Electrowinning of lead from scrap lead acid batteries using deep eutectic solvents

In this study, a sustainable lead recovery method was developed at low temperature and with less energy using lead paste (a mixture of PbSO4, PbO2, PbO, and Pb) supplied by a scrap battery recovery facility operating in our country, without the need for high-temperature melting processes. In the first stage, the sulfur in the PbSO4 of the lead paste was removed with sodium carbonate (Na2CO3). The desulfurized lead paste was mixed with ChCl-MA and ChCl-SA deep eutectic solvents (DES) prepared using choline chloride (ChCl) with malonic acid (MA) C3H4O4, and citric acid (SA) C6H8O7, at a 1:1 molar ratio, and was dissolved, respectively. The dissolution amounts of the lead paste were obtained as 3.896 mg/kg and 1.480 mg/kg for ChCl-MA and ChCl-SA, respectively. Lead recovery was achieved in electrolysis experiments after the dissolution process. A full factorial experimental design with two levels consisting of three factors, such as solvent concentration, temperature, and current, was used in the electrolysis experiments. The highest cathodic current efficiency was calculated as 75.19% with a specific energy requirement of 781.5 kWh/ton for the electrolysis experiments with ChCl-MA solvent. In addition, the cathodic current efficiency of 38.76% and specific energy requirement of 1625 kWh/ton were determined with the ChCl-SA experiments.