Preparation of aluminium hydroxide by reacting sodium aluminate solutions with mineral acid

Abstract

AbstractThe preparation of aluminium hydroxide from sodium aluminate solutions by varying the alkaline concentration at a fixed molar ratio of Na2O: Al2O3 has been investigated on addition of hydrochloric or nitric acids. The resulting materials have been examined by X‐ray diffraction study, infrared spectrophotometry, thermogravimetrical and differential analyses. As a result, it was found that precipitates generally exist as pseudoboehmite or bayerite, but the formation of bayerite is enhanced by a low rate of addition of acid, higher temperature or higher alkaline concentration. In this case, the composition of the precipitates was little influenced at different molar ratios of Na2O: Al2O3. When the precipitates from sodium aluminate solutions at low and higher alkali concentrations were aged in the mother liquors, pseudoboehmite therein transformed to hydrargillite and bayerite, respectively.