Adsorption of per- and polyfluoroalkyl substances (PFAS) by ionic liquid-modified clays: Effect of clay composition and PFAS structure

Ecosystem-wide PFAS characterization and environmental behavior at a heavily contaminated desert oasis in the southwestern U.S

Record-high PFAS contamination levels were recently reported in birds and small mammals from Holloman Lake, a high-salinity wastewater oasis located in southern New Mexico, USA. We expanded the PFAS screening to surface water, soils, algae, invertebrates, fish, reptiles, and a larger number of plants, birds, and mammals to examine the fate, transport, and bioaccumulation of PFAS in the ecosystem and generate contamination profiles across both the water-land interface and multiple trophic levels. C5 and C6 perfluorocarboxylic acids, both of them known degradation products of 6:2 FTS, were the dominant PFAS in surface water in the lake. In contrast, perfluorooctanesulfonic acid (PFOS) was the main PFAS found in sediments along the shoreline, with the number of fluorinated carbons in the alkyl chain and clay minerals both appearing to play a key role in soil sorption. High soil PFAS concentrations up to 900 m from the edge of the water could not be explained by air transport of contaminated dust and instead seemed related to past inundation events involving contaminated water. Higher PFAS concentrations along the main body of the lake included an extraordinary 30,000 ng/g ww of PFOS recorded for a composite saltcedar (Tamarix sp.) tissue sample. Bioaccumulation pervaded the ecosystem's food webs and trophic levels, with PFAS detection in all species and all types of animal tissue (blood, liver, muscle, and bone). Contamination involved mainly PFOS, followed by perfluorohexanesulfonic acid (PFHxS), with the observed concentrations of PFAS increasing concomitantly among tissue types but the liver bioaccumulating at a faster rate.

Adsorption of Per- and Polyfluoroalkyl Substances by Edible Nutraceutical-Amended Montmorillonite Clays: In Vitro, In Vivo and In Silico Enterosorption Strategies

Exposure of animals and humans to PFAS through contaminated water and foods pose significant threats to public health. To tackle this challenge, this study aimed to develop edible clays that might enhance the binding, detoxification, and elimination of PFAS in the gastrointestinal tract. Montmorillonite clays (CM) were amended with caffeine (CMCAF), curcumin (CMCUR), and riboflavin (CMRIB), and the binding efficacy for a mixture of four PFAS (PFOS, GenX, PFOA and PFBS) was determined. In vitro studies were used to explore adsorption isotherms while computational simulations investigate PFAS mixture, delineate the contribution of each PFAS molecule to clays and determine if amended clays can contribute to enhanced binding of different PFAS in the mixture. In vivo models (Lemna minor and Hydra vulgaris) were used to validate in vitro and in silico studies and establish the safety and effectiveness of these amended clays. The resulting Qmax and Kd values along with the curved shape of the Langmuir plot indicated saturable binding of GenX, PFOA and PFOS to active surfaces of CM and the amended clays. All three clays demonstrated a slightly higher binding capacity for GenX than the parent clay. Furthermore, the simulations elucidated the binding contribution of each PFAS molecule to parent and amended clays as well as predicting how amended clays can contribute to mechanisms of binding of different PFAS in the mixture. The proof-of-concept for the efficacy of the clays was established in Caenorhabditis elegans, Lemna minor and Hydra vulgaris, where the clays (at 1% w/v inclusion) protected against toxicities of the four PFAS controls. This protection could be attributed to PFAS binding to the amended clays and the biological activities of these nutraceuticals (caffeine, riboflavin, and curcumin) including antioxidative, anti-inflammatory and modulatory activities which mitigate the oxidative stress and inflammatory effects of PFAS. These edible toxin binders may be delivered in mixtures as additives in flavored drinking water and food to decrease PFAS exposure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11270-025-07930-2.

