Toxicity of perfluorooctane sulfonate and perfluorooctanoate

Persistent perfluorinated organic compounds, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are used in a variety of industrial applications. They are very stable in the environment, distribute widely in the global environment and in wild life, and are detected in human sera. Our searches have detected ppt levels of PFOS and PFOA in the surface water of Japan and China; their levels are generally more than ten times higher in city areas. Neither PFOS nor PFOA is removed by the purification process of city water. Both PFOS and PFOA are detected in sera of all the people of Japan and China (about 1000 times as high as those in surface water), and their concentrations are increasing in both countries, especially in China. PFOS and PFOA primarily distribute to the liver and cause the liver toxicity. They also cause developmental toxicity. PFOS which is not genotoxic in a variety of assay system including our in vivo comet assay, induced tumors of the liver, thyroid and mammary gland of rats. PFOA which is weakly carcinogenic is not mutagenic in many studies including our in vivo comet assay.

Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)

Fluorochemicals(FCs)are oxidatively recalcitrant,environmentally persistent,and resistant to most conventional treatment technologies.FCs have unique physiochemical properties derived from fluorine which is the most electronegative element.Perfluorooctanesulfonate(PFOS),and perfluorooctanoate(PFOA)have been detected globally in the hydrosphere,atmosphere and biosphere.Reducing treatment technologies such as reverses osmosis,nano-filtration and activated carbon can remove FCs from water.However,incineration of the concentrated waste is required for complete FC destruction.Recently,a number of alternative technologies for FC decomposition have been reported.The FC degradation technologies span a wide range of chemical processes including direct photolysis,photocatalytic oxidation,photochemical oxidation,photochemical reduction,thermally-induced reduction,and sonochemical pyrolysis.This paper reviews these FC degradation technologies in terms of kinetics,mechanism,energetic cost,and applicability.The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration,background organic and metal concentration,and available degradation time.

Histological Assessment and Transcriptome Analysis Provide Insights into the Toxic Effects of Perfluorooctanoic Acid to Juvenile Half Smooth Tongue Sole Cynoglossus semilaevis

Perfluorooctanoic acid(PFOA)is a widespread synthetic persistent organic pollutant that may enrich along the food chain and affect the growth,development,reproduction,and lipid metabolism of aquatic organisms,particularly the benthic organisms.How-ever,the toxic effects of PFOA on the half-smooth tongue sole Cynoglossus semilaevis,a commercial benthic fish in China,have rarely been reported.Because juvenile fish are sensitive to environmental pollutants,in the present study,histological assessment and tran-scriptome sequencing were performed to determine the short-term impact of PFOA on juvenile half-smooth tongue soles.Histologi-cal analysis showed that PFOA exposure caused hepatocyte rupture,intestinal villi breakage,increased goblet cell count,and brain ab-normal.Transcriptome results showed that some interesting signaling pathways,such as glycolysis/gluconeogenesis,PPAR signaling pathway and GABAergic synapse signaling pathway,were enriched after PFOA exposure.In addition,some metabolic,immune and neural genes were differentially expressed,which including ependymin,hbb1-like and gad 1,and they were up-regulated after 14 days of exposure.Transcriptome results also indicated that half-smooth tongue sole might improve energy metabolism in response to PFOA toxicity after 7 days of exposure.These findings provide a basis for studying the ecological effects of PFOA on marine benthic fishes.

Photodegradation of perfluorooctanoic acid by 185 nm vacuum ultraviolet light

The photodegradation of persistent and bioaccumulative perftuorooctanoic acid （PFOA） in water by 185 nm vacuum ultraviolet （VUV） light was examined to develop an effective technology to deal with PFOA pollution. PFOA degraded very slowly under irradiation of 254 nm UV light. However, 61.7% of initial PFOA was degraded by 185 nm VUV light within 2 h, and defluorination ratio reached 17.1%. Pseudo first-order-kinetics well simulated its degradation and defluorination. Besides, fluoride ion formed in water, 4 shorter-chain perfluorinated carboxylic acids （PFCAs）, that is, perfluoroheptanoic acid, perfluorohexanoic acid, perfluoropentanoic acid, and perfluorobutanoic acid. These were identified as intermediates by LC-MS measurement. These PFCAs consecutively formed and further degraded with irradiation time. According to the mass balance calculation, no other byproducts were formed. It was proposed that PFCAs initially are decarboxylated by 185 nm light, and the radical thus formed reacts with water to form shorter-chain PFCA with one less CF2 unit.

