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[Display omitted] • Emerging PFAS removal technologies were reviewed systematically. • Adsorbed long and short-chain PFAS are replaced by coexisting organic compounds. • Novel membranes and adsorbent selectivity for shorter C-F chains must be developed. • Holes destabilize the PFCAs to unstable perfluoroalkyl radicals. Perfluoroalkyl substances (PFAS) are a group of synthetic organic chemicals extensively used in consumer and industrial applications over the past decades. The current literature lacks a comprehensive review of the mechanisms and degradation pathways of long- and short-chain PFASs. The overall concentration of perfluorobutanoic acid in aquatic systems ranged from 1.15 to 6280 ng/L, while perfluorobutane sulfonic acid varied from 0.01 to 4520 ng/L. Prior to 2015, perfluorooctanoic acid (PFOA) concentrations in wastewater treatment facilities ranged from 92 to 66,000 ng/L, while levels decreased after 2015 (3–100 ng/L) as PFAS production decreased. This systematic literature review compiles the latest evidence of the mechanism and pathway degradation of emerging technologies, such as advanced oxidation processes, membrane separation, adsorption, and biological transformation of PFAS, which were reviewed comprehensively. Bibliometric assessment was performed using keyword-based search criteria, and network maps were created using VOS Viewer. Activated carbon showed >90 % elimination of long-chain PFAS. Nanofiltration and reverse osmosis membranes were observed to be effective for perfluorooctane sulfonic acid and PFOA removal, with rejection efficiencies of >99 % in aqueous matrices with different membrane materials. Pilot scale studies showed that granular activated carbon and biosolid-based biochar sorbed more than 80 % of long-chain PFAS and 19–27 % of short-chain PFAS. Short-chain precursors like fluorotelomers degrade 60–100 % more effectively with mixed microbial strain cultures. Two main challenges have been identified: (a) Operational complexity on a large scale and the transformation of toxic byproducts, and (b) Emerging technologies have certain removal effects on short-chain PFASs. [ABSTRACT FROM AUTHOR]

• Electrochemical Sensing of PFOA with Nanoenabled Functionalized electrodes. • Highly sensitive and selective PFOA sensor with 24 ppt LOD and 80 LOQ. • Sensor is stable over at least 200 cycles with 97 % reproducibility. • Detection in matrices with interferents shows a 100 ± 10 % recovery. • Proposed mechanism to explain the electrochemical reduction of PFOA. Perfluorooctanoic acid (PFOA) is a pollutant of emerging concern due to its high persistence, bioaccumulation, and potential toxicity. Numerous studies report its presence in water sources, soils, and food at sub-ppb levels. Here, we describe the design of an electrochemical sensor based on a self-assembled monolayer (SAM) of the 1H,1H,2H,2H -Perfluorodecanethiol (PFDT), into gold nanoparticles (AuNPs) electrodeposited on glassy carbon electrode (GCE) for PFOA detection. The GCE coated with AuNPs was characterized using scanning electron microscopy (SEM). The average size of AuNPs is estimated as 16 nm ± 07 nm, and the electrode surface coverage is 39 % ± 2%. The calculated coverage of (Γ*) of chemisorbed PFDT molecules was found to be 8.26 × 10−10 mol cm−2. PFOA electroanalysis and quantification were performed by square wave adsorptive cathodic stripping voltammetry (SW-AdCSV) and measurements were verified by liquid chromatography-tandem mass spectrometry LC/MS-MS. We worked in a range of 100 to 5000 ppt, the PFOA concentration has a linear relationship with the stripping current (R2 = 0.996). The limits of detection (LOD) and quantification (LOQ) are 24 and 80 ppt, respectively. Analyses of tap and brackish samples performed by spiking tap water with known PFOA concentrations show precision and accuracy above 95%. The nano-enabled electrode is stable for at least 200 cycles. The reproducibility across similarly prepared but different electrodes is above 97%. The sensor shows the ability to quantify PFOA even in a matrix with other perfluoroalkyl substances as interferents, with a recovery percentage (Δi 0 –Δi int)/Δi 0) within of 100 ± 10%. [ABSTRACT FROM AUTHOR]

[Display omitted] • DBD/sulfite system effectively mitigated membrane fouling and enhanced PFOA degradation. • Membrane fouling could be mitigated through the presence of e aq - , SO 3 ∙ - , ∙ OH, SO 4 ∙ - , and ∙ O 2 -. • The degradation of PFOA was attributed to the presence of ∙ OH, SO 4 ∙ - , and e aq -. • The degradation pathway and mechanism of PFOA were proposed. • The mechanism underlying the mitigation of membrane fouling was elucidated. The present study employed a dielectric barrier discharge (DBD)/sulfite system to mitigate membrane fouling and enhance the degradation of perfluorooctanoic acid (PFOA) in surface water. Results showed that the membrane flux was remarkably enhanced by 93.6%, and the degradation of PFOA showed an impressive increase of 87.9%. The synergistic redox effect of free radicals, including hydroxyl radical (•OH), sulfate radical (SO 4 ∙ - ), electron ( e - /e aq -), su-peroxide anion radicals ( ∙ O 2 -), and other radical, played a crucial role in mitigating membrane fouling, accounting for 36.26%, 30.10%, 18.69%, 6.75%, and 8.20%, respectively. The correlation analysis revealed that effective removal of UV 254 and TOC emerged as the most crucial factors positively contributing to mitigating membrane fouling. Additionally, SO 4 ∙ - , •OH, and e aq - were identified as the primary active substances responsible for attacking PFOA, accounting for 41.30%, 25.20%, and 23.70%, respectively. The degradation pathway of PFOA was proposed through analysis using density functional theory and mass spectrometry, reducing the biotoxicity of its degradation products. This study presents a suitable strategy for simultaneous mitigation of membrane fouling and enhancement of PFOA degradation, which holds great potential for advancing the field of water treatment towards practical applications. [ABSTRACT FROM AUTHOR]

Present work demonstrate an efficient strategy of regulating the molecular conformation in PEDOT:PSS for ordered PEDOT domains and favorable band alignment, leading to the formation of true-blue PeLEDs with peak EQE up to 6.86% and maximum luminance of 854.10cd/m2 at wavelength of 478 nm. And we achieved the success of air-processed blue PeLEDs based on PFOA modified PEDOT:PSS. [Display omitted] • PFOA regulates the molecular conformation of PEDOT:PSS, improving carrier transport and alignment with the perovskite layer. • The PeLEDs with PFOA reach a peak external quantum efficiency of 6.86 % and a maximum luminance of 854.10 cd/m2 at a wavelength of 478 nm, which are the record values for the pure-bromide quasi-2D PeLEDs in the true-blue region. • The blue PeLEDs were successfully fabricated under ambient conditions (≈25 % RH and 20 °C), owing to the hydrophobic fluorine-carbon (C-F) chains of PFOA. The pure-bromide quasi-2D perovskite has shown advantages in fabrication of blue perovskite light-emitting diodes (PeLEDs) due to its relatively good color stability and capability of moisture resistance. However, the performances of efficiency and luminance of pure-bromide quasi-2D PeLEDs with true-blue (470 nm−480 nm) emission are still inferior. Here, we show a interfacial modification strategy of involving perfluorooctanoic acid (PFOA) to a hole transport layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), to improve the performances of the true-blue PeLEDs. The PFOA regulates the molecular conformation of PEDOT:PSS, forming ordered PEDOT domains that improves the carrier transport and a more favorable band alignment with the perovskite emissive layers. The achieved true-blue PeLEDs show peak EQE of 6.86 % and maximum luminance of 854.10 cd/m2 at wavelength of 478 nm, which are the record values for the pure-bromide quasi-2D PeLEDs in true-blue region. Moreover, owing to the hydrophobic fluorine-carbon (C-F) chains of PFOA, we successfully fabricate the blue PeLEDs in air condition without inert gas protection. This work paves the way for commercial applications in next-generation display technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Degradation of four PFAS in (waste)water was investigated in a hybrid nonthermal plasma-ozonation cascade reactor. • The PFAS degradation efficiency increased in the order of PFBA (11 %) < PFHxA (32 %) < PFOA 80 %) < PFDA (90 %) after plasma-ozonation treatment. • The reactions occurring in the plasma chamber are responsible for PFAS degradation. • Reductive species (such as e aq − and Ar+) are mainly responsible for PFAS defluorination. • Without additional ozone dosing, the ozonation chamber enhances ozone utilization efficiency (55%) in the degradation of bulk organics. The widespread use of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the last century has caused serious pollution of water bodies around the world, threatening the health of humans and other organisms. In this work, a novel cascade reactor configuration, comprised of a dielectric barrier discharge (DBD) plasma chamber connected with an ozonation chamber was used to treat municipal secondary effluent loaded with several PFAS. The electrical energy per order (EE/O) for degradation of perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) amounts 180 and 100 kWh/m3, respectively. While the short-chain PFAS (perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA)) were difficult to be degraded, i.e. degradation percentage < 32 % after 60 min, 80–90 % of the longer PFAS (PFOA and PFDA) were degraded within 60 min. The degradation of PFAS mainly occurred in the plasma chamber rather than in ozonation chamber. This is because that reductive species produced in plasma chamber, such as hydrated electrons (e aq −) and Ar+, played a direct role in defluorination, while oxidative species, including OH, O, O 2 −, 1O 2 , O 3 , and H 2 O 2 , has a very limited contribution for defluorination. Enhancing the utilization of reductive species is crucial to degrade PFAS. Perfluoroalkyl carboxylic acids (PFCA) generated during the plasma reactions may have a potential risk for environment. As such, further optimization should focus on full mineralization. This study provides an approach to solve the problem of PFAS-contaminated wastewater, which is of the importance to promote the application of nonthermal plasma technique in water treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PFAS removal performance with different iron minerals were discussed in CWs. • Iron minerals reduced PFAS content in water and substrate and promoted plant uptake. • Iron minerals increased the EPS capacitance and promoted electron transfer in CWs. • Gene relate to EPS synthesis and defluorination were enriched in iron-based CWs. Perfluorooctanoic acid (PFOA) and perfluorooctane sulphonic acid (PFOS) pollution existed widely in constructed wetlands (CWs). Iron minerals have been proved to enhance PFOS and PFOA removal in CWs. However, the microbial extracellular electron transfer mechanisms mediated by iron minerals remain unclear. To strengthen the removal of PFOA and PFOS, and explore the mechanisms, in this study, four kinds of iron-based CWs were constructed with magnetite, siderite, sponge iron, and hematite. Results reflected that the addition of iron minerals increased the PFOS and PFOA removal by 7.27 %-16.42 % than that in control group. XRD and XPS results show that iron minerals can promote the formation of Fe(Ⅲ) (hydrogen)oxides that conducive to electron transfer. The electrochemical characterization of extracellular polymer (EPS) and microbial electron transport activity showed that iron minerals improve the capacitance and electron transfer properties of EPS. Microbial results showed that magnetite and siderite improved the diversity of microorganisms that associated with PFOA and PFOS degradation (e.g. Geobacter, Shewanella, and Pseudomonas). Furthermore, both magnetite and siderite can promote extracellular protein secretion (p < 0.05), and increase the abundance of genes that related to extracellular-related cytochrome synthesis pathway (K02275, K01784), EPS synthesis (pgi, pgm, ugp), and defluorine (K01560, K01561, K01563). This study provides insight into the mechanisms of the PFOA and PFOS removal process and contributes a new perspective to further enhance the treatment of new pollutants in CWs. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D MOFs-based nanosheets with rich oxygen vacancies were designed. • The Kirkendall effect successfully regulated the oxygen vacancies. • The presence of oxygen vacancies improved the photocatalytic ability of the cathode. • PFOA degradation and TOC removal efficiency reached 93 % and 92 % in 180 min. • The mechanism of adsorption and degradation of PFOA in heterogeneous systems was described clearly. In heterogeneous solar photo-electro-Fenton (SPEF) degradation of perfluorooctanoic acid (PFOA), improving the binding energy between the catalyst and PFOA on a surface molecular level to facilitate absorption, diffusion, and degradation is a great challenge. Herein, we attained this goal in two steps: First, developing of two-dimensional (2D) MOFs-based CoFe nanosheets with layered structures as photo-electrocatalysts, which own abundant unsaturated coordination sites to accelerate rapid mass transport and charge transfer. Secondly, the construction of abundant oxygen vacancies (OVs) at low temperatures in 2D CoFe causes hybridization of the d-band of Fe and LUMO orbital of O in PFOA, enhancing PFOA's binding capacity by theoretical analysis. OVs also reduced the band gap of CoFe and increased the efficiency of electron-hole separation, thereby improving photo-electrocatalytic activity and enabling rapid degradation of PFOA. Moreover, it can maintain a good degradation effect in complex ionic background conditions and actual water samples. These findings extend the applications of catalysts and consolidate the effect of OVs on photo-electrocatalysis for wide environmental applications. [ABSTRACT FROM AUTHOR]

