Most gallium is extracted from the crude aluminum hydroxide solution of the Bayer process for producing alumina and aluminum, gallium is concentrated in bypass master solutions after Al(OH)3 separating. Mercury-anode electrolysis brings to gallium separation. Hydrolysis of the amalgam with alkali metal hydroxide yields Ga(OH)3. Electrolysis then gives gallium metal.
In lime-soda bauxite or nepheline ore processing gallium is concentrated in the last fractions separated during the carbonization process. For additional refinement the hydroxides residue is treated by lime milk. While the most part of Al bottoms, gallium in transferred into the solution. By CO2 passing-through gallium concentrate is separated (6-8% O3), and then dissolved in alkali from which gallium is recovered electrolytically.
The residual anode alloy which remains after all refining by the method of three-layer electrolysis, also may be used for obtaining gallium. In zinc production sublimates which appear after processing of residues of leaching zinc roasted product may serve as a source of gallium.
Liquid product obtained from electrolysis and flushed by water and acids (HCl, HNO3) contains 99.9-99.95% Ga. More pure metal may be produced by zone melting or growing single crystals on fusion. |