Vg Sx Theory Various Experimets 288793

8/13/2019 Vg Sx Theory Various Experimets 288793

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S O L V E N T E X T R A C T I O N IN T H EWINNING O FC O PP ER , N IC K E L A N D C O B A L T

A . J . VAN DERZEEUW


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SOLVENT EXTRACTI ON I N THE WNNI NG OF COPPER, NI CKELAND COBALT

TER VERKRI J GI NG VAN DE GRAAD VAN DOCTOR I N DE TECHNI SCHEWETENSCHAPPEN AAN DE TECHNI SCHEHOGESCHOOL DELFT, OP GEZAGVAN DE RECTOR MAGNI FI CUS, PROF. I R. B. P. TH. VELTMAN, I NHET OPENBAAR TE VERDEDI GEN TEN OVERSTAAN VAN HET COLLEGEVAN DEKANEN OP DONDERDAG 10 NOVEMBER 1983 TE 16. 00 UUR

p - 2 5 2 . S }

PROEFSCHRI FT

DOOR

ABRAHAM J OHANNES VAN DERZEEUWGEBOREN TE SCHI EDAM

SCHEI KUNDI GI NGENI EUR

D R U K K E R I J E L I N K WI J K BV - UT RE CHT


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DI T PROEFSCHRI FTI S GOEDGEKEURDDOORDE PROMOTORENPROF. I R. H. J . ROORDA

ENPROF. I R. J . A. WESSEL I NGH


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AanAnneke, E v e l i n e en E r i ken de n ag ed ac h t e ni s va nmi j n Ou d er s .


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DANKBETUI GI NGDe D i r e c t i e vanh e t KONI NKL I J KE / SHELL LABORATORI UM t eAms t e r d a m ben i ke r k e n t e l i j k v o o r de r u i me g e l e g en h ei d d i e mi j s t e ed s g e bo de n i somt ep u b l i c e r e n of i n h e t o pen ba ar t es p r e ke n o v er g e d ee l t e n vanh e t we r kdati n d i t p r o e f s c h r i f t i s v er z a me l d .

ACKNOWLEDGEMENTI am i n de bt e d t ot h e CANADI AN I NSTI TUTE OF MI NI NG ANDMETALLURGY, t heELSEVI ER SCI ENTI F I C PUBLI SHI NG COMPANY, t heI NSTI TUTI ON OF CHEMI CALENGI NEERS, t heI NSTI TUTI ON OF MI NI NGANDMETALLURGY, and t heSOCI ETY OFCHEMI CAL I NDUSTRY f o r p er mi s s i o n t o r e p r o d uc e t h e p ap er s u s e d i n t h i st h e s i s and o r i g i n a l l y pu bl i s h e d u n d e r t h e i r c o p y r i g h t .


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CONTENTSI NTRODUCTI ON, SURVEY OF THE THE SI S .PART ONE

A.B.C.D

PART TWOPAPERS

A 1.

4.

C l a s s i f i c a t i o n of SX me t hod s f o r me t a l s .So l v e nt e x t r a c t i o n i n t he copper i n d u s t r y .Co mpo s i t i o n and mode of a p p l i c a t i o n of some c o mme r c i a l r e a g en t s .Re f e r e n c e s t o PART ONE.

St udy of t heh y dr o g e n at i o n of t heVERSATI C a c i d s a l t s of c o p p e r ,n i c k e l and c o b a l t .Me t a l s e x t r a c t i o n w i t h c a r b o x y l i c a c i d s . I . Co mpo s i t i o n ofc o mp l e x e s w i t h n i c k e l , c o b a l t ( I I ) and i r o n ( I I I ) .Me t a l s e x t r a c t i o n w i t h c a r b o x y l i c a c i d s . I I . E f f e c t of t e mp er a t u r eon t he e x t r a c t i o n of Cu, N i , C o ( I I ) , Zn, F e ( I I I ) and C o ( I I I ) .P u r i f i c a t i o n of z i n c c a l c i n e l e a c h s o l u t i o n s by e xc ha n gee x t r a c t i o n w i t h t he z i n c s a l t of VERSATI C a c i d .

B 1. S e l e c t i v e copper e x t r a c t a n t s of t he5 - a l k y l - 2 - h y d r o x y p h en y la l k y l ke t o x i me t y p e.

2. Hy d r o c a r b o n s o l v e n t d i l u e n t s i nh y dr o xy - o xi me s o l v e n t e x t r a c t i o np r o c e s s e s .

3. Or g a n i c and p h y s i c o - c h emi c a l a s pe c t s of p r o p e r t i e s of h y d r o x y -o x i me e x t r a c t a n t s .

4. K i n e t i c s and me c h a n i s m of copper e x t r a c t i o n w i t h 5 - a l k y l - 2 -h y d r o x y p h e n y l a l k y l k et o x i me s .I d ea s and p r a c t i c e i n t hed es i g n of s o l v e n t e x t r a c t i o n r e a g e n t s .1

PART THREABCD

H i s t o r y of t hea ut h or ' s i n vo l v emen t i n SX.Comment s t o t he pa pe r s .The f u t u r e .Re f e r e n c e s t o PART THREE.

NOTES added a f t e r c omp l e t i o n o f t he t h e s i s .SUMMARY/SAMENV ATTI NGCURRI CULUM VI TAE

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I NTRODUCTI ONL i q u i d / l i q u i d e x t r a c t i o n o f me t a l s ( e i t h e r a s i o n s o r s a l t s ) f r o m a n aqueousi n t o a n o r g a n i c p h a s e h a s been o b s e r v e d a l r e a d y l o n g a g o . I n 1 8 4 2 P e l i g o tf o un d t h a t ur a ni um c o u l d b e e x t r a c t e d f r o m n i t r i c a c i d w i t h e t h e r . D e s p i t ev a r i o u s o t h e r e xa mp l e s f o un d i n l a t e r y e a r s t h e p o s s i b i l i t i e s r e ma i n edl a r g e l y u n o bs e r v e d u n t i l H. F i s c h e r i n t r o d u c e d ' d i t h i z o n e ' ' a s a s e l e c t i v ea n a l y t i c a l r e a ge nt f o r v a r i o u s me t a l i o n s i n 1 9 2 4 . " D i t h i z o n e ' ' c o mp l e x e so f t e n p r e c i p i t a t e d a n d g r a v i me t r i c me t hod s wer e t h en u s e d f o r t h e i r q ua n t i t a t i v e d e t e r m i n a t i o n . I n o t h e r c a s e s however t h e c o mp l e x e s c o u l d b e e x t r a c t e d i n t o o r g a n i c s o l v e n t s a n d t h en d et e r mi n ed s p e c t r o p h o t o m e t r i c a l l y .F r o m t h en o n l i q u i d / l i q u i d e x t r a c t i o n ( o r s o l v e n t e x t r a c t i o n , S X , i n t h ef u r t h e r t e x t ) became a v e r y i mp o r t a n t t o o l i n t h e h ands o f t h e a n a l y t i c a lc h e mi s t , a n d t h i s h a s been s o e v e r s i n c e .A s a g e n e r a l t e r m, l i q u i d / l i q u i d e x t r a c t i o n o r s o l v e n t e x t r a c t i o n wo u l d b et a k e n t o c o v e r s u c h d i f f e r e n t p r o c e s s e s a s f u r f u r a l e x t r a c t i o n o f a r o ma t i c si n pe t r o l e u m r e f i n i n g , e x t r a c t i o n s w i t h s u p e r c r i t i c a l C O 2 i n f o o d t e c h n o l o g ya n d p h a r m a c e u t i c a l c h e mi s t r y , a n d l i q u i d me t a l - l i q u i d s l a g ex ch ang er e a c t i o n s i n me t a l l u r g y ^ . However , f o r t h e p r e s e n t p ur p os e t h e t e r ms s h a l lb e u s e d i n t h e mor e r e s t r i c t e d me a n i n g d e f i n e d i n t h e o pe ni n g p ar a g r a ph .T h e p r o c e s s c a n t h e n b e d e s c r i b e d a s o n e i n wh i c h a n i n o r g a n i c p h a s ec o n t a i n i n g a s o l u t e i s i n t i m a t e l y c o n t a c t e d w i t h a n o r g a n i c p h a s e w i t h wh i c hi t i s i mmi s c i b l e , i n o r d e r t o t r a n s f e r t h e s o l u t e i n some f o r m i n t o t h eo r g a n i c p h a s e . T o t h i s e n d t h e o r g a n i c p h a s e ma y o r ma y n o t c o n t a i n a ne x t r a c t a n t . Once t h e g o a l i s a c h i e v e d t h e c o n t a c t i s t e r m i n a t e d a n d t h ep h a s e s a r e s e p a r a t e d . O f t e n t h i s p r o c e s s o f e x t r a c t i o n i s f o l l o w e d b y i t sr e v e r s e , i n wh i c h t h e s o l u t e - l o a d e d o r g a n i c p h a s e i s c o n t a c t e d w i t h a s e co ndi n o r g a n i c p h a s e t o t r a n s f e r t h e s o l u t e i n t o t h e l a t t e r . T h i s i s o f t e nr e f e r r e d t o a s " s t r i p p i n g ' 1 o r " b a c k - e x t r a c t i o n " .Nowadays SX o f me t a l s f i n d s a p p l i c a t i o n i n a mu l t i t u d e o f f i e l d s , f r o mq u a n t i t a t i v e a n d q u a l i t a t i v e a n a l y s i s o f t r a c e me t a l s , v i a wa s t e wa t e rp u r i f i c a t i o n , t o l a r g e s c a l e me t a l p r o d u c t i o n .F i r s t i n d u s t r i a l u s e o f S X o f me t a l s da t e s b a c k t o t h e Ma n h a t t a n p r o j e c tf o r t h e p r o d u c t i o n f o r pu r e ur a ni u m compounds. D u r i n g a n d a f t e r Wo r l d Wa r I IS X a s a u n i t o p e r a t i o n wa s f u r t h e r d ev e l o p ed a n d y i e l d e d advanced me t h o d s

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f o r t h e r e c o ve r y of u r a n i u m; h a f n i u m, z i r c o n i u m and some o t h er r e l a t i v e l yl o w- v o l u me me t a l s ' . The g r e a t i n d u s t r i a l br e ak t h r o u gh i n b a s e me t a l s camei n t h e mi d s i x t i e s , when i t became p o s s i b l e t o a ppl y SX i n t h e wi n ni n g o fc o p p e r , t o p u r i f y and c o n c e n t r a t e t h e c op p e r s o l u t i o n s p r i o r t o e l e c t r o -wi n ni n g .Al t h ou gh f r om a t e c h no l o g i c a l p o i n t of v i ew SX o f me t a l s c a n be c o n s i d e r e da u n i t o pe r a t i o n , i t s p o s i t i o n as a l i n k i n a c h a i n of o pe r a t i o ns wh i c hs h o ul d l e ad u l t i m a t e l y t o t h e wi n n i n g , i n one f o r m o r an ot h er , of t he p ur eme t a l ( s ) r e q u i r e s f i n e a da pt a t i o n t o t h e o t h er pr o c es s e s i n v o l v e d.

FEED C I RC UI TFEED

EXTRACTANT C I RC UI TLOADED EXTRACTANT

FEED PREPARATI ON( ORE L E A CHI N G,MATTE D I S S OL U T I ON ,

ETC. )

BACK- EXTRACTI ON CI RC UI TS TRI P L I QUOR

METAL PRODUCTI ON( ELEC TROW NNI NG,DI RECT REDUCTI ON,S AL T CR YS T AL L I Z A TI ON)

BARREN EXTRACTANT S TRI P SOLUTI ON

F i g . 1A s i mp l e SX c i r c u i t i n i t s c on t e xt

I n i t s ( i d e a l l y ) c ompl e t e l y c y c l i c o pe r a t i o n t h e o r g a n i c e x t r a c t a n t p ha secomes i n t o c o nt a c t wi t h i n o r g a n i c f eed and b ac k - e x t r a c t i o n p h a s e s wh i c hd i f f e r g r e a t l y .F a c t o r s l i k e c o n c e n t r a t i o n and n at u r e of f e ed i m p u r i t i e s , c o nc e nt r a t i o n o ft he me t a l ( s ) wa n t e d , f l o w r a t e o f t he f e ed , p o s s i b i l i t y o f b a c t e r i a l o rf un g oi d g r o wt h s , e t c . , w i l l i n f l u en c e t h e a t t i t u d e of t h e o pe r a t i o ns manageron i t ems i n wh i c h he has some l i b e r t y : c h o i c e o f r e ag en t , r ea gent c o nc e nt r a t i o n , c h o i c e o f d i l u e n t , r a t i o bet ween o r g a n i c and i n o r g a n i c p h a s e v o l u me s .They w i l l however a l s o c o nf r o nt h i m wi t h some " f a c t s of l i f e , l i k e r a t eand q u a l i t y of p h a s e s e pa r a t i o n s t h r o ug ho ut t h e p r o c e s s , pr e s en ce of c r u d( a muddy s e mi - s o l i d c o n t a i n i n g q u i t e h i g h r e ag ent and d i l u e n t c o n c e n t r a t i o ns ,wh i c h t ends t o c o l l e c t a t t h e i n t e r f a c e i n t h e s e t t l e r s and t o i n c r e a s e i n

