Application of Ionizing Radiation in Decomposition of Perfluorooctane Sulfonate (PFOS) in Aqueous Solutions

Abstract The radiolytic methods of PFOS decomposition in aqueous solutions investigated in this work for potential environmental applications are based on the use of gamma rays or a beam of accelerated electrons (EB) under different chemical conditions in irradiated solutions. The most active reagents in the employed conditions are hydrated electrons from water radiolysis. There are also ·OH and ·H radicals which take part in the occurring reactions. In the presence of formate and 2-propanol in irradiated solutions, the reductive radicals derived from them (CO2·–, (CH2)2C·-OH) are able to induce reductive decomposition of PFOS. In turn, in the presence of tert-butanol, the radicals derived from the alcohol and PFOS dimerize forming alkyl-substituted derivatives. The most favorable conditions for irradiation were achieved in neutral deaerated solutions and aerated solutions containing 10 mM 2-propanol. In γ-irradiation processes the pseudo-first order rate-constants of PFOS decomposition are 0.0197 min-1 (0.310 kGy-1), and 0.0060 min-1 (0.0947 kGy-1), respectively, under both conditions. Due to a big difference in the dose-rate between the two employed types of radiation (gamma and EB), the values of pseudo-first order rate constants of PFOS decomposition are different, namely 0.0197 min-1 (0.310 kGy-1) and 0.368 s-1 (0.0184 kGy-1), respectively, for γ and EB radiation used for decomposition of 0.1 mg L-1 PFOS in neutral, deaerated solution. The EB-irradiation processes for PFOS decomposition are much more efficient than any other AO/RPs reported so far and can be easily employed at a technological scale for very large volumes of treated solutions. The gamma irradiation-based PFOS decomposition requires smaller absorbed doses and it does not require any external energy input because of the use of the isotope source of radiation.