The Analysis of Fe Behavior in Zinc Pressure Leaching
881
Iron Precipitation as Hematite During Oxygen Pressure
Leaching
During the pressure leaching, when the temperature of Fe 2 O 3 –SO 3 –H 2 O system is
50 °C, relatively stable goethite (α-FeOOH) starts to exist in the system. When the
temperature is increased to 120 °C, Fe 2 O 3 is precipitated out of the solution, and the
stability of Fe 2 O 3 phase is gradually improved with the increased temperature [4].
Moreover, goethite and jarosite will generate Fe 2 O 3 from the hydrolysis reaction with
the increased temperature. The reaction formula of iron precipitation as hematite is
presented as follows:
2Fe
2+
+ 0.5O 2 + 2H 2 O → Fe 2 O 3 + 4H
−
(9)
2Fe
3+
+ 3H 2 O → Fe 2 O 3 + 6H
+
(10)
At high temperature, α-FeOOH hydrolysis reaction formula is as follows:
2α − FeOOH → Fe 2 O 3 ↓ +H 2 O
(11)
At high temperature, jarosite hydrolysis reaction formula is as follows:
A 2 Fe 6 (SO 4 ) 4 (OH) 12 → 3Fe 2 O 3 ↓ +2A
+
+ 6H
+
+ 4SO
2−
4 + 3H 2 O
(12)
In the autoclave, when the temperature reaches 140 °C and the solution contains
less than 15 g/l acid, the iron is precipitated mostly as jarosite and goethite with
some hematite. With the increase of temperature in the autoclave, hematite increases
continuously, and at 155 °C or higher, iron is precipitated mainly as hematite [5].
Conclusions
(1) Analysis is made of the behavior of Fe in the oxygen pressure leaching
process of zinc sulfide concentrate under different control conditions of the
autoclave to provide a reasonable process selection reference and theoretical
basis for different comprehensive recovery requirements of various zinc sulfide
concentrates.
(2) The behavior of iron during oxygen pressure leaching is theoretically analyzed.
When the pressure, temperature, and final acid in the primary oxygen pressure
leaching is controlled at 11 kPa, 150 °C, and 10 g/l, respectively, the iron is precipitated as jarosite into the residue mainly with some precipitated as hematite.
Moreover, a small amount of iron is precipitated as goethite into the residue.
When the pressure, temperature, and the final acid of primary oxygen pressure
leaching is controlled at 4.5 kPa, 110 °C, and 10 g/l–15 g/l, respectively, most
881
Iron Precipitation as Hematite During Oxygen Pressure
Leaching
During the pressure leaching, when the temperature of Fe 2 O 3 –SO 3 –H 2 O system is
50 °C, relatively stable goethite (α-FeOOH) starts to exist in the system. When the
temperature is increased to 120 °C, Fe 2 O 3 is precipitated out of the solution, and the
stability of Fe 2 O 3 phase is gradually improved with the increased temperature [4].
Moreover, goethite and jarosite will generate Fe 2 O 3 from the hydrolysis reaction with
the increased temperature. The reaction formula of iron precipitation as hematite is
presented as follows:
2Fe
2+
+ 0.5O 2 + 2H 2 O → Fe 2 O 3 + 4H
−
(9)
2Fe
3+
+ 3H 2 O → Fe 2 O 3 + 6H
+
(10)
At high temperature, α-FeOOH hydrolysis reaction formula is as follows:
2α − FeOOH → Fe 2 O 3 ↓ +H 2 O
(11)
At high temperature, jarosite hydrolysis reaction formula is as follows:
A 2 Fe 6 (SO 4 ) 4 (OH) 12 → 3Fe 2 O 3 ↓ +2A
+
+ 6H
+
+ 4SO
2−
4 + 3H 2 O
(12)
In the autoclave, when the temperature reaches 140 °C and the solution contains
less than 15 g/l acid, the iron is precipitated mostly as jarosite and goethite with
some hematite. With the increase of temperature in the autoclave, hematite increases
continuously, and at 155 °C or higher, iron is precipitated mainly as hematite [5].
Conclusions
(1) Analysis is made of the behavior of Fe in the oxygen pressure leaching
process of zinc sulfide concentrate under different control conditions of the
autoclave to provide a reasonable process selection reference and theoretical
basis for different comprehensive recovery requirements of various zinc sulfide
concentrates.
(2) The behavior of iron during oxygen pressure leaching is theoretically analyzed.
When the pressure, temperature, and final acid in the primary oxygen pressure
leaching is controlled at 11 kPa, 150 °C, and 10 g/l, respectively, the iron is precipitated as jarosite into the residue mainly with some precipitated as hematite.
Moreover, a small amount of iron is precipitated as goethite into the residue.
When the pressure, temperature, and the final acid of primary oxygen pressure
leaching is controlled at 4.5 kPa, 110 °C, and 10 g/l–15 g/l, respectively, most