Facile Preparation of Self-Assembled Polydopamine-Modified Electrospun Fibers for Highly Effective Removal of Organic Dyes

Preparation and characterization of acetate cellulose electrospun nanofibers membrane: Potential application on wastewater treatment

Development of nanofiber membranes with the ability to remove organic dye such as Indigo Carmine (IC) from effluent wastewater is of immense help to the textile industry. In the present study, we investigate the preparation of cellulose acetate (CA) nanofiber membranes with optimized performances using electrospinning technique for effective removal of Indigo Carmine (IC) dye. Electrospinning parameters and solvent system containing acetic acid were adjusted to obtain CA nanofibers membranes which better suits dye removal application. The obtained nanofiber membranes were characterized using Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR) and contact angle analysis. Results show that nanofiber webs with optimized electrospinning parameters were continuously formed and are substantially free of defects such as beading, with an average diameter of 950 ± 50 nm. Hydrophobicity of membranes were successfully modified and showed important increase of contact angle values from 37° to 107°. The stirring time was varied to improve the solution homogeneity and consequently the response of membranes in filtration treatment. The CA membranes performance was evaluated through water flux and permeability measurement and tested on IC dye removal. The results showed a rate of dye removal around 83 % and a maximum adsorption capacity (Qm) of 13.09 mg/g for the optimized CA membranes.

Synthesis of Tubular Hydroxyapatite and Its Application in Polycaprolactone Scaffold Materials

Nano-hydroxyapatite (HAp) is an ideal material in the field of biomedicine due to its good biocompatibility and bioactivity. However, a significant drawback of pure HAp materials is their inferior mechanical properties. Therefore, in this rigorous investigation, the optimal calcium-to-phosphorus ratio for the synthesis of HAp was meticulously delineated, followed by its nuanced modification using KH550 (γ-aminopropyltriethoxysilane). This was further amalgamated with polycaprolactone (PCL) with the aim of providing a superior material alternative within the domain of bone scaffold materials. The post-modified HAp demonstrated enhanced interfacial compatibility with PCL, bestowing the composite with superior mechanical characteristics, notably a peak bending strength of 6.38 ± 0.037 MPa and a tensile strength of 3.71 ± 0.040 MPa. Scanning electron microscope (SEM) imagery revealed an intriguing characteristic of the composite: an initial ascension in porosity upon HAp integration, subsequently followed by a decline. Beyond this, the composite not only exhibited stellar auto-degradation prowess but also realized a sustained release cycle of 24 h, markedly optimizing drug utility efficiency. A kinetic model for drug dispensation was developed, positing an adherence to a pseudo-second-order kinetic principle. In tandem, through the formulation of an intra-particle diffusion model, the diffusion mechanisms pre- and post-modification were deeply probed. Cytotoxicity assays underscored the composite's exemplary biocompatibility. Such findings accentuate the vast potential of the modified HAp-PCL composite in bone tissue engineering, heralding a novel and efficacious avenue for impending bone defect amelioration.

Nanofiber-based sorbents: Current status and applications in extraction methods

Advanced sorbents gradually become a research hotspot on account of the increasing attention paid to environmental problems. Due to the prominent physicochemical features of nanofibers (NFs), such as high porosity, large surface area, favorable interconnectivity, high adsorption capacity, wettability, and the possibility of surface modification using functional groups, these nanostructures are regarded as excellent candidates for extraction applications. Therefore, the research in the field of NFs and their nanocomposites has been increasing in recent years. In the present review, we summarize the most recent studies on NFs-based sorbents focusing on strategies for preparation, characterization, and their unique capabilities as porous sorbents in various sorbent-based extraction methods. Moreover, we further described the performance and selectivity of sorbents to achieve improved extraction efficiency. Finally, some perspectives on the challenges and outlook are provided to aid future investigations related to this topic.

Review of the Recent Advances in Electrospun Nanofibers Applications in Water Purification

Recently, nanofibers have come to be considered one of the sustainable routes with enormous applicability in different fields, such as wastewater treatment. Electrospun nanofibers can be fabricated from various materials, such as synthetic and natural polymers, and contribute to the synthesis of novel nanomaterials and nanocomposites. Therefore, they have promising properties, such as an interconnected porous structure, light weight, high porosity, and large surface area, and are easily modified with other polymeric materials or nanomaterials to enhance their suitability for specific applications. As such, this review surveys recent progress made in the use of electrospun nanofibers to purify polluted water, wherein the distinctive characteristics of this type of nanofiber are essential when using them to remove organic and inorganic pollutants from wastewater, as well as for oil/water (O/W) separation.

