SEPARATION BY SOLVENT-EXTRACTION OF TELLURIUM(IV) AND SELENIUM(IV) WITH TRI-N BUTYL-PHOSPHATE - SOME MECHANISTIC ASPECTS

The mechanism of tellurium separation from selenium in hydrochloric acid media by solvent extraction with tri-n butyl phosphate in kerosene was investigated in a batch-stirred glass cell. The dependence of extraction on acid, metal and extractant concentration and temperature were studied. The results suggested a ''preferred range'' for the above parameters with regard to selectivity and extraction efficiency. Based on the results, extraction equilibria for the two elements were suggested indicating the extracted species to be TeCl4(TBP)3 and SeOCl2(TBP)2 at 3-5 M initial acid concentration and H2SeOCl4(TBP)2 at 10 M initial acid concentration. The extraction data further showed that extraction of tellurium was exothermic in nature while that of selenium was endothermic.