Investigation on the sonocatalytic degradation of acid red B in the presence of nanometer TiO2 catalysts and comparison of catalytic activities of anatase and rutile TiO2 powders

Here, the nanometer anatase and rutile titanium dioxide (TiO2) powders were introduced to act as the sonocatalysts during the ultrasonic degradation of azo dye-acid red B which was chosen as model compound. The ultrasound of low power was used as an irradiation source to induce TiO2 particles performing catalytic activity. It was found that the processes of sonocatalytic degradation were different between nanometer anatase TiO2 and nanometer rutile TiO2. For nanometer anatase TiO2 catalyst, the acid red B was mainly oxidated by the holes on the surface of nanometer anatase TiO2 particles, so that the decolorization and degradation happened at the same time. For the nanometer rutile TiO2 catalyst, the acid red B was mainly oxidated by the OH radicals from the ultrasonic cavitation, so that the decolorization of azo bond takes place primarily, and then the degradation of naphthyl ring does. The intermediates of acid red B in the presence of nanometer anatase and rutile TiO2 powders have been monitored by UV-vis spectra and high performance liquid chromatography (HPLC), respectively. All experiments indicated that the degradation effect of acid red B in the presence of nanometer anatase TiO2 powder was obviously better than that in the presence of nanometer rutile TiO2 powder. Hence, the method of sonocatalytic degradation for organic pollutants in the presence of nanometer anatase TiO2 powder is expected to be promising as an advisable choice for the treatment of organic wastewaters in future. (c) 2006 Published by Elsevier B.V.