TY - JOUR
T1 - Sustained hydrated electron production for enhanced reductive defluorination of PFAS in groundwater
AU - Xiong, Xingaoyuan
AU - Luo, Zirui
AU - Luo, Shuang
AU - Bai, Lu
AU - Shang, Yanan
AU - Junker, Allyson L.
AU - Wei, Zongsu
PY - 2025/7/1
Y1 - 2025/7/1
N2 - Hydrated electrons (eaq‒; ‒2.9 V) are effective at defluorinating per- and polyfluoroalkyl substances (PFAS), but production of eaq‒ often requires excess source chemicals, anoxic environment, and harsh pH conditions. To improve the feasibility of the reductive process, we harnessed phenol as a source chemical yielding four eaq‒ stoichiometrically and utilized dithionite (DTN) to catalyze phenol cycle for sustained eaq‒ yields. The added DTN not only scavenges dissolved oxygen, the eaq‒ trap, but also reductively transforms phenol degradation product, p-benzoquinone, to hydroquinone which yields more eaq‒ upon UV irradiation. In the UV/phenol/DTN system, up to 70 % defluorination of PFOA solution was achieved while the impact of groundwater matrix was minor on the degradation performance of PFOA, PFOS and GenX. Especially in acidic conditions, •H, the conjugate acid of eaq‒, is the dominant radical for decomposing the three tested PFAS. Density functional theory calculations reveal hydrogen bonding and van der Waals interactions between PFAS and phenol, facilitating both decarboxylation and fluorine elimination in PFAS structures. The combined experimental and theoretical evidence demonstrated the capability of the new UV/phenol/DTN method to sustain eaq‒ production for effective defluorination of PFAS in the groundwater matrix.
AB - Hydrated electrons (eaq‒; ‒2.9 V) are effective at defluorinating per- and polyfluoroalkyl substances (PFAS), but production of eaq‒ often requires excess source chemicals, anoxic environment, and harsh pH conditions. To improve the feasibility of the reductive process, we harnessed phenol as a source chemical yielding four eaq‒ stoichiometrically and utilized dithionite (DTN) to catalyze phenol cycle for sustained eaq‒ yields. The added DTN not only scavenges dissolved oxygen, the eaq‒ trap, but also reductively transforms phenol degradation product, p-benzoquinone, to hydroquinone which yields more eaq‒ upon UV irradiation. In the UV/phenol/DTN system, up to 70 % defluorination of PFOA solution was achieved while the impact of groundwater matrix was minor on the degradation performance of PFOA, PFOS and GenX. Especially in acidic conditions, •H, the conjugate acid of eaq‒, is the dominant radical for decomposing the three tested PFAS. Density functional theory calculations reveal hydrogen bonding and van der Waals interactions between PFAS and phenol, facilitating both decarboxylation and fluorine elimination in PFAS structures. The combined experimental and theoretical evidence demonstrated the capability of the new UV/phenol/DTN method to sustain eaq‒ production for effective defluorination of PFAS in the groundwater matrix.
KW - Dithionite
KW - Hydrated electron
KW - Hydrogen atom
KW - Per- and polyfluoroalkyl substances
KW - Phenol
UR - http://www.scopus.com/inward/record.url?scp=86000464767&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2025.123401
DO - 10.1016/j.watres.2025.123401
M3 - Journal article
C2 - 40081177
AN - SCOPUS:86000464767
SN - 0043-1354
VL - 279
JO - Water Research
JF - Water Research
M1 - 123401
ER -