Amphiphilic Perfluoropolyether Copolymers for the Effective Removal of Polyfluoroalkyl Substances from Aqueous Environments

Unveiling the Differential Intensity of Fluorous Active Sites Toward Selective Polyfluoroalkyl Substance Removal: Insights into Adsorption and Desorption Trade-Offs

The design of selective sorption sites for per- and polyfluoroalkyl substance (PFAS) removal, integrated with efficient regenerative strategies, remains a critical yet underexplored challenge. While existing technologies prioritize adsorption capacity over regenerative sustainability, we engineered a fluorinated hydrogel with tailored fluorous binding sites to target PFAS via their hydrophobic C-F termini. This design achieved over 90% PFAS removal efficiency in real water matrices (e.g., tap and lake water), at environmentally relevant concentrations (1 μg L-1), with robust resistance to competing background ions and natural organic matter. Selectivity correlated strongly with PFAS chain length (F9 > F12 > F6), driven by stable adsorption configurations (C-F···F-C vs C-H···F-C) and a favorable adsorption energy of -29.06 kcal mol-1. Leveraging controlled noncovalent F···F interactions, the hydrogel enabled efficient desorption (60-80% efficiency using 1% NaCl, 1% NH4Cl, or 0.5% NH4OH-NH4Cl) without structural degradation. Full regeneration (>92% recovery) was achieved with 50% methanol, supporting five reuse cycles with minimal performance decline. In continuous operation, using 1% NaCl achieved a 10-fold PFAS enrichment, while 50% methanol enabled a significantly higher 51-fold enrichment. Both approaches reduced eluent consumption by 20-50% compared to conventional activated carbon and resins. Overall, balancing PFAS adsorption and desorption trade-offs significantly reduces environmental footprint and operational costs, providing a sustainable strategy for PFAS remediation.

Infrared Spectroscopic Signatures of the Fluorous Effect Arise from a Change of Conformational Dynamics

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds widely employed in society due to their chemical inertness. These substances accumulate in the environment, from where they enter human bodies, leading to harmful effects like cancer. PFAS exhibit omniphobic properties, which often cause them to separate from both aqueous and organic phases, forming a fluorous phase. Yet, the physical nature of this fluorous effect is unknown. Here, we shed light on the fluorous effect by analyzing the infrared absorption spectra of perfluorinated and semifluorinated alkanes in various solvents. We find that specific bands in the C-F stretching vibrational region exhibit selective behaviors in fluorous and nonfluorous environments. In a fluorous environment, these bands undergo significant broadening, and the asymmetric CF3 stretching bands decrease in intensity. Using static density functional theory calculations and force-field molecular dynamics simulations, we decipher the underlying molecular mechanisms: The decrease in absorption intensities is related to the intermolecular vibrational coupling of the perfluoroalkyl chains, while an acceleration of conformational changes in the carbon backbone of the molecules causes the observed band broadening. Given the high specificity of the reported spectral changes to a fluorous environment, bands in the C-F stretching range can serve as spectroscopic markers for the fluorous phase, facilitating the study of PFAS aggregation. Such knowledge can lead to the rational design of absorber materials for PFAS, which are aimed at mitigating their environmental impact.

Harnessing Fluorine Chemistry: Strategies for Per- and Polyfluoroalkyl Substances Removal and Enrichment

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous, recalcitrant, bioaccumulative, and toxic. Effective concentration technologies are essential for remediating these compounds, a major focus of environmental science and engineering today. This review provides a comprehensive overview of PFAS, from fundamental chemistry to current research, encompassing fluorine chemistry, PFAS synthesis, and their applications. The review specifically thoroughly examines how fluorine chemistry can be utilized to enhance PFAS removal and enrichment, highlighting examples of aromatic/direct fluorination and aliphatic per- and polyfluorination, where the latter induces the fluorous effect. A comprehensive list of reactions used to design or modify PFAS sorbents is summarized, serving as a resource for ongoing research. Finally, insights are offered into how fluorine chemistry can be studied and employed to further improve PFAS characterization and management.

