Extraction of gallium(III) and aluminium(III) with O,O-dialkyldithiophosphoric acids

The extraction of Ga(3+) and Al(3+) with the liquid cation-exchangers di-n-butyldithiophosphoric acid (DBTPA) and di-(2-ethylhexyl)dithiophosphoric acid (DETPA) in kerosene, in the presence and absence of alcohols and tri-n-butyl phosphate (TBP) has been studied. Both Ga(3+) and Al(3+) can be extracted in the form of a neutral complex, MA(3), but the distribution coefficient of Ga(3+) is the higher by about two orders of magnitude, which can be the basis of the solvent extraction separation of gallium and aluminium. The differences can be explained by the interaction between the sulphur donor atoms of the extractants and the d(10) electronic shell of Ga(3+) as well as by the lower steric hindrance of ligands co-ordinated to Ga(3+).