Photochemical degradation of environmentally persistent perfluorooctanoic acid (PFOA) in the presence of Fe(Ⅲ)

Environmentally persistent and bioaccumulative perfluorooctanic acid （PFOA） was difficult to be decomposed under the irradiation of 254 nm UV light. However, in the presence of 80μmol/L Fe（Ⅲ）, 80% of PFOA with initial concentration of 48μmol/L （20 mg/L） was effectively degraded and 47.8% of fluorine atoms in PFOA molecule were transformed into inorganic fluoride ion after 4 h reaction. Shorter chain perfluorocarboxylic acids bearing C3-C7 and fluoride ion were detected and identified by LC/MS and IC as the degradation products in the aqueous solution. It was proposed that complexes of PFOA with Fe（Ⅲ） initiated degradation of PFOA irradiated with 254 nm UV light.

PREPARATION OF PERFLUOROOCTANOYL-MODIFIED POLY(VINYL-ALCOHOL)S AND THEIR ADSORPTION AT AN AIR-WATER INTERFACE

Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750. The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water. It was shown by experimental measurement at 30.0 +/- 0.1 degreesC that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration, e.g. about 0.1 g/mL. Obviously, macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants. The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.

Synthesis and Characterization of Perfluorooctanoic Acid Anionic Surfactant Doped Nanosize Polyaniline

Surfactant doped polyaniline was synthesized in the aqueous solution of aniline and anionic surfactant of perfluorooctanoic acid (PFO) by chemical synthesis using potassium peroxy disulphate as an oxidant by varying the aniline to surfactant ratio. The solubility of the chemically prepared surfactant doped polyaniline (PANI) was ascertained and it showed good solubility in dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetone, acetonitrile, ethanol, aceticacid, trichloroethylene, dichloromethane, tetrahydrofuran, ethylacetate, diethylether, toluene, chloroform and sparingly soluble in n-hexane and water. The prepared polymers were characterized by fourier transform infrared spectroscopy (FTIR), UV-visible, X-ray diffraction (XRD), cyclic voltammetric (CV), EIS and scanning electron microscopy (SEM). The analysis of UV-visible and FTIR showed that aniline has been polymerized to PANI in its conducting emeraldine form. FTIR spectra showed that the peaks at 1670, 3315 and 1400 cm-1 corresponded to PFO. FTIR spectra showed that amine peak observed at 1593 cm-1 was shifted to lower wave number due to the interaction between PANI and the surfactant. SEM analysis showed that the variation in morphology of doped PANI was predominantly dependent on the concentration of the surfactant. Elemental analysis was done by energy dispersive spectroscopic (EDAX) which shows the presence of C, N, O, S and F. XRD pattern showed that the formation of nanosized (18 nm) and crystalline polymer. CV studies of the synthesized polymer exhibited good adherent behavior on electrode surface. It exhibited three oxidation peaks at approximately 0.283 V, 0.541 V and 0.989 V and two reduction peaks at 0.1421 and 0.3854 V. Electrical conductivity of PFO doped PANI was studied by impedance spectroscopic method.

Can perfluorooctanoic acid be effectively degraded usingβ-PbO_(2)reactive electrochemical membrane?

Aqueous perfluorooctanoic acid(PFOA)elimination has raised significant concerns due to its persistence and bioaccumulation.Althoughβ-PbO_(2)plate anodes have shown efficient mineralization of PFOA,it remains unclear whether PFOA can be effectively degraded usingβ-PbO_(2)reactive electrochemical membrane(REM).Herein,we assessed the performance of Ti/SnO_(2)-Sb/La-PbO_(2)REM for PFOA removal and proposed a possible degradation mechanism.At a current density of 10 mA/cm2and a membrane flux of 8500(liters per square meter per hour,LMH),the degradation efficiency of 10 mg/L PFOA was merely8.8%,whereas the degradation efficiency of 0.1 mg/L PFOA increased to 96.6%.Although the porous structure of theβ-PbO_(2)REM provided numerous electroactive sites for PFOA,the generated oxygen bubbles in the pores could block the pore channels and adsorb PFOA molecules.These hindered the protonation process and significantly impeded the degradation of high-concentration PFOA.Quenching experiments indicated that·OH played dominant role in PFOA degradation.The electrical energy per order to remove 0.1 mg/L PFOA was merely 0.74 Wh/L,which was almost an order of magnitude lower than that of other anode materials.This study presents fresh opportunities for the electrochemical degradation of low-concentration PFOA usingβ-PbO_(2)REM.

