PFAS化学物質は永遠ではない(PFAS chemicals do not last forever)

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紫外線照射下で亜硫酸塩とヨウ化物を使用すると、水中のPFASを数時間で破壊することができる The use of sulfite and iodide under ultraviolet light can destroy PFAS in water in a few hours

2022-05-19 カリフォルニア大学リバーサイド校(UCR)

紫外線(UV)と亜硫酸塩を使用する水処理リアクターにヨウ化物を加えると、PFAS(永久化学物質)に含まれる炭素-フッ素原子の最大90%がわずか数時間で破壊されることが、カリフォルニア大学リバーサイド校の環境工学研究者が率いる新しい研究で明らかになった。ヨウ化物を加えることで反応速度が4倍まで加速され、エネルギーと化学物質を節約することができます。

<関連情報>

UV/亜硫酸塩+ヨウ化物によるペルフルオロスルホン酸塩およびペルフルオロカルボン酸塩の分解促進。反応機構とシステム効率 Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies

Zekun Liu, Zhanghao Chen, Jinyu Gao, Yaochun Yu, Yujie Men, Cheng Gu, and Jinyong Liu
Environmental Science&Technology  Published:February 28, 2022
DOI:https://doi.org/10.1021/acs.est.1c07608

Abstract

The addition of iodide (I) in the UV/sulfite system (UV/S) significantly accelerated the reductive degradation of perfluorosulfonates (PFSAs, CnF2n+1SO3) and perfluorocarboxylates (PFCAs, CnF2n+1COO). Using the highly recalcitrant perfluorobutane sulfonate (C4F9SO3) as a probe, we optimized the UV/sulfite + iodide system (UV/S + I) to degrade n = 1–7 PFCAs and n = 4, 6, 8 PFSAs. In general, the kinetics of per- and polyfluoroalkyl substance (PFAS) decay, defluorination, and transformation product formations in UV/S + I were up to three times faster than those in UV/S. Both systems achieve a similar maximum defluorination. The enhanced reaction rates and optimized photoreactor settings lowered the EE/O for PFCA degradation below 1.5 kW h m–3. The relatively high quantum yield of eaq from I made the availability of hydrated electrons (eaq) in UV/S + I and UV/I two times greater than that in UV/S. Meanwhile, the rapid scavenging of reactive iodine species by SO32– made the lifetime of eaq in UV/S + I eight times longer than that in UV/I. The addition of I also substantially enhanced SO32– utilization in treating concentrated PFAS. The optimized UV/S + I system achieved >99.7% removal of most PFSAs and PFCAs and >90% overall defluorination in a synthetic solution of concentrated PFAS mixtures and NaCl. We extended the discussion over molecular transformation mechanisms, development of PFAS degradation technologies, and the fate of iodine species.

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