Facile fabrication of composite cellulose fibrous materials for efficient and consecutive dyeing wastewater treatment

Fabricating dye adsorbents with efficient adsorption properties is of great significance in the treatment of printing and dyeing wastewater. Herein, composite materials of polydopamine decorated cellulose fibrous nonwovens (PDA@CF NWs) were fabricated by constructing a PDA functional layer on the surface of cellulose fibers via in situ polymerization. In addition, a three-dimensional adsorbent of 3D PDA@CF NWs with good hydrophilicity, structural stability, and compression resistance could be obtained using a facilely laminating and traditional loop bonding reinforcing technique. Attributed to the efficient and uniform loading of an active PDA functional layer, the resulting PDA@CF NWs exhibited a relatively large adsorption capacity of around 91 mg g⁻¹ towards the template dye of methylene blue within a fast equilibrium time of 2 h, which was superior to most of the fibrous adsorbents. In addition, the treatment column of 3D PDA@CF NWs exhibited a breakthrough capacity of 40.9 mg g⁻¹, reaching nearly 50% of the static saturated dye-binding capacity. More importantly, the 3D PDA@CF NWs column could effectively and continuously separate the mixture of different dyes under gravity, highlighting an excellent practical performance. Thus, the PDA@CF NWs are expected to provide a promising candidate for environment-friendly, large-scale and efficient treatment of industrial printing and dyeing wastewater.

Composite materials of polydopamine decorated cellulose fibrous nonwovens were fabricated for efficient and consecutive dyeing wastewater treatment.

Multistructured Electrospun Nanofibers for Air Filtration: A Review

Air filtration materials (AFMs) have gradually become a research hotspot on account of the increasing attention paid to the global air quality problem. However, most AFMs cannot balance the contradiction between high filtration efficiency and low pressure drop. Electrospinning nanofibers have a large surface area to volume ratio, an adjustable porous structure, and a simple preparation process that make them an appropriate candidate for filtration materials. Therefore, electrospun nanofibers have attracted increased attention in air filtration applications. In this paper, first, the preparation methods of high-performance electrospun air filtration membranes (EAFMs) and the typical surface structures and filtration principles of electrospun fibers for air filtration are reviewed. Second, the research progress of EAFMs with multistructures, including nanoprotrusion, wrinkled, porous, branched, hollow, core-shell, ribbon, beaded, nets structure, and the application of these nanofibers in air filtration are summarized. Finally, challenges with the fabrication of EAFMs, limitations of their use, and trends for future developments are presented.

Modified Electrospun Polymeric Nanofibers and Their Nanocomposites as Nanoadsorbents for Toxic Dye Removal from Contaminated Waters: A Review

Electrospun polymer nanofibers (EPNFs) as one-dimensional nanostructures are characterized by a high surface area-to-volume ratio, high porosity, large number of adsorption sites and high adsorption capacity. These properties nominate them to be used as an effective adsorbent for the removal of water pollutants such as heavy metals, dyes and other pollutants. Organic dyes are considered one of the most hazardous water pollutants due to their toxic effects even at very low concentrations. To overcome this problem, the adsorption technique has proven its high effectiveness towards the removal of such pollutants from aqueous systems. The use of the adsorption technique depends mainly on the properties, efficacy, cost and reusability of the adsorbent. So, the use of EPNFs as adsorbents for dye removal has received increasing attention due to their unique properties, adsorption efficiency and reusability. Moreover, the adsorption efficiency and stability of EPNFs in aqueous media can be improved via their surface modification. This review provides a relevant literature survey over the last two decades on the fabrication and surface modification of EPNFs by an electrospinning technique and their use of adsorbents for the removal of various toxic dyes from contaminated water. Factors affecting the adsorption capacity of EPNFs, the best adsorption conditions and adsorption mechanism of dyes onto the surface of various types of modified EPNFs are also discussed. Finally, the adsorption capacity, isotherm and kinetic models for describing the adsorption of dyes using modified and composite EPNFs are discussed.

Preparation of a Hybrid Membrane from Whey Protein Fibrils and Activated Carbon to Remove Mercury and Chromium from Water

Water contamination by mercury and chromium has a direct effect in human health. A promising technology to remove heavy metals by membrane filtration is the use of hybrid membranes produced with whey protein fibrils (WPF) and activated carbon (AC). In this study, the best conditions to produce WPF by heat treatment were determined to maximize the removal of mercury and chromium from water using a central composed design. The results indicated that the best conditions to prepare WPF were 74 °C, 7 h and 3.8% of whey protein with adsorption capacities of 25 and 18 mg/g and removal efficiencies of 81 and 57% for mercury and chromium, respectively. WPF and AC were used to prepare a hybrid membrane that was characterized using transmission electron microscopy, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area measurements. Batch filtration experiments were performed with the hybrid membrane for chromium and mercury removal at 25, 50 and 100 mg/L to determine its adsorption capacities. A high performance of the hybrid membrane was demonstrated removing efficiently mercury and chromium from water, thus supporting more than ten filtration cycles.

