ACCELERATED MASS-TRANSFER OF PALLADIUM(II) THROUGH A SELECTIVE SOLID-SUPPORTED LIQUID MEMBRANE CONTAINING CYANEX-471

The mass transfer of Pd(II) from aqueous feed chloride solutions containing SCN- through a solid-supported liquid membrane (SSLM) consisting of Cyanex 471 dissolved in cumene was studied. The influence of hydrodynamic conditions and chemical composition of the system on the permeation rate, mainly the effect of feed aqueous SCN-, was investigated. Two different approaches were used to explain the behaviour of the membrane system. First, a 2(3) experimental factorial design showed a slight influence of the chemical parameters, especially SCN- and Pd(II) concentrations. Second, a diffusion model was applied to characterize the mass transfer of Pd(II); thus the diffusion coefficients of organic permeating species and the thickness of the aqueous diffusion layer were estimated. The proposed liquid membrane process was applied to the separation of palladium from platinum in a synthetic sample solution at concentrations similar to that obtained in the leaching of spent automotive catalysts. The results indicated that Pd(II) can be separated effectively from Pt(IV).