pourbaix diagram of cadmium

5/24/2018 Pourbaix Diagram of Cadmium

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C hemi ca l Geo l ogy , 5 4 ( 1 9 8 6 ) 2 7 1 - - 2 7 8 2 7 1El s ev ie r S c i ence P ub l i she r s B .V . , Am s t e rd am - - P r i n t ed i n The N e t he r l ands[3 ]

G E O C H E M IC A L B EH A V IO R O F A N T IM O N Y A R S E N ICC A D M IU M A N D T H A L LIU M :E h -p H D I A G R A M S F O R 2 5C 1 -B A R P R E S S U R E

D O U G L A S G . B R O O K I N SD e p a r t m e n t o f G e o l o g y, U n i v e r s it y o f N e w M e x i c o , A l b u q u e r q u e , N M 8 7 1 3 1 U . S .A . )

( R e c e i v e d S e p t e m b e r 5 , 1 9 8 5 ; a c c e p t e d f o r p u b l i c a ti o n O c t o b e r 1 , 1 9 8 5 )

A b s t r a c tB r o o k i n s, D . G . , 1 9 8 6 . G e o c h e m i c a l b e h a v i o r o f a n t i m o n y , a r s en i c, c a d m i u m a n d t h a l li u m : E h - - p H d i a g r a m sfo r 25 C , 1 -ba r p res s u re . C hem . Geo l . , 54 : 271 - -278 .

New Eh - -pH d i ag ram s have b een de r i ved fo r S b , As , C d and T1. Thes e d i ag ram s a re u s e fu l i n d i scus s ingt he com m on as s oc i a t i on o f s eve ra l o r a l l o f t hes e e l em en t s a round ep i t he rm al Au depos i t s . S l i gh t d i f f e ren -c e s in p H , E h o r b o t h p H - - E h a r e s u f f ic i e n t t o a c c o u n t f o r p a r t it i o n in g o f t h e s e e l e m e n t s f r o m d e p o s it todepos i t . I n add i t i on , ch l o r i de co nce n t r a t i on - -pH d i ag ram s fo r Au , Hg and T1 a re u s e fu l t o fu r t h e r d i s cus st h e r o l e o f c h l o r id e ( a n d p o s s i b ly c h lo r i d e c o m p l e x e s ) in t h e m i g r a t i o n o f s o m e o f t h e s e e l e m e n t s u n d e rl o w T ,P cond i t i ons .

1 . n t r o d u c t i o nM a n y e l e m e n t s h a v e b e e n p r o p o s e d a s

p a t h f i n d e r e l e m e n t s f o r t e l e t h e r m a l - - x e n o -t h e r m a l - - e p i t h e r m a l o r e d e p o s i t s o f g o l d .T h e s e i n c l u d e S b , A s , C d , T 1 , M n , H g a n d A g ,a m o n g o t h e r s . T h a l l i u m , i n p a r t i c u l a r , h a sa t t r a c t e d m u c h i n t e r e s t a s a g o l d p a t h f i n d e r( I k r a m u d d i n e t al . , 1 9 8 3 ) . L e s s e r b u t n o n e -t h e l e s s i m p o r t a n t t r a c e s o f S b , A s a n d C d( a n d o t h e r s ) a r e a ls o c o m m o n a r o u n d t h e s el o w - p r e s s u r e g o l d d e p o s i t s .

T h i s n o t e w i ll p r e s e n t n e w E h - - p H d i a g r a m sf o r t h e e l e m e n t s S b , A s , C d a n d T 1; a s w e l la s p u b l i s h e d C l - - p H d i a g ra m s f o r T 1 - - H g - - A u( B a es a n d M e s m e r , 1 9 7 6 ) a n d a t t e m p t t o ex -p l a i n w h y c e r t a i n e l e m e n t s s u c h a s T1 a r eu s e fu l p a t h f i n d e r s f o r A u a n d o t h e r m e t a l s .