Polydopamine Microsphere-Incorporated Electrospun Fibers as Novel Adsorbents for Dual-Responsive Adsorption of Methylene Blue

The usually inconvenient detection and uneasy recycling of polydopamine (PDA) with sphere morphology as an adsorbent restrict its actual applications in wastewater purification. Thus, novel composite fibers were fabricated via the electrospinning technique by integrating polydopamine microspheres (PDA-MPs) with pH/temperature dual-responsive copolymers. The insoluble fraction of the fabricated composite fibers can be maintained to a value above 89% after being immersed in aqueous solutions with different pH values. Also, the regeneration efficiency of the composite fibers can also remain above 80% after undergoing five adsorption-desorption cycles. These results both indicated that the fabricated composite fibers can avoid secondary pollution during the adsorption process effectively. In addition, the presence of abundant N-isopropyl acrylamide (NIPAM) units within the fibers could make it have a relatively higher water swelling ability of 4643%, which could further offer relatively larger inner spaces to accommodate the dye molecules. Meanwhile, by incorporating β-cyclodextrin (β-CD), methacrylic acid (MAA), PDA, and NIPAM components, plentiful active adsorption sites could be supplied to interact with methylene blue (MB) dye. So, the adsorption experiments of the composite fibers showed a maximum adsorption capacity of 1722.1 mg/g at pH 9.0 and a temperature of 55 °C. Furthermore, the pseudo-second-order kinetic model of adsorption suggested that it is a chemisorption process. Moreover, the adsorption experimental data can be better described by Langmuir models, inferring its monolayer adsorption. The adsorption thermodynamic studies revealed that adsorption is a spontaneous and endothermic process. Also, the increase of temperature facilitated the adsorption processes, owing to the increase of adsorbent's hydrophobicity and molecules' reactivity. The present work suggested that the combination of smart-responsive polymers and PDA-MPs could form an unprecedented system to be a promising candidate adsorbent for wastewater treatment.

New Mussel Inspired Polydopamine-Like Silica-Based Material for Dye Adsorption

A straightforward and economic procedure has been developed for the synthesis of a new polydopamine-like silica-based material that has been obtained by oxidation of catechol with KIO4 followed by reaction with 3-aminopropyltrimethoxysilane. All techniques adopted for characterization showed that the obtained material is rich in different functional groups and the morphological analyses revealed dimensions in the nanometric range. The hybrid material has been characterized by several techniques showing its polydopamine-like nature, and preliminary observations for dye adsorption have been reported.

Foam Separation of Dyes Using Anionic, Cationic, and Amphoteric Surfactants

Foam separation can selectively remove a target substance from a solution via adsorption of the substance with the surfactant at the surface of the bubble. A cationic dye, methylene blue, and an anionic dye, Fast Green FCF, were prepared as substances to be removed via foam separation. Anionic (sodium dodecyl sulfate, SDS), cationic (dodecyltrimethylammonium chloride, DTAC), and amphoteric (3-(dodecyldimethylammonio)propane-1-sulfonate, SB-12) surfactants were used in the foam separation process. The effectiveness of the surfactants for removing the cationic methylene blue increased as follows: DTAC < SB-12 < SDS. On the other hand, the effectiveness of the surfactants for removing the anionic Fast Green FCF was in the opposite order. The dyes were effectively adsorbed by the foams via electrostatic interactions between the oppositely charged surfactant and the dye molecules. Since amphoteric surfactants have both anionic and cationic charges in a molecule, they could effectively remove both dyes in the foam separation process. Therefore, it was found that the amphoteric surfactant was highly versatile. Analysis of the kinetics of the removal rate showed that the aqueous solutions of monomers could remove the dyes more effectively than micellar solutions in foam separation.

Interface Coassembly and Polymerization on Magnetic Colloids: Toward Core-Shell Functional Mesoporous Polymer Microspheres and Their Carbon Derivatives

Core-shell structured magnetic mesoporous polymer or carbon-based microspheres not only possess the combined merits of magnetic particles and stable mesoporous shell but also provide various organic functional groups for further modification and immobilization of active sites, thus opening up more possibility for various applications. Herein, a bottom-up soft-templating strategy is developed to controllably synthesize core-shell magnetic mesoporous polydopamine microspheres (MMP) and their derivative magnetic mesoporous carbon (MMC) microspheres via an amphiphilic block copolymer-directed interface assembly and polymerization (denoted as abc-DIAP) approach. The obtained uniform MMP microspheres have a well-defined structure consisting of magnetic core, silica middle layer and mesoporous PDA shell, uniform mesopores of 11.9 nm, high specific surface areas (235.6 m2 g-1) and rich functional groups. They show fast magnetic separation speed and superior performance in selective adsorption of Cyt.C from complex biosample solutions. Moreover, they can be in situ converted into core-shell magnetic mesoporous carbon (MMC) for efficient in-pore immobilization of ultrafine Au nanoparticles for high-efficiency catalytic epoxidation of styrene with high conversion (88.6%) and selectivity (90.1%) toward styrene oxide.

