Sonophotocatalytic degradation of methyl orange by nano-sized Ag/TiO2 particles in aqueous solutions

Sonophotocatalytic behaviour of methyl orange (MeO) in aqueous solution illuminated by light generated by a xenon lamp was investigated. For all three kinds of photocatalysts: Degussa P25 (75% anatase, 25% rutile, with a surface area of 55.07 m2/g), Yili TiO2 (mainly anatase, with a surface area of 10.45 m2/g) and Ag/TiO2 (silver loaded on Yili TiO2), the degradation followed pseudo-first order kinetics. The results showed a synergistic effect between sonolysis and photocatalysis. Some parameters affecting the sonophotocatalytic degradation of MeO with nanoparticles Ag/TiO2 were determined. The results indicated that the degradation ratio of MeO increased with the increase of ultrasonic power. An optimum 60 mg/L of Ag/TiO2 added to relatively low concentrations of MeO was proved to have the most effective degradation efficiency. The study on the effects of hydroxyl radical (OH) scavengers (i.e. mannitol and dimethyl sulfoxide) on the MeO degradation indicated that OH radicals played an important role during MeO degradation, which enhanced MeO to be completely decomposed.