| Our country has abundant resources of zinc mineral. However, with rapid development of our national economy in recent decades, the resources of zinc sulfide and high grade zinc oxide ore have been increasingly depleted. Low grade zinc oxide ore and sulfur oxygen mixed zinc ore have gradually become the main raw material for zinc smelting. At present, as a result of technique and economic, most of that has been storage or non-mined. It has become an important project to utilize it economically and rationally. In this paper, therefore, the low grade zinc oxide ore and the sulfur oxygen mixed zinc ore was treated by mineral transformation and leaching.Firstly, low grade zinc oxide ore and sulfur oxygen mixed zinc ore with lower alkali gangue was treated by concentrated sulfuric acid curing method for phase transformation. The zinc silicate Zn4Si2O7(OH)2-H2O was transformed into SiO2 particles and ZnSO4 after cured. The results can effectively realize the liquid-solid separation. At the same time, based on the high oxidation property of concentrated sulfuric acid, ZnS was directly oxidized and dissolved into the solution. By drawing the phase equilibrium diagram of Zn-S-H-O and Si-O-H systems, the feasibility and critical value of Zn4Si2O7(OH)2-H2O transformation into SiO2 were expounded theoretically. Low grade zinc oxide ore was treated by concentrated sulfuric acid curing method. The result indicated that, in curing stage, with the decrease of the water content in the mineral, i.e., the increase of the concentration of sulfuric acid, the leaching rate of zinc and iron dissolution rate first increased and then decreased. The dissolution rate of the silicon decreased gradually, and finally remained at about 0.5%; with the increase of the amount of sulfuric acid, the leaching rate of zinc and iron was increased, while the silicon dissolution rate decreased gradually. Zinc recovery can reach 98%, iron dissolution rate was 43% and silicon dissolution was only 0.56%. Under the conditions: curing at room temperature, sulfuric acid content was 1288.00kg/t, containing 50% water, curing for 3h, and during water leaching period liquid-solid of 5:1mL/g, temperature of 50℃, stirring speed of 400rpm, leaching for 3h. The silica gel can be effectively avoided. Sulfur oxygen mixing zinc ore also treated by concentrated sulfuric acid curing. The study showed that the amount of sulfuric acid, water content in mineral and curing temperature on zinc leaching rate have obvious effects in curing stage. The adding way of oxidant H2O2 and mechanical activation had a certain impacts on the leaching rate of zinc. In curing period, dosage of sulfuric acid of 1204kg/t, sulfate concentration was 98%, curing at temperature was 300 ℃ for 3h and during water leaching, liquid to solid ratio of 5:1mL/g, at temperature of 50℃, stirring speed of 400rpm, leaching for 3h, zinc leaching rate can reach 90% and silica gel can be also avoided.Secondly, as for the sulfur oxygen mixed zinc ore with high alkali gangue was treated by low temperature roasting method for phase transformation. According to its characteristics, the sphalerite and hemimorphite in the ore were transformed into ZnO, and the sulfur was fixed as CaSO4 by CaCO3 contained in the ore after oxidation roasted process at lower temperatures. The results indicated that, at the calcination temperature at 300℃, the calcine was leached in ammonia-sulfate solution. When the total ammonia concentration was 8.0mol/L, leaching temperature of 35℃, liquid to solid ratio of 10:1, stirring speed of 450rpm, zinc leaching rate can reach 75%. It was obviously higher than the leaching rate of 52% which was directly leached. At the same time, the emission of SO2 in the roasting could be eliminated and the formation of silica gel in the leaching was thoroughly avoided. |
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