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Adsorption of heavy metals at low concentrations using granular coals Tin Tun, U. 1976

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"ADSORPTION OF HEAVY METALS AT LOW CONCENTRATIONS USING GRANULAR COALS"  by U.^Tin Tun B.Sc.  (Eng.), U n i v e r s i t y o f M a n i t o b a , 1972  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department o f C i v i l  Engineering  We accept t h i s t h e s i s as conforming  t o the r e q u i r e d  standard  The U n i v e r s i t y o f B r i t i s h Columbia  0  May,  1976  U. T i n Tun,  1976  In  presenting  an  advanced  the I  Library  further  for  degree shall  agree  scholarly  by  his  of  this  written  thesis  in  at  University  the  make  that  thesis  purposes  for  partial  freely  permission may  be  It  financial  fulfilment of of  available for  by  the  understood  gain  for  extensive  granted  is  British  shall  reference  Head  be  requirements  Columbia,  copying  that  not  the  of  copying  agree  and  of my  I  this  that  study. thesis  Department or  for  or  publication  allowed without  my  permission.  of  University  ^Qt,WH 'cM >  of  British  2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5  Date  it  representatives.  Department The  this  3//V)rW/ 1976  CAQ<^>Q1  Columbia  ^  Qvv/(l  ^•A^MJULV*  WS^,  ABSTRACT  The  a d s o r p t i o n o f low c o n c e n t r a t i o n s o f heavy m e t a l s , such as z i n c ,  c o p p e r , l e a d and mercury, by v a r i o u s B r i t i s h Columbia c o a l s was i n v e s t i g a t e d . F i v e B r i t i s h Columbia c o a l s were used as a d s o r b e n t s f o r t h e f o u r heavy metals d e s c r i b e d above.  Batch  t e s t s were r u n on a l l f i v e c o a l s ,  namely, Hat Creek O x i d i s e d , Hat Creek U n o x i d i s e d , Cominco O x i d i s e d , Cominao Ash Waste and Cominco P r o d u c t i o n C o a l . t e s t s was found t o be 60 mins.  Batch  The optimum c o n t a c t time f o r b a t c h t e s t s p r o v i d e d a q u i c k comparison o f  the a d s o r p t i v e c a p a c i t i e s o f t h e f i v e c o a l s . the b e s t p e r f o r m i n g  Based on t h e b a t c h t e s t s d a t a ,  c o a l from each o f t h e Hat Creek and Cominco groups, namely,  Hat Creek O x i d i s e d and Cominco Ash Waste were chosen f o r f u r t h e r i n v e s t i g a t o r y work u s i n g column t e s t s . For t h e column t e s t s , t h e i n f l u e n t c o n c e n t r a t i o n s were 2 mg/£ and l e s s f o r z i n c , copper and l e a d .  Column work w i t h mercury was c a r r i e d out  w i t h i n f l u e n t c o n c e n t r a t i o n s o f 5 yg/& and l e s s . Column t e s t s showed t h e f o l l o w i n g : a)  V a r y i n g t h e c r o s s - s e c t i o n a l a r e a o f t h e c o a l column from  .001  f t  2  capacity.  t o .002 f t has no s i g n i f i c a n t i n f l u e n c e on t h e a d s o r p t i v e 2  Both columns have d i a m e t e r s more than 10 times t h a t o f  the average c o a l p a r t i c l e . b)  The most c r u c i a l f a c t o r a f f e c t i n g a d s o r p t i v e c a p a c i t y i s t h e  pH o f t h e i n f l u e n t .  There i s a d e f i n i t e d e c r e a s e i n c a p a c i t y w i t h  d e c r e a s i n g pH. c)  The c a p a c i t y d e c r e a s e s w i t h i n c r e a s i n g f l o w r a t e , b u t t h e  r e l a t i o n s h i p i s not l i n e a r .  The d e c r e a s e i n c a p a c i t y due t o a  f l o w r a t e i n c r e a s e from 1 t o 3 I g p m / f t  ii  2  i s much g r e a t e r than t h e  iii  d e c r e a s e i n c a p a c i t y due d)  t o an i n c r e a s e from 3 t o 5 I g p m / f t .  Comparing the a d s o r p t i v e a f f i n i t i e s of z i n c , copper and  lead,  i t i s seen t h a t l e a d d i s p l a y e d the g r e a t e s t a f f i n i t y w i t h copper second and z i n c t h i r d .  At 10% b r e a k t h r o u g h c o n c e n t r a t i o n , the  c a p a c i t i e s d i s p l a y e d by Cominco Ash Waste c o a l f o r l e a d , copper z i n c were i n the r a t i o of 12:6:1. c o n c e n t r a t i o n s i n v o l v e d were 4.0 f l o w r a t e was e)  The  i n f l u e n t pH and  and 2 mg/£  and  initial  r e s p e c t i v e l y , and  the  1 Igpm/ft . 2  Using i n f l u e n t s c o n t a i n i n g a mixture  of z i n c , copper and  r e s u l t s i n s m a l l e r i n d i v i d u a l c a p a c i t i e s f o r Zn, Cu and Pb would be a c h i e v e d w i t h s i n g l e s o l u t e i n f l u e n t s .  But the  lead  than  total  o v e r a l l c a p a c i t y of the c o a l f o r heavy m e t a l s i s g r e a t e r w i t h mixed i n f l u e n t s than w i t h any s i n g l e s o l u t e i n f l u e n t . f)  T e s t s w i t h mercury i n f l u e n t s show t h a t d e t e r i o r a t i o n of  the  c o n c e n t r a t i o n of the mercury s o l u t i o n occurs at c o n c e n t r a t i o n of 5 yg/I ?  g)  and  less.  Of the two  c o a l s chosen f o r column t e s t work, Hat  Creek  O x i d i s e d i s the s u p e r i o r c o a l w i t h r e g a r d t o the a d s o r p t i v e c a p a c i t y of heavy m e t a l s .  T e s t s run at an i n f l u e n t pH o f 4.0  c o n c e n t r a t i o n s of 2 mg/£  and  influent  of each m e t a l , showed the r a t i o o f c a p a c i t i e s  of Hat Creek O x i d i s e d : Darco a c t i v a t e d c a r b o n : Cominco Ash Waste f o r Zn t o be 12.1  : 1.0  and  made to c o r r e l a t e the column e f f l u e n t pH w i t h  the  f o r Pb t o be 3.8 An attempt was  : 1.2 : 0.7  e f f l u e n t metal concentration. pronounced at lower i n f l u e n t pH  : 1.0, :  f o r Cu t o be 11.9  : 1.7  1.0.  I t was  found t h a t t h i s c o r r e l a t i o n i s more  values.  iv  D u r i n g the c o u r s e of the column work, a growth of fungus was observed a t the top o f the c o a l columns. c a p a c i t i e s were a f f e c t e d by t h i s fungus.  I t i s p o s s i b l e that  adsorptive  TABLE OF CONTENTS PAGE ABSTRACT  ii  TABLE OF CONTENTS  v  LIST OF TABLES  vii  LIST OF FIGURES  viii  ACKNOWLEDGEMENTS  x  CHAPTERPTER 1  INTRODUCTION  2  GENERAL NOTES ON ADSORBENTS AND ADSORBATES USED IN THIS STUDY  4  2.1  Types o f C o a l  4  2.2 2.3  Coal Preparation P e r c e n t Recovery o f 28/48 S i z e F r a c t i o n from Raw Commercial C o a l  5 5  O p t i m i z i n g t h e C o a l P r e p a r a t i o n Procedure f o r I n c r e a s e d P e r c e n t Recovery o f 28/48 S i z e Fraction  5  S y n t h e t i c Wastewaters  6  2.4  2.5 3  1  BATCH TESTS  8  3.1  Introduction  8  3.2  Batch T e s t i n g Procedure  9  3.3  D e t e r m i n a t i o n o f Optimum C o n t a c t Time  10  3.4  E f f e c t s o o f pH on A d s o r p t i v e C a p a c i t y o f Coal  14  3.5  E f f e c t s o f I n i t i a l C o n c e n t r a t i o n Change and C o a l Weight Change on P e r c e n t Removal  16  3.6  A d s o r p t i o n Isotherms  f o r Copper  19  3.7  A d s o r p t i o n Isotherms  f o r Lead  24  3.8  A d s o r p t i o n Isotherms v  f o r Zinc  26  VI  CHAPTER  PAGE 3.9  A d s o r p t i o n Isotherms f o r Mercury  33  3.10  B a t c h T e s t s - Summary and C o n c l u s i o n s  33  COLUMN TESTS  37  4.1  Introduction  37  4.2  Column T e s t i n g Apparatus  39  4.3  Column T e s t i n g P r o c e d u r e  41  4.4  B r e a k t h r o u g h Curve  43  4.5  B r e a k t h r o u g h Curves f o r Z i n c a)  Calculations  43  E f f e c t of Varying the Cross-Sectional A r e a o f t h e C o a l Bed  45  b)  E f f e c t o f V a r y i n g t h e I n f l u e n t pH  47  c)  E f f e c t o f V a r y i n g t h e Flow Rate  51  d)  E f f e c t of Varying the I n f l u e n t Concentration  54  4.6  B r e a k t h r o u g h Curves f o r Copper  61  4.7  B r e a k t h r o u g h Curves f o r Lead  65  4.8  B r e a k t h r o u g h Curves f o r I n f l u e n t s C o n t a i n i n g a M i x t u r e o f Z i n c , Copper and Lead  69  C o r r e l a t i o n o f E f f l u e n t pH w i t h E f f l u e n t Concentration  77  4.10  B r e a k t h r o u g h Curves f o r Mercury  83  4.11  Column T e s t s - Summary and C o n c l u s i o n s  86  4.9  RECOMMENDATIONS  92  BIBLIOGRAPHY  94  LIST OF TABLES PAGE TABLE 2.1  S y n t h e t i c Wastewaters  3.1  E f f e c t s o f pH on t h e A d s o r p t i v e C a p a c i t y o f Coal  15  E f f e c t o f Changing C o a l Weight & I n i t i a l C o n c e n t r a t i o n i n t h e Same P r o p o r t i o n on t h e P e r c e n t Removal  18  3.3  Comparison o f H.C. OX and CO:ASH  35  3.4  Comparison o f t h e C a p a c i t i e s o f Two C o a l s f o r Each o f t h e Four Heavy M e t a l s  36  C o n t a c t Times f o r a 1 0 - i n c h Column a t G i v e n Flow R a t e s  38  3.2  4.1 4.2  7  E f f e c t o f Changing C r o s s - S e c t i o n a l A r e a o f t h e C o a l Bed  45  4.3  E f f e c t o f V a r y i n g t h e I n f l u e n t pH  48  4.4  E f f e c t of V a r y i n g t h e Flow Rate  52  4.5 4.6  E f f e c t o f V a r y i n g t h e I n f l u e n t pH Comparison o f A d s o r p t i v e C a p a c i t i e s o f Columns  58  Run w i t h Z i n c I n f l u e n t s o f 0.5 mg/£ and 2.0 mg/I  59  4.7  E f f e c t o f V a r y i n g pH w i t h Copper I n f l u e n t s  63  4.8  Comparison o f A d s o r p t i v e C a p a c i t i e s f o r Copper  4.9  and Z i n c  65  C a p a c i t i e s f o r Lead  68  4.10(a) A d s o r p t i o n C a p a c i t i e s U s i n g M i x e d I n f l u e n t s 4.10(b) A Comparison Between H.C. OX, CO:ASH and DARCO A c t i v a t e d Carbon w i t h Regard t o 'their C a p a c i t i e s f o r t h e Three M e t a l s from M i x e d I n f l u e n t s a t a pH o f 4.0 4.10(c) P e r c e n t D e c r e a s e i n C a p a c i t y on Changing t h e I n f l u e n t t o One C o n t a i n i n g a M i x t u r e of S o l u t e s vi x  74  75 75  LIST OF FIGURES FIGURE 3.1(a) 3.1(b) 3.1(c) 3.2  PAGE C o n t a c t Time - E q u i l i b r i u m C o n c e n t r a t i o n f o r Copper  11  C o n t a c t Time - E q u i l i b r i u m C o n c e n t r a t i o n f o r Copper  12  C o n t a c t Time - E q u i l i b r i u m C o n c e n t r a t i o n f o r Copper  13  E f f e c t s on P e r c e n t Removal When Changing One Parameter W h i l e K e e p i n g t h e Other F i x e d  17  3.3(a)  Copper A d s o r p t i o n Isotherms  20  3.3(b)  Copper A d s o r p t i o n Isotherms  21  3.3(c)  Copper A d s o r p t i o n Isotherms  22  3.3(d)  Copper A d s o r p t i o n Isotherms  23  3.4  Lead A d s o r p t i o n Isotherms  25  3.5(a)  Z i n c A d s o r p t i o n Isotherms  27  3.5(b)  Z i n c A d s o r p t i o n Isotherms  28  3.5(c)  Z i n c A d s o r p t i o n Isotherms  29  3.6(a)  Mercury A d s o r p t i o n Isotherms  30  3.6(b)  Mercury A d s o r p t i o n Isotherms  31  3.6(c)  Mercury A d s o r p t i o n Isotherms  32  4.1(a)  C o n s t a n t H y d r a u l i c Head A p p a r a t u s  40  4.1(b)  Double Tank Feed M o d i f i c a t i o n  40  4.2  A T y p i c a l B r e a k t h r o u g h Curve  44  4.3  E f f e c t of Changing C r o s s - S e c t i o n a l A r e a o f t h e C o a l Bed  46  4.4  E f f e c t o f V a r y i n g t h e I n f l u e n t pH  49  4.5 4.6  of Flow Rate Rate ff oo rr H.C. CO:ASH EE ff ff ee cc tt o f VV aa rr yy ii nn gg Flow OX  55 56  viii  ix FIGURE  PAGE  4.7  E f f e c t o f V a r y i n g t h e I n f l u e n t pH  57  4.8  E f f e c t o f V a r y i n g t h e pH on C o a l C a p a c i t y f o r Copper  62  4.9(a)  E f f e c t o f V a r y i n g t h e pH w i t h Lead I n f l u e n t s  66  4.9(b)  Fungus Growing a t t h e Top o f C o a l Column  67  4.10(a)  B r e a k t h r o u g h Curves f o r H.C.OX w i t h Mixed Influents B r e a k t h r o u g h Curves f o r C0:ASH w i t h Mixed Influents  71 72  B r e a k t h r o u g h Curves f o r DARCO A c t i v a t e d w i t h Mixed I n f l u e n t s  73  4.10(b) 4.10(c) 4.11  B r e a k t h r o u g h Curves f o r Mercury  Carbon 84  ACKNOWLEDGEMENTS  The  a u t h o r wishes t o express h i s g r a t i t u d e t o Dr. W.K. Oldham  f o r h i s h e l p and e n d u r i n g  patience.  Thanks a r e a l s o extended t o Dr. R.D. Cameron, Dr. D.S. M a v i n i c and Mrs.  E. McDonald f o r t h e i r k i n d a s s i s t a n c e on v a r i o u s a s p e c t s o f t h e  research. G r a t i t u d e i s a l s o owed t o Mr. P. S i e w e r t o f M i n e r a l  Engineering  Department f o r h i s h e l p on t h e p r e p a r a t i o n o f t h e c o a l s and t o Mr. A.S. D h i l l o n o f Geochemistry Department f o r h i s h e l p on mercury d e t e c t i o n . The  a u t h o r a l s o w i s h e s t o express h i s g r a t i t u d e t o t h e P o l l u t i o n  C o n t r o l B r a n c h , Water Resources S e r v i c e , Department o f Lands, F o r e s t s , and Water Resources o f the P r o v i n c e o f B r i t i s h Columbia f o r p r o v i d i n g t h e n e c e s s a r y funds f o r t h i s  research.  x  Chapter 1 INTRODUCTION  A l o t of r e s e a r c h has been done and an adequate amount o f d a t a compiled on the a d s o r p t i o n o f o r g a n i c p o l l u t a n t s by a c t i v a t e d carbon. Advanced waste treatment for  p l a n t s such as the one a t Lake Tahoe, C a l i f o r n i a ,  example, employ g r a n u l a r a c t i v a t e d carbon t o remove v a r i o u s types  o r g a n i c c o n s t i t u e n t s i n the wastewaters w i t h a good degree of  of  success.  Weber and M o r r i s i n t h e i r work w i t h a c t i v a t e d carbons  and  o r g a n i c s o l u t e s r e p o r t e d h i g h a d s o r p t i o n c a p a c i t i e s f o r o r g a n i c s such as nitrochlorobenzene  and h i g h m o l e c u l a r w e i g h t s u l f o n a t e d  alkylbenzenes.  (12) The Rand C o r p o r a t i o n  conducted a study w i t h a 10,000 gal/day  p i l o t p l a n t w i t h 18/120 mesh c o a l as a consumable p r e c o a t f i l t e r raw sewage and secondary e f f l u e n t .  for treating  They r e p o r t e d a 90% decrease i n suspended  s o l i d s and about 50% d e c r e a s e i n phosphates and C.O.D. when raw sewage o r secondary e f f l u e n t was  t r e a t e d w i t h the c o a l f i l t e r .  R e l a t i v e l y s p e a k i n g , t h e r e has not been much work done on c o a l as (3) an adsorbent of i n o r g a n i c s such as the heavy m e t a l s .  Hendren  reported  good a d s o r p t i o n c a p a c i t i e s f o r l e a d , copper and z i n c u s i n g g r a n u l a r c o a l s . The  c o a l s used were from B r i t i s h Columbia, namely, Hat Creek and  coals.  Of s e v e r a l s i z e f r a c t i o n s t e s t e d , 28/48 mesh f r a c t i o n was  Crowsnest found t o  d i s p l a y good a d s o r p t i o n c a p a c i t i e s as w e l l as s a t i s f a c t o r y h y d r a u l i c f l o w properties.  The major p o r t i o n of h i s work was  c e n t r a t i o n s o f 10-100  done a t i n f l u e n t waste con-  mg/£.  S i g w o r t h and S m i t h ^  l i s t e d the a d s o r p t i o n p o t e n t i a l s o f v a r i o u s  i n o r g a n i c compounds by a c t i v a t e d carbon. with high adsorption a f f i n i t i e s .  They a t t r i b u t e d mercury and  lead  A c c o r d i n g t o t h e i r l i s t , copper and z i n c  were c l a s s i f i e d as h a v i n g o n l y a s l i g h t p o t e n t i a l f o r a d s o r p t i o n by a c t i v a t e d carbon. B r i t i s h Columbia has v a s t c o a l r e s e r v e s . 1  The p r e s e n t p r o d u c t i o n of  2  c o a l i n B r i t i s h Columbia i s about 7 m i l l i o n tons per y e a r .  I t , therefore,  seems b o t h l o g i c a l and w i s e t h a t the p o s s i b l e p o t e n t i a l f o r u s i n g B.C. as a d s o r b e n t s f o r heavy m e t a l s , p r i o r to i t s use investigated.  A l t h o u g h c e r t a i n t y p e s of a c t i v a t e d c a r b o n may  be  display  fair  c a p a c i t i e s f o r heavy m e t a l s , a c t i v a t e d carbon i s r e l a t i v e l y expen-  s i v e at about $500/ton. may  well  Another good r e a s o n f o r d o i n g such an i n v e s t i g a t i o n would  an economic one. adsorption  as a f u e l , s h o u l d be  coals  w e l l t u r n out  The  p r e s e n t p r i c e of c o a l i s $15-$22 per t o n .  t h a t the c o s t of u s i n g  i s c h e a p t e r than u s i n g  It  a c o a l system to remove heavy m e t a l s  an a c t i v a t e d carbon system.  When making an economic comparison of the two  systems, one  must t a k e  i n t o account the p e r c e n t r e c o v e r y of u s a b l e c o a l s i z e f r a c t i o n s from the commercial c o a l as w e l l as the i n d i v i d u a l a d s o r p t i v e weight b a s i s .  The  raw  c a p a c i t i e s on a u n i t  p e r c e n t r e c o v e r y of u s e f u l c o a l s i z e f r a c t i o n s t h a t  s e r v e as a d s o r b e n t s i n column o p e r a t i o n s w i l l c r u c i a l l y d e t e r m i n e the  can economics  of such a c o a l system. The  notion  that coal adsorption  may  fare poorly  a t v e r y low  concen-  t r a t i o n s of i n f l u e n t heavy m e t a l has been i n the minds of many.  To  t h i s a s p e c t of c o a l use,  used i n t h i s  the i n f l u e n t heavy m e t a l c o n c e n t r a t i o n s  r e s e a r c h are a l l v e r y low.  For z i n c , copper and  t i o n s are i n the range of 0.5 the i n f l u e n t c o n c e n t r a t i o n concentrations  mg/£  to 2.0  mg/£.  investigate  l e a d , the i n f l u e n t c o n c e n t r a I n the case of mercury,  used f o r the column t e s t s was  5 ug/Jl.  These  are i n the range of p e r m i s s a b l e l e v e l s o u t l i n e d by the P o l l u t i o n  C o n t r o l Branch f o r the above heavy m e t a l s i n i n d u s t r i a l e f f l u e n t s . In t h i s research, under b a t c h c o n d i t i o n s .  The  f i v e d i f f e r e n t B r i t i s h Columbia c o a l s were e f f e c t s of c o n t a c t t i m e , of pH,  and  of  studied  varying  3  i n i t i a l concentrations  were i n v e s t i g a t e d .  The b a t c h t e s t s p r o v i d e d  comparison of the performance o f the f i v e c o a l s . of the Hat gations  Creek group and  under column o p e r a t i n g The  .001  ft  the Cominco group was  2  and  One  quick  t y p e o f c o a l from each  chosen f o r f u r t h e r i n v e s t i -  conditions.  