EXTRACTION OF COBALT(II) BY CYANEX-302

The extraction equilibria of Co(II) from 1.0 M KCI medium by the comme rcial extractant Cyanex 302 (bis(2,4,4-trimethylpentyl)monothiophosphi nic acid) dissolved in toluene has been studied. The effects of pH, ex tractant concentration and metal concentration on the extraction behav iour have been examined. The influence of bis(2,4,4,-trimethylpentyl)d ithiophosphinic acid, one of the minor impurities of Cyanex 302 and al so the major component in Cyanex 301 on the extraction of cobalt has a lso been considered. Experimental data have been treated graphically a nd numerically by means of the computer program LETAGROP-DISTR, and ca n be explained by assuming the extraction of the species CoR(2)(HR), C o-2(HR)(2), CoL(2) and CoClL(HL), HL being bis(2,4,4-trimethylpentyl)d ithiophosphinic acid and HR standing for bis(2,4,4-trimethylpentyl)mon othiophosphinic acid. Conditional equilibrium constants of the extract ion process are also given.