Extraction equilibria of Zn(II) from chloride medium by Cyanex 302 in toluene

The extraction of Zn(II) from 1.0 M KCl by Cyanex 302 dissolved in toluene was studied as a function of the total extractant concentration, the equilibrium pH and the total metal concentration. Experimental data, treated both graphically, using curve-fitting analysis, and numerically, by the computer program LETAGROP-DISTR, can be explained by assuming the extraction of the species ZnClR(HR), ZnR(2)(HR)(2), ZnL(2) and ZnL(2)(HL) (HR)(3), where (HR) stands for bis(2,4,4-trimethylpentyl)monothiophosphinic acid, the active component of Cyanex 302, and (HL) represents bis(2,4,4-trimethylpentyl)dithiophosphinic acid, the active component of Cyanex 301 extractant, which is present in commercial Cyanex 302 as a minor component.