Reduction of lead in the lead sulfide-molten sodium hydroxide system

Abstract

Based on thermodynamic investigations of the reduction of lead from its sulfide compounds using the electron-donating properties of sulfur of its sulfide, we studied the effect of various factors on the reduction of lead (“metallization”) in molten sodium hydroxide. In the range of temperatures of smelting PbS with the alkali (470–510°C), there occurs a “burst” metallization reaching 95% at T = 550°C; at T = 650°C, the process is completed in 15 min; at 650–500°C, the reduction of the metal occurs in the diffusion region. The NaOH: PbS weight ratio (α) exerts a direct effect on the yield of the compact metal (‘lens’). At α = 1.8−0.8, the yield of the compact metal is 96–98%. It has been confirmed experimentally that the chemism of the utilization of elementary sulfur is related to a disproportionation of the latter with the accumulation of S2− and SO42− ions and the possible formation of polysulfide sulfur Sn2−.