Gallium Solvent Extraction from Sulfuric Acid Solutions Using OPAP

Abstract

The U.S. Bureau of Mines investigated solvent extraction methods for recovering gallium from sulfuric acid leach filtrates produced from hydrometallurgical zinc residues. These filtrates typically had pH values of 0 to 0.5, too low for effective gallium recovery by traditional extractants. Of the nine extractants tested, octylphenyl acid phosphate (OPAP) was the most effective. Gallium stripping was accomplished using a 1.5 M-H₂SO₄ liquor. A continuous solvent extraction system was designed and operated for 32.4 hr, treating a 0.32 g/L Ga and 20 g/L Fe filtrate. Overall gallium recovery in the system was 94%.