Eco-Friendly Extraction of Lead from Galena by In Situ Electrochemical Reduction in ChCl-EG Deep Eutectic Solvent

Abstract

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.

Ionometallurgy: an academic exercise or promising approach?

“…Metal separation was achieved by Fe(OH) 3 precipitation by the addition of water and the subsequent recovery of copper metal by electrodeposition or cementation. 130 However, especially for suldes [131][132][133] but also for other chalcogenides, [133][134][135] electrolytic mineral dissolution appears to be an even more promising reaction route. Thereby, a slurry of the mineral and the DES is typically paint-cast on the anode.…”

“…[131][132][133][134][135] The dissolved metal ions can subsequently be directly reduced at the cathode. 131,132,134,135 Fig. 5 shows an example set-up of this approach.…”

“…However, especially for sulfides 131–133 but also for other chalcogenides, 133–135 electrolytic mineral dissolution appears to be an even more promising reaction route. Thereby, a slurry of the mineral and the DES is typically paint-cast on the anode.…”

“…Electrolytic dissolution of the mineral proceeds by the oxidation of the chalcogenide anion. [131][132][133][134][135] The dissolved metal ions can subsequently be directly reduced at the cathode. 131,132,134,135 Fig.…”