Extraction of Gallium and Vanadium from Alunite Residue (Red Mud) by Sulphating Roasting and Leaching

Red mud containing significant amounts of alumina, iron oxide, titanium dioxide and other valuable components (Ga 0.003-0.005 mass %, V 0.050-0.099 mass %) is the main waste in the alkaline extraction of alumina from alunites according to the Bayer method and a promising raw material for obtaining gallium and vanadium. The degree of sulphatization of gallium and vanadium from red mud during sulphating roasting was investigated. The technological scheme of sulphating process includes three main stages: 1) missing the moistened initial material with concentrated sulphuric acid; 2) sulphating roasting; 3) water leaching of the sulphated mass. The majority of minerals are transformed through sulphatization into the corresponding sulphate compounds. During subsequent roasting, unstable sulphates (mainly ferric sulphate) are decomposed to form the corresponding oxides, while other metals remain in the form of sulphates (Al-2(SO4)(3), Ga-2(SO4)(3), VOSO4). As a result of leaching of the sulphated mass with water, iron and silicon oxides stay in the residue, while the sulphates of aluminium, gallium and vanadium pass into solution. The maximal degree of gallium and vanadium sulphatization under the conditions of laboratory experiments was detected within the range of 600-640 degrees C. The determination changes in the mineralogical composition of the sulphated mass of red mud were studied by means of thermogravimetry and differential thermal analysis. The developed method of gallium and vanadium extraction from red mud is distinguished by its simplicity and efficiency.