anion halaman 1

8/12/2019 ANION HALAMAN 1

1/7

Clays and Clay Minerals Vol. 31, No. 4, 305-311, 1983.

A N I O N E X C H A N G E P R O P E R T IE S O FH Y D R O T A L C I T E L I K E C O M P O U N D S

SHIGEO MI YATAK y ow a Chem ica l I ndus t r y Co. , L td . , 305 Y ashimanish i -machiTakam atsu , K agaw a , 761-01 , J apan

A bs t r ac t - - I on - exchan ge i so the r ms be tw een hydr o ta lc i te - like compou nds ( H T) of the N O 3- , CI- , and SO 4-forms and F , 0 % Br , I , OH - , SO42-, CO3z- , and N aphthol Y e l low S ( N Y S 2-) ions w er e de te r mined ,and the spac ing and the w id th of the 003 r ef lec tion w er e measur ed as a f unc t ion of H T compo s i t ion . Theion- exchange equi l ib r ium cons tan t f or H Ts of mono va len t an ions a r e in the sequence O H - > F > Cl >Br- > NO3- > I , those for divalen t anion s are in the sequence CO3~- > NY S z- > SO42- . The ion -exchan geequi l ib r ium cons tan ts t end to inc r ease as the d iamete r s of the an ions dec r ease , and the c r ys ta l l i t e s ize inthe 001 d i r ec t ion tends to inc r ease w i th an ions having h igher se lec t iv i ty . The O H - f or m of H T has thesma lles t basal spac ing and the largest crys tal l i te s ize in the 001 direct ion .K ey W or ds - -- A nion exchange , A n ion se lec t iv i ty , Cr ys ta l li t e s ize , H y dr o ta lc i te , N aphthol Y e l low S , X - r aypow d er d i f fr ac t ion .

I N T R O D U C T I O NH y d r o t a l c i t e - l i k e c o m p o u n d s ( H T ) c a n b e r e p r e -

s e n t e d b y t h e f o l l o w i n g f o r m u l a : [ M g l_ x A I x+[Ax/nn - . m H 2 0 ] x - , w h e r e i n 0 < x < 0 . 3 3 , a n d A n - is a ne x c h a n g e a b l e a n i o n h a v i n g a v a l e n c e o f n. T h e s e c o m -p o u n d s a r e s im i l a r t o th e m i n e r a l h y d r o t a l c i t e ,M g n A I z (O H ) 1 6 C O 3 "4 H 2 0 ( M i y a t a a n d K u m u r a , 1 97 3;T a y l o r , 1 97 3; M i y a t a , 1 97 5). H T c o n s i s t s o f p o s i t i v e l yc h a r g e d b r u c i t e - l i k e l a y e r s [ M g , x A I ~(O H )2 ] ~+ a l t e r -n a t i n g w i th d i s o r d e r e d , n e g a t i v e l y c h a r g e d i n t e r l a y e r s[A m H z O ] 9 M g a n d A I a r e r a n d o m l y d i s t r i b u t e da m o n g t h e o c t a h e d r a l p o s i t i o n s , a n d t h e O H l a y e r s e -q u e n c e i s - B C - C A - A B - B C - ( A l lm a n n , 1 96 8).

H T i s s t a b l e t o 4 0 0 ~ b u t t r a n s f o r m s i n t o aM g O - A I 2 0 3 s o l i d s o l u t i o n ( M g ,- 3 x/ zA l x O ) b y h e a t i n g t o5 0 0 ~1 7 6 T h i s s o l id s o l u t io n r e h y d r a t e s a n d c o m -b i n e s a n i o n s t o f o r m H T i n t h e p r e s e n c e o f w a t e r a n da n i o n ( M i y a t a a n d O k a d a , 1 97 7; M i y a t a , 1 98 0). C o n -s e q u e n t l y , b o t h H T a n d h e a t - t r e a t e d H T a r e c a p a b l e o fc a p t u r i n g a n i o n s a n d a r e t h e r e f o r e u s e f u l a s h a l o g e ns c a v e n g e r s f o r p o l y o l e f i n e s p r o d u c e d b y Z i e g l e r c a ta -l y s t o r F r i d e l - C r a f t c a t a l y s t a n d t h e r m a l s t a b i l i z e r s f o rp o l y v i n y l c h l o r i d e e t c . ( M i y a t a a n d K u r o d a , 1 98 1a ,1 98 1b ). A c c o r d i n g l y , t h e i o n - e x c h a n g e p r o p e r t i e s o fh y d r o t a l c i t e - l i k e c o m p o u n d s a r e im p o r t a n t . T h e p r e s -e n t a r t i c l e o f h y d r o t a l c i t e r e p o r t s t h e s y n t h e s i s o f th eN O 3 - , C I - , a n d S O 4 - f o r m s a n d t h e i o n - e x c h a n g e i s o -t h e r m s a n d i o n s e l e c ti v i t y f o r t h e s e c o m p o u n d s a n d F - ,C I - , B r - , I % O H , S O 4 2 -, C O 3 z - , a n d N a p h t h o l Y e l l o wS 2 - a n i o n s .

