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Anodic oxidation of phenolics found in coal conversion effluents Chettiar, Meenakshi 1982-12-31

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ANODIC OXIDATION OF PHENOLICS FOUND IN COAL CONVERSION EFFLUENTS  by  MEENAKSHI' CHETTIAR ( M . S c , U n i v e r s i t y o f Madras, India  A THESIS SUBMITTED  1978)  IN PARTIAL FULFILMENT OF  THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  in  THE FACULTY OF GRADUATE STUDIES (Chemical  E n g i n e e r i n g Department)  We a c c e p t t h i s t h e s i s as conforming to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA December 1981  (c)  Meenakshi C h e t t i a r , 1981  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  Itis  understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l n o t be allowed without my  permission.  Department o f The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date  Columbia  written  ABSTRACT  Anodic oxidation effluents  of  the major  was i n v e s t i g a t e d .  anode o f  electrodeposited  individually in a batch p-cresol,  in  lead dioxide. ranging  system.  were s t u d i e d .  of  variation  on t h e r e m o v a l  Oxidation  chemical  complete  the  monohydric  the  structure  coal  of  the  postulated results  of  for  a few  initial  was f o u n d the  of  and a p p l i e d  the  oxidation  p h e n o l i c s was  between t h e  w i t h a mass t r a n s f e r  oxygen  rate  compounds. at  current  Complete o x i d a t i o n be d i f f i c u l t  of  although  several  cases.  anodic oxidation A mixture  concentrations  of  reported  was a l s o o x i d i z e d .  of  on  five as  Up t o 95%  obtained. spectrometer  anodic oxidation oxidation  and  process  by i n c r e a s i n g t h e  compound was a c h i e v e d i n  present  current  by gas c h r o m a t o g r a p h y  concentration.  phenolic  0-cresol,  cases.  conversion wastewaters  the  solutions  and c a t e c h o l .  p h e n o l i c s was f o u n d t o  A gas c h r o m a t o g r a p h / m a s s products  treated  aqueous  concentration  The e f f e c t  in  phenolic  of  in  conversion  a p a c k e d bed  o x y g e n demand ( C . O . D . ) and b i o l o g i c a l  p h e n o l s w h i c h were  for  oxidation  of  correlation  Pb02 and t h e  the  1 gpl  p h e n o l i c s was f a v o u r e d  carbon i n the  removal  No d i r e c t  typical  of  and d e c r e a s i n g t h e  the o r g a n i c  initial  carbon a n a l y z e r .  of  in  coal  Compounds s t u d i e d w e r e p h e n o l ,  in  demand ( B . O . D . ) was d e t e r m i n e d  density  up t o  S o l u t i o n s were a n a l y z e d p r i m a r i l y  organic  in  The p h e n o l i c s w e r e  2,3-Xylenol, 3,4-Xylenol, resorcinol  The e f f e c t s  by t o t a l  that arise  E x p e r i m e n t s were performed  concentrations  recirculation  phenolics  in  typical  a n a l y z e r was u s e d t o runs.  Reaction routes  process.  Comparisons o f  model  presented for  ii  are  examine  the a few  were  experimental experiments.  TABLE OF CONTENTS Page ABSTRACT  i i  LIST OF TABLES  vi  LIST OF FIGURES  vii  ACKNOWLEDGEMENTS  x  CHAPTER 1  2  INTRODUCTION  1  1.1  P h e n o l i c s i n coal  processing effluents  1.2  Typical  1.3  A v a i l a b l e methods o f treatment o f p h e n o l i c wastes and i n t e r e s t f o r t h i s study  composition o f coal  1 3  LITERATURE SURVEY  5  2.1  General concepts  5  2.2  L i t e r a t u r e review on t h e e l e c t r o c h e m i c a l oxidation of selected  2.3  phenolics  8  2.2.1  Anodic o x i d a t i o n o f phenol  9  2.2.2  E l e c t r o l y t i c oxidation of cresols  9  2.2.3  Anodic o x i d a t i o n o f X y l e n o l s  12  2.2.4  Anodic o x i d a t i o n o f d i h y d r i c phenols  13  2.2.5  O x i d a t i o n o f p h e n o l i c mixtures  14  Importance o f c h o i c e o f experimental c o n d i t i o n s  ... 15  2.3.1  Nature o f e l e c t r o d e m a t e r i a l s  15  2.3.2  Current density-anode p o t e n t i a l  16  2.3.3  Nature o f t h e e l e c t r o l y t e  18  2.3.4  E f f e c t o f pH  18  2.3.5 ^ C e l l 3  c o n v e r s i o n wastes  1  configuration  BASIS AND EXTENT OF EXPERIMENTAL STUDY  i ii  19 21  CHAPTER 4  Page EXPERIMENTAL APPARATUS AND METHODS  23  4.1  Apparatus  23  4.1.1  D e s c r i p t i o n of equipment  23  4.1.2  Flow diagram of the apparatus  27  4.2  Experimental methods  27  4.2.1  Anodization  27  4.2.2  Electrochemical phenol i e s  4.2.3  4.2.4 4.3  5  process oxidation of individual  30  Experimental m o d i f i c a t i o n s made with c e r t a i n phenolies  31  Anodic o x i d a t i o n of p h e n o l i c m i x t u r e s  33  A n a l y t i c a l techniques  33  4.3.1  A n a l y s i s of phenols  33  4.3.2  Total organic  34  4.3.3  Biological  4.3.4  Chemical oxygen demand a n a l y s i s  35  4.3.5  GC/MS A n a l y s i s  36  4.3.6  Accuracy and r e p r o d u c i b i l i t y  37  carbon a n a l y s i s  oxygen demand a n a l y s i s  35  RESULTS AND DISCUSSION  39  5.1  of i n d i v i d u a l phenolies  39  5.1.1  Anodic o x i d a t i o n o f phenol  39  5.1.2  Oxidation  of p - c r e s o l  42  5.1.3  Oxidation  of 0-cresol  46  5.1.4  Oxidation  o f 2,3-Xylenol  48  5.1.5  Oxidation  of 3,4-Xylenol  52  5.1.6  Oxidation  of resorcinol  56  5.1.7  Oxidation  of catechol  62  5.2  Oxidation  Comparison o f performance o f d i f f e r e n t p h e n o l i c s 5.2.1  ..  66  E f f e c t of v a r i a t i o n of i n i t i a l concentration  66  5.2.2  E f f e c t of v a r i a t i o n of applied current  69  5.2.3  Substituent effents  69  5.2.4  Effect of d i f f u s i v i t y  72  5.3  Oxidation  5.4  Reaction  o f phenolic mixtures efficiency f o r a typical iv  74 run  79  CHAPTER  Page 5.5  Cell  voltage  80  5.6  Comparison o f experimental mathematical models  r e s u l t s with 82  6  CONCLUSIONS  86  7  FURTHER WORK  88  NOMENCLATURE  90  BIBLIOGRAPHY  93  APPENDIX 1  Specification of a u x i l l i a r y  2  Experimental  data  105  3  Mathematical  model  162  4  Calculations  169  5  R e l e v a n t data  176  v  equipment and m a t e r i a l s  ... 97  LIST OF TABLES  TABLE I II III  Page Composition o f s y n t h e t i c coal c o n v e r s i o n wastewater Comparison  o f h a l f wave p o t e n t i a l v a l u e s  V VI  Fundamental  Appendix-2  using  Pb02 anode  s p e c i f i c a t i o n s o f the e l e c t r o l y t i c c e l l  D i f f u s i v i t i e s o f the p h e n o l i c Results  compounds i n water  17 ... 25 73  o b t a i n e d from the o x i d a t i o n o f mixture o f  monohydric VII  10  E f f e c t o f c u r r e n t d e n s i t y and type o f e l e c t r o l y t e on C.O.D. removal  IV  2  phenols  (run 8-3)  78  V a r i a t i o n o f Av  81  Experimental data t a b l e s f o r :  Run 1-1 to Run 1-5  Anodic o x i d a t i o n o f phenol  105-111  Run 2-1 t o Run 2-5  Anodic o x i d a t i o n o f p - c r e s o l  112-116  Run 3-1 t o Run 3-5  Anodic o x i d a t i o n o f 0 - c r e s o l  117-121  Run 4-1 t o Run 4-5  Anodic o x i d a t i o n o f 2,3-Xylenol  122-126  Run 5-1 t o Run 5-5  Anodic o x i d a t i o n o f 3,4-Xylenol  127-131  Run 6-1 t o Run 6-5  Anodic o x i d a t i o n o f r e s o r c i n o l  132-136  Run 7-1 t o Run 7-5  Anodic o x i d a t i o n o f c a t e c h o l  137-145  Run 8-1 t o Run 8-3  Anodic o x i d a t i o n o f mixture o f monohydric phenols o f i n t e r e s t  146-151  Anodic o x i d a t i o n  152  Run 9-1 t o Run 9-8  f o r GC/MS a n a l y s i s  Appendix-3 A-l A-2  T h e o r e t i c a l 2,3-Xylenol f r a c t i o n a l c o n v e r s i o n vs time f o r a mass t r a n s f e r c o n t r o l l e d batch system T h e o r e t i c a l r e s o r c i n o l f r a c t i o n a l c o n v e r s i o n vs time f o r a mass t r a n s f e r c o n t r o l l e d batch system  vi  167 168  LIST OF FIGURES FIGURE  Page  1  Components o f a simple e l e c t r o l y t i c c e l l  2  Side view o f the general u n d i v i d e d c e l l (N.T.S.) Components o f the e l e c t r o l y t i c c e l l  3  Experimental  setrup  4  Various  5  Flow diagram o f the apparatus  6  Deposition  5 arrangement 24  f o r anodic o x i d a t i o n  components o f the c e l l  26 26 28  o f condensation product d u r i n g the  oxidation of catechol  32  7  Cone, e f f e c t on % phenol o x i d i z e d a t 10 A  40  8  Current  40  9  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c  e f f e c t on % phenol o x i d i z e d  (1 g/1 runs)  carbon i n phenol a t 10 A  43  10  Cone, e f f e c t on % p - c r e s o l  o x i d i z e d a t 10 A  11  Current  12  E f f e c t o f cone, on r a t e of o x i d a t i o n o f o r g a n i c  e f f e c t on % p - c r e s o l  oxidized  (1 g/1 runs)  carbon i n p - c r e s o l Cone, e f f e c t on % o - c r e s o l  14  Current  15  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c  o x i d i z e d a t 10 A  e f f e c t on % o - c r e s o l  oxidized  (1 g/1 runs)  carbon i n o - c r e s o l  47 47  49  16  Cone, e f f e c t on % 2,3-Xylenol  17  Current  18  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n 2,3-Xylenol a t 10 A E f f e c t o f c u r r e n t on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n 2,3-Xylenol (1 g/1 runs) Cone, e f f e c t on % 3,4-Xylenol o x i d i z e d a t 10 A  20  44  45  13  19  44  o x i d i z e d a t 10 A  e f f e c t on 2,3-Xylenol o x i d i z e d  vii  (1 g/1 run)  50 51  53 54 55  FIGURE  Page  21  Current  22  Cone, e f f e c t on % r e s o r c i n o l o x i d i z e d a t 10 A  23  Current  24  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n r e s o r c i n o l a t 10 A  60  E f f e c t o f c u r r e n t on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n r e s o r c i n o l (1 g/1 runs)  61  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n c a t e c h o l a t 10 A  63  E f f e c t o f c u r r e n t on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n c a t e c h o l (1 g/1 runs)  64  V a r i a t i o n o f f i n a l % o x i d i z e d with i n i t i a l of p h e n o l i c s a t 10 A  67  25  26  27  28  29  30  31  32  33  34  35  36  e f f e c t on % 3,4^Xylenol o x i d i z e d  e f f e c t on % r e s o r c i n o l o x i d i z e d  Variation of i n i t i a l at 10 A Variation of final (1 g/1 runs)  r a t e with i n i t i a l  (1 g/1 runs) .. 55  (1 g/1 runs)  58 .. 59  concentration  concentration 68  % o x i d i z e d with a p p l i e d  current 70  V a r i a t i o n o f i n i t i a l r a t e o f o x i d a t i o n with c u r r e n t (1 g/1 runs) E f f e c t o f nature o f p h e n o l i c s (10 A, 2 h r s ; run 8-1)  on % o x i d a t i o n  E f f e c t o f nature o f p h e n o l i c s (10 A, 3 h r s ; run 8-2)  on % o x i d a t i o n  E f f e c t o f nature o f p h e n o l i c s (10 A, 5 h r s ; run 8-3)  on % o x i d a t i o n  applied 71  75  76  77  GC/MS a n a l y s i s o f f i n a l (run 9-1)  product from phenol  oxidation  GC/MS a n a l y s i s o f f i n a l o x i d a t i o n (run 9-3)  product from p - c r e s o l  154  155  37  Mass spectrum showing the presence o f 4-Hydroxy-4-Methyl2,5-Cyclohexadiene-l-one 156  38  GC/MS a n a l y s i s d f f i n a l o x i d a t i o n (run 9-2)  product from  viii  o-cresol 157  FIGURE 39  Page GC/MS a n a l y s i s o f f i n a l o x i d a t i o n (run 9-4)  product from  GC/MS a n a l y s i s o f f i n a l o x i d a t i o n (run 9-5)  product from  40  41  42  MS c o n f i r m a t i o n or isomer  2,3-Xylenol 158 3,4-Xylenol 159  o f t r a c e s o f 2,3-Dimethyl  hydroquinone 160  GC/MS a n a l y s i s o f f i n a l product o f o x i d a t i o n o f mixture and X y l e n o l s (run 9-8)  161  Appendix 3 A-l  Schematic  representation  ix  o f a m u l t i p i e pass system  162  ACKNOWLEDGEMENTS  I wish t o p l a c e on r e c o r d my s i n c e r e g r a t i t u d e t o P r o f . Paul  Watkinson,  under whose guidance and encouragement t h i s work was c a r r i e d o u t . My g r a t e f u l acknowledgement i s due t o my husband, Mohan C h e t t i a r f o r h i s suggestions  and t h o u g h t f u l n e s s .  t h e i r cooperation, I would l i k e  patience  Thanks a r e due t o our parents f o r  and s a c r i f i c e s .  t o express my a p p r e c i a t i o n f o r the a s s i s t a n c e o f  P r o f . C o l i n Oloman and f o r h i s s i n c e r e  interest.  A l s o acknowledged a r e the s t a f f o f the Chemical and  Environmental Further  Mrs.  Engineering  Laboratory  Engineering  department  for their enthusiastic assistance.  thanks a r e due t o Tim Ma f o r h e l p i n g with  GC/MS a n a l y s i s ,  C h r i s t i n e Lee f o r t y p i n g the m a n u s c r i p t , Mrs. Bea K i r z s a n and my  husband f o r the d r a f t i n g o f f i g u r e s .  x  1.  CHAPTER 1  INTRODUCTION  1.1  P h e n o l i c s i n coal  The  term  processing effluents  "phenols"  but an assortment  i n waste water i n c l u d e s not o n l y phenol  o f o r g a n i c compounds c o n t a i n i n g one o r more hydroxyl  groups a t t a c h e d t o an aromatic Phenols  P e r m i s s i b l e l e v e l s o f phenols by the U.S. Environmental  Technology  ring.  have a high p o l l u t i o n p o t e n t i a l  e s t a b l i s h phenol  (CgHgOH)  in industrial  due to t h e i r  toxicity.  wastes have been e s t a b l i s h e d  P r o t e c t i o n Agency (EPA).  These g u i d e l i n e s  l e v e l s o f 0.1 mg/l f o r the Best P r a c t i c a l  Control  C u r r e n t l y A v a i l a b l e f o r 1977, and 0.02 mg/l f o r the Best  A v a i l a b l e C o n t r o l Technology  E c o n o m i c a l l y A c h i e v a b l e f o r 1983 [ 1 ] .  Coal g a s i f i c a t i o n , coal phenolic-waste of the t o t a l  problems.  l i q u e f a c t i o n and coke oven p l a n t s have  I t has been r e p o r t e d t h a t 60 t o 80 p e r c e n t  o r g a n i c carbon  (T0C) i n the o r g a n i c contaminants  from  coal  c o n v e r s i o n systems i s p h e n o l i c i n nature [ 2 ] .  1.2  Typical  composition  o f coal  Wastewater composition process technology and coal For p o l l u t i o n c o n t r o l  c o n v e r s i o n wastes  appears  t o be r e l a t i v e l y  independent o f  f e e d i n the case o f p h e n o l i c c o n s t i t u e n t s [ 2 ] .  s t u d i e s , i t i s convenient t o d e f i n e a s i m u l a t e d  wastewater which approaches the composition  of real  coal  waters from v a r i o u s processes. Table I p r o v i d e s a t y p i c a l such a s y n t h e t i c wastewater [3] as might a r i s e from  c o n v e r s i o n wastecomposition o f  the condensate (gas  TABLE I COMPOSITION OF SYNTHETIC COAL CONVERSION WASTEWATER COMPOUND  STRUCTURAL FORMULA  OH 1.  CONCENTRATION  mg/l  2000  Phenol <§>  OH  2.  Resorcinol  3.  Catechol  4.  Acetic Acid  1000  OR OH 1000  CH C00H 3  OH 5.  GH„  O-Cresol  400  400  OH 6.  P-Cresol  250  <§>  CH. 7.  3,4-Xylenol  CH 8.  2,3-Xylenol  CH, 3  3  13 CH  C H  9.  250  250 3  120  Pyridine  COOH 10.  100  Benzoic Acid C H 2  11.  4-Ethylpyridine  # OH:  12.  4-Methylcatechol  5  OH:  100  100  CH„ Only the l i s t o f compounds p r e s e n t i n c o n c e n t r a t i o n s o f 100 mg/l or above i s presented h e r e . The a c t u a l c o m p o s i t i o n o f the s y n t h e t i c waste can be found i n Appendix 5.  3.  l i q u o r ) o f a coal  gasifier.  For example, the Synthane process  about 0.4 - 0.6 tons o f condensate water o f t h i s approximate per ton o f coal  1.3  The  composition  gasified [3].  A v a i l a b l e methods o f treatment this  produces  o f p h e n o l i c wastes and i n t e r e s t f o r  study  c h o i c e between r e c o v e r y OH d e s t r u c t i o n o f p h e n o l i c s can be made  on the b a s i s o f economics.  The v a l u e o f the r e c o v e r e d product should be  balanced a g a i n s t both the c o s t o f r e c o v e r y and the c o s t o f p o l l u t i o n systems r e q u i r e d f o r the d e s t r u c t i o n o f the c h e m i c a l s . c a b l e o n l y t o c o n c e n t r a t i o n s i n the percentage o f about 50 G.P.M. [1].  Although  control  Recovery i s a p p l i -  range and t o flows i n excess  s  r e c o v e r y becomes l e s s c o s t l y as the  c o n c e n t r a t i o n i n c r e a s e s , r e c o v e r y p r o c e s s e s may produce streams which require  effluent  treatment.  Treatment p r o c e s s e s  i n c l u d e i n c i n e r a t i o n t e c h n i q u e s , a d s o r p t i o n on  a c t i v a t e d c a r b o n , v a r i o u s chemical and  i o n exchange r e s i n p r o c e s s e s .  phenol  wastewater c o n t r o l  o x i d a t i o n methods, b i o l o g i c a l o x i d a t i o n A review o f a l t e r n a t i v e methods o f  [4] and c o s t comparison between v a r i o u s  p r o c e s s e s c u r r e n t l y being used  [5], reveals that biological  the best a v a i l a b l e c h o i c e to degrade these wastes. ideal  biological  treatment  treatment i s  However, even i n an -  environment, many o p e r a t i n g problems have been a s s o c i a t e d .  B e s i d e s , the a b i l i t y o f t h i s process t o produce e f f l u e n t phenol  concen-  t r a t i o n s o f l e s s than 500 ppb on a c o n s i s t e n t b a s i s i s q u e s t i o n a b l e and hence i s not recommended i f phenol  removal  i s the primary concern [ 4 ] .  For example, i n a s e r i e s o f t e s t runs with phenol ranging from 450 t o 4800 ppm [ 3 ] , i t was found c o n c e n t r a t i o n was i n c r e a s e d , a breakthrough  i n l e t concentrations  t h a t as the phenol  p o i n t was reached  inlet  where  4.  additional phenol  i n l e t phenol  resulted in a significant  increase  i n the e f f l u e n t  concentration. New  methods f o r t r e a t i n g p h e n o l i c  because o f the  i n t e n s i t y o f the  e f f l u e n t s have been attempted  p o l l u t i o n problem and  the  highly  [6,7]  restrictive  f u t u r e p o l l u t i o n c o n t r o l standards expected. Dephenolization been attempted  [81.  o f these e f f l u e n t s by e l e c t r o - o x i d a t i v e methods I n v e s t i g a t i o n o f the f e a s i b i l i t y o f anodic  of the major p h e n o l i c s  i n Table I i s the  The  to the o x i d a t i o n o f the  work i s r e s t r i c t e d  t r a t i o n s equal research  was  to or g r e a t e r  m o t i v a t e d by the  than 250  mg/l  s u b j e c t of the phenolics  present present  oxidation study. i n concen-  i n the s y n t h e t i c waste.  r e s u l t s of p r e v i o u s  work [9] t h a t  This  revealed  the p o s s i b i l i t y o f e s s e n t i a l l y complete removal o f phenol by e l e c t r o oxidation  under c e r t a i n c o n d i t i o n s .  has  5.  CHAPTER 2  LITERATURE SURVEY  2.1  General  concepts  An e l e c t r o c h e m i c a l can  reactor  be performed d i r e c t l y  components and fundamental  i s a device  i n which chemical  by the i n p u t o f e l e c t r i c a l operation  energy.  o f an e l e c t r o c h e m i c a l  reactions  The b a s i c  process  v i s u a l i z e d from F i g . 1.  d.c. power supply  electrolyte solution  Fig.  1  diaphragm  Components o f a simple  electrochemical  reactor  can be  6. The anode and cathode are immersed i n the e l e c t r i c a l l y electrolyte.  conducting  The e l e c t r o d e s a r e connected o u t s i d e the bath to the t e r m i n a l s  o f a d.c. power supply.  When an emf o f s u f f i c i e n t  e l e c t r o n t r a n s f e r occurs  between the e l e c t r o d e s and the e l e c t r o l y t e .  results  i n a flow of e l e c t r i c i t y  r e a c t i o n a t each e l e c t r o d e .  magnitude i s a p p l i e d , This  i n the e x t e r n a l c i r c u i t and chemical  In a chemical  anode and r e d u c t i o n a t the cathode.  sense, o x i d a t i o n occurs  The diaphragm i n i t s simple  a t the  form a c t s  as a kind o f f i l t e r . Consider  a general  reversible electrode reaction at equilibrium  r  0 + ze  0)  R r ' o  0 represents  the o x i d i s e d form and R r e p r e s e n t s  same substance.  In the case, when r  The r a t e o f the forward  r  r  where i  c  =  reaction, r  k  Similarly,  o • W  constant  flow.  i s given by  r  c  point of discharge.  and C  Q  i s the c o n c e n t r a t i o n  o f 0 a t the  - a <Y k  i s the r a t e o f o x i d a t i o n , i  the anodic  i s no net c u r r e n t  c u r r e n t d e n s i t y f o r the c a t h o d i c r e a c t i o n , k i s  rate constant  Q  0  C  the e l e c t r o c h e m i c a l  where r  = r , there  r  W = c o  i s the p a r t i a l  r  the reduced form o f the  f  l  i s the p a r t i a l  r e a c t i o n , k, and C a r e the c o r r e s p o n d i n g a i and c o n c e n t r a t i o n o f R r e s p e c t i v e l y .  current density f o r electrochemical  rate  7.  The  c u r r e n t d e n s i t y , i i s given  between i„ and i . c a  The r a t e c o n s t a n t s  o f the e l e c t r o d e p o t e n t i a l  [10],  .0 . _  k a  =  k  o  e  x  transfer coefficient. electrode potential (1-a)|V  | drives  constant  i n terms  azFlV*  (l-a^F|V ,  p  under standard  k and k, can be expressed c a  by the formulae  where k° and k° a r e r a t e c o n s t a n t s c a potential  by the modulus o f the d i f f e r e n c e  (  referenced  |V | d r i v e s  the r e v e r s e  )  to a p a r t i c u l a r e l e c t r o d e r  c o n d i t i o n s and a i s a c o n s t a n t  Equations  3  (2) and (3) imply  known as the charge  t h a t a f r a c t i o n o f the  the forward r e a c t i o n and the remainder  reaction.  