Photochemically deposited nano-Ag/sol-gel TiO_2-In_2O_3 mixed oxide mesoporous-assembled nanocrystals for photocatalytic dye degradation

摘要

This work focused on the improvement of the photocatalytic activity for Congo Red (CR) azo dye degradation of mesoporous-assembled 0.95TiO_2-0.05In_2O_3 mixed oxide photocatalyst (with a TiO_2-to- In_2O_3 molar ratio of 0.95:0.05) by loading with Ag nanoparticles. The mesoporous-assembled 0.95TiO_2-0.05In_2O_3 mixed oxide photocatalyst was synthesized by a hydrolytic sol-gel method with the aid of a structure-directing surfactant, prior to loading with various Ag contents (0.5-2 wt.%) by a photochemical deposition method. The optimum Ag loading content was found to be 1.5 wt.%, exhibiting a great increase in photocatalytic CR dye degradation activity. The 1.5 wt.% Ag-loaded 0.95TiO_2-0.05In_2O_3 mixed oxide photocatalyst was further applied for the CR dye degradation in the presence of water hardness. Different types (Ca~(2+) and Ca~(2+)-Mg~(2+) mixture) and concentrations (200 and 500 mg/l) of water hardness were investigated. The results showed that the water hardness reduced the photocatalytic CR dye degradation activity, particularly for the extremely hard water with 500 mg/l of Ca~(2+)-Mg~(2+) mixture. The adjustment of initial solution pH of the CR dye-containing hard water to an appropriate value was found to improve the photocatalytic CR dye degradation activity under the identical reaction conditions.