T h i s n o t e d o e s n o t p r e t e n d t o c o v e r t h eb a c k g r o u n d g e o c h e m i s t r y o f t h e e l e m e n t sS b , A s , C d a n d T 1 , a n d t h e r e a d e r i s r e f e r r e dt o g e n e r a l g e o c h e m i c a l l i t e r a t u r e f o r s u c hi n f o r m a t i o n . S o m e k e y r e f e r e n c e s w il l b ei d e n t i f i e d a s t h e y p e r t a i n t o th i s w o r k , h o w -e v e r .2 . P r e v i o u s w o r k

T h e u s e o f E h - - p H d i a g r a m s f o r a s s i s t a n c ein d e a l in g w i t h g e o c h e m i c a l p r o b l e m s h a sb e e n d e s c r i b e d , f o r e x a m p l e , b y G a r re l s a n dC h r is t ( 1 9 6 5 ) , K r a u s k o p f ( 1 9 7 9 ) , V e r i n k( 1 9 7 9 ) a n d B r o o k i n s ( 1 9 8 4 ) . P r e v i o u s E h - - p Hd i a g r a m s f o r S b a n d C d h a v e b e e n g i v e n b yB r o o k i n s ( 1 9 7 8 ) , a n d f o r A s b y B r o o k i n s( 1 9 7 9 ) a n d L o n g m i r e ( 1 9 8 3 ) . T h e d a t a u s e d


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272in these earlier works were subject to fairlylarge errors, however, and these three di-agrams have been recalculated here. No prev-ious diagram, using modern data, has beenatte mpt ed for T1, however.

The role of total dissolved C1 in affectingthe geochemical behavior of the elementsSb, As, Cd and T1 is not well known, butBaes and Mesmer (1976) have calculated thetota l Cl--pH diagrams for the stability fieldsof Hg, Au and T1. Some of their work, withpermission, are presented herein to helpinterpret the Eh--pH diagrams. The authorassumes, however, responsibility for all dis-cussion and conclusio ns drawn involving theirwork.3. Ther modyn amic data

In order to be as consistent as possible, Ihave restr ic ted my choice of thermodynamicdata to that presented by Wagman et al.(1982). The data are presented in Table I.All Gibbs free energies of f orm ati on (A G}) forthe species of interest have been recalculatedto kilocalories per mole (kcal. mo1-1) andonly 298.15 K, and 1-bar pressure data havebeen employed. Further, since I am mostinterested in trace amounts of the elementsSb, As, Cd and T1 in waters, activities fordissolved amounts of these elements aretak en at 10 -8 and 10 -6 . Th ese values arechosen in accord with the approaches of theearlier workers (i.e. Garrels and Christ, 1965;Brookins , 1978 , 1984) and, since the di-agrams are for generic purposes only, theseactivities are assumed to be equal to concen-tration (molalit ies) and unaffected by ionicstrength. While an over-simplification, thiswill not drastically change the Eh--pH di-agrams presented. Finally, the errors for thethermodynamic data are discussed in detailby Wagman et al. (1982) and the readeris referred to this source for detail . The readeris also reminded that not shown fo r theEh--pH diagrams are stability fields for mostsulfide complexes, etc., due to a lack oftherm odynam ic data .

TABLE IGibbs free energies of formation for speciesSpecies AG~(kcal. mol -~ )

A r s e n i c :AsS --16.80As:S 3 --40.30As203 --137.66H3AsO4 --183.08H~AsO~ --180.01HAsO:~ --170.69AsO~- --154.97

C a d m i u m :Cd 2 --18.55CdS --37.40CdO --54.59CdO~- --67.97CdOH+ --62.40HCdO --86.88Cd(OH)2 --113.19CdCO: --159.99

A n t i m o n y :SbO --42.33SbO~ --81.31Sb2S ~ --41.49S b 2 S ~ - - 2 3 . 7 8H S b O : - - 9 7 . 3 9S b O H ) 3 - - 1 6 3 . 7 7S b 2 0 4 - - 1 9 0 . 1 8Sb:O~ --198.18

T h a l l i u m :Tl --7.74TI(OH)~ --58.48TIOH~ --3.80T ~O --35.20T120 ~ --74.50T120 --82.98TI(OH)~ --121.18TI2S --22.39

O t h e r s :H2S --6.65HS- +2.89SOt --177.95H20 --56.69H:CO~ --148.94HCO3 --140.26C O ~ - - - 1 2 6 . 1 7All data from Wagman et al. (1982).


