Reaction dependent extraction of copper and nickel using hollow fibers

The competitive extraction of copper and nickel with kerosene solutions of HDEHP [di-(2-ethylhexyl) phosphoric acid] has been studied in a hollow fiber membrane module. The data showed that the reaction changes from first order to second order as the extraction proceeds. The first-order behavior largely results from mass transfer resistances in the membrane and in the aqueous boundary layer. The second-order reaction, occurring in dilute solution, is a consequence of an interfacial reaction. The results have implications for other metals.