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v o l u me wi t h t i me , t h us n e c e s s i t a t i n g t h e o p er a t o r t o s h u t down h i s p l a n ta t i n t e r v a l s f o r c l e a n i n g ) , e t c .The o f t e n r a t h e r s e v e r e h i g h l y a c i d i c c o n d i t i o n s u s ed i n t h e s t r i p p i n go p e r a t i o n put h i g h demands o n t h e s t a b i l i t y o f t h e r e a g en t . Re qu i r e me nt sof p u r i t y o n t h e i n o r g a n i c b a c k - e x t r a c t i o n s o l u t i o n wh i c h pr o c e ed s t of u r t h e r me t a l - wi n ni ng o pe r a t i o n s o f t e n d i c t a t e c r i t e r i a o f r e a ge nt s e l e c t i v i t y . I n v e r s e l y , i n c as e s wh er e t h i s s e l e c t i v i t y c a nn ot be a c h i e v e d , ab l e ed s t r e am f r o m t h e b a c k - e x t r a c t i o n c i r c u i t may be n e c e s s a r y t o keepsome c o nt a mi n at i o n a t an a c c ept a bl e l e v e l o f c o nc e n t r a t i o n .F r o m t h e d es i g n er s ' p o i n t o f v i ew t h e u n p r e d i c t a b i l i t y and o f t e n a l s ot h e c h a n g e a b i l i t y o f f e ed f a c t o r s s uc h a s i n d i c a t e d ab o v e , t o g e t h er wi t han u n s a t i s f a c t o r y l e v e l o f k n o wl e d g e on t h e r e a g e nt ' s pe r f o r ma nc e andp r o p e r t i e s pu t s l i m i t a t i o n s on t h e a c c u r a c y wi t h wh i c h p l a n t c a n be d es i g n e d .Ot h e r l i m i t i n g c o n d i t i o n s a r e b e i n g pu t t o d e s i g n e r and o p er a t o r by t womor e p r o p e r t i e s i n h er e nt t o t h e r e ag en t s u s ed . F i r s t l y , many of t h e r e a c t i o n si n SX p r a c t i c e o c c u r bet ween t wo i mmi s c i b l e p h a s e s and bet ween ( h y dr a t e d)me t a l i o n s and l a r g e l y o r t o t a l l y n o n - i o n i z e d r ea gent mo l e c u l e s . T h i s makess u c h r e a c t i o n s i n h e r e n t l y s l o w. Ac h i e v i n g e q u i l i b r i u m t a kes c o n s i d e r a b l et i me , and mor e o f t e n t h an no t s t a g e e f f i c i e n c i e s f a l l s h o r t o f 10 0 %. Hencep l a n t d es i g n must be a da pt e d t o t h i s f a c t . Se c o nd l y , e s p e c i a l l y t h e c h e l a t i n g t y p e o f SX r e a g en t s h a v e r a t h e r h i g h mo l e c u l a r we i g h t s ( L I X 65 N: 3 39 ) .I n o r d er t o ens u r e h a n d l a b i l i t y o f t h e s o l u t i o n s , r ea gen t c o n c en t r a t i o n sc a nn ot be i n c r e a s e d t o o much. The s t o i c h i o me t r y o f t h e r e a c t i o n s i s o f t e n( f o r a b i v a l e n t me t a l ) 1 i o n t o 2 mo l e c ul e s o f t h e r e ag en t . F r e qu en t l ysome e x t r a f r e e r e ag ent i s needed t o keep t h e c o mp l e x es i n s o l u t i o n . Hencel a r g e v o l u me s t r e ams o f r e a g en t s o l u t i o n s a r e o f t e n n ec e s s a r y t o a c h i e v e agood e x t r a c t i o n .The i m p o s s i b i l i t y per s e , a t l e a s t a t an a c c e pt a bl e c o s t , t o r u n t h e v a r i o u sc i r c u i t s i n v o l v e d f u l l y c y c l i c and s e l f - c o n t a i n e d may caus e p r ob l ems o f ane nv i r o nme nt a l n a t u r e , wh i c h h a v e t o be r e c o g n i z e d by p l a n t d es i g ne r , r e ag en ts u p p l i e r and p l a n t o pe r a t o r a l i k e .

REFERENCE1. Ros enbaum, J . B. , P r o c . AI ME Me et i n g on Hy d r o me t a l l u r g y , Ch i c a g o 1 97 3,p. 169. AI ME, New Yo r k 1973 .

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SURVEY OF THE THESI SI n t h e f i r s t p a r t a s u r v e y w i l l be g i v e n o f t h e v a r i o u s me t h o ds o f SX f o rme t a l s , i n d i c a t i n g e x i s t i n g and p o t e n t i a l a p p l i c a t i o n s f o r e ach me t h o d i na c t u a l me t a l - w i n n i n g p r a c t i c e . C o n s i d e r i n g t he enor mous number o f p a p e r s ,b o o k s , c o n f e r e n c e p r o c e e d i n g s e t c . no a t t e mp t w i l l be made t o a c h i e v ec o mpl e t e ne s s . I n t h i s p a r t a l s o some i n f o r m a t i o n w i l l be g i v e n o n t h ec o mp o s i t i o n o f v a r i o u s r e a g e n t s wh i c h a r e , o r h av e be en , a v a i l a b l e on t h emar ket and on t h e i r most u s u a l modes o f a p p l i c a t i o n .Th e s e c o n d p a r t c o n t a i n s t h e f u l l t e x t o f t h e a u t h o r ' s p a pe r s on s e v e r a la s p e c t s o f SX o f m e t a l s .I n t h e t h i r d p a r t a h i s t o r i c ov er v i e w o f t h e d ev el o pme nt o f t h e a u t h o r ' si n t e r e s t i n t h e f i e l d o f SX and r e l a t e d a r e a s w i l l be g i v e n . A l s o comment sa r e p r o v i d e d t o t h e p a pe r s p r e s e n t e d , wh i c h have beenmade n e c e s s a r y byt h e p r o g r e s s o f s c i e n c e i n t h e f i e l d . At t h e e nd a r a t h e r s p e c u l a t i v e v i e wt o t h e f u t u r e o f SX i s g i v e n , t o g e t h e r w i t h a b r i e f c o mpa r i s o n o f SX w i t hsome r e l a t e d p r o c e s s e s .

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PARTONEA. CLASSI FI CATI ON OF SX METHODS FOR METALSSo l v e nt e x t r a c t i o n f o r me t a l s c a nbe c l a s s i f i e d i n4 c a t e g o r i e s :

1. SX bymeans of s a l t f o r ma t i o n w i t h a ni o ns ,2 . SX bymea ns of s a l t f o r ma t i o n w i t h c a t i o n s ,3 . SX bymea ns of c h e l a t i o n ,4. " r e a l " SX.

T h e s e c a t e g o r i e s w i l l be d i s c u s s e d i n t h e above s e q u e n c e .1. SX bymeans of s a l t f o r ma t i o n w i t h a ni o nsMos t me t a l i o n s a r ec a pa bl e of f o r mi ng s a l t s w i t h s u i t a b l e a c i d s . I f t hea c i d c a nbe c h o s e n s u c h t h a t b o t h t h e a c i d and i t s me t a l s a l t a r e s o l u b l ei n an o r g a n i c p h a s e b u t i n s o l u b l e i nwa t e r , SX of t h eme t a l i o nf r omanaqueous med i um i s , at l e a s t i n p r i n c i p l e , p o s s i b l e .S u i t a b l e a c i d s may be c a r b o x y l i c and s u l f o n i c a c i d s of r e as o n ab l y h i g hmo l e c u l a r we i g h t s , d i - e s t e r s of ph os p h or i c a c i d , mo no - e s t e r s of p ho s p h on i ca c i d s , e t c . :

R- ZOOH - PO( OH)IRAmongst t h e c a r b o x y l i c a c i d s t h r ee t y p es have been s t u d i e d o f t e n :h i g h l y b r a n c h ed a l i p h a t i c a c i d s :

R'R" C- COOH

CH3c y c l o - a l k y l s u b s t i t u t e d a l i p h a t i c a c i d s :

VERSATI C a c i d s ( S h e l l )

( e xa mp l e ) ( C H . ) -2 n COOH n aph t h en i c a c i d s ( S h e l l and o t h e r

f u n c t i o n a l i z e d a l i p h a t i c a c i d s :-COOH

B ra - br o mo l a ur i c a c i d ( I s r a e l iMi n i n g I n s t i t u t e )

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Of t h e s e , VERSATI C a c i d s f i n d t h e wi d es t a p p l i c a t i o n a l s o i n h y dr o me t a l -l u r g i c a l p r o c e s s e s .Of t h e ph os p h or i c a c i d d e r i v a t i v e s i t s d i - e s t e r w i t h 2 - e t h y l h e x a n o l h a sbeen s t u d i e d most f r e q u e n t l y , a n d i t i s a l s o a p p l i e d i n p r a c t i c e . I t c a nb e f o un d i n t h e S X l i t e r a t u r e under a number o f names a n d a b b r e v i a t i o n s ,a . o . d i - ( 2 - e t h y l h e x y l ) ph o s ph or i c a c i d , b i s - ( 2 - e t h y l h e x y l ) p h os p h or i ca c i d , a n d o f t e n a s DEHPA o r D-2EHPA.I n p r i n c i p l e t h e r e a c t i o n be t ween t h e a c i d s d e s c r i b e d s o f a r a n d t h e me t a li o n i s a s i mp l e s a l t f o r m a t i o n . Hence, f o r c a r b o x y l i c a c i d s :

Me X + + x R- COOH < > ( R C OO) Me + x H +a q - x o r g a qAp a r t f r o m f o r ma l o b j e c t i o n s o n e mi g h t h a v e a g a i n s t w r i t i n g H + , t h i se q u a t i o n i s g r o s s l y s i m p l i f i e d , a s w i l l come t o b e d i s c u s s e d i n p a r t t h r e eo f t h i s t h e s i s . N e v e r t h e l e s s t h e g e n e r a l i d e a i s v a l i d : a c i d i t y i s g e n e r a t e d , a n d t h e r e a c t i o n i s a n e q u i l i b r i u m o n e .I t f o l l o w s t h a t t h e r e a c t i o n i s p H d e p en d e nt , a n d t h a t e a c h me t a l i o n i se x t r a c t e d b e s t a t a n o wn s p e c i f i c pH v a l u e . Ro ug h l y i t c a n b e s t a t e d t h a tf o r a n y me t a l t h e p H o f o pt i mu m e x t r a c t i o n f o r no r ma l n o n - f u n c t i o n a l i z e dc a r b o x y l i c a c i d s ( e . g . VERSATI C o r na ph t h en i c a c i d s ) i s t h a t a t wh i c h t h eh y dr o x i d e o f t h e me t a l s t a r t s t o b e f o r me d . F o r s u c h a n a c i d a n e x t r a c t i o n /p H s e q u e n c e f o r a number o f i mpo r t a nt me t a l i o n s i s f o r e x a mp l e :F e 3 + C u 2 + Z n 2 + N i 2 + / C o 2 + Mn2 + F e 2 + C a 2 + Mg2 + Na +/ K +2 p H > 8F o r a c i d s h a v i ng a g r e a t e r s t r e n g t h , l i k e a - b r o mo l a ur i c o r s u l f o n i c a c i d s ,t h e s e q u e n c e r e ma i n s l a r g e l y t h e s ame, b u t t h e s c a l e s h i f t s t o l o we r p Hv a l u e s a n d mi g h t g e t s omewha t c o mp r e s s e d . F o r a n a c i d l i k e DEHPA, wh i c h

2+shows a s e l e c t i v i t y f o r Z n , t h i s i o n s h i f t s t o l o we r p H v a l u e s a n d. . . 2 +c ha n ge s p o s i t i o n w i t h e . g . C u .A n i m p l i c a t i o n o f t h e p H dependence i s t h a t i n g e n e r a l t h e e x t r a c t i o n o fa me t a l i o n w i t h s u c h a r e a g e n t consumes a n e u t r a l i z i n g a g e n t i f o n e a i msf o r c o mp l e t e r e a c t i o n . T h i s i s o f c o u r s e a c o s t f a c t o r , a n d u p t o n o wt h i s h a s been a h i n dr a nc e f o r a r e a l br e ak t h r o u gh o f c a r b o x y l i c a c i de x t r a c t i o n o f b a s e me t a l s .

