The mineralogical characterization of lead-acid battery paste

The paste component of spent lead-acid batteries was subjected to mineralogical examination to identify the phases present and their morphological relationships. The battery paste consists principally of PbSO4 and PbO2 (both tetragonal and orthorhombic forms) together with lesser amounts of Pb2O(SO4), Pb2O3, Pb metal, gypsum and silicates. Although both PbO2 and Pb2O3 are detected as inclusions in PbSO4, they occur principally as large oxide intergrowths. The major occurrence of Pb2O(SO4) is as masses of intergrown fibrous crystals. Lead metal occurs principally as inclusions in large particles of PbSO4. Most of the Sb in the battery paste is present in solid solution in PbO2, Pb2O3 and Pb2O(SO4). Reaction of the battery paste with Na2CO3 solution rapidly converts the PbSO4 to Pb-3(CO3)(2)(OH)(2) and then to NaPb2(CO3)(2)(OH). Although Pb2O(SO4) and Pb metal react slowly in Na2CO3 media, neither PbO2 nor Pb2O3 are significantly affected.