Porous Electrospun Fibers Embedding TiO2 for Adsorption and Photocatalytic Degradation of Water Pollutants

Prediction of Nanoparticle Photoreactivity in Mixtures of Surface Foulants Requires Kinetic (Non-equilibrium) Adsorption Considerations

The adsorption of foulants on photocatalytic nanoparticles can suppress their reactivity in water treatment applications by scavenging reactive species at the photocatalyst surface, screening light, or competing for surface sites. These inhibitory effects are commonly modeled using the Langmuir-Hinshelwood model, assuming that adsorbed layer compositions follow Langmuirian (equilibrium) competitive adsorption. However, this assumption has not been evaluated in complex mixtures of foulants. This study evaluates the photoreactivity of titanium dioxide (TiO2) nanoparticles toward a target compound, phenol, in the presence of two classes of foulants ─ natural organic matter (NOM) and a protein, bovine serum albumin (BSA) ─ and mixtures of the two. Langmuir adsorption models predict that BSA should strongly influence the nanoparticle photoreactivity because of its higher adsorption affinity relative to phenol and NOM. However, model evaluation of the experimental phenol decay rates suggested that neither the phenol nor foulant surface coverages are governed by Langmuirian competitive adsorption. Rather, a reactivity model incorporating kinetic predictions of adsorbed layer compositions (favoring NOM adsorption) outperformed Langmuirian models in providing accurate, unbiased predictions of phenol degradation rates. This research emphasizes the importance of using first-principles models that account for adsorption kinetics when assumptions of equilibrium adsorption do not apply.

Enhancing photocatalytic wastewater treatment: investigating the promising applications of nickel ferrite and its novel nanocomposites

Water contamination ranks highest among the challenges posed by the rapidly increasing environmental contamination, which is thought to be the most pressing issue globally. The development of innovative techniques for the successful removal of diverse types of undesirable pollutants from wastewater would therefore yield a huge return on investment. Nowadays, the removal of many organic and synthetic pollutants from the environmental matrix is anticipated to be possible by photocatalytic degradation, owing to its low energy consumption, high catalytic activity, and low overall cost. In this context, magnetic nanoparticles received greater attention as photocatalytic materials from the scientific community in wastewater treatment for the removal of different kinds of pollutants due to their specific properties. The present study provides an overview of the recent advances in water treatment using nickel ferrite nanoparticles and their nanocomposites as photocatalysts. Furthermore, a proposed mechanism for these photocatalysts to generate active free radicals under visible and ultraviolet light has been described. The review concludes that photocatalysts based on NiFe2O4 have potential applications in water purification technologies. However, more research is still needed to determine their practical application in water treatment facilities.

Highly Efficient Photocatalytic Degradation of Organic Pollutants Using a Polyvinylidene Fluoride/Polyvinylpyrrolidone-Cuprous Oxide Composite Membrane

Enhancing the efficiency of photocatalysts in the removal of organic pollutants is of vital importance in wastewater treatment. In this work, a set of composite membranes that can be used for efficient removal of the organic dyes, such as methyl orange (MO), methylene blue (MB), and Congo red (CR), were prepared through coblending/electrospinning techniques using polyvinylidene fluoride (PVDF) as the substrate, polyvinylpyrrolidone (PVP) as the dispersing agent and wettability regulator, and cuprous oxide (Cu2O) as the photocatalyst. The results showed that Cu2O particles were well encapsulated in the electrospun PVDF/PVP fibers, and the composite membranes exhibited apparently enhanced hydrophilicity. Furthermore, compared with the pure Cu2O particles, the composite membranes not only showed a higher photocatalytic degradation ratio for MO (93.6%) but also showed a much higher degradation rate (62.4 mg/(mg·h)) in comparison with the other reported Cu2O-based composite photocatalytic materials in the literature. In addition, the membrane sample also had excellent recycling stability, and the retention rate of its removal ability maintained 92.1% after 5 times of recycling. Furthermore, the composite membranes also showed high removal ability toward MB and CR, with photocatalytic degradation ratios of 81.4 and 76.1%, respectively. This work indicates that the prepared PVDF/PVP-Cu2O composite membranes possess promising application prospects in wastewater treatment.

A Review of the Preparation of Porous Fibers and Porous Parts by a Novel Micro-Extrusion Foaming Technique

This review introduces an innovative technology termed "Micro-Extrusion Foaming (MEF)", which amalgamates the merits of physical foaming and 3D printing. It presents a groundbreaking approach to producing porous polymer fibers and parts. Conventional methods for creating porous materials often encounter obstacles such as the extensive use of organic solvents, intricate processing, and suboptimal production efficiency. The MEF technique surmounts these challenges by initially saturating a polymer filament with compressed CO2 or N2, followed by cell nucleation and growth during the molten extrusion process. This technology offers manifold advantages, encompassing an adjustable pore size and porosity, environmental friendliness, high processing efficiency, and compatibility with diverse polymer materials. The review meticulously elucidates the principles and fabrication process integral to MEF, encompassing the creation of porous fibers through the elongational behavior of foamed melts and the generation of porous parts through the stacking of foamed melts. Furthermore, the review explores the varied applications of this technology across diverse fields and imparts insights for future directions and challenges. These include augmenting material performance, refining fabrication processes, and broadening the scope of applications. MEF technology holds immense potential in the realm of porous material preparation, heralding noteworthy advancements and innovations in manufacturing and materials science.

Upscaling of Electrospinning Technology and the Application of Functionalized PVDF-HFP@TiO2 Electrospun Nanofibers for the Rapid Photocatalytic Deactivation of Bacteria on Advanced Face Masks

In recent years, Electrospinning (ES) has been revealed to be a straightforward and innovative approach to manufacture functionalized nanofiber-based membranes with high filtering performance against fine Particulate Matter (PM) and proper bioactive properties. These qualities are useful for tackling current issues from bacterial contamination on Personal Protective Equipment (PPE) surfaces to the reusability of both disposable single-use face masks and respirator filters. Despite the fact that the conventional ES process can be upscaled to promote a high-rate nanofiber production, the number of research works on the design of hybrid materials embedded in electrospun membranes for face mask application is still low and has mainly been carried out at the laboratory scale. In this work, a multi-needle ES was employed in a continuous processing for the manufacturing of both pristine Poly (Vinylidene Fluoride-co-Hexafluoropropylene) (PVDF-HFP) nanofibers and functionalized membrane ones embedded with TiO2 Nanoparticles (NPs) (PVDF-HFP@TiO2). The nanofibers were collected on Polyethylene Terephthalate (PET) nonwoven spunbond fabric and characterized by using Scanning Electron Microscopy and Energy Dispersive X-ray (SEM-EDX), Raman spectroscopy, and Atomic Force Microscopy (AFM) analysis. The photocatalytic study performed on the electrospun membranes proved that the PVDF-HFP@TiO2 nanofibers provide a significant antibacterial activity for both Staphylococcus aureus (~94%) and Pseudomonas aeruginosa (~85%), after only 5 min of exposure to a UV-A light source. In addition, the PVDF-HFP@TiO2 nanofibers exhibit high filtration efficiency against submicron particles (~99%) and a low pressure drop (~3 mbar), in accordance with the standard required for Filtering Face Piece masks (FFPs). Therefore, these results aim to provide a real perspective on producing electrospun polymer-based nanotextiles with self-sterilizing properties for the implementation of advanced face masks on a large scale.

