Complete mineralization of perfluorooctanoic acid (PFOA) by γ-irradiation in aqueous solution

Decomposition of perfluorooctanoic acid (C7F15COOH, PFOA) has been gaining increasing interests because it is a ubiquitous environmental contaminant and resistant to the most conventional treatment processes. In this work, the rapid and complete mineralization of PFOA and simultaneous defluorination were achieved by gamma-ray irradiation with a Co-60 source. The degradation rate of PFOA by gamma-ray irradiation would be high, and a pseudo-first-order kinetic rate constant of 0.67 h(-1) could be achieved in the N-2 satured condition at pH 13.0. The experimental results and quantum chemical calculation confirmed that two radicals, i.e., hydroxyl radical ((OH)-O-center dot) and aqueous electrons (e(aq)(-)), were responsible for the degradation of PFOA, while only either e(aq)(-) or (OH)-O-center dot might not be able to accomplish complete mineralization of PFOA. The synergistic effects of (OH)-O-center dot and e(aq)(-) involved in the cleavage of C-C and C-F bonds, and therefore complete mineralization of PFOA were achieved. The intermediate products were identified and the degradation pathway was also proposed. The results of this study may offer a useful, high-efficient approach for complete mineralizing fluorochemicals and other persistent pollutants.