Poroplastic membranes containing ion exchange liquids were studied for separating cobalt from nickel-containing solutions similar to ammoniacal laterite leaches. The driving force for cobalt transport was differences in ph and composition between the leach and extraction streams. Using a diketone ion exchange liquid, a leach ph of 6.5 to 7.0, and a strip ph of 2.3, Cobalt was extracted from a 750-ppm solution containing 2,500 ppm of nickel at rates ranging from 1 to 10 ug/cm2.Min in single membrane cells. Rates were variable, with evidence that cross-membrane flow patterns were a key factor; a reproducible rate of 30 ug/cm2.Min would be economically viable. Loss of transport, observed after several days of continuous operation, was restored by flushing membranes with fresh ion exchange liquid. A major effort was devoted to preparing thin, leak-free membranes; the resulting membranes endured operating conditions without mechanical failure.