Photocatalytic Activity of Mesoporous alpha-Fe2O3 Synthesized via Soft Chemistry and Hard Template Methods for Degradation of Azo Dye Orange II

Abstract

The photocatalytic activities of two samples of α-Fe2O3 nanoparticles have been evaluated. One sample has been synthesized by a precipitation method with oxalic acid (soft method), and the other sample has been produced with the aid of a hard template (nanocasting with silica). The photodegradation of azo dye Orange II (OII), a model water pollutant, has been used as a benchmark reaction. It has been found that the synthetic method has a deep effect on the photocatalytic activity of the tested hematites, since sample created with the soft method is notably more photoactive than the one made with nanocasting procedure (k = 8.9 × 10− 3 min−1 vs. k = 1.6 × 10−3 min−1 respectively) when irradiated with UV light. Similar higher activity of the soft method sample has been found when visible light was used as excitation source (k = 8.3 × 10−3 min−1 vs. k = 0.4 × 10−3 min−1 respectively). The enhanced surface adsorption of OII on the sample prepared via the soft methodology, which is ten times higher than the adsorption on sample prepared via the nanocasting path, could explain the better photocatalytic performance of the former material.