column t e s t s used a c o a l bed w i t h a c r o s s - s e c t i o n a l a r e a o f a c o a l depth of 10 i n c h e s .  D u r i n g the column s t u d i e s ,  e f f e c t s of v a r y i n g c r o s s - s e c t i o n a l a r e a , i n f l u e n t pH, concentration  a  were a l s o i n v e s t i g a t e d .  f l o w r a t e and  the influent  A l t h o u g h the l a b o r a t o r y s c a l e column  t e s t s cannot s u p p l y d a t a t h a t are i m m e d i a t e l y u s e f u l f o r f u l l s c a l e  design,  they n o n e t h e l e s s g i v e w o r t h w h i l e i n f o r m a t i o n  capaci-  t i e s under f l o w - t h r o u g h column o p e r a t i o n  on r e l a t i v e a d s o r p t i o n  conditions.  The  column d a t a  then be used to compare w i t h o t h e r documented removal methods.  can  Chapter 2 GENERAL NOTES ON ADSORBENTS AND ADSORBATES USED IN THIS STUDY  2.1  Types o f C o a l The  adsorbents  B r i t i s h Columbia.  used i n t h i s r e s e a r c h a r e a l l c o a l s n a t i v e t o  F i v e c o a l s were used i n t h e B a t c h T e s t s and two o f these  f i v e were chosen f o r Column T e s t s . 1.  The f i v e c o a l s a r e : -  Hat Creek O x i d i s e d i s t h e c o a l p i c k e d up from t h e s u r f a c e o f  the c o a l seams a t Hat Creek. 2.  Hat Creek U n o x i d i s e d i s o b t a i n e d from a m i x t u r e o f core samples  o f t h e Hat Creek c o a l d e p o s i t s .  The core samples were from depths  o f 50' - 1,000' below the s u r f a c e o f t h e ground. 3.  Cominco O x i d i s e d i s t h e c o a l t h a t had been exposed t o o x i d a t i o n  processes 4.  and consequently  had l o s t i t s c o k i n g p r o p e r t i e s .  Cominco Ash Waste i s t h e c o a l w i t h a h i g h p e r c e n t a g e o f i n e r t  ashes and non v o l a t i l e m a t t e r .  I t i s t h e waste p r o d u c t  i n a coal  cleaning process. 5. The  Cominco P r o d u c t i o n i s t h e c o a l t h a t i s produced f o r m a r k e t i n g . l a s t t h r e e c o a l s d e s c r i b e d above, namely, t h e Cominco c o a l s  were a l l s u p p l i e d d i r e c t l y by C o n s o l i d a t e d M i n i n g and S m e l t i n g Company, L t d . from T r a i l , B r i t i s h Columbia.  They were r e c e i v e d i n a crushed form and were  s e a l e d i n p l a s t i c bags. The  a b b r e v i a t i o n s used h e r e i n f o r t h e f i v e c o a l s a r e as f o l l o w s ; H.C. OX  -  Hat Creek O x i d i s e d  H.C. UN  -  Hat Creek U n o x i d i s e d  CO: OX  Cominco O x i d i s e d  CO:ASH  Cominco Ash Waste  C0:PR0D  Cominco P r o d u c t i o n 4  5  2.2.  Coal  Preparation The c o a l was washed w i t h t a p w a t e r t o g e t r i d o f d i r t p a r t i c l e s .  A f t e r b e i n g d r i e d i n an oven, i t was p u t through a T r a y l o r G y r a t o r y C r u s h e r w i t h h" opening (-3% mesh), and then put through a Massco Cone Crusher w i t h an  .0083" opening (-65 mesh).  I t was s u b s e q u e n t l y d r y - s i e v e d  m e c h a n i c a l s h a k e r and 28/48 mesh s c r e e n s .  using a  Wet s i e v i n g o f t h e 28/48 c o a l  p a r t i c l e s was t h e n done t o remove t h e f i n e s s t u c k t o t h e 28/48 p a r t i c l e s . F u r t h e r removal o f f i n e s was a c c o m p l i s h e d by backwashing t h e c o a l i n a p l e x i g l a s s column.  When almost a l l the f i n e s were removed, t h e c o a l was d r i e d a t  103° C. f o r about 40 h o u r s . with nitrogen  I t was then t r a n s f e r r e d i n t o a b o t t l e ,  gas and k e p t s e a l e d  u n t i l use.  flushed  A f t e r each sample e x t r a c t i o n ,  the b o t t l e was r e f l u s h e d w i t h n i t r o g e n and r e s e a l e d .  2.3  P e r c e n t Recovery o f 28/48 S i z e F r a c t i o n from Raw Commercial C o a l (3) Based on Hendren's f i n d i n g s  t i o n with respect to adsorptive  on t h e o p t i m a l p a r t i c l e s s i z e f r a c -  capacity  as w e l l as h y d r a u l i c  T y l e r mesh s i z e f r a c t i o n was chosen f o r t h i s e n t i r e Following  the c o a l crushing  f l o w , t h e 28/48  research.  procedure o u t l i n e d p r e v i o u s l y ,  about  13% o f t h e i n i t i a l raw c o a l w e i g h t was r e c o v e r e d i n t h e 28/48 s i z e range i n the case o f H.C. OX.  The p e r c e n t r e c o v e r y f i g u r e i n t h e 28/48 s i z e range  f o r CO:ASH was about 14%. 2.4  Optimizing the Coal Preparation Procedure f o r Increased Percent Recovery of 28/48 S i z e F r a c t i o n A point  t o n o t e i s t h a t a 65 mesh was used i n t h e f i n a l  crusher.  T h i s means most o f t h e c o a l was c r u s h e d t o a s i z e . f i n e r t h a n t h e 28/48 s i z e range, and most o f t h e c o a l t h e r e f o r e went r i g h t through t h e 48 s c r e e n .  6  Thus, t h e c r u s h i n g p r o c e d u r e w i l l prove c r u c i a l when t h e o v e r a l l economics of the system a r e c o n s i d e r e d . the  There i s no r e a s o n n o t t o expect  p e r c e n t r e c o v e r y i n the 28/48 s i z e f r a c t i o n t o be i n c r e a s e d tremendously  from t h e f i g u r e s s t a t e d above f o r the two c o a l s i f t h e f o l l o w i n g s t e p s a r e taken:1.  Use t h e p r o p e r t y p e o f c r u s h e r o r a s e r i e s o f c r u s h e r s  t h a t w i l l m i n i m i z e t h e f r a c t i o n o f c o a l s m a l l e r than 48 mesh s i z e . 2. of  Use an o p t i m a l c l o s e d - c i r c u i t system t h a t a l l o w s r e c r u s h i n g c o a l p a r t i c l e s b i g g e r than 28 mesh s i z e .  3.  Use t h e type o f s c r e e n t h a t w i l l m i n i m i z e f u r t h e r p a r t i c l e  break-up. 4.  Use a method o f removal o f t h e r e m a i n i n g s l i m e and f i n e s  t h a t w i l l n o t enhance f u r t h e r f r a c t u r e of t h e c o a l p a r t i c l e s . U n f o r t u n a t e l y , t h e r e w i l l always be a c e r t a i n p e r c e n t a g e l o s t as s l i m e and f i n e s which a r e removed by wet s i e v i n g and backwashing p r o c e s s e s . S l i m e i s made up o f f i n e s s m a l l e r than .08 mm o r 200 mesh s i z e .  Slime r e s i s t s  w e t t i n g a c t i o n of t h e w a t e r and f l o a t s t o t h e t o p .  2.5  Synthetic  Wastewaters  The waste s o l u t i o n s were p r e p a r e d s y n t h e t i c a l l y i n t h e l a b o r a t o r y . The m a t e r i a l s used t o make up a 1000 mg/£ s t o c k s o l u t i o n o f t h e heavy m e t a l are  l i s t e d i n TABLE 2.1.  7  TABLE 2.1 SYNTHETIC WASTEWATERS  HEAVY METAL  MATERIALS USED TO MAKE 1000 mg/Jl STOCK SOLUTION SOLUTE  SOLVENT  Cu  Copper Oxide  Zn  Z i n c Oxide  II  II  II  Pb  Lead M e t a l  II  II  II  Hg  Mercuric  Chloride  Dilute Nitric  Acid  D i s t i l l e d Water  The m a t e r i a l s used a r e t h e same as t h e ones used i n Atomic Absorption stock s o l u t i o n s .  The p r e p a r e d 1000 mg/i  s t o c k s o l u t i o n was then used t o make up  d i l u t i o n s of a desired concentration. When t h e p r e p a r e d waste s o l u t i o n was found t o be t o o a c i d i c , t h e pH was a d j u s t e d as r e q u i r e d by a d d i t i o n of NaOH.  P r e l i m i n a r y t e s t s showed  t h a t NaOH does n o t i n t e r f e r e w i t h t h e a d s o r p t i o n p r o c e s s .  Chapter 3 BATCH TESTS  3.1  Introduction Emphasis was l a i d on i n i t i a l c o n c e n t r a t i o n s o f 2 mg/£ and l e s s .  Throughout the b a t c h t e s t s , a l l f i v e c o a l s were t e s t e d w i t h 2 mg/&  initial  c o n c e n t r a t i o n s o f c o p p e r , l e a d and z i n c , w i t h the b e s t two c o a l s b e i n g f u r t h e r s u b j e c t e d t o t e s t s w i t h i n i t i a l c o n c e n t r a t i o n s o f 1 mg/£ and 0.5 mg/£, as w e l l as w i t h some h i g h e r c o n c e n t r a t i o n s .  Copper t e s t s were t h e e x c e p t i o n  where a l l f i v e c o a l s were s u b j e c t e d t o t e s t s w i t h h i g h e r  concentrations.  Mercury t e s t s were done i n v e r y low c o n c e n t r a t i o n s o f 15 - 50 'Hg/£ f o r most of t h e b a t c h  tests.  An optimum p r a c t i c a l c o n t a c t time was i n v e s t i g a t e d f o r two r e a s o n s : to save t i m e , and t o m i n i m i z e p a r t i c l e break-up o f t h e c o a l w h i c h i s f a v o u r e d with long periods of shaking. I t was s u s p e c t e d adsorption process.  t h a t t h e pH would p l a y an i m p o r t a n t  r o l e i n the  The e f f e c t s o f pH on t h e a d s o r p t i v e c a p a c i t y o f c o a l  were i n v e s t i g a t e d w i t h z i n c , copper and l e a d s o l u t i o n s . From the b a t c h coal) versus is for  t e s t s d a t a , a p l o t o f c a p a c i t y (mg adsorbed/ g o f  e q u i l i b r i u m c o n c e n t r a t i o n (mg/£) can be drawn.  Such d a t a d i s p l a y  c a l l e d an "ADSORPTION ISOTHERM", w h i c h i s s i m p l y a f u n c t i o n a l e x p r e s s i o n the v a r i a t i o n o f a d s o r p t i o n w i t h c o n c e n t r a t i o n o f a d s o r b a t e i n b u l k  s o l u t i o n a t constant  temperature.  Commonly, t h e amount o f adsorbed m a t e r i a l  p e r u n i t w e i g h t o f adsorbent i n c r e a s e s w i t h i n c r e a s i n g c o n c e n t r a t i o n , b u t n o t in direct proportion. The major p o r t i o n o f t h e b a t c h t e s t s i n v o l v e d determing t h e a d s o r p t i o n isotherms  f o r t h e f o u r heavy m e t a l s under s t u d y ,  ( i . e . , Zn, Cu,  Pb and Hg) under v a r i o u s c o n d i t i o n s o f pH, i n i t i a l c o n c e n t r a t i o n , type o f  8  9  adsorbent and o t h e r parameters. 3.2  Batch Testing Procedure A)  F o r Copper, Lead and Z i n c 1.  The r e q u i r e d amount of c o a l was p l a c e d i n a 250 ml  Erlenmeyer  flask. 2.  One hundred m i l l i l i t r e s  c o n c e n t r a t i o n was 3.  of the s y n t h e t i c wastewater o f known  added t o the f l a s k .  The f l a s k was c l o s e d w i t h a r u b b e r s t o p p e r and shaken w i t h  a w r i s t - a c t i o n s h a k e r f o r the r e q u i r e d c o n t a c t t i m e .  Shaking  i n t e n s i t y was such t h a t the wastewater was w e l l a g i t a t e d b u t not s e v e r e enough t o move the c o a l around and b r e a k the p a r t i c l e s . 4.  The c o a l was  filtered  o f f and the c l e a r f i l t r a t e was a n a l y s e d  by Atomic A d s o r p t i o n S p e c t r o s c o p y f o r the e q u i l i b r i u m c o n c e n t r a t i o n of m e t a l i o n s .  The a n a l y s i s f o r c o p p e r , l e a d and z i n c was i n  accordance w i t h "Water A n a l y s i s by Atomic A d s o r p t i o n - V a r i a n Techtron". B)  For Mercury The p r o c e d u r e i s the same as f o r c o p p e r , z i n c and l e a d d e s c r i b e d  p r e v i o u s l y up to the p o i n t when the s h a k i n g i s completed.  The s o l v e n t  testing  i s a c c o m p l i s h e d as f o l l o w s : a)  I n s t e a d of f i l t e r i n g ,  i n t o a t e s t tube.  50 m£ of wastewater i s s i m p l y decanted  D e c a n t i n g i s done i n s t e a d of f i l t r a t i o n  any mercury b e i n g adsorbed by the f i l t e r b)  to avoid  paper.  The decanted s o l u t i o n i s p l a c e d i n a c o o l e r f o r about 1 hour.  10  c)  0.5 ml o f c o n c e n t r a t e d ^ S O ^  *  s  then added t o the sample to  a l l o w o v e r n i g h t s t o r a g e o f the sample w i t h o u t v o l a t i l i z a t i o n of mercury. d)  B e f o r e t e s t i n g on the atomic a b s o r p t i o n s p e c t r o p h o t o m e t e r ,  0. 5 ml of 6 p e r c e n t p o t a s s i u m permanganate i s added.  The t e s t  tube  i s then shaken and a l l o w e d to s i t f o r about 20 m i n u t e s . e)  Three m i l l i l i t r e s of sample i s t r a n s f e r r e d t o a t e s t i n g  and d i l u t e d up to 100  flask  ml.  f)  0.5 m i l o f 10 p e r c e n t h y d r o x y l a m i n e h y d r o c h l o r i d e i s added.  g)  Two  m i l l i l i t r e s of 10 p e r c e n t SnCJ^  1 S  added j u s t b e f o r e  a n a l y s i s by the c o l d vapour t e c h n i q u e a c c o r d i n g to "Water A n a l y s i s by Atomic A b s o r p t i o n - V a r i a n T e c h t r o n " . The above procedure g i v e s r i s e t o a d e t e c t i o n l i m i t o f .05 yg/£ mercury.  C o n f i d e n c e decreases w i t h l e v e l s below .05. vg/l due to  of  background  interference. 3.3  D e t e r m i n a t i o n of Optimum C o n t a c t Time Batch t e s t s were done on H.C.  OX and H.C.  e q u i l i b r i u m c o n c e n t r a t i o n at v a r i o u s contact times. was.  2.0  UN t o determine  the  The pH of the s o l u t i o n  and the r e s u l t s a r e shown i n F i g u r e 3.1(a). The same k i n d o f t e s t s were done w i t h the Cominco c o a l s a t a  pHof5.2.  The d a t a o b t a i n e d f o r t h i s s e r i e s o f t e s t s are shown i n F i g u r e 3.1(b). From the r e s u l t s , the f o l l o w i n g c o n c l u s i o n s can be made:1.  C o n t a c t time o f 60 mins. w i l l a c h i e v e n e a r l y a l l o f the  u l t i m a t e removal  ( i . e . , 93 p e r c e n t and g r e a t e r o f the u l t i m a t e  removal). 2.  A c i d o r n e u t r a l c o n d i t i o n s do n o t i n f l u e n c e the optimum c o n t a c t  11  FIG. 3.1 (a) CONTACT TIME - EQUILIBRIUM CONCENTRATION FOR COPPER  12  FIG. 3.1 (b) CONTACT T I M E - EQUILIBRIUM CONCENTRATION FOR COPPER  Contact  Time -  minutes  13  FIG. 3.1 (c) CONTACT TIME - EQUILIBRIUM CONCENTRATION FOR COPPER  Contact  time - minutes  14  time.  The e q u i l i b r i u m c o n t a c t  time curve l e v e l s out by the end  of 60 mins. The Cominco c o a l s were n e x t b a t c h t e s t e d w i t h copper a t an i n i t i a l concentration  o f 10 mg/1  i n s t e a d o f 50 mg/Jl.  The w e i g h t of c o a l was a l s o  p r o p o r t i o n a t e l y d e c r e a s e d f i v e times from 20 gm t o 4 gm ( F i g u r e The r e s u l t s i n d i c a t e t h a t an optimum c o n t a c t at d i f f e r e n t concentrations by  time o f 60 minutes s t i l l  and c o a l w e i g h t s .  holds  This f a c t i s f u r t h e r supported  r e s u l t s i n F i g u r e 3.2, where an optimum c o n t a c t  time o f 1 hour i s s t i l l  v a l i d a t d i f f e r e n t c o m b i n a t i o n s o f c o a l w e i g h t and i n i t i a l E x t e n d i n g the c o n t a c t  3.1(c)).  concentration.  time t o 3 o r 4 hours c o n t r i b u t e s v e r y  little  to f u r t h e r removal and may even enhance p a r t i c l e break-up and consequent s i z e r e d u c t i o n o f t h e 28/48 c o a l . 3.4  E f f e c t s of pH on A d s o r p t i v e  Capacity  of Coal  S e v e r a l b a t c h t e s t s were performed t o i n v e s t i g a t e the e f f e c t o f pH on the a d s o r p t i o n  process.  S i n c e H.C. OX had so f a r d i s p l a y e d a g r e a t e r a d s o r p t i v e than the o t h e r c o a l s , i t was used f o r t h i s s e t of b a t c h t e s t s . t r a t i o n o f waste was i n i t i a l l y contact and  time was 1 h o u r .  capacity  The concen-  2 mg/il, the w e i g h t o f c o a l was 1 gm and the  T e s t s were performed a t pH v a l u e s o f 1.5, 2.5, 4.0  5.8 f o r s o l u t i o n s c o n t a i n i n g each of c o p p e r , l e a d and z i n c . The r e s u l t s a r e shown i n t a b u l a r form i n T a b l e 3.1.  d e f i n i t e r e l a t i o n s h i p between pH and a d s o r p t i v e  capacity.  There i s a  A t pH o f 1.5 the  c a p a c i t y was n i l f o r a l l t h r e e m e t a l s a t t h e s e low c o n c e n t r a t i o n s . i n c r e a s e o f pH t h e r e i s a c o r r e s p o n d i n g r i s e i n c a p a c i t y ,  W i t h the  i n t h e case o f l e a d ,  the c o a l had adsorbed t h e m e t a l t o w e l l below the d e t e c t i o n l i m i t a t a pH o f 5.5.  15  TABLE 3.1 EFFECTS OF pH ON THE ADSORPTIVE CAPACITY OF COAL  Metal  I n i t i a l concentration  =  2.0  Coal  =  H.C. OX  C o a l Weight  =  1 gm  pH  Equilibrium concentration a f t e r 1 hour  mg/I  mg Adsorbed / gm c o a l  (mg/A)  Cu  Zn  Pb  1.5  2.00  0.000  2.5  1.20  0.080  4.0  0.30  0.170  5.6  0.25  0.175  2.00  0.000  2.5  1.62  0.038  4.0  0.43  0.157  6.2  0.30  0.170  1.5  2.00  0.000  2.5  0.80  0.120  4.0  0.00  0.200  5.5  0.00  0.200  1.5  .  16  F o l l o w i n g the t r e n d of the r e s u l t s , the c a p a c i t y s h o u l d even be g r e a t e r a t a pH of 7 b u t , s i n c e the emphasis was on a c i d i c w a s t e s , no were done a t h i g h e r pH v a l u e s .  tests  I t can be seen t h a t t h e r a t e o f change i n  a d s o r p t i v e c a p a c i t y p e r u n i t change i n pH i s d i f f e r e n t f o r each m e t a l . 3.5  E f f e c t s of I n i t i a l C o n c e n t r a t i o n Change & C o a l Weight Change on P e r c e n t Removal T a b l e 3.2 shows the e f f e c t of changing c o a l w e i g h t and  initial  c o n c e n t r a t i o n i n the same p r o p o r t i o n on the p e r c e n t removal a c h i e v e d . 20 gm of c o a l and 50 mg/Ji^Cu, 91 p e r c e n t removal i s a c h i e v e d . b o t h parameters t o h a l f (10 gm of c o a l and 25 mg/£  With  By r e d u c i n g  Cu) 87 p e r c e n t removal i s  a c h i e v e d and when the parameters are d i v i d e d by 5 t o 4 gm of c o a l and 10 Cu, 92 p e r c e n t removal i s seen.  mg/£  T a k i n g the n o i s e and o t h e r i n h e r e n t e r r o r s  i n t o c o n s i d e r a t i o n , i t can be c o n c l u d e d t h a t when c o a l w e i g h t and  initial  c o n c e n t r a t i o n a r e b o t h changed i n the same p r o p o r t i o n , the p e r c e n t removal s t a y s about the same.  The p e r c e n t removals were c a l c u l a t e d from v a l u e s a t  c o n t a c t time of 60 m i n u t e s .  F i g u r e 3.2 shows the r e s u l t s of v a r y i n g  parameter by f i v e times w h i l e k e e p i n g the o t h e r parameter f i x e d .  The  one following  p o i n t s summarize the d a t a : 1.  S t a r t i n g o f f w i t h 1 gm of Cominco Ash c o a l and 50 mg/Jl Cu  r e s u l t e d i n 19 p e r c e n t removal a t 1 hour c o n t a c t t i m e ; 2.  