The Analysis of Fe Behavior in Zinc Pressure Leaching
879
In the process of oxygen pressure leaching of zinc sulfide concentrate, the iron
reported to the solution in the secondary oxygen pressure leaching returns to the
primary oxygen pressure leaching. The iron can be selectively retained in the solution
or precipitated into the residue. By controlling the conditions of the primary oxygen
pressure leaching in the autoclave, the iron is mainly precipitated in three forms:
namely as goethite, jarosite, and hematite. When the iron is precipitated into the
residue, the siderophiles like gallium, germanium, and indium will also report to the
residue with the precipitation of Fe.
Iron Precipitation as Goethite During Oxygen Pressure
Leaching
In the Fe 2 O 3 –SO 3 –H 2 O system, the control temperature of iron precipitation as
goethite is generally above 90 °C, and the high temperature is favorable for accelerating the iron precipitation speed and increasing the iron precipitation rate. In primary
oxygen pressure leaching, some goethite will be precipitated under the controlled
acidity [1, 2]. The reaction formula is as follows:
Fe
2+
+ H 2 O + 0.5O 2 → FeOOH ↓ +2H
+
(4)
Fe
3+
+ 2H 2 O → FeOOH ↓ +3H
+
(5)
Normally, the formation of goethite requires a lower acidity, and the formation
of the stable goethite requires the pH value of >2. Therefore, the goethite formation
reaction is not the main reaction of iron precipitation in autoclave during oxygen
pressure leaching of zinc sulfide concentrate.
Iron Precipitation as Jarosite During Oxygen Pressure
Leaching
Under certain temperature, acidity, and in the presence of monovalent cation (A
+ ),
ferric ions in the sulfuric acid system will form the jarosite minerals [3]. The reaction
formula for the formation of jarosite is as follows:
Fe
3+
+ H 2 O + SO 4
2−
→ Fe(OH)SO 4 + H
+
(6)
2Fe(OH)SO 4 + 2H 2 O → Fe 2 (OH) 4 SO 4 + 2H
+
+ SO 4
2−
(7)
879
In the process of oxygen pressure leaching of zinc sulfide concentrate, the iron
reported to the solution in the secondary oxygen pressure leaching returns to the
primary oxygen pressure leaching. The iron can be selectively retained in the solution
or precipitated into the residue. By controlling the conditions of the primary oxygen
pressure leaching in the autoclave, the iron is mainly precipitated in three forms:
namely as goethite, jarosite, and hematite. When the iron is precipitated into the
residue, the siderophiles like gallium, germanium, and indium will also report to the
residue with the precipitation of Fe.
Iron Precipitation as Goethite During Oxygen Pressure
Leaching
In the Fe 2 O 3 –SO 3 –H 2 O system, the control temperature of iron precipitation as
goethite is generally above 90 °C, and the high temperature is favorable for accelerating the iron precipitation speed and increasing the iron precipitation rate. In primary
oxygen pressure leaching, some goethite will be precipitated under the controlled
acidity [1, 2]. The reaction formula is as follows:
Fe
2+
+ H 2 O + 0.5O 2 → FeOOH ↓ +2H
+
(4)
Fe
3+
+ 2H 2 O → FeOOH ↓ +3H
+
(5)
Normally, the formation of goethite requires a lower acidity, and the formation
of the stable goethite requires the pH value of >2. Therefore, the goethite formation
reaction is not the main reaction of iron precipitation in autoclave during oxygen
pressure leaching of zinc sulfide concentrate.
Iron Precipitation as Jarosite During Oxygen Pressure
Leaching
Under certain temperature, acidity, and in the presence of monovalent cation (A
+ ),
ferric ions in the sulfuric acid system will form the jarosite minerals [3]. The reaction
formula for the formation of jarosite is as follows:
Fe
3+
+ H 2 O + SO 4
2−
→ Fe(OH)SO 4 + H
+
(6)
2Fe(OH)SO 4 + 2H 2 O → Fe 2 (OH) 4 SO 4 + 2H
+
+ SO 4
2−
(7)