• BN degrades PFOA ∼ 2.5–3.5 × faster than TiO 2 at neutral and acidic pH. • Surface hydrophobicity of BN promotes the PFOA surface sorption. • BN hydrophobicity directs the holes to preferentially react with physisorbed PFOA. • BN hydrophobicity suppresses the competitive hole oxidation of surface hydroxyls. Boron nitride (BN) photodegrades perfluorooctanoic acid (PFOA) in water under 254-nm light illumination more rapidly than TiO 2 , which is hypothesized due to its greater surface hydrophobicity. We investigated the role of hydrophobicity on PFOA photocatalysis by comparing BN with anatase TiO 2 under reaction conditions, for which the exposed surface areas were the same. BN exhibited ∼ 3.5 × faster PFOA degradation rate compared to TiO 2 under acidic pH conditions. PFOA adsorption experiments showed that BN had ∼ 2 × higher PFOA surface coverage, consistent with its higher surface hydrophobicity, as corroborated by contact angle measurements. Both materials were comparatively less photocatalytically active at neutral pH, but BN still exhibited ∼ 2.7 × faster PFOA degradation rate, due to less electrostatic attraction between the PFOA headgroup and the catalyst surface. Langmuir-Hinshelwood rate law analysis suggests BN and TiO 2 have comparable photogenerated hole surface concentrations, and density functional theory calculations show that the holes for both photocatalysts can react with surface hydroxyls and with adsorbed PFOA. However, BN has comparatively less surface hydroxyl groups and more adsorbed PFOA, which favors hole reaction with the latter, resulting in a higher PFOA degradation rate. These insights into the role of surface hydrophobicity serve as rationally-guided design principles for improved heterogeneous photocatalysis of persistent surfactants, including the broad suite of per- or poly-fluoroalkyl substances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-MOFs derived CNF/Cu-C dual-functional membrane catalyst was synthesized. • Simultaneously efficient visual detection and SPEF degradation of PFOA are proposed. • PFOA inhibited peroxidase-like activity of CNF/Cu-C by hindering Cu active sites. • Enhanced degradation and mineralization efficiency of PFOA via SPEF are achieved. • States of active Cu species is regulated for enhanced photo-electric property. Developing bi-functional materials to simultaneously detect and degrade persistent pollutant perfluorooctanoic acid (PFOA) is of significant importance for environmental and human health. In this study, a copper-based mimic enzyme colorimetric detecting sensor coupling with solar photo-electro-Fenton degradation (SPEF) system was built based on Cu/carbon nanofiber (CNF-Cu/C) membrane. Self-supporting flexible CNF-Cu/C membrane was successfully prepared by solvothermal method with further secondary seed growth and in-situ thermal reduction. Based on calcination temperature regulation, the obtained CNF-Cu/C membrane derived from MOFs/polyacrylonitrile (HKUST/PAN) membrane was characterized by 3D carbon fiber network dispersed with porous carbon skeleton embedded copper species, which exhibited good dispersibility, cycling stability and excellent electrical conductivity. With excellent peroxidase-like activity, CNF-Cu/C can rapidly detect PFOA based on the inhibition of color reaction of tetramethylbenzidine (TMB) with detection limit of 0.133 μM. Furthermore, CNF-Cu/C also exhibited outstanding optical properties and oxygen redox reaction (ORR) activity, and the removal efficiency of PFOA in Cu-SPEF system reached 98.22 % within 180 min under optimal conditions. Based on the results of free radical quenching experiment, EPR experiment and HPLC-MS experiments, the degradation mechanism and degradation path of PFOA by SPEF system were further speculated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel CN layer coated flower-like WO 3 /W photoanode was successfully synthesized. • The photoelectrode exhibited sunlight-driven photocatalytic and reusability. • The photoelectrode used to degrade PFOA and generate electricity. • A new electron transfer channel is constructed due to the formation of W–N–C bond. • The PFOA degradation mechanism and decomposion pathway were analyzed. Photoelectrocatalysis (PEC) system has been proven to be effective in degrading perfluorooctanoic acid (PFOA) and generating electricity as a goal to solve the problems of environmental pollution and energy shortages simultaneously. In this study, we utilized a flower-like WO 3 in-situ generated on tungsten foil (WO 3 /W), and then doped with a CN layer by immersing it in urea solution and then undergoing calcination (CN-WO 3 /W), to degrade PFOA and generate electricity. The growth mechanism of WO 3 /W with different morphologies prepared under various experimental conditions was analyzed in order to explain the reasons for the superior performance of the flower-like structure compared to other morphologies. Under the irradiation of simulated sun-light, the power density reached its peak at 0.11 mW/cm2 when current density was 0.14 mA/cm2 with PFOA as fuel. CN-WO 3 /W displayed a steady state photocurrent density of 6.1 mA/cm2 at 1.2 V (vs. Ag/AgCl) under simulated sun-light irradiation and a high PFOA degradation of 95 %, which is much higher than that of WO 3 /W. Due to distinctive flower-like structure, stable W–N–C bond, narrower energy band (from 2.67 to 2.41 eV), more acquisition of visible light, and strong oxidation capability, the CN-WO 3 /W exhibited high stability and reusability for simultaneous PEC degradation of PFOA (almost unchanged after 9 cycles) and electricity generation (without activity loss during the 24 h test) under simulated sun-light irradiation. Based on the scavenger-quenching experiments the possible degradation pathways of PFOA were suggested. This work provides a way to design and synthesize the photoanode to construct reaction system for high-performance photocatalytic PFOA degradation and electricity generation. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV/S outperformed UV/PS in degrading PFOA in synthetic IEX regeneration waste. • PFOA was degraded efficiently in wastes containing either Na 2 SO 4 , Na 2 SO 3 or NaCl. • Dimerization was discovered at high initial concentrations of salt and PFOA. • Dimerization of PFOA affects the underlying degradation mechanisms significantly. • Excluding dimerization overestimates prediction of required fluence for treatment. The ultraviolet/sulfite (UV/S) destruction of perfluorooctanoic acid (PFOA) in seven solutions, representing ion exchange (IEX) regeneration wastes, was investigated, where Na 2 SO 4 , Na 2 SO 3 and NaCl were the most promising regenerants in degrading PFOA. A complete degradation and 94.7 % defluorination of 10 ppm PFOA were achieved in 10 % (1.7 M) NaCl regenerant containing waste within fluence of 248 J.cm−2. Among the four investigated key parameters (pH, sulfite dose, temperature, and initial PFOA concentration), an unexpected trend was observed for the effect of PFOA initial concentration on degradation efficiency. At outset of process, higher initial PFOA concentrations led to substantial decrease in PFOA concentration, but this trend reversed as the process continued. This drop in concentration is explained based on the fast aggregation of PFOA as revealed in molecular dynamic simulations and thermodynamic calculation. The reactivity of aggregates toward e aq - was three orders of magnitude less than that of monomers. Incorporating aggregation into the kinetic model led to a noteworthy improvement in the model prediction of PFOA concentration profiles, closely aligned with the experimental data. Neglecting aggregation kinetics in models can lead to an overestimation of the required fluence for PFOA degradation, with significant cost implications for large-scale treatment system design. This study underscores the critical and often underestimated issue of PFAS aggregation and its profound implications for the effectiveness of UV/S treatment in addressing IEX regeneration wastes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The two-component oxidant system persulfate + MnO 2 is active at low temperatures. • MnO 2 is a primary oxidant rather than a catalyst. • Persulfate acts as a secondary oxidant which re-oxidizes MnO x. • The advantage of MnO 2 over direct persulfate oxidation is highest at low temperatures. • Singlet oxygen 1O 2 does not play a major role in the oxidation process. MnO 2 can be used in advanced oxidation processes to activate peroxydisulfate (PS) and generate reactive species such as sulfate radicals (SO 4 •-), hydroxyl radicals (•OH) and singlet oxygen (1O 2) for the abatement of organic water contaminants. Alternatively, one can use MnO 2 as particulate oxidant which, in contrast to PS, is active already at low temperatures. This low-temperature activity is particularly attractive for in situ groundwater treatment. The roles of PS and MnO 2 as oxidant and catalyst, respectively, may invert: MnO 2 functions as primary oxidant and PS works as re-oxidant of reduced Mn-oxides. In this way, the limited oxidation capacity of particulate MnO 2 can be overcome. So far, such reaction systems have not been extensively explored. In the present study, the degradation of 4-hydroxybenzoic acid (HBA) by PS + MnO 2 was studied under various experimental conditions, by varying reaction temperature (15–45 °C), reagent concentrations, and water matrix. Both PS and MnO 2 alone have the ability to effect the oxidation of HBA. In the co-presence of PS and MnO 2 , a fast removal of HBA from water was achieved even at low temperatures (half-life of HBA about 0.5 h with 2.4 g L-1 MnO 2 at 25 °C), owing to a synergic effect between the two components. Quenching experiments indicate that the primary HBA oxidation step is a heterogeneous reaction on the MnO 2 surface rather than a homogeneous reaction driven by SO 4 •- or 1O 2 , as frequently reported in literature. This is in line with results from the PS driven oxidation of perfluorooctanoic acid which is not significantly enhanced in the presence of MnO 2. [ABSTRACT FROM AUTHOR]

