Separation of Co, Ni and Cu by solvent extraction using di-(2-ethylhexyl) phosphonic acid, PC 88A

Abstract In this paper experimental data on the distribution of base metals (Mn, Cu, Co and Ni), i.e., distribution coefficient ( D ) against initial aqueous acidity ( H i ) at various initial concentrations ( C i ) of metals have been determined using di-(2-ethylhexyl) phosphonic acid (PC 88A) in kerosene (mainly paraffinic and naphthenic hydrocarbon in the C10–C14 range) and utilised to derive the mathematical models of their extraction behaviour. The effect of loading of the metal in the organic phase on the separation factor ( β ) has been incorporated in the mathematical models. These models were incorporated in a computer program to calculate the concentrations of metals in the organic and aqueous phases in counter-current solvent extraction cascades. The process parameters such as the phase ratio, acidity of the feed and scrub solution, number of extraction, scrubbing stages, etc. have been optimised to obtain the desired purity and recovery of Co and Ni. The computed parameters have been utilised for running counter-current extraction processes using mini-mixer-settlers. Kilogram quantities of Co and Ni of 99.5% purity and about 95% recovery have been produced. This paper summarises the basic approach and philosophy of utilisation of the experimental data in terms of mathematical models for the development of the solvent extraction process.