Assessment of ampicillin removal efficiency from aqueous solution by polydopamine/zirconium(iv) iodate: optimization by response surface methodology

Polydopamine/zirconium(iv) iodate was prepared by incorporating polydopamine into zirconium iodate gel and studied as an effective adsorbent for ampicillin. In order to characterize the prepared composite, FTIR, XRD, TGA-DTA, SEM and TEM were used. The effects of experimental variables on ampicillin removal were examined using response surface methodology. The optimum conditions for ampicillin removal were 7, 130 min, 20 mg/20 mL and 50 mg L-1 for pH, contact time, adsorbent dose and initial ampicillin concentration, respectively. Under the optimum conditions, the maximum ampicillin removal percentage was found to be 99.12%. The Langmuir isotherm and pseudo-second-order kinetic models explained the removal process more appropriately. The maximum adsorption capacity at 303 K was 100.0 mg g-1. Thermodynamic study revealed that the ampicillin adsorption was spontaneous and endothermic in nature. The reusability of the prepared material was also explored.

Acid Dye Removal from Aqueous Solution by Using Neodymium(III) Oxide Nanoadsorbents

In the current work, neodymium oxide (Nd₂O₃) nanoparticles were synthesized and characterized by means of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The major aim/investigation of this research was to fit/model and optimize the removal of Acid Blue 92 (AB92) dye from synthetic effluents (aqueous solutions) using the adsorption process based on neodymium oxide (Nd₂O₃) nanoparticles. To optimize the adsorption conditions, central composite design (CCD) based on response surface methodology (RSM) was applied. The effects of pH (3-9), adsorbent dosage (0.1-1 g/L), initial concentration of AB92 (100-300 mg/L), and contact time (10-100 min) on the adsorption process were investigated. Apart from equilibrium and kinetic experiments, thermodynamic evaluation of the adsorption process was also undertaken. The adsorption process was found to have the best fitting to Langmuir isotherm model and pseudo-second-order kinetic equation. Also, the process was found to be spontaneous and favorable with increased temperature. The optimal conditions found were: pH = 3.15, AB92 concentration equal to 138.5 mg/L, dosage of nanoadsorbent equal to 0.83 g/L, and 50 min as contact time, which resulted in 90.70% AB92 removal. High values for the coefficient of determination, R² (0.9596) and adjusted R² (0.9220) indicated that the removal of AB92 dye using adsorption can be explained and modeled by RSM. The Fisher's F-value (25.4683) denotes that the developed model was significant for AB92 adsorption at a 95% confidence level.

One-step fabrication of bifunctional self-assembled oligopeptides anchored magnetic carbon nanoparticles and their application in copper (II) ions removal from aqueous solutions

Copper ion (Cu (II)) pollution has attracted much attention due to its remarkable toxic domino effect at excess amount. Efficient Cu (II) ions removal is thus a prerequisite for wastewater recycling. Herein, we present a facile and environmentally benign strategy to fabricate thiol (SH)-functionalized Fe₃O₄@C nanoparticles (denoted as Fe₃O₄@C-SH NPs) based on one-step self-assembling of a bifunctional oligopeptide with a sequence of Cys-Lys-Cys-Lys-Cys-Lys (CK-VI) for highly efficient removal of copper ions (Cu (II)) in aqueous solutions. Under the physiological conditions, CK-VI readily self-organized into a robust and tailor-made functional monolayer predominately composed of well-packed β-sheets on the surface of Fe₃O₄@C NPs with their thiol groups standing on the outermost layer. The resulting Fe₃O₄@C-SH NPs containing abundant thiol active sites exhibited excellent adsorption capacity (up to 28.8 mg g^-1) and selectivity for Cu (II) ions over coexisting ions. Compared with other covalent grafting methods with multistep processes and in harsh conditions, the proposed oligopeptides assembly-based coating method makes it possible to rapidly fabricate the Fe₃O₄@C-SH NPs in a simple mild one-step aqueous process with low cost. The current study provides facile and environmentally friendly approaches to rapidly tailor multifunctional surfaces of NPs for various toxic metal ions removal from wastewater.

