Material composition and properties of red mud coming from domestic alumina processing plant

Red Mud from domestic alumina plant contains high excess alkaline components and traces of many toxic heavy metals. The results showed that Red Mud contains as main components hematite, goethite, residual aluminium oxide-hydroxides, desilication products (DSP), TiO2 and does not contain radioactive elements such as Uranium (U), Thorium (Th). U and Th in Red Mud are less than the average concentration values of Uranium (4ppm) and Thorium (12 ppm) in the earth's crust. Physical structural composition of domestic Red mud can be classified by an equilateral triangle iron oxide/hydroxide-sandy components-clays (23.2÷53.7% iron oxide/hydroxide; 34.1÷63.8% sandy components; 7.3÷34.1% clays). Chemical composition of red mud is, by weight (%w/w): Fe2O3Tot in the range 31.02 to 47.04; Na2O: 2.45÷5.39; CaO: 3.01÷20.86; K2O: 0.02÷0.07; MgO: 0.05÷ 0.73; Al2O3: 10.97÷22.78; SiO2: 1.09÷8.28; TiO2: 2.59÷ 5.76; Loss of Ignition (LOI): 13.03÷ 38.75. Red Mud also contains traces of some heavy metals and valuable metals (Cr, Mn, Zn, V, Ga, Gd, Sc, etc.) and has the pH in the range 13.0 ÷ 11.9 (when it is fresh) and 9÷10 (when it is aged) respectively. The search results are an important basis to select the proper treatment and recovery this waste as secondary resources for ceramic materials production (ceramic foams).