Hydrothermal Acid Conversion And Silicon Precipitation Behavior Of High Silicon - Zinc Deposits

High silica zinc ore is an important resource to extract zinc, soluble silicon in hemimorphite and willemite is easy to form a large number of colloidal silica during conventional zinc hydrometallurgy process, which seriously affects the filter property of leaching pulp and increase the loss of zinc. Previous research work has showed that silicic acid can readily transform into easily filtered silica precipitate by hydrothermal acid conversion technology.This thesis mainly researches on the hydrothermal acid conversion experiment of pure silicate zinc ore, the influence factors of filter property of leaching pulp, and the polymerization precipitation behavior of silica under hydrothermal acid conversion process. The conclusions as follows:(1) The hydrothermal acid conversion experiments of pure hemimorphite and willemite indicate that:under temperature of 120 ℃, liquid-solid ratio of 10, sulfuric acid concentration of 0.83 mol/L, average particle size of 55 μm, stirring speed of 600 rpm and leaching time 30 min, the zinc leaching rate of pure hemimorphite is over 96% and silica conversion rate is above 92%, the leach residue is amorphous; under temperature of 120 ℃, liquid-solid ratio of 10, sulfuric acid concentration of 0.88 mol/L, average particle size of 55μm, stirring speed of 600 rpm and leaching time 30 min, the zinc leaching rate of pure willemite is greater than 99% and silica conversion approximate 92%, tridymite is the main phase with cristobalite and keatite as secondary phases in the silica precipitate.(2) The hydrothermal acid conversion technology can obtain the filterable pulp, and the structural morphology of silica colloidal particle in liquid phase is the main factor on filtration property of pulp. Temperature and pH are important for filtration property of pulp, elevating temperature can enhance the polymerization reaction of silica and change the structural morphology of silica in liquid phase; adjusting the pH of pulp can exacerbate the depolymerization of silica in liquid phase to improve the filtration property of pulp. The optimum amount of sulfuric acid should be controlled at 0.9 to 1.1 times of the theoretical value of mineral reaction, and the final point pH should be about 3.(3) The researches on polymerization rate and supersaturation of silica show that the polymerization and precipitation rates of silica increase first and then decrease. Combined with TEM detection and analysis, the mechanism of soluble silicon transformation into precipitation is the compact arrangement of nucleation inside to facilitate silica colloidal particles forming a dense and reticular macromolecular structure. At the same time, supersaturation of silica, temperature and pressure of system are important factors on the crystal transition of silica.The hydrothermal acid conversion technology of high silicon zinc ore can efficiently extract of zinc and separate of zinc and silicon, overcoming the treatment problem of soluble silicon.