Hydrogen-polarized vacuum ultraviolet photolysis system for enhanced destruction of perfluoroalkyl substances

By Gongde Chen, Sitao Liu, Qingyang Shi, Jay Gan, Bosen Jin, Yujie Men, and Haizhou Liu
JHM Letters
December 1, 2022
DOI: 10.1016/j.hazl.2022.100072

Reductive water treatment using hydrated electrons (eaq−) is a promising technology to destruct perfluoroalkyl substances; however, it faces challenges of slow reaction kinetics, undesirable chemical addition, and high energy consumption. Herein, we developed a hydrogen (H2)-polarized water photolysis system using vacuum UV (VUV) light at 185 nm for reductive destruction of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The 185-nm photons directly photolyzed H2O and OH^- into HO·, H·, and eaq−. H2 elevated the quasi steady-state concentration of eaq− 18 times in untuned VUV systems through eliminating the scavenging effect of dissolved oxygen and converting hydroxyl radicals (HO·/O·^-) into eaq−. The polarization effect of H2 increased the degradation of PFOA from 10 % to 95 % and the defluorination from 17 % to 94 % and led to 87 % of defluorination for PFOS. The pH impacted VUV photon adsorption between H2O and OH^- and shifted the equilibrium between H· and eaq−, which led to an optimal pH of 10.3 for PFOA destruction. The presence of chloride and sulfate enhanced the production of eaq− and promoted PFOA destruction. H2-polarized VUV water photolysis systems produced high levels of eaq− from clean water constituents and significantly reduced energy consumption for PFAS treatment under mild alkaline conditions.

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