Zinc Oxide Mineral Alkali Extraction Of New Technology Research,

With the increasing shortage of Zinc sulfide ore, Zinc oxide resources are gradually developed and utilized. Aiming at the status that hemimorphite in Zinc oxide mine is difficult to deal with, we proposed a new alkaline process to treat hemimorphite, and carried out systematic conditions and theoretical studies. The specific contents are as follows:1). Drawed the lgC-pH diagram of Zn-Si-H2O system, and analized the thermodynamic conditions with caustic soda to treat hemimorphite. We can learn that in alkaline leaching process of hemimorphite, Zn and silicon entered into solution with Zn (OH)42- and H2SiO42- respectively. We also studied its dynamics mechanism, and determined its activation energy E= 45.7 kJ/mol, the reaction order n= 1.4, which showed that the leaching process was controlled by chemical reaction.2). Designed the process flow with Alkaline to treat low-silicon hemimorphite. First of all, extract Zn in alkali solution from low-silicon hemimorphite in a hot ball mill reactor. In order to control the leaching of SiO2, CaO was added into NaOH solution during the leaching process. When CaO dosage is 1 time of the theoretical quantity, temperature is 110℃, NaOH concentration is 4.5 mol/L, liquid-solid ratio (L/S) is 10:1 and leaching time is 1h, the recovery of Zn is 93%, but the decomposition rate of SiO2 is only 7.3%. And then, add the solid Na2S into leaching solution, in which the ion of S2- and ZnO22- will be formed as the precipitation ZnS, and the ion of Na+ will be formed as NaOH combined with OH-. When the reaction temperature is 60℃, the molar ratio of S to Zn is 0.95:1 and the reaction time is 15 minutes, the precipitation rate of Zn is 93%.The mother liquor after Zn precipitation will be sent to leach Zn again. When the CaO dosage is 1.25 times of the theoretical quantity, temperature is 110℃, NaOH concentration is 5 mol/L, liquid-solid ratio (L/S) is 10:1 and leaching time is 1h, the recovery of Zn remains around 91%, but other elements are not accumulated during the leaching process.3). Planed the process of Zn alkali extraction from high-silicon hemimorphite. Firstly, extract Zn in alkali solution from high-silicon hemimorphite in a hot ball mill reactor. When the reaction temperature is 130℃, NaOH concentration is 8 mol/L, liquid-solid ratio (L/S) is 8:1 and leaching time is 1h, the recovery of Zn is 95% and the decomposition rate of SiO2 is 64%. Then add the solid Na2S into leaching solution. When the reaction temperature is 60℃, the molar ratio of S to Zn is 0.98:1 and the reaction time is 15 minutes, the precipitation rate of Zn is 95%. After that, add the solid CaO into the mother liquor. When the reaction temperature is 60℃, CaO dosage is 1.5 times of the theoretical quantity and the reaction time is 1 h, the desilication rate is 96% The desilicated mother liquor will be sent to leach Zn again. When the reaction temperature is 130℃, NaOH concentration is 8.5mol/L, liquid-solid ratio (L/S) is 8:1 and leaching time is 1h, the recovery of Zn remains about 93%, but other elements are not accumulated during the leaching process.