedures f o l l o w a  standard B0D5 t e s t procedure [ 4 9 ] . An a c c l i m a t i z e d the  kraft mill  seed i s maintained by  C o u n c i l , and i t was used i n both s e r i e s  of t e s t s .  pH Measurement and C a l i b r a t i o n The pH measurements and adjustments were with a Corning Model 10, pH meter. 4.00,  performed  B u f f e r s o l u t i o n s of pH  7.00, and 10.0 were used i n the ranges  5.5 to 8.5, and 8.5 to 12.0 r e s p e c t i v e l y .  1.5 to 5.5,  The instrument  was s t a n d a r d i z e d before a s e t of readings was taken; was n e g l i g i b l e .  drift  54  S t i r r e r Speed  Calibration  The H e l l e r motor c o n t r o l l e r was a Jones Motrola Corp. hand tachometer. showed that the c a l i b r a t i o n was  calibrated  Repeated  accurate and  using  tests  reproducible  to w i t h i n 5 to 10 per c e n t .  Floatable  S o l i d s Determination  The s o l i d s t e s t s  performed on the system were  done according to the standard t e s t f o r "Residue on Evaporation"  [49].  Total  system i n which  f l o a t a b l e s o l i d s was  dosage was  taken to be, f o r a  stoichiometric,  the  difference  between the "Residue on E v a p o r a t i o n " of the s o l u t i o n time zero minus 15 seconds  (when the i n i t i a l  at  sample was  taken  i n a l l cases) and the "Residue on E v a p o r a t i o n " of a f i l t e r e d sample which was  taken a f t e r the run was  completed.  c a s e s , the completion of the f l o t a t i o n run was by the f a c t that a s t a b l e The  filters  fritted  froth  In a l l  signalled  could no longer be  produced.  used were C o r n i n g , Gooch Type with a " F i n e "  d i s c and were capable of removing, c o m p l e t e l y , the  t u r b i d i t y of the s o l u t i o n , p a r t i a l removals of f l o a t a b l e s o l i d s were judged on the same b a s i s . Tests were performed with 50 ml a l i q u o t s tion  i n order to get a s u f f i c i e n t amount of s o l i d s  of s o l u f o r an  55  accurate weight. 2603 balance  on a S a r t o r i u s  and were accurate to the nearest 0.4  Cleaning The in  Weights were taken  greasy, fine  precipitate  the process n e c e s s i t a t e d s p e c i a l i z e d  a flotation  mg.  Procedures  extremely  g l a s s w a r e , and  Model  flotation  f r i t t e d ware c l e a n i n g p r o c e d u r e s .  r u n , the f l o t a t i o n  cell  and  cell, Following  the a s s o c i a t e d  equipment were scoured with methanol and Laboratory glassware was  produced  r i n s e d with water.  scoured twice with methanol, then  washed i n a soap-water s o l u t i o n , f o l l o w e d by r i n s i n g l a r g e volumes of water.  Glassware, used i n w e i g h i n g ,  with was  a d d i t i o n a l l y d r i e d by c l o t h , placed i n a 205° F oven f o r 15 minutes, then allowed to cool dessicator.  f o r 30 minutes i n a  F r i t t e d ware, the d i f f u s e r s  were soaked o v e r n i g h t i n a chromic solution  and the  acid-sulfuric  and then backwashed to whiteness  filters, acid  with tap water.  E l e c t r o p h o r e t i c M o b i l i t y and/or Zeta  Potential  Meas urement E l e c t r o p h o r e t i c m o b i l i t y was Meter.  Procedures  are o u t l i n e d  the manufacturer, Zeta-Meter  measured with a Zeta-  i n the o p e r a t i n g manual of  Inc.  The  system c o n s i s t s of an  56  i l l u m i n a t o r , an e l e c t r o p h o r e s i s control tion  unit.  A b i n o c u l a r microscope  of the p a r t i c l e s .  procedure  Additional  was used  f o r observa-  i n f o r m a t i o n and the  can be gained by c o n s u l t i n g the manual [ 5 0 ] .  Rotameter  Calibration  The manufacturer's for l i q u i d  c e l l , and an e l e c t r i c a l  calibration  curves were  checked  s e r v i c e by timing a measured volume of the f l u i d  in q u e s t i o n .  Since a number of checks y i e l d e d  no departure  from the s u p p l i e d c u r v e s , no f u r t h e r c a l i b r a t i o n was  under-  taken. Since c a l i b r a t i o n  curves were u n a v a i l a b l e f o r a i r  s e r v i c e they were p r e p a r e d , as needed, using a Wet Test Meter manufactured by P r e c i s i o n S c i e n t i f i c U.S.A.  Co., C h i c a g o ,  CHAPTER 8  RESULTS AND DISCUSSION  General - the Effluent Previously, i t was mentioned  that the effluent  behaves, in a sense, as a pH indicator because i t s colour changes with pH.  Figures 10 and 11 i l l u s t r a t e this property  for a f i r s t caustic extraction stage and a total or combined mill  effluent. Note that the f a m i l i a r "S" shape of the  colour versus pH curve is much more noticeable for the more d i l u t e , total mill  effluent.  In Chapter 7, i t was noted that the effluent was stored at a temperature of 4° centigrade. This precaution was necessary because the e f f l u e n t , p a r t i c u l a r l y the total mill ture.  variety, i s very active b i o l o g i c a l l y , at room temperaAppreciable b i o l o g i c a l action was observed in samples  which were l e f t at room temperature in about 5 to 6 days. In addition, although i t proved to be a much slower process, some lightening in colour was noted in samples room temperature.  stored at  Test results revealed no such colour  57  tn  FIGURE 11 Colour versus pH for Total Mill Effluent  60  change and no a p p r e c i a b l e b i o l o g i c a l  a c t i o n i n the e f f l u e n t  which had been s t o r e d at 4° c e n t i g r a d e .  Foam F r a c t i o n a t i o n (Batch) Table operation. used.  Results  1 illustrates  the r e s u l t s of t y p i c a l  Note that i n the f i r s t  run no s u r f a c t a n t was  With maximum a e r a t i o n , a foam height of only  inches was o b t a i n e d .  compared with  t a i n s the r e s i n  three  This r e s u l t i s to be expected because  the 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 has l i t t l e activity  batch  the t o t a l  mill  natural  surface  e f f l u e n t , which  acids from the p u l p i n g o p e r a t i o n .  con-  No c o l o u r  removal i s reported because the foam could not be made to r i s e to the removal  port.  With a dosage of 1 x IO" 3 moles per l i t e r octylamine  hydrochloride  cent were r e a l i z e d . obtained ing  colour reductions  Note that the h i g h e s t  o f n-  o f 22 and 35 per r e d u c t i o n was  at an i n c r e a s e d a i r sparge r a t e and a longer  foam-  time. The  r e s u l t s of the batch  runs , while  not s p e c t a c u l a r ,  seemed to i n d i c a t e that the c o n s t r u c t i o n of a continuous flow system was warranted. made with  first  As n o t e d , a l l batch  c a u s t i c e x t r a c t i o n stage  runs were  effluent.  