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c o b a l t and n i c k e l c o n t a i n e d i nh i g h l y c o n c e n t r a t e d ammoni um s u l f a t e s o l u t i o n so b t a i n e d a f t e r a p p l i c a t i o nof t he S h e r r i t - G o r d o n r e d u c t i o n of c o b a l t / n i c k e ls o l u t i o n s . 1 I n J a pa n Sumi t omo useVERSATI C a c i d f o r t he s i mu l t a ne ou s

2e x t r a c t i o n of c o b a l t and n i c k e l . " The me t a l s ar et h en s t r i p p e d t o g e t h e rw i t h aqueous HC1, and s e p a r a t i o n i st h en a c c o mpl i s h e d by s e l e c t i v ee x t r a c t i o n of t he c o b a l t o c h l o r i d a t e c o mp l e x w i t h t r i - i s o o c t y l a mi n e . A l s oi n J a pa n, VERSATI C a c i d i s u s e d i n a c o mp l i c a t e d mu l t i - s t a g e s e p a r a t i o np r o c e s s f o r r a r e e a r t h me t a l s .A p r o c e s s wh i c h i s now b e i n g s t u d i e d by L u r g i anda p pr o a c h e s c o mme r c i a l i z a t i o n i s t her e mo v a l of f e r r i c i o n s f r o m z i n c s u l f a t e e l e c t r o l y t e , u s i n ga n e x c h a n g e r e a c t i o n w i t h t he z i n c s a l t of VERSATI C a c i d^ ^ ^

2 F e3 + + 3 ZnV f > 2 F e V - , + 3 Z n

2 +

a q 2 or g *= 3 or g aqDEHPA i s u s e d i n t he e x t r a c t i o n of z i n c f r o m v a r i o u s s o l u t i o n s at r a t h e rl o w pH. Two p r o c e s s e s u s i n g DEHPA h av e been d e v el o pe d f o r t he s e p a r a t i o no f c o b a l t f r o m n i c k e l . The f i r s t , ^ c a r r i e d out at n o r ma l t e mpe r a t u r e , has

8 been p i l o t e d and s u bs e q ue nt l y s h e l v e d . The s e c o n d one, wh i c h a p p l i e sh i g h e r t e mpe r a t u r e s , i s now o p e r a t i o n a l at Ma t t h e y Ru s t e nb ur g R e f i n e r si n So u t h A f r i c a . I t i s a v e r y i n t e r e s t i n g p r o c e s s , i n t h a t i t u s e st het e mp er a t u r e - d e pe n de n t t r a n s i t i o n of Co2 f r o m t he o c t a h e d r a l s i x - c o - o r d i n -q . 2+a t i o n t o t he t e t r a h e d r a l f o ur - c o - o r d ma t i o n . ' The f o u r - c o - o r d i n a t e d Coi s much more s e l e c t i v e l y e x t r a c t e d t h an t he s i x - c o - o r d i n a t e d i o n .A p h os p h on i c a c i d e s t e r i s u s e d by Ni p po n Mi n i n g t o e x t r a c t c o b a l t s e l e c t i v e l y f r o m n i c k e l s u l f a t e s o l u t i o n s . ^ S e p a r a t i o n be t ween c o b a l t andn i c k e l i s much b e t t e r t h a n f o r DEHPA. The f o r mu l a of t hep r o d uc t i s

R~0 y QR = 2 - e t h y l h e x y l

OHEven b e t t e r p r o s p e c t s f o r t he s e p a r a t i o n of c o b a l t f r o m n i c k e l h av e beenopened by t hea nnounc ement of p h o s p h i n i c a c i d s by Cya nami d ^

VT h e s e h a v e a p p a r e n t l y e ve n b e t t e r s e p a r a t i o n f a c t o r s i n f a v o u r of c o b a l tt h a n t hep h os p h on i c a c i d s .

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2 . S X b y means o f s a l t f o r m a t i o n w i t h c a t i o n sSome m e t a l - c o n t a i n i n g a n i o ns ma y b e e x t r a c t e d i n t o o r g a n i c l a y e r s b ys u i t a b l e c a t i o n i c s p e c i e s , s u c h a s l o n g - c h a i n a l i p h a t i c t e r t i a r y o r s e c o n d a r y a mi n e s a l t s , ammoni umo r s u l f o n i u m compounds, e t c . T h e mos t w i d e l yknown ex amp l es a r e t h e A l a mi n e / A l i q u a t r a n g e ( He nk e l ) a n d t h e a l mo s ti d e n t i c a l Adogens ( Sh er e x Ch emi c a l s ) :

( i s o - C0H, _ , ) , , N Al a mi n e 3 3 6( i s o - C g H1 7 ) 3 N+ - Co Cl ?a q a q 4 a q2 R . N + C l ~ + C o C l 2 ( R, N+) Co Cl ? + 2 C l "4 o r g 4 a q 4 2 . 4 o r g a q

Al t h ou gh bo t h r e a c t i o n s a r e e q u i l i b r i a , t h e s e c o n d o n e l i e s f a r t o t h er i g h t . T h e f i r s t o n e i s s t r o n g l y dependent o n t h e C l c o n c e n t r a t i o n .Th er e f o r e t h e o v e r a l l r e a c t i o n i s [ C l ] d e pe n d e nt , i n about t h e s ame w a ya s t h e c a r b o x y l i c a c i d e x t r a c t i o n i s [ H* ] d e pe n d en t . Hence t h e me t a l sc o n c e r n e d c a n b e p u t o n a [ C l ] s c a l e :

C d 2 + B i 3 + F e 3 + Z n 2 + C u 2 + C o 2 + F e 2 + Mn2 +0 [ C l ~ ] , M

W t h r e s p e c t t o s e p a r a t i o n s e t c . t h e s ame c o n s i d e r a t i o n s a r e v a l i d a sd i s c u s s e d p r e v i o u s l y f o r c a r b o x y l i c a c i d e x t r a c t i o n s , b u t no w o f c o u r s er e l a t e d t o [ C l ] . A v er y a t t r a c t i v e a s p e c t o f t h i s t y p e o f r e a c t i o n i st h a t ( s i n c e t h e o v e r r i d i n g f a c t o r i s [ C ~ ~ ] ) b a c k - e x t r a c t i o n o f t h e me t a lf r o m t h e e x t r a c t a n t c a n b e c a r r i e d o u t b y d e c r e a s i n g t h e c h l o r i d e c o n c e n t r a t i o n i n t h e aqueous p h a s e , i n o t h er wor d s q u i t e o f t e n s t r i p p i n g w i t hp l a i n wa t e r i s s u f f i c i e n t .A p p l i c a t i o n s i n p r a c t i c e

2+ . .I n t h e s e q u e n c e g i v e n above N i i s ma n i f e s t l y a bs e n t : u n de r n o r ma l c o n d i t i o n s2 + . . .N i does n o t f o r m a n i o n i c h a l i d e c o mp l e x es . T h i s mar ked d i f f e r e n c e w i t h2+ 2+ . 2+C o p r o v i d es a n e x c e l l e n t means o f s e p a r a t i n g C o f r o m N i i n c h l o r i d emed i um w i t h v er y h i g h s e l e c t i v i t y .

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I t i s t h e r e f o r e u nd er s t a nd ab l e t h a t s e v e r a l v a r i a t i o n s o f t h i s s e p a r a t i o n1 3ha ve f o un d t e c h n i c a l a p p l i c a t i o n s i n t h eme t a l - wi n n i n g i n d u s t r y .F a l c o n b r i d g e N i k k e l v e r k i nNor way a ppl y t h e p r i n c i p l e t o t wo d i f f e r e n t2+s o l u t i o n s : Adogen 2 81 ( a s e c o n da r y a mi n e ) i s u se d t o e x t r a c t Cu and2+Co f r om a c h l o r i d e n i c k e l ma t t e l e a c h l i q u o r , a nd t r i - i s o o c t y l a mi n e2+( Al a mi n e 336 ? ) i s u s e d t o e x t r a c t Co f r o m a s o l u t i o n o f i mp ur e n i c k e lh y dr o x i d e i naqueous HC1 . So c i t L e N i c k e l ( n o wMi nemet ) u s e Adogen 3 8 12+( a t e r t i a r y a mi n e ) t o e x t r a c t Co f r o m i mpu r e n i c k e l e l e c t r o l y t e . Ni p po nMi n i n g u s e " t r i o c t y l a m i n e " f o r t h e s ame pu r p o s e . Mt a l l ur g i e Hoboken-Ov e r p e l t f i n d s e v e r a l a p p l i c a t i o n s f o r Al a mi n e 3 3 6 .T h e Zi n c e x p r o c e s s o f Te c ni c a s Re u ni d a s u s e s a s e c o n d a r y a mi n e( A mb e r l i t e LA2) f o r e x t r a c t i n g z i n c ( a nd s m a l l amount s o f o t h er me t a l s t h a tf o r m h a l i d e c o mp l e x e s , ma i n l y c o p pe r , cadmi um a nd i r o n ) f r o m t h e i r co mp l exs u l f i d e l e a c h i n g s o l u t i o n .

14 . .I n t h e n u c l e a r i n d u s t r y Al a mi n e 3 3 6 o r s i m i l a r pr o du c t s a r e o f u s e i nt h e p u r i f i c a t i o n o f p l u t o n i u m- c o n t a i n i n g s o l u t i o n s .3 . SX o f me t a l s by means o f c h e l a t e f o r ma t i o nC h e l a t i n g a g en t s ha ve a v a i l a b l e a s a l t - f o r mi n g and an e l e c t r o n - d o n a t i n gf u n c t i o n i n one mo l e c ul e . Th e s a l t - f o r m i n g f u n c t i o n i s i n mos t c a s e s ag r o u p c o n t a i n i n g a c t i v e h y d r o g e n : a l i p h a t i c o r p h e n o l i c OH g r o u p s , c a r b -o x y l i c a c i d g r o u p s , t h i o l o r s u l f o n i c a c i d g r o u p s . The e l e c t r o n - d o n a t i n gf u n c t i o n may be any a t o m o r g r o up wh i c h i s a b l e t o c o mp l e x w i t h me t a l i o n st h r o ug h l o ne e l e c t r o n p a i r s :

Ap a r t f r o m t h e c ombi n at i o n o f s a l t - f o r m i n g a nd e l e c t r o n - d o n a t i n g c a p a c i t yi n one mo l e c ul e , s e v e r a l o t h er c r i t e r i a mus t be met by a g o o d c h e l a t i n ga g en t . Th e mos t i mpo r t a nt one i s r i n g s i z e : t h e r i n g f o r me d b y t h eme t a li o n , t h e s a l t - f o r m i n g f u n c t i o n , t h e e l e c t r o n - d o n a t i n g g r o u p a nd a l l t h eat oms i nb e t ween s h ou l d be f i v e - o r s i x - me mb er e d.T h e n e t c h e mi c a l r e a c t i o n b e t ween a n a p p r o p r i a t e ( a r b i t r a r i l y b i v a l e n t )me t a l i o n and a c h e l a t i n g r e a g en t c a n , s i m p l i f i e d , b e g i v e n a s :

2 RH + Me2 + < > MeR + 2 H+o r g a q 2 o r g a q

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I n a s c h ema t i c s t r u c t u r a l wa y i t c a n b e p i c t u r e d a s :

I t w i l l b e c l e a r t h a t c h e l a t i n g r e a g e n t s w i l l o n l y f o r m c o mp l e x e s a sshown i n t h i s e q u a t i o n w i t h me t a l i o n s t h a t a r e k e e n t o a b s o r b t h e e l e c t r o n sd o na t e d b y t h e r e a g e n t . Such me t a l i o n s a l mo s t a l l h a v e p a r t l y empt y i n n e rd - e l e c t r o n s h e l l s .I n mos t c h e l a t i n g r e a g e n t s u s e d i n a n a l y t i c a l c h e mi s t r y o r i n d u s t r y t h es a l t - f o r m i n g f u n c t i o n h a s a r e l a t i v e l y l o w a c i d i t y . Re a g e n t s w i t h a l c o h o l i co r p h e n o l i c OH g r o u ps a r e o f t e n u s e d . I n f a c t t h e a c i d i t y o f t h e s e g r o upsi s s o l o w t h a t t h e r e ma r k a bl e s t a b i l i t y o f many c h e l a t e s c a n n o t b e e x p l a i n e do n t h a t b a s i s a l o n e . I t i s t h e e l e c t r o n - d o n a t i n g f u n c t i o n wh i c h i s r e s p o n s i b l e f o r t h e s t r e n g t h o f t h e c o mpl e x es .Towar ds me t a l s wh i c h d o n o t a c c o mo d a t e t h e e l e c t r o n - d o n a t i n g f u n c t i o n t h ec h e l a t i n g r e a g e n t s b eha ve l i k e ( v e r y ) weak a c i d s , f o r mi n g n o r ma l s a l t s a tt h e e x pe c t e d h i g h p H v a l u e s .I t w i l l b e c l e a r f r o m t h e i n t r o d u c t i o n t h a t a n i mp o r t a n t s t i mu l u s f o r S Xcame f r o m t h e needs o f a n a l y t i c a l c h e mi s t r y . A v e r y l a r g e number o f o r g a n i ccompounds w i t h c h e l a t i n g p r o p e r t i e s have been p r o po s e d o v e r t h e y e a r s t os a t i s f y t h e s e r e q u i r e me n t s , a n d many s t i l l f i n d a p p l i c a t i o n s i n t h i s f i e l d .T wo v i r t u e s have been o f e x t e n s i v e u s e h e r e . F i r s t l y , t h e a b i l i t y o f t h er e a g e n t s t o c o mp l e x a me t a l i o n s e l e c t i v e l y o r ev en s p e c i f i c a l l y f r o m ami x t u r e a l l o w e d t h e s e p a r a t i o n a n d q u a n t i t a t i v e d e t e r mi n a t i o n o f s u c h ame t a l i n p r e f e r e n c e o f o t h e r o n e s , i n dependence o n r e a c t i o n c o n d i t i o n s .Se c o nd l y , many c h e l a t e s h a v e v e r y s p e c i f i c l i g h t a b s o r p t i o n s , wh i c h c a nb e u s e d f o r t h e i r d e t e r m i n a t i o n b y s p e c t r o p h o t o me t r i c me t h o ds .A f t e r a p p r o p r i a t e c h e mi c a l a d a p t a t i o n some o f t h e compounds c a n b e made t os e r v e i n i n d u s t r i a l a p p l i c a t i o n s . Such c a t e g o r i e s h a v e t o meet a t l e a s t t h ef o l l o w i n g c r i t e r i a :

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s o l u b i l i t y i n s u i t a b l e o r g a n i c d i l u e n t s ,s t a b i l i t y upon s t o r a ge and i n use,a c c ept a bl e p r o p e r t i e s w i t h r e s p e c t t o t o x i c i t y e t c . ,r e v e r s i b l e c h e l a t i o n p r o p e r t i e s ,a c c ept a bl e c o s t pe r f o r ma n c e t o t heu s er .

