@article{cheng_meng_knappe_2025, title={Removal of Per- and Polyfluoroalkyl Substances (PFAS) in fixed bed anion exchange reactors: Factors determining PFAS uptake capacity and models predicting PFAS breakthrough}, volume={268}, ISSN={["1879-2448"]}, url={https://doi.org/10.1016/j.watres.2024.122629}, DOI={10.1016/j.watres.2024.122629}, journal={WATER RESEARCH}, author={Cheng, Lan and Meng, Pingping and Knappe, Detlef R. U.}, year={2025}, month={Jan} }
 @article{guelfo_ferguson_beck_chernick_doria-manzur_faught_flug_gray_jayasundara_knappe_et al._2024, title={Lithium-ion battery components are at the nexus of sustainable energy and environmental release of per- and polyfluoroalkyl substances}, volume={15}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-024-49753-5}, DOI={10.1038/s41467-024-49753-5}, abstractNote={Abstract Lithium-ion batteries (LiBs) are used globally as a key component of clean and sustainable energy infrastructure, and emerging LiB technologies have incorporated a class of per- and polyfluoroalkyl substances (PFAS) known as bis-perfluoroalkyl sulfonimides (bis-FASIs). PFAS are recognized internationally as recalcitrant contaminants, a subset of which are known to be mobile and toxic, but little is known about environmental impacts of bis-FASIs released during LiB manufacture, use, and disposal. Here we demonstrate that environmental concentrations proximal to manufacturers, ecotoxicity, and treatability of bis-FASIs are comparable to PFAS such as perfluorooctanoic acid that are now prohibited and highly regulated worldwide, and we confirm the clean energy sector as an unrecognized and potentially growing source of international PFAS release. Results underscore that environmental impacts of clean energy infrastructure merit scrutiny to ensure that reduced CO 2 emissions are not achieved at the expense of increasing global releases of persistent organic pollutants.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Guelfo, Jennifer L. and Ferguson, P. Lee and Beck, Jonathan and Chernick, Melissa and Doria-Manzur, Alonso and Faught, Patrick W. and Flug, Thomas and Gray, Evan P. and Jayasundara, Nishad and Knappe, Detlef R. U. and et al.}, year={2024}, month={Jul} }
 @article{ruyle_pickard_schultes_fredriksson_heffernan_knappe_lord_meng_mills_ndungu_et al._2023, title={Interlaboratory Comparison of Extractable Organofluorine Measurements in Groundwater and Eel (<i>Anguilla rostrata</i>): Recommendations for Methods Standardization}, volume={57}, ISSN={["1520-5851"]}, url={https://doi.org/10.1021/acs.est.3c04560}, DOI={10.1021/acs.est.3c04560}, abstractNote={Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds.}, number={48}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Ruyle, Bridger J. and Pickard, Heidi M. and Schultes, Lara and Fredriksson, Felicia and Heffernan, Amy L. and Knappe, Detlef R. U. and Lord, Heather L. and Meng, Pingping and Mills, Marc A. and Ndungu, Kuria and et al.}, year={2023}, month={Nov}, pages={20159–20168} }
 @article{meng_destefano_knappe_2022, title={Extraction and Matrix Cleanup Method for Analyzing Novel Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances in Fruits and Vegetables}, volume={70}, ISSN={["1520-5118"]}, url={https://doi.org/10.1021/acs.jafc.1c07665}, DOI={10.1021/acs.jafc.1c07665}, abstractNote={Per- and polyfluoroalkyl ether acids (PFEAs) are a subclass of per- and polyfluoroalkyl substances (PFAS) that are detected with increasing frequency in environmental matrices. Diet can be an important route of PFEA exposure, but the presence of PFEAs in food is poorly understood. Extraction methods for food samples exist for traditionally studied PFAS, but their suitability for PFEAs and other novel PFAS remains unknown. In this study, an extraction and matrix cleanup method was developed to quantify 45 PFAS, including 13 PFEAs, 3 perfluoroalkane sulfonamides, and 6 fluorotelomer carboxylic acids in 10 types of fruits and vegetables. Homogenized samples were extracted with basic methanol, and resulting extracts were diluted with water and cleaned up using solid-phase extraction with weak anion-exchange cartridges. The method was validated by performing spike-recovery experiments at spike levels of 1 ng/g in all 10 matrices and 0.1 ng/g in 2 matrices. For PFAS without a corresponding isotopically labeled internal standard (IS), adopting an IS with a similar chromatographic retention time generated the most accurate recoveries. Dependent upon the matrix, recoveries of 38-44 PFAS (including 10-13 PFEAs) fell within 50-150% for samples spiked at 1 ng/g. Recoveries of 40 and 38 PFAS in blueberries and corn, respectively, fell within 50-150% for samples spiked at 0.1 ng/g. Method quantification limits (MQLs) of PFAS in pure solvents were determined as the lowest calibration level with an accuracy between 70 and 130%. To compensate for matrix effects, a matrix factor was applied on the basis of the analyte response in different matrices relative to the pure solvent. The MQLs of 45 PFAS (including 13 PFEAs) in 10 matrices ranged from 0.025 to 0.25 ng/g. Overall, this method is capable of sensitively quantifying 45 PFAS in many fruits and vegetables.}, number={16}, journal={JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY}, publisher={American Chemical Society (ACS)}, author={Meng, Pingping and DeStefano, Noelle J. and Knappe, Detlef R. U.}, year={2022}, month={Apr}, pages={4792–4804} }
