Effect of Precipitation Temperature, pH and Agitation on the Acid Reactivity of Aluminum Hydroxycarbonate Gel

Abstract

A completely randomized 2³-factorial design study of the precipitation of aluminum hydroxycarbonate gel by the reaction of aluminum chloride with sodium carbonate and sodium bicarbonate showed that the precipitation temperature and end-point pH were significant in terms of the rate of acid neutralization at the 0.01 level and that stirring speed was significant at the 0.05 level. No significant interactions occurred between the parameters. The most reactive gels were precipitated at 25°, pH 6.5 and either 15 or 500 rpm. After aging for 105 days at 25° these gels exhibited a twelvefold greater rate of acid neutralization than the least reactive gel which was precipitated at 4°, pH 5.8 and 15 rpm. The results are analyzed in terms of the effect of each parameter on the particle size and structure of aluminum hydroxycarbonate gel