Compounds t h a t s a t i s f y t h e s e c r i t e r i a and ar e or h av e been a v a i l a b l ei nc o mme r c i a l q u a n t i t i e s f a l l i n f o u r c l a s s e s :

a l i p h a t i c hy d r o x y - o x i me sC C-

I IOH Nv OH

a r o ma t i c h y dr o xy - o x i me s

k^ , whe r e a s C a l v i n a n dW l ma r t h s u ppo s ed k^ >> k _ 3 k .Co mp a r i n g o u r r e s u l t s wi t h t h os e o f Ch a l k a nd Ha l p er n a n d C a l v i n a n dW l ma r t h , t h eo bv i o us c o n c l u s i o n i s t h a t t h e s p l i t t i n g o f h y d r o g en may beh omo l y t i c o r h e t e r o l y t i c , a n d c a n b e i n f l u e n c e d n o t o n l y by v a r y i n gt h es o l v e n t b u t a l s o b y s u i t a b l e c h a n g e o f t h ea n i o n. C l e a r l y , VERSATI C a c i da ni o ns h a v e a f u nda me n t a l l y d i f f e r e n t i n f l u e n c e o n t h e r e d u c t i o n a s co mpar edw i t h h ept a no a t e . I t i s l o g i c a l t o assume t h a t t h e f a c t t h a t t h er e a r e t wobr a nc h i n gs s o c l o s e t o t h e c a r b o x y l i c g r o u p i s r e s p o n s i b l e f o r t h e d i f f e r ence. T h i s , howe ve r , i s a n a s s u mpt i o n a nd wo u l d need f u r t h e r i n v e s t i g a t i o n .The r e a c t i o n s d es c r i b e d i n t h i s paper a r e mu c h f a s t e r t h an t h os e i n v e s t i g a t e dby Ch a l k a n d Ha l p er n . Th i s i s i l l u s t r a t e d i nTa bl e 1 , wh i c h l i s t s t h e h a l f -l i v e s o f Cu ( I I ) - Cu ( I ) r e d uc t i o ns i nb o t h s y s t ems .

1. Ch al k , A. J . a nd Ha l pe r n , J . , J . Am. Ch em. So c . 1 9 5 9 , 8 1 , 58462. C a l v i n , M. and W l ma r t h , W R. , J . Am. Ch em. S o c . 1 9 5 6 , 7 8 , 1 3 01

Cu V 2 + H2 bk 2CuV. H + Cu V 2 ^k

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2 CuV + H 2 , >k - 3

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Ta bl e1H a l f - l i v e s of Cu ( I I ) - Cu ( I ) r e d u c t i o n i n t h e s y s t em Cu ( I I ) VERSATI C a c i ds a l t i nk er o s e n e at 1 4 0 C and1at mH2 >Be l o w d o t t e d l i n e : h a l f - l i v e s of s ame r e d u c t i o n i nCh a l k a nd Ha l pe r n ' ss y s t e ms .

Cu ( I I ) , M h a l f - l i f e , mi n .0.016 420.033 340.033 420.042 480.126 22

0.03 ca1100.35 ca125

C u p r i c h e pt a no at e i nh e pt a no i c a c i d at145 CX X C u p r i c h e pt a no a t e i no c t a d ec a n e at 1 4 5 C.F r o m t h eabove r e a c t i o n s e q u e n c e , t o g e t h er w i t h t h e a s s u mpt i o n t h a tk_^, k > k 2> k , i t f o l l o w s t h a t

/ k [ H ][ CuV. H ] = [ CuV] / = [ C u V ] ^ / ^

^3o r , s i n c e

[ CuV] = [ Cu V 2 ] o - [ Cu V2 ][ Cu V. H1 = ( X - X) VKTJ o v J

Mo r e o v er ,

i n wh i c h k j = H, ]S u b s t i t u t i o n of t h ev a l u e f o r CuV. H i n t o e qu a t i o n4 g i v e s

- - j j j r = k X +k 2 - \ / K ^ ( X ) ( X Q - X) (5)wh i c h i s c o mp l e t e l y e q u i v a l e n t t ot h e r a t e l a w o f e qu a t i o n2.

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F o r t h e n i c k e l - c a t a l y s e d C u ( I I ) - C u ( I ) r e d u c t i o n t h e f o l l o w i n g mech an i s mi s p r o p o s e d :

K l2 Ni V2 + H 2 ( > 2 N i V + 2 HV ( 6 )

K2 N i V + H 2 N i 2 V 2 H 2 ( 7 )

kCuV + Ni - V- H, ^ CuV. H + HV + 2 N i V ( 8 )2 - 2 , 2 2

k 4CuV. H + Cu V2 > 2 C u V + HV ( 9 )

K 52 C u V + N i 2 V 2 H 2 < * v 2 CuV. H + 2 N i V ( 1 0 )T h i s scheme a s a wh o l e a p pe a r s t o b e a p l a u s i b l e e x t e n s i o n o f t h eC u ( I I ) - C u ( I ) r e d u c t i o n d e s c r i b e d b e f o r e . That a r e du c e d n i c k e l s p e c i e s( p r o b a b l y a N i ( I ) compound) p l a y s a n i mp o r t a n t r o l e i s e v i d e n t f r o m o u rmeas ur ement s . T h e o n e s p e c u l a t i v e e l e me n t i s t h a t t h i s s p e c i e s i s a di me r .T h e j u s t i f i c a t i o n f o r t h i s l i e s i n t h e e x p e r i me n t a l e vi d en c e t h a t t h er e l a t i o n bet weenmaxi mum r a t e a n d n i c k e l c o n c e n t r a t i o n i s s e c o nd - o r d er .I n t h e above scheme N i 2 V 2 H 2 p l a y s a p a r t o n l y i n i n c r e a s i n g t h e a c t u a lc o n c e n t r a t i o n o f ' a c t i v a t e d h y dr o gen ' . As s u mi n g t h a t t h e e q u i l i b r i a 6, 7a n d 1 0 a r e e s t a b l i s h e d r a p i d l y a s c ompar ed t o t h e r a t e s o f 8 a n d 9 , i tf o l l o w s t h a t

[ N i 2 V 2 H 2 ] = i q K 2 [ N i V 2 ] 2 ( 1 1 )i n wh i c h K' ^ = K [ H ] / [ HV] 2 a n d K 2 = K 2 [ H ] . F u r t h e r , f r o m 8 a n d 9i t f o l l o w s f o r t h e r a t e o f d e c r e a s e o f C u ( I I ) :

" f t = k 3 [ N i 2 V 2 H 2 ^ 0 0 + k 4 [ C u V - H ] ( x ) ( 1 2 )i n wh i c h X = [ C u V ] .

/ [ C u V ] 2 [ N i 2 V 2 H 2 ][ Cu V. H] = K U 2 = [ G u v ] WK- KY [ N i V ] V= V X)A/V 5 ( 1 3 )

S u b s t i t u t i o n o f e q u a t i o n s 1 1 a n d 1 3 i n t o 1 2 g i v e s f o r t h e r a t e :

" o f = k 3 K l K 2 [ N i V 2 ^ ( X ) + k 4 V ^ 5 ( X X ) ( X > ( U )T h e maxi mumv a l u e o f t h i s e q u a t i o n a t c o n s t a n t X ^ i s e v i d e n t l y p r o p o r t i o n a lt o t h e s q u a r e o f t h e i n i t i a l N i c o n c e n t r a t i o n .

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A 2. METALS EXTRACTI ON WTH CARBOXYL I C ACI DSI . Co mpo s i t i o n o f c o mp l e x es w i t h n i c k e l , c o b a l t ( I I ) a nd i r o n ( I I I )A. J . v a n d e r Ze eu w.Hy d r o me t a l l u r g y 1 9 7 9, 4, 2 1

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I NTRODUCTI ONT h e r e s u l t s o f t h e l i q u i d / l i q u i d e x t r a c t i o n o f a me t a l f r o m a n aqueouss o l u t i o n w i t h a c i d i c r ea g en t s a r e o f t e n r e p o r t e d a s a p l o t o f l o g D, i . e .t h e l o g a r i t h m o f t h e d i s t r i b u t i o n c o e f f i c i e n t , v e r s u s p H . T h e d i s t r i b u t i o nc o e f f i c i e n t i s t h e n u s u a l l y d e f i n e d a s t h e q u o t i e n t o f t h e a n a l y t i c a lc o n c e n t r a t i o n s o f t h e me t a l i n t h e o r g a n i c a n d i n t h e i n o r g a n i c p h a s e .I d e a l l y , s u c h a p l o t i s a s t r a i g h t l i n e w i t h a s l o p e e q u a l t o t h e numbero f e x t r a c t a n t g r o u ps bound t o t h e me t a l t h r o u gh c o v a l e n t b o nds . However ,f o r s e v e r a l r e a s o n s t h i s i d e a l i s s e l do m a t t a i n e d . F i r s t , t h e i o n i cs t r e n g t h i n t h e aqueous s o l u t i o n a n d t h e a c t i v i t i e s o f t h e s p e c i e s i n t h eo r g a n i c l a y e r a r e n o t a l wa y s c o n s t a n t t h r o u g ho ut t h e e x t r a c t i o n . I t i st h e r e f o r e g e n e r a l l y a c c e pt e d t h a t s l o p e a n a l y s i s i s o n l y wa r r a nt e d when

- 3l o w c o n c e n t r a t i o n s o f me t a l i o n s ( e . g . < 1 0 M) a r e e x t r a c t e d f r o maqueous s o l u t i o n s c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f a b u l k i o n ( u s u a l l yh a v i n g a n o p p o s i t e c h a r g e) w i t h r e l a t i v e l y l a r g e e x c e s s e s o f t h e e x t r a c t a n t .Even when t h e s e c o n d i t i o n s a r e s a t i s f i e d , e f f e c t s s u c h a s e x t e n s i v eh y d r o l y s i s o f t h e me t a l i o n s i n t h e a que ou s p ha se a n d p o l y m e r i z a t i o n o ft h e o r g a n i c me t a l c o mp l e x e s ma y d i s t u r b t h e p i c t u r e .I n t h e p a s t , t h e c o mp o s i t i o n o f e x t r a c t e d co mp l e x e s wa s u s u a l l y e s t i ma t e db y s u b j e c t i n g a number o f l o g D/ pH c u r v e s , o b t a i n e d under d i f f e r e n t c a r e f u l l y c h o s e n s e t s o f c o n d i t i o n s w i t h r e s p e c t t o c o n c e n t r a t i o n o f e x t r a c t a n t1 - 4 5a n d e x t r a c t e d i o n , t o a co mb i ne d g r a p h i c a l a n a l y s i s . J a y co c k a n d J o ne sh a v e d e v i s e d a g r a p h i c a l met hod t h a t needs o n l y o n e l o g D/ p H c u r v e . Acommon f e a t u r e o f a l l t h es e met h o ds i s t h a t t h e meas ur ement s h a v e t a k e np l a c e under c o n d i t i o n s wh i c h a pp r o a c h t h e i d e a l a s c l o s e l y a s p o s s i b l e .T h e p r e s e n t paper d e s c r i b e s a n o n - g r a p h i c a l t r e at me nt wh i c h makes i t p o s s i b lt o o b t a i n a n i d e a o f t h e c o mp o s i t i o n o f c o mp l e x es i n e x pe r i me nt s pe r f o r me da t c o n c e n t r a t i o n s o f e x t r a c t a n t a n d me t a l t h a t a r e mor e r e a l i s t i c . I t i sc l e a r l y i l l u s t r a t e d t h a t i nmany c a s e s t h e o r e t i c a l di s a d v an t a g es d o n o thamper i t s p r a c t i c a l a p p l i c a b i l i t y . A s a r u l e , o n e l o g D/ p H c u r v e w i l ls u f f i c e t o g i v e s a t i s f a c t o r y r e s u l t s . T h e p r o c e d u r e h a s been a p p l i e d t o t h ee x t r a c t i o n o f me t a l s w i t h o r g a n i c a c i d s , e . g . VERSATI C a n d o c t a n o i c a c i d s .I t mus t b e s t a t e d t h a t t h e met hod o n l y r e v e a l s t h e mos t l i k e l y c o mp o s i t i o n s .

