Recovery of gallium from strong acidic sulphate leach solutions of zinc refinery residues using a novel phosphate ester extractant

A novel phosphate ester extractant (H2R) was used to extract gallium directly from strong acidic sulphate leach solutions of zinc refinery residues. The results indicated that the application acidity of H2R significantly exceeded those of P507 and P204 (two commonly used phosphate esters), and could directly extract gallium from the solutions with relatively high acidity (20–120 g/L H2SO4). In batch tests, 98.54% of gallium was extracted from solutions containing 0.205 g/L gallium and 107.80 g/L H2SO4 in four-stage counter current extraction, by using an organic system consisting of 40% (v/v) H2R in sulfonated kerosene with an A/O ratio of 1:1 at laboratory temperature (27 ± 1 °C) for 10 min. Meanwhile, extractions of other metals (germanium, zinc, copper, arsenic, and cadmium) were negligible, except for that of iron. After scrubbing using 20 g/L H2SO4 at an A/O ratio of 1:1, 99.13% of gallium in the loaded organic was selectively stripped using 200 g/L H2SO4 solution via five-stage counter current stripping with an A/O ratio of 1:4 at 27 ± 1 °C for 10 min, followed by using 7 mol/L HCl solution to strip co-extracted iron for recycling. Over the whole process, 96.71% of gallium was recovered and enriched in the pure gallium sulphate strip liquor with a concentration of 0.793 g/L. The results of continuous running tests demonstrated that H2R could be used to selectively recover gallium from strong acidic sulphate leach solutions of zinc refinery residues, with high stability and good cycling performance.