Recovery and separation of gallium(III) and germanium(IV) from zinc refinery residues : Part II: Solvent extraction

The extraction of both Ga(III) and Ge(IV) was achieved using an organic system consisting of tri(octyl-decyl) amine (N235), tributyl phosphate (TBP) in sulfonated kerosene from iron-removed leach solution. The extraction equilibria of both metals were obtained within 10 min at 30 °C. More than 99.0% Ga(III) and 99.8% Ge(IV) were extracted in a three-stage counter current extraction using an organic system consisting of 20% (v/v) N235, 10% (v/v) TBP and 70% (v/v) sulfonated kerosene at an A/O ratio of 3:1 and 30 °C for 10 min. Over 99.0% Ga(III) was selectively stripped from the loaded organic solution by three-stage counter current stripping using 2.5 mol/L H2SO4 at an A/O ratio of 1:2 and 30 °C for 15 min, resulting in a loaded strip liquor containing 3.8 g/L Ga(III). After Ga(III) stripping, 99.8% Ge(IV) was stripped by two-stage counter current stripping using 4 mol/L NaOH at an A/O ratio of 1:3 and 40 °C for 15 min, resulting in a final loaded strip liquor containing 8.3 g/L Ge(IV). A conceptual flowsheet has been developed to recover Ga(III) and Ge(IV) from zinc refinery residues using two-stage leaching with H2SO4 and oxalic acid, subsequently, iron removal with iron powder and solvent extraction with N235 and TBP.