Sr separation and purification from refractory zinc electrolytic anode slime with Pb and Sr cocrystallization by mechanochemical ball milling

Zinc electrolytic anode slime (ZEAS) contains high contents of Mn, Zn, Sr and Pb, showing a great economic value and potential threats to environment. During the formation of ZEAS, Pb and Sr in the electrolyte were simultaneously crystallization crystallized to form a mixcrystal structure, which dramatically impedes the dissolution of Sr with a small conventional Sr leaching efficiency of 26.06%. In this study, a high-efficiency leaching method of Sr from refractory ZEAS by mechanochemical ball milling-soda converting-acid leachingpurifying-carbonating was proposed. Mechanochemical ball milling enhances the leaching efficiency of Sr by destroying the Pb and Sr cocrystallization structure and greatly improved the reaction rate of the subsequent process. The leaching efficiency of Sr is increased to 83.03%. Moreover, the Sr leaching efficiency reaches 96.81% under the optimum mechanochemical ball milling, soda conversion and acid leaching conditions. In the purification process, the optimum pH value of 13.2 and the recovery of Sr is 94.57%. The comprehensive recovery rate of Sr is above 90%, and SrCO3 product with purity above 96% was prepared. In addition, the separation and recovery mechanism of Sr was studied, and the enrichment direction of Pb, Mn, Zn, and Ca elements were also evaluated.