• Cathodic Fenton-like system with anodic oxidation could degrade PFOA. • Modified rGAs cathodes effectively promoted PFOA degradation. • PFOA removal rate of 98.25% on Fe 3 O 4 -rGA and 98.91% on Cu-rGA cathode were achieved. • PFOA degradation mechanisms of ⋅OH and direct electron transfer synergy were proposed. Perfluorooctanoic acid (PFOA) pollution in aqueous environments has attracted considerable attention. Due to its high chemical stability, PFOA is very difficult to degrade, posing potential risks to human health. Therefore, it is of significance to find an efficient and eco-friendly way to remove PFOA from the environment. In this study, reduced graphene oxide aerogel (rGA) using the microbubble templating method was loaded with Fe 3 O 4 and Cu nanoparticles (NPs) to obtain Fe 3 O 4 -rGA and Cu-rGA, which were then prepared into cathodes. Heterogeneous Fenton-like system with Fe 3 O 4 /Cu-rGA cathodes coupled boron-doped diamond (BDD) electrodes were used to efficiently degrade PFOA in aqueous solutions. The parameters for PFOA degradation were optimized to be initial current density of 20.0 mA cm−2, initial electrolyte pH of 6, and electrolyte (Na 2 SO 4) concentration of 10 mM. After 360 min, the Fe 3 O 4 -rGA and Cu-rGA systems achieved PFOA removal efficiencies of 98.25 % and 98.91 %, respectively, which were 16.7 % and 17.5 %, respectively, higher than that achieved by the system using a commercial graphite electrode. PFOA was completely removed in 720 min and the F− production rates were 62.29 % and 65.48 % in the Fe 3 O 4 -rGA and Cu-rGA systems, respectively. PFOA degradation followed pseudo first-order kinetics in both systems (R2 > 0.99). The results of free radical quenching experiment and electrochemical performance experiment showed that the abundant active sites and excellent electrocatalytic properties of Fe 3 O 4 -rGA and Cu-rGAs promoted the formation of ⋅OH radicals for efficient PFOA degradation. In conclusion, coupling heterogeneous Fenton-like systems with Fe 3 O 4 or Cu NPs-loaded rGA and BDD electrooxidation have great potential in the treatment of PFOA wastewaters in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel biochar modified by wet ball-milling with FeCl 3 and pyrolysis. • Modified biochar has dispersed Fe0/Fe 3 C, multi-stage pores, and graphitized carbon. • PFAS sorption is enhanced by pore-filling, electrostatic and hydrophobic interaction. • PFBA sorption on Fe/C composite depends more on electrostatic interaction than PFOA. • Our novel sorbent excellent co-removal of various chain length PFAS in natural water. Legacy long-chain per-/polyfluoroalkyl substances (PFAS) are being replaced by short-chain homologs, which have been widely detected in the environment. To achieve the co-removal of different chain length PFAS, this study systematically explored the single and synergistic effects of FeCl 3 -impregnation, wet ball-milling and different carbonization temperatures on the surface chemistry and pore structures of different biochars as well as sorption performances and mechanisms towards long-chain perfluorooctanoic acid (PFOA) and short-chain perfluorobutyric acid (PFBA). As a consequence, we presented a new method to synthesize magnetic sorbents by wet ball-milling with FeCl 3 solution and high-temperature carbonization. Through this process, we tailored a magnetic porous Fe-doped graphitized biochar (named Fe-M−BC 900) that contains abundant dispersed positive iron sites with stable Fe0/Fe 3 C, multi-stage pore structure, highly hydrophobic graphite-like carbon, and O-containing functional groups. Fe-M−BC 900 exhibited a high sorption capacity of 10.1 mg PFBA/g and 39.1 mg PFOA/g. PFAS sorption on Fe-M−BC 900 was mainly governed by pore-filling, electrostatic interaction, and hydrophobic partitioning. The sorption of PFBA on Fe-doped biochars depends more on electrostatic interaction and is less affected by hydrophobic partitioning compared to PFOA. Finally, we demonstrated that Fe-M−BC 900 performed high co-removal rates (>96 %) for a wide range of legacy and emerging PFAS with different chain lengths and functional groups in natural waters (∑PFAS: 142 ∼ 265 μg/L) and simulated wastewater (∑PFAS: 600 μg/L), with a high relative sorption capacity of > 91 %, even after four consecutive recycling processes. This new adsorbent could help water facilities comply with upcoming PFAS regulations if tested on a larger scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • OA with 8 carbons provides better adsorption capacity through steric hindrance. • –COOH competes between OA/H 2 bpydc and H 2 bpdc to bind Zr cluster to form defects. • L-cysteine modification introduces more adsorption sites such as –COOH and –SH. • Easy recyclability and separation of aerogel beads were provided. • Adsorption capacity for Pb2+, Cd2+ and Cu2+ increased by 66.2, 10.7 and 5.8 times. Threats caused by heavy metal ions have prompted people to develop porous and functionalized materials to remove them. Metal–organic frameworks (MOFs) show potential for heavy metal ions removal due to the high specific surface area, tunable pore size, flexible designability and favorable stability. However, the intrinsic microporous structure and powder form limit their applications. Herein, we designed a shapeable aerogel bead incorporated with L-cysteine-modified defective UiO-67 for Pb(II), Cd(II) and Cu(II) adsorption. The pristine UiO-67 powders were firstly modified by introducing the modulator (octanoic acid) and an extra ligand (2,2′-bipyridine-5,5′-dicarboxylic acid) to construct defects, both of them competed with the original ligand to coordinate to Zr clusters, resulting in an increased BET surface area (from 337.66 to 1,037.14 m2/g) and mesoporous ratio (from 34 % to 74 %) of the pristine UiO-67. Then, the graft of L-cysteine containing –COOH and –SH introduced more active adsorption sites. Moreover, the powder material was incorporated into sodium alginate aerogel beads which enhanced the recyclability and further improved the adsorption capacity for Pb(II), Cd(II) and Cu(II). These appealing advantages endow the adsorbent with quicker adsorption equilibrium (240 min), and outstanding removal capacities for Pb(II) of 661.2 mg/g, Cd(II) of 296.2 mg/g and Cu(II) of 326.4 mg/g. The chelation and ions exchange between the numerous functional groups including –COOH, –OH and –SH and the heavy metal ions are the main mechanisms for effective adsorption. This work provided a novel approach for the application of MOFs in environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • SA-Cu/rGO anode was fabricated with high electrocatalytic activity. • 92.5% defluorination and 94.4% TOC removal of PFOA was achieved in 2 h. • Two degradation mechanisms contributed to the defluorination and mineralization. • Sulfate radicals mediated an energetically favorable pathway of PFOA defluorination. In this study, an electrocatalytic system using reduced graphene oxide supported single-atom copper (SA-Cu/rGO) anode was constructed for perfluorooctanoic acid (PFOA) defluorination. The successful doping of SA-Cu elevated the oxygen evolution potential and electrochemical active surface area of the anode and provided high electrocatalytic properties. Under optimum initial conditions with a peroxymonosulfate (PMS) concentration of 10 mM, a current density of 15 mA·cm−2, and an unadjusted pH of 7.75, the SA-Cu/rGO system achieved 98.8% removal ratio, 92.5% defluorination, and 94.4% mineralization of 20 mg·L-1 PFOA in 120 min. Kinetic studies indicate PFOA degradation following a pseudo-first-order model, with a rate constant of 4.7 × 10−2 min−1. The presence of PMS in the electrocatalytic system significantly improved the degradation rate and defluorination ratio. Radical trapping and quenching experiments confirmed that both · OH and · SO 4 - radicals contributed to PFOA degradation, with · SO 4 - playing a more important role in defluorination. The system show high flexibility in initial PFOA concentrations (0.2–20 mg·L−1) and environmental pH values (3.0–10.0), as well as good durability. The electrocatalytic degradation mechanism of PFOA was proposed through determination of intermediates and density functional theory (DFT) calculation. The total short-chain perfluorocarboxylic acids (PFCAs) intermediates generated throughout the degradation were far from sufficient recovery of the PFOA loss, indicating that apart from the · OH mediated decarboxylation-hydroxylation-elimination-hydrolysis (DHEH) pathway, the · SO 4 - mediated decarboxylation-hydroxylation-oxidation-decarbonyl fluoride (DHOD) pathway may play a significant role in the near-complete defluorination and mineralization of PFOA. Moreover, DFT calculations suggest that the DHOD pathway is energetically favorable over DHEH. This study provides a further understanding of the defluorination mechanism of PFOA in electrocatalytic systems and demonstrates that electrochemical degradation with single-atom copper catalyst is an promising method for PFOA remediation in aqueous environment. [ABSTRACT FROM AUTHOR]

