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.