As the e l e c t r o c h e m i c a l  rate  depends e x p o n e n t i a l l y on the e l e c t r o d e p o t e n t i a l as well as the  temperature, adjustment o f the p o t e n t i a l would l e a d t o a wide v a r i a t i o n of r e a c t i o n r a t e . The and  *  total  the t o t a l  *  e l e c t r o l y s i n g v o l t a g e , AV which i s the sum o f V and V a c ohmic drop i s e a s i e r t o measure than the anode p o t e n t i a l 3  *  *  V, or. cathode p o t e n t i a l V . a a  In order  *  *  t o measure V, o r V . a r e f e r e n c e a c  e l e c t r o d e has t o be connected a t the s u r f a c e o f the anode o r cathode and the d i f f e r e n c e i n p o t e n t i a l between the e l e c t r o d e under c o n s i d e r a t i o n and the  s o l u t i o n should  be measured.  importance because the o p e r a t i n g  The t o t a l  e l e c t r o l y s i n g voltage  c o s t o f the e l e c t r o l y t i c  process  i s of will  depend on i t s power requirement, which i s d i r e c t l y r e l a t e d t o the v o l t a g e drop through the c e l l  a t a given  current density.  Besides,  i f the p o t e n t i a l  of the e l e c t r o d e  i s i n the r i g h t range, many s i d e r e a c t i o n s such as the  anodic  o f oxygen and c a t h o d i c  formation  formation  o f hydrogen can occur  8.  i n aqueous s o l u t i o n s , r e s u l t i n g i n the l o s s o f c u r r e n t The  concentration  of a r e a c t a n t A, a t the  s u r f a c e o f the  i s r e l a t e d to both the r a t e o f the e l e c t r o c h e m i c a l o f mass t r a n s f e r from the bulk o f the  Mass t r a n s f e r flux=k (C/\^ m  -  efficiency.  r e a c t i o n and  s o l u t i o n to the e l e c t r o d e  For a given  f u n c t i o n of the e l e c t r o d e c o n f i g u r a t i o n and  fluid  can  be o b t a i n e d  t h e o r e t i c a l expressions  from standard  texts  [11].  For  In very d i l u t e  reaction i s dictated  current e f f i c i e n c y w i l l  tend  to be low.  l i m i t of c o n c e n t r a t i o n s  below which e l e c t r o c h e m i c a l  2.2  the  There must t h e r e f o r e be a p r a c t i c a l  Some c o u p l i n g of e l e c t r o c h e m i c a l  processes  design  systems, i t  At t h i s l i m i t i n g c u r r e n t c o n d i t i o n ,  biochemical  is a  for transfer coefficients  by mass t r a n s f e r p r o c e s s e s .  inefficient.  surface,  s p e c i e s , km  dynamics.  might be expected t h a t the r a t e of e l e c t r o c h e m i c a l  very  rate  (4)  m  and  the  )  where k. i s the mass t r a n s f e r - c o e f f i c i e n t .  purposes, e m p i r i c a l  electrode  o x i d a t i o n would become and  chemical  or  might be of i n t e r e s t i n these s i t u a t i o n s .  L i t e r a t u r e review on the e l e c t r o c h e m i c a l  o x i d a t i o n of s e l e c t e d  phenolies  A substantial literature exists in this f i e l d . covers  This  literature  a v a r i e t y of anodes, c u r r e n t d e n s i t i e s , e l e c t r o l y t e s and  operating  conditions.  products have been The  not u n e x p e c t e d l y , a wide range of o x i d a t i o n  obtained.  a v a i l a b l e information  oxidation of phenolics dioxide  And  other  i s very l i m i t e d  concerning  the l a s t stages  of the  anodic  to open c h a i n compounds or e v e n t u a l l y to carbon because most o x i d a t i o n s t u d i e s were aimed a t  9.  s y n t h e s i s of compounds and  e l u c i d a t i o n of the r e a c t i o n mechanisms r a t h e r  than a t d e s t r u c t i o n o f the o r g a n i c s  2.2.1  Anodic o x i d a t i o n of phenol  E a r l y s t u d i e s o f the anodic and  f o r waste treatment.  co-workers  [12-16].  o x i d a t i o n of phenol were done by F i c h t e r  They r e p o r t e d  t h a t phenol o x i d a t i o n a t a l e a d  d i o x i d e e l e c t r o d e i n s u l p h u r i c a c i d media r e s u l t s i n the f o r m a t i o n  of  hydroquinone, p-benzoquinone, c a t e c h o l , m a l e i c  a c i d , monophenyl e t h e r  pyrocatechol,  dihydroxy diphenyl.  final and  2,4'  products obtained  carbon d i o x i d e .  o f the o x i d a t i o n of diphenyl  2.2.2  the  i s an  suggestions  The  have been made about the mechanism  In more r e c e n t p u b l i c a t i o n s [15-20] the  d e r i v a t i v e s has  not been  presence  reported.  r e l a t i v e ease o f o x i d a t i o n of v a r i o u s p h e n o l i c  s u b s t i t u e n t s present  on the r i n g .  The  compounds depends  h a l f wave p o t e n t i a l  value  i n d i c a t i o n of the e f f e c t o f adding d i f f e r e n t s u b s t i t u e n t groups  to the p h e n o l i c potential  on  ring.  The  h a l f wave p o t e n t i a l , {E  the p o l a r o g r a p h i c  l i k e OH  and  negative  alkyl  values  ease o f o x i d a t i o n . and  groups are p r e s e n t ,  and  t h i s should The  are presented  i n Table  II.  The  ) i s d e f i n e d as  When e l e c t r o n - d o n a t i n g the  E^ i s s h i f t e d  be accompanied by an  e f f e c t of the  para p o s i t i o n s .  1  curve when the c u r r e n t i s equal  the mass t r a n s f e r l i m i t i n g c u r r e n t .  ortho  4,4'  were o x a l i c a c i d , f o r m i c a c i d , carbon monoxide  A few  [12].  and  E l e c t r o l y t i c ; o x i d a t i o n of c r e s o l s  The on  d i h y d r o x y diphenyl  of  E  1  substituents  values  Based on  the  the  to one  substituents  towards more  increase  i n the  i s greatest at  the  f o r the phenols of i n t e r e s t half-wave p o t e n t i a l  half  values,  TABLE II COMPARISON OF HALF WAVE POTENTIAL VALUES  £-2  Conditions of measurement -  Reference  Phenol  0.633  Acetate buffer pH 5.6; graphite electrode  [21]  p-Cresol O-Cresol  0.543 0.556  Catechol  0.139  Resorcinol  0.490  [25]  Hydroquinone  0.018  [25]  2,4-Xylenol  0.459  3.4- Xylenol  0.513  [21]  3.5- Xylenol  0.587  [21]  Name o f p h e n o l i c compound  Note:  volt  [21] [21]  Acetate buffer pH 5.6; graphite electrode  A l l half-wave p o t e n t i a l s a r e r e p o r t e d with the S.C.E.  [25]  wax-impregnated g r a p h i t e anode  [21]  r e f e r e n c e to  p-cresol  should be more s u s c e p t i b l e  p-cresol media i n a c e l l detected  oxidation  at polished  with a diaphragm  by n.m.r  to anodic o x i d a t i o n lead electrodes  than phenol [ 2 2 ] .  (PLE) i n s u l p h u r i c  [23] r e s u l t e d i n the f o l l o w i n g  products  analysis.  OH p-cresol  (£)  CH  40%  3  4-Hydroxy-4methylcyclohexa-2, 5-dienone  HO C H  0 p-Benzoquinone  (ft)  20% 3  (ft)  33%  0  0  Methyl-p-benzoquinone  (jjf  7%  3  0  E x t r a c t i o n o f the lead anode with hot methylene c h l o r i d e y i e l d e d a f t e r e v a p o r a t i n g a mixture o f c o u p l i n g  OH  OH  OH t£)  CH  CH n  OH  3  products o f the type;  n = 0,1,2 e t c . 3  S i m i l a r e l e c t r o l y s i s o f 0 - c r e s o l [23] y i e l d e d  OH 0-cresol  tOj  C H  3  12% 0  C^T™  Methyl-p-benzoqui none  3  75%  0 OH Methyl  hydroquinone  (0 OH  3  13%  acid  12.  E x t r a c t i o n o f the anode w i t h hot methylene c h o r i d e y i e l d e d which n.m.r  indicated  tars  to be c o u p l i n g products o f O - c r e s o l .  In a study o f the e f f e c t o f anode m a t e r i a l , PbOg-C anode (prepared by anodic p r e c i p i t a t i o n o f l e a d d i o x i d e on a carbon rod) i s r e p o r t e d to behave i n a s i m i l a r manner to the PLE with r e s p e c t to the r a t e o f c o n v e r s i o n and % y i e l d o f c e r t a i n p r o d u c t s . p-cresol  resulted  products on a PLE  An  increase in i n i t i a l  concentration of  i n the p r o d u c t i o n o f l a r g e r percentages  of coupling  [23].  In a comparison o f anodic o x i d a t i o n o f c r e s o l s  [24], p - c r e s o l  r e p o r t e d to have a l a r g e r % c o n v e r s i o n (96%) than O-cresol similar  under  conditions.  On  the b a s i s o f c y c l i c voltammetric  [23] i t was  concluded  t h a t the phenol  s t u d i e s on a l e a d d i o x i d e anode  i s o x i d i s e d c h e m i c a l l y by  d i o x i d e on the anode s u r f a c e , and the reduced is oxidised  ( v i a d i r e c t charge  i s p a r t o f the anode  2.2.3  (90%)  is  lead  l e a d s p e c i e s thus formed  t r a n s f e r ) r a p i d l y back to Pb  ( I V ) , as i t  itself.  Anodic o x i d a t i o n o f X y l e n o l s  E l e c t r o o x i d a t i o n o f 2,4-Xylenol  and  2,6-Xylenol  under c o n d i t i o n s  r e p o r t e d f o r the c r e s o l s with a PLE has been r e p o r t e d [ 2 3 ] . products were o b t a i n e d from 2,4-Xylenol  following  2,6-Xylenol.  OH.  OH  (J^r 3 CH  OH  and  The  HC  CH  3  (2,2'-dihydroxy-3,3'5,5 -tetramethyl ,  biphenyl)  3  0 2,4-Xylenol  HO  CH. 3  (4-hydroxy-2,4-dimethylcyclohexa-2,5-dienone)  13.  2,6-dimethyl-p-benzoquinone)  H3C CH' o^f)r(5^:0 (3,3' ,4,4'-tetramethyldiphenoquinone) 3  Although 2,3-Xylenol and 3,4-Xylenol are the Xylenols of greatest importance in coal wastewaters, no data are available on anodic oxidation of these compounds.  However, corresponding products analogous to the  above mentioned ones can be expected.  2.2.4  Anodic oxidation of dihydric phenols As evidenced by their half-wave potentials [Table II], the dihydric  phenols, resorcinol and catechol are easier to oxidise than phenol i t s e l f . Nash, Skauen and Purdy [25] report a similar trend in half-wave potential values of dihydric phenols as obtained in reference 26. It has been suggested [26] that during the oxidation of resorciinbl, radicals are generated which then may polymerize and deposit on the electrode. The kinetics and mechanism of coulometric oxidation of catechol at controlled potential have been investigated [27]. The oxidation is said to proceed as a two-electron process: .e  0 - C H (0H) 6  4  2  —  0 - C H 0 + 2H  +  6  4  2  + 2e  (5)  It has been pointed out by several investigators [28,29] that O-benzoquinone in aqueous solutions decomposes giving catechol and  2-hydroxyquinone or 4-hydroxyquinone, the i s given  by  Eq.  (6).  2C H 0 6  The  s t o i c h i o m e t r i c course of which  4  + H0  2  -  2  l a t t e r product  C H (0H) 6  4  2  + C H 0 (0H) 6  3  (6)  2  (2-hydrpxyquinone or 4-hydroxyquinone) i s s a i d  to condense r a p i d l y g i v i n g a substance of high m o l e c u l a r chemical  composition.  both by hydroxyl 5 to 8.  The  ions and  However, a t low  r e a c t i o n i s reported  [28,29] to be  excess amounts of c a t e c h o l pH  weight and  a t pH  unknown  accelerated  values  c o n d i t i o n s , the c a t a l y t i c e f f e c t of  from  catechol  i s n e g l i g i b l e [27].  2.2.5  Oxidation  of phenolic  mixtures  A number of e l e c t r o d e r e a c t i o n s are p o s s i b l e when s e v e r a l are p r e s e n t  i n the r e a c t a n t  produced as i n t e r m e d i a t e s  s o l u t i o n o r , when d i f f e r e n t phenols  during  the o x i d a t i o n .  know which e l e c t r o d e r e a c t i o n s are f a v o u r e d . of p o t e n t i a l and on c u r r e n t and  electrode  reactors  [30]  are  I t i s o f i n t e r e s t to  An a n a l y s i s o f the  k i n e t i c parameters on  r a t e d i s t r i b u t i o n has  mixed e l e c t r o c h e m i c a l  phenolics  effect  reaction s e l e c t i v i t y  been made f o r  plug-flow  i n which a sequence of  and  In an attempt i t was  [8] to o x i d i s e a phenol and  is l i t t l e  such as those a r i s i n g  case  problem. t r i c h l o r o p h e n o l mixture  found t h a t both c o n s t i t u e n t s were a t t a c k e d  Otherwise t h e r e  back  reactions  takes p l a c e , however a p p l i c a t i o n of such an a n a l y s i s to the p r e s e n t i s a complex mathematical  and  information  on  a t about the  same r a t e .  the o x i d a t i o n of p h e n o l i c  i n coal conversion e f f l u e n t s .  mixtures  15.  2.3  Importance o f c h o i c e o f experimental  The  conditions  f a c t o r s which determine the r a t e and product d i s t r i b u t i o n o f  the anodic  oxidation o f phenolics  a t a g i v e n temperature and f l o w r a t e a r e as follows.  (i) (ii) (iii) (iv) (v) The  2.3.1  nature o f anode m a t e r i a l c u r r e n t d e n s i t y - anode p o t e n t i a l nature o f the e l e c t r o l y t e e f f e c t o f pH cell  configuration  e f f e c t s o f these f a c t o r s a r e as f o l l o w s .  Nature o f e l e c t r o d e  Gladisheva  and Lavrenchuk [15] have compared the performance o f  d i f f e r e n t anode m a t e r i a l s e l e c t r o deposited same o p e r a t i n g  such as n i c k e l , smooth platinum,  lead d i o x i d e .  g r a p h i t e and  T h e i r experiments showed t h a t under the  c o n d i t i o n s , the h i g h e s t o x i d a t i o n r a t e o c c u r r e d  dioxide electrode. others  materials  on the l e a d  The l e a d d i o x i d e anode was found to be s u p e r i o r to  i n terms o f s t a b i l i t y and ease o f o p e r a t i o n . The  platinum  same r e s u l t was obtained  by F i o s h i n e t a l [20] when comparing  and l e a d d i o x i d e e l e c t r o d e s  o x i d a t i o n o f phenol  to quinone.  powers o f the e l e c t r o d e s  i n the study o f e l e c t r o c h e m i c a l  I t has been suggested t h a t the a d s o r p t i v e  towards the o r g a n i c  i n a d d i t i o n t o the o v e r p o t e n t i a l  substrate  plays a major  role  o f the e l e c t r o d e s .  Sucre and Watkinson [31] r e p o r t e d  that e l e c t r o d e p o s i t e d lead  i s a b e t t e r anode than anodised l e a d shot  dioxide  i n terms o f phenol o x i d a t i o n and  c o r r o s i o n r e s i s t a n c e f o r p h e n o l i c waste treatment a p p l i c a t i o n s . A packed bed anode i s a good c h o i c e s o l u t i o n s because i t provides  for oxidation of dilute  phenolic  l a r g e r e l e c t r o d e s u r f a c e areas per u n i t  cell  16.  volume compared to simple  flat  plate electrode  f i n e p a r t i c l e s which would g i v e l a r g e e x t e r n a l to c e l l  [32].  However, the use o f very  s u r f a c e areas might l e a d  blockage i n a p p l i c a t i o n s where s o l i d s a r e present  or a r e produced by the o x i d a t i o n .  Also  spatial  i n the wastewater  electrode potential variations  i n packed bed c e l l s can be so l a r g e t h a t l o s s o f r e a c t i o n s e l e c t i v i t y  will  result. Considering  the nature o f e l e c t r o d e p o s i t e d l e a d d i o x i d e , methods used  f o r the e l e c t r o d e p o s i t i o n o f PbC^ on i n e r t s u b s t r a t e containing  l e a d have been summarized  Pb 2> u n i f o r m l y  coated  f o r t h i s case.  These anodes a r e being  n  Engineering  2.3.2  on a g r a p h i t e  i n reference  and Production  Current  substrate  from e l e c t r o l y t e s  [33].  Electrodeposited  has been recommended  [19,31]  c o m m e r c i a l l y made by P a c i f i c  Co. o f Nevada.  d e n s i t y - anode p o t e n t i a l  From a study o f the e f f e c t o f d i f f e r e n t v a r i a b l e s on phenol  oxidation,  2 i t was concluded t h a t i n the range o f 50-2000 A/m , the c u r r e n t d e n s i t y was the s t r o n g e s t Table  r a t e determining  f a c t o r [15].  The r e s u l t s a r e given i n  III. From the t a b l e i t can be seen t h a t , s t a r t i n g with  466 mg/l o f chemical  oxygen demand (C.O.D.) a t a c u r r e n t d e n s i t y o f 50 A/m , the f i n a l was  420 mg/l a f t e r 5 h, whereas a t 2000 A/m  30 mg/l i n 1 hour. elsewhere [ 3 1 ] . potential control  2  the C.O.D. dropped to  S i m i l a r e f f e c t s o f c u r r e n t d e n s i t y have been  Experiments may be performed under a c o n s t a n t  using a p o t e n t i o s t a t .  the c u r r e n t  density.  C.O.D.  reported  anode  But i t appears to be much e a s i e r to  TABLE I I I EFFECT OF CURRENT DENSITY AND TYPE OF ELECTROLYTE ON C.O.D. REMOVAL USING P b 0  Current density  A/m  2  50  500  1000  2000  Notes:  2  ANODE  Time o f Electrolysis (h)  F i n a l C.O.D. (mg/l o f 0 )  I  5  307  II  5  420  I  3  90  II  5  120  I  1  30  II  2  75  Electrolyte  2  I  0.5  0  II  1.0  30  Initial  phenol c o n c e n t r a t i o n = 200 mg/l  Initial  C O .,D. c o n c e n t r a t i o n = 466 mg/l o f 0  Electrolyte  I - 1 g/1 NaCl, 1.5 g/1  Electrolyte  II - 3 g/1  Na S0 2  4  Na S0 2  4  2  18. 2.3.3  Nature of the electrolyte Chloride salts have been used as electrolytes in phenolic waste  treatment studies [Table III]. This electrolyte gives rise to undesirable chlorination products.  As chlorinated phenols are more objectionable than  phenol itself, i t appears desirable to use an inert supporting electrolyte such as sodium sulphate.  From the point of view of reduction in C.O.D.,  however sodium chloride would be preferable as seen in Table III. Other electrolytes, such as  Mrfi^Oj,NH^  and  H2SO4  have also been "  tested using a packed bed graphite electrode [16]. Sucre [31] showed that the rate of phenol oxidised is unchanged by increasing the conductivity of the electrolyte.  2.3.4  Effect of pH From the relationship between half wave potential and pH for the  oxidation of phenol [34] i t can be expected that a high pH would make phenol more easily oxidizable. Due to the ability of phenols to exist in the ionized or unionized form depending on the pH of the solution, pH is believed to play a major role in the mechanism of electron transfer during the oxidation process. No definitive results could be found in the reviewed literature about the effect of pH on further oxidation of intermediate products.  However  Sucre and Watkinson [31] report that oxidation of phenol was more rapid under acidic conditions but the oxidation of the total organic carbon was favoured by alkaline conditions.  2.3.5  Cell  In  configuration  the study o f e l e c t r o c h e m i c a l  p r o d u c t i o n , C o v i t z [17] r e p o r t e d  o x i d a t i o n o f phenol f o r hydroquinone  t h a t the r e a c t i o n can be c o n t r o l l e d to  produce hydroquinone a t over 90% y i e l d  i n an u n d i v i d e d c e l l  The mechanism proposed f o r the e l e c t r o l y t i c  in acid  media.  process i s as f o l l o w s [ 3 5 ] .  OH +  H0  + 4 Ii + 4 e  -  2  (7)  Cathodic r e a c t i o n  (8)  0H  0 ...+ ll + 2 H + 2 e  [I  Anodic r e a c t i o n  OH  o  +  ^  Overall  reaction  (9)  From t h i s r e a c t i o n scheme, i t i s obvious t h a t i n an u n d i v i d e d p-benzoquinone the  cell  can be reduced a t the cathode to produce hydroquinone.  process i s c a r r i e d  out i n a d i v i d e d c e l l , p-benzoquinone  c o n t a c t the cathode and t h e r e f o r e no hydroquinone would Another i n t e r e s t i n g  possible reaction  be  would  If  not  produced.  i n an u n d i v i d e d c e l l  o x i d a t i o n o f hydroquinone back to p-benzoquinone, which would  i s the  compete  with the phenol f o r o x i d a t i o n a t the anode, thus l o w e r i n g the c u r r e n t e f f i c i e n c y f o r phenol tion  oxidation.  in this connection.  Reference [31] p r o v i d e s v a l u a b l e informa-  Rates o f phenol o x i d a t i o n were r e p o r t e d l y  similar  i n d i v i d e d and u n d i v i d e d c e l l s .  Even i n terms o f T.O.C. removal, no  improvement was o b t a i n e d with the d i v i d e d c e l l c o n t r o l l e d c o n d i t i o n s provided  even under optimum pH  by an a n i o n i c membrane.  t h a t t h e r e would be no p a r t i c u l a r advantage i n choosing  Thus i t appears divided cell  operation. Due to the l a c k o f a v a i l a b l e i n f o r m a t i o n about the e f f e c t o f c e l l c o n f i g u r a t i o n f a c t o r s on the anodic  o x i d a t i o n o f other p h e n o l i c s o f  i n t e r e s t , these e f f e c t s have been d i s c u s s e d f o r phenol S i m i l a r e f f e c t s may be expected  f o r other p h e n o l i c s .  (C5H5OH)  alone.  CHAPTER 3  BASIS AND EXTENT OF EXPERIMENTAL STUDY  The  aim o f t h i s work was to study  o x i d a t i o n o f t h e major p h e n o l i c s s t u d i e s o f t h e anodic 2,3-Xylenol,  the f e a s i b i l i t y o f e l e c t r o c h e m i c a l  i n coal p r o c e s s i n g  o x i d a t i o n o f phenol,  3,4-Xylenol,  ortho  effluents.  c r e s o l , para  r e s o r c i n o l , and c a t e c h o l  c u r r e n t was s t u d i e d by r e c i r c u l a t i n g  cresol,  are r e p o r t e d .  o f the p h e n o l i c s , the e f f e c t o f v a r i a t i o n o f i n i t i a l applied  Experimental  For each  c o n c e n t r a t i o n and  s o l u t i o n from a feed tank  through a packed bed c e l l . The  e f f e c t s o f the above v a r i a b l e s a r e r e p o r t e d  fractional  o x i d a t i o n o f both the p h e n o l i c s and the t o t a l  (T.O.C.) versus As  i n terms o f the organic  time.  t h i s work i s o r i e n t e d towards waste treatment, the e f f e c t s o f  the o x i d a t i o n on chemical  oxygen demand (C.O.D.) and b i o l o g i c a l  demand (B.O.D.) have been r e p o r t e d  i n s e l e c t e d cases.  to obtain  phenolics  oxygen  Gas chromatograph/  Mass spectrometer a n a l y s i s was used t o i d e n t i f y the products and  carbon  the percentages o f the o x i d a t i o n products  of oxidation  from each o f the  studied.  S y n t h e t i c mixtures o f p h e n o l i c s o f i n t e r e s t made up by mixing the monohydric p h e n o l i c s  i n proportions  under chosen c o n d i t i o n s t o study the mixture.  