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Novel donor-acceptor reagents in annulation sequences : total synthesis of oplopanane-type sesquiterpenoids Gavai, Ashvinikumar Vasant 1986

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NOVEL DONOR-ACCEPTOR REAGENTS IN ANNOTATION SEQUENCES. TOTAL SYNTHESIS OF OPLOPANANE-TYPE SESQUITERPENOIDS By ASHVINIKUMAR VASANT GAVAI Sc., Indian Institute of Technology, Bombay, 1979 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (DEPARTMENT OF CHEMISTRY) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1986 1 Ashvinikumar Vasant Gavai, 1986 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 of the requirements f o r an advanced degree at the The U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree that p e r m i s s i o n f o r e x t e n s i v e copying of 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 of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of 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 not be allowed without my w r i t t e n p e r m i s s i o n . Department of S o i l Science The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: OCTOBER, 1986 ABSTRACT An i n v e s t i g a t i o n of the e f f e c t s of s o i l o r g a n i c matter on boron r e t e n t i o n and r e l e a s e i n s o i l s was c a r r i e d out on s o i l s from B r i t i s h Columbia. The e f f e c t of s o i l humic a c i d on boron a d s o r p t i o n was s t u d i e d i n d e t a i l as a f u n c t i o n of pH, boron c o n c e n t r a t i o n i n e q u i l i b r i u m s o l u t i o n , i o n i c s t r e n g t h and d i f f e r e n t c a t i o n s . Boron a d s o r p t i o n by C a - p r e c i p i t a t e d humic a c i d was found h i g h l y pH-dependent, with the maximum a d s o r p t i o n at pH around 9.5, and remained l i t t l e changed below pH around 6.5. Boron a d s o r p t i o n isotherms by v a r i o u s humic a c i d s were s t u d i e d at two pH l e v e l s and i t was found that the i n c r e a s e of boron a d s o r p t i o n with an i n c r e a s e of boron i n e q u i l i b r i u m s o l u t i o n at a higher pH l e v e l (8.5-9.0) was much more pronounced than that at a lower pH l e v e l (near n e u t r a l ) . The a d s o r p t i o n conformed q u i t e w e l l to the F r e u n d l i c h e m p i r i c a l equation and was f a i r l y w e l l d e s c r i b e d by the Langmuir theory. The b and kb v a l u e s c a l c u l a t e d from the Langmuir equation i n c r e a s e d with i n c r e a s i n g pH whereas k values decreased with i n c r e a s e of pH w i t h one e x c e p t i o n . High i o n i c s t r e n g t h i n s o l u t i o n f a v o r e d boron a d s o r p t i o n by s o i l humic a c i d . By comparing the b v a l u e s (high pH l e v e l ) , the amount of boron adsorbed by the two humic a c i d s , WH-HA(a) and LA-HA(b), i n c r e a s e d 21% and 12 %, r e s p e c t i v e l y , with an i n c r e a s e of s o l u t i o n i o n i c s t r e n g t h from 0.03 to 0.3. However, at lower pH l e v e l s , the e f f e c t seemed i n s i g n i f i c a n t . i i R e s u l t s i n d i c a t e d that humic a c i d s e x t r a c t e d from d i f f e r e n t s o i l s or by d i f f e r e n t e x t r a c t i o n methods adsorbed very d i f f e r e n t amounts of boron. The d i f f e r e n c e was a t t r i b u t e d to the c o n t r i b u t i o n of i r o n present i n the humic a c i d samples, and i t was confirmed e x p e r i m e n t a l l y that A l or Fe p r e c i p i t a t e d humic a c i d adsorbed much more boron than C a - p r e c i p i t a t e d humic a c i d . No s i g n i f i c a n t amount of boron a d s o r p t i o n by s o i l p o l y s a c c h a r i d e s was observed at pH near n e u t r a l . However, s t u d i e s on boron a d s o r p t i o n by organo-clay complexes i n d i c a t e d that c o a t i n g of s o i l p o l y s a c c h a r i d e s on i l l i t e , m o n t m o r i l l o n i t e and k a o l i n i t e reduced boron a d s o r p t i o n by 31.6%, 44.5% and 76.7%, r e s p e c t i v e l y , i f compared with that by the pure c l a y s . The e f f e c t of c o a t i n g of the f u l v i c p olyphenol on those c l a y s seemed the l e a s t , e s p e c i a l l y on m o n t m o r i l l o n i t e . From the r e s u l t s of these e q u i l i b r i u m s t u d i e s , i t i s proposed that s o i l o r g a n i c matter may p l a y an important r o l e on boron a d s o r p t i o n i n s o i l s with a l k a l i n e r e a c t i o n , high i n or g a n i c matter cont e n t , and hi g h i n e x t r a c t a b l e i r o n and aluminum c o n t e n t s . However, the e f f e c t would be n e g l i g i b l e i n s o i l s with low organic matter content but h i g h i n c l a y or s e s q u i o x i d e c o n t e n t s . TABLE OF CONTENTS ABSTRACT i i TABLE OF CONTENTS i v LIST OF FIGURES . v i i LIST OF TABLES ix LIST OF APPENDIXES X ACKNOWLEDGEMENTS x i i 1 . INTRODUCTION 1 2. LITERATURE REVIEW 4 2.1 Boron i n S o i l 4 2.1.1 S o l u t i o n Chemistry of Boron 4 2.1.2 Boron Content i n S o i l s 6 2.1.3 Boron D e f i c i e n c y and T o x i c i t y i n S o i l s 9 2.2 Boron R e a c t i o n s i n S o i l 11 2.2.1 A d s o r p t i o n by C l a y M i n e r a l s 11 2.2.2 A d s o r p t i o n by Organic Matter 13 2.2.3 A d s o r p t i o n by Hydroxy Oxides of A l and Fe .16 2.2.4 Proposed Boron A d s o r p t i o n Mechanisms 20 2.3 Boron A d s o r p t i o n Isotherms and A Way of Making Boron F e r t i l i z e r Recommendation 23 2.3.1 A d s o r p t i o n M o d e l l i n g 23 2.3.2 A Way of Making F e r t i l i z e r Recommendation .27 3. MATERIALS AND METHODS 29 3.1 S o i l s 29 3.2 Organic Matter F r a c t i o n s 30 3.2.1 I s o l a t i o n of S o i l Humic A c i d and F u l v i c Polyphenol 30 3.2.2 I s o l a t i o n of the S o i l P o l y s a c c h a r i d e 32 3.3 Clay M i n e r a l s ... 35 3.4 Boron A d s o r p t i o n Experiments 36 3.4.1 E q u i l i b r a t i o n of Boron with S o i l HA 36 3.4.2 Boron E q u i l i b r a t i o n with A l - and ~ F e - p r e c i p i t a t e d HA 37 3.4.3 E q u i l i b r a t i o n of Boron with S o i l P o l y s a c c h a r i d e ..38 3.4.4 Boron E q u i l i b r a t i o n with Pure C l a y M i n e r a l s 38 3.4.5 Boron E q u i l i b r a t i o n with Organo-Clay Complexes . .. 39 3.4.6 I o n i c Strength Adjustment 41 3.4.7 A d s o r p t i o n of the Three Organic C o n s t i t u e n t s by C l a y M i n e r a l s 41 3.4.8 S o l u t i o n Boron A n a l y s i s 41 3.5 Examination of Ash i n Organic Samples 45 3.5.1 Ash Content 45 3.5.2 Elemental A n a l y s i s of the Ash .....45 4. RESULTS AND DISCUSSION 46 4.1 Boron A d s o r p t i o n by S o i l Humic A c i d 46 4.1.1 Development of a Method to Study Boron A d s o r p t i o n by Humic A c i d 46 4.1.2 E f f e c t of pH on Boron A d s o r p t i o n 49 4.1.3 Boron A d s o r p t i o n Isotherms 53 4.1.4 E f f e c t s of C a t i o n s on Boron A d s o r p t i o n ....63 4.1.5 E f f e c t of I o n i c S t r e n g t h on Boron A d s o r p t i o n .....66 4.2 Boron R e a c t i o n with S o i l P o l y s a c c h a r i d e 71 4.3 Boron A d s o r p t i o n by Clay and Organo-Clay Complexes 75 4.3.1 I n t e r a c t i o n of the Organic C o n s t i t u e n t s w i t h Clay M i n e r a l s 75 4.3.2 Boron A d s o r p t i o n by the Three C l a y M i n e r a l s 77 v 4.3.3 Boron A d s o r p t i o n by the Organo-Clay Complexes 79 4.4 The S i g n i f i c a n c e of S o i l Organic Matter on Boron A d s o r p t i o n and the P o s s i b l e A d s o r p t i o n Mechanisms .87 5. SUMMARY AND CONCLUSIONS 92 6. REFERENCES 97 7. APPENDIXES , 108 v i LIST OF FIGURES FIGURE PAGE 1. Boron a d s o r p t i o n by s o i l humic a c i d s as a f u n c t i o n of pH 50 2. The r e l a t i o n s h i p of %B complexed as a f u n c t i o n of pH f o r the h y p o t h e t i c a l s o l u t i o n of 0.1M t a r t a r i c a c i d or 0.1M mannitol i n s o l u t i o n with 0.001M b o r i c a c i d 52 3. The amount of boron adsorbed by humic a c i d s e x t r a c t e d with 0.1M NaOH + 0.1M Na.P.O. at pH 8.5-9.0 54 4. The amount of boron adsorbed by humic a c i d s e x t r a c t e d by 0.5M NaOH (with s o n i f i c a t i o n ) at pH 8.5-9.0 55 5. The amount of boron adsorbed by humic a c i d s at lower pH c o n d i t i o n s 56 6. P l o t of the r e g r e s s i o n e quations f o r l o g x/m (B adsorbed) versus l o g c (B i n e q u i l i b r i u m s o l u t i o n ) at pH 8.5-9.0 58 7. P l o t of the r e g r e s s i o n equation f o r l o g x/m versus l o g c at lower pH c o n d i t i o n s ... 59 8. Boron a d s o r p t i o n by f r e s h A l - and Fe-p r e c i p i t a t e d humic a c i d , LA-HA(b), at pH 6.8-7.2 as compared wit h t h a t by C a - p r e c i p i t a t e d LA-HA(b) 64 9. Boron a d s o r p t i o n by f r e e z e - d r i e d A l - and F e - p r e c i p i t a t e d humic a c i d , LA-HA(b), at pH 5.0 as compared wit h t h a t by Ca-p r e c i p i t a t e d LA-HA(b) 67 10. Boron a d s o r p t i o n by WH-HA(a) as a f f e c t e d by the s o l u t i o n i o n i c s t r e n g t h and pH 68 11. Boron a d s o r p t i o n by LA-HA(b) as a f f e c t e d by the s o l u t i o n i o n i c s t r e n g t h and pH 69 12. Isotherms f o r the a d s o r p t i o n s of s o i l p o l y s a c c h a r i d e , humic a c i d and polyphenol on C a - s a t u r a t e d k a o l i n i t e ( a ) , v i i i l l i t e ( b), and m o n t m o r i l l o n i t e (c) 76 13. Boron a d s o r p t i o n isotherms f o r C a - s a t u r a t e d k a o l i n i t e (pH 6.3-6.7), m o n t m o r i l l o n i t e (pH 7.5-7.8) and i l l i t e (pH 7.5-7.8) ~ 78 14. Boron a d s o r p t i o n isotherms f o r PSS-coated k a o l i n i t e (pH 6.3-6.7), m o n t m o r i l l o n i t e (pH 7.5-7.8) and i l l i t e (pH 7.4-7.8) 80 15. Boron a d s o r p t i o n isotherms f o r PP-coated k a o l i n i t e (pH 5.3-5.7), m o n t m o r i l l o n i t e (pH 6.0-6.2) and i l l i t e (pH 5.8-6.2) 84 16. Boron a d s o r p t i o n isotherms f o r HA-coated k a o l i n i t e (pH 5.4-5.7), and m o n t m o r i l l o n i t e (pH 5.6-5.9) 85 v i i i LIST OF TABLES TABLE PAGE 1. D i s t r i b u t i o n of boron i n common rock types 6 2. The p r o p o r t i o n of the s o i l p o l y s a c c h a r i d e e x t r a c t e d with s e v e r a l s e l e c t e d e x t r a c t a n t s .... 33 3. Main parameters used f o r boron a n a l y s i s by I CP 42 4. V a r i a t i o n of boron v a l u e s measured by ICP with f l u c t u a t i o n of temperature 44 5. Boron a d s o r p t i o n by v a r i o u s humic a c i d s at pH 8.5-9.0 expressed by F r e u n d l i c h equation and Langmuir equation 60 6. Boron a d s o r p t i o n by v a r i o u s humic a c i d s at pH 6.2-7.2 expressed by F r e u n d l i c h equation and Langmuir equation 60 7. V a r i a t i o n of Langmuir c o n s t a n t s , b, k, and bk v a l u e s , with pH and humic a c i d samples 61 8. Ash content (% of OM) of the organic samples ... 63 9. Langmuir c o n s t a n t s , b and k, f o r the p o l y s a c c h a r i d e coated and uncoated c l a y s , and the % r e d u c t i o n i n the amount of boron a d s o r p t i o n 81 10. Langmuir c o n s t a n t s , b and k, f o r p o l y p h e n o l -coated and humic a c i d - c o a t e d c l a y s 86 i x LIST OF APPENDIXES APPENDIX PAGE 1 . Boron a d s o r p t i o n as a f u n c t i o n of pH ( I n i t i a l B c o n e , 1.11 umol/mL) 109 2. Boron a d s o r p t i o n by WH-HA(a) at pH 8.5-9.0 and 1=0.03, (89% HA p r e c i p i t a t e d ) 110 3. Boron a d s o r p t i o n by WH-HA(a) at pH 6.8-7.2 and 1 = 0.03, (90% HA p r e c i p i t a t e d ) 110 4. Boron a d s o r p t i o n by WH-HA(a) at pH 8.5-9.0 and 1 = 0.3, (91% HA p r e c i p i t a t e d ) 110 5. Boron a d s o r p t i o n by WH-HA(a) at pH 6.8-7.0 and 1=0.3, (92% HA p r e c i p i t a t e d ) 111 6. Boron a d s o r p t i o n by LA-HA(b) at pH 8.5-9.0 and 1 = 0.03, (90% HA p r e c i p i t a t e d ) 111 7. Boron a d s o r p t i o n by LA-HA(b) at pH 5.8-6.2 and 1 = 0.03, (95% HA p r e c i p i t a t e d ) 111 8. Boron a d s o r p t i o n by LA-HA(b) at pH 8.5-9.0 and 1 = 0.3, (95% HA p r e c i p i t a t e d ) 112 9. Boron a d s o r p t i o n by LA-HA(b) at pH 5.8-6.2 and 1 = 0.3, (96% HA p r e c i p i t a t e d ) 112 10. Boron a d s o r p t i o n by CH-HA(a) at pH 8.5-9.0 and 1 = 0.03, (95% HA p r e c i p i t a t e d ) 113 11. Boron a d s o r p t i o n by CH-HA(a) at pH 6.2-6.5 and 1=0.03, (95.5% HA p r e c i p i t a t e d ) 113 12. Boron a d s o r p t i o n by LA-HA(a) at pH 8.5-9.0 and 1 = 0.03, (94% HA p r e c i p i t a t e d ) 113 13. Boron a d s o r p t i o n by LA-HA(a) at pH 6.6-6.7 and 1=0.03, (94.6% HA p r e c i p i t a t e d ) 114 14. Boron a d s o r p t i o n by CH-HA(b) at pH 8.5-9.0 and 1=0.03, (86.5% HA p r e c i p i t a t e d ) 114 15. Boron a d s o r p t i o n by LA-HA(b)-Fe complex ( f r e s h ) at pH 6.7-6.9 and 1=0.03 114 16. Boron a d s o r p t i o n by LA-HA(b)-Fe complex x ( f r e e z e - d r i e d ) at pH 5.0 and 1 = 0.03 115 17. Boron a d s o r p t i o n by LA-HA(b)-Al complex ( f r e s h ) at pH 7.0-7.2 and 1=0.03 115 18. Boron a d s o r p t i o n by LA-HA(b)-Al complex ( f r e e z e - d r i e d ) at pH 5.0 and 1 = 0.03 116 19. Boron a d s o r p t i o n by C a - i l l i t e , pH 7.5-7.8 .... 116 20. Boron a d s o r p t i o n by C a - M o n t m o r i l l o n i t e , pH 7.5-7.8 117 21. Boron a d s o r p t i o n by C a - k a o l i n i t e , pH 6.3-6.7 117 22. Boron a d s o r p t i o n by P S S - i l l i t e , pH 7.4-7.8 ... 118 23. Boron a d s o r p t i o n by PSS-Montmorillonite, pH 7.5-7.8 118 24. Boron a d s o r p t i o n by P S S - k a o l i n i t e , pH 6.3-6.7 118 25. Boron a d s o r p t i o n by P P - i l l i t e , pH 5.8-6.2 .... 119 26. Boron a d s o r p t i o n by PP-Mo n t m o r i l l o n i t e , pH 6.0-6.2 119 27. Boron a d s o r p t i o n by P P - k a o l i n i t e , pH 5.3-5.7 120 28. Boron a d s o r p t i o n by HA-Montmorillonite, pH 5.6-5.9 120 29. Boron a d s o r p t i o n by H A - k a o l i n i t e , pH 5.4-5.7 121 30. The i n c r e a s e of d 0 0 1 spacing with the i n c r e a s e of the amount of PSS adsorbed by C a - m o n t m o r i l l o n i t e 121 31. A d s o r p t i o n of PSS, HA and PP on three types of c l a y m i n e r a l s (mg/50mg c l a y ) 122 x i ACKNOWLEDGEMENTS I would l i k e to express s i n c e r e g r a t i t u d e t o my reseach s u p e r v i s o r , Dr. L. E. Lowe, f o r h i s p a t i e n t guidance, c o n s i d e r a t i o n and support d u r i n g the course of t h i s study. My s i n c e r e a p p r e c i a t i o n i s a l s o extended to Dr. L. M. L a v k u l i c h f o r h i s p r o v i d i n g me with the c l a y m i n e r a l samples and h i s h e l p f u l i n s t r u c t i o n s and a d v i c e . I would a l s o l i k e to thank members of my committee, Dr. A. A. Bomke f o r h i s p r o v i d i n g me with v a l u a b l e i n f o r m a t i o n , and Dr. C. G. Kowalenko f o r h i s p a r t i c i p a t i o n and a d v i c e . The expert t e c h n i c a l a s s i s t a n c e of us i n g ICP p r o v i d e d by Miss E. Wolterson, and of using Carbon Ana l y s e r and other l a b f a c i l i t i e s p r o v i d e d by Mrs. Esther Y i p i s a l s o g r a t e f u l l y acknowledged. I a l s o wish to acknowledge the a s s i s t a n c e of many people of t h i s department as w e l l as other department without which t h i s t h e s i s would not have been p o s s i b l e . The s c h o l a r s h i p from the M i n i s t r y of Educat i o n of the People's Republic of China i s a l s o acknowledged. F i n a l l y I would l i k e to thank my wife Xiangping f o r her encouragement, understanding and p a t i e n c e d u r i n g the course of t h i s study. x i i 1. INTRODUCTION Boron i s an e s s e n t i a l element f o r the normal growth of p l a n t s . Boron d e f i c i e n c y has been r e p o r t e d i n many s o i l s of the world, s i n c e boron i s h i g h l y mobile and e a s i l y l e a c h e d . V a r i o u s s o i l components have been r e p o r t e d to be r e s p o n s i b l e f o r boron r e t e n t i o n and r e l e a s e i n s o i l s . S o i l a d s o r p t i o n s i t e s a ct as a pool from which boron i s s u p p l i e d to s o l u t i o n or where boron i s adsorbed, depending on the changes i n s o l u t i o n boron c o n c e n t r a t i o n and the a f f i n i t y of s o i l f o r boron. Organic matter has been thought to be one of the major s o i l components r e s p o n s i b l e f o r boron r e t e n t i o n and r e l e a s e i n s o i l s . I t was r e p o r t e d that the c o n t r i b u t i o n of o r g a n i c matter to the t o t a l boron content of s o i l s ranged from 10% i n s o i l s low i n o r g a n i c matter to 100% i n peat s o i l s (Berger, 1965). A good r e l a t i o n s h i p between s o i l o r g a n i c matter content and w a t e r - s o l u b l e boron content has been found by a number of r e s e a r c h e r s . Parks and White (1952) suggested that the complex formation between di-hydroxy organic compounds and boron was the reason f o r boron r e t e n t i o n i n s o i l s , but t h i s has not yet been supported by r e s e a r c h d a t a . Bingham et a l . (1971) concluded that s o i l o r g a n i c matter had a s m a l l e f f e c t on boron a d s o r p t i o n by s o i l s d e r i v e d from v o l c a n i c ash d e p o s i t s with o r g a n i c carbon ranging from 6 to 14%. By p a r t i a l d e s t r u c t i o n of o r g a n i c matter with H 2 0 2 f Mezuman and Keren (1981) found that the 1 2 e f f e c t of o r g a n i c matter on boron a d s o r p t i o n was n e g l i g i b l e . They suggested that the boron a s s o c i a t e d with o r g a n i c matter o r i g i n a t e d from boron a s s i m i l a t i o n i n biomass r a t h e r than from chemical a d s o r p t i o n . Harada and Tamai (1968) r e p o r t e d that d e s t r u c t i o n of o r g a n i c matter r e s u l t e d i n an i n c r e a s e i n boron a d s o r p t i o n of the s o i l s , which was c o n t r a d i c t o r y to that observed by Olson and Berger (1946). I t has long been r e c o g n i z e d that b o r i c a c i d can r e a c t with v a r i o u s d i o l o r g a n i c compounds to form complexes. S o i l p o l y s a c c h a r i d e i s known to be r i c h i n d i o l - o r g a n i c compounds, sugges t i n g that t h i s component c o u l d form complexes with boron. S o i l p o l y s a c c h a r i d e can be h y d r o l y s e d to v a r i o u s sugars, such as glucose, mannose, g a l a c t o s e , and g l u c u r o n i c a c i d , which have been demonstrated to r e a c t with b o r i c a c i d (Boeseken, 1949). However, there i s no experimental evidence so f a r of a r e a c t i o n between b o r i c a c i d and s o i l p o l y s a c c h a r i d e . S o i l o r g a n i c matter i s a l s o known to r e a c t with s o i l c l a y m i n e r a l s to form organo-clay complexes. The a d s o r p t i o n of o r g a n i c m a t e r i a l s onto c l a y s w i l l a l t e r the s u r f a c e , and thereby a l t e r s u r f a c e r e a c t i v i t y (Greenland, 1965). Most of the r e s e a r c h has been done on boron a d s o r p t i o n by pure c l a y m i n e r a l s or i n d i v i d u a l s o i l s , whereas the r e t e n t i o n of boron by s o i l organo-clay complexes, which are p r e s e n t more or l e s s i n every type of s o i l , has been l a r g e l y n e g l e c t e d . The main o b j e c t i v e of t h i s i n v e s t i g a t i o n was to examine the r e l a t i v e importance of o r g a n i c matter i n boron r e t e n t i o n 3 and r e l e a s e i n s o i l s as compared with that on c l a y m i n e r a l s . To accomplish t h i s o b j e c t i v e , v a r i o u s s o i l o r g a n i c c o n s t i t u e n t s were e x t r a c t e d and boron a d s o r p t i o n isotherms by the s o i l o r g a n i c c o n s t i t u e n t s , c l a y or the organo-clay complexes were s t u d i e d . The e f f e c t s of pH, i o n i c s t r e n g t h , and d i f f e r e n t c a t i o n s on boron a d s o r p t i o n by s o i l humic a c i d were a l s o i n c l u d e d . 