Biological conversion of anglesite (PbSO4) and lead waste from spent car batteries to galena (PbS)

Lead paste, a solid mixture containing PbSO4, PbO2, PbO/Pb(OH)(2) precipitate, and elemental Pb, is one of the main waste fractions from spent car batteries. Biological sulfidation represents a new process for recovery of lead from this waste. In this process the lead salts in lead paste are converted to galena (PbS) by sulfate-reducing bacteria. This paper investigates a continuous process for sulfidation of anglesite (PbSO4), the main constituent of lead paste, and lead paste, consisting of a laboratory-scale gaslift bioreactor to which a slurry of anglesite or lead paste was supplied. Sulfate or elemental sulfur was added as an additional sulfur source. Hydrogen gas served as an electron donor for the biological reduction of sulfate and elemental sulfur to sulfide by sulfate- and sulfur-reducing bacteria. Anglesite was almost completely converted to galena at a loading rate of 19 kg of PbSO4 m(-3) day(-1), producing a sludge of which the crystalline lead phases consisted of >98% PbS (galena) and 1-2% elemental Pb. With lead paste, stable sulfidation rates of up to 17 kg of lead paste m(-3) day(-1) were demonstrated, producing a sludge of which the crystalline lead phases consisted of an estimated >96% PbS, 1-2% elemental Pb, and 1-2% PbO2.