Effects of sodium salts on the sulfidation of lead smelting slag

Abstract

The effects of sodium salts on the sulfidation behavior, phase transformation, ZnS particle growth, and zinc floatability of lead smelting slag (LSS) were investigated by roasting experiments and flotation tests. The roasting results indicated that sodium salt additives could enhance the reactivity of zinc sulfidation and the percentage of liquid phase and thus promoted the sulfidation of LSS and the growth of ZnS particles. However, with the increase in temperature, the positive effects were reduced because the reactivity of the sulfidation and the percentage of liquid phase were not the determining factors at high temperatures. The effect of Na2CO3 was stronger than Na2SO4, while Na2SO4 was stronger than NaCl on the sulfidation of zinc and the growth of ZnS particles. The addition of Na2CO3 or Na2SO4 favored the conversion of marmatite to wurtzite, which could be evaporated at temperatures above 1000°C. Flotation test results revealed that sodium salt additives had different influences on the zinc grade and recovery at different temperatures. Na2CO3 was the best additive in roasting for increase in zinc grade, due to the formation of metallic iron rather than iron sulfides.