The nature  o u t l i n e d i n Table  I were o x i d i z e d  t h e i r s u s c e p t a b i l i t y to oxidation i n  and q u a n t i t i e s o f o x i d a t i o n products  from the  m i x t u r e are r e p o r t e d . Comparisons have been made among the v a r i o u s  phenolics  to c o r r e l a t e  t h e i r behaviour i n response t o v a r i a t i o n s i n a p p l i e d c u r r e n t d e n s i t y and initial  concentration.  F i n a l l y , the data  from a few o f the experimental  22.  runs have been analyzed  by comparison with mathematical  the c o n t r o l l i n g f a c t o r s governing On  the  models to  understand  process.  the b a s i s o f a p r i o r study on phenol  [31] the f o l l o w i n g o p e r a t i n g  c o n d i t i o n s were f i x e d d u r i n g t h i s work.  Anode  Cell  Packed bed of e l e c t r o d e p o s i t e d l e a d d i o x i d e , packing p a r t i c l e s i z e - 0.7-1.1 configuration  m.m  Undivided  Supporting e l e c t r o lyte  Sodium s u l p h a t e , 5 g / l + H2SO4 2 i [electrical conductivity 8 x 10" {Q, c.m)~ ]  Operating mode  Batch-recirculation  pH  2-3  Period  of  oxidation  2 hours  system  CHAPTER 4  EXPERIMENTAL APPARATUS AND  4.1  METHODS  Apparatus  4.1.1  D e s c r i p t i o n o f equipment  The  apparatus of Sucre [31] was  alterations. represented  The  s i d e view o f the general  i n F i g . 2.  the anode and  c o n t a c t with the anodic  The  electrolysis.  The  divided-cell  arrangement i s  c o n s i s t s of two  f l a t plates,  anode c u r r e n t feeder  packing, which i s c o n t a i n e d  separated  anolyte i n l e t  i s a t the top.  B a s i c a l l y , the c e l l  cathode c u r r e n t f e e d e r s .  neoprene gasket  r e t a i n e d with r e l a t i v e l y minor  i n a 3 mm  from the cathode by a saran  A commercial  the e x i t of any  thick slotted  screen.  i s l o c a t e d a t the bottom o f the c e l l  This f a c i l i t a t e s  and  the  prevent  c o r r o s i o n and  eventual  from r e f e r e n c e  a t the p o i n t o f i n t r o d u c t i o n o f  Fig.  plate.  adapted f o r t h i s  The  d e t a i l s of  purpose can  be  the  obtained  [31].  S p e c i f i c a t i o n s o f the d i f f e r e n t in Table  feeder.  d e t e r i o r a t i o n o f the l e a d d i o x i d e  the e l e c t r o l y t e through the g r a p h i t e coated o u t l e t connections  elements of the c e l l  are  provided  IV. 3 shows the a u x i l i a r y equipment used i n the p r o c e s s .  The  sequence o f arrangement o f the v a r i o u s l a y e r s i n the c e l l d i s p l a y i n g the v a r i o u s steps i n c e l l  the  anode c o n s i s t i n g o f an e l e c t r o d e p o s i t e d l e a d  l a y e r , s u i t a b l e p r e c a u t i o n s were taken  i n l e t and  outlet  gases produced d u r i n g  d i o x i d e c o a t i n g on a g r a p h i t e p l a t e i s used as the anode c u r r e n t To  i s in  assembly i s shown i n F i g . 4.  Fig.  ELECTROLYTE OUTLET  a  = 1.6 mm THICK INSULATOR  b  = 1.6 mm THICK CATHODIC FEEDER P L A T E (S.S. 316)  c  = S A R A N S C R E E N T O HOLD ANODIC PACKING  d  = ANODIC PACKING ELECTRODEPOSITED L E A D DIOXIDE PARTICLES SIZE 0 . 7 < dp < I.I mm  2  NEOPRENE  e = ANODIC C U R R E N T F E E D E R • L E A D DIOXIDE COATED GRAPHITE P L A T E 3 cm THICK  ELECTROLYTE INLET  a  b c d t a  Side view o f the g e n e r a l (N.T.S.)  undivided c e l l  arrangement  TABLE IV FUNDAMENTAL SPECIFICATIONS OF THE ELECTROLYTIC CELL  Dimensions o f the anode and cathode chambers: Length = 38 cm Width Thickness  =  5 cm  =  3 mm  Anode p a r t i c l e s - crushed Pb0  PEPCON  electrodeposited  2  p a r t i c l e s i z e - 0.7-1.1 mm weight - 250 gm Anode backing  p l a t e - PEPCON Pb02 coated  P r o t e c t i v e screen  - saran  Cathode  - 316 SS p l a t e  *  graphite  P a c i f i c E n g i n e e r i n g and P r o d u c t i o n Co. o f Nevada  Fig. 4  V a r i o u s components of the  cell  27.  4.1.2  Flow diagram  A schematic  o f the apparatus  flow diagram  o f the equipment i s r e p r e s e n t e d i n F i g . 5.  Pump PU-1 d e l i v e r s the e l e c t r o l y t e the c e l l ,  the liquid  flow r a t e i s c o n t r o l l e d  i s measured w i t h rotameter R - l . are  from tanks T-1, T-2 o r T-3 to by a d j u s t i n g v a l v e V-4 and  Pressure and temperature  a t the entrance  measured i n P - l . Filter  particles  F - l , l o c a t e d a t the o u t l e t o f the c e l l  t h a t might  flow c i r c u i t .  be c a r r i e d  T h i s g l a s s wool  out o f the c e l l  i s used  and which might  f i l t e r also f a c i l i t a t e s  s e p a r a t i o n i n GL-1 by agglomerating  to c o l l e c t small  small gas bubbles  damage the  the gas l i q u i d produced  i n the  electrolysis. In for  GL-1, a bed o f g l a s s beads p r o v i d e s e x t r a agglomeration s u r f a c e  the gas bubbles.  I f the gas bubbles a r e c a r r i e d out with the l i q u i d  flow, the p r o g r e s s i v e accumulation o f gas i n the e l e c t r o l y t e would the r e s u l t s o f the experiments. and the l i q u i d in  the c e l l  liquid  affect  The gas i s r e l e a s e d a t the top o f GL-1  flows to the heat exchanger,  i s removed by c o o l i n g water.  H.E., where the heat generated  From t h e heat exchanger, the  flows back to the feed tanks T-1 or T-2. The c e l l  The c e l l  was powered by a 1 KVA D.C power s u p p l y , P.S. (Appendix 1 ) .  c u r r e n t was a d j u s t e d w i t h the power-supply  meter, and the v o l t a g e  drop a c r o s s the e l e c t r o d e s was measured by the v o l t m e t e r , V.  4.2  4.2.1  Experimental methods  A n o d i z a t i o n process  B e f o r e each experiment, F^SO^  t h e Pb02 was anodized by e l e c t r o l y s i s  [ 3 6 ] , to minimize changes i n a c t i v i t y over time.  i n 20%  When the packing  Fig.  5  Flow diagram of  the  apparatus  Legend f o r  Fig.  (P.S.)  -  POWER SUPPLY  (V)  -  VOLTMETER  (E.C.)  -  ELECTROLYTIC CELL  (T-1)  -  ELECTROLYTE TANK (CONTAINS  5  PHENOLICS)  (T-2)  - ANODISATION TANK  (T-3)  - WATER TANK  (PU-1)  -  PUMP  (R-l)  -  ROTAMETER  (P-l)  -  P R E S S . & TEMP. GAUGE  (F-l)  -  FILTER  (GL-1)  - GAS-LIQ.  SEPARATOR  (V-l)  -  (V-2)  - ANODISATION TANK SHUT OFF VALVE  (V-3)  - WATER TANK SHUT OFF VALVE  (V-4)  -  ELECTROLYTE FLOW CONTROL VALVE  (V-5)  -  LIQUID SAMPLE VALVE  (V-6)  - L I Q U I D L E V E L CONTROL VALVE IN GL-1  (H.E.)  -  ELECTROLYTE TANK SHUT OFF VALVE  HEAT EXCHANGER  (C-l)  - COOLING WATER  INET  (C-2)  - COOLING WATER  OUTLET  (D)  -  DRAIN  was  anodized  f o r the f i r s t time, a 12 h a n o d i z a t i o n time was  for  s u c c e s s i v e experiments the standard  recommended by Sucre [ 3 1 ] . and  V-3  were shut o f f and  power supply was  turned  up s i m u l t a n e o u s l y . About 21  tank T-2  drained  then r e c y c l i n g to tank T-2  was  A f t e r a n o d i z a t i o n , the shut o f f .  Valve  through the c e l l .  V-3  The  p r a c t i c a l l y zero and indicating  4.2.2  was  the  Before In Tank T-1,  pump was  the e l e c t r o l y t e was  was  the t o t a l  readjusted  q u a n t i t i e s o f the p h e n o l i c  The  shut o f f and  distilled  was  i n Appendix  In o r d e r  (cd  D.C.  was  prepared  - 526.3 A/m  ). and  simultaneously was  contained  i n the  cell.  washed i n d i s t i l l e d  g/1).  made up to 8 1.  with  pumped  phenolics  The  initial  The  water.  quantity desired  then d i s s o l v e d i n d i s t i l l e d  i f necessary  was  increased  by adding a c o n s t a n t  The  V-2  the c u r r e n t dropped to  s u l p h u r i c a c i d (0.44  volume was  started  water,  tank was  pH o f the  NaOH or H2S0 . 4  compound added i n each o f the runs  well  electrolyte  The  actual  are  2.  v a l v e V - l was  a d j u s t i n g v a l v e V-4.  Pump PU-1  water from T-3  thoroughly  by means o f a magnetic s t i r r e r .  measured and  recorded  to 10A  The  4  on f o r 1 h.  washed u n t i l  amount o f the p h e n o l i c compound was and  2  opened and  oxidation of individual  each run, the c e l l  added to T-1,  20°/ H S 0 .  p o t e n t i a l d i f f e r e n c e through the c e l l  ( 5 g / l ) of sodium s u l p h a t e and  agitated  was  adjusted  carried  was  f i l l e d with  t h a t e s s e n t i a l l y no e l e c t r o l y t e was  Electrochemical  1 h as  o f f through D to purge the system  opened and  cell  was  Valve V-2  c u r r e n t was  o f s o l u t i o n was  time was  but  To c a r r y out the a n o d i z a t i o n , v a l v e s V - l  on.  The  anodization  allowed,  opened and  the r e q u i r e d flow r a t e was  Immediately the c u r r e n t was  to p r o v i d e  s e t by  s e t a t the d e s i r e d  some time f o r the s t a b i l i z a t i o n o f flows  value.  and  c u r r e n t , 3 1 o f the e l e c t r o l y t e was d i s c a r d e d a f t e r cell,  r a t h e r than  recycling  i t to T - l .  passing  The e l e c t r o l y s i s  through the  time was measured  from the moment the e l e c t r o l y t e was r e c y c l e d to tank T - l .  Samples o f about  t h i r t y ml were withdrawn through V-5 a t i n t e r v a l s o f 15 min f o r a n a l y t i c a l purposes.  The e l e c t r o l y s i s was c a r r i e d  washed with d i s t i l l e d  water.  In order  anode, the c u r r e n t was on w h i l e  4.2.3  Experimental  on f o r 2 h.  Then the c e l l  was  to a v o i d the r e d u c t i o n o f the PbO^  the washing step  proceeded.  m o d i f i c a t i o n s made with c e r t a i n  phenolics  Among the p h e n o l i c s s t u d i e d , the p - c r e s o l was i n s o l u b l e i n d i s t i l l e d water.  T h e r e f o r e a few p e l l e t s o f NaOH  were added t o o b t a i n the p - c r e s o l  s o l u t i o n and a s u i t a b l e q u a n t i t y o f H2S0^ was added to get the d e s i r e d pH  range. The  x y l e n o l s were s o l u b l e o n l y i n hot water ( ^  e l e c t r o l y t e was made up to 8 1 with heat  hot water.  50°C).  Hence the  The c o o l i n g water to the  exchanger was c a r e f u l l y lowered d u r i n g the anodic  X y l e n o l s because i n the higher c o n c e n t r a t i o n runs  o x i d a t i o n o f the  (1 g/1 r u n s ) , the x y l e n o l s  came o u t o f the s o l u t i o n when the e l e c t r o l y t e was c o o l e d d u r i n g the r u n . With the c r e s o l s , 2,3-Xylenol  and c a t e c h o l as t h e r e was e x c e s s i v e  foaming, the e l e c t r o l y t e began t o o v e r f l o w  from GL-1.  of  provided with an a i r vent was  e l e c t r o l y t e , a two-holed rubber  used t o cover  GL-1.  From the s t o p p e r , a tube was connected t o T - l , to  r e c y c l e the o v e r f l o w i n g During  stopper  To a v o i d the l o s s  liquid.  experiments with c a t e c h o l , i n a d d i t i o n to e x c e s s i v e  a brownish b l a c k , i n s o l u b l e condensation initial  c o n c e n t r a t i o n s equal  blocked  the g l a s s wool  product was formed i n runs  t o or g r e a t e r than  i n the f i l t e r ,  foaming,  decreased  0.5 g/1.  This  with  product  the voidage i n the packed  bed anode, caused  problems i n the g a s - l i q u i d  values f o r maximum a t t a i n a b l e flow r a t e s . as can  be seen i n F i g . 6.  the c a t e c h o l runs.  s e p a r a t o r and  The  resulted  saran screen was  T h e r e f o r e , the screen had  i n small  a l s o blocked  to be changed  after  To overcome the problem o f e x c e s s i v e foaming and  Fig.  pushing  6  D e p o s i t i o n o f condensation product d u r i n g the o x i d a t i o n o f c a t e c h o l  up o f the g l a s s beads from G L - 1 , and  the i n l e t and  g l a s s beads were r e p l a c e d by g l a s s wool  o u t l e t o f the e l e c t r o l y t e to GL-1  were  interchanged.  4.2.4  Anodic o x i d a t i o n o f p h e n o l i c mixtures  M i x t u r e s o f phenol, c r e s o l s and x y l e n o l s were made up by weighing out the  p h e n o l i c s i n t h e same p r o p o r t i o n s as they a r e found i n s y n t h e t i c  c o n v e r s i o n wastewaters distilled  water.  ( T a b l e I) and d i s s o l v i n g  Addition of ^ £ 5 0 ^ ,  them i n d i v i d u a l l y i n  H^SO^ and adjustment  made and a l l the steps e l a b o r a t e d i n 4.2.2 were f o l l o w e d . the  total  (run  electrolysis  time alone was v a r i e d .  o f pH were In these runs,  For one o f these runs  8-3), i n a d d i t i o n to the a n a l y s i s o f phenols and T.O.C., C.O.D. and  B.O.D. a n a l y s i s were performed  on the i n i t i a l  and f i n a l  B.O.D. a n a l y s i s r e s u l t s a r e r e p o r t e d , 1 I samples the  coal  beginning o f t h e run before r e c y c l i n g  sample  . Wherever  were c o l l e c t e d , both a t  to T-1 was s t a r t e d and a f t e r the  e l e c t r o l y s i s was complete.  4.3  Analytical  The  techniques  samples  c o l l e c t e d were analyzed f o r phenols, t o t a l o r g a n i c  carbon and i n some cases C.O.D. and B.O.D.  Products o f o x i d a t i o n o f  typical  possible.  4.3.1  runs were i d e n t i f i e d  by GC/MS where  A n a l y s i s o f phenols  C o n c e n t r a t i o n o f the phenols was determined u s i n g a flame i o n i z a t i o n d e t e c t o r . h y d r i c phenols and f o r d i h y d r i c  by gas chromatography  D i f f e r e n t columns were used f o r mono-  phenols.  o p e r a t i n g c o n d i t i o n s a r e g i v e n i n Appendix  Equipment s p e c i f i c a t i o n s and 1.  Fresh standard s o l u t i o n s o f the phenols i n the d e s i r e d range were prepared by a c c u r a t e l y weighing out t h e phenols used to prepare the e l e c t r o l y t e f o r the experiments.  Before the i n j e c t i o n o f the samples,  phenol  standards were i n j e c t e d  under the same c o n d i t i o n s and the c a l i b r a t i o n ; ! c u r v e o f peak h e i g h t s vs . \ phenol c o n c e n t r a t i o n was c o n s t r u c t e d .  As the phenol  peaks were narrow,  the peak h e i g h t s r a t h e r than peak areas were used d i r e c t l y .  In a few  c a s e s , peaks o f one o r two o x i d a t i o n products were observed. did  These  not i n t e r f e r e with the a n a l y s i s o f the phenols, and they were not  further identified.  When mixtures o f monohydric  phenols were a n a l y s e d ,  the column temperature was s u i t a b l y a d j u s t e d to o b t a i n r e t e n t i o n t h a t had r e a s o n a b l e time i n t e r v a l s The  samples  between the d i f f e r e n t  t h i s case a t lower c o n c e n t r a t i o n s . were i n j e c t e d u n t i l  Large e r r o r s would be expected i n  In a l l c a s e s , however, standards and  the v a r i a t i o n  In the a n a l y s i s o f c a t e c h o l for resorcinol  i n peak h e i g h t s was o n l y 2-3%.  attempts with the carbowax column used  proved to be u n s u i t a b l e even a t c o n d i t i o n s o f maximum  d e t e c t a b i l i t y w i t h t h e flame i o n i z a t i o n d e t e c t o r . c o n c e n t r a t i o n c o u l d not be determined e s t i m a t e was made. methyl  anilinium  of catechol  Total  The  Attempts  Hence the c a t e c h o l  except i n one case where a rough  o f methylating  the samples  with TMAH ( T r i  hydroxide) f o l l o w e d by a n a l y s i s o f the methyl  with the column m a t e r i a l  o r g a n i c carbon  total  peaks.  [37] the peaks were broad, but uniform.  Hence the peak heightswere a g a i n used.  samples  times  were a n a l y s e d w i t h i n a day to avoid d e g r a d a t i o n [ 3 1 ] .  For t h e a n a l y s i s o f r e s o r c i n o l  4.3.2  peaks  OV-17 a l s o proved  derivative  futile.  analysis  o r g a n i c carbon a n a l y z e r c o n t a i n s two f u r n a c e s : one f o r t o t a l  * Catechol i n t h e samples was e x t r a c t e d with e t h e r f o l l o w e d by e v a p o r a t i o n o f t h e e t h e r and a d d i t i o n o f c a l c u l a t e d q u a n t i t i e s o f the m e t h y l a t i n g agent.  carbon and one f o r i n o r g a n i c carbon. a t a temperature o f 1000°C to carbon d i o x i d e .  The  The t o t a l  carbon f u r n a c e o p e r a t e s  to c o n v e r t a l l the carbon p r e s e n t i n the sample  i n o r g a n i c carbon f u r n a c e operates a t 150°C  o n l y the i n o r g a n i c carbon i n the sample to carbon d i o x i d e . carbon d i o x i d e produced The t o t a l  i s d e t e c t e d i n an i n f r a r e d a n a l y z e r [ 3 8 ] .  s u b t r a c t i n g the i n o r g a n i c carbon from the t o t a l  cases o n l y the t o t a l  sample was~<2%.  Under the pH  negligible.  Hence i n a l l  carbon has been r e p o r t e d as T.O.C.  The c a l i b r a t i o n graphy. V a r i a t i o n  carbon.  procedure was  s i m i l a r to t h a t used  i n gas  For T.O.C. a n a l y s i s , i t was  p o s s i b l e to use the same  i n the a n a l y s i s o f the phenols knowing the f r a c t i o n o f S p e c i f i c a t i o n and  c o n d i t i o n s o f the T.O.C. a n a l y z e r are a l s o given i n Appendix  Biological  operating  1.  oxygen demand a n a l y s i s  In cases where the b i o l o g i c a l a n a l y s i s was  chromato-  i n peak h e i g h t i n s u c c e s s i v e i n j e c t i o n o f a c e r t a i n . '  o r g a n i c carbon present i n 1 g o f the phenol.  4.3.3  by  found t h a t the c o n c e n t r a t i o n and v a r i a t i o n o f  i n o r g a n i c carbon present i n the samples was  standards used  The amount o f  o r g a n i c carbon (T.O.C.) i n the sample i s c a l c u l a t e d  c o n d i t i o n s used, i t was  to c o n v e r t  performed  oxygen demand (B.O.D.) i s r e p o r t e d  by Wood L a b o r a t o r y L t d .  The  the  seed b a c t e r i a f o r  B.O.D. a n a l y s i s were grown by an enrichment process u s i n g B.O.D. water supplemented  4.3.4  with phenolics.  Chemical  oxygen demand a n a l y s i s  The chemical oxygen demand (C.O.D.) d e t e r m i n a t i o n p r o v i d e s a measure o f the oxygen e q u i v a l e n t o f t h a t p o r t i o n o f the o r g a n i c matter i n a sample  36.  t h a t i s s u s c e p t i b l e to o x i d a t i o n by a s t r o n g chemical o x i d a n t [ 3 8 ] . the  e f f l u e n t contains only r e a d i l y a v a i l a b l e organic b a c t e r i a l  t o x i c m a t t e r , the C.O.D. v a l u e can be used to approximate carbonaceous  reference [39].  4.3.5  the u l t i m a t e  by the dichromate r e f l u x method o u t l i n e d  in  v  The t e s t was repeated f o r each sample to t e s t the r e p r o -  The c a l c u l a t i o n s a r e presented i n Appendix  4.  GC/MS a n a l y s i s  A Hewlett-Packard equipped w i t h a f u l l y was  food and no  B.O.D. v a l u e s .  C.O.D. was determined  ducibility.  Where  gas chromatograph  /'mass spectrometer combination  i n t e r a c t i v e data system  (HP-1000 s e r i e s  used to a n a l y s e the c o m p o s i t i o n and nature o f the f i n a l  a few o f the t y p i c a l  o x i d a t i o n runs.  For t h i s  computer)  sample from  purpose one run was performed _2  with each o f the p h e n o l i c s s t u d i e d a t a c u r r e n t d e n s i t y o f 526.3 A/m for  2 hrs with an i n i t i a l  run  was performed  c o n c e n t r a t i o n o f 1g/1 (Appendix  w i t h a m i x t u r e o f monohydric  s i m i l a r t o t h a t used  i n run 8-3.  The f i n a l  runs were g i v e n f o r the GC/MS a n a l y s i s . Mr. Tim Ma.  the  One s i m i l a r  phenols o f c o m p o s i t i o n  sample from a l l o f the above  T h i s a n a l y s i s was performed by  The r e s u l t s a r e r e p o r t e d i n Appendix  t i o n s and equipment s p e c i f i c a t i o n s can be found All  2).  ,  2.  The o p e r a t i n g c o n d i -  i n Appendix  1 .  the products were i d e n t i f i e d with standard data o b t a i n e d f o r  compounds i n the mass s p e c t r o m e t e r .  In cases where the p o s s i b i l i t y  of  two isomers has been r e p o r t e d , the mass spectrometer data was i n s u f f i c i e n t  to  distinguish  between them.  An example f o r such a case has been enclosed  (Appendix 2 ) . The  samples  10 ml samples  f o r the a n a l y s i s were prepared by the f o l l o w i n g  o f the f i n a l  samples  were i n d i v i d u a l l y e x t r a c t e d  procedure.  twice with  37.  50 ml o f methylene c h l o r i d e .  The o r g a n i c phase was s e p a r a t e d , d r i e d with  anhydrous MgSO^ and evaporated dissolved  i n a rotary evaporator..  The r e s i d u e was  i n 10 ml o f methylene c h l o r i d e and g i v e n f o r GC/MS a n a l y s i s .  In the case o f r e s o r c i n o l  and c a t e c h o l no products were d e t e c t e d .  v  For c a t e c h o l the c l e a r l a y e r and the suspended black product were s e p a r a t e l y e x t r a c t e d with methylene c h l o r i d e .  However i n these cases the e x t r a c t i o n  i n to the methylene c h l o r i d e phase was i n e f f i c i e n t .  With the a v a i l a b l e  column, the s o l v e n t c h o i c e was l i m i t e d , and t h e r e f o r e o t h e r s o l v e n t s were not t r i e d .  An a l t e r n a t i v e attempt  to i n t r o d u c e the sample d i r e c t l y  probe i n order  i n to the mass spectrometer.  i d e n t i f i c a t i o n s were made i n t h i s  4.3.6  was made with a s o l i d  No d e f i n i t e  attempt.  Accuracy and r e p r o d u c i b i l i t y  Care was taken to m a i n t a i n a c c u r a c y i n a l l the a n a l y s e s . d u c i b i l i t y o f r e s u l t s was checked.  The r e p r o -  For the a n a l y s i s o f the p h e n o l i c s and  T.O.C, i n j e c t i o n s were repeated u n t i l  the v a r i a t i o n s  i n peak h e i g h t s  were w i t h i n 3%. R e p r o d u c i b i l i t y o f the o x i d a t i o n process was t e s t e d and found good.  