E X P E R I M E N T A LH y d r o t a l c it e - li k e c o m p o u n d s c o r r e s p o n d i n g t o t h e

a b o v e m e n t i o n e d f o r m u l a i n w h ic h x i s a b o u t 0 . 3 a n dA " - i s N O 3 , C I - , o r S O4 2- w e r e p r e p a r e d b y t h e m e t h -Copyright 9 1983, The Clay Minerals Society

o d d e s c r i b e d b y M i y a t a (1 97 5) a n d M i y a t a et al. (1977) .A t x = a b o u t 0 . 3 , t h e i o n - e x c h a n g e c a p a c i t y o f t h ep r o d u c t s w a s h i g h , a n d b y - p r o d u c t s d id n o t fo r m . As m a l l a m o u n t o f C O~ 2 - w a s i n c o r p o r a t e d i n t o t h e p r o d -u c t s , b u t b e c a u s e t h e C O 3 2 - i s h i g h l y s e l e c t e d b y t h e s ec o m p o u n d s a s c o m p a r e d w i t h o t h e r a n i o n s , t h e i o n -e x -c h a n g e r e a c t i o n o f C O3 2 - w a s i g n o r e d .Determination of ion exchange isotherm

A n a m o u n t o f e a c h H T c a l c u l a t e d t o g i v e a n i o n - e x -c h a n g e c a p a c i t y o f 2 t o 5 m e q w a s p l a c e d i n a fl a s k w i t ha g r o u n d g l a s s s to p p e r a n d a n a p p r o p r i a t e a m o u n t o f a0 .1 N a q u e o u s s o l u t io n o f e a c h t h e a f o r e m e n t i o n e d a n -i o n s w a s a d d e d . T h e f l a s k w a s p l a c e d i n a c o n s t a n t t e m -p e r a t u r e v e ss e l ( 25 ~ a n d s h a k e n o v e r n i g h t . T h e c o n -t e n t s o f t h e f l a sk w e r e t h e n f i l t e re d a n d t h e a n i o nc o n c e n t r a t i o n i n th e f i l tr a te d e t e r m i n e d . T h e a n i o n s o -l u t i o n s u s e d w e r e p r e p a r e d b y u s i n g N a F , N a B r , K I ,N a O H , N a 2C O 3 , N a 2 SO 4 , an d N a p h t h o l Y e l l o w S ( an -a l y t i c a l g r a d e m a d e b y W a k o P u r e C h e m i c a l C o . , L t d . ,c h e m i c a l f o r m u l a C , 0 H 4N z N a zO s S " 3 H 2 0 ) .

T h e i n d i v i d u a l a n i o n s w e r e q u a n t i t a t i v e l y d e t e r -m i n e d b y t h e f o ll o w i n g m e t h o d : O H , b y t i tr a t i o n w i th0 . 1 N H C I ; F - b y t i t r a t i o n w i t h 0 . 1 N t h o r i u m n i t r a t eu s i n g A l i z a r in R e d S a s a n i n d i c a t o r i n a c c o r d a n c e w i t ht h e m e t h o d o f Ja p a n S t a n d a r d A s s o c i a t i o n (1 9 6 5a ); C I - ,B r - , a n d I - , b y t h e V o l h a r d m e t h o d ( N i p p o n B u n s e k iK a g a k u k a i , 1 96 1); C O 32 - b y t h e m e t h o d o f J a p a n S t a n -d a r d A s s o c i a t i o n (1 9 6 5 b ); N O 3 , b y r e d u c i n g N O 3 - o ft h e s a m p l e w i t h a m i x t u r e o f N a O H s o l u t i o n a n d D e -b a l d a a l l o y t o f o r m N H 3 a n d b a c k t i t r a t i n g e x c e s s s u l-f u r ic a c i d h a v i n g N H 3 a b s o r b e d i n i t w i t h a q u e o u sN a O H ; S O 4 2- , b y t h e g r a v i m e t r i c a n a l y s is o f b a r i u ms u l fa t e ; a n d N a p h t h o l Y e l l o w S , p h o t o m e t r i c a l l y b ym e a s u r i n g t h e a b s o r b a n c e a t 4 3 0 n m u s i n g a H i t a c h iM o d e l 1 0 1 S p e c t r o p h o t o m e t e r .

