| Autor: |
Rao U; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States., Su Y; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States., Khor CM; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States., Jung B; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States., Ma S; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States., Cwiertny DM; Department of Civil and Environmental Engineering, University of Iowa, Iowa City, Iowa 52242, United States., Wong BM; Department of Chemical & Environmental Engineering, Materials Science & Engineering Program, University of California, Riverside, California 92521, United States., Jassby D; Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095-153, United States. |
| Abstrakt: |
Per and polyfluoroalkyl substances (PFAS), legacy chemicals used in firefighting and the manufacturing of many industrial and consumer goods, are widely found in groundwater resources, along with other regulated compounds, such as chlorinated solvents. Due to their strong C-F bonds, these molecules are extremely recalcitrant, requiring advanced treatment methods for effective remediation, with hydrated electrons shown to be able to defluorinated these compounds. A combined photo/electrochemical method has been demonstrated to dramatically increase defluorination rates, where PFAS molecules sorbed onto appropriately functionalized cathodes charged to low cell potentials (-0.58 V vs Ag/AgCl) undergo a transient electron transfer event from the electrode, which "primes" the molecule by reducing the C-F bond strength and enables the bond's dissociation upon the absorption of a hydrated electron. In this work, we explore the impact of headgroup and chain length on the performance of this two-electron process and extend this technique to chlorinated solvents. We use isotopically labeled PFAS molecules to take advantage of the kinetic isotope effect and demonstrate that indeed PFAS defluorination is likely driven by a two-electron process. We also present density functional theory calculations to illustrate that the externally applied potential resulted in an increased rate of electron transfer, which ultimately increased the measured defluorination rate. |