Synthesis of Homoallylamine Covalent Organic Frameworks Via Hosomi-Sakurai Reaction Under Mild Conditions

One-pot multicomponent reactions (MCRs) are a valuable strategy to synthesize functional covalent organic frameworks (COFs) in a single step. Most reported COF syntheses involve solvothermal processes, and because of the harsh reaction conditions, such as high temperature or high pressure, large-scale production of COFs has been limited. The synthesis of homoallylamine substituted COFs via a one-pot Hosomi-Sakurai reaction is reported. At room temperature the reaction of allyltriethylgermane with either terephthalaldehyde or [1,1'-biphenyl]-4,4'-dicarbaldehyde, and 1,3,5-tris(4-aminophenyl)benzene (TAPB) is catalyzed by Sc(OTf)3 to produce two COFs: TAPB-1P-Allyl COF and TAPB-BP-Allyl COF. The allyl functionalized COFs shows high crystallinity, with micropores ranging from 3.2 to 3.9 nm, for TAPB-1P-Allyl COF and TAPB-BP-Allyl COF respectively, and both COFs are hydrolytically stable at different pH levels. Post-synthetic modification of these COFs with iodomethane produces methylated cationic COFs that demonstrates >98% adsorption efficiencies below the detection limit of perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) from aqueous solutions. After four cycles adsorption efficiency remains high with concentrations of PFOA below the detection limit.

Removal of perfluoroalkyl acids and precursors with silylated clay: Efficient adsorption and enhanced reuse

Organically modified clays (organoclays) have been considered effective adsorbents for the treatment of per- and polyfluoroalkyl substances (PFAS). However, the stability of organoclays prepared through the conventional cation exchange approach has been a major concern for their practical application. In this study, we reported the development of a new organically functionalized clay by grafting pillared clay substrate with an organosilane through covalent bonding. The performance of the silylated clay (QAG-ZrMT) was systematically compared with an organoclay prepared from ion exchange (HDTMA-ZrMT) for the adsorption of two legacy perfluoroalkyl acids: perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and two precursor compounds 5:3 fluorotelomer carboxylic acid (5:3FTCA) and 6:2 fluorotelomer sulfonic acid (6:2FTS). Compared to HDTMA-ZrMT, QAG-ZrMT showed substantially improved performance for adsorption of less hydrophobic PFAS (e.g., 5:3FTCA), which could be related to the stronger electrostatic interactions between PFAS and QAG-ZrMT than HDTMA-ZrMT. More importantly, QAG-ZrMT could be conveniently regenerated and reused for multiple cycles with robust performance. In contrast, HDTMA-ZrMT almost completely lost its capacity for PFAS removal after regeneration, due to the loss of organic functional groups during solvent regeneration. Results can shed light on the design of efficient and regenerable organoclay adsorbents for remediation of PFAS-contaminated water matrices.

Heavy-Metal Ions Control on PFAS Adsorption on Goethite in Aquatic Systems

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants that often co-occur with heavy metals. Despite their prevalence, the mobility of PFAS in complex, multicomponent systems, particularly at the molecular scale, remains poorly understood. The vast diversity of PFAS and their low concentrations alongside anthropogenic and natural substances underscore the need for integrating mechanistic insights into the sorption models. This study explores the influence of metal cations (Cu(II), Cd(II), and Fe(II)) on the adsorption of four common PFAS (PFOA, PFOS, PFDA, and GenX) onto goethite (α-FeOOH), a common iron (oxyhydr)oxide in both aquatic and terrestrial environments. PFAS adsorption was highly dependent on the PFAS type, pH, and metal ion concentration, with a surface complexation model effectively predicting these interactions. Cu(II) and Cd(II) enhanced PFOS and PFDA adsorption via ternary complexation while slightly reducing PFOA and GenX adsorption. Under anoxic conditions, Fe(II) significantly increased the adsorption of all PFAS, showing reactivity greater than those of Cu(II) and Cd(II). Additionally, natural organic matter increased PFAS mobility, although metal cations in groundwater may counteract this by enhancing PFAS retention. These findings highlight the key role of metal cations in PFAS transport and offer critical insights for predicting PFAS behavior at oxic-anoxic environmental interfaces.

