ElectroLeaching-ElectroChemical Deposition (EL-ECD) of gold and palladium in a deep eutectic solvent (DES)

International audience; Precious metal refining from ore or electronic devices includes hydrometallurgical processes with major concern about toxicity or wastewater production. As an alternative, one-step electroleaching-electrochemical deposition process (EL-ECD) using ionic liquid mixtures was evaluated for palladium and gold recovery. A halide based ionic liquid combined with a diluting ionic liquid was chosen among ten electrolytes after cyclic voltammetry and potentiostatic experiments. These low viscous electrolytes allow complexing Au and Pd, leading to metal leaching at low anodic potential. Moreover, the complexes formed could be simultaneously deposited at the cathode. Metal behaviour is similar for all halide anions tested (chloride, bromide and iodide). Results show that chloride based mixtures are the more suitable electrolyte providing the highest leaching faradic yield. This process appears more sustainable than conventional processes (chlorination, cyanide leaching) thanks to the electrolyte stability limiting solvent losses but also workers exposition.