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4 . E h - - p H d i a gr a m sT h e E h - - p H d i a g r a m s , c a l c u l a t e d f o l l o w i n g

t h e m e t h o d s d e s c r i b e d i n B r o o k i n s ( 1 9 8 4 ) ,a r e s h o w n f o r S b , A s , C d a n d T 1 a s F i g . 1 A ,B , C a n d D , r e s p e c t i v e l y . T h e s e a r e d i s c u s s e di n t u r n .T r a n s p o r t o f S b i n h y d r o t h e r m a l w a t e r sm a y b e a s ac i d ic o r b a s i c o x y i o n s , S b O o rS b O ~ , r e s p e c t i v e l y , u n d e r m i l d l y o x i d i z i n gc o n d i t i o n s ( i. e. j u s t a b o v e t h e s u l f i d e - - s u l f a t ef e n c e ) a s s h o w n i n F i g. 1A . U n d e r re d u c i n g ,n e a r - n e u t r a l t o m o r e a lk a l in e c o n d i t i o n s ,t r a n s p o r t a s a s u lf i d e c o m p l e x s u c h a s S b : S ~ -i s p o s s i b l e ( n o t e : a c t i v i t y o f t o t a l d i ss o l v e dS = 1 0 -3 a s s u m e d ) . B y f a r th e b u l k o f t h es t a b i l i t y f i e ld o f w a t e r i s c o v e r e d b y s o l idS b s p e c i e s ( S b 2 S 3 , S b ( O H ) 3 , S b 2 0 4 , S b 2 0 5 ) ,t h u s s u g g e st in g t h a t S b t r a n s p o r t m u s t t a k ep l a c e a t m o d e r a t e l y l o w E h - v a lu e s . N o d a t aa r e a v a i l a b l e f o r c h l o r i d e c o m p l e x e s o f S b .T r a n s p o r t o f S b s p e c i e s a s a c h l o r i d e c o m -p l e x is d i f fi c u l t t o a s se ss . B o y l e a n d J o n a s s o n( 1 9 8 4 ) s u g g e s t t h a t s p e c i e s s u c h a s S bC136 ,S bC 13 , Sb O C 1 , e t c . , m a y b e l o c a l l y i m p o r t a n ti n c h l o r i d e - r i c h a c i d i c h o t s p r i n g w a t e r s . N od a t a a r e a v a i la b l e f o r t h e a q u e o u s s p ec i e s,h o w e v e r .T h e E h - - p H d i a g r a m f o r A s is s h o w n a sF i g. l B . O n l y o n e a c t i v i t y ( 1 0 -6 ) h as b e e na s s u m e d f o r d i s s o lv e d A s s p e c i es f o r c o n -v e n i e n c e . W i d e t r a n s p o r t b y A s ( V ) s p e c ie sa b o v e t h e s u l f i d e - - s u l f a t e f e n c e i s i n d i c a t e d( H 3 A s O 4 , H 2 A s O ~ , H A s O2 4 , A s O ~ - ) . A s m a l lf i e l d o f A s 2 0 3 m a y s e r v e a s a p a r t i a l b a r r i e rt o d i s s o l v e d A s m i g r a t i o n u n d e r a c i di c m i l d -l y - o x i d i z i n g c o n d i t i o n s . U n d e r s u l f i d e - s t a b l ec o n d i t i o n s , A s m o b i l i t y s h o u l d b e f ai r lyl i m i t e d ( i gn o r i ng s u l f id e c o m p l e x e s ) . A g a i n,A s -- C 1 c o m p l e x e s a r e n o t w e l l d e f i n e d a n dn o t h e r m o d y n a m i c d a t a a re a v a il ab l e f o rs u c h s p e c ie s . B o y l e a n d J o n a s s o n ( 1 9 8 4 )p o i n t o u t t h a t S b is a g o o d p a t h f i n d e r e le -m e n t f o r a w i d e v a r i e t y o f m i n e r a l d e p o s i t s ,i n c l u d in g A u . F u r t h e r , s o m e s i m i la r b e h a v i o ro f S b w i t h A s i s a l so n o t e d , p o s s i b l y d u e t oz o n e o f f o r m a t i o n o f S b ( O H ) 3 a n d A s :O 3 .T h e C d E h - - p H d i a g r a m i s s h o w n a s F i g.