For example i n repeated runs o f phenol  10 A with an i n i t i a l  and r e s o r c i n o l  to be  oxidation at  c o n c e n t r a t i o n o f 1 g/1, the f o l l o w i n g r e s u l t s were  o b t a i n e d a f t e r 2 hours o f o x i d a t i o n .  % oxidised Name o f Compound Trial  I  Trial  phenol  89.6  89.2  resorcinol  71 .6  68.2  II  The r e s u l t s o b t a i n e d with a few o f the phenol with the c o r r e s p o n d i n g r e s u l t s o b t a i n e d by Sucre  runs were compared  [31].  As seen  below,  t h e r e i s a r e a s o n a b l e agreement.  % oxidation after  working a t 10 A with phenol 0.1  initial  concentration of  Ref  [31]  Present study  98 (Run 3-3)  100 (Run  100 (Run 3-31)  89.6  1-4)  gm/1  % o x i d a t i o n a f t e r 120 mins, working a t 10 A with phenol 1  Source  60 mins,  gm/1  initial  concentration of  (Run  1-1)  CHAPTER 5  RESULTS AND  5.1  Oxidation  5.1.1  of i n d i v i d u a l  phenolics  Anodic o x i d a t i o n of phenol  A typical is  p l o t of r e s u l t s o f the r e c i r c u l a t i n g  batch  o x i d a t i o n runs  shown i n F i g . 7 where % phenol o x i d i z e d i s p l o t t e d versus  t h r e e d i f f e r e n t values of i n i t i a l phenol c o n c e n t r a t i o n was 910 mg/l, 55.3%  phenol c o n c e n t r a t i o n .  As  the % phenol o x i d i z e d a f t e r 30 minutes decreased  to 30.2%  although  the a b s o l u t e  found to be covered  with  initial  and  from 88.9%  When the c e l l a deposit  o f p-benzoquinone and  compounds p r e s e n t .  Tar formation  has  was  opened, the cathode  of yellow  constant  surface  tar-like material.  by i t s r e a c t i o n with  the  and  phenolic  been encountered i n l i t e r a t u r e  117,19]and an .attempt to overcome t h i s problem has Fig.  to  the % phenol o x i d i z e d  T h i s t a r must have been formed p r i m a r i l y by the o l i g o m e r i z a t i o n polymerization  to  amount of phenol o x i d i z e d i n a given  However, i n run 1-5,  l e v e l l e d o f f a f t e r 1 hour.  time f o r  the  i n c r e a s e d from 108'mg/l to 683 mg/l  time g e n e r a l l y i n c r e a s e d .  was  DISCUSSION  been r e p o r t e d  [19].  8 shows the e f f e c t of i n c r e a s i n g the a p p l i e d c u r r e n t a t a initial  c o n c e n t r a t i o n of phenol.  c u r r e n t i s to r a i s e the i n i t i a l s l o p e s of the curves  The  e f f e c t of i n c r e a s i n g the  r a t e of phenol o x i d a t i o n as shown by  a t the beginning  of the runs.  However, the  the  initial  r a t e i s not p r o p o r t i o n a l to the c u r r e n t s i n c e t h e r e i s a l a r g e r i n c r e a s e in  r a t e as the c u r r e n t i s i n c r e a s e d from 5A to 1 OA  A p o s s i b l e reason  f o r t h i s i s t h a t with  than from 10A  to  15A.  i n c r e a s i n g c u r r e n t s more hydro-  quinone i s produced and  i t s o x i d a t i o n to p-benzoquinone may  f r a c t i o n s o f the c u r r e n t .  Stated  i n another way,  f o r phenol o x i d a t i o n f a l l s o f f with production  perhaps supported by the o b s e r v a t i o n smell  due  increases. t h a t the  only  efficiency  i n t e n s i t y of the  7% and  products (dimers) were d e t e c t e d .  mechanism f o r the r e a c t i o n  Based on proposed.  The  The  the products o b t a i n e d , first  hydroquinone 10.9%.  coupling  [40]. the f o l l o w i n g r e a c t i o n scheme i s  step i s the formation  o r hydroquinone.  No  12.6%,  absence o f such products r u l e s out  o f "phenoxonium i o n " by  e l e c t r o p h i 1 i c a t t a c k o f the aromatic n u c l e u s , of c a t e c h o l  i n the  s o l u t i o n however showed  (Appendix 2) the f o l l o w i n g c o n s t i t u e n t s : unreacted phenol  the r a d i c a l  yellow  increased.  GC/MS a n a l y s i s of the t r e a t e d phenol  p-benzoquinone 69.5%, c a t e c h o l  the  This postulate i s  to p-benzoquinone appeared to i n c r e a s e  t r e a t e d s o l u t i o n as the a p p l i e d c u r r e n t was The  the c u r r e n t  i n c r e a s i n g a p p l i e d c u r r e n t and  of p-benzoquinone probably  c o l o u r a t i o n and  carry increasing  followed  by the  formation  Hydroquinone gets o x i d i z e d f u r t h e r by  l o s s o f 2 e l e c t r o n s to form p-benzoquinone.  The  the  f a c t t h a t 6 times more  p-benzoquinone than hydroquinone i s formed shows t h a t under  present  c o n d i t i o n s the o x i d a t i o n o f hydroquinone to p-benzoquinone i s  favoured.  The  An  cathodic  reduction  of p-benzoquinone i s not as  t i o n f o r t h i s i s presented OH  0  i n Section 0  © j OH  OH  HOH 0  0  5.4. OH  important.  explana-  During the anodic o x i d a t i o n o f phenol study, i t i s obvious t h a t phenol  under c o n d i t i o n s chosen f o r the  goes through v a r i o u s o x i d a t i o n  and r e s u l t s p a r t l y i n the f o r m a t i o n o f carbon d i o x i d e . F i g . 9, the a c t u a l  q u a n t i t y o f phenol  As seen  states from  o x i d i z e d c o m p l e t e l y to carbon  d i o x i d e i s about 22% and 18% i n runs 1-4  and 1-5  respectively.  [ I t should  be noted t h a t whenever % T.O.C. o x i d i z e d has not been r e p o r t e d , the net change i n T.O.C. was  p r a c t i c a l l y u n d e t e c t a b l e due to the high c o n c e n t r a t i o n  of carbon p r e s e n t i n s o l u t i o n s ] .  5.1.2  Oxidation of p-cresol  E f f e c t s o f v a r i a t i o n o f c o n c e n t r a t i o n and c u r r e n t shown i n F i g . 10 and 11 are found to be s i m i l a r to those observed i n the case o f phenol. However a t e v e r y s t a g e , the % p - c r e s o l with phenol carbon  itself.  i s lower than t h a t observed  A s i m i l a r r e s u l t i s observed i n % t o t a l o r g a n i c  ( F i g . 12) o x i d i z e d .  These  based on the half-wave p o t e n t i a l the u n r e a c t i v e nature o f p - c r e s o l or due  oxidized  to the r e t a r d i n g  t r e n d s are c o n t r a r y to e x p e c t a t i o n s values.  T h i s might  be e i t h e r due to  under the c o n d i t i o n s o f p r e s e n t work  i n f l u e n c e o f the c a t h o d i c r e d u c t i o n o f the o x i d i z e d  product r e s u l t i n g  in regeneration of p-cresol.  In the GC/MS a n a l y s i s a  l a r g e r percentage  (84.2) o f u n o x i d i z e d p - c r e s o l  was  comparison  to the o x i d a t i o n product (15.8).  identified in  Besides the expected  o x i d a t i o n p r o d u c t , 4-hydroxy-4-methyl-cyclohexa-2,5,  d i e n e - l - o n e (which  has been confirmed from the mass spectrum), no o t h e r o x i d a t i o n product such as methyl-p-benzoquinone ideal  has been i d e n t i f i e d .  c o n d i t i o n s o f time, p o t e n t i a l  anodic o x i d a t i o n o f p - c r e s o l  Hence the r e q u i r e d  or e l e c t r o d e a c t i v i t y f o r the  were not p r o v i d e d i n t h i s  study.  complete  Fig. 9 E f f e c t of cone, oh rate of oxidation o f organic carbon i n phenol at 10 A. _.  Fig. 1 2  E f f e c t of cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon in p - c r e s o l .  cn  46.  5.1.3  Oxidation  In the  of  0-cresol  study of the e f f e c t of i n i t i a l  concentration  oxidation  ( F i g . 13)  i t i s observed t h a t i n run  a f t e r 96.8%  oxidation  showing the expected r e t a r d i n g i n f l u e n c e due reaction.  the  the  of 0 - c r e s o l  more f a v o u r e d c o m p e t i t i v e  3-4,  on  rate levels o f f to a  T h i s r e a c t i o n i s p r o b a b l y oxygen  evolution. In F i g . 14, the percent  where the  oxidized  initial  concentration  i s e s s e n t i a l l y l i n e a r l y dependent on  t i o n , the % o x i d a t i o n / u n i t time i n c r e a s e s l i n e a r manner u n l i k e the reported  i n the  proportions methyl  hydroquinone and  of i n t e n s e y e l l o w of methyl  anodic o x i d a t i o n  phenol  reported  colouration  starting  methyl  In  addi-  i n a near  large  Products  in similar  benzoquinone  compound, 0 - c r e s o l .  i s supported by the  0-cresol,  p-cresol.  (see Chapter 2) are d e t e c t e d  work, v i z . 69.8%  11.3%  and  of  19.0%  Observation  concentration  benzoquinone observed i n the t r e a t e d s o l u t i o n .  The for  present  time.  with a p p l i e d c u r r e n t  t r e n d observed with phenol  l i t e r a t u r e {23]  i n the  i s about 1 gpl  by the  formation  path appears to be  s i m i l a r to t h a t  of "phenoxonium i o n " .  products would be as  The  reported  formation  of  the  follows:  -2e  0-cresol  methyl  No  products formation  t a r or c o u p l i n g  As methyl  hydroquinone  Methyl  was  Benzoquinone  observed with  0-cresol.  benzoquinone, the main product of anodic o x i d a t i o n  has  F i g . 13  Cone, e f f e c t on % o - c r e s o l a t 10 A  oxidized  F i g . 14  C u r r e n t e f f e c t on (1 g/1 runs)  % o-cresol  oxidized  the same q u a n t i t y of o r g a n i c carbon o r g a n i c carbon is carried  5.1.4  as the s t a r t i n g m a t e r i a l , the %  o x i d i z e d changes v e r y l i t t l e  ( F i g . 15) as the  process  on.  Oxidation of  2,3-Xylenol  Based on the s t r u c t u r e o f 2 , 3 - X y l e n o l , s u b s t i t u t i o n of the methyl groups i n the r i n g  should i n c r e a s e the e l e c t r o n d e n s i t y a t the  atom to which the hydroxyl to  carbon  group i s a t t a c h e d , making i t more s u s c e p t i b l e  anodic o x i d a t i o n than phenol  and  the c r e s o l s .  Experiments  with  2,3-Xylenol  d i d show i n c r e a s e d s u s c e p t i b i l i t y .  F i g . 16 shows t h a t  2,3-Xylenol  gets o x i d i z e d c o m p l e t e l y w i t h i n two  hours even a t the  initial  c o n c e n t r a t i o n s . o f 380 and  The  current effect  ( F i g . 17)  r a t e o f o x i d a t i o n being extremely with 2,3-Xylenol the above run  t h e r e was  (run 4-2).  625  mg/l.  i s however more c r i t i c a l slow i n 5A run.  lower v o l t a g e c o r r e s p o n d i n g  a p p l i e d c u r r e n t might have an important t i o n and  the r a t e of o x i d a t i o n .  role  with  to the  i n reducing the gas  I t should be noted,  equal  4-2  initial  and 4-3  d i s s o l u t i o n and  e v a p o r a t i o n o f 2,3-Xylenol  the curve f o r run 4-1  low evolu-  however t h a t the Although  were intended to have the same i n i t i a l  c o n c e n t r a t i o n s were not achieved  runs  foaming i n  usual c o n c e n t r a t i o n e f f e c t a l s o comes i n t o p l a y i n F i g . 17. runs 4-1,  the  U n l i k e the other  no e x c e s s i v e gas e v o l u t i o n and The  higher  because of  i n hot water.  would have been f a r t h e r removed from  concentration  non-uniform Otherwise t h a t of  run 4-3, i n F i g . 17. The The  % T.O.C. o x i d i z e d c o u l d be measured i n a l l runs with  initial  t h i s case.  c o n c e n t r a t i o n s from G.C. T h i s c o u l d be due  2,3-Xylenol  and T.O.C. a n a l y s i s do not agree i n  to the v i g o r o u s r e a c t i o n which  started  30  KEY  RUN NO.  INITIAL CONC. ppm  •  3-4  95  •  3-5  505  Q U (0 5  TIME  F i g . 15  (min)  E f f e c t - o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon tn o - c r e s o l  ;  ;  50.  «OOL  F i g . 16  Cone, e f f e c t on % 2,3-Xylenol at  10. A .  ..  oxidized  TIME  F i g . 17  (min)  C u r r e n t e f f e c t on % 2,3-Xylenol (1 g/1 run)  oxidized  well  b e f o r e r e c y c l i n g was s t a r t e d .  with an i n c r e a s e  in initial  concentration,  ( F i g . 18). The e f f e c t o f c u r r e n t i n F i g . 19. the c u r r e n t 15A  Besides, contrary  to  expectation,  a l a r g e r % T.O.C. i s o x i d i z e d  on % T.O.C. o x i d i z e d  There i s a s i g n i f i c a n t i n c r e a s e  can be observed  i n % T.O.C. o x i d i z e d when  i s r a i s e d from 5A to 10A although the t r e n d  between 10A and  i s not c l e a r - c u t . The  treated  s o l u t i o n when s u b j e c t e d  t o GC/MS a n a l y s i s  showed the  f o l l o w i n g compounds OH  0  0 CH  L  °3  and  2,3-Xylenol  hydroquinone.  The presence o f o n l y  t h a t the l o s s o f 2 e l e c t r o n s with the e q u i l i b r i u m almost  irreversible.  5.1.5  Oxidation  2.6% 4-hydroxy-2,4dimethyl, 2,5-cyclohexadiene-1-one Based on the products  identified,  i s p r o b a b l y s i m i l a r to t h a t o u t l i n e d f o r t r a c e s o f 2,3-dimethyl  from 2,3-dimethyl  hydroquinone shows  hydroquinone i s r a p i d ,  s h i f t e d i n such a way as t o make t h i s r e a c t i o n  o f 3,4-Xylenol  Based on i t s s t r u c t u r e , 3,4-Xylenol The E  t h a t o f phenol.  OH  3  2,3-dimethyl benzoqui.none  the mechanism o f the o x i d a t i o n  2,3-Xylenol.  HC  79.8%  t r a c e s o f 2,3-dimethyl  phenol.  0  3 0  17.6% .  CH  TT  PM  3  x  o f 3,4-Xylenol  The usual  of the c o n c e n t r a t i o n  well  should be as r e a c t i v e as  (0.513 V) i s much lower [21] than  marked t r e n d s a r e observed i n the p l o t s  e f f e c t ( F i g . 20) and the c u r r e n t  e f f e c t ( F i g . 21).  30  KEY  o (A O  O  20)  RUN NO.  INITIAL CONC. ppm  4- 1  625  •  4-5  380  •  4-4  97  0 K <  z 4  U OC  o  10  120  60  TIME  F i g . 18  (min)  E f f e c t o f cone, on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n 2,3-Xylenol a t 10 A.  tn to  •gg  The T.O.C. a n a l y s i s showed t h a t t h e r e was l e s s than 5% o x i d a t i o n o f the o r g a n i c carbon  i n a l l the runs and hence these r e s u l t s have not  been r e p o r t e d . The  poor r e s u l t s o b t a i n e d i n the anodic o x i d a t i o n o f 3,4-Xylenol  under the p r e s e n t c o n d i t i o n s c o u l d be because o f the low s o l u b i l i t y o f 3,4-Xylenol  i n water.  A few i n s o l u b l e o i l y d r o p l e t s were noted  e l e c t r o l y t e which a l s o c o u l d have a f f e c t e d t h a t t h e r e i s no measurable decrease o b s e r v a t i o n t h a t 3,4-Xylenol the c o n d i t i o n s used.  the whole p r o c e s s .  i n the The f a c t  i n T.O.C. f u r t h e r supports the  i s r e s i s t a n t to anodic o x i d a t i o n under  The low o x i d a t i o n o f o r g a n i c carbon c o u l d not  be due t o the f o r m a t i o n o f some n o n - o x i d i s a b l e o x i d a t i o n product because the o n l y products t h a t were i d e n t i f i e d s t a r t i n g compound, 3,4-Xylenol  i n the t r e a t e d  s o l u t i o n were the  a t 77.9%, and the f o l l o w i n g  compound  4-hydroxy, 2,4-dimethyl, 2-5-cyclohexadiene-l-one a t 22.1%  The  above'mentioned product was o b t a i n e d from the o x i d a t i o n o f 2,3-Xylenol  and has a l s o been o b t a i n e d  [23] from  the anodic o x i d a t i o n o f 2 , 4 - X y l e n o l .  T h e r e f o r e i t must have a s t a b l e c o n f i g u r a t i o n among the p o s s i b l e  isomers  o f the o x i d a t i o n products o b t a i n a b l e from v a r i o u s x y l e n o l s .  5.1.6  Oxidation of Resorcinol  S u b s t i t u t i o n o f a hydroxyl group i n the meta p o s i t i o n o f phenol decreases  the h a l f wave p o t e n t i a l .  Due t o the e l e c t r o n donating  nature  of the s u b s t i t u e n t , r e s o r c i n o l should anodic  oxidation.  resorcinol  T h i s was found t o be t r u e .  i s destroyed  concentration  completely  tage o x i d a t i o n i n a given  the usual  pronounced e f f e c t  shows t h a t with i s an i n c r e a s e  the i n i t i a l  i n decreasing  concentrathe percen-  ( F i g . 23) f o l l o w s  Anodic o x i d a t i o n o f r e s o r c i n o l i s very i n t e r e s t i n g carbon d i o x i d e f o r m a t i o n .  a decrease i n i n i t i a l i n % organic  current, although there trend  the i n i t i a l  time.  from the p o i n t o f view o f a c h i e v i n g  the exact  Increasing  e f f e c t o f c u r r e n t on the r a t e o f o x i d a t i o n trend.  during  As seen from F i g . 22,  i n 60 minutes provided  i s lower than 500 mg/l.  t i o n t o 1200 mg/l has a well  The  be more e a s i l y o x i d i z e d  carbon o x i d i z e d .  i s a slight  i s unclear  concentration  increase  F i g . 24  o f r e s o r c i n o l , there  With an i n c r e a s e i n % organic  in applied  carbon o x i d i z e d ,  ( F i g . 25).  As mentioned i n s e c t i o n 4.3.5, none o f the o x i d a t i o n products o f resorcinol  could  was used.  Thus no d e f i n i t e c o n c l u s i o n  route  be i d e n t i f i e d  i n t h i s case.  observations  by GC/MS a n a l y s i s even when a s o l i d  can be made about the r e a c t i o n  However a few comments can be made based on the  made d u r i n g  the runs.  In s p i t e o f the f a c t t h a t there was an observable of o r g a n i c  rate of oxidation  carbon, t h e r e was no foaming o r n o t i c e a b l e gas e v o l u t i o n .  T h i s suggests t h a t the foaming observed i n the 0 - c r e s o l 2,3-Xylenol  probe  runs was perhaps due to the formation  a c t i v e compounds r a t h e r than being  simply  runs and  o f some s u r f a c e  due t o gas e v o l u t i o n .  During the r e s o r c i n o l runs the e l e c t r o l y t e remained c o l o u r l e s s for  the f i r s t  30 minutes and became y e l l o w  c o l l e c t e d a t the beginning  thereafter.  o f the runs were y e l l o w  s l o w l y became c o l o u r l e s s i n f i v e minutes.  A l s o the samples  during  c o l l e c t i o n and  T h i s suggests t h a t the r e a c t i o n  F i g . 23  C u r r e n t e f f e c t on % r e s o r c i n o l o x i d i z e d (1 g/1  runs)  cn  T  KEY 100  h  RUN NO. INITIAL CONC. ppm  •  6-4  87  •  6-5  490  •  6- 1  1200  z  TIME  F i g . 24  (min)  E f f e c t of cone, on r a t e of o x i d a t i o n o f o r g a n i c carbon i n r e s o r c i n o l a t 10 A  KEY  RUN NO.  1 (A)  •  6-2  5  •  6- 1  10  T  6-3  15  TIME  F i g . 25  (min)  E f f e c t of c u r r e n t on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n r e s o r c i n o l (1 g/1 runs)  l e a d i n g t o the formation its  equilibrium shifted  t r a t i o n s o f the i n i t i a l  5.1.7  Oxidation  o f the y e l l o w  o x i d i z e d product o f r e s o r c i n o l has  towards the forward r e a c t i o n o n l y a t high oxidation  product.  o f catechol  Anodic o x i d a t i o n o f c a t e c h o l from i t s s t r u c t u r e .  was found t o be very v i g o r o u s  Among the p h e n o l i c s  studied, catechol  in  The maximum o x i d a t i o n o f o r g a n i c  run 7-5 ( F i g . 2 6 ) . With higher  (1000  initial  carbon  (62.7%) was  concentrations  o f carbon achieved  o f catechol  mg/l), the curve l e v e l s o f f a f t e r 90 minutes o f o x i d a t i o n  t h a t probably  showing  an e l e c t r o - i n a c t i v e compound o r a compound t h a t i s h i g h l y  r e s i s t a n t t o anodic Besides,  as expected  proved t o be  most s u s c e p t i b l e t o complete o x i d a t i o n l e a d i n g to the formation dioxide.  concen-  as expected  o x i d a t i o n under the p r e s e n t [27] the c a t a l y t i c  conditions  e f f e c t o f catechol  i s formed. described i n  S e c t i o n 2.2.4 seems t o be n e g l i g i b l e under the low pH c o n d i t i o n s o f the experiment. An i n c r e a s e i n a p p l i e d c u r r e n t does not q u i t e seem t o favour the oxidation o f organic and  carbon because the trends  followed  i n run 7-1 (10A)  7-3 (15A) a r e s i m i l a r ( F i g . 27) a l t h o u g h a lower r a t e o f o x i d a t i o n  o f o r g a n i c carbon i s observed i n the case o f 5A r u n . As  indicated e a r l i e r ,  (Chapter 4 ) , the c o n c e n t r a t i o n  the runs c o u l d not be determined by the usual inapplicable f o r concentrations conditions  GC technique which was  below 200 mg/l.  (run 7-1, 1000 mg/l, i n i t i a l  of catechol i n  However, under  c o n e , 1 0 A ) , i t was  typical  found by  T h i s i s supported by the f a c t t h a t the r e a c t i o n appeared t o be l e s s v i g o r o u s , with l e s s gas e v o l u t i o n and foaming a f t e r the f i r s t 90 minutes.  F i g . 27  E f f e c t o f c u r r e n t on r a t e o f o x i d a t i o n o f o r g a n i c carbon i n catechol (1. g/1 runs)  GC  u s i n g the carbowax column t h a t about 150 mg/l o f c a t e c h o l  a f t e r 2 hours o f anodic the o r g a n i c carbon. all  remained  o x i d a t i o n i n which there was 45.6% o x i d a t i o n o f  A black product  runs except i n run (7-4)  o f p o l y m e r i z a t i o n was produced i n  where the lowest  t r a t i o n o f c a t e c h o l was used.  (100 mg/l)  initial  concen-  Attempts t o c h a r a c t e r i z e the black  preci-  p i t a t e were not s u c c e s s f u l . The  observations  two-electron  process  made i n the c a t e c h o l  runs suggest t h a t the i n i t i a l  l e a d i n g to the f o r m a t i o n  o f 0-quinone i s f o l l o w e d  immediately by i t s decomposition and condensation. solution collected  i n the i n i t i a l  formed the condensation Unfortunately, in  product  stage  The pale  o f the process  yellow  spontaneously  which p r e c i p i t a t e d o u t o f the samples.  none o f the products  o f o x i d a t i o n c o u l d be i d e n t i f i e d  the GC/MS a n a l y s i s . In o r d e r  to e v a l u a t e  the anodic  o x i d a t i o n process  from the p o i n t  o f view o f e f f l u e n t treatment o f waste c o n t a i n i n g c a t e c h o l , B.O.D. and C.O.D. r e s u l t s a r e r e p o r t e d . there  (Appendix 2, runs 7-2, 7-3).  