THE REMOVAL OF ZINC FROM SOLUTIONS BY FOAM SEPARATION .1. FOAM SEPARATION OF COMPLEX ZINC ANIONS

The effectiveness of zinc foam separation by cetyltrimethylammonium collector increases with increasing chloride, bromide, iodide, and thiocyanate concentration and in relation to the nature of the ligands it follows the order: Zn(Cl)42- <Zn(Br)42- <Zn(SCN)42- ≤Zn(I)42-. Moreover, the experiments show the separation sequence: Co(SCN)42- <Zn(SCN)42- <Cd(SCN)42-. In the presence of acids, the zinc thiocyanate complex removal (and the amounts of zinc in the sublate) decrease with increasing acid concentration in the following sequence: HClO4<H3PO4<HCl<H2SO4< no acid. The surface tension of zinc foam separation media decreases with increasing bromide or chloride concentration while it increases with increasing thiocyanate or iodide concentration and changes as follows: Br-<Cl-<SCN-<I-. Moreover, measurements in the presence of different metals and thiocyanate show the surface tension sequence: Co<Zn<Cd. The interpretation of the effectiveness of zinc complex removal as well as the changes in interface phenomena are based on the analysis of interactions in the foam separation medium. The results of foam separation are compared with those of solvent extraction and paper chromatography. © 1990.