Occurrence of short- and ultra-short chain PFAS in drinking water from Flanders (Belgium) and implications for human exposure

SHORT: and ultra-short chain perfluoroalkyl substances (S- and US-PFAS) are alternatives for the long-chain PFAS which have been more regulated over time. They are highly mobile in the environment and can easily reach drinking water sources which can become an important human exposure route. Furthermore, there have been growing concerns about the presence of PFAS in Flanders. Because of this, human exposure to S- and US-PFAS through Flemish drinking water was evaluated in this study. For this purpose, the presence of 2 S-PFAS (PFBS and PFBA) and 5 US-PFAS (PFPrS, PFEtS, TFMS, PFPrA and TFA) was investigated in 47 tap water samples, collected from different Flemish provinces, and 16 bottled waters purchased in Flanders. Out of the 7 target PFAS, 4 (PFBA, PFBS, PFPrS and PFEtS) were detected at concentrations above LOQ in tap water. In bottled water, only TFMS was present above its LOQ. PFAS concentrations in all analyzed water samples ranged from <0.7 to 7.3 ng/L for PFBS, <0.03-15.0 ng/L for TFMS and <0.9-12.0 ng/L for PFBA. PFPrS was only detected once above its LOQ, at 0.6 ng/L. No value could be reported for PFPrA due to high procedural blanks resulting in a high LOQ, nor for TFA due to high matrix effect. No significant differences in PFAS concentrations were seen in tap water among different drinking water companies, provinces, nor between the two types of analyzed bottled water (natural mineral water vs spring water). The use of a commercial carbon filter significantly reduced the median concentrations of the studied compounds in tap water. Finally, it was estimated that the presence of S- and US-PFAS in Flemish drinking water does not pose an immediate threat to human health, as concentrations were at least two orders of magnitude below the available guidance values.

Natural mineral and industrial solid waste-based adsorbent for perfluorooctanoic acid and perfluorooctane sulfonate removal from surface water: Advances and prospects

PER: and polyfluorinated alkyl substances, especially perfluorooctanoic acid and perfluorooctane sulfonic acid (PFOX), have attracted considerable attention lately because of their widespread occurrence in aquatic environment and potential biological toxicity to animals and human beings. The development of economical, efficient, and engineerable adsorbents for removing PFOX in water has become one of the research focuses. This review summarized the recent progress on natural mineral and industrial solid based adsorbent (NM&ISW-A) and removal mechanisms concerning PFOX onto NM&ISW-A, as well as proposed the current challenges and future perspectives of using NM&ISW-A for PFOX removal in water. Kaolinite and montmorillonite are usually used as model clay minerals for PFOX removal, and have been proved to adsorb PFOX by ligand exchange and electrostatic attraction. Fe-based minerals, such as goethite, magnetite, and hematite, have better PFOX adsorption capacity than clay minerals. The adsorbent prepared from industrial solid waste by high temperature roasting has great potential application prospects. Fabricating nanomaterials, amination modification, surfactant modification, fluorination modification, developing versatile composites, and designing special porous structure are beneficial to improve the adsorption performance of PFOX onto NM&ISW-A by enhancing the specific surface area, positive charge, and hydrophobicity. Electrostatic interaction, hydrophobic interaction, hydrogen bond, ligand and ion exchange, and self-aggregation (formation of micelle or hemimicelle) are the main adsorption mechanisms of PFOX by NM&ISW-A. Among them, electrostatic and hydrophobic interactions play a considerable role in the removal of PFOX by NM&ISW-A. Therefore, NM&ISW-A with electrostatic functionalities and considerable hydrophobic segments enables rapid, efficient, and high-capacity removal of PFOX. The future directions of NM&ISW-A for PFOX removal include the preparation and regeneration of engineerable NM&ISW-A, the development of coupling technology for PFOX removal based on NM&ISW-A, the in-depth research on adsorption mechanism of PFOX by NM&ISW-A, as well as the development of NM&ISW-A for PFOX alternatives removal. This review paper would be helpful the comprehensive understanding of NM&ISW-A potential for PFOX removal and the PFOX removal mechanisms, and identifies the gaps for future research and development.

