Oxidative decomposition of perfluorooctanesulfonate in water by permanganate

Experiments were conducted to examine the oxidative decomposition of perfluorooctanesulfonate (PFOS), a widely distributed and highly resistant emerging organic pollutant, by permanganate in aqueous solutions. At 65°C and pH 4.2, 46.8% of the PFOS was decomposed by permanganate, with a F ^- yield of 5.3% and a SO42- yield of 36.9%. The effects of temperature, initial permanganate concentration, and pH on PFOS decomposition efficiency were systematically investigated with batch experiments. Increasing the temperature and initial permanganate concentration effectively accelerated the rate of PFOS decomposition. However, increased pH decreased the PFOS decomposition rate, therefore indicating that a more acidic solution favors the decomposition of PFOS by permanganate. Moreover, the autocatalysis effect was found to accelerate the rate of PFOS decomposition by the in situ formed MnO ₂ from the reduction of permanganate and, thus, the addition of MnO ₂ to the reaction solution also increased the decomposition rate. Under acidic conditions, the addition of organic acids can enhance their complexation with Mn(V) and Mn(VI). Therefore, the duration of the Mn(VII) reduction intermediates, which are highly active and easily disproportionated and autodecomposed, can be further prolonged to facilitate the oxidative decomposition of PFOS.