Combined sonochemical and short-wavelength UV degradation of hydrophobic perfluorinated compounds

•PFCs were decomposed by ultrasonication and short-wavelength UV irradiation.•Ultrasonic cavitation thermally decomposed hydrophobic PFCs effectively.•UV helped to decompose hydrophilic PFCs such as degradation intermediates of hydrophobic PFCs.•Combined use of ultrasonication and UV irradiation is useful for hydrophobic PFCs treatment. Perfluorochemicals (PFCs), which are common in the aquatic environment, are toxic substances that have high chemical and heat resistance because of their strong C-F bonds. We investigated the effect of ultrasonication and short-wavelength UV irradiation on the degradation of perfluorooctane, perfluoropropionic acid, and perfluorooctanoic acid, which are examples of hydrophobic, hydrophilic, and intermediate PFCs, respectively. The results confirmed that ultrasonication was more effective for decomposing hydrophobic PFCs and UV irradiation was more effective for decomposing hydrophilic PFCs. Therefore, defluorination of the degradation intermediates was improved by a combination of ultrasonication and UV irradiation. Our results can be applied to the decomposition treatment of PFCs that have various levels of water solubility in the aquatic environment.