Fe/Al binary oxide aerogels and xerogels for catalytic oxidation of aqueous contaminants

Abstract

Abstract Iron oxides and supported iron materials have been widely used as heterogeneous catalysts to oxidize aqueous organic contaminants in the presence of H2O2. One approach to enhance the catalyst performance is to synthesize micro- or meso-porous iron oxides with large surface areas and to control surface composition and catalyst structure through the use of two metal constituents. In this study, xerogels and aerogels of Fe/Al binary oxides were synthesized using a propylene oxide-driven sol–gel method. The effect of synthesis parameters including the ratio of Fe to Al in the precursor solutions, annealing temperature, and drying method were varied independently. The resultant solids were evaluated for their ability to catalyze H2O2 activation and phenol oxidation. The ratio of Fe/Al was found to have a prominent effect on the catalytic activity of the solids, with an optimal activity occurring at an intermediate Fe loading reflecting the important of Fe dispersion. Higher annealing temperature led to enlarged pore size that facilitates access to the internal reactive surface. Xerogels, despite having moderately smaller surface areas than the aerogel counterparts, exhibited consistently higher oxidant generation efficiency and phenol oxidation rates, indicating it is a more favorable method for making porous iron-containing materials for catalytic wet oxidation applications.