I n c r e a s i n g the amount of c o a l 5 times and u s i n g the same  50 mg/£ 3.  Cu s o l u t i o n r e s u l t e d i n 47 p e r c e n t removal a t 1 h o u r ;  W i t h a copper c o n c e n t r a t i o n o f 10 mg/£  and the same c o a l w e i g h t ,  73 p e r c e n t removal was o b t a i n e d i n 1 hour - an i n c r e a s e i n p e r c e n t removal o v e r t h a t of case (1) by 54 p e r c e n t .  T h i s i s about double  FIG. 3.2 E F F E C T S ON PERCENT REMOVAL WHEN CHANGING O N E P A R A M E T E R WHILE K E E P I N G THE OTHER FIXED 1 7  \ \  Igm COAL  5  19 % Removal  9™ COAL  4 7 % Removal  pH = 5.2 CoaI = Cominco  Ash  Waste Element = Cu  gm COAL  30  45  6CK Contact  120 time - minutes  73%^Removal  180  210  18  TABLE 3.2  EFFECT OF CHANGING COAL WEIGHT & INITIAL CONCENTRATION IN THE SAME PROPORTION ON THE PERCENT REMOVAL C o a l = Cominco Ash Waste pH = 5.2  C o a l Weight (gm)  Initial Concentration Gag/A Cu)  Equilibrium Concentration @ 1 hr (mg/Jl Cu)  Percent Removal of Cu  20  50  4.5  91  10  25  3.3  87  4  10  0.8  92  the i n c r e a s e a c h i e v e d by i n c r e a s i n g t h e c o a l w e i g h t 5 t i m e s . This increase i n percent  removal when t h e waste c o n c e n t r a t i o n i s  lowered promises a good p o l i s h i n g j o b by c o a l treatment A p o s s i b l e e x p l a n a t i o n f o r t h i s increase i n percent be the v e r y s l i g h t i n c r e a s e i n pH on d i l u t i o n . and a t 10 mg/£ t h e pH was a p p r o x i m a t e l y c o u l d be the change i n t h e c o n t r o l l i n g  5.3.  a t low c o n c e n t r a t i o n s .  removal on d i l u t i o n  could  A t 50 mg/£ t h e pH was 5.2 Another p o s s i b l e e x p l a n a t i o n  o r l i m i t i n g phase o f t h e r e a c t i o n .  At  h i g h s o l u t e c o n c e n t r a t i o n s , t h e a v a i l a b l e exchange s i t e s might be l i m i t i n g ; w h i l e a t lower s o l u t e c o n c e n t r a t i o n s , t h e boundary l a y e r c o n c e n t r a t i o n might be l i m i t i n g .  gradient  19  3.6  A d s o r p t i o n Isotherms f o r Copper 1.  F i g u r e 3.3(a) shows a d s o r p t i o n i s o t h e r m s  f i v e types of c o a l s .  The  i n i t i a l c o n c e n t r a t i o n s of copper i s 2 mg/Z  c o a l w e i g h t i s changed from 1.0 isotherm.  f o r copper w i t h a l l  t o 10.0  and  gm t o g i v e the d a t a p o i n t s on  A l l f i v e c o a l s brought the c o n c e n t r a t i o n down to 0.3 mg/£  the  the and  less.  The b e s t performance i s d i s p l a y e d by C0:0X and CO:ASH where the e q u i l i b r i u m c o n c e n t r a t i o n i s b r o u g h t down t o 0.05  mg/Z.  For a q u i c k comparison w i t h  v a t e d carbon, some Darco A c t i v a t e d Carbon (Grade 12 x 20) was  also tested.  r e s u l t i n g a d s o r p t i o n i s o t h e r m f o r a c t i v a t e d carbon shows the copper t i o n b e i n g brought down t o u n d e t e c t a b l e  levels.  Taking  acti-  instrument  The  concentranoise  into  a c c o u n t , i t c o u l d be i n t e r p r e t e d t h a t t h e r e i s p r a c t i c a l l y no d i f f e r e n c e between the b a t c h removal e f f i c i e n c y of a c t i v a t e d carbon and C0:ASH or C0:0XIDISED a t low i n i t i a l c o n c e n t r a t i o n s of copper. 2.  F i g u r e 3.3(b) shows i s o t h e r m d a t a f o r C0:ASH and H.C.OX c o a l s  w i t h i n i t i a l c o n c e n t r a t i o n s of 1.0 w e i g h t was The  v a r i e d from 0.5  mg/£. and 0.5  gm t o 3.0  mg/£  o f copper.  gm to g i v e the p o i n t s on the  d a t a shows t h a t CO:ASH reduces the c o n c e n t r a t i o n to .01 mg/Z  a s o l u t i o n o f 1.0 c o n t a i n i n g 0.5  mg/Z,  mg/Z.  and  to u n d e t e c t a b l e  The  coal  isotherm. when t r e a t i n g  l e v e l s when t r e a t i n g a s o l u t i o n  I t i s f u r t h e r e v i d e n t th/at CO:ASH p r o v i d e s  higher  removal e f f i c i e n c i e s a t these low s o l u t e c o n c e n t r a t i o n s t h a n does H.C. 3.  F i g u r e 3.3(c) shows copper i s o t h e r m s  c o a l w e i g h t s of 0.5 to  300 mg/Z  for a l l f i v e coals, using  gm and i n i t i a l s o l u t e c o n c e n t r a t i o n r a n g i n g from 2  of copper.  mg  mg/Z  At h i g h e r c o n c e n t r a t i o n s , b o t h of the Hat Creek c o a l s  have a g r e a t e r c a p a c i t y than any of the Cominco c o a l s . c a p a c i t y of 6.0  OX.  The H.C.  OX reaches a  Cu/gm c o a l at an e q u i l i b r i u m c o n c e n t r a t i o n of about 170 mg/Z  CO:ASH and C0:0X seem to behave i d e n t i c a l l y w i t h r e g a r d to copper i n b o t h h i g h  Cu.  20  FIG. 3.3 (a) COPPER ADSORPTION ISOTHERMS pH = 5 . 3 I n i t i a l concentration = 2 m g / l i t r e  I—I—I  0.05 0.1  I  0.2  Equilibrium  I  X  X  H.C . Oxidized  A  A  H.C . Unoxidized  • — •  Co; Production  o—o  Co: Ash  • — •  Co =O x i d i z e d  • — •  Act vated  I  0.4  I  I  Carbon  I  0.6  c o n c e n t r a t i o n - mg / litre Cu  I  0.8  INITIAL CONCENTRATION  0I 0  1  1  O.OI  0.02  1  1  1  0.04  I  0.06  Equilibrium  I  I  0.08  I  I  0.10  I  concentration mg/litre Cu  I  0.12  i  i  0.14  FIG. 3.3(c) COPPER ADSORPTION I S O T H E R M S .  pH = 5.0 —  5.4  Coal weight = 0.5g  Equilibrium concentration mg/litre Cu  22  24  and low e q u i l i b r i u m c o n c e n t r a t i o n s . 4.  F i g u r e 3.3(d) shows a d s o r p t i o n i s o t h e r m s  c o a l s u s i n g c o a l w e i g h t s of 1.0 from 2 mg/I  t o 50 mg/£.  H.C.  f o r H.C.  OX and CO:ASH  gm and i n i t i a l copper c o n c e n t r a t i o n s  OX performs b e t t e r at h i g h e r  ranging  concentrations  w h i l e the CO:ASHhas. a g r e a t e r c a p a c i t y at copper c o n c e n t r a t i o n s of 2 mg/£ less.  (Note the i n t e r s e c t i o n of two i s o t h e r m s  a t about 0.5  and  mg/ii, e q u i l i b r i u m  concentration). C o n s i d e r i n g the copper i s o t h e r m r e s u l t s and a few o t h e r p r a c t i c a l f a c t o r s , C0:ASH and H.C. 1.0 mg/Jo and 0.5  mg/£  OX were chosen f o r t e s t s w i t h i n i t i a l c o n c e n t r a t i o n s of  w h i l e v a r y i n g the c o a l w e i g h t and a l s o f o r t e s t s w i t h a  f i x e d c o a l w e i g h t of 1 gm w h i l e v a r y i n g the i n i t i a l c o n c e n t r a t i o n s from 2 mg/Z 50 mg/£. 3.7  T h i s p r o c e d u r e i s a p p l i e d i n z i n c and l e a d t e s t s a l s o .  A d s o r p t i o n Isotherms f o r Lead 1.  A l l f i v e c o a l s were t e s t e d u s i n g a s o l u t e c o n c e n t r a t i o n of 2 mg/Ji  of l e a d , w h i l e the c o a l w e i g h t was  v a r i e d from 1.0  t o 4.0  gm.  The pH was  A l l f i v e c o a l s reduced the s o l u t e c o n c e n t r a t i o n to u n d e t e c t a b l e the t e s t s performed.  T h i s "super" performance may  5.2.  levels i n a l l  be e x p l a i n a b l e by e i t h e r a  v e r y h i g h a f f i n i t y of the c o a l s f o r l e a d , or the r e l a t i v e l y h i g h d e t e c t i o n l i m i t for  lead.  The  d e t e c t i o n l i m i t s f o r the elements of c o n c e r n are shown below.  Element  D e t e c t i o n L i m i t by Atomic A b s o r p t i o n  Hg  .05 yg/£ f o r a 3 mil sample ( c o l d vapour t e c h n i q u e )  Zn  0.01  mg/£  (flame  technique)  Cu  0.04  mg/£  (flame  technique)  Pb  0.10  mg/£  (flame  technique)  -  26  2.  F i g u r e 3.4 shows the a d s o r p t i o n i s o t h e r m s  of a l l f i v e coals  u s i n g an adsorbent w e i g h t of 1.0 gm and i n i t i a l l e a d c o n c e n t r a t i o n s  ranging  from 2mg/£ tb.50mg/£. Hat Creek c o a l s p e r f o r m b e t t e r than Cominco c o a l s a t higher concentrations.  H.C.  OX performed the b e s t and a c h i e v e d a c a p a c i t y  o f 5 mg adsorbed/gm o f c o a l a t an e q u i l i b r i u m c o n c e n t r a t i o n of 1.2 3.8  mg/i.  A d s o r p t i o n Isotherms f o r Z i n c 1.  F i g u r e 3.5(a) shows the a d s o r p t i o n i s o t h e r m s  u s i n g an i n i t i a l c o n c e n t r a t i o n o f 2 mg/i from 0.5 gm t o 4.0 gm.  f o r a l l f i v e coals  Zn w i t h adsorbent w e i g h t s b e i n g v a r i e d  The Hat Creek c o a l s were found to be b e t t e r p e r f o r m e r s  i n t h i s c o n c e n t r a t i o n range,, w i t h t h e H.C. OX r e d u c i n g the z i n c c o n c e n t r a t i o n to  0.12 mg/£  ( u s i n g 4 gm o f c o a l ) .  p r a c t i c a l l y no s c a t t e r whatsoever.  The Hat Creek c o a l s have i s o t h e r m s  with  T h i s c o u l d mean t h a t the Hat Creek c o a l s  have a d s o r p t i o n p r o p e r t i e s more homogeneously d i s t r i b u t e d throughout the c o a l mass than the Cominco c o a l s . 2.  F i g u r e 3.5(b) shows the i s o t h e r m s  f o r H.C. OX and C0:ASH c o a l s  w i t h i n i t i a l s o l u t e c o n c e n t r a t i o n s o f 1.0 mg/£ Zn and 0.5 mg/£ Zn. w e i g h t was v a r i e d from 0.5 gm t o 3.0 gm.  The H.C.  The c o a l  OX shows a g r e a t e r capa-  c i t y than C0:ASH a t a l l e q u i l i b r i u m c o n c e n t r a t i o n s t e s t e d .  With an i n i t i a l  c o n c e n t r a t i o n o f 0.5 mg/£, the H.C. OX reduced the c o n c e n t r a t i o n t o 0.02 With an i n i t i a l z i n c c o n c e n t r a t i o n o f 0.5 mg/ft, the i s o t h e r m s  mg/£.  f o r the two  c o a l s came c l o s e r t o each o t h e r , i n d i c a t i n g a s m a l l e r d i f f e r e n c e i n c a p a c i t y w i t h i n t h i s range o f e q u i l i b r i u m c o n c e n t r a t i o n s . 3.  Isotherms f o r H.C.  OX and C0:ASH w i t h i n i t i a l  zinc  t i o n s r a n g i n g from 2\mg/£ t o 50 mg/£ a r e shown i n F i g u r e 3 . 5 ( c ) . w e i g h t was f i x e d a t 1.0 gm.  H.C.  concentraThe c o a l  OX performs b e t t e r , showing a c a p a c i t y o f  2.13 mg adsorbed/gm c o a l a t an e q u i l i b r i u m s o l u t e c o n c e n t r a t i o n o f 28.7 mg/£.  ,1 0  1  1  I  0.1  0.2  0.3  I  I  I  I  I  I  I  I  I  0.4  0.5  0.6  0.7  0.8  0.9  1.0  1.2  1.4  Equilibrium  concentration  mg/litre  Zn  I 1.6  28  FIG. 3.5(b) Z I N C ADSORPTION  ISOTHERMS  pH = 6.0 Initial concentration = I mg/litre Zn and 0.5mg/litre Zn  0  0.03 0.05  0.10  0.15  0.20  Equilibrium concentration mg/litre Zn  0.25  0.30  30.  3.9  A d s o r p t i o n Isotherms f o r Mercury 1.  I n F i g u r e 3.6(a)  r e s u l t s a r e shown from a s e r i e s o f t e s t s  u s i n g i n i t i a l s o l u t e c o n c e n t r a t i o n s o f 50 yg/£ from 1 gm to 4 gm.  The  isotherms  Hg, w i t h c o a l w e i g h t s v a r y i n g  show t h a t the Hat Creek c o a l s have h i g h e r  a d s o r p t i v e c a p a c i t i e s than do the Cominco c o a l s . very s i m i l a r isotherms, 2.  The  two Cominco c o a l s have  i n d i c a t i n g very s i m i l a r adsorptive p r o p e r t i e s .  F i g u r e 3.6(b) shows i s o t h e r m ' r e s u l t s f o r H.C.  OX and C0:ASH  w i t h i n i t i a l mercury c o n c e n t r a t i o n s of 15 yg/ft and 30 yg/£. was  v a r i e d from 0.5  gm  to 3.0  gm.  H.C.  good p e r c e n t 3.  H.C.  W i t h an i n i t i a l  OX produced an e f f l u e n t c o n t a i n i n g 3 yg/£,  isotherms  t i o n s r a n g i n g from 100 yg/£ shown i n F i g u r e 3 . 6 ( c ) . H.C.  tested.  removal even a t t h i s low i n i t i a l The  The  f o r H.C.  ( i . e . , from .1 mg/£  c o a l w e i g h t used was  1.0  gm.  concentra-  to 2.0 The  mg/£)  s l o p e of  OX i s o t h e r m i s v e r y much s t e e p e r than t h a t o f the CO:ASH i s o t h e r m  of 0.18  3.10  indicating  OX and CO:ASH w i t h i n i t i a l  to 2000 yg/£  concentra-  concentration.  c a t i n g a s i g n i f i c a n t c a p a c i t y advantage u s i n g H.C.  0.21  c o a l weight  OX d i s p l a y s a g r e a t e r c a p a c i t y than  CO:ASH a t a l l e q u i l i b r i u m c o n c e n t r a t i o n s t i o n o f 15 yg/£,  The  OX.  are the  indi-  I t reached a c a p a c i t y  mg adsorbed/gm c o a l a t an e q u i l i b r i u m mercury c o n c e n t r a t i o n of  mg/£.  Batch T e s t s - Summary and 1.  The  Conclusions  optimum c o n t a c t time f o r b a t c h t e s t s to a c h i e v e a h i g h  p e r c e n t a g e of u l t i m a t e e q u i l i b r i u m c o n c e n t r a t i o n w i t h i n a s h o r t p r a c t i c a l p e r i o d o f time was 2.  The  found to be 1 h o u r . a d s o r p t i v e c a p a c i t y o f c o a l f o r copper, l e a d and z i n c was  found to i n c r e a s e as the pH was  r a i s e d from 1.5  t o 6.2.  The r a t e o f change  i n a d s o r p t i v e c a p a c i t y p e r u n i t change i n pH i s d i f f e r e n t f o r each m e t a l .  F I G . 3.6(a) MERCURY ADSORPTION  ISOTHERMS  pH = 5.8 Initial concentration = 50ug/l  (0.050mg/litre)  Equilibrium concentration mg/litre Hg  FIG.  3.6  (b)  MERCURY ADSORPTION ISOTHERMS  pH = 5.8 Initial concentration = 15 ug/l and 30 ug/l of Hg  0 I 0  I  I  I  I  0.005 0.010 0.015 Equilibrium concentration mg/litre  I  0.020 Hg  pH = 5.4 — Coal  5.8  weight = 1 g  Initial concentrations = IOOug/1 — 2,OOOug/l  m 3J  34  3.  When c o a l w e i g h t and i n i t i a l m e t a l c o n c e n t r a t i o n a r e b o t h  changed i n t h e same p r o p o r t i o n , t h e p e r c e n t removal s t a y s about t h e same. 4.  D i l u t i n g t h e waste r e s u l t e d i n a s i g n i f i c a n t l y g r e a t e r  increase  i n p e r c e n t removal than would be o b t a i n e d when t h e c o a l w e i g h t i s i n c r e a s e d i n s t e a d by t h e same p r o p o r t i o n . 5.  (a) Of t h e two Hat Creek c o a l s , H.C. OX was the b e t t e r p e r -  former w i t h c o p p e r , z i n c and mercury as t h e a d s o r b a t e .  I n t h e case o f l e a d ,  H.C. OX has a g r e a t e r c a p a c i t y w i t h i n t h e 2 mgl I - 50 mg/H e q u i l i b r i u m conc e n t r a t i o n range.  No d i f f e r e n t i a t i o n c o u l d be made when t h e e q u i l i b r i u m con-  c e n t r a t i o n was below 2 mg/H Pb.  Among t h e Cominco c o a l s , C0:0X and CO:ASH  d i s p l a y e d t h e same i s o t h e r m w i t h 2 mg/i Cu i n i t i a l  concentration.  I n almost  a l l o f t h e r e m a i n i n g e x p e r i m e n t s w i t h l e a d , z i n c and mercury, CO:OX appeared to be o n l y m a r g i n a l l y b e t t e r than CO:ASH. On t h e b a s i s o f t h e s e r e s u l t s , H.C. OX and CO:ASH were chosen as the b e s t o f each c o a l type f o r t h e column t e s t phase o f t h e p r o j e c t . was  CO:ASH  chosen because i t performed almost as w e l l as C0:0X, and i t has a b e t t e r  p r o d u c t i o n p o t e n t i a l because o f i t s g r e a t e r (b)  availability.  T a b l e 3.3 shows t h e comparison o f H.C. OX and CO:ASH  with regard t o t h e i r adsorptive c a p a c i t i e s .  T a b l e 3.3 i n d i c a t e s a d s o r p t i v e  s u p e r i o r i t y : o f H.C. OX w i t h l e a d , z i n c and mercury.  I n t h e case o f copper,  H.C. OX has a g r e a t e r a d s o r p t i v e c a p a c i t y i n t h e h i g h e r i n i t i a l range (2.0 mg/Jl - 50 mg/1), w h i l e i n t h e l o w e r i n i t i a l  concentration  c o n c e n t r a t i o n range o f  2.0 mg/i and l e s s t h e s i t u a t i o n i s r e v e r s e d and CO:ASH p r o v e d t o be t h e s u p e r i o r one. (c)  T a b l e 3.4 shows a comparison o f performance o f a p a r t i -  c u l a r c o a l w i t h each o f t h e f o u r heavy m e t a l s .  W i t h i n t h e e q u i l i b r i u m concen-  35  t r a t i o n range o f .03 mg/Z  t o 30.0 mg/£, l e a d has t h e g r e a t e s t a f f i n i t y f o r  a d s o r p t i o n by b o t h c o a l s .  Copper p r o v e d t o have t h e second h i g h e s t a f f i n i t y ,  z i n c t h i r d and mercury l a s t w i t h r e g a r d t o a d s o r p t i o n by b o t h c o a l s .  TABLE 3.3 COMPARISON OF H.C. OX AND CO:ASH  Note:  The c o a l w i t h a b e t t e r a d s o r p t i o n performance i s p r i n t e d i n the relevant s l o t .  Element  Cu  I n i t i a l C o n c e n t r a t i o n s o f Wastewater 0.5 mg/£  1.0 mg/£  2.0 mg/£  CO:ASH  CO:ASH  CO:ASH  Pb Zn  Hg  UNDIFFERENTIABLE  -*  H.C. OX  H.C. OX  H.C. OX  15 ug/£  30 yg/£  50 yg/£  H.C. OX  H.C. OX  H.C. OX  2.0 mg/£ - 50 mg/£  H.C. OX -»-  H.C. OX H.C. OX  100 yg/£ -• 2000 yg/£ (.1 mg/£ - 2.0 mg/£) H.C. OX  36  TABLE 3.4 Comparison o f t h e C a p a c i t i e s o f Two C o a l s F o r Each o f t h e Four Heavy M e t a l s Equilibrium C o n c e n t r a t i o n (mg/Jl)  Coal  H.C. OX  .05  BDL*  ,.015  .035  .080  .10  >.10  .10  .07  .25  .50  3.20  .50  .35  .37  l.O  4.80  .90  .55  >5.0  2.50  .98  10.0  >5.0  3.00  1.27  30.0  >5.0  4.80  2.17  .03  BDL*  .18  .003  .03  .10  > .20  .20  .008  .032  .50  1.50  .43  .035  .08  1.0  1.68  .50  .065  .155  5.0  1.98  .95  .20  10.0  2.30  1.28  .25  30.0  3.10  1.38  .45  5.0  CO:ASH  C a p a c i t y (mg adsorbed/gm c o a l ) Pb Cu Hg Zn  NOTE: 1.  * BDL means t h e e q u i l i b r i u m c o n c e n t r a t i o n i s below d e t e c t i o n l i m i t and c o n s e q u e n t l y t h e c a p a c i t y cannot be determined.  2.  S e v e r a l b l a n k s a r e shown i n t h e Hg column due t o t h e f a c t t h a t Hg was n o t t e s t e d a t these h i g h e r c o n c e n t r a t i o n s .  37  Chapter 4 COLUMN TESTS  4.1  Introduction Based on t h e r e s u l t s o f t h e b a t c h t e s t s , H.C. OX'from t h e Hat Creek  group and CO:ASH from t h e Cominco group o f c o a l s were chosen f o r f u r t h e r i n v e s t i g a t o r y work w i t h c o n t i n u o u s f l o w , f i x e d - b e d columns. On t h e b a s i s o f t h e d a t a from t h e b a t c h t e s t s and from a few p r e l i m i n a r y column t e s t s a t v a r i o u s v a l u e s o f t h e i n f l u e n t pH, t h e maximum a d s o r p t i v e c a p a c i t y o f a p a r t i c u l a r column was s u s p e c t e d t o o c c u r a t an i n f l u e n t pH near n e u t r a l i t y  (6 t o 7?5). I n i t i a l r e s u l t s i n d i c a t e d t h a t a t such a n e u t r a l  pH, and under t h e l a b o r a t o r y c o n d i t i o n s used i n t h i s r e s e a r c h , i t would  take  more than t e n o r e l e v e n days f o r any s i g h o f m e t a l b r e a k t h r o u g h t o o c c u r .  