Solvent extraction of tetravalent titanium from acidic chloride solutions by 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester

The extraction of titanium(IV) from hydrochloric acid solutions has been investigated using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (EHEHPA≡HX) in xylene as an extractant. The results demonstrate that the extraction of titanium(IV) occurs via the following reaction: TiO 2 aq++2(HX) 2org⇔TiO(HX 2) 2org+2H + aq where (HX) 2 refers to the dimeric form of EHEHPA. The equilibrium constant of the extracted complex has been estimated by non-linear regression analysis taking into account the aqueous phase complexation of the metal ion with inorganic ligands and plausible complexes extracted into the organic phase. The effect of the nature of the diluent on the extraction of titanium(IV) with EHEHPA has been studied and correlated with the dielectric constant. The extraction behaviour of titanium(IV) has also been compared with that of other metal ions viz. iron(III), magnesium(II), vanadium(V), chromium(VI), manganese(II), zinc(II) and zirconium(IV), which are associated with titanium in the waste chloride liquors of the titanium minerals processing industry.