An environment-friendly strategy for recovery of α-PbO from spent lead paste: Based on the thermochemical reduction of PbO2 with ammonium sulfate

During the process of recycling lead from waste lead-acid batteries, how to minimize the wastage of chemical reagents and prevent secondary pollution is a significant research subject. In this study, a method for preparing α-PbO based on low-temperature thermochemical reduction of PbO2 was proposed. Using (NH4)2SO4 as the roasting agent, the purity of PbSO4 in spent lead paste was improved by reducing PbO2 at low temperatures. The thermochemical mechanism revealed that the thermochemical process consists of three different stages of (NH4)2SO4 decomposition and PbO2 reduction. The purity of PbSO4 in spent lead paste could be increased to 98.43 % by controlling the thermal reaction conditions (M (SO42−: TPb) molar ratio of 1:1, roasting temperature, and time of 340 °C and 1.5 h, respectively). Then, the desulfurization of PbSO4 with (NH4)2CO3 obtained PbCO3, and α-PbO with a purity of 96.87 %-98.57 % could be obtained by pyrolysis of PbCO3. Finally, 95.63 % of NH4+, 97.34 % of SO42−, and 77.71 % of CO32− could also be recovered for the regeneration of (NH4)2SO4 and (NH4)2CO3. This study provides a feasible technology for green recycling of spent lead paste.