Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet

Wang, Yuan; Zhang, Pengyi

doi:10.1016/j.jes.2014.09.003

Cited by 40 publications

(34 citation statements)

References 47 publications

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“…The order of concentration followed PFPeA > PFBA > perfluoropropionic acid (PFPA) > trifluoroacetic acid (TFA) demonstrating the longer chain intermediates appeared at the start of the reaction followed by decomposition to shorter chain products. Investigating PFOA degradation using 254 nm UV during UV/H 2 O 2 /Fe 2+ process, Tang et al [41] found that the degradation intermediates included the short chain perfluorocarboxylic acids containing 2, 3 4, 5 and 6 carbon atoms and fluoride ions which is in agreement with others [23,64]. Liang et al [32] also identified perfluoronated carboxylic acids with 2-7 carbon atoms during VUV/Fe 3+ degradation of PFOA.…”

Section: Reaction By-products During Uv/vuv Photodegradationsupporting

confidence: 53%

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Umar

2021

Water

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Perfluoroalkyl and polyfluoroalkyl substances (PFASs) consist of a group of environmentally persistent, toxic and bio-accumulative organic compounds of industrial origin that are widely present in water and wastewater. Despite restricted use due to current regulations on their use, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) remain the most commonly detected long-chain PFAS. This article reviews UV-based oxidative and reductive studies for the degradation of PFAS. Most of the UV-based processes studied at lab-scale include low pressure mercury lamps (emitting at 254 and 185 nm) with some studies using medium pressure mercury lamps (200–400 nm). A critical evaluation of the findings is made considering the degradation of PFAS, the impact of water quality conditions (pH, background ions, organics), types of oxidizing/reducing species, and source of irradiation with emphasis given to mechanisms of degradation and reaction by-products. Research gaps related to understanding of the factors influencing oxidative and reductive defluorination, impact of co-existing ions from the perspective of complexation with PFAS, and post-treatment toxicity are highlighted. The review also provides an overview of future perspectives regarding the challenges in relation to the current knowledge gaps, and future needs.

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Section: Reaction By-products During Uv/vuv Photodegradationsupporting

confidence: 53%

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Umar

2021

Water

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“…These results may be explained that excessive OH − will react with

{SO}_{4}^{‐}

· to produce ·OH that has no ability to decompose PFOA (Vecitis, Park, Cheng, Mader, & Hoffmann, 2009), reducing the utilization rate of

{SO}_{4}^{‐ ∙}

. In addition, there was a competition between OH − and PFOA for the absorption of 185 nm photons because of the high absorption coefficient of OH − (3,000 M −1 cm −1 ) (Wang & Zhang, 2014). In general, the experimental results showed that with the increase of the initial pH, both the conversion of

{SO}_{4}^{‐ ∙}

and the absorption of photons by hydroxide are confined within a certain range, resulting in a small decrease in the defluorination rate of PFOA.…”

Section: Resultsmentioning

confidence: 99%

The defluorination of perfluorooctanoic acid by different vacuum ultraviolet systems in the solution

Lin

Liu

et al. 2020

Water Environment Research

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Perfluorooctanoic acid (PFOA) is one kind of persistent organic pollutants that is often detected in water. In recent years, the effective degradation technologies of PFOA have attracted widespread attentions. Thus, in this study, the defluorination efficiency of PFOA in different systems (i.e., ultraviolet (UV), vacuum ultraviolet (VUV), vacuum ultraviolet/persulfate (VUV/PS) and vacuum ultraviolet/residual chlorine (VUV/RC)) was evaluated. Moreover, the different impact factors (i.e., the initial concentrations of persulfate and PFOA, temperature, anions, and initial pH values) on PFOA degradation by VUV/PS system were investigated. The results showed that VUV system was more effective than UV system for PFOA defluorination. VUV system combined with persulfate would further enhance the defluorination efficiency while residual chlorine would decrease it. In VUV/PS system, the defluorination efficiency of PFOA was the best as the molar ratio of PFOA and persulfate at 1:60. Moreover, higher temperature, lower initial PFOA concentration, and acid condition were favorable for the defluorination of PFOA. Under the different influence factors, the defluorination efficiency of PFOA fitted well to the first‐order reaction kinetic model. When the temperature was range from 20°C to 40°C, the value of activation energy was 8.73 kJ/mol. Besides, the inhibition effect of three kinds of anions on PFOA defluorination followed the order: NO3‐ > Cl− > CO32‐. Practitioner points The defluorination efficiency of perfluorooctanoic acid (PFOA) in water by different VUV systems was compared. VUV system is more effective than UV system for PFOA defluorination. Persulfate will enhance the defluorination efficiency by VUV system. Hypochlorite will decrease the defluorination efficiency by VUV system.

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“…As alluded to previously, wet and dry deposition processes are believed to dominate the atmospheric fate of PFOA, given its slow oxidation and inefficient photolysis processes [21,22]. However, a recent report suggests that reaction with Criegee intermediates (CIs) is also likely to be significant in determining the atmospheric fate of PFOA, though it is important to note that this study did not explicitly investigate the impact of this loss process on a global scale [23].…”

Section: Introductionmentioning

confidence: 94%

Investigating the Atmospheric Sources and Sinks of Perfluorooctanoic Acid Using a Global Chemistry Transport Model

et al. 2020

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Perfluorooctanoic acid, PFOA, is one of the many concerning pollutants in our atmosphere; it is highly resistant to environmental degradation processes, which enables it to accumulate biologically. With direct routes of this chemical to the environment decreasing, as a consequence of the industrial phase out of PFOA, it has become more important to accurately model the effects of indirect production routes, such as environmental degradation of precursors; e.g., fluorotelomer alcohols (FTOHs). The study reported here investigates the chemistry, physical loss and transport of PFOA and its precursors, FTOHs, throughout the troposphere using a 3D global chemical transport model, STOCHEM-CRI. Moreover, this investigation includes an important loss process of PFOA in the atmosphere via the addition of the stabilised Criegee intermediates, hereby referred to as the “Criegee Field.” Whilst reaction with Criegee intermediates is a significant atmospheric loss process of PFOA, it does not result in its permanent removal from the atmosphere. The atmospheric fate of the resultant hydroperoxide product from the reaction of PFOA and Criegee intermediates resulted in a ≈0.04 Gg year−1 increase in the production flux of PFOA. Furthermore, the physical loss of the hydroperoxide product from the atmosphere (i.e., deposition), whilst decreasing the atmospheric concentration, is also likely to result in the reformation of PFOA in environmental aqueous phases, such as clouds, precipitation, oceans and lakes. As such, removal facilitated by the “Criegee Field” is likely to simply result in the acceleration of PFOA transfer to the surface (with an expected decrease in PFOA atmospheric lifetime of ≈10 h, on average from ca. 80 h without Criegee loss to 70 h with Criegee loss).

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Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet

Cited by 40 publications

References 47 publications

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

The defluorination of perfluorooctanoic acid by different vacuum ultraviolet systems in the solution

Investigating the Atmospheric Sources and Sinks of Perfluorooctanoic Acid Using a Global Chemistry Transport Model

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