• Macro-porous anode is effective for degrading PFOA. • Sulfate can enhance PFOA degradation at neutral pH. • Low localized pH in the pore is responsible for production of SO 4 − radicals and PFOA oxidation. The present study investigated the electrochemical degradation of perfluorooctanoic acid (PFOA) by macro-porous titanium suboxide (p-TiSO) anode in the presence of sulfate at pH-neutral condition (pH 6.9 ± 0.3). Based on initial PFOA concentration of 0.1 mmol L−1, current density of 10 mA cm−2 and electrolysis of 2 h, the removal efficiencies of PFOA were 97.1% and 90.8% for Na 2 SO 4 electrolyte (k app = 2.1 h−1) and NaNO 3 electrolyte (k = 0.84 h−1), corresponding to defluorination efficiency of 61.4% and 54.2%, respectively. The 2.3-fold enhancement of oxidation rate should be originated from the production of sulfate radicals (SO 4 −) by activation of sulfate via direct electron transfer with anode and indirect OH-mediated oxidation under the potential of 3.01–3.41 V versus standard hydrogen electrode (SHE). The production of OH and SO 4 − could be verified on a qualitative basis by using electron spin resonance (ESR) technology. Localized pH measurement achieved with a Pt/IrO x ultra-micro electrode revealed significantly lower pH inside the pores of p-TiSO anode (pH 2.6) compared to that in bulk electrolyte (pH 6.1). The formation of pH gradient should be attributed to surface interaction and diffusion restriction in the porous structure, and the resulting low pH was favorable for enhancing oxidizability of OH toward activation of bisulfate and oxidation of PFOA pollutant. This study offers a proof-in-concept demonstration of electrochemical activation of sulfate and PFOA degradation without need for chemical addition and pH adjustment, which can be realized by simply creating macro-porous structure of anode materials in electrochemical advanced oxidation process. [ABSTRACT FROM AUTHOR]

[Display omitted] • All PFAS degrade quickest at 580 kHz ultrasonic frequency. • GenX degrades at a higher rate than PFOA and PFOS at optimal frequency. • No by-products from truncation were detected in samples. • Surface activity of PFAS appears to play a role in degradation competitiveness. • Calorimetric efficiency is recommended for normalizing degradation performance. Sonolytic degradation kinetics of hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) were studied for the first time at four high ultrasonic frequencies (375, 580, 860 and 1,140 kHz) and three power densities (200, 300 and 400 W/L), and compared to the degradation of previously studied perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The frequency of 580 kHz displayed the highest degradation of all three PFAS tested. Within each frequency, the degradation performance increased consistently with increasing power density. Degradation rates were highest for GenX over PFOA to PFOS (k GenX = 0.0501 min−1, k PFOA = 0.0444 min−1, k PFOS 0.0153 min−1), which is in direct agreement with their reported thermal stability (PFOS > PFOA > GenX). No known by-product formation as expected from the literature on truncation mechanism was detected in the samples (i.e. shorter chain carboxylic acid PFAS). Fluorine mass balance experiments at 580 kHz and 400 W/L confirmed that GenX defluorinated fastest among the three tested PFAS and had lowest loss of fluorine in the mass balance. Degradation experiments with a mixture of all three PFAS displayed lower degradation rates than the individual experiments, where PFOA exhibited the largest reduction in degradation rate (by 31%), followed by GenX (by 19%), and finally by PFOS (by 17%). Overall, our study demonstrates that ultrasound can provide effective destruction of different PFAS (70–90% fluorine from mitigated PFAS was detected as inorganic fluoride) with a similar energy demand to alternative PFAS treatment methods reported in literature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coordination number of Co-SAC is optimized for electrocatalytic PFOA degradation. • Reductive and oxidative degradation processes are integrated within one system. • Nearly complete mineralization and defluorination of PFOA are achieved. • A synergetic chain-shortening mechanism for PFOA degradation is proposed. Concerns about the environmentally persistent and bioaccumulative per/polyfluoroalkyl substances (PFAS) in water are emerging since their potentially harmful effects on humans. However, the rapid mineralization and defluorination of PFAS are rarely achieved although various techniques have been developed. Hereby, a bifunctional single-atom catalyst (SAC) characterizing a Co-CN 2 configuration is constructed, which can simultaneously induce the degradation of PFOA and reduce O 2 to H 2 O 2. Oxidative and reductive degradation are intergraded within one system for perfluorooctanoic acid (PFOA) degradation with the immobilized Fe 2 O 3 as a Fenton catalyst. Consequently, 96.1% of PFOA is degraded over Co-CN 2 -Fe 2 O 3 at −0.06 V in an H-cell equipped with a gas diffusion cathode. The defluorination efficiency reaches 95.9% in 120 min. The Co site shielding experiment combined with the ·OH quench experiment validates that both reductive and oxidative degradation processes are indispensable in rapid and complete PFOA mannerization and defluorination. A reduction and oxidation cooperative chain shortening mechanism is proposed for PFOA degradation based on the intermediates analysis and shielding experiment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Adsorbed GenX on ACs and resins can be replaced by the hydrophobic PFOA. • The blocking effect has little effect on the adsorption of GenX on ACs. • Spent ACs and resins can be regenerated by ethanol and 92 °C NaCl solutions. • Anion exchange, electrostatic and hydrophobic interactions are involved in GenX sorption. Abstract As a typical alternative to perfluorooctanoic acid (PFOA), perfluoro-2-propoxypropanoic acid (GenX) has been detected worldwide in aquatic environment and attracted great concerns recently, but their adsorptive removal from water is not clear. In this study, the adsorption behavior and mechanism of GenX on granular activated carbon (GAC), powdered activated carbon (PAC), anion-exchange resins (IRA400 and IRA67) were compared. The particle size of activated carbon (AC) affected the initial adsorption rate but exhibited little influence on the adsorption capacity for GenX. The initial adsorption kinetics of GenX on the three granular adsorbents (GAC, IRA67 and IRA400) followed the intraparticle diffusion-controlled adsorption. IRA67 had the highest adsorption capacity of 3.22 mmol/g for GenX, higher than IRA400 (2.78 mmol/g) and much higher than the two ACs (0.79 mmol/g). When GenX was co-removed with perfluorooctanoic acid (PFOA) in competitive system, the adsorbed amounts of GenX on the four adsorbents decreased significantly, and adsorbed GenX was replaced by PFOA with increasing time. The small adsorbent size could speed up the replacement process, and the polyamine group on the resins was more prone to producing this effect than the quaternary ammonium group. PAC was more suitable for GenX removal at low pH, while IRA400 was better used at high solution pH. The spent AC and resins were successfully regenerated in the ethanol and NaCl solution, respectively, and their regeneration efficiency was significantly enhanced in hot water. The adsorption mechanisms including anion exchange, electrostatic interaction and hydrophobic interaction were involved in the GenX adsorption. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • HA in UV/iodide system increases the decomposition ratio of PFOA by 58.8% at 1.5 h. • The π-complexes formed by HA and I 2 inhibit the quenching of e aq − by I 2. • The reduction of I 2 to I− by HA allowed the continuous production of e aq −. • Quinone moieties act as electron shuttles leading to the reduction of I 2 to 2 I−. Abstract Perfluorooctanoic acid (PFOA) is a stable perfluoro-surfactant due to the contribution of electronegative fluorine atoms and the high strength of C F bonds (116 kcal/mol). However, UV irradiation of iodide at 254 nm produces hydrated electrons (e aq −) that react with PFOA to initiate its photo-reductive decomposition. In this study, we investigate the role of humic acid (HA) during the decomposition of PFOA at λ max = 254 nm as mediated by the formation of e aq −. Results show that, in UV/iodide/HA system, the decomposition and defluorination ratios of PFOA at 1.5 h were increased to 67.5% and 23.5%, respectively, compared with iodide-photolysis alone results as 8.7% and 3.3%, respectively, at room temperature (25 °C) and pH 10.0 under anaerobic conditions. Kinetic analysis indicated that the PFOA decomposition fit the first-order kinetics with a rate constant of 0.822 h−1. Reaction mechanism accounting for the effects of HA on the photo-reductive decomposition of PFOA is proposed that the aromatic rings of HA react with I 2 to form π-complexes, which effectively inhibits the reactive quenching of e aq − by I 2. After adduct formation and subsequent oxidation of phenolic hydroxy groups by I 2 , I− is regenerated, which allows for the continuous photo-production of e aq −. The quinone moieties in HA effectively act as electron shuttles leading to the reduction of I 2 back to 2 I−. The reaction sequence involving HA provides a catalytic cycle that leads to the continuous production of e aq −, which in turn drives the decomposition and defluorination of PFOA. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Flower-like nanostructure of NiAl-LDH was synthesized on micro-patterned polymer. • The hierarchical structure showed good amphiphobicity after fluorination. • The amphiphobic surface possessed excellent self-cleaning performance. • The amphiphobic surface exhibited good mechanical and chemical robustness. • The coating can be used in anti-contaminant, self-cleaning, and biomedical device. Abstract Many superhydrophobic surfaces lose their repellency to water owing to the contamination of organic liquids or mechanical damage. Though amphiphobic coatings can repel both water and organic liquids, the poor mechanical and chemical stabilities significantly restrict their practical applications. Herein, we demonstrated a hydrothermal method to synthesize micro-patterned substrates bearing NiAl layered double hydroxide with flower-like nanostructures, which resemble the surface morphology of a lotus leaf. The surface was further modified by a low-surface-energy material of perfluorooctanoic acid through a solution immersion method. The binder-free coating formed in-situ on the substrate showed a good adhesion quality of 5B (ASTM D-3359). The coating possessed high repellency to different liquid droplets, including water, diiodomethane, ethylene glycol, soybean oil, etc., with surface tensions ranging from 72.7 to 22.4 mN m−1. Due to the excellent self-cleaning property, the contaminant on the surface was easily cleaned as the water droplet rolled off. Moreover, the coating exhibited good mechanical and chemical robustness in some extreme conditions, such as gas blowing, sea sand abrasion, and chemical immersion tests. These good performances made the coating possible to be applied widely in various practical applications. [ABSTRACT FROM AUTHOR]

Nowadays, an increasing emission of chemically resistant perfluorinated compounds (PFCs) to the natural environment, together with a global presence of those anthropogenic pollutants in both natural and treated waters and in both human and animal organisms, poses a great environmental challenge. A limited efficiency of their removal by commonly employed technologies prompts a search for more efficient and more cost-effective methods. Recent decades brought in water management an intense progress in Advance Oxidation Processes, based on decomposition of pollutants by free radicals, which can be produced in different ways. This review presents the recent advances in those methods for decomposition of the most commonly occurring PFCs in the natural environment – perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). For this purpose, there have been developed particular methods based on an oxidation and reduction of target pollutants, generally abbreviated as AO/RPs. The review, which was based on 180 cited references, includes photolytic and photocatalytic methods, electrochemical processes as well as sonolytic and radiolytic methods with the use of ionizing radiation, wet chemnical oxidation methods, ozonation and Fenton processes. Attempts on comparison of the developed methods, their applications to real samples and molecular mechanisms of occurring transformations are provided. [ABSTRACT FROM AUTHOR]