305


2/7

3 0 6 M i y a t a lays and lay Minerals1 . 0 N 0 3 C O 3 C I - N Y S N 0 3 - $ 0 41 0O H

0 . 80 . 8

o e , . . , < o e0 4

0 2 O.

0 0 , 2 0 . 4 0 . 6 0 . 8 1 .0 0~ A 0 0 2 0 . 4 0 . 6 0 . 8 1 .0SAF i g u r e 1. I o n - e x c h a n g e i s o t h er m s f o r t h e H T - N O 3 - O H - ( (3 ),H T - N O 3 - F - ( e ) , H T - N O 3 - C 1 - ( /k ), H T - N O 3 - B r - ( ~ ) , a n d H T -N O 3- I- (113) sys tem s a t 0 .1 to ta l norm al i ty and 25~

X-ray powder diffraction XRD) analyses were car-ried out using Ni-filtered CuKa radiation with a PhilipsX-ray diffractometer after drying the products at 60~for 20 hr.

RESULTS AND DISCUSSIONThree different HT exchangers HT-NO3, HT-C1, HT-SO4) were prepared. Their chemical compositions are

listed in Table 1.Prior to measuring ion-exchange isotherms the sta-bility of HT-NO3 in NaF and NaOH solutions was de-termined by examining the molar ratio of Mg to AI inthe HT-NO3 using the lattice parameter a Miyata, 1980)before and after contact with the solution. The molarratio of Mg to A1 in HT-NO3 did not change, and AI wasvirtually undetectable in the solution. Accord ingly, AIin HT does not react with F- or OH- anions.

Ion-exchange isotherms at 25~ in a total ion con-centration of 0.1 N of HT-NO3-OH-, HT-NO3-F-, HT-T a b le 1 . C h e m ic a l a n a ly s e s a n d fo rmu la e fo r h y d ro ta l c i t e -l i k e c o mp o u n d s s tu d ie d .

HT-NOa HT-CI HT-SO4(wt. ) (wt. ) (wt. )A1203 17.5 18.4 17.6M gO 32.5 36. I 34. ICO2 1.05 0.77 0.77NO3 17.0C1 12.3SO4 15.7x 0.299 0.287 0.290

HT-NO3: Mgo.ro2Alo.2~(OH)2(NO3)o.268(CO3)o.61s"m H 2 0 .HT-CI: Mg0.r13A10.2sr(OH)2C10.zrs(CO3)0.014"m H z O .HT-SO4: Mg0.r10A10.zgo(OH)2(SO4)0.137(CO3)0.01~"m H 2 0 .

F ig u re 2 . Io n -e x c h a n g e i s o th e rms fo r t h e H T -N O 3 -S O 4 2 - ( e ) ,H T - N O 3 - C O 3z ( 9 H T - C 1 - N Y S 2 - ( A ) , a n d H T - S O 4 - C O 3 2 -(~ ) s y s t e ms a t 0 . 1 to ta l n o rma l i ty a n d 2 5~

NO3-CI-, HT-NO3-Br-, HT-NO3-I -, HT-NO3-SO42-,HT-NO3-CO32-, HT-C1-NYS2-, and HT-SO4-CO32-systems are shown in Figures 1 and 2. In the ion-ex-change isotherms, St, for example, on the abscissa rep-resents the equivalent fraction of a F- ion based on thetotal anion concentration in an aqeous solution at equi-librium, and HT)v, for example, on the ordinate rep-resents the equivalent fraction of the F - ion exchangedonto HT.The selectivity coefficients K~o) of HT with re-. [. 4

2 . 22 . 0

z ~ l 8O zw e

J 1 . 2I.O0 80 . 6 ~ I i i0 0 . 2 0 . 4 0 . 6 0 . 8

H T ) o .1.0

F i g u r e 3. S e l e c t i v it y c o e f f ic i e n t f o r t h e H T - N O 3 - O H - s y s -t e m a s a f u n c t i o n o f H T c o m p o s i t i o n .