Fluorinated Block Copolymer: An Important Sorbent Design Criteria for Effective PFOA Removal from Its Aqueous Solution

An important question remains unresolved, despite extensive studies on polymer-based sorbents for adsorbing poly and perfluoro alkyl substances (PFAS): How does the positioning of the fluorine-rich segment in polymer affect PFAS removal? Herein, we designed a linear, uncharged triblock copolymer incorporating a fluorinated moiety in the polymer backbone, which effectively removed perfluorooctanoic acid (PFOA) from water. In contrast, polymers without fluorogenic moiety or with it in the side chains showed significantly poorer PFOA removal. Our finding suggests that PFOA adsorption is more influenced by C-F···F-C interactions when the fluorinated segment is in the polymer backbone, not in the side chain.

Cooperative Molecular Interaction-Based Highly Efficient Capturing of Ultrashort- and Short-Chain Emerging Per- and Polyfluoroalkyl Substances Using Multifunctional Nanoadsorbents

The short-chain (C4 to C7) and ultrashort-chain (C3 to C2) per- and polyfluoroalkyl substances (PFAS) are bioaccumulative, carcinogenic to humans, and harder to remove using current technologies, which are often detected in drinking and environmental water samples. Herein, we report the development of nonafluorobutanesulfonyl (NFBS) and polyethylene-imine (PEI)-conjugated Fe3O4 magnetic nanoparticle-based magnetic nanoadsorbents and demonstrated that the novel adsorbent has the capability for highly efficient removal of six different short- and ultrashort-chain PFAS from drinking and environmental water samples. Reported experimental data indicates that by capitalizing the cooperative hydrophobic, fluorophilic, and electrostatic interaction processes, NFBS-PEI-conjugated magnetic nanoadsorbents can remove ∼100% short-chain perfluorobutanesulfonic acid within 30 min from the water sample with a maximum absorption capacity q m of ∼234 mg g-1. Furthermore, to show how cooperative interactions are necessary for effective capturing of ultrashort and short PFAS, a comparative study has been performed using PEI-attached magnetic nanoadsorbents without NFBS and acid-functionalized magnetic nanoadsorbents without PEI and NFBS. Reported data show that the ultrashort-chain perfluoropropanesulfonic acid capture efficiency is the highest for the NFBS-PEI-attached nanoadsorbent (q m ∼ 187 mg g-1) in comparison to the PEI-attached nanoadsorbent (q m ∼ 119 mg g-1) or carboxylic acid-attached nanoadsorbent (q m ∼ 52 mg g-1). In addition, the role of cooperative molecular interactions in highly efficient removal of ultrashort-chain PFAS has been analyzed in detail. Moreover, reported data demonstrate that nanoadsorbents can be used for effective removal of short-chain PFAS (<92%) and ultrashort-chain PFAS (<70%) simultaneously from reservoir, lake, tape, and river water samples within 30 min, which shows the potential of nanoadsorbents for real-life PFAS remediation.

Additives Capable of Stably Supplying Anions/Cations for Homogeneous Lithium Deposition/Stripping

One of the important factors leading to lithium dendrites is a slow lithium-ion mass transport and imbalanced distribution of the Li+ concentration and nuclei sites on the anode surface. To achieve uniform lithium deposition during the charge and discharge process, we introduce a homemade new copolymer (with the quaternary ammonium group N3R+I- on its side chain as the main functional group), named P35, as a functional electrolyte additive to regulate the lithium deposition. Theoretical calculations show that under the strong coordinating interaction between I- and N3R+, P35 preferentially adsorbs onto the lithium foil surface, effectively countering the adsorption of lithium salt anions such as PF6-. Moreover, the positive charge carried by the quaternary ammonium salt group of P35 could interact with PF6- to limit their mobility. Consequently, the dipole interaction on lithium ions is diminished, leading to an enhancement in the transport rate and a decrease in the concentration gradient of lithium ions. Furthermore, a more efficient SEI was formed due to the dual charges electrostatic shield formed by N3R+I-. Li-Li symmetric cells and Li-LiFePO4 full cells assembled with electrolytes with P35 exhibit better rate performance, smaller polarization, and smoother deposition morphology in comparison to the cells without the P35 additive.

