THE MINERALOGICAL CHARACTERIZATION OF LEAD-ACID-BATTERY PASTE

The paste component of spent lead-acid batteries was subjected to mine ralogical examination to identify the phases present and their morphol ogical 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 p rincipally as large oxide intergrowths. The major occurrence of Pb2O(S O4) is as masses of intergrown fibrous crystals. Lead metal occurs pri ncipally 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 conv erts the PbSO4 to Pb-3(CO3)(2)(OH)(2) and then to NaPb2(CO3)(2)(OH). A lthough Pb2O(SO4) and Pb metal react slowly in Na2CO3 media, neither P bO2 nor Pb2O3 are significantly affected.