Photo-chemical/catalytic oxidative/reductive decomposition of per- and poly-fluoroalkyl substances (PFAS), decomposition mechanisms and effects of key factors: a review

Esfahani, Ehsan Banayan; Zeidabadi, Fatemeh Asadi; Zhang, Shengyang; Mohseni, Madjid

doi:10.1039/d1ew00774b

Cited by 25 publications

(27 citation statements)

References 197 publications

(444 reference statements)

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“…For decades, per- and polyfluoroalkyl substances (PFAS) chemicals have been widely used in various consumer, medical, and industrial products. − Owing to environmental persistence and being notoriously hazardous, the long-chain PFAS chemicalsperfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS)have been prohibited under international regulations. , However, many short-chain fluorinated alternatives remain in use, and they could also be accumulated via physicochemical degradation pathways of longer-chain PFAS. − Even though the use of hydrated electron (e aq – )-based advanced reductive technology (e aq – -ART) has recently shown to be effective to destruct both perfluoroalkyl carboxylates (PFxA, x = number of carbons comprising the hydrophobic tail) and perfluoroalkyl sulfonates (PFxS), − PFxS with short fluoroalkyl chains such as PFBS (C 4 F 9 SO 3 – ) remains an exceptional case and displays very sluggish reactivity . To date, the abundance of short-chain PFAS from numerous sources has already been detected in most locations on the planet. − Recent toxicological studies revealed that the potential threats to human health posed by analogs had been underestimated due to increased solubility, mobility, and inertness. − Thus, their complete removal and decomposition from the aquatic environment has become an urgent concern.…”

Section: Introductionmentioning

confidence: 99%

Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

Jiang

Adjei

Denisov

et al. 2022

Environ. Sci. Technol. Lett.

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The role of the short-lived hydrated electron (e aq − ) has recently begun to be appreciated in per-and polyfluoroalkyl substances (PFAS) remediations; nevertheless, few studies to date focused on short-chain PFAS, and their effective defluorination has been limited by an insufficient mechanistic understanding, which starts with the elusive initial step of e aq − reduction. Herein, this study uses pulse radiolysis to clarify the rate constant of the e aq − reaction with a highly recalcitrant short-chain PFAS, perfluorobutanesulfonate (PFBS, C 4 F 9 SO 3 − ), and verify chain length dependence. The measured values contradict earlier results from laser photolysis but reconcile with the apparent degradation profiles and theoretical predictions. Besides, we first disclose radiolytic carbon dioxide radicals (CO 2 −• ) to defluorinate PFBS with an initial reaction constant of 4.8 × 10 7 M −1 s −1 , and it achieves selective cleavage on the more obstinate C−F bond than e aq − even under a neutral condition. Quantitative 60 Co γ-ray irradiation experiments further show that initial reduction occurs through a defluorination pathway rather than a desulfurization pathway, and the redox potential of PFBS exceeds −2.0 eV. This radiolytic study addressed the long-standing mechanistic contradictions regarding short-chain PFAS degradation and suggested ionizing radiation as a versatile and direct treatment technique.

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Section: Introductionmentioning

confidence: 99%

Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

Jiang

Adjei

Denisov

et al. 2022

Environ. Sci. Technol. Lett.

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“…These data demonstrate that the different exposure wavelengths do not produce significantly different TPs. Photodegradation of PFASs can occur, although at a low extent, and the reactions are dependent on irradiation wavelength and intensity, PFAS concentration and structure, and exposure duration . Thus, we expected to see different TPs between the two wavelengths and potentially more TPs in the 193 nm exposures due to the greater photon energy of 193 nm photons, which can induce greater PFAS degradation .…”

Section: Resultsmentioning

confidence: 99%

“…30 However, previous studies noted the importance of long irradiation times (>12 h) to achieve even negligible photolysis of PFASs. 30 Therefore, we conclude that the exposure durations used in these experiments, which mimic those of fabs, are not sufficient to induce significant photodegradation of PFASs at either 248 or 193 nm (Figure 3).…”