Reprocessible, Reusable, and Self-Healing Polymeric Adsorbent for Removing Perfluorinated Pollutants

Here, we report a reprocessible, reusable, self-healing, and form-switching polymeric adsorbent for remediating fluorinated pollutants in water. The copolymer hydrogel is designed to contain fluorophilic segments and cationic segments to induce strong binding with perfluorinated pollutants. The sorption performance reveals rapid and quantitative removal of these pollutants, driven by the synergistic effect of fluorophilic and electrostatic interaction. Importantly, a disulfide-containing dynamic crosslinker plays a crucial role in imparting multifunctionality. This enables self-healing by the restoration of crosslinks at the cut surfaces by disulfide exchange reactions and allows for the repeated use of the adsorbent via multiple adsorption-desorption cycles. Furthermore, the adsorbent is reprocessible by cleaving the crosslinks to afford linear copolymers, which can be repolymerized into a hydrogel network on demand. Also, form-switching capability is showcased through the aqueous self-assembly of linear copolymers into a fluorinated micelle, serving as another form of adsorbent for pollutant removal.

Fluoropolymer sorbent for efficient and selective capturing of per- and polyfluorinated compounds

Per- and poly-fluoroalkyl substances (PFAS) have gained widespread attention due to their adverse effects on health and environment. Developing efficient technology to capture PFAS from contaminated sources remains a great challenge. In this study, we introduce a type of reusable polymeric sorbent (PFPE-IEX + ) for rapid, efficient, and selective removal of multiple PFAS impurities from various contaminated water sources. The resin achieves >98% removal efficiency ([PFPE-IEX + ] = 0.5-5 mg mL-1, [PFAS]0 = 1-10 ppb in potable water and landfill leachate) and >500 mg g-1 sorption capacity for the 11 types of examined PFAS. We achieve efficient PFAS removal without breakthrough and subsequent resin regeneration and demonstrate good PFAS recovery in a proof-of-concept cartridge setup. The outcomes of this study offer valuable guidance to the design of platforms for efficient and selective PFAS capture from contaminated water, such as drinking water and landfill leachate.

Characterization of a mixed mode fluorocarbon/weak anion exchange sorbent for the separation of perfluoroalkyl substances

The ubiquitous presence and persistence of per- and polyfluoroalkyl substances (PFAS) in the environment have raised concerns in the scientific community. Current research efforts are prioritizing effective PFAS remediation through novel sorbents with orthogonal interaction mechanisms. Recognized sorption mechanisms between PFAS and sorbents include hydrophobic, electrostatic, and fluorine-fluorine interaction. The interplay of these mechanisms contributes significantly to improved sorption capacity and selectivity in PFAS separations. In this study, a primary/secondary amine-functionalized polystyrene-divinylbenzene (Sepra-WAX) polymer was modified to create a fluorinated WAX resin (Sepra-WAX-KelF-PEI). The synthesis intermediate (Sepra-WAX-KelF) was also tested to assess the improvement of the final product (Sepra-WAX-KelF-PEI). The adsorption capacity of Sepra-WAX, Sepra-WAX-KelF, and Sepra-WAX-KelF-PEI, and their interactions with PFAS were evaluated. The effect of pH, ionic strength, and organic solvents on PFAS sorption in aqueous solution was also investigated. The sorbents showed varied adsorption capacities for perfluorooctanoic acid, perfluoropentanoic acid, perfluoro-n-decanoic acid, and hexafluoropropylene oxide dimer acid, with the average extraction capacity of the four analytes being Sepra-WAX-KelF-PEI (523 mg/g) > Sepra-WAX (353 mg/g) > Sepra-WAX-KelF (220 mg/g). Sepra-WAX-KelF-PEI provided the highest adsorption capacity for all analytes tested, proving that the combination of electrostatic and hydrophobic/fluorophilic interactions is crucial for the effective preconcentration of PFAS and its future applications for PFAS remediation from aqueous solutions.

