Abstract: This invention relates to the recovery of gallium from scrubber dust containing aluminum and fluoride. In carrying out the process of the invention gallium is recovered from a particulate solid of the basic material by means of a process comprising the following steps:A. preparing a mixture of the solid with an excess of an alkali;B. sintering the said mixture;C. leaching the sintered product obtained with an aqueous solution;D. cementation of the gallium present in the resulting squeous solution with a metal more electropositive than gallium; andE. collecting the solid gallium precipitate obtained by cementation.

Abstract: An improved wet caustic process of the Bayer method for the extraction of alumina from bauxite containing amounts of both goethite and a monohydrated alumina wherein lime is added only after the bauxite slurry has been heated to a digestion temperature of at least 200.degree.C.

Abstract: A method for preparing a coating grade kaolin clay from a crude clay including discoloring iron contaminants in the form of iron pyrites. The clay is roasted in an oxidizing atmosphere to convert at least a portion of the sulfurous contaminants to a form exhibiting increased magnetic susceptibility and increased solubility in chemical leachants. Thereafter, the clay is formed into an aqueous slurry and subjected to a magnetic field to remove at least part of the converted components, and then subjected to conventional leaching and filtering operations.

Abstract: Production of an activated type alumina from aluminum dross by digestion with water, preferably pressurized. The peculiar properties associated with trace compounds present in the product make it useful for the recovery of noxious effluents from furnacing processes, including those burning fossil fuels and those used for smelting both aluminum and steel, wherein the alumina beneficially incorporates in the metallurgical flux.

Abstract: A method for processing bauxites according to the Bayer technology, with an increased yield in Al.sub.2 O.sub.3 and with decreased caustic soda losses, starting particularly from goethite bauxites of boehmite and/or diaspore type and carrying out the digestion at 180.degree.C to 300.degree.C using an aluminate liquor containing Na.sub.2 O.sub.caustic in a concentration of 80 to 300 g./l. The digestion is carried out in the presence of a calcium compound in an amount corresponding to 2 to 6 % of CaO calculated for the dry weight of bauxite and of a sulfate salt in an amount corresponding to 1.0 to 7.0 g./l. of sulfate ion concentration, whereby the goethite content of the bauxite is converted into hematite. The process provides advantageous conditions for the complete dissolution of the boehmite and diaspore content of bauxite in the vicinity of the equilibrium molar ratio, and enables to recover efficiently the caustic soda losses in the Bayer process itself, requiring no supplementary operation.