Preparation of Sodium Aluminate From Basic Aluminium Sulfate

by César A. Contreras, Satoshi Sugita, & Esthela Ramos AZojomo, August 2006 A method for preparing sodium aluminate from basic aluminum sulfate (BAS) is presented. The process consists of two steps. In the first step, BAS was transformed into sodium dawsonite (NaAl(OH)₂CO3) by treating BAS with sodium carbonate aqueous solution at various temperatures and times. The best experimental conditions for preparing sodium dawsonite were established. In the second step of this work, sodium aluminate was obtained by heating sodium dawsonite. In this case, several samples of sodium dawsonite were heated at different temperatures in the range of 600-1100°C for 30 minutes. Sodium dawsonite decomposed at 320°C with the evolution of carbon dioxide and water. At 500°C, a pattern corresponding to a transition alumina was observed by X-ray diffraction. The first traces of crystalline sodium aluminate could be detected in the solid heated at 800°C, whereas at 1000°C a mixture of sodium aluminate and alpha alumina was obtained. Thus, the scheme of phase evolution on progressive heating could be expressed as sodium dawsonite, amorphous, transition alumina (gamma/eta) and crystalline sodium aluminate. By this method, crystalline sodium aluminate could be obtained under mild conditions by heating sodium dawsonite at 900°C for 30 minutes. Read more