878
L. Chen
Mechanism of Oxygen Pressure Leaching of Zinc and Iron
from Zinc Sulfide Concentrate
Oxygen pressure leaching of zinc sulfide concentrate is an intensive leaching process. Currently, the pressure leaching of Zn sulfide concentrate is mainly based on
the two-stage countercurrent pressure leaching. In primary pressure leaching, different reaction conditions are controlled based on different raw material composition. The leaching pressure, temperature, and final acid of sulfide concentrate rich
in siderophiles such as gallium, germanium, and indium are controlled at 4.5 kPa,
110 °C, and 15 g/l, respectively, while the leaching pressure, temperature, and final
acid of sulfide concentrate free of siderophiles is controlled at 11 kPa, 150 °C, and
10 g/l, respectively. In the secondary pressure leaching, the leaching pressure is basically controlled at 11 kPa, the temperature is controlled at 150 °C, and the final acid
is controlled at 50–70 g/l.
Zinc sulfide concentrate reacts in the autoclave under given temperature, acidity,
and partial pressure of oxygen. The sulfur in the concentrate as sulfide is oxidized
into elemental sulfur and goes to the leached residue. In the Secondary leaching
process, most of zinc and Fe in the sulfide concentrate as ZnS·FeS and Fe 7 S 8 as
well as the scattered metals like gallium, germanium, indium, and copper can be
dissolved out of sulfide concentrate, and will go to the leachate as soluble sulphate,
before going back in countercurrent way to the primary oxygen pressure leaching,
while only little pyrite (FeS 2 ) and chalcopyrite (CuFeS 2 ) can be dissolved. The main
chemical reaction formulas of oxygen pressure leaching of zinc sulfide concentrate
are as follows:
ZnS · FeS + 4H
+
+ O2 → Zn
2+
+ Fe
2+
+ 2H 2 O + 2S
0
↓
(1)
2Fe 7 S 8 + 42H
+
+ 11.5O 2 → 14Fe
3+
+ 21H 2 O + 16S
0
↓
(2)
ZnS · FeS + 2Fe
3+
→ Zn
2+
+ 3Fe
2+
+ 2S
0
↓
(3)
During the reaction, iron acts as a medium to transfer oxygen and promotes the
reaction. Meanwhile, gallium, germanium, and indium are simultaneously leached
into the solution.
Analysis of Fe Behavior Under Different Oxygen Pressure
Leaching Conditions
Iron ions are stable only under high acid, while under certain acidity and temperature,
iron is liable to combine with water or other ions in water to generate precipitation.
L. Chen
Mechanism of Oxygen Pressure Leaching of Zinc and Iron
from Zinc Sulfide Concentrate
Oxygen pressure leaching of zinc sulfide concentrate is an intensive leaching process. Currently, the pressure leaching of Zn sulfide concentrate is mainly based on
the two-stage countercurrent pressure leaching. In primary pressure leaching, different reaction conditions are controlled based on different raw material composition. The leaching pressure, temperature, and final acid of sulfide concentrate rich
in siderophiles such as gallium, germanium, and indium are controlled at 4.5 kPa,
110 °C, and 15 g/l, respectively, while the leaching pressure, temperature, and final
acid of sulfide concentrate free of siderophiles is controlled at 11 kPa, 150 °C, and
10 g/l, respectively. In the secondary pressure leaching, the leaching pressure is basically controlled at 11 kPa, the temperature is controlled at 150 °C, and the final acid
is controlled at 50–70 g/l.
Zinc sulfide concentrate reacts in the autoclave under given temperature, acidity,
and partial pressure of oxygen. The sulfur in the concentrate as sulfide is oxidized
into elemental sulfur and goes to the leached residue. In the Secondary leaching
process, most of zinc and Fe in the sulfide concentrate as ZnS·FeS and Fe 7 S 8 as
well as the scattered metals like gallium, germanium, indium, and copper can be
dissolved out of sulfide concentrate, and will go to the leachate as soluble sulphate,
before going back in countercurrent way to the primary oxygen pressure leaching,
while only little pyrite (FeS 2 ) and chalcopyrite (CuFeS 2 ) can be dissolved. The main
chemical reaction formulas of oxygen pressure leaching of zinc sulfide concentrate
are as follows:
ZnS · FeS + 4H
+
+ O2 → Zn
2+
+ Fe
2+
+ 2H 2 O + 2S
0
↓
(1)
2Fe 7 S 8 + 42H
+
+ 11.5O 2 → 14Fe
3+
+ 21H 2 O + 16S
0
↓
(2)
ZnS · FeS + 2Fe
3+
→ Zn
2+
+ 3Fe
2+
+ 2S
0
↓
(3)
During the reaction, iron acts as a medium to transfer oxygen and promotes the
reaction. Meanwhile, gallium, germanium, and indium are simultaneously leached
into the solution.
Analysis of Fe Behavior Under Different Oxygen Pressure
Leaching Conditions
Iron ions are stable only under high acid, while under certain acidity and temperature,
iron is liable to combine with water or other ions in water to generate precipitation.