Enhanced Mass Transfer of Ozone and Emerging Pollutants through a Gas-Solid-Liquid Reaction Interface for Efficient Water Decontamination

Ozone (O3), as an environmentally friendly oxidant, is widely used to remove emerging pollutants and ensure the safety of the water supply, whereas the restricted accessibility of O3 and limited collision frequency between pollutants and O3 will inevitably reduce the ozonation efficiency. To promote the chemical reactions between O3 and target pollutants, here we developed a novel gas-solid-liquid reaction interface dominated triphase ozonation system using a functional hydrophobic membrane with an adsorption layer as the O3 distributor and place where chemical reactions occurred. In the triphase system, the functional hydrophobic membrane simultaneously improved the interface adsorption performance of emerging pollutants and the access pathway of O3, leading to a marked enhancement of interfacial pollutant concentration and O3 levels. These synergistic qualities result in high ciprofloxacin (CIP) removal efficiency (94.39%) and fast apparent reaction rate constant (kapp, 2.75 × 10-2 min-1) versus a traditional O3 process (41.82% and 0.48 × 10-2 min-1, respectively). In addition, this triphase system was an advanced oxidation process involving radical participation and showed excellent degradation performance of multiple emerging pollutants. Our findings highlight the importance of gas-solid-liquid triphase reaction interface design and provide new insight into the efficient removal of emerging pollutants by the ozonation process.

Efficient Chemical-Free Degradation of Waterborne Micropollutants with an Immobilized Dual-Porous TiO2 Photocatalyst

Photocatalytic advanced oxidation processes (AOPs) promise a chemical-free route to energy-efficient degradation of waterborne micropollutants if long-standing mass transfer and light management issues can be overcome. Herein, we developed a dual-porous photocatalytic system consisting of a mesoporous (i.e., 2-50 nm pores) TiO2 (P25) photocatalyst supported on macroporous (i.e., >50 nm pores) fused quartz fibers (P25/QF). Our reusable photocatalytic AOP reduces chemical consumption and exhibits excellent energy efficiency, demonstrated by degrading various pharmaceutical compounds (acetaminophen, sulfamethoxazole, and carbamazepine) in natural waters with electrical energy per order (EEO) values of 4.07, 0.96, and 1.35 kWh/m3, respectively. Compared to the conventional H2O2/UVC AOP, our photocatalytic AOP can treat water without chemical additives while reducing energy consumption by over 2800%. We examine these improvements based on mass transport and optical (UVA and UVC) transmittance and demonstrate that the enhancements scale with increasing flow rate.

Exploring the viability of a floating photocatalyst in a continuous stirred tank reactor system for continuous water treatment

The use of photocatalysts in continuous stirred tank reactor (CSTR) systems allows for efficient and continuous water treatment, thus meeting the demand for scalable technology and comparative data in large-scale implementations. Hence, this study aims to explore the feasibility of a floating photocatalyst within a CSTR system for continuous water treatment. An expanded polystyrene (EPS)-TiO2 composite was synthesized following established methodologies, and their efficacy in removing the water pollutant methylene blue (MB) was compared for both batch and CSTR systems. A nonlinear first-order model was identified as the most suitable approach to accurately simulate MB degradation under experimental conditions, and the calculated pseudo-first-order degradation rate constant (k') for the CSTR system (0.0126-0.0172/min) was found to be superior to that observed for the batch system (0.0113/min). In addition, an increase in the flow rate reduced the retention time, leading to lower MB removal efficiency for the CSTR system. In addition, the EPS-TiO2/UV system with a CSTR configuration was found to efficiently use light and energy based on the calculated quantum yield (Φ = 2.86 × 10-4) and electrical energy per order (EEO = 857.46 kWh/m3/order). The findings of this study contribute to the development of sustainable and efficient water treatment strategies, offering valuable insight into the implementation of practical water treatment processes.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications

From scientific and technological points of view, poly(vinylidene fluoride), PVDF, is one of the most exciting polymers due to its overall physicochemical characteristics. This polymer can crystalize into five crystalline phases and can be processed in the form of films, fibers, membranes, and specific microstructures, being the physical properties controllable over a wide range through appropriate chemical modifications. Moreover, PVDF-based materials are characterized by excellent chemical, mechanical, thermal, and radiation resistance, and for their outstanding electroactive properties, including high dielectric, piezoelectric, pyroelectric, and ferroelectric response, being the best among polymer systems and thus noteworthy for an increasing number of technologies. This review summarizes and critically discusses the latest advances in PVDF and its copolymers, composites, and blends, including their main characteristics and processability, together with their tailorability and implementation in areas including sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidic, tissue engineering, and antimicrobial applications. The main conclusions, challenges and future trends concerning materials and application areas are also presented.

A sustainable management of polycyclic aromatic hydrocarbons to synthesize microporous organic polymers for adsorptive desulphurization of fuels

A sustainable management of carcinogenic polycyclic aromatic hydrocarbons (PAHs) to synthesize a series of high surface area (SABET of 563-1553 m2 g-1) microporous polymeric adsorbents is reported. The products with high yield (>90%) were obtained within only 30 min at a low temperature of 50 °C using a microwave-assisted approach with 400 W microwave power followed by 30 min of ageing by raising the temperature to 80 °C. The synthesized adsorbents are used for removing another category of carcinogenic pollutants i.e., polycyclic aromatic sulphur heterocycles (PASHs) from model and real fuels. Adsorptive desulphurization experiment in batch mode could reduce the sulphur from high concentrated model (100 ppm) and real (102 ppm) fuels to 8 ppm and 45 ppm respectively. Similarly, desulphurization of model and real fuels with ultralow sulphur concentrations of 10 and 9 ppm, respectively, reduced the final concentration of sulphur to 0.2 and 3 ppm, respectively. Adsorption isotherms, kinetics, and thermodynamic studies have been conducted using batch mode experiments. Adsorptive desulphurization using fixed bed column studies show the breakthrough capacities of 18.6 and 8.2 mgS g-1, for the same high concentrated model and real fuels, respectively. The breakthrough capacities of 1.1 and 0.6 mgS g-1 are estimated for the ultralow sulphur model and real fuels, respectively. The adsorption mechanism, based on the spectroscopic analysis (FTIR and XPS) demonstrates the role of π-π interactions between the adsorbate and adsorbent. The adsorptive desulphurization studies of model and real fuels from batch to fixed bed column mode would offer an in-depth understanding to demonstrate the lab-scale findings for industrial applications. Thus, the present sustainable strategy could manage two classes of carcinogenic petrochemical pollutants, PAHs and PASHs, simultaneously.

