Persulfate oxidation of perfluorooctanoic acid under the temperatures of 20–40 °C

Treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water using persulfate (S2O82-) oxidation with heating or UV radiation has been found effective. However, applications of this process to remediate PFOA contamination require a relatively high temperature (70–90 °C) or energy-consuming irradiation to proceed. The objectives of this study were to investigate persulfate oxidation of PFOA under relatively low temperatures (20–40 °C), more commonly encountered in the natural environment and to evaluate the effects of pH (pH = 2.5, 3.6, 7.1 and 11.0) and persulfate doses (20–200 mM) on the reaction rate for this temperature range. PFOA compounds (241.5 μM) with 200 mM persulfate were almost completely decomposed under an initial pH of 2.5 after 72 h at 40 °C and after 215 h at 30 °C. Even under such a low temperature of 20 °C, the decomposition efficiency reached 80.5% after 648 h. Lower pH or higher persulfate doses resulted in a faster PFOA degradation. A series of kinetic experiments (20, 26, 30 and 40 °C) on PFOA degradation by persulfate oxidation were conducted, and a model was developed that successfully predicted the PFOA decay at various reaction times in this low temperature range (20–40 °C).

► PFOA can be effectively decomposed and mineralized at relatively low temperatures (20–40 °C). ► A lower system pH or higher persulfate doses resulted in a faster PFOA degradation rate. ► A model was developed that predicted the PFOA decay at various reaction times.