Precipitating sandy aluminium hydroxide from sodium aluminate solution by the neutralization of sodium bicarbonate

In the sinter process for alumina production, it is still difficult to produce sandy aluminium hydroxide by the carbonation of sodium aluminate solution. Therefore, a precisely controllable and feasible process for the precipitation of sandy aluminium hydroxide from the supersaturated sodium aluminate solution neutralized by sodium bicarbonate aqueous solution is proposed for the first time, in which the neutralization reagent (NaHCO3) can be efficiently recycled by the carbonation of the produced sodium carbonate aqueous solution. The influencing factors of the precipitation, i.e. the pH value, the initial NaOH concentration, the temperature and the addition rate of neutralization agent, were investigated. All the aluminium hydroxides precipitated in the research were identified as gibbsite type. The gibbsite products had regular globular morphology and narrow size distribution whose minimum residue on a 44 mu m mesh was 92-94%. (C) 2009 Elsevier B.V. All rights reserved.