Electrospun Nanofiber Membranes with Various Structures for Wound Dressing

Electrospun nanofiber membranes (NFMs) have high porosity and a large specific surface area, which provide a suitable environment for the complex and dynamic wound healing process and a large number of sites for carrying wound healing factors. Further, the design of the nanofiber structure can imitate the structure of the human dermis, similar to the natural extracellular matrix, which better promotes the hemostasis, anti-inflammatory and healing of wounds. Therefore, it has been widely studied in the field of wound dressing. This review article overviews the development of electrospinning technology and the application of electrospun nanofibers in wound dressings. It begins with an introduction to the history, working principles, and transformation of electrospinning, with a focus on the selection of electrospun nanofiber materials, incorporation of functional therapeutic factors, and structural design of nanofibers and nanofiber membranes. Moreover, the wide application of electrospun NFMs containing therapeutic factors in wound healing is classified based on their special functions, such as hemostasis, antibacterial and cell proliferation promotion. This article also highlights the structural design of electrospun nanofibers in wound dressing, including porous structures, bead structures, core-shell structures, ordered structures, and multilayer nanofiber membrane structures. Finally, their advantages and limitations are discussed, and the challenges faced in their application for wound dressings are analyzed to promote further research in this field.

Dissolved organic matter promotes photocatalytic degradation of refractory organic pollutants in water by forming hydrogen bonding with photocatalyst

Removing refractory organic pollutants in real water using photocatalysis is a great challenge because coexisting dissolved organic matter (DOM) can quench photogenerated holes and thus prevent generation of reactive oxygen species (ROS). Herein, for the first time, we develop a hydrogen bonding strategy to avoid the scavenging of photoexcited holes, by which DOM even promotes photocatalytic degradation of refractory organic pollutants. Theoretical calculations combined with experimental studies reveal the formation of hydrogen bonding between DOM and a hydroxylated S-scheme heterojunction photocatalyst (Mo-Se/OHNT) consisting of hydroxylated nitrogen doped TiO2 (OHNT) and molybdenum doped selenium (Mo-Se). The hydrogen bonding is demonstrated to change the interaction between DOM and Mo-Se/OHNT from DOM-Ti (IV) to a hydrogen bonded complexation through the hydroxyl/amine groups of DOM and the OHNT in Mo-Se/OHNT. The formed hydrogen network can stabilize excited-state of DOM and inject its electron to the conduction band rather than the valence band of the OHNT upon light irradiation, realizing the key to preventing hole quenching. The electron-hole separation in Mo-Se/OHNT is consequently improved for generating more ROS to be involved in removing refractory organic pollutants. Moreover, this hydrogen bonding strategy is generalized to nitrogen doped zinc oxide and graphitic carbon nitride and applies to real water. Our findings provide a new insight into handling the DOM problem for photocatalytic technology towards water and wastewater treatment.

A novel continuous all-weather photo-electric synergistic treatment system for refractory organic compounds and its application in degrading enrofloxacin

A novel continuous all-weather photo-electric synergistic treatment system was proposed in this study for refractory organic compounds, which overcame the defects of conventional photo-catalytic treatments that rely on light irradiation and thus cannot achieve all-weather continuous treatment. The system used a new photocatalyst (MoS2/WO3/carbon felt) with the characteristics of easy recovery and fast charge transfer. The system was systematically tested in degrading enrofloxacin (EFA) under real environmental conditions in terms of treatment performance, pathways and mechanisms. The results showed that the EFA removal of photo-electric synergy substantially increased by 1.28 and 6.78 times, compared to photocatalysis and electrooxidation, respectively, with an average removal of 50.9% under the treatment load of 832.48 mg m-2 d-1. Possible treatment pathways of EFA and mechanism of the system were found to be mainly the loss of piperazine groups, the cleavage of the quinolone portion and the promotion of electron transfer by bias voltage.

Electrospun Nanofiber-Based Bioinspired Artificial Skins for Healthcare Monitoring and Human-Machine Interaction

Artificial skin, also known as bioinspired electronic skin (e-skin), refers to intelligent wearable electronics that imitate the tactile sensory function of human skin and identify the detected changes in external information through different electrical signals. Flexible e-skin can achieve a wide range of functions such as accurate detection and identification of pressure, strain, and temperature, which has greatly extended their application potential in the field of healthcare monitoring and human-machine interaction (HMI). During recent years, the exploration and development of the design, construction, and performance of artificial skin has received extensive attention from researchers. With the advantages of high permeability, great ratio surface of area, and easy functional modification, electrospun nanofibers are suitable for the construction of electronic skin and further demonstrate broad application prospects in the fields of medical monitoring and HMI. Therefore, the critical review is provided to comprehensively summarize the recent advances in substrate materials, optimized fabrication techniques, response mechanisms, and related applications of the flexible electrospun nanofiber-based bio-inspired artificial skin. Finally, some current challenges and future prospects are outlined and discussed, and we hope that this review will help researchers to better understand the whole field and take it to the next level.

Photocatalysts for a sustainable future: Innovations in large-scale environmental and energy applications

The growing environmental and energy crises have prompted researchers to seek new solutions, including large-scale photocatalytic environmental remediation and the production of solar hydrogen using photocatalytic materials. To achieve this goal, scientists have developed numerous photocatalysts with high efficiency and stability. However, the large-scale application of photocatalytic systems under real-world conditions is still limited. These limitations arise at every step, including the large-scale synthesis and deposition of photocatalyst particles on a solid support, and the development of an optimal design with high mass transfer and efficient photon absorption. The purpose of this article is to provide a detailed description of the primary challenges and potential solutions encountered in scaling up photocatalytic systems for use in large-scale water and air purification and solar hydrogen production. Additionally, based on a review of current pilot developments, we draw conclusions and make comparisons regarding the main operating parameters that affect performance, as well as propose strategies for future research.

Adsorption-Controlled Wettability and Self-Cleaning of TiO2

Molecular adsorption on solids is inevitable and has significant influences on the wettability of materials, while the tuning mechanism of the wettability from molecular adsorption is yet to be understood. Using molecular dynamics (MD) simulations, we comprehensively studied the relation between the wettability of the TiO₂ surface and the adsorption of water and carboxylic acid molecules. Our results reveal that the increasing amount of surface hydroxyl groups from the decomposition adsorption of H₂O increases the hydrophilicity of TiO₂, providing molecular-level evidence for the previously proposed mechanism of photo-induced hydrophilicity. By contrast, the surface wettability becomes tunable with water contact angles changing from 0 to ∼130° through length adjustment of the adsorbed carboxylic acids. The TiO₂ surface is hydrophilic with the adsorption of short-alkyl-chain carboxylic acids (e.g., HCOOH) and becomes hydrophobic when longer-alkyl-chain carboxylic acids (H(CH₂)_nCOOH, n > 2) are present. Furthermore, long-alkyl-chain acids also increase surface oleophilicity, while the adsorption of HCOOH and CH₃COOH significantly enhances the oleophobicity of TiO₂. Water molecules can also more easily penetrate the space between oily contaminants and adsorbed short acid molecules, thereby further increasing its self-cleaning capacity. The present simulations not only reveal the mechanism of wettability caused by molecular adsorption but also provide a promising method to create materials with controllable wettability and high self-cleaning efficiency.