Untargeted metabolomic analysis of pregnant women exposure to perfluorooctanoic acid at different degrees

Perfluorooctanoic acid(PFOA)is a novel type of persistent synthetic organic pollutant,and its exposure on pregnant women can cause some adverse effects,such as pregnancy-induced hypertension,gestational diabetes mellitus,and preeclampsia.Therefore,understanding the metabolic changes caused by PFOA exposure is of great significance to protect pregnant women from its adverse effects.In this study,the metabolomes from the urine samples of pregnant women exposure to PFOA at different degrees were analyzed by GC-MS and LC-MS.The samples in different groups were distinguished and the differential metabolites were screened based on the VIP value,FC,and P-value of each comparison group through multivariate statistical analysis.The pathways related to differential metabolites were searched to reveal the effects of PFOA exposure on metabolic changes in pregnant women at different degrees.Finally,the ROC of differential metabolites was performed,and the differential metabolites with large area under the curve(AUC)values were selected and compared to identify the mutually differential metabolites.Meanwhile,these metabolites were fitted with a multivariable to explore if they could be used to distinguish different groups.The quantitative comparison of mutually differential metabolites revealed that the levels of L-cysteine,glycine,and 5-aminovaleric acid were positively correlated with the degree of PFOA exposure,indicating that different degrees of PFOA exposure could affect the synthesis or degradation of GSH and change the metabolism of oral or intestinal microbiota.Additionally,they may cause oxidative stress and abnormal fat metabolism in pregnant women.

Photo-induced surface frustrated Lewis pairs for promoted photocatalytic decomposition of perfluorooctanoic acid

Heterogeneous photocatalysis has gained substantial research interest in treating per-and polyfluoroalkyl substances(PFAS)-contaminated water.However,sluggish degradation kinetics and low defluorination efficiency compromise their practical applications.Here,we report a superior photocatalyst,defected Bi_(3)O(OH)(PO_(4))_(2),which could effectively degrade typical PFAS,perfluorooctanoic acid(PFOA),with high defluorination efficiency.The UV light irradiation could in situ generate oxygen vacancies on Bi_(3)O(OH)(PO_(4))_(2) through oxidation of the lattice hydroxyls,which further promotes the formation of Lewis acidic coordinately unsaturated bismuth sites.Then,the Lewis acidic sites couple with the proximal surface hydroxyls to constitute the surface frustrated Lewis pairs(SFLPs).With the in-depth spectroscopic analysis,we revealed that the photo-induced SFLPs act as collection centers to effectively adsorb PFOA and endow accessible pathways to transfer photogenerated holes to PFOA rapidly.Consequently,activation of the terminal carboxyl,a ratelimiting step for PFOA decomposition,could be easily achieved over the defected Bi_(3)O(OH)(PO_(4))_(2) photocatalyst.These results suggest that SFLPs exhibit great potential in developing highly efficient photocatalysts to degrade persistent organic pollutants.

Screening ionic liquids for efficiently extracting perfluoroalkyl chemicals (PFACs) from wastewater

Liquid-liquid extraction(LLE)using ionic liquids(ILs)-based methods to remove perfluoroalkyl chemicals(PFACs),such as perfluorooctanoic acid(PFOA)and perfluorooctane sulfonic acid(PFOS),from wastewater,is an important strategy.However,the lack of physicochemical and LLE data limits the selection of the most suitable ILs for the extraction of PFACs.In this work,1763 ILs for PFACs extraction from water were systematically screened using COSMOtherm to estimate the infinite dilution activity coefficient(lnγ^(∞))of PFOA and PFOS in water and ILs.To evaluate the accuracy of COSMOtherm,8 ILs with various lnγ^(∞)values were selected,and their extraction efficiency(E)and distribution coefficient(D_(exp))were measured experimentally.The results showed that the predicted lnγ^(∞)decreased as the increase of experimental extraction efficiency of PFOA or PFOS,while the tendency of predicted distribution coefficient(D_(pre))was consistent with the experimental(D_(exp))results.This work provides an efficient basis for selecting ILs for the extraction of PFACs from wastewater.

Photocatalytic defluorination of perfluorooctanoic acid by surface defective BiOCl:Fast microwave solvothermal synthesis and photocatalytic mechanisms

There is an urgent need for developing cost-effective methods for the treatment of perfluorooctanoic acid(PFOA)due to its global emergence and potential risks.In this study,taking surface-defective BiOCl as an example,a strategy of surface oxygen vacancy modulation was used to promote the photocatalytic defluorination efficiency of PFOA under simulated sunlight irradiation.The defective BiOCl was fabricated by a fast microwave solvothermal method,which was found to induce more surface oxygen vacancies than conventional solvothermal and precipitation methods.As a result,the asprepared BiOCl showed significantly enhanced defluorination efficiency,which was 2.7 and33.8 times higher than that of BiOCl fabricated by conventional solvothermal and precipitation methods,respectively.Mechanistic studies indicated that the defluorination of PFOA follows a direct hole(h^+)oxidation pathway with the aid of·OH,while the oxygen vacancies not only promote charge separation but also facilitate the intimate contact between the photocatalyst surface and PFOA by coordinating with its terminal carboxylate group in a bidentate or bridging mode.This work will provide a general strategy of oxygen vacancy modulation by microwave-assisted methods for efficient photocatalytic defluorination of PFOA in the environment using sunlight as the energy source.

