PROPERTIES OF HYDROXYALUMINUM SILICATE IONS FORMED BY INSTANTANEOUS MIXING OF SODIUM ORTHOSILICATE AND ALUMINUM CHLORIDE SOLUTIONS

Abstract

We obtained concentrated solutions of hydroxyaluminum silicate (HAS) ions by instantaneously mixing aluminum chloride solution and sodium orthosilicate solutions with different concentrations of NaOH. The Si/A1 molar ratio of the HAS ions purified by dialysis was in a narrow range from 0.35 to 0.39 irrespective of the NaOH/Al ratio. Heating the HAS solutions at near boiling point gave allophane and small amount of imogolite as well dispersed sol. On the other hand, heating HAS solutions after dialysis yielded boehmite as precipitate and allophane as well dispersed sol, but gave no detectable amount of imogolite although there was little chloride ion disturbing development of imogolite structure. These experimental results showed that the Si/A1 molar ratio of HAS ion is significantly lower than that of imogolite and free monosilicic acid is incorporated during development of imogolite tubes. This suggests that better imogolite yield will be achieved by addition of monosilicic a cid to the dialyzed HASsolutions before heat treatment or by removal of chloride ion during heating.