Enhancing decomposition rate of perfluorooctanoic acid by carbonate radical assisted sonochemical treatment

Perfluorooctanoic acid (PFOA) is a recalcitrant organic pollutant in wastewater because of its wide range of applications. Technologies for PFOA treatment have recently been developed. In this study, PFOA decomposition by sonochemical treatment was investigated to determine the effects of NaHCO₃ concentrations, N₂ saturation, and pH on decomposition rates and defluorination efficiencies. The results showed that PFOA decomposition by ultrasound treatment only (150 W, 40 kHz), with or without saturated N₂, was <25% after 4 h reaction. The extent and rate of PFOA decomposition and defluorination efficiencies of PFOA, however, greatly increased with the addition of carbonate radical reagents. PFOA was completely decomposed after 4 h of sonochemical treatment with a carbonate radical oxidant and saturated N₂. Without saturated N₂, PFOA was also decomposed to a high (98.81%) degree. The highest PFOA decomposition and defluorination efficiencies occurred in N₂ saturated solution containing an initial NaHCO₃ concentration of 30 mM. Sonodecomposition of PFOA with CO₃^? radical was most favorable in a slightly alkaline environment (pH = 8.65). There isn’t any shorter-chain perfluorinated carboxylic acids detected except fluorine ions in final reaction solution.