As expected,  i s a l a r g e r % r e d u c t i o n i n B.O.D. a t a higher c u r r e n t .  between the two extreme values  o f c u r r e n t used  (5A and 15A),  However there i s  o n l y a small  d i f f e r e n c e i n r e d u c t i o n o f B.O.D. achieved  experiment.  The treatment b r i n g s about 81% r e d u c t i o n i n B.O.D. value  at  an a p p l i e d c u r r e n t o f 15A.  The change i n the C.O.D. values  r e s u l t o f the o x i d a t i o n i s comparable with carbon^ with  d u r i n g the  as a  the % o x i d a t i o n o f o r g a n i c  but t h e ' e f f e c t of increase i n the r e d u c t i o n of C.O.D. values  i n c r e a s e i n c u r r e n t i s more s i g n i f i c a n t .  66.  5.2  Comparison o f performance of d i f f e r e n t  5.2.1  E f f e c t of v a r i a t i o n of i n i t i a l  An  i n c r e a s e i n the i n i t i a l  phenolics  concentration  c o n c e n t r a t i o n of the p h e n o l i c s  studied  i s accompanied by a drop i n the % of o x i d a t i o n i n 2 hours ( F i g . 28). phenol  runs do not f o l l o w the t r e n d due  cathode s u r f a c e i n run 1-5 oxidized completely  to the d e p o s i t i o n of t a r s on  as mentioned e a r l i e r .  a t a l l the  initial  2,3-Xylenol  concentrations  was  The the  however  studied.  In o r d e r to d i s c u s s r a t e s l o g i c a l l y , c o n t r o l l e d - p o t e n t i a l e l e c t r o lysis  (cpe) c a r r i e d out with a p o t e n t i o s t a t should  than c o n s t a n t constant  c u r r e n t experiments as the f a c t o r a f f e c t i n g  i s the p o t e n t i a l .  the i n i t i a l  r a t e was  In the p r e s e n t  the i n i t i a l  a maximum value with t h a t a t an  initial  o x i d a t i o n can  study,  based on the time i n t e r v a l  compound o x i d i z e d i n c r e a s e d l i n e a r l y with 2,3-Xylenol,  be performed  time.  the  rather  rate  the c a l c u l a t i o n  of  d u r i n g which % p h e n o l i c Except i n the case of  o x i d a t i o n r a t e s f o r a l l the p h e n o l i c s go  increasing concentration  concentration  be o b t a i n e d .  The  ( F i g . 29).  of about 500 mg/l, a c t u a l v a l u e s of the  through  This indicates  the best r a t e of initial  rates,  however do not seem to have a d i r e c t c o r r e l a t i o n to the s t r u c t u r e o f the p h e n o l i c s .  This i n d i c a t e s that besides  other f a c t o r s l i k e d i f f u s i o n a l adsorption role  e f f e c t s and  i n the anodic  the nature  e f f e c t s , nature  of the o x i d a t i o n  products,  optimum p o t e n t i a l range can perhaps p l a y a major  process.  An  i n c r e a s e i n the i n i t i a l  seems to a c c e l e r a t e the r a t e o f o x i d a t i o n of 2,3-Xylenol t r a t i o n range s t u d i e d .  of the s u b s t i t u e n t s ,  concentration i n the  concen-  N A M E OF COMPOUND  KEY  V  PHENOL  •  o-CRESOL  too  p-CRESOL  oc O 80 x  (Vi  a «  •  RESORCINOL  o  2,3  XYLENOL  •  3,4  XYLENOL  60  x o  40  20  0.0  4.0  2.0  INITIAL  Fig.  28  V a r i a t i o n of of  8.0  6.0 CONC.  final  phenolics at  OF  PHENOLICS  XIO  6  % oxidized with  10 A  14.0  12.0  10.0  mole / m  16.0  3  initial  concentration  5.2.2  E f f e c t o f v a r i a t i o n of a p p l i e d  With  current  an i n c r e a s e i n a p p l i e d c u r r e n t , t h e r e i s an i n c r e a s e i n t h e  % o x i d a t i o n a f t e r 2 hours o p e r a t i o n  i n a l l cases ( F i g . 30).  of oxidation increases  3,4-Xylenol,  i n the order  r e s o r c i n o l , phenol, 2,3-Xylenol. the i n c r e a s e i s between 5A and to 15A.  The  initial  10A  than i n the case o f i n c r e a s e from  is insignificant.  a p p l i e d c u r r e n t , the data  obtained  t h a t the  trend f o l l o w e d with  obtained  with  and  the f i n a l  %  T h i s e f f e c t i s more s i g n i f i c a n t when  r a t e of o x i d a t i o n ( F i g . 31)  10A  final  p-cresol, 0-cresol,  i n c r e a s e s with  i n a p p l i e d c u r r e n t except i n the case of p - c r e s o l where the r a t e between 5A and  The  final  the  with  initial  % oxidized.  10A  increase  increase in  In t h i s study of the e f f e c t  d i f f e r e n t phenolics  of  indicates  r a t e s i s d i f f e r e n t from t h a t  T h i s i n d i c a t e s t h a t the k i n e t i c s  the t r a n s p o r t phenomena a s s o c i a t e d with  each process  are complex  and  deserve f u r t h e r i n v e s t i g a t i o n .  5.2.3  Subsitutuent  As  effects  referred earlier,  ( s e c t i o n s 2.2.2) most s t u d i e s o f  e f f e c t s are based on s h i f t s o f half-wave p o t e n t i a l s . present  study, i t i s obvious t h a t there  the half-wave p o t e n t i a l values  (Table  equation  I I ) and  final  ox  % oxidized.  activity  the  The  coefficients  reduced forms i n t o account as shown by the  following  [41]  D RT ox In ( nF D Red  where D  However from  i s no d i r e c t c o r r e l a t i o n between  half-wave p o t e n t i a l does take the d i f f u s i o n and o f the o x i d i z e d and  substituent  and  D  Red  Red  (10)  ox  are the d i f f u s i o n c o e f f i c i e n t s of the o x i d i z e d  and  KEY  V  PHENOL  •  o - CRESOL  100  so ce  NAME OF COMPOUND  p - CRESOL  •  RESORCINOL  •  2,3  XYLENOL  O  3,4  XYLENOL  O X CM  S 60 a u X  o  40  20  6 APPLIED  Fig.  30  8  10  CURRENT  V a r i a t i o n of f i n a l (1 g/1 r u n s )  14  (A)  % oxidized with applied  current  16  22.0  KEY  NAME OF COMPOUND  20.01  C  16.0  M «  E  (0  12.0  •  PHENOL  •  o-CRESOL  •  p-CRESOL  •  RESORCINOL  A  2,3  XYLENOL  O  3,4  XYLENOL  o  u i< cc  8.0  I  -I  < p 2  4.0  _i_  0.01  6  10  8 (A)  APPLIED CURRENT Fig.  31  Variation of applied  initial  current  12  rate of o x i d a t i o n with  (1 g/1  runs)  14  16  reduced forms, r e s p e c t i v e l y , and But  the  s h i f t of the  f  and  f ^  half-wave p o t e n t i a l  are  the a c t i v i t y  (AEj  ) ^2  coefficients.  caused by  v  introducing  A  the s u b s t i t u e n t X i n to the parent molecule chosen as a r e f e r e n c e i n which X = H i s r e l a t e d [41] r e a c t i o n by eq.  '  to the e q u i l i b r i u m c o n s t a n t s  =  ^ r  (  1  A  1  K  ° 9  >x  -  where K i s the e q u i l i b r i u m constant  of the  A log K = log  represents  - l o g Kp,  where K  Q  Although the s h i f t  i n Ei  not  o c c u r r i n g a t the e l e c t r o d e  and  play a  On  and reference  reaction k i n e t i c s , in  r a t e of d i f f u s i o n o f the  reactant  be c o n t r o l l e d by the Besides,  adsorption  gas  cases.  processes  evolution, further  e f f e c t s a l l of which need  role.  diffusivity  theoretical diffusivity  i n Table V. by the  surface.  intermediates  f u r t h e r i n v e s t i g a t i o n may  The  f o r the  be e x a c t l y t r u e with the p r e s e n t  o v e r a l l r a t e o f the r e a c t i o n s may  E f f e c t of  the value  R,  of half-wave p o t e n t i a l s , i t i s assumed t h a t the o v e r a l l  to the e l e c t r o d e , which may  5.2.4  r e a c t i o n 0 + ze  i s r e l a t e d to the  r a t e of the r e a c t i o n .is l i m i t e d by the  o x i d a t i o n of the  W  H.  system f o r which X =  The  the  (11)  (AE%)x  the d e t e r m i n a t i o n  for  compound,  the  values  b a s i s of d i f f u s i v i t y ,  (Appendix 4) have been presented i f the r e a c t i o n s are c o n t r o l l e d \  r a t e o f mass t r a n s p o r t of the p h e n o l i c molecules to the  the ease of o x i d a t i o n  should  be as  follows.  phenol > d i h y d r i c phenols > c r e s o l s >  xylenols  electrode,  73.  In  the p r e s e n t study, a t an a p p l i e d c u r r e n t o f 10A, with an i n i t i a l  concentration of lgpl  o f the p h e n o l i c compound, the i n i t i a l  rate of  o x i d a t i o n f o l l o w s the order ( F i g . 3 1 ) .  phenol  > 2,3-Xylenol  > resorcinol  >  p-cresol  > 3,4-Xylenol  > O-cresol  TABLE V DIFFUSIVITIES OF THE PHENOLIC COMPOUNDS IN WATER  *  Molal volume o f the p h e n o l i c compound a t i t s normal b o i l i n g p o i n t  Name o f phenolic compound  cnr/sec  3  x 10  6  cm /s 2  cm /g.mole Phenol  105  8.5  p-cresol  126  7.7  O-cresol  126  7.7  2,3-Xylenol  147  7.4  3,4-Xylenol  147  7.4  resorcinol  112  8.3  catechol  112  8.3  T h i s t r e n d conforms t o the o r d e r expected v a l u e s except f o r 2,3-Xylenol and  3,4-Xylenol  which takes precedence  which has a h i g h e r i n i t i a l  d e r i n g the % o x i d i z e d  i n two hours  Calculation outlined  over  resorcinol  r a t e than O - c r e s o l .  Consi-  ( F i g . 30) under s i m i l a r c o n d i t i o n s  the o r d e r seems t o be d i f f e r e n t from above.  *  from the d i f f u s i v i t y  i n Appendix 4.  T h e r e f o r e , even though  74.  d i f f u s i v i t y might c o n t r o l the r a t e of o x i d a t i o n oxidations  5.3  other  Oxidation  i n the  initial  f a c t o r s which deserve f u r t h e r a t t e n t i o n do  of phenolic  stages o f  play a  role.  mixtures  When the monohydric p h e n o l i c s  are mixed i n about the  same concen-  t r a t i o n s as they are found i n the wastewater of Table I, the e x t e n t which the p h e n o l i c s order  as  were o x i d i z e d  time decreased i n the  following  shown i n F i g . 32-34.  OH  OH  phenol  OH  o-cresol  This leads 1)  2)  OH  2,3-Xylenol  us to the f o l l o w i n g  OH  p-cresol  3,4-Xylenol  conclusion.  S u b s t i t u t i o n of methyl  the ease of  tion  i n a given  to  ( e l e c t r o n donating group) decreases  oxidation.  S u b s t i t u t i o n i n the ortho p o s i t i o n i s p r e f e r a b l e  to s u b s t i t u -  i n the para p o s i t i o n . 3)  No  d e f i n i t e conclusion  can  be drawn about the  preference  of  para p o s i t i o n over meta. Mass t r a n s f e r e f f e c t s would have a l s o aided phenol and  0-cresol  rest.  mixture o x i d a t i o n  The  as t h e i r i n i t i a l  runs (runs 8-1,  the p e r i o d of treatment i s i n c r e a s e d , Even a f t e r 95.8% did  not f l a t t e n out  obtained.  8-2,  i s higher 8-3)  better oxidations  than  prove t h a t can  be  o x i d a t i o n of the p h e n o l i c mixture (run 8-3), showing t h a t by i n c r e a s i n g the  or by using more optimal be  concentration  i n the o x i d a t i o n  p e r i o d of  of the as  obtained. the  curve  oxidation  c o n d i t i o n s , v i r t u a l l y complete o x i d a t i o n might  F i g , 32  E f f e c t o f nature of p h e n o l i c s (1 OA, 2 h r s ; run 8-1)  on %  oxidation  ;  F i g . 34  E f f e c t o f nature of p h e n o l i c s  on % o x i d a t i o n  (10 A,  5 h r s ; run  8-3)  From the GC/MS a n a l y s i s o f the t r e a t e d s o l u t i o n , a l l the products obtained  from t h e i n d i v i d u a l  p h e n o l i c runs were i d e n t i f i e d .  r e s u l t i n g from the i n t e r a c t i o n o f the o x i d a t i o n products p h e n o l i c s was i d e n t i f i e d .  No product  of different  T h i s c o u l d be due t o one o f the f o l l o w i n g  causes: 1) occurrence 2)  Conditions  o f the experiment were not f a v o u r a b l e  f o r the  o f any c o u p l i n g r e a c t i o n between the p r o d u c t s . Products  o f such i n t e r a c t i o n s d i d not show up on the chromato-  graph e i t h e r due t o t h e i r d i f f e r e n t nature negligible  o r due to t h e i r presence i n  concentrations.  Although the p h e n o l i c s m a i n t a i n the m i x t u r e ,  their individual  t h e r e i s an i r r e g u l a r g r a d a t i o n  i n a l l cases.  behaviour even i n  i n their rates of oxidation  T h i s c o u l d be due t o t h e d i f f e r e n t competing r e a c t i o n s  taking place  simultaneously.  A comparison i s made between the T.O.C, B.O.D. and C.O.D. a n a l y s i s of the i n i t i a l  and the t r e a t e d sample from Run 8-3 i n Table V I .  TABLE VI RESULTS OBTAINED FROM THE  OXIDATION OF MIXTURE  OF MONOHYDRIC PHENOLS (RUN  Time min 0  %  T.O.C. mg/l  8-3) i = 526 A/m"  2  C.O.D. mg/l  B.O.D. mg/l  1480  4291  2783  300  1160  3502  1210  Reduction  21.6  18.4  56.5  I t can be n o t i c e d t h a t the T.O.C. and C.O.D. r e d u c t i o n values and  comparable whereas B.O.D. value  h a l f the i n i t i a l value o b t a i n e d  5.4  Reaction  value.  i s brought down t o a value  in biological  efficiency  f o r a t y p i c a l run  o x i d a t i o n i s complex.  run 9-1.  The o x i d a t i o n  a r e p-benzoquinone, hydroquinone and c a t e c h o l .  about 4% o f the o r g a n i c carbon was converted monoxide.  than  treatment f o r f i v e days [ 4 2 ] ,  For example, c o n s i d e r the o x i d a t i o n o f phenol, reported  less  T h i s B.O.D. r e d u c t i o n i s comparable to the  I t i s apparent t h a t the mechanism o f anodic  products  a r e small  Besides  i n t o carbon d i o x i d e and carbon  Benzoquinone i s generated i n the anode compartment  with  c a t e c h o l , hydroquinone, carbon d i o x i d e and oxygen, and i t may be converted to hydroquinone a t the cathode.  I f the process  proceeds to produce o n l y •,  the above compounds, the sum o f the c u r r e n t e f f i c i e n c i e s f o r the format i o n o f these  products  on the anode should  be 1 . 0 .  As gas a n a l y s i s was not done, the f r a c t i o n  o f carbon o x i d i z e d to  CO and C0£ i s unknown, t h e r e f o r e c u r r e n t e f f i c i e n c y  i s reported  extreme v a l u e s o f the carbon monoxide t o carbon d i o x i d e r a t i o s . current e f f i c i e n c y  assuming The  (Appendix 4) i s found to be 0.43 - 0.63 depending on  the r a t i o o f CO t o CO2 formed.  Presumably there a r e o t h e r  occurring which account f o r the r e s t o f the c u r r e n t . c o u l d be the f o r m a t i o n  These r e a c t i o n s  o f oxygen from water e l e c t r o l y s i s  of some other o x i d a t i o n product  t h a t has not been  Moreover, as no p r e c a u t i o n  reactions  o r the f o r m a t i o n  identified.  has been taken to decrease the c o n v e c t i o n  o f benzoquinone t o the cathode, r e d u c t i o n o f benzoquinone t o hydroquinone followed  by the non-productive  o x i d a t i o n o f t h a t hydroquinone back to  benzoquinone c o u l d account f o r a l o s s i n c u r r e n t e f f i c i e n c y .  However,  80.  hydrogen evolution at the cathode would compete with the thermodynamically favoured reduction of benzoquinone at the cathode. From the carbon balance, i t can be seen that 21% of the carbon has not shown up in the products identified.  Presumably there are other unidenti-  fied products which account for this discrepancy.  Carbon loss could have  also occurred due to deposition of tar products on the electrodes during the process.  5.5  Cell voltage The cell voltage V-is given by AV = V . mm  +  TI  'a  + In'c I + Vohm . 1  The variation between V. ,.. . , and V-. iniiia I  dependent on V ^  (12)  1  , may be particularly  Tl na i  for a constant applied current.  m  The potential drop  across the packed bed should have been ideally measured by using probes at various points in the bed.  However this drop was found to be very  small in similar experiments when the potential profile was measured in a packed bed copper electrode under the conditions of constant current electrolysis [43]. ohm (Appendix 4) increases with the applied current.  V  It is  d i f f i c u l t to compare the change in cell voltage at different applied currents for a particular phenolic compound on the basis of V different currents because ri  and n a  current.  at  in eq. 12 will change with applied c  From Table VII i t can be seen that the cell voltage increases  during the anodic oxidation of 2,3-Xylenol, 3,4-Xylenol With 2,3-Xylenol evolution.  Q n m  and catechol.  and catechol there was an excessive foaming and gas  This would decrease the effective electrolyte conductivity  according to the following equation  TABLE VII VARIATION OF AV  Name o f p h e n o l i c compound ( I n i t i a l cone. 1 gpl)  5A runs  1 OA runs  15A runs  I n i t i a l AV volts  F i n a l AV vol t s  I n i t i a l AV volts  F i n a l AV volts  I n i t i a l -AV vol ts  F i n a l AV vol t s  Phenol  6.15  6.0  7.1  7.1  12.7  10.7  p-Cresol  5.4  5.4  7.9  7.5  12.4  10.8  O-Cresol  6.0  5.9  9.2  8.0  11.3  9.1  2,3-Xylenol  5.0  5.9  6.5  8.3  8.6  10.6  3,4-Xylenol  4.4  4.8  5.9  6.3  7.4  7.5  resorcinol  5.5  5.2  7.4  6.7  10.8  9.7  catechol  3.8  4.4  5.3  6.2  6.9  7.0  K  = K  eg  e  (1 - f)°  where f i s the f r a c t i o n of gas t h a t depending on the gas electrolyte  i n the f i x e d  (13)  /c  i n the e l e c t r o l y t e .  I t has  been r e p o r t e d  l o a d i n g , the e f f e c t i v e c o n d u c t i v i t y of bed  can  be lowered from 10-90% [441.  the ohmic drop would i n c r e a s e c o n s i d e r a b l y and  the c e l l  shows a d i s t i n c t  presence o f the  and  i n c r e a s e i n these c a s e s .  water e l e c t r o l y s i s  The  increase t h i s e f f e c t .  A decrease i n c e l l be a t t r i b u t e d to one e f f e c t of gas 1) heating  i n the c e l l  experiments 2)  An  screen a  similar  ( s e c t i o n 5.1.5).  i s observed i n s e v e r a l c a s e s .  This  o f the f o l l o w i n g e f f e c t s which can c o u n t e r a c t  i n c o n d u c t i v i t y of the e l e c t r o l y t e due or due  to the nature  o f the e l e c t r o l y t e was  may  the  of the products  to e i t h e r formed.  The  found to i n c r e a s e i n s i m i l a r  [31]. intermediate  cathode r e a c t i o n f o r example c a t h o d i c  of p-benzoquinone i n phenol thus d e c r e a s i n g 3)  thus  evolution.  Increase  conductivity  voltage  Therefore  voltage  With 3,4-Xylenol  i n c r e a s e i n r e s i s t a n c e i s expected as i n d i c a t e d e a r l i e r  the  reduction  runs can occur a t a high c a t h o d i c p o t e n t i a l  the e f f e c t i v e c e l l  P h y s i c a l changes may  voltage.  occur  i n the c u r r e n t f e e d e r s o r the  bed  particles.  5.6  Comparison of experimental  r e s u l t s with mathematical  models  To t e s t whether mass t r a n s f e r of the p h e n o l i c compound from bulk e l e c t r o l y t e  to the  the  s u r f a c e o f the e l e c t r o d e c o n t r o l s the r a t e of  d i s a p p e a r a n c e o f the p h e n o l i c compound, c a l c u l a t i o n s were performed  with  83.  2,3-Xylenol of  and r e s o r c i n o l  r u n s , i n a manner s i m i l a r to the c a l c u l a t i o n s  Sucre [ 3 1 ] . Fractional  c o n v e r s i o n o f the p h e n o l i c compound X was r e l a t e d  mass t r a n s f e r groups (Appendix  3) by the f o l l o w i n g  equation  X = 1 - exp [ {exp ( J L _ ) - 1 } | - - J l _  The  sample c a l c u l a t i o n s  with  ]  (  1 4  )  (Tables A - l and A-2) a r e r e p r e s e n t e d as a  band o f c o n v e r s i o n vs time i n F i g s . 16, 17, 22 and 23. In  F i g . 16, i t can be seen  lowest i n i t i a l  c o n c e n t r a t i o n (97 mg/l) approaches  c o n t r o l l e d r e g i o n i n 15 minutes. tical  t h a t the curve c o r r e s p o n d i n g t o the  and experimental  the mass  transfer-  Between 30 and 45 minutes,  the t h e o r e -  c u r v e s c o i n c i d e i n t h i s c a s e , w h i l e with the i n i t i a l  c o n c e n t r a t i o n o f 625 mg/l, the curve almost c o i n c i d e s with the t h e o r e t i c a l r e g i o n a f t e r 60 minutes.  Thus i n the case o f 2,3-Xylenol  enhancement o f mass t r a n s p o r t by foaming  may be expected  runs where as d e s c r i b e d  by Nam's e t a l [45]', the r a t e o f o x i d a t i o n seems to be c o n t r o l l e d by mass t r a n s f e r a t i n i t i a l  c o n c e n t r a t i o n s i n the range o f 0.1 g/1.  f a c t i n run 4.4  c o n c e n t r a t i o n 97 mg/l),  the experimental it  (initial  curve exceeds the t h e o r e t i c a l  In  i n about 45 minutes  region.  i s hard t o conclude whether t h i s can be a t t r i b u t e d  At t h i s point, to the e x c e s s i v e  gas e v o l u t i o n , although i t seems l i k e l y from F i g . 17 where the curve r e p r e s e n t i n g the r a t e o f o x i d a t i o n a t an a p p l i e d c u r r e n t o f 5A i s f a r below the mass t r a n s f e r c o n t r o l l e d r e g i o n .  I t may be r e c a l l e d  t h i s p a r t i c u l a r r u n , gas e v o l u t i o n was not d i s t i n c t . a p p l i e d c u r r e n t (15A) the experimental  A t the h i g h e s t  curve approaches  r e g i o n o n l y a f t e r 90 minutes with h i g h e r i n i t i a l C o n s i d e r i n g the e f f e c t o f i n c r e a s i n g  that i n  the t h e o r e t i c a l  c o n c e n t r a t i o n s (1 g / 1 ) .  the i n i t i a l  concentration i n  the  runs with r e s o r c i n o l  noticeable  gas e v o l u t i o n  transfer controlled  (group 6) F i g . 22 where there was no foaming o r the experimental  region.  curves a r e c l o s e r t o the mass  I t should be remembered, however t h a t the  d i f f u s i v i t y o f r e s o r c i n o l molecules i s l a r g e r than t h a t o f 2,3-Xylenol a l t h o u g h the change i n d i f f u s i v i t y the  t h e o r e t i c a l mass t r a n s f e r  has been taken i n t o account i n c a l c u l a t i n g  region.  F i g . 23 l e a d s again to the s u s p i c i o n i n mass t r a n s f e r .  