Eco-friendly and efficient strategy for lead recovery from spent lead paste by bagged cathode solid-phase electroreduction

Abstract

Spent lead paste is a registered hazardous solid waste containing high-grade lead. Disposal of spent lead paste with high efficiency and the low energy consumption is of great importance in the view of environment and resource recycling. Herein, a novel, eco-friendly and cost-effective process for direct electroreduction of spent lead paste with bagged cathode to produce metallic lead in Na2SO4 electrolyte is proposed. Thermodynamic analysis proves that direct solid-phase electroreduction of spent lead paste in Na2SO4 electrolyte is feasible. The bagged cathode improves the lead recovery ratio and current efficiency. The mechanism of the solid-phase electroreduction is discussed, and the optimum electroreduction conditions are established, under which a cathode current efficiency of 98.5%, desulfurization rate of 99.6%, lead recovery ratio of 97.3%, and energy consumption of 587.2 kWh per ton paste are achieved. The electrolyte can be facilely regenerated and recycled by neutralization with lime. A closed-loop, economical and high-efficiency process for manufacturing metallic lead from spent lead paste has thus been proposed, which can be potentially used for practice.