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 liqu id membranes which contain di(2-ethylhexyl)phosphoric acid (D2EHPA) di ssolved in kerosene as a carrier. The permeation rate equations are de rived considering the aqueous film diffusion of metal ions toward and out of the membrane and diffusion through the membrane of D2EHPA and i ts metal complexes. The mass transfer coefficients of the metal ions a re 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 t he diffusional resistance in the membrane phase is dominant.