This  fact  61  Table 1 Typical  Batch Operation  Foam F r a c t i o n a t i o n  Data  1  2  1st Caus t i c Extraction Stage  1st C a u s t i c Extraction Stage  11.15  11.15  11.15  Column pH  11.15  11.15  11.15  Surfactant C o n c e n t r a t i on  None  n-oamine HCL* 1 x IO-3 M  n-oamine HCL* 1 x 10" 3 M  RUN  NO.  Effluent Type  Original  pH  Liquid Volume  1950 ml  Liquid Hei ght  13 inches  Foam Hei ght  3 inches  Foami ng Time A i r Sparge Rate start finish  *  1950  1st C a u s t i c "* Extraction Stage  1950  13 inches  13 inches  12  12 inches  inches  25 min.  70 min.  102.5 cucm/sec 102.5 cucm/sec  13.3 cm 3 /sec 61.5 cm 3 /sec  aged s u r f a c t a n t n-octylamine  3  hydrochloride  150 min.  22.7 cm 3 /sec 71 .2 cm 3 /sec (CONTINUED)  62  Table  RUN  NO,  1  1  (continued)  2  3  Feed C o l o u r (Pt-Co U n i t s )  -  13,400  13,000  Bottoms C o l o u r (Pt-Co U n i t s )  -  10 ,500  8,500  % reduction in Bottoms C o l o u r  -  22%  35%  63  is  especially significant  i n view of l a t e r r e s u l t s  the actual mechanism of the removal  Foam F r a c t i o n a t i o n  (Continuous)  concerning  process.  Results  Despite some c o n s i d e r a b l e e f f o r t i n p e r f e c t i n g the equipment from a process continuous stages.  s t a n d p o i n t , the study o f the  flow system never r e a l l y  Table 2 i l l u s t r a t e s  experimental  runs.  formed with f i r s t  got past the i n i t i a l  four t y p i c a l  The e a r l y runs  mode  (No.'s 1 & 2) were per-  caustic extraction  surfactant solutions  continuous  stage e f f l u e n t and aged  ( i n t h a t they had been made up, i n w a t e r ,  some time p r e v i o u s l y ) of n-dodecy1 amine h y d r o c h l o r i d e .  Be-  cause of the r a t h e r low c o l o u r removals and the d i f f i c u l t y i n observing what was happening i n t h i s h i g h l y concentrated s o l u t i o n , a sample of t o t a l  mill  e f f l u e n t was o b t a i n e d .  O r i g i n a l l y , i t was a n t i c i p a t e d t h a t the l e s s  concentrated  s o l u t i o n might lead to a b e t t e r performance, a f a c t which is  quite often c i t e d  happened proved trials of  i n the l i t e r a t u r e  [46].  to be much more d r a m a t i c .  (No.'s 3 and 4 - Table 2 ) , with  1 x IO" 3 moles per l i t e r ,  t i o n , compared with  What a c t u a l l y  The f i r s t  a n-octylamine  two dosage  r e v e a l e d a much b e t t e r s e p a r a -  the previous r e s u l t s .  A third  t r i a l , with  a d i d o d e c y l d i m e t h y l ammonium bromide dosage of 1 x 10" 3 moles  Table 2 Typi c a l Continuous O p e r a t i o n  RUN  NO.  E f f l u e n t Type  Column pH  Surfactant C o n c e n t r a t i on  Aerated L i q u i d Volume  Foam  Height  Combined Feed Flow (F)  Foam F r a c t i o n a t i o n  1  2  Port Mellon 1st C.E. Stage  Port Mellon 1 s t . C.E. stage  11.2  2.04  3 Harmac total mill  11 .2  n-ddamine HCL* 1 x 10" 4 M  I  ic  n-ddamine HCL 1 x 10'11 M  2.04  Data  I  12 inches  12 inches  55 ml/min  27.5 ml/min  aged s u r f a c t a n t n-dodecylamine h y d r o c h l o r i d e  Harmac total mil 1  4.8  4.8  Octylamine- HCL 10 x IO - " M  Octylamine HCL 10 x 1 0" ** M  2.04 Z  2.04  I  12 inches  24 inches  105 ml/min  58 ml/min (CONTINUED)  Table 2 (continued)  RUN  1  NO,  Residence Time  Bottoms Flow (B)  Recycle  37 min  Colour (Pt-Co) Bottoms ( X J  19 min  35 min  25 ml/min  61.5 ml/mi n  46 ml/min  -  -  -  2 ml/min  57.6 cm 3 /sec  44.2 cm 3 /sec  27.9 cm3/min  42.6  Colour (Pt-Co) Combined Feed  74 min  3  49 ml/min  (R)  A i r Flow  2  cm 3 /sec  10,100  10,100  2,100  2,100  9,600  9,200  1 ,170  1 ,040  tt  (CONTINUED)  Table 2 (continued)  RUN  1  NO,  2  3  4  Removal  -S- x ~ I *J 1  F  100%  16%  18 %  68 %  61 %  X  Remarks  Some coalescence of foam ( i . e . internal reflux at t h i s a i r r a t e )  Coales cence minimal n o t i c e a precipitate (?) adhering to w a l l s of column at top of foam  Large part of removal j u s t due to bulk r e moval of l i q u i d  Note s m a l l e r foam volume  cn cn  67  per l i t e r ,  resulted  in a v i r t u a l l y colourless  removal process was  solution.  The  not, however, a result of the presumed  foam fractionation technique.  It was  very c l e a r l y a coagu-  l a t i o n , with the quaternary ammonium surfactant the coagulating chemical.  In retrospect,  acting  as  i t became clear  that the foam fractionation technique probably never had operated.  The  intense colour of the more highly  caustic extraction  effluent had  In f a c t , a precipitate had but  i t s significance had  Table 2).  the walls of the time, i t was which was  concentrated  masked the actual mechanism.  been noticed  in the e a r l i e r runs  not been appreciated (see  This precipitate had  run 2 -  been observed adhering to  column near the foam removal port.  assumed to be very fine particulate  derived from the raw Thus, the i n i t i a l  ^  At  that  material  effluent.  results of the continuous foam  fractionation revealed, without a doubt, that the mechanism was  not as supposed.  s u l t s , the  As a direct consequence of these re-  research e f f o r t was  shifted to the ion f l o t a t i o n  technique.  Ion  Flotation Results General Preliminary t r i a l s established  the mechanism of  removal process as ion f l o t a t i o n , or as previously  the  mentioned,  68  precipitate  flotation  col 1 e c t o r - c o l 1igend  of the t h i r d  product was  type.  The  s u b l a t e or  formed immediately  the a d d i t i o n of the c o l l e c t o r to the f l o t a t i o n the passage of a i r through froth  formation and  scum was  the s o l u t i o n  its partial  and  removed.  p a r t i c l e s were, i n most c a s e s , not v i s i b l e until  i t collapsed.  t i o n of t h i s  experiments.  to 29 were performed with  that an a l k y l more s u i t a b l e . situation  effluent.  Port Mellon  i n the  froth  total  However, the extremely  mill  2.5  effluent.  choice i n have been  poor chemical  foam f r a c t i o n a t i o n  2.45  liters  supply  available  as  experiments made  In a l l but three experimental  Combined with  through  didodecyldimethyl  and the f a c t that the s u r f a c t a n t was  approximately  to 3 were  Runs 4  would l i k e l y  4, 5, and 6, the s u r f a c t a n t was  methanol. was  mill  14-carbon molecule  the only c h o i c e .  runs  sublate  It i s r a t h e r an unfortunate  a r e s u l t of the e a r l i e r it  The  Runs 1 through  s u r f a c t a n t used, i n a l l c a s e s , was  ammonium bromide.  insoluble  Appendix B provides a summary of  performed with Harmac t o t a l  The  With  Figure 12 i s a diagrammatic r e p r e s e n t a -  phenomenon.  