To  overcome t h i s i m p r a c t i c a l i t y w i t h r e g a r d t o t h e time f a c t o r , t h e pH was reduced to  4.0, w h i c h gave r i s e t o a b r e a k t h r o u g h w i t h i n a r e a s o n a b l e p e r i o d o f time;--  Then an e x t r a p o l a t i o n f a c t o r , d e r i v e d from p r e v i o u s column t e s t data.was employed t o g i v e an e s t i m a t e o f t h e a d s o r p t i v e c a p a c i t y a t an i n f l u e n t pH o f 6.0 «W.5. J.  The i n f l u e n t m e t a l c o n c e n t r a t i o n s were a t 2 mg/£ and l e s s f o r z i n c ,  copper and l e a d , and l e s s than 5 yg/£ f o r mercury. neighbourhood  These f i g u r e s a r e i n t h e  o f p e r m i s s a b l e l e v e l s , s e t up by t h e P o l l u t i o n C o n t r o l Board o f  B r i t i s h Columbia, f o r d i s c h a r g e o f t h e s e m e t a l s i n t o v a r i o u s types o f r e c e i v i n g waters. The f l o w r a t e s t e s t e d were between one and f i v e I g p m / f t . 2  These  f l o w r a t e s a r e r e p r e s e n t a t i v e o f t h e ones used i n r a p i d sand f i l t r a t i o n and a c t i v a t e d carbon a d s o r p t i o n systems. The c o a l depth was m a i n t a i n e d a t t e n i n c h e s f o r t h e f o l l o w i n g r e a s o n s : 1)  t o ensure t h a t t h e depth i s g r e a t e r than t h e c r i t i c a l b e d depth t o p r e v e n t  p e n e t r a t i o n o f c o n c e n t r a t i o n i n excess o f b r e a k t h r o u g h c o n c e n t r a t i o n a t zero t i m e ;  38  2)  t o s a t i s f y p r a c t i c a l c o n s i d e r a t i o n s t h a t t h e b r e a k t h r o u g h does n o t t a k e  too  long a p e r i o d of time.  E x c e s s i v e l y deep beds o f c o a l w i l l r e s u l t i n l o n g  p e r i o d s o f time f o r b r e a k t h r o u g h s t o o c c u r .  The depth o f t h e c o a l b e d i s an  i m p o r t a n t c r i t e r i o n whenever c o m p a r a t i v e work i s done, s i n c e t h e c o n t a c t time i s p r i m a r i l y dependent on the bed depth f o r a g i v e n f l o w r a t e .  T a b l e 4.1  shows t h e c o r r e s p o n d i n g c o n t a c t times f o r t h e f l o w r a t e s l i s t e d , based on an empty column and a c o a l - f i l l e d  column o f 10 i n c h e s .  TABLE 4.1 CONTACT TIMES FOR A 10-INCH COLUMN AT GIVEN FLOW RATES  FLOW RATE Igpm/ft  2  CONTACT TIME ( M i n ) inches/min  Empty Column  Coal-filled  1  1.92  5.21  2.86  5  9.60  1.04  0.58  F o r t h e c a l c u l a t i o n o f t h e a c t u a l c o n t a c t time f o r a c o a l - f i l l e d p o r o s i t y o f t h e c o a l column i s n e c e s s a r y .  Column  column, t h e  From t h e l i t e r a t u r e on bed p o r o s i t y ,  p a c k i n g , e t c . ( 1 1 , pp.537), a g r a p h , r e l a t i n g s p h e r i c i t y , type o f p a c k i n g and p o r o s i t y , was used t o e s t i m a t e the p o r o s i t y .  W i t h an assumed s p h e r i c i t y o f t h e  p a r t i c l e s o f 0.6 and a normal type o f p a c k i n g , t h e r e s u l t a n t p o r o s i t y was e s t i m a t e d a t 0.55.  39  Example  Calculation  for Actual  1 Based  Igpm/ft on a n  Contact  Time  1.92  in/min  =  2  empty  contact  c o l u m n o f 10  time  =  10  = Using the  actual  contact  The of  pH,  copper  or  the  portion  pH  an e f f l u e n t  1 1.92  5.21  min  of  0.55,  =  5.21  min  =  2.86  min  done w i t h on  in/min  c o l u m n o f 10 X  o f the column work  general objective of  t h e two  v a l u e s o f 4.0  pH  and  f o r mercury of  zinc  as  the atomic  inches  0.55  (i.e.,  investigating  the adsorbate.  absorption  the  Z i n c was  effects chosen  spectrophotometer  than  coals  tested  t e s t s was  for zinc,  to obtain  copper  and  some  lead  figures  at  5.7.  were  run w i t h  influents  i n the 5 yg/£  range,  with  Apparatus  From p r e l i m i n a r y generally,  of the column  7.5.  Column T e s t i n g  holding  in X  lead.  Tests  would,  factor  coal-filled  e t c . ) was  capacities  influent  4.2  of  i t i s more s e n s i t i v e  The for  time  major  flow r a t e ,  because  the p o r o s i t y  inches  column  tests,  i t was  n o t o c c u r b e f o r e 24 h o u r s  tank of adequate i n every  size  24 h o u r s  f o r the i n f l u e n t  filled  once  Figure  4.1(b) a r e s c h e m a t i c diagrams  passes  through  the c o a l  had  o r so  column and  apparent elapsed.  that This  i n order that  for practical  through  the b u r e t t e ,  necessitated  the tank  convenience.  of the apparatus used.  out  breakthrough  As  Figure the  could  be  4.1(a)  liquid  the l i q u i d  a  level  and  40  To  B  ToC  FIG. 4.1 (b) DOUBLE TANK FEED MODIFICATION  G l a s s wool Glass beads  FIG. 4.1 (a) CONSTANT HYDRAULIC HEAD APPARATUS  A  I N F L U E N T HOLDING T A N K  B  SEPARATORY  C  ERLENMEYER  D  BURETTE  FUNNEL FLASK  41  in C w i l l f a l l .  J u s t as the l e v e l f a l l s below t h a t of the opening of  t u b i n g connected t o B, a i r w i l l e n t e r through as shown, and up through  the t u b i n g i n t o B.  the  the h o l e i n the s t o p p e r of T h i s w i l l reduce the  C,  partial  vacuum i n A and B and more l i q u i d w i l l f a l l i n t o C u n t i l the p a r t i a l vacuum i n A and B above the l i q u i d l e v e l s i s i n e q u i l i b r i u m w i t h the h y d r a u l i c heads supported  i n A and  B.  Thus, we have a c o n s t a n t head of AH as shown i n F i g u r e 4.1(a) t o d r i v e the l i q u i d through  the c o a l column.  F o r the f l o w r a t e to remain c o n s t a n t  a f t e r b e i n g s e t , i t i s e s s e n t i a l t h a t the h y d r a u l i c d r i v i n g head remains The tubing.  constant.  element B ( s e p a r a t o r y f u n n e l ) can be s i m p l y r e p l a c e d by a s t r a i g h t  U s i n g a s e p a r a t o r y f u n n e l p r o v i d e s the system w i t h a d d i t i o n a l i n f l u e n t  s t o r a g e volume. F i g u r e 4.1(b) shows the m o d i f i e d set-up t h a t was tests at 5 Igpm/ft  2  used when r u n n i n g  where a l a r g e r i n f l u e n t s t o r a g e volume was  necessary.  t h e r e are two t a n k s , i n s t e a d of one, connected t o the r e s t of the  Here,  apparatus  a c c o r d i n g t o the same p r i n c i p l e s . 4.3  Column T e s t i n g P r o c e d u r e A)  Copper, L e a d and The 1)  Zinc  l a b o r a t o r y p r o c e d u r e c o n s i s t s o f the f o l l o w i n g s t e p s : The  i n f l u e n t s o l u t i o n of a d e s i r e d m e t a l c o n c e n t r a t i o n i s p r e p a r e d  and i t s pH a d j u s t e d to the d e s i r e d v a l u e . 2)  Enough c o a l t o f i l l  10 i n c h e s of the b u r e t t e i s weighed out i n  a beaker. 3)  D i s t i l l e d w a t e r i s added so t h a t the c o a l i n the beaker i s  c o m p l e t e l y submerged.  The  c o n t e n t s are then s u b j e c t e d t o a slow  ' f o r . about - f i v e minutes i n o r d e r to expel..; a l l t h e entrapped  boil  a i r and  to  42  t h o r o u g h l y wet 4)  the  coal.  The w e t t e d c o a l i s then t r a n s f e r r e d i n t o the b u r e t t e , w h i c h i s  packed at the bottom w i t h g l a s s w o o l and g l a s s beads.  During  this  t r a n s f e r , the c o a l i n the b u r e t t e i s c a r e f u l l y k e p t submerged t o prevent 5)  The  any re-entrapment of a i r . i n f l u e n t s o l u t i o n i s i n t r o d u c e d i n t o the c o a l column, and  the b u r e t t e v a l v e i s a d j u s t e d to a c h i e v e the d e s i r e d f l o w r a t e . 6)  The  e f f l u e n t i s sampled a t d e s i r e d i n t e r v a l s .  7)  The pH o f the e f f l u e n t samples i s measured.  8)  The m e t a l c o n c e n t r a t i o n of the e f f l u e n t samples i s measured w i t h  an Atomic A b s o r p t i o n Spectrophotometer as i n the B a t c h  Testing  Procedure. F o r most of the t e s t s , the system was  k e p t r u n n i n g u n t i l the e f f l u e n t  c o n c e n t r a t i o n exceeded a l e v e l of twenty t o t h i r t y p e r c e n t of t h e i n f l u e n t concentration. B)  Mercury The  p r o c e d u r e i s the same as f o r z i n c , copper and l e a d , b u t  e f f l u e n t samples are s u b j e c t e d t o a p r e t r e a t m e n t t e s t e d on the Atomic A b s o r p t i o n This pretreatment 1)  the  d e s c r i b e d below, b e f o r e  being  Spectrophotometer.  c o n s i s t s of the f o l l o w i n g s t e p s :-  100 ml of the e f f l u e n t i s c o l l e c t e d and c o o l e d i n a r e f r i g e r a t o r  f o r about 1 hour.  Care must be taken t h a t the c o n t a i n e r of  the  c o l l e c t e d e f f l u e n t has a p e r f e c t s e a l i n g cap t h a t w i l l p r e v e n t  any  v o l a t i l i z a t i o n of the mercury. 2)  1 mJl of c o n c e n t r a t e d  sample.  s u l f u r i c a c i d i s added to the  cooled  T h i s i s done t o f i x the mercury i n the s o l u t i o n b e t t e r  thus t o e n a b l e o v e r n i g h t  storage.  and  43  3)  About 20 minutes b e f o r e t e s t i n g on the Atomic A b s o r p t i o n  S p e c t r o p h o t o m e t e r , 1 m£ o f 6 p e r c e n t p o t a s s i u m permanganate i s added. 4)  The c o n t a i n e r i s then shaken and a l l o w e d t o s i t .  The t o t a l c o n t e n t s o f t h e c o n t a i n e r ,  2 ml o f r e a g e n t s , a r e t r a n s f e r r e d  100 ml o f e f f l u e n t and  to a t e s t i n g f l a s k .  5)  Then 0.5 ml o f 10 p e r c e n t NH^OH.HCl i s added.  6)  F i n a l l y 2.0 ml o f 10 p e r c e n t S n C ^ i s added j u s t b e f o r e a n a l y s i s  on the Atomic A b s o r p t i o n Spectrophotometer by t h e c o l d  vapour  technique. The above p r o c e d u r e e n a b l e d a c c u r a t e d e t e c t i o n  down t o a l i m i t o f  0.05 pg/A. 4.4  B r e a k t h r o u g h Curve  Calculations  A t y p i c a l b r e a k t h r o u g h curve i s shown i n F i g u r e 4.2. b r e a k t h r o u g h c o n c e n t r a t i o n o f 0.5 mg/l was chosen.  An a r b i t r a r y  A h o r i z o n t a l l i n e i s drawn  through t h i s 0.5 mg/'l mark t o i n t e r s e c t t h e curve and a v e r t i c a l l i n e i s then drawn through t h i s i n t e r s e c t i o n . adsorbed and t h e m i l l i g r a m s  A f t e r h a v i n g determined t h e m i l l i g r a m s  of zinc  o f z i n c p a s s e d t h r o u g h , ( r e f e r t o F i g u r e 4.2) t h e  f o l l o w i n g two c a l c u l a t i o n s can be done.  1)  mg o f Zn adsorbed gm o f c o a l i n column  2)  mg o f Zn passed o u t t h r o u g h e f f l u e n t l i t r e s of treated  =  e f f l u e n t at breakthrough c o n c e n t r a t i o n =  4.5  mg o f Zn adsorbed p e r gm o f c o a l ,  Average e f f l u e n t c o n c e n t r a t i o n i n mg/l  B r e a k t h r o u g h Curves f o r Z i n c The b a t c h t e s t s showed t h a t t h e a d s o r p t i o n i s o t h e r m s f o r z i n c had t h e  l e a s t s c a t t e r o f t h e heavy m e t a l s t e s t e d .  Due t o t h i s f a c t and t h e f a c t  that  44  FIG.4.2 A TYPICAL BREAKTHROUGH CURVE  THIS AREA BELOW THE CURVE REPRESENTS THE WEIGHT OF ZINC IN MILLIGRAMS PASSED OUT THROUGH THE EFFLUENT  45  z i n c i s more s e n s i t i v e on the Atomic A b s o r p t i o n Spectrophotometer t h a n l e a d o r c o p p e r , z i n c was  chosen as the main i m p u r i t y f o r column t e s t s to i n v e s t i g a t e  the e f f e c t s of a b s o r p t i v e c a p a c i t y caused a)  a)  by:-  V a r i a t i o n s i n c r o s s - s e c t i o n a l a r e a of the c o a l bed.  b)  "  i n influent  pH.  c)  "  i n flow r a t e .  d)  "  i n i n f l u e n t metal concentration.  E f f e c t of V a r y i n g the C r o s s - S e c t i o n a l A r e a of the C o a l  Bed  A f t e r a few t r i a l column t e s t s w i t h b u r e t t e s of v a r i o u s d i a m e t e r s a v a i l a b l e i n the l a b o r a t o r y , the c h o i c e of the c r o s s - s e c t i o n a l a r e a t o be used was  narrowed down between t h a t o f the 50 ml b u r e t t e (.001  the 100 ml b u r e t t e (.002  ft ).  f t ) and t h a t of 2  U s i n g the s m a l l e r a r e a of .001  2  f t would mean 2  a p r a c t i c a l convenience of h a v i n g t o use l e s s c o a l per column and l e s s t o t a l l i q u i d to reach b r e a k t h r o u g h .  On the o t h e r hand, care must be t a k e n not t o  go  below the c r i t i c a l d i a m e t e r and encourage w a l l e f f e c t s , w h i c h w i l l reduce the a d s o r p t i v e c a p a c i t y of the c o a l column. F i g u r e 4.3  shows the b r e a k t h r o u g h curves  performed u s i n g bed areas of .001 From TABLE 4.2,  f t  2  and  f o r the column t e s t s  .002 f t . 2  i t i s apparent t h a t t h e r e i s o n l y a s l i g h t d e c r e a s e  i n a d s o r p t i v e c a p a c i t y when the c r o s s - s e c t i o n a l a r e a was to 0.001  f t . Therefore,  0.001  2  f t  2  decided  f o r the r e s t o f the s t u d y .  would be e x p e r i e n c e d used.  i t was  changed from 0.002 f t  2  t o use the 50 ml b u r e t t e w i t h a  I t was  suspected  though, t h a t w a l l e f f e c t s  i f a s m a l l e r d i a m e t e r b u r e t t e t h a n the 50 ml b u r e t t e were  m Influent =2.0 mg/1  Zn  COAL  BED  CROSS-SECTIONAL  AREA  *  *  . 0 0 2 ft.  o-  o  .001 ft.  m  WEIGHT  Influent p H = 5.7 Flow rate = I l g p m / f t .  O 2  B e d depth = 10 inches  2  2  3 8 gm  O  2 0 gm  "n  o x > z:  Coal = C O ' A S H  -z. o o  ^3  O CO CO CO _'  m a  >  m >  o m o  g  CD  m o 12  14  16  18  20  V O L U M E OF LIQUID T R E A T E D (LITRES)  30  ON  47  TABLE 4.2 EFFECT OF CHANGING CROSS-SECTIONAL AREA OF THE COAL BED C r o s s - s e c t i o n a l Area of C o a l Bed (ft )  Note-  C a p a c i t y (mg/gm) at 10%  25%  50%  0.001  0.378  0.503  0.624  0.002  0.438  0.540  0.692  Average E f f l u e n t C o n c e n t r a t i o n (mg/ ) a t - 10%  25%  .046  .133  .310  .042  .113  .308  10%, .25%, 50% r e f e r s t o the b r e a k t h r o u g h c o n c e n t r a t i o n o f 10% o f the i n f l u e n t , 25% o f t h e i n f l u e n t and 50% o f t h e i n f l u e n t . n o t a t i o n w i l l be used h e n c e f o r t h  b)  : so%  This  i n t h e TABLES.  E f f e c t o f V a r y i n g t h e I n f l u e n t pH Many o t h e r r e s e a r c h e r s have found t h a t t h e pH o f t h e i n f l u e n t p l a y s a  c r i t i c a l r o l e i n determining  the a d s o r p t i v e c a p a c i t y .  The pH o f a s o l u t i o n  from w h i c h a d s o r p t i o n occurs may, f o r one o r more o f a number o f r e a s o n s , i n f l u e n c e the e x t e n t o f a d s o r p t i o n .  Because hydrogen and h y d r o x i d e  ions are  adsorbed q u i t e s t r o n g l y , t h e a d s o r p t i o n of o t h e r i o n s i s i n f l u e n c e d by t h e pH (9)  of t h e s o l u t i o n .  Weber  found t h a t , i n g e n e r a l , a d s o r p t i o n o f t y p i c a l  p o l l u t a n t s from w a t e r i s i n c r e a s e d w i t h d e c r e a s i n g pH.  organic  I n many c a s e s , t h i s may  r e s u l t from n e u t r a l i s a t i o n o f n e g a t i v e charges a t t h e s u r f a c e o f t h e carbon w i t h i n c r e a s i n g h y d r o g e n - i o n c o n c e n t r a t i o n , thereby  reducing hindrance of  d i f f u s i o n and making a v a i l a b l e more o f t h e a c t i v e s u r f a c e o f t h e carbon. F i g u r e 4.4 shows t h e b r e a k t h r o u g h curves o b t a i n e d a t i n f l u e n t pH v a l u e s o f 3.0, 4.0 and 5.7 f o r b o t h H.C. OX and C0:ASH c o a l s .  There i s a  d e f i n i t e decrease i n a d s o r p t i v e c a p a c i t y w i t h d e c r e a s i n g pH i n b o t h TABLE 4.3 summarises t h e r e s u l t s o f F i g u r e 4.4 i n a t a b u l a r form. a b r e a k t h r o u g h o f 10 percent  cases. H.C. OX a t  shows a c a p a c i t y decrease o f 84 p e r c e n t when t h e  TABLE 4.3 E F F E C T  Breakthrough Cone, as Percent of I n f l u e n t Cone.  10% = .2mg/£  25% = .5mg/£  50%%==1.0mg/£  Capei c i t y  Influent pH  (mg/'gm) CO:ASH HSCf.'OXK  I N F L U E N T  Average E f f l u e n t Cone, (n H.C.OX CO:ASH  p H  Throug h p u t * ( l i t r es) CO:ASH H.C.OX  3  0.138  .013  .030  .252  ,0.85  0.10  4  1.582  .074  .017  .070  10.33  0.72  5.7  9.716  .370  .010  .027  63.47  3.72  3  0.204  .014  .107  .194  1.41  0.13  4  1.805  .105  .059  .110  12.00  1.15  5.7  10.481  .491  .037  .126  69.33  5.22  3  0.260  .018  .323  .344  1.95  0.22  4  •1.96.1  ,'146  .129  .345  13.33  1.68  10.943  .627  .082  .310  74.00  7.40  5.7  *THROUGHPUT  O N I l N G w A D S Q ^ R P t i O N J 3 F , " V A R ^ ' g i - T H E  s i g n i f i e s t h e t o t a l volume o f l i q u i d t h a t has passed through t h e column a t any p a r t i c u l a r time.  Influent = 2mg/1 Z n Flow rate= I l g p m / f t  2  B e d depth = 10 inches Coal w e i g h t = H . C 0 X = l 3 g m CO^ASH = 2 0 g m  12  13  VOLUME  v  58  59  60  O F LIQUID T R E A T E D  62 (LITRES)  66  68  70  72  74  50 pH was depressed from 5.7 t o 4.0.  On f u r t h e r d e p r e s s i n g t h e pH t o 3.0, t h e  decrease i n c a p a c i t y was 99 p e r c e n t . S i m i l a r l y , a t b r e a k t h r o u g h c o n c e n t r a t i o n s of 25 p e r c e n t and 50 p e r c e n t o f i n f l u e n t c o n c e n t r a t i o n , t h e d e c r e a s e i n c a p a c i t y was 83 p e r c e n t and 82 p e r c e n t , r e s p e c t i v e l y , when t h e pH was d e p r e s s e d from 5.7 t o 4.0.  On f u r t h e r d e p r e s s i o n o f pH t o 3.0, t h e d e c r e a s e i n c a p a c i t y  was 98 p e r c e n t and 98 p e r c e n t , r e s p e c t i v e l y .  Thus, f o r H.C. OX under t h e t e s t  c o n d i t i o n s s t a t e d i n F i g u r e 4.4, t h e average c a p a c i t y d e c r e a s e , over t h e range of 10 p e r c e n t t o 50 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n s , i s 83 p e r c e n t when the pH was d e p r e s s e d from 5.7 t o 4.0, and 98 p e r c e n t when f u r t h e r d e p r e s s e d t o a pH o f 3.0.  