Sonochemical degradation of polycyclic aromatic hydrocarbons: a review

Combined cavitation and oxidation allow efficient and cheap removal of polycyclic aromatic hydrocarbons (PAHs) following the generation of reactive oxygen species. Here, we review the removal of PAHs by sonochemistry, biodegradation, photodegradation, Fenton oxidation, ozone oxidation, and photochemical oxidation. We discuss factors controlling cavitation under sonochemical irradiation in various reactors such as ultrasonic horn, ultrasonic bath and longitudinal horn. The longitudinal horn-type sonochemical reactor has wide operating capacity of 9.5 L with higher power dissipation of 9.5 W and energy efficiency of 59.2%. Degradation is highly dependent on gas sources such as CO₂, Ar, O₂, H₂, and He. Phenanthrene degradation efficiency increases from 30 to 70% with decreasing phenanthrene concentration from 4 to 1 mg/L at constant ultrasound frequency 20 kHz at 25 °C. Reduction of phenanthrene in sediments ranges from 12.9 to 48.3%. Combined ultrasonic and photo-Fenton oxidation treatments of PAHs are more efficient than solely ultrasonic.