Development of Spiral-Type Supported Liquid Membrane Module for Separation and Concentration of Metal Ions

Abstract

Experiments on the single permeation of cobalt, nickel, and zinc, and the simultaneous permeation of cobalt and nickel were performed using newly developed spiral-type supported liquid membrane modules. These metal ions were successfully separated and concentrated. EHPNA (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) was used as the carrier of cobalt and nickel, and D2EHPA (di-(2-ethylhexyl)phosphoric acid) for the recovery of zinc. In these modules the flow pattern of both feed and stripping solutions is plug flow, which led to very high recovery of metal ions. For example, 99.97% of cobalt in the feed was recovered in a once-through operation, and cobalt could be pumped against its concentration gradient even if the ratio of the metal concentration in the strip phase to that in the feed phase was as high as 70,000. It was confirmed by a life test of the module that the membrane was stable for more than one month without appreciable decrease in metal flux, and that the degraded membrane could be easily and rapidly regenerated without interrupting the permeation of metal ions by re-impregnating the module with the organic membrane solution. The degree of removal for both single and simultaneous permeation of cobalt and nickel was satisfactorily simulated by design equations of the module and the flux equations in which the formation of aggregates of metal-carrier complexes was taken into account.