Functioned hollow glass microsphere as a self-floating adsorbent: Rapid and high-efficient removal of anionic dye

Rapid, high-efficient adsorbents with efficient solid-liquid separation ability has broad application prospects in the treatment of dye wastewater. In this study, polydopamine and methacryloyloxyethyltrimethyl ammonium chloride were grafted onto hollow glass microspheres to prepare the enhanced polydopamine shell structure adsorbent with self-floating ability. Furthermore, the adsorbent achieves high-efficiency surface solid-liquid separation, which overcomes the disadvantages of the traditional separation methods. Characterizations of the as-synthesized microspheres were performed using various techniques such as SEM, EDS, BET, XPS, FT-IR, TGA and XRD. The adsorbent achieved rapid and high-efficient adsorption of alizarin cyanine green F via the interactions of electrostatic attracting and π-π stacking, and under the optimal experimental conditions, the removal efficiency of 0.10 m mol L^-1 dye solution reaches 94.51%, and the adsorption process reaches equilibrium within 60 min. Adsorption isotherms and kinetics data of the adsorbent were well fitted by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The as-synthesized adsorbent has excellent recyclability, and its adsorption performance can be maintained after 5 cycles of reuse. The self-floating adsorbent has great potential for the removal of dissolved contaminants and cost-effective separation.

Self-assembly of sponge-like kaolin/chitosan/reduced graphene oxide composite hydrogels for adsorption of Cr(VI) and AYR

The assembly of graphene oxide with biomass or polymers to form 3D hydrogels with excellent mechanical properties has become a research hotspot. In this work, the sponge-like kaolin/chitosan (CS)/reduced graphene oxide (rGO) composite was prepared for adsorption by simple self-assembly without cross-linking agent. The morphology, composition, surface properties, and pore size of as-prepared materials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), zeta potential analyzer, Brunauer-Emmett-Teller surface area measurement (BET), and scanning electron microscopy (SEM). The effects of raw material ratio, contact time, temperature, pH, ionic strength, and recycling times on adsorption performance were investigated in detail. The results indicate that the composite has good absorption capacity for Cr(VI) and alizarin yellow R (AYR). Besides, composite hydrogel also exhibits excellent flexibility and good repeatability, which confirms its great potential as an adsorbent to remove pollutants in the water environment.

Highly Dispersed Ag2S Nanoparticles: In Situ Synthesis, Size Control, and Modification to Mechanical and Tribological Properties towards Nanocomposite Coatings

A facile in situ synthesis approach and a size control strategy were established to obtain Ag₂S nanoparticles in polyimide (PI) composite coatings. Such Ag₂S nanoparticles in the composite coatings were characterized, and the effects of the as-obtained Ag₂S nanoparticles of different sizes on the mechanical and tribological properties of the nanocomposite coatings were investigated. Results indicate that the in situ synthesized Ag₂S nanoparticles exhibited good dispersibility and bimodal and multimodal size distribution in the nanocomposite coatings. The size of the Ag₂S nanoparticles can be effectively controlled by adjusting the substituent alkyl chain length of single-source precursor, and these Ag₂S nanoparticles exhibited superior improvement to mechanical and tribological properties of the nanocomposite coatings. More importantly, the Ag₂S nanoparticles with the proper grain size and bimodal size distribution provided the optimal mechanical and tribological properties for the nanocomposite coatings, and the excellent tribological properties were attributed to their outstanding mechanical properties and strong ability to form a homogenous and stable protective tribofilm.

Improved degradation of anthraquinone dye by electrochemical activation of PDS

Electrochemical oxidation (EO) coupled with peroxydisulfate (PDS) activation as a synergistic wastewater treatment process (PDS/EO) was performed to degrade anthraquinone dye-Reactive Brilliant Blue (RBB) in aqueous solution. Introducing PDS into the EO improved the RBB removal than the sole PDS and conventional EO systems. The RBB could activate PDS to a certain degree by itself. By the comparison of various inorganic ions addition, it showed that adding NO₃^- as the background electrolyte was more effective than the systems using the Cl^- and SO₄^2-, respectively. In this PDS/EO-NO₃^- system, increasing PDS concentration (1-5 mmol L^-1) and current density (5-10 mA cm^-2) considerably promoted the degradation of RBB. The adjustment of the solution pH displayed that the acidic and neutral condition was beneficial to the RBB removal, and the synergistic effect was inverse ratio to the RBB initial concentration. Furthermore, the scavenger experiments verified that both SO₄^·- and HO· were the major active substances in the RBB decomposition, and other reactive oxygen species also had considerable contributions. Thereinto NO₃^- only act a catalytic agent to improve the generation of active matters in the PDS/EO-NO₃^-. Overall, the proposed synergistic process could serve as an efficient method for the degradation of anthraquinone dye.

Facile preparation of self-assembled hydrogels constructed from poly-cyclodextrin and poly-adamantane as highly selective adsorbents for wastewater treatment

Self-assembled hydrogel materials constructed from cyclodextrin polymer (P-CD)/adamantane-modified poly acrylic acid (PAA-Ad) were designed and prepared via host-guest interactions. It was observed that the prepared supramolecular hydrogels had an interconnected three-dimensional porous network. In addition, the obtained hydrogels showed a recovery performance and it was confirmed that the host-guest interactions between β-cyclodextrin and adamantane were the main driving force for the formation of the hydrogels. The mechanical properties of the hydrogels could be adjusted by varying the concentrations of PAA-Ad. In particular, the prepared supramolecular hydrogels exhibited superior performances in water purification. The results demonstrated that the hydrogels possessed different mechanisms in the adsorption of the four typical poisonous organic dye molecules used, including bisphenol A (BPA), 4-aminoazobenzene (N-Azo), methylene blue (MB), and rhodamine B (RhB). The hydrogels mainly adsorbed N-Azo by host-guest interaction and adsorbed BPA by host-guest interaction and hydrogen bond synergy. They also adsorbed MB and RhB by hydrogen bonding and electrostatic interaction.

