A Comparative Study on the Precipitation of Hydrated Alumina from Different Sources

Hydrated alumina from three different sources like sodium aluminate liquor, waste aluminium dross and synthetic salt like aluminium sulfate were studied to obtain various form of aluminium hydroxide. Boehmite (Al2O3.H2O), a form of hydrated alumina, has better performance in obtaining alumina, as the enthalpy of dehydration of boehmite is less as compared to gibbsite due to the less number of water molecules in the crystal lattice as compared to gibbsite. Precipitation of hydrated alumina was also studied by using synthetic aluminium sulfate solution with aqueous ammonia and alternating the sequence of reagent addition. Subsequently, the variation in the pH of precipitation and followed by variation of the ageing temperature produced a range of hydrated alumina with different phases and crystallinities. In another option hydrated alumina was precipitated from the sulfuric acid leach liquor of waste aluminium dross by varying the pH of the precipitation followed by temperature of ageing.