 @article{fang_meng_schaefer_knappe_2023, title={Removal and destruction of perfluoroalkyl ether carboxylic acids (PFECAs) in an anion exchange resin and electrochemical oxidation treatment train}, volume={230}, ISSN={["1879-2448"]}, DOI={10.1016/j.watres.2022.119522}, abstractNote={Perfluoroalkyl ether carboxylic acids (PFECAs) are a group of emerging recalcitrant contaminants that are being developed to replace legacy per- and polyfluoroalkyl substances (PFAS) in industrial applications and that are generated as by-products in fluoropolymer manufacturing. Here, we report on the removal and destruction of four structurally different PFECAs using an integrated anion exchange resin (AER) and electrochemical oxidation (ECO) treatment train. Results from this work illustrated that (1) flow-through columns packed with PFAS-selective AERs are highly effective for the removal of PFECAs and (2) PFECA affinity is strongly correlated with their hydrophobic features. Regeneration of the spent resin columns revealed that high percentage (e.g., 80%) of organic cosolvent is necessary for achieving 60-100% PFECA release, and regeneration efficiency was higher for a macroporous resin than a gel-type resin. Treatment of spent regenerants showed (1) >99.99% methanol removal was achieved by distillation, (2) >99.999% conversion of the four studied PFECAs was achieved during the ECO treatment of the still bottoms after 24 hours with an energy per order of magnitude of PFECA removal (EE/O) <1.03 kWh/m3 of total groundwater treated, and (3) >85% of the organic fluorine was recovered as inorganic fluoride. Trifluoroacetic acid (TFA), perfluoropropionic acid (PFPrA), and perfluoro-2-methoxyacetic acid (PFMOAA) were confirmed via high-resolution mass spectrometry as transformation products (TPs) in the treated still bottoms, and two distinctive degradation schemes and four reaction pathways are proposed for the four PFECAs. Lastly, dissolved organic matter (DOM) inhibited uptake, regeneration, and oxidation of PFECAs throughout the treatment train, suggesting pretreatment steps targeting DOM removal can enhance the system's treatment efficiency. Results from this work provide guidelines for developing effective separation-concentration-destruction treatment trains and meaningful insights for achieving PFECA destruction in impacted aquatic systems.}, journal={WATER RESEARCH}, author={Fang, Yida and Meng, Pingping and Schaefer, Charles and Knappe, Detlef R. U.}, year={2023}, month={Feb} }
 @article{meng_jiang_wang_huang_wang_yu_cousins_deng_2020, title={Role of the air-water interface in removing perfluoroalkyl acids from drinking water by activated carbon treatment}, volume={386}, ISSN={["1873-3336"]}, DOI={10.1016/j.jhazmat.2019.121981}, abstractNote={Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) is a worldwide problem. In this study, we for the first time revealed the role of the air-water interface in enhancing the removal of long-chain perfluoroalkyl carboxylic (PFCAs; CnF2n+1COOH, n ≥ 7) and perfluoroalkane sulfonic (PFSAs; CnF2n+1SO3H, n ≥ 6) acids, collectively termed as perfluoroalkyl acids (PFAAs), through combined aeration and adsorption on two kinds of activated carbon (AC). Aeration was shown to enhance the removal of long-chain PFAAs through adsorption at the air-water interface and subsequent adsorption of PFAA-enriched air bubbles to the AC. The removal of selected long-chain PFAAs was increased by 50–115 % with the assistance of aeration, depending on the perfluoroalkyl chain length. Aeration is more effective in enhancing long-chain PFAA removal as air-water interface adsorption increases with PFAA chain length due to higher surface activity. After removing adsorbed air bubbles by centrifugation, up to 80 % of the long-chain PFAAs were able to desorb from the sorbent, confirming the contribution of the air-water interface to the adsorption of PFAAs on AC. Aeration during AC treatment of water could enhance the removal of long-chain PFAAs, and improve the performance of AC during water treatment.}, journal={JOURNAL OF HAZARDOUS MATERIALS}, author={Meng, Pingping and Jiang, Xiangzhe and Wang, Bin and Huang, Jun and Wang, Yujue and Yu, Gang and Cousins, Ian T. and Deng, Shubo}, year={2020}, month={Mar} }