YOU Leming, ZHANG Shuguang, ZHANG Xufu, XIAO Shijie, ZHANG Jun, JIANG Meiguang, GUO Xiaowen, ZHOU Yafei, XIA Fachao
High-arsenic white dust was processed by adopting a process consisting of alkaline roasting and water leaching to remove the arsenic therein, and the water leaching residue was then subjected to first-stage sulfuric acid leaching for separation between copper and zinc, followed by second-stage hydrochloric acid leaching for separation between lead and bismuth, so as to comprehensively recover various metals. The effects of alkali-to-ore ratio, roasting temperature and time on arsenic removal by water leaching, along with the suitable process parameters for two stages of acid leaching and stepwise treatment of acid leachate were systematically explored. Firstly, 3 h roasting at 300 ℃ with alkali-to-ore ratio of 0.9 followed by water leaching of calcine achieved arsenic removal rate of 98.88%; and then, the obtained leaching residue with liquid-to-solid ratio of 4 mL/g was leached at 90 ℃for 2 hours with sulfuric acid at an initial concentration of 2.5 mol/L, resulting in the leaching rates of copper and zinc reaching 98.32% and 99.14%, respectively. After that, the sulfuric acid leaching residue at a liquid-to-solid ratio of 4 mL/g was leached at 90 ℃ for 2 hours with hydrochloric acid at concentration of 2.5 mol/L, leading to the bismuth leaching rate up to 98.42%. The previously obtained sulfuric acid leachate was then added by 1.1 times the theoretical amount of sodium sulfide, resulting in copper precipitation rate of 99.87%, and the generated solution was then subjected to evaporation and crystallization, resulting in a zinc recovery of 99.23%. While the previously generated hydrochloric acid leachate was neutralized to pH of 3, leading to a bismuth recovery rate of 99.74%. It is concluded that such combined process can actualize comprehensive recovery and utilization of valuable elements in high-arsenic dust.