S i m i l a r l y , f o r CO:ASH a t 10 p e r c e n t , 25 p e r c e n t and 50 p e r c e n t  b r e a k t h r o u g h c o n c e n t r a t i o n s , t h e d e c r e a s e i n c a p a c i t y on d e p r e s s i o n o f pH from 5.7 t o 4.0 i s 80 p e r c e n t , 79 p e r c e n t and 77 p e r c e n t , r e s p e c t i v e l y .  On f u r t h e r  d e p r e s s i o n o f pH t o 3.0, t h e c a p a c i t y d e c r e a s e i s 96 p e r c e n t , 97 p e r c e n t and 97 p e r c e n t , r e s p e c t i v e l y .  Thus, f o r CO:ASH under t h e same t e s t c o n d i t i o n s t h e  average c a p a c i t y d e c r e a s e i s 79 p e r c e n t when t h e pH i s lowered from 5.7 t o 4.0, and 97 p e r c e n t when t h e pH i s f u r t h e r d e p r e s s e d t o 3.0. The p e r c e n t d e c r e a s e s i n a d s o r p t i o n w i t h d e c r e a s i n g pH f o r b o t h : types o f c o a l s a r e a p p r o x i m a t e l y t h e same.  This decrease i n a d s o r p t i o n w i t h  (9) d e c r e a s i n g pH i s c o n t r a r y t o what Weber  found.  The r e a s o n f o r t h i s d i s c r e -  pancy may be due t o t h e f a c t t h a t he was w o r k i n g w i t h o r g a n i c p o l l u t a n t s and a c t i v a t e d carbon w h i l e i n t h i s s t u d y t h e c o m b i n a t i o n i s heavy m e t a l s and granular coal. S i n c e t h e hydrogen i o n can a l s o be adsorbed, i t i s s u s p e c t e d t h a t t h e hydrogen i o n i s i n c o m p e t i t i o n w i t h t h e heavy m e t a l i o n f o r t h e a c t i v e on t h e c o a l s u r f a c e .  sites  As t h e pH i s d e p r e s s e d , t h e hydrogen i o n c o n c e n t r a t i o n  i n c r e a s e s and more a c t i v e s i t e s a r e made u n a v a i l a b l e t o t h e heavy m e t a l .  Thus,  the drop i n c a p a c i t y on l o w e r i n g t h e pH may be p a r t l y due t o t h i s c o m p e t i t i o n by t h e hydrogen i o n .  A n o t h e r r e a s o n f o r t h i s drop i n c a p a c i t y may be due t o  51  a change i n the complex f o r m u l a t i o n of the heavy m e t a l w i t h d e c r e a s i n g The  lower pH f a v o r s the awuo complex w h i c h may  pH.  not be as r e a d i l y adsorbed.  (3) Hendrey  found the same decrease i n a d s o r p t i o n w i t h  pH i n h i s work on heavy m e t a l s w i t h g r a n u l a r c o a l .  decreasing  S i n c e the pH f a c t o r i s so  c r u c i a l to the f a v o u r a b l e outcome o f the a d s o r p t i o n system u s i n g  granular  c o a l , more r e s e a r c h s h o u l d be done i n t h i s a r e a to f i n d out the e x a c t s h i p s between pH and a d s o r p t i o n . some k i n d of p r e - t r e a t m e n t  may  An i m p o r t a n t  be n e c e s s a r y  p o i n t t o make n o t e of i s t h a t  when t r e a t i n g a c i d i c wastes w i t h  t h i s type o f system, i n o r d e r t h a t the pH of the wastes may ensure r e a s o n a b l e c)  relation-  be i n c r e a s e d t o  adsorption c a p a c i t i e s .  E f f e c t of V a r y i n g the Flow Rate The e f f e c t o f f l o w r a t e on the a d s o r p t i v e c a p a c i t y was  by v a r y i n g the f l o w r a t e between 1-5  investigated  I g p m / f t , a range r e p r e s e n t a t i v e o f f l o w 2  r a t e s employed i n modern r a p i d sand f i l t r a t i o n and a c t i v a t e d carbon a d s o r p t i o n systems. Due  t o the l a b o r a t o r y equipment a v a i l a b l e and o t h e r p r a c t i c a l con-  s i d e r a t i o n s , the e x a c t f l o w r a t e s used were 1.01 5.06  Igpm/ft . 2  I g p m / f t , 3.04 2  Whenever f l o w r a t e s of 1 I g p m / f t , 3 I g p m / f t 2  2  Igpm/ft  2  and  and 5 I g p m / f t  2  are mentioned i n t h i s t h e s i s , the e x a c t v a l u e s are the ones mentioned above. I f the a d s o r p t i o n c a p a c i t i e s of two  columns, s i m i l a r i n a l l r e s p e c t s  but the f l o w r a t e , a r e f o r a l l p r a c t i c a l purposes the same, then the  logical  i n d u s t r i a l b e n e f i t would be to use the h i g h e r f l o w r a t e and save the c o s t o f b u i l d i n g columns w i t h l a r g e r d i a m e t e r s when t r e a t i n g h i g h e r volumes o f w a s t e water.  However, the p o s s i b i l i t y of s a v i n g o p e r a t i n g c o s t by b u i l d i n g a l a r g e r  column must a l s o be borne i n mind. F i g u r e 4.5  and F i g u r e 4.6  show the b r e a k t h r o u g h curves  f l o w r a t e s o b t a i n e d f o r C0:ASH and H.C.  OX,  at d i f f e r e n t  r e s p e c t i v e l y . TABLE 4.4  is a  TABLE 4 . 4 EFFECT ON ZINC.vADSQRPTION- OF '.VARYENGtfTHEI'iFLOW RATE Breakthrough Cone, as Percent of Influent Cone.  Flow Rate (Igpm/ft ) 2  Cap acity (mg/gm) H.C.OX CO:ASH  Average Effluent Throujghput Cone. (mg/A) ( l i t : res) •H.H.C.Y0X, ;oeo;:-ASH H. :.HY.C.OXO AGO:ASH  1  9.716  .386  .008  .039  62.8  3.85  3  5.402  .231  .032  .065  35.4  2.33  5  5.571  .161  .019  .106  36.3  1.66  •25%  1  10.481  .503  .040  .124  68.9  5.30  25%  3  7.080  .358  .123  .190  48.7  3.85  5  6.696  .288  .087  .194  45.3  3.12  .627  —  .289  —  7.33  10%  1 50%  —  3  9.697  .536  .363  .429  76.0  6.76  5  8.258  .491  .266  .493  61.2  6.45  53  a t a b u l a r summary o f the above two f i g u r e s .  I t shows t h e c a p a c i t y , average  e f f l u e n t c o n c e n t r a t i o n and t h e c o r r e s p o n d i n g throughput a t 10 p e r c e n t , 25 p e r c e n t and 50 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n s . At a b r e a k t h r o u g h c o n c e n t r a t i o n o f 10 p e r c e n t , H.C. OX undergoes a 44 p e r c e n t decrease i n c a p a c i t y when f l o w r a t e was changed from 1 t o 3 I g p m / f t  2  and a 43 p e r c e n t d e c r e a s e when t h e f l o w r a t e was r a i s e d t o 5 I g p m / f t . '--At t h e 2  b r e a k t h r o u g h c o n c e n t r a t i o n o f 25 p e r c e n t , i t s u f f e r s a 32 p e r c e n t c a p a c i t y decrease a t 3 I g p m / f t  2  and a 36 p e r c e n t c a p a c i t y d e c r e a s e a t 5 I g p m / f t . 2  The  d a t a f o r 50 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n was n o t o b t a i n a b l e f o r 1 I g p m / f t due t o time c o n s i d e r a t i o n s . For CO:ASH, a t 10 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n , t h e c a p a c i t y decrease was 40 p e r c e n t when f l o w r a t e was changed from 1 t o 3 I g p m / f t , and 2  58 p e r c e n t when f l o w r a t e was changed t o 5 I g p m / f t . 2  A t 25 p e r c e n t b r e a k t h r o u g h  c o n c e n t r a t i o n , t h e c a p a c i t y d e c r e a s e was 29 p e r c e n t a t 3 I g p m / f t at 5 I g p m / f t . 2  at 3 I g p m / f t  2  2  and 43 p e r c e n t  A t 50 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n , i t was o n l y 15 p e r c e n t and 22 p e r c e n t a t 5 I g p m / f t . 2  Both c o a l s d i s p l a y e d a s i g n i f i c a n t drop i n c a p a c i t y when t h e f l o w r a t e was changed from 1 t o 3 I g p m / f t . 2  However, when t h e f l o w r a t e was f u r t h e r  r a i s e d t o 5 I g p m / f t , t h e a d d i t i o n a l p e r c e n t d e c r e a s e i n c a p a c i t y was much 2  smaller.  I n t h e case o f CO:ASH, a t a l l t h r e e b r e a k t h r o u g h c o n c e n t r a t i o n s , t h e  a d d i t i o n a l p e r c e n t decrease i n c a p a c i t y when f l o w r a t e was f u r t h e r r a i s e d t o 5 Igpm/ft  2  was a p p r o x i m a t e l y h a l f t h e p e r c e n t d e c r e a s e i n c a p a c i t y when f l o w  r a t e was changed from 1 t o 3 I g p m / f t  2  ( i . e . , a t 25 p e r c e n t b r e a k t h r o u g h  c o n c e n t r a t i o n s , t h e d e c r e a s e was 29 p e r c e n t a t 3 I g p m / f t 5 Igpm/ft  2  and 43 p e r c e n t a t  , an a d d i t i o n a l decrease o f 14 p e r c e n t , w h i c h i s a p p r o x i m a t e l y  h a l f o f 29 p e r c e n t . )  As f o r H.C. OX, t h i s a d d i t i o n a l p e r c e n t decrease i n  2  54  c a p a c i t y when f l o w r a t e was f u r t h e r r a i s e d t o 5 I g p m / f t to the p e r c e n t  2  was s m a l l compared  decrease when f l o w r a t e was changed from 1 t o 3 I g p m / f t . 2  L i t e r a t u r e on a c t i v a t e d c a r b o n a d s o r p t i o n s t a t e s t h a t t h e throughput corresponding  t o a p a r t i c u l a r breakthrough c o n c e n t r a t i o n i s decreased w i t h  increased flow r a t e . statement.  F i g u r e 4.5 and F i g u r e 4.6 agree w i t h t h i s  general  An i n t e r e s t i n g p o i n t t o n o t e , however, i s t h a t t h e curves  converge  at h i g h e r breakthrough c o n c e n t r a t i o n s , i n d i c a t i n g that the percent d i f f e r e n c e i n c a p a c i t y between d i f f e r e n t f l o w r a t e s d e c r e a s e s as t h e p e r m i s s i b l e b r e a k through c o n c e n t r a t i o n i s i n c r e a s e d .  Thus, t h e c h o i c e between b u i l d i n g t h i c k e r  columns o r s t e p p i n g up t h e f l o w r a t e , as d i s c u s s e d e a r l i e r , would r e s t h e a v i l y on t h e p o l l u t i o n c o n t r o l r e g u l a t i o n s on a l l o w e d waste l e v e l s i n t h e e f f l u e n t . I f t h e a l l o w e d l e v e l i s v e r y low, t h e b r e a k t h r o u g h c o n c e n t r a t i o n w i l l have t o be c o r r e s p o n d i n g l y  low and t h e use o f h i g h f l o w r a t e s may be i m p r a c t i c a l .  On t h e o t h e r hand, i f a h i g h e r b r e a k t h r o u g h c o n c e n t r a t i o n i s p e r m i s s i b l e , then a h i g h e r f l o w r a t e may be c o n t e m p l a t e d . made o n l y a f t e r a c a r e f u l e x a m i n a t i o n  Of c o u r s e , these d e c i s i o n s c o u l d be  o f t h e b r e a k t h r o u g h curves and a  thorough a n a l y s i s o f c a p i t a l and o p e r a t i n g c o s t s .  d)  E f f e c t of Varying the I n f l u e n t Concentration F i g u r e 4.7 shows t h e b r e a k t h r o u g h curves  i n f l u e n t c o n c e n t r a t i o n o f 0.5 mg/£.  f o r t e s t s r u n w i t h an  By changing t h e i n f l u e n t  concentration  from 2 mg/I (as used i n p r e v i o u s t e s t s ) t o 0.5 mg/£, an attempt was made t o f i n d out whether the c a p a c i t y a t a p a r t i c u l a r b r e a k t h r o u g h c o n c e n t r a t i o n would increase o r decrease,  g i v e n a l l o t h e r parameters t o be t h e same.  The main  o b j e c t i v e h e r e i s t o compare t h e c a p a c i t i e s a t a common b r e a k t h r o u g h  concentra-  t i o n , namely 0.2 mg/Jl, f o r t e s t s r u n a t a pH o f 5.7 b u t w i t h d i f f e r e n t  influent  55  FIG.  4 . 5  EFFECT OF VARYING FLOW RATE FOR CO=ASH  o • *  Influent = 2 mg/l Zn. pH =5.7 Bed depth = 10 inches Coal weight = 20gm  o | Igpm/ft. • 3 Igpm/ft * 5 Igpm/ft.  2  2  2  2:0  •—  1.5 ••  cn  E, Z  1.3 •-  o rr z  Ul  o z o o hz  l l - -  i. i  1.0.9 • .7 ••• /  LU  EF  _l  .5 • .4 ••  // /  .2 •• 0 0  I  2  3  4  5  6  7  8  9  VOLUME OF LIQUID TREATED (LITRES)  10  II  -o I Igpm/ft. -• 3 Igpm/ft. -* 5 Igpm/ft.  2  2  2  Influent = 2 mg/l Zn pH = 5.7 Bed depth = 10 inches Coal weight' = 13 gm  m -n  m o  -< FT  9  ^  m o p  b x  40 50 60 VOLUME OF LIQUID TREATED (LITRES)  ON  -.5 pH = 4.0  T4  CO'ASH Zl H.C. OX  •+ pH=4.0 -* pH=5.7 pH=4.0  Influent =0.5mg/l Zn. Flow rote= I Igpm/ft Bed depth = 10 inches Coal weight = 20gm (C0 ASH) = l3gm(H.C.0X) :  cn + 3 e  /  pH=5.7  pH=4.0  < rr UJ  o z o o  UJ  3  U_ LL. LLI  0  12 14 16 18 VOLUME OF LIQUID TREATED(LITRES)  . m -n Z 3 P  F ° m  .  —I  >  3D  -a -< I  2  58  concentrations. T h e . p e r t i n e n t d a t a on F i g u r e 4.7 i s shown i n TABLE 4.5.  TABLE 4.5 EFFECT OF VARYING THE INFLUENT pH  Breakthrough Concentration as p e r c e n t o f i n f l u e n t cone.  Influent pH  H.C.OX,. CO:ASH  10% --?.05')mg/Jrj'/~-  4  .708  5.7 25% = .125mg/A  4 5.7  = .2 mg/A  4 5.7  50% = .25 mg/A  4  Average E f f l u e n t Concen t r a t i o n (mg/ A ) H.C.OXX CO:ASH  Throu ghput ( l i tres) H.C.OX CO: ASH  .026  .003  .019  18.40  **  .332  **  .009  **  .751  .037  .009  .050  19.75  **  .426  **  .028  **  .786  .057  .021  .096  21.33  **  .486  **  .051  **  .078  .090  .142  32.16  .533  **  .074  **  1.025  5.7  Footnote:-  Capac: i t y (mg/g;m)  **  1.05 13.43 1.60 17.83 2.83 21.66 4.22 24.71  A column was n o t r u n f o r H.C. OX a t a pH o f 5.7 due t o time c o n s i d e r a t i o n s . The c a p a c i t y f o r H.C. OX a t a pH o f 5.7, f l o w r a t e o f 1 I g p m / f t , i n f l u e n t c o n c e n t r a t i o n o f 0.5 mg/A Zn and a t a b r e a k t h r o u g h c o n c e n t r a t i o n of 0.2 mg/A was a r r i v e d a t by u s i n g a f a c t o r as d e s c r i b e d below. 2  D a t a from TABLE 4.3 and TABLE 4.5 were combined  t o form TABLE 4.6,  which shp  w h i c h shows a comparison o f c a p a c i t i e s a t a b r e a k t h r o u g h c o n c e n t r a t i o n o f 0.2 mg/A  f o r t e s t s r u n w i t h z i n c i n f l u e n t s o f 0.5 mg/A  flow r a t e of 1 Igpm/ft . 2  and a t a  From TABLE 4.6, w i t h i n f l u e n t c o n c e n t r a t i o n o f 2 mg/A, 370  CO:ASH d i s p l a y e d a c a p a c i t y i n c r e a s e by a f a c t o r o f i n c r e a s e from 4 t o 5.7.  and 2.0 mg/A,  'Q-J^ ~  -*  ,u  ^  u e  t  o  t  *  ie  P**  But a t an i n f l u e n t c o n c e n t r a t i o n o f 0.5 mg/A and under 486 the same change i n pH, i t shows an i n c r e a s e by a f a c t o r o f ' = 8.53.  59  TABLE 4.6 COMPARISON OF ADSORPTIVE CAPACITIES OF COLUMNS RUN WITH ZINC INFLUENTS OF 0.5 mg/£ AND 2.0 mg/l,  Breakthrough Concentration (mg/i Zn)  Influent Cone, (mg/l Zn) 0.5  0.2 2.0  Influent pH  Capa c i t y (mg /gm) H.C.OX CO:ASH  4  .786  .057  5.7  8.23*  .486  4  1.582  .074  5.7  9.716 .  .370  *by c a l c u l a t i o n , n o t t e s t - see pg. 60 Therefore,  the r a t i o :  i n c r e a s e f a c t o r w i t h 0.5 mg/l, i n f l u e n t i n c r e a s e f a c t o r w i t h 2.0 mg/l i n f l u e n t  _  8.53 5  For H.C. OX, w i t h an i n f l u e n t c o n c e n t r a t i o n of 2 mg/1 and under the same change of pH, t h e c a p a c i t y i n c r e a s e i s by a f a c t o r y p f  ^* 1.582  =  6.14.  Using  the r a t i o d e s c r i b e d above, H.C. OX w i t h an i n f l u e n t c o n c e n t r a t i o n o f 0.5 mg/l s h o u l d e x p e r i e n c e an i n c r e a s e i n c a p a c i t y by a f a c t o r of c6.14 X 1.706 ( i . e . assuming t h a t t h e same r a t i o o f f a c t o r s Therefore,  .786 X 10.5  t h e c a p a c i t y of H.C. OX a t 0.2 mg/A  =  10.5  i s v a l i d f o r H.C. OX a l s o ) . effluent  concentration,  w i t h an i n f l u e n t pH of 5.7 and an i n f l u e n t c o n c e n t r a t i o n o f 0.5 mg/A, about  =  s h o u l d be  8.23 mg/gm.  L o o k i n g a t TABLE 4.6, a t t h e common b r e a k t h r o u g h c o n c e n t r a t i o n of 0.2 mg/£, CO:ASH w i t h an i n f l u e n t pH of 4.0 :shows a d e c r e a s e i n c a p a c i t y from .074 t o 0057 (23 p e r c e n t d e c r e a s e ) when i n f l u e n t c o n c e n t r a t i o n was changed from 2.0 mg/£ t o 0.5 mg/£.  But a t a pH o f 5.7, CO:ASH, under t h e same changes,  e x p e r i e n c e s an i n c r e a s e i n c a p a c i t y from .370 t o .486 (31 p e r c e n t i n c r e a s e ) .  60  S i m i l a r l y , f o r H.C. OX, a t 0.2 mg/A b r e a k t h r o u g h c o n c e n t r a t i o n and a t a pH of 4.0, t h e r e i s a d e c r e a s e i n c a p a c i t y from 1.582 t o 0.786 (50 p e r c e n t decrease) and a t a pH o f 5.7,the d e c r e a s e i s from 9.716 t o 8.230 (15 p e r c e n t d e c r e a s e ) when i n f l u e n t c o n c e n t r a t i o n was changed from 2.0 mg/£ t o 0.5 mg/A. T h i s l a s t f i g u r e o f 8.230 f o r t h e c a p a c i t y o f H.C. OX a t a pH o f 5.7 i s o n l y an e s t i m a t e a r r i v e d a t by u s i n g d e r i v e d f a c t o r s as d e s c r i b e d previously.  Only a l o n g - t e r m  column t e s t w i l l p r o v i d e a more e x a c t  evaluation  of t h e c o a l c a p a c i t y under t h e i n d i c a t e d o p e r a t i n g c o n d i t i o n s . The  pH o f t h e i n f l u e n t seems t o be an i m p o r t a n t  f a c t o r i n determining  the change i n c a p a c i t y t h a t o c c u r s when t h e i n f l u e n t c o n c e n t r a t i o n i s changed. For b o t h c o a l s , t h e r e i s a d e c r e a s e i n c a p a c i t y when i n f l u e n t c o n c e n t r a t i o n i s lowered from 2.0 mg/£ t o 0.5 mg/£ a t a pH o f 4.0.  But a t a pH o f 5.7 and under  the same i n f l u e n t c o n c e n t r a t i o n changes, CO:ASH e x p e r i e n c e s  an i n c r e a s e w h i l e  H.C. OX s t i l l shows a d e c r e a s e i n c a p a c i t y . Under a s e t o f c o n d i t i o n s where t h e c a p a c i t y i n c r e a s e s on l o w e r i n g the i n f l u e n t c o n c e n t r a t i o n , an i m p o r t a n t p r a c t i c a l a p p l i c a t i o n i s o b v i o u s . For example, two v o l u m e t r i c a l l y e q u a l waste streams o f , s a y , z i n c and copper o f 2 mg/il each c o u l d be combined t o r e s u l t i n 1 mg/£ each of Zn and Cu b e f o r e b e i n g passed t h r o u g h a c o a l column.  T h i s would r e s u l t i n b e t t e r a d s o r p t i o n  c a p a c i t i e s than i f t h e w a s t e streams were passed through s e p a r a t e  columns  individually. From t h e d a t a above, i t i s c l e a r t h a t c l o s e a t t e n t i o n must be p a i d to t h e i n f l u e n t pH b e f o r e any attempts a r e made i n c e r t a i n cases t o b e t t e r t h e a d s o r p t i o n c a p a c i t y by l o w e r i n g t h e i n f l u e n t  concentration.  I n v e s t i g a t i n g t h e c a p a c i t y s e n s i t i v i t y t o pH change a t d i f f e r e n t i n f l u e n t c o n c e n t r a t i o n s , i t i s seen from TABLE 4.6 t h a t a t t h e common 0.2 mg/£ breakthrough,  C0:ASH shows an 80 p e r c e n t d e c r e a s e w i t h an i n f l u e n t  concentration  61  of 2 mg/£ 0.5  mg/£  and an 88 p e r c e n t d e c r e a s e w i t h an i n f l u e n t c o n c e n t r a t i o n of when the pH i s changed from 5.7  to 4.0  i n b o t h cases.  a decrease of 84 p e r c e n t w i t h i n f l u e n t of 2 mg/£, 0.5  mg/£  the d e c r e a s e was  decrease i n c a p a c i t y due  H.C.  