Effect of inhibitors on the degradation of perfluorooctanoic acid (PFOA) by ultrasonic-assisted inorganic anions: degradation mechanism and pathway

Abstract Perfluorooctanoic acid (PFOA) is a notable polyfluoroalkyl substance (PFASs) contaminating global water environment. This study investigated the effect of inhibitors on the degradation of PFOA by ultrasonic-assisted inorganic anions. Among NO3–, SO42–, and HCO3– anions use to assist in PFOA degradation by ultrasonic (US), SO42– showed higher result. When tert-butanol (t-BuOH) was used as a radical scavenger to find out which radical play role in PFOA degradation and the highest PFOA decomposition efficiency (94.9%) was observed in NaNO3/t-BuOH, US system with 30 mM NaNO3– initial concentration. We did not detect any shorter-chain perfluorinated carboxylic acids (PFCAs) except for PFOA and F– anions in the final reaction solution that mean PFOA was decomposed directly to CO, CO2 and HF. Meanwhile, HCO3– anions showed the lowest degradation efficiency. In terms of energy efficiency, the energy consumption in US/sulfate system was seen to be comparable to that of sonolysis.