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T h e a c t u a l c o mp o s i t i o n ( s ) c a n n o t be e s t a b l i s h e d t h i s wa y . A s t h e met hoda t t e mpt s t o s t ud y t h e c o mpo s i t i o n o f o r g a n i c p h a s e me t a l c o mp l e x e s u n d e rr e a l i s t i c c o n d i t i o n s , i t s a p p l i c a t i o n t o c o mme r c i a l e x t r a c t a n t s s eemsj u s t i f i e d e s p e c i a l l y a s t h e component s o f VERSATI C 1 0 a r e s o s i m i l a r t h a tt h ey ma y b e s a f e l y r e g a r d e d a s a s i n g l e a c i d t y p e .DERI VATI ON OF EXTRACTI ON EQUATI ON AND COMPUTATI ONALMETHODT h e s y mb ol s u s e d i n t h i s s e c t i o n a r e l i s t e d a t t h e e n d o f t h e p a p e r .I n t h e mos t g e n e r a l i z e d wa y t h e o v e r a l l e x t r a c t i o n o f a me t a l i o n f r o m a naqueous l a y e r w i t h a n a c i d i c e x t r a c t a n t ma y b e w r i t t e n a s f o l l o w s :

M + " + m ( H A) < * - ( MA . m H A) + n H + ( 1 )a q p p , o r g x n x a qT h e c o mp l e x (MA mH A ) ^ w i l l f u r t h e r b e d e no t e d a s C. I n t h i s g e n e r a l i z e dc o n c e p t n i s n o t n e c e s s a r i l y e q u a l t o t h e v a l e n c y o f t h e me t a l i o n M.We ma y n o w d e f i n e a n o v e r a l l e q u i l i b r i u m c o ns t a nt f o r t h i s r e a c t i o n :

r r , i ij x r n i n l / x n , [ C U g [ H ] a q Tc . o r eTH .aqK ~ ' r t " ( 2 1

r n f f i / n i x \ ( n + m ) l p ( n + m ) l p v /[ M ] a q | ( HA p J l o r g 7 M, a q T( HA) p, o r gT h e r e s u l t s o f t h e me a s u r e me n t s g e n e r a l l y a r e v a l u e s o f t h e a n a l y t i c a ld i s t r i b u t i o n c o e f f i c i e n t D, d e f i n e d a s :

D =[ M W M ] aq ( 3 )[ C l = [ I M ] * * = mSS-g)** = [ M ] o r g [ M 1 < - ^ ( l ) ^

F u r t h e r , i t f o l l o w s f r o m e q . 3 t h a t [ M l = D [ M 1 , a n d h e n c eL J o r g L J a q

[ C l ^ g = 0 [ M] a q [ M] ' * ( i ) , / * . ( 4 )S u b s t i t u t i o n o f e q . 4 i n t o 2 g i v e s f o r K ' :

g f - L _ . - . I - _g

o r , t a k i n g l o g a r i t h m s :l o g D = l o g K ' - l o g B + ( ( x - l ) / : t ) l o g [ M] o r g + ( 1 / x ) l o g x + n p H + ( 5 )

+ ( ( n + m) / p ) l o g ( H A ) p .

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We may f u r t h e r w r i t e :[ H A i = L H A l r g + L H A i a q + [ A i ; q + ( n + m ) [ M ; r g

Si n c e t h e s o l u b i l i t y of HA and t he c o mp l e x i n t h e aqueous p h a s e w i l l bel o w, we may n e g l e c t [ A ^ a nd [ HA ^ , wh i c h g i v e s :

P* I = [ * L g + ( n + m ) [ M i r gP* i r g = [ M i ( n + n) [M ^

S u b s t i t u t i o n o f t h i s v a l u e i n t o e q. 5 g i v e s :log /J = l o g K - lo g B + lx -l)/x) l o g [ M] o r g + ( 1 / j c l o g x + npH +

P ' p 'o r , by r e a r r a n g e me n t an d a s s u mi n g t h at l o g B i s c o ns t a nt :

l o g K = l o g / J - ( (* - 1 ) / J C ) lo g [ M] o r g - 1/x) lo g JC - npH -/ [HAI n + m \*

l o g I [ M] o r g I . (6)\ P P /

Ap ar t f r o m t h e pa r a me t e r s n , m x , a nd p, t h i s f o r mu l a o n l y c o n t a i n sknown o r me a s u r a bl e v a l u es . I f eq. 6 h o l d s , c h oo s i n g a s u i t a b l e s e t ofn, m x and p s h o u l d g i v e an a pp r o x i ma t e l y c o ns t a nt v a l u e f o r l o g K o vert he r a n g e o f me a s u r e me n t s .The s i m p l i f i c a t i o n i n t h e d e r i v a t i o n t h a t l o g B i s c o ns t a nt i s o n l y wa r r a nt edi n t h r e e c a s e s . F i r s t , i f a l l a c t i v i t y c o e f f i c i e n t s a r e e qu al t o 1, l o g Bw i l l be 1 and K' = K. S e c on d , i f a l l a c t i v i t y c o e f f i c i e n t s , a l t h ou g h d i f f e r e n tf r o m 1, a r e c o n s t a n t t h r o ug h ou t t h e s e r i e s o f me a s u r e me n t s , l o g B w i l l bea c o n s t a nt and t h e r e f o r e a c o n s t a nt ( t h oug h no t r e a l i s t i c ) v a l u e w i l l bef ound f o r l o g K ( i . e . l o g K e qu a l s l o g K' mi n u s a c o n s t a n t ) . I n our o p i n i o nt h e s e t wo s i t u a t i o n s a r e n o t l i k e l y t o o c c u r . The t h i r d p o s s i b i l i t y i s t h a tan y c h a n g e s i n t h e a c t i v i t y c o e f f i c i e n t s d ur i n g e x t r a c t i o n r e s u l t i n av a l u e of l o g B wh i c h , c o n s i d e r i n g t h e i n a c c u r a c i e s o f me a s u r e me n t , w i l lh ar d l y , i f a t a l l , a f f e c t t h e c o mp ut a t i o ns . Th i s s eems t o be t h e c a s e , s i n c ei n p r a c t i c e t h e p r o p o s e d f o r mu l a c a n be u s e d wi t h c o nf i d e n c e f o r j u dg i n gt h e c o n s t a n c y o f l o g K, and h e n c e f o r f i n d i n g t h e b e s t f i t t i n g c o mpo s i t i o nsf o r t h e c o mp l e x ov er a c o n s i d er a b l e r a n g e o f me a s u r e me n t s .

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The e v a l u a t i o n was c a r r i e d out w i t h t hea i dof a c o mp ut e r p r o g r a mby wh i c ht h e p e r mu t a t i o n of v a l u e s f o r n, mand x was pe r f o r me d . The r e s u l t s of t hec o mp ut a t i o ns ar e r e p o r t e d h e r e a s : ( a) an a v e r a g e v a l u e f o r l o gK ov e r t her a n g e of me a s u r e me n t s , ( b) a s l o p e c o e f f i c i e n t f o r t he b e s t f i t t i n g s t r a i g h tl i n e t h r o ug h a l l c a l c u l a t e d l o gK v a l u e s , ( c ) an e s t i ma t i o n of t he p o s s i b i l i t y of a s t r a i g h t l i n e w i t h s l o p e z e r o b e i n g dr awn t h r o u g h a l l l o gKv a l u e s . T h i s e s t i m a t i o n was made v i aS t u d en t ' s t - t e s t . For any s et ofmeaaur ement s a t - v a l u e was c a l c u l a t e dand compar ed w i t h a c r i t i c a l t - v a l u e ,known f r o m s t a t i s t i c a l t a b l e s , u s i n g 95 %p r o b a b i l i t y t w o - s i d e d . A s t r a i g h tl i n e w i t h s l o p e 0 was assumed t o be p o s s i b l e i f t , < t . ; t h i shasr c a l c c r i tbeen i n d i c a t e d i n t he t a b l e s by an a s t e r i s k . I n a d d i t i o n , t he t a b l e s i nmos t c a s e s a l s o g i v e t hemeas u r ed v a l u e s of pH and l o gDEXPERI MENTALThe me t a l s t o be e x t r a c t e d wer e d i s s o l v e d i n t hef o r m of t h e i r s u l f a t e s .The t o t a l amount of s u l f a t ewas a d j u s t e d t o 0. 55 M by t he a d d i t i o nofMgSO or Na S0, .4 2 4The e x t r a c t i o n s wer e c a r r i e d out i n a c y l i n d r i c a l l y s h a p e d s e p a r a t o r y f u n n e le qu i p pe d w i t h an e l e c t r i c s t i r r e r ( 2 000 r e v / mi n ) and an i n l e t f o r t hen e u t r a l i z i n g a g en t . For t hee x t r a c t i o n90 m of t h e me t a l s o l u t i o nwasc o n t a c t e d w i t h 100 m of t he o r g a n i c a c i d s o l u t i o n , and , w h i l e s t i r r i n g ,10m of a d i l u t e aqueous NH, s o l u t i o nwas s l o w l y added. The d i l u t i o noft h e NH. j was c h o s e n so as t o r e a c h p r e - e s t i ma t e d e x t r a c t i o n . For e achmeas ur ement t h i s p r o c e d u r e was r e p e a t e d . T h i s met hod was f o l l o w e d i n o r d e rt o h a v e a c o n s t a n t p h a s e r a t i o at e q u i l i b r i u mof1/1and a c o n s t a n t s u l f a t ec o n c e n t r a t i o n of 0. 5 MA l l s t i r r i n g t i me s wer e 3 m n a f t e r a d d i t i o nof t hen e u t r a l i z i n g a g e n t .S e t t l i n g t i me s wer e k e p t at 5 mi n . The t e mpe r a t u r ewas 25 C.

l l e t a l c o n c e n t r a t i o n s wer e d e t e r mi n ed by a t o mi c a b s o r p t i o n s p ec t r o ph o t o me t r y( P e r k i n E l me r 403 ) : i n t he i n o r g a n i c l a y e r s a f t e r s u i t a b l e d i l u t i o n w i t h1 N HNO and i n t he o r g a n i c l a y e r s a f t e r b a c k wa s h i n g w i t h 1 N HNO f o l l o w e dby s u i t a b l e d i l u t i o n of t he s t r i p p i n g l a y e r w i t h 1 N HNORESULTSC o b a l t and n i c k e lF o r c o b a l t and n i c k e l t he e x t r a c t i o n b e h a v i o u r w i t h VERSATI C s o l u t i o n sp r o v e d t o be s t r o n g l y dependent on t he c o n c e n t r a t i o n s i n v o l v e d , andmor ep a r t i c u l a r l y on t he r a t i o R be t ween t he e x t r a c t a n t and me t a l c o n c e n t r a t i o n sa n d i t s v a r i a t i o n d u r i n g t he e x t r a c t i o n s .

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7 Ni 0.199 M, VERSATIC 0.5 M, R. 18 -4ON i 0.108 M, VERSATIC 05 M, R: 20-5.5A N i 0 204 M, VERSATIC 1.0 M; R: 45-5 .3 Ni 0 0213 M, VERSATIC 1.0 M; R 50 0-50

log D

, 1 I I 1 I5 5 6 6 5 7 7.5pH

F i g . 1E x t r a c t i o n of n i c k e l w i t h VERSATI C 10 s o l u t i o n s . Ba c k g r o u n d : 0. 5 M MgSOF i g . 1 i l l u s t r a t e s f o r n i c k e l t h a t upon d e c r e a s i n g R t h e s l o p e of t hel o g D/ pH g r a p h d e c r e a s e s . At h i g h R t h i s s l o p e i s J . 2, wh er eas at l o w R i tu l t i m a t e l y becomes 2 HV) 2 and( C o V 2 ) 2 > r e s p e c t i v e l y , whe r e V s t a nd s f o r t h e VERSATI C a n i o n . I n t h e n i c k e lc a s e s e t s f o r ( n, m, x ) of ( 2 , 0 , 2 ) and ( 2 , 1 , 2 ) appear t o be a c c e p t a b l e t o o ,b u t ( 2 , 2 , 2 ) g i v e s a b e t t e r f i t , i . e . has a l o we r c a l c u l a t e d v a l u e f o r ta n d a l o we r s l o p e c o e f f i c i e n t ^I n t h e e v a l u a t i o n of e xp er i me nt s w i t h c a r b o x y l i c a c i d s p hasbeen t a k e nt o be 2. I t i s known f r o m t h e l i t e r a t u r e ( r e f . 1-5) t h a t c a r b o x y l i c a c i d si n v a r i o u s n o n - a q ue o u s a p o l a r s o l v e n t s a r e d i me r i c .S e e however t h e d i s c u s s i o n s e c t i o n .

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Ta bl e1E x t r a c t i o n o f 0. 021 3MN i w i t h 1 . 0 0 MVERSATI C. Ba c k g r o u n d: 0 . 5 MMgSO

E x p . p H Metal in Metal in logDn o . o r g . layer inorg. layer(mol/1) (mol/1)1 5.80 0.0046 0.01 67 -0. 56002 6.00 0.0097 0.0114 -0.07013 6.20 0.01 53 0.0060 0.40654 6.40 0.01 89 0.0024 0.8963Number ofobservations = 4Critical t value f o r B l = 4.30 (95%two-sidedand 2 degrees of freedom); f values be lowt h e critical level are marked with anasterisk.PermutationsN o . n m X lo g K Bl Student's t

(mean value) (slope coe ff.)1 1 0 1 - 5.7787 1.427 1.574 x 10'2 2 0 1 -11.7201 4.442 x10"' 5.204 x 10'3 1 1 1 - 5.6201 1.444 1.692 x 10'4 2 1 1 -11.5560 4.717 x10"' 6.060 x 10'5 1 2 1 - 5.4560 1.471 1. 890 X 10'6 2 2 1 -11.3864 5.111 x 1 0-' 7.165 X 10'7 1 0 2 - 4.9430 9.1 82 X10"' 1.002 X 10'8 2 0 2 -10.8845 -6.552 x10-" *7.21 3 X10-'9 1 1 2 - 4.7845 9.344 x10"' 1. 029 X 10'10 2 1 2 -1 0.7204 3.796 X 1 0" *4.236 X10"'11 1 2 2 - 4.6204 9.620 X 1 0" 1.074 X 10'12 2 2 2 -1 0.5507 1.359 x 10"' *1. 546 X10"'

