In a closed vessel, the solubility of oxygen in water varies with pressure and temperature, as shown in Figures 8 and 9. The hot-pressure oxygen leaching of sulfide minerals is an electrochemical reaction mechanism. When the oxygen pressure is small, the leaching speed is almost linear with the oxygen pressure; when the oxygen pressure is high, the leaching speed is independent of the oxygen pressure; when the oxygen pressure is moderate (0.5-2.5 MPa) The leaching speed is parabolic with oxygen pressure. The pH value of the slurry has little effect on the leaching speed, but the ammonia concentration has a great influence on the ammonia leaching. As can be seen from Fig. 8, the solubility of oxygen in the ammonia solution increases with the increase of the ammonia concentration. Tests have shown that increasing the concentration of ammonia accelerates the dissolution of nickel . When the leaching temperature is greater than 120 ° C, the molten sulfur can enclose the sulfide ore particles and hinder the dissolution of the sulfide minerals. Thus, sulfur leaching material (e.g., multi-metal matte), using the working temperature of 180 ~ 200 ℃. When leaching high-sulfur materials (mineral materials), it is preferable to use an operating temperature of 110 to 115 °C. The temperature of ammonia leaching is usually 70 ~ 80 ° C.
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Oxygen may be processed hot leaching oxide ores and sulfide waste containing pyrite, it may be carried out in the acid or ammonia in solution:
A hot acid leaching oxygen leaching a sulfide ore sphalerite: leaching conditions of 110 ~ 120 ℃, P o2 = 0.14 MPa, and a particle size of less than 325 mesh, 2 to 4 hours, the leaching rate of 99% was electric immersion electrowinning Zinc, the waste electrolyte returns to leaching.
Chalcopyrite: Leaching conditions are 110-120 ° C, P o2 = 1.4-3.54 MPa, and particle size is less than 325 mesh.
Further leaching nickel-cobalt sulfide ore, galena, copper-zinc sulfide ores, nickel matte like.
When low temperature hot pressed oxyacid leaching sulfide ore, some elemental sulfur can be recovered by flotation or screening.
b Acid-free leaching of pyrite containing pyrite The pyrite is oxidized to ferric sulfate, then hydrolyzed to iron oxide and sulfuric acid, and the precipitated sulfuric acid can leach other metal oxide ore. Soft manganese ore leaching reaction is:
2FeS 2 +7O 2 +2H 2 O=2FeSO 4 +2H 2 SO 4
MnO 2 +2FeSO 4 +2H 2 SO 4 =MnSO 4 +Fe 2 (SO 4 ) 3
+2H 2 O
c The reaction of preparing elemental sulfur from pyrite to produce elemental sulfur is:
The iron sulfide or pyrrhotite obtained by thermally decomposing pyrite is slurried in a dilute acid of pH=1.0, and leached at 110 ° C, P o2 =1.01 MPa for 4 hours, and the iron oxide slag has a high iron content. Can be sent to iron making.
B Ammonia leaching hot oxygen when hot oxygen ammonia leaching, where the soluble metal complexes with ammonia are generated into the solution, but the leaching rate of cobalt, platinum group metals and partitioned immersion leached. Therefore, hot pressed oxy ammonia leaching should treat mineral raw materials with a cobalt content of less than 3% and a low platinum group metal content. The ammonia leaching reaction is:
When the pH is high, a large amount of sulfur is always oxidized to sulfate. The test shows that the oxidation order of sulfide minerals is: Cu 2 S>CuS at 120 ° C, P o2 =1.01 MPa, [NH 3 ] is 1 mol [r], and ammonium sulfate concentration is 0.5 mol [r]. Cu 3 FeS 3 >CuFeS 2 >Pbs>Fes>FeS 2 >ZnS.
The ammonia concentration should be strictly controlled during ammonia leaching, otherwise it will easily form insoluble high ammonia complex, such as [Co(NH 3 ) 6 ] 2+ . This process has been successfully used to treat Ni-Cu-Co sulfide ore in 1953. Leaching at 70-80 ° C, air P = 0.456 ~ 0.659 MPa for 20 ~ 24 hours, the final output of nickel powder, drilling powder, copper sulfide and ammonium sulfate and other products. In addition, mineral raw materials such as chalcopyrite, galena and copper-zinc ore can be processed.
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