Decomposition of perfluorooctanoic acid by microwaveactivated persulfate： Effects of temperature, pH, and chloride ions

Microwave-hydrothermal treatment of persis- tent and bioaccumulative perfluorooctanoic acid （PFOA） in water with persulfate （S2O2-） has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects ofpH （pH= 2.5, 6.6, 8.8, and 10.5）, chloride concentra- tions （0.01-0.15 mol.L-1）, and temperature （60℃, 90℃, and 130℃） on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol.L^-1 at 90℃ and 0.06mol.L^-1 at 60℃, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.

Photocatalytic degradation of perfluorooctanoic acid with β-Ga_2O_3 in anoxic aqueous solution

Perfluorooctanoic acid （PFOA） is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical （HO.） due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron （ecb） coming from the β-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids （PFCAs, CnF2n＋1COOH, 1 ≤ n ≤ 6） were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics （k = 0.0239 min-1, t1/2 = 0.48 hr）. PFCAs （CnF2n＋xCOOH, 1 ≤ n≤ 7） were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves ec-b attacking the carboxyl of CnF2n＋1COOH, resulting in decarboxylation and the generation of CnFzn＋1. The produced CnF2n＋1 reacted with H2O, forming CnF2n＋1OH, then CnF2n＋1OH underwent HF loss and hydrolysis to form CnF2,＋1COOH.

A comparative study of bismuth-based photocatalysts with titanium dioxide for perfluorooctanoic acid degradation

Bismuth-based material has been broadly studied due to their potential applications in various areas,especially used as promising photocatalysts for the removal of persistent organic pollutants(POPs) and several approaches have been adopted to tailor their features.Herein,the bismuth-based photocatalysts(BiOCl,BiPO4,BiOPO4/BiOCl) were synthesized by hydrothermal method and advanced characterization techniques(XRD,SEM,EDS elemental mapping,Raman and UV-vis DRS) were employed to analyze their morphology,crystal structure,and purity of the prepared photocatalysts.These synthesized photocatalysts offered a praiseworthy activity as compared to commercial TiO2(P25) for the degradation of model pollutant perfluorooctanoic acid(PFOA) under 254 nm UV light.It was interesting to observe that all synthesized photocatalysts show significant degradation of PFOA and their photocatalytic activity follows the order:bismuth-based catalysts> TiO2(P25)> without catalyst.Bismuth-based catalysts degraded the PFOA by almost 99.99% within 45 min while this degradation efficiency was 66.05% with TiO2 under the same reaction condition.Our work shows that the bismuth-based photocatalysts are promising in PFOA treatment.

Adsorption mechanisms of PFOA onto activated carbon anchored with quaternary ammonium/epoxide-forming compounds: A combination of experiment and model studies

When wood-based activated carbon was tailored with quaternary ammonium/epoxide(QAE) forming compounds(QAE-AC), this tailoring dramatically improved the carbon's effectiveness for removing perfluorooctanoic acid(PFOA) from groundwater. With favorable tailoring, QAE-AC removed PFOA from groundwater for 118,000 bed volumes before halfbreakthrough in rapid small scale column tests, while the influent PFOA concentration was 200 ng/L. The tailoring involved pre-dosing QAE at an array of proportions onto this carbon, and then monitoring bed life for PFOA removal. When pre-dosing with 1 mL QAE, this PFOA bed life reached an interim peak, whereas bed life was less following 3 mL QAE pre-dosing, then PFOA bed life exhibited a steady rise for yet subsequently higher QAE pre-dosing levels. Large-scale atomistic modelling was used herein to provide new insight into the mechanism of PFOA removal by QAE-AC. Based on experimental results and modelling, the authors perceived that the QAE's epoxide functionalities cross-linked with phenolics that were present along the activated carbon's graphene edge sites, in a manner that created mesopores within macroporous regions or created micropores within mesopores regions. Also, the QAE could react with hydroxyls outside of these pore, including the hydroxyls of both graphene edge sites and other QAE molecules. This latter reaction formed new pore-like structures that were external to the activated carbon grains. Adsorption of PFOA could occur via either charge balance between negatively charged PFOA with positively charged QAE, or by van der Waals forces between PFOA's fluoro-carbon tail and the graphene or QAE carbon surfaces.