2. LITERATURE REVIEW 2.1 BORON IN SOIL 2.1.1 SOLUTION CHEMISTRY OF BORON Boron i s the f i r s t member of the t h i r d p e r i o d i c group, with an atomic number of f i v e . A l l boron compounds have a valence based on the e x c i t e d s t a t e of boron 1 s 22s 12p^2py, and a c c o r d i n g l y are t r i v a l e n t . However, boron chemistry i s not of B 3 + ions because of i t s very h i g h i o n i z a t i o n p o t e n t i a l s , and t h e r e f o r e i s of c o v a l e n t boron compounds i n which the remaining 2p l e v e l i s a v a i l a b l e f o r bonding. Boron possesses the c h a r a c t e r i s t i c of e l e c t r o n - d e f i c i e n c y because of i t s incomplete o c t e t i n BX 3 compounds and thus behaves as e l e c t r o n a c c e p t o r or as Lewis a c i d , i n which boron a c h i e v e s i t s maximum c o o r d i n a t i o n with approximately sp3 h y b r i d i z a t i o n toward many Lewis bases or e l e c t r o n donors, such as p o l y h y d r i c a l c o h o l s and amines. T h e r e f o r e , t r i c o o r d i n a t e boron compounds have a s t r o n g tendency to i n t e r a c t with those e l e c t r o n donors to form t e t r a c o o r d i n a t e boron s t r u c t u r e s . For example, b o r i c a c i d i s known f o r i t s a b i l i t y to r e a c t with p o l y h y d r i c a l c o h o l s (such as g l y c e r o l , m a n n i t o l , e t c . ) t o form complex a c i d s s t r o n g e r than the b o r i c a c i d i t s e l f . The d i s s o c i a t i o n c o n s t a n t s of m a n n i t o l - b o r i c and g l y c e r o l - b o r i c a c i d s are 6 x 10" 6 and 3 x 10~ 7, r e s p e c t i v e l y , whereas b o r i c a c i d , o n l y 6.0 x 4 5 1 0 " 1 0 ( N e m o d r u k a n d K a r a l o v a , 1 9 6 5 ) . U t i l i z a t i o n o f n u c l e a r m a g n e t i c r e s o n a n c e (Good a n d R i t t e r , 1962 ) a n d Raman s p e c t r o s c o p y ( S e r v e s s a n d C l a r k , 1957 ) h a v e shown B ( O H ) 3 m o l e c u l e s t o h a v e a t r i g o n a l p l a n a r s t r u c t u r e a n d B ( O H ) i t o be t e t r a h e d r a l i n a q u e o u s s o l u t i o n . T h i s d i f f e r e n c e i n s t r u c t u r e c a n l e a d t o d i f f e r e n c e s i n t h e a f f i n i t y o f v a r i o u s s o i l c o m p o n e n t s f o r t h e s e two b o r o n s p e c i e s ( K e r e n a n d B i n g h a m , 1 9 8 5 ) . B o r o n o c c u r s i n a q u e o u s s o l u t i o n a s b o r i c a c i d , B ( O H ) 3 . I n a c c o r d a n c e w i t h t h e e l e c t r o n c o n f i g u r a t i o n o f b o r o n , E d w a r d s e t a l . ( 1 9 5 5 ) s u g g e s t e d t h a t i t f o r m s a n i o n n o t by s p l i t t i n g o f f H + t o f o r m B ( O H ) i , b u t by a d d i t i o n o f O H - t o f o r m B ( O H ) H , i . e . B ( O H ) 3 + 2 H 2 0 == B ( O H ) , + H 3 0 + T h i s r e a c t i o n i s r e v e r s i b l e a n d t h e a n i o n i c f o r m , B ( O H ) a , g e n e r a l l y c o n s t i t u t e s l e s s t h a n 1% o f t h e s o l u t i o n b o r o n a t pH v a l u e s b e l o w 7 ( O e r t l i a n d G r g u r e v i c , 1 9 7 5 ) . T h u s i t i s c o n c l u d e d t h a t u n d i s s o c i a t e d B ( O H ) 3 , o t h e r t h a n t h e p o l y o l s c o m p l e x e d b o r i c a c i d , i s t h e p r e d o m i n a n t f o r m o f b o r o n i n m o s t s o i l s a n d p l a n t s o l u t i o n s . H o w e v e r , when t h e c o n c e n t r a t i o n o f b o r i c a c i d i s i n c r e a s e d t o a v a l u e h i g h e r t h a n 0 . 1 M , i t s f i r s t d i s s o c i a t i o n c o n s t a n t i n c r e a s e s c o n s i d e r a b l y by t h e f o r m a t i o n o f s t r o n g e r p o l y b o r i c a c i d s ( E v a n s a n d S p a r k s , 1 9 8 3 ) . N e v e r t h l e s s , t h i s h i g h l e v e l o f b o r o n g e n e r a l l y w o u l d n o t o c c u r i n c u l t i v a t e d s o i l s . 6 2.1. 2 BORON CONTENT IN SOILS Boron has been r e p o r t e d to be present i n almost a l l s o i l types of the world. Many r e f e r e n c e s are a v a i l a b l e on the boron s t a t u s of s o i l s . Three c a t e g o r i e s of s o i l boron have been r e c o g n i z e d : (1) t o t a l boron; (2) a c i d s o l u b l e boron (or maximum a v a i l a b l e boron); and (3) water s o l u b l e boron (or r e a d i l y a v a i l a b l e boron). (I) Total Boron in Soil T o t a l boron i n c l u d e s the boron p r e s e n t i n s o i l s o l u t i o n , boron adsorbed on s o i l c o l l o i d s , t h a t i n c o r p o r a t e d i n o r g a n i c matter, and i n v a r i o u s s o i l m i n e r a l s such as the very r e s i s t a n t m i n e r a l , t o u r m a l i n e . However, the bulk of the boron comes from s o i l m i n e r a l s . Hence, the boron content of s o i l i s p r i m a r i l y r e l a t e d to the boron content of the parent m a t e r i a l from which the s o i l was d e r i v e d . The d i s t r i b u t i o n of boron among the common rock types i s shown i n Table 1 (Evans and Sparks, 1983). Table 1 - D i s t r i b u t i o n of Boron i n Common Rock Types Rock C l a s s Rock Type B C o n c e n t r a t i o n (ug/g) Igneous G r a n i t e 15 B a s a l t 5 Sedimentary Limestone Sandstone Shale 20 35 100 7 T h e r e f o r e , igneous rocks c o n t a i n approximately 10 ppm boron on average whereas sedimentary rocks depending upon t h e i r g e n esis range from 2 to 100 ppm boron. T o t a l s o i l boron content v a r i e s c o n s i d e r a b l y , from 2 to 200 ppm, depending on the c l i m a t i c c o n d i t i o n s and the parent m a t e r i a l s from which the s o i l was d e r i v e d because boron i s a r e l a t i v e l y mobile n u t r i e n t i n s o i l . An average t o t a l boron content of s o i l s i s re p o r t e d t o be about 30 to 40 ppm (Gupta, 1979; Jackson, 1970; Bingham, 1973; Xuan, 1983). Some B r i t i s h Columbia s o i l s were r e p o r t e d low i n t o t a l boron, g e n e r a l l y l e s s than 20 ppm (Kowalenko, 1979). T o t a l boron content of a s o i l i s probably of l i t t l e a g r i c u l t u r a l s i g n i f i c a n c e because l e s s than 5 per cent of the t o t a l s o i l boron i s u s u a l l y a v a i l a b l e f o r c rop use (Gupta, 1968). (2) Acid Soluble Boron A c i d s o l u b l e boron or maximum a v a i l a b l e boron u s u a l l y r e f e r s to s o l u t i o n boron, p r e c i p i t a t e d boron, adsorbed boron on s o i l c o l l o i d s and that i n c o r p o r a t e d i n org a n i c matter. T h i s f r a c t i o n i s probably of g r e a t e r importance to p l a n t growth because of e q u i l i b r i a e x i s t i n g between adsorbed and s o l u b l e boron (Bingham, 1973). A c i d s o l u b l e boron was found to be a s m a l l f r a c t i o n of the t o t a l f o r sandy m i n e r a l s o i l s , a p p roximately h a l f f o r many f i n e t e x t u r e d m i n e r a l s o i l s , and a m a j o r i t y of the t o t a l f o r s o i l s that are hig h i n mi n e r a l and o r g a n i c c o l l o i d s (Jackson, 1970). Elseewi and Elmalky (1979) e s t i m a t e d t h i s a c i d - s o l u b l e boron f r a c t i o n to range 8 from 1.4 to 22.8 ppm, with an average of 10.2 ppm. They a l s o r e p o r t e d that a c i d s o l u b l e boron ranged from 2 to 67% of the t o t a l boron, with an average of 12.6%. In g e n e r a l , the o v e r a l l s i g n i f i c a n c e of knowing the t o t a l and a c i d s o l u b l e boron might g i v e a p i c t u r e of the c a p a c i t y f a c t o r of the s o i l to supply s o l u b l e boron through e q u i l i b r i u m between the v a r i o u s forms of boron i n s o i l s . (3) Water Soluble Boron The t o t a l boron content of a s o i l i s not a r e l i a b l e index of the adequacy of supply of boron f o r p l a n t growth. Hot water s o l u b l e boron i s c l o s e l y r e l a t e d to p l a n t uptake and a s s i m i l a t i o n (Bingham, 1973). The amount of hot water s o l u b l e boron has been r e p o r t e d to range from 0.05 to over 50 ppm, the m a j o r i t y of s o i l s having v a l u e s l e s s than 3 ppm ( S i l l a n p a a , 1972; Xuan, 1983). Gupta (1968) found that hot water s o l u b l e boron ranged from 0.38 to 4.67 ppm a f t e r h i s i n v e s t i g a t i o n on a number of s o i l s from e a s t e r n Canada. The C o a s t a l s o i l s of western Canada, as r e p r e s e n t e d by those of the F r a s e r V a l l e y , were found d i s t i n c t l y low i n t o t a l boron (< 20 ppm) and q u i t e low i n a v a i l a b l e boron, g e n e r a l l y l e s s than 0.70 ppm with the exce p t i o n of a v a i l a b l e boron i n the heavy-textured recent a l l u v i a l s o i l ( F e n n e l l and L a i r d , 1949). More r e c e n t l y , i t was r e p o r t e d that 64% of the 2004 r o u t i n e samples of B r i t i s h Columbia p r o v i n c e were i n the low to very low boron range, i . e . below 0.5 ppm (Kowalenko, 1985). S i n c e boron i s h i g h l y mobile and e a s i l y leached, and 9 i t s a v a i l a b i l i t y i s o f t e n low i n areas of h i g h r a i n f a l l such as t r o p i c a l humid regions (Page and Paden, 1954; Gupta, et a l . , 1985). However, a r i d and s e m i a r i d r e g i o n soils-show boron c o n c e n t r a t i o n s ranging from 10 to 40 ppm or more, with the h i g h c o n c e n t r a t i o n s being t o x i c to most p l a n t s (Evans and Sparks, 1983). 2. 1. 3 BORON DEFICIENCY AND TOXICITY IN SOILS Boron d e f i c i e n c y has been r e p o r t e d a l l over the world. In one or more c r o p s , d e f i c i e n c i e s have been d e t e c t e d i n every s t a t e of the U n i t e d S t a t e s (Berger, 1962; S i l l a n p a a , 1972), and i n e i g h t of the ten p r o v i n c e s of Canada (Hurst and Macleod, 1936; Mackay et a l . , 1962; MacQuarrie, et a l . , 1983). In g e n e r a l , s o i l s l i k e l y to be d e f i c i e n t i n boron are (Lucas and Knezek, 1972): 1. s o i l s d e r i v e d from s o i l parent m a t e r i a l s low i n boron such as a c i d igneous rocks; 2. s o i l s leached to a c i d r e a c t i o n ; 3. s o i l s i n areas of moderate to heavy r a i n f a l l ; 4. l i g h t - t e x t u r e d sandy s o i l s ; 5. a l k a l i n e s o i l s ; and 6. s o i l s having a moisture d e f i c i t d u r i n g the growing season. The range between d e f i c i e n t , adequate and t o x i c s o i l boron c o n c e n t r a t i o n s f o r crop p r o d u c t i o n i s r a t h e r narrow, 10 and v a r i e s with crop s p e c i e s and environmental c o n d i t i o n s such as l i g h t i n t e n s i t y (Bingham, 1973; Lucas and Knezek, 1972) . T o x i c i t y i s not as widespread as boron d e f i c i e n c y . I t occurs i n those areas e i t h e r due to h i g h l e v e l s of boron i n s o i l s or due to a d d i t i o n s of boron i n i r r i g a t i o n water or as a r e s u l t of improper or o v e r f e r t i l i z a t i o n with boron f e r t i l i z e r s such as borax, b o r i c a c i d , e t c . (Keren and Bingham, 1985; Gupta, et a l . , 1985). E x c e s s i v e c o n c e n t r a t i o n s of boron are very o f t e n found i n s a l i n e s o i l s i n areas with e x c e s s i v e e v a p o r a t i o n but l i t t l e or no d r a i n a g e . I r r i g a t i o n water i s o f t e n a cause of h i g h s o i l B l e v e l s (Chauhan and Powar, 1978). However, i r r i g a t i o n water boron l e v e l s are seldom hi g h enough to i n j u r e p l a n t s d i r e c t l y . I t i s the c o n t i n u e d use and c o n c e n t r a t i o n i n the s o i l due to e v a p o t r a n s p i r a t i o n t h a t l e a d s to the e v e n t u a l t o x i c i t y problems (Gupta, et a l . , 1985). I t should be s t r e s s e d t hat i n a s s e s s i n g the c r i t i c a l ( i n j u r i o u s ) boron c o n c e n t r a t i o n f o r i r r i g a t i o n water, the p h y s i c a l - c h e m i c a l p r o p e r t i e s of the s o i l , such as t e x t u r e , pH, composition e t c . , must be take i n t o c o n s i d e r a t i o n because of the i n t e r a c t i o n between boron and s o i l . 11 2.2 BORON REACTIONS IN SOIL The d i s t r i b u t i o n of boron between the s o i l s o l i d s and s o l u t i o n i s of p a r t i c u l a r s i g n i f i c a n c e i n view of the r e l a t i v e l y narrow range between boron d e f i c i e n c y and t o x i c i t y i n p l a n t s . The a d s o r p t i o n c h a r a c t e r i s t i c s of a s o i l can i n f l u e n c e the p a r t i t i o n of boron between s o i l s o l i d s and s o l u t i o n . (Singh, 1964, 1971; R u s s e l l , 1973). V a r i o u s s o i l components, i n c l u d i n g c l a y m i n e r a l s , hydroxy oxides of A l and Fe, and s o i l o r g a n i c matter, show a f f i n i t y f o r boron i n s o i l s , and a number of f a c t o r s , such as s o i l pH, t e x t u r e , type of c l a y , m i n e r a l c o a t i n g s on the c l a y s , CEC , exchangable ion composition, i o n i c s t r e n g t h , moisture, w e t t i n g and d r y i n g and temperature were re p o r t e d to a f f e c t boron a d s o r p t i o n and d e s o r p t i o n by the s o i l c o l l o i d s . Most s t u d i e s have been r e p o r t e d on pure s o i l c o n s t i t u e n t s such as pure c l a y s , Fe- and A l - o x i d e s and organic matter components. 2. 2. 1 ADSORPTION BY CLAY MINERALS On a weight b a s i s , i l l i t e i s the most r e a c t i v e with boron and k a o l i n i t e i s the l e a s t , while m o n t m o r i l l o n i t e i s somewhere between i l l i t e and k a o l i n i t e . However, on a s u r f a c e area b a s i s boron a d s o r p t i o n on m o n t m o r i l l o n i t e i s much l e s s (Hingston, 1964; F l e e t , 1965; Sims and Bingham, 1967; Couch and Grim, 1968; Keren and Bingham, 1981). I t i s assumed that boron i s adsorbed on the c l a y edges r a t h e r than 1 2 on the p l a n a r s u r f a c e s s i n c e the c a l c u l a t e d boron c o n c e n t r a t i o n at the c l a y s u r f a c e having 8 m2/g s u r f a c e edge area i s about 6.6 x 10" 5mol/g c l a y , which i s of the same order of magnitude as t h a t found f o r i l l i t e (1.5 x 10" 5 mol/g) (Couch and Grim, 1968; Keren and Mezuman, 1981; Keren and Bingham, 1985). I t has a l s o been shown that boron a d s o r p t i o n i n c r e a s e s with d e c r e a s i n g p a r t i c l e s i z e of the c l a y m i n e r a l s on a weight b a s i s (Keren and Talpaz,1984), and t h e r e f o r e , f i n e t e x t u r e d s o i l s were found to f i x more boron than coarse t e x t u r e d ones (Wear and P a t t e r s o n , 1962; Singh, 1971). N a t u r a l l y o c c u r r i n g i l l i t e s c o n t a i n s e v e r a l times more boron than other l a y e r s i l i c a t e s and have the h i g h e s t s o r b i n g c a p a c i t y ( F l e e t , 1965; Hingston, 1964; Couch and Grim 1968). Couch and Grim (1968) proposed a two-step mechanism f o r boron r e t e n t i o n by i l l i t e s , v i z . , a r a p i d r e a c t i o n and a slow a d s o r p t i o n process of d i f f u s i o n . They suggested that the former was due to r a p i d chemical a d s o r p t i o n of t e t r a h e d r a l B(OH);; anion on the " f r a y e d edge s i t e s " of i l l i t e f l a k e s and the l a t t e r to slower d i f f u s i o n of boron i n t o t e t r a h e d r a l s t r u c t u r a l s i t e s i n the c r y s t a l . They a l s o suggested that poor c r y s t a l l i n i t y , lower potassium content and g r e a t e r abundance of mixed-layer m a t e r i a l of i l l i t e may e x p l a i n i t s h i g h a d s o r p t i o n c a p a c i t y . The presence of l a r g e amounts of aluminum and/or s i l i c o n i n i l l i t e may be another reason why t h i s mineral adsorbs more boron than other types of c l a y s ( G r i f f i n and Buran, 1974). 1 3 2. 2. 2 ADSORPTION BY ORGANIC MATTER Organic matter has an important i n f l u e n c e on the n u t r i e n t h o l d i n g c a p a c i t y of s o i l s . An e a r l y study by Midgley and Dunklee (1939) i n d i c a t e d an unusual i n c r e a s e d borate a d s o r p t i o n with excess lime r a t e s by a podsol A, h o r i z o n and a marine peat moss. The o r g a n i c matter of these s o i l s seemed r e s p o n s i b l e f o r t h i s lime a c t i v a t e d B f i x a t i o n , and a number of lime m a t e r i a l s such as c a l c i u m , barium, magnesium and sodium carbonates were shown e q u a l l y e f f e c t i v e i n f i x i n g b o r a t e s . Berger and P r a t t (1963) found that a l a r g e p a r t of the t o t a l boron i n s o i l s i s a s s o c i a t e d w i t h the organic matter i n t i g h t l y bound compounds. However t h i s boron can be r e l e a s e d to s o i l s o l u t i o n , i n forms a v a i l a b l e to p l a n t s , by m i c r o b i a l a c t i v i t i e s . More r e c e n t l y , E l r a s h i d i and O'Connor (1982) showed that the percentage of o r g a n i c carbon e x p l a i n e d 90% of the v a r i a n c e of adsorbed boron by 10 s o i l s from New Mexico. P a l i w a l and Mehta (1973) r e p o r t e d that boron r e t e n t i o n i n c r e a s e d with an i n c r e a s e i n the organic matter content of s o i l . O x i d a t i o n of s o i l o r g a n i c matter r e s u l t e d i n a s i g n i f i c a n t r e l e a s e of boron i n forms a v a i l a b l e f o r p l a n t s and caused a s l i g h t decrease i n boron f i x a t i o n (Olson and Berger, 1946). Calcium s a t u r a t e d humus e x t r a c t e d with Na 2C0 3-NaHC0 3 was found to r e t a i n as much as 630 ug B/g humus, which i s much higher than that r e t a i n e d by c l a y m i n e rals (Parks and White, 1952). Many other r e p o r t s showed a good r e l a t i o n s h i p between s o i l o r g a n i c matter 14 content and s o i l a v a i l a b l e boron content. Berger and Truog (1945) i n v e s t i g a t e d the r e l a t i o n s h i p of org a n i c matter content and s o i l pH t o the content of a v a i l a b l e boron f o r 34 v i r g i n and 48 c u l t i v a t e d s o i l s and concluded that s o i l s having a pH below 7.3 and c o n t a i n i n g c o n s i d e r a b l e o r g a n i c matter u s u a l l y c o n t a i n e d adequate s u p p l i e s of a v a i l a b l e boron and a l l s o i l s c o n t a i n i n g l e s s than 2% of o r g a n i c matter and a l s o those c o n t a i n i n g s i g n i f i c a n t amounts of ca l c i u m carbonate were i n v a r i a b l y low i n a v a i l a b l e boron. Very s i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t s (r=0.83 and it it r=0.79 ) between per c e n t of organic matter content and hot water s o l u b l e boron c o n t e n t i n s o i l s were ob t a i n e d by M i l j k o v i c et a l . (1966) and Martens (1968). S i m i l a r o b s e r v a t i o n s were made by other r e s e a r c h e r s (Midgley and Dunklee,1940; Hatcher et a l . f 1967; Gupta, 1968; Singh, 1971; and John et a l . , 1977.) S o i l o r g a n i c matter i s known to be e n r i c h e d with a l c o h o l i c and p h e n o l i c h y d r o x y l s , and c a r b o x y l groups (Stevenson, 1982). I t i s a l s o known that b o r i c a c i d i s a b l e to i n t e r a c t with such d i - h y d r o x y l (or p o l y o l ) o r g a n i c compounds to form complexes. The i n t e r a c t i o n can be formulated as f o l l o w s (Boeseken, 1949): =C-OH B(OH) 3 =c-o t =c-o =C-OH The r e a c t i o n p r o d u c t s , monodiol b o r i c a c i d and b i s d i o l b o r i c a c i d , are co m p a r a t i v e l y s t r o n g a c i d s . T h i s p r o p e r t y of b o r i c 15 a c i d i s a l s o o f t e n used f o r i t s s e p a r a t i o n from other compounds and a l s o f o r the d e t e r m i n a t i o n of the c o n f i g u r a t i o n of the carbohydrates (Nemedruk and K a r a l o v a , 1965). More i n f o r m a t i o n about t h i s aspect can be found i n the l i t e r a t u r e of boron chemistry and chemistry of c a r b o h y d r a t e s . F o r s y t h (1950) i n h i s s t u d i e s of the composition of the s o l u b l e p o l y s a c c h a r i d e f r a c t i o n of s o i l o rganic matter, found that the p o l y s a c c h a r i d e p r e p a r a t i o n s from widely d i f f e r e n t s o i l s had very s i m i l a r p r o p e r t i e s . Upon h y d r o l y s i s they gave the same sugars, g a l a c t o s e , glucose, mannose, a r a b i n o s e , x y l o s e , and g l u c u r o n i c a c i d , although the p r o p o r t i o n s v a r i e d to some extent i n the d i f f e r e n t samples. A l l these compounds meet the requirements fo r complex formation with b o r i c a c i d , and most of them have been demonstrated to r e a c t with b o r i c a c i d (Boeseken, 1949). I t appears, t h e r e f o r e , that the complex formation between d i - h y d r o x y l s and b o r i c a c i d o f f e r s the e x p l a n a t i o n f o r boron r e t e n t i o n by s o i l humus as proposed by Parks and White (1952). In a study on the pH-dependent s o r p t i o n of boron by s o i l o r g a n i c matter, H u e t t l ( l 9 7 6 ) concluded t h a t : 1. the n e u t r a l b o r i c a c i d s p e c i e s was adsorbed on the pH-dependent a-hydroxy c a r b o x y l i c a c i d s i t e at low pH, and the pH-dependent borate s p e c i e s was sorbed on the pH-dependent c / s - d i o l s i t e s at higher pH v a l u e s ; 2. the s o r p t i o n of boron by o r g a n i c matter d i d not f o l l o w s i n g l e - s i t e Langmuir theory, and there were i n d i c a t i o n s t h a t m u l t i - s i t e s o r p t i o n was o c c u r r i n g ; 16 3. the s o r p t i o n of boron by organic matter i n c r e a s e d r e l a t i v e l y s l o w l y with a r i s e i n pH to about 6, at which p o i n t the i n c r e a s e became very d r a s t i c with f u r t h e r pH r i s e to at l e a s t pH 8. However, Bingham et a l . (1971) and Mezuman and Keren (1981) r e c e n t l y q u e s t i o n e d the importance of s o i l o r g a n i c matter i n boron a d s o r p t i o n . Bingham et a l . (1971) r e p o r t e d that o r g a n i c matter had a small e f f e c t on boron a d s o r p t i o n f o r -a number of amorphous s o i l s . Mezuman and Keren (1981) s t u d i e d the e f f e c t of o r g a n i c matter on boron a d s o r p t i o n by a s o i l c o n t a i n i n g 1.2% o r g a n i c matter and found i t to be n e g l i g i b l e . Furthermore, Harada and Tamai (1968) r e p o r t e d that d e s t r u c t i o n of o r g a n i c matter l e d to an i n c r e a s e i n boron a d s o r p t i o n of the s o i l s , and assumed that s o i l o r g a n i c matter a c t e d r a t h e r to decrease boron a d s o r p t i o n by forming c l a y - m e t a l - o r g a n i c matter complexes i n s o i l s . T h e r e f o r e , the exact f u n c t i o n a l nature of s o i l o r g a n i c matter on boron a d s o r p t i o n i n s o i l s and a v a i l a b i l i t y of boron to p l a n t s remains l i t t l e known. 