An Immobilized Liquid Membrane Containing Tri-Isobutyl Phosphite Sulfide for the Selective Separation of Silver from Base Metals

The present work studies the mass transfer and separation of Ag⁺through a liquid membrane immobilized in a micro porous laminar membrane from some base metals, e.g. Cu, Zn, Pb, Fe. The transport of silver from aqueous nitrate solutions to ammonia aqueous solutions have been studied. The active liquid membrane consist of a solution of triisobutyl phosphine sulphide, Cyanex 471, dissolved in isopropylbenzene absorbed in a micro porous film of polyvinildene fluoride. The results have been analyzed by a linear diffusion model which interprets closely the experimental transport data. Diffusion coefficient of the permeating species and the thickness of the aqueous diffusion layer were determined. The selectivity of silver transport through the liquid membrane provides an effective silver separation from solutions containing the base metals Cu, Fe, Pb and Zn. Such results have been applied to a treatment of the sulfide mineral spharelite.