1 C . W h i l e a l a r g e s t a b i l i t y f i e l d f o r C d S i sp r e s e n t u n d e r s u l f id e - s t a b le E h - - p H , a b o v et h e s u l f i d e - - s u l f a te f e n c e C d s h o u l d b e v e r ym o b i l e a t n e a r -n e u t r a l a n d a c i d p H - v a l u e . T h isi s c o n s i s t e n t , f o r e x a m p l e , w i t h o b s e r v e dC d m o b i l i t y a t t h e O k l o n a t u r a l r e a c t o r ,G a b o n ( B r o o k i n s , 1 9 7 8 , 1 9 8 4 ) , a s o n l y s m a l lf i e l d s o f C d C O 3 a n d C d ( O H ) 2 , a n d a t h i g hp H , a r e p r e s e n t u n d e r o x i d i z i n g c o n d i t i o n s .M o b i l i t y a s C d 2 ( a s s u m e d t o b e m o r e a b u n -d a n t t h a n C d O H ) a n d / o r C d O ~ u n d e r o x i d iz -i n g c o n d i t i o n s i s a s s u m e d . H o w e v e r , i n t h ep H r a n ge o f 8 - -1 0 , C d C O 3 - - C d ( O H ) 3 m a yp r e v e n t C d m o b i l i t y .

T h e E h - - p H d i a g r a m f o r T 1 i s s h o w n i nF i g. 1 D . W h i le m o s t o f t h e E h - - p H f i e ld isc o v e r e d b y s o l i d s p e c i e s , f r o m m i l d l y t os t r o n g l y o x i d i z i n g c o n d i t i o n s , T 1 2 0 , T 1 2 0 3 ,T1 2 0 4, t h e r e i s a s i g n i f i c a n t l y l a r g e f i e l d f o rT 1 t h a t e x i s t s f r o m a c i d i c t o s l i g h t ly a l k a l i n ep H u n d e r r e d u c i n g c o n d i t i o n s t o , a s a f u n c -t i o n o f d e c r e a s in g p H , s o m e w h a t o x id i z i n g,a c i di c c o n d i t i o n s . T h i s is i m p o r t a n t f o r s e v e ra lr e a s o n s ( d i s c u s s e d b e l o w ) . S o m e T 1 - - C l - - p Hd a t a h a v e b e e n d e t e r m i n e d o r c a l c u l a t e d ( B a e sa n d M e s m e r , 1 9 7 6 ) , t h e i m p o r t a n c e o f w h i c hi s d i s c u s s e d l a t e r i n th i s p a p e r .5 . D i s c u s s i o n