Efficient removal of dyes from aqueous solutions using short-length bimodal mesoporous carbon adsorbents

Ordered mesoporous carbons (OMCs) with controlled mesopore lengths and volumes were synthesized and investigated to remove the model dye methylene blue (MB) from aqueous solutions. The pore size, specific surface area, pore volume, and pore length of OMCs (CMK-3, sCMK-3, and sCMK-5) were analyzed and benchmarked against commercial activated carbon (AC). CMK-3 and sCMK-3 had narrow pore size distributions (PSDs) centered at ∼4.4 nm, whereas the PSD of sCMK-5 was bimodal, derived from the same pores as CMK-3 (∼4.4 nm) and the inner diameter of the carbon nanotubes (∼5.8 nm). The pore length decreased from 743 nm for CMK-3 to 173 nm for sCMK-3 and 169 nm for sCMK-5, facilitating the MB accessibility and efficient utilization of internal mesopores. The MB adsorption on the prepared adsorbents was well described by a pseudo-second-order kinetic model (R² > 0.999), and the initial adsorption rate (h) on sCMK-5 was 34.07-fold faster than that on commercial AC. The Langmuir model adequately explained the equilibrium adsorption data, and the increase in the Langmuir maximal adsorption capacity (q_m) of the OMCs was proportional to the specific surface area. The MB adsorption on sCMK-5 was endothermic and spontaneous, and proceeded primarily through physical adsorption as well as chemisorption reacting with oxygen atoms in hydroxyl groups. The prepared adsorbents were also suitable for polishing textile wastewater containing color-causing substances along with the background organic matter. These OMCs are promising for treating wastewater as efficient adsorbents for large molecular pollutants such as dyes.

Simultaneous Cr (VI) reduction and diazinon oxidation with organometallic sludge formation under photolysis: kinetics, degradation pathways, and mechanism

In this study, simultaneous removal of an organic matter (diazinon, DIZ) and an inorganic substance (chromium, Cr) was used. Breaking down of organic matter by UV irradiation produces various radicals, including sulfides, carboxyl, hydroxyl, hydrated electrons, and various organic radicals that are highly reactive and help us to precipitation inorganic substance (Cr). The optimal condition was 30:1 DIZ:Cr molar ratio, pH 9, and about 100% and 82.3% of DIZ and Cr were obtained in 30 min. Cr deposition was very slow at first. After the destruction of the DIZ structure, Cr deposition began, and various types of sludge with disturbed properties were formed. These sledges were analyzed by FTIR analysis and showed that green sludge could be chromium (III) hydroxide; brown sludge due to chromium (III) hydroxide, tiny green crystals from chromium (III) oxide, red brick from chromium (II) acetate chromium trioxide, as well as black sludge caused by chromium oxide were identified. In UV/DIZ/Cr process, kobs and robs range obtained 0.33-0.15 and 16.8-23.4 $ with both Cr and DIZ concentration increased from 50 to 150 mg L-1. Also, EEO for Cr precipitation was 24.65 to 5.74 and for DIZ 12.54 to 4.73 (kwh m-3). Depending on the amount of energy consumption, TCS was 37.19 to 10.47 for Cr precipitation and 4.46 to 1.25 $. It is important to note that when both pollutants are exposed to ultraviolet light, more energy and cost are generally required from UV/DIZ process and less than of UV/Cr process. But it should be noted that in fact 50 mg L-1 of chromium and 50 mg L-1 of DIZ are being removed at the same time. In UV/DIZ and UV/Cr processes that are exposed to ultraviolet radiation alone, only one of them is removed. Also, when these two pollutants are being removed at the same time, the total amount of energy is much less than the total energy consumption of the pollutants one by one.

3D hierarchical LDHs-based Janus micro-actuator for detection and degradation of catechol

Micro/nanomotors that combine the miniaturization and autonomous motion have attracted much research interest for environmental monitoring and water remediation. However, it is still challenging to develop a facile route to produce bifunctional micromotors that can simultaneously detect and remove organic pollutants from water. Herein, we developed a novel Janus micromotor with robust peroxide-like activity for simultaneously colorimetric detection and removal of catechol from water. Such laccase (Lac) functionalized Janus micromotor consisted of calcined MgAl-layered double hydroxides (MgAl-CLDHs) nanosheets and Co₃O₄-C nanoparticles (Lac-MgAl-CLDHs/Co₃O₄-C), revealing unique 3D hierarchical microstructure with highly exposed active sites. The obtained Janus micromotors exhibited autonomous motion with a maximum velocity of 171.83 ± 4.07 µm/s in the presence of 7 wt% H₂O₂ via a chemical propulsion mechanism based on the decomposition of H₂O₂ by Co₃O₄-C layer on the hemisphere surface of Janus micromotors. Owing to the combination of autonomous motion and high peroxide-like activity, Lac-MgAl-CLDHs/Co₃O₄-C Janus micromotors could sensitively detect catechol with the limit of detection of 0.24 μM. In addition, such Janus micromotors also could quickly degrade catechol by •OH generated from a Fenton-like reaction. It is a first step towards using autonomous micromotors for highly selective, sensitive, and facile detection and quick removal of catechol from water.

Electrically conductive TiO2/CB/PVDF membranes for synchronous cross-flow filtration and solar photoelectrocatalysis

Combining photocatalysis (PC) and membrane filtration (MF) has emerged as an attractive technology for water purification, however, the water purification efficiency and membrane fouling are still challenging. Herein, we report a novel photoelectrocatalytic (PEC) membrane mediated by a ternary polyvinylidene fluoride (PVDF)-carbon black (CB)-TiO₂ composite conductive membrane synthesized by a phase inversion method assisted by the mixed surfactants of polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). The resultant electrically conductive TiO₂/CB/PVDF membrane features a homogeneous surface with obvious pore size of 20-150 nm, a thickness ∼116 μm, and an average resistivity as low as ∼3.165 Ω∙m. The cooperation of PVP and SDS surfactants dramatically improves the organic-inorganic interactions and thus eventually enhances the porosity, stability of porous structure, mechanical stability, and conductivity and electrochemical properties of the hybrid membrane. Upon the solvent evaperation of the wellblended casting solution and the phase inversion, TiO₂/CB preferentially exist on the surface of PVDF membrane, enabling the efficient PEC degradation of organic pollutants. The synergistic coupling of TiO₂ and CB in PVDF membrane results in efficient PEC properties with bi-functional membrane antifouling and enhanced water purification in azo dyes decolorization under the stationary mode and in our lab-made continuous cross-flow PEC system, superior to those by photocatalysis and electrocatalysis. The developed synchronous MF and PEC system mediated by the conductive TiO₂/CB/PVDF membrane proves to a feasible route to improving the self-cleaning properties of the polymer membrane while simultaneously increasing the water decontaminating efficiency.

