Sonophotocatalysis in advanced oxidation process: A short review

Abstract

Sonophotocatalysis involves the use of a combination of ultrasonic sound waves, ultraviolet radiation and a semiconductor photocatalyst to enhance a chemical reaction by the formation of free radicals in aqueous systems. Researchers have used sonophotocatalysis in a variety of investigations i.e. from water decontamination to direct pollutant degradation. This degradation process provides an excellent opportunity to reduce reaction time and the amount of reagents used without the need for extreme physical conditions. Given its advantages, the sonophotocatalysis process has a futuristic application from an engineering and fundamental aspect in commercial applications. A detailed search of published reports was done and analyzed in this paper with respect to sonication, photocatalysis and advanced oxidation processes.

Experimental Study of Influencing Factors and Kinetics in Catalytic Removal of Methylene Blue with TiO2 Nanopowder

“…Nanoparticles show a great tendency to aggregate due to high surface energy combined with their high surface area to volume ratio [18] but ultrasonic irradiation can disperse the catalyst particles more efficiently. Despite all these things, when the amount of TiO 2 increases more than 1 g/l the catalyst particles may agglomerate and this results decreasing in removal percentage [19]. As the results show, the optimum amount of catalyst for sonocatalysis is more than the amount for photocatalysis.…”

Ultrasonic cavitation induced degradation of Congo red in aqueous solutions

“…The split second collapse of the bubble creates localized supercritical conditions with extremely high temperature and pressure, electrical discharge and plasma effects. These extreme conditions create hydroxyl (·OH), hydrogen (H · ), hydroperoxyl (HO 2 · ) radicals and hydrogen peroxide from the aqueous solution [22]. According to the Fenton reaction, Fe 2+ can react with H 2 O 2 to produce ·OH in weakly acidic media (pH 2-3), so Fe 2+ can accelerate the sonolytic degradation of pollutants.…”

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU

“…Supercritical water oxidation, sonolysis, γ-ray irradiation, microwaves and pulsed electron beam are also alternative AOPs. Several reports including many review papers have been published in this field (Feng et al, 2013;Gogate and Pandit, 2004a;Hoffmann et al, 1995;Ikehata and El-Din, 2005;Joseph et al, 2009;Levec and Pintar, 2007;Mishra et al, 1995;Nidheesh and Gandhimathi, 2012;Pera-Titus et al, 2004;Serpone et al, 2010).…”