Preparation of high-purity lead oxide from spent lead paste by low temperature burning and hydrometallurgical processing with ammonium acetate solution

Abstract

Lead sulfate, lead dioxide and lead oxide are the main components of lead paste in a spent lead-acid battery. In addition, there are a few impurities in spent lead paste, which have great influence on the performance of the new battery; therefore, it is necessary to remove them. In this study, a novel approach with low temperature burning and hydrometallurgical processing with NH₄AC is developed to recover lead from spent lead paste. First, some of the impurities are converted to metal oxides by the calcination of spent lead paste at low temperature. Second, the metal oxides are transformed into soluble sulphates by the reaction between the calcination products and dilute H₂SO₄ and H₂O₂ (5.0%). Then, the solids are separated from the solution by filtration; the solids are mainly PbSO₄, BaSO₄ and CaSO₄. NH₄AC is used as the leaching solution for PbSO₄, and CO₂ is introduced to obtain pure PbCO₃. Under the optimized leaching conditions (leaching temperature at 40 °C for 20 min, 10.0 wt% NH₄AC), the lead recovery ratio is about 99.9%. The calcination product of lead carbonate is PbO, and high-purity lead oxide is obtained. The initial discharge capacity of high-purity lead oxide is about 158 mA h g⁻¹, and the capacity loss is less than 2% after 80 cycles.