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 ^{{radical dot}}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.