0) 4. In aluminum extraction by the Bayer's process, alumina is extracted from bauxite by sodium hydroxide at high temperature and pressures. Al,0, (s) +20H (aq)> 2Al, (aq) + H,O() Solid impurities such as Fe,O; and SiO, are removed and then Al(OH)4 is reprecipitated. Al(OH) Al,0, 2H,O(s)+20H (aq) In the industrial world: a carbon dioxide is added to precipitate the alumina D. temperature and pressure are dropped and the super- saturated solution is seeded Cboth (a) and (b) are practiced d .the water is evaporated. (IIT-JEE 1999) ciO TiO. + Fe,O..