Cadmium(II) extraction from phosphoric media by bis(2,4,4-trimethylpentyl) thiophosphinic acid (Cyanex 302)

Cadmium extraction from phosphoric acid at different concentrations (0.7–8.8 M) by the commercial reagent Cyanex 302 in kerosene has been studied. Experimental results have been treated graphically and numerically and the formation of the species CdR2(HR) in the organic phase has been proposed. The value of the equilibrium constant increases with the phosphoric concentration in the aqueous media. Small Cyanex 302 concentrations in the organic phase are enough to remove Cd(II) quantitatively from phosphoric acid solutions.