Sulfobetaine Zwitterions with Embedded Fluorocarbons: Synthesis and Interfacial Properties

We describe the preparation of a new set of fluorinated sulfobetaine (FSB) zwitterionic polymers in which fluorocarbon moieties are attached directly to the zwitterionic components. An efficient two-step modification to the conventional sulfobetaine methacrylate monomer synthesis gave access to a series of polymer zwitterions containing varying extents of fluorocarbon character. FSB methacrylates proved amenable to homo- and copolymerizations using reversible addition-fragmentation chain transfer (RAFT) conditions, affording polymers with molecular weights ranging from 5 to 20 kDa and with low molecular weight distributions. Thin films of FSB homopolymers on glass proved stable to aqueous environments and exhibited increasing hydrophobicity with fluorocarbon content, as well as remarkably large water contact angle hysteresis values that enable pinning of water droplets on hydrophobic surfaces, reminiscent of the "petal effect" found in nature. FSB-containing copolymers in aqueous media demonstrated markedly reduced oil-water interfacial tension values, even with moderate (20-50 mol %) FSB incorporation.

Insights into PFAS environmental fate through computational chemistry: A review

Per- and polyfluoroalkyl substances (PFAS) are widely used chemicals that exhibit exceptional chemical and thermal stability. However, their resistance to degradation has led to their widespread environmental contamination. PFAS also negatively affect the environment and other organisms, highlighting the need for effective remediation methods to mitigate their presence and prevent further contamination. Computational chemistry methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD) offer valuable tools for studying PFAS and simulating their interactions with other molecules. This review explores how computational chemistry methods contribute to understanding and tackling PFAS in the environment. PFAS have been extensively studied using DFT and MD, each method offering unique advantages and computational limitations. MD simulates large macromolecules systems however it lacks the ability model chemical reactions, while DFT provides molecular insights however at a high computational cost. The integration of DFT with MD shows promise in predicting PFAS behavior in different environments. This work summarizes reported studies on PFAS compounds, focusing on adsorption, destruction, and bioaccumulation, highlighting contributions of computational methods while discussing the need for continued research. The findings emphasize the importance of computational chemistry in addressing PFAS contamination, guiding risk assessments, and informing future research and innovations in this field.

Advancing PFAS Sorbent Design: Mechanisms, Challenges, and Perspectives

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals characterized with persistence and multisurface resistance. Their accumulation in the environment and toxicity to human beings have contributed to the rapid development of regulations worldwide since 2002. The sorption strategy, taking advantage of intermolecular interactions for PFAS capture, provides a promising and efficient solution to the treatment of PFAS contaminated sources. Hydrophobic and electrostatic interactions are the two commonly found in commercially available PFAS sorbents, with the fluorous interaction being the novel mechanism applied for sorbent selectivity. The main object of this Perspective is to provide a critical review on the current design criteria of PFAS sorbents, with particular focus on their sorption and interaction mechanisms as well as limitations. An outlook on future innovative design for efficient PFAS sorbents is also provided.

2D Fluorinated Graphene Oxide (FGO)-Polyethyleneimine (PEI) Based 3D Porous Nanoplatform for Effective Removal of Forever Toxic Chemicals, Pharmaceutical Toxins, and Waterborne Pathogens from Environmental Water Samples

Although water is essential for life, as per the United Nations, around 2 billion people in this world lack access to safely managed drinking water services at home. Herein we report the development of a two-dimensional (2D) fluorinated graphene oxide (FGO) and polyethylenimine (PEI) based three-dimensional (3D) porous nanoplatform for the effective removal of polyfluoroalkyl substances (PFAS), pharmaceutical toxins, and waterborne pathogens from contaminated water. Experimental data show that the FGO-PEI based nanoplatform has an estimated adsorption capacity (qm) of ∼219 mg g-1 for perfluorononanoic acid (PFNA) and can be used for 99% removal of several short- and long-chain PFAS. A comparative PFNA capturing study using different types of nanoplatforms indicates that the qm value is in the order FGO-PEI > FGO > GO-PEI, which indicates that fluorophilic, electrostatic, and hydrophobic interactions play important roles for the removal of PFAS. Reported data show that the FGO-PEI based nanoplatform has a capability for 100% removal of moxifloxacin antibiotics with an estimated qm of ∼299 mg g-1. Furthermore, because the pore size of the nanoplatform is much smaller than the size of pathogens, it has a capability for 100% removal of Salmonella and Escherichia coli from water. Moreover, reported data show around 96% removal of PFAS, pharmaceutical toxins, and pathogens simultaneously from spiked river, lake, and tap water samples using the nanoplatform.