Self-Assembled Naphthylidene-Containing Schiff Base Anchored Polystyrene Nanocomposites Targeted for Selective Cu(II) Ion Removal from Wastewater

Self-assembled composite adsorbents that combine the controllability of self-assembly with a mild operation process are promising for removal of heavy metal ions in wastewater. The design and preparation of functionalized composite adsorbent materials with multiple-site adsorption ability remain the most attractive in effectively removing heavy metal ions. Inspired by the macroporous structure of charged polystyrene (PS) resin and chelation of Schiff bases with heavy metal ions, smart composite adsorbents are constructed based on the combination and synergistic effect of multiple hydrophobic, π-π stacking, and electrostatic noncovalent interactions between polystyrene resin and naphthylidene-containing Schiff base (NSB). The resulting hybrid nanomaterials (PS-NSB) have uniform porous structures and well-defined and multiple target sites. These properties promote diffusion of the target ion, increase the binding site, and enhance the removal efficacy. This study offers a new strategy to harness a self-assembled Schiff base with integrated flexibility and multifunctions to enhance target metal ion specific binding and removal effects, highlighting opportunities to develop smart composite adsorbents.

Highly Efficient Catalytic Performances of Nitro Compounds and Morin via Self-Assembled MXene-Pd Nanocomposites Synthesized through Self-Reduction Strategy

With development of the society, the problem of environmental pollution is becoming more and more serious. There is the urgent need to develop a new type of sustainable green material for degradable pollutants. However, the conventional preparation method is limited by conditions such as cumbersome operation, high energy consumption, and high pollution. Here, a simple method named self-reduction has been proposed, to synthesize highly efficient catalytic nitro compounds and morin self-assembled MXene-Pd nanocomposites. Palladium nanoparticles were grown in situ on MXene nanosheets to form MXene@PdNPs. MXene@PdNPs composites with different reaction times were prepared by adjusting the reduction reaction time. In particular, MXene@PdNPs20 exhibited a high catalytic effect on 4-NP and 2-NA, and the first-order rate constants of the catalysis were 0.180 s-1 and 0.089 s-1, respectively. It should be noted that after eight consecutive catalytic cycles, the conversion to catalyze 4-NP was still greater than 94%, and the conversion to catalyze 2-NA was still greater than 91.8%. Therefore, the research of self-assembled MXene@PdNPs nanocomposites has important potential value for environmental management and sustainable development of human health, and provides new clues for the future research of MXene-based new catalyst materials.

Preparation of Palladium Nanoparticles Decorated Polyethyleneimine/Polycaprolactone Composite Fibers Constructed by Electrospinning with Highly Efficient and Recyclable Catalytic Performances

Nano-sized palladium nanoparticles showed high catalytic activity with severe limitations in catalytic field due to the tendency to aggregate. A solid substrate with large specific surface area is an ideal carrier for palladium nanoparticles. In present work, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/PCL@PdNPs) composite catalysts were successfully designed and prepared by electrospinning and reduction methods using PEI/PCL elexctrospun fiber as carrier. The added PEI component effectively regulated the microscopic morphology of the PEI/PCL fibers, following a large number of pit structures which increased the specific surface area of the electrospun fibers and provided active sites for loading of the palladium particles. The obtained PEI/PCL@PdNPs catalysts for reductions of 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) exhibited extremely efficient, stable, and reusable catalytic performance. It was worth mentioning that the reaction rate constant of catalytic reduction of 4-NP was as high as 0.16597 s−1. Therefore, we have developed a highly efficient catalyst with potential applications in the field of catalysis and water treatment.

Editorial for the Special Issue on 'Application and Behavior of Nanomaterials in Water Treatment'

The simultaneous population explosion and the growing lack of clean water today requires disruptively innovative solutions in water remediation [...].