2. 2. 3 ADSORPTION BY HYDROXY OXIDES OF AL AND FE Hydroxy o x i d e s of A l and Fe occur i n s o i l s as thermodynamically u n s t a b l e p r e c i p i t a t e s , depending on s o i l pH and Eh c o n d i t i o n s , and as c o a t i n g s of these forms on c l a y m i n e r a l s and o r g a n i c c o l l o i d s . They have been shown to adsorb l a r g e amounts of boron (Hatcher et a l . , 1967; Sims 1 7 and Bingham, 1968a; McPhail et a l . , 1972; Keren and Gast, 1983). The amount of boron adsorbed by hydroxy-Al at pH 9.5 was about 7.5 times g r e a t e r than that by C a - m o n t m o r i l l o n i t e under the same c o n d i t i o n s (Keren and Gast, 1983; Keren and Mezuman, 1981). Boron r e t e n t i o n by hydroxy-Fe and - A l m a t e r i a l s was a l s o found to be pH dependent w i t h maximum r e t e n t i o n o c c u r r i n g i n the a l k a l i n e range. The hydroxy aluminum m a t e r i a l s r e t a i n e d boron i n amounts t h a t were an order of magnitude g r e a t e r than the amounts r e t a i n e d by the hydroxy i r o n m a t e r i a l s (Sims and Bingham, 1968a). Aging the p r e c i p i t a t e s tended to s i g n i f i c a n t l y reduce the amounts of boron adsorbed (Sims and Bingham, 1968a; McPhail et a l . , 1972). A c c o r d i n g to Sims and Bingham (1968a), the amount of boron combined with the p r e c i p i t a t e d i r o n at pH 9 decreased with time from 680 to 420 wg B/g as the samples were aged from 1 to 42 days, while f o r the p r e c i p i t a t e d aluminum under the same c o n d i t i o n s , the decrease was from about 3750 to 500 ug B/g. Hatcher et a l . (1967) showed that when a c i d s o i l s were limed, the primary r e a c t i o n was the replacement of exchangeable A l and hydroxy-Al c a t i o n s and t h e i r p r e c i p i t a t i o n as aluminum hydroxide, A l ( O H ) 3 . They p o s t u l a t e d t h a t lime-induced boron d e f i c i e n c y i n p l a n t s was caused by decreases i n the boron c o n c e n t r a t i o n of the s o i l s o l u t i o n r e s u l t i n g from a d d i t i o n a l a d s o r p t i o n by the A l ( O H ) 3 that p r e c i p i t a t e d on l i m i n g . They f u r t h e r concluded that A l ( O H ) 3 and s i m i l a r hydroxy-Al m a t e r i a l s were the major s o i l 18 c o n s t i t u e n t s c a u s i n g boron r e t e n t i o n by s o i l s . A number of workers (Okazaki and Chao, 1968; Bingham et a l . , 1971; Bingham and Page, 1971; Schalscha et a l . , 1973) have s t u d i e d boron a d s o r p t i o n on s o i l s d e r i v e d form v o l c a n i c d e p o s i t s i n which a l l o p h a n e and f r e e Fe oxides are the major s o i l c o n s t i t u e n t s of the s u r f a c e r e t e n t i o n . Hydrous oxide c o a t i n g s of A l and Fe on l a y e r s i l i c a t e s were found to s i g n i f i c a n t l y i n c r e a s e the amount of boron adsorbed (Sims and Bingham, 1968b). M o n t m o r i l l o n i t e and k a o l i n i t e coated with o x i d e s , e s p e c i a l l y of A l , e x h i b i t e d a marked i n c r e a s e i n boron a d s o r p t i o n . Washing v e r m i c u l i t e with NaCl l e d to a decrease i n boron a d s o r p t i o n . I t was suggested that A l oxides had been removed from the i n t e r l a y e r p o s i t i o n s r e s u l t i n g i n the decreased a d s o r p t i o n . Sims and Bingham (1968b) a l s o found that hydroxy-aluminum coated on m o n t m o r i l l o n i t e was l e s s r e t e n t i v e on a weight b a s i s than that when coa t e d on k a o l i n i t e . T h i s f i n d i n g i n d i c a t e s that hydroxy-aluminum may e x i s t as an i n t e r l a y e r between the m o n t m o r i l l o n i t e p l a t e l e t s and t h a t p a r t of the hydroxy-aluminum s u r f a c e i s not a v a i l a b l e f o r boron a d s o r p t i o n . The oxide c o a t i n g s appeared to be more important than the c l a y m i n e r a l s themselves as boron-adsorption s i t e s . Two mechanisms of boron a d s o r p t i o n on hydrous oxides of A l and Fe have been proposed by Sims and Bingham (1968a): 19 Anion exchange mechanism, \ OH. ^OH HO OH" N OH^  OH M M + B = .M ~M '' OH HO'' NOH '' O*^  N0H OH N B / - + OH" HO7' N0H Borate becoming the end member of A l - and Fe(OH) x polymers, \ X)H J>H HO OH" N JOH ^OH OH ^ + V - X V X X HO OH ' 0 X 'OH N0H They a l s o suggested that the r e a c t i o n may be analogous to the formation of the b o r a t e - d i o l complex, i . e . , \ ^OH ^OH HO OH" \ ^OH O .OH M M + B' = M ~M B + 2H 20 '' N 0 ^ ^OH HO' N0H \ T N o ' N0H These r e a c t i o n s are a l l pH dependent wi t h maximum boron r e t e n t i o n o c c u r i n g at pH about 8.5. The decrease i n a d s o r p t i o n a t higher pH i s a t t r i b u t e d t o i n c r e a s i n g OH" co m p e t i t i o n f o r the a d s o r p t i o n s i t e s . The r e d u c t i o n of a d s o r p t i o n with aging i s assumed to be a r e s u l t of changes i n the s u r f a c e p r o p e r t i e s of the s o l i d m a t r i x . As the f r e s h p r e c i p i t a t e s aged or d r i e d , t h e i r c r y s t a l l i n i t y i n c r e a s e d and t h e r e f o r e s u r f a c e area decreased r e s u l t i n g i n l e s s c a p a c i t y f o r boron r e t e n t i o n (McPhail, e t a l . , 1972; Evans and Sparks, 1983). The high e r r e t e n t i o n of A l r e l a t i v e to Fe m a t e r i a l was p o s s i b l y due to the abundance of OH" groups of A1(0H) 3 and A l - c o a t e d m a t e r i a l s compared wi t h Fe(OH) 3 and Fe-coated m a t e r i a l s (Sims and Bingham, 1968a). 20 2. 2. 4 PROPOSED BORON ADSORPTION MECHANISMS A number of r e a c t i o n s between boron and s o i l have been suggested, i n c l u d i n g : 1. s o r p t i o n of borate i o n s , B(OH)j; 2. s o r p t i o n of molecular b o r i c a c i d , B(OH) 3; 3. f o r m a t i o n of o r g a n i c complexes; 4. e n t r y of boron i n t o the c l a y m i n e r a l l a t t i c e ; and 5. p r e c i p i t a t i o n of i n s o l u b l e b o r a t e s with alumina and s i l i c a (Hingston, 1964). More r e c e n t l y , Keren and Bingham (1985) proposed two approaches to e x p l a i n the boron a d s o r p t i o n p r o c e s s e s : 1. e l e c t r o s t a t i c chemical approach, i n which the adsorbents had an i o n i z a b l e s u r f a c e due to amphoteric behaviour of s u r f a c e groups, and 2. s u r f a c e complexation approach, i n which the s u r f a c e was c o n s i d e r e d as a l i g a n d . The c r y s t a l s t r u c t u r e of an oxide and the c l a y p a r t i c l e edge s u r f a c e s g i v e r i s e t o s u r f a c e c a t i o n s which are not f u l l y c o o r d i n a t e d i n t o the " i d e a l " i o n i c l a t t i c e and may r e s u l t i n a r e s i d u a l charge on s u r f a c e l i g a n d s (Keren and Gast, 1983; Keren and Bingham, 1985). In an aqueous s o l u t i o n such s u r f a c e s i t e s w i l l be h y d r o x y l a t e d and changed i n a manner as f o l l o w s : OH" Va 0 21 OH" V* 0 OH" -1 A l + OH- A l OH 2 1/2 OH" 1/2 T h e r e f o r e , The e l e c t r o s t a t i c c h e m i c a l approach t r e a t s the s u r f a c e s of the oxides and the broken edges of c l a y m i n e r a l s as the p l a t e with a v a r i a b l e s u r f a c e charge and s u r f a c e p o t e n t i a l (depending on the r e v e r s i b i l i t y of a d s o r p t i o n of H + or OH" ions by the s u r f a c e ) , and the charge was n e u t r a l i z e d i n aqeuous s o l u t i o n s by adsorbed ions having an o p p o s i t e charge. T h i s approach i s p r o b a b l y i n s i g n i f i c a n t by c o n s i d e r i n g t h a t even under lower pH (pH < PZC) c o n d i t i o n s the s u r f a c e i s p o s i t i v e l y charged, and because the u n d i s s o c i a t e d B(OH) 3 s p e c i e s are predominant i n the system, t h e r e f o r e , the coulombic f o r c e s are not i n v o l v e d i n boron a d s o r p t i o n . The approach thus f a i l e d to e x p l a i n some of the e x p e r i m e n t a l r e s u l t s of boron a d s o r p t i o n by c l a y m i n e r a l s (Keren and Gast, 1982). Surface complexation seems the most p l a u s i b l e e x p l a n a t i o n s i n c e boron can be s p e c i f i c a l l y adsorbed on m i n e r a l edge s u r f a c e s and hydroxy-Al and -Fe polymers through a mechanism r e f e r r e d as l i g a n d exchange. The adsorbed s p e c i e s d i s p l a c e OH" (or H 20) from the s u r f a c e and form p a r t l y c o v a l e n t bonds with the s t r u c t u r a l c a t i o n s (Hingston, et a l . , 1974; Keren and Bingham, 1975). Some p o s s i b l e c l a y s u r f a c e complex c o n f i g u r a t i o n s f o r boron are shown as f o l l o w s (Keren and Bingham, 1985): 22 OH HO \ / OH HO. OH HO - B - OH B V / \ o o o 0 A l - A l A l A l T h i s i s supported by the experimental r e s u l t s t h a t boron a d s o r p t i o n by v a r i o u s s o i l c o n s t i t u e n t s i n c r e a s e s with an i n c r e a s e of pH or i o n i c s t r e n g t h , i r r e s p e c t i v e of the s i g n of the net s u r f a c e charge (Keren and O'Connor, 1982; Keren and Gast, 1983; Hingston et a l . , 1974). The suggested mechanism f o r the r e a c t i o n of o r g a n i c s i t e s (Boeseken, 1949) w i t h boron i s s i m i l a r t o the h y d r o x y l replacements f o r i n o r g a n i c s i t e s . Other mechanisms suggested by Hingston (1964) must a l s o o perate under c e r t a i n c i r c u m s t a n c e s . I n c o r p o r a t i o n of boron i n t o the c r y s t a l l i n e s t r u c t u r e of s i l i c a t e m i n e r a l s i s e s p e c i a l l y t rue f o r i l l i t e . Harder (1961) observed that boron added to i l l i t e c l a y had not reached e q u i l i b r i u m i n 153 days, suggesting a slow p r o c e s s of boron i n c o r p o r a t i o n i n t o c r y s t a l l i n e s t r u c t u r e of the s i l i c a t e m i n e r a l s . T h i s mechanism i s a l s o supported by other r e s e a r c h e r s (Couch and Grim, 1968; F l e e t , 1965). Because of the s i m i l a r i t y between the t e t r a h e d r a l s t r u c t u r e of the borate s p e c i e s and that of s i l i c o n or aluminum i n the s i l i c a t e c r y s t a l , S t u b i c a n and Roy (1963) observed by i n f r a - r e d s p ectroscopy t h a t AlO„ groups c o u l d be r e p l a c e d with BO, groups i n the t e t r a h e d r a l l a y e r of the mica and c l a y m i n e r a l s t r u c t u r e s . P r e c i p i t a t i o n 23 of i n s o l u b l e borates with alumina and s i l i c a , was proven by Parks and Shaw (1941). They found that boron i n a p r e c i p i t a t e of C a - S i - A l was very i n s o l u b l e i n hot water. 2.3 BORON ADSORPTION ISOTHERMS AND A WAY OF MAKING BORON  FERTILIZER RECOMMENDATION When boron i s added i n t o a s o i l , i t w i l l p a r t i t i o n between a s o l i d phase (adsorbent) and a s o l u t i o n phase. The amount of boron adsorbed from the s o l u t i o n c o n t a i n i n g added boron i s an i n d i c a t i o n of the i n t e n s i t y - c a p a c i t y e q u i l i b r i u m f a c t o r . V a r i o u s a d s o r p t i o n isotherms are the best way to d e s c r i b e such a d s o r p t i o n r e a c t i o n s i n s o i l systems. The boron a d s o r p t i o n isotherm method of s o i l t e s t i n g may a l s o p r o v i d e a more ac c u r a t e e s t i m a t e of the f e r t i l i z e r r e q u i r e d to b r i n g the s o i l to an optimum boron l e v e l . T h i s i s important when making f e r t i l i z e r recommendations s i n c e c o n v e n t i o n a l s o i l t e s t s f o r hot-water e x t r a c t a b l e boron are unable to r e v e a l the s o i l f i x i n g power (or c a p a c i t y ) and thus may l e a d to erroneous f e r t i l i z e r recommendations (Shumway and Jones, 1972). 2. 3. 1 ADSORPTION MODELLING A number of equations (models) have been used to d e s c r i b e boron a d s o r p t i o n isotherms, i n c l u d i n g the F r e u n d l i c h equation, the Langmuir equation and a 24 phenomenological equation proposed by Keren et a l . (1981). The F r e u n d l i c h equation was r e p o r t e d to f i t the boron a d s o r p t i o n isotherms q u i t e w e l l over the whole range of boron c o n c e n t r a t i o n s t u d i e d ( F l e e t , 1965; Lerman, 1966; Couch and Grim, 1968; E l r a s h i d i and O'Connor, 1982). E l r a s h i d i and O'Connor (1982) found that the equation was a p p l i c a b l e to boron c o n c e n t r a t i o n s from 0 to 100 m g « L _ 1 f o r a l l 10 s o i l s . The equation can be expressed as f o l l o w s : x/m = a • c*3 where: x/m = amount of boron adsorbed per u n i t weight of adsorbent; c = e q u i l i b r i u m c o n c e n t r a t i o n of adsorbate i n s o l u t i o n ; and a and b = e m p i r i c a l c o n s t a n t s . To determine i f the data are i n agreement with the F r e u n d l i c h isotherm, i t i s more convenient to use the l o g a r i t h m i c form, i . e . log(x/m) = l o g a + b«log c A p l o t of log(x/m) versus l o g ( c ) y i e l d s a s t r a i g h t l i n e with a slope of b and an i n t e r c e p t of log(a) i f the data conform to the F r e u n d l i c h isotherm. T h i s equation has a l i m i t a t i o n t h a t i t does not p r e d i c t a maximum q u a n t i t y of a d s o r p t i o n . The f l e x i b i l i t y of the two c o n s t a n t s allows f o r easy curve 2 5 f i t t i n g but does not guarantee accuracy i f the data i s e x t r a p o l a t e d beyond the experimental p o i n t s . T h i s may be true f o r the other two eq u a t i o n s . The Langmuir equation (Langmuir, 1918) was developed through the k i n e t i c theory of gases to d e s c r i b e a d s o r p t i o n of gases on s o l i d s . The equation was then adapted by other r e s e a r c h e r s to d e s c r i b e the a d s o r p t i o n of ions from s o l u t i o n by s o l i d s . A number of i n v e s t i g a t o r s have r e p o r t e d t h a t boron a d s o r p t i o n by s o i l s or some s o i l c o n s t i t u e n t s a t a given pH c o u l d be s u c c e s s f u l l y d e s c r i b e d by the Langmuir equation but over a l i m i t e d range of boron c o n c e n t r a t i o n s (Hingston, 1964; Biggar and Fireman, 1960; Singh, 1964; Bingham et a l . , 1971). D e v i a t i o n s from Langmuir theory are common at h i g h c o n c e n t r a t i o n s of boron i n s o l u t i o n . The equation i s given below: x/m = bkc/(l+kc) or c/x/m = 1/bk + c/b where: x/m = boron adsorbed per mass of adsorbent; c = c o n c e n t r a t i o n of boron i n e q u i l i b r i u m s o l u t i o n ; k = s l o p e / i n t e r c e p t and i s a constant r e l a t e d to bonding energy; and b = 1/slope or i s the maximum a d s o r p t i o n parameter. I t was found that the value (b) f o r the monolayer of adsorbed boron i n c r e a s e d with pH, whereas the value (k) decreased with pH f o r k a o l i n i t e and m o n t m o r i l l o n i t e but 26 i n c r e a s e d s l i g h t l y f o r i l l i t e (Hingston, 1964). S o i l s were found to vary i n t h e i r c a p a c i t y to f i x boron and i n the energy of r e t e n t i o n . For example, the k v a l u e s i n c r e a s e d with c l a y content and d e v i a t i o n s from the equation were found as the number of w e t t i n g and d r y i n g c y c l e s i n c r e a s e d (Biggar and Fireman, 1960). There are a l s o s e v e r a l l i m i t a t i o n s of u s i n g t h i s e quation, which a r e : (1) i t on l y p r e d i c t s a l i n e a r r e l a t i o n s h i p at low boron c o n c e n t r a t i o n s and can not a c c u r a t e l y p r e d i c t boron a d s o r p t i o n as a f u n c t i o n of pH; (2) i t does not allow f o r two boron s p e c i e s with v a r y i n g a f f i n i t i e s f o r the c l a y as i n the case of boron a d s o r p t i o n ; (3) d i f f e r e n t v a l u e s of b and k must be a s s i g n e d a t g i v e n pH v a l u e s t o p r e d i c t a d s o r p t i o n . Another equation f o r d e s c r i b i n g boron a d s o r p t i o n by s o i l s and s o i l c o n s t i t u e n t s was d e r i v e d by Keren et a l . (1981) i n an attempt to overcome the above d i f f i c u l t i e s . T h i s model i s based on the assumption t h a t B(OH) 3, B(OH)i, and OH - are a l l competing f o r the same a d s o r p t i o n s i t e s . The equation d e s c r i b e s boron a d s o r p t i o n as a f u n c t i o n of both e q u i l i b r i u m boron c o n c e n t r a t i o n and the pH of the suspension s o l u t i o n , and i s expressed as f o l l o w s (Keren et a l . , 1981; Mezuman and Keren, 1981): Q V K H B + K B ( B ) ] 1 + K H B(HB) + K B(B) + K Q H(OH) where: Q B T = t o t a l amount of adsorbed boron; 27 T m = the maximum boron a d s o r p t i o n ; KHB' K B ' a n c ^ K0H = a f f i n i t y c o e f f i c i e n t s r e l a t e d to the b i n d i n g energy f o r the s p e c i e s B(OH) 3, B(OH)^, and OH -, r e s p e c t i v e l y ; and (HB), (B), and (OH) = the s o l u t i o n a c t i v i t i e s of the above s p e c i e s , r e s p e c t i v e l y . The four parameters i n the equation, three a f f i n i t y c o e f f i c i e n t s and the maximum boron a d s o r p t i o n v a l u e , can be c a l c u l a t e d from experimental r e s u l t s with a computer program. The equation was found to agree with experimental r e s u l t s of boron a d s o r p t i o n by c l a y m i n e r a l s , h y d r o x y - A l , and s o i l s (Keren et a l . , 1981; Keren and Gast, 1981; Keren and Mezuman, 1981; Keren and O'Connor, 1982; Mezuman and Keren, 1981; Keren and Gast, 1983). The pH of the maximum boron a d s o r p t i o n on C a - m o n t m o r i l l o n i t e , C a - i l l i t e , and C a - k a o l i n i t e was r e p o r t e d to be 9.7, 9.3, and 9.0, r e s p e c t i v e l y . 2. 3. 2 A WAY OF MAKING FERTILIZER RECOMMENDATION A c c o r d i n g to the o b s e r v a t i o n s of Hatcher et a l . (1959), Ryan et a l . (1977), and Keren et a l . (1985b), p l a n t s respond p r i m a r i l y to the c o n c e n t r a t i o n of boron i n s o i l s o l u t i o n , independently of the amount of boron t h a t i s adsorbed by a s o i l . The l a c k of u n i v e r s a l i t y of hot water s o l u b l e boron to p r e d i c t boron a v a i l a b i l i t y may, t h e r e f o r e , be due to hot water e x t r a c t i n g boron from s o i l s o l u t i o n as w e l l as that 28 adsorbed on s o i l c o l l o i d s . Shumway and Jones (1972) i n d i c a t e d that a l t h o u g h c o n v e n t i o n a l methods of s o i l boron d e t e r m i n a t i o n have p r o v i d e d reasonable estimates of p l a n t a v a i l a b l e boron, these t e s t s have f a i l e d to p r e d i c t a c c u r a t e l y the boron f e r t i l i z e r r e q u i r e d on s o i l s found to be d e f i c i e n t . Boron a d s o r p t i o n isotherms have been used to e x p l a i n boron a d s o r p t i o n phenomena i n s o i l . I t was a l s o suggested that t h i s method of s o i l t e s t i n g may p r o v i d e an estimate of the f e r t i l i z e r r e q u i r e d to b r i n g the s o i l to an optimum boron l e v e l (Shumway and Jones, 1972). I t was found that boron added was l i n e a r with re s p e c t to boron i n e q u i l i b r i u m s o l u t i o n with boron c o n c e n t r a t i o n s ranging from 0.1 to 0.8 ppm, and boron f e r t i l i z e r r e q u i r e d to a d j u s t the e q u i l i b r i u m s o l u t i o n c o n c e n t r a t i o n c o u l d be c a l c u l a t e d from the l e a s t squares r e g r e s s i o n equation of the two v a r i a b l e s . The method takes i n t o c o n s i d e r a t i o n the p h y s i c a l and chemical c h a r a c t e r i s t i c s of the s o i l , and t h e r e f o r e , has a c o n s i d e r a b l e agronomic s i g n i f i c a n c e i n both p r e v e n t i o n of boron t o x i c i t y and c o r r e c t i o n of boron d e f i c i e n c y . 