A closed-loop ammonium acetate leaching-electrodeposition route for metallic lead recovery from spent lead paste

The hydrometallurgical electrodeposition process has become a hot research field for metallic lead recovery from spent lead paste due to its energy-efficient and eco-friendly features. However, traditional electrodeposition process is usually carried out under strong acid or alkaline systems, accompanied by the side reaction of lead dioxide. This study proposed a closed-loop ammonium acetate leaching-electrodeposition route for metallic lead recovery from spent lead paste. The spent lead paste was firstly leached by a neutral leaching solution of NH₄Ac, HAc and H₂O₂. After filtration, the leaching solution was electrodeposited to produce metallic lead. Anion exchange membrane was introduced to avoid anodic lead dioxide generation in the electrodeposition process. Under the optimal conditions, the cathode current efficiency and energy consumption were 91.62 % and 625 kWh/t Pb, respectively. The NH₄Ac leachant was regenerated from the eletrolyte by removing soluble SO₄^2- with addition of Ba(Ac)₂ to generate BaSO₄ by-product. The regenerated NH₄Ac leachant was then reused in the next-round leaching process, thus realizing a closed-loop process. In five leachant recirculation processes, the leaching ratio, electrodeposition ratio and total recovery ratio of lead remained relatively stable, within the ranges of 95.7–97.3 wt %, 98.6–99.6 wt % and 94.4–96.4 wt %, respectively. By upgrading of the metallic Pb product, the purity could finally reach 99.998 %. This study proposes an environmentally and economically friendly process for lead recovery from spent lead paste and other lead-containing wastes.