Extraction and separation of zinc and cadmium chlorides by TOPO from mixed media

The effect of water-miscible alcohols and acetone on the extraction and separation of Cd and Zn chlorides by TOPO was systematically investigated. The maximum extraction of Zn chloride with 0.1M TOPO decreases in the order: acetone > methanol > ethanol > 2-propanol > 2-butanol. For alcohols, the sequence of decreasing extractability is thus parallel to the order of their dielectric constants. This can be explained by the increase of HCl extraction by TOPO in the same direction. The presence of additives in the polar phase prevents the formation of a bulky white precipitate encountered during extraction of ZnCl2 from pure aqueous solutions. A decrease of Cd chloride extraction was generally noticed in presence of additives; this is more noticeable for the longer chain alcohols. The highest separation factor (E) for ZnCl2, and CdCl2 in 0.48M HCl is obtained from 30% methanol (13.8 compared to about 3.8 in absence of methanol) and from 10-20% acetone where it reaches 30.