Phosphotungstic acid (H 3 PW 12 O 40 , HPW)/bimodal mesoporous silica (BMS) multifunctional catalysts were prepared and employed as photocatalyst for perfluorooctanoic acid (PFOA) degradation under vacuum ultraviolet light (VUV). Lower PFOA concentration, appropriate HPW/BMS dosage (0.2 g·L −1 ) and acidic condition (pH = 3–4) were more favorable for PFOA defluorination in VUV/HPW/BMS system. Furthermore, we analyzed the intermediates produced during PFOA decomposition by HPLC/MS/MS, which were shorter-chain perfluorinated carboxylic acids (PFCAs) with C 7 , C 6 , C 5 , C 4 , C 3 and C 2 . The defluorination mechanism of PFOA was proposed, i.e., direct photolysis played an important role in PFOA defluorination under VUV radiation (λ = 185 nm), while the defluorination of PFOA was simultaneously photocatalytically decomposed and defluorinated in the presence of HPW/BMS (λ = 254 nm). [ABSTRACT FROM AUTHOR]

Over the past two decades, groundwater contaminated with chlorinated organic compounds has been successfully remediated via reductive dehalogenation by zero-valent iron. While reductive defluorination of the environmentally persistent perfluorooctanoic acid (PFOA) by Fe 0 and Zn 0 is thermodynamic favorable, no successful zero-valent metal applications have been reported yet. Consequently, we developed a combined experimental-theoretical approach based on density functional theory to predict the kinetics of reductive PFOA defluorination as a function of reduction potential. The theoretical model was calibrated with experimental results for the reductive dehalogenation of the structurally similar compound tetrachloroperfluorooctanoic acid to account for the typical non-standard conditions in remedial systems, such as increased pH and metal surface passivation. Our model estimate reveals that the half-lives for the first reductive PFOA defluorination step are ∼8 years for Zn 0 and ∼500,000 years for Fe 0 at metal-to-water ratios typical for permeable reactive barriers. Therefore, we conclusively document that – in contrast to chlorinated solvents – reductive dehalogenation by zero-valent metals is not a viable remedial approach for PFOA unless suitable catalysts are identified. [ABSTRACT FROM AUTHOR]

The esterification reaction of glycerol and caprylic acid catalyzed by immobilized lipase has been investigated in the present work quantifying the intensification benefits based on the use of supercritical carbon dioxide pretreatment. Factors influencing the progress of enzymatic reaction such as the pretreatment conditions, reaction time, reaction temperature, molar ratio of the two reactants, type of enzyme and its loading were varied to establish the effect on the progress of reaction. Optimum conditions for pretreatment using supercritical CO 2 were established as time of 1 h, pressure of 100 bars and temperature of 50 °C. Use of pretreatment under optimized conditions resulted in a conversion of free fatty acids to tricaprylin as 97.3% in 6 h of reaction time at 50 °C and molar ratio of 4:1 (caprylic acid: glycerol), which was three times higher as compared to the conventional approach (without any pretreatment) performed under same conditions. Two types of immobilized biocatalysts as Novozyme 435 and Lipozyme RM were used and it was established that Novozyme 435 showed better catalytic activity as compared to Lipozyme RM, though importantly both were active even in the presence of supercritical carbon dioxide used as pretreatment. Reuse of both the enzymes up to 15 cycles with supercritical carbon dioxide pretreatment did not affect the activity significantly. The quality analysis of the synthesized product was performed using various physiochemical tests based on the determination of acid value and peroxide value. Overall, it has been established that use of supercritical carbon dioxide pretreatment was more efficient and enhanced the rate of synthesis of tricaprylin significantly as compared to conventional approach. Understanding into effect of reaction and pretreatment parameters also enabled in maximizing the intensification benefits. [ABSTRACT FROM AUTHOR]

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are persistent organic pollutants in the environment and have serious health risks, including endocrine disrupting properties, immunotoxicity and developmental effects etc. The photochemical degradation has been proven to be a low-cost, efficient and sustainable technology for the removal of PFOX (X = A or S) in water. At present, most of the investigations have been conducted in ultrapure water and at concentrations much higher comparing to those detected in the real wastewaters. Furthermore, there are few studies about the toxicity of treated water. In this paper, the state of knowledge on the photocatalytic degradation of PFOX, including photo-oxidative and photo-reductive degradation, is reviewed comprehensively. Compared with photo-oxidation, photo-reduction appears to be more suitable for the PFOX removal since it is more favorable for the defluorination of PFOX and further complete mineralization. The effects of key parameters on the photocatalytic degradation and defluorination process of PFOX are commendably accessed, such as light wavelength, photocatalyst concentration, initial PFOX concentration, pH, reaction atmosphere, temperature, and coexisting organic or inorganic matters. The mechanisms of PFOX photodegradation process are also elucidated in detail. This paper will help to deeply understand PFOX decomposition process and put forward better perspectives in the future for researchers who work in this field. [ABSTRACT FROM AUTHOR]

Hybrid nanostructured materials play an increasing role in environmental applications. This study developed a hybrid nanocomposite (Pb-BFO/rGO) using a microwave-assisted hydrothermal method, which grafted Pb-doped BiFeO 3 (BFO) nanoparticles on reduced graphene oxide (rGO) sheets. Pb-BFO/rGO was used as a heterogeneous catalyst in a microwave enhanced Fenton-like process (MW-Fenton-like) for the decomposition of perfluoroocatanoic acid (PFOA), a perfluorinated compound present in water bodies with high bioaccumulation and toxicity for human being. The results reveal that Pb-BFO/rGO has large specific surface area (∼84.2 m 2 g −1 ), small crystallite sizes (∼3.3 nm) and multiple functional groups such as carboxyl groups and Fe-O groups. Compared with the bare BFO and Pb-BFO, Pb-BFO/rGO showed greater catalytic efficiencies for H 2 O 2 activation for PFOA degradation with the removal ratio of 90.0% from 30.0 mg L −1 to 50.0 mg L −1 within 5.0 min in the MW-Fenton-like process. Microwave irradiation was shown to significantly influence the degradation of PFOA through energy transfer and cross-coupling reactions. Pb-BFO/rGO absorbed the microwave energy, which facilitated the decomposition of H 2 O 2 and the generation of hydroxy radicals ( OH), which is responsible for the PFOA degradation. The degradation pathway of PFOA was investigated by detecting the degradation byproducts using UPLC-MS/MS and ICP/MS. Five kinds of short-chain perfluorinated carboxylic acids and fluoride ion were identified. The overall findings provide new insight into the novel hybrid catalysis for Fenton-like and other water treatment applications. [ABSTRACT FROM AUTHOR]

As one of the most reactive species, hydrated electron (e aq − ) is promising for decomposing recalcitrant organic pollutants, such as perfluorooctanoic acid (PFOA). In this study, PFOA decomposition was systematically investigated using a high photon flux ultraviolet (UV)/sulfite system. It showed had fast PFOA decomposition kinetics through significant promotion of e aq − production at favorable pH condition (pH > 9.2). At initial solution pH 9.2, with initial dissolved oxygen (DO) about 5 mg/L, and at around 25 °C, all PFOA was decomposed to less fluorinated compounds within 10 min from its initial concentration of 38.7 μM. Accompanying PFOA decomposition, short chain perfluorocarboxylic acids (PFCAs) and less fluorinated compounds were detected, indicating a stepwise decomposition mechanism. The k obs of PFOA decomposition was 0.455 min −1 , and approximately 6–910 folds faster than those reported by other reductive methods. At a fixed UV photon flux, PFOA decomposition kinetics showed a positive linear dependence with the initial sulfite dosage. Increasing initial sulfite dosage at a less favorable pH condition (pH 8.0) showed enhancement in PFOA decomposition. But it does not work at acidic and neutral pH conditions. The residual sulfite in the treated solution has acute toxicity, but it can be efficiently removed by using aeration. The outcomes of study will extend the understanding of the high photon flux UV/sulfite treatment system, and help to facilitate its further practical use in recalcitrant organic pollutants decomposition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrodeoxygenation (HDO) of octanoic acid was conducted over RuSn/SiAl catalysts. • The doping of SiO 2 enabled formation of Ru 3 Sn 7 alloy and Si-OH on Al 2 O 3 surface. • Ru 3 Sn 7 alloy exhibited high hydrogenation activity of octanoic acid to octanol. • The presence of Brønsted acid sites on Si-OH improved octanol dehydration activity. • The cooperative metal-support interaction resulted in high HDO activity. The ever-increasing demand for substitute energy sources encourages the usage of biofuels as transportation fuel; however, the unstable properties and low calorific value of biofuels caused by high oxygen content limits their direct application. In this study, we report the upgrading of a model biofuel in octanoic acid by hydrodeoxygenation (HDO) using RuSn supported on SiO 2 -doped Al 2 O 3 (SiAl). The presence of SiO 2 on Al 2 O 3 was crucial for the formation of Ru 3 Sn 7 alloy phase because SiO 2 modified the metal-support interaction between RuSn and Al 2 O 3. The alloy phase conferred significant hydrogenation activity to convert octanoic acid to octanol and minimized carbon loss by reducing decarbonylation activity. The deposition of SiO 2 also resulted in improved acidity, which increased with increasing SiO 2 loading from 10 to 30 %, due to the formation of isolated terminal silanols (Si-OH). The presence of the silanol groups was important for dehydration of octanol to octane, since the silanols retained octenes longer on the support, facilitating over-hydrogenation. The cooperative metal-support activity on RuSn/SiAl enables high and selective hydrogenation and dehydration activity for upgrading fatty acids in biofuel to hydrocarbons. [ABSTRACT FROM AUTHOR]

