Liquid-liquid extraction of gallium from Bayer process liquor using Kelex 100 in the presence of surfactants

The solvent extraction of gallium from a concentrated Bayer process liquor containing similar or equal to 450 g/l of Na2O, similar or equal to 80 g/l of Al2O3 and 190 +/- 20 ppm of gallium was investigated using 12 vol.% Kelex 100, a 7-alkyl substituted-8 hydroxyquinoline as extractant, 12 vol.% isodecanol as modifier and kerosene as diluent. At 1.0:1.0 organic to aqueous phase ratio and at room temperature, 80% of gallium was recovered in 3 h. In order to improve upon the kinetics of extraction, the addition of surfactants in the organic phase was studied. The addition of octylamine to the organic phase was found to reduce the rate of gallium extraction as well as its recovery. Additions of petroleum sulphonate up to 0.5 vol.% of organic phase has increased the rate of gallium extraction by reducing the equilibrium time to 45 min along with 80% recovery of gallium. When the petroleum sulphonate addition was increased to 2.5 vol.%, the rate of extraction and the recovery decreased significantly. The Versatic 10 volume percentage was studied at 1.0, 2.5, 5.0 and 10 by adjusting the kerosene volume percentage. Gradual increase in the volume percentage of Versatic 10 resulted in a decrease in the equilibrium time, and the maximum recovery of 98% of gallium was obtained at 2.5 vol.% Versatic 10 in 15 min. With further increase in the Versatic 10 volume percentage, the gallium recovery was decreased. (C) 1999 Elsevier Science B.V. All rights reserved.