3. MATERIALS AND METHODS 3.1 SOILS Three s o i l samples were used as sources of org a n i c matter i n t h i s study, namely: 1. the Ap h o r i z o n of the Langley s o i l , which i s a p o o r l y d r a i n e d Humic L u v i c G l e y s o l developed on marine d e p o s i t • i n Langley, B r i t i s h Columbia, Canada; 2. the Bhf h o r i z o n of the Whonnock s o i l , which i s c l a s s i f i e d as an O r t h i c D u r i c Ferro-Humic Podsol developed on g l a c i a l t i l l i n Burke Mountain, Vancouver, Canada; 3. Ah h o r i z o n of a Chernozemic s o i l (no s e r i e s name a s s i g n e d ) , which i s c l a s s i f i e d as an O r t h i c Black Chernozem and was sampled near Kamloops, B r i t i s h Columbia, Canada. I t i s a l a b o r a t o r y sample a v a i l a b l e from Dr. Lowe. 1 S o i l samples were chosen r a t h e r a r b i t r a r i l y because a main goal of t h i s i n v e s t i g a t i o n was to look a t the boron a d s o r p t i o n by s o i l o r g a n i c m a t e r i a l s , i r r e s p e c t i v e which s o i l they were e x t r a c t e d from. Three types of s o i l s were s e l e c t e d i n order to look at the r e p r o d u c i b i l i t y of boron a d s o r p t i o n by s o i l humic a c i d s from d i f f e r e n t s o urces. These s o i l s were a l s o l o c a l , convenient sources. Langley s o i l and Chernozemic s o i l were used as sources of s o i l p o l y s a c c h a r i d e 1Dr. L. E. Lowe, Department of S o i l S c i e n c e , The U n i v e r s i t y of B r i t i s h Columbia. 29 30 because they c o n t a i n e d a r e l a t i v e l y h i g h amount; whereas Whonnock s o i l c o n t a i n e d a r e l a t i v e l y high amount of the f u l v i c p o l y p h e n o l , and was t h e r e f o r e used as a source of the p o l y p h e n o l . The s o i l s were a i r - d r i e d a f t e r sampling and f i b r o u s m a t e r i a l s (mainly grass r o o t s ) and numerous l a r g e quartz g r a i n s or stones were removed. The a i r - d r i e d s o i l s were then ground to pass a 60-mesh s i e v e , w e l l mixed and s t o r e d i n p l a s t i c bags. 3.2 ORGANIC MATTER FRACTIONS 3. 2. I ISOLATION OF SOIL HUMIC ACID AND FULVIC POLYPHENOL (I) Extraction and Purification of Soil Humic Acid (HA) The method used f o r the i s o l a t i o n of s o i l humic a c i d and f u l v i c p o l y p h e n o l was based on one developed by Lowe (1975, 1980) with some m o d i f i c a t i o n s . The procedures were as f o l l o w s : Twenty gram s o i l samples were e x t r a c t e d with 150mL 0.1M NaOH + 0.1M N a „ P 2 0 7 i n 250 mL c e n t r i f u g e b o t t l e by shaking o v e r n i g h t on a r e c i p r o c a l shaker. The suspensions were c e n t r i f u g e d f o r 15 min at 6000 rpm (5858 r c f ) using a Sorvall Superspeed RC 2-B and e x t r a c t s decanted. The s o i l r e s i d u e s were r e - e x t r a c t e d with lOOmL e x t r a c t a n t f o r 1 h and the e x t r a c t s were combined and a c i d i f i e d to pH about 1.5 with 6M HC1 to separate the humic and f u l v i c a c i d f r a c t i o n s . 31 The a c i d i f i e d e x t r a c t was c e n t r i f u g e d f o r 15 min at 6000 rpm and the supernatant ( F u l v i c a c i d f r a c t i o n ) was decanted. The p r e c i p i t a t e (Humic a c i d f r a c t i o n ) was r e d i s s o l v e d with 0.1M NaOH and r e - a c i d i f i e d to pH about 1.5 and then c e n t r i f u g e d . The supernatants (FA) were combined, and the p r e c i p i t a t e s (HA) were r e d i s s o l v e d with 0.1M NaOH. The a l k a l i n e HA f r a c t i o n was p u r i f i e d by d i a l y s i n g the HA a g a i n s t d e m i n e r a l i z e d water using V i s k i n g D i a l y s i s t u b ing fo r 3 days.- The water i n the 4L beaker was changed 3-4 times a day. T h i s HA suspension was f u r t h e r c o n c e n t r a t e d u s i n g a D i a f l o PM-10 membrane (M.W.>10,000) on an Amicon Model TCF-10 p r e s s u r i z e d c e l l (Amicon C o r p o r a t i o n , Lexington, Mass), and then f r e e z e - d r i e d u sing a Freeze dryer 18, Labconco, and s t o r e d i n a g l a s s b o t t l e . The HAs e x t r a c t e d with t h i s method from the s o i l s were named as LA-HA(a), CH-HA(a), and WH-HA(a), r e s p e c t i v e l y . (2) Extraction and Purification of Soil Fulvic Polyphenol (PP) The f u l v i c a c i d f r a c t i o n e x t r a c t e d from Langley s o i l and Chernozemic s o i l were d i s c a r d e d s i n c e they c o n t a i n e d a r e l a t i v e l y s m a l l amount of the f u l v i c p o l y p h e n o l s . The f u l v i c a c i d f r a c t i o n of Whonnock s o i l was c o l l e c t e d as the only source of s o i l f u l v i c polyphenol because t h i s s o i l c o n t a i n e d a r e l a t i v e l y l a r g e amount of p o l y p h e n o l s . The s o i l p o l yphenol was o b t a i n e d by pa s s i n g the f u l v i c a c i d f r a c t i o n through the PVP ( P o l y v i n y l p y r r o l i d o n e ) column which had 32 been p r e v i o u s l y washed (Lowe, 1975; 1980). Most of the c o l o r e d m a t e r i a l ( p o l y p h e n o l i c r i c h f r a c t i o n ) was removed by PVP and the e l u a t e c o n t a i n e d a p o l y s a c c h a r i d e r i c h f r a c t i o n and s o l u b l e s a l t s , which was d i s c a r d e d . Those adsorbed p o l y p h e n o l s were then e l u t e d with 0.1N NaOH u n t i l most c o l o r e d m a t e r i a l s were removed. The a l k a l i n e e l u a t e was saved as the polyphenol f r a c t i o n . T h i s f r a c t i o n was then immediately passed through Rexyn ( H + ) - r e s i n column to remove excess Na + and other p o l y p h e n o l i c complexed c a t i o n s . T h i s p u r i f i e d p o l y p h e n o l i c s o l u t i o n has a pH around 2.0. S i m i l a r l y to the HA, t h i s p u r i f i e d polyphenol s o l u t i o n was c o n c e n t r a t e d on a membrane YM-2 (M.W.>1,000), f r e e z e - d r i e d , and then s t o r e d i n a g l a s s b o t t l e , and d e s i g n a t e d as WH-PP. 3. 2. 2 ISOLATION OF THE SOIL POLYSACCHARIDE (I) Ext r act i on of the Soil Polysaccharide S i n c e a l a r g e amount of s o i l p o l y s a c c h a r i d e was d e s i r e d , and p o l y s a c c h a r i d e i s only a minor c o n s t i t u e n t of most s o i l s , the c h o i c e of the e x t r a c t i o n method depended on the e f f i c i e n c y of the e x t r a c t a n t and time a v a i l a b l e . S e v e r a l e x t r a c t i o n methods were t e s t e d before the bulk e x t r a c t i o n of the s o i l p o l y s a c c h a r i d e was commenced, and the r e s u l t s are shown i n Table 2. Two s o i l samples were used, which were the Langley and the Chernozemic s o i l s , s i n c e a p r e v i o u s experiment i n d i c a t e d that they c o n t a i n e d r e l a t i v e l y high 33 Table 2 - The P r o p o r t i o n of the S o i l P o l y s a c c h a r i d e E x t r a c t e d with S e v e r a l S e l e c t e d E x t r a c t a n t s S o i l E x t r a c t i o n C o n d i t i o n s PSS (% S o i l ) Chernozemic 0. 5N HC1 16 hr 0. 20 0. 2N NaOH 16 hr 0. 25 0. 5N NaOH 16 hr 0. 33 0. 2N NaOH 4 hr with s o n i f i c a t i o n 0. 34 0. 5N NaOH 4 hr with s o n i f i c a t i o n 0. 43 Langley 0. 5N HC1 16 hr 0. 31 0. 2N NaOH 16 hr 0. 15 0. 5N NaOH 16 hr 0. 44 0. 2N NaOH 4 hr with s o n i f i c a t i o n 0. 23 0. 5N NaOH 4 hr with s o n i f i c a t i o n 0. 53 amounts of the s o i l p o l y s a c c h a r i d e . The r e s u l t s (Table 2) i n d i c a t e d t h a t the e x t r a c t i o n of the s o i l p o l y s a c c h a r i d e by 0.5M NaOH with the a i d of s o n i f i c a t i o n was the most e f f e c t i v e . The e x t r a c t i o n procedure was as f o l l o w s : A 200 g s o i l sample was weighed i n t o a 2 L p l a s t i c b o t t l e , and 1500mL of 0.5M NaOH was added, and the a i r i n the b o t t l e was d i s p l a c e d w i t h N 2 to minimize the p o s s i b l e o x i d a t i o n of the humic substances. The s o i l suspension was then put i n t o the water bath of a Branson Ultrasonic Cleaner, B-32 and su b j e c t e d to s o n i f i c a t i o n ( i n p u t power, 150 watts) f o r 4 h, and was then immediately c e n t r i f u g e d and the a l k a l i n e e x t r a c t was f r a c t i o n a t e d i n t o humic a c i d and f u l v i c a c i d as d e s c r i b e d i n 3.2.1.(1). A p o r t i o n of the humic a c i d sample was a l s o c o l l e c t e d and p u r i f i e d , and the HAs e x t r a c t e d with t h i s 34 method from the Langley s o i l and the Chernozemic s o i l were named as LA-HA(b) and CH-HA(b), r e s p e c t i v e l y . The f u l v i c a c i d f r a c t i o n was again passed through the PVP column to remove the p o l y p h e n o l i c f r a c t i o n and the e l u a t e was saved as the p o l y s a c c h a r i d e f r a c t i o n . _> (3) Purification of Soil Polysaccharide A f t e r the s o i l p o l y s a c c h a r i d e f r a c t i o n was obtained, i t was' then d i a l y s e d and c o n c e n t r a t e d on a D i a f l o YM-5 (M.W.>5,000) membrane. Twice i t s volume of acetone was added to p r e c i p i t a t e the s o i l p o l y s a c c h a r i d e , which was then c e n t r i f u g e d . The p r e c i p i t a t e was r e d i s s o l v e d i n d e m i n e r a l i z e d water and f i l t e r e d through Whatman No.1 f i l t e r paper, and r e p r e c i p i t a t e d with acetone. F i n a l l y , the p o l y s a c c h a r i d e was f r e e z e - d r i e d , and s t o r e d i n a g l a s s b o t t l e . The d r i e d p o l y s a c c h a r i d e powder, l a b e l l e d as CH-PSS and LA-PSS, was s l i g h t l y y e l l o w i s h c o l o r e d suggesting the presence of c e r t a i n amount of humic substances. T h i s method was s e l e c t e d i n s t e a d of u s i n g F o r s y t h ' s f r a c t i o n a t i o n method ( F o r s y t h , 1947) because the l a t t e r method was r e p o r t e d to encounter d i f f i c u l t i e s i n o b t a i n i n g high recovery of adsorbed f r a c t i o n s (Lowe, 1975; C h e s h i r e , 1979). 35 3.3 CLAY MINERALS Three types of c l a y m i n e r a l s were used i n t h i s study, m o n t m o r i l l o n i t e (No.25, b e n t o n i t e from Upton, Wyoming), i l l i t e (No.35, from F a t h i a n , I l l i n o i s ) , and k a o l i n i t e (No.5, from Bath, South C a r o l i n a ) . They are a l l samples of Clay m i n e r a l standards, American Petroleum I n s t i t u t e , P r o j e c t 49, d i s t r i b u t e d by Wards N a t u r a l Science E s t a b l i s h m e n t . Clay m i n e r a l s were prepared f o l l o w i n g the method of P a c i e j e w s k i (1985) with some m o d i f i c a t i o n s . About 200 g of each c l a y m i n e r a l was hand ground with a p e s t l e and mortar and passed through a 60 mesh s i e v e . A 10% c l a y suspension i n 1M N a d was shaken 3 times. Each time the suspension was separated by c e n t r i f u g a t i o n u s i n g the Sorvall Superspeed RC2-B at 6,000 rpm (5858 r c f ) f o r 15 minutes, and then washed 3 times with d e m i n e r a l i z e d water to remove the excess NaCl. K a o l i n i t e had to be d i s p e r s e d with 0.5M NaOH s i n c e 1M NaCl f a i l e d to d i s p e r s e the c l a y . The l e s s than 2 micron c l a y f r a c t i o n was o b t a i n e d by c e n t r i f u g i n g the c l a y suspensions a t 750 rpm f o r 5.3 min u s i n g an International Equipment Co. Centrifuge, head No. 277, 250 mL c e n t r i f u g e b o t t l e s with 10cm l i n e , and 1cm of sediment. (Lab Manual, PP 184-186, S o i l Science Department, The U n i v e r s i t y of B r i t i s h Columbia), and the supernatant s o l u t i o n s were c o l l e c t e d . The r e s i d u e s were resuspended i n water and r e c e n t r i f u g e d , and t h i s procedure was repeated 3 times. 36 C a l c i u m - s a t u r a t e d c l a y was obtained by washing the sodium s a t u r a t e d c l a y m i n e r a l s 3 times with 1N C a C l 2 , f o l l o w e d by 3 washes with d e m i n e r a l i z e d water. These Ca - s a t u r a t e d c l a y s were then f r e e z e - d r i e d and s t o r e d i n g l a s s b o t t l e s . 3.4 BORON ADSORPTION EXPERIMENTS 3. 4. 1 EQUILIBRATION OF BORON WITH SOIL HA One t e n t h gram a i r - d r i e d humic a c i d sample was d i s s o l v e d i n 5-10 mL of water i n a 50 mL p l a s t i c v i a l . One mL of 0.25M C a C l 2 was then added to p r e c i p i t a t e the humic a c i d , and the pH of the mixture was a d j u s t e d with 0.1M NaOH or 0.1M HC1. The pH of the system had to be a d j u s t e d approximately 0.5 u n i t above or below that d e s i r e d because of the r e - e q u i l i b r a t i o n w i t h i n the system. T h i s mixture was then t r a n s f e r r e d i n t o a 25mL v o l u m e t r i c f l a s k , which had been p r e v i o u s l y acid-washed. A l i q u o t s of boron s o l u t i o n w i t h the same pH as d e s i r e d but v a r y i n g i n c o n c e n t r a t i o n s were added and made up to volume with d e m i n e r a l i z e d water. A blank s o l u t i o n e x c l u d i n g the a d d i t i o n of HA was a l s o i n c l u d e d . The B-HA mixture was then t r a n s f e r r e d i n t o a p l a s t i c b o t t l e and shaken o v e r n i g h t on a r e c i p r o c a l shaker. The mixture was c e n t r i f u g e d at 6000 rpm f o r 10 min to remove the C a - p r e c i p i t a t e d HA, and the pH of the suspension was measured immediately a f t e r c e n t r i f u g a t i o n . The amount of 37 boron adsorbed by HA was c a l c u l a t e d by the d i f f e r e n c e between the amount of boron added (the blank s o l u t i o n ) and that found i n the e q u i l i b r i u m s o l u t i o n . Humic a c i d remaining i n s o l u t i o n was a n a l y s e d by an Astro-Model 1850 Total Organic Carbon Analyser. Approximately 90% of HA was p r e c i p i t a t e d , and the amount of HA remained i n s o l u t i o n was not accounted f o r i n boron a d s o r p t i o n . 3. 4. 2 BORON EQUILIBRATION WITH AL- AND FE~PRECIPITATED HA One t e n t h gram a i r - d r i e d LA-HA(b) was d i s s o l v e d i n 10 mL of water i n a 50 mL c e n t r i f u g e tube. One mL of 0.25M A1C1 3 or F e C l 3 was added to p r e c i p i t a t e the humic a c i d , and made up to 20 mL. The suspension was then shaken s e v e r a l times and c e n t r i f u g e d . The supernatant was poured i n t o a 200 mL v o l u m e t r i c f l a s k . The p r e c i p i t a t e ( A l - or Fe-HA complexes) was washed 3 times with 20 mL of d e m i n e r a l i z e d water and the supernatants were combined and made up to the volume i n order to determine the amount of A l or Fe being adsorbed by HA. F i v e t o ten mL of water and 1 mL of 0.25M C a C l 2 s o l u t i o n were then added to the washed A l - or Fe-HA complexes, and the pH a d j u s t e d . Boron a d s o r p t i o n was examined with procedures s i m i l a r to that d e s c r i b e d f o r HA (3.4.1). 38 3. 4. 3 EQUILIBRATION OF BORON WITH SOIL POLYSACCHARIDE An a l i q u o t (l5mL) of p o l y s a c c h a r i d e i n C a C l 2 s o l u t i o n ( c o n t a i n i n g 0.034 g a i r - d r i e d PSS) and 4mL of boron s o l u t i o n v a r y i n g i n c o n c e n t r a t i o n s were p i p e t t e d i n t o a 50mL p l a s t i c b o t t l e and w e l l mixed. The pH of the p o l y s a c c h a r i d e and b o r i c a c i d s o l u t i o n s was a d j u s t e d to about 6.5 bef o r e t h e i r mixing. One mL of 8% (w/v) c e t y l p y r i d i n i u m c h l o r i d e (CP) was then added to p r e c i p i t a t e charged p o l y s a c c h a r i d e s and boron-complexed p o l y s a c c h a r i d e s i f p r e s e n t . The f i n a l volume was 20mL with 0.01M CaCl present i n s o l u t i o n . The blank s o l u t i o n s e x c l u d i n g PSS were a l s o prepared. The mixture was then shaken o v e r n i g h t on a r e c i p r o c a l shaker and c e n t r i f u g e d . The supernatant was analyzed f o r boron c o n t e n t . The carbon content of the s o l u t i o n was not determined because of the a d d i t i o n of c e t y l p y r i d i n i u m c h l o r i d e . 3. 4. 4 BORON EQUILIBRATION WITH PURE CLAY MINERALS Boron a d s o r p t i o n by the c l a y m i n e r a l s was s t u d i e d by shaking the c l a y samples (0.3g of i l l i t e 2 , or 0.5g of m o n t m o r i l l o n i t e or k a o l i n i t e ) f o r 24 h at room temperature with 25 mL of boron s o l u t i o n i n 0.01M C a C l 2 at pH 6.5 v a r y i n g i n c o n c e n t r a t i o n s . I n i t i a l boron c o n c e n t r a t i o n s of the s o l u t i o n s ranged from 0 to 2.78 umol/ml. The samples were shaken f o r 24 h f o r convenience although the a d s o r p t i o n 2Because only l i m i t e d amount of i l l i t e was a v a i l a b l e . 39 c o u l d be e s t a b l i s h e d i n l e s s than 2 h (Hingston, 1964; Keren and Mezuman, 1981; Keren, 1982). A f t e r the e q u i l i b r a t i o n , the c l a y suspension was c e n t r i f u g e d and the supernatant was a n a l y s e d f o r boron c o n t e n t . The pH of the s o l u t i o n was a l s o determined. The amount of boron adsorbed was determined by the d i f f e r e n c e between the amount added and that found i n s o l u t i o n at - e q u i l i b r i u m . 3. 4\ 5 BORON EQUILIBRATION WITH ORGANO-CLAY COMPLEXES (1) Polysaccharide-Clay Complexes A procedure s i m i l a r to that f o r c l a y m i n e r a l s (3.4.4) was used, except t h a t the c l a y m i n e r a l was f i r s t r e a c t e d with 20mL of the p o l y s a c c h a r i d e s o l u t i o n c o n t a i n i n g 0.013g of LA-PSS. The s o l u t i o n was shaken i n a 50mL po l y p r o p y l e n e c e n t r i f u g e tube (with cap) f o r 24 h, c e n t r i f u g e d and the supernatant was a n a l y s e d f o r carbon content to determine the amount of p o l y s a c c h a r i d e adsorbed by the c l a y m i n e r a l s . The amount of s o i l p o l y s a c c h a r i d e adsorbed by c l a y s ranged from 13.0 to 22.6 mg/g c l a y , and i t was assumed that the organo-clay complexes were formed. An a l i q u o t (25mL) of boron s o l u t i o n (same as i n 3.4.4) was then added to commence a d s o r p t i o n , and the same procedures were then f o l l o w e d as d e s c r i b e d i n 3.4.4. The volume of s o l u t i o n remaining i n the c l a y a f t e r c e n t r i f u g a t i o n was taken i n t o account i n c a l c u l a t i o n of the boron a d s o r p t i o n . A f t e r the e q u i l i b r a t i o n 40 with 25mL of boron s o l u t i o n , about 8 to 12% of those adsorbed p o l y s a c c h a r i d e s were desorbed f o r the three c l a y m i n e r a l s . (2) Soil Polyphenol- and Humic Acid-Clay Complexes E i g h t grams of m o n t m o r i l l o n i t e and k a o l i n i t e were added to 160 mL of the polyphenol (WH-PP) or humic a c i d (LA-HA(b)) s o l u t i o n c o n t a i n i n g 1.6 g s o i l polyphenol or humic a c i d . F i v e grams of i l l i t e were added i n t o lOOmL of the polyphenol s o l u t i o n . The pH of the s o l u t i o n was a d j u s t e d to about 6.5, and the organo-clay suspension was shaken on a r e c i p r o c a l shaker f o r 24 h at room temperature. The suspension was c e n t r i f u g e d and the r e s i d u e was f r e e z e - d r i e d f o r the organo-clay complexes. The supernatant was a l s o a n a l y s e d f o r carbon content i n order to determine the amount of the polyphenol or humic a c i d adsorbed by the c l a y m i n e r a l s . A procedure s i m i l a r to that f o r c l a y a d s o r p t i o n (3.4.4) was then used. A f t e r the e q u i l i b r a t i o n of the PP-clay complexes with 25 mL of boron s o l u t i o n , most of the polyphenol remaining i n the complexes was r e l e a s e d i n t o s o l u t i o n , which made the s o l u t i o n y e l l o w i s h c o l o r e d . S i m i l a r l y , the humic a c i d s remaining i n H A - k a o l i n i t e complexes was r e l e a s e d i n t o s o l u t i o n , but subsequently p r e c i p i t a t e d i n C a + + s o l u t i o n . Humic a c i d - m o n t m o r i l l o n i t e complexes f a i l e d to be completely d i s p e r s e d a f t e r shaking f o r 24 h. 41 3. 4. 6 IONIC STRENGTH ADJUSTMENT The i o n i c s t r e n g t h was i n a l l cases kept at 0.03 with C a C l 2 throughout the boron a d s o r p t i o n experiments u n l e s s otherwise s p e c i f i e d . Higher i o n i c stength (I = 0.3) was used and a d j u s t e d with C a C l 2 when stu d y i n g the e f f e c t of i o n i c s t r e n g t h on boron a d s o r p t i o n by humic a c i d s . S o l u t i o n i o n i c s t r e n g t h was c a l c u l a t e d a c c o r d i n g to e q u a t i o n , I=1/2Ic^z?, where I i s the i o n i c s t r e n g t h ; c^ i s the c o n c e n t r a t i o n of the i t h i o n ; and z^ i s the valence of the i t h i o n . 