Reductive degradation of perfluoroalkyl compounds with aquated electrons generated from iodide photolysis at 254 nm

Park, Hyunwoong; Vecitis, Chad D.; Cheng, Jie; Dalleska, Nathan F.; Mader, Brian T.; Hoffmann, Michael R.

doi:10.1039/c1pp05270e

Cited by 85 publications

(54 citation statements)

References 55 publications

(57 reference statements)

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“…In addition, high pH promoted the conversion of H • to e − aq (No. (33) and (34)). Thus, pH exerted its influence through changing the SO 2− 3 fraction and the interconversion of H • and e − aq .…”

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confidence: 99%

Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

et al. 2018

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Bromate (BrO − 3 ) residue in drinking water poses a great health risk. Ultra-fast reduction of BrO − 3 , under aerobic conditions, was realized using an ultraviolet (UV)/sulfite process in the presence of iodide (UV/sulfite/iodide). The UV/sulfite/iodide process produced BrO − 3 removal efficiency of 100% at about 5 min with complete conversion to bromide, while UV/sulfite induced 13.1% BrO − 3 reduction under the same conditions. Hydrated electrons, generated from the photolysis of sulfite and iodide, was confirmed as the main contributor to BrO − 3 degradation (77.4% of the total contribution). As the concentration of iodide was kept constant, its presence remarkably enhancing the generation of hydrated electrons led to its consideration as a homogeneous catalyst in the UV/sulfite/iodide system. Sulfite played a role not only as a hydrated electron precursor, but also as a reactive iodine species shielding agent and a regenerant of iodide. Results surrounding the effects on common water quality parameters (pH, bicarbonate, nitrate, natural organic matter, and solution temperature) indicated that preferred degradation of BrO − 3 occurred in an environment of alkaline pH, low-content natural organic matter/bicarbonate/nitrate, and high natural temperature.(I − )/nitrilotriacetic acid [14,15], vacuum-UV irradiation [7], and photoexcitation of organic chromophores [16]. From a practical perspective, the key for-based ARPs is generating e − aq efficiently under ambient conditions. Hydrated electron generation by UV activation of sulfite (UV/sulfite) is promising due to its oxygen self-cleaning property. However, e − aq generation by UV/sulfite was dependent on a high concentration of sulfite and high pH due to the relatively low absorptivity and the protonation of sulfite. Recently, Li etc.[17] proposed a UV/sulfite/I − process to generate e − aq , and successfully realized efficient degradation of monochloroacetic acid (12.86 µM·min −1 ). Enhanced production of e − aq through such a process was based on two facts: (1) both sulfite and I − act as e − aq precursors; (2) sulfite can reduce the e − aq scavenging by reactive iodine species (RIS, e.g., I • , I •− 2 , and I − 3 ). Given the similar rate constant of e − aq toward monochloroacetic acid (1.0 × 10 9 M −1 ·s −1 [18]) and BrO − 3 (3.4 × 10 9 M −1 ·s −1 [10]), it is reasonable to speculate that the UV/sulfite/I − process can also degrade BrO − 3 with high efficiency. Yet, to the authors' knowledge, there exist no other reports using this process to degrade BrO − 3 under aerobic conditions. Furthermore, the BrO − 3 degradation performance using the UV/sulfite/I − process under aerobic conditions, and the possible factors that may affect the degradation efficiency (i.e., pH, anions, and natural organic matter (NOM)) are yet to be investigated.In this work, we aimed to (1) investigate the reduction efficiency of BrO − 3 in prepared water and real water in the UV/sulfite/I − process; (2) explore the mechanism of BrO − 3 reduction (role of sulfite/I − and contributo...