T h e r o l e o f s p e c ie s o t h e r t h a n S o n t h em e t a l - - w a t e r s y s t e m E h - - p H d i ag r a m s f o r S b ,A s , C d a n d T 1 is n o t w e l l k n o w n . Y e t i n t h ec a se o f T 1, B a e s a n d M e s m e r ( 1 9 7 6 ) h a v ec a l c u l a t e d t h e C l - - p H d i a g r a m f o r T 1 s p e c ie s .T h i s i s s h o w n a s F i g. 2 A . I n a d d i t i o n , a l s of r o m t h e i r w o r k , F i g. 2 B a n d C s h o w s t h eC l - - p H d i a g r a m s f o r H g a n d A u s p e ci e s. T h e s ew i ll b e d i s c u s s e d b e l o w .I t i s a p p a r e n t f r o m i n s p e c t i o n o f F ig . 1t h a t t h e r e a r e s i g n i f i c a n t d i f f e r e n c e s in t h eE h - - p H d i ag r a m s f o r t h e f o u r e l e m e n t s inq u e s t i o n . A l t h o u g h a ll c a n b e t r a n s p o r t e di n s o l u t i o n t o g e t h e r u n d e r v e r y a c i d i c m i l d l y -o x i d i z i n g c o n d i t i o n s , a t o t h e r E h - - p H c o n d i -t i o n s t h e y e x h i b i t q u i t e d i f f e r e n t b e h a v i o r .A t i n t e r m e d i a t e - p H m i l d l y - o x i d i z i n g c o n d i -t i o n s , T 1 - - C d - -A s c a n s t i ll b e t r a n s p o r t e d


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t o g e t h e r , b u t n o t S b . U n d e r h ig h e r- p H c o n -d i t i o n s C d - - A s c a n s t il l b e m o b i l e , b u t n o tT 1 - -S b . F r o m t h e E h - - p H d i a g r a m s a l o n e ,o n e w o u l d h a v e t o a r g u e f o r a c i d ic o x i d i z in g( E h = 0 . 4 5 V o r s o ) f o r t h e t r a n s p o r t o f t h eg r o u p S b - - A s - - C d - -T 1 . A n y s h i f t in e i t h e r p Ho r E h w i ll r e m o v e o n e o r m o r e s p e c ie s f r o ms o l u t i o n . I n a c t u a l i t y , t h i s m a y a c c o u n t f o rh a l o e s o f , f r o m A u o r e o u t w a r d , o f A s, t h e nS b , t h e n T 1 w i t h C d f ix e d i n f a r t h e s t r e m o v e ds e c o n d a r y s u l fi d e s ( n o t e : t h i s k i n d o f z o n a -t i o n i s f o r a g e n e r i c c a s e o n l y ) .

