Crystallization of Homogeneously Precipitated Alumina Hydrate Gels in Aqueous Solution of Various Organic Reagents

Abstract

Alumina hydrate gels were synthesized by the homogeneous precipitation method using either aluminum sulfate and urea or sodium aluminate and ethylenechlorohydrin, and effects of the difference in raw materials and of the addition of various organic reagents on the crystallization of the gels in sodium hydroxide aqueous solution were investigated using X-ray powder diffraction.
Results were as follows:
(1) When glycerin or ethylene glycol more than 40ml is added to the aqueous solution, the crystallization of the gels is inhibited.
(2) When 1, 4-dioxane or ethyl alcohol is added to the aqueous solution, the crystallization proceeds with the same product as when no organic reagent is added.
(3) When no organic reagent is added to the aqueous solution, the alumina hydrate gel from aluminum sulfate and urea gives bayerite as crystallization product and the one from sodium aluminate and ethylenechlorohydrin gives a mixture of bayerite, hydrargillite and pseudo-boehmite.
These results indicate that both the synthetic method of gels and the addition of organic reagents have an effect on the crystallization process of the homogeneously precipitated alumina hydrate gels.