Recent Developments of Electrospinning-Based Photocatalysts in Degradation of Organic Pollutants: Principles and Strategies

Electrospinning is a simple and cheap process for forming one-dimensional (1D) nanofibers with controllable size, morphology, and chemistry. Besides these, the ultrahigh surface area with industrialization capability has attracted extensive interest in the research community. On the other hand, a photocatalytic process is a promising method for degrading organic pollutants that cannot be removed by conventional wastewater treatment. This review focuses on the recent progress of electrospun nanofibers for the photocatalytic degradation of water pollutants. The linkage between the electrospinning technique and the photocatalytic process is classified into two main categories: (1) polymeric electrospun nanofibers as a sacrificed template to form 1D photocatalysts and (2) polymeric electrospun nanofibers as a carrier of photocatalyst materials. We have thoroughly discussed the principles and fundamental issues of electrospinning as well as two main strategies to design and fabricate nanofiber-based photocatalysts for the ideal photodegradation of organics pollutants. The results of data mapping using VOSviewer demonstrated the recent trend and the importance of this field among researchers and engineers. Moreover, we have elaborated on the limitations and potential benefits of the two categories of electrospinning-based photocatalyst fabrication and practical application that will open new directions for future research.

Improvement of Floxin photocatalytic degradability in the presence of sulfite: Performance, kinetic, degradation pathway, energy consumption and total cost of system

In this study, photocatalytic degradability of Floxin antibiotic by UV/ZnO/sulfite (UZS) advanced oxidation process was evaluated. The degradation rate of Floxin antibiotic by UV/ZnO (UZ) and UV alone processes were 30% and 15%, respectively, within 5 min. It was observed sulfite has a synergistic effect on the performance of UZ, as the complete destruction of Floxin was achieved when sulfite was introduced into the photocatalytic medium. The complete degradation of Floxin by UZS was obtained at pH of 12.0, sulfite/ZnO molar ratio of 1:3 after 5 min of reaction. According to kinetic studies, the observed rate of Floxin degradation (r_obs (mg L^-1 min)) by UZS was 63 and 25 times that of UV alone and UZS, respectively. The values of energy consumption and the total cost for UV alone, UZ and UZS processes were estimated to be (50 kWh m^-3 and 1.4 $ m^-3), (20 kWh m^-3 and 0.98 $ m^-3) and (0.78 kWh m^-3 and 0.82 $ m^-3), respectively.

Hypercrosslinking porous polymer layers on TiO2-graphene photocatalyst: Enhanced adsorption of water pollutants for efficient degradation

Solar-driven photocatalysis offers an environmentally friendly and sustainable approach for the degradation of organic pollutants in water without chemical additives, but the low specific surface area and adsorption capacity of common photocatalysts restricts the surface reactions with the contaminants. Herein, we hypercrosslinked polymer layers on TiO₂-graphene surface to enlarge the specific surface area from 136 to 988 m²/g, leading to a high adsorption capacity of sulfadiazine as 54.3 mg/g, which is 15.5 times that of TiO₂-graphene (3.5 mg/g). The adsorption kinetics reveals the combination of physical and chemical adsorption by porous benzene-based polymer for sulfadiazine enrichment. Besides, the polymer layers with broad light absorption enable the composite to function efficiently as visible-light-driven photocatalysts. Thus, the as-designed composite exhibits excellent performance for sulfadiazine removal by integrating the adsorptive and photocatalytic processes, especially for the diluted sulfadiazine solution. More importantly, the porous polymer layer can function as a filter for weakening the interference of TiO₂ surface with the natural matters from complex water matrices. Based on the identification of dominant reactive species, the possible attacking pathway and the sulfadiazine subsequent degradation are presented. Further, the enhanced adsorption and photodegradation efficiency can also be achieved for the removal of other typical pollutants such as 4-chlorophenol and methylene blue. This study highlights an adsorption-enhanced-degradation mechanism for water pollutants that can direct the design of high-performance photocatalysts under visible light.

Advanced functional nanofibers: strategies to improve performance and expand functions

Nanofibers have a wide range of applications in many fields such as energy generation and storage, environmental sensing and treatment, biomedical and health, thanks to their large specific surface area, excellent flexibility, and superior mechanical properties. With the expansion of application fields and the upgrade of application requirements, there is an inevitable trend of improving the performance and functions of nanofibers. Over the past few decades, numerous studies have demonstrated how nanofibers can be adapted to more complex needs through modifications of their structures, materials, and assembly. Thus, it is necessary to systematically review the field of nanofibers in which new ideas and technologies are emerging. Here we summarize the recent advanced strategies to improve the performances and expand the functions of nanofibers. We first introduce the common methods of preparing nanofibers, then summarize the advances in the field of nanofibers, especially up-to-date strategies for further enhancing their functionalities. We classify these strategies into three categories: design of nanofiber structures, tuning of nanofiber materials, and improvement of nanofibers assemblies. Finally, the optimization methods, materials, application areas, and fabrication methods are summarized, and existing challenges and future research directions are discussed. We hope this review can provide useful guidance for subsequent related work.

Graphical abstract

Constructing mesoporous Zr-doped SiO2 onto efficient Z-scheme TiO2/g-C3N4 heterojunction for antibiotic degradation via adsorption-photocatalysis and mechanism insight

Novel modified-TiO₂/Zr-doped SiO₂/g-C₃N₄ ternary composite is fabricated via an in-situ grow of porous Zr-SiO₂ layer to TiO₂/g-C₃N₄ heterojunction, which exhibits well adsorption-photocatalytic performance under simulated solar light irradiation. The nano-size mesoporous TiO₂ are dispersed on the lamellar g-C₃N₄, and the Zr-SiO₂ is in-situ fabricated onto the surface of g-C₃N₄ sheets. The adsorption occurs on the SiO₂ layers, and doping Zr element to SiO₂ enhances the adsorption of pollutants, while the photocatalytic reaction occurs on the valence band (VB) of TiO₂ and conduction band (CB) of g-C₃N₄, which gives reactive oxygen species of ∙O₂^-, h⁺, and ∙OH for high efficient decomposition of antibiotics, i.e. berberine hydrochloride (98.11%), tetracycline (80.76%), and oxytetracycline (84.84%). The excellent adsorption capacity and Z-scheme photoinduced charge carrier migration behavior endowed the novel material with enhanced berberine hydrochloride (BH) removal in water, which approximately 2.5 and 3.8 folds than that of pure g-C₃N₄ and sole TiO₂, respectively. Three degradation pathways are unraveled by LC-MS and theoretical calculations. Furthermore, the toxicity of intermediates was evaluated by the Toxicity Estimation Software Tool (T.E.S.T.), the result demonstrated a good application potential of M-TiO₂/Zr-SiO₂/g-C₃N₄ as an novel adsorptive photocatalyst.

