Donnan Membrane Effect-Aided Separation of Metal Cyanide Complexes by Hyperfiltration through Cellulose Acetate Membranes

Abstract

Abstract Permeation behavior of cyanide complexes of copper, zinc, and silver through cellulose acetate membranes was investigated in the presence of “activating salt” (succinate or polyvinyl sulfate). In hyperfiltration with high-performance membranes (CA-87), both activating salts effectively enhanced the permeability of negatively charged Group Ib metal (I) cyanide complexes (Donnan membrane effect); the phenomenon was caused by selective affinity of these metal cyanide complexes to the membrane phase. However, with low-performance membranes (CA-75) such selective permeations were reduced by a contribution of increased solute-solvent flow, and all the metal cyanide-complexes showed relatively high permeabilities. The polymer-type activating salt, polyvinyl sulfate, did not permeate through the low-performance membrane but showed an effectiveness in enhancing the permeability of the cyanide complexes under low-pressurized conditions. Taking advantage of this, a new technique, a Donnan membrane effect-ai...