OX  shows  w h i l e a t an i n f l u e n t of  91 p e r c e n t under the same change i n pH.  The  percent  t o l o w e r i n g of pH i s g r e a t e r i n the case of 0.5  mg/£  i n f l u e n t c o n c e n t r a t i o n , i n d i c a t i n g a g r e a t e r s e n s i t i v i t y of c a p a c i t y response to pH change a t lower i n f l u e n t 476  concentrations.  B r e a k t h r o u g h Curves f o r Copper The  a d s o r p t i o n c a p a c i t i e s f o r copper were i n v e s t i g a t e d f o r b o t h c o a l s  u s i n g an i n f l u e n t of 2 mg/£ v a l u e s of 4.0  and  Cu and a f l o w r a t e of 1 I g p m / f t  2  at i n f l u e n t  5.7.  There are o n l y t h r e e b r e a k t h r o u g h curves shown i n F i g u r e although  f o u r columns were t e s t e d .  absent i n F i g u r e 4.8  The  curve f o r H.C.  OX  s i n c e i t s e f f l u e n t c o n c e n t r a t i o n was  a f t e r 5 days of throughput ( i . e . 33.4 more time w a i t i n g f o r the b r e a k t h r o u g h ,  litres).  a f a c t o r , as i n d i c a t e d i n s e c t i o n  OX  4.8,  at a pH of 5.7 still  undetectable  made to stop the column  at a pH of 5.7  by the use  the  throughput and average e f f l u e n t c o n c e n t r a t i o n i s shown i n T a b l e  The main o b j e c t i v e s f o r r u n n i n g  t h i s s e r i e s of columns were:  To d e t e r m i n e the a d s o r p t i o n c a p a c i t y f o r copper at a pH o f  and under the t e s t c o n d i t i o n s d e s c r i b e d i n F i g u r e 2)  of  4.4(d).  A t a b u l a r summary of F i g u r e 4.8 w i t h r e s p e c t to c a p a c i t y and  1)  is  T h e r e f o r e , r a t h e r t h a n spend  a d e c i s i o n was  and e s t i m a t e the a d s o r p t i o n c a p a c i t y of H.C.  corresponding  pH  4.8.  To d e t e r m i n e t h e change i n c a p a c i t y f o r copper a t d i f f e r e n t  values.  5.7  pH  4.7.  FIG. 4.8  f o  cvi  oo  -+  in  ^  T T  ro oo  —  O  ^  I—I—I—I—H  (I/DUJ ) N 0 I 1 V U 1 N 3 0 N C O  ^  1  ^ , <a- ro  OJ _  —I—|—I—I—h  lN3n~ldd3  CM  63  The a d s o r p t i o n c a p a c i t i e s f o r H.C. OX a t a pH o f 5.7 a r e shown i n i t a l i c s i n T a b l e 4.7 s i n c e these f i g u r e s were n o t a r r i v e d a t e x p e r i m e n t a l l y ,  TABLE 4.7  EFFECT OF VARYING pH WITH. COPPER INFLUENTS  Breakthrough Concentration as P e r c e n t o f I n f l u e n t Cone.  Influent pH  10% = 0.2 mg/£  Capa c i t y (mg/ gm) H.C.OX 'CO: ASH H.C.OX CO:ASH  4 5.7  25% = 0.5 mg/iH  4 5.7  50% = 1 . 0 mg/£  4 5.7  3.986  A v e r a ge E f f l u e nt Cone.(mg/Z) H.C.OX CO:ASH  0.467  12.396  .016  1.182  4.281  0.545  13.442 4.634  0.634  15.524 •  1.601  25.95  .032 .038  28.25  .081 .116  4.72 12.00  .072  1.370  but e s t i m a t e d by t h e p r o c e d u r e d e s c r i b e d below. i n f l u e n t o f 2 mg/a  .008  Throu ghput ( l i tres) H.C.OX CO: ASH  5.62 14.30  .206  31.80  .220  7.11 17.90  F o r C0:ASH w i t h a z i n c  ( T a b l e 4 . 3 ) , a t t h e 10 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n ,  the c a p a c i t y i n c r e a s e f a c t o r due t o t h e pH change from 4.0 t o 5.7 i s . 370 =  5.00. U s i n g a copper i n f l u e n t o f 2 mg/£ under t h e same  conditions,  .074  1 182 the i n c r e a s e f a c t o r i s — ~ 0.467  =  2.53 ( T a b l e 4.7).  i n c r e a s e f a c t o r w i t h Cu i n f l u e n t  Therefore, the r a t i o of 2.53  =  i n c r e a s e f a c t o r w i t h Zn i n f l u e n t  c n  =  ,  . 5ub-  5.00  Now f o r H.C. OX w i t h a z i n c i n f l u e n t o f 2 mg/i, t h e c a p a c i t y i n c r e a s e f a c t o r under t h e same c o n d i t i o n s , i s  ^* 1.582  =  6.14. T h e r e f o r e , f o r H.C. OX, w i t h a  copper i n f l u e n t o f 2 mg/£ and under t h e same pH changes, t h e c a p a c i t y i n c r e a s e f a c t o r s h o u l d be 66.14 X .506 =  3.11. M u l t i p l y i n g t h e c a p a c i t y o f H.C. OX a t  64  a pH of 4.0 ( T a b l e 4.7) by t h i s f a c t o r p r o v i d e s a c a l c u l a t e d c a p a c i t y o f H.C. OX a t t h e h i g h e r pH o f 12.396 mg/gm. S i m i l a r l y , a t b r e a k t h r o u g h c o n c e n t r a t i o n s of 25 p e r c e n t and 50 p e r c e n t , the i n c r e a s e f a c t o r s w i t h copper i n f l u e n t s f o r H.C. OX a r e 3.14 and 3.35, respectively.  M u l t i p l y i n g these f a c t o r s by t h e c o r r e s p o n d i n g c a p a c i t i e s o f  H.C. OX a t a pH of 4.0 r e s u l t s i n t h e e s t i m a t e d c a p a c i t i e s a t a pH o f 5.7 as shown i n TABLE 4.7 i n i t a l i c s . D a t a i n TABLE 4.7 i n d i c a t e s a d e c r e a s e i n a d s o r p t i o n c a p a c i t y w i t h d e c r e a s i n g pH f o r b o t h t y p e s o f c o a l as i n t h e case w i t h z i n c a d s o r b a t e . From TABLE 4.7 a g a i n , f o r C0:ASH a t b r e a k t h r o u g h c o n c e n t r a t i o n s of 10 p e r c e n t , 25 p e r c e n t and 50 p e r c e n t , t h e p e r c e n t d e c r e a s e i n c a p a c i t y due t o t h e pH change from 5.7 t o 4.0 i s 61 p e r c e n t , 60 p e r c e n t and 60 p e r c e n t , r e s p e c t i v e l y . Thus, over t h e range of b r e a k t h r o u g h c o n c e n t r a t i o n s s t a t e d above, t h e average p e r c e n t decrease i n c a p a c i t y f o r CO:ASH due t o a change o f pH from 5.7 t o 4.0 i s 60 p e r c e n t .  I n t h e case o f H.C. OX, due t o t h e same change i n pH, t h e  p e r c e n t d e c r e a s e i n c a p a c i t y a t 10 p e r c e n t , 25 p e r c e n t and 50 p e r c e n t b r e a k through c o n c e n t r a t i o n s i s 68 p e r c e n t , 68 p e r c e n t and 70 p e r c e n t , r e s p e c t i v e l y . T h i s g i v e s an average p e r c e n t d e c r e a s e o f 69 p e r c e n t f o r H.C. OX under t h e same c o n d i t i o n s .  The average p e r c e n t d e c r e a s e due t o t h e d e p r e s s i o n of pH i s  about t h e same f o r b o t h c o a l s , as was t h e case w i t h z i n c a d s o r b a t e . Comparing t h e p e r c e n t d e c r e a s e i n c a p a c i t y o f copper and z i n c due t o the l o w e r i n g o f pH from 5.7 t o 4.0, i t i s seen from TABLE 4.3 and TABLE 4.7 t h a t b o t h c o a l s d i s p l a y a l o w e r p e r c e n t d e c r e a s e w i t h copper  influents.  From TABLE 4.3 and TABLE 4.7, t h e r a t i o s of c a p a c i t i e s f o r copper v s . . c a p a c i t i e s f o r z i n c a r e shown i n TABLE 4.8.  I t i s c l e a r from TABLE 4.8  t h a t t h e d i f f e r e n c e i n terms of p e r c e n t a g e between a d s o r p t i v e c a p a c i t i e s f o r copper and z i n c i s g r e a t e r a t t h e l o w e r pH o f 4.0 f o r b o t h t y p e s of c o a l .  65  TABLE  4.8  COMPARISON OF ADSORPTIVE CAPACITIES FOR  Range of Breakthrough Concentrations  ZINC  C a p a c i t y f o r Copper Capacity f o r Zinc H.C. OX CO:ASH  Influent pH  4 10% -  COPPER AND  •.22;4-v"V!255  50% 5.7  1.3  ^1.4  4.3  ^6.3  2.6  -V3.2  T h i s d i f f e r e n c e i s more pronounced i n the case o f C0:ASH.  4.7  B r e a k t h r o u g h Curves f o r Lead Three columns were t e s t e d w i t h l e a d as the a d s o r b a t e ,  u s i n g CO:ASH w i t h i n f l u e n t pH v a l u e s of 5.7 H.C.  OX  a t a pH o f 4.0.  The  H.C.OOX a t a pH of 5.7 was  and 4.0,  two of them  and the t h i r d one  with  o t h e r parameters were as s t a t e d i n F i g . 4.9(a) ,  not t e s t e d because t h e r e was  good r e a s o n  to b e l i e v e  t h a t i t w o u l d take an e x c e s s i v e l y l o n g p e r i o d o f time f o r i t s b r e a k t h r o u g h to occur.  Thus, an e s t i m a t e f o r the c a p a c i t y o f H.C.  goal instead.  a t a pH o f 5.7 was  T h i s e s t i m a t e would be based on the t h r e e c o l u m n s t e s t e d  p r e v i o u s d a t a from z i n c and The  OX  the  and  on  copper t e s t s .  main o b j e c t i v e s h e r e were similar-to<r. t h o s e f o r copper t e s t s ;  •that.is; t o d e t e r m i n e the c a p a c i t y a t a pH of 5.7 s t a t e d i n F i g u r e 4.9(a) and  and under t h e t e s t c o n d i t i o n s  a l s o t o i n v e s t i g a t e the p e r c e n t  c i t y f o r l e a d on l o w e r i n g the  d e c r e a s e i n capa-  pH).  F i g u r e 4.9(a) shows o n l y one b r e a k t h r o u g h c u r v e , t h a t of CO:ASH a t a pH of 4.0.  The  b r e a k p o i n t s due  o t h e r two  columns were stopped without^ h a v i n g  reached  their  t o e x c e s s i v e f l o w problems caused by the appearance o f a fungus.  As the fungus accumulated a t the top of the c o a l column, the p r e s s u r e  drop  E F F L U E N T CONCENTRATION UNDETECTABLE AFTER  Influent = 2 m g / l  Pb  Flow rate = I I g p m / f t .  2  CO = A S H at p H = 5 . 7 - 4 0 Litres  B e d depth = 10 inches  H.C. O X at p H = 4 . 0 - 6 0 Litres  Coal w e i g h t - H.C. OX = I 3 g m C0  :  ASH=20gm  pH=4.0 (CO ASH) :  2  4  6  8  10  12  14  V O L U M E O F LIQUID T R E A T E D ( L I T R E S )  16  18  20  6 7  FIG. 4.9(b) FUNGUS GROWING AT THE TOP OF COAL COLUMN  68 across the c o a l bed Increased.  When t h e f l o w r a t e c o u l d no l o n g e r be m a i n t a i n e d  at  1 Igpm/ft  even on f u l l y opening t h e b u r e t t e v a l v e , a vacuum was a p p l i e d  at  t h e e f f l u e n t end o f t h e b u r e t t e .  2  rate a 1 Igpm/ft  2  f o r about another  T h i s enabled  t h e maintenance o f t h e f l o w  8 l i t r e s o f throughput.  then dropped a g a i n due t o f u r t h e r a c c u m u l a t i o n  The f l o w r a t e  o f t h e fungus.  At t h i s point  the runs were d i s c o n t i n u e d . In  t h e case o f CO:ASH a t a pH o f 5.7, t h e throughput on d i s c o n t i n -  u a t i o n was 40 l i t r e s w h i l e f o r H.C. OX a t a pH o f 4.0, i t was 60 l i t r e s .  As  shown on F i g . 4 . 9(b), t h e w h i t e f l u f f y fungus was about 1/8 i n c h t h i c k on t o p (  1  o f t h e c o a l column when t h e runs were stopped.  I t a l s o permeated i n t o t h e v o i d s  between t h e c o a l p a r t i c l e s t o about 1/4 i n c h from t h e t o p o f t h e c o a l column. F i g u r e 4.9(b) a l s o shows pockets  o f gas c r e a t e d a l o n g t h e l e n g t h o f t h e c o a l ,  column due t o t h e vacuum a p p l i e d a t the e x i t end. TABLE 4.9 i s a t a b u l a r r e p r e s e n t a t i o n o f F i g u r e 4 . 9 ( a ) .  No attempt  i s made t o e s t i m a t e t h e b l a n k s shown i n TABLE 4.9 because t h e r e a r e t o o many unknowns i n v o l v e d .  However, a minimum e s t i m a t e can be made f o r H.C. OX a t a TABLE 4.9 CAPACITIES FOR LEAD  Breakthrough Concentration As P e r c e n t o f I n f l u e n t Cone. 10% = 0.2 mg/  Influent pH  4  Capac]-ty (mg/j ;m)  A v e r a j 5e E f f l u e :nt Cone, (iiig/A) H.C.OX CO: ASH  H.C.OX  CO:ASH  —  0.903  —  —  1.101  1.329  Throu ghput ( l i t res) H.C.OX  CO:ASH  .017  —  9.11  —  .088  —  11.42  —  .252  —  15.14  5.7 25% = 0.5 mg/  4 5.7  50% = 1.0 mg/  4 5.7  69  pH of 4.0 from t h e d a t a on MIXED INFLUENTS.  (TABLE 4.10(a)).  Since the  c a p a c i t y f o r a p a r t i c u l a r m e t a l u s i n g an i n f l u e n t c o n t a i n i n g t h a t m e t a l o n l y as a d s o r b a t e i s g r e a t e r than t h e c a p a c i t y f o r t h e same m e t a l when t h e i n f l u e n t c o n t a i n s t h a t m e t a l p l u s a ^ m i x t u r e o f o t h e r m e t a l s (See s e c t i o n 4.7), t h e c a p a c i t y f o r l e a d o f H.C. OX a t a pH o f 4.0 w i t h mixed i n f l u e n t s i s a minimum estimate  f o r t h e same c a p a c i t y when t h e i n f l u e n t c o n s i s t s o n l y o f l e a d .  10 p e r c e n t b r e a k t h r o u g h , t h i s minimum e s t i m a t e  At  of t h e c a p a c i t y f o r l e a d o f  H.C. OX a t a pH o f 4.0 i s 2.536 mg/gm as shown i n TABLE 4.10(a). D a t a from TABLES 4.3, 4.7 and 4.9 show t h a t f o r COrASH, a t a pH o f 4.0 and a t 10% b r e a k t h r o u g h c o n c e n t r a t i o n ,  the r a t i o of c a p a c i t i e s f o r zinc :  copper : l e a d i s e q u a l t o 1 : 6 : 12. 4.8  B r e a k t h r o u g h Curves f o r I n f l u e n t s C o n t a i n i n g Z i n c , Copper and Lead  a Mixture of  I n w a s t e streams such as m u n i c i p a l sewage, t h e r e u s u a l l y i s a m i x t u r e of d i s s o l v e d heavy m e t a l s i n s t e a d o f j u s t one s i n g l e a d s o r b a t e . heavy m e t a l s i n s o l u t i o n may m u t u a l l y  These v a r i o u s  enhance a d s o r p t i o n , may a c t r e l a t i v e l y (9)  i n d e p e n d e n t l y o r may m u t u a l l y  depress a d s o r p t i o n .  Some r e s e a r c h e r s  have  fround w i t h a c t i v a t e d carbon and mixed s o l u t i o n s t h a t each s o l u t e competes i n some way w i t h t h e a d s o r p t i o n o f t h e o t h e r . the o t h e r s o l u t e s i n t h e m i x t u r e a d v e r s e l y  I t was found t h a t t h e p r e s e n c e of affects the adsorption  of a p a r t i c u l a r  s o l u t e , l e a d i n g t o a more r a p i d b r e a k t h r o u g h of t h i s s o l u t e when u s i n g a mixed s o l u t i o n than when u s i n g a pure s o l u t i o n c o n t a i n i n g o n l y t h a t p a r t i c u l a r s o l u t e . A column each f o r H.C. OX, CO:ASH and DARCO A c t i v a t e d Carbon GRADE 12X20 was r u n a t 1 I g p m / f t  2  and a t a pH o f 4.0. The i n f l u e n t used c o n s i s t e d o f  2 mg/£ each o f z i n c , copper and l e a d .  The pH was chosen as 4.0 i n s t e a d o f 5.7,  because a t 5.7 t h e b r e a k t h r o u g h times would be e x c e s s i v e l y l o n g , e s p e c i a l l y f o r H.C. OX.  The b a s i c o b j e c t i v e s f o r r u n n i n g  t h e above mentioned t h r e e columns  70 were t h e f o l l o w i n g : 1)  To compare t h e t h r e e t y p e s o f a d s o r b e n t s w i t h r e g a r d t o t h e i r  a d s o r p t i v e c a p a c i t i e s f o r z i n c , copper and l e a d from w a t e r  containing  a m i x t u r e o f t h e s e metals a t a pH o f 4.0. 2)  To determine t h e change i n c a p a c i t i e s f o r z i n c , copper and l e a d  at  a pH o f 4.0 t h a t o c c u r s when a mixed i n f l u e n t i s used r a t h e r t h a n  a pure s o l u t i o n c o n t a i n i n g o n l y one a d s o r b a t e . As i n t h e l e a d t e s t s , t h e w h i t e fungus appeared i n a l l t h r e e columns. For  CO:ASH and DARCO A c t i v a t e d Carbon, t h e fungus appeared o n l y a f t e r  b r e a k t h r o u g h s f o r a l l t h r e e m e t a l s had o c c u r r e d . the to  total  B u t i n t h e case o f H.C. OX,  fungus appeared b e f o r e t h e l e a d and copper b r e a k t h r o u g h c u r v e s c o u l d b e g i n r i s e sharply.  I t may be due t o t h e f u n g u s , t h a t f o r H.C. OX,' t h e e f f l u e n t  c o n c e n t r a t i o n f o r l e a d began t o drop and t h a t f o r copper f a i l e d t o r i s e s h a r p l y a f t e r t h e appearance o f t h e fungus a t a throughput o f about 18 l i t r e s . can be observed q u i t e c l e a r l y i n F i g u r e 4 . 1 0 ( a ) .  This  The appearance o f t h e fungus  i n t h e columns c o n t a i n i n g C0:ASH and DARCO A c t i v a t e d Carbon a l s o took p l a c e a t a throughput o f about 18 l i t r e s , b u t t o t a l b r e a k t h r o u g h s f o r a l l t h r e e m e t a l s i n t h e s e two columns had o c c u r r e d l o n g b e f o r e throughput reached 18 l i t r e s .  The  curves f o r CO:ASH and DARCO A c t i v a t e d Carbon a r e shown i n F i g u r e 4.10(b) and Figure 4.10(c), r e s p e c t i v e l y . A summary o f t h e i m p o r t a n t d a t a from F i g u r e s 4 . 1 0 ( a ) , 4.10(b) and 4.10(c) i s p r e s e n t e d i n TABLE 4.10(a).  A performance  comparison between  H.C. OX, CO:ASH and DARCO A c t i v a t e d Carbon w i t h r e g a r d t o t h e i r c a p a c i t i e s f o r the  t h r e e m e t a l s from mixed i n f l u e n t s , a t a pH o f 4.0, may be made from t h e  d a t a i n TABLE 4 . 1 0 ( a ) .  F o r t h e sake o f c l a r i t y and b r e v i t y , t h i s  comparison,  as shown i n TABLE 4 . 1 0 ( b ) , i s done o n l y f o r t h e 10 p e r c e n t b r e a k t h r o u g h . c o n c e n t r a t i o n , .('ing/ )0. 2img/&)«le!t i S a e l e a r „ th:atiH,<2(. 0X is t h e . b e s t -perc  former o f t h e t h r e e .  £  H.C. OX i s about 12 t i m e s b e t t e r . , than C0:ASH  0-  -O CU  X—  - * PB -A  CD  JJ  Ph = 4.0 Influent = 2mg/l each of Cu., Pb. and Zn Flow rate = I Igpm/ft. Bed depth = 10 inches Coal weight = 13 gm  ZN  m  >  2  JO  o c  CD X  o c  JO  <  m co ~n o  JJ  cn E  o  6 rr LU O z o c_>  X  6  ^  Q  X  m o  UJ  3  Lu UJ  c m  10  12  14  16  18  VOLUME OF LIQUID TREATED ( LITRES)  20  22  24  26 27  CD  VOLUME  O F LIQUID T R E A T E D  (LITRES)  CO  m > Q  O  x—  * PB.  *  !• ZN.  —\  Ph=4.0  CU.  X  JO  Influent = 2mg/l each of Zn., Pb. and Cu. Flow rate = I Igpm/ft. Bed depth = 10 inches Coal weight = 9.5gm.  o c  2  CD  o c < m co  3 O E  5 5  < or  o  o z: o o  m o o >  111 3  CD  o  UUJ  X  t-  6  7  8  10  12  14  16  VOLUME OF LIQUID TREATED (LITRES)  18  -+-  20  22  m o cm  CO  TABLE 4.10(a) ADSORPTION CAPACITIES USING MIXED INFLUENTS Metal Tested = Zn, Breakthrough Cone, as Percent of I n f l u e n t Cone.  I n f l u e n t pH = 4.0 Capacity ''(mg/gm)'  c  f  Ave rage EfAvesrage E f f l ilent c. (mg/Gori c . (mg/l) ; Coi H.C.OX CO:ASH Act.C Act.C 0.088 .00188 .033 .062  H.C.OX  C0:ASH  10%  0.871  0.072  25%  1.036  0.106  0.133  .086  .116  50%  1.190  0.122  0.165  .196  .266  1'hroughput (litres) H.C.OX  CO:ASH  5.70  0.77  0.41 •  .168  7.00  1.09  0.60  .326  8.50  1.42  0.85  M e t a l T e s t e d = Cu, I n f l u e n t pH = 4.0  Act.C :  !  -i  -  10%  2.393  0.201  0.337  .019  .037  .048  15.60  2.05  1.58  25%  2.773  0.280  0.443  .079  .137  .142  18.63  2.95  2.31  0.347  0.603  .303  .330  4.08  3.44  50% M e t a l T e s t e d = Pb, 10%  —  —  I n f l u e n t pH = 4.0  2.536  •  0.675  0.489  .015  .041  .054  16.48  25%  —  0.931  0.659  —  .134  .136  —  50%  —  1.183  0.844  —  .313  .323  —  6.84  2.33  9.95  3.33  13.94  4.77  TABLE 4.10(b) A COMPARISON BETWEEN H.C. OX, CO:ASH AND DARCO ACTIVATED CARBON WITH REGARD TO THEIR CAPACITIES FOR THE THREE METALS FROM MIXED INFLUENTS AT A pH OF 4.0 M Metal Tested  B r e a k t h r o u g h Cone, as P e r c e n t o f I n f l u e n t Cone.  