China Nonferrous Metallurgy

The rotary kiln boiler dust of a zinc smelter in Xinjiang had a high silicon content, which resulted in the formation of a large amount of colloidal silica in the leachate, causing difficulty in the separation of the solid and liquid. Based on this situation, a combined process of two-stage leaching and recovery of zinc from high-silicon boiler dust + neutralization for silicon removal was developed by taking advantage of the easy leaching feature of soluble silicon under low acid conditions. The results showed that an effective separation of silicon was achieved and the zinc, iron and soluble silicon leaching rates were 61.23%, 3.21% and 95.23% respectively when the endpoint pH value of the first-stage leaching was controlled at 2.0; the silicon removal rate of the first-stage lechate reached above 90% after neutralization by lime and silicon-removal agent for silicon removal; the zinc content in the residue was reduced to 1.43% after high-temperature and high-acid leaching of the first-stage leachate, accomplishing an efficient recovery of zinc in the high-silicon boiler dust; a high-efficiency selective leaching of silicon was realized through the process, the leaching of iron was inhibited and the formation of an unexpected amount of ferric hydroxide colloid was also avoided during lime neutralization for silicon removal.