Preparation of an aluminum oxo-hydroxide gel in organic medium

A new method has been developed to prepare aluminum oxohydroxide containing spinnable material and gel. Partial hydrolysis of Al(NO₃)₃·9H₂O in 1-propanol at 78°C produces a spinnable, viscous mixture. The role of the propanol in the hydrolysis proved to be to decrease the polarity of the solvent. In this medium the dissociation of nitric acid is driven back and it decomposes to nitrous gases resulting in the increase of pH in the solution. The conditions have been optimized to obtain the highest hydrolysis degree and to avoid precipitation of basic aluminum nitrate. The resulting optimal temperature is 76–80°C, the time needed is at least 15 h in the case of a laboratory scale preparation. Increasing the ratio of propanol: water and the concentration of Al(III) to the maximum value, leads to the decomposition of 54% of the initial amount NO₃^– ion. By careful drying, the decomposition continues to about 70% and a solid foam comes into existence from the viscous mixture. This foam is able to swell in water, the degree of swelling in mass is about 10. The drying of swollen gel was examined. The spinnable mixture most likely contains polymer chains built up by H-bonds, the foam and the gel probably contain platelets.