Title : Sonophotocatalysis in advanced oxidation process: A short review
Abstract:
Sonophotocatalysis integrates ultrasonic cavitation, ultraviolet/visible irradiation, and a semiconductor photocatalyst to generate reactive oxygen species (e.g., hydroxyl radicals) that accelerate the oxidative degradation of aqueous pollutants. This review synthesizes published experimental and engineering studies to evaluate mechanistic synergy, performance gains, and practical barriers to scale-up. Ultrasound enhances mass transfer, promotes catalyst surface cleaning and dispersion, and produces localized high-temperature/pressure microenvironments; simultaneous photoexcitation of the semiconductor produces electron–hole pairs that further generate radical species. The combined action yields higher radical fluxes, faster degradation kinetics, and lower chemical dosing than either sonocatalysis or photocatalysis alone. We analyze reported parameters that control performance—ultrasound frequency and power, light wavelength and intensity, catalyst composition and morphology, reactor geometry, and water matrix effects—and summarize typical outcomes across pollutant classes (dyes, pharmaceuticals, endocrine disruptors, and persistent organics). Laboratory studies consistently report synergistic rate enhancements and improved catalyst stability due to ultrasound-induced anti-fouling and deagglomeration. Key engineering challenges identified include energy efficiency of ultrasound at scale, uniform coupling of cavitation and irradiation in larger reactors, and economical catalyst recovery or immobilization for continuous operation. Based on the literature, we recommend targeted strategies for pilot and commercial development: optimize combined ultrasound and light regimes rather than treating them independently; design reactors that maximize spatial overlap of cavitation zones and illuminated regions; adopt immobilized, magnetic, or otherwise separable catalysts to simplify downstream handling; and perform pilot tests on real waters to quantify matrix effects and lifecycle energy balances. Sonophotocatalysis offers a promising pathway for intensified, low-temperature advanced oxidation with reduced reagent use, but realization at commercial scale will require integrated advances in reactor engineering, catalyst design, and energy optimization.
Keywords Sonophotocatalysis; cavitation; photocatalysis; advanced oxidation processes; reactor design; catalyst recovery; water treatment.