• PFOA had no significant effect on the nitrogen removal efficiency of anammox system. • PFOA could bind with proteins in EPS with multiple binding sites. • PFOA reduced the absolute abundances of functional bacteria and genes. • PFOA changed the metabolic pathways of anammox consortia. Perfluorooctanoic acid (PFOA) is ubiquitous in aquatic environment, posing serious threats to human health, while the potential of anaerobic ammonium oxidation (anammox) process in treating PFOA-containing wastewater and the response mechanism of anammox consortia to PFOA remain unknown. In this study, the comprehensive effects of PFOA on anammox granules and their interaction mechanism were investigated based on molecular simulation and metabolomic analysis. The environmental concentrations (≤2.0 mg/L) of PFOA had no impact on the anammox process performance. However, microbial consortia structure and functional gene abundances changed under the exposure of PFOA. By contrast, Prokaryotes were more sensitive to PFOA than eukaryotes. In addition, PFOA regulated microbial metabolic pathways, including amino acid metabolism and nucleotide metabolism, by changing the cell energy allocation strategy. Molecular docking simulation suggested that the effects of PFOA on key proteins in anammox bacteria were significantly different. These findings provide insights into the interaction between anammox consortia and PFOA, and further promote the implementation of anammox process to treat fluorine-containing wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adsorption and electrochemical properties were improved by Fe/ N -doping. • The degradation is controlled near the ·OH generation zone. • Focusing active reaction region can improve PFOA degradation. In this study, Fe/N co-doped graphene electrode (Fe/ N -GE@GF) was fabricated and a synergistic electrochemical process of the cathode was proposed for the efficient degradation of perfluorooctanoic acid (PFOA). The oxygen reduction reaction (ORR) capacity and hydroxyl radical (•OH) production were the key parameters for the degradation efficiency of PFOA. The ORR was enhanced due to the strong interaction between N -Fe bonds. During the electrochemical reaction, the electron transfer is accelerated due to the interaction between FeOx and N, which enhances the ORR of hydrogen peroxide (H 2 O 2) generation. In addition, the co-doped Fe/N also enhances the adsorption capacity of the cathode such as carbon, pyridine-N, and graphene-N further hindering the desorption of PFOA, assuring controlling the reaction region. The Fe/ N -GE@GF provided an adequate interaction between the •OH generation and the catalytic degradation region by improving the selectivity of the 2e-ORR and •OH generation. The region of PFOA degradation and •OH generation were both controlled near the cathode, which is referred to here as the "focused active reaction region". PFOA is enriched by the formation of •OH and pyridine-N bonds in the focused active reaction region. The •OH generated in situ efficiently aids the degradation of PFOA. In this electrocatalytic process, the catalytic degradation efficiency of PFOA is increased to 95 % and the TOC removal rate of PFOA increased to 90 % after 3 h, indicating that the enrichment of PFOA around the cathode continuously and efficiently interacts with the •OH generated in situ with the action of Fe/ N -GE@GF system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal destruction mechanisms and kinetics predicted with chemical accuracy. • Chemicals ranked for incinerability according to U.S. EPA Thermal Stability Index. • PFOA and HFPO-DA decompose at lower temperatures than other common organics. • Branching of the perfluoroalkyl chain reduces required incineration temperatures. • Incineration pathways and kinetics depend on (variable) waste stream composition. Thermal treatment is currently the only full-scale technology for the destruction of per- and polyfluoroalkyl substances (PFAS) in wastes. However, concerns exist about the emission of incomplete combustion products from incinerators. To address critical knowledge gaps around the incinerability of PFAS, highest-level coupled cluster theory was applied to elucidate the primary thermal destruction pathways, mechanisms, and kinetics for perfluorooctanoic acid (PFOA) and hexafluoropropylene oxide dimer acid (HFPO-DA, sometimes referred to as "GenX"). These PFAS were then ranked based on U.S. EPA's Thermal Stability Index, which ranges from Class 1 for the most thermally stable chemicals to Class 7 for the most thermally labile chemicals. Initial decomposition of both carboxylic acids proceeds through HF elimination at the α -carbon, but for PFOA surprisingly shifts towards C-COOH bond dissociation in the presence of ammonia due to ammonium stabilization of the variational transition state. Branching substantially reduces the required incineration temperatures, while chain length has no impact on perfluoroalkyl carboxylic acid (PFCA) decomposition rates. Bimolecular reactions with secondary species such as counterions and radicals have lower activation barriers than unimolecular decomposition, but their second-order kinetics depend on concentration and thus waste stream composition, which varies in practice. Simulating radical concentrations under typical incineration conditions, the determined free energies of activation suggest an incinerability ranking for linear PFOA in Class 3, for branched PFOA in Class 4, and for HFPO-DA as well as both PFOA and HFPO-DA ammonium salts in Class 5. Collectively, the temperatures needed to destroy 99.99% of PFOA, HFPO-DA, and other PFCAs in 2 seconds gas residence time are well below those of other commonly incinerated organic compounds such as chlorobenzene (Class 1). Ultimately, sufficient supply of radical donors is critical to ensure safe, efficient, and complete destruction of PFAS during thermal treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The removal of C, N, P, and PFCs was enhanced by iron-carbon micro-electrolysis. • The main process and mechanism of N removal were illuminated. • The negative effect of PFCs on functional microorganisms was elucidated. The poor removal capacity of the wastewater treatment plants (WWTPs) on perfluorinated compounds (PFCs) results in the desirability of advanced treatment. Therefore, this study mainly discusses the enhanced removal mechanism of iron-carbon constructed wetlands on chemical oxygen demand (COD), phosphorus, nitrogen, perfluorooctanoic acid (PFOA), and perfluorobutanesulfonic acid (PFBS). The results showed that the removal efficiencies of most pollutants increased with the extension of hydraulic retention time (HRT) (1d, 2d, 3d). During the 3-day HRT, the average removal efficiencies in F1 (iron-carbon wetland, 100 μg/L PFCs) for COD, total phosphorus (TP), total nitrogen (TN), PFOA, and PFBS were 61.88 %, 67.92 %, 58.26 %, 78.12 %, and 80.60 %, respectively. Compared with C1 (common gravel wetland, 100 μg/L PFCs), the corresponding removal efficiencies increased by 4.68 %, 24.53 %, 10.07 %, 16.52 %, and 13.16 %, respectively. However, the removal effect of F2 (iron-carbon wetland, 200 μg/L PFCs) became worse due to the high concentration of PFCs. Further study found that the efficient removal of phosphorus in F1 was the precipitation and coagulation of Fe(III) and Fe(II). Meanwhile, the removal of nitrogen mainly relied on autotrophic and heterotrophic denitrification. Simultaneously, the combination with Feammox (the process of anaerobic ammonium oxidation coupled to iron reduction) and other pathways promoted nitrogen removal and iron cycling in F1. Further mass balance calculation of PFOA and PFBS in iron-carbon wetland found that among all matrixes (coarse sand, gravel, and iron-carbon), the contribution rate of iron-carbon to the removal PFCs was the highest. In addition, the enrichment of microorganisms related to Fe(II)-dependent autotrophic denitrification and the cultivation of iron-reducing bacteria reconfirmed the iron cycle. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOPs) have been used as an alternative and effective option for treatment of industrial wastewater, especially in the case of the non-biodegradable compounds. Despite of several well developed AOPs, the majority of them are effective only at acidic or neutral pH, namely Fenton related processes, making the list of available effective advanced oxidation technologies strongly limited. In many cases, industrial effluents are formed at basic pH conditions. This paper reviews the state of the art of AOPs exclusively at alkaline pH, the type of compounds and effluents effectively degraded, the influence of pH on the efficiency of the processes, economic evaluation and degradation pathways. Spent caustic, polyester and acetate fiber dye effluents, phenol, acidic and sulfur based compounds, specific dyes and drugs were effectively degraded at basic pH. Factors like point of zero charge, pKa of the compounds, amount of radicals produced and activation of the oxidants are crucial factors that affect the treatment efficiency of AOPs at basic pH. H 2 O 2 and O 3 were the cheapest processes while peroxone was the most expensive. The treatment costs were in general too expensive and unrealistic using the methodology used in the literature. The alternative methodology proposed in this paper reduced the treatment costs by three orders of magnitude to values more realistic and economical feasible. Literature regarding treatment of real effluents using AOPs at basic pH is scarce and further research is needed to perform complete analysis. It is important to present some alternatives regarding the treatment of alkaline effluents without pH correction using such technologies. [ABSTRACT FROM AUTHOR]

Perfluoroalkyl and polyfluoroalkyl substances are priority contaminants of global concern. It is urgent to remove them from the environment. Adsorption is an efficient approach, but the adsorption capacity and regeneration of adsorbent were not satisfactory. In the present study, mesoporous melamine-formaldehyde resin microsphere (MMFRS) was fabricated through suspension polymerization. Owing to its mesoporous property and large anion-exchange capacity of 0.3 mmol/g, MMFRS was applied to the adsorption of perfluorooctanoic acid, a model target. The sorption kinetics obeyed pseudo-second-order equation and the sorption isotherms fitted both Freundlich and Langmuir models well. MMFRS exhibited a superiority over commercial powdered activated carbon on the adsorption amount. The sorption could reach equilibrium within 24 h. In addition, the material could be easily and economically regenerated by dilute NH 3 ·H 2 O (7.5 mM); a regeneration percentage (>85%) after 20 recycles was obtained. This study provides a facile, environmentally-friendly and low energy-consumption strategy for removal of perfluorooctanoic acid from aqueous solution in waste-water treatment. [ABSTRACT FROM AUTHOR]

There remains a significant need for developing new photocatalytic system to degrade perfluorooctanoic acid (PFOA), a typical persistent organic pollutant. In this study, highly efficient BiOCl nanosheets were prepared by a simple hydrolytic method and employed to decompose PFOA. The UV irradiation BiOCl system decomposed nearly all the added PFOA after 12 h, yielding a defluorination of 59.3% and a minimization ratio of 52.5%. The photocatalytic defluorination rate constant of PFOA on BiOCl was 16.53 μmol L −1 h −1 , being 1.7 and 14.6 times higher than that on commercial In 2 O 3 and TiO 2 (P25), respectively. It was demonstrated the photocatalytic degradation of PFOA on BiOCl mainly followed the direct hole-induced oxidative pathway, and the PFOA degradation was positively correlated with the amount of oxygen vacancies in BiOCl. The oxygen vacancies not only acted as the electron scavengers to suppress the charge recombination, but also favored to bind PFOA tightly on the BiOCl surface through a special monodentate coordination, which is beneficial for the hole oxidation of PFOA. [ABSTRACT FROM AUTHOR]

Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) using a nanocrystalline boron-doped diamond (BDD) anode was investigated in a series of bench-scale batch experiments. Experiments focused on assessing the impacts of chloride electrolyte and of hydroxyl radical scavenger tert -butyl alcohol (TBA) on both the rates of PFOA and PFOS removal, and the corresponding rates of defluorination. Treatment of PFOA and PFOS in natural groundwater at concentrations that might be observed in the field (0.3 and 0.6 mg/L PFOA and PFOS, respectively) was also evaluated and compared to results obtained in electrolyte solutions with elevated PFOA and PFOS concentrations (15 and 10 mg/L, respectively). Results showed that the presence of chloride and TBA had minimal effects (decreasing rates by <20%) on PFOA/PFOS removal and defluorination for the range of applied current densities (3–50 mA/cm 2 ), at both the low and elevated PFOA/PFOS concentrations. The latter observation is consistent with direct oxidation of PFOA/PFOS at the electrode surface rather than reaction with electrochemically generated hydroxyl radicals. In addition, treatment rates of PFOA and PFOS in natural groundwater were within a factor of two of those measured in electrolyte at a current density of 15 mA/cm 2 (for both low and concentration experiments). These findings indicate that hydroxyl radical scavengers that may be present in natural groundwater are unlikely to have a major adverse impact on PFOA and PFOS electrochemical treatment. Finally, it was demonstrated that perchlorate produced by BDD oxidation of Cl − could be biologically treated in bioaugmented sand columns, with a 3 order-of-magnitude removal observed within a 9-day residence time. [ABSTRACT FROM AUTHOR]

[Display omitted] • PFOS and PFOA destruction in a continuous flow SCWO reactor are characterized. • PFOS was found to be the most recalcintrant, mineralizing at 650⁰C. • Intermediates in liquid and gas phases are identified as a function of temperature. • Reaction routes of PFOS destruction in SCWO are proposed. Effective end-of-life technologies are needed for remediation of PFAS-containing byproducts and wastewater effluent streams. We describe a continuous flow supercritical water oxidation (SCWO) reactor operated in an autogenic regime achieved by introducing pilot fuel and compressed air; this system can achieve sufficient temperatures to destroy-one of the most recalcitrant PFAS -- perfluorooctane sulfonic acid (PFOS). We parametrically investigate PFOS and perfluorooctanoic acid (PFOA) destruction at temperatures between 410 °C and 650 °C. Targeted LC-MS/MS analysis suggests that oxidative C S bond cleavage initiates PFOS degradation, followed by decarboxylation to facilitate sequential -CF 2 elimination and chain shortening. Trifluoroacetic acid (TFA) was found to be the most recalcitrant intermediate product in the effluent, persisting at T = 600 °C and residence time of ∼ 32 s, emphasizing the need for TFA monitoring in SCWO treatment of PFAS-impacted matrices. Analysis of gaseous products shows the presence of the volatile organofluorine (VOF) such as 1H-perfluoroalkane at T = 420–530 °C; the GS/MS spectra of gaseous reaction products suggest that other VOFs may be present. Free fluoride measurement by ion chromatography shows complete PFOS defluorination at T = 650 °C. Overall, this work establishes the operational envelope for SCWO treatment of PFAS-impacted liquids and suggests the chemical routes for PFAS destruction. Additional characterization of intermediate species in gas and liquid effluent is required to fully elucidate a chemical reaction mechanism for PFAS destruction in SCWO environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • F pollutants are reused in the preparation of F-doped carbon catalysts. • Uniform F doping is achieved by grafting F fragments onto graphite sheet (GS). • The small size of WO 3 are in-situ synthesized and loaded. • The WO 3 @F-doped GS catalyst shows excellent OER activity and stability. • DFT calculation reveals the synergistic effect of F doping and WO 3 loading on OER. Electrochemical oxygen evolution reaction (OER) is an important anodic semi-reaction for energy storage and conversion. In this work, Perfluorooctanoic acid (PFOA), an aqueous pollutant, is degraded into F-containing fragments and captured to prepare ultrasmall WO 3 decorated F-doped graphite sheets (WO 3 @F-GS) via a plasma-induced assembly method. WO 3 @F 0.1 -GS achieves a low overpotential of 298 mV and Tafel slope of 77.6 mV dec-1, as low as that of RuO 2. Meanwhile, WO 3 @F 0.1 -GS exhibits good stability in both OER and overall water splitting in 1 M KOH. The synergistic effect of WO 3 and F enhances the electrocatalytic performance. Density functional theory calculations prove W4+ coordinates with F-doping resulting in enhanced adsorption of OH– and decreased energy barrier of OH deprotonation, leading good activity. The steric hindrance of F and WO 3 loading hinder the stacking of graphitic layers and improve the stability. This work not only provides a mild synthesis strategy of F-doping, but also provides a novel reutilization approach for fluoride waste. [ABSTRACT FROM AUTHOR]

Water reuse is an alternative strategy targeting water shortages. In this study, electron beam (eBeam) irradiation was investigated as a method for removing bromate and perfluorooctanoic acid (PFOA) from a synthetic water designed to simulate a treated wastewater intended for potable water reuse. In the absence of oxygen, an exponential model was able to relate bromate concentration to absorbed dose. However, a more complex model was needed to describe PFOA defluorination, so a model was developed that assumed formation of one partially defluorinated intermediate and this model was used to describe the relationship between free fluoride concentration and absorbed dose. Nitrate negatively affected the removal of bromate and the dose constant was inversely proportional to the nitrate concentration as predicted by a simple model that assumes the presence of radical scavengers. In contrast, the presence of nitrate improved the degradation of PFOA, possibly due to formation of oxidizing radicals or by other reactions of nitrate degradation products. Fulvic acid and alkalinity exerted negligible influences on bromate removal. Fulvic acid dampened the defluorination efficiency, probably due to the scavenging of oxidizing radicals such as the hydroxyl radical ( OH). Alkalinity was found to accelerate PFOA defluorination, possibly because of the formation and reactivity of the carbonate radical (CO 3 − ). As pH increased from 5.0 to 7.3, the dose constant for bromate removal increased from 0.45 kGy −1 to 0.69 kGy −1 , but it barely changed when pH was further increased to 9.0. In the presence of oxygen, both contaminants were degraded less efficiently and showed more complex patterns of degradation. Pretreatment to remove dissolved oxygen would probably be needed to apply eBeam in practice for degradation of bromate and PFOA. [ABSTRACT FROM AUTHOR]

In this study, four photochemical reaction parameters, including the reaction atmosphere, extra inorganic oxidant, inorganic anion and organic matter, were investigated in an aqueous environment to determine their effects on perfluorooctanoic acid (PFOA) photodecomposition. The photochemical defluorination of PFOA was conducted by vacuum ultraviolet light (VUV) using ferric ions as the catalyst. Both direct photolysis and photocatalysis were involved in the reaction. PFOA was completely decomposed by VUV irradiation with and without ferric ions within 72 or 144 h, respectively. There was no significant evidence indicating that the type of atmosphere (oxygen, nitrogen, or air) had any effect on the decomposition results. However, OH radicals generated during the photolysis process profoundly affected the decomposition of PFOA. The introduction of persulfate inhibited the mineralization of PFOA in the VUV/Fe 3+ system. Inorganic anions hindered the defluorination of PFOA in the following order: HCO 3 − > SO 4 2− > NO 3 − ∼ Cl − > ClO 4 − . The adverse effects of organic matter, including volatile organic compounds and dissolved natural organic compounds, were also examined. This study is beneficial to the understanding of the photodecomposition of other similar perfluorinated compounds (PFCs). [ABSTRACT FROM AUTHOR]