Zn  10%  Cu  10%  Pb  10%  CO:ASH  DARCO A c t . Carbon  H.C. OX  0.072  0.088  1.0  1.2  0.201  0.337  1.0  1.7  0.675  0.489  2.536  1.0*  0.7  3.8  0.871 12.1 2.393 11.9  C a p a c i t y (mg/gm) ReReiativiaCapacity* Capacity Relative  (mg/gm) Capacity*  C a p a c i t y (mg/gm) Relative  Capacity*  * " R e l a t i v e C a p a c i t y " s i g n i f i e s t h e r a t i o o f c a p a c i t i e s w i t h t h e c a p a c i t y o f C0:ASH as t h e base.  PERCENT DECREASE IN CAPACITY ON CHANGING THE INFLUENT TO ONE CONTAINING A MIXTURE OF SOLUTES H.C. 0 X Metal C a p a c i :y (BiGap.g£ i t y (mg/gm) Mixture of Single Heavy % Metal Solute Solutes Decrease  CO:ASH C a p a c i l :y (mg/gm) Single M i x t u r e of Solute Solutes  % Decrease  Zn  1.582  0.871  45  0.074  0.072  3  Cu  3.986  2.393  40  0.467  0.201  57  0.903  0.675  25  Pb  —  2.536  I n f l u e n t pH = 4.0 Breakthrough c o n c e n t r a t i o n  =  10 p e r c e n t  of i n f l u e n t  concentration  76  f o r z i n c and copper and about 4 times b e t t e r than CO:ASH f o r l e a d .  DARCO  a c t i v a t e d c h a r c o a l has t h e same range o f a d s o r p t i v e c a p a c i t y as CO:ASH. I t i s s l i g h t l y b e t t e r than CO:ASH i n t h e case o f z i n c and copper, and s l i g h t l y worse than CO:ASH i n t h e case o f l e a d .  I t i s somewhat s u r p r i s i n g t h a t an  a c t i v a t e d carbon w i t h a tremendous advantage i n s u r f a c e a r e a showed a poor performance i n comparison w i t h H.C. OX.  B u t , on t h e o t h e r hand, t h e raw  m a t e r i a l used t o p r e p a r e t h e c a r b o n , t h e method and temperature o f a c t i v a t i o n and t h e type o f gas used f o r a c t i v a t i o n may a l l a f f e c t t h e s e l e c t i v i t y o f t h e f i n a l product. W i t h t h e r e l e v a n t d a t a from TABLES 4.3, 4.7, 4.9 and 4 . 1 0 ( a ) , a comparison was made between t h e c a p a c i t i e s e x p e r i e n c e d w i t h s i n g l e s o l u t e i n f l u e n t s and w i t h i n f l u e n t s c o n t a i n i n g a m i x t u r e o f s o l u t e s . cases was 4.0.  ThenpH i n b o t h  The p e r c e n t decrease i n c a p a c i t y , due t o t h i s change i n t h e  n a t u r e o f t h e i n f l u e n t , i s c a l c u l a t e d f o r z i n c , copper and l e a d a t a 10 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n ( i . e . , 0.2 mg/A), as shown i n TABLE 4 . 1 0 ( c ) . H.C. OX seems t o e x p e r i e n c e about t h e same p e r c e n t d e c r e a s e i n c a p a c i t y f o r b o t h z i n c and copper on changing t h e i n f l u e n t t o one o f mixed solutes.  U n f o r t u n a t e l y , t h e f i g u r e f o r l e a d under s i n g l e s o l u t e i n f l u e n t i s  u n a v a i l a b l e due t o t h e fungus problem as d e s c r i b e d i n s e c t i o n 4.6. n o t h i n g can be c o n c l u d e d f o r l e a d i n t h i s  Thus,  respect.  The p e r c e n t d e c r e a s e i n c a p a c i t y d i s p l a y e d by CO:ASH under change o f i n f l u e n t i s g r e a t e s t f o r copper ( 5 7 % ) .  this  I n t h e case o f l e a d , t h e  p e r c e n t decrease i s 25 p e r c e n t , w h i l e f o r z i n c e t h e decrease was o n l y 3 p e r c e n t . T h e r e f o r e , i t can be c o n c l u d e d t h a t t h e c a p a c i t y f o r a heavy m e t a l decreases when t h e r e a r e o t h e r heavy m e t a l s p r e s e n t i n t h e i n f l u e n t .  This i s  p r o b a b l y due t o t h e o c c u p a t i o n o f some a c t i v e s i t e s by these o t h e r heavy  77  metals.  Under t h i s environment o f c o m p e t i t i o n  f o r a c t i v e s i t e s , the c a p a c i t y  f o r a p a r t i c u l a r heavy m e t a l i s l e s s than t h a t o b t a i n e d  under a c o m p e t i t i o n -  f r e e environment o f a s i n g l e s o l u t e i n f l u e n t . I t may a l s o be n o t e d t h a t t h e t o t a l c a p a c i t y f o r z i n c , copper and l e a d from a mixed i n f l u e n t d i s p l a y e d by t h e H.C. OX column i s e q u a l t o 5.800 mg/gm w h i c h i s much more than t h e c a p a c i t y f o r any i n d i v i d u a l heavy m e t a l from a s i n g l e s o l u t e i n f l u e n t .  CO:ASH a l s o e x h i b i t e d t h i s c h a r a c t e r i s t i c w i t h  a t o t a l c a p a c i t y f o r z i n c , copper and l e a d o f 0.948 mg/gm from a mixed i n f l u e n t . W i t h a s i n g l e s o l u t e , a p a r t i c u l a r type o f a c t i v e s i t e o n l y i s o c c u p i e d . p a r t i c u l a r type may form j u s t a s m a l l f r a c t i o n o f t h e t o t a l s i t e s . m i x t u r e o f s o l u t e s , more than one type o f a c t i v e s i t e i s used up.  This  But w i t h a Thus, a  greater f r a c t i o n of the t o t a l s i t e s i s u t i l i s e d .  4.9  C o r r e l a t i o n o f E f f l u e n t pH w i t h E f f l u e n t  Concentration  I n t h e e a r l y p a r t o f the column t e s t s , t h e pH o f t h e e f f l u e n t was measured a t t h e b e g i n n i n g  and j u s t b e f o r e  t h e end o f t h e run.  (Just f o r the  sake o f i n f o r m a t i o n , t h i s was done w i t h t h e f i r s t few columns.) t h a t t h e pH o f t h e e f f l u e n t was about 6.0 i n t h e b e g i n n i n g the pH o f the i n f l u e n t j u s t b e f o r e A n o t i o n was n u r t u r e d  Therefore,  and v e r y c l o s e t o  t h e end o f t h e t e s t .  t h a t t h e pH o f the, e f f l u e n t c o u l d somehow s e r v e  as an i n d i c a t o r o f the e f f l u e n t c o n c e n t r a t i o n i s adsorbable.  I t was n o t e d  of the metal.  The hydrogen i o n  when t h e e f f l u e n t pH d e c r e a s e s from about 6.0 t o  the pH o f t h e i n f l u e n t n e a r t h e end o f t h e t e s t , a c o n c l u s i o n may be drawn t h a t breakthrough w i t h regard  t o the hydrogen i o n has o c c u r r e d .  I f t h i s breakthrough  of t h e hydrogen i o n c o i n c i d e s w i t h t h a t o f t h e m e t a l , t h e n a c l e a r - c u t c o r :  r e l a t i o n can be drawn between e f f l u e n t pH and t h e e f f l u e n t c o n c e n t r a t i o n o f the m e t a l .  I f t h e two b r e a k t h r o u g h s do n o t c o i n c i d e , t h e pH o f t h e e f f l u e n t  78  c o r r e s p o n d i n g t o the b r e a k t h r o u g h o f the m e t a l may be n o t e d .  Then t h i s  pH  of the e f f l u e n t n o t e d can s e r v e as an i n d i c a t o r of the m e t a l b r e a k t h r o u g h i n f u t u r e i d e n t i c a l columns, p r o v i d e d : 1)  T h i s v a l u e of the pH has been proven t o remain c o n s t a n t  whenever b r e a k t h r o u g h o f the m e t a l o c c u r s . 2)  The e f f l u e n t pH s t e a d i l y approaches  t h a t o f the i n f l u e n t  as the experiment p r o c e e d s , w i t h o u t s u f f e r i n g any random decreases and  increases.  I f some k i n d of c o r r e l a t i o n between e f f l u e n t pH and e f f l u e n t m e t a l c o n c e n t r a t i o n can be brought to l i g h t , the a u t h o r can t h i n k of two  direct  b e n e f i t s such a s : 1)  I n the course of r e s e a r c h work, an i n e x p e n s i v e and compact  pH meter may be used to i n d i c a t e the b e g i n n i n g of the m e t a l breakthrough.  Once the b r e a k t h r o u g h i s about t o s e t i n , then  the e f f l u e n t c o n c e n t r a t i o n may  be t e s t e d on the more e x p e n s i v e  and cumbersome Atomic A b s o r p t i o n Spectrophotometer the d a t a f o r the b r e a k t h r o u g h c u r v e .  t o get  This procedure  would  e l i m i n a t e the time and t r o u b l e of u s i n g the Atomic A b s o r p t i o n Spectrophotometer b e f o r e the b e g i n n i n g of the m e t a l breakthrough. 2)  I n the p r a c t i c a l a p p l i c a t i o n of c o a l a d s o r p t i o n columns,  the pH meter may be used r o u t i n e l y t o i n d i c a t e the s a t u r a t i o n s t a t e o f the column, once the c o r r e l a t i o n between the e f f l u e n t pH and the e f f l u e n t m e t a l c o n c e n t r a t i o n has been worked out under a c t u a l p l a n t  conditions.  TABLE 4.11 COMPARISON OF EFFLUENT pH AND EFFLUENT CONCENTRATION TEST NUMBERS  Test Parameters Coal Type  CO:ASH  Flow Rate (Igpm/ft )  (3)  H.C.OX  H.C.OX  (4) CO:ASH  (6)  H.C.OX  CO:ASH  (7)  (8)  H.C.OX  CO:ASH  1  1  1  1  1  1  1  3.0  3.0  4.0  4.0  4.0  4^0  4.0  4.0  2mg/AZn  2mg/£Zn  2mg/£Cu  4mg/£Cu  2mg/£ Pb  2mg/£ Pb  0. 5mgA, Zn  0.5mg/£Zn  Influent pH  oAo  A  B  A  BB  A  B  A  B  58  5?2  :  Q'M 7?0  6?4  6.100 5.8  0.00 5.2  0.00 7.0  0.00 6.4  0.00 6.2  0.00 6.2  0.00 6.0  0.00 6.1  1.27 3.4  0.00 5.7  0.00 6.0  0.00 6.9  0.00 6.7  0.00 4.3  0.00 6.1  0.11 5.9  1.27 3.3  0.00 5.4  0.00 5.9  0.00 6.3  0.00 6.6  0.40 4.2  0.00 5.8  0.17 5.4  1.32 3.2  0.05 5.7  0.00 4.3  0.00 6.9  0.00 6.1  0.70 4.2  0.00 6.3  0.21 4.5  1.35 3.3  0.18 5.4  0.00 4.2  0.00 5.6  0.00 4.0  0.80 4.2  0.00 6.1  0.31 4.2  1.37 3.2  1.21 3.3  0.30 4.1  1.10 4.2  0.00 4.0  1.30 4.1  0.12 5.6 -  0.32 4.5  1.51 3.2  1.22 3.2  0.40 4.1  1.35 4.2  1.50 4.1  0.20 4.8  0.33 4.2  0.60 4.0  1.80 4.1  0.22 4.3  0.37 4.1  0.23 4.2  0.43 4.0  B  1.64 3.1  1.23 4.0 NOTE:-  (5)  1  2  Influent Cone.  (2)  (1)  A  =  Effluent concentration i n mg/£  B  =  Effluent pH vo  TABLE 4.11  (Continued)  J  TEST NUMBERS  Test Parameters  (9)  (10)  C o a l Type  H.C. OX  CO:ASH  Flow Rate (Igpm/ft )  1  1  1  1  4.0  4.0  5.7  5.7  2  I n f l u e n t pH I n f l u e n t Cone.  H.C. OX  2mg JSmg /'I ~ eacnn of ?b-5:P2mg/£ each o f Zn, Cu & Pb Zn, Cu & Pb A(Zn) A(Cu) A(Pb) BB  (12)  (11)  A(Zn) A((Cu) A(Pb)  2mg/£ Zn B  A  B  CO:ASH  2mg/£ Cu A  B  0.00  0.00  0.00  §.1 0.04  0.00  0.00  6.3  0.00 7.0  0.00  6.6  0.00  0.00  0.00  5.8 1.70  0.20  0.00  5.6  0.00 6.0  0.00  6.0  0.18  0.00  0.00  5.9 2.00  1.50  0.20  4.2  0.00 7.6  0.00  6.8  0.42  0.00  0.00  5.6 2.00  1.70  0.30  4.1  0.00 5.9  0.05  6.2  2.00  0.05  0.00  5.0 2.00  2.00  0.75  4.1  0.00 7.5  0.40  5.8  2.00  0.10  0.00  4.6 2.00  2.00  1.45  4.0  0.00 7.0  0.70  6.9  2.00  0.15  0.10  4.3 2.00  2.00  1.60  4.0  0.27 5.7  1.10  6.7  2.00  0.65  0.15  4.1  1.20  7.0  1.25  5.7  TABLE 4.11  TEST  Test Parameters  (13)  (14)  C o a l Type  H.C . OX.  C00,: ASH  3 5 .7  Flow Rate (Igpm/ft ) 2  I n f l u e n t pH  I n f l u e n t Cone. ' 22-mg/JGZn  (Continued)  NUMBERS (15)  (16)  (17)  H.C. OX  CO:ASH  CO:ASH  3  5  5  1  5. 7  5. 7  5.7  5.7  2mg/l Zn  2mg/£Zn  2mg/£ Zn  0.5mg/£Zn  B  A  B  0.00  6.1  0.00  6.6  0.00  7.1  0.04  7.0  0.15  6.8  0.00  7.2  0.17  6.1  0.00  7.0  0.14  5.9  0.30  6.7  0.17  6.6  0.46  7.2  0.00  7.2  0.53  7.0  0.47  6.6  0.55  5.8  0.67  7.1  0.00  6.3  0.77  5.7  0.65  6.4  0.73  5.7  0.89  7.3  0.01  6.3  0.85  5.7  0.81  6.5  •1.00  6.1  1.21  6.5  0.05  6.7  1.06  7.0  1.04  6.1  1.29  6.0  1.33  7.2  0.07  6.7  1.11  7.2  1.39  6.3  1.37  5.7  1.44  6.0  0.10  6.2  1.67  6.2  0.21  7.2  A  A  B  A  B  00000 66,33  A  B  0,0000 66'; 9  82  TABLE 4.11  i s a comparison of the e f f l u e n t pH w i t h  c e n t r a t i o n i n the e f f l u e n t . s t e a d i l y as the e f f l u e n t  T e s t s #1 and  #2 show t h a t the e f f l u e n t pH  concentration increases.  to 3.4  concentration while i s due  occurred  the change i n pH  from 3.4  of hydrogen i o n undergoes a change by to 3.4,  to 3.0  i t takes  the molar  a f a c t o r of 10.  a change i n molar c o n c e n t r a t i o n of 10 from 3.4  to 3.0.  f l u c t u a t e i n v a l u e when i t i s above 5.0 t r e n d below a pH of 4.0  with  e a s i l y understood when one  —6 8.0  X 10  takes  10  to 3.9.  The  and  -3 9 - 4 '  -3 4  concentration  - 10  -5  drops  = 3.8  X 10  -3.4 - 10  -4  ;  -4  "  = 6.0  X 10  to  pH of the e f f l u e n t seems to  only f o l l o w s a d e f i n i t e downward  i n c r e a s i n g breakthrough of the m e t a l .  understands t h a t i t o n l y takes  10  - 10  0  '  i o n to cause a s h i f t  = 26.0  X 10  -6  molesM  This i s  - 10  =  i n pH of 5.7  to 5.0,  to the dynamic n a t u r e  take w i t h  g a i n or net l o s s d u r i n g the u n s a t u r a t e d  i n the net g a i n or net l o s s show up +  and  from  5.7  infinitesimal  stage of the  to  be  where  shifts  column.  i n the pH range of 5.0  i o n c o n c e n t r a t i o n necessary  4.0  may  of the e q u i l i b r i u m a d s o r p t i o n p r o c e s s  the hydrogen ions are i n a s t a t e of g i v e and  because the changes i n H  while i t  f o r the n e e d l e to s h i f t  Thus, the f l u c t u a t i o n of the e f f l u e n t pH between 5.0  i n p a r t due  shifts  This  4"  moles/H of H  i n the net  drop i n  Thus, when the pH  the change i n molar c o n c e n t r a t i o n i s 10  b r i n g about a drop i n pH  The  occurs more s l o w l y .  -3 while  #2.  r a p i d l y over a s m a l l change i n e f f l u e n t  to the f a c t t h a t f o r every u n i t change of pH,  from 5.0  drops  Thus, a c o r r e l a t i o n i s  p o s s i b l e under the t e s t parameters d e s c r i b e d i n T e s t s #1 and pH from about 5.0  the metal.con-  These  5.7  to produce a change i n  pH i n t h i s range are extremely s m a l l . T e s t s #3  to #10  have an i n f l u e n t pH of 4.0.  r e l a t i o n i s p o s s i b l e f o r T e s t s #3, such a c o r r e l a t i o n . T e s t s #9  & 10.  The  influent  F o r T e s t #9,  4, 6,  7 and  8.  Of these  T e s t #5  t e s t s , pH  shows no  c o n s i s t s of a z i n c , copper and  cor-  promist  of  l e a d mixture i n  c o r r e l a t i o n i s p o s s i b l e f o r the copper b r e a k t h r o u g h  and  83  d i s c o u r a g i n g f o r z i n c and l e a d b r e a k t h r o u g h s .  I n t h e case o f Test #10, t h e  c o r r e l a t i o n i s f a i r f o r copper and l e a d f r a c t i o n s and n o t p o s s i b l e zinc, since  f o r the  t h e b r e a k t h r o u g h f o r z i n c o c c u r r e d a t an e f f l u e n t pH above 5.6,  and as p r e v i o u s l y  mentioned, t h e pH o f t h e e f f l u e n t randomly  fluctuates i n  the range of 5.0 t o 5.7. The pH o f t h e i n f l u e n t was 5.7 f o r T e s t s #11 t o #17. d e f i n i t e l y not possible  f o r a l l these t e s t s s i n c e  randomly between 7.6 and 5.7 w i t h i n c r e a s i n g  Correlation i s  t h e e f f l u e n t pH f l u c t u a t e s  e f f l u e n t metal concentration.  e f f l u e n t pH i s n o t l i k e l y t o go below 5.7 s i n c e  The  t h e i n f l u e n t pH happens t o be  5.7. • T h e r e f o r e , t e s t s w i t h an i n f l u e n t pH o f 5.7 have no hope o f such a correlation. A c o n c l u s i o n may be drawn t h a t when t h e i n f l u e n t pH i s as l o w as 3.0, a c o r r e l a t i o n between t h e e f f l u e n t pH and t h e e f f l u e n t m e t a l c o n c e n t r a t i o n i s most l i k e l y t o o c c u r .  When t h e i n f l u e n t pH i s above 5.0, t h e chances o f  such a c o r r e l a t i o n a r e p r a c t i c a l l y n i l .  B u t , when t h e i n f l u e n t pH i s about  4.0, t h e p o s s i b i l i t y o f such a c o r r e l a t i o n w i l l depend on t h e t e s t p a r a m e t e r s , i . e . , t h e p a r t i c u l a r c o m b i n a t i o n o f c o a l type and type o f heavy m e t a l i n t h e influent. 4.10  B r e a k t h r o u g h Curves f o r Mercury F i g u r e 4.11 shows p l o t s o f e f f l u e n t c o n c e n t r a t i o n o f mercury v e r s u s  volume o f l i q u i d t r e a t e d .  The i n f l u e n t c o n c e n t r a t i o n o f mercury  s e r i e s of e x p o n e n t i a l curves j o i n e d by v e r t i c a l l i n e s .  i s shown as a  The i n f l u e n t c o n c e n t r a t i o n  i s a t 5 yg/£ when a new b a t c h o f i n f l u e n t i s made and p u t i n t o t h e system.  But  the n e x t day, about 6 hours b e f o r e r e f i l l i n g t h e system w i t h 5 yg/A Hg, t h e i n f l u e n t i n t h e system was t e s t e d and found t o be 2.1 yg/& Hg.  This indicates  the mercury had v o l a t i l i s e d o v e r n i g h t from 5 ug/£ t o 2.1 yg/£.  that  F o r l a c k o f more  AVERAGE INFLUENT = 3.lOug/1 Hg pH =7.5  •I  0  1  1  I  2  13  1 4  1 5  1 6  1—H 7 8  INFLUENT — COAL WEIGHT  1 9  1 10  1 1 15 20 VOLUME OF LIQUID TREATED (Litres)  • •  '  1 25  :  • 30  85  d a t a , t h i s d e t e r i o r a t i o n o f t h e i n f l u e n t c o n c e n t r a t i o n i s assumed t o be e x p o n e n t i a l and, t h e r e f o r e , r e p r e s e n t e d by e x p o n e n t i a l decay c u r v e s .  When  a new b a t c h o f 5 yg/& i n f l u e n t e n t e r s t h e s y s t e m , t h e i n f l u e n t c o n c e n t r a t i o n shoots back up t o 5 yg/£ and t h i s moment i s r e p r e s e n t e d by t h e v e r t i c a l j o i n i n g t h e exponential curves.  S i g w o r t h and S m i t h ^ ^ mentioned  lines  a similar  f l u c t u a t i o n o f t h e i n f l u e n t c o n c e n t r a t i o n i n a d s o r p t i o n systems o f a c t i v a t e d carbon and m e t h y l mercury c h l o r i d e i n f l u e n t s . F o r purposes o f c a p a c i t y c a l c u l a t i o n s i f b r e a k t h r o u g h s had been r e a c h e d , 3.45 yg/£ would have been chosen as t h e average i n f l u e n t c o n c e n t r a t i o n f o r = t h e n t i m e F v a r i a t i o n l o f i n f l u e n t mercury  assumed i n F i g u r e 4.11.  A column each f o r H.C. OX and CO:ASH was r u n a t a pH o f 7.5. The main o b j e c t i v e f o r r u n n i n g t h e s e two columns was t o f i n d out t h e c a p a c i t i e s o f the two c o a l s f o r mercury i n t h e i n f l u e n t range o f 5 yg/A and a t near n e u t r a l pH o f 7.5. The b r e a k t h r o u g h s f o r b o t h columns f a i l e d t o o c c u r even a f t e r a throughput o f 30 l i t r e s .  I t was d e c i d e d t o s t o p t h e runs r a t h e r t h a n w a i t  i n d e f i n i t e l y f o r t h e b r e a k t h r o u g h s t h a t showed no s i g n s o f a p p r o a c h i n g . and S m i t h ^  Sigworth  r e p o r t e d a column t e s t i n v o l v i n g g r a n u l a r a c t i v a t e d carbon and  m e t h y l m e r c u r i c c h l o r i d e i n f l u e n t o f 25 yg/£ w h i c h f a i l e d t o show a b r e a k t h r o u g h even a f t e r a throughput t i m e o f 3 months. was  A c c o r d i n g t o t h e two a u t h o r s , mercury  c a t e g o r i s e d as a m e t a l o f good a d s o r p t i o n p o t e n t i a l .  