I n t h e c a s e s o f v e r y l o w R t h e e v a l u a t i o n s g i v e a n a v e r a g e f o r m u l a( Ni V. 2 H V ) 2 f o r n i c k e l ( o r ( n, m, x ) = ( 1 , 2 , 2 ) ) , s e e Ta bl e 3 , a n d ( C o V . l o r2 H V ) 2 f o r c o b a l t ( o r ( n, m, x ) = ( 1 , 1 o r 2 , 2 ) ) . F o r n i c k e l a s e t ( 1 , 1 , 1 )wo u l d seem t o bee q u a l l y a c c e p t a b l e , b u t f o r r e a s o n s t o bed i s c u s s e d l a t e rwe p r e f e r ( 1 , 2 , 2 ) .F o r v a l u e s o f R i n t h e i n t e r m e d i a t e r a n g e s e t s ( n, m, x ) o f ( l j , 2 , 2 ) f o rn i c k e l ( T a b l e 4 ) a n d ( l j , l o r 2 , 2 ) f o r c o b a l t wer e f o un d t o g i v e t h e b e s tf i t , i . e . t h e c o mp o s i t i o n s wer e N i 2 V . j . 4 HV a n d Co2V. j . 2 - 4 HV , r e s p e c t i v e l y .I n t h e e x t r a c t i o n o f c o b a l t w i t h a l a r g e e x c e s s o f o c t a n o i c a c i d ( 1M a c i dv s . 0 . 0 5 Mc o b a l t ) t h e c o mp l e x f o r me d h a d t h e c o m p o s i t i o n Co A2. 0 - 1 - 2 HA( T a b l e 5 ) . Some d i me r i c c o mp o s i t i o n s , e s p . ( Co A2. 2 HA ) 2 > a l s o f i t . Ho wev er ,t h e b e s t f i t t i n g s t r a i g h t l i n e t h r o ug h a l l l o g D/ pH meas u r ement s a s d e t e r mi n e d by t h e co mput er h a d a s l o p e o f e x a c t l y 2 a t a n e x p l a n a t i o n l e v e l o fo v e r 98 %. I t i s awe l l - k n own f a c t ( s e e e . g . r e f . 1) t h a t t h e p r e s e n c e o f

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T a b l e 2E x t r a c t i o n o f 0 . 0 2 MC o w i t h 0 . 5 0 MVERSATI C. Ba c k g r o u n d: 0 . 5 MMgSO

E x p . p l i Metal in Metal in logDn o . o r g . layer inorg. layer(mol/1) (mol/1)1 6.40 0.0037 0.0163 -0.64402 6.60 0.0085 0.0115 -0.13133 6.80 0.0141 0.0059 0.37844 7.00 0.0177 0.0023 0.88625 7.20 0.0192 0.0008 1.38026 7.40 0.0198 0.0002 1.9956Number of observations = 6Critical fvalue forBl = 2.78 (95%t wo-sidedand 4 degrees of freedom); ( values belowt h e critical level aremarked with anasterisk.PermutationsN o . n m x logK Bl Student's (mean value) (slope coeff.)

1 1 0 I - 5.9487 1.613 3.860 X10'2 2 0 1 -12.5289 6.361 X 10-' 1.611 X 10'3 1 1 1 - 5.6289 1. 636 4.143 v 10'4 2 1 1 -12.1958 6.759 X10"' 1.881 x10'5 1 2 1 - 5.2958 1.675 4.663 x 10'6 2 2 1 -11.8486 7.340 X10"' 2.299 x10'7 1 0 2 - 5.1 387 1.270 1.1 49 X 10'8 2 0 2 -11.7190 2.930 X10"' 2. 7299 1 1 2 4.8190 1.293 1.204 X 10'10 2 1 2 -11.3859 3.329 X10"' 3.26411 1 2 2 4.4859 1.332 1.307 X 10'12 2 2 2 -11.0387 3.910 X 10"' 4.1 43

p o l y m e r i c s p e c i e s i n t h e o r g a n i c p h a s e ma y l e a d t o a n i n c r e a s e i n s l o p e .Ou r e x t r a c t i o n s w i t h VERSATI C u n de r c o mp a r a b l e c o n d i t i o n s gave s l o p e sc o n s i d e r a b l y h i g h e r t h a n 2 . We t h e r e f o r e b e l i e v e t h a t f o r o c t a n o i c a c i dt h e monomer i c c o mp o s i t i o n s f i t b e t t e r w i t h a l l k nown f a c t s , wh e r e a sVERSATI C 10f o r ms ma i n l y p o l y m e r i c ( d i me r i c ) c o mpl e xe s .A t a v e r y h i g h l o a d i n g ( 0 . 2 M Co v s . 0 . 5 M o c t a n o i c a c i d ) t h e mo s tp r o b a b l e c o mp l e x e s wer e f o un d t o b e ( i n t h i s s e q u en c e ) : ( Co A, ^, C o A ,Co A2 . 2HA a n d ( Co A2. 2 H A ) ^. I n t h i s c a s ewe c a n n o t r u l e o u t t h e d i me r i cc o mp o s i t i o n s , s i n c e t h e s i mp l e r e a s o n i n g g i v e n above w i l l c e r t a i n l y n o tb e v a l i d under t h e s e e x t r e me c o n d i t i o n s . A t t h e s e h i g h l o a d i n g s i t wa so b s e r v e d t h a t t h e c o mp l e x p r e c i p i t a t e d f r o m t h e o r g a n i c l a y e r a t a l o gDo f about 1 . 0 , i . e . a t a c o b a l t c o n c e n t r a t i o n i n t h e o r g a n i c l a y e r o fabout 0 . 1 8 M. T h e p r e c i p i t a t e h a d a c o mp o s i t i o n ( a f t e r t h or o ug h d r y i n ga t 50C a n d 1 3 3 P a ) o f C o A .

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Ta bl e3E x t r a c t i o n of 0. 199MNi w i t h 0. 5MVERSATI C. Backg r o und 0. 3MMgSO

E x p . p H Metal in Metal in logDno. org. layer inorg. layer(mol/1) (mol/1)1 6.00 0.0300 0.1690 0.75082 6.20 0.0470 0.1520 -0.50973 6.40 0.0624 0.1366 -0.34034 6.60 0.0770 0.1220 -0.19995 6.80 0.0893 0.1097 -0.08946 7.00 0.0995 0.0995 0.0000Number ofobservations = 6Critical t value for Bl = 2.78 (95%two-sidedand 4 degrees of freedom); f values belowthe critical level aremarked with anasterisk.PermutationsNo. n m x logK B l Student's t

(mean value) (slope coeff. )1 1 0 1 - 6.4821 -2.285 x 10"' 3.4122 2 0 1 -1 2.5725 -1 .097 1.604 X 103 1 1 1 - 6.0725 -9. 722 x 10-' *1.4214 2 1 1 -12.0542 -7.971 x 10"' 1.283 X 105 1 2 1 - 5.5542 2.028x 10"' 3.2656 2 2 1 -11.3527 -1.236 x 10"' 7.5057 1 0 2 - 6.0309 -4.807 X 10"' 1.392 X 108 2 0 2 -12.1213 -1.349 3.748 X 109 1 1 2 - 5.6213 -3.494 x 10"' 9.70410 2 1 2 -11.6030 -1.049 3.518 X 1011 1 2 2 5.1030 -4.938 x 1 0-' *1.65512 2 > 2 -10.9015 -3.758 x 10"' 1. 507 X 10

Ta bl e4E x t r a c t i o n of 0 . 204MNi w i t h 1. 00MVERSATI C. Backg r o und 0. 3MMgSO

logD p H Metal inorg. layer(mol/1)

log K for n m xogD p H Metal inorg. layer(mol/1) 1,2,2 1.5,2,2 2,2,2 1.5,1,2

-0.8800 5.50 0.0238 -5.2190 -7.8758 -10.5298 -8.0592-0.6900 5.60 0.0346 -5.1871 -7.8851 -10.5786 -8.0846-0.5200 5.70 0.0473 -5.1567 -7.8935 -10.6237 -8.1133-0.3600 5.80 0.0620 -5.1211 -7.8929 -10.6570 -8.1389-0.2100 5.90 0.0778 -5.0813 -7.8876 -10.6801 -8.1622-0. 0800 6.00 0.0926 -5.0502 -7.8893 -10.7098 -8.1945-0.0600 6.10 0.1090 -4.9997 -7.8672 -10.7097 -8.2102-0. 1 800 6.20 0.1228 -4.9642 -7.861 3 -1 0.7261 -8.2397-0. 3000 6.30 0.1 359 -4.9243 -7.8496 -10.7337 -8.2654-0.4200 6.40 0.1478 -4.8821 -7.8349 -10.7363 -8.2886-0.5200 6.50 0.1567 -4.8627 -7.8469 -10.7698 -8.3318-0.6100 6.60 0.1638 -4.8556 -7.8735 -10.8207 -8.3854

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Ta bl e5E x t r a c t i o n o f 0. 05MCo w i t h 1 . 00Mo c t a n o i c a c i d i nk e r o s e n e . Ba c k g r o un d0. 5HNaS0.

E x p . p H Metal in Metalin logDn o. o r g . layer inorg. layer(mol/l) (mol/1)

1 5.42 0.0210 0.0300 -0.15492 5.55 0.0320 0.0190 0.22643 5.89 0.0437 0.0073 0.77724 6.10 0.0500 0.0021 1.37675 6.21 0.0510 0.0021 1.38546 5.42 0.0190 0.0300 -0.19847 5.55 0.0300 0.0190 0.19848 5.89 0.0420 0.0073 0.75999 6.10 0.0480 0.0021 1.359010 6.21 0.0490 0.0021 1.3680

Numberofobservations= 10Critical t value fo r B l = 2.31 (95%t wo-sidedand 8 degrees of freedom);rvalues bel owth e critical level aremarked with an asterisk.PermutationsN o . n m x log K B l Student'st

(mean value) (slope coeff.)1 1 0 1 - 4.9652 1.014 1.040x10'2 2 0 1 -10.6222 4.013 X10 *4.065x10 '3 1 1 1 - 4.7882 1.040 1.054 x10'4 2 1 1 -10.4261 8.628x10- *8.550 10 '5 1 2 1 - 4.5921 1.086 1.076 X 10'6 2 2 1 -10.2094 1.550 X 10 ' *1.4877 1 0 2 - 4.3969 7.809 10 ' 9.0418 2 0 2 -10.0540 -1.929 10 1 *2.2169 1 1 2 - 4.2200 8.070 10 ' 9.269

10 2 1 2 - 9.9578 -1.467 x10 ' *1.66111 1 2 2 - 4.0238 8.532 10 ' 9.65212 2 2 2 - 9.6411 -7.799 10 ' *8.610x10 '

T r i v a l e n t i r o nTh e co mp l e x e s f o r me d when t r i v a l e n t i r o n i s e x t r a c t e d w i t h al a r g e e x c e s so f VERSATI C a c i d ( s e eTa bl e 6 ) a l l h av e i ncommon t h a t t h e s t o i c h i o me t r i c -a l l y ex p ec t e d number of c a r b o x y l a t e g r o u p s i s p r e s e nt . F o u r o u t o f f i v eo f t h e co mp l e x e s a r e d i me r s , wh i c h o n l y d i f f e r i n t h e number o f s o l v a t i n ga c i d mo l e c ul e s . Th e p o s s i b l e co mp l e x e s a s i n d i c a t e d b y o u r e v a l u a t i o n t h e na r e ( F eV3 >3 HV) 2 > ( F eV3 . 2 HV>, ( F eV3 . HV) 2 , ( F eV ) 2 > and ( F eV3 . 3 HV ) 3 > i nd ec r e a s i n g o r d er o f p r o b a b i l i t y .Whenamor e c o nc e nt r a t e d t r i v a l e n t i r o n s o l u t i o n i s e x t r a c t e d w i t h amor ed i l u t e VERSATI C s o l u t i o n ( Ta bl e 7 ) , t h r ee co mp l e x e s l i e w i t h i n t h e l i m i t sof p r o b a b i l i t y , v i z . ( F e V 2 ) 3 > ( F eV3 . HV ) 2 and ( F eV3 . HV ) 3 . Oft h es ewep r e f e rt h e f i r s t , b e c a u s ea good v a l u e f o r St u de n t ' s t - f a c t o r i s comb i ned w i t h t h el o we s t f a c t o r f o r t h e s l o p e c o e f f i c i e n t .

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Ta bl e6E x t r a c t i o n of 0. 02 MF e ( I I I ) w i t h 1.00 MVERSATI C 10i n k er o s en e.Ba c k g r o u n d 0. 5MNa-SO

Exp PH Metalin Metalin log Uno. org.layer(mal/I) inorg.layer(mol/1)1 2.70 0.0030 0.0168 0.74822 2.76 0.0044 0.0150 0.53263 2.80 0.0060 0.0X34 0.34904 2.84 0.0074 0.0119 0.20635 2.90 0.0107 0.0098 0.03826 2 90 0.0121 0.0080 0.17977 3.00 0.0134 0.0066 0.30768 3.06 0.0152 0.0042 0.55869 3.25 0.0179 0.0012 1.1737Numberofobservations= 9Critical (valueforBl = 2.36 (95%two-sided and7 degrees of freedom);(values belowthecritical levelaremarked withanasterisk.PermutatiNo. togK(mean value) (slope coeff.)