3. 4. 7 ADSORPTION OF THE THREE ORGANIC CONSTITUENTS BY CLAY  MINERALS Ten mL of LA-HA(b), or WH-PP, or CH-PSS v a r y i n g i n c o n c e n t r a t i o n s was r e a c t e d with 50 mg of C a - s a t u r a t e d i l l i t e , k a o l i n i t e and m o n t m o r i l l o n i t e . pH of the o r g a n i c s o l u t i o n s were a d j u s t e d around n e u t r a l b e f o r e the r e a c t i o n was commenced. A f t e r 36 h e q u i l i b r a t i o n , the suspension was c e n t r i f u g e d and the supernatant was analysed f o r carbon co n t e n t . The amount of the o r g a n i c m a t e r i a l adsorbed was c a l c u l a t e d by the d i f f e r e n c e between the amount added and that found i n the e q u i l i b r i u m s o l u t i o n . 3.4.8 SOLUTION BORON ANALYSIS I n d u c t i v e l y - c o u p l e d plasma (ICP) was used f o r s o l u t i o n boron a n a l y s i s throughout the boron a d s o r p t i o n experiments. 42 The instrument used f o r t h i s study was a Jarrel I-Ash Series 1100 AtomComp. The main parameters used f o r boron d e t e r m i n a t i o n by ICP are l i s t e d i n T a b l e 3. Ta b l e 3 - Main Parameters Used f o r Boron A n a l y s i s by ICP Plasma at 27.13 MHZ I n c i d e n t , 1.1 Kw; R e f l e c t e d , 5 - 1 0 watts Gas Flows Plasma, 16 1/min; N e b u l i z e r , 0.8 1/min at 30 l b / i n c h N e b u l i z e r Cross-Flow Sample Flow Rate 3.5 ml/min Height of O b s e r v a t i o n 17 mm above c o i l Wavelength 249 nm T h i s technique p r o v i d e s s e v e r a l d i s t i n c t advantages over other c o l o r i m e t r i c methods as d e s c r i b e d by G e s t r i n g and Soltanpour (1981a; 1981b). One of the advantages of using ICP f o r boron a n a l y s i s i s t h a t a c o l o r l e s s s o l u t i o n i s not r e q u i r e d , and ICP i s not s u b j e c t to the i n t e r f e r e n c e s by other elements, such as N O 5 , C, e t c . T h i s made i t p o s s i b l e to a n a l y s e boron of those o r g a n i c s o l u t i o n s . However, one disadvantage of u s i n g ICP f o r boron a n a l y s i s (as w e l l as f o r other elements) i s i t s i n s t a b i l i t y w ith the f l u c t u a t i o n s of 43 the room temperature. An example i s i l l u s t r a t e d i n Table 4 3, i n which boron values measured i n c r e a s e d with temperature i n c r e a s e . I t was noted that when the temperature went up, the i n c r e a s e of the boron v a l u e s measured was l e s s pronounced (<1%) than the decrease of boron v a l u e s measured (<2%) when the temperature went down. Although t h i s v a r i a t i o n was r e l a t i v e l y s m a l l , i t would g r e a t l y a f f e c t the r e s u l t s s i n c e boron adsorbed by HA or c l a y s , e t c . was o f t e n l e s s than 10 to 20%, or even lower, f o r example under lower pH c o n d i t i o n s . T h e r e f o r e , a 1% of v a r i a t i o n of the measured data means 5 to 10% of v a r i a t i o n of the r e s u l t s . However, i n order t o minimize the a n a l y t i c a l e r r o r , every p a i r of the d u p l i c a t e s was measured i n the f o l l o w i n g o r d e r , R e p l i c a t i o n 1 - Blank - R e p l i c a t i o n . 2 , and a l l samples were measured i n the order from low c o n c e n t r a t i o n to hig h c o n c e n t r a t i o n of boron i n s o l u t i o n . T h e r e f o r e , the experimental e r r o r c o u l d be c o n t r o l l e d to around 10%. 3Temperature was recorded on a 2802A Thermomet er, Hewlett, Packar d. Table 4 - V a r i a t i o n of Boron Values Measured by ICP with the F l u c t u a t i o n of Temperature Temperature Temperature Increase (C°) Sequence 22.37 22.58 22.79 23.00 23.18 B (ppm) 8.89 8.89 8.98 9.06 9.11 % Increase 0.0 1.0 0.9 0.6 Average 0.61 Temperature Temperature Decrease (C°) Sequence 23.18 23.05 22.59 22.18 B (ppm) 9.11 8.98 8.90 8.74 % Increase -1.4 -0.9 -1.8 Average (%) -1.37 45 3.5 EXAMINATION OF ASH IN ORGANIC SAMPLES 3. 5. I ASH CONTENT One gram of the or g a n i c samples was f i r s t oven d r i e d at 105 °C f o r 4 h to determine the amount of water present i n the samples. The ash contents (%) of the or g a n i c samples were then determined by h e a t i n g the oven - d r i e d samples at 700 °C f o r 4 hours (Dormaar et a l . , 1970; Loeppert and Volk, 1974). The samples were then reweighed to determine the amount of i n o r g a n i c m a t e r i a l p r e s e n t . 3. 5. 2 ELEMENTAL ANALYSIS OF THE ASH One t e n t h gram a i r - d r i e d o r g a n i c samples was weighed i n t o a p l a s t i c beaker, d i s s o l v e d i n d e m i n e r a l i z e d water and made up to lOOmL i n a v o l u m e t r i c f l a s k . The s o l u t i o n was then s u b j e c t e d to ICP a n a l y s i s . There was a good agreement ( c o r r e l a t i o n c o e f f i c i e n t g r e a t e r than 0.999) between the known amounts and the val u e s measured by ICP of those elements i n the standard s o l u t i o n . 4. RESULTS AND DISCUSSION 4.1 BORON ADSORPTION BY SOIL HUMIC ACID 4. 1.1 DEVELOPMENT OF A METHOD TO STUDY BORON ADSORPTION BY  HUMIC ACID There are few papers d e a l i n g with boron e q u i l i b r a t i o n s t u d i e s by s o i l o r g a n i c m a t e r i a l s (Parks and White, 1952; H u e t t l , 1976). One d i f f i c u l t y i n s t u d y i n g boron a d s o r p t i o n by s o i l humic a c i d might be due to i t s high s o l u b i l i t y i n water which makes i t d i f f i c u l t t o separate the adsorbent (HA) from the adsorbate (boron i n t h i s c a s e ) . U n l i k e s o i l or c l a y s , humic a c i d can not be se p a r a t e d from i t s s o l u t i o n phase by c e n t r i f u g a t i o n at a pH near or above n e u t r a l . T h e r e f o r e , an a l t e r n a t i v e method has to be developed before the s t u d i e s of boron a d s o r p t i o n by HA can be commenced. In the s t u d i e s of Parks and White (1952) and H u e t t l (1976), they used c e l l o p h a n e bags and d i a l y s i s tubes c o n t a i n i n g o r g a n i c m a t e r i a l s i n s i d e (humus by Parks and White, and muck s o i l by H u e t t l ) to e q u i l i b r a t e w i t h boron i n C a C l 2 s o l u t i o n o u t s i d e of the membrane. T h i s method was not employed -in t h i s i n v e s t i g a t i o n because of the f o l l o w i n g reasons: 1. A main reason i s that the e q u i l i b r a t i o n by using t h i s membrane c e l l i s too time consuming so t h a t i t i s not f e a s i b l e to study the l a r g e number of samples d e s i r e d . For example, Parks and White (1952) r e p o r t e d t h a t the e q u i l i b r a t i o n took 46 47 9 days. 2. Another reason i s that the D i a l y s i s Tubing 4 a v a i l a b l e i n our l a b can r e t a i n only molecular weight 12,000 or h i g h e r . In a d d i t i o n , the p r e l i m i n a r y experiment showed t h a t t u bing i t s e l f r e l e a s e s a s i g n i f i c a n t amount of carbon i n t o s o l u t i o n . A p r e v i o u s experiment a l s o showed that 0.01M C a C l 2 i n s o l u t i o n was s u f f i c i e n t to p r e c i p i t a t e more than 90% of humic a c i d at pH around 8, and even at pH 12, more than 80% of humic a c i d was p r e c i p i t a t e d . T h e r e f o r e , a m o d i f i e d method, i . e . to separate the HA p r e c i p i t a t e s by c e n t r i f u g a t i o n i n s t e a d of u s i n g a membrane c e l l , was employed in t h i s i n v e s t i g a t i o n . Although some smal l HA molecules s t i l l remained i n s o l u t i o n at higher pH to make the s o l u t i o n y e l l o w i s h c o l o r e d , i t d i d not a f f e c t the boron a n a l y s i s by ICP. A d d i t i o n a l l y , those HA f r a c t i o n s which remained i n s o l u t i o n were not accounted f o r i n boron a d s o r p t i o n . Two advantages by u s i n g t h i s c e n t r i f u g a t i o n method are then obvious: 1. I t i s r e l a t i v e l y simple and f a s t , and this'makes i t p o s s i b l e to do v a r i o u s boron a d s o r p t i o n isotherms by HA; 2. I t i s reasonable by s e l e c t i n g 0.01M C a C l 2 to p r e c i p i t a t e HA and to keep the s o l u t i o n i o n i c s t r e n g t h r e l a t i v e l y constant because t h i s c o n c e n t r a t i o n i s commonly encountered i n a g r i c u l t u r a l s o i l s , a c c o r d i n g to Hingston (1964) . 4 See " D i r e c t i o n s f o r use D i a l y z e r Tubing", No. 4465-A2, Authur H. Thomas Co., P h i l a d e l p h i a , PA 19105, U.S.A. 48 An u n d e s i r e d f e a t u r e of us i n g t h i s p r e c i p i t a t i o n method i s that some of the r e a c t i o n s i t e s on HA may have been occupied by Ca. These r e a c t i o n s i t e s (with C a + + ) are mainly -COOH, or -COO" groups, a c c o r d i n g to IR s t u d i e s by Lakatos, et a l . (1972), and C a + + does not re a c t with a l c o h o l i c -OH groups. The p r e v i o u s Experimental r e s u l t s a l s o showed t h a t i t d i d not a f f e c t the amount of boron adsorbed by HA no matter how b o r i c a c i d was added i n t o HA s o l u t i o n b e f o r e or a f t e r C a C l 2 was added. T h i s might be e x p l a i n e d i n t h a t C a + + has a higher a f f i n i t y to r e a c t with those c a r b o x y l groups. T h e r e f o r e , i t i s mostly a l c o h o l i c -OH groups of HA which remain f o r boron complexation. Another approach was giv e n c o n s i d e r a t i o n o r i g i n a l l y , i . e . an u l t r a f i l t r a t i o n method with a membrane. T h i s method al l o w s one to separate l a r g e molecular weight HA from f r e e b o r i c a c i d i n s o l u t i o n without adding C a C l 2 . I t was done on an Ami con Model TCF-10 p r e s s u r i z e d d i a f i l t r a t i o n c e l l . The method was e v e n t u a l l y g i v e n up because of the f o l l o w i n g reasons: 1. The p r e l i m i n a r y experiment showed that the r e p r o d u c i b i l i t y very poor. T h i s was p a r t l y due to the l a r g e experimental e r r o r i n v o l v e d and p a r t l y due to small boron a d s o r p t i o n c a p a c i t y by humic a c i d i n t h i s r e l a t i v e l y pure system; 2. Another l i m i t a t i o n of u s i n g t h i s method was that a l a r g e amount of sample (at l e a s t 200mL HA+B s o l u t i o n ) had to be prepared because of the l a r g e u l t r a f i l t r a t i o n u n i t ; 49 3. I f a very h i g h c o n c e n t r a t i o n of HA i s d e s i r e d i n order to r a i s e the p r e c i s i o n of the experiment, the membrane w i l l probably be plugged by HA under the high p r e s s u r e ; 4. The s e p a r a t i o n procedure by using t h i s method i s extremely slow. 4. I. 2 EFFECT OF PH ON BORON ADSORPTION ' Boron a d s o r p t i o n by three humic a c i d s as a f u n c t i o n of pH at a s p e c i f i c boron c o n c e n t r a t i o n (1.11 umol/mL) was s t u d i e d . R e s u l t s ( F i g u r e 1) i n d i c a t e d that the amount of boron adsorbed was h i g h l y pH dependent f o r a l l three humic a c i d samples, which remained l i t t l e changed up to pH about 6.5, and then became very s u b s t a n t i a l with i n c r e a s e of pH to approximately 9.5. With f u r t h e r pH i n c r e a s e , the amount of boron adsorbed decreased r a p i d l y . W ithin the range of boron c o n c e n t r a t i o n s t u d i e d (from 0 to 2.59 umol/mL), the amount of boron adsorbed by humic a c i d i s s i g n i f i c a n t l y h i g h e r a t pH 8.5-9.0 than t h a t at lower pH ( F i g u r e s 3 - 5 ) . T h i s o b s e r v a t i o n i s i n accordance with H u e t t l (1976), who observed t h a t the amount of boron sorbed by a muck s o i l i n c r e a s e d very slowly to approximately pH 6, with a s i g n i f i c a n t l y i n c r e a s e d a d s o r p t i o n with f u r t h e r pH i n c r e a s e . The changes of boron a d s o r p t i o n with pH are a l s o very s i m i l a r to t h a t observed f o r c l a y m i n e r a l s and s e s q u i o x i d e s (Bingham, 1968a; Sims and Bingham, 1967; Keren, et a l . , 1981; Keren and Gast, 1983). The e x p l a n a t i o n was given t h a t 50 F i g u r e 1 - Boron a d s o r p t i o n by s o i l humic a c i d s as a f u n c t i o n of pH. 51 at low pH, B(OH) 3 predominated and i t s a f f i n i t y to c l a y s and se s q u i o x i d e s was r e l a t i v e l y low, while at higher pH up to 9, the B(OH);; c o n c e n t r a t i o n i n c r e a s e d r a p i d l y which had a r e l a t i v e l y s t r o n g a f f i n i t y to c l a y s and s e s q u i o x i d e s . F u r t h e r i n c r e a s e s i n pH r e s u l t e d i n an enhanced OH -c o n c e n t r a t i o n r e l a t i v e to B(OH)«, and boron a d s o r p t i o n decreased r a p i d l y due to the com p e t i t i o n by OH - at the a d s o r p t i o n s i t e s . T h i s may a l s o o f f e r the e x p l a n a t i o n f o r the observed boron a d s o p t i o n by HA. H u e t t l (1976) e x p l a i n e d that the mechanism of the pH-dependent a d s o r p t i o n of boron by s o i l o r g a n i c matter was much l i k e t h a t of the combination of r e a c t i o n s between b o r i c a c i d and mannitol, and t a r t a r i c a c i d , which r e p r e s e n t e d the models of d i o l and a-hydroxy-carboxyl o r g a n i c compounds. F i g u r e 2 shows the r e l a t i o n s h i p of % boron complexed as a f u n c t i o n of pH f o r the h y p o t h e t i c a l s o l u t i o n of 0.1M t a r t a r i c a c i d or 0.1M mannitol i n s o l u t i o n with 0.001M b o r i c a c i d ( a f t e r H u e t t l , 1976). T h i s i n d i c a t e s that the complexation between mannitol and b o r i c a c i d i s favored by hig h pH, while f o r t a r t a r i c a c i d , low pH i s fa v o r e d . Knoeck and T a y l o r (1969) have i n d i c a t e d from the NMR s p e c t r a l data t h a t only the a n i o n i c borate s p e c i e s r e a c t with mannitol to form a complex. Higher pH f a v o r s the formation of borate i o n , so as to i n c r e a s e i t s complexation with m a n n i t o l . On the other hand, K u s t i n and P i z e r (1969) proposed that the complexation between t a r t a r i c a c i d and b o r i c a c i d i n c l u d e s a t t a c k of a n u c l e o p h i l i c a l c o h o l i c oxygen on the e l e c t r o n d e f i c i e n t boron with 52 F i g u r e 2 - The r e l a t i o n s h i p of %B complexed as a f u n c t i o n of pH f o r the h y p o t h e t i c a l s o l u t i o n of 0.1M t a r t a r i c a c i d or 0.1M mannitol i n s o l u t i o n with 0.001M b o r i c a c i d ( a f t e r H u e t t l , 1976). 53 concurrent r e l e a s e of water ( i n the t a r t a r i c a c i d r e a c t i o n ) or h y d r o x y l ( i n the b i t a r t r a t e r e a c t i o n ) . T h e r e f o r e , i t was assumed that a-hydroxy-carboxyl groups at low pH and d i o l hydroxys at h i g h pH of s o i l humic a c i d were r e s p o n s i b l e f o r boron a d s o r p t i o n . However, u n l i k e t a r t a r i c a c i d , the amount of boron adsorbed by CH-HA(b) and LA-HA(b) at lower pH was extremely low. One p o s s i b l e e x p l a n a t i o n was due to the l o s s of boron a d s o r p t i o n s i t e s (a-hydroxy-carboxyls) s i n c e C a + + was p r e f e r e n t i a l l y adsorbed by these a d s o r p t i o n s i t e s . T h i s was supported e x p e r i m e n t a l l y by the f a c t t h a t t h e r e was no e f f e c t on the amount of boron adsorbed by humic a c i d no matter how b o r i c a c i d was added i n t o humic a c i d before or a f t e r C a C l 2 was added. Parks and White (1952) a l s o r e p o r t e d that H + - s a t u r a t e d humus r e t a i n e d two times more boron than C a - s a t u r a t e d humus. 4. 1. 3 BORON ADSORPTION ISOTHERMS A l l f i v e HA samples were e q u i l i b r a t e d w i t h b o r i c a c i d at two d i f f e r e n t pH l e v e l s i n order to examine the changes of the amount of boron adsorbed by HA with i n c r e a s e of boron c o n c e n t r a t i o n i n s o l u t i o n . R e s u l t s showed ( F i g u r e s 3 to 5) t h a t the amount of boron adsorbed at high pH l e v e l (8.5-9.0) was s i g n i f i c a n t l y h i g h e r than that at low pH l e v e l (5.8-7.2) and i n c r e a s e d c o n s i s t e n t l y with the i n c r e a s e of the added boron in s o l u t i o n . The r e s u l t s a l s o i n d i c a t e d that on a weight b a s i s the amount of boron adsorbed by humic a c i d at 54 Equil. B in solution, (umol/ml) Figure 3 - The amounts of B adsorbed by humic acids extracted with 0.1M NaOH + 0.1M Na«P 20 7 at pH 8.5-9.0. 55 < X o E 3 80 70-60-60-40 TO 9 a O 30 0) "O < m 20 10-Legend O LA-HA(b) ^^^^^^ + r ' . . . - B • o 0.4 0.8 1.2 1.6 2 2.4 Equil. B in solution, (umol/ml) 2.8 F i g u r e 4 - The amounts of B adsorbed by humic a c i d s e x t r a c t e d by 0.5M NaOH (with s o n i f i c a t i o n ) a t pH 8.5-9.0. 56 F i g u r e 5 - The amounts of B adsorbed by humic a c i d s at lower pH c o n d i t i o n s . 57 low pH was approximately the same order of magnitude as that of i l l i t e , and s l i g h t l y higher than that of m o n t m o r i l l o n i t e and k a o l i n i t e , although no d i r e c t comparison c o u l d be made s i n c e the amount of boron adsorbed v a r i e d with c l a y m i n e r a l s p e c i e s as w e l l as humic a c i d samples (Hinston, 1964; S e c t i o n 4.3). However, the amount of boron adsorbed by HA at pH 8.5-9.0 was about an order of magnitude gre a t e r than that r e t a i n e d by those c l a y s on a weight b a s i s . T h i s may a l s o imply the importance of humus i n boron r e t e n t i o n i n those a l k a l i n e s o i l s . F i g u r e s 6 and 7 show the l o g a r i t h m i c p l o t s of c ( e q u i l i b r i u m B c o n c e n t r a t i o n i n s o l u t i o n , umol/mL) a g a i n s t x/m (amount of boron adsorbed, umol/g HA), and the r e l a t i o n s h i p s between l o g c and l o g x/m, and t h e i r r e l a t i o n s h i p c o e f f i c i e n t s (r) are a l s o t a b u l a t e d i n Tables 5 and 6 (see F r e u n d l i c h E q u a t i o n ) . The r e g r e s s i o n l i n e s i n F i g u r e s f i t t e d the experimental data q u i t e w e l l over the ranges of boron c o n c e n t r a t i o n s s t u d i e d , i n d i c a t i n g the obedience of the s o r p t i o n process to the F r e u n d l i c h e q u a t i o n . The c o r r e l a t i o n c o e f f i c i e n t s of the r e g r e s s i o n l i n e s at pH 8.5-9.0 ranged from 0.97 to 0.99, while at lower pH c o n d i t i o n s ranged from 0.84 to 0.98 with one e x c e p t i o n , LA-HA(b), which had a c o r r e l a t i o n c o e f f i c i e n t , r=0.38 ( s i n c e i t adsorbed a r e l a t i v e l y low amount of boron). I t was a l s o noted t h a t the l i n e s were almost p a r a l l e l with the s l o p e s ranged from 0.578 to 0.737 f o r pH 8.5-9.0, i n d i c a t i n g the s i m i l a r i t y i n boron a d s o r p t i o n . L i n e s i n F i g u r e s 3 to 5 were 58 F i g u r e 6 - P l o t of the r e g r e s s i o n equations f o r l o g x/m (B adsorbed) versus l o g c (B i n e q u i l i b r i u m s o l u t i o n ) at pH 8.5-9.0. 59 F i g u r e 7 - P l o t of the r e g r e s s i o n equation f o r l o g x/m v e r s u s l o g c at lower pH c o n d i t i o n s . Table 5 - Boron Adsorption by Various Humic A c i d s at pH 8.5-9.0 as Expressed by F r e u n d l i c h Equation and Langmuir Equation Humic A c i d F r e u n d l i c h Equation Y(logx/m) = loga + blogC Langmuir Equation y'(C/x/m) = 1/bk + C/b WH-HA(a) Y = 1 .710 + 0.578 log C 0.99 = 0.0133 + 0.00483 C 0.92 LA-HA(a) Y = 1 .532 + 0.737 log C 0.98 = 0.0204 + 0.00747 C 0.80 CH-HA(a) Y = 1 .466 + 0.646 log C 0.98 r = 0.0184 + 0.0137 C 0.93 LA-HA(b) Y = 1 .478 + 0.658 log C 0.99 y' = 0.0243 + 0.0068 C 0.93 CH-HA(b) Y = 1 .417 + 0.686 log C 0.97 y' = 0.0202 + 0.0169 C 0.88 Table 6 - Boron Adsorption by Vari o u s Humic Acids a t pH 6.2-7.2 as Expressed by F r e u n d l i c h Equation and Langmuir Equation F r e u n d l i c h Equation Langmuir Equation Humic A c i d — Y(logx/m) = loga + blogC r y'(C/x/m) = 1/bk + C/b r WH-HA(a) Y = 1.293 + 0.608 l o g C 0.98 y' = 0.0243 + 0.0237 C , 0.98 LA-HA(a) Y = 0.926 + 0.877 l o g C 0.97 y' = 0.0912 + 0.0243 C 0.65 CH-HA(a) Y = 0.713 + 0.505 log C 0.84 y' = 0.0859 + 0.0996 C 0.86 LA-HA(b) Y = 0.414 + 0.389 l o g C 0.38 Y' - 0.5374 + 0.3613 C 0.39 61 thus drawn a c c o r d i n g to the F r e u n d l i c h e q u a t i o n , x/m = a«c^, whereas the symbols r e p r e s e n t e d the experimental data. The f i t between the e x p e r i m e n t a l r e s u l t s and the Langmuir theory was f a i r l y good a l t h o u g h i t was not as good as t h a t f o r the F r e u n d l i c h equation ( T a b l e s 5 and 6). The b, k, and kb v a l u e s c a l c u l a t e d from the Langmuir equation, x/m = bkc/(1+kc), are a l s o t a b u l a t e d i n Table 7, i n which the product of kb v a l u e s and b v a l u e s show an i n c r e a s e with i n c r e a s e of pH, whereas k v a l u e s [except LA-HA(a)] decrease with the i n c r e a s e of pH. T h i s i s a l s o i n accordance with the f i n d i n g s by H u e t t l (1976), who found that the a d s o r p t i o n isotherms of boron by muck humus obeyed the F r e u n d l i c h equation,.but d e v i a t e d from the Langmuir e q u a t i o n . T h i s may a l s o imply that boron a d s o r p t i o n by Ca-humic a c i d i s a chemical complexation between borate ions and d i - h y d r o x y l Table 7 - V a r i a t i o n of Langmuir Constants, b, k, and bk v a l u e s , with pH and Humic A c i d Samples Humic A c i d pH b k bk WH-HA(a) 8.5-9.0 6.8-7.2 207.2 42.18 0.363 0.977 75.20 41.22 LA-HA(a) 8.5- 9.0 6.6- 6.7 1 33.9 41 .20 0.366 0.266 49.01 1 0.96 CH-HA(a) 8.5-9.0 6.2-6.5 73.08 1 0.04 0.745 1 . 