Photocatalytic decolorization of methyl orange in aqueous medium of TiO2 and Ag–TiO2 immobilized on γ-Al2O3

TiO2, synthesized through a sol–gel procedure with acetylacetone chelating agent, was immobilized on γ-Al2O3 and deposited with photoreduced Ag. The prepared catalysts were characterized and applied for decolorization of methyl orange (MO). The photoactivity of TiO2/γ-Al2O3 is affected by the H2O/Ti molar ratio applied in the sol–gel process. The optimal calcination temperatures of the TiO2/γ-Al2O3 locate in the ranges from 723 to 773 K and 773 to 873 K as TiO2 prepared with H2O/Ti of 10 and 1, respectively. Incorporating photoreduced Ag to TiO2/γ-Al2O3 leads to reduction reaction of methyl orange in addition to oxidation reaction, and yields a significant increment in decolorization efficiency. The optimal Ag load on TiO2/γ-Al2O3 and dosage of Ag/TiO2/γ-Al2O3 in the photodecolorization of methyl orange are about 1.0% and 1.0 g/L, respectively. The photocatalytic rate is proportional to the Ag load and catalyst dosage raised to the powers of 0.45 and 0.71, respectively.