1 , 0 -2.7127 2.473 1.527 x10'2 0 1 5.1678 1.492 9.1273 0 1 -8.2183 5.255 X 10" 3.1614 1 1 1 2.5555 2.492 1.524 x10'5 1 1 -5.3061 1.525 9.1766 1 1 -8.0521 5.723 x10-' 3.3647 1 2 1 -2.3939 2.525 1.519 X10'8 2 1 -5.1399 1.572 9.2439 2 1 7.8811 6.334 x 10" 3.61610 1 3 1 -2.2276 2.572 1.512 X10'11 3 1 -4.9689 1.633 9.32512 3 1 -7.7054 7.095 x 10 ' 3.91013 1 0 2 -1.8322 1.773 1.686 x 10'14 0 2 -4.5873 7.933 x 10" 7.51815 0 2 7.3379 -1.738 x 10" *1.63716 1 1 2 -1.6751 1.793 1.699 x10'17 1 2 -4.4256 8.261 x 10" 7.78418 1 2 -7.1716 -1.270 x 10" '1.18519 1 2 2 -1.5134 1.826 1.721 X10'20 2 2 -4.2594 8.729 x 10" 8.14321 3 2 7.0007 -6.589 x 10" '6.051X 10"22 1 3 2 -1.3472 1.872 1.747 x10'23 3 2 -4.0884 9.341 X 1 0' 8.57724 3 2 -6.8249 1.014 x 10-' '9.103X1025 1 0 3 1.4970 1.540 1.344 X10'26 0 3 -4.2521 5.602 X 10" 4.90327 0 3 -7.0027 4.069 X 10 3.57828 1 1 3 -1.3399 1.560 1.365 X10'29 1 3 -4.0905 5.930 X10"' 5.21530 1 3 6.8365 3.601 X 10" 3.18331 1 2 3 -1.1783 1.593 1.401 X 10'32 2 3 -3.9242 6.398 X 10-' 5.65533 2 3 -6.6655 -2.990 x 10-' 2.65234 1 3 3 -1.0120 1.639 1.449 X10'35 2 3 3 -3.7533 7.009 x 10"' 6.2183 3 3 -6.4898 -2.229 x 10-' '1.978

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Ta bl e7E x t r a c t i o n o f 0 . 1 MF e ( I I I ) w i t h 0. 50 MVERSATI C10i n k er o s e ne.Backg r o und 0. 4 MNaSO

Exp. pH Metal m Metalin logno. org. layer(mol/1) morg. layertmol/1)1 2.35 0.0027 0.1039 1.58532 2.57 0.0121 0.0923 -0.88243 2.60 0.0161 0.0887 0.74114 2.60 0.0188 0.0806 0.63225 2.60 0.0205 0.0793 -0.58756 2.67 0.0216 0.0756 0.54417 2.65 0.0242 0.0728 0.47838 2.66 0.0258 0.0710 0.43969 2.70 0.0276 0.0685 -0.3948

10 2.70 0.0297 0.0652 -0.341511 2.70 0.0323 0.0638 -0.295612 2.79 0.0355 0.0609 -0.234413 2.76 0.0373 0.0577 0.189511 2.80 0.0430 0.0529 0.090015 2.80 0.0459 0.0502 0.038916 2.84 0.0491 0.0471 0.018117 2.81 0.0505 0 0437 0.062818 2.85 0.0534 0.0403 0.122219 2.90 0.0565 0.0376 0.176920 293 0.0605 0.0339 0 2516Numberofobservations 20.Criticalfvalue for61=2.10(95% two-sided and18degreesoffreedom), ( values belowthecritical levelatemarkedwithan asterisk.Permutations

2.7401510527 4321

-2.39124.71816.99932.00414.2853-6.51001.57133.7960-5.94602.11404.47906.80S91.76504.09196.37321.37793.6592

-5.88390.94523.16995.31981.8636

-4.2287-6.5555-1.51473.84156 1228

-1 1275-3.40885.6335

-0.6948-2.9195-5.0694

2.1871.362 x6.9112 3621.6911.2212.6912.2212 0303.2213 0303.2591.0922.672 x4.040 x1.2675.959 1.263 *1.5951.1269.356 x2.1261.9352.1647.273x9.782 x7.691 x9.021 x2 308 x2 387 x1.2307.613 x5.706 x1.7611.5701.799

1.696 x 10'1.040 x 10'5.0291,803 x 10'1.231 x 10'7.7991.958 x 10'1.418 x 10'9.8582.057x 10'1.471 x 10'1.034 x 10'1.375 x 10'3.0523.8081.447 x 10'5.617

*8.819x 10 '1 504 x 10'7.8624.4061.484 X 10'9.1156.3991.007 x10'

'1.1827.3121,090 x 10'2.195*1.6261.170 X 10'5.1872.5961.200 x 10'7.1445,156

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DI SCUSSI ON2+ 2-

I n mos t ex p er i me nt s c o n s i d e r a b l e amount s o f Mg an d SO wer e p r e s e n ti n t h e aqueous p h a s e , s i n c e c o n d i t i o n s had been c h os e n t o r e s e mbl e t h o s emet w i t h i n a p r a c t i c a l p r o b l e m unde r i n v e s t i g a t i o n . Th e p r e s e n c e o f t h e s ei o n s mi g h t c a us e c o mp l i c a t i o n s i n i n t e r p r e t i n g t h e r e s u l t s o f t h ee x t r a c t i o n s .

2+F i r s t , Mg i s e x t r a c t e d by VERSATI C 1 0 i n t h e h i g h e r pH r a n g e s . At pH7. 0 t h e l o g v a l u e s f r o m a 0. 5 M MgSO s o l u t i o n a g a i n s t 0. 5 , 1 and 2 MVERSATI C 10 a r e - 1 . 8 , - 1.0 and - 0. 4, r e s p e c t i v e l y . At t h i s l e v e l t h eamount o f e x t r a c t a n t us e d t o c o mp l e x Mg i n t h e e x pe r i me nt o f T ab l e 3 i sl e s s t ha n 5 %, and h e n c e we c h o s e 7 . 0 t o be t h e h i g h e s t pH v a l u e u s e di n t h e c a l c u l a t i o n i n t h i s c a s e . At pH 6. 4 t h e l o g D v a l u e s f r o m aMg0.5 M MgS04 s o l u t i o n a g a i n s t 0. 5 , 1 and 2 M VERSATI C 10 ar e < - 4, < - 4,a nd c a . - 2, r e s p e c t i v e l y . I n t h e e xp er i me nt s pr e s e n t e d i n Ta bl e 1, 6. 4was t h e r e f o r e c h o s e n a s a s a f e maxi mumpH f o r t h e c a l c u l a t i o n s . S i m i l a rc r i t e r i a wer e a p p l i e d i n o t h e r ex pe r i me nt s wh i c h a r e n ot t a b u l a t e d h e r e .The second c o mp l i c a t i o n mi g h t a r i s e f r o m c o mp l e xi n g o f t h e me t a l s w i t hs u l f a t e a ni o ns i n t h e aqueous p h a s e . F l e t t o b s e r v e d t h a t z i n c f o r mss t r o n g comp l exes w i t h s u l f a t e g i v i n g u n d i s s o c i a t e d ZnSO, and t h e a n i o n2-[ ZnCSO ) ] , a nd h e c a l c u l a t e d t h e a s s o c i a t i o n c o n s t a nt s . I n t h i s c a s et h e s e a s s o c i a t i o n s e x e r t a c l e a r i n f l u e n c e upon t h e e x t r a c t i o n o f Zn

w i t h n aph t h en i c a c i d . As h b r o o k^ f o und t h a t c o b a l t i n t h e pr e s e nc e o fs u l f a t e i o n s shows a de g r e e o f a s s o c i a t i o n t o CoSO^, and a l s o f o und ani n f l u e n c e upon t h e e x t r a c t i o n , t h o ug h l e s s p r o no un c ed t h a n i n t h e c a s es t u d i e d by F l e t t .A c o r r e c t i o n t e r m, a na l o go us t o t h a t g i v e n by F l e t t ^ , mi g h t be i n c l u e d e di n e q. 6. I n t h e s t u dy o f a s i n g l e l o g D/ pH c u r v e a t c o n s t a n t s u l f a t ec o n c e n t r a t i o n ( as i s done i n t h i s wo r k ) t h e e x pe r i me nt a l c o n d i t i o n s s h ou l dl e a d t o a c o ns t a nt v a l u e f o r t h i s c o r r e c t i o n t e r m, a nd t h i s wo u l d t h e r e f o r eno t a f f e c t t h e b a s i c c a l c u l a t i o n s . Th e e x t e n t o f s u l f a t e c o mp l e x i n g , i twas f o u n d , c a n s a f e l y be n e g l e c t e d , s i n c e t h e v a r i a t i o n o f pH w i t h2l o g [ SO ] was v i r t u a l l y n i l ( Ta bl e 8 ) .F r o m t h e r e s u l t s g i v e n i t appea r s t h a t t h e pa r a me t e r s n ( t h e number o fc o v a l e n t l y bound c a r b o x y l a t e g r o u ps ) and x ( t h e d eg r e e o f p o l y m e r i z a t i o nof t h e o r g a n i c c o mp l e x ) c a n be de t e r mi n ed u na mbi g uo us l y i n mos t c a s e s .Th e p a r ame t e r m ( t h e number o f s o l v a t i n g a c i d mo l e c u l e s pe r me t a l i o n ) ,h o we v e r , i s no t a l way s s t r i c t l y d e f i n e d ( i . e . a f f e c t s t h e c a l c u l a t i o n s t o

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Ta bl e8, 2-I n f l u e n c e of SO c o nc e n t r a t i o non e x t r a c t i o n o f F e ( I I I ) , Ni and Cowi t hVERSATI C 1 0. Me t a l s s o l u t i o n s madeupf r o m (Mg+me t a l ) s u l f a t e s .

Metal ion Concentra tion Versatic(mol/1) (mol/1)Fe(III)

Ni(II)

Co(II)

0.005

0.05

s o . 1(mol/1) log S O , ' - p H 0

1.50 0.176 2.20.20 -0.699 2.21.45 0.161 5.970.45 -0.347 5.921.48 0.170 6.310.48 -0. 31 9 6.28

a l e s s e r e x t e n t ) . Al t h ou gh t h i s ma t h e ma t i c a l i n s u f f i c i e n c y mi g ht o n l ybedue t oi n ac c u r a c y o f mea s u r emen t , i t c o u l d a l s o i n d i c a t e t h e s i mu l t a ne ou se x i s t e n c e of s e v e r a l c o mpl e xe s . Ob v i o u s l y t h e s e wo ul d t h en ma i n l y d i f f e rw i t h r e s p e c t t ot he number of s o l v a t i n g l i g a n d s , r a t h e r t h an wi t h r e s p ec tt o t h e - mor e i mpo r t a nt - number of c o v a l e n t l y bound g r o u p s . I nt h e d i s c u s s i o n be l o w s u c h d i f f e r e n t c o mp l e x e s a r e o n l y r e f e r r e d t oi na f ew c a s e s ,o n l y t h e c o mp l e x e s g i v i n g t h e b e s t f i t a r e u s u a l l y me nt i o n ed .When l a r g e e x c e s s e s of VERSATI C a c i d a r e a v a i l a b l e andt h e n i c k e l c on c e n t r a t i o n i n t h e aqueous l a y e r i s r e l a t i v e l y l o w, t h i s me t a l ( i n c ompl et eagr eement wi t h l i t e r a t u r e d a t a 1 ) t e nd s t of o r m c o mp l e x e s ( N i V2 - 2 HV ) 2 . Ats m a l l e r r a t i o s R i t was f o un d t h a t c o mp l e x e s wi t h l e s s t h a n t wo c o v a l e n t l ybound c a r b o x y l a t e g r o ups pe r n i c k e l a t o m a r e f o r me d. T h i s a ppa r e nt v i o l a t i o n of t h e b i v a l e n c yof n i c k e l maybemos t e a s i l y ex pl a i n edby a s s u mi n gt h a t t h e r e ma i n i n g v a l e n c i e s a r e o c c u pi e d byc o v a l e nt bonds wi t h ana n i o nX, t h e n at u r e of wh i c h i s no t r e ve a l e dbyt h e pr e s e n t p r o c e d ur e . Then t h er e a l f o r mu l a e wo ul d beNi 2 V, X . 4 HVand ( Ni VX . 2 HV) 2 , r e s p e c t i v e l y . As r e g a r d st h e n at u r e of t h e l i g a n d X weas s ume t h a t a ' r e a l ' a n i o n f r o m t h e s o l u t i o n( e . g . s u l f a t e ) wo ul d p r o b ab l y r e nd er t h e c o mp l e x much l e s s r e a d i l y e x t r a c t -a bl e t h a n i t i s i n p r a c t i c e . A l o g i c a l as s u mpt i o n i s t h a t X =OH. Thes t r u c t u r e of t h e c o mp l e x e s mi g h t t h en bea t wi nned o c t a h ed r o n , wi t honeo r t wo h y d r o x y l g r o ups asb r i d g es . Th i s i s a l s o t h e r e as o n f o r r e j e c t i n gt he f o r mu l a Ni V. HV ( o r , f o r t h a t ma t t e r , Ni VOH. HV) f o r t he n i c k e l co mp l exo bt a i n ed at l ow R: t h i s c o mp l e x i s c o v a l e n t l y s a t u r a t e d , bu t c o - o r d i n a t e l yu ns a t u r a t e d and, f u r t h e r mo r e , wo ul d h a v e a r a t h e r pr o no un ced ' h y d r o x i d e'c h a r a c t e r , wh i c h i n o ur o p i n i o n wo ul d meana poor e x t r a c t a b i l i t y .