3/7

Vol . 31, No. 4 , 1983 An ion exchange of hydrota lci te - like com pou nds 307

0 . 6 b

1.4

L~O0~I.O0 . 8

- 0 . 8- 1 .0l0 0 . 2 0 . 4 0 . 6 0 8 1 .0H T ) F

F i g u r e 4 . S e l e c t i v i ty c o e f f ic i e n t f o r t h e H T - N O 3 - F - s y s t e ma s a f u n c t i o n o f H T c o m p o s i t i o n .

1.00 . 80 . 6

. 0 m 0 . 4~ z 0 . 2

. . . 1 - o . a- o . 4

- o . 6

i

o 0 2 0 4 o e o ; oH T ) a r

F i g u r e 6 . S e l e c t i v it y c o e f f ic i e n t f o r t h e H T - N O a - B r - s y s t e ma s a f u n c t i o n o f H T c o m p o s i t i o n .s p e c t t o N O 3 w e r e c a l c u l a t e d f ro m t h e i o n - e x c h a n g ei s o t h e r m s i n F i g u r e s 1 a n d 2 in a c c o r d a n c e w i t h t h e f o l-l o w i n g e q u a t i o n s .

W h e n n = 1 ,K ANo~ = (HT)A SNo3 /(HT)~o, SA,

W h e n n = 2 ,KAos = H T ) O .S S N o j H T ) N o 3 S O .LNO3

A c c o r d i n g t o F i g u r e s 1 a n d 2 , i o n - e x c h a n g e i s o t h e r m so f H T - N O 3 - O H - , H T - N O 3 - F - , H T - N Q - S O 4 z -, H T -N O 3 - C O 3 z - , H T - C I - N Y S 2 -, a n d H T - S O 4 - C O 3 2 - s y s -

t e m s a r e n e a r l y o f t h e L a n g m u i r t y p e . T h e i o n - e x -c h a n g e i s o t h e r m s o f t h e H T - N O 3 - I s y s t e m a r e n o t o ft h e L a n g m u i r t y p e .

F i g u r e s 3 t o 9 s h o w t h e l o g a r i t h m o f s e l e c t i v i t y c o e f -f i c i e n t s a s a fu n c t i o n o f t h e m o l e f r a c t i o n o f a n i o n A o nt h e H T . T h e e q u i l i b r i u m c o n s t a n t ( K e ) w a s c a l c u l a t e db y u s i n g t h e m e t h o d o f G a i n e s a n d T h o m a s (1 9 53 ) fr o mt h e f o l l o w i n g e q u a t i o n

ft HT)A=Il o g K e = l o g K ~ o 3 d ( H T ) A ,HT)A=0i n w h i c h ( H T ) A i s th e m o l e f r a c t i o n o f a n i o n A o n t h eH T . T h e i n t eg r a l i n t h e a b o v e e q u a t i o n w a s g r a p h i c a l l y

1 . 00 . 80 . 6

~ r 0 . 4~ , O . 2

- J - 0 . 2- 0 . 4

- 0 . 8- 0 . 8- . 0 0

0 . 80 . 40 . 2

g o- 0 . 2- 0 . 4

- - . l - 0 . ~- 0 . 8

- I . 0- I . 2

- I . 40 . 2 0 . 4 0 . 6 0 . 8 1 .0 0H T ) c t .

F i g u r e 5 , S e l e c t i v it y c o e f f ic i e n t f o r t h e H T - N O 3 - C I - s y s t e ma s a f u n c t i o n o f H T c o m p o s i t i o n .

O 0 ~0

0.2 0 .4 o .e o .8 i.oH T ) I

Figur e 7 . Se lec t iv i ty coef f ic ien t f or the H T - N O 3 - I - sys temas a f unc t ion of H T com pos i t ion .


4/7

308 Miyata lays and lay Minerals

N%

2 . 22 . 01 . 81 6

m 1 . 4z o 1 . 2 0 0.

O~ 1 0o o_ 1 o e0 60 40 20 I Io o . z 0 . 4 0 . 6 . o

HT)mrsFigure 8. Select ivity coefficient for the HT-CI-NYS2- sys-tem as a function of HT composition.

1 4

o ~ 1 . 2

O~ 1 00_J0.8

0 6

o 0 . 2 0 . 4 0 . 6 o . o . o(HT)cFigure 9. Select ivity coefficient for the HT-SO4-COs 2- sys-tem as a function of HT composition.

evaluated by calculating the area under the curve inFigures 3 to 9. The calculated Gaines and Thom as equi-librium constants are listed in Table 2.

