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.

A sustainable method, with minimal pollution and low energy cost in comparison with the conventional smelting method, is proposed for treating components of spent lead acid batteries with oxalate and sodium oxalate. The pure lead oxalate precursor of PbC2O4 is the only product crystallized in the leaching experiment. Lead oxalate is readily crystallized from the solution due to its low solubility and can be combusted to directly produce lead oxide as a precursor for making new battery pastes. Both lead oxalate and the oxide products have been characterized by means of thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results show that the lead oxides synthesized at different calcination temperatures are comprise of α-PbO and β-PbO. The batteries assembled using the novel lead oxide powder as the positive active material show good cyclic stability for 50 charge/discharge cycles. The cell using lead oxide powder containing 15 wt% β-PbO exhibits excellent initial capacity, cycling performance and high-rate discharge characteristics and can deliver a discharge capacity of 180 mA h g−1 at 30 mA g−1 and more than 60 mA h g−1 at 240 mA g−1. Within 50 cycles, its capacity loss is low (5%) with excellent cyclic stability.

•Sorbents synthesized from CFA and NaOH/CaO are efficient for sulfuric acid mist removal.•Suitable CFA/activator ratio and amount of water during sorbent preparation favor the removal efficiency.•The higher hydrothermal reaction temperature and time, the higher removal capacity of the sorbents.Sorbents from coal fly ash (CFA) activated by NaOH, CaO and H2O were prepared for H2SO4 mist removal from lead-acid battery plants. The effects of parameters including temperature, time, the ratios of CFA/activator and water/solid during sorbent preparation were investigated. It is found that the synthesized sorbents exhibit much higher removal capacity for H2SO4 mist when compared with that of raw coal fly ash and CaO except for H2O activated sorbent and this sorbent was hence excluded from the study because of its low capacity. The H2SO4 mist removal efficiency increases with the increasing of preparation time length and temperature. In addition, the ratios of CFA/activator and water/solid also impact the removal efficiency, and the optimum preparation conditions are identified as: a water/solid ratio of 10:1 at 120 °C for 10 h, a CFA:CaO weight ratio of 10:1, and a NaOH solution concentration of 3 mol/L. The formation of rough surface structure and an increased surface area after NaOH/CaO activation favor the sorption of H2SO4 mist and possible sorption mechanisms might be electrostatic attractions and chemical precipitation between the surface of sorbents and H2SO4 mist.