The widespread environmental occurrence of per- and polyfluoroalkyl substances (PFAS) has attracted significant regulatory, research, and media attention because of their toxicity, recalcitrance, and ability to bioaccumulate. Perfluorooctane sulfonate (PFOS) is a particularly troublesome member of the PFAS family due to its immunity to biological remediation and radical-based oxidation. In the present study, we present a heterogeneous reductive degradation process that couples direct electron transfer (ET) from surface-modified carbon nanotube electrodes (under low potential conditions) to sorbed PFOS molecules using UV-generated hydrated electrons without any further chemical addition. We demonstrate that the ET process dramatically increases the PFOS defluorination rate while yielding shorter chain (C3–C7) perfluorinated acids and present both experimental and ab initio evidence of the synergistic relationship between electron addition to sorbed molecules and their ability to react with reductive hydrated electrons. Because of the low energy consumption associated with the ET process, the use of standard medium-pressure UV lamps and no further chemical addition, this reductive degradation process is a promising method for the destruction of persistent organic pollutants, including PFAS and other recalcitrant halogenated organic compounds.

During the global spread of COVID‐19, high demand and limited availability of melt‐blown filtration material led to a manufacturing backlog of N95 Filtering Facepiece Respirators (FFRs). This shortfall prompted the search for alternative filter materials that could be quickly mass produced while meeting N95 FFR filtration and breathability performance standards. Here, an unsupported, nonwoven layer of uncharged polystyrene (PS) microfibers was produced via electrospinning that achieves N95 performance standards based on physical parameters (e.g., filter thickness) alone. PS microfibers 3–6 μm in diameter and deposited in an ~5 mm thick filter layer are favorable for use in FFRs, achieving high filtration efficiencies (≥97.5%) and low pressure drops (≤15 mm H2O). The PS microfiber filter demonstrates durability upon disinfection with hydroxyl radicals (•OH), maintaining high filtration efficiencies and low pressure drops over six rounds of disinfection. Additionally, the PS microfibers exhibit antibacterial activity (1‐log removal of E. coli) and can be modified readily through integration of silver nanoparticles (AgNPs) during electrospinning to enhance their activity (≥3‐log removal at 25 wt% AgNP integration). Because of their tunable performance, potential reusability with disinfection, and antimicrobial properties, these electrospun PS microfibers may represent a suitable, alternative filter material for use in N95 FFRs.

Novel nanomaterials, such as carbon nanofibers (CNFs), present a unique opportunity to advance photoelectrochemical drinking water treatment by integrating a photocatalyst to improve material properties and performance. To this end, we have fabricated electrospun CNF-TiO2 composite photoelectrodes with high surface area, conductivity, chemical stability, and mechanical strength for use in photoelectrochemical water treatment applications. The CNF-TiO2 physical, chemical, and electrical properties can be tailored to influence drinking water pollutant transformation pathways by selectively varying fabrication parameters (e.g. TiO2 content, carbonization temperature). Integrating the photocatalyst into the nonwoven CNF framework provides a material that transforms emerging organic pollutants with diverse chemical properties via photochemical (UV/Vis radiation), electrochemical (applied potential) and photoelectrochemical (UV/Vis radiation + applied potential) processes at circumneutral pH. The favored transformation pathway is primarily influenced by carbonization temperature, which controls the CNF-TiO2 electrical conductivity and crystal structures. Electrical resistance decreases almost logarithmically with increasing carbonization temperatures (450 to 1000 °C) to produce composites with more orderly carbon structure (graphitic) and more conductive photocatalyst (rutile TiO2). At higher carbonization temperatures (≥ 1000 °C), pollutants with diverse chemical properties (e.g. log Kow) rapidly sorb to the composite electrode surface. The effect of CNF-TiO2 composite structure on pollutant sorption dramatically overwhelms sorption effects due to pollutant chemical properties. At lower carbonization temperatures (< 1000 °C), composite properties provide minimal pollutant sorption. While composites processed at higher carbonization temperatures encourage direct electrochemical pollutant transformation at photoelectrode surface, lower carbonization temperatures suggest composites are well-suited for indirect photochemical pollutant transformation. Herein we present photoelectrodes carbonized at different temperatures and their performance in transforming model organic pollutants. Outcomes of this work will help identify the types and properties of next-generation photoelectrode materials that are most promising for improving photoelectrochemical cells purposed for drinking water treatment.

Electrochemical (EC) and photoelectrochemical (PEC) water treatment systems are gaining popularity, necessitating new electrode materials that offer reliable performance across diverse application platforms. For applications specifically targeting dilute chemical pollutants...