A ReaxFF-based molecular dynamics study of the destruction of PFAS due to ultrasound

This work uses a computational approach to provide a mechanistic explanation for the experimentally observed destruction of per- and polyfluoroalkyl substances (PFAS) in water due to ultrasound. The PFAS compounds have caused a strong public and regulatory response due to their ubiquitous presence in the environment and toxicity to humans. In this research, ReaxFF -based Molecular Dynamics simulation under several temperatures ranging from 373 K to 5,000 K and different environments such as water vapor, O2, N2, and air were performed to understand the mechanism of PFAS destruction. The simulation results showed greater than 98% PFAS degradation was observed within 8 ns under a temperature of 5,000 K in a water vapor phase, replicating the observed micro/nano bubbles implosion and PFAS destruction during the application of ultrasound. Additionally, the manuscript discusses the reaction pathways and how PFAS degradation evolves providing a mechanistic basis for the destruction of PFAS in water due to ultrasound. The simulation showed that small chain molecules C1 and C2 fluoro-radical products are the most dominant species over the simulated period and are the impediment to an efficient degradation of PFAS. Furthermore, this research confirms the empirical findings observations that the mineralization of PFAS molecules occurs without the generation of byproducts. These findings highlight the potential of virtual experiments in complementing laboratory experiments and theoretical projections to enhance the understanding of PFAS mineralization during the application of ultrasound.

Imparting Selective Fluorophilic Interactions in Redox Copolymers for the Electrochemically Mediated Capture of Short-Chain Perfluoroalkyl Substances

With increasing regulations on per- and polyfluoroalkyl substances (PFAS) across the world, understanding the molecular level interactions that drive their binding by functional adsorbent materials is key to effective PFAS removal from water streams. With the phaseout of legacy long-chain PFAS, the emergence of short-chain PFAS has posed a significant challenge for material design due to their higher mobility and hydrophilicity and inefficient removal by conventional treatment methods. Here, we demonstrate how cooperative molecular interactions are essential to target short-chain PFAS (from C4 to C7) by tailoring structural units to enhance affinity while modulating the electrochemical control of capture and release of PFAS. We report a new class of fluorinated redox-active amine-functionalized copolymers to leverage both fluorophilic and electrostatic interactions for short-chain PFAS binding. We combine molecular dynamics (MD) simulations and electrosorption to elucidate the role of the designer functional groups in enabling affinity toward short-chain PFAS. Preferential interaction coefficients from MD simulations correlated closely with experimental trends: fluorination enhanced the overall PFAS uptake and promoted the capture of less hydrophobic short-chain PFAS (C ≤ 5), while electrostatic interactions provided by secondary amine groups were sufficient to capture PFAS with higher hydrophobicity (C ≥ 6). The addition of an induced electric field showed favorable kinetic enhancement for the shortest PFAS and increased the reversibility of release from the electrode. Integration of these copolymers with electrochemical separations showed potential for removing these contaminants at environmentally relevant conditions while eliminating the need for chemical regeneration.

Efficient Removal of Perfluorinated Chemicals from Contaminated Water Sources Using Magnetic Fluorinated Polymer Sorbents

Efficient removal of per- and polyfluoroalkyl substances (PFAS) from contaminated waters is urgently needed to safeguard public and environmental health. In this work, novel magnetic fluorinated polymer sorbents were designed to allow efficient capture of PFAS and fast magnetic recovery of the sorbed material. The new sorbent has superior PFAS removal efficiency compared with the commercially available activated carbon and ion-exchange resins. The removal of the ammonium salt of hexafluoropropylene oxide dimer acid (GenX) reaches >99 % within 30 s, and the estimated sorption capacity was 219 mg g-1 based on the Langmuir model. Robust and efficient regeneration of the magnetic polymer sorbent was confirmed by the repeated sorption and desorption of GenX over four cycles. The sorption of multiple PFAS in two real contaminated water matrices at an environmentally relevant concentration (1 ppb) shows >95 % removal for the majority of PFAS tested in this study.

