Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation

The microwave-hydrothermal decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in aqueous solution using persulfate activated by zero-valent iron (ZVI) at 60 and 90 °C was examined. The results of laboratory study reveal that when PFOA is treated with 5 mM persulfate (PS) and ZVI at 90 °C for 2 h, 67.6% of PFOA is effectively decomposed to form shorter-chain perfluorinated carboxylic acids (PFCAs) and fluoride ions, with 22.5% defluorination efficiency. Introducing ZVI into the PFOA solution with PS addition will lead to synergetic effect that accelerates the PFOA decomposition rate, and reduces the reaction time. ZVI not only decomposes PFOA, but also releases ferrous ions to lower the activation energy of PS while forming sulfate free radicals at a lower reaction temperature. The combined use of ZVI and persulfate will lead to significant savings in energy consumption and reduction of process time.