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 e nhancement was isolated. The use of ultrasound during photocatalysis had a pronounced effect on the rate and efficiency of salicylic acid destruction s as compared with UV-light photocatalysis alone. The possible reasons of t he increased activity under ultrasonication were proposed: aggregate breaka ge and photocatalytic utilization of species produced by the ultrasound. Th e combination of the action of ultrasonic waves and UV-assisted photocataly sis yielded synergistic effects for the catalysts with smaller particle siz e (such as Hombikat), while no enhancement was observed for the largest par ticle size photocatalyst (Aldrich anatase). Degussa P25 exhibited the highe st overall activity for the degradation of salicylic acid and moderate enha ncement of activity by ultrasound. The presence of intermediates in the bul k solution was observed during the purely photocatalytic degradation of phe nol. The presence of ultrasound, however, allows to eliminate the toxic int ermediates by the sonolysis in the bulk solution. (C) 2001 Elsevier Science B.V. All rights reserved.