the ion f l o t a t i o n  cell.  the subsequent  c o l l a p s e , the  buoyed to the s u r f a c e and  following  dissolved  runs,  i n 50 ml  of e f f l u e n t , the  of  solution  mole per cent methanol, a value well  below that which would produce s o l u b i 1 i s a t i o n  effects  [51].  69  Scum  collecting  • + _»--_Hydrocarbon c h a i n o  -  FIGURE 12 Schematic Drawing of Scum Formation  70  The  Col 1ector-Col 1igend  Ratio  The  unknown composition  and  r a t h e r the  unknown d i s t r i b u t i o n  the c o l l i g e n d make c a l c u l a t i o n mole r a t i o  impossible.  formed with can be  total  considered  mill  is  of molecular of the  e f f l u e n t , the  colligend  per l i t e r  ratio.  of s u r f a c t a n t was  sufficient  about 2100  u n i t s of c o l o u r per l i t e r .  r a t i o of about 2.8  x 10" 5  ppm  on  13  surfactant  to a f f e c t  moles  virtually The  original  the Pt-Co s c a l e or  Thus a col 1 e c t o r - c o l 1 i g e n d  moles of s u r f a c t a n t per  100  units  e f f l u e n t colour is required. The  data  from experimental  used i n p l o t t i n g  The  s u r f a c t a n t dosage of 1.0  loaded  foam was  Figure 13 were e x t r a c t e d  runs in which a l l parameters except dosage  were maintained c o n s t a n t . low  and  Figure  i l l u s t r a t e d , a dosage of about 6 x 10'1*  e f f l u e n t c o l o u r was  of  concentration  the e f f l u e n t c o l o u r removed  complete removal of the chromophoric m a t e r i a l .  2100  per-  to have been approximately constant  a p l o t of per cent c o l o u r removal versus As  w e i g h t s , of  collector-colligend  used as an approximate e q u i v a l e n t  dosage.  w e i g h t , or  However, s i n c e a l l runs were  the c o l l e c t o r dosage d i v i d e d by can be  molecular  f a c t that even at the  x 10 _lt  moles per l i t e r  produced, i n d i c a t e s that the s u b l a t e  remains s u r f a c e a c t i v e .  This deduction  very a stable, probably  i s supported by  the  71  FIGURE 13 Percent Colour Removal versus Surfactant Dosage  72  assumption that the dosage i s very much below what could be considered  a s t o i c h i o m e t r i c one and t h e r e f o r e uncombined  s u r f a c t a n t molecules probably  do not e x i s t .  t e s t , by d e f i n i t i o n , i n v o l v e s f i l t r a t i o n remove a l l traces of the t u r b i d i t y flotation how well  recovery  the process  works.  or the s u b l a t e , the  as a f u n c t i o n of s u r f a c t a n t  Note that a maximum recovery  factant concentration  i s reached at a dosage  and t h a t an i n c r e a s e i n s u r -  to 8.0 x IO"1* moles per l i t e r  causes a decreased r e c o v e r y . recovery  of the samples to  A c c o r d i n g l y , Figure 14 shows  of 6.0 x IO"1* moles per l i t e r  flotation  results  has been widely  explains this  actually  A complete summary o f the  i s contained  i n Appendix C.  That the presence of excess c o l l e c t o r w i l l flotation  the c o l o u r  i s perhaps a more v a l i d measurement of  the per cent f l o t a t i o n recovery dosage.  Since  reported  [51,48].  phenomenon by suggesting  often  inhibit  P i n f o l d [42]  t h a t the s u b l a t e  parti cles . . . probably become coated with a layer of surfactant as the concentration of the latter is raised. As this layer will be arranged with the long-chain groups of the collector in contact with the hydrophobic surface of the precipitate and the ionic groups oriented towards the water, the arrangement renders the particles more hydrophilic, and they float less easily.  F I G U R E 14 Percent Flotation R e c o v e r y v e r s u s S u r f a c t a n t D o s a g e  74  In a d d i t i o n , the i n c r e a s e d to a competition for  a place  the  flotation  amount of c o l l e c t o r could  between the s u b l a t e  and the s u r f a c t a n t  on the bubble s u r f a c e , thereby f u r t h e r  ions  impairing  efficiency.  Collector Micelle As  lead  Formation  noted, m i c e l l e formation was i n h i b i t e d i n the  standard way, by d i s s o l v i n g the s u r f a c t a n t  i n methanol.  Three r u n s , numbers 4, 5, and 6, were performed i n which no methanol was used.  Except f o r the f a c t that  pre-mix time (up to 30 minutes) was r e q u i r e d  a much  longer  i n order to  d i s s o l v e the s u r f a c t a n t , the runs were not n o t i c e a b l y f e r e n t from other e q u i v a l e n t  dif-  ones i n which methanol was  used. Based on Shinoda's data [45] the c r i t i c a l concentration is  (CMC) f o r d i d o d e c y l d i m e t h y l  1.8 x 10 _If moles per l i t e r .  micelle  ammonium c h l o r i d e  Since the e f f e c t o f a d i f -  f e r e n t h y d r o p h i l i c group i s not l a r g e , the CMC of the s u r f a c t a n t used, d i d o d e c y l d i m e t h y l expected to be very nearly  ammonium bromide, can be  1.8 x IO-1* moles per l i t e r .  A  number of f a c t o r s might, however, b r i n g about a change i n the  CMC; added s a l t s  such as NaCl would lower the CMC and  added methanol would tend to r a i s e the CMC of the s u r f a c t a n t in  question.  75  Based on the r e s u l t s of the three runs d e s c r i b e d  experimental  above and upon the f a c t that the s u b l a t e i s  formed immediately, and the f r e e s u r f a c t a n t  concentration  t h e r e f o r e g r e a t l y reduced i n a matter of l e s s c o l l e c t o r m i c e l l e formation This  than a second,  was not considered  to be a f a c t o r .  i s thought to be true d e s p i t e the f a c t that the dosages  used would o r d i n a r i l y  r e s u l t i n m i c e l l e formation  i n an  aqueous s o l u t i o n . The has  question  of m i c e l l e formation  not been s a t i s f a c t o r i l y  resolved.  i n the s u b l a t e  Perhaps the s l i g h t l y  l e s s than complete f l o t a t i o n  recovery  of s u b l a t e m i c e l l e formation  and a corresponding  i n the s u r f a c e  activity  was due to some s o r t reduction  of the p r e c i p i t a t e .  Si  As  n o t e d , pH can have a marked e f f e c t on the f l o -  t a t i o n system because of the l a r g e number o f ways i n which it  can a f f e c t the nature of both the c o l l e c t o r and the  colligend.  On the b a s i s of c o l o u r removal, i . e . s u b l a t e  p r e c i p i t a t e d and e i t h e r removed by the f l o t a t i o n by the subsequent f i l t e r i n g  of the a n a l y t i c a l  pH appears to be unimportant.  