Leaching of Spent Lead Paste by Oxalate and Sodium Oxalate Solution and Prepared Leady Oxide Powder in Nitrogen and Air for Lead Acid Battery

An environmental friendly recycling process is investigated to recover lead as leady oxide from spent lead-acid battery paste. In this study, sodium oxalate as a desulfurizer and oxalate acid as a reducing agent have been used to leach three major components (PbSO4, PbO2 and PbO) respectively to obtain the optimal reaction conditions for real industrial spent lead paste leaching. In this sodium oxalate and oxalate acid leaching system, no extra reducing agent was needed any more to reduce PbO2. The results show that sodium oxalate exhibits much higher desulfurization efficiency for PbSO4, and PbO2 can be reduced easily in oxalate acid solution under the optimum conditions with an ratio of 1.25:1, an ratio of 2:1 at 60°C for 70 min. Lead oxalate precursor is calcined in air or N2, porous α-PbO is the only product in air and the calcination products are PbO and metallic Pb in N2 confirmed by morphology and structure characterizations, which is appropriate for lead-acid battery manufacturing. The recycling products were reused directly in lead-acid battery assembling as positive active materials and the assembled batteries show a good cyclic stability in 50 discharge/charge cycles.