Bridging the gap to practicality: A green methanesulfonic acid system enhanced with synergistic additives for efficient and high-quality lead electro-refining

Green methanesulfonic acid (MSA) system offers a promising alternative to the traditional fluosilicic acid (H2SiF6) method for lead electro-refining. However, the MSA system has yet to produce efficient electro-refining process, high-quality cathodic lead and stable anodic dissolved layer concurrently, which is crucial for its practical application. Herein, we propose an MSA-based system — enhanced with Lugalvan NES (NES) and calcium lignosulfonate (CL) — for efficient and high-quality lead electro-refining. In both proof-of-concept and separate high-flux flow operations, we achieve a low energy consumption of 73.06 kWhe/t Pb and a high Faradaic efficiency of 99.11 %. Dense deposits with ultra-low grain sizes under 20 nm and high purities of over 99.99 %, and uniform dissolved layers with moderately adhesive anode mud are obtained. Theoretical simulations reveal the HOMO and LUMO energy levels of the additives and their adsorption energy on the Pb interface. Electrochemical analysis indicates a cathodic three-dimensional nucleation process and an anodic mechanism of uniform dissolution. A modular micro-kinetics model is developed to elucidate energy performance. These advances represent a significant step forward for lead electro-refining, achieving efficient operation and high-quality output while reducing energy use and surpassing the efficacy of the traditional method.