T h e E h - - p H d i a g r a m f o r T1 ( F ig . 1 D )is a l so u s e f u l t o e x p l a i n t h e c o m m o n f i xa -t i o n o f T1 i n K - b e a r i n g m i n e r a l s f o u n d i na l t e ra t i o n h a l o e s a r o u n d s o m e o r e d e p o s i ts .T h e i o n i c r a d i u s o f T1 i s 1 . 4 9 A , w h i c h i sv e r y c l o s e t o t h a t o f K o f 1 . 3 3 A ( S h a w ,1 9 5 2 ) , a n d s u b s t i t u t i o n o f T1 f o r K is b o t hp r o b a b l e a n d o b s e r v e d ( s e e a l so V o s k r e s e n s -k a y a , 1 9 5 9 ) . I n ca s e s w h e r e T 1 - -K d i a d o c h yi s p o s s i b l e , t h i s w i l l a l l o w i t t o b e s e g r e g a t e df r o m t h e r e m a i n i ng S b - - A s - -C d . A n y o x y -h y d r o x i d e p h a s e s w i ll p r e s u m a b l y r e m o v e S ba n d A s in t h e s a m e r o c k s w h e r e T 1 - - K f i xa -t i o n h a s o c c u r r e d . O n l y C d w o u l d b e t r an s -p o r t e d f u r t h e r i n t h i s c as e .T h e C l - - p H d i a g r a m s ( F ig . 2 ) f o r T 1 - - H g - -A u a r e u s e f u l i n t h a t t h e r e la t i v e i m p o r t a n c eo f c h l o r i d e c o m p l e x e s o f t h e s e m e t a l s c a nb e e x a m i n e d . W h i le E h c o n d i t i o n s a re n o tg i v en i n B a e s a n d M e s m e r ( 1 9 7 6 ) , t h e E hm u s t b e a s s u m e d t o b e q u i t e h i g h , i .e . h i ghe n o u g h t h a t t h e s p e c i e s T l ( I I I) , H g ( I I ) a n dA u ( I I I ) p r e d o m i n a t e . F r o m t h e E h - - p H di -a g r a m f o r T 1 ( F ig . 1 D ) , i t w o u l d a p p e a r t h a tT l ( I V ) s h o u l d b e t h e s p e c i e s c o e x i s t i n g w i t hH g ( I I ) a n d A u ( I I I ) , b u t d a t a a r e n o t a v a il -a b l e .B a e s a n d M e s m e r ( 1 9 7 6 ) p o i n t t o t h e im -p o r t a n c e o f c h lo r i d e - -h y d r o x i d e c o m p l e x e sf o r t h e m e t a l s T 1 - - H g - - A u . I n d e e d , t h e s p e c i e sT 1O H C1 + i s c o n s i d e r e d b y B a e s a n d M e s m e r( 1 9 7 6 ) t o b e i m p o r t a n t , a s a r e H g O H C 1 a n dA u O H ( C 1 ) : -- A u ( O H ) 2 C 1 . W h a t t h ei r w o r ki n d i c a t e s i s t h a t a ll t h r e e m e t a l s , T 1 - - H g - - A um a y b e t r a n s p o r t e d a s c h l o r i d e - - h y d r o x i d ec o m p l e x e s f o r t h e c o n d i t i o n s g i v e n . I n n a t u r a l

277s e t ti n g s , s i m i l ar c o m p l e x e s m a y b e a s i m p o r -t a n t i f n o t m o r e s o . T h e p r o b l e m o f A us p e c i e s is c o m p l i c a t e d b y t h e f a c t t h a t w h i l eA u ( I ) is k n o w n , t h e r e a r e v er y f e w t h e r m o -d y n a m i c d a t a f o r A u ( I ) s p e c i es . T h e l i m i t e dd a t a ( W a g m a n e t al ., 1 9 8 2 ) d o , h o w e v e r , s ug -g e s t t h a t A u ( 0 ) w i ll o x i d i z e t o A u ( I ) inA u C l~ a t a n E h o f r o u g h l y 1 . 2 5 V , a p p r o x i -m a t e l y r i g h t a t t h e u p p e r s t a b i l i t y l i m i t o fw a t e r u n d e r p H = 0. T h e E h f o r A u ( I ) t oA u ( I I I ) i s h i g h e r t h a n t h i s f o r a ll s p e c i e s.F u r t h e r , w h i l e t h e b o u n d a r i e s f o r A u ( 0 ) - -A u ( I I I ) s p e c i e s s u c h a s H 2 A u O ~ a n d H A u O ~ -f a ll a b o v e t h e w a t e r s t a b i l i t y fi e ld , in t h e o r yt h e A u ( I ) s p e c i e s s h o u l d f a l l b e l o w t h e m .T h i s c o u l d b r i n g s o m e a q u e o u s A u ( I ) s p ec i e si n t o t h e s t a b i l i t y fi e ld f o r w a t e r . T h e r e v i se dE h - - p H d i ag r am f o r A u - - C I - - S - - H - O b y t h ew r i t e r w i ll b e p u b l i s h e d s e p a r a t e l y ( D . G .B r o o k i n s , i n p r e p . ) .6 . C o n c l u s i o n s

T h e c o n c l u s i o n s f r o m t h is w o r k a r e a sf o l l o w s :

( 1 ) T h e g r o u p T 1 - - C d - - A s - - S b c a n b e t r an s -p o r t e d t o g e t h e r u n d e r a c i d i c o x i d i z i n g c o n d i -t i o n s .( 2 ) U n d e r h i gh p H b u t s t il l o x i d i z i n g c o n -d i t io n s , A s - - C d m a y r e m a i n m o b i l e , b u tT 1 - -S b m a y b e i n c o r p o r a t e d i n t o s o li d s.

