Preparation of basic lead oxide from spent lead acid battery paste via chemical conversion

A process with potentially reduced environmental impact was studied to recover lead as ultra-fine lead oxide from lead paste in spent lead acid batteries. The lead paste was desulfurized first and then reacted with citric acid to produce lead citrate. Finally, lead citrate was calcined at low-temperature to obtain ultra-fine lead oxide. The desulfurized paste, lead citrate and the recovered lead oxide were characterized by XRD. When desulfurized by Na2CO3, NaHCO3 or (NH4)2CO3, the desulfurization rate of lead paste was over 99.0% under initial C/S ratio of 2, 35 °C, and slurry density of 100 g/L. The lead carbonate and basic lead carbonate could be prepared from desulfurized paste, which was acidified with CO2 gas after being desulfurized by sodium carbonate. The lead citrate precursor, Pb(C6H6O7)·H2O, was prepared by leaching desulfurized paste with citric acid and H2O2. Ultra-fine PbO/Pb powder with particle size of 100–500 nm was obtained at 370 °C. This process is found to be simple, pollution-free and high efficient in the recovery of valuable lead oxide from spent lead acid battery paste, which can replace the traditional smelting method.