These data show that the ion selectivities of mono-valent anions are in the order of OH- > F- > CI- >Br - > NO3- > 1-, and that divalen t anions hav e higherion selectivities than mono valent anions. Of the mono-valent anions tested, O H- and F- have particularly highion selecti vities, and CO3 z is the most sele ctive of thediva lent anions. Fi gures 10 and 11 show the basal spac-ing, d 003), and the width of the 003 reflection, B 003),as a function of the mole fraction of anion A in the HT.The basal spacing decrease s almost continuously belowthat of HT-NOs d 003) = 8.79 ~,). In the HT -C I- NY S2-system, how ever, two basal spacings correspondin g tothe HT-CI and H T-NY S were obse rved at HTNvs molefract ions o f 0.4 to 0.75. W hen the mole fractio n of HTNvsTable 2. The Gaines-Thomas equilibrium constant for hy-drotalcite-like compounds and the selectivity coefficient forDowex1 anion-exchange resins.

An 1log KNO~Anion(A ) log Ke Dowex 1 Loading Dowex 2 LoadingOH- 1.42 - 1.62 0. 23 -0. 70 0.6F- I. 19 - 1.62 0.82 - 1.40 0.30C1- 0.263 -0.58 -- -0.52 - -Br- 0.082 -0.13 0.6 0 -0.16 0.64NOs- 0 0 0.62 0 - -I- -0 .60 0.36 0.73 0.35 0.73CO32 1 . 8 4 . . . .NYS 2- 1 . 4 6 . . . .SO42- 1.39 - - - - -0.11 0.55

Peterson 1954).

is less than about 0.6, the diffrac tion intensity of the 003reflection corresponding to HT-CI is stronger than thatcorresponding to HT-Naphthol Yellow S, and con-versely, the former is weaker than the latter when themole fractio n of HTNys is more than about 0.7.

Thus, where no great difference in radius exists be-tween two anions in question, the XRD patterns of the003 reflection of the two HTs corresponding to the twoanions overlap and are seen as one diffraction pattern;however, where the difference in radius between twoanions is relatively large, as in the HT- NO3 -O H-, HT-NO3- F-, HT-NO3-CO32 systems, the XRD pattern ofthe 006 reflection is split into two. This split of the 006reflection is 4.44 A and 4.00 .~ for the HT-NO3-OH-system, 4.44 ~ and 4.07 ~ for the HT -N Os -F - system,and 4.44 ,~ and 4.04 ~ for the HT-NO3-COz z- system.In each split, the former corresponds to HT-NOz andthe latter corresponds to HT-OH, HT-F, HT-CO3, re-spectively.

On the other hand, the width of the 003 reflections,B 003), which is nearly inv ersel y prop ortio nal to theTable 3. Basal spacing d 003) and the width of the 003 re-flection at HT)A = 0.9-1.0.Anio ns Basal spacing (A) 003 width (~OH- 7.55 0.64F- 7.66 0.88CI- 7.86 0.77Br- 7.95 0.92NOz- 8.79 1.13I 8.16 1.45CO32- 7.65 0.69NYS 2 13.00 0.96SO4z- 8.58 1.40


5/7

V ol . 31 , N o. 4 , 1983 A n ion exchange of hydr o ta lc i te - l ike com poun ds 309

1 o, ~ , ~ I t ~ ~ I I

o , , ~ , o k , . o sO - - o . . _ O . O.

- - . . . . - - - -

~ s . o l ~ t o . 5 ~ g a o .8~ . 5 1 i i - . u O I i i I 00 . 4o o ~ o . o . ~ o . s . o o o . 2 o . e o . o . oHT)o. HT)NysFigu re 10. Basal spacing ( 9 and the width of the 003 ref lec-t ion ( ~ ) f or the H T- N O 3- O H - sys tem as a func t ion of H T com-posit ion.c r y s t a l l i t e si z e , i n c r e a s e s w h e n ( H T) A is r e l a t i v e l y s m a l l ,a n d s u b s e q u e n t l y d e c r e a s e s p r o g r e s s i v e l y u n t il f in a l lyi t is s m a l l e r t h a n t h a t o f t h e o r i g i n a l m a t e r i a l .