Figure  However, on the b a s i s of f l o t a t i o n  process or  test procedure,  15 i l l u s t r a t e s  recovery  this.  of the s u b l a t e ,  76  77  pH c o n t r o l this  proved  point.  pH o f 5.1.  to be very c r i t i c a l .  Figure 16 i l l u s t r a t e s  Note that the best recovery i s obtained at a The recovery at 4.5, while u l t i m a t e l y  a s i m i l a r level  has a c o n s i d e r a b l y slower  rate of removal.  At pH 5.6 recovery i s a l s o s i g n i f i c a n t l y worse. these experimental  runs were performed with  dosage of 8.0 x I O - 4 moles per l i t e r , h i g h e r than the optimum. totally values  suppressed  likely  Note that  a surfactant  a dosage  F l o t a t i o n was found  slightly to be almost  when the pH was adjusted to extreme  ( r e f e r to experimental The  reaching  interpretation  runs 9 and 10, Appendix B ) . of the previous r e s u l t s  r e l a t e d to the charge which the c o l l i g e n d  i s very  possesses.  While i t might be p o s s i b l e to measure the e l e c t r o p h o r e t i c m o b i l i t y of the l a r g e r molecular fragments which make up the chromophoric f r a c t i o n with  the help of l a s e r o p t i c s , i t  was not p o s s i b l e to do so with the a v a i l a b l e The  zeta potential  was measured, however, as a f u n c t i o n of  pH, f o r various f l o t a t i o n  cell  were d e r i v e d from experimental  s o l u t i ons. runs  dosage of 8 x 10 _ I t moles per l i t e r . results  equipment.  of such measurements.  A l l solutions  performed at a s u r f a c t a n t Figure 17 d e t a i l s the  Thus, assuming t h a t the a d d i -  t i o n of the same 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 t a n t would a l t e r the p a r t i c l e  charge by a s i m i l a r amount, at l e a s t i n  10  20  30  40  50  TIME ( MINUTES) FIGURE 16 Percent Flotation Recovery at Various pH Values  60  70  80  79  FIGURE..1.7 Zeta Potential versus pH for Flotation Cell Surfactant  Dosage  8x10" fV1oles/Liter 4  Solution,  80  the region of pH 4 to pH 10, then the o r i g i n a l  zeta  potential  might be expected to have been more negative by a constant increment.  Thus, i n the region of optimum f l o t a t i o n , the  c o l l i g e n d needs l e s s s u r f a c t a n t to s a t i s f y e l e c t r i c a l trality.  T h e r e f o r e the q u a n t i t y of s u r f a c t a n t r e q u i r e d would  be l e s s and  p r e c i s e l y the r i g h t amount of s u r f a c t a n t would  be a v a i l a b l e to produce dispersion  a stable froth  of the s u b l a t e .  and so prevent re-  In the lower pH range  excess  a v a i l a b l e s u r f a c t a n t could a l s o have a d e l e t e r i o u s The  neu-  effect.  recovery rate curves of Figure 16 tend to support  explanation.  The  a slower i n i t i a l  lower than optimum pH curve  (pH 4.5)  r a t e , during which time the excess  tant i s w a s t e f u l l y removed.  The  this has  surfac-  h i g h e r than optimum pH  curve (pH 5.6), while i t maintains the same i n i t i a l  rate as  the optimum, has a lower u l t i m a t e recovery because a f r o t h of  the r e q u i r e d s t a b i l i t y  cannot be  maintained.  While the above e x p l a n a t i o n would seem to be p o s s i b l e , much more work i s needed before i t can be accepted as  fact.  Bubble In of  Size  experimental runs 11 through  to 29 two  known n o m i n a l , maximum pore d i a m e t e r , were used.  spargers The  81  per  cent f l o t a t i o n  d i f f e r e n t pH pH  of 4.5,  recovery  rate curves are compared at  v a l u e s , at the optimum of 5.1  f o r the two  spectively.  s p a r g e r s , i n Figures  In each c a s e , the  s m a l l e r bubble s i z e  and  a f f e c t e d an  at a lower  18 and  f i n e r sparger  and,  improved recovery  19  an i n c r e a s e d  area  f o r adsorption  re-  hence, rate.  r e s u l t i s not s u r p r i s i n g because the s m a l l e r bubble yields  two  This  size  of the s u r f a c e  active  materi a l .  A i r Sparge Rate A second parameter determining the for adsorption  i s the  a i r sparge r a t e .  volume of a i r would a l s o be of r e c o v e r y . i s not  the  Increasing  case. ml  per sec was  optimum value  very  not  this  slightly  s u f f i c i e n t to cause  a i r requirements reach  r a p i d l y and  rate  that  However, an a i r sparge rate of  Thus, the  the  expected to i n c r e a s e the  Figure 20 would seem to i l l u s t r a t e  lower than 1.5 flotation.  area a v a i l a b l e  a maximum or  further increases  in a i r  sparge rates caused r e - d i s p e r s i o n of the s u b l a t e .  The  that the m a t e r i a l  might  being  f l o a t e d i s already  a solid  cause t h i s - a m p l i f i c a t i o n of a commonly reported Also r e l a t e d to the  a i r sparge rate i s the  effect  fact  [42].  volume of foam  100  10  20  30  40  50  60  70  TIME (MINUTES) FIGURE 18 Percent Flotation Recovery at pH 5-1 for Two Sparger Porosities  TIME( MINUTES) FIGURE 19 Percent Flotation Recovery at pH 4.5 for Two Sparger Porosities  FIGURE 20 Percent Flotation Recovery at Various Air Sparge Rates  85  produced.  I n c r e a s i n g the a i r r a t e , at a constant s u r f a c t a n t  dosage, g r e a t l y i n c r e a s e s the amount of foam produced as Figure 21  illustrates. This property  of the system would be of i n d u s t r i a l  importance because, at an optimum r a t e of removal, i t would be d e s i r a b l e to minimize foam production requirements. was  the usual  Note that the o r i g i n a l 2.5 l i t e r s .  and a e r a t i o n power  flotation  to  volume  Thus, at the optimum a i r sparge  r a t e , the volume of foam produced represents cent of the o r i g i n a l  cell  solution.  about 2.6 per  This f i g u r e can be c o n t r a s t e d  the 10 to 20 per cent,and even higher, foam production of  the foam f r a c t i o n a t i o n  runs.  Foam p r o d u c t i o n surfactant.  i s also related  to the dosage of  Figure 22 i s a p l o t of foam volume as a f u n c -  t i o n of s u r f a c t a n t dosage.  Generally,as  s u r f a c t a n t dosage  d e c r e a s e s , so too does the volume of foam produced.  The  s l i g h t minima at a s u r f a c t a n t dosage of between 4 x 10"1* and  5 x 10 _It moles per l i t e r can be r a t i o n a l i z e d by the  observations  of the next  section.  C o l l e c t o r Pre-mix Time N o r m a l l y , f o l l o w i n g the a d d i t i o n of the s u r f a c t a n t solution  to the e f f l u e n t the f l o t a t i o n  cell  solution  was  FIGURE 21 Foam Volume versus Air Sparge Rate  FIGURE 22 Foam Volume versus Surfactant Dosage  88  stirred  f o r two  an a d d i t i o n a l  minutes.  In a number of experimental  three minutes was  allowed.  