The isolation of gallium begins with the collection of gallium that is extracted as a byproduct in trace amounts from mineral ore processing. Some minerals which contain gallium include bauxite, germanite, and sphalerite; coal and diaspore are also composed of minute amounts of gallium.
Most of the gallium that is isolated comes out as a byproduct from the processing of alumina and aluminum. The Bayer process is used to produce the aluminum products. The Bayer process uses bauxite, and begins by washing bauxite in a heated solution of sodium hydroxide. The alumina in bauxite is converted to aluminum hydroxide which is dissolved in the hydroxide solution. Components of bauxite, such as gallium, do not dissolve under this process and are collected from the alkaline solutions. Further processing of gallium amalgam, using mercury cell electrolysis and hydrolysis with sodium hydroxide, forms sodium gallate. This compound is reduced to pure gallium through electrolysis.