I t can be observed t h a t a t h i g h e r i n i t i a l  of r e s o r c i n o l , u n l i k e tal  the o b s e r v a t i o n made with 2,3-Xylenol  curve i s f a r below the t h e o r e t i c a l  current  about the r o l e o f gas e v o l u t i o n  region  concentration the experimen-  even a t the h i g h e s t  (Run 6-3).  Any  discussion  o f the above e f f e c t s depends on the a c c u r a c y o r  a p p l i c a b i l i t y o f the mass t r a n s f e r c o e f f i c i e n t c o r r e l a t i o n used. the  applied  Although  e q u a t i o n o f P i c k e t t and Stanmore [46] used i n Ref. 31 has been m o d i f i e d  to improve i t s a p p l i c a b i l i t y to p r e s e n t case by c o n s i d e r i n g  .the c o r r e c t i o n  with a double l a y e r o f packed bed based on the s u g g e s t i o n s i n Ref. 10, pg.161, i t i s s t i l l bed  electrode.  a poor c o r r e l a t i o n f o r a gas e v o l v i n g ,  The e q u a t i o n s used i n .the  randomly packed  p r e s e n t study t o determine  k  are  Sh  - 0.66 Re  Sh = 0.62 Re  There a r e c o r r e l a t i o n s  0.56  0.56  Sc  Sc  0.33  (15)  0.33  (16)  [47] r e l a t i n g the volume o f gas evolved t o mass  t r a n s f e r c o e f f i c i e n t which show t h a t when there i s hydrogen o r oxygen evolution,  the r a t e o f mass t r a n s f e r  increases.  Correlations  are also  m  available The  f o r e l e c t r o c h e m i c a l processes  overall  involving  c a p a c i t y c o e f f i c i e n t f o r mass t r a n s f e r  can be c a l c u l a t e d  k a Q  from equations  = k a (1 + V g )  gaseous r e a c t a n t s [ 4 8 ] . i n the present s e t up  o f the type  (17)  n  m  where Vg, t h e volume o f gas evolved would be needed.  As the pressure  drop was not measured, a more a c c u r a t e c a l c u l a t i o n o f mass c o e f f i c i e n t has not been attempted.  transfer  CHAPTER 6  CONCLUSIONS  An i n v e s t i g a t i o n was made o f the anodic in  o x i d a t i o n o f major p h e n o l i c s  coal p r o c e s s i n g waste from the p o i n t o f view o f e f f l u e n t  Experiments were performed with 3,4-Xylenol,  phenol,  treatment.  O-cresol, p - c r e s o l , 2,3-Xylenol,  r e s o r c i n o l , c a t e c h o l and mixtures o f the f i v e monohydric  phenols. 1.  G e n e r a l l y , the percentage o x i d a t i o n o f the p h e n o l i c s i n a given  time was f a v o u r e d initial  by i n c r e a s i n g the a p p l i e d c u r r e n t and d e c r e a s i n g  the  v  c o n c e n t r a t i o n o f the p h e n o l i c s .  2.  Complete o x i d a t i o n o f the o r g a n i c carbon under p r e s e n t  condi-  t i o n s o f 5 1 o f p h e n o l i c s o l u t i o n with c o n c e n t r a t i o n range 0.1 g/1 to 1 g/1 o f p h e n o l i c compound to  recirculated  f o r a two hour p e r i o d , o c c u r r e d  a s i g n i f i c a n t e x t e n t o n l y i n the case o f 2 , 3 - X y l e n o l ,  r e s o r c i n o l and  catechol. 3.  From the comparison o f the performance o f d i f f e r e n t  t h e r e i s no simple  c o r r e l a t i o n o f the r a t e s o f o x i d a t i o n with the s t r u c t u r e  and  d i f f u s i v i t y o f the p h e n o l i c compounds.  ing  r e a c t i o n r a t e a t an a p p l i e d c u r r e n t o f 10A with an i n i t i a l  The observed  t i o n o f 1 gpl o f the p h e n o l i c compounds was phenol, r e s o r c i n o l , p - c r e s o l , 3,4-Xylenol, 4. at  phenolics,  concentra-  2,3-Xylenol,  o-cresol.  When the s y n t h e t i c mixture  concentrations corresponding  order o f d e c r e a s -  o f f i v e monohydric phenols  to a t y p i c a l  present  c o a l c o n v e r s i o n waste was  o x i d i z e d , about 96% o f the p h e n o l i c s were o x i d i z e d i n 5 hours. w i t h which the p h e n o l i c s were o x i d i z e d was as f o l l o w s  The ease  87.  phenol  > 0 - c r e s o l > 2,3-Xylenol  > p-cresol  > 3,4-Xylenol  As a r e s u l t o f the treatment, T.O.C. and C.O.D. were reduced w h i l e the r e d u c t i o n i n the B.O.D. v a l u e was about 5.  by about  56%.  The products o f the o x i d a t i o n process were i d e n t i f i e d  runs o f the i n d i v i d u a l  20%  p h e n o l i c s and p h e n o l i c m i x t u r e .  for typical  From the nature  o f the products and o b s e r v a t i o n s made i n the r u n s , p o s s i b l e r o u t e s f o r the o x i d a t i o n s were proposed  i n most c a s e s .  products were i n the form o f quinones  Most o f the o x i d a t i o n  o r hydroquinones.  None o f these  o x i d a t i o n products have been i n c l u d e d [49] i n the EPA l i s t o f o r g a n i c priority 6.  pollutants. Comparison of the experimental  r e s u l t s from two d i f f e r e n t s e t s  of runs with a mass t r a n s f e r model i n d i c a t e d t h a t the d e p l e t i o n o f phenolics i s controlled the p h e n o l i c compound  by mass t r a n s f e r when the c o n c e n t r a t i o n o f  i s low.  CHAPTER 7  FURTHER WORK  Further conversion  o f the p r o c e s s .  To o b t a i n a complete understanding  Routine a n a l y s i s o f the gaseous products  chromatographic a n a l y s i s should  be  o f the t e c h n i c a l  be attempted.  performed on a l l the samples. Presentation density  The o x i d a t i o n  products  b)  o f a complete study  o f d i f f e r e n t anodic  on the e f f e c t o f c u r r e n t  oxidation  Formation o f d e f i n i t e c o n c l u s i o n s under d i f f e r e n t o p e r a t i n g  2.  i n the  products.  about e f f l u e n t q u a l i t y  conditions.  E l e c t r o d e p o t e n t i a l v a r i a t i o n s should  be determined by using  r e f e r e n c e e l e c t r o d e s l o c a t e d a t c e r t a i n p o i n t s i n the bed. a s s i s t with 3.  the m o d e l l i n g  This would  o f the p r o c e s s .  The r o t a t i n g d i s c e l e c t r o d e can be used with a l l o f the above  phenolics  t o e l u c i d a t e the k i n e t i c s o f e l e c t r o o x i d a t i o n under  operating  conditions.  4. provided  For f u t u r e experiments with with  prevent  prolonged  should  T h i s would l e a d to  [50] and % c u r r e n t e f f i c i e n c y u t i l i z e d  formation  study.  by o r s a t o r gas  be monitored p e r i o d i c a l l y and a complete GC/MS a n a l y s i s  a)  to  o f the  the f o l l o w i n g recommendation are made on the b a s i s o f t h i s  1.  should  treatment o f coal  e f f l u e n t s would c o n t r i b u t e the e s t a b l i s h m e n t  feasibility process,  i n v e s t i g a t i o n o f the e l e c t r o c h e m i c a l  valves  should  the packed bed a s e r i e s o f f i l t e r s  be added to the r e c y c l e loop o f the equipment  the b u i l d u p o f t h e suspended condensation periods  different  of operation.  product  during  5. chemicals 6.  The work should be extended i n coal  t o the study o f treatment  p r o c e s s i n g e f f l u e n t s and hence the a c t u a l  As an e l e c t r o c h e m i c a l process  o f a l l the  effluent.  has s e v e r a l advantages over  o x i d a t i o n process  [51] the p r e s e n t process should be s c a l e d up f o r  continuous  As a p a r t o f the water p u r i f i c a t i o n  runs.  wastes, a l a r g e r c e l l  chemical  system f o r i n d u s t r i a l  assembly with a m u l t i p l i c i t y o f t r e a t i n g zones would  be r e q u i r e d . 7.  S t u d i e s should be performed  o x i d a t i o n as a f i n a l  to t e s t the a p p l i c a t i o n o f anodic  p o l i s h i n g step a f t e r b i o l o g i c a l  o r any o t h e r  ment t h a t i s not capable o f d e s t r o y i n g the p h e n o l i c s c o m p l e t e l y .  treatA  packed bed, i f s u f f i c i e n t l y long and a p p r o p r i a t e l y p o l a r i z e d , can p o s s i b l y f u n c t i o n as an e l e c t r o c h e m i c a l f i l t e r which w i l l  reduce  of a l l e l e c t r o c h e m i c a l l y o x i d i s a b l e s p e c i e s t o a l e v e l d e s i r a b l y low f o r optimum b i o l o g i c a l  treatment.  the c o n c e n t r a t i o n t h a t can be  T h i s suggests the  p o s s i b i l i t y o f use o f anodic o x i d a t i o n as a p r i o r step to any o t h e r treatment.  90.  NCMENCXATURE  Typical units specific surface area of the bed current density referred to the surface area of the feeder plate  2,3 m /m A/m  2  current efficiency  C.E  concentration of the oxidized form at the point of discharge  mg/l  concentration of reactant i n the bulk of solution  mg/l  concentration of reactant at the surface of the electrode  mg/l  Cr  concentration of the reduced form at the point of discharge  mg/l  dp  average particle diameter  m  D  diffusivity of the phenolic compound in water  m /s  C  o  CA s  Ox,> Red  D  D  diffusion coefficients  E  half wave potential  AE  shift i n half wave potential  F  Faraday's constant  f  ox, Red f  2  V  coul/g equiv.  activity coefficients applied current  A  electrochemical reaction rate constant  m/s  \  mass transfer coefficient  m/s  k a o  overall capacity coefficient  Keg  effective electrolyte conductivity  K  equilibrium constant  I k  r  -1  (Km)  91  Typical L  length o f the c e l 1  m  N  e l e c t r o l y t e flow rate  m /s  R  universal  Re,  units  3  gas c o n s t a n t  kJ/k mol °K  Reynolds number based on p a r t i c l e diameter  p  Sc  Schmidt  S  t h i c k n e s s o f t h e bed ( i n the d i r e c t i o n of current)  m  T  temperature  °K  time o f e l e c t r o l y s i s  S  t  number  * t t  d i m e n s i o n l e s s time m  S  superficial  m/s  3  u V  r e s i d e n c e time i n the mixing tank  a  velocity  anode p o t e n t i a l  V  cathode p o t e n t i a l  V  * V  c  V .„ mi n  minimum c e l l  AV  total  V  i r drop i n e l e c t r o l y t e  V  W  width o f the bed  m  X  phenol  y  variable  z  number o f e l e c t r o n s a s s o c i a t e d w i t h the anodic o x i d a t i o n  Q n m  Greek  cell  voltage a  voltage  V V  f r a c t i o n a l conversion length o f t h e bed  m  Letters  a  transfer  coefficient  0  experimental  flow r a t e o f e l e c t r o l y t e  m /sec  92.  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The e l e c t r o c h e m i c a l e x t r a c t i o n o f copper ions from d i l u t e aqueous s o l u t i o n s . " J . App. Electrochem. 4, 323 (1974).  33.  C a r r , J.P., and Hampson, N.A. "The l e a d d i o x i d e e l e c t r o d e . " Chem. Rev. 72, No. 6, 679 (1972).  34.  Ronlan, A., "Phenols." Encyclopaedia o f e l e c t r o c h e m i s t r y elements. M. Dekkar, New York, V o l . X I , 242 (1978).  35.  R i f i , M.R., and C o v i t z , F.H. I n t r o d u c t i o n M. Dekkar, New York (1974).  36.  S h i e l d s , J.R., and C o u l l , J . "Rate s t u d i e s i n the e l e c t r o c h e m i c a l o x i d a t i o n o f phenol." T r a n s . Am. Electrochem. Soc. 80_, 113 (1941).  37.  V l a d i m i r , K. " A n a l y s i s o f d i h y d r i c phenols by gas chromatography." J . Chromatogr. 5_7, 132 (1971 ).  38.  Wesley, W. Water q u a l i t y e n g i n e e r i n g & Noble, New York, (1970).  39.  Standard methods f o r the examination o f water and waste water. T h i r t e e n t h e d i t i o n , APHA.AWWA.WPCF (1971).  40.  Papouchado, L., e t a l . "Anodic o x i d a t i o n pathways o f p h e n o l i c compounds, P a r t 2 Stepwise e l e c t r o n t r a n s f e r s and coupled hydroo x y l a t i o n s . " J . E l e c t r o a n a l . Chem. 65, 275 (1975).  41.  Zuman, P. The e l u c i d a t i o n o f o r g a n i c P r e s s , New York (1969).  42.  S i n g e r , P.C., e t a l . Report Summary: T r e a t a b i l i t y and assessment o f coal c o n v e r s i o n wastewaters: Phase 1, EPA-600/7-79-248 (June 1980).  43.  Yoshizava, S., e t a l . "Cathodic r e d u c t i o n o f nitrobenzene on the packed bed copper e l e c t r o d e . " B u l l e t i n o f the Chemical S o c i e t y o f Japan, 49,, No. 11 , 2889 (1976).  44.  Neale, G.H., and Nader, W.K. " P r e d i c t i o n o f t r a n s p o r t processes w i t h i n porous media: D i f f u s i v e f l o w processes w i t h i n an homogeneous swarm o f s p h e r i c a l p a r t i c l e s . " A.I.Ch.E. J o u r n a l , 19, 112 (1973).  ;  to organic  o f the  electrochemistry.  f o r p r a c t i c i n g engineers.  electrode processes.  Barnes  Academic  96.  45.  Nam's, L., and McLaren, F. "Rapid mass t r a n s p o r t to e l e c t r o d e s i n foamed e l e c t r o l y t e . " J . Electrochem. Soc. 117, 1527 (1970).  46.  P i c k e t t , D.J., and Stanmore, B.R. "An experimental study o f a s i n g l e l a y e r packed bed cathode i n an e l e c t r o c h e m i c a l f l o w r e a c t o r . " J . App. Electrochem. 5_, 95 (1975).  47.  Sedahmed, G.H. "Mass t r a n s f e r behaviour o f gas e v o l v i n g p a r t i c u l a t e bed e l e c t r o d e . " J . App. Electrochem. 9_, 37 (1979).  48.  01oman, C. " T r i c k l e bed e l e c t r o c h e m i c a l r e a c t o r s . " J . Electrochem. Soc. 126, No. 11, 1885 (1979).  49.  P a t t e r s o n , J.W., and Kodukala, P.S. " B i o d e g r a d a t i o n o f o r g a n i c p o l l u t a n t s . " CEP, 77_, No. 4, 48 (1981 ).  50.  Oloman, C. " E l e c t r o - o x i d a t i o n o f benzene i n a f i x e d J . App. Electrochem. 1_0, 553 (1980).  51.  Weinberg, N.L., and Weinberg, H.R. " E l e c t r o c h e m i c a l o x i d a t i o n o f o r g a n i c compounds." Chem. Rev. 68_, No. 4, 445 (1968).  52.  L i , K.Y., Kuo, C.H., and Weeks, J.L. " K i n e t i c study o f ozone-phenol r e a c t i o n i n aqueous s o l u t i o n s . " A.I.Ch.E. J o u r n a l , 25_, No. 4, 583 (1979).  53.  Brockmann, H.E., and Oke, T.O. "Gas chromatography o f b a r b i t u r a t e s , p h e n o l i c a l k a l o i d s and xanthene bases, f l a s h heater m e t h y l a t i o n by means o f t r i m e t h y l a n i l i n i u m hydroxide." J . o f Pharm. S c i . 58_, 370 (1969).  54.  P e r r y , R.H., and C h i l t o n , C H . Chemical e d i t i o n , McGraw H i l l , New York (1973).  55.  R e i d , C.R., and Sherwood, T.K. The p r o p e r t i e s o f gases and Second e d i t i o n , McGraw H i l l , New York (1966).  56.  Hayduk, W., and L a u d i e , H. " P r e d i c t i o n o f d i f f u s i o n c o e f f i c i e n t s f o r n o n e l e c t r o l y t e s i n d i l u t e aqueous s o l u t i o n s . " A.I.Ch.E. J o u r n a l 20_, 611 (1974).  bed  hazardous  reactor."  e n g i n e e r s handbook. F i f t h  liquids.  APPENDIX 1  S p e c i f i c a t i o n o f A u x i l l i a r y Equipment  and M a t e r i a l s  Power s u p p l y  Sorenson DCR 4D-25B Voltmeter range: 0-40V  Ammeter range:  0-30A ( s m a l l e s t d i v i s i o n  = 1 A)  Voltmeter Central  Sceintific  Co., D.C. Voltmeter = .010 V)  S c a l e s : 0-1.5 V o l t s  (smallest  division  (smallest  division  = .10 0-15  Volts  V)  Rotameter  Brooks, f u l l  view i n d i c a t i n g rotameter  Type: 7-1110 Tube No.: R-7M-25-1 F l o a t : 316 s t a i n l e s s s t e e l Max. f l o w : 1400 cc/min  ( s . g . = 1)  S c a l e : 0-100% l i n e a r  Gas  l i q u i d separators  2.5 cm I.D. and 60 cm long from the bottom  g l a s s tube.  L i q u i d o u t l e t l o c a t e d a t 40 cm  (except f o r group VII where the i n l e t and o u t l e t were  i n t e r c h a n g e d ) bed: 2 mm diameter g l a s s  beads.  98.  Filter  3.0 cm I.D. and 15 cm long g l a s s tube f i l l e d with g l a s s wool  (Merck).  Pressure gauge  Marsh-type 3-100-SS with 316 s t a i n l e s s s t e e l  tube s c a l e 0-30 p s i (% p s i / d i v )  Pump B a r r i s h Pumps Co., N.Y. Model type: 12A-60-316 Flow d a t a : 21 G.P.H. a t 40 p s i d , 29 G.P.H. a t 0 p s i d . (psid indicates d i f f e r e n t i a l  pressure)  Pump p r e s e t a t 45 p s i d .  pH meter  C o r n i n g , Model 7 0 1 A / d i g i t a l E l e c t r o d e : BJC-combination  i o n a l y z e r (accuracy ± 0.01 pH) electrode  Tubings  1.  Imperial Eastman "Poly F l o " 66-P-3/8".  2.  PVC h"  schedule 40 p i p i n g .  Valves  1.  Whitey, f o r g e d body r e g u l a t i n g , 316 S.S. 3/8" c o n n e c t i o n s .  2.  PVC-%" v a l v e (chemline p l a s t i c ) .  .  99. Fittings  Swagelok compression t u b i n g 316 S.S.  fitting  3/8"  P l a s t i c screen  S u p p l i e d by Chicopee Manufacturing Co., Georgia  Saran type Max.  o p e r a t i n g temperature = 125°F  Chemical r e s i s t a n c e : good r e s i s t a n c e to a c i d s and most a l k a l i s top l a y e r , s t y l e 6100900, weight/sq.yd. = 7 oz. bottom  l a y e r , s t y l e 61010XX, weight/sq.yd. = 10.6  A n a l y t i c equipment  a)  and o p e r a t i n g c o n d i t i o n s  Gas chromatography Gas  oz.  specifications  specifications  chromatograph  Manufacturer: V a r i a n Aerograph Model: 1440 Detection:  s e r i e s , s i n g l e column model flame i o n i z a t i o n  Chromatographic  detector  columns  S u p p l i e r : Western  Chromatography  S u p p l i e s , New  Westminster,  B.C.  Material : glass 1.  Column used f o r a n a l y s i s o f monohydric Dimensions: 2 mm  I.D.,  6.4 mm  O.D.,  phenols  6 f e e t long  -  Packing: 10% SP-2100 on 100/120 S u p e l c o p o r t ( d e t a i l s o f the packing  100.  are given i n B u l l e t i n Operating  742D by S u p e l c o , I n c . ) .  conditions  I n j e c t o r port temperature Column temperature 130°C phenolic mixtures) D e t e c t o r temperature C a r r i e r gas  N  C a r r i e r gas flow A i r flow H  2  flow  (brought to 115°C  for analysis of  175°C  pr He  2  150°C  .  30 ml/min  300 ml/min 30 ml/min  Attenuation - varied  for different  concentrations  Recorder Model: Sargent SRG-GC, S e r i a l Response  2.  1 mV  full  number 237 0073  scale  Column used f o r a n a l y s i s o f d i h y d r i c Dimensions: 2 mm  I.D.,  Packing: Porapak  P (80/100 mesh) - support  Carbonax Operating  6.4 mm  20 M - s t a t i o n a r y  Column temperature D e t e c t o r temperature C a r r i e r gas He  phase  260°C  220°C 280°C  (oxygen c o n t e n t under 10 p.p.m)  C a r r i e r gas flow 22 ml/min A i r flow  300 ml/min  H  37 ml/min  flow  1 m long  conditions  I n j e c t o r port temperature  9  O.D.,  phenols  Recorder  3.  Model : Watanabe MC  641, S e r i a l  Response  scale  1 mV  full  number 575283  Column attempted f o r c a t e c h o l a n a l y s i s Dimensions: 2 mm  I.D.,  P a c k i n g : 3% OV-17  6.4 mm  O.D.,  on chromosorb  [52,53]  1 m long  W (HP) 80/100 mesh  Operating c o n d i t i o n s Injection  port temperature  Column temperature  140°C  D e t e c t o r temperature C a r r i e r gas  300°C  300°C  He  C a r r i e r gas flow  40 ml/min  A i r flow  300 ml/min  H  40 ml/min  2  flow  Recorder Model: hp 17505 A Range 0.1-100 MV Syringe Supplier:  Unimetrics  Sample s i z e : 1 y l  T.O.C. a n a l y s i s s p e c i f i c a t i o n s Model: Beckman 915 t o t a l A n a l y z e r : Beckman 865 Operating  o r g a n i c carbon  infrared  analyzer  Conditions  Temperature  o f the t o t a l  Oxygen flow  250 ml/min  carbon channel  1000°C  Syringe Hamilton w i t h automatic  plunger  Sample s i z e 50 u l Recorder Model:  Hewlett Packard 7127A  Response: 1 mV  full  scale  Chart speed: 1 cm/min  GC/MS A n a l y s i s  specifications  Manufacturer: Model:  Hewlett-Packard  5985B (Quadropole mass  spectrometer)  F u l l y i n t e r a c t i v e data  system  HP-1000 s e r i e s Chromatographic  computer  column  Supplier:  Hewlett-Packard  Material:  Fused  Dimensions: Liquid  silica  0.32 mm  phase:  capillary  I.D. 25 metres  SE-54 ( S i l i c o n e  Operating  conditions  Injection  p o r t temperature  Temperature Carrier  long  gum)  260°C  program 30°C to 260°C a t 8°C/min  gas He  Linear v e l o c i t y :  50-80 cm/sec  Mass spectrometer c o n d i t i o n s Mode o f i o n i z a t i o n :  Electron  Ion source temperature: Electron  Impact (70 eV)  200°C  m u l t i p l i e r : 1600-2000 V  (1)  Run  (2,3,4)  time 40  Start,  stop masses 41,500 amv  (6)  A/D  (7)  T h r e s h o l d 40 min  (8)  Scan s t a r t d e l a y i  (14)  Measurements per datum p o i n t [  Ion source temperature  Solid  Probe I n l e t  Temperature  3.0]i  [202.0]  conditions  program: 30°C to 250°C a t  25°C/min  Reagents  Phenol  - loose c r y s t a l s ,  reagent grade  Matheson Coleman & B e l l p-Benzoquinone  -  Practical  Matheson Coleman & B e l l S i l v e r N i t r a t e - Fine reagent MBW  Chemicals  Sodium S u l f a t e - Anhydrous,  granular, Analytical  Mallinckrodt Sodium Hydroxide - p e l l e t s , reagent American Sulfuric  S c i e n t i f i c and. Chemical  agent - reagent A.C.S. Allied  Chemical  Buffer - Fisher S c i e n t i f i c p - c r e s o l , 0-cresol BDH Resorcinol  (2 ±  0.02)  - crystalline  L a b o r a t o r y Chemicals  - laboratory  grade  F i s h e r S c i e n t i f i c Company  <  group  grade  Catechol  - P y r o c a t e c h i n (resublimed) Fisher S c i e n t i f i c  2.3- Dimethyl 3.4- Dimethyl  phenol phenol  _  1  Company a  b  o  r  a  t  o  r  v  a  laboratory  Fisher S c i e n t i f i c  r  a  d  e  grade  Company  Magnesium S u l f a t e - Anhydrous,  powder, A n a l y t i c a l reagent  Ma 1 1 i n c k r o d t Methylene  c h l o r i d e - Dow Chemical  M e t h y l a t i n g agent  o f Canada L t d .  (Methelute)  P i e r c e Chemicals Co. Rockford Water f o r s o l u t i o n s - L a b o r a t o r y , s i n g l e d i s t i l l e d  water  APPENDIX 2  Experimental  Data  C h a r a c t e r i s t i c s f o r a l l experiments a)  Mode o f  operation:  Batch experiments u s i n g b)  undivided  cell  Cell description: Cathode: Anode:  s t a i n l e s s steel Pb0  electrodeposited Pacific  Size:  0.7  < dp  < 1.1  2  feeder  crushed and  and  Production  plate  s i z e d (obtained Co.,  from  Nevada)  mm  250  V o l u m e :  n.337 °g/c.c =  gm  5  fraction  Separation:  Pb0  Engineering  Weight:  Void  plate  e l e c t r o d e p o s i t e d on g r a p h i t e  2  Particles:  316  (e) =  two Pb0  5  ^  2  2 2  2  c  "  [54]  3  =  0.59  l a y e r s o f saran 2  particles.  