T a b l e 3 s u m m a r i z e s t h e b a s a l s p a c i n g a n d t h e w i d t h so f t h e 0 0 3 r e f l e c ti o n f o r v a r i o u s H T s w i t h ( H T ) A o f 0 . 9t o 1 .0 . T h e r e l a t i o n s h i p b e t w e e n t h e b a s a l s p a c i n g a n dt h e e q u i l i b r i u m c o n s t a n t i n a n i o n - e x c h a n g e e q u i l i b r i-u m o f m o n o v a l e n t a n i o n s i s p l o t t e d in F i g u r e 1 2. F i g u r e12 d e m o n s t r a t e s t h a t e x c e p t f o r H T - N O 3 , t h e e q u i li b -r i u m c o n s t a n t o f H T i n c r e a s e s w i th d e c r e a s i n g b a s a ls p a c i n g , a n d t h e r a n k o f t h e b a s a l s p a c i n g a g r e e s w i t ht h e r a n k o f t h e i o n i c r a d i i , i . e . , F - ( 1 .3 6 A ) < C I - ( 1. 81A ) < B r - ( 1 .9 5 ~ ,) < I - ( 2 . 1 6 ~ ) . T h e s e r e s u l t s a l s o a g r e ew i t h t h e c o n c l u s i o n o f M i y a t a (1 97 5) i n t h a t t h e b a s a ls p a c i n g i s s u b s t a n t i a l l y d e t e r m i n e d b y t h e s u m o f th et h i c k n e s s o f th e b a s i c l a y e r ( w h i c h d e c r e a s e s w i t h a ni n c r e a s e i n x b u t a t a s m a l l e r r a t e t h a n t h a t o f th e i n -t e r l a y e r ) a n d t h e s i z e o f t h e a n i o n i n t h e i n t e r l a y e r .T h e r e f o r e , a m a i n f a c t o r t h a t d e t e r m i n e s t h e s e l e c t i v i t yo f th e a n i o n - e x c h a n g e o f H T i s t h e d i a m e t e r o f a b a r e ,n o n - h y d r a t e d a n i o n .

T h e e q u i l i b ri u m c o n s t a n t o f H T i s j u s t o p p o s i t e t ot h a t o f t h e a n i o n - e x c h a n g e r e s in s D o w e x - 1 a n d D o w e x -2 , a l s o l i s t e d i n T a b l e 2 ( P e t e r s o n , 1 9 54 ); i . e . , t h e i o ns e l e c t i v i t y o f t h e l a t t e r d e p e n d s u p o n t h e d i a m t e r o f ahydr ted a n i o n .

T h e w i d t h o f 0 03 r e f l e c t i o n , B ( 0 03 ) , a l s o d e c r e a s e sw i t h t h e i o n s e l e c t i v i t y . I n o t h e r w o r d s , t h e c r y s t a l l i t es i z e o f H T i n c r e a s e s w i t h i n c r e a s i n g i o n s e l e c t i v i t y ( T a -b l e s 2 a n d 3 ). I n v i e w o f t h e r e l a t i o n s h i p s h o w n i n F i g -u r e 1 2, t h e b a s a l s p a c i n g o f H T - N O a i s u n e x p e c t e d l yl a r g e . T o f i n d a c a u s e o f t h i s , t w o d i f f e r e n t H T - N O 3p r o d u c t s i n w h i c h x w a s 0 .2 5 0 a n d 0 .2 8 0 w e r e p r e p a r e da n d t h e b a s a l s p a c i n g s d e t e r m i n e d t o b e 8 . 34 , ~ a n d 8 . 4 0~ . , r e s p e c t i v e l y . I f t h e s e d a t a a r e c o n s i d e r e d i n c o n -

Figu re 11. Basal spacing (9 and width of the 003 ref lect ion( ~ ) f or the H T- C I - N Y S ~- sys tem as a f unc t ion of H T com-posit ion.j u n c t i o n w i t h t h e f a c t t h a t t h e b a s a l s p a c i n g w a s 8 . 79a t x = 0 . 30 4 , t h e b a s a l s p a c i n g o f H T - N O 3 i n c r e a s e sw i t h a n i n c r e a s e i n x , a t h i g h e r v a l u e s o f x . T h u s , t h er e l a t i o n s h i p i s i n c o n s i s t e n t w i t h t h e r e l a t i o n s h i p g e n -e r a l l y o b s e r v e d f o r H T - C O 3 , e t c . , i . e . , t h a t x i s i n v e r s e -l y p r o p o r t i o n a l t o t h e b a s a l s p a c i n g . T h e r e a s o n w h yH T - N O 3 h a s a n u n e x p e c t e d l y l a r g e b a s a l s p a c i n g a th i g h e r v a l u e s o f x i s p r e s u m a b l y d u e t o r e p u l s i o n b e -

2 . 0

1 . 0

VO- , !

