Fluorine-tailed glass fibers for adsorption of volatile perfluorinated compounds via F-F interaction

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.

Electrochemical Sensing of Perfluorooctanoic Acid via a Rationally Designed Fluorine-Functionalized Cu-MOF and In-Depth Analysis of Sensing Mechanism

Perfluorooctanoic acid (PFOA), a prominent member of the per- and polyfluoroalkyl substance (PFAS) family, has emerged as a new perpetual pollutant posing significant environmental and health risks, necessitating developing highly selective materials for its sensitive detection in water. In this work, we developed an electroactive fluorine-functionalized Cu-MOF (F-Cu-NH2BDC) through postmodification of the copper-2-amino-terephthalic acid (Cu-NH2BDC) MOF with 2,3,5,6-tetrafluoroterephthalaldehyde (TFTA). Experimental and computational results suggested that F-F interactions between the decorated tetrafluorobenzaldehyde groups and PFOA, as well as among the PFOA molecules themselves, would induce self-aggregation of PFOA molecules on the surfaces or in the pores of F-Cu-NH2BDC. This specific aggregation inhibited contact and electron transfer between F-Cu-NH2BDC and the electrolyte, resulting in a decrease in the inherent electrochemical Cu2+/Cu+ redox signal from F-Cu-NH2BDC. Based on this, an F-Cu-NH2BDC-based label- and probe-free PFOA electrochemical sensor was exploited with an excellent linear range from 5 pM to 500 μM and an extremely low detection limit of 3.54 pM, surpassing most currently reported electrochemical and nonelectrochemical PFAS sensors. This sensor also exhibited good stability, reproducibility, and anti-interference performance, enabling the accurate measurement of PFOA concentrations in actual commercial drinking water. These findings shed light on the design of PFAS sensors utilizing the F-F interaction as the working mechanism.

Fluorine-fluorine interaction-driven colorimetric sensor for PFOA-sensitive detection using F-functionalized Ce-UiO-66-NH2 MOF with oxidase-like activity

A novel colorimetric sensor was designed for sensitive perfluorooctanoic acid (PFOA) detection based on a fluorine-functionalized Ce-metal-organic framework (F-Ce-UiO-66-NH2) with oxidase-like activity, using 3,3',5,5'-tetramethylbenzidine (TMB) as the chromogenic substrate. This F-Ce-UiO-66-NH2 was synthesized through ligand exchange and post-modification with pentafluorobenzaldehyde (PFBA) on the basis of Ce-terephthalic acid (Ce-UiO-66), incorporating pentafluorophenyl groups that enhance the material's affinity for PFOA, leading to a more sensitive absorbance change in the presence of PFOA. Experimental and computational assays revealed that oxidase-like activity of F-Ce-UiO-66-NH2 primarily arises from hydroxyl radicals (•OH) generated through the conversion of superoxide radicals (•O2-). Furthermore, PFOA molecules were shown to undergo self-aggregation on the F-Ce-UiO-66-NH2 surface via fluorine-fluorine (F-F) interactions between PFOA molecules and the pentafluorophenyl groups as well as between PFOA themselves, blocking the active Ce sites and hindering the interaction of O2 and TMB with F-Ce-UiO-66-NH2, thereby diminishing its oxidase-like activity. Owing to these sophisticated mechanisms, this colorimetric sensor demonstrated a broad linear detection range from 0.5 to 210 µM with a low detection limit of 0.41 µM for PFOA, enabling precise quantification of PFOA concentrations in real environmental water samples. This work introduces a new strategy for constructing field-deployable colorimetric sensors based on F-F interaction, offering very valuable insights into the design and operational principle for PFAS detection.

Understanding the Selective Removal of Perfluoroalkyl and Polyfluoroalkyl Substances via Fluorine-Fluorine Interactions: A Critical Review

As regulatory standards for per- and polyfluoroalkyl substances (PFAS) become increasingly stringent, innovative water treatment technologies are urgently demanded for effective PFAS removal. Reported sorbents often exhibit limited affinity for PFAS and are frequently hindered by competitive background substances. Recently, fluorinated sorbents (abbreviated as fluorosorbents) have emerged as a potent solution by leveraging fluorine-fluorine (F···F) interactions to enhance selectivity and efficiency in PFAS removal. This review delves into the designs and applications of fluorosorbents, emphasizing how F···F interactions improve PFAS binding affinity. Specifically, the existence of F···F interactions results in removal efficiencies orders of magnitude higher than other counterpart sorbents, particularly under competitive conditions. Furthermore, we provide a detailed analysis of the fundamental principles underlying F···F interactions and elucidate their synergistic effects with other sorption forces, which contribute to the enhanced efficacy and selectivity. Subsequently, we examine various fluorosorbents and their synthesis and fluorination techniques, underscore the importance of accurately characterizing F···F interactions through advanced analytical methods, and emphasize the significance of this interaction in developing selective sorbents. Finally, we discuss challenges and opportunities associated with employing advanced techniques to guide the design of selective sorbents and advocate for further research in the development of sustainable and cost-effective treatment technologies leveraging F···F interactions.

Amendment of Sargassum oligocystum bio-char with MnFe2O4 and lanthanum MOF obtained from PET waste for fluoride removal: A comparative study

The use of biomass and waste to produce adsorbent reduces the cost of water treatment. The bio-char of Sargassum oligocystum (BCSO) was modified with MnFe2O4 magnetic particles and La-metal organic framework (MOF) to generate an efficient adsorbent (BCSO/MnFe2O4@La-MOF) for fluoride ions (F-) removal from aqueous solutions. The performance of BCSO/MnFe2O4@La-MOF was compared with BCSO/MnFe2O4 and BCSO. The characteristics of the adsorbents were investigated using various techniques, which revealed that the magnetic composites were well-synthesized and exhibited superparamagnetic properties. The maximum adsorption efficiencies (BCSO: 97.84%, BCSO/MnFe2O4: 97.85%, and BCSO/MnFe2O4@La-MOF: 99.36%) were achieved under specific conditions of pH 4, F- concentration of 10 mg/L, and adsorbent dosage of 3, 1.5, and 1 g/L for BCSO, BCSO/MnFe2O4, and BCSO/MnFe2O4@La-MOF, respectively. The results demonstrated that the experimental data adheres to a pseudo-second-order kinetic model. The enthalpy, entropy, and Gibbs free energy were determined to be negative; thus, the F- adsorption was exothermic and spontaneous in the range of 25-50 °C. The equilibrium data of the process exhibited conformity with the Langmuir model. The maximum adsorption capacities of F- ions were determined as 10.267 mg/g for BCSO, 14.903 mg/g for the BCSO/MnFe2O4, and 31.948 mg/g for BCSO/MnFe2O4@La-MOF. The KF and AT values for the F- adsorption were obtained at 21.03 mg/g (L/mg)1/n and 100 × 10+9 L/g, indicating the pronounced affinity of the BCSO/MnFe2O4@La-MOF towards F- than other samples. The significant potential of the BCSO/MnFe2O4@La-MOF magnetic composite for F- removal from industrial wastewater, makes it suitable for repeated utilization in the adsorption process.