Recent advances and remaining barriers to the development of electrospun nanofiber and nanofiber composites for point-of-use and point-of-entry water treatment systems

In this review, we focus on electrospun nanofibers as a promising material alternative for the niche application of decentralized, point-of-use (POU) and point-of-entry (POE) water treatment systems. We focus our review on prior work with various formulations of electrospun materials, including nanofibers of carbon, pure metal oxides, functionalized polymers, and polymer-metal oxide composites, that exhibit analogous performance to media (e.g., activated carbon, ion exchange resins) commonly used in commercially available, certified POU/POE devices for contaminants including organic pollutants, metals (e.g., lead) and persistent oxyanions (e.g., nitrate). We then analyze the relevant strengths and remaining research and development opportunities of the relevant literature based on an evaluation framework that considers (i) performance comparison to commercial analogs; (ii) appropriate pollutant targets for POU/POE applications; (iii) testing in flow-through systems consistent with POU/POE applications; (iv) consideration of water quality effects; and (v) evaluation of material strength and longevity. We also identify several emerging issues in decentralized water treatment where nanofiber-based POU/POE devices could help meet existing needs including their use for treatment of uranium, disinfection, and in electrochemical treatment systems. To date, research has demonstrated promising material performance toward relevant targets for POU/POE applications, using appropriate aquatic matrices and considering material stability. To fully realize their promise as an emerging treatment technology, our analysis of the available literature reveals the need for more work that benchmarks nanofiber performance against established commercial analogs, as well as fabrication and performance validation at scales and under conditions simulating POU/POE water treatment.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Immobilized BiOCl0.75I0.25/g-C3N4 nanocomposites for photocatalytic degradation of bisphenol A in the presence of effluent organic matter

The BiOCl_0.75I_0.25/g-C₃N₄ nanosheet (BCI-CN) was successfully immobilized on polyolefin polyester fiber (PPF) through the hydrothermal method. The novel immobilized BiOCl_0.75I_0.25/g-C₃N₄ nanocomposites (BCI-CN-PPF) were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy EDS, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) to confirm that BCI-CN was successfully immobilized on PPF with abundant oxygen vacancies reserved. Under simulated solar light irradiation, 100 % of bisphenol A (BPA) with an initial concentration of 10 mg·L^-1 was degraded by BCI-CN-PPF (0.2 g·L^-1 of BCI-CN immobilized) after 60 min. A similar photocatalytic efficiency of BPA was obtained in the presence of effluent organic matter (EfOM). The photocatalytic degradation of BPA was not affected by EfOM <5 mg-C/L. In comparison, the photocatalytic performance was considerably inhibited by EfOM with a concentration of 10 mg-C/L. Furthermore, photogenerated holes and superoxide radicals predominated in the photocatalytic degradation processes of BPA. The total organic carbon (TOC) removal efficiencies of BPA and EfOM were 75.2 % and 50 % in the BCI-CN-PPF catalytic system. The BPA removal efficiency of 94.9 % was still achieved in the eighth cycle of repeated use. This study provides a promising immobilized nanocomposite with high photocatalytic activity and excellent recyclability and reusability for practical application in wastewater treatment.

Optical Absorption Investigations for efficient Crystal Violet Dye removal from wastewater via Carbon nanotubes: Montmorillonite based Nanocomposite

The current study reports a facile method to fabricate functionalized multi-walled carbon nanotubes and montmorillonite clay mineral-based nano-composite matrix and its detailed characterization using spectroscopic and morphological techniques. The nanocomposites have been studied for their potential applications in the treatment of contaminated water using batch adsorption studies. The investigations conducted using optical absorption spectroscopic measurements for the adsorption process indicate that the nanocomposite matrix can effectively remove almost 98% of the dye from aqueous solution. The nanocomposites have showed fast and strong adsorption behaviour for the dye with the maximum adsorption capacity (q_m ) of ~ 467.3 mg g^-1 in 25 min. The experimental data at equilibrium were also correlated with the theoretical adsorption isotherm and kinetic models. The results demonstrate that the experimental data fits well to the Freundlich adsorption isotherm model and conforms to second order kinetics. Furthermore, the nanocomposite exhibits good recyclability without any marked decrease in the adsorption performance even after five adsorption cycles of usage which indicates its potential application as reusable adsorbent for the efficient removal of hazardous dyes from contaminated water.

Few-layered Bi4O5I2 nanosheets enclosed by {1 0-1} facets with oxygen vacancies for highly-efficient removal of water contaminants

Few-layered Bi₄O₅I₂ nanosheets (FL-Bi₄O₅I₂) were synthesized by intergrowth with Bi₂O₂CO₃ under room temperature. The photoactivity of FL-Bi₄O₅I₂ was 2.5 and 9.5 times higher than that of Bi₄O₅I₂ nanoflakes (NF-Bi₄O₅I₂, about 30 nm thickness) and standard visible-light-driven N-TiO₂, respectively. Moreover, FL-Bi₄O₅I₂ exhibited a wide pH application range (3.0 - 10.0) and excellent photostability. The characterization results showed FL-Bi₄O₅I₂ was consisted of 5 - 8 layers with thickness of 4 - 7 nm and enclosed by {1 0 - 1} facets. The ultrathin characteristics could accelerate the charge transfer to the surface due to the shortened transport distance. Compared to NF-Bi₄O₅I₂, surface oxygen vacancies and the more negative CB potential were formed on FL-Bi₄O₅I₂. The photogenerated electrons were confirmed to be captured by surface oxygen vacancies to effectively reduce surface adsorbed O₂ into HO₂^•/O₂^•-, leaving more h⁺ to oxidize organic pollutants. This process was further facilitated by the more negative CB potential of FL-Bi₄O₅I₂, resulting in the highly efficient removal of pollutants.

Comparative study of energy consumption, kinetic, and performance between conventional and baffled photocatalytic reactor (BPCR) to ofloxacin photo-degradation

Regarding the cost-effective photo-degradation of ofloxacin (OFL), present study investigates UV/sulfite /ZnO (USZ) in reactor conventional (without baffles) and baffled photocatalytic reactor (BPCR). The optimal condition was 0.77:2:50 sulfite/ZnO/OFL molar ratio, pH 7, and 30 min reaction time for 100% degradation of 200 mg L^-1 concentration of OFL. As information obtained, the UZI process reduces the BOD and COD level about 66% to 86.29% within 80 min reaction, respectively. Also, BOD/COD ratio initial from 0.26 reaches 0.6 after 30 min of reaction time. Kinetic investigation increasing OFL concentration, k_obs and r_obs increase, and, secondly, in the conventional and BPCR reactor, k_obs increase is about 17% and 50% with increasing OFL concentration from 50 to 200 mgL^-1. Also, figure-of-merit E_Eo varies from 12.66 to 17.41 and 7.26 to 10.15 kWhm³ for conventional reactor and 8.66-13.61 to 5.24-8.12 kWhm³, respectively. Also, kinetic model E_Eo declines from 15.23 to 8.61 and from 13.31 to 5.37 kWh m^-3 in conventional and BPCR, respectively. Total cost of the system (TCS) decreases from 7.31 to 2.16 $ in conventional reactor and 4.57 to 0.55 $ in PCBR reactor. Total cost of the system (TCS) was investigated at different concentrations.

