Eco-Friendly Extraction Of Lead From Galena By In Situ Electrochemical Reduction In Chcl-Eg Deep Eutectic Solvent

One-step electrochemical extraction of metallic lead from solid galena in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES) was studied for the first time. Cyclic voltammetry on a Pt powder microcavity electrode shows that solid galena can be directly reduced to metallic lead by a one-step, two-electron transfer reaction at a potential of -0.47 V (vs Ag). The constant voltage electrolysis using galena powders as cathode in the range of 5 h to 30 h reaction time and 3.0 V to 3.8 V cell voltage further proves that metallic lead can be obtained at the cathode. With the extension of reaction time, the morphology of lead powders transforms from interconnected wax to irregular rod-like and needle particles. As the cell voltage is elevated, the microstructure of metallic lead changes from irregular flake and rod to nano-needle particles. The direct electrolysis process of solid galena is analyzed, and a schematic diagram is also exhibited. It is pointed out that the close contact between galena powders and current collector is the key to facilitate the in situ reduction. These findings put forward a green and convenient route for direct extraction of metals from sulphide ores at near room temperature.