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The present paper describes the design and operation of the first large-scale extraction and separation of metals from a complex matrix using an ionic liquid. The liquid was a deep eutectic solvent based on choline chloride. The hydrogen-bond donors were mixed to optimize solubility and fluid viscosity. It was found that the incorporation of a fine particulate dust actually decreased the viscosity of the fluid. The present paper shows that selective extraction of zinc and lead can be achieved through judicious choice of the hydrogen-bond donor and it is also shown that metals in solution can be separated using cementation with zinc powder. Electrowinning of pure zinc is demonstrated but scale-up tests suggest that the process is relatively slow and has poor current efficiency. An alternative methodology was developed to rapidly recover the zinc from solution using dilute ammonia solution. It is also shown for the first time that cementation can be efficiently carried out in ionic liquids because the recovered metal is porous and allows thick layers to be deposited.
Abbott et al. (Fri,) studied this question.