Formation of CaV2O6, CaSiO3 and CaMnO3 Salts During Thermo Chemical Leaching for Extraction of Alumina from Red Mud by Lime Soda Ash Sinter Process

Abstract

Impurities like V2O5, SiO2 and MnO2 present in sodium aluminate liquor during thermo chemical leaching has a detrimental effect on the efficiency of alumina extraction from red mud. The objective of this study was to obtain information on the immobilisation of above impurities from red mud followed by formation of CaV2O6, CaSiO3 and CaMnO3 salts. During thermo chemical leaching alumina is extracted by sintering using Na2CO3 and Lime grit waste material of Alumina refinery plant. During extraction of alumina from Bauxite by Bayer’s process, cationic impurities like Si, V, Mn of Bauxite and anionic impurities of liquor like chloride, sulphate and carbonate form Sodalite or Cancrinite resulting in soda and alumina loss (Sod or Can, ideal formula Na8 (Al6Si6O24) X2. YH2O; X-=Cl-, OH-,1/2CO32-,1/2SO42-, Al(OH)4-). In order to minimise the loss, a novel economic method was studied using lime soda sinter process. During sintering Sodalite or Cancrinite content of red mud form CaV2O6, CaSiO3 and CaMnO3,salts which enhance the alumina extraction. These impurities form CaV2O6, CaSiO3 and CaMnO3 salts,which confirm the decomposition of Sodalite or Cancrinite by X-Ray Diffractometer (XRD) & Scanning Electron Microscope (SEM) and discarded with leached red mud. The effect of Na2CO3 and CaO additive, sintering temperature, time and leaching of alumina extraction study was carried out. Studies show that it was possible to extract alumina from red mud with maximum alumina extraction by immobilisation of impurities and formation of CaV2O6, CaSiO3and CaMnO3 salts.