160 54.44 1 1 .65 LA-HA(b) 8.5-9.0 5.8-6.2 167.6 2.768 0.306 0.672 51 .29 1 .860 CH-HA(b) 8.5-9.0 59.05 0.84 49.60 62 groups, r a t h e r than p h y s i c a l a d s o r p t i o n . Another o b s e r v a t i o n must a l s o be noted here t h a t the amount of boron adsorbed by v a r i o u s humic a c i d samples v a r i e d c o n s i d e r a b l y ( f i g u r e 1 and f i g u r e s 3-5). The WH-HA(a) adsorbed the h i g h e s t amount of boron, while the CH-HA(b) adsorbed the l e a s t . T h i s was i n accordance with the o b s e r v a t i o n by Parks and White (1952), that the humus e x t r a c t e d with N a 4 P 2 0 7 r e t a i n e d 15 to 30 times more boron than that e x t r a c t e d with Na 2C03-NaHC0 3. However, the d i f f e r e n c e observed i n t h i s study was s m a l l e r than t h a t they observed. Two p o s s i b l e e x p l a n a t i o n s f o r t h i s o b s e r v a t i o n might be, f i r s t l y , due to the l o s s of a d s o r p t i o n s i t e s on humic a c i d s ( b ) which were e x t r a c t e d with 0.5M NaOH with the a i d of s o n i f i c a t i o n . T h i s i s p o s s i b l e because the e x t r a c t a n t was so d r a s t i c t h at some decomposition or s t r u c t u r a l m o d i f i c a t i o n of the humic a c i d would be expected. The second e x p l a n a t i o n might be more p l a u s i b l e , i . e . due to the l a r g e amount of ash present i n WH-HA(a) sample. By l o o k i n g at the ash content and the elemental composition of those HA samples (Table 8), and u s i n g the boron a d s o r p t i o n data at h i g h pH at 1.11 umol/mL boron added i n s o l u t i o n , a s i g n i f i c a n t c o r r e l a t i o n c o e f f i c i e n t (r=0.886* ) between amount of boron adsorbed and the ash content (%) was o b t a i n e d . An even higher (at 1% s i g n i f i c a n c e l e v e l ) c o r r e l a t i o n c o e f f i c i e n t (r=0.966 or r 2=0.933) e x i s t e d between the amount of boron adsorbed and Fe content (mmol/g HA). T h e r e f o r e , the content of i r o n alone e x p l a i n e d more 63 Table 8 - Ash Content (% of OM) of the Organic Samples Elemental A n a l y s i s Samples Water Ash S i Fe A l Ca Mg Na WH-PP 15.2 1 .6 0.00 0.00 0.06 0. 00 0. 00 0.18 CH-PSS 14.2 5.8 0.01 0.01 0.66 0. 07 0. 00 1 .80 LA-PSS 12.8 3.8 0.00 0.01 0.24 0. 00 0. 00 0.87 CH-HA(b) 10.2 14.2 1 .73 0.54 0.86 0. 01 0. 12 5.51 CH-HA(a) 12.8 19.0 2.48 0.73 0.97 0. or 0. 25 6.81 LA-HA(b) 11.3 20.5 1 .93 2.76 2.34 0. 01 0. 08 5.23 LA-HA(a) 6.9 27.0 2.89 3.41 2.05 0. 04 0. 16 7.27 WH-HA(a) 13.3 34. 1 0.71 9.41 1 .50 0. 00 0. 01 10.5 than 93% of the v a r i a t i o n of the amount of boron adsorbed by v a r i o u s humic a c i d samples. T h i s i s a p l a u s i b l e e x p l a n a t i o n because F e 3 + or the hydroxy i r o n may c o n t r i b u t e to boron a d s o r p t i o n due to i t s p o s i t i v e charge and i t s h y d r o x y l s . In order t o c o n f i r m the c o n t r i b u t i o n s of Fe and A l , the boron a d s o r p t i o n on Fe- and A l - p r e c i p i t a t e d HA was measured. 4.1.4 EFFECTS OF CATIONS ON BORON ADSORPTION The e f f e c t s of i r o n and aluminum on boron a d s o r p t i o n by s o i l humic a c i d were s t u d i e d u s i n g the Langley HA(b) m a t e r i a l . R e s u l t s ( F i g u r e s 5 and 8) showed that the F e - p r e c i p i t a t e d HA adsorbed more boron than e i t h e r A l - or C a - p r e c i p i t a t e d HA, and the C a - p r e c i p i t a t e d HA adsorbed the F i g u r e 8 - B a d s o r p t i o n by f r e s h A l - and F e - p r e c i p i t a t e d humic a c i d [LA-HA(b)] at pH 6.8-7.2 as compared with t h a t by C a - p r e c i p i t a t e d LA-HA(b). 65 l e a s t . T h i s c o n f i r m s the above c o n c l u s i o n t h a t v a r i o u s s o i l humic a c i d s or those e x t r a c t e d with d i f f e r e n t methods adsorbed d i f f e r e n t amounts of boron due to the c o n t r i b u t i o n of Fe and A l . The a d s o r p t i o n isotherms by Fe- and A l - p r e c i p i t a t e d HA were a l s o w e l l d e s c r i b e d by the Langmuir equation with the c o r r e l a t i o n c o e f f i c i e n t s g r e a t e r than 0.96. The c a l c u l a t e d Langmuir c o n s t a n t s , b v a l u e s , f o r Fe-and Al-HA were 23.37 and 9.73 wmol/g HA, r e s p e c t i v e l y , which were much high e r than that of Ca-HA, b=2.77 umol/g HA 5. The d i f f e r e n c e observed f o r the amounts of boron adsorbed by Fe-and Al-HA ( F i g u r e 8) might be e x p l a i n e d by the o b s e r v a t i o n that Langley HA(b) adsorbed more Fe (9.22% or 1.65 mmol/g HA) than A l (2.24% or 0.83 mmol/g HA). The c o n t r i b u t i o n of Fe and A l to the boron a d s o r p t i o n by humic a c i d may not be caused on l y by the p r e c i p i t a t e d A l or Fe hydrous oxides a t t h i s pH c o n d i t i o n (near n e u t r a l ) . C o n s i d e r i n g the amounts of boron adsorbed by A l - and Fe-hydrous o x i d e s alone, which are 900 ug/g at pH 6.3 and 10 ug/mL boron added i n s o l u t i o n (Hatcher, 1967), and 520 ug/g at pH 6 and 833 ug/mL boron added i n s o l u t i o n (Sims and Bingham, 1968a), the c o n t r i b u t i o n s of A l and Fe-hydrous p r e c i p i t a t e s i n t h i s case would be only 900 x 2.24% = 20.16ug (or 1.86umol) and 520 x 9.22% = 47.94ug (or 4.43 umol) boron adsorbed per gram HA, and t h i s i s much lower than the d i f f e r e n c e observed. T h e r e f o r e , i t may imply that 5The b value of Ca-HA may not be r e l i a b l e because of the d e v i a t i o n from the Langmuir e q u a t i o n . However, the same c o n c l u s i o n might be drawn by comparing the l i n e s i n F i g u r e 8. 66 A l and Fe are not i n p r e c i p i t a t e d form but i n complexed form with humic a c i d . A c c o r d i n g to S c h n i t z e r and Skinner (1963a; 1963b; 1964), a l l A l and Fe would be pres e n t as Al(OH)£ and Fe(0H)2 or p a r t l y as A l ( O H ) 3 and Fe(OH) 3. T h e r e f o r e , these complexed A l - and Fe-hydrous oxides i n the humic a c i d accounted f o r the l a r g e r boron a d s o r p t i o n because, u n l i k e w e l l c r y s t a l l i z e d hydrous o x i d e s , there were more f r e e A l -or Fe- h y d r o x y l s a v a i l a b l e f o r boron complexation. Another experiment was done by u s i n g the f r e e z e - d r i e d A l - and Fe-HA complexes. The d r i e d A l - and Fe-HA complexes were completely i n r i g i d form and i n s o l u b l e i n water, or not l i k e the o r i g i n a l p r e c i p i t a t e s which were more or l e s s l i k e c o l l o i d s . The r e s u l t s (shown i n F i g u r e 9) i n d i c a t e that they have much sm a l l e r boron f i x a t i o n c a p a c i t y as compared with those f r e s h p r e c i p i t a t e s . T h i s i s mainly because of the i n c r e a s e of the c r y s t a l l i n i t y of the f r e e z e - d r i e d A l - and Fe-HA p r e c i p i t a t e s , and t h e r e f o r e , l e s s s u r f a c e area or l e s s A l - and Fe-hydrous oxides exposed f o r boron complexation. T h i s i s s i m i l a r to the f i n d i n g t h at the f r e s h p r e c i p i t a t e d A l - and Fe-hydrous oxides adsorbed much more boron than that by aged A l - and Fe- p r e c i p i t a t e s (Sims and Bingham, 1968a; Hatcher et a l . , 1967). 4.1.5 EFFECT OF IONIC STRENGTH ON BORON ADSORPTION F i g u r e s 10 and 11 show the e f f e c t of s o l u t i o n i o n i c s t r e n g t h and pH on boron a d s o r p t i o n by WH-HA(a) and LA-HA(b). The amount of boron adsorbed at hi g h e r i o n i c 67 F i g u r e 9 - B a d s o r p t i o n by f r e e z e - d r i e d A l - and Fe-p r e c i p i t a t e d humic a c i d [LA-HA(b)] at pH 5.0 as compared with t h a t by the f r e s h p r e c i p i t a t e s (dotted l i n e s , c o p i e d from F i g u r e 8 ) . 68 0 0.4 0.8 1.2 1.6 2 2.4 2.8 Equil. B in solution, (umol/ml) Figure 10 - B adsorption by WH-HA(a) as affected solution ionic strength and pH. by the 69 F i g u r e 11 - B a d s o r p t i o n by LA-HA(b) as a f f e c t e d by the s o l u t i o n i o n i c s t r e n g t h and pH. 70 s t r e n g t h (I =0.3) was c o n s i s t a n t l y higher than that at lower i o n i c s t r e n g t h (I = 0.03) f o r both WH-HA(a) and LA-HA(b) at pH 8.5-9.0. Based on b values (see Table 8 and Appendixes 4 and 8) c a l c u l a t e d from the Langmuir e q u a t i o n , the amount of boron adsorbed by the two humic a c i d s , WH-HA(a) and LA-HA(b), i n c r e a s e d from 21% and 12% with an i n c r e a s e of s o l u t i o n i o n i c s t r e n g t h from 0.03 to 0.3. However, at low pH l e v e l s (pH 5.8-7.2) the e f f e c t of i o n i c s t r e n g t h on boron a d s o r p t i o n by the two HA samples was ra t h e r s m a l l . A main reason might be due to that at t h i s low pH c o n d i t i o n , the boron s p e c i e s adsorbed should be mainly B(OH) 3 r a t h e r than B(OH)«, and t h e r e f o r e , the neg a t i v e e l e c t r i c a l f i e l d had no e f f e c t on B(OH) 3 a d s o r p t i o n by HAs because there was no coulombic r e p u l s i o n f o r c e s between B(OH) 3 and the HA c o l l o i d a l s . The amount of boron adsorbed by m o n t m o r i l l o n i t e and i l l i t e were a l s o r e p o r t e d to be a f f e c t e d by the s o l u t i o n i o n i c s t r e n g t h (Keren and O'Connor). They found t h a t i n c r e a s i n g the NaCl c o n c e n t r a t i o n from 0.02M to 0.07M and 0.36M, the amount of boron adsorbed by Na-montmorillonite i s i n c r e a s e d by about 10% and 50%, r e s p e c t i v e l y . The t h i c k n e s s of the d i f f u s e double l a y e r of the plana r s u r f a c e s i s 4.38, 2.38, and 1.03 nm f o r 0.02, 0.07, and 0.36M NaCl c o n c e n t r a t i o n s i n s o l u t i o n , r e s p e c t i v e l y . T h e r e f o r e , the i n f l u e n c e of the negative e l e c t r i c f i e l d of the c l a y p a r t i c l e s i n the v i c i n i t y of p l a t e l e t edges i s l i k e l y l e s s i n the Na c l a y at the higher e l e c t r o l y t e c o n c e n t r a t i o n than 71 at the lower e l e c t r o l y t e c o n c e n t r a t i o n . Or i n another words, i n c r e a s i n g i o n i c s t r e n g t h depressed the e l e c t r i c a l f i e l d a s s o c i a t e d with the c l a y p a r t i c l e edges and thus reduced the r e p u l s i o n between the s u r f a c e and the borate i o n s . T h i s may a l s o o f f e r an e x p l a n a t i o n f o r the observed boron a d s o r p t i o n by the two humic a c i d s at two i o n i c s t r e n g t h l e v e l s . A c c o r d i n g to Stevenson (1982), s o i l humic a c i d c a r r i e s an average t o t a l a c i d i t y of about 670 meq/lOOg and i s n e g a t i v e l y charged i n s o l u t i o n s near or above n e u t r a l . T h e r e f o r e , i t i s expected t h a t the complexation between n e g a t i v e l y charged borate ions (at hi g h pH l e v e l ) and the humic a c i d c o l l o i d s be much favored by higher i o n i c s t r e n g t h i n s o l u t i o n . 4.2 BORON REACTION WITH SOIL POLYSACCHARIDE T h i s chapter r e p o r t s the experiment of boron e q u i l i b r a t i o n with s o i l p o l y s a c c h a r i d e . However, the experimental data are not pre s e n t e d s i n c e they were r a t h e r poor and c o n s i d e r e d u n r e l i a b l e . Some d i s c u s s i o n of the experimental methods and t h e i r l i m i t a t i o n s are given below. S o i l p o l y s a c c h a r i d e i s a minor but important p o r t i o n of s o i l o r ganic matter. Upon h y d r o l y s i s i t g i v e s v a r i o u s sugars, such as g a l a c t o s e , g l u c o s e , mannose, ara b i n o s e , and x y l o s e , e t c . , although the p r o p o r t i o n s may vary to some 72 extent i n the d i f f e r e n t samples (Cheshire, 1979; Forsyth,1950; Lowe, 1978). Most of these sugars, a c c o r d i n g to Boeseken (1949), were demonstrated to r e a c t with b o r i c a c i d . T h e r e f o r e , Parks and White (1952) suggested that the d i o l compounds or p o l y s a c c h a r i d e s i n s o i l s would complex the boron and render i t u n a v a i l a b l e to p l a n t s f o r a p e r i o d of time. However, upon the decomposition of the s o i l p o l y s a c c h a r i d e s i n t o s i m p l e r compounds, boron fo r m e r l y h e l d would be r e l e a s e d . I t was, t h e r e f o r e , one of the i n i t i a l o b j e c t i v e s of t h i s study to look at the boron a d s o r p t i o n on the s o i l p o l y s a c c h a r i d e and to f i n d a p o s s i b l e p r e f e r e n t i a l a d s o r p t i o n of boron by s o i l p o l y s a c c h a r i d e or humic a c i d . S i m i l a r to the s t u d i e s on boron a d s o r p t i o n by s o i l humic a c i d , an experimental method had to be developed before the i n v e s t i g a t i o n c o u l d be c a r r i e d out. U n f o r t u n a t e l y , there i s no s p e c i f i c l i t e r a t u r e d e a l i n g with the boron a d s o r p t i o n by s o i l p o l y s a c c h a r i d e , and t h i s author d i d not f i n d a s a t i s f a c t o r y method to do so e i t h e r , a l t h o u g h s e v e r a l p o s s i b l e approaches were given c o n s i d e r a t i o n . These approaches are d i s c u s s e d below: 1. U l t r a f i l t r a t i o n Approach: As d e s c r i b e d i n S e c t i o n 4.1.2 f o r humic a c i d , the same problems were encountered. No measurable amount of boron was adsorbed by s o i l p o l y s a c c h a r i d e w i t h i n the l i m i t s of experimental e r r o r . 2. E l e c t r i c a l C o n d u c t i v i t y Approach: According to Boeseken (1949) the complexation between p o l y o l s and b o r i c a c i d causes the formation of the monodiol b o r i c a c i d or 73 b i d i o l b o r i c a c i d which are comparatively s t r o n g a c i d s , and t h e r e f o r e cause the enhancement of the e l e c t r i c a l c o n d u c t i v i t y . I t was thus designed that by adding a c e r t a i n amount of b o r i c a c i d s o l u t i o n i n t o the s o i l p o l y s a c c h a r i d e s o l u t i o n one should be a b l e to observe the changes of e l e c t r i c a l c o n d u c t i v i t y by comparing the sum of the c o n d u c t i v i t i e s of the s o i l p o l y s a c c h a r i d e s o l u t i o n and b o r i c a c i d s o l u t i o n of the same c o n c e n t r a t i o n i f the complexation does take p l a c e . However, the r e s u l t s d i d not show any measurable enhancement of the c o n d u c t i v i t y . T h i s might be due p a r t l y to no or only l i t t l e complexation having taken p l a c e , p a r t l y due to low c o n c e n t r a t i o n s of the s o i l p o l y s a c c h a r i d e and b o r i c a c i d s o l u t i o n s used, and p a r t l y due to the r e l a t i v e l y high a c i d i t y of s o i l p o l y s a c c h a r i d e which c o n t r i b u t e s to the r e l a t i v e l y h i g h e l e c t r i c a l c o n d u c t i v i t y of the s o l u t i o n , and t h e r e f o r e small changes of the c o n d u c t i v i t y would be covered up. 3. P r e c i p i t a t i o n by C e t y l p y r i d i n i u m Approach: T h i s approach i s based on the p r i n c i p l e that p o l y a n i o n s , such as a c i d i c p o l y s a c c h a r i d e s and p o l y s a c c h a r i d e - b o r a t e complexes, can form s a l t s with detergent c a t i o n s , such as C e t y l p y r i d i n i u m , which are very i n s o l u b l e i n water ( S c o t t , 1955; 1965). The experimental procedure has been d e s c r i b e d i n 3.4.3. However, the r e s u l t s d i d not show any s i g n i f i c a n t amount of boron a d s o r p t i o n by the s o i l p o l y s a c c h a r i d e s w i t h i n the l i m i t s of the experimental 74 e r r o r . The experimental data were r a t h e r r a d i c a l and the r e p r o d u c i b i l i t y was very poor. N e v e r t h l e s s , the method i t s e l f has not yet been v e r i f i e d and t h e r e f o r e , the r e l i a b i l i t y of the r e s u l t s are a l s o q u e s t i o n a b l e . From the d i s c u s s i o n above, and c o n s i d e r i n g t h a t the p o l y s a c c h a r i d e f r a c t i o n i s a r e l a t i v e l y minor c o n s t i t u e n t of the s o i l o r g a n i c matter, there i s no i n d i c a t i o n t h a t the s o i l p o l y s a c c h a r i d e i t s e l f p l a y s an important r o l e i n boron r e t e n t i o n i n s o i l s . By c o n s i d e r i n g the s t r u c t u r a l c o n f i g u r a t i o n of the p o l y s a c c h a r i d e and because of the l i n k a g e between the two adjacent hydroxyls of those monosugars, some or most of the c / s - d i o l s are no longer present i n the p o l y s a c c h a r i d e , and t h e r e f o r e , i t may account f o r no s i g n i f i c a n t amount of boron being complexed with the s o i l p o l y s a c c h a r i d e although those monosugars (upon the h y d r o l y s i s of the s o i l p o l y s a c c h a r i d e s ) show high tendency to complex with boron. I t has been shown that t r ans-diols do not complex with boron because of i t s hydroxyl groups being f i x e d i n an u n f a v o r a b l e p o s i t i o n (Boeseken, 1949; Pesetsky and E l d r e d , 1969). Another reason might be due to the low a f f i n i t y of B(OH) 3 f o r the hydroxyls at t h i s low pH c o n d i t i o n as t h i s i s the case of the r e a c t i o n between b o r i c a c i d and mannitol (4.1.3). 75 4 . 3 BORON ADSORPTION BY CLAY AND ORGANO-CLAY COMPLEXES 4. 3. 1 INTERACTION OF THE ORGANIC CONSTITUENTS WITH CLAY  MINERALS The a d s o r p t i o n of the three organic c o n s t i t u e n t s , humic a c i d , p o l y p h e n o l , and p o l y s a c c h a r i d e , by three c l a y m i n e r a l s was s t u d i e d i n order to examine the r e a c t i v i t y of d i f f e r e n t o r ganic c o n s t i t u e n t s with c l a y m i n e r a l s . The r e s u l t s are shown i n F i g u r e 12 6. S o i l p o l y s a c c h a r i d e was, t h e r e f o r e , found to be the most r e a c t i v e with those c l a y m i n e r a l s , and much more was adsorbed on C a - m o n t m o r i l l o n i t e . X-ray d i f f r a c t i o n 7 s t u d i e s showed that some of the s o i l p o l y s a c c h a r i d e was adsorbed i n the i n t e r l a m e l l a r spaces of the C a - m o n t m o r i l l o n i t e . With the i n c r e a s e of the amount of the p o l y s a c c h a r i d e adsorbed (from 3.54 to 21.12 mg/50mg c l a y ) , d 0 o i s p a c i n g of the C a - m o n t m o r i l l o n i t e i n c r e a s e d from 14.82 A to 17.73 A (see Appendix 30). S o i l p o l y p h e n o l , on the other hand, was the l e a s t r e a c t i v e with those c l a y s . A p r e l i m i n a r y experiment a l s o i n d i c a t e d that the adsorbed p o l y s a c c h a r i d e was more d i f f i c u l t to be desorbed by washing with water, whereas most polyphenol or humic a c i d c o u l d be desorbed by washing once with water. S i m i l a r o b s e r v a t i o n s were made by Greenland (1956b) and Rashid, et a l . (1972). An important aspect of the formation of the organo-clay 6 D a t a of the n e g a t i v e a d s o r p t i o n were omitted from the diagram. 7The x-ray d i f f r a c t i o n s t u d i e s were c a r r i e d out on a P h i l i p s X-ray D i f f T a c t o m e t e r . The c o n d i t i o n s used were: F e - f i l t e r e d Co r a d i a t i o n (CoKa 1.54050A), 40Kv, 20mA, scanning from 3° to 33° at the speed of 1°(20)/min. 76 10 >i m C7> E o ID cn i E ! 0) . O U O U l ( a ) a Polysaccharide • Humic Acid _ ° Polyphenol 40 80 120 OM Added, ( m g / l O m l ) 160 F i g u r e 12 - Isotherms f o r the a d s o r p t i o n s of p o l y s a c c h a r i d e , humic a c i d and polyphenol on C a - s a t u r a t e d k a o l i n i t e ( a ) , i l l i t e ( b ) , and m o n t m o r i l l o n i t e ( c ) . 