Improved catalytic activity on the thermal decomposition of ammonium perchlorate and efficient adsorption of uranium using a novel ultra-low density Al2O3-based aerogels

The ultra-low density AlCl3-chitosan composite aerogel was prepared via a novel solution-freeze-drying technology. Then, the AlCl3-chitosan aerogel was carbonized or calcined to remove the chitosan template, yielding ultra-low density Al2O3-based aerogels with good formation ability. The density of Al2O3-based aerogels were about 9 mg/cm(3) via this method. Moreover, the Al2O3-based aerogel obtained from the calcination of AlCl3-chitosan aerogel copied the open networks of thin flakes layered structure of chitosan template. The as-prepared Al2O3 aerogel had a low thermal conductivity of about 0.039 W/m K after high temperature treatment at 1000 degrees C, demonstrating its good thermal insulation property. The results of TG/DSC showed that the Al2O3-(0.2 wt% Pt) catalysts could decrease decomposition temperature of ammonium perchlorate (AP) by 51.1 degrees C and the exothermic heat was increased from 133.2 J/g to 1552.7 J/g. The maximum adsorption amounts for U(VI) of Al2O3 aerogel reached 769.9 mg/g, which was about 2 times higher than that of Al2O3 with other forms. Accordingly, the Al2O3 aerogel with thin flakes layered structure and ultra-low density possessed great potential application in thermal insulation, adsorption and catalyst supports. Meanwhile, the solution-freeze-drying technology is simple and easy to control, providing a new strategy for the preparation of ultra-low density metal oxide aerogels.