| With the increasing exhaustion of high-quality zinc ore resources, more and more attention has been paid to the exploitation and utilization of refractory high-silicon zinc ore resources that are widespread in China. Developing the new method of zinc hydrometallurgy process for high-silicon zinc ores has important implications for expanding raw material sources of zinc smelting and improving the level of zinc hydrometallurgy process in our country. Thus, realizing the effective separation of zinc and silicon and exploring the method of solving the problem of filtration difficulty that is brought out by the soluble silicon present in acid leaching slurry of high-silicon zinc ores is one of key research subjects in the field. In order to optimize high-temperature acid conversion environments of the effective separation of zinc and silicon in acidic system and improve the leaching and recovery rate of zinc, this paper starts with H4SiO4that can be simultaneously formed and dissolved into leaching solution with the extraction of zinc from high-silicon zinc ores, focusing on this idea that H4SiO4could be transformed into SiO2before gelation based on the high-temperature thermodynamic properties of H4SiO4in acidic system, using the different kinds of high-silicon zinc ores as the main research objects, the research on the basic theory and adjust technology of high-temperature acid conversion for high-silicon zinc ores has been carried out for solving the problem that is brought out by the liquid-solid separation difficulty of acid leaching slurry obtained from the traditional hydrometallurgical process for extracting zinc from high-silicon zinc ores and for laying the basis for realizing the industrial application of high-silicon zinc ores. The main research work and research results are as follows in this dissertation:(1) The analysis of technological mineralogy on the three different kinds of high-silicon zinc ores (hemimorphite, willemite and high-silicon mixed sulphide-oxide zinc ores) was carried out by means of chemical phase composition, XRD and SEM-EDS. The main mineral phases present in the ore sample of hemimorphite include hemimorphite (44.31%) and quartz (41.41%). The major zinc-bearing phase in the ore sample of willemite is willemite, and the gangue mineral is mainly quartz. There are various minerals in the high-silicon mixed sulphide-oxide zinc ores, and its composition is complex. The major zinc-containing phases in the ore sample are sphalerite and hemimorphite, and the main phase composition of lead is galena and cerussite. The iron from the ore sample is presented mainly with the form of pyrite and troilite. Quartz is the main gangue mineral accompanied with a little calcite and muscovite.(2) The thermodynamic trend of high-temperature acid conversion for high-silicon zinc ores was analyzed. The thermodynamic trend in the chemical reaction involved in hemimorphite and willemite is quite significant under the system of high-temperature acid conversion, and the thermodynamic trend in the chemical reaction of hemimorphite is higher than willemite. The thermodynamic stable region for H4SiO4that can be simultaneously formed during leaching of hemimorphite and willemite becomes smaller and eventually vanishes as temperature increases. However, the thermodynamic stable region for SiO2formed by the transformation of H4SiO4increases with the increase of temperature. Higher temperatures may be helpful for turning H4SiO4into SiO2. Thermodynamically, H4SiO4is transformed spontaneously into SiO2under the influence of the temperature field of above392K. The thermodynamic stable region for SiO2becomes larger as the activity of the solute silicon increases, and SiO2present in the high-temperature aqueous solution is stable in a broad range of E-pH. Improving the activity of the solute silicon and temperature will make the conversion of H4SiO4into SiO2easier to occur.(3) The kinetics mechanism of high-temperature acid conversion process was investigated for high-silicon zinc ores. The high-temperature acid conversion reaction of hemimorphite followed a shrinking core model with "ash" layer diffusion as the main rate-controlling step. The apparent activation energy was determined to be44.9kJ/mol. The high-temperature acid conversion process of pure willemite was well interpreted by the grain model with product layer diffusion as the main rate-controlling step and the shrinking core model was used to represent the reaction of each grain. The apparent activation energy was found to be22.06kJ/mol. The total rate of zinc extraction was controlled by solid-state diffusion during high-temperature acid conversion of hemimorphite and willemite. Under the system of high-temperature acid conversion, hemimorphite and willemite broke down quickly and liberated zinc and soluble silicon, and then the soluble silicon entering the solution in the form of H4SiO4was transformed into SIO2precipitation under the influence of the temperature field of393K. The formation of silicon dioxide precipitation having excellent filtration property greatly improved the separative performance of liquid-solid from slurry, and realized the effective separation of zinc and silicon during high-temperature acid conversion of high-silicon zinc ores.(4) The high-temperature acid conversion behavior of high-silicon zinc ores was studied. The soluble silicon in the ore sample of high-silicon zinc ores exists as hemimorphite and willemite and can be simultaneously dissolved in H4SiO4form with the extraction of zinc from high-silicon zinc ores. The main factor influencing the conversion of H4SiO4into SiO2precipitation is temperature. The result for turning H4SiO4into SiO2precipitation is best when investigating at the temperature ranging from413to433K. Under the optimum conditions, the extraction of zinc from the different kinds of high-silicon zinc ores was above97%, and the iron and silica concentrated in the conversion product. The controlled extraction of zinc would be realized based on the said conditions. The high-temperature acid conversion technology is an effective method for the treatment of high-silicon zinc ores.(5) The countercurrent circulating leaching and zinc concentration experiments of multicomponent solution were carried out under the system of high-temperature acid conversion. On the basis, the migration enrichment of zinc, iron and silica in leaching solution and their distributing law were discussed. Through the countercurrent circulating leaching experiments that experienced4cycles under the said system, the zinc concentration of leaching solution got the maximum enrichment, and the zinc content reached to125.62g/L. The change in the concentration of iron and silica was not obvious, and the contents of iron and silica were about0.5g/L in leaching solution. Meantime, the leaching slurry having excellent filtration property was obtained. |
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