Sediment Bacteria and Phosphorus Fraction Response, Notably to Titanium Dioxide Nanoparticle Exposure

Titanium dioxide nanoparticle (TiO₂ NP) toxicity to the growth of organisms has been gradually clarified; however, its effects on microorganism-mediated phosphorus turnover are poorly understood. To evaluate the influences of TiO₂ NPs on phosphorus fractionation and the bacterial community, aquatic microorganisms were exposed to different concentrations of TiO₂ NPs with different exposure times (i.e., 0, 10, and 30 days). We observed the adhesion of TiO₂ NPs to the cell surfaces of planktonic microbes by using SEM, EDS, and XRD techniques. The addition of TiO₂ NPs resulted in a decrease in the total phosphorus of water and an increase in the total phosphorus of sediments. Additionally, elevated TiO₂ NPs enhanced the sediment activities of reductases (i.e., dehydrogenase [0.19–2.25 μg/d/g] and catalase [1.06–2.92 μmol/d/g]), and significantly decreased the absolute abundances of phosphorus-cycling-related genes (i.e., gcd [1.78 × 10⁴–9.55 × 10⁵ copies/g], phoD [5.50 × 10³–5.49 × 10⁷ copies/g], pstS [4.17 × 10²–1.58 × 10⁶ copies/g]), and sediment bacterial diversity. TiO₂ NPs could noticeably affect the bacterial community, showing dramatic divergences in relative abundances (e.g., Actinobacteria, Acidobacteria, and Firmicutes), coexistence patterns, and functional redundancies (e.g., translation and transcription). Our results emphasized that the TiO₂ NP amount—rather than the exposure time—showed significant effects on phosphorus fractions, enzyme activity, phosphorus-cycling-related gene abundance, and bacterial diversity, whereas the exposure time exhibited a greater influence on the composition and function of the sediment bacterial community than the TiO₂ NP amount. Our findings clarify the responses of phosphorus fractions and the bacterial community to TiO₂ NP exposure in the water–sediment ecosystem and highlight potential environmental risks of the migration of untreated TiO₂ NPs to aquatic ecosystems.

Impact of reaction parameters for photodegradation pharmaceuticals in wastewater over gold/titania photocatalyst synthesized by pyrolysis of NH2-MIL-125(Ti)

The efficient remediation of pharmaceuticals, including wastewater, remains a remarkably challenging issue for water regeneration. Herein, porous Au/TiO₂ synthesized by pyrolysis of NH₂-MIL-125(Ti) was utilized to be an efficient photocatalyst for mineralization of trimethoprim (TMP) and Metronidazole (MNZ) as the parent compound. The effects of different factors, including TMP and MNZ concentrations, light intensity, H₂O₂ concentration, Au/TiO₂ dosage, and pH value of reaction solution on the degradation and mineralization performances during UV and visible light (VIS), were addressed. The porous Au/TiO₂ photocatalyst exhibited superior photocatalytic degradation of TMP and MNZ under UV and VIS illumination. The optimum pH values were 4; the optimum dosage of Au/TiO₂ was 1.5 g/L, H₂O₂ concentration was 9.8 mM, TMP and MNZ concentrations was 10 ppm, and their photodegradation efficiency was 100% after 30 min illumination time and mineralization efficiency 98.2% after 3 h illumination for TMP and MNZ, respectively under UV illumination, however, the photodegradation efficiency was 100% after 50 min illumination and mineralization efficiency 96.3% after 4.5 h illumination time for TMP and MNZ, respectively under VIS illumination. The real wastewater matrix with 10 mg/L of TMP and MNZ were subjected to 60 min of illumination under similar optimum conditions of synthetic solution. The results indicated that photodegradation efficiency was determined to be 100% after 70 min illumination time for removal of both TMP (k = 3.4 × 10^-2 min^-1) and MNZ (k = 2.87 × 10^-2 min^-1). This is ascribed to the incorporation of Au NPs onto TiO_2, reducing the photoinduced electron-hole recombination, thus promoting the photocatalytic performance. The possible mechanism for photodegradation of antibiotics was also discussed. The demonstration of photocatalysis mechanism over Au/TiO₂ photocatalyst can provide some directing in the enhancement of novel photocatalysts based on MOFs doped by noble metal.

N-CQDs from reed straw enriching charge over BiO2-x/BiOCl p-n heterojunction for improved visible-light-driven photodegradation of organic pollutants

Green bismuth-based photocatalysts have attracted extensive attention in the field of PPCPs photodegradation. The improved carrier separation efficiency still remains a key factor to enhance photocatalytic performance. Herein, N-doped biomass carbon quantum dots (N-CQDs) decorated p-n heterojunction photocatalyst BiO_2-x/BiOCl was prepared using a facile ion-etching strategy, and it displayed a markedly enhanced catalytic activity in the photodegradation of sulfonamide antibiotics. Calculated by the differential charge density, the doped N-CQDs could gather photogenerated electrons, which indicated that the introduction of N-CQDs into BiO_2-x/BiOCl would effectively inhibit the recombination of photogenerated charge carriers. In addition, photocatalytic performance and density functional theory (DFT) calculation results revealed that the photogenerated electrons tended to transfer from p-BiOCl to n-BiO_2-x through N-CQDs, which could generate ·O₂^- and photogenerated h⁺ to oxidize the target pollutants. Benefiting from the synergistic effect of accelerated separation of e^--h⁺ in p-n heterojunction and the electron-rich performance of N-CQDs, the superb TOC removal efficiencies (89.40% within 120 min visible-light irradiation) and toxicity reduction performance of photodegradation intermediates were achieved. As a consequence, this work will provide a design of high-quality photocatalysts and a green-promising strategy for bismuth-based photocatalysts in the water treatment of PPCPs.

In situ engineering of highly conductive TiO2/carbon heterostructure fibers for enhanced electrocatalytic degradation of water pollutants

Rational design of nanocomposite electrode materials with high conductivity, activity, and mechanical strength is critical in electrocatalysis. Herein, freestanding, flexible heteronanocomposites were fabricated in situ by carbonizing electrospun fibers with TiO₂ nanoparticles on the surface for electrocatalytic degradation of water pollutants. The carbonization temperature was observed as a dominant parameter affecting the characteristics of the electrodes. As the carbonization temperature increased to 1000 °C, the conductivity of the electrode was significantly enhanced due to the high degree of graphitization (I_D/I_G ratio 1.10) and the dominant rutile phase. Additionally, the formation of TiO₂ protrusions and the C-Ti heterostructure were observed at 1000 °C, which contributed to increasing the electrocatalytic activity. When 1.5 V (vs. Ag/AgCl) was employed, electrocatalytic experiments using the electrode achieved 90% degradation of crystal violet and 10.9-87.5% for an array of micropollutants. The electrical energy-per-order (EEO) for the removal of crystal violet was 0.7 kWh/m³/order, indicative of low-energy requirement. The efficient electrocatalytic activity can be ascribed to the fast electron transfer and the strong ability to generate hydroxyl radicals. Our findings expand efforts for the design of highly conductive heteronanocomposites in a facile in situ approach, providing a promising perspective for the energy-efficient electrocatalytic degradation of water pollutants.