Supramolecular assemblies of a newly developed indole derivative for selective adsorption and photo-destruction of perfluoroalkyl substances

Per-/polyfluoroalkyl substances (PFASs) contamination has caused worldwide health concerns, and increased demand for effective elimination strategies. Herein, we developed a new indole derivative decorated with a hexadecane chain and a tertiary amine center (named di-indole hexadecyl ammonium, DIHA), which can form stable nanospheres (100-200 nm) in water via supramolecular assembly. As the DIHA nanospheres can induce electrostatic, hydrophobic and van der Waals interactions (all are long-ranged) that operative cooperatively, in addition to the nano-sized particles with large surface area, the DIHA nanocomposite exhibited extremely fast adsorption rates (in seconds), high adsorption capacities (0.764-0.857 g g^-1) and selective adsorption for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), outperformed the previous reported high-end PFASs adsorbents. Simultaneously, the DIHA nanospheres can produce hydrated electron (e_aq^-) when subjected to UV irradiation, with the virtue of constraining the photo-generated e_aq^- and the adsorbed PFOA/PFOS molecules entirely inside the nanocomposite. As such, the UV/DIHA system exhibits extremely high degradation/defluorination efficiency for PFOA/PFOS, even under ambient conditions, especially with the advantages of low chemical dosage requirement (μM level) and robust performance against environmental variables. Therefore, it is a new attempt of using supramolecular approach to construct an indole-based nanocomposite, which can elegantly combine adsorption and degradation functions. The novel DIHA nanoemulsion system would shed light on the treatment of PFAS-contaminated wastewater.

Hydrolytically Stable Ionic Fluorogels for High-Performance Remediation of Per- and Polyfluoroalkyl Substances (PFAS) from Natural Water

PFAS are known bioaccumulative and persistent chemicals which pollute natural waters globally. There exists a lack of granular sorbents to efficiently remove both legacy and emerging PFAS at environmentally relevant concentrations. Herein, we report a class of polymer networks with a synergistic combination of ionic and fluorous components that serve as granular materials for the removal of anionic PFAS from water. A library of Ionic Fluorogels (IFs) with systematic variation in charge density and polymer network architecture was synthesized from hydrolytically stable fluorous building blocks. The IFs were demonstrated as effective sorbents for the removal of 21 legacy and emerging PFAS from a natural water and were regenerable over multiple cycles of reuse. Comparison of one IF to a commercial ion exchange resin in mini-rapid small-scale column tests demonstrated superior performance for the removal of short-chain PFAS from natural water under operationally relevant conditions.

Ultra-stable all-solid-state sodium metal batteries enabled by perfluoropolyether-based electrolytes

Rechargeable batteries paired with sodium metal anodes are considered to be one of the most promising high-energy and low-cost energy-storage systems. However, the use of highly reactive sodium metal and the formation of sodium dendrites during battery operation have caused safety concerns, especially when highly flammable liquid electrolytes are used. Here we design and develop solvent-free solid polymer electrolytes (SPEs) based on a perfluoropolyether-terminated polyethylene oxide (PEO)-based block copolymer for safe and stable all-solid-state sodium metal batteries. Compared with traditional PEO SPEs, our results suggest that block copolymer design allows for the formation of self-assembled nanostructures leading to high storage modulus at elevated temperatures with the PEO domains providing transport channels even at high salt concentration (ethylene oxide/sodium = 8/2). Moreover, it is demonstrated that the incorporation of perfluoropolyether segments enhances the Na⁺ transference number of the electrolyte to 0.46 at 80 °C and enables a stable solid electrolyte interface. The new SPE exhibits highly stable symmetric cell-cycling performance at high current density (0.5 mA cm^-2 and 1.0 mAh cm^-2, up to 1,000 h). Finally, the assembled all-solid-state sodium metal batteries demonstrate outstanding capacity retention, long-term charge/discharge stability (Coulombic efficiency, 99.91%; >900 cycles with Na₃V₂(PO₄)₃ cathode) and good capability with high loading NaFePO₄ cathode (>1 mAh cm^-2).

Interaction of Short-Chain PFAS with Polycationic Gels: How Much Fluorination is Necessary for Efficient Adsorption?

