MODELING OF THE COMPETITIVE PERMEATION OF COBALT AND NICKEL IN A DI(2-ETHYLHEXYL)PHOSPHORIC ACID SUPPORTED LIQUID MEMBRANE PROCESS

This paper presents a mass transfer model for the permeation of cobalt(II) and nickel(II) ions from sulfate solutions through supported liquid membranes which contain di(2-ethylhexyl)phosphoric acid (D2EHPA) dissolved in kerosene as a carrier. The permeation rate equations are derived considering the aqueous film diffusion of metal ions toward and out of the membrane and diffusion through the membrane of D2EHPA and its metal complexes. The mass transfer coefficients of the metal ions are determined using a permeation cell. It is found that the calculated permeation rates are in good agreement with the measured ones. Higher selectivity in the separation of cobalt and nickel is obtained when the diffusional resistance in the membrane phase is dominant.