[Display omitted] • ISBC enables both heavy metal recovery from sludge and PMS activation. • The k obs of ISBC/PMS system to remove PFOA was 28.4 times that of PMS alone. • Pyridine nitrogen, carbonyl and iron species were the main sites for PMS activation. • A nonradical pathway of PFOA might enhance its defluorination and mineralization. The harmful effects on environment and human health caused by the widespread use of perfluorooctanoic acid (PFOA) have appealed much attention. However, traditional advanced oxidation processes (AOPs) are usually inefficient for PFOA degradation. In this study, iron species self-doped biochar derived from municipal sludge (ISBC) was synthesized by a simple method of EDTA-citric acid (CA) leaching/pyrolysis, exploring an efficient activation method of peroxymonosulfate (PMS) for PFOA degradation. Results showed that most of heavy metals were recovered from the sludge via the EDTA-CA pretreatment, at the same time, the special coral-like porous structure were formed in ISBC. A larger specific surface area and pore volume, as well as uniform Fe and N elements distribution of ISBC facilitated the reaction of surface PMS activation, which contributed to the enhancement in PFOA removal. Notably, it was found that pyridinic nitrogen and ketonic and quinone groups were key active sites, and their mediated singlet oxygen (1O 2) was confirmed to be the dominated reactive species for PFOA removal in ISBC/PMS system, instead of the radicals mediated by iron species. Furthermore, a possible PFOA degradation pathway by the nonradical 1O 2 oxidation was studied by combining density functional theory (DFT) calculation with experimental results. This study proposes a potential method to recover sludge heavy metals and activate PMS for PFOA and other organics simultaneously, which provides a valuable process for the water treatment and high value utilization of excess sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • The rapid method of electro-deposition was used to load PANI on GF. • It overcomes the secondary pollution coming from traditional EF. • Graphite N was the active catalytic site for the production of H2O2. • Pyrrolic-N enhanced the PFOA adsorption capacity of the cathode. The present study describes the coating of modified graphite felt (GF) with graphene (GE) and polyaniline (PANI). GF was doped with nitrogen atoms by a series of modification and electrolytic deposition. Tests of different types of N content and cathodic catalytic oxidation performance confirmed that the graphite N introduction promoted the production of H 2 O 2 in the 2e- process. Pyridine N catalyzed the H 2 O 2 decomposition to produce •OH. The amount of H 2 O 2 produced by GF, GF-GE, and GF-GE@PANI system was 11 mg L-1, 70 mg L-1, and 180 mg L-1, respectively. The doping of graphene increased H 2 O 2 yield, and the electrolytic deposition of PANI converted H 2 O 2 to •OH rapidly. It was proved that the N atom provided by graphene was graphite N, which was the active catalytic site for the production of H 2 O 2. The perfluorooctanoic acid (PFOA) removal at 180 min was 24.1% and 49.8% in the GF and GF-GE systems, respectively. The GF-GE@PANI system achieved 100% PFOA removal within 160 min. It was demonstrated that the enrichment of PANI with pyridine N provided many active sites for improving the conversion of H 2 O 2 to •OH and in-situ degrading organic pollutants, offering an alternative for wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • BN/TiO 2 composite was synthesized through simple calcination of nontoxic powders. • BN/TiO 2 is a type II heterojunction with improved charge carrier separation. • Under UV-C, BN/TiO 2 degraded short-chain PFOA intermediates faster than BN and TiO 2. • Under UV-A, BN/TiO 2 degraded PFOA faster than TiO 2 , while BN was inactive. Boron nitride (BN) has the newly-found property of degrading recalcitrant polyfluoroalkyl substances (PFAS) under ultraviolet C (UV-C, 254 nm) irradiation. It is ineffective at longer wavelengths, though. In this study, we report the simple calcination of BN and UV-A active titanium oxide (TiO 2) creates a BN/TiO 2 composite that is more photocatalytically active than BN or TiO 2 under UV-A for perfluorooctanoic acid (PFOA). Under UV-A, BN/TiO 2 degraded PFOA ∼ 15 × faster than TiO 2 , while BN was inactive. Band diagram analysis and photocurrent response measurements indicated that BN/TiO 2 is a type-II heterojunction semiconductor, facilitating charge carrier separation. Additional experiments confirmed the importance of photogenerated holes for degrading PFOA. Outdoor experimentation under natural sunlight found BN/TiO 2 to degrade PFOA in deionized water and salt-containing water with a half-life of 1.7 h and 4.5 h, respectively. These identified photocatalytic properties of BN/TiO 2 highlight the potential for the light-driven destruction of other PFAS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Damaged RO membranes with 39 ∼ 66% salt rejection ratios rejected PFOA/PFOS by > 85% • Electrostatic repulsion and size exclusion may play key role in PFOA/PFOS rejection. • Upgraded used RO membranes can be an economically sustainable alternative for RO/NF. Removal of per- and polyfluoroalkyl substances (PFAS) from water use cycles has now become an urgent task due to their wide spread in water environment and associated adverse health effects. Despite the effectiveness of nanofiltration (NF) and reverse osmosis (RO) for PFAS removal, the high cost related to the high pressure operation and membrane replacement mostly limit the application in the actual drinking water treatment. In this study, we investigated the rejection of the two most typical PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by the chlorine treated RO membranes (Dow FILMTEC™ SW30HR) with five different salt rejection ratios from 12% to 66%, which simulated the used membranes upgraded for the permeability. The damaged membranes were further characterized for their contact angle and zeta potential, and elemental composition was analyzed by X-ray photoelectron spectroscopy. The lab-scale cross-flow filtration tests demonstrated that the damaged RO membranes with 39 ∼ 66% salt rejection ratios achieved over 85% rejection of both PFOA and PFOS, which was comparable or even superior performance to that previously reported for NF membranes. Characterization of damaged membranes suggested that electrostatic repulsion and size exclusion both played an important role in the rejection of PFOA and PFOS by the damaged membrane. The present study provides new insights into the energy-efficient and material-saving, thereby economically sustainable, membrane process for the removal of the legacy PFAS. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel, eco-friendly composited sponge dotted by a ternary catalyst was fabricated. • The sponge removes >90% and 80% of fluoroquinolones in batch and dynamic water systems. • The improved performance is owed to the synergistic adsorption and photodegradation. • The sponge is self-purified by photodegradation. • The sponge is stable and easily recovered without mass loss. In this work, a 3D lignosulfonate composited poly(vinyl formal) (PVF) sponge impregnated by BiVO 4 /polyaniline (PANI)/Ag ternary photocatalyst (PLS-BiVO 4 /PANI/Ag) was designed and fabricated. The synergistic adsorption-photodegradation of five fluoroquinolones (FQs) antibiotics onto PLS-BiVO 4 /PANI/Ag was investigated. Incorporating lignosulfonate as a carrier on PVF sponge improved its structural properties and enhanced its adsorption performance toward FQs. The BiVO 4 /PANI/Ag ternary photocatalyst was well-dispersed and tightly bound to the composited sponge, thus it efficiently degraded the adsorbed FQs through surface photodegradation. PLS-BiVO 4 /PANI/Ag achieved >90% removal efficiency for all examined FQs within 2.0 h in a batch system, while it maintained a steady 80% removal efficiency for 30.0 h in a continuous dynamic treatment system. Photoelectric characterizations and ESR results showed that BiVO 4 /PANI/Ag was consistent with the type II heterostructure and effectively improved the utilization of visible light and the separation of photogenerated electron-hole pairs. The hole was the dominant active species in the degradation of FQs, while the main degradation pathways included defluorination, decarboxylation and destruction of piperazine ring. The prepared composited sponge is thus characterized by its high performance, convenient operation, eco-friendliness, and practicality in real water treatment systems since it undergoes self-purification and is easily recovered from water without mass loss. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pH was varied for an ethanol-based chain-elongation microbiome with extraction. • Mildly-acidic pH (5–6) led to n- caproate (C6) production. • Near-neutral and neutral pH (6.75 and 7.0) led to n -caprylate (C8) production. • A maximum n -caprylate production rate of 75.6 ± 0.6 mmol C L-1 d-1 was obtained. • Near-neutral and neutral pH was linked to more diverse microbiomes. The pH is a critical parameter in chain-elongating bioreactors, affecting: (1) the concentration of inhibitory undissociated carboxylic acids, which in turn affects the efficiency of product extraction; (2) the thermodynamics; and (3) the kinetics. Here, we examined the effect of five different pH levels (5.5 to 7.0) on n- caprylate (C8) production using an anaerobic sequencing batch reactor (ASBR) with continuous membrane-based liquid–liquid extraction (pertraction). We found that the product spectrum was directed by pH: mildly acidic pH (5–6) led to n- caproate (C6) production, while near-neutral and neutral pH (6.75–7) favored n- caprylate production. In particular, the pH of 6.75 led to the maximum values of volumetric n- caprylate production rate (75.6 ± 0.6 mmol C L-1 d-1; 0.06 g L-1 h-1) and n- caprylate concentration in the fermentation broth (420 mM C; 7.57 g L-1). Given that methane production remained low at near-neutral and neutral pH, we theorized that the high concentration of undissociated n- caprylic acid (5.71 mM C) inhibited methanogenesis. We then demonstrated such an inhibitory effect at neutral pH in: (1) microcosm experiments; and (2) the continuous bioreactor by adding methanogenic sludge. Furthermore, 16S rRNA gene sequencing analysis revealed that near-neutral and neutral pH led to more diverse microbial communities than at mildly-acidic pH. For the first time, we report predominant n -caprylate production in a microbiome at near-neutral and neutral pH conditions where methanogenesis was controlled by the inhibitory effects of undissociated n- caprylic acid. At the same time, extraction of this species occurred even at near-neutral and neutral pH. [ABSTRACT FROM AUTHOR]

[Display omitted] • LDH was modified with organic functional groups through covalent bonding. • Modification of LDH with organic groups substantially improved PFOA sorption. • Polyfluoroalkyl-modified LDH (LDH-CF) outperformed alkyl-modified LDH (LDH-CH). • PFOA sorption was enhanced via synergy of electrostatic and hydrophobic interactions. • LDH-CF was efficient for the removal of various classes of PFAS. Sorption is recognized as an effective and economical approach for the practical treatment of water contaminated with per- and polyfluoroalkyl substances (PFAS). In this study, we reported the development, characterization, and evaluation of a family of new organically functionalized layered double hydroxide (LDH) adsorbents for PFAS removal with a primary focus on perfluorooctanoic acid (PFOA). The organic functional groups were introduced to the Zn-Al LDH by covalent bonding through a post-grafting process. The organically functionalized LDHs were very efficient for PFOA adsorption, likely due to the synergy of the positively charged structural layers of LDHs that provide strong electrostatic interactions and the modified organic functional groups that provide enhanced hydrophobic interactions to capture PFOA. Specifically, our adsorption kinetics and isotherm studies found that organically functionalized LDHs exhibited faster adsorption kinetics and greater adsorption capacities for PFOA than the unmodified LDH. Furthermore, organically functionalized LDHs showed substantially improved performance for PFOA removal under various water chemistry conditions in comparison to the unmodified LDH, and remained more effective following repeated adsorption-regeneration cycles. The best-performed organically functionalized LDH also exhibited high efficiency for the treatment of a mixture of PFAS with varied fluoroalkyl chain lengths and functionalities. Results of this work suggested that organically functionalized LDHs hold great promises for the treatment of PFAS-contaminated water. [ABSTRACT FROM AUTHOR]

Novel biomass energy self-driven solar photo-electro-Fenton system for efficient mineralization of PFOA. [Display omitted] • The novel biomass energy driven solar photo-electro-Fenton system was constructed. • CoFe-OVs@CNF electrode exhibited both photocatalytic and electrocatalytic ability. • PFOA was highly mineralized within 300 min with low energy consumption. • The toxicity evolution during PFOA degradation was evaluated. The smart eco-friendly biomass energy driven electrical degradation system was established by coupling of glucose fuel cells (GFC) and solar photo-electro-Fenton (SPEF) processes, which was proposed for the green, economical and efficient degradation of perfluorooctanic acid (PFOA). The CoFe alloy nanoparticles with oxygen defects (O*) based on metal–organic frameworks (MOFs) were decorated on polyacrylonitrile (PAN)-driven carbon nanofiber (CNF) membrane to obtain the bifunctional photocathode (CoFe-OVs@CNF) with both extraordinary photo-catalytic and electro-catalytic abilities. PFOA was highly mineralized on CoFe-OVs@CNF through the synergy of photocatalytic oxidation and electro-Fenton processes. Moreover, the energy consumption for degradation was generated from direct electro-oxidation of glucose as the clean power on anode (GFC). The possible mechanism and degradation pathway for PFOA mineralization was investigated in detail according to intermediate analysis, active species verification and the valence state change of Co and Fe on cathode. Besides, the toxicity evolution during PFOA degradation was also evaluated to deeper insight into risk assessment of intermedia products and relative toxicity, intending to prove the potential for practical elimination of PFOA and other toxicity recalcitrant pollutants in wastewater by GFC-SPEF system. [ABSTRACT FROM AUTHOR]