Removal of polyfluorinated telomer alcohol by Advanced Oxidation Processes (AOPs) in different water matrices and evaluation of degradation mechanisms

Abstract

Due to the phase-out of some poly-/perfluoroalkyl substances (PFASs), different PFASs such as fluorotelomer alcohols (FTOHs) have been adopted as alternatives in the market causing their release into the environment. However, there is little information about their fate and degradation by advanced oxidation processes (AOPs) in literature. The aim of the present study is to fill this gap by evaluating the degradability and fate of newly produced polyfluorinated telomer alcohol, namely, 2-(1,1,2-trifluoro-2-hepta fluoropyloxy-ethylsulfonyl)-ethanol (TFHFESE) in different water matrices using various AOPs, including ultraviolet (UV) photolysis, UV/H2O2, solar photolysis, solar/H2O2, O3, and O3/H2O2. While TFHFESE was degraded 76 % by the ozonation process, the presence of H2O2 decreased the process efficiency. UV-based processes provided 98.7 %–100 % degradation of TFHFESE. The presence of H2O2 increased the defluorination ratio for UV processes. However, defluorination ratios were much lower for UV process than that with ozonation process. No significant effect of water matrix on the degradation of TFHFESE was observed, except ozonation. The role of hydroxyl radicals for the degradation of TFHFESE was investigated using isopropanol (i-PrOH). The degradation of TFHFESE by ozonation was mostly promoted by the reaction of molecular ozone instead of hydroxyl radicals. In contrast, the presence of i-PrOH quenched the generated hydroxyl radicals during UV-based processes indicating degradation was provided by OH. The proposed degradation pathways during AOPs are given which included the loss of CH2 group, HF elimination, CF2 flake off and oxidative degradations. Due to volatilization of TFHFESE, the intermediate m/z 327 was also detected for UV-based processes.