EFFECT OF MIXED ADDITIVES ON EXTRACTION O F ZINC(II) AND -TRIFLUORO-4-MERCAPTO-4-(2-THIENYL)-3-BUTENE-2-ONE

One of the disadvantages of a synergistic extraction is that the addit ion of a synergist usually decreases the selectivity for a particular metal ion in the extractive separation. However, the addition of the s ynergist to a chelate extraction system may increase the number of fac tors controlling the selectivity. Thus, synergistic extraction system with mixed additives (1,10-phenanthroline = phen and pyridine = py/4-m ethyl-pyridine = 4-me-py) was adopted, aiming to improve mutual separa tion of their ions. When -trifluoro-4-mercapto-4-(2-thienyl)-3-butene- 2-one (STTA) was used as the chelating agent, the addition of mixed ad ditives, phen and py or 4-me-py, increased the extractability of Cd-II compared with the addition of a single additive. In particular, the e ffect of phen and 4-me-py was remarkable. On the other hand, no such e ffect was observed in Zn-II extraction. Hence, the degree of mutual se paration between Cd-II and Zn-II was improved by the addition of the m ixed neutral ligands.