as good b u t a l i t t l e below mercury.  Lead was a l s o c l a s s e d  Copper was c l a s s e d as a m e t a l o f s l i g h t  a d s o r p t i o n p o t e n t i a l and z i n c was a l s o i n t h e s l i g h t c a t e g o r y b u t below  copper.  S i n c e F i g u r e 4.11 shows two h o r i z o n t a l l i n e s f o r t h e e f f l u e n t conc e n t r a t i o n s o f t h e two columns w i t h o u t any h i n g o f b r e a k t h r o u g h s , t h e c a p a c i t i e s at p a r t i c u l a r b r e a k t h r o u g h c o n c e n t r a t i o n s cannot be c a l c u l a t e d .  I t can be n o t e d ,  however, t h a t t h e p e r c e n t removal o f mercury i s 75 p e r c e n t i n t h e case o f CO:ASH ;  86  and 90 p e r c e n t i n t h e case o f H.C. OX.  The p e r c e n t removals were based on  the average i n f l u e n t c o n c e n t r a t i o n o f 3.1,. .ug/&.  The e f f l u e n t from t h e H.C. OX  column has an average of 0.3 ug/£ and t h i s c o n c e n t r a t i o n i n t h e e f f l u e n t s t a y e d almost c o n s t a n t w i t h i n c r e a s i n g t h r o u g h p u t .  The e f f l u e n t from t h e C0:ASH  column e x h i b i t e d t h e same s o r t o f b e h a v i o r w i t h an average e f f l u e n t c o n c e n t r a t i o n of 0.8 pg/£.  I t i s s u s p e c t e d t h a t the r e a s o n f o r the e f f l u e n t c o n c e n t r a t i o n  never b e i n g a t 0.0 yg/& even a t t h e b e g i n n i n g o f t h e r u n may be due t o t h e e x t r e m e l y low d r i v i n g f o r c e o f 3.45 ug/£ i n f l u e n t c o n c e n t r a t i o n . T h i s may make i t v e r y h a r d f o r the adsorbent t o t o t a l l y adsorb t h e mercury "even when t h e adsorbent i s h i g h l y u n s a t u r a t e d a t t h e b e g i n n i n g of t h e t e s t .  4.11  Column T e s t s - Summary and C o n c l u s i o n s C o n c l u s i o n s drawn from t h e i n v e s t i g a t i o n s c a r r i e d o u t i n t h e Column  T e s t s a r e as f o l l o w s : 1)  No s i g n i f i c a n t change i n c a p a c i t y o c c u r s by v a r y i n g t h e c r o s s -  s e c t i o n a l a r e a o f t h e c o a l bed w i t h i n t h e range o f 0.001 f t - 0 . 0 0 2 f t 2  The 28/48 s i z e f r a c t i o n has an average d i a m e t e r o f 0.7 mm.  The c o a l  bed c r o s s - s e c t i o n a l a r e a o f 0.001 f t has a d i a m e t e r o f 10.9 mm, 2  i s 16 times b i g g e r than 0.7 mm.  2  which  S i m i l a r l y , c r o s s - s e c t i o n a l area of  0.002 f t corresponds t o a d i a m e t e r o f 15.4 mm, w h i c h i s 22 times 2  g r e a t e r than the average p a r t i c l e d i a m e t e r .  F o r p a r t i c l e s shaped as  those o f 28/48 c o a l , t h e w a l l e f f e c t would most p r o b a b l y s e t i n i f the column diameter were l e s s than about 10 times t h e average diameter.  T h e r e f o r e , t h e use o f columns s m a l l e r t h a n those s e l e c t e d  f o r t h i s work would r u n t h e r i s k o f p r o v i d i n g u n r e a l i s t i c 2)  particle  results.  A d e f i n i t e decrease i n a d s o r p t i v e c a p a c i t y i s evident w i t h  d e c r e a s i n g i n f l u e n t pH.  The p e r c e n t d e c r e a s e i n c a p a c i t y f o r a  .  87  g i v e n d e c r e a s e i n pH i s a p p r o x i m a t e l y CO:ASH w i t h z i n c i n f l u e n t s .  t h e same f o r b o t h H.C. OX and  S i n c e t h e pH o f t h e i n f l u e n t i s a  c r i t i c a l f a c t o r i n determining  the adsorptive c a p a c i t y , s p e c i a l  emphasis s h o u l d be l a i d on t h e i n v e s t i g a t i o n o f more d e t a i l e d r e l a t i o n s h i p s between pH and c a p a c i t y i n f u t u r e r e s e a r c h o f t h i s type. Of a l l t h e t e s t parameters w i t h t h e e x c e p t i o n o f c o a l t y p e , t h e i n f l u e n t pH i s t h e most c r u c i a l as f a r as a d s o r p t i v e c a p a c i t y i s concerned.  A d e c r e a s e i n pH means a d e c r e a s e i n c a p a c i t y .  Therefore,  f o r a c i d i c w a s t e s , such as c e r t a i n i n d u s t r i a l w a s t e s , some form o f pre-treatment  t o r a i s e t h e pH b e f o r e p a s s i n g t h e wastes t h r o u g h t h e  c o a l column may be an i m p o r t a n t 3)  consideration.  As t h e f l o w r a t e was i n c r e a s e d from 1 I g p m / f t  a corresponding  2  to 5 Igpm/ft ,  d e c r e a s e i n a d s o r p t i v e c a p a c i t y was n o t i c e d .  2  This  d e c r e a s e was h i g h l y s i g n i f i c a n t when t h e f l o w r a t e was i n c r e a s e d from 1 t o 3 I g p m / f t . 2  2 Igpm/ft  2  On f u r t h e r i n c r e a s i n g t h e r a t e by a n o t h e r  to 5 Igpm/ft , the corresponding 2  much s m a l l e r than t h e p r e v i o u s one.  d e c r e a s e i n c a p a c i t y was  T h i s s u g g e s t s t h e r e l a t i v e ease  of changing t h e r a t e from 3-5 I g p m / f t , s h o u l d o c c a s i o n demand i t , 2  without  s u f f e r i n g s i g n i f i c a n t decreases i n c a p a c i t y .  -The p e r c e n t d e c r e a s e s i n c a p a c i t y , due t o i n c r e a s i n g f l o w r a t e , become lessmail'ef.ess a t h i g h e r b r e a k t h r o u g h c o n c e n t r a t i o n s .  Thus,  the c h o i c e o f whether t o use a h i g h e r f l o w r a t e o r b u i l d a t h i c k e r column i s a l s o i n f l u e n c e d by t h e p e r m i s s i b l e b r e a k t h r o u g h c o n c e n t r a t i o n w h i c h would be s e t by t h e l o c a l r e g u l a t o r y agency. 4)  Whether t h e c a p a c i t y would d e c r e a s e o r i n c r e a s e upon l o w e r i n g  88  the i n f l u e n t c o n c e n t r a t i o n was and on the t y p e of c o a l .  found t o depend on the i n f l u e n t  A t a pH of 4.0,  the g e n e r a l t r e n d i s a  decrease i n c a p a c i t y on l o w e r i n g the i n f l u e n t c o n c e n t r a t i o n . of. 5.7,  pH  At a  pH  the type of c o a l used determines the d i r e c t i o n of change of  capacity with decreasing  influent concentration.  T h i s i n d i c a t e s the  p o s s i b i l i t y of combining waste streams to lower the i n f l u e n t concent r a t i o n of the waste components w i t h the aim o f r a i s i n g the capacities.  adsorptive  Of c o u r s e , t h i s s o r t of d i l u t i o n b e f o r e treatment  p e r t a i n o n l y t o cases where the adsorbent - pH c o m b i n a t i o n an i n c r e a s e i n c a p a c i t y on l o w e r i n g the i n f l u e n t The p e r c e n t  decrease i n c a p a c i t y due  would  favours  concentration.  to a d e c r e a s e i n pH i s more  pronounced at lower i n f l u e n t c o n c e n t r a t i o n s .  C o n s e q u e n t l y , more  a t t e n t i o n w i l l have t o be p a i d t o pH c o n d i t i o n s of waste streams of lower i n f l u e n t 5) 5.7.  The  concentrations.  c a p a c i t y i n c r e a s e s as the i n f l u e n t pH i n c r e a s e s from 3.0  The h i g h e s t c a p a c i t i e s a r r i v e d a t i n t h i s r e s e a r c h were  corresponding  t o a pH of 5.7.  TABLE 4.12  to  those  l i s t s the c a p a c i t i e s f o r  z i n c , copper and l e a d to 10 p e r c e n t b r e a k t h r o u g h c o n c e n t r a t i o n , where i n f l u e n t pH and c o n c e n t r a t i o n i s 5.7  and 2 mg/£,  r e s p e c t i v e l y , and  the f l o w r a t e i s 1 I g p m / f t . 2  " '.iaiUnder; the s a m e c o n d i t i o n s , :  but w i t h an i n f l u e n t pH o f 4.0,  the  r a t i o of c a p a c i t i e s f o r z i n c : copper : l e a d i s e q u a l t o 1 : 6 : 12 for  CO:ASH c o a l .  The h i g h c a p a c i t y f o r l e a d may  the f a c t t h a t l e a d has  a h i g h atomic w e i g h t .  be p a r t l y due  to  T h i s o r d e r of magnitude  o f a d s o r p t i v e c a p a c i t i e s f o r the t h r e e m e t a l s i s i n agreement w i t h the r e s u l t s of the Batch  Tests.  89  TABLE 4.12 CAPACITIES AT A pH OF 5.7 AND AT A BREAKTHROUGH CONCENTRATION OF 10 PERCENT OF INFLUENT CONCENTRATION CAPA CITIES  Note:  6)  mg/gm  Zn mg/gm  Cu mg/gm  CO:ASH  0.370  1.182  —  H.C. OX  9.716  12.396  —  Pb mg/gm  1)  Capacity; x>f H.C. OX f o r copper i s shown i n i t a l i c s s i n c e t h i s f i g u r e i s o n l y an e s t i m a t e and n o t a r r i v e d a t e x p e r i m e n t a l l y ( S e c t i o n 4.5)  2)  The c a p a c i t i e s f o r l e a d a r e undetermined s i n c e t h e runs were stopped b e f o r e t h e o c c u r r e n c e o f b r e a k throughs ( S e c t i o n 4.7)  From column t e s t s a t a pH o f 4.0 w i t h i n f l u e n t s  containing  2 mg/£ each o f z i n c , copper and l e a d , t h e a d s o r p t i v e c a p a c i t i e s o f DARCO A c t i v a t e d Carbon a r e i n t h e same range as those o f CO:ASH.  The  c a p a c i t i e s o f H.C. OX a r e much h i g h e r than t h o s e o f t h e a c t i v a t e d carbon o r C0:ASH.  W i t h r e g a r d t o z i n c and copper, H.C.OX i s 12 times  h i g h e r i n c a p a c i t y than C0:ASH.  I n t h e case o f l e a d , H.C. OX d i s -  p l a y e d a c a p a c i t y 4 times t h a t o f CO:ASH. There i s a mutual i n h i b i t i o n o f a d s o r p t i o n when t h e r e i s more than one heavy m e t a l i n t h e i n f l u e n t .  Although the a d s o r p t i v e  c a p a c i t y d e c r e a s e s f o r each i n d i v i d u a l m e t a l when the i n f l u e n t i s a mixture rathernthan a s i n g l e s o l u t e s o l u t i o n , the t o t a l capacity f o r heavy m e t a l s a c h i e v e d w i t h mixed i n f l u e n t s i s h i g h e r than any o f t h e i n d i v i d u a l c a p a c i t i e s encountered w i t h s i n g l e s o l u t e i n f l u e n t s . s u g g e s t s t h e p o s s i b i l i t y o f combining waste s t r e a m s , c o n t a i n i n g  This  90  different heavy metals, before passing them through the adsorption column.  Such a procedure would result i n a higher t o t a l capacity  of the coal than would be achieved i f the i n d i v i d u a l streams were passed through separate columns. 7)  An attempt was made to correlate the effluent pH with the  metal concentration i n the effluent.  I t was found that the effluent  pH i s generally around 6.0 at the beginning of each column test, and decreases with column age u n t i l the effluent pH reaches that of the influent when column exhaustion has occurred.  The chances of a  c o r r e l a t i o n between effluent pH and effluent metal concentration increase with decreasing pH of the i n f l u e n t .  In other words, the  c o r r e l a t i o n i s more evident when the influent pH i s farther away from 6.0.  At an influent pH of 5.7, there was no correlation.  At  an influent pH of 4.0, the occurrence of a correlation depended on the combination of coal type and type of heavy metal i n the i n f l u e n t . And at an influent pH of 3.0, the c o r r e l a t i o n was  pronounced.  For columns where this correlation e x i s t s , a saving i n time and expenses may be r e a l i s e d by using a pH meter instead of other sophisticated 8)  equipment that i s more expensive and cumbersome.  The tests with mercury proved to be somewhat d i f f i c u l t .  influent concentration of mercury deteriorated with time. column capacity c a l c u l a t i o n purposes, the o r i g i n a l influent  The  Thus, for concen-  t r a t i o n of 5 yg/Jt could not be used as a base, but rather, an average influent concentration over the period of the test had to be determined. Capacities could not be calculated before breakthroughs occurred.  since the runs were stopped  I t might have taken intolerably long  periods of time f o r breakthroughs to have occurred.  The presence of  91  mercury i n the e f f l u e n t was of each column t e s t . 0 . 8 u g / £ f o r H.C.  OX  The  d e t e c t a b l e even at the v e r y  e f f l u e n t c o n c e n t r a t i o n was  ug/£  and CO:ASH, r e s p e c t i v e l y , r i g h t from t h e  t o the end of the t e s t s .  This gives a percent  average i n f l u e n t c o n c e n t r a t i o n of 77 f o r H.C.  0.3  beginning  percent  and  beginning  r e m o v a l , b a s e d on  f o r C0:ASH and 91  the  percent  OX.  For f u t u r e r e s e a r c h w i t h mercury, a more s t a b l e form or complex of mercury s h o u l d be used i n s t e a d of H g C ^ j w h i c h was research.  used i n t h i s  U s i n g a more s t a b l e complex of m e r c u r y , p r e f e r a b l y a type  o f complex found i n sewage, w o u l d e l i m i n a t e t h e p r o b l e m of d e t e r i o r a t i n g c o n c e n t r a t i o n o f mercury when r u n n i n g i n f l u e n t s of e x t r e m e l y  low mercury c o n c e n t r a t i o n s .  the  column t e s t s w i t h  92  Chapter  5  RECOMMENDATIONS  Based on t h i s r e s e a r c h and o t h e r works done on the a d s o r p t i o n of heavy m e t a l s by g r a n u l a r c o a l s , f u r t h e r r e s e a r c h i s i n d i c a t e d : 1)  S i n c e H.C.  OX i s f a r s u p e r i o r than the o t h e r types of c o a l  t e s t e d , f i r s t p r i o r i t y s h o u l d be g i v e n t o t h i s c o a l f o r use as adsorbent 2)  i n an advanced waste treatment  an  process.  A t t e m p t s s h o u l d be made to grow some c u l t u r e s of t h e  mentioned i n t h i s t h e s i s , so t h a t f u n g a l spores c o u l d be f o r an e x a c t i d e n t i f i c a t i o n of the fungus.  Research  fungus, obtained  s h o u l d a l s o be  done on the i n v e s t i g a t i o n o f t h e heavy m e t a l removal mechanism of the fungus.  I s the heavy m e t a l b e i n g c o n v e r t e d i n t o some form of a  s a l t c r y s t a l and entrapped  i n the mycelium, or i s i t s i m p l y b e i n g  adsorbed by the mycelium, a r e q u e s t i o n s of h i g h i n t e r e s t . 3)  More d e t a i l e d a n a l y s i s on the c o r r e l a t i o n between e f f l u e n t  pH  and m e t a l c o n c e n t r a t i o n i n the e f f l u e n t s h o u l d be done w i t h columns where the i n f l u e n t pH i s l e s s than 4.0. when the i n f l u e n t pH i s above 4.0. 4)  There i s no  correlation  (Refer to S e c t i o n  4.9)  For f u t u r e r e s e a r c h w i t h mercury i n f l u e n t s , a more s t a b l e  complex of mercury s h o u l d be used.  T h i s i s to overcome the problem  of d e t e r i o r a t i n g i n f l u e n t c o n c e n t r a t i o n e x p e r i e n c e d i n t h i s r e s e a r c h , where H g C ^ 5)  was  used as an  influent.  Removal of heavy metals i n s o l u t i o n u s i n g g r a n u l a r c o a l s  s h o u l d be f u r t h e r i n v e s t i g a t e d w i t h o r g a n i c s p r e s e n t i n the waste solution.  The  g o a l of t h i s i n v e s t i g a t i o n s h o u l d be t o  determine  the removal e f f i c i e n c i e s a t low heavy m e t a l c o n c e n t r a t i o n s from a r e a l m u n i c i p a l sewage.  93  6)  The p o s s i b l e  having this  used  superior by  i t as an a d s o r b e n t ,  possibility  treatment  system  the treatment  should  facility  needed  The f i n a l  would h e l p  heavy metals  a  I f they  H.C.  pollution  after Should  advanced  waste  be-economically  Having  a power p l a n t  t h e economic  picture  as t h e a d s o r b e n t  fuel  close  material,  the required coal.  s h o u l d be t o i n v e s t i g a t e where t h e  would  e n d up when t h e c o a l  s t a y down w i t h  destination.  this  OX p o s s e s s e s  the ash, then  the n e c e s s a r y p r e c a u t i o n s t o prevent final  may  H.C. OX b e c h o s e n  taken  adsorbed fuel.  systems.  then  f o r use as a s a t i s f a c t o r y  step  source,  s h o u l d be i n v e s t i g a t e d .  using granular coals  Should  as a f u e l  t o be f e a s i b l e ,  f i r s t b e shown t h a t  properties 7)  prove  to other treatment  tremendously. it  use of granular c o a l  I f they  i s burned  a landfill  l e a c h i n g would be  f l y up t h e s t a c k , t h e n  c o n t r o l m e a s u r e s may h a v e  to be  as  with  their  special a i r  undertaken.  BIBLIOGRAPHY  C u l p , R.L. and C u l p , G.L., 1971.  "Advanced Wastewater Treatment".  E c k e n f e l d e r , J r . , W.W. , 1966. "Industrial McGraw-Hill Series i n Sanitary Science.  Water Pollution  Control".  Hendren, M.K., 1974. "Coal Treatment of Wastewaters". T h e s i s f o r Master of A p p l i e d Science, C i v i l E n g i n e e r i n g , U n i v e r s i t y of B r i t i s h Columbia. L e o n a r d , J.W. and M i t c h e l l , D.R., 1968. S e e l e y W. Mudd S e r i e s .  "COAL Preparation".  M e t c a l f & Eddy I n c . , 1972. "Wastewater Engineering". McGraw-Hill S e r i e s i n Water R e s o u r c e s and E n v i r o n m e n t a l E n g i n e e r i n g . N e t z e r , A. and Norman, J.D., 1972. "Removal of Trace Metals from Wastewater by Activated Carbon". MfcMaster U n i v e r s i t y , Wastewater R e s e a r c h Group - R e p o r t 72-305-1. Shannon, E. and S i l v e s t o n , P., "Studies on the Use of Coal for Waste Treatment" Water - 1968, C h e m i c a l Eng. P r o g r e s s Symposium S e r i e s , pp. 198-206. 3  S i g w o r t h , E.A. and S m i t h , S.B., 1972. Adsorption by Activated Carbon.- J o u r n a l AWWA, 64-386. Vermeulen, T., 1958. Separation Chemical Engineering 2:147.  by Adsorption  Weber, W.J., 1972. "Physicochemical Control" - W i l e y - I n t e r s c i e n c e .  Processes  of Inorganic Compounds  Methods.  Advanced  for Water Quality  Weber, W.J. and M o r r i s , J . C , 1964. Equilibria and Capacities Adsorption on Carbon. Amer. Soc. C i v i l Engs., S a n i t a r y D i v . , 90 (SA3):79. W e n z e l , L.A. e t a l . , 1959. W i l e y & Sons, I n c .  "Principles  of Unit Operations".  for  John  "Development of a Coal Based Sewage Treatment Process" O f f i c e of C o a l R e s e a r c h , U.S. Dept. o f t h e I n t e r i o r , U.S. Government P r i n t i n g O f f i c e , Washington, D.C. (1972). 3  

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