| Zinc ferrite of excellent performance, versatility, large market demand is synthesized by pure compounds. High costs, complex process and small production limit the application and large-scale production of zinc ferrite. It is urgent to research and develop a new technology of industrial application value of zinc ferrite preparation. Zinc resources are rich in our country, zinc sulfide concentrates with iron in the traditional wet process inevitably generate zinc ferrite and it exits in the leaching slag. Zinc ferrite was being destructed to recover zinc and iron resources.The destruction of zinc ferrite is characterized by complex process, high energy and material consumption, difficult treatment of iron slag, difficult recovery of valuable metals and serious environmental pollution.Zinc calcine with 53.22% zinc and 14.20% iron obtained in a smelter in Guangxi was studied and zinc ferrite in the hydrometallurgy was separated as a separate product. Sulfuric acid leaching was used in this paper.The influence of sulfuric acid concentration, liquid to solid ratio, leaching temperature, stirring speed and leaching time on the leaching of zinc and iron was investigated. The optimum condition of zinc ferrite preparation was obtained through sulfuric acid leaching by comparing the dissolution rule of pure zinc ferrite and zinc ferrite in zinc calcine. The X-fluorescence, X-ray diffraction, chemical analysis were used to study the leaching residue. The main conclusions were as follows:(1) The acid consumption of zinc oxide in zinc calcine is fit to the metrological relation of chemical equation.35 g of sulfuric acid is enough to dissolve all the zinc oxide in 50 g of zinc calcine, zinc oxide has priority over iron minerals in acid consumption. It consumes almost all of the acid when the acid amount is less than the theoretical acid consumption of zinc oxide while iron minerals hardly consume acid. Only sulfuric acid amount exceed the theoretical acid consumption of zinc oxide and zinc oxide was dissolved all did iron minerals consume the remaining sulfuric acid and the leaching rate of iron increases with the increasing of the remaining amount of sulfuric acid.(2) The effect of liquid to solid ratio on the leaching of zinc and iron, in essence, is the influence of dosage of sulfuric acid. Stirring speed impacts the leaching velocities and has little influence on the leaching rate of zinc and iron. The effect of leaching temperature on the leaching of zinc and iron related to the amount of sulfuric acid. The leaching rate of zinc and iron are low when sulfuric acid is inadequate, while it is increase with the increasing of leaching temperature with sufficient amount of sulfuric acid, and it is more obvious with iron.(3) The effect of leaching time on the leaching rate of zinc and iron also related to the dosage of sulfuric acid. The leaching rate of zinc increases with the leaching time and the leaching rate of iron is under 1% when the sulfuric acid is inadequate. The leaching rate of zinc changed little with the increasing of leaching time while the leaching rate of iron increased significantly.(4) From the mineral dissolution order, zinc oxide primarily dissolved when the concentration of sulfuric acid is less than 120 g/L, showing as the obviously disappeared of ZnO diffraction peaks, and the diffraction peaks of iron minerals changed little. Fe2O3 and Zn2SiO4 dissolved mainly at 120g/L to 160g/L sulfuric acid concentration,showing as the apparent disappearance of diffraction peaks of Fe2O3 and Zn2SiO4 Zinc ferrite dissolved obviously when the sulfuric acid concentration is greater than 200 g/L and the diffraction peaks of zinc ferrite weakened in XRD patterns.(5) The solubility of zinc in pure zinc ferrite approximately varied linearly with sulfuric acid concentration and leaching temperature. It is increased significantly when the sulfuric acid concentration was less than 200 g/L while it changed small over 200 g/L. The solubility of zinc in pure zinc ferrite changed slowly with the increasing of leaching temperature under 55℃, while it is increased significantly with the increasing of temperature when the temperature is higher than 55℃.(6) Zinc ferrite dissolves little at different acidities and temperatures when the leaching time is 5 min to 30 min. Zinc ferrite began to dissolve when the sulfuric acid concentration was greater than 200 g/L and the leaching temperature reached 75℃ for 60 min to 90 min or the sulfuric acid concentration was over 120 g/L and the leaching temperature reached 75℃for 120 min to 180 mm.(7) The optimum conditions for the preparation of zinc ferrite from zinc calcine by sulfuric acid leaching is that the liquid to solid ratio of 7, stirring speed of 400rpm, the sulfuric acid concentration of 120 g/L to 160 g/L, the leaching temperature of 75℃ to 85℃ for 120 min to 180 min.(8) It can obtain 83% to 86% of zinc ferrite under optimal conditions. It still needed to further separation and purification in the presence of mineral impurities such as quartz, anglesite, hematite and arcanite.In summary, according to the present situation of zinc leaching residue treatment at home and abroad, zinc ferrite from zinc leaching residue was separated as an independent product and studied its appropriate application in accordance with its nature, opened up the new utilize models of zinc ferrite byproduct of zinc hydrometallurgy. The experiment study has a certain innovation and the academic value.The results has certain practical significance for both the comprehensive utilization of resources and the sustainable development. |
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