Section: Pfas Standards and Reagentsmentioning

confidence: 99%

“…Over 75% of the TF of each material remains unexplained after these mass balance analyses, indicating the stability of the organofluorine-containing constituents (e.g., fluoropolymers) of these photolithography materials during photolithography. 30 Additionally, materials intended for 193 nm exposures behave similarly under both exposure wavelengths, which has been unexplored prior to this study. These data do not support our hypothesis that organofluorine-containing compounds undergo significant transformations to generate PFASs that explain a greater portion of the TF in the materials under the chemical conditions of these simulated photolithography experiments.…”

Section: Pfas Standards and Reagentsmentioning

confidence: 99%

“…29,50 Photochemical degradation of long-chain PFASs has been observed at 254 nm wavelengths but only in systems with the addition of a strong chemical oxidant like titanium dioxide (TiO 2 ). 29,30,51 Therefore, the prescribed conditions of photolithography are apparently insufficient to induce transformations of organofluorine-containing constituents in these materials.…”

Section: Pfas Standards and Reagentsmentioning

confidence: 99%

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Exploring the Evolution of Organofluorine-Containing Compounds during Simulated Photolithography Experiments

Jacob,

Helbling

2023

Environ. Sci. Technol.

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One potential source of per-and polyfluoroalkyl substances (PFASs) in electronics fabrication wastewater are the organofluorine-containing compounds used in photolithography materials such as photoresists and top antireflective coatings (TARCs). However, the exact identities of these constituents are unknown and transformation reactions that may occur during photolithography may result in the formation of unknown or unexpected PFASs. To address this knowledge gap, we acquired five commercially relevant photolithography materials, characterized the occurrence of organofluorine-containing compounds in each material, and performed simulated photolithography experiments to stimulate any potential transformation reactions. We found that photoresists and TARCs have total fluorine (TF) concentrations in the g L −1 range, similar to the levels of other industrial and commercial products. However, the target and suspect PFASs present in these materials can only explain up to 20% of the TF in a material. We evaluated wastewater samples collected after simulated photolithography experiments and used a mass balance approach to assess the extent of transformations. Although a number of target, suspect, and nontarget PFASs were identified in the wastewater samples, the extent of transformation was limited and the fluorine contained in the PFASs could not explain more than an additional 1% of the TF in the photolithography materials.

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High aspect ratio triangular front contacts for solar cells fabricated by string‐printing

Voorde

Andersons

Saive

2023

Progress in Photovoltaics

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We are presenting a novel method to fabricate high aspect ratio, triangular cross‐section solar cell front contacts, henceforth referred to as string‐printing. We optimized string‐printing to yield contacts with an aspect ratio larger than 1 and a light redirection efficiency or effective transparency of 67%, thereby mitigating most of the optical losses inherent to flat metallic front grids. In string‐printing, a string coated with silver paste approaches a substrate until contact is made. Withdrawing the string then leaves behind silver paste on the substrate. Here, we describe the fabrication method and show initial results including current density‐voltage curves of string‐printed silicon heterojunction solar cells, as well as the effective transparencies of the contacts. String‐printing is a scalable, low‐temperature process with high potential to boost commercial solar cell efficiency and lower the module price per Watt.

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Photo-chemical/catalytic oxidative/reductive decomposition of per- and poly-fluoroalkyl substances (PFAS), decomposition mechanisms and effects of key factors: a review

Abstract: Per- and poly-fluoroalkyl substances (PFAS) are a group of diverse anthropogenic chemicals with a wide range of industrial and commercial applications. Worldwide detection of legacy and emerging PFAS, as well...

Cited by 25 publications

References 197 publications

Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

Transient Kinetics of Short-Chain Perfluoroalkyl Sulfonate with Radiolytic Reducing Species

Exploring the Evolution of Organofluorine-Containing Compounds during Simulated Photolithography Experiments

High aspect ratio triangular front contacts for solar cells fabricated by string‐printing

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