The short-chain per- and polyfluorinated alkyl substances (PFAS), introduced to replace the legacy PFAS compounds, turned out to be as toxic and harmful as their longer-chain predecessors and even harder to sequester from contaminated water sources. In this work, molecular dynamics (MD) simulations are employed to investigate the adsorption mechanism of GenX, a representative compound for short-chain PFAS, on a polycationic hydrogel with various extents of fluorination in its backbone and cross-linkers. Simulations indicate that the presence of fluorinated segments next to cationic groups in the polymer gel structure provides the most efficient environment for GenX adsorption. The combination of electrostatic and hydrophobic interactions offered by the cationic-fluorophilic segments amplifies the binding of GenX molecules compared to polymer segments with nonfluorinated cationic or noncationic fluorinated segments. Moreover, such a gel demonstrates high selectivity toward GenX against its hydrogenated analogue.

A dual grafted fluorinated hydrocarbon amine weak anion exchange resin polymer for adsorption of perfluorooctanoic acid from water

Perfluorooctanoic acid (PFOA) is a persistent and recalcitrant organic contaminant of exceptional environmental concern, and its removal from water has increasingly attracted global attention due to its wide distribution and strong bioaccumulation. Adsorption is considered an effective technique for PFOA removal and more efficient PFOA sorbents are still of interest. This study developed a dual grafted fluorinated hydrocarbon amine weak anion exchange (WAX) polymeric resin (Sepra-WAX-KelF-PEI) for PFOA removal from water. This polymer was synthesized by a two-step amine grafting reaction procedure involving first the reaction of the Sepra-WAX hydrocarbon polymer with poly(vinylidinefluoride-chlorotrifluoroethylene) (Kel-F 800) and then a second reaction with polyethyleneimine (PEI). Characterization of the synthesized polymers was performed using scanning electron microscopy and elemental analysis (F and Cl) by energy dispersive X-ray spectroscopy. The PFOA adsorption performance evaluations were conducted by packed column flow analyses with on-line detection. The results show the breakthrough of the Sepra-WAX-KelF-PEI synthesized with optimum stoichiometry was two times better than the starting anion exchange polymer Sepra-WAX, and six times better than powdered activated carbon, when using the same column size. The adsorption mechanisms of this novel adsorbent including hydrophobic interaction and electrostatic interaction were also clarified in this study. The adsorption kinetic parameters of the two optimum synthesized sorbents were determined using the Thomas model, the Yoon-Nelson model, and batch isotherm studies, and compared with those found with activated carbon and the starting WAX resin. Good agreement of the batch isotherm and column studies with respect to adsorption capacities trends between all three polymers (Sepra-WAX, Sepra-WAX-KelF, and Sepra-WAX-KelF-PEI) were noted.

Biological Utility of Fluorinated Compounds: from Materials Design to Molecular Imaging, Therapeutics and Environmental Remediation

The applications of fluorinated molecules in bioengineering and nanotechnology are expanding rapidly with the controlled introduction of fluorine being broadly studied due to the unique properties of C-F bonds. This review will focus on the design and utility of C-F containing materials in imaging, therapeutics, and environmental applications with a central theme being the importance of controlling fluorine-fluorine interactions and understanding how such interactions impact biological behavior. Low natural abundance of fluorine is shown to provide sensitivity and background advantages for imaging and detection of a variety of diseases with ¹⁹F magnetic resonance imaging, ¹⁸F positron emission tomography and ultrasound discussed as illustrative examples. The presence of C-F bonds can also be used to tailor membrane permeability and pharmacokinetic properties of drugs and delivery agents for enhanced cell uptake and therapeutics. A key message of this review is that while the promise of C-F containing materials is significant, a subset of highly fluorinated compounds such as per- and polyfluoroalkyl substances (PFAS), have been identified as posing a potential risk to human health. The unique properties of the C-F bond and the significant potential for fluorine-fluorine interactions in PFAS structures necessitate the development of new strategies for facile and efficient environmental removal and remediation. Recent progress in the development of fluorine-containing compounds as molecular imaging and therapeutic agents will be reviewed and their design features contrasted with environmental and health risks for PFAS systems. Finally, present challenges and future directions in the exploitation of the biological aspects of fluorinated systems will be described.