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C o - e x t r a c t e d wa t e r can h a r d l y makeas i z e a b l e c o n t r i b u t i o nasal i g a n d . I tc a n bes e en f r o m Ta bl e9and10 t h a t t heamount of c o - e x t r a c t e d wa t e r i sl e s s t h an s t o i c h i o me t r i c bo t h f o r l ow and h i g h l o a d i n g s . The g r a d u a l i n c r e a s ei n wa t e r c o - e x t r a c t i o n i s p r o b a b l y due t o t he e mu l s i f y i n g a c t i o n of t heme t a l VERSATI C s a l t s .Th e a mb i g u i t y ofmr e f e r r e d t oabo v e i s not v e r y ma r k e d f o r our n i c k e le xpe r i me nt s . I n t hec a s e of c o b a l t h o wev er i t i s h a r d l y p o s s i b l e t o d e f i n et h e p a r a me t e r f o r e x t r a c t i o n w i t h VERSATI C. I t i s h i g h l y l i k e l y t h a t i n t h i ss p e c i f i c c a s e s e v e r a l c omp l e xe s w i t h d i f f e r e n t number s of s o l v a t i n g a c i dmo l e c ul e s ar ep r e s e n t s i mu l t a n e o u s l y . T h i s i s c o n f i r me d byt he f a c t t h a td u r i n g t he e x t r a c t i o nof c o b a l t w i t h VERSATI C 10 t he c o l o u r of t he o r g a n i cs o l u t i o n s h i f t s f r o mad i s t i n c t p i n k ( t y p i c a l of o c t a h e d r a l c o - o r d i n a t i o n)a t l owl o a d i n g s t o p u r p l e and u l t i m a t e l y b l u i s h at h i g h e r l o a d i n g s . At v e r yh i g h l o a d i n g s t he s o l u t i o n i s d ar k b l u e ( t y p i c a l of t e t r a h e d r a l c o - o r d -8 9i n a t i o n ) . I t has a l s o been o b s e r v e d t h a t i n t he e x t r a c t i o nof c o b a l t w i t h

Ta bl e9C o - e x t r a c t i o n of wa t e r i n t he e x t r a c t i o nof n i c k e l w i t h 1. 0MVERSATI C 10.Va l u es c o r r e c t e d f o r s o l u b i l i t y of wa t e r i n VE RSATI C s o l u t i o n . K a r l F i s c h e rt i t r a t i o n s . (xChecked and c o n f i r me d by GL C) .

O r g . N i. cone. Org.H, 0cone. Corrected H j 0 o r g ( c o r r )(mol/1) (Karl Fischer) org. H3 0cone. ~ ~(mol/1) (mol/1) N l 0.020

0.002 0.024 0.004 20.0056 0.025 0.005 0.90.009 0.029 0.009 10.011 0.030 0.01 0.90.016 0.026 0.006 0.4

Ta bl e10C o - e x t r a c t i o n of wa t e r i n t hee x t r a c t i o nof n i c k e l w i t h 0. 5MVERSATI C10.Va l u es c o r r e c t e d f o r s o l u b i l i t y of wa t e r i n VERSATI C s o l u t i o n . K a r l F i s c h e rt i t r a t i o n s . ( X c h e c k e d and c o n f i r me d by GL C) .

O r g . Nicone. Org.H3 0cone. Corrected H j 0o r g (c o r T.)(mol/1) (Karl Fischer) org. H, 0cone. ~:(mol/1) (mol/1) N l m- 0.018 -

0.006 0.024 0.006 10.024 0.028 0.008 0.330.042 0. 036 x 0.018 0.430.056 0.048 0.030 0.530.103 0.070X 0.052 0.50

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VERSATI C 9 1 1 ( a g r a d e s l i g h t l y d i f f e r e n t f r o m VERSATI C 1 0 , w i t h a wi d ermo l e c u l a r we i g h t d i s t r i b u t i o n ) t h e v i s i b l e s p e c t r u m shows t wo d i s t i n c tp e a k s , o n e i n t h e r e d a n d o n e i n t h e b l u e r e g i o n , whose r a t i o o f ma g n i t u de s h i f t s i n f a v o u r o f t h e b l u e o n e a s t h e e x t r a c t i o n p r o c e e d s . I n o u re x t r a c t i o n o f c o b a l t w i t h o c t a n o i c a c i d we d i d n o t o b s e r v e a n y c o l o u r9s h i f t , even a t v e r y h i g h l o a d i n g s . Howeve r , C r a b t r e e a n d R i c e f o un d t h a ta l s o i n t h i s c a s e s e v e r a l s p e c i e s a r e p r e s e n t , a l t h o u g h t h e s o l u t i o n sr e ma i n ed p i n k .I t i s n o t e a s y t o e x p l a i n wh y , a t h i g h l o a d i n g s , n i c k e l a n d c o b a l t comp l e x e s w i t h VERSATI C t e n d t o i n c o r p o r a t e o t h e r l i g a n d s r a t h e r t h a n u s et h e a v a i l a b l e s o l v a t i n g a c i d mo l e c u l e s , a s do c o b a l t - o c t a n o i c a c i d comp l e x e s . B e s i d e s b e i n g h e a v i l y b r a n c h e d , VERSATI C i s a c o n s i d e r a b l y weakera c i d t h an o c t a n o i c a c i d . Whe r eas t h e l a t t e r h a s a n a c i d d i s s o c i a t i o nc o n s t a n t o f 4 . 8 9 1 0 , t h e p K o f VERSATI C 9 1 1 i s about 7 . 1 47 , a n d we s e e n oar e a s o n wh y VERSATI C 1 0 s h o u l d d i f f e r g r e a t l y f r o m VERSATI C 9 1 1 i n t h i sr e s p e c t . A c o mpa r i s o n o f t h e r e s u l t s p e r t a i n i n g t o VERSATI C 1 0 a n do c t a n o i c a c i d s u gg es t s t h a t t h e l a t t e r , s t r o n g e r , a c i d t e nd s t o f o r mmonomer i c c o mp l e x e s wh er eas t h e weaker VERSATI C a c i d ma i n l y f o r ms d i me r i cc o mp l e x es . On t h e o t h e r h a n d , F l e t c h e r a n d F l e t t 1 f o un d a d i m e r i c s t r u c t u r ef o r t h e c o b a l t - n a p h t h e n i c a c i d c o mp l e x , w h i l e n aph t h en i c a c i d i s a b ou ta s s t r o n g a s a no r ma l a l i p h a t i c f a t t y a c i d 1 } I n t h i s c o n t e x t i t i s i n t e r e s t i n g t o n o t e t h a t t h e s l o p e s f o un d b y F l e t c h e r a n d F l e t t 1 1 f o r t h e c o b a l te x t r a c t i o n s wer e a l mo s t e x a c t l y 2 . 0 , wh er eas f o r VERSATI C e x t r a c t i o n s u n d e rc o mp a r a b l e c o n d i t i o n s s l o p e s h i g h e r t h a n 2 wer e f o un d i n t h e p r e s e n t s t u d y .I t h a s been o b s e r v e d i n t h e f o r e g o i n g t h a t a h i g h e r s l o p e mi g h t p o i n t t op o l y m e r i z a t i o n i n t h e o r g a n i c p h a s e . I t c o u l d b e i l l u m i n a t i n g t o e v a l u a t et h e n u me r i c a l d a t a o f t h e abo v e a ut h or s b y t h e p r e s e n t me t h o d.F o r i r o n s i m i l a r r e a s o n i n g t o t h a t f o r c o b a l t a n d n i c k e l c a n b e a p p l i e d .T h i s e v a l u a t i o n s u gg es t s t h a t v a r i o u s c o mp l e x e s w i t h t h r e e c a r b o x y l a t eg r o u ps p e r me t a l a t o m ma y e x i s t , wh er eas under s u i t a b l e c o n d i t i o n s ac o mp l e x ( F e V ^ ) ^ ma y a l s o b e f o r me d. S i n c e t h e v a l e n c y o f t h e t r i v a l e n ti r o n mus t b e s a t i s f i e d a t h i r d c o v a l e n t l y bound l i g a n d , mos t p r o b a b l y OH,mus t b e p r e s e n t a n d t h e r e f o r e t h e c o mp l e x ma y h a v e t h e f o r mu l a ( F eV2 0H) . j .

4 . . .Tanaka e t a l . c o nc l u de d t h a t t r i v a l e n t i r o n i s e x t r a c t e d b y c a p r i c a c i da s a n u n s o l v a t e d t r i m e r , b u t t h e y c o u l d n o t d i s t i n g u i s h be t ween ( F e A j ) ^a n d F e . j ( 0H) g _ p Ap. T h e l a t t e r f o r mu l a i s a g e n e r a l i z e d f o r m o f o u r( F eV2 0H) . j . T h e e x i s t e n c e o f c o mp l e x e s be t ween t r i v a l e n t i r o n a n d a c e t i c a c i d

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w i t h t he f o r m u l a [ Fe^( OH) ^( OAc ) ] OAc i s known f r om t he l i t e r a t u r e , andmay g i v e some s u p p o r t t o our v i e w.A t t he moment no c o n c l u s i o n can be d r awn w i t h r e s p e c t t o t hed i f f e r e n c e sbet ween Ta n ak a ' s r e s u l t s f o r i r o n and our own. As was t hec a s e w i t h c o b a l t ,t h ey may be due t o d i f f e r e n c e s be t ween t he a c i d s u s e d , but f o r a c o mp l e t eu n d e r s t a n d i n g mor e wo r k wo u l d be n e c e s s a r y .NOMENCLATUREM me t a l i o n s ( w i t h o u t a c h a r g e s i g n ) i n any p o s s i b l e c o mp l e xHA a c i d e x t r a c t a n tA a n i o n of e x t r a c t a n tB a c t i v i t y c o e f f i c i e n t p r o d u c t

i n i t i a l e x t r a c t a n t c o n c e n t r a t i o n , t a ken as monomerY a , b a c t i v i t y c o e f f i c i e n t of s p e c i e s a i np h as e bP d eg r e e of p o l y me r i z a t i o n of e x t r a c t a n t i n d i l u e n tn number of c o v a l e n t l y bound e x t r a c t a n t g r o u p s i nc o mp l e xm number of e x t r a c t a n t mo l e c ul e s bound as s o l v a t i o n mo l e c u l e sX d eg r e e of p o l y m e r i z a t i o n of t hee x t r a c t e d c o mp l e xC e x t r a c t e d c o mp l e xK e q u i l i b r i u m c o n s t a n t w i t h r e s p e c t t o c o n c e n t r a t i o n sK' e q u i l i b r i u m c o n s t a n t w i t h r e s p e c t t o a c t i v i t i e sREFERENCES1 . F l e t c h e r , A.W and F l e t t , D. S. , J . A p p l . Chem 1964, 1_4 2502 . S h i k h ee va , L. V. , Ru s s . J . I n o r g . Chem 1965, 10, 8083 . Ko j i ma , I . , Uc h i d a , M and T a n a k a , M , J . I n o r g . N u c l . Chem 1970, 32, 13334. T a n a k a , 11. et a l . , P r o c . I n t . S o l v e n t E x t r . Co n f . Go t h e n bu r g 1 9 6 6 , p. 154.

N o r t h - H o l l a n d , Ams t er dam, 1967.5 . J a y c oc k , M J . and J o nes , A. D. , i b i d . p. 1606. F l e t t , D. S. , i b i d . p.607 . As h b r o o k , A.W, J . I n o r g . N u c l . Chem1972, 34_, 17218. He s l o p, R. B. and Ro bi n s o n , P. L. , I n o r g a n i c Ch emi s t r y , 3 r ed. , p. 701

E l s e v i e r , Ams t er dam, 19679. C r a b t r e e , H. E. and R i c e , N. M, P r o c . I n t . S o l v e n t E x t r . Co nf . L y o n1974,

p . 711. S C I , 1974.1 0 . Handbook of Ch emi s t r y and P h y s i c s , 46 ed. , 19651 1 . K i r k , R. E. and Ot hmer , D. F. ( e d s . ) , E n c y c l o p e d i a of Ch e mi c a l Te c hn ol o g y ,

2 n d e d . , V o l . 13, p. 729. Wi l e y - I n t e r s c i e n c e , New Y o r k1967.

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METALS EXTRACTI ON WTH CARBOXYL I C ACI DSI I . E f f e c t o f t e mpe r a t u r e on t h e e x t r a c t i o n o f Cu , N i , C o ( I I ) , Zn ,

F e ( I I I ) and C o ( I I I ) .A. J . v a n d e r Ze eu w.Hy d r o me t a l l u r g y 1 97 9 , 4, 3 9 .

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I NTRODUCTI ONThe e f f e c t o f t h e e x t r a c t i o n t e mpe r a t u r e o n t h e l i q u i d / l i q u i d e x t r a c t i o no f me t a l s w i t h r e ag en t s c o n t a i n i n g a c t i v e h y d r o g e n h a s never been i n v e s t -1 2i g a t e d i n muc h d e t a i l . Some f r a gme nt a r y r e p o r t s e x i s t ' wh i c h i ng e ne r a ls h o w t h a t i n ma ny c a s e s t h e d i s t r i b u t i o n c o e f f i c i e n t d e c r e a s e s w i t h i n c r e a s i n g t e mpe r a t u r e .

3F u r t h e r t o o u r wor k o n t h e c omp o s i t i o n o f me t a l c o mp l e x e s w i t h VERSATI Ca c i d a s t u d y o f t h e e f f e c t o f t e mpe r a t u r e on t h e d i s t r i b u t i o n c o e f f i c i e n t sand c o mp l e x c o mpo s i t i o ns i nt h e s e s y s t e ms i s now r e p o r t e d.EXPERI MENTALMe t a l s o l u t i o n sUn l e s s s t a t e d o t h e r wi s e , a l l me t a l s o l u t i o n s wer e 0. 05 M A s u l f a t e b a c k g r o und c o n c e n t r a t i o no f a ppr o x i ma

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