O

- I . 0 t t7 . 5 8 . 0 8 . 5Ba s a l s pa c ing X )

Figur e 12. Re la t ionsh ip be tw een the basa l spac ing and theequi l ib r ium cons tan t log K e .


6/7

310 Miyata Clays and Clay Mineralstween NO3- ions. Because NOz- is monova lent and oc-cupies a space correspon ding to three oxygens, the spaceoccupied by NO3- in the interlayer is greater than thatoccupied by other anions such as CI- and Br-. When xis small and the re pulsion betw een NO.~ ions is small,NO3- is oriented in the interlayer such that the bonddirection of N-O, i.e., the plane formed by NO3-, isparallel to the basic layer. But as x increases, the re-pulsion between NO3- ions becomes stronger, such thatthe N- O bond direction of NOa- may be no longer par-allel to the basic layer. This o rientati on change of NOa-in the interl ayer leads to the increase of inter layer thick-ness. If the arr angement of NOa- ions in the interlayerdoes not change as a result of the repulsion betweenNOz ions, the basal spacing at x = 0.304 will be closeto 8. I2 ~ which is anticipated from the relation show nin Figure 12.

It is worth noting that HT-OH shows the smallest basalspacing and the largest crystallite size of the mono- anddivale nt anion forms studied (Table 3). This small spac-ing is presumed to be due to the fact that the ionic di-amete r of OH- is nearl y equal to that of HzO in the in-terlayer, and hydrogen bonding is great among OH-,interlayer water, and OH of basic layers. Accordingly,the crystal structure of liT -OH consists of three oxygenlayers derived from two oxygen layers of the basic layerand one oxygen layer of the interlayer. This structurehas the cl osest pack ing of atoms in the 001 directio n.

Table 2 also shows that divalent anions generally havehigher ion selectivity than mon ovalent anions. In par-ticular, NYS z- has high selectivity despite the fact thatits ionic diameter is about 189 times larger than SO42-.This is due presumably to the difference in bondingstrength to Mg or AI in the basic layer betw een NYS z-and SO4z-.

CONCLUSIONSHydrotalcite-like compounds are some of the few in-

organic anion exchangers that have relatively high ca-pacities of about 3 meq/g. Anion-excha nger resins in-duce an ion-exchange reaction with a hydrated anion,whereas, HT-compounds induce ion-exchange reac-

tions with bare, non-hyd rated anions. Accordingly, theion-exchange equilibrium constants for HTs are in thesequence OH > F- > C1- > Br- > I- for monova lentanions, and in the sequence CO3~- > NYS 2- > SO4~-for divalent anions. By utilizing their characteri stic ionselectivity, HTs are expected to find applic ation in theremoval of acid d yes , HPO4 2-, CN -, CrO4 2-, AsO43-,(Fe(CN)6) 4-, etc. fr om waste waters, as well as in theneutralization and thermal stabilization of halogen-con-taining polymers.

REFERENCESAllmann, R. (1968) The crystal structure ofpyroaurite: ActaCryst. 24, 972-977.Gaines, G. L. and Thomas H. C. (1953) Adsorption studieson clay minerals. II. A formation of the thermodynamics ofexchange adsorption: J. Chem. Phys. 21, 714--718.Japanese Standards Association (1965a) Japan IndustrialStandard K-882l, Sodium Fluoride: Japanese Standards

Association, Tokyo, Japan.Japanese Standards Association (1965b) Japan IndustrialStandard R-9101, Chemical Analysis of Gypsum: JapaneseStandards Association, Tokyo, Japan.Miyata, S. (1975) The syntheses of hydrotalcite-like com-pounds and their structure and physico-chemical proper-ties.- -The systems Mg2+-Ala+-NO3 , MgZ+-AP+-CI-,Mg~+-AP+-CIO4 , NiZ+-AIa+-c1 and Zn2+-AP+-CI-: Clay Miner.23, 36%375.Miyata, S. (1980) Physico-chemical properties of synthetichydrotalcites in relation to compositions: Clay Miner. 28,50--56.Miyata, S. and Kumura, T. (1973) Synthesis of new hydro-talcite-like compounds and their physico-chemical proper-ties: Chem. Lett. 843-848.Miyata, S. and Kuroda, M. (1981a) U.S. Pat. 4,284,762.Miyata, S. and Kuroda, M. (1981b) U.S. Pat. 4,299,759.Miyata, S. and Okada, A. (1977) Synthesis of hydrotalcite-like compounds and their physico-chemical properties--Thesystems MgZ+-AI3+-SO42- and Mg2+-A13+-CrO42-:ClayMiner. 25, 14-18.Miyata, S., Shiji, N., and Suzuki, T. (1977) Japan Patent No.880824.Nippon Bunseki Kagakukai (1961) Bunseki kaga ku binvan:maruzen, Tokyo, p. 517.Peterson, S. (1954) Anion exchange processes: Ann. N.Y.Acad. Sci. 57, 144-158.Taylor, H. F. W. (1973) Crystal structure of some doublehydroxide minerals: Min. Mag. 39, 377-389.

