THE SEPARATION OF ZINC(II) AND CADMIUM(II) BY LIQUID-LIQUID-EXTRACTION

The extraction of Zn(II) and Cd(II) from thiocyanate solutions with bi s-2-ethylhexyl, sulphoxide (B2EHSO) in benzene as an extractant has be en studied by tracer techniques. For comparison, extraction has also b een carried out with tributylphosphate (TBP). The extraction data have been analysed by both graphical and theoretical methods by taking int o account complexation of the metal in the aqueous phase by inorganic ligands and plausible complexes extracted into the organic phase, The results demonstrate that Zn(II) is extracted as Zn(SCN)(2)2B2EHSO and Zn(SCN)(2).2TBP. In the case of Cd(II), the extracted species are Cd(S CN)(2).4B2EHSO/4TBP, The synergistic extraction of Zn(II) and Cd(II) w ith mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and B 2EHSO or TBP or trioctylphosphine oxide (TOPO) from acetate buffer sol utions has also been investigated. Zn(II) is extracted as Zn(PMBP)(2). B2EHSO/TBP/TOPO. On the other hand, Cd(II) is found to be not extracte d with these mixed-ligand systems under the experimental conditions. T hese results also demonstrate the mutual separation of Zn(II) and Cd(I I) using the synergistic extraction with HPMBP in the presence of vari ous neutral oxodonors.