Environmental factors affecting degradation of perfluorooctanoic acid(PFOA) by In2O3 nanoparticles

Nanophotocatalysts have shown great potential for degrading poly-and perfluorinated substances(PFAS).In light of the fact that most of these catalysts were studied in pure water,this study was designed to elucidate effects from common environmental factors on decomposing and defluorinating perfluorooctanoic acid(PFOA)by In2O3 nanoparticles.Results from this work demonstrated that among the seven parameters,pH,sulfate,chloride,H2O2,In2O3 dose,NOM and O2,the first four had statistically significant negative effects on PFOA degradation.Since PFOA is a strong acid,the best condition leading to the highest PFOA removal was identified for two pH ranges.When pH was between 4 and 8,the optimal condition was:pH=4.2;sulfate=5.00 mg/L;chloride=20.43 mg/L;H2O2=0 mmol/L.Under this condition,PFOA decomposition and defluorination were 55.22 and 23.56%,respectively.When pH was between 2 and 6,the optimal condition was:pH=2;sulfate=5.00 mg/L;chloride=27.31 mg/L;H2O2=0 mmol/L.With this condition,the modeled PFOA decomposition was 97.59%with a defluorination of approximately 100%.These predicted results were all confirmed by experimental data.Thus,In2O3 nanoparticles can be used for degrading PFOA in aqueous solutions.This approach works best when the target contaminated water contains low concentrations of NOM,sulfate and chloride and at a low pH.

Determination of polyfluoroalkyl compounds in water and suspended particulate matter in the river Elbe and North Sea,Germany

The distribution of polyfluoroalkyl compounds(PFCs)in the dissolved and particulate phase and their discharge from the river Elbe into the North Sea were studied.The PFCs quantified included C_(4)-C_(8) perfluorinated sulfonates(PFSAs),6∶2 fluorotelomer sulfonate(6∶2 FTS),C_(6) and C_(8) perfluorinated sulfinates(PFSiAs),C_(4)-C_(12) perfluorinated carboxylic acids(PFCAs),perfluoro-3,7-dimethyl-octanoic acid(3,7m_(2)-PFOA),perfluorooctane sulfonamide(FOSA),and n-ethyl perfluroctane sulfonamidoethanol(EtFOSE).PFCs were mostly distributed in the dissolved phase,where perfluorooctanoic acid(PFOA)dominated with 2.9–12.5 ng/L.In the suspended particulate matter FOSA and perfluorooctane sulfonate(PFOS)showed the highest concentrations(4.0 ng/L and 2.3 ng/L,respectively).The total flux ofΣPFCs from the river Elbe was estimated to be 802 kg/year for the dissolved phase and 152 kg/year for the particulate phase.This indicates that the river Elbe acts as a source of PFCs into the North Sea.However,the concentrations of perfluorobutane sulfonate(PFBS)and perfluorobutanoic acid(PFBA)in the North Sea were higher than that in the river Elbe,thus an alternative source must exist for these compounds.

The occurrence of per-and polyfluoroalkyl substances(PFASs) in fluoropolymer raw materials and products made in China

Perfluorooctanoic acid(PFOA), its salts, and related compounds were listed as new persistent organic pollutants by the Stockholm Convention in 2019.In this study, the occurrence of residues of PFOA and other per-and polyfluoroalkyl substances(PFASs) in raw materials and fluoropolymer products from the Chinese fluoropolymer industries are reported for the first time.The PFOA concentrations in raw materials and fluoropolymer products were in the range of 6.7 to 1.1 × 10^(6) ng/g, and <MDL(method detection limit) to 5.3 × 10^(3) ng/g,respectively.Generally, the levels of PFOA in raw materials were higher than in products,implying that PFOA in the emulsion/dispersion resin could be partly removed during the polymerization or post-processing steps.By tracking a company’s polytetrafluoroethylene(PTFE) production line, it was found that over a 5 year period, the residual levels of PFOA in emulsion samples declined from 1.1 × 10^(6) to 28.4 ng/g, indicating that the contamination of PFOA in fluoropolymer products from production source gradually decreased after its use had been discontinued.High concentrations of HFPO-TrA(2.7 × 10^(5) to 8.2 × 10^(5) ng/g) were detected in some emulsion samples indicating this alternative has been widely applied in fluoropolymer manufacturing in China.