PFAS-CTAB Complexation and Its Role on the Removal of PFAS from a Lab-Prepared Water and a Reverse Osmosis Reject Water Using a Plasma Reactor

Plasma-Generated Free Electrons Induced Perfluorooctanoic Acid Efficient Degradation at the Gas-Liquid Interface

Low-temperature plasma, generating both reductive electrons and diverse oxidative species, has demonstrated considerable potential for the degradation of perfluorooctanoic acid (PFOA). However, limited understanding of electron propagation mechanisms during discharge has led previous research to focus on hydrated electrons (eaq-) while neglecting free electrons (e-). In this study, a consistent and modeled dielectric barrier discharge (DBD) plasma was employed to degrade PFOA. Contribution analysis indicated that reactions driven by e- were dominant, with substantial contributions from hydroxyl radical (•OH)-mediated oxidation. By integrating a kinetic model with a streamer solver, a basic discharge unit model was developed. Simulation of e- streamer propagation identified a high-intensity response electric field formed by the e- memory effect, with a peak strength of 1.816 × 106 V/m. This electric field facilitated a secondary acceleration of e-, allowing e- to penetrate the surface water layer and directly attack PFOA via chain-shortening mechanisms. The delocalized state of e- restricted degradation primarily to the gas-liquid interface, minimizing interference from the surrounding medium. This study highlights the previously overlooked role of e- and provides essential theoretical insights for the plasma-based treatment of PFOA-contaminated water.

Best Practices for Experimental Design, Testing, and Reporting of Aqueous PFAS-Degrading Technologies

Increased awareness of pervasive per- and polyfluoroalkyl substances (PFAS) contamination and the need for zero-pollution treatment solutions necessitate the scientific and engineering community to respond urgently and systematically. Existing approaches lack reproducible and standardized methods to report the technological treatment capabilities. Consequently, it is difficult to compare innovations and accurately assess their potential. In this Perspective, we shed light on hurdles encountered in the lab-scale research and development of aqueous PFAS destruction technologies with a focus on chemical methods and offer recommendations for overcoming them. Best practices are provided for developing robust PFAS laboratory protocols covering crucial aspects such as experimental planning, sample storage and analysis, and waste management. Further, we present five criteria to standardize reporting on performance and advances in PFAS degrading technologies: 1) scope, 2) defluorination efficiency, 3) relative energy consumption, 4) material stability, and 5) unit process considerations. Through the dissemination of these insights, we aim to foster progress in the development of highly effective treatment solutions.

Per- and polyfluoroalkyl substances in environment and potential health impacts: Sources, remediation treatment and management, policy guidelines, destructive technologies, and techno-economic analysis

Per- and polyfluoroalkyl Substances (PFAS), also known as forever chemicals and ubiquitous persistence, pose significant public health challenges due to their potential toxicity, particularly in drinking water and soil contamination. However, PFAS occurrence and their concentrations in different environmental matrices vary globally, but factors influencing trends, transport, fate, toxicity, and interactions with co-contaminants remain largely unexplored. Therefore, this review critically examines the state-of-the-art worldwide PFAS sources, distribution, and pathways, and evaluates how PFASs are processed in wastewater treatment, generally, which causes severe problems with the quality and safety of drinking water. Importantly, the review also underscores health issues due to PFAS consumption and recent research trends on developing effective treatment strategies to manage PFAS contamination. Potential effects of PFAS were linked to urban land use and the proportion of wastewater effluent in streamflow. Besides, major emphasis was provided on challenges for conventional treatment, destructive technologies, environmental accumulation, precursor transformation, and cost-investment related to PFAS removal technologies. To combat PFAS contamination, this review proposes a framework that promotes the comprehensive identification of prevalent compounds, with a focus on their eradication through knowledge-based and targeted analysis. Additionally, it explores the ongoing debate surrounding PFAS laws and legal frameworks, offering ideas for enhancing contamination management. Lastly, this review provides a strategic plan for improving response and preparedness, serving as a foundation for addressing future environmental challenges and informing health risk assessments.

