Ion exchange equilibria during zinc and cadmium solvent exctraction with tetraoctylammonium rhodanide

The reaction of interphase exchange in extraction system Na2SO4-H2SO4-R4NSCN (R-octyl) have been investigated. In neutral and weak-acid solutions (pH>3) the negligible exchange of ions SO42--SCN- is observed, with increase of media acidity (pH<3) the reactions of exchange HSO4--SCN- and thiocyanic acid extraction with formation in organic phase of compounds R4NHSO4 and R4NH(SCN)2 play the appreciable role. The constants of all these reactions are calculated. Zinc and cadmium are extracted from thiocyanate and mixed thiocyanate-sulphate media well. Zinc is extracted better in the region of thiocyanatesm - i small concentrations, but cadmiun the region of high concentrations. It is conditioned by the unequal contribution of complexation function with the change of the aqueous phase composition of extractable zinc and cadmium complexes (R4N)2M(SCN)4 is established by the infrared spectroscopy