Hydrochemical processing of fine kaolinite fraction of high-siliceous bauxite with preliminary chemical activation

Abstract

For processing of low-quality bauxite, it is impossible to use the most simple and economical Bayer hydroalkali method. In spite of the fact that there are various hydrochemical methods allowing to use substandard alumina-containing raw materials the problem of technology improvement is actual. In this work we investigated the possibility of processing kaolinite fraction of bauxite by hydrochemical method, by improving it through preliminary chemical activation and use of active form of calcium oxide during leaching in high-modulus recycled aluminate solution. The developed technology allows to extract aluminum into solution with high efficiency, to regenerate recycled leaching solutions and to obtain waste sludge suitable for construction. Preliminary chemical activation of fine crystalline fraction by thermochemical treatment in sodium hydrogen carbonate solution at elevated pressure allowed to transform the initial phase composition, eliminate the kaolinite phase, which is difficult to detect by hydrochemical method. The developed method of obtaining the active form of calcium oxide by CaO quenching in Na₂SO₄ solution at elevated temperature and pressure made it possible to carry out hydrochemical stripping of fine crystalline fraction in one stage. The conducted studies have shown the possibility of effective processing of kaolinite fraction of gibbsite-kaolinite bauxite by hydrochemical method by leaching in high-modulus aluminate solution with addition of active form of calcium oxide, after changing the initial phase composition by the method of preliminary chemical activation in sodium hydrogen carbonate solution.