Facile Preparation and Enhanced Catalytic Properties of Self-Assembled Pd Nanoparticle-Loaded Nanocomposite Films Synthesized via the Electrospun Approach

In recent years, people pay more attention to environmental pollution and the treatment of sewage has become the focus of recent research. Palladium nanoparticles have good catalytic properties but are easy to agglomerate. Therefore, we used the electrospinning technology to prepare a uniform composite nanofiber film based on polyacrylic acid (PAA) and polyvinyl alcohol (PVA), which demonstrated that they are good carriers of palladium nanoparticles to make the nanoparticles well dispersed. Furthermore, carbon nanotubes (CNTs) were added to increase the specific surface area of the composite nanofiber film and improve its mechanical properties. The successfully synthesized PAA/PVA/CNT-COOH@palladium nanoparticle (PdNP) composite fiber films were characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetry analysis. p-Nitrophenol and 2-nitroaniline were utilized as typical pollutants to further evaluate the catalytic performance of PAA/PVA/CNT-COOH@PdNP composite fiber films. The PAA/PVA/CNT-COOH@PdNP composite fiber films exhibited enhanced catalytic performance and could be reused for eight consecutive cycles. This work provided new clues for the preparation and application of composite electrospun film materials.

Polyethylenimine Assisted Bio-Inspired Surface Functionalization of Hexagonal Boron Nitride for Enhancing the Crystallization and the Properties of Poly(Arylene Ether Nitrile)

Semi-crystalline poly(arylene ether nitrile) (PEN) has exhibited remarkable potential in various fields. However, the inherent drawbacks of PEN such as slow crystalline rate and low crystallinity limit its further development. To alleviate this problem, the choice of nanofiller as nucleation agent and the interfacial compatibility between nanofiller and PEN matrix are two momentous factors that need to be considered. Accordingly, in this work, functionalized hexagonal boron nitride (h-BN@(PDA+PEI)) was successfully synthesized via polyethylenimine (PEI) assisted bio-inspired surface functionalization, and then homogeneously dispersed in the PEN resin using solution casting method to obtain functional polymer nanocomposite films with strengthening the crystallization behavior, mechanical and dielectric properties. Various testing methods including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD), and polarizing microscope (POM) were applied to intricately analyze the effect of h-BN@(PDA+PEI) on the crystallization behavior of PEN composites. The testing results certificated that the h-BN@(PDA+PEI) can effectively improve the crystallinity (from 6.56% to 14.90%), and the spherulite size of PEN was reduced while the nucleation density of nanocomposites was raised. Furthermore, the non-isothermal crystallization kinetics demonstrated that 2 wt% h-BN@(PDA+PEI) could significantly reduce the cold crystallization temperature (T_p) and the crystallization activation energy (E_a) (from 359.7 KJ/mol to 292.8 KJ/mol), while it improved the crystallization rate (K_c) of PEN. In addition, the mechanical and dielectric properties of nanocomposite films were also reinforced to further broaden the application of semi-crystalline PEN. Therefore, the h-BN@(PDA+PEI) can function as an effectual nucleating agent and enhance the performance of PEN.

Robust and anti-fatigue hydrophobic association hydrogels assisted by titanium dioxide for photocatalytic activity

Currently, robust and functional hydrogels have attracted extensive attention due to their potential applications in wastewater treatment, farmland water conservation and other fields. Herein, a series of hydrophobic association hydrogels assisted by titanium dioxide (TiO2) was fabricated via one-pot in situ photo-induced polymerization. TiO2 nanoparticles could act as both photo-initiators and physical crosslinking points. The TiO2-assisted hydrophobic association hydrogels exhibited a high tensile strength of 306 kPa, superior compression strength of 2.17 MPa and excellent fatigue resistance. Simultaneously, the incorporation of TiO2 endowed the hydrogel with photocatalytic capacity for dye wastewater treatment based on the inherent nature of TiO2. The results indicated that the hydrogels contributed to the degradation of various ionic dyes including methylene blue, rhodamine B and bromophenol blue, and the removal of methylene blue achieved a rate of 96.63%. Significantly, the hydrogel could be repeatedly utilized and the removal rate showed no evident decrease after five cycles, indicating that the hydrogels could be powerful candidates as photocatalysts for dye wastewater treatment.

Facile Preparation of Porous Rod-like Cu x Co3-x O4/C Composites via Bimetal-Organic Framework Derivation as Superior Anodes for Lithium-Ion Batteries

To meet growing demand of energy, lithium-ion batteries (LIBs) are under enormous attention. The development of well-designed ternary transition metal oxides with high capacity and high stability is important and challengeable for using as electrode materials for LIBs. Herein, a new and highly reversible carbon-coated Cu-Co bimetal oxide composite material (Cu x Co3-x O4/C) with a one-dimensional (1D) porous rod-like structure was prepared through a bimetal-organic framework (BMOF) template strategy followed by a morphology-inherited annealing treatment. During the annealing process, carbon derived from organic frameworks in situ fully covered the synthesized bimetal oxide nanoparticles, and a large number of porous spaces were generated in the MOF-derived final samples, thus ensuring high electrical conductivity and fast ion diffusion. Benefiting from the synergetic effect of bimetals, the unique 1D porous structure, and conductive carbon network, the as-synthesized Cu x Co3-x O4/C delivers a high capacity retention up to 92.4% after 100 cycles, with a high reversible capacity still maintained at 900 mA h g-1, indicating an excellent cycling stability. Also, a good rate performance is demonstrated. These outstanding electrochemical properties show us a concept of synthesis of MOF-derived bimetal oxides combining both advantages of carbon incorporation and porous structure for progressive lithium-ion batteries.