screen  between c a t h o d i c  plate  and  E l e c t r o p l a t e r s tape used f o r adhesion  where n e c e s s a r y .  Group I  Anodic o x i d a t i o n o f Phenol  Group II  Anodic o x i d a t i o n o f  p-Cresol  Group I I I  Anodic o x i d a t i o n o f  0-Cresol  Group IV  Anodic o x i d a t i o n of 2,3-Xylenol  Group V  Anodic o x i d a t i o n o f 3,4-Xylenol  Group VI  Anodic o x i d a t i o n of  Resorcinol  I 106.  Group VII  Anodic o x i d a t i o n o f c a t e c h o l  Group V I I I  Anodic o x i d a t i o n o f m i x t u r e o f monohydric  Group IX  Anodic o x i d a t i o n s f o r GC/MS a n a l y s i s  phenolics of i n t e r e s t  Temperatures All  experiments were s e t up a t a temperature o f 22-24°C w i t h the use  o f heat exchanger except i n the groups  IV, V and VIII which were c a r r i e d  out a t 40-45°C.  Anodization Before each experiment the anode was t r e a t e d w i t h 20% ^ S O ^ (2.5-3.5  V o l t s ) f o r 1 hour.  a t 10 A  RUN  Electrolyte  5 g/1 0.44  Na S0 2  g/1  1 gm/1  i(A/m" )  KA)  (c .c/min)  Initial pH  770  1 .9  2  4  H S0 2  4  10  526.3  phenol  t (min)  Comment:  1-1  AV (volts)  phenol mg/l  %• o x i d i z e d  0  7.10  910  0  15  7.10  750  17.6  30  7.10  635  30.2  45  7.10  480  47.3  60  7.10  350  61 .5  75  7.10  300  67.0  90  7.10  200  78.0  105  7.10  140  84.6  120  7.10  95  89.6  The net change i n T.O.C. was p r a c t i c a l l y u n d e t e c t a b l e due to the high amount o f carbon present i n s o l u t i o n .  RUN  Electrolyte  1-2  i(A/m" )  1(A)  2  (c.c/min) 5 g/1 Na2S0  Initial pH  4  0.44 g/1 H S 0 2  4  263.2  5  719.25  1 g/1 phenol  t (min)  AV (volts)  phenol mg/l %  oxidized  0  6.15  970  0  15  6.15  875  9.8  30  6.15  750  22.7  45  6.10  670  30.9  60  6.10  595  38.7  75  6.05  533  45.1  90  6.00  432  55.5  105  6.00  330  66.0  120  6.00  291  70.0  2.16  RUN  Electrolyte  5 g/1 0.44 1 g/1  Na S0 2  g/1  1-3  (c.c/min)  Initial pH  679  2.11  i(A/m" )  1(A)  2  4  H2SO4  15  789.5  phenol  t (min)  AV (volts)  phenol mg/l %  oxidized 0  0  12.70  1010  15  12.70  805  20.3  30  12.65  545  46.0  45  11.50  480  52.5  60  11.30  350  65.4  75  11 .00  265  73.8  90  11.00  195  80.7  105  10.60  130  87.1  120  10.70  80  92.1  RUN 1-4  Electrolyte  5 g/1 N a S 0 2  1(A)  )  4> (c.c/min)  Initial pH  770  2.33  4  0.44 g/1 H S 0 2  i(A/m  4  10  526.3  0.1 g/1 phenol  AV  t (min)  (volts)  0  7.40  108  15  7.20  30  phenol mg/l % oxidized  T.O.C. mg/l % oxidized  0  84.5  0  46  57.4  82.0  3.0  6.90  12  88.9  79.0  6.0  45  6.65  2  98.2  78.0  7.0  60  6.60  0  100.0  73.5  13.0  75  6.50  72.0  14.0  90  6.50  70.3  17.0  105  6.40  69.0  18.0  120  6.40  66.0  22.0  Comment:  T.O.C. r e p o r t e d i s a c t u a l l y the t o t a l carbon because the c o n c e n t r a t i o n o f i n o r g a n i c carbon and i t s v a r i a t i o n was n e g l i g i b l e i n a l l cases.  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  0.5 g/1  t (min)  i(A/m"  )  * (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  1-5  4  10  526.3  784  2.56  phenol  AV (volts)  phenol mg/l % oxidized  T.O.C. mg/l % oxidized 555  0  31.6  535  4.0  305  55.3  525  6.0  8.40  208  69.6  520  7.0  60  8.60  168  75.4  508  9.4  75  8.65  160  76.6  498  11.4  90  8.70  168  75.4  485  14.0  105  8.70  168  75.4  475  16.0  120  8.70  168  75.4  455  18.0  0  8.40  683  15  8.35  467  30  8.40  45  0  RUN 2-1  Electrolyte  5 g/1  Na S0 2  0.44 g/1 1 g/1  Initial pH  623  2.3  2  4  H S0 2  (c.c/min)  i(A/m~ )  KA)  10  4  526.3  p-cresol  t (min)  AV (volts)  0  7.9  823  0  15  8.20  780  5.2  30  8.00  625  24.1  45  7.80  540  34.4  60  8.30  485  41 .1  75  8.15  433  47.4  90  7.50  390  52.6  105  7.70  355  56.9  120  7.50  305  62.9  mg/l  p-cresol % oxidized  113.  RUN  Electrolyte  5 g/1  Na S0 2  0.44 g/1 1 g/1  (c.c/min)  Initial PH  64.1  2.1  i(A/m" )  KA)  2  4  H S0 2  2-2  263.2  5  4  p-cresol  t (min)  AV (volts)  p-cresol mg/l % oxidized 0  0  5.40  1100  15  5.60  960  12.7  30  5.45  920  16.4  45  5.45  860  21.8  60  5.50  740  32.7  75  5.45  720  34.6  90  5.45  710  35.5  105  5.45  640  41.8  120  5.40  590  46.4  RUN  Electrolyte  2-3  i(A/m" )  KA)  2  (c.c/min) 5 g/1  Na S0 2  4  0.44 g/1 H 'S0 2  1 g/1  Initial pH  4  789.5  15  616  p-cresol  t (min)  AV (volts)  mg/l  p-cresol % oxidized 0  0  12.4  1100  15  11.6  775  29.6  30  11.1  625  43.2  45  11.1  545  50.5  60  11.0  535  51.4  75  10.9  470  57.3  90  11.0  450  59.1  105  10.8  365  66.8  120  10.8  325  70.5  2.40  115.  RUN 2 - 4  Electrolyte  5 g/1  Na S0  0 . 4 4 g/1 0.1  g/1  t (min)  2  1(A)  )  * ' (c.c/min)  Initial pH  672  1.74  4  H S0 2  i(A/m  4  10  526.3  p-cresol  AV (volts)  p-cresol mg/l % oxidized  T.O.C. mg/l % oxidized  0  8.00  69  0  72.0  0  15  7.50  40  41.3  70.2  2.5  30  7.40  26  61.6  69.3  3.8  45  7.30  19  72.5  68.4  5.0  60  7.20  15  79.0  68.1  5.4  75  7.30  11  84.8  66.7  7.4  90  7.40  9  87.0  62.9  12.6  105  7.50  8  88.4  61 .1  15.2  120  7.50  6  91 . 3  60.1  16.6  RUN 2-5  Electrolyte  5 g/1  Na S0 2  1(A)  0.5 g/1  )  * (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  i(A/m  4  10  526.3  668.5  2.36  p-cresol  t (min)  AV (volts)  p-cresol mg/l % oxidized  0  8.7  355  15  8.5  300  30  8.3  45  0  T.O.C. mg/l % oxidized 300  0  15.5  300  0  223  37.2  300  0  8.0  208  41 .4  300  0  60  7.9  193  45.6  300  0  75  7.8  168  52.7  300  0  90  7.5  140  60.6  300  0  105  7.7  125  64.8  299  0.3  120  7.6  115  67.6  292  2.7  RUN 3-1  Electrolyte  Initial  i(A/m" )  KA)  2  (c.c/min) 5 g/1  Na S0 2  0.44 g/1 1 g/1  4  H S0 2  PH  10  4  2.34  658  526.3  0-cresol  AV  t (min)  (volts)  0  9.2  853  0  15  8.6  790  7.4  30  8.0  735  13.8  45  7.9  600  29.7  60  8.0  555  34.9  75  8.0  470  44.9  90  8.0  405  52.5  105  8.0  368  56.9  120  8.0  300  64.8  mg/l  0-cresol % oxidized  RUN  Electrolyte  5 g/1  Na S0 2  '  ifA/m"*)  $ (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  1(A)  3-2  5  4  263.2  658  2.43  1 g/1 O-cresol  t (min)  AV (volts)  O-cresol mg/l % oxidized  0  6.0  995  0  15  5.9  978  1.7  30  6.0  905  9.1  45  6.0  770  22.6  60  6.0  742  25.4  75  5.9  715  28.1  90  5.9  620  37.7  105  5.9  572  42.5  120  5.9  535  46.2  RUN 3.-3  Electrolyte  5 g/1  Na S0 2  0.44 g/1 1 g/1  2  (c.c/min)  Initial PH  630  2.61  4  H S0 2  4>  i(A/m' )  1(A)  15  4  789.5  0-cresol  t (min)  AV (volts)  0-cresol mg/l % oxidized  0  11.3  905  0  15  10.0  855  5.5  30  9.5  657  25.4  45  9.3  585  35.4  60  9.1  515  43.1  75  9.0  400  55.8  90  9.0  310  65.8  105  9.0  220  75.7  120  9.1  170  81 .2  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  0.1 g/1  i(A/m~^)  <f> (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  3-4  4  10  526.3  686  2.35  O-cresol  t (min)  AV (volts)  O-cresol mg/l % oxidized  0  8.0  95  15  7.8  65  30  7.6  45  T.O.C. mg/l % oxidized 90  0  31.6  85  5.6  33  65.3  83  7.8  7.5  17  82.1  83  7.8  60  7.5  13  86.3  -  75  7.5  7  92.6  82  8.9  90  7.5  5  94.7  81  10.0  105  7.7  3  96.8  80  11.1  120  7.7  3  96.8  80  11.0  0  -  RUN 3 - 5  Electrolyte  5 g/1  Na S0  0 . 4 4 g/1 0 . 5 g/1  2  1(A)  )  <J> (c.c/min)  Initial pH  4  H S0 2  i(A/m  4  10  526.3  669  2.48  0-cresol  t (min)  AV (volts)  0-cresol mg/l % oxidized  T.O.C. mg/l % oxidized  0  8.1  505  0  570  0  15  7.7  395  21.8  545  4.39  30  7.5  320  36.6  545  4.39  45  7.3  265  47.5  545  4.39  60  7.3  238  52.9  545  4.39  75  7.2  198  60.8  545  4.39  90  7.2  165  67.3  545  4.39  105  7.2  115  77.2  528  7.37  120  7.2  88  82.6  520  8.77  RUN 4-1  Electrolyte  5 g/1  Na S0 2  1(A)  * (c.c/min)  Initial pH  784  2.54  4  0.44 g/1 H S 0 2  i(A/m~*)  4  10  526.3  1 g/1  2,3-Xylenol  t (min)  AV (volts)  0  6.5  625  15  6.6  455  30  6.8  45  2,3-Xylenol mg/l % oxidized  T.O.C. mg/l % oxidized 578  0  27.2  560  3.1  325  48.0  550  4.8  7.3  205  67.2  525  9.2  60  7.7  140  77.6  515  10.9  75  7.9  75  88.0  500  13.5  90  8.1  22  96.5  495  14.4  105  8.2  0  100.0  483  16.4  120  8.3  0  100.0  458  20.8  0  RUN  Electrolyte  5 g/1  Na S0 2  1 g/1  i(A/m~ ) £  4» (c.c/min)  Initial pH  777  2.5  4  0.44 g/1 H S 0 2  1(A)  4-2  4  5  263.2  2,3-Xylenol  t (min)  AV (volts)  2,3-Xylenol mg/l % oxidized  0  5.0  830  15  5.1  712  30  5.2  45  T.O.C. mg/l % oxidized 714  0  14.2  712  0.4  625  24.7  710  0.7  5.3  595  28.3  707  1.1  60  5.4  515  38.0  705  1 .4  75  5.5  450  45.8  702  1.8  90  5.6  375  54.8  700  2.1  105  5.7  310  62.7  695  2.8  120  5.9  260  68.7  687  3.9  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  1 g/1  i(A/m*  )  * (c.c/min)  Initial pH  791  2.58  4  0.44 g/1 H S 0 2  4-3  4  15  789.5  2,3-Xylenol  t (min)  AV (volts)  2,3-Xylenol mg/l % oxidized  0  8.6  780  15  8.9  555  30  9.7  45  0  T.O.C. mg/l % oxidized 707  0  28.9  705  0.3  380  51.3  697  1 .4  10.3  235  69.9  686  2.7  60  10.6  155  80.1  663  6.2  75  10.7  95  87.8  620  12.3  90  10.7  50  93.6  592  16.3  105  10.7  30  96.2  585  17.3  120  10.6  0  100.0  580  18.0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  1 g/1  i(A/m ) - 2  * (c.c/min)  Initial pH  791  2.36  4  0.44 g/1 H S 0 2  4-4  4  10  526.3  2,3-Xylenol  t (min)  AV (volts)  2,3-Xylenol mg/l % oxidized  0  7.0  97  15  6.8  46  30  7.0  45  T.O.C. mg/l % oxidized 73.5  0  52.6  73.5  0  24  75.8  73.5  0  7.3  15  84.5  73.5  0  60  7.4  6  93.8  73.5  0  75  7.4  0  100.0  71.3  3.1  90  7.4  0  100.0  69.0  6.1  105  7.4  0  100.0  66.0  10.2  120  7.4  0  100.0  66.0  10.2  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  4-5  i(A/m"  )  $ (c.c/min)  Initial pH  864.5  2.3  4  0.44 g/1 H S 0 2  4  10  526.3  0.5 g/1 2,3Xylenol  t (min)  AV (volts)  2,3-Xylenol mg/l % oxidized  T.O.C. mg/l % oxidized  0  7.4  380  0  251 .3  0  15  7.2  295  22.4  251 .3  0  30 '  7.9  160  57.9  251 .3  0  45  8.5  82  78.4  251.3  0  60  8.8  33  91.3  243.8  3.0  75  8.9  17  95.5  240.0  4.5  90  8.7  5  98.7  237.8  5.4  105  8.5  0  100.0  232.5  7.5  120  8.4  0  100.0  219.0  12.8  RUN 5-1  Electrolyte  5 g/1  Na S0 2  1(A)  i(A/m" )  • (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  10  4  526.3  819  2.32  1.2 g/1 3,4Xylenol  AV  t (min)  (volts)  0  5.9  1110  0  15  6.5  1025  7.7  30  6.5  900  18.9  45  6.5  825  25.7  60  6.5  785  29.3  75  6.4  690  37.8  90  6.4  655  41.0  105  6.3  623  43.9  120  6.3  600  46.0  3,4-Xylenol mg/l % oxidized  RUN 5-2  Electrolyte  5 g/1  Na S0 2  1(A)  i(A/m  )  * (c.c/min)  Initial pH  805  2.34  4  0.44 g/1 H S 0 2  5  4  263.2  1.2 g/1 3,4Xylenol  t (min)  AV (volts)  3,4-Xylenol mg/l % oxidized  0  4.4  1290  0  15  4.7  1250  3.1  30  4.8  1218  5.6  45  4.8  1140  11 .6  60  4.8  1085  15.9  75  4.8  1030  20.2  90  4.8  1000  22.5  105  4.8  965  25.2  120  4.8  915  29.1  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  5-3  i(A/ni  )  * (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  15  4  789.5  805  2.25  1.2 g/1 3,4Xylenol  t (min)  AV (volts)  3,4-Xylenol mg/l % oxidized  0  7.4  1175  15  7.8  890  24.3  30  7.7  765  34.9  45  7.6  675  42.6  60  7.6  581  50.6  75  7.6  515  56.2  90  7.6  465  60.4  105  7.6  423  64.0  120  7.5  395  66.4  0  RUN  Electrolyte  5 g/1 N a S 0 2  0.44 g/1  1(A)  H S0 2  i(A/m" )  10  4  5-4  526.3  cf) (c.c/min)  Initial pH  819  2.33  4  0.1 g/1 3,4Xylenol  AV  3,4-Xylenol mg/l % oxidized  t (min)  (volts)  0  6.6  103  15  6.3  67  35.4  30  6.3  48  53.9  45  6.4  33  68.0  60  6.4  27  73.8  75  6.4  22  79.1  90  6.4  19  81.6  105  6.4  17  83.8  120  6.3  14  86.9  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  5-5  i(A/m" ) 2  * (c.c/min)  Initial pH  784  2.32  4  0.44 g/1 H S 0 2  10  4  526.3  0.5 g/1 3,4Xylenol  t (min)  AV (volts)  3,4-Xylenol mg/l % oxidized  0  6.6  515  15  6.4  393  23.7  30  6.2  290  43.7  45  6.1  230  55.3  60  6.1  196  61.9  75  6.1  165  68.0  90  6.0  143  72.2  105  5.9  130  74.8  120  6.0  108  79.0  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  1 g/1  i(A/m"*)  * (c.c/min)  Initial pH  805  2.16  4  0.44 g/1 H S 0 2  6-1  4  10  526.3  Resorcinol  t (min)  AV (volts)  Resorcinol mg/l % oxidized  T.O.C. mg/l % oxidized  0  7.4  1200  0  725  0  15  7.2  1130  5.8  715  1.4  30  7.2  970  19.2  665  8.3  45  7.0  855  28.8  660  9.0  60  7.0  695  42.1  653  9.9  75  7.0  635  47.1  635  12.4  90  7.0  545  54.6  625  13.8  105  6.9  420  65.0  625  13.8  120  6.7  380  68.3  625  13.8  RUN 6-2  Electrolyte 5 g/1 Na S0 2  i(A/m" )  < J > (c.c/min)  5  263.2  763  2  Initial pH  4  0.44 g/1 H S0 2  1(A)  4  2.3  1 g/1 Resorcinol  t (min)  AV (volts)  0  5.5  1230  0  750  0  15  5.5  1190  3.3 -  750  0  30  5.4  1150  6.5  700  6.7  45  5.3  1105  10.2  700  6.7  60  5.3  1000  18.7  700  6.7  75  5.3  980  20.3  675  10.0  90  5.2  930  24.4  675  10.0  105  5.3  855  30.5  658  12.3  120  5.2  810  34.2  658  12.3  Resorcinol mg/l % oxidized  T.O.C. mg/l % oxidized  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  1 g/1  t (min)  i(A/m  )  * (c.c/min)  Initial pH  4  0.44 g/1 H S 0 2  6-3  4  15  789.5  784  2.23  Resorcinol  AV (volts)  Resorcinol mg/l % oxidized  T.O.C. mg/l % oxidized 715  0  11.2  715  0  890  26.1  670  6.3  9.3  755  37.3  640  10.5  60  9.0  650  46.1  635  11.2  75  9.3  510  57.7  630  11.9  90  9.4  425  64.7  615  14.0  105  9.5  310  74.3  578  19.2  120  9.7  200  83.4  585  18.2  0  10.8  1205  15  9.9  1070  30  9.3  45  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  i(A/m~ )  * (c.c/min)  £  Initial pH  4  0.44 g/1 H S 0 2  6-4  4  0.1 g/1 R e s o r c i n o l  10 /  526.3  816  2.59  /• —  t (min)  AV (volts)  Resorcinol mg/l % oxidized  0  8.2  87  15  8.0  40  54.0  55  14.5  30  7.8  0  100.0  52  20.6  45  7.7  0  100.0  47  28.2  60  8.0  0  100.0  41  37.4  75  8.5  0  100.0  37  44.3  90  8.8  0  100.0  33  49.9  105  9.0  0  100.0  31  52.7  120  9.0  0  100.0  ' 26  61.1  0  T.O.C. mg/l % oxidized 66  0  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  i(A/m~ )  <f> (c.c/min)  Initial pH  10  526.3  798  1.45  4  0.44 g/1 H S 0 2  6-5  4  0.5 g/1 Resorcinol  t (min)  AV (volts)  Resorcinol mg/l % oxidized  0  3.4  490  15  3.5  285  41 .8  330  12.5  30  3.5  145  70.4  308  18.3  45  3.5  20  95.9  288  23.6  60  3.5  0  100.0  267  29.2  75  3.5  0  100.0  245  35.0  90  3.5  0  100.0  245  35.0  105  3.5  0  100.0  255  32.4  120  3.5  0  100.0  230  39.0  0  T.O.C. mg/l % oxidized 377  0  RUN 7-1  Electrolyte  5 g/1  Na S0 2  Initial pH  798  2.39  2  4  0.44 g/1 H S 0 2  (c.c/min)  i(A/m' )  KA)  10  4  526.3  1 g/1 Catechol  Comment:  T.O.C. mg/l % oxidized  t (min)  AV (volts)  0  5.3  800  0  15  6.5  755  5.6  30  6.6  635  20.6  45  6.5  575  28.1  60  6.5  515  35.6  75  6.4  468  41.5  90  6.3  400  50.0  105  6.2  410  48.8  120  6.2  435  45.6  A l l the samples were c e n t r i f u g e d and T.O.C. a n a l y s i s was performed on the c e n t r i f u g a t e i n the case o f c a t e c h o l runs.  138.  RUN 7-2  Electrolyte  5 g/1 N a S 0 2  Ini t i a l PH  823  2.34  2  4  0.44 g/1 H S 0 2  (c.c/min)  i(A/m~ )  KA)  263.2  5  4  1 g/1 Catechol  t (min)  AV (volts)  T.O.C. mg/l %  oxidized  0  3.8  720  0  15  4.3  705  2.1  30  4.5  635  11.8  45  4.6  570  20.8  60  4.6  535  25.7  75  4.5  495  31.3  90  4.5  455  36.8  105  4.4  410  43.1  120  4.4  390  45.8  RUN  Electrolyte  5 g/1 N a S 0 2  0.44 g/1  1(A)  i(A/min~^)  15  4  H S0 2  7-3  789.5  * (c.c/min)  Initial pH  840  2.30  4  1 g/1 Catechol  T.O.C. mg/l %  t (min)  AV (volts)  0  6.9  535  15  7.2  463  13.5  30  7.4  410  23.4  45  7.3  365  31 .8  60  7.2  343  35.9  75  7.1  318  40.6  90  7.1  308  42.4  105  7.0  263  50.8  120  7.0  270  49.5  oxidized 0  14:0.  RUN 7-4  Electrolyte  5 g/1 N a S 0 2  Initial PH  84.4  2.34  2  4  0.44 g/1 H S 0 2  (c.c/min)  i(A/m~ )  1(A)  10  4  526.3  0.1 g/1 Catechol  t (min)  AV (volts)  T.O.C. mg/l %  0  5.8  84  0  15  5.9  78  7.1  30  5.9  75  10.7  45  5.9  69  18.5  60  5.9  65  22.6  75  5.9  60  28.6  90  5.8  46  45.2  105  5.8  43  48.8  120  5.8  39  53.6  oxidized  RUN  Electrolyte  5 g/1  Na S0 2  1(A)  i(A/m" ) 2  * (c.c/min)  Initial pH  833  2.52  4  0.44 g/1 H S 0 2  7-5  10  4  526.3  0.5 g/1 C a t e c h o l  T.O.C. % oxidized  t (min)  (volts)  0  5.5  335  15  5.8  295  11.9  30  5.9  255  23.9  45  5.8  200  40.3  60  5.7  180  46.3  75  5.7  175  47.8  90  5.6  160  52.2  105  5.6  155  53.7  120  5.6  125  62.7  AV  mg/l  0  142.  B.O.D. A n a l y s i s  B.O.D. A n a l y s i s  (Runs 7-2, 7-3)  r e s u l t s Run 7-2 (5 amps)  B.O.D. (5 days a t 20°C) ppm: Initial Final  sample  ( t = 0 min)  930  sample ( t = 120 min)  240  % Reduction i n B.O.D.  B.O.D. A n a l y s i s  74  r e s u l t s Run 7-3 (15 amps)  B.O.D. (5 days a t 20°C) ppm: Initial Final  sample ( t = 0 min)  600  sample ( t = 120 min)  117  % Reduction i n B.O.D.  81  143.  C.O.D. A n a l y s i s  (Runs 7-2, 7-3)  .(mg/D  23.90  2.85  2103.3  10  21.05  5.70  2103.3  20  24.70  2.05  1512.9  10  23.00  3.75  1383.8  Dilution ( i f any)  I n i t i a l sample (run 7-2) ( t = 0 min)  20  F i n a l sample (run 7-2) ( t = 120 min)  Titre-FAS (m.l)  C.O.D.  Blank-Sample (m.l)  Sample D e s c r i p t i o n  Average C.O.D. mg/l  2103.3  1448.3  % Reduction i n C.O.D. 31 .1  I n i t i a l sample (run 7-3) ( t = 0 min)  F i n a l sample (run 7-3) (t = 120 min)  20  24.30  2.45  1884.5  10  22.25  4.50  1660.5  20  25.4  1 .35  996.3  10  24.3  2.45  904.1  1772.5  950.2  % Reduction i n C.O.D. 46 .4  144.  COMPARISON OF PERFORMANCE OF DIFFERENT PHENOLICS 1. Variation of final % oxidized with initial concentration of phenolics at 10 A 2. Variation of initial rate with initial concentration at 10 A 3.  Variation of final % oxidized with applied current (1 g/1 runs)  4. Variation of initial rate of oxidation with applied current (1 g/1 runs)  Name of Compound Phenol  O-Cresol  p-Cresol  Resorcinol  2,3-Xylenol  3,4-Xylenol  Final % oxidized  Initial cone, Initial cone. Initial rate Initial rate mole/m3 x 106 ppm/min ppm g.mol/sec x 10°  100.0  108  1.15  75.4  683  7.26  14.40  89.6  910  9.67  10.67  96.8  95  0.88  2.00  1 .54  82.6  505  4.68  7.33  5.66  64.8  853  7.90  4.20  3.24  69  0.64  1 .93  1 .47  91 .3  4.13  3.66 12.75 9.45  67.6  355  3.29  3.67  2.83  62.9  823  7.62  2.87  2.21  100.0  87  0.78  2.90  2.20  100.0  490  4.45  11 .50  8.70  68.3  1200  7.67  5.81  100.0  97  0.80  3.40  2.32  100.0  380  3.12  5.67  3.87  100.0  625  5.12  11 .33  7.74  86.9  103  0.84  2.40  1 .66  79.0  515  4.22  8.13  5.55  9.10  5.67  3.87  46.0  mo  10.90  Note: Similar data could not be obtained from catechol runs because concentrations of catechol samples were not determined. ./cont'd  145.  COMPARISON OF PERFORMANCE OF DIFFERENT PHENOLICS/cont d 1  Applied current (Amps)  Name o f Compound  Phenol  O-Cresol  p-Cresol  Resorcinol  2,3-Xylenol  3,4-Xylenol  Note:  %  cases.  