Abstract
The kinetics of the carbonation method for producing aluminum hydroxide from sodium aluminate solution was investigated in this study. In the first stage of this process, only neutralization occurs. However, after a critical point, precipitation of aluminum hydroxide starts and the aluminate ion will decrease accordingly. Yet near the end of this batch process, sodium alumino-carbonate will become dominant due to the excessive presence of bicarbonate ions. Both bayerite and pseudoboehmite were observed in this work. Generally, pseudoboehmite occurs at high critical supersaturations, which cause extensive nucleation and generate large numbers of fine particles. On the other hand, the formation of bayerite is favored at low critical supersaturations. Therefore, crystal growth will be more important and its sizes larger. Finally, a precipitation boundary between these two phases is presented either in terms of a variable X or in terms of the two operating parameters, i. e. , CO//2 absorption rate and initial aluminate concentration.