This  additional  time appeared to have marked e f f e c t over a narrow dosage range (3 x 10 -If this was  to 6 x 10 _1+  surfactant  moles per l i t e r ) .  range the formation of l a r g e r than  normal  In  particles  o b s e r v e d , p o s s i b l y by a simple c o a g u l a t i o n mechanism.  In a d d i t i o n , the rate of removal was characteristics  much f a s t e r and  loaded with s u b l a t e upon i t s p a r t i a l agulation  once, a dense b l a c k , o i l y scum.  certainly  became  collapse.  In the  coat  No sure e x p l a n a t i o n can  f o r the e x i s t e n c e of t h i s r e l a t e d , i n some way,  As  visibly  rdgime, the f l o a t e d m a t e r i a l became, almost  be o f f e r e d  the  of the f r o t h were markedly d i f f e r e n t .  mentioned, i n normal o p e r a t i o n the f r o t h  the  runs  regime, although  to the charge  i t is  possessed  by  precipitate. The  decrease  c o a g u l a t i o n , a l s o , probably r e s u l t s  i n a net  in s u r f a c e a c t i v e m a t e r i a l i n the s o l u t i o n .  minima i n the foam volume versus s u r f a c t a n t dosage  The  curve,  r e f e r r e d to i n the preceding s e c t i o n , i s probably a r e s u l t of t h i s  decrease.  B0D  5  Removal  As mentioned p r e v i o u s l y , a number of runs were p e r formed i n which no methanol was  used to d i s s o l v e the  surfactant.  89  Although  these experiments  uate the e f f e c t s  were conducted  B0D5 removal i n the presence have been p a r t i c u l a r l y meaningful the methanol i t s e l f .  ameters of two f l o t a t i o n tests.  removal. of methanol would not  because of the l a r g e B0D5  Table 3 d e t a i l s  the o p e r a t i n g par-  runs and the r e s u l t s  BOD5 removal, f o r the i d e n t i c a l  and 30 per c e n t .  of the B0Ds  c o n d i t i o n s , was 18  Whether or not the B0D5 removal i s t o t a l l y  r e l a t e d to the i o n f l o t a t i o n  itself  or o c c u r r e d simply  because the e f f l u e n t was aerated and the r e s u l t i n g removed i s a matter of some doubt. Goergia  [ 3 0 ] , using no s u r f a c t a n t s , i n d i c a t e s  12 per cent of the t o t a l  B0D 5 .  were reported and were r e l a t e d tall  that the can account  Removals of 6 per cent  to a 50% r e d u c t i o n i n the  o i l content of the e f f l u e n t .  the removals  foam  Previous work at Rome,  n a t u r a l l y s u r f a c e a c t i v e , B0D5 producing f r a c t i o n for  to e v a l -  of methanol on the system, the absence of  methanol provided a chance to t e s t B0Ds  of  primarily  Thus, i t i s l i k e l y  experienced were a consequence of the n a t u r a l  surface a c t i v i t y  and the ion f l o t a t i o n  Identification  of a d d i t i o n a l  technique. types of m a t e r i a l s  which were removed i n the course of the f l o t a t i o n beyond the scope  process was  of the work, as o u t l i n e d p r e v i o u s l y .  e v e r , the absorbance  speculation.  How-  versus wavelength s p e c t r a produced  r e s u l t of the c o l o u r t e s t put forward an i n t e r e s t i n g for  that  as a  area  As shown i n Figure 23, a t r a c i n g of such a  90  Table 3 Biological  Oxygen Demand Removal Data  6  RUN NO, Surfactant C o n c e n t r a t i on (moles/1iter)  Air  10 x IO"1*  Sparge Rate (cm 3 /sec)  Pre-Mix Time (min)  Flotation  Colour  Removal  Reduction  (%)  (%)  pH  7.9  7.9  23  29  99  99  96  97  5.1  5.1  Foam Volume (ml)  510  B0D5 Waste  B0D5 C e l l  BOD5  Residual  Reduction  10 x 1 0 " ^  Solution  200  220  140  180  30%  18%  WAVELENGTH FIGURE  (NANOMETERS)  23 Absorbance versus Wavelength for Run 3  92  scan f o r f l o t a t i o n  run number 3, a l a r g e q u a n t i t y of m a t e r i a l  which absorbs i n the u l t r a v i o l e t  region  A d m i t t e d l y , some of the molecules which region w i l l  absorb i n the v i s i b l e  also absorb i n the u l t r a v i o l e t .  large reduction fraction  (< 400 nm) i s removed.  However, the  i n absorbance cannot be due to j u s t  alone.  K i n e t i c s of the F l o t a t i o n  Recovery  An attempt was made to f i t f l o t a t i o n reversible, first described Min  this  order r e a c t i o n .  data to a  The equation used was  i n Chapter 5 and was used by Rubin et al.  [(M-R)/M] was p l o t t e d  data of f l o t a t i o n  versus time i n Figure 24 f o r the  runs numbers 16 and 20.  taken to be the f r a c t i o n  [35].  R and M were  of the s u b l a t e removed at time t  and u l t i m a t e l y , r e s p e c t i v e l y .  These data were s e l e c t e d  because they were i l l u s t r a t i v e  of runs i n which  affecting first  the rate of removal were s t u d i e d .  parameters  The r e v e r s i b l e  order r e a c t i o n equation d i d not f i t the data very  even as an a p p r o x i m a t i o n .  well,  A p l o t of log(M-R) versus l o g  time ( F i g u r e 25) was also performed f o r runs 16 and 20. These data s a t i s f y  the e q u a t i o n :  log(M-R) = logA - mlogt  (3)  93  TIME (MINUTES)  FIGURE 24 Plot of M-Ln[(M-R)/MJ versus Time for Runs 16&20  Log(M-R) =Log 1.7- 0-79Log t i  Run20 Log(M-R) = Log0.88-0.82Logt  M i l l  001 10  10-  100.  1000-  TIME (MINUTES) <X3 •fa  FIGURE 25  Plot of Log(M-R) versus Log(time) for Runs 16&20  95  f a i r l y w e l l , but because i t i s a 1 o g a r i t h m e t i c and  relatively  nificant. within  insensitive  to changes, t h i s may  Because removals are r a p i d  a few  minutes, i t was  and  concluded  an  Ion  Industrial  The described tially ion  Flotation  that b e t t e r techniques  c o l l e c t o r recovery step of the  treatment  presented  process  pulp m i l l wastes i s presented  is  r e c y c l e d to the f l o t a t i o n taken  treatment is  probably  data.  "Grenoble  system.  A proposed  In the  i s mixed with  cell.  The  be n e c e s s a r y .  Process,"  i n Figure 5, i s par-  i n Figure 26.  o f f to sewer or f o r r e c y c l e . will  kinetic  f o r the p u r i f i c a t i o n  c o l l e c t o r from the recovery stage and  complete  Process  a p p l i c a b l e to the ion f l o t a t i o n  flotation  sig-  System as Part of  Treatment  i n Chapter 3, and  not be  virtually  would be r e q u i r e d i n order to get meaningful  The  relationship  the  purified  of process, effluent  underflow  In e i t h e r c a s e , f u r t h e r The  collapsed froth  d i r e c t e d to the c o l l e c t o r recovery system.  An  organic  s o l v e n t of s u f f i c i e n t chain length that i t i s i n s o l u b l e i n water ( i s o - o c t a n e or p a r a f i n o i l ) i s added to the c o l l a p s e d f r o t h , f o l l o w e d by the a d d i t i o n  of a concentrated  s o l u t i o n , l i k e l y white l i q u o r from the pulp m i l l recovery system.  