77 complexes i s i t s i n f l u e n c e on the c l a y s u r f a c e and thereby the i n t e r a c t i o n between c l a y and the e l e c t r o l y t e , e t c . The q u e s t i o n i s what e f f e c t has the c o a t i n g of s o i l o r g a n i c m a t e r i a l s on c l a y m i n e r als on boron a d s o r p t i o n ? 4. 3. 2 BORON ADSORPTION BY THE THREE CLAY MINERALS Boron a d s o r p t i o n by the Ca - s a t u r a t e d i l l i t e , m o n t m o r i l l o n i t e and k a o l i n i t e was s t u d i e d i n order to compare the r e s u l t s with the boron a d s o r p t i o n by HA and by the organo-clay complexes and to r e v e a l the r e l a t i v e importance of s o i l o r ganic matter on boron a d s o r p t i o n i n s o i l s as i t was the main o b j e c t i v e of t h i s study. The r e s u l t s are shown i n F i g u r e 13. The l i n e s i n the f i g u r e were a l s o drawn a c c o r d i n g to the F r e u n d l i c h e q u a t i o n , whereas the symbols r e p r e s e n t the averages of d u p l i c a t e experimental r e s u l t s . The r e s u l t s were i n accordance with the f i n d i n g s by other i n v e s t i g a t o r s (Hingston, 1964; Keren and Mezuman, 1981; Keren and O'Connor, 1982), and the c o n c l u s i o n to be drawn here i s that the boron a d s o r p t i o n by i l l i t e was much g r e a t e r than that by both m o n t m o r i l l o n i t e and k a o l i n i t e . Although the r e s u l t s were b e t t e r d e s c r i b e d by the F r e u n d l i c h E q u a t i o n , they were a l s o f a i r l y w e l l d e s c r i b e d by the Langmuir e q u a t i o n . The Langmuir c o n s t a n t s , b and k values which are l i s t e d i n Table 9 ("uncoated" c l a y s ) , are s i m i l a r to those found by Hingston (1964). 7 8 F i g u r e 13 Boron a d s o r p t i o n isotherms f o r Ca - s a t u r a t e d k a o l i n i t e (pH 6.3-6.7), m o n t m o r i l l o n i t e (pH 7.5-7.8) and i l l i t e (pH 7.5-7.8). 79 4. 3. 3 BORON ADSORPTION BY THE ORGANO-CLAY COMPLEXES (1) Soil Pol ysacchari de-Cl ay Complexes An experiment was c a r r i e d out by u s i n g the s o i l p o l y s a c c h a r i d e e x t r a c t e d from the Langley s o i l and the three c l a y m i n e r a l s . The experimental procedures have been d e s c r i b e d i n 3.4.5, and the amount of p o l y s a c c h a r i d e coated on k a o l i n i t e , m o n t m o r i l l o n i t e , and i l l i t e was 13.0, 18.3 and 22.& mg/g c l a y , r e s p e c t i v e l y . A f t e r the e q u i l i b r a t i o n with 25 mL of boron s o l u t i o n , about 1.0, 2.2, and 2.5 mg/g c l a y of those adsorbed p o l y s a c c h a r i d e s were desorbed from k a o l i n i t e , m o n t m o r i l l o n i t e , and i l l i t e , r e s p e c t i v e l y . The r e s u l t s ( F i g u r e 14) i n d i c a t e that the c o a t i n g of the s o i l p o l y s a c c h a r i d e on the three c l a y s s i g n i f i c a n t l y reduced the boron a d s o r p t i o n as compared with that by those "uncoated" c l a y s ( F i g u r e 13). S i m i l a r to the boron a d s o r p t i o n by the "uncoated" c l a y s , the P S S - i l l i t e complex adsorbed the hi g h e s t amount of boron, whereas the P S S - k a o l i r i i t e adsorbed the l e a s t . The a d s o r p t i o n isotherms were a l s o f a i r l y w e l l d e s c r i b e d by the Langmuir e q u a t i o n . The Langmuir c o n s t a n t s , b (the maximum boron a d s o r p t i o n parameter) and k (which i s r e l a t e d to bonding energy) val u e s of the PSS-coated and uncoated c l a y s and the percent of r e d u c t i o n i n the amount of boron a d s o r p t i o n (based on b va l u e s ) are l i s t e d i n Table 9. T h e r e f o r e , the r e d u c t i o n s of boron a d s o r p t i o n by PSS-coated i l l i t e , m o n t m o r i l l o n i t e and k a o l i n i t e r e l a t i v e to that on the uncoated c l a y s were 31.6%, 44.5%, and 76.7%, 80 F i g u r e 14 Boron a d s o r p t i o n isotherms f o r PSS-coated k a o l i n i t e (pH 6.3-6.7), m o n t m o r i l l o n i t e (pH 7.5-7.8) and i l l i t e (pH 7.4-7.8). Table 9 - Langmuir Constants, b and k, for the Polysaccharide-Coated and Uncoated Clays, and % Reduction in the Amount of Boron Adsorption Uncoated Clay PSS Coated Clay Clay Type % Reduction pH b k pH b k I l l i t e 7.5-7.8 16.80 2.00 7.5-7.8 11.49 1.70 31.6 Montmorillonite 7.5-7.8 6.00 1.30 7.4-7.8 3.33 2.33 44.5 Kaolinite 6.3-6.7 3.85 1.80 6.3-6.7 1.30 0.35 76.7 82 r e s p e c t i v e l y . The o b s e r v a t i o n was supported by the evidence t h a t d e s t r u c t i o n of org a n i c matter l e d to an in c r e a s e i n boron a d s o r p t i o n of the s o i l s (Harada and Tamai, 1968). I t was suggested that the s t r o n g c o m p e t i t i o n and b l o c k i n g of the boron a d s o r p t i o n s i t e s by the s o i l p o l y s a c c h a r i d e accounted f o r the s i g n i f i c a n t r e d u c t i o n i n boron a d s o r p t i o n by the three c l a y m i n e r a l s . I t may be a l s o p a r t l y due to the low boron a d s o r p t i o n c a p a c i t y of the s o i l p o l y s a c c h a r i d e as d i s c u s s e d p r e v i o u s l y . The former e x p l a n a t i o n i s q u i t e p o s s i b l e because of the str o n g complexation between the s o i l p o l y s a c c h a r i d e and c l a y m i n e r a l s . I t has been i n d i c a t e d t hat the complexation between c l a y s and the polymers was mainly through H-bonding, or through c o o r d i n a t i o n with c a t i o n s , or through the coulombic a t t r a c t i o n between p o s i t i v e l y charged c l a y edge s u r f a c e s and the n e g a t i v e l y charged s o i l p o l y s a c c h a r i d e (Greenland, 1956a; 1956b; P a r f i t t and Greenland, 1970; Mortland, 1970). T h e r e f o r e , fewer a d s o r p t i o n s i t e s on both c l a y and the s o i l p o l y s a c c h a r i d e were a v a i l a b l e f o r boron complexation. However, the o b s e r v a t i o n was t o t a l l y c o n t r a d i c t o r y to that by Olson and Berger (1946), who observed that o x i d a t i o n of s o i l o r ganic matter r e s u l t e d i n a s i g n i f i c a n t r e l e a s e of boron and caused a s l i g h t decrease i n boron f i x a t i o n . (2) Humic Acid- and Pol yphenol-CI ay Complexes Based on above o b s e r v a t i o n s , the a d s o r p t i o n of boron on HA-clay and PP-clay complexes were a l s o determined i n order 83 to examine the e f f e c t s of the " c o a t i n g " of s o i l humic a c i d or polyphenol on boron a d s o r p t i o n by c l a y m i n e r a l s . The amounts of the polyphenol o r i g i n a l l y adsorbed by i l l i t e , m o n t m o r i l l o n i t e and k a o l i n i t e were 3.4%, -4.4%, and 2.0%, r e s p e c t i v e l y , and f o r the humic a c i d adsorbed by m o n t m o r i l l o n i t e and k a o l i n i t e , which were -3.2%, and 8.7%, r e s p e c t i v e l y . The apparent n e g a t i v e a d s o r p t i o n of the polyphenol and the humic a c i d by m o n t m o r i l l o n i t e might be e x p l a i n e d by that m o n t m o r i l l o n i t e adsorbed more s o l v e n t (water) than the sorbate (polyphenol or humic a c i d ) . However, a c e r t a i n amount of polyphenol or humic a c i d remained i n the r e s i d u e a f t e r c e n t r i f u g a t i o n of the organo-montmorillonite mixture. R e s u l t s are shown i n F i g u r e s 15 and 16 8. The boron a d s o r p t i o n s on the two organo-clay complexes was l e s s by comparing that on the "uncoated" c l a y s i n F i g u r e 15. However, i t should be a l s o noted that the pH c o n d i t i o n s were unexpectedly d i f f e r e n t f o r the two systems, and the e x p l a n a t i o n s were, t h e r e f o r e , c o m p l i c a t e d . N e v e r t h l e s s , i t was d e f i n i t e t h a t the boron a d s o r p t i o n was l e s s a f f e c t e d by the " c o a t i n g " of s o i l p o l y p h e n o l than that of s o i l p o l y s a c c h a r i d e on m o n t m o r i l l o n i t e . Even at that low pH c o n d i t i o n , the percentage of r e d u c t i o n i n the boron a d s o r p t i o n by PP-montmorillonite complex was only 23.3, l e s s 8The boron a d s o r p t i o n s on H A - i l l i t e complex and P P - i l l i t e complex were not done because of the l i m i t e d amount of i l l i t e a v a i l a b l e . 84 F i g u r e 15 - Boron a d s o r p t i o n isotherms f o r PP-coated k a o l i n i t e (pH 5.3-5.7), m o n t m o r i l l o n i t e (pH 6.0-6.2) and i l l i t e (pH 5.8-6.2). 85 F i g u r e 16 - Boron a d s o r p t i o n isotherms f o r HA-coated k a o l i n i t e (pH 5.4-5.7), and m o n t m o r i l l o n i t e (pH 5.6-5.9). Table 10 - Langmuir Constants, b and k, for Polyphenol-Coated and Humic Acid-Coated Clays PP-Coated Clay HA-Coated Clay Clay Type pH b k PH b k I l l i t e 5.8-6.2 8.69 0.79 / / / Montmorillonite 6.0-6.2 4.60 2.21 5.6-5.9 11.86 0.089 K a o l i n l i t e 5.3-5.7 1 .05 4.16 5.4-5.7 2.08 0.50 87 than that by PSS-montmorillonite which was 44.5 (Table 9). T h i s may be e x p l a i n e d by the f a c t that only n e g l i g i b l e (or " a p p a r e n t l y n e g a t i v e " ) amount of s o i l polyphenol was adsorbed by m o n t m o r i l l o n i t e , t h e r e f o r e , more s i t e s were a v a i l a b l e f o r boron complexation. Table 10 l i s t s the Langmuir c o n s t a n t s , b and k v a l u e s , f o r the PP-coated and the HA-coated c l a y s . A l a r g e d e v i a t i o n from the Langmuir equation was found f o r HA-coated c l a y s . 4.4 THE SIGNIFICANCE OF SOIL ORGANIC MATTER ON BORON  ADSORPTION AND THE POSSIBLE ADSORPTION MECHANISMS The present i n v e s t i g a t i o n of the e f f e c t of s o i l o r ganic matter on boron a d s o r p t i o n suggests that f a c t o r s such as pH, organic matter c o n t e n t , c l a y types and content, and i r o n and aluminum co n t e n t s should be taken i n t o c o n s i d e r a t i o n i n a s s e s s i n g the r e l a t i v e importance of s o i l o r g a n i c matter i n boron r e t e n t i o n and r e l e a s e i n s o i l s . pH e x e r t s a marked i n f l u e n c e on boron a d s o r p t i o n by s o i l humic a c i d . W i t h i n the pH range of most c u l t i v a t e d s o i l s (presumably pH around n e u t r a l ) , boron a d s o r p t i o n by Ca-humic a c i d , (as represented by CH-HA(b) and LA-HA(b), F i g u r e s 1 and 5), was found to be of the same order of magnitude as that r e p o r t e d f o r c l a y m i n e r a l s on a weight b a s i s (Hingston, 1964; Sims and Bingham, 1967; Keren and O'Connor, 1982). However, with the i n c r e a s e of pH up to a t l e a s t pH 9.5, there i s a marked 88 i n c r e a s e i n boron r e t e n t i o n by s o i l humic a c i d , which i s s e v e r a l - f o l d more than that r e t a i n e d by c l a y m i n e r a l s , or even higher depending on the types of c l a y m i n e r a l s . I t i s supposed that the i n c r e a s e d boron a d s o r p t i o n at higher pH c o n d i t i o n i s due to the higher a f f i n i t y of B ( O H ) H f o r the d i o l compounds of s o i l o r ganic matter. T h i s pH-dependent nature of boron a d s o r p t i o n by s o i l o r g a n i c matter as w e l l as c l a y m i n e r a l s p a r t l y accounted f o r the e x c e s s i v e c o n c e n t r a t i o n s of boron o f t e n found i n a l k a l i n e s o i l s . T h i s i s supported by the evidence that boron moves more slowly than other s a l t s , such as Na +, d u r i n g the r e c l a m a t i o n of a l k a l i n e s o i l s . For example, the s a l t content of a s o i l was reduced to l e s s than 20% of the i n i t i a l v a lue w i t h 30.4 cm of water f o r each 30.4 cm depth of s o i l c o n s i d e r e d , whereas 3 times more water was r e q u i r e d f o r the same percentage r e d u c t i o n i n boron (Keren and Bingham, 1985). Boron a d s o r p t i o n by s o i l s and s o i l o r g a n i c matter i s r e v e r s i b l e with-the changes of pH. At lower pH c o n d i t i o n s , l e s s boron can be adsorbed by s o i l c o l l o i d s . For example, Pra t h e r (1977) r e p o r t e d t h a t lowering s o i l pH c o u l d e f f e c t i v e l y i n c r e a s e boron c o n c e n t r a t i o n i n s o i l s o l u t i o n and i n c r e a s e the r a t e of boron l e a c h i n g d u r i n g r e c l a m a t i o n of hig h boron s o i l s . I t has been a l s o shown that s o i l o r g a n i c matter as w e l l as c l a y m i n e r a l s adsorb more boron at high e r i o n i c s t r e n g t h and t h i s a l s o accounts f o r the hig h boron content found i n those s a l i n e s o i l s . 89 Most c u l t i v a t e d s o i l s c o n t a i n about 1 to 5% o r g a n i c matter and have a pH around n e u t r a l i t y . Since boron a d s o r p t i o n i s d i s t i n c t l y a f f e c t e d by c l a y types and c o n t e n t s , the e f f e c t of s o i l o r ganic matter on boron r e t e n t i o n would be n e g l i g i b l e i n those s o i l s h i g h i n c l a y content and r i c h i n 2:1 c l a y m i n e r a l s such as i l l i t e . As has been demonstrated e a r l i e r , the c o a t i n g of s o i l o r g a n i c matter even reduces boron a d s o r p t i o n by c l a y m i n e r a l s , e s p e c i a l l y the c o a t i n g with s o i l p o l y s a c c h a r i d e s , because of the complexation between s o i l o r g a n i c matter and c l a y m i n e r a l s . In a d d i t i o n , s o i l t e x t u r e has a marked e f f e c t on boron a d s o r p t i o n . Keren and Talpaz (1984) have shown that boron a d s o r p t i o n by the s m a l l e r c l a y p a r t i c l e s was much g r e a t e r than by the l a r g e r c l a y p a r t i c l e s at both low pH and high pH l e v e l s . I t was a l s o r e p o r t e d that more added boron would remain i n s o i l s o l u t i o n i n c o a r s e - t e x t u r e d s o i l s than in f i n e - t e x t u r e d s o i l s (Keren et a l . , 1985b). S o i l o r g a n i c matter, however, would be expected to p l a y a major r o l e i n boron r e t e n t i o n i n s o i l s h i g h i n o r g a n i c matter and low i n c l a y c o n t e n t , f o r example, i n peat s o i l s . Under lower pH c o n d i t i o n s , the pH-dependent boron a d s o r p t i o n s i t e s , a-hydroxy-carboxyl groups i n s o i l o r g a n i c matter would be l a r g e l y r e s p o n s i b l e f o r the boron r e t e n t i o n ( H u e t t l , 1976). The present i n v e s t i g a t i o n a l s o showed that only a small p a r t of boron i n s o l u t i o n c o u l d be adsorbed by humic a c i d under lower pH c o n d i t i o n s and a l s o d i - and t r i - v a l e n t c a t i o n s may have hig h e r a f f i n i t y f o r those c a r b o x y l s . T h i s may suggest 90 that boron i s not t i g h t l y bonded to those a-hydroxy-carboxyl groups and i s r e v e r s i b l e depending on the boron c o n c e n t r a t i o n i n s o i l s o l u t i o n . John et a l . (1977) r e p o r t e d t h a t p l a n t adsorbed more boron from an o r g a n i c s o i l than the o r t h e r two m i n e r a l s o i l s from pots t h a t r e c e i v e d r a t e s of boron a p p l i c a t i o n from 0 to 2 ppm, s u g g e s t i n g a good r e l a t i o n s h i p between boron a v i l a b i l i t y and o r g a n i c matter co n t e n t . The r e l a t i o n s h i p was a l s o found by a number of r e s e a r c h e r s (Berger and Truog, 1945; Martens, 1968; M i l j k o v i c et a l . , 1966). Two p o s s i b l e mechanisms might be i n v o l v e d t h a t : 1. s o i l o r g a n i c matter may a c t as " c o a t i n g " on s o i l c l a y m i n e r a l s and thus prevent boron a d s o r p t i o n by s o i l c l a y m i n e r a l s or other s o i l c o n s t i t u e n t s and render more boron i n t o s o i l s o l u t i o n ; 2. s o i l s h i g h i n organic matter content r e t a i n boron through a-hydroxy-carboxyl groups, which i s r e a d i l y e x t r a c t a b l e with hot water. Another t h i n g that should be taken i n t o c o n s i d e r a t i o n i s that s o i l o r g a n i c matter u s u a l l y c o n s t i t u t e s only a small p a r t of the s o i l , and i t has a s i m i l a r boron f i x a t i o n c a p a c i t y to c l a y m i n e r a l s at lower pH. T h e r e f o r e , i t i s u n l i k e l y t h a t i t would c o n t r i b u t e much to the boron a d s o r p t i o n by a s o i l (Bingham, et a l . , 1971; Mezuman and Keren, 1981; S c h a l s c h a , et a l . , 1973). I t must a l s o be noted t h a t an o v e r a l l s i g n i f i c a n c e of one f a c t o r c o n t r i b u t i n g to boron a d s o r p t i o n might cover up the c o n t r i b u t i o n of other f a c t o r ( s ) . T h i s may a l s o be one of the reasons f o r the disagreement i n the l i t e r a t u r e about the c o n t r i b u t i o n of 91 s o i l o r g a n i c matter to boron a d s o r p t i o n . Iron and aluminum present i n s o i l s have a s i g n i f i c a n t e f f e c t on boron r e t e n t i o n by s o i l s . Hatcher et a l . (1967) and Sims and Bingham (1968b) i n d i c a t e d t h a t hydroxy Fe and A l compounds were the major s o i l c o n s t i t u e n t s determining boron r e t e n t i o n c h a r a c t e r i s t i c s . The r e s u l t s of the present i n v e s t i g a t i o n a l s o showed a marked i n f l u e n c e of Fe and A l on boron a d s o r p t i o n by the s o i l humic a c i d . The formation of A l - and Fe- humic a c i d complexes i n c r e a s e d boron a d s o r p t i o n to l e v e l s higher than that found f o r A l - or Fe-hydrous oxides or humic a c i d i t s e l f . I t i s l i k e l y t h a t A l or Fe are o n l y i n d i v i d u a l l y complexed with humic a c i d and u n l i k e the polymerized A l - or Fe-hydrous oxides (Sims and Bingham, 1968a), and t h e r e f o r e more a d s o r p t i o n s i t e s are a v a i l a b l e i n A l - or Fe-HA complexes f o r boron complexation. I t i s thus expected t h a t those s o i l s h i g h i n Fe or A l and o r g a n i c matter c o n t e n t s would have a very high boron f i x a t i o n c a p a c i t y . However, more experimental data of s o i l a n a l y s i s would be needed to prove the above hypotheses. 