Hydrometallurgical recovery of lead from spent lead-acid battery paste via leaching and electrowinning in chloride solution

Recycling spent lead-acid batteries has always been a research hotspot. Although traditional pyrometallurgical smelting is still the dominant process, it has serious environmental drawbacks, such as the emission of lead dust and SO2, and high energy consumption. This study presents a clean process for recycling spent lead-acid battery paste. The lead in paste was recovered via hydrometallurgical leaching and electrowinning in chloride solution. The leaching ratio of lead was > 99% under optimum conditions: temperature of 90 degrees C, CaCl2 concentration of 400 g/L, Fe2+ concentration of 5 g/L, pH 1.0, and leaching time of 2 h. The appropriate minimum Pb concentration and optimum current density for electrowinning were determined to be 10 g/L and 200 A/m(2), respectively. Cathode lead powders with a purity of 99.6% were obtained via electrowinning. The current efficiency and the power consumption at 200 A/m(2) were 96.3% and 85.9 kWh per ton of lead produced, respectively. Due to the use of soluble anode (iron), the energy consumption of the electrowinning process was considerably reduced and the chlorine evolution was avoided. The electrowinning has obvious economic advantages over cementation, and the metallic lead with high purity can be obtained using this method. Furthermore, as the spent electrolyte containing ferrous ions is recyclable, the consumption of reagents and the liquid effluent are minimised. The final leaching residue is a mixture of harmless akaganeite and calcium sulphate. The experimental results show that the proposed process is promising for the recovery of lead from spent lead-acid battery paste.