Separations and recovery of indium and gallium using bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272)

The extraction of indium(III) and gallium(III) along with the associated metal ions from hydrochloric acid medium by bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) has been studied. The extraction profiles of indium(III) and gallium(III) have been investigated as a function of type and molarity of the acid, nature of organic diluent and concentration of the metal ion and the extractant. The extracting species have been identified as In(OH)R2, Ga(OH)R2 and H+GaCl4·2R. It has been possible to strip In(III) and Ga(III) from the organic phase by appropriate molarity of HCl. Conditions for a number of binary and ternary separations of analytical interest have been optimized. The developed conditions have been extended to recover pure In(III) from sphalerite and galena and Ga(III) from bottom ash and electronic waste. Loading capacity of the extractant was evaluated and the results reveal that Cyanex 272 can hold indium(III) up to one-fifteenth and gallium(III) up to one-twentieth of its molar concentration. The hydrolytic stability and regeneration capacity of the extractant has been assessed.