Properties of Lewatit® TP272, a commercial solvent impregnated cation exchange resin for cobalt recovery

The typical hydrometallurgical processing of nickel and cobalt ores involves the precipitation of a mixed nickel–cobalt intermediate product. Alternatively, cobalt could be separated from nickel while in the aqueous phase using solvent extraction. However, solvent extraction has some problems including the need for considerable area for the separators, management of fire hazard, and operational issues such as contamination with organic cross-over with sequential solvent extraction unit operations. The use of an ion exchange resin can mitigate some of these issues; however, conventional cation exchange resins are not sufficiently selective for cobalt over nickel. Solvent impregnated resin offers the engineering advantages of ion exchange resin and the chemical selectivity of the solvent extraction process. This paper describes key properties of a new commercial solvent impregnated resin, Lewatit® TP272, including cobalt and nickel loading as a function of pH and cobalt loading isotherms at pH 5.5 and 5.0 which are identified as the ideal conditions to recover cobalt. The chemical degradation of this solvent impregnated resin was also determined by exposing the resin to greater than pH 6 solutions, which are conditions outside the recommended operating range for this resin. The capacity of the degraded resin was restored by reimpregnating the resin using a Cyanex® 272-ethanol–water mixture. Optical images of resin containing the blue cobalt complex reveal the porous structure