Georgiana Moise, Petre Capota, Lenuta Enache, Eleonora Neagu, Valentin Dragut, Daniel Mihaiescu, Luminita Mara, Andreea Chirea, Rodica Zavoianu, Andrei Sarbu
Alumina plant
Abstract:
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).