Impacts of Perfluoroalkyl Substances on Aqueous and Nonaqueous Phase Liquid Dechlorination by Sulfidized Nanoscale Zerovalent Iron

Per- and poly fluoroalkyl substances (PFASs) are often encountered with nonaqueous phase liquid (NAPL) in the groundwater at fire-fighting and military training sites. However, it is unclear how PFASs affect the dechlorination performance of sulfidized nanoscale zerovalent iron (S-nFe0), which is an emerging promising NAPL remediation agent. Here, S-nFe0 synthesized with controllable S speciation (FeS or FeS2) were characterized to assess their interactions with PFASs and their dechlorination performance for trichloroethylene NAPL (TCE-NAPL). Surface-adsorbed PFASs blocked materials' reactive sites and inhibited aqueous TCE dechlorination. In contrast, PFASs-adsorbed particles with improved hydrophobicity tended to enrich at the NAPL-water interface, and the reactive sites were re-exposed after the PFASs accumulation into the NAPL phase to accelerate dechlorination. This PFASs-induced phenomenon allowed the materials to present a higher reactivity (up to 1.8-fold) with a high electron efficiency (up to 99%) for TCE-NAPL dechlorination. Moreover, nFe0-FeS2 with a higher hydrophobicity was more readily enriched at the NAPL-water interface and more reactive and selective than nFe0-FeS, regardless of coexisting PFASs. These results unveil that a small amount of yet previously overlooked coexisting PFASs can favor selective reductions of TCE-NAPL by S-nFe0, highlighting the importance of materials hydrophobicity and transportation induced by S and PFASs for NAPL remediation.

The untold story of PFAS alternatives: Insights into the occurrence, ecotoxicological impacts, and removal strategies in the aquatic environment

Due to increasing regulations on the production and consumption of legacy per- and polyfluoroalkyl substances (PFAS), the global use of PFAS substitutes increased tremendously, posing serious environmental risks owing to their bioaccumulation, toxicity, and lack of removal strategies. This review summarized the spatial distribution of alternative PFAS and their ecological risks in global freshwater and marine ecosystems. Further, toxicological effects of novel PFAS in various freshwater and marine species were highlighted. Moreover, degradation mechanisms for alternative PFAS removal from aquatic environments were compared and discussed. The spatial distribution showed that 6:2 chlorinated polyfluorinated ether sulfonate (6:2 CI-PFAES, also known as F-53B) was the most dominant emerging PFAS found in freshwater. Additionally, the highest levels of PFBS and PFBA were observed in marine waters (West Pacific Ocean). Moreover, short-chain PFAS exhibited higher concentrations than long-chain congeners. The ecological risk quotients (RQs) for phytoplankton were relatively higher >1 than invertebrates, indicating a higher risk for freshwater phytoplankton species. Similarly, in marine water, the majority of PFAS substitutes exhibited negligible risk for invertebrates and fish, and posed elevated risks for phytoplanktons. Reviewed studies showed that alternative PFAS undergo bioaccumulation and cause deleterious effects such as oxidative stress, hepatoxicity, neurotoxicity, histopathological alterations, behavioral and growth abnormalities, reproductive toxicity and metabolism defects in freshwater and marine species. Regarding PFAS treatment methods, photodegradation, photocatalysis, and adsorption showed promising degradation approaches with efficiencies as high as 90%. Finally, research gaps and future perspectives for alternative PFAS toxicological implications and their removal were offered.