The  resulting  two  caustic chemical  phases are s e p a r a t e d ; the  Surfactant  Total mill or acidified caustic extraction effluent  Solvent Froth  PURIFICATION  REGENERATION STAGE  STAGE. 0*0  v.  Aqueous phase  Surfactant, extraction, stages  Flotation C e l l NaOH Solution Purified effluent to recycle or sewer  Dark NaOH solution to pulp mill liquor cycle CO  cn  FIGURE 26 Proposed Ion Flotation Process For Purification of Pulp Mill Effluents  97  s u r f a c t a n t c o n t a i n i n g o r g a n i c phase  is retained for further  p r o c e s s i n g and the h i g h l y coloured c a u s t i c s o l u t i o n turned to the m i l l  recovery system.  is re-  The s u r f a c t a n t i s  separated from the o r g a n i c s o l v e n t and produced i n a form suitable  for  recycle.  The proposed system has a number of advantages: a.  a d i l u t e o i l - i n - w a t e r emulsion i s not wasted w i t h the p u r i f i e d underflow as i n the Grenoble P r o c e s s ,  b.  no troublesome sludge r e q u i r e s dewatering and d i s p o s a l ,  c.  some c r e d i t the  d.  f o r a e r a t i o n i s gained f o r  subsequent BOD  5  removal  a l l chemicals used loop  system,  are p a r t  of closed  systems; only make-up amounts are  required, e.  horsepower  f.  only  requirements w i l l be q u i t e  s m a l l volumes  of collapsed froth  small, need  be handled, making r e c o v e r y system tankage requirements modest.  98  C l e a r l y , before the proposed system i s ready f o r a p p l i c a t i o n or even f o r a p i l o t have to be  p l a n t t r i a l , much f u r t h e r work w i l l  performed.  CHAPTER 9  CONCLUSIONS  a. ion  The mechanism of removal was e s t a b l i s h e d as  f l o t a t i o n or perhaps, more l o g i c a l l y , p r e c i p i t a t e  tation  of the t h i r d  b.  [42] t y p e .  Flotation  recovery and c o l o u r removal were  found to be i n excess of 95 per c e n t , at optimum  c.  not of  sensitive  dosage, and  pre-mix t i m e .  d. of  conditions.  The f l o t a t i o n system was found to be  to pH, bubble s i z e , a i r sparge r a t e , c o l l e c t o r collector  flo-  An attempt at r e l a t i n g  recovery data to a r e v e r s i b l e , successful.  the ion f l o t a t i o n  first  order r e a c t i o n  rate was  Rate of recovery data d i d f i t an equation  the form: 1og(M-R) = l o g A - mlogt  99  100  e.  An  ion f l o t a t i o n  treatment  covery of a l l process c h e m i c a l s , was purification  of k r a f t pulp m i l l  p r o c e s s , with r e -  proposed  effluents.  for  the  CHAPTER  10  RECOMMENDATIONS FOR FURTHER STUDY  There are theory of the the  many problems to be  flotation  theory to the  k r a f t pulp m i l l  present research has found in the  of the  If  of a convenient s t a r t i n g point  Because of the  directed  application  e f f l u e n t system.  potential  proposed p u r i f i c a t i o n system, the  should be plant  i n the  both i n  been u s e f u l , such u s e f u l n e s s w i l l  definition  further study.  process and  solved  towards p r e p a r i n g the  the of the be for  s o c i a l importance research e f f o r t system f o r a p i l o t  evaluation. The  areas of most immediate i n t e r e s t , t h e r e f o r e ,  a.  A f a i r l y wide range of c a t i o n i c  are:  should be  reviewed and  batch f l o t a t i o n should be  trials.  the  surfactants  most s u i t a b l e ones s e l e c t e d  The  surfactants  ultimately  selected  commercially a v a i l a b l e or r e a d i l y produced by  mercial means.  101  for  com-  102  b.  The p o s s i b i l i t y  a true p r e c i p i t a t e modification  should be c o n s i d e r e d .  could enhance the d e s i r a b i l i t y  from an economic chemical  flotation  of modifying the process to This  of the process  point of view, p r o v i d i n g the  precipitating  i s l e s s expensive than the s u r f a c t a n t , which i s  u s u a l l y the c a s e . including  This study would almost c e r t a i n l y  the c o a g u l a t i o n  regime mentioned  C o l l e c t o r Pre-mix Time i n Chapter 8. almost c e r t a i n l y , more a p r e c i p i t a t e  This  involve  i n the s e c t i o n regime  flotation  on  was,  than an ion  f 1 o t a t i on.  c.  A fundamental  study of the charge c a r r i e d  the chromophoric molecular fragments should be attempted. be p r e d i c t e d , p o s i t i v e  i n the raw  While the success of t h i s  by  effluent study cannot  r e s u l t s would l a y the b a s i s f o r a  more thorough understanding of the f l o t a t i o n  mechanisms.  P a r t i c l e m o b i l i t y measurements should a l s o be used as a r o u t i n e t e s t i n the f l o t a t i o n  d. flotation  trials.  A b e t t e r method of f o l l o w i n g the k i n e t i c s of  recovery must be developed.  Perhaps  the  radioactive  tagging or even simple t u r b i d i t y measurements would prove to be more adequate. of the k i n e t i c s  When the method i s d e v e l o p e d , study  of removal  of the ion f l o t a t i o n  or the true  103  precipitate size  and  flotation  system should be  a i r r a t e , temperature e f f e c t s w i t h i n  that could be significant  e.  a p p l i c a b l e f o r an actual  the  bubble range  p r o c e s s , and  the  other  parameters.  Following  adequate completion of the  four i t e m s , a bench l a b o r a t o r y cell  r e l a t e d to:  should be developed.  u n i t operations  s c a l e continuous  After specification  of the s u r f a c t a n t  of a p i l o t p l a n t system could economic a n a l y s i s  performed.  regeneration  above  flotation of the  actual  stage,  design  be contemplated and  preliminary  REFERENCES  National Council f o r A i r and Stream T e c h n i c a l B u l l e t i n No. 228 (1969).  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Fed., V o l . 41, No. 2, Part 1, 222 (1970). T e j e r a , N.E. and D a v i s , M.W., 10, 1931 (1970). B e r g e r , N.F. 245 (1959).  and  T a p p i . V o l . 53,  No.  Brown, R.I., T a p p i , V o l . 42, No.  National Bulletin  Council f o r Stream Improvement T e c h n i c a l No. 122 (1959).  National Bulletin  Council f o r Stream Improvement T e c h n i c a l No. 1 57 ( 1 962) .  3,  106  [25]  "Summary Report, Advanced Waste Treatment Research Program," FWPCA Res. S e r . Pub. No. WP-20-AWTR-19 (1968).  [26]  Pulp and Paper Research I n s t i t u t e of Canada P r o j e c t Report 1-1, "The Use of High M o l e c u l a r Weight Amines f o r P u r i f i c a t i o n of Pulp M i l l E f f l u e n t s (1971).  [27]  Karger, B.L., B r i e v e s , R.B., L e m l i c h , R., Rubin, A . J . and Sebba, F., S e p a r a t i o n S c i . , V o l . 2, 401 (1967).  [28]  L e m l i c h , R., 16 (1968).  [29]  G i b b s , J.W., " C o l l e c t e d Works," V o l . 1, Longmans, Green, and Co., New York (1928).  [30]  Federal Water P o l l u t i o n Control Admin. Res. S e r . Report DAST-3, "Foam S e p a r a t i o n of K r a f t P u l p i n g Wastes" (1969).  [31]  Rose, J . L . and S e b a l d , J . F . , T a p p i , V o l . 51, No. 314 (1968).  [32]  G r i e v e s , R.B. and Wood, R-.K., AI CHE No. 4, 456 (1964).  [33]  L e m l i c h , R., " P r i n c i p l e s of Foam F r a c t i o n a t i o n , " Chap. 1 i n "Progress i n S e p a r a t i o n and P u r i f i c a t i o n , " V o l . 1, P e r r y , E.S. ( e d i t o r ) I n t e r s c i e n c e , New York (1968).  [34]  Gaudin, A.M., " F l o t a t i o n , " New York (1957).  [35]  Rubin, A . J . , Johnson, J.D. and Lamb, J . C , Ind. and Eng. Chem. Process Design and D e v e l . , V o l . 5, No. 4, 369 (1966).  [36]  Sebba, F. , Nature, V o l . 1 84 , 1062  Ind. and  Eng. Chem., V o l . 60, No.  10,  7,  J o u r n . , V o l . 10,  2nd, ed.,  McGraw-Hill,  (1959).  107  [37]  Langmuir, I. and S c h a e f e r , V . J . , J o u r n . Am. Chem. Soc., V o l . 59, 2400 (1937).  [38]  Sebba, F. , Nature, V o l . 1 88, 736 (1 960).  [39]  Baarson, R.E. and Ray, C.L., " P r e c i p i t a t e F l o t a t i o n , a New Metal E x t r a c t i o n and C o n c e n t r a t i o n Technique," AIMMPE Symposium, D a l l a s , Tex. (1963).  [40]  Rubin, A . J . and Johnson, J.D., A n a l . Chem., V o l . 39, No. 3, 298 (1967).  [41]  S e n n e t t , P. and O l i v e r , J.P., j o u r n a l  [42]  P i n f o l d , T.A., "Ion F l o t a t i o n , " Chap. 4 i n " A d s o r p t i v e Bubble S e p a r a t i o n Techniques," L e m l i c h , R. ( e d i t o r ) Academic P r e s s , New York (1972).  [43]  Adamson, A.W., " P h y s i c a l Chemistry of S u r f a c e s , " 2nd ed., I n t e r s c i e n c e Pub., New York (1967).  [44]  D a v i s , J.T. and R i d e a l , E . K. , "I n t e r f aci al 2nd ed., Academic P r e s s , New York (1963).  [45]  S h i n o d a , K. , "The Formation of M i c e l l e s , " Chap. 1 i n " C o l l o i d a l S u r f a c t a n t s , " Hutchinson and Van Rysselberghe ( e d i t o r s ) , Academic P r e s s , New York (1963).  [46]  Sebba, F. , "Ion F l o t a t i o n , " American York (1962).  [47]  R i c e , N.W. and Sebba, F., J . A p p l . Chem., V o l . 15, 105 (1965) .  [48]  G r i e v e s , R.B. and B h a t t a c h a r y y a , D., J . A p p l . Chem., Vol . 19 , 1 15 (1 969) .  [49]  Standard Methods f o r Examination of Water and Wastewater, 12th ed., American P u b l i c Health A s s o c i a t i o n , I n c . , New York (1965) .  unknown.  Phenomena,"  E l s e v i e r , New  108  [50]  Zeta-Meter I n c . , Operating Manual, 1720 New York, N.Y.  First  Ave.,  [51]  Lusher, J.A. and Sebba, F., J o u r n . A p p l . Chem., Vol 1 5 , 577 ( 1965) .  [52]  B r i t i s h Columbia Research C o u n c i l , Progress Report No. 2, "Colour Measurement of Bleached K r a f t Pulp M i l l E f f l u e n t s " (1971).  [53]  Rubin, A . J . , J o u r n . Amer. Water Works A s s o c . , V o l . 60, 832 (1968).  NOMENCLATURE  R  :  the i d e a l  gas law c o n s t a n t .  T  :  the absolute  temperature.  a..  :  the a c t i v i t y  of the i t h component.  r.  :  the s u r f a c e excess component.  R'  :  fraction  of c o l l i g e n d  removed at time t .  M'  :  fraction  of c o l l i g e n d  removed at steady  t  :  t i m e , i n minutes.  k  :  constant  XT  :  c o l o u r of the c o l l a p s e d foam, or foamate.  XD  :  c o l o u r of the bottoms.  F  :  v o l u m e t r i c flow rate of the feed  B  :  v o l u m e t r i c flow rate of the bottoms stream.  c o n c e n t r a t i o n of the i t h  state.  d e f i n e d i n equation (2).  a  109  stream.  no  volumetric flow of reflux stream. B0D5  :  the five day b i o l o g i c a l oxygen demand, defined in reference [ 4 9 ] .  CMC  :  c r i t i c a l micelle concentration, defined in reference [ 4 5 ] .  nm . :  nanometer ( I O  -9  meters)  fraction of c o l l i g e n d - c o l l e c t o r product removed at time t . M  :  fraction of colligend-col1ector product ultimately removed.  A  :  constant, defined in equation (3)  m  :  constant, defined in equation (3)  effluent:  refers to the applicable pulp mill waste water stream.  APPENDIX A  THE MODIFIED COLOUR TEST  Absorbance s p e c t r a , f o r the v i s i b l e  r e g i o n , are  s i m i l a r f o r the a c i d , c a u s t i c , p u l p i n g , and, of c o u r s e , the of  total  effluents.  Figure Al shows that absorbance  the 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 i n c r e a s e s with d e c r e a s -  ing  mill  wavelength over the v i s i b l e  a dilution  region.  In the  of about 50 r e v e a l s a pronounced  250 and 275  ultraviolet,  shoulder between  nm.  In order to check the e f f l u e n t ' s behaviour with r e s p e c t to Beer's Law, samples of c a u s t i c e f f l u e n t were d i l u t e d by f a c t o r s 25.0, 35.7, and 50.0. adherence to Beer's Law  extraction  of 2.5, 5.0, 10.0,  Figure A2 i l l u s t r a t e s  20.0,  the c l o s e  over the absorbance range 0.2  to  1.2. Although development  there has been some work [52] on the  of c o l o u r e s t i m a t i o n  a p p l i c a b l e to k r a f t pulp m i l l not yet been f u l l y  directly  e f f l u e n t s , these methods have  demonstrated.  111  procedures more  T h e r e f o r e , the c o l o u r  WAVELENGTH (NANOMETERS) FIGURE A1 Absorbance versus Wavelength for Various Concentrations of First Caustic Extraction Stage Effluent  CONCENTRATION AS A FRACTION OF FULL STRENGTH (FS) FIGURE A 2 Absorbance versus Concentration of Caustic Extraction Effluent  w  114  standard s e l e c t e d was the widely used c o b a l t and platinum salt solution.  Figure A3 shows the absorbance s p e c t r a f o r  three c o n c e n t r a t i o n s of the standard s o l u t i o n . meaningful  ( i . e . the hue of the s o l u t i o n  same as the standard) mill  Because  i s roughly the  absorbance measurements of the k r a f t  e f f l u e n t can be made at any wavelength between 450 fl  and 550 nm, the p r e c i s e wavelength o f the f i r s t maxima of the Pt-Co standard was chosen. l i s h e d as 455.7 nm. especially  This wavelength was e s t a b -  The choice of wavelength  convenient f o r another  length, a dilution  also  proved  reason; with a 40 mm path  of ten f o r the untreated 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 and a d i l u t i o n  of two f o r the t o t a l  mill  e f f l u e n t produced an absorbance i n the d e s i r a b l e 0.5 to 1.1 range.  