293
A)
B)
Eh-pH Diagram of Copper Species
Eh-pH Diagram of Iron Species
1.2
1.2
2
H
Fe2+
2O
0.4
(Fe2+ +S)
0.4
GOETHITE
(FeOOH)
Eh
Cu2(OH)2CO3
O
Cu3 (OH)4 SO4
0.8
25o C
1 atm
S CO2 =
10-3
S S = 10-1
Cu4 (OH)6 SO4
CuSO4. 5 H2O
JAROSITE
KFe3 (SO4)2(OH)6
0.8
25o C
1 atm
Fe3+
O
2
H
2O
CuO
Eh
(FeS2 +S)
CuS
Cu2O
0.0
0.0
(Fe3 O4)
FeS 2
Cuo
(Fe2+ +H2S)
- 0.4
- 0.4
Cu2S
H
2O
H
2O
H
H
2
2
FeS
From Lopez and Titley (1995)
From B.B. Hunshaw in Schmitt (1963)
- 0.8
- 0.8
0
2
4
6
8
pH
10
12
14
0
2
4
6
8
10
12
14
pH
FIGURE 59a. Stability relations among some iron compounds in water at 25oC and 1
atmosphere total pressure. Modified from Lopez and Titley (1995). The figure shows
the leaching environment at relatively high Eh and low pH in the northwest quadrant of
the diagram where T. ferrooxidans catalyze dissolution reactions by converting ferrous
ion into ferric ion.
FIGURE 59b. Stability relations among some copper compounds in water at 25oC and 1
atmosphere total pressure. Modified from B.B. Hunshaw in Schmitt (1963). The figure
shows the leaching environment at relatively high Eh and low pH in the northwest
quadrant of the diagram where ferric dissolution of chalcocite and covellite results in
soluble copper sulfate. Subsequent enrichment of pyrite and chalcopyrite below the
water table would occur in the southwest quadrant of the diagram.