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.

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The application of moderate pressures (50 bar) of CO 2 to binary liquid solvent mixtures at room temperature can induce changes in phase behaviour; both inducing miscibility and splitting miscible mixtures. The cause of this phase change behaviour was found to be due to the balance between enthalpic and entropic terms that define the Gibbs energy of mixing and, hence, the partition coefficient. In the majority of binary solvent mixtures, the solvents were miscible at ambient pressure with two phases forming upon application of CO 2 . For some mixtures, the phase behaviour was found to be very composition dependent and in only five systems did no phase change occur.

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