Data-Driven Insights into Resin Screening for Targeted Per- and Polyfluoroalkyl Substances Removal Using Machine Learning

In this study, we address the challenge of screening resins and optimizing operation conditions for the removal of 43 perfluoroalkyl and polyfluoroalkyl substances (PFASs), spanning both long- and short-chain fluorocarbon variants, across diverse water matrices, using machine learning (ML) models. We first develop ML models that can accurately predict removal efficiency of PFASs based on resin properties, operation conditions, and water matrix. The model performance is validated by using both a test set and our own experimental tests. The key features from resin properties, operation conditions, and water matrix influencing PFAS removal as well as their interaction effects are comprehensively investigated. We finally target long-chain (e.g., PFOS, PFOA) and short-chain PFASs (e.g., PFBS, GenX), using the developed ML models to inversely screen resins and determine the optimal operation conditions under a specified water matrix. Experimental tests demonstrated that our ML-guided approach achieves the desired removal efficiency (RE) for these PFASs, with RE values reaching 86.56% for PFBS and 83.73% for GenX, outperforming many reported resins. This work underscores the potential of ML methodologies in resin screening and operational optimization across diverse water matrices, enabling the efficient removal of structurally varied PFAS compounds.

Challenges in PFAS Postdegradation Analysis: Insights from the PFAS-CTAB Model System

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used for their oil and water-repellent properties. Their environmental persistence and potential health risks have raised significant concerns. As PFAS degrades through remediation or natural processes, they form complex mixtures of the original chemicals, transformation byproducts, and degradation additives. Analyzing PFAS after degradation presents analytical challenges due to possible chemical and physical interactions, including ion pairing, micelle formation, and complexation. These factors can significantly impact the precision and accuracy of PFAS measurements, yet they are often overlooked in PFAS degradation studies. In this work, we demonstrate that with the addition of ppb-level cetyltrimethylammonium bromide (CTAB), a cationic surfactant used in PFAS plasma-based degradation, the PFAS calibration curve linearity, sensitivity, and reproducibility are severely compromised. Isotopically labeled internal standards cannot fully correct these issues. Furthermore, the standard EPA methods 537.1, 533, and 1633 could not accurately recover PFAS concentrations in the PFAS and CTAB mixtures, with severe matrix effects observed for longer-chain and nitrogen-containing PFAS. Among these methods, Method 1633 is currently the most suitable option for postdegradation analysis. Method 1633 showed the lowest CTAB interference because this method used another weak ion pair additive, formic acid or acetic acid (in commercial lab analysis), to acidify the sample before LC-MS/MS analysis and added an isotopically labeled internal standard. For future PFAS degradation studies, we recommend systematically evaluating the matrix effect on the PFAS quantification using a recovery matrix to validate the analytical methods before use.

Tailoring hierarchical MnO2 nanostructures on self-supporting cathodes for high-mass-loading zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) with MnO2 cathodes have promising application prospects; however, their performance is hindered by their low efficiency and insufficient life. By leveraging the nanomicellar properties of cetyltrimethylammonium bromide (CTAB), a hierarchical δ-MnO2 with 2D/3D structure was directionally grown on a modified carbon cloth (CC) collector for realizing high-mass-loading AZIBs. Experimental results reveal the synergistic effects of micro/nano hierarchically structured MnO2-CC heterointerfaces in accelerating the electron migration and transfer rate of Zn2+/H+. Functioning as a conductive skeleton and flexible substrate, CC efficiently improves the reaction kinetics and buffers the interfacial stress resulting from the structural evolution of MnO2 during the long-term electrode reaction. This phenomenon is investigated using advanced characterisation techniques, including X-ray absorption fine structure spectroscopy, Kelvin probe force microscopy, and theoretical simulations. The fabricated electrode exhibits superior electrochemical properties, such as high capacity (409.6 mA h g-1 at 0.1 A g-1) and reliable cycling performance (with 86.6% capacity retention after 2000 cycles at 1.0 A g-1). Even at a high mass loading of 6.0 mg cm-2, the battery retains 81.8% of its original capacity after 1300 cycles. The proposed interface engineering strategy provides valuable insights into realising high-loading and long-life AZIBs.

Environmental Occurrence and Biotic Concentrations of Ultrashort-Chain Perfluoroalkyl Acids: Overlooked Global Organofluorine Contaminants

Per- and polyfluoroalkyl substances (PFASs) are a large group of anthropogenic fluorinated chemicals. Ultrashort-chain perfluoroalkyl acids (PFAAs) have recently gained attention due to their prevalence in the environment and increasing environmental concerns. In this review, we established a literature database from 1990 to 2024, encompassing environmental and biological concentrations (>3,500 concentration records) of five historically overlooked ultrashort-chain PFAAs (perfluoroalkyl carboxylic and sulfonic acids with less than 4 carbons): trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), trifluoromethanesulfonic acid (TFMS), perfluoroethanesulfonate (PFEtS), and perfluoropropanesulfonate (PFPrS). Our data mining and analysis reveal that (1) ultrashort-chain PFAAs are globally distributed in various environments including water bodies, solid matrices, and air, with concentrations usually higher than those of longer-chain compounds; (2) TFA, the most extensively studied ultrashort-chain PFAA, shows a consistent upward trend in concentrations in surface water, rainwater, and air over the past three decades; and (3) ultrashort-chain PFAAs are present in various organisms, including plants, wildlife, and human blood, serum, and urine, with concentrations sometimes similar to those of longer-chain compounds. The current state of knowledge regarding the sources and fate of TFA and other ultrashort-chain PFAAs is also reviewed. Amid the global urgency to regulate PFASs, particularly as countries worldwide have intensified such efforts, this critical review will inform scientific research and regulatory policies.