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Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

et al. 2018

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“…In this way, Fwas generated during the hydrolysis process. While based on the low concentration of Fdetected in the solution, it was 16 obviously that this hydrolysis is not the main pathway for C n F 2n+1 • decomposition. On the other hand, the fluorine atoms at the chain-terminal of C n F 2n+1 • were gradually replaced by hydrogen atoms due to the nucleophilic substitution hydrodefluorination, the C-F bonds transformed into C-H bonds via the Si-H/C-F redistribution (conversion into C-H) [17].…”

Section: Decomposition Mechanisms Of Pfosmentioning

confidence: 99%

“…According to the previous researches, PFOS decomposition started with the cleavage of -F 2 C-SO 3 H bond, thus the focus of PFOS decomposition was how to realize initial activation of sulfonate group [13,14]. Sulfonate group in PFOS is 4 recalcitrant to traditional advanced oxidation processes (AOPs), while the hydrated electron (e aq -) induced reduction has been recently demonstrated to be effective to activate the sulfonate group [15,16]. However, due to the high reactivity of e aq with other coexistent oxidative species in solution, a large amount of chemical agent (molar concentration, I -: PFOS = 500 : 1) that can promote the e aq production was necessary to ensure fast decomposition kinetics [16].…”

Section: Introductionmentioning

confidence: 99%

“…Sulfonate group in PFOS is 4 recalcitrant to traditional advanced oxidation processes (AOPs), while the hydrated electron (e aq -) induced reduction has been recently demonstrated to be effective to activate the sulfonate group [15,16]. However, due to the high reactivity of e aq with other coexistent oxidative species in solution, a large amount of chemical agent (molar concentration, I -: PFOS = 500 : 1) that can promote the e aq production was necessary to ensure fast decomposition kinetics [16]. Inspired by these researches, conduction band electron (e cb -) generated by light irradiation with strong reduction ability as well, can probably substitute for e aq to activate the sulfonate group.…”

Section: Introductionmentioning

confidence: 99%

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Directional electron transfer mechanisms with graphene quantum dots as the electron donor for photodecomposition of perfluorooctane sulfonate

Huang

Yin

et al. 2017

Chemical Engineering Journal

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Graphene quantum dots (GQDs) were synthesized via the oxygen-driven unzipping of graphene under ultra-high frequency ultrasonication, and then attached to the SiC nanoparticles by the hydrothermal method to form the SiC/GQDs nanocomposites. The SiC/GQDs exhibited superior photoactivity over the decomposition of perfluorooctane sulfonate (C 8 F 17 SO 3 H, PFOS), which was even harder to decompose than perfluorooctanoic acid (PFOA). This work presented the first instance of employing photoexcited semiconductor nanomaterials to realize the improvement from the activation of the -F 2 C-COOH bond in PFOA to the activation of -F 2 C-SO 3 H in PFOS. The decomposition rate constants (k) of 2-CF 3 -PFOS, 6-CF 3 -PFOS and linear-PFOS with SiC/GQDs were 0.127 h −1 , 0.115 h −1 , 0.098 h −1 , and the corresponding half-lives were 5.5 h, 6.0 h, 7.1 h, respectively. The ratio of k (the branched isomers : the linear isomers) significantly reduced from the 967 times via vacuum ultraviolet (VUV) photolysis to the same order of magnitude in this work.The X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) were conducted to investigate the electronic properties of SiC/GQDs, revealing the centermost directional electron transfer process during the reaction. The photogenerated electron originated from the π-π* transition of the C=C bond and the n-π* transition of the C=O bond under UV excitation, transferred to SiC nanoparticles due to the heterojunction structure of SiC/GQDs, and then further transferred to the accumulated PFOS on the surface of SiC/GQDs for the electron-withdrawing property of sulfonate group, leading to the critical activation of sulfonate group. The decomposition mechanisms of PFOS involved the ionic headgroup cleavage, hydrolysis, hydrodefluorination, and the C-C bond scission.

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“…The ultrasonic and reductive transformation of a limited number of legacy PFAS have been reported [162][163][164], however we are unaware of any reports on the ultrasonic or reductive transformation of emerging PFAS. Herein, we reported the study of the transformation of "GenX" using radiolysis, TiO2 photocatalysis and sonolysis, and predict the reaction pathways of pyrolytic degradation of "GenX".…”

Section: Introductionmentioning

confidence: 98%

Fundamental Mechanistic Studies on the Ultrasonic Treatment of Problematic Water Pollutants and Toxins

Cui¹

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Reductive degradation of perfluoroalkyl compounds with aquated electrons generated from iodide photolysis at 254 nm

Cited by 85 publications

References 55 publications

Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

Directional electron transfer mechanisms with graphene quantum dots as the electron donor for photodecomposition of perfluorooctane sulfonate

Fundamental Mechanistic Studies on the Ultrasonic Treatment of Problematic Water Pollutants and Toxins

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