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Electrocatalytic recovery of elements from complex mixtures using deep eutectic solvents

Andrew P. Abbott, Robert C. Harris, Fay Holyoak, Gero Frisch, Jennifer Hartley, Gawen R. T. Jenkin
Green chemistry 2015 v.17 no.4 pp. 2172-2179
arsenic, catalysts, catalytic activity, chemical precipitation, copper, electrochemistry, electron transfer, energy efficiency, gold, green chemistry, iodine, redox potential, silver, solubility, solutes, solvents, wastes, zinc
The dissolution and subsequent selective recovery of elements from complex mixtures naturally necessitates redox chemistry. The majority of processes involve hydrometallurgical dissolution followed by selective chemical precipitation or electrochemical winning. The atom and energy efficiencies of these processes are poor, leading to a large volume of aqueous waste which needs to be treated before disposal. In this study it is demonstrated that electrocatalysis is an atom effective method of carrying out digestion and subsequently recovering elements from solution. Here, deep eutectic solvents are used to simplify the speciation of solutes and to allow redox potentials to be modified, compared to standard aqueous values. The redox catalyst used is iodine, as it demonstrates high solubility, fast electron transfer and the ability to oxidise most elements, including precious metals such as gold. The efficacy of this electrocatalytic method is demonstrated using three samples; Cu/Zn, Ga/As and Au/Ag/sulfidic ore.