I n i t i a l rate ppm/mi n  I n i t i a l rate g.mol/sec x 10°  5  70.0  6.33  5.61  10  89.6  10.67  9.45  15  92.1  13.67  12.11  5  46.2  3.00  2.32  10  62.9  3.93  3.03  15  81 .2  7.67  5.92  5  46.4  6.00  4.63  10  50.0  6.60  5.09  15  70.5  15.83  12.21  5  34.2  2.78  2.10  10  68.3  7.67  5.81  15  83.4  10.00  7.57  5  68.7  7.87  5.38  10  100.0  11 .33  7.74  15  100.0  15.00  5  29.1  2.40  1 .64  10  46.0  7.00  4.78  15  66.4  13.67  9.34  The r a t e s were determined all  Fi na 1 oxidized  from t h e l i n e a r  10.25  p o r t i o n o f the curves i n  RUN 8-1  Electrolyte  0.16  g/1  p-Cresol  0.44  5 g/1  g/1  Na S0  H S0  0.20  g/1  2,3-Xylenol  1.37  g/1  phenol 0.17  g/1  0.28  g/1  0-cresol  2  4  2  4  1(A)  i(A/m" )  10  526.3  2  $ c.c/min  Initial pH  823  2.48  3,4-Xylenol ^  t (min)  AV (volts)  mg/l 1250  0  248  0  122  0  5.5 5.6  1190  4.8  240  3.2  116  15  1110  11.2  234  5.7  998  20.2  208  6.0  850  32.0  6.0  798  90  * oxidized  mg/l  % oxidized  mg/l  3,4-Xylenol  2,3-Xylenol  p-Cresol  0-Cresol  Phenol  % oxidized  mg/l  % oxidized  mg/l  * oxidized  Total mg/l  Total * oxidized  137  0  139  0  1896  0  131  4.6  131  5.8  1808  4.6  4.9  9.5  139  0  9.2  5.7  124  1722  115  16.1  139  17.2  9.8  115  1570  110  0  16.1  28.5  28.3  17.2  98  1359  101  7.2  27.0  129  181  31.1  19.7  97  1306  98  3.6  27.8  134  179  29.2  36.2  1232  35.0  6.0  101  17.2  9.4  32.7  126  167  32.1  40.4  93  745  1161  38.8  101  17.2  3.6  105  36.3  134  158  34.3  678  45.8  90  6.0  1088  42.6  98  19.7  3.6  120  38.7  134  152  35.0  615  50.8  89  6.0  30 45 60 75  5.8 5.9  0  RUN 8-2  Electrolyte  5 g/1  Na S0 2  4  0.44  g/1 H S 0  1.33  g/1  phenol  0.30  g/1  O-cresol  2  4  0.18  g/1  p-cresol  0.16  g/1  2,3-Xylenol  0.17  g/1  3,4-Xylenol  Phenol  t (min)  I (A)  (volts)  mg/l  cd. (A/m" ) 2  10  526.3  0-cresol  % oxidized  mg/l  Average flow rate c.c/min  793  2.36  P- Cresol  % oxidized  mg/1  Initial pH  2,3-Xylenol  % oxidized  mg/l  3,4-Xylenol  % oxidized  mg/1  Total  Total  % oxidized  mg/l  % oxidized  .1889  0  0  5.2  1200  0  291  0  143  0  124  0  131  0  15  5.5  1093  8.9  269  7.6  137  4 .2  117  5 .7  130  0.8  1746  7.6  30  5.7  948  21 .0  240  17.5  120  16 1  103  16 9  116  11 .5  1527  19.2  45  5.8  898  25.2  238  18.2  121  15 4  103  16 .9  128  2.3  1488  21.2  60  5.8  840  30.0  220  24.4  116  18 9  99  20 2  125  4.6  1401  25.8  75  5.8  735  38.8  212  27.2  114  20 3  95  23 4  123  6.1  1279  32.3  90  5.9  700  41.7  208  28.5  116  18 9  99  20 2  131  0  1254  33.6  105  5.9  605  49.6  184  36.8  108  24 5  87  29 8  123  6.1  1107  41.4  120  5.9  520  56.7  164  43.6  102  28 7  82  33 9  124  5.3  992  47.5  135  5.9  475  60.4  157  46.1  102  28 7  80  35 5  126  3.8  941  150  50.2  5.9  400  66.7  143  50.9  99  30 8  76  38 7  128  2.8  846  55.2  165  5.9  350  70.8  126  56.7  93  35 0  73  41 1  130  0.8  773  59.1  180  5.9  305  74.6  111  61.9  88  38 5  67  46 0  119  9.2  690  63.5  RUN 8-3  Electrolyte  5 g/1 Na ,so 4 0.44  g/1  H S0  1.14  g/1 phenol  0.27  g/1 O - c r e s o l  t  AV  2  4  0.14  g/1 p-cresol  0.14  g/1 2,3-Xylenol  0.14  g/1 3,4-Xylenol  (volts)  mg/l  0  5.2  1070  (A/m" )  10  526.3  2  % oxidized 0  mg/l 246  Average flow rate c.c/min  % oxidized 0  mg/1 127  Initial pH  2.38  794.5  3,4-Xylenol  2,3-Xylenol  P- Cresol  0-Cresol  Phenol  (min)  I (A)  % oxidized 0  mg/l 109  % oxidized 0  mg/l 122  Total  Total  % oxidized  mg/l  % oxidized  0  1674  0 6.0  101  7.3  112  8.2  1573  1.6  99  9.2  117  4.1  1534  8.4  123  3.2  104  4.6  122  0  1451  13.3  22.0  103  18.9  96  11.9  114  6.6  1240  25.9  154  37.4  90  29.1  83  23.9  101  17.2  1013  39.5  47.4  143  41 .9  90  29.1  88  19.3  118  3.3  1002  40.l'  520  51.4  140  43.1  80  37.0  80  26.6  97  20.5  917  45.2  428  60.0  118  52.0  79  37.8  70  35.8  106  13.1  801  52.2  15  5.4  1005  6.1  228  7.3  127  0  30  5.5  970  9.4  223  9.4  125  45  5.6  885  17.3  217  11 .8  60  5.7  735  31 .3  192  75  5.8  593  44.6  90  5.8  563  105  5.8  120  5.8  .cont'd  RUN 8 - 3 / c o n t ' d  &V  t  1  1 i j  j j  % oxidized  mg/l  % oxidized  mg/1  mg/1  3,4-Xylenol  2,3-Xylenol  P- Cresol  0- Cresol  Phenol  % oxidized  t oxidized  mg/l  mg/l  % oxidized  Total mg/l  Total % oxidizt  (min)  (volts)  61.8  73  42.5  62  13.1  60.2  69.0  94  667  332  106  5.8  43.1  135  69.1  65  48.8  55  49.5  67.2  76  549  75.7  23.8  5.7  260  93  150  72.0  60  52.8  50  54.1  72.0  69  468  81.5  25.4  5.7  198  91  165  75.2  52  59.1  39  64.2  77.5  61  377  86.7  32.0  5.6  142  83  180  48  62.2  35  67.9  82.3  36  85.4  297  91.1  32.0  5.6  95  83  195  91.5  42  66.9  25  77.1  85.8  21  238  92.7  41 .0  5.6  78  72  210  92.7  39  69.3  21  80.7  87.9  18  203  94.9  42.6  5.6  55  70  225  96.3  38  70.1  14  90.6  9  158  96.0  55.7  43  54  5.6  87.2  240  97.2  34  73.2  12  89.0  91 .8  7  137  97.4  54.1  5.6  28  56  255  98.4  29  77.2  9  94.2  4  97  99.1  63.1  10  45  5.6  91.7  270  28  78.0  7  93.6  95.0  0  100.0  83  100.0  60.7  5.6  0  48  285  24  81.1  4  95.8  0  100.0  71  100.0  65.2  0  43  5.6  96.3  300 1  —  ;  i  j  i  I  j  i  •  j  i  <JZ>  150.  T.O.C. A n a l y s i s r e s u l t s , Run 8-3  T.O.C. % oxidized  t (min)  mg/l  0  1480  0  60  1380  6.8  120  1320  10.8  180  1290  12.8  240  1260  14.9  300  1160  21 .6  B.O.D. A n a l y s i s r e s u l t s , Run 8-3  B.O.D. (5 days a t 20°C) ppm: Initial Final  sample(t = 0 min)  sample  % Reduction  27.83  ( t = 300 min) 1210 i n B.O.D.  56.52  15.1  C.O.D. A n a l y s i s r e s u l t s , Run 8-3  Sample  Description  I n i t i a l sample ( t = 0 min)  F i n a l Sample ( t = 300 min)  Dilution ( i f any)  Titre-FAS (m.l)  10  14.20  Blank-Samp!e (m.l)  C.O.D. (mg/l)  11 .20  4310  Average C.O.D. mg/l  4291 10  14.30  11.10  4271  10  16.20  9.20  3540  10  15.40  9.00  3463  3502  % Reduction i n C.O.D.  18.4  RUN  Electrolyte  5 g/1 0.44  Na S0 2  g/1  1 gm/1  9-1  i(A/m" )  KA)  (c . c / m i n )  Initial pH  760  2.34  2  4  H S0 2  10  4  526.3  Phenol  t (min)  AV (volts)  mg/l  phenol % oxidized  0  5.60  975  0  15  5.65  850  12.8  30  5.60  675  30.8  45  5.60  565  42.1  60  5.60  390  60.0  75  5.65  305  68.7  90  5.75  200  79.5  105  5.75  145  85.1  120  5.75  105  89.2  153.  Other p h e n o l i c runs 1 g/1, i = 526.3 A/m  Run No.  Name o f phenolic compound (and i n i t i a l pH)  Initial voltage  f o r GC/Ms a n a l y s i s r u n s , 2 hours' o x i d a t i o n  Final voltage vol t s  dp c.c/min  Comments  9-2  O-Cresol (2.35)  6.2  6.55  826  Foaming-increasing as o x i d a t i o n proceeded.  9-3  p-Cresol (2.38)  6.15  6.25  812  Foaming-increasing as o x i d a t i o n proceeded.  9-4  2.3- Xylenol (2.31)  5.85  9.35  777  E x c e s s i v e foaming, s o l u t i o n turned y e l l o w .  9-5  3.4- Xylenol (2.34)  6.05  6.15  847  9-6  Resorcinol (2.39)  6.10  6.35  819  C l e a r , pale brown solution obtained.  9-7  Catechol (2.40)  5.75  6.5  840  Vigorous r e a c t i o n , s o l u t i o n turned deep y e l l o w , brown and black i n 15 mins, foaming a s s o c i a t e d with f o r m a t i o n o f black p r e c i p i t a t e .  9-8  Phenol-9gms 0-Cresol-2gms p-Cresol-1gm 5.35 2.3- X y l e n o l 1 gm 3.4- Xylenol l gm (2.3)  5.85  630  S o l u t i o n turned pale y e l l o w with s l i g h t foaming towards the end.  ^KEEHIPHENOL Hilt-jig  OXIDRTION  (SAMPLE' " I " Q5008 |  11;  msaa  0.5 UL S E - 5 4 ) D500S  5003  PHENOL OH  "-  r  r  r  •" i -  f"  7512 P-EEN20QUIN0NE :-l}07.7 108.6 R=264.52 . HYi'ROQU I NONE O H  CATECHOL OH -OH  OH  X. iniffir»iiT4nn 17895:]  n  80  1  1  1  i  1  159  236  316  395  474  F i g . 35  1  r  5 5 4 i-l-:  -i  GC/MS a n a l y s i s o f f i n a l o x i d a t i o n (run 9-1)  Area T a b l e E n t r i e s :  1  'IB  79 0  T  S69  r —i 948  product from  phenol  %  FRN 5008  Time  Mass  Area  1  4.8  94.0  4793.  12.6  2  3.6  108.0  26452.  69.5  3  8.8  110.0  2660.  7.0  4  10.1  110.0  4131.  10.9  Entry  r  1 O £ 8 11 0 7  >-CRESOL  OXIDATION  (FINfiL  SRMPLE)  SE-54  pgatl  2UL  5804  M E T H Y L H Y D R O Q U I N O N E OR 4-HYDR0XY-4-METHYL -2,S-CYCLOHEXflDINENE-1-ONE  234  F i g . 36  934  467  1335  362 18  1629  GC/MS a n a l y s i s o f f i n a l o x i d a t i o n (run 9-3)  Area Table E n t r i e s : Entry  11&S  2696  2329  2563  product from  FRN 5004  Time  Mass  Area  1  6.9  124.0  14282.  2  6.5  108.0  76352.  %' 15.8 -  84.2  2?96  3W3U  p-cresol  P-CRESOL  OXIDATION  100-,  ( F I N O L SAMPLE)  S E - 5 4 2UL  11381  I 4 - M E T H Y L - 2 , 5 - C V C L 0 H E X H D IE N E - 1 - 9 H E 1 09  60  57  si  6. y a 46 H  71 124  153  Lu_  1 a9  F i g . 37  126  140  Mass spectrum showing the presence of 4-Hydroxy-4-Methyl2,5-Cyclohexadiene-l -one -  5884  •MaaaaO-CRESOL •5W5M30  -  OXIDPTION 8C/MIN  260  ( S E - 5 4 2UL)  HJJ;I  sues  1387 0-CRESOL 10 7. 7 108.6 Bp  5103.  —i  1 1 1 —i 1 1 1 METHYL BEHZOQUI NONE ( 2 , E.-CYCLOHEXHli I EHE- 1 , 4-D I ONE , 2-METHYL )  r  1 157 METHYL HYDR0QUIH0NE OR 4-HYDR0XY-4-METHYL - C Y C L 0 H E XfiD I E H E - 1 - 0 N E  M430  ,H  •"'  20Q  1  1  401  601  F i g . 38  ~  T  801'  n  1802  1 1202  1 1402  1 1603  U  1 1998  1 2198  n—  2398  GC/MS a n a l y s i s o f f i n a l product from o - c r e s o l o x i d a t i o n (run 9-2)  Area t a b l e e n t r i e s : FRN 5005 Time  Mass  Area  %  1  6.0  108.0  5103  11.17  2  5.1  122.0  31879  69.80  3  11.2  124.0  8687  19.02  Entry  158.  •a3aM2 . 3  XYLENOL  (2UL  •Jan  SE-54)  see?  2 ,3-XYLENOL  3236  1  1  1  "i"  1.  1  1  2,3-D I METHYL  ;135.7 .136:6  -1  r  1  1  r  BENZOQUINONE  1 264 4 - H Y D R 0 X Y - 2 , 4 - D IM E T H Y L 2,5-C Y C L 0 H E X fi It I E H E - 1 - 0N1  347  —1— 129  r-  i  172  215  Fig.  39  i  259  1  1  1  1  1  361  345  387  429  473  1 559  1  1  6Ui  FRN  5007 Area  1  645 fcB'd  GC/MS a n a l y s i s o f f i n a l product from 2,3-Xylenol o x i d a t i o n (run 9-4)  Area t a b l e e n t r i e s : Entry  1  516  Time  Mass  %  1  8.2  122.0  7423.  17.59  2  7.0  136.0  33709.  79.82  3  12.8  138.0  1021.  2.59  1  •HgnS3,4XYLEN0L OXIDATION  EH2Q  (2UL SE-54)  5886  4-HYDR0XY-2,4-DIMETHYL-2, 5-CYCLOHEXSDIENE-1-ONE  1248 ,  137.7 138.6  0=14121  -|  1  1  1  1  n  i  i  r  1  1  1  3,4-«YLEN0L  0=497.49. 80728  fi  u  -i 1 •-: 1  "i—  1  261  38ft  1  1  r—"—i  1  519  AR0  780  1042 1 169 1299 1430 1561 lfeyii  911  V  F i g . ,40; GC/MS a n a l y s i s o f f i n a l product from 3,4-Xylenol o x i d a t i o n (run 9-5) Area  table entries:  FRN 5006  Time  Mass  Area  c lo  1  9.6  138.0  14121.  22 .11  2  8.6  122.0  49749.  79 .89  Entry  r  TRACE  AMOUNT  OF  2 , 3-D I M E T H Y L - H Y D R O Q U I HONE  135  OR  ISOMER  91  54  104  117 65  1  1  ''  i' " 50  41  60  70  3S  •aa  188  I  1 1  " I " ' 1  1  116  MS c o n f i r m a t i o n o f t r a c e s o f 2,3-Dimethyl  hydroquinone  16.1  Fig.  42  GC/MS a n a l y s i s / o f , . f i n a l and  Xylenols  (run  product  of  oxidation  9-8)  of  mixture  :  PHENOL ,CRESOLS AND XYLENOLS OXIDATION (2UL S E - 5 4 ) •-.)Pt»a39-269 8 C M I N 4^y»i<»*,4-r1ETrtYL-2,S-CYCL0HEXADIENE-l-0NE  123.. > 124". 6  1  METHYL | BENZO I QUINONE fl  CATECHOL AND HYDROQUINONE  j|  2 , 3 AND 3 , 4 XYLENOLS DIOCTYL SEBACATE | INTERFERENCE ION  | DIMETHY HYDROQUINONE OR ISOMER 1  2,3-D IMETHY BENZOQUI NONE OR ISOMER *P-BENZOQUINONE  ' P AND 3-CRESOLS ti.  1  PHENOL  2 33  466  HREA  700  9 33  THELE  1166 1399 1632 1365 209? 2332 2565 2793 30 31  ENTRIES:  5003  Mass.  Ti me  Ent ry  FRN  OMPOUNDS : OH OH  6  OH  <§> &  •2  11 . 1 .<y  9311. 31376. 17290. 16670. 30741.  •J  1 1. 2 6. 2 5. ii 3 .  OH  OH  CH; CH  CH,  :  CH,  CH,  OXIDATION  1.. 0 1 3. 4 5. 7. 9 4. 7  29 17. 37563. 14724. 22154. 13130. 31433.  124.0 7.0 110. 0 10.2 110.0 3.7 3 122. 0 5. 1 4 122. 0 3.2 5 122. 0 3.5 6 1 33. 0 9.3 7 136. 0 7.3 3 103. 0 3. 4 9 103. 0 6.4 10 103.0 6. 0 1 1 94.0 4.9 12 C f l L C U L f l T E y. DM E N T R Y t*: 1  PRODUCTS  <? 0  0  • • 0  0,  0  0  108  122  136  0 CH, HO CH  o r OH  J  138  3  OH  OH  OH  138  110  Art  OH . . 0  110  124  OH  124  I  162.  APPENDIX 3  Mathematical  In t h i s study, a m u l t i p l e - p a s s  Model  system  (5 1) o f s o l u t i o n c i r c u l a t e d c o n t i n u o u s l y c o n d i t i o n s , i f the packed  i s used i n a f i x e d  through the bed.  volume  Under these  bed e l e c t r o d e i s connected to a r e s e r v o i r  c o n t a i n i n g s o l u t i o n o f volume V , the c o n c e n t r a t i o n  o f the p h e n o l i c  compound d e c r e a s e s w i t h the time o f e l e c t r o - o x i d a t i o n .  (+)  (-)  Flow  rate = N  Volume = V  Fig.A-1  Schematic r e p r e s e n t a t i o n o f a m u l t i p l e pass system .  At any i n s t a n t , the i n l e t c o n c e n t r a t i o n tration  i s Co."  As approached  conditions.C-j and C  2  C  2  r  r  is  and the o u t l e t concen-  by P i c k e t t Ref. 10, p. 178, f o r i d e a l  limiting  can be r e l a t e d as f o l l o w s  k r  m  ~„r,  /  = C| [ exp (  A . IT)  Hll  n \ , ) ]  (A.l)  The a n o d i c o x i d a t i o n o f the p h e n o l i c compound can be c o n t r o l l e d by  163  mass t r a n s f e r mathematical would and  model when t h e  reaction.  reaction  is  the e l e c t r o c h e m i c a l  a. mass t r a n s f e r  c o n t r o l l e d model  CQ a s  phenol c o n c e n t r a t i o n  Eq.  ?  =  C  exp [{  N  exp -  has been t r e a t e d  * t  , C  31  2  potential  Hence  here.  c a n be r e l a t e d  to  the  follows  (  A . 2 c a n be s i m p l i f i e d  vary too.  a  process  v a r y the e l e c t r o d e  2  k aL C  obtain  by t h e l a t t e r  reaction constant w i l l  F o l l o w i n g t h e a p p r o a c h made by S u c r e initial  An a t t e m p t t o  controlled  be v e r y c o m p l i c a t e d b e c a u s e a s C-j and C  kr,  only  or the e l e c t r o c h e m i c a l  .  ) -  by u s i n g t h e  k aL  f  1 }  • ]  following  '  (A.2)  substitutions  t = — = dimensionless time m k aL  Q  =vr^—  X  CQ - Cp = -^p = fractional 0  conversion  = 1 - exp [{exp  1}  = d i m e n s i o n l e s s mass t r a n s f e r  group  L  whence: X  E s t i m a t i o n o f mass t r a n s f e r Due  to  the l a c k of  under the c o n d i t i o n s of  (-Q)  It of  -  Q]  proper c o r r e l a t i o n s the  0 - 5 6  has been r e p o r t e d  regularly  t*  coefficient.  present  Stanmore u s i n g a s i n g l e l a y e r  Sh = 0 . 8 3 R e  -  Sc  mass t r a n s f e r  0  ,  3  coefficients  t h e a p p r o a c h made by P i c k e t t  p a c k e d bed e l e c t r o d e  [10]  packed e l e c t r o d e  study,  for  has been u s e d  [46],  3  (A.3)  t h a t d a t a by S t a n m o r e on a d o u b l e  layer  indicated  that values of  k  m  obtained  were  and  164.  about 20-25% lower than t h a t given by eq. A.3.  Thus c a l c u l a t i o n s  were  based on the equation  Sh = a R e " 0  5 6  Sc " 0  3 3  (A.4)  with upper and lower bounds o f a = 0.66 and a = 0.62 r e s p e c t i v e l y . sample c a l c u l a t i o n i s given below.  A  165.  Calculation  of theoretical  f r a c t i o n a l conversion  S p e c i f i c s u r f a c e area  5=  i f mass t r a n s f e r  controls  o f t h e bed,  0.59 (Appendix 2)  Assume § = 0.75 [54] -  J_ 0.3  a  +  = 9.41  Superficial  u =  6(1 - 0.59) 0.75 x 0.09  cm  - 1  v e l o c i t y o f the l i q u i d ,  1 mi n 60 sec  0.8 1/tnin 5 1 x 0.3 cm  =8.89 cm/s  D  2,3-Xylenol  D resorcinol  = 7.0 x 10  cm /s  6  = 8.3 x 1 0 "  2  6  cm /s 2  [Table V]  [Table V]  (see S e c t i o n 2,i Appendix 4 f o r c a l c u l a t i o n o f d i f f u s i v i t y  values)  166.  Re = ^J2.  =  8.89 cm/s x 0.09 cm _  v  8  Q  0:01 cm /s 2  c o n s i d e r group-4  s  v •  =  c  U  0-01 cm /s 2  7.0 x 1 0 '  =  1  4  2  g  cm /s  b  2  expanding eq. A.4,  k dp  n  .  0.56  r ^dp ,  - n aa  m  = o.66 x - ° * 0 9 ~ 7  k m  Q  3  V  x 80 '  6  0  0  = 6.61 x 1 0 "  0.33 r  x 1429 "  5 6  0  3 3  cm/s  The lower l i m i t o f k i s obtained m  from eq. A.5 as f o l l o w s  k  1429 "  m  = 0.62 x  7  -°  nQ°" 0.09 X  x SO '  6  0  n  5 6  x  0  3 3  = 6.19 x 1 0 " cm/s 3  Therefore  k ranges from 6.61 x 10 m °  -3  -3 cm/s t o 6.19 x 10 cm/s  k aL k 9.41 cm" 38 cm _ m _ JTJ u 8.89 cm/s 1  n 4  The extreme  Q  1  Q  2  = 0.25 = 0.27  v a l u e s o f Q would  t h e r e f o r e be  167.  The  2,3-Xylenol  f r a c t i o n c o n v e r s i o n f o r mass t r a n s f e r  i s g i v e n by  X = 1 - exp [{exp (-Q) -1 } t * - Q ]  **  =  t  =  m  m  5 1 Q i 0.8 1/rmn  =  N  m  The control  t 7 t  6.250  mm  range o f t h e o r e t i c a l  f r a c t i o n a l c o n v e r s i o n f o r mass  transfer  a t v a r i o u s time i n t e r v a l s are shown i n Table A - l .  TABLE A - l T h e o r e t i c a l 2,3-Xylenol f r a c t i o n a l c o n v e r s i o n vs time f o r a mass t r a n s f e r c o n t r o l l e d batch system  t(min)  t  l  x2  0  0.22  0.24  15  2.4  0.54  0.57  30  4.8  0.73  0.76  45  7.2  0.84  0.86  60  9.6  0.91  0.92  75  12.0  0.94  0.96  90  14.4  0.97  0.98  105  16.8  0.98  0.99  120  19.2  0.99  0.99  0  X  168.  S i m i l a r treatment f o r group 6 experiments  Sc=  °^ 8.3 x 10 0 1  C  m  S  k = 9.25 x 1 0 " m  Q  1  = 0.28  Q  2  = 0.30  :  , cm /s  =  2  3  1  2  0  4  cm/s  The r e s o r c i n o l f r a c t i o n a l c o n v e r s i o n f o r mass t r a n s f e r c o n t r o l i s shown i n Table A-2.  TABLE A-2 T h e o r e t i c a l r e s o r c i n o l f r a c t i o n a l c o n v e r s i o n vs time f o r a mass t r a n s f e r c o n t r o l l e d batch system  t(min)  t  *  X  l  X  2  0  0.24  0.26  15  2.4  0.58  0.60  30  4.8  0.76  0.79  45  7.2  0.87  0.89  60  9.6  0.92  0.94  75  12.0  0.96  0.97  90  14.4  0.98  0.98  105  16.8  0.99  0.99  120  19.2  0.99  0.99  0  169.  APPENDIX 4  Calculations  1.  C . O . D . a n a l y s i s - sample c a l c u l a t i o n s  Sample Description  Dilution ( i f any)  Initial sample (t=0 min)  8-3)  Blank-Sample (ml)  COD (mg/l)  10  14.2  11.2  4310  10  14.3  11 .1  4271  10  16.2  9.2  3540  10  16.4  9.0  3463  Average COD (mg/l) 4291  Final sample (t=300 min) i.e.  Titre-FAS (ml)  (run  3502  18.4% r e d u c t i o n  in  C.O.D.  T i t r e - F A S ( i n ml) Values f o r the Blank and Standard Samples  Blank Sample  Average:  Standard Sample  25.45  26.00  25.35  26.00  25.4  26.00  For the s t a n d a r d sample v a l u e s ,  N  FAS  2 5 2 5 T i t r e - F A S ( m l ) " " 26T0  =  N '  =  °-  0 9 6 1  x 8000 x D i l u t i o n f a c t o r ( i f Sample vol ume  r a c t o r  C.O.D.  p A S  =  0.0962 x 8000 x 10  =  (ml) 3 g 4  8  (mg/1) = F a c t o r x Blank-Sample  any)  170.  2.  C a l c u l a t i o n of d i f f u s i v i t y  The  diffusivity  where  =  o 12  Change  7.4 x 10"  =  y  0  were c a l c u l a t e d by using  h  T  2  mutual d i f f u s i o n of s o l u t e 1 i n s o l v e n t 2 a t very  M2 = m o l e c u l a r weight o f T = temperature,  low  solute  cnr/sec "  = " a s s o c i a t i o n parameter" o f s o l v e n t  X  the  [55]  (0 K 2 )  8  concentration, *  phenolics  of the p h e n o l i c s  r e l a t i o n s h i p o f WiIke and  D  of  [IT]  .  solvent  K  1^2 = v i s c o s i t y o f s o l u t i o n ( s o l v e n t ) , cp V.| = molal i n cm D  12  phenol  =  7.4  volume of the  3  /g mole  xlO-  x 10"  ,  (2.26  8  1 x  = 8.5  s o l u t e a t i t s normal  6  x 18)* x 297  (105) U  boiling  / (  r  e  f  e  r  t Q  p >  3^  R  D?„  E  F  >  b  cm /,s 2  Improved value o f a s s o c i a t i o n parameter put f o r t h by Hayduk Laudie [56,] has been used.  Note:  point  X y l e n o l s c a l c u l a t e d a t 40°C  and  5 5 )  171.  3.  Calculation of current e f f i c i e n c y f o r a typical  phenol run  The s t o i c h i o m e t r y o f the predominant p r o c e s s e s which occurs i n the o x i d a t i o n o f phenol (run 9-1) a r e as f o l l o w s OH 1.  6 [I  +11  H0  —  6 C0  +  HoO  —  || ll  2  + 28 H  2  +  + 28 e"  OH + 4 e"  +  0 OH  OH  +  HoO -  II :i  +  2  H + 2 e" +  OH OH  OH  (f^j  + 4 H  + H 0 - ([^r 2 H + 2 e' 0H+  +  2  OH +  5 H0 2  —  6 CO  + 16 H  C o n s i d e r a carbon balance. Amount o f phenol o x i d i z e d = (975-105) = 870 mg/l R e s u l t s from GC/MS a n a l y s i s o f f i n a l  sample  % Phenol  12.6  Benzoquinone  69.5  Hydroquinone  10.9  Catechol  7.0  Actual  quantity  o f phenol = 105 mg/l  Actual  q u a n t i t y o f benzoquinone = 579.2 mg/l  +  + 16 e"  Actual  q u a n t i t y o f hydroquinone = 90.8 mg/l  Actual  quantity of catechol  =58.3 mg/l  Cone, o f o r g a n i c carbon i n s t a r t i n g  solution =  71.4 x 975 93.3  = 746.1 mg/l cone, o f o r g a n i c carbon i n the p r o d u c t s  = 105 x  + 579.2 x  7 T 7  j  i ^ + (90.8 + 58.3)  = 562.7 mg/l  cone, o f o r g a n i c ' c a r b o n t h a t l e f t the s o l t u i o n (from T.O.C. a n a l y s i s ) = 29.8 mg/l  cone, o f o r g a n i c carbon unaccounted from carbon balance = 153.6 mg/l = (21%)  Calculation of current  efficiency  * % C.E. f o r the f o r m a t i o n o f benzoquinone  = 579.2 mg/l x 5 1 x  Ig mole x 107.4 g  x 96500 c o u l / e q x 4 eq/mole x 100  10 A x 120 min x  60 sec  min  = 14.5  % C.E. f o r f o r m a t i o n o f c a t e c h o l  = 149.1 mg/l x 5 1 x  Ig mole x 109.4  and hydroquinone  x 96500 c o u l / e q x 2 eq/mole x 100 10° mg  1.0. A x 120 min x  * % C.E. =  F Z (moles o x i d i z e d ) x 100 It  60 Sec mi n  173.  = 1.83  % C.E. f o r the f o r m a t i o n o f CC^ [Assume 100% c o n v e r s i o n t o C0 1 2  = 29.8 mg/l x 5 1 x  1  ^  m  °  l d  9  1  x  e  \ 10  x 96500 c o u l / e q x 28 eq/mole x 100  9  mg  10 A x 120 min x  6  ^  0  = 46.6  % C.E. f o r the f o r m a t i o n o f CO Assume 100 % c o n v e r s i o n t o CO  29.8 mg/l x 5 1 x  1  9  m  u  °  1  e  x  9  1 x 96500 c o u l / e q x 16 eq/mole x 100 10 mg 9  10 A x 120 min x  6  ^  0  26.6  Total  c u r r e n t e f f i c i e n c y = 42.9 - 62.9 depending on C0:C0  *Gas analysis by G.C. corresponding to the time of collection of the f i n a l sample was as follows: %H , 68.42; %C0 , 6.54; %0 , 24.73; %CO, 0.31 2  2  CO:CO2 was found to vary as follows 1:7.4 (after 90 minutes of oxidation) 1:21.0 (after 120 minutes of oxidation)  2  174.  4.  C a l c u l a t i o n of V ^  in  m  the  electrolyte  cathode  saran screen  Vohm  . oh V  = i m  'V a S  w h e r e V'^ i s The quantity  last of  i  - d.-S  +  r  d  the l i q u i d  two f a c t o r s  i ^ c - S  function  ir S a  a  across  the  K electrolyte  sj 0 ( d u e t o  c  - V  bed.  L  potential  are n e g l i g i b l e .  g a s e v o l v e d and t y p e o f  Consider  a  +  ; i r ^ S ^ w o u l d d e p e n d on  screen. It  c a n be a p p r o x i m a t e d a s  K ebed  the  high c o n d u c t i v i t y  of  the e l e c t r o l y t e  [31]  bed)  ^ebed  Average c o n d u c t i v i t y  ; electrolyte  = 1.12  of  ohm.m  the  = 0.895(f2m)'  follows.  ohm- ('  V  5  runs)  A  263.2 A/m  x 1.12 ohm m x 0.003 m  0.88 v o l t s  ohm (  y  l0 A  runs)  526.3 A/m x 1.12 ohm.m x 0.003 m 2  1.77 v o l t s ohm (  V  1 5  A  runs)  789.5 A/m 2.65 v o l t s  2  x 1.12 ohm.m x 0.003 m  \  176.  APPENDIX 5  Relevant P h y s i c a l  data  ACTUAL COMPOSITION OF SYNTHETIC COAL CONVERSION WASTEWATER OUTLINED IN TABLE I Compound  C o n c e n t r a t i o n , mg/l  1.  Phenol  2000  2.  Resorcinol  1000  3.  Catechol  1000  4.  Acetic  5.  o-Cresol  400  6.  p-Cresol  250  7.  3,4-Xylenol  250  8.  2,3-Xylenol  250  9.  P y r i d i ne  120  10.  Benzoic A c i d  100  11 .  4-Ethyl p y r i d i n e  100  12.  4-Methylcatechol  100  13.  Acetophenone  50  14.  2-Indanol  50  15.  Indene  50  16.  Indole  50  17.  5-Methylresorcinol  50  18.  2-Naphthol  50  19.  2,3,5-Trimethylphenol  50  20.  2,-Methylquinoline  40  Acid  400  177.  Compound  Concentration  21 .  3,5-Xylenol  40  22.  3-Ethylphenol  30  23.  Aniline  20  24.  Hexanoic  25.  1-Naphthol  20  26.  Qui no!ine  10  27.  Naphthalene  5  28.  Anthracene  0.1  29.  MgS0 .7H 0  22.5  30.  CaCl  27.5  4  Acid  2  2  20  0.34  31 . FeNaEDTA  3820  32.  NH C1  33.  Phosphate b u f f e r :  4  KH P0 2  4  170  K HP0  4  435  2  Na HP0 .7H 0 2  4  2  668  

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