Thus, the e f f l u e n t c o l o u r procedure  can now be  summari zed.  Preparation  of  1.  Colour  The sample was f i l t e r e d  Gooch Type f r i t t e d ified  Samples  disc f i l t e r .  through  The f r i t t e d  a Corning, d i s c was c l a s s -  as ' F i n e , 1 corresponding to a nominal, maximum pore  diameter  of 4, 5.5 microns.  The porous f i l t e r s  be capable of completely removing the t u r b i d i t y tion  and the use of f i l t e r  proved to of the s o l u -  aids was t h e r e f o r e not n e c e s s a r y .  WAVELENGTH (NANOMETERS) FIGURE A3 Absorbance versus Wavelength for Various Strengths of the Pt-Co Standard Solution  116  2. next d i l u t e d  I f the samples  r e q u i r e d d i l u t i o n , they were  followed by pH adjustment to pH 7.6  with e i t h e r concentrated NaoH or  ± 0.02  NCI.  Colour Measurement 1. was  The Unicam SP.800B scanning spectophotometer  set up to operate from 275 to 600  absorbance was of o p e r a t i o n  2.  The  baseline  set using a d i s t i l l e d water b l a n k .  can be found in the machine o p e r a t i n g  Details manual.  The absorbance spectrum of the sample  produced, using a 50 mm tion  nm.  l i g h t pathlength.  was  Following  comple-  of the c o l o u r sample s c a n s , the a p p l i c a b l e spectrum of  a holmium f i l t e r was length  r u n , i n order to determine the wave-  accurately.  3.  The absorbance of the c o l o u r sample was  mined at 456 nm and converted to Pt-Co u n i t s calibration  4.  deter-  from the  graph.  The d i l u t i o n  c o r r e c t i o n , i f any, was  made.  117  P r e p a r a t i o n of the C a l i b r a t i o n 1.  The  1000  by d i s s o l v i n g 2.492 gm (K2Pt in  C l 6 ) and  distilled  chloric acid. standard  'ppm  of potassium  water c o n t a i n i n g 100 The  volume was mg  prepared  chioroplatinate  ml  chloride  (Co C l 2 • 6H 2 0)  of concentrated  adjusted to one  per l i t e r  of using the terms  hydro-  liter.  This  as P t , hence the common  'Pt-Co c o l o u r u n i t s '  and  as Pt-Co' i n t e r c h a n g e a b l y .  2. of  c o l o u r u n i t standard was  2.000 gm-of cobaltous  contained 1000  convention  Graph  Colour s t a n d a r d s , at v a r i o u s c o n c e n t r a t i o n s  Pt-Co, were prepared  3.  The  against d i s t i l l e d  4.  by v o l u m e t r i c  dilution.  absorbance of each standard was water at 456  nm  as i n the preceding  An expanded v e r s i o n of Figure A4 was  using the r e s u l t s  measured  of the previous measurement.  case.  prepared  COLOUR (Pt-Co UNITS OR PPM AS Pt) FIGURE A4 Absorbance versus Colour Concentration  APPENDIX B  SUMMARY OF ION FLOTATION DATA Run No.  MeOH  Surfactant Cone, x 10"1* (moles/1)  Di f f u s e r Speci f i cation  PH  Pre-mi x Ti me (min)  Air  Sparge Rate (cm 3 /sec)  Col our Reducti on (percent)  U l t i mate Flotation Recovery (percent)  Foam Vol . (ml)  1  /  5.0  NA  8.14  0.5  NA  94.3  NA  NA  2  /  10.0  NA  7.71  0.5  NA  99.2  NA  177  3  /  10.0  NA  7.7  0.5  NA  99.3  100  340  4  None  10.0  NA  5.1  23  7.9  95.9  99  NA  5  None  5.0  NA  5.15  10  7.9  NA  NA  NA  6  None  10.0  NA  5.15  29  7.9  96.0  99  530  7  /  5.0  NA  5.15  7.0  7.9  96.0  57  NA  8  /  8.0  NA  5.15  2.0  7.9  97.2  98  185  9  /  8.0  NA  2.14  2.0  7.9  92.0  <10%  NA  10  /  8.0  NA  2.0  7.9  95.0  <50%  NA  11  •  8.0  Med.  2.0  7.2  85.0  NA  NA  12.0 1 .57  (CONTINUED)  APPENDIX B (Conti nued)  Run No.  MeOH  Surfactant Cone, x 10"* (moles/1)  Di f f u s e r Speci f i cation  pH  Pre-mi x Ti me (mi n)  Air  Sparge Rate (cm 3 /sec)  Col our Reducti on (percent)  Ultimate Flotation Recovery (percent)  Foam Vol . (ml)  12  /  8.0  Med.  7.68  2.0  7.2  97  76  1 50  13  /  8.0  Med.  9.8  2.0  7.2  93  72  180  14  /  8.0  Med.  5.61  2.0  7.2  NA  77  120  15  /  8.0  Med.  4.51  2.0  7.2  98  86  260  16  /  8.0  Med.  5.1  2.0  7.2  98  91  140  10.0  Med.  5.1  2.0  7.2  NA  NA  NA  17 18  /  10.0  Med.  5.1  2.0  7.2  NA  NA  510  19  /  8.0  Fine  4.5  2.0  7.2  NA  91  330  20  /  8.0  Fine  5.14  2.0  7.2  NA  90  170  21  /  8.0  Fi ne  5.1  2.0  2.4  NA  91  90  22  /  8.0  Fi ne  5.1  2.0  1 .5  NA  97  65  23  /  8.0  Fine  5.1  2.0  NA  89  245  17.1  (CONTINUED)  ro o  APPENDIX B (Continued)  Run No.  MeOH  Surfactant Cone, x IO"1* (moles/1)  Di f f u s e r Speci f i c a t i on  pH  Pre-mi x Time (mi n)  Air  Sparge Rate (cm 3 /sec)  Col our Reducti on (percent)  U l t i mate Flotation Recovery (percent)  Foam Vol . (ml)  24  /  6.0  Fine  5.1  5.0  2.4  NA  93.5  75  25  /  4.0  Fine  5.1  5.0  2.4  NA  90  50  26  /  2.0  Fine  5.13  5.0  2.4  56.4  <10%  100  27  /  8.0  Fine  5.10  5.0  2.4  97.5  90%  170  28  /  3.0  Fine  5.12  5.0  2.4  83  40%  80  29  /  1.0  Fi ne  5.11  5.0  2.4  30  NA  40  APPENDIX C  FLOTATION RECOVERY RESULTS  RUN  NO. 3 Percent Flotation Recovery  Time (mi nutes)  0.0 25.0 64.8 84.0 93.9 96.6 99.3 99.7 99.9  0.0 3.0 6.0 9.0 13.0 15.0 22.0 33.0 38.0  RUN  NO. 4 Percent Flotation Recovery  Time (mi nutes)  0.0 29.1 37.1 51.0 70.6 71 .4 80.0 84.4 100.0  0.0 2.0 4.0 6.0 8.0 10.0 15.0 30.0 107.0  1 22  RUN Time (mi nutes)  NO. 6 Percent Flotation Recovery  0.0 2.0 5.0 8.0 13.0 28.0  0.0 59.2 82.1 90.5 97.5 98.4  RUN Ti me (mi nutes)  NO. 8 Percent Flotation Recovery 0.0 43.5 72.7 75.6 89.2 92.1 98.2 98.2  0.0 1 .0 2.0 4.0 6.0 10.0 21 .0 34.0  RUN NO. 12 Time (mi nutes) 0.0 2.5 4.5 12.0 41 .0 63.0  Percent Flotation Recovery 0.0 2.5 11 .0 34.5 71 .0 76.0  RUN  NO.  13 Percent F I o t a t i on Recovery  Ti me (mi nutes)  0.0 1.7 14.5 22.3 40.1 60.4 72.3  0.0 4.4 10.4 16.0 30.5 62.0 94.0  RUN  NO.  14 Percent F I o t a t i on Recovery  Time (mi nutes)  0.0 36.6 44.1 54.6 68.3 78.5  0.0 3.0 5.0 9.0 18.5 60.0  RUN Ti me (mi nutes) 0.0 4.0 7.1 10.0 30.4 77.0  NO.  15 Percent Flotation Recovery 0.0 10.3 15.5 30.4 78.0 86.2  RUN  NO.  16 Percent F I o t a t i on Recovery  Time (minutes) 0.0 3.15 5.0 10.0 23.15 31 .5 75.0  0.0 30.0 36.8 59 .6 75.6 84.0 90.5  RUN  NO.  19 Percent F I o t a t i on Recovery  Ti me (mi nutes) 0.0 5.0 11.0 24.0 54.3 65.0  0.0 18.8 45.9 76.8 89.0 89 .2  RUN Ti me (minutes) 0.0 2.2 5.0 11 .5 20.15 55.0  NO.  20 Percent Flotation Recovery 0.0 47.3 68.1 81 .0 87.9 92.1  RUN  NO.  21 Percent F l o t a t i on Recovery  Ti me (mi nutes) 0.0 2.6 5.15 12.6 25.2 36.0  0.0 34.3 59.2 87.8 89.9 91 .2  RUN  NO.  22 Percent F l o t a t i on Recovery  Ti me (mi nutes)  0.0 76.6 80.5 93.2 97.7  0.0 4.4 8.4 15.3 42.15  RUN Ti me (mi nutes) 0.0 3.4 9.75 16.7 60.0  NO.  23 Percent F l o t a t i on Recovery 0.0 32.1 59.2 79 .0 87.3  

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