Efficient degradation of F-53B as PFOS alternative in water by plasma discharge: Feasibility and mechanism insights

The frequent detection of 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) in various environments has raised concerns owing to its comparable or even higher environmental persistence and toxicity than perfluorooctane sulfonate (PFOS). This study investigated the plasma degradation of F-53B for the first time using a water film plasma discharge system. The results revealed that F-53B demonstrated a higher rate constant but similar defluorination compared to PFOS, which could be ascribed to the introduction of the chlorine atom. Successful elimination (94.8-100 %) was attained at F-53B initial concentrations between 0.5 and 10 mg/L, with energy yields varying from 15.1 to 84.5 mg/kWh. The mechanistic exploration suggested that the decomposition of F-53B mainly occurred at the gas-liquid interface, where it directly reacted with reactive species generated by gas discharge. F-53B degradation pathways involving dechlorination, desulfonation, carboxylation, C-O bond cleavage, and stepwise CF2 elimination were proposed based on the identified byproducts and theoretical calculations. Furthermore, the demonstrated effectiveness in removing F-53B in various coexisting ions and water matrices highlighted the robust anti-interference ability of the treatment process. These findings provide mechanistic insights into the plasma degradation of F-53B, showcasing the potential of plasma processes for eliminating PFAS alternatives in water.

Anti-Wound Dehiscence and Antibacterial Dressing with Highly Efficient Self-Healing Feature for Guided Bone Regeneration Wound Closure

Guided bone regeneration (GBR) is a well-established technique for preserving and enhancing alveolar ridge structures. Success in GBR relies on fulfilling the Primary wound closure, Angiogenesis, Space maintenance, and Stability (PASS) principles. Conventional methods, involving titanium meshes and sutures, have drawbacks, including the need for secondary removal and customization challenges. To address these issues, an innovative multifunctional GBR dressing (MGD) based on self-healing elastomer (PUIDS) is introduced. MGD provides sutureless wound closure, prevents food particle accumulation, and maintains a stable environment for bone growth. It offers biocompatibility, bactericidal properties, and effectiveness in an oral GBR model. In summary, MGD provides a reliable, stable osteogenic environment for GBR, aligning with PASS principles and promoting superior post-surgery bone regeneration.

Biochar and surfactant synergistically enhanced PFAS destruction in UV/sulfite system at neutral pH

The UV/sulfite-based advanced reduction process (ARP) emerges as an effective strategy to combat per- and polyfluoroalkyl substances (PFAS) pollution in water. Yet, the UV/sulfite-ARP typically operates at highly alkaline conditions (e.g., pH > 9 or even higher) since the generated reductive radicals for PFAS degradation can be quickly sequestered by protons (H+). To overcome the associated challenges, we prototyped a biochar-surfactant-system (BSS) to synergistically enhance PFAS sorption and degradation by UV/sulfite-ARP. The degradation and defluorination efficiencies of perfluorooctanoic acid (PFOA) depended on solution pH, and concentrations of surfactant (cetyltrimethylammonium bromide; CTAB), sulfite, and biochar. At high pH (8-10), adding biochar and BSS showed no or even small inhibitory effect on PFOA degradation, since the degradation efficiencies were already high enough that cannot be differentiated. However, at acidic and neutral pH (6-7), an evident enhancement of PFOA degradation and defluorination efficiencies occurred. This is due to the synergies between biochar and CTAB that create favorable microenvironments for enhanced PFOA sorption and deeper destruction by prolonging the longevity of reductive radicals (e.g., SO3•-), which is less affected by ambient pH conditions. The performance of UV/sulfite/BSS was further optimized and used for the degradation of four PFAS. At the optimal experimental condition, the UV/sulfite/BSS system can completely degrade PFOA with >30% defluorination efficiency for up to five continuous cycles (n = 5). Overall, our BSS provides a cost-effective and sustainable technique to effectively degrade PFAS in water under environmentally relevant pH conditions. The BSS-enabled ARP technique can be easily tied into PFAS treatment train technology (e.g., advanced oxidation process) for more efficient and deeper defluorination of various PFAS in water.