( 3 ) U n d e r i n t e r m e d i a t e - p H m o d e r a t e - E hc o n d i t i o n s , T 1 - - C d - -A s c a n b e t r a n s p o r t e dt o g e t h e r , b u t n o t S b .

( 4 ) H a l o e s o f t h e e l e m e n t s S b - - T 1 - - C d - - A sa b o u t e p i t h e r m a l A u d e p o s i ts ar e c o m m o n ;t h e E h - - p H d i ag r a m s h e l p e x p l a in s o m e , b u tc e r t a i n l y n o t a ll , o f t h e h a l o e s n o t e d .

( 5 ) T h e r o l e o f c h l o r i d e c o m p l e x e s i s n o tw e l l u n d e r s t o o d , y e t t h e C l - - p H d i ag r a m sf o r H g - - A u - - T 1 s p e c i e s ( f r o m B a e s a n dM e s m e r , 1 9 7 6 ) s t r o n g l y s u g g e s t t h a t s u c hc o m p l e x e s a r e v e r y i m p o r t a n t f o r t r a n s p o r t o fn o t o n l y H g - -A u - -T 1 , b u t f o r o t h e r e l e m e n t sa s w e l l .cknowledgementsT h a n k s a r e d u e t o D r . C h a r l e s B a e s , a n d


8/8

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J o h n W i l e y S o n s , P u b l i s h e rs , f o r p e r m i s s i o nf o r u s e o f t h e d i a g r a m s s h o w n a s F i g. 2 .B . K a l m a n a s s i s t e d i n t h e c a l c u l a t i o n s , a n dE . S t e w a r t d i d t h e d r a f t i n g o f F i g . 1 .

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029E, 422 pp.Brookins, D.G., 1984. Geochemical Aspects of Radio-active Waste Disposal. Springer, New York, N.Y.,345 pp.Garrels, R.M. and Christ, C.L., 1965. Solutions,Minerals and Equilibria. Harper & Row, NewYork, N.Y., 450 pp.

Ikramuddin, M., Asmeron, Y., Nordstrom, P.M.,Kinart, K.P., Martin, W.M., Digby, S.J.M., Elden,D.N., Nijak, W.F. and Afemari, A.A., 1983.Thallium -- a potential guide to mineral deposits.J. Geochem. Explor., 19: 465--490.Krauskopf, K.B., 1979. Intro duct ion to Geochemis-try. McGraw-Hill, New York, N.Y., 2nd ed.,617 pp.Longmire, P.A., 1983. Geoche mistry, diagenesis andcontaminant transport of uranium tailings, GrantsMineral Belt, New Mexico. M.S. Thesis, Universityof New Mexico, Albuquerque (unpublished).Shaw, D.M., 1952. The geochemistry of thallium.Geochim. Cosmochim. Acta, 2: 118--130.Verink, E.D., 1979. Simplified procedure for con-structing Pourbaix diagrams. J. Educ. ModulesMat. Sci. Eng., 1: 535--560.Voskresenskaya, N.T., 1959. Geoch emistr y of thal-lium and rubidium in igneous rocks. Geochem.Int., 4: 559--565.Wagman, D.D., Evans, W.H., Parker, V.B., Schumm,R.H., Halow, I., Bailey, S.M., Churney, K.L. andNuttall, R.L., 1982. The NBS tables of chemicalthermodynamic properties: selected values for in-organic and C, a nd C2 organic substa nces in SIunits. J. Phys. Chem. Ref. Data, Vol. 11, Suppl. 2,390 pp.

pourbaix diagram of cadmium

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