Rapid removal of PFOA and PFOS via modified industrial solid waste: Mechanisms and influences of water matrices

Emerging perfluoroalkyl and polyfluoroalkyl substances contaminate waters at trace concentrations, thus rapid and selective adsorbents are pivotal to mitigate the consequent energy-intensive and time-consuming issues in remediation. In this study, coal combustion residuals-fly ash was modified (FA-SCA) to overcome the universal trade-off between high adsorption capacity and fast kinetics. FA-SCA presented rapid adsorption (t_eq = 2 min) of PFOX (perfluorooctanoic acid and perfluorooctanesulfonic acid, collectively), where the dynamic adsorption capacity (q_dyn = q_m/t_eq) was 2-3 orders of magnitude higher than that of benchmark activated carbons and anion-exchange resins. Investigated by advanced characterization and kinetic models, the fast kinetics and superior q_dyn are attributed to (1) elevated external diffusion driven by the submicron particle size; (2) enhanced intraparticle diffusion caused by the developed mesoporous structure (V_meso/V_micro = 8.1); (3) numerous quaternary ammonium anion-exchange sites (840 μmol/g), and (4) appropriate adsorption affinity (0.031 L/μmol for PFOS, and 0.023 L/μmol for PFOA). Since the adsorption was proven to be a synergistic process of electrostatic and hydrophobic interactions, effective adsorption ([PFOX]_ini = 1.21 μM, concentration levels of highly-contaminant-sites) was obtained at conventional natural water chemistries. High selectivity (>85.4% removal) was also achieved with organic/inorganic competitors, especially compounds with partly similar molecular structures to PFOX. In addition, >90% PFOX was removed consistently during five cycles in mild regeneration conditions (pH 12 and 50 °C). Overall, FA-SCA showed no leaching issues of toxic metals and exhibits great potential in both single-adsorption processes and treatment train systems.

Diazinon pesticide photocatalytic degradation in aqueous matrices based on reductive agent release in iodide exciting under UV Irradiation

Regarding the cost-effective degradation of diazinon (DIZ), the present study was conducted to develop and UV/iodide process in a photo catalyst reactor. CCD modeling applied and the results shows that the highest R-squared value (adjusted R-squared: 0.9987), the lowest P-value (2.842 e - 10), the lowest AIC (14.54), and the most insignificant lack-of-fit (0.73) belonged to the second-order model. Based on second-order model, the stationary points for time, iodide: DIZ (molar ratio %), DIZ concentration, and pH were 6.99 min, 80.15% iodide: DIZ (molar ratio %), 3.34, mg L^-1, and pH 7.34 (- log₁₀[H⁺]), respectively. The maximum reduction efficiency of 97.22% was obtained at the experimental conditions. The LC-MS analyses from optimal condition implied that all the DIZ molecules and its intermediates breaking to simple compounds during 15 min of processing. The data shown UI process reduced the BOD and COD levels by about 66% and 86.29% within 80 min of photoreaction, respectively. Furthermore, in kinetic investigation, with the increase in DIZ concentration, k_obs and r_obs increased and secondly, the conventional and PCBR reactor k_obs increased by about respectively 17% and 50% with an increase in DIZ concentration from 5 to 15 mgL^-1. Additionally, when the DIZ concentration increase from 5 to 15 mg L^-1, r_obs increased in the conventional and PCBR reactors respectively about 4.9 and 6 times. Figure-of-merit E_Eo changed from 12.66-17.41 to 7.26-10.15 kWhm³ for the conventional reactor, and 8.66-13.61 to 5.24-8.12 kWhm³ in PCBR, when the DIZ concentration increasing from 5 to 15 mg L^-1. Consequently, in the PCBR reactor, the energy consumption reduced by 14% at 5 mg L^-1 DIZ concentration and by 60% at 15 mg L^-1 DIZ concentration. Also, total cost of the system (TCS) decreases from 4.52 to 1.46 $ in conventional reactor and 1.47 to 0.42 $ in PCBR reactor when the DIZ concentration increase from 5 to 15 mg L^-1.

MIL-101(Fe)@TiO2 nanotube composite material is used for the solid phase extraction of non-steroidal anti-inflammatory drugs under the synergy of multiple interactions

Increasing the adsorption sites and effective interactions between sorbents and the targets can improve the solid-phase extraction (SPE) efficiency. Herein, based on the advantages of MOFs and TiO₂ nanotubes (TiO₂ NTs), an MIL-101(Fe)@TiO₂ NT composite was prepared and applied to extract non-steroidal anti-inflammatory drugs (NSAIDs) from water samples coupled with high performance liquid chromatography (HPLC). Through characterization, it was established that MIL-101(Fe) was effectively composited on the surface and inside the TiO₂ nanotubes, increasing effective adsorption sites. The obtained composite material well retains the structure and functional groups of the two original materials, and while retaining the original force with the target, it achieves a synergistic effect and produces more interactions with the target. Therefore, the extraction efficiency was greatly improved. The recovery efficiency reached 97.7-105.1% with an RSD of less than 6.71%, the detection limit was 0.1-0.2 μg L^-1, and the linear range was 1-200 μg L^-1 with a determination coefficient of 0.9972-0.9994. Owing to the stability of the two original materials, the composite material could be recycled and reused to extract NSAIDs up to 15 times without a loss of the recovery rate. Satisfactory results were obtained when it was used to extract NSAIDs from the Yellow River. These results indicate that the synthesized MIL-101(Fe)@TiO₂ NT material is a promising sorbent to extract NSAIDs at trace concentrations with high efficiency and long lifetimes.

On the Versatile Role of Electrospun Polymer Nanofibers as Photocatalytic Hybrid Materials Applied to Contaminated Water Remediation: A Brief Review

A wide variety of materials, strategies, and methods have been proposed to face the challenge of wastewater pollution. The most innovative and promising approaches include the hybrid materials made of polymeric nanofibers and photocatalytic nanoparticles. Electrospun nanofibers with unique properties, such as nanosized diameter, large specific surface area, and high aspect ratio, represent promising materials to support and stabilize photocatalytic nanosized semiconductors. Additionally, the role performed by polymer nanofibers can be extended even further since they can act as an active medium for the in situ synthesis of photocatalytic metal nanoparticles or contribute to pollutant adsorption, facilitating their approach to the photocatalytic sites and their subsequent photodegradation. In this paper, we review the state of the art of electrospun polymer/semiconductor hybrid nanofibers possessing photocatalytic activity and used for the remediation of polluted water by light-driven processes (i.e., based on photocatalytic activity). The crucial role of polymer nanofibers and their versatility in these types of procedures are emphasized.