Chiral Nanostructured Composite Films via Solvent-Tuned Self-Assembly and Their Enantioselective Performances

Chiral nanostructures exhibited distinctive functions and attractive applications in complex biological systems, which demonstrated the subject of many outstanding research studies. In this work, various hierarchical composite film nanostructures were designed via supramolecular self-assembly using chiral amphiphilic glutamate derivatives and achiral porphyrin derivatives and their macroscopic enantioselective recognition properties were investigated. We have found that intermolecular hydrogen-bonding interactions between water (donor and acceptor) and N, N-dimethylformamide (DMF) as well as chloroform (CHCl₃) (acceptor only) and DMF could subtly alter the molecular packing and significantly affected the supramolecular self-assembled nanostructures and triggered circular dichroism (CD) signal reversal. Present research work exemplified a feasible method to fabricate chiral flower-like and brick-like nanostructure films in different mixed solvents and large-scale chiral transfer from the molecular level to complex structures, which also provided a facile approach to identify certain l-/d-amino acids by means of contact angle detection using present obtained self-assembled composted films.

Facile Preparation of Carbon Nanotube-Cu2O Nanocomposites as New Catalyst Materials for Reduction of P-Nitrophenol

The effective synthesis and self-assembly of nanocomposites were of key importance for a broad range of nanomaterial applications. In this work, new carbon nanotube (CNT)-Cu2O nanocomposites were successfully synthesized via a facile approach. CNT was selected as the anchoring substrate to load Cu2O nanoparticles to prepare composite catalysts with well stability and good reusability. It is discovered that the prepared CNT-Cu2O nanocomposite materials could be effectively controlled via regulating preparation temperature and time without the use of any stabilizing agents. The nanostructures of synthesized composites were well characterized by many techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). And the prepared CNT-Cu2O nanocomposites with optimized preparation conditions as new catalyst displayed excellent catalytic performance on the reduction reaction of p-nitrophenol, demonstrating potential applications for environmental governance and composite materials.

Preparation and Dye Degradation Performances of Self-Assembled MXene-Co3O4 Nanocomposites Synthesized via Solvothermal Approach

Two-dimensional metal carbides or nitrides (MXenes) demonstrated wide applications in energy storage, water treatment, electromagnetic shielding, gas/biosensing, and photoelectrochemical catalysis due to their higher specific surface area and excellent conductivity. They also have the advantages of flexible and adjustable components and controllable minimum nanolayer thickness. In this study, a cube-like Co3O4 particle-modified self-assembled MXene (Ti3C2) nanocomposite has been prepared successfully by a simple solvothermal method. The Co3O4 particles are well dispersed on the surface and inner layers of the Ti3C2 sheets, which effectively prevent the restacking of Ti3C2 sheets and form an organized composite structure. The physical properties of these nanocomposites were studied by using XRD, SEM, EDX, TEM, and XPS. The performance of the obtained samples was evaluated as new nanocatalysts for degrading methylene blue and Rhodamine B in batch model experiments. The prepared Mxene-Co3O4 nanocomposites can be well regenerated and reused for eight consecutive cycles, indicating potential wide applications in wastewater treatment and composite materials.

Preparation of Self-Assembled Composite Films Constructed by Chemically-Modified MXene and Dyes with Surface-Enhanced Raman Scattering Characterization

The effective functionalization and self-assembly of MXene are of crucial importance for a broad range of nanomaterial applications. In this work, we investigated the aggregates of sulfanilic acid-modified MXene (abbreviated as MXene-SO3H) with three model dyes at the air⁻water interface and demonstrated the morphological and aggregation changes of composite films, using Langmuir-Blodgett (LB) technology, as well as excellent uniformity and reproducibility by using surface-enhanced Raman scattering (SERS) spectra. This research has found that cationic dye molecules were adsorbed onto negatively charged MXene-SO3H particles mainly through electrostatic interaction and the particles induced dyes to form highly ordered nanostructures including H- and/or J-aggregates corresponding to monomers in bulk solution. The surface pressure-area isotherms from different dye sub phases confirmed that the stable composite films have been successfully formed. And the spectral results reveal that different dyes have different types of aggregations. In addition, the SERS spectra indicated that the optimal layers of MXene-SO3H/methylene blue (MB) films was 50 layers using rhodamine 6G (R6G) as probe molecule. And the formed 50 layers of MXene-SO3H/MB films (MXene-SO3H/MB-50) as SERS substrate were proved to possess excellent uniformity and repeatability.