Received 17 May 1982; accepted2 January 1983)

Pe31OMe---EbI~IHollpe:leJ1eHbiHOHO-O6MeHHbIeH3oTepMbIMe:~jlyFH~poTa,rlhKHTO-RO~[O6HblMH oe:IHHeHH-aMn if 'r ) Tana NO3, CI H SO4 a aonaMH F- , CI-, Br-, I- , OH- , SO4~-, COs2-, H~e.TToro HaqbTo:la S (hKHS2-), a TaK~e 61,1rim n3mepenbi npoMen F- > CI- > Br- > NOa- >I-, a JIJIfl~IHBa.rleHTHbIX aHHOHOB----BcaeJIymmeM nop~JlKe: CO3z- > )KHS2- > SO42-. I [OCTOgHHbleHOHO-O6MeH-noro paBHoBecH~ yBeJInqHBa.nncbnpH yMem,mennn ~lnaMeTpOB aHnOHO8, a pa3Mep KpHCTaJIJIHTOB B001 nanpaanenHn yae~n,~Haa~c~ ~1~ aHHonoa C m,~coKofi ceJ1eKTHBHOCTbtO.OH THII FT nMe~naHMenbulafinpoMe~yTor rl naa6oabmnfi paaMep KpHcTa.m'mTOaa 001 Hanpaaaeni~rl. [E.G.]


7/7

Vol. 31, No. 4, 1983 Anio n exchange of hydrotalcite-like comp oun ds 311

Resiimcc Die Ionenau stausch isothe rme zwische n Hydrotalkit-fi.hnlichen Verbindung en (HT) der NO3-,CI-, und SO4- Form un d F- , CI-, Br -, I-, OH- , SO42-, CO3z , sowie Naphtolgelb S (NYSZ-)-lonen wurdenbestimmt, und der Abs tand und die Breite des 003 Reflexes wurde als Funktion der HT -Zusammen setzunggemessen. Die Ionenaustauschgleichgewichtskonstanten fir die HTs mit einwertigen Anionen haben dieReihenfloge OH > F- > CI- > Br- > NO3- > I ; die mit zweiwertigen Anionen die Reihenfolge CO32-> NYS z- > SO42 . Ihre lonenaustaus chgleich gewicht skonst antenhaben die Tendenz mit abnehmendemDurch messer des Anions zuzu nehmen . Die Kristallitgr6ge in der 001 Richtung hat bei Anionen mit h6hererSelektivit5t die Tendenz zuzunehm en. Die OH-Fo rm von HT h at den kleinsten Basisabstand und die gr6gteKristallitgr6ge in der Richtung 001. [U.W.]R6sum6-----Des sot hermes d' 6change d'i ons entre des compos6s semblables ft. l'hydro talcite (HT) de fo rmeNQ -, CI-, et SO4-, et les ions F , CI-, Br -, I- , OH , SO42-, CO32-, et Napht hol Yellow S (NYS 2-) ont6t6 d6termin6es, et l 'esp acemen t et la largeur de la r6flection 003 ont 6t6 mesur6s en fonction de la compo-sition d'HT. La constante d'6quilibre d'6change d'ions pour des HT d'anions monovalents sont dans las6quence OH- > F- > C1- > Br- > NO3- > I-, ceux pour des anions divalents sont dans la s6quenceCO3~- > NYS 2- > SO42-. Les constan tes d'6quilibre d'6change d'ions ont tendance augment er propor-tionnellement a une diminution de diam/~tre des anions, et la taille du cristallite dans la direction 001 atendance ~ accroitre avec les anions ayant un plus grand selectionnement. La forme OH- d'HT a l'espa-cement basal le plus petit et la taille de cristallite la plus grande dans la direction 001. [D.J.]

anion halaman 1

Documents