Sonophotocatalytic destruction of organic contaminants in aqueous systems on TiO2 powders

The effect of ultrasound on the photodegradation of salicylic acid on four commercial titania powders was studied. The system exhibiting the highest enhancement was isolated. The use of ultrasound during photocatalysis had a pronounced effect on the rate and efficiency of salicylic acid destruction as compared with UV-light photocatalysis alone. The possible reasons of the increased activity under ultrasonication were proposed: aggregate breakage and photocatalytic utilization of species produced by the ultrasound. The combination of the action of ultrasonic waves and UV-assisted photocatalysis yielded synergistic effects for the catalysts with smaller particle size (such as Hombikat), while no enhancement was observed for the largest particle size photocatalyst (Aldrich anatase). Degussa P25 exhibited the highest overall activity for the degradation of salicylic acid and moderate enhancement of activity by ultrasound. The presence of intermediates in the bulk solution was observed during the purely photocatalytic degradation of phenol. The presence of ultrasound, however, allows to eliminate the toxic intermediates by the sonolysis in the bulk solution.