Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

Abstract

The role of the short-lived hydrated electron (e aq − ) has recently begun to be appreciated in per-and polyfluoroalkyl substances (PFAS) remediations; nevertheless, few studies to date focused on short-chain PFAS, and their effective defluorination has been limited by an insufficient mechanistic understanding, which starts with the elusive initial step of e aq − reduction. Herein, this study uses pulse radiolysis to clarify the rate constant of the e aq − reaction with a highly recalcitrant short-chain PFAS, perfluorobutanesulfonate (PFBS, C 4 F 9 SO 3 − ), and verify chain length dependence. The measured values contradict earlier results from laser photolysis but reconcile with the apparent degradation profiles and theoretical predictions. Besides, we first disclose radiolytic carbon dioxide radicals (CO 2 −• ) to defluorinate PFBS with an initial reaction constant of 4.8 × 10 7 M −1 s −1 , and it achieves selective cleavage on the more obstinate C−F bond than e aq − even under a neutral condition. Quantitative 60 Co γ-ray irradiation experiments further show that initial reduction occurs through a defluorination pathway rather than a desulfurization pathway, and the redox potential of PFBS exceeds −2.0 eV. This radiolytic study addressed the long-standing mechanistic contradictions regarding short-chain PFAS degradation and suggested ionizing radiation as a versatile and direct treatment technique.

Time-resolved Observation of Surface-Bound Carbon Dioxide Radical Anions on Metallic Nanocatalyst

“…1b-d). These data depicted a landscape of the formation and decay process of CO 2 •radicals in our conditions and in the absence of metal catalysts, similar to those reported in the literature 29,30 .…”

Influence of Carbonate Speciation on Hydrated Electron Treatment Processes

“…While most studies to date show that increasing dissolved carbonate acts to inhibit rates of e aq – ARPs, , a recent report suggests that CO 2 •– , itself, may react with more recalcitrant PFASs (e.g., perfluorobutane sulfonate) . However, the importance of PFAS reactions compared to other processes that rapidly consume CO 2 •– , including near diffusion-limited recombination reactions, remains to be established. ,, Still, further studies of the fate and reactivity of CO 2 •– are warranted, given the likelihood for generation of this transient species during e aq – ARPs in carbonate-containing natural water matrices.…”

“…, itself, may react with more recalcitrant PFASs (e.g., perfluorobutane sulfonate). 47 However, the importance of PFAS reactions compared to other processes that rapidly consume CO 2…”

Predicting Degradation Mechanisms in Lithium Bistriflimide “Water‐In‐Salt” Electrolytes For Aqueous Batteries

“…In the literature, another reaction is also reported, which corresponds to an electron attachment reaction, leading to the release of a fluoride anion, after the formation of a transient dianion [46] . However, this reaction is rather slow [49] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr {\rm TFSI}{^{- }}+{\rm e}{^{- }}\rightarrow {^{\bullet}}{\rm CF}{_{2}}{\rm SO}{_{2}}{\rm N}{^{- }}{\rm SO}{_{2}}{\rm CF}{_{3}}+{\rm F}{^{- }}\hfill\cr}}$$$ …”