-
5/24/2018 Pourbaix Diagram of Cadmium
1/8
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
-
5/24/2018 Pourbaix Diagram of Cadmium
2/8
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).
-
5/24/2018 Pourbaix Diagram of Cadmium
3/8
273
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
-
5/24/2018 Pourbaix Diagram of Cadmium
4/8
bO
.
+1.3~
i
Sb205
~
0.5I
EhV) -0.
5
Sb204
O.OL
~b(OH)3
SbZS
0.9
I
~
I
0
2
4
6 pHI
I
1
Amo
@
2CbP
I
I
8
I0
1
1
Eh+13
I
I
I
I
[
I
Asc
,~
25C,1borP
43As04
z
H2As
04
v)A,~
HA~O~-
0
2
4
6
8
I0
1
pH~
1
-
5/24/2018 Pourbaix Diagram of Cadmium
5/8
1.3
+1.0
+0.5
EhV)
0.0
-0.5
l
~
~Cadmium
~
.
2,.5CIbarP
~
_
/
TOH3
-8 0
2
4
6
8
t0
pH
2
,7 ~
-4
0
6
8 0
/H Au
OH)2Cl
OI
2
4
6
8
I
pH
AO
I 12
-1 Ob
-2
-
4 -6
\HG/
HgCL
~,~
H9OH)2
HgCI+ Fg
2 I 2
q
12
~
-2040
-6
/~~AOH3C
/o~/0/
AOH3
~-AO2C
8
8
I
I
t
I
I
I
=
I
I
I
2
4
6
8
1
0
4
6
8
1
1
1
pH
pH
,@
12
t4
Fg2C
aopHdaamopohoownsyem
omBaMem1
eo
whpmsoseo
da
ATCOH
BHCOH
CACOH
-
5/24/2018 Pourbaix Diagram of Cadmium
7/8
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
-
5/24/2018 Pourbaix Diagram of Cadmium
8/8
278
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 .
e f e r e n c e sBaes, C.F. and Mesmer, R.E., 1976. The
Hydrolysisof Cations. Wiley--In terscienc e, New York, N.Y.,325
pp.Boyle, R.W. and Jonasson, I.R., 1984. The geo-chemistry of
antimony and its use as an indicatorelement in geochemical
prospecting. J. GeochemExplor., 20: 223--302.Brookins, D.G., 1978.
Eh--pH diagrams for elementsfrom Z = 40 to Z = 52: applicatio n to
the Oklonatural reactor, Gabon. Chem. Geol., 23: 324--243.Brookins,
D.G., 1979. Uran ium deposits of theGrants, New Mexico mineral belt
(II). U.S. Dep.Energy, Washington, D.C., Rep. BFEC-GJO-76-
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.