Slurry photodegradation of 2,4-dichlorophenoxyacetic acid: A comparative study of impregnated and sol–gel In2O3–TiO2 mixed oxide catalysts

The synthesis, characterization and photocatalytic properties of impregnated In2O3/TiO2 and In2O3–TiO2 sol–gel catalysts were reported. A specific surface area was obtained on the In2O3–TiO2 catalysts prepared by the sol–gel method (153 m2/g) which was three times higher than that on the In2O3/TiO2 impregnated catalysts (58 m2/g). The XRD spectra of the samples showed the anatase phase as the only crystalline phase present in both catalysts. The determination of the Eg band gap by UV–vis spectroscopy showed a band gap of 3.5 eV for the In2O3–TiO2 photocatalysts while for the In2O3/TiO2 samples it was of 3.1 eV. The obtained photoactivity for the 2,4-dichlorophenoxyacetic acid degradation by the In2O3–TiO2 sol–gel catalysts (t1/2 = 35 min) was higher than the obtained by the In2O3/TiO2 impregnated catalysts (t1/2 = 88). The higher activity showed by the sol–gel photocatalysts can be related with specific surface area effects combined with those produced by the formation of highly dispersed In2O3 particles; and by the insertion of some In3+ cations in the titania framework.