5. SUMMARY AND CONCLUSIONS S o i l o r g a n i c matter has been thought to be one of the most important components of a s o i l r e s p o n s i b l e f o r boron r e t e n t i o n . However, few e q u i l i b r i u m s t u d i e s of boron a d s o r p t i o n by s o i l o r g a n i c matter, or i n d i v i d u a l organic c o n s t i t u e n t s have been done, and some workers have q u e s t i o n e d the importance of s o i l o r g a n i c matter i n boron a d s o r p t i o n i n s o i l s . T h e r e f o r e , the nature of s o i l o r g a n i c matter e f f e c t s on boron r e t e n t i o n and r e l e a s e i n s o i l s and i t s r e l a t i v e s i g n i f i c a n c e to other s o i l c o n s t i t u e n t s have not yet been adequately c l a r i f i e d . Three d i f f e r e n t s o i l o r g a n i c c o n s t i t u e n t s , namely humic a c i d , f u l v i c p o l y p h e n o l , and p o l y s a c c h a r i d e , were i s o l a t e d from three types of s o i l s . Because humic a c i d o f t e n r e p r e s e n t s a l a r g e p a r t of s o i l o r g a n i c matter and i s more e a s i l y p r e c i p i t a t e d by v a r i o u s d i - or t r i - v a l e n t c a t i o n s , most boron a d s o r p t i o n s t u d i e s were done on C a - p r e c i p i t a t e d humic a c i d as a f u n c t i o n of pH. The r e s u l t s i n d i c a t e d that boron a d s o r p t i o n on C a - p r e c i p i t a t e d humic a c i d was h i g h l y pH dependent. The s o r p t i o n remained l i t t l e changed with a r i s e i n pH to around 6.5 at which p o i n t the i n c r e a s e became very sharp with f u r t h e r pH r i s e to about 9.5. At higher pH l e v e l s (pH 8.5-9.0), a l l humic a c i d samples adsorbed s i g n i f i c a n t amounts of boron, which were about an order of magnitude g r e a t e r than that by c l a y m i n e r a l s under the same c o n d i t i o n s . On the other hand, a much s m a l l e r amount of 92 93 boron was adsorbed by the humic a c i d at lower pH l e v e l s (near n e u t r a l ) . These were of the same order of magnitude as found f o r the c l a y m i n e r a l s . Boron a d s o r p t i o n isotherms on v a r i o u s s o i l humic a c i d s were a l s o found to conform to the F r e u n d l i c h e m p i r i c a l equation over the whole range of boron c o n c e n t r a t i o n s t u d i e d , and to be f a i r l y w e l l d e s c r i b e d by the Langmuir equation, although the c o r r e l a t i o n was not as good as that f o r the F r e u n d l i c h equation i n g e n e r a l . The b and kb v a l u e s c a l c u l a t e d a c c o r d i n g to the Langmuir equation was found to i n c r e a s e with i n c r e a s e of pH, and k values decreased with i n c r e a s e of pH, except i n the case of boron a d s o r p t i o n on LA-HA(a). The e f f e c t of s o l u t i o n i o n i c s t r e n g t h on boron a d s o r p t i o n by s o i l humic a c i d was s t u d i e d and i t was found t h a t i n c r e a s e of s o l u t i o n i o n i c s t r e n g t h i n c r e a s e d boron a d s o r p t i o n at higher pH l e v e l . By comparing the b v a l u e s , the amount of boron adsorbed by the two humic a c i d s , WH-HA(a) and LA-HA(b), i n c r e a s e d 21% and 12%, r e s p e c t i v e l y , w i t h the i n c r e a s e of s o l u t i o n i o n i c s t r e n g t h from 0.03 to 0.3. However, the e f f e c t seemed i n s i g n i f i c a n t at lower pH l e v e l s . The r e s u l t s a l s o i n d i c a t e d that boron a d s o r p t i o n by s o i l humic a c i d s , e x t r a c t e d from d i f f e r e n t s o i l s or with d i f f e r e n t e x t r a c t i o n methods, v a r i e d c o n s i d e r a b l y . A h i g h l y s i g n i f i c a n t c o r r e l a t i o n was o b t a i n e d between boron a d s o r p t i o n and i r o n content of the humic a c i d samples, s u g g e s t i n g the c o n t r i b u t i o n of i r o n to the a d s o r p t i o n . T h i s 94 was confirmed by the a d s o r p t i o n experiment on A l - and F e - p r e c i p i t a t e d humic a c i d . I t was found that F e - p r e c i p i t a t e d humic a c i d adsorbed about ten times more boron than d i d C a - p r e c i p i t a t e d humic a c i d . The i n c r e a s e of boron a d s o r p t i o n by A l - p r e c i p i t a t e d humic a c i d was l e s s pronounced than that of F e - p r e c i p i t a t e d humic a c i d . The f r e e z e - d r i e d Fe- and A l - p r e c i p i t a t e d humic a c i d adsorbed much l e s s boron than those f r e s h A l - and F e - p r e c i p i t a t e d humi-c a c i d . T h i s i s a t t r i b u t e d to the c o a g u l a t i o n of the f r e e z e - d r i e d A l - or Fe-HA p r e c i p i t a t e s , with the r e s u l t that l e s s s u r f a c e area or l e s s a d s o r p t i o n s i t e s were a v a i l a b l e f o r boron complexation. Boron a d s o r p t i o n on s o i l p o l y s a c c h a r i d e was s t u d i e d but no evidence was o b tained i n d i c a t i n g s i g n i f i c a n t boron s o r p t i o n by s o i l p o l y s a c c h a r i d e . The l a c k of p o s i t i v e r e s u l t s , may w e l l have been due to methodological l i m i t a t i o n s . F u r t h e r s t u d i e s are needed in order to e l u c i d a t e the p o s s i b l e complexation of s o i l p o l y s a c c h a r i d e with b o r i c a c i d . Three types of c l a y m i n e r a l s were prepared and boron a d s o r p t i o n on these pure c l a y m i n e r a l s and the o r g a n i c matter coated c l a y m i n e r a l s were s t u d i e d at pH near n e u t r a l . R e s u l t s showed that s o i l p o l y s a c c h a r i d e was most r e a c t i v e with c l a y m i n e r a l s , e s p e c i a l l y with m o n t m o r i l l o n i t e , whereas s o i l polyphenol was the l e a s t r e a c t i v e . C o ating of s o i l p o l y s a c c h a r i d e on the three c l a y m i n e r a l s s i g n i f i c a n t l y reduced boron a d s o r p t i o n . By comparing that to the pure 95 c l a y s , c o a t i n g of s o i l p o l y s a c c h a r i d e on i l l i t e , m o n t m o r i l l o n i t e , and k a o l i n i t e reduced boron a d s o r p t i o n by 31.6, 44.5, and 76.7%, r e s p e c t i v e l y , and the e f f e c t of c o a t i n g of s o i l polyphenol on those c l a y s seemed l e a s t pronounced, e s p e c i a l l y on m o n t m o r i l l o n i t e , although the d i r e c t comparison was not p o s s i b l e because of the d i f f e r e n t pH c o n d i t i o n s used. From the r e s u l t s of these e q u i l i b r i u m s t u d i e s , i t i s proposed that s o i l o r g a n i c matter may p l a y an important r o l e i n boron r e t e n t i o n i n s o i l s r e l a t i v e l y high i n organic matter content and with a l k a l i n e r e a c t i o n , or h i g h i n e x t r a c t a b l e i r o n and aluminum c o n t e n t s , and may p l a y a major r o l e i n peat s o i l s . However, the e f f e c t would be n e g l i g i b l e i n most mineral s o i l s with r e l a t i v e l y low o r g a n i c matter content but h i g h i n c l a y or s e s q u i o x i d e c o n t e n t s . At high pH c o n d i t i o n s , boron i s assumed to be mainly complexed by c/'s-diol f u n c t i o n a l groups of s o i l o r g a n i c matter. Whereas at lower pH c o n d i t i o n s , a-hydroxy c a r b o x y l i c f u n c t i o n a l groups Of s o i l o r g a n i c matter i s r e s p o n s i b l e f o r boron complexation. However, s i n c e v a r i o u s d i - or t r i - v a l e n t c a t i o n s may have higher a f f i n i t y f o r those c a r b o x y l groups, the boron a d s o r p t i o n by s o i l o r g a n i c matter may thus be a f f e c t e d . 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A P P E N D I X E S SYMBOLS FOR THE APPENDIXES I = I o n i c s t r e n g t h ; C = I n i t i a l added B c o n c e n t r a t i o n , (umol/mL); C = E q u i l i b r i u m B c o n c e n t r a t i o n , (umol/mL); and x/m = Amount of B adsorbed, (umol/g). 108 109 Appendix 1 - B A d s o r p t i o n as a F u n c t i o n of pH ( I n i t i a l B c o n e , 1.11 umol«mL) LA-•HA(b) CH-•HA(b) WH- •HA (a) pH x/m pH x/m PH x/m 3.47 2.46 0.00 3.21 2.52 2.52 3.28 7.69 5.13 4.50 0.00 0.00 5.02 -2.52 2.52 5.90 6.41 6.41 5.08 2.46 2.46 7.22 9.68 5.38 7.50 19.99 18.41 6.03 4.93 0.00 8.93 32.50 32.50 8.63 44.32 39. 1 0 7.92 19.93 19.93 9.90 34.59 27.75 9.46 65.25 67.85 8.82 40.41 35.65 1 1 .80 20.89 23.87 11.85 44.68 47.30 9.40 52.82 45.04 11.1 26.46 26.46 1 1 .7 21 .90 26.00 Appendix 2 - B A d s o r p t i o n by WH-HA(a) at pH 8 . 5 - 9 . 0 and 1 = 0 . 0 3 , (89% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 0 . 1 8 5 0 . 1 2 8 1 6 . 0 1 0 . 3 7 0 0 . 2 8 5 2 3 . 8 8 0 . 7 4 0 0 . 6 1 2 3 5 . 9 6 1 . 1 1 0 0 . 9 1 6 5 4 . 4 9 1 . 4 8 0 1 . 2 6 2 61 . 2 4 1 . 8 5 0 1 .591 7 2 . 7 5 2 . 5 9 0 2 .351 6 7 . 1 4 5 . 1 8 0 4 . 7 1 9 1 2 9 . 4 9 7 . 4 0 0 6 . 8 2 5 1 6 1 . 5 2 0 . 0 0 8 0 - o . 8928 1 . 2 0 4 4 0 .01 19 - 0 . 5452 1 . 3 7 8 0 0 .01 70 - o . 21 32 1 . 5 5 5 8 0 . 0 1 6 8 - 0 . 0381 1 . 7 3 6 3 0 . 0 2 0 6 0 . 1011 1 . 7 8 7 0 0 . 0 2 1 9 0 . 201 7 1 . 8 6 1 8 0 . 0 3 5 0 0 . 371 3 1 . 8 2 7 0 0 . 0 3 6 4 0 . 6739 2 . 1 1 22 0 . 0 4 2 3 0 . 8341 2 . 2 0 8 2 Appendix 3 - B A d s o r p t i o n by WH-HA(a) at pH 6 . 8 - 7 . 2 and 1 = 0 . 0 3 , (90% HA p r e c i p i t a t e d ) c C x/m C/x/m lo g C l o g x/m 0 0 . 0 - - -0 . 185 0 . 165 5 . 5 6 0 . 0 2 9 7 - 0 . 7 8 2 5 0 . 7 4 5 1 0 . 3 7 0 0 . 3 2 6 1 2 . 2 2 0 . 0 2 6 7 - 0 . 4 8 6 8 1 .0871 0 . 7 4 0 0 .681 1 6 . 3 9 0 . 0 4 1 5 - 0 . 1 6 6 9 1 . 2 1 4 6 1 .110 1 . 0 4 0 1 9 . 4 4 0 . 0 5 3 5 0 . 0 1 7 0 1 . 2 8 8 7 2 . 2 2 0 2 . 1 1 5 2 9 . 1 7 0 . 0 7 2 5 0 . 3 2 5 3 1 . 4 6 4 9 3 . 7 0 0 3 .561 3 8 . 6 1 0 . 0 9 2 2 0 . 5 5 1 6 1 . 5 8 6 7 Appendix 4 - B A d s o r p t i o n by WH-HA(a) at pH 8 . 5 - 9 . 0 and 1 = 0 . 3 , (91% HA p r e c i p i t a t e d ) C C x/m C/x/m lo g C l o g x/m 0 0 0 . - - -0 . 1 8 5 0 . 1 26 1 6 . 2 1 0 . 0 0 7 8 - 0 . 9 9 9 6 1 . 2 0 9 8 0 . 3 7 0 0 . 2 7 6 2 5 . 8 2 0 . 0 1 0 7 - 0 . 5 5 9 1 1 . 4 1 2 0 0 . 7 4 0 0 . 5 9 0 4 1 . 2 1 0 . 0 1 4 3 - 0 . 2 2 9 1 1 . 6 1 5 0 1 . 1 1 0 0 . 8 9 5 5 9 . 0 7 0 . 0 1 5 2 - 0 . 0 4 8 2 1 . 7 7 1 4 1 . 4 8 0 1 . 2 2 8 6 9 . 2 3 0 . 0 1 7 7 0 . 0 8 9 2 1 . 8 4 0 3 1 . 8 5 0 1 . 5 5 2 81 . 8 7 0 . 0 1 9 0 0 . 1909 1 .9131 2 . 5 9 0 2 . 2 3 5 9 7 . 5 2 0 . 0 2 2 9 0 . 3 4 9 3 1 . 9 8 9 1 5 . 1 8 0 4 . 6 4 0 1 4 8 . 3 5 0 . 0 3 1 3 0 . 6 6 6 5 2 . 1 7 1 3 7 . 4 0 0 6 . 6 8 0 1 9 7 . 8 0 0 . 0 3 3 8 0 . 8 2 4 8 2 . 2 9 6 2 111 Appendix 5 - B A d s o r p t i o n by WH-HA(a) at pH 6.8-7.0 and 1=0.3, (92% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 . 1 46 1 0.60 0.0138 -0.8356 1.0253 0 .370 0 .316 1 4.67 0.0215 -0.5003 1.1664 0 .740 0 .681 16.03 0.0425 -0.1669 1.2049 1 .110 1 .032 21 .20 0.0487 0.0137 1.3263 2 .220 2 .096 33.70 0.0622 0.3214 1.5276 3 .700 3 .541 43.21 0.0820 0.5491 1.6356 Appendix 6 - B A d s o r p t i o n by LA-HA(b) at pH 8.5-9.0 and 1=0.03, (90% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0. 153 8.89 0.0172 -0.8153 0.9489 0 .370 0. 321 13.61 0.0236 -0.4935 1.1339 0 .740 0.657 23.06 0.0285 -0. 1824 1.3629 1 .110 0.996 31 .67 0.0314 -0.0017 1.5006 1 .480 1 .350 36.11 0.0374 0.1303 1.5576 1 .850 1 .720 36.11 0.0476 0.2355 1.5576 2 .590 2.375 59.72 0.0398 0.3757 1.7761 3 .700 3.409 80.83 0.0422 0.5326 1.9076 5 .180 4.902 77.22 0.0635 0.6904 1 .8877 7 .400 7.025 104.17 0.0674 0.8466 2.0177 Appendix 7 - B A d s o r p t i o n by LA-HA(b) at pH 5.8-6.2 and 1=0.03, (95% HA p r e c i p i t a t e d ) C* C x/m C/x/m l o g C l o g x/m 0 0 0 _ - -0 . 185 0. 183 0.53 0.3450 -0.7375 -0.2757 0 .370 0. 354 4.21 0.0841 -0.4510 0.6243 0 .740 0. 739 0.26 2.8420 -0. 1314 -0.5850 1 .110 1 . 097 3.42 0.3210 0.0402 0.5340 2 .220 2. 190 7.89 0.2780 0.3404 0.8971 3 .700 3. 694 1 .58 2.3380 0.5670 0.1987 1 1 2 Appendix 8 - B A d s o r p t i o n by LA-HA(b) at pH 8.5-9.0 and 1=0.3, (95% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 . 1 48 9.74 0.0152 -0.8297 0.9886 0 .370 0 .313 1 5.00 0.0209 -0.5045 1.1761 0 .740 0 .627 29.74 0.0211 -0.2027 1.4733 1 .110 0 .988 32.11 0.0308 -0.0052 1.5066 1 .480 1 .295 48.68 0.0266 0.1123 1.6874 1 .850 1 .667 48. 16 0.0346 0.2219 1.6827 . 2 .590 2 .303 75.53 0.0305 0.3623 1.8781 3 .700 3 .385 82.89 0.0408 0.5300 1.9185 5 .180 4 .815 96.05 0.0501 0.6826 1.9825 7 .400 6 .948 1 18.95 0.0584 0.8419 2.0754 Appendix 9 - B A d s o r p t i o n by LA-HA(b) at pH 5.8-6.2 and 1=0.3, (96% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 . 185 0 .170 3.91 0.0435 -0.7696 0.5922 0 .370 0 .362 2.08 0.1740 -0.4413 0.3181 0 .740 0 .720 5.21 0. 1382 -0.1427 0.7168 1 .110 1 . 104 1 .56 0.7077 0.0430 0.1931 2 .220 2 .218 0.52 4.2654 0.346.0 -0.2840 3 .700 3 .674 6.77 0.5427 0.5651 0.8306 Appendix 10 - B A d s o r p t i o n by CH-HA(a) at pH 8.5-9.0 and 1=0.03, (95% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0. 154 8.16 0.0189 -0.8123 0.9117 0 .370 0.311 15.53 0.0200 -0.5072 1.1912 0 .740 0.666 19.47 0.0342 -0.1765 1.2894 1 .110 0.999 29.21 0.0342 0.0004 1.4655 1 .480 1.315 43.42 0.0303 0. 1189 1.6377 1 .850 1 .699 39.74 0.0428 0.2302 1.5992 2 .590 2.412 46.84 0.0515 0.3824 1.6706 Appendix 11 - B Ad s o r p t i o n by CH-HA(a) at pH 6.2-6.5 and 1=0.03, (95.5% HA p r e c i p i t a t e d ) c C x/m C/x/m l o g C log x/m 0 0 0 - - -0. 185 0. 179 1 .57 0.1140 -0.7471 0.1959 0.370 0.350 5.24 0.0668 -0.4559 0.7193 0.740 0.725 3.93 0.1845 -0.1397 0.5944 1.110 1 .091 4.97 0.2195 0.0378 0.6964 1 .480 1 .461 4.97 0.2940 0.1650 0.6964 1 .850 1.813 9.69 0.1871 0.2580 0.9863 2.590 2.562 7.33 0.3495 0.4890 0.8651 Appendix 12 - B Ad s o r p t i o n by LA-HA(a) at pH 8.5-9.0 and 1=0.03, (94% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C log x/m 0 0 0 - • - -0 .185 0 . 1 50 9.31 0.0161 -0.8239 0.9689 0 .370 0 .318 1 3.83 0.0230 -0.4976 1 . 1408 0 .740 0 .659 21 .54 0.0326 -0.1811 1 . 3332 0 .110 0 .999 29.52 0.0338 0.0004 1.4701 1 .480 1 .295 49.20 0.0263 0. 1123 1 .6920 1 .850 1 .646 54.26 0.0303 0.2164 1.7345 2 .590 2 .357 61 .97 0.0380 0.3724 1.7922 Appendix 13 - B A d s o r p t i o n by LA-HA(a) at pH 6.6-6.7 and 1=0.03, (94.6% HA p r e c i p i t a t e d ) C c x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 .179 1 .59 0. 1126 -0.7471 0.2014 0 .370 0 .357 3.44 0.1038 -0.4473 0.5366 0 .740 0 .710 7.93 0.0895 -0.1487 0.8993 1 .110 1 .073 9.78 0.1097 0.0306 0.9903 1 .480 1 .424 1 4.80 0.0962 0.1540 1 . 1703 1 .850 1 .811 10.31 0.1757 0.2580 1.0133 2 .590 2 .525 17.18 0.1470 0.4020 1.2350 Appendix 14 - B Adsorption i by CH-HA(b) at pH 8.5-9.0 and 1=0.03, (86.5% HA p r e c i p i t a t e d ) C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 .161 6.94 0.0232 -0.7932 0.8414 0 .740 0 .652 25.43 0.0256 -0.1858 1 .4053 1 .110 1 .032 22.54 0.0458 0.0137 1.3530 1 .850 1 .722 36.99 0.0466 0.2360 1.5681 Appendix 15 -- B A d s o r p t i o n by LA-HA(b)-Fe Complex (Fresh) at pH 6.7-6.9 and I = 0.03 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 . 1 33 0 .118 3.75 0.0315 -0.9281 0.5740 0 .666 0 .632 8.50 0.0744 -0.1993 0.9294 0 .628 9.50 0.0661 -0.2020 0.9777 1 .110 1 .053 1 4.60 0.0721 0.0223 1 . 1644 1 .776 1 .707 17.25 0.0999 0.2324 1 .2368 1 .714 1 5.50 0. 1106 0.2340 1 . 1903 Appendix 16 - B A d s o r p t i o n by LA-HA(b)-Fe Complex (F r e e z e - d r i e d ) at pH 5.0 and 1=0.03 c C x/m C/x/m l o g C l o g x/m 0 0 0 - -0 .185 0 .181 1 .00 0.1810 -0.7423 0.0000 0 .179 1 .50 0.1193 -0.7471 0. 1761 0 .370 0 .362 2.00 0.1810 -0.4413 0.3010 0 .362 2.00 0.1810 -0.4413 0.3010 0 .740 0 .728 3.00 0.2427 -0.1379 0.4771 0 .725 3.75 0.1933 -0. 1397 0.5740 1 .110 1 .096 3.50 0.3131 0.0398 0.5441 1 .091 4.75 0.2297 0.0378 0.6767 1 .480 1 .461 4.75 0.3076 0.1647 0.6767 1 .462 4.50 0.6532 0.1649 0.6532 1 .850 1 .831 4.75 0.3855 0.2627 0.6767 1 .840 2.50 0.7360 0.2648 0.3979 Appendix 17 - B A d s o r p t i o n by LA -HA(b)-Al Complex (Fresh) at pH 7. 0-7.2 and 1=0.03 C C x/m C/x/m l o g C log x/m 0 0 0 - - -0 . 133 0 . 1 20 3.25 0.0369 -0.9208 0.5119 0 .666 0 .636 7.50 0.0848 -0.1965 0.8751 0 .632 8.50 0.0744 -0.1993 0.9294 1 .110 1 .084 6.50 0.1668 0.0350 0.8129 1 .776 1 .740 9.00 0.1933 0.2405 0.9542 1 .740 9.00 0.1933 0.2405 0.9542 Appendix 18 - B A d s o r p t i o n by LA-HA(b)-Al Complex ( F r e e z e - d r i e d ) at pH 5.0 and 1=0.03 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 . 185 0 .185 0.00 - -0.7330 -0 . 184 0.25 0.7360 -0.7350 -0.6021 0 .370 0 .367 0.75 0.4893 -0.4353 -0.1249 0 .366 1 .00 0.3660 -0.4365 0.0000 0 .740 0 .733 1 .75 0.4189 -0.1350 0.2430 0 .730 2.50 0.2920 -0.1367 0.3979 1 .110 1 .101 2.25 0.4893 0.0418 0.3522 1 .101 2.25 0.4893 0.0418 0.3522 1 .480 1 .461 4.75 0.3076 0.1647 0.6767 1 .470 2.50 0.5880 0.1673 0.3979 1 .850 1 .831 3.50 0.5231 0.2627 0.5441 1 .836 4.75 0.3865 0.2639 0.6767 Appendi X 19 - B Ad s o r p t i o n by Ca- I l l i t e , pH 7.5-7.8 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 . 1 30 4.58 0.0284 -0.8860 0.6609 0 . 1 24 5.08 0.0244 -0.9066 0.7059 0 .370 0 .296 6.17 0.0480 -0.5290 0.7903 0 .298 6.00 0.0497 -0.5260 0.7781 0 .740 0 .636 8.67 0.0734 -0.1965 0.9380 0 .632 9.00 0.0702 -0.1993 0.9542 1 .110 0 .981 1 0.75 0.0913 -0.0083 1.0314 0 .987 1 0.25 0.0963 -0.0057 1.0107 1 .850 1 .708 11.83 0.1444 0.2325 1.0730 1 .700 1 2.50 0. 1360 0.2304 1.0969 2 .775 2 .582 1 6.08 0. 1606 0.4120 1.2063 2 .614 1 3.42 0.1948 0.4173 1.1278 1 17 Appendix 20-B A d s o r p t i o n by M o n t m o r i l l o n i t e , pH 7.5-7.8 C C x/m C/x/m log C l o g x/m 0 0 0 - - -0.185 0. 159 0. 157 1 .30 1 .40 0.1223 0.1121 -0.7990 -0.8041 0.1139 0.1461 0.370 0.331 0.335 1 .95 1 .75 0.1697 0.1914 -0.4802 -0.4750 0.2900 0.2430 0.740 0.675 0.681 3.25 2.95 0.2077 0.2308 -0. 1707 -0.1669 0.5120 0.4700 1.110 1 .052 1 .040 2.90 3.50 0.3628 0.2971 0.0220 0.0170 0.4624 0.5441 1 .850 1 .793 1 .776 2.85 3.70 0.6291 0.4800 0.2536 0.2494 0.4548 0.5682 2.775 2.666 2.667 5.45 5.40 0.4892 0.4939 0.4259 0.4260 0.7364 0.7324 Appendix 21 - B Ad s o r p t i o n by K a o l i n i t e , pH 6.3-6.7 C C x/m C/x/m l o g C log x/m 0 0 0 - - -0. 185 0. 164 0. 163 1 .05 1.11 0.1562 0.1468 -0.7852 -0.7878 0.0212 0.0453 0.370 0.348 0.342 1.11 1 .40 0.3135 0.2443 -0.4584 -0.4660 0.0453 0.1461 0.740 0.699 0.696 2.05 2.20 0.3410 0.3164 -0.1555 -0. 1574 0.3118 0.3424 1.110 1 .058 1 .056 2.60 2.70 0.4069 0.3911 0.0245 0.0237 0.4150 0.4314 1 .850 1 .794 1 .794 2.80 2.80 0.6407 0.6407 0.2538 0.2538 0.4472 0.4472 2.775 2.716 2.704 2.95 2.55 0.9207 1.0604 0.4339 0.4320 0.4698 0.4065 Appendix 22 - B A d s o r p t i o n by P S S - I l l i t e , pH 7.4-7.8 c C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0. 185 0 . 1 54 2.58 0.0597 -0.8125 0.4116 0.370 0 .324 3.83 0.0846 -0.4895 0.5832 0.740 0 .662 6.50 0.1018 -0. 1791 0.8129 1.110 1 .032 6.50 0.1588 0.0137 0.8129 1 .850 1 .738 9.33 0.1863 0.2400 0.9699 2.775 2 .664 9.25 0.2880 0.4255 0.9661 Appendix 23 -- B A d s o r p t i o n by PSS-Montmorillonite pH 7. 5-7.8 C C x/m C/x/m log C log x/m 0 0 0 - - -0.185 0 .165 1 .00 0.1650 -0.7825 0.0000 0.370 0 .344 1 .30 0.2646 -0.4634 0.1139 0.740 0 .703 1 .85 0.3800 -0.1530 0.2672 1.110 1 .055 2.75 0.3836 0.0233 0.4393 1 .850 1 .794 2.80 0.6407 0.2538 0.4472 2.775 2 .719 2.80 0.9711 0.4344 0.4472 Appendix 24 - B Adsorpt ion by PSS-• K a o l i n i t e , pH 6.3-6.7 C C x/m C/x/m lo g C l o g x/m 0 0 0 - - -0. 185 0 . 1 76 0.45 0.3911 -0.7545 -0.3468 0.370 0 .359 0.55 0.6527 -0.4449 -0.2596 0.740 0 .731 0.45 1.6244 -0. 1361 -0.3468 1.110 1 .108 0.10 11.080 0.0445 -1.0000 1 .850 1 .830 1 .00 1.8300 0.2625 0.0000 2.775 2 .756 0.95 2.9011 0.4403 -0.0223 Appendix 25 - B A d s o r p t i o n by P P - I l l i t e , pH 5.8-6.2 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 . 1 70 1 .25 0.1360 -0.7696 -0.0969 0 . 1 69 1 .33 0.1271 -0.7721 0.1239 0 .370 0 .354 1 .33 0.2662 -0.4510 0.1239 0 .354 1 .33 0.2662 -0.4510 0.1239 0 .740 0 .699 3.42 0.2044 -0.1555 0.5340 0 .686 4.50 0.1524 -0.1637 0.6532 1 .110 1 .054 4.67 0.2257 0.0228 0.6693 1 .058 4.33 0.2443 0.0245 0.6365 1 .850 1 .806 3.66 0.4934 0.2567 0.5635 1 .789 5.08 0.3522 0.2526 0.7059 2 .775 2 .695 6.67 0.4040 0.4306 0.8241 2 .706 5.75 0.4706 0.4323 0.7597 Appendix 26 - B A d s o r p t i o n by PP- M o n t m o r i l l o n i t e pH 6.0-6.2 C C x/m C/x/m log C l o g x/m 0 0 0 - .- -0 .185 0 . 1 56 1 .45 0.1076 -0.8069 0.1614 0 . 1 58 1 .35 0.1170 -0.8013 0.1303 0 .370 0 .334 1 .80 0.1856 -0.4763 0.2553 0 .335 1 .75 0.1914 -0.4750 0.2430 0 .740 0 .686 2.70 0.2541 -0.1637 0.4314 1 .110 1 .043 3.35 0.3113 0.0183 0.5250 1 .053 2.85 0.3695 0.0224 0.4548 1 .480 1 .413 3.35 0.4218 0.1501 0.5250 1 .850 1 .769 4.05 0.4368 0.2477 0.6075 2 .590 2 .514 3.80 0.6616 0.4004 0.5798 1 20 Appendix 27 - B A d s o r p t i o n by PP-- K a o l i n i t e , pH 5.3-5.7 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0. 185 0. 178 0. 176 0.40 0.45 0.4450 0.3911 -0.7496 -0.7545 -0.3979 -0.3468 0.370 0.360 0.360 0.50 0.50 0.7200 0.7200 -0.4437 -0.4437 -0.3010 -0.3010 0.740 0.728 0.724 0.60 0.80 1.2133 0.9050 -0.1379 -0.1403 -0.2218 -0.0969 1.110 1 .091 1 .091 0.95 0.95 1.1484 1.1484 0.0378 0.0378 -0.0223 -0.0223 1 .480 1 .462 1 .461 0.90 0.95 1.6244 1.5379 0.1649 0.1647 -0.0458 -0.0223 1.850 1 .821 1 .831 1 .45 0.95 1.2559 1.9274 0.2603 0.2627 0.1614 -0.0223 2.590 2.571 2.575 0.95 0.75 2.7063 3.4333 0.4101 0.4108 -0.0223 -0.1249 Appendix 28 • - B A d s o r p t i o n by pH 5. i HA-Montmorillonite 6-5.9 C C x/m C/x/m l o g C l o g x/m 0 0 0 - - -0. 185 0. 179 0. 176 0.30 0.45 0.5967 0.3911 -0.7471 -0.7545 -0.5229 -0.3468 0.370 0.362 0.35 1.0371 -0.4401 -0.4559 0.740 0.730 0.50 1.4600 -0.1367 -0.3010 1.110 1 .091 1 .096 0.95 0.70 1.1484 1.5657 0.0378 0.0398 -0.0223 -0.1549 1 .480 1 .451 1 .45 1.0007 0.1617 0.1614 1 .850 1.812 1 .90 0.9537 0.2582 0.2788 2.590 2.543 2.35 1.0821 0.4053 0.3711 Appendix 29 - B A d s o r p t i o n by H A - K a o l i n i t e , pH 5.4-5.7 C* c x/m C/x/m l o g C l o g x/m 0 0 0 - - -0 .185 0 .181 0.20 0.9050 -0.7423 -0.6990 0 .180 0.25 0.7200 -0.7447 -0.6021 0 .370 0 .359 0.55 0.6527 -0.4449 -0.2596 0 .361 0.45 0.8022 -0.4425 -0.3468 0 .740 0 .735 0.25 2.9400 -0.1337 -0.6021 0 .733 0.35 2.0943 -0.1349 -0.4559 1 .110 1 .091 0.95 1.1484 0.0378 -0.0223 1 .101 0.45 . 2.4467 0.0418 -0.3468 1 .480 1 .461 0.95 1.5379 0.1647 -0.0223 1 .461 0.95 1.5379 0.1647 -0.0223 1 .850 1 .818 1 .60 1.1363 0.2596 0.2041 1 .822 1 .40 1.3014 0.2605 0.1461 2 .590 2 .567 1.15 2.2322 0.4094 0.0607 2 .571 0.95 2.7063 0.4101 -0.0223 Appendix 30 - The Increase of d 0 0 ! Spacing (A) with the Increase of the Amount of PSS Adsorbed (mg/50mg c l a y ) by Ca-M o n t m o r i l l o n i t e Added Adsorbed d 0 o ! 13. 6 3 .54 1 4 .82 40. 8 1 2 .80 1 5 .22 68. 0 16 .52 1 6 .05 95. 2 18 .75 16 .66 136. 0 21 .12 17 .73 1 22 Appendix 31 - A d s o r p t i o n of PSS, HA and PP on Three Types of Clay M i n e r a l s (mg/50mg c l a y ) P o l y s a c c h a r i d e Humic A c i d Polyphenol Added Sorbed Added Sorbed Added Sorbed K a o l i n i t e 13.6 1.18 20 -0.06 20 -0.95 40.8 6.28 60 5.13 60 3.15 68.0 6.56 100 7.78 100 -1.04 95.2 6.36 1 40 7.23 1 40 1 .39 136.0 6.64 200 7.42 200 3.86 I l l i t e 13.6 1 .94 20 -2.45 20 -0.51 40.8 8.18 60 3.93 60 2.48 68.0 9.06 1 00 7.67 100 1 .94 95.2 8.83 1 40 9.01 1 40 2.59 136.0 8.39 200 8.22 200 3.32 M o n t m o r i l l o n i t e 13.6 3.54 20 -1 .99 20 -1 .07 40.8 12.80 60 1 .00 60 1 .88 68.0 16.52 1 00 1 .30 100 -0.21 95.2 18.75 1 40 1 .41 1 40 -1 .40 1 36.0 21.12" 200 0.73 200 1 .90 

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