Poor Dispersion Research Articles

Incorporating 2D porous organic polymer nanosheets into high-temperature proton-exchange membranes for low H3PO4 loss

Phosphoric acid (PA)-doped ion exchange membranes have been recognized as a classical high-temperature proton exchange membrane (HT-PEM) material. Nonetheless, the leaching of PA from membranes occurs progressively during operation, inevitably diminishing overall performance. In this study, we present a novel approach for crafting two-dimensional porous organic polymer nanosheets (NS-POPs) synthesized through nano-interfacial azo-coupling polymerization. The prepared NS-POPs possessed different pore structures with main pore sizes of 0.55 nm and 1.19 nm, which were derived from the discrepancy of monomer structure. Subsequently, the NS-POPs were successfully incorporated into polybenzimidazole to create mixed-matrix membranes due to the good interface compatibility, characterized by homogeneity and stability facilitated by the 2D nature of NS-POPs. As a comparison, POPs with non-2D properties prepared by the solution method cannot be successfully obtained in good MMMs due to poor dispersibility and interface compatibility. Furthermore, the profusion of pore structures and the presence of N/O-rich functional groups in NS-POPs significantly enhance their PA uptake capacity with up to 289 %, consequently boosting proton conductivity. As a result, the composite membrane doped with NS-POPs demonstrated a maximum conductivity of up to 143 mS cm−1 at 180 °C, which is approximately 2.97 times that of pure membrane. And the peak power density of H2/O2 fuel cell based on the composite membrane was 378 mW cm−2, which was higher than PBI. Most significantly, the confinement effect exerted by the small pores in NS-POPs enables composite membranes to maintain a higher PA retention of up to 74 % even after a 48 h of high-temperature and high-humidity treatment. Our study introduces an innovative and straightforward approach to synthesizing porous organic polymer nanosheets. This work not only advances the understanding of the impact of interface compatibility on composite membrane fabrication, but also establishes a versatile technology for modulating pore size and managing PA leaching in HT-PEMs.

A seven-year-based characterization of aerosol light scattering properties at a rural central European site

Our study investigates the temporal variability of aerosol light scattering properties measured at three wavelengths (total scattering coefficient, backscattering coefficient, Ångström scattering exponent, hemispheric backscattering ratio and asymmetry parameter) at the rural background site of the National Atmospheric Observatory Košetice over a period of over seven years (2012–2019). The influence of fog and cloudiness on aerosol light scattering properties (ASP), together with their comparison to particle number size distribution was also investigated. The overall medians of total scattering (σsp) and backscattering coefficient (σbsp), hemispheric backscattering ratio (b) and asymmetry parameter (g) measured at 550 nm and Ångström scattering exponent (SAE_450/700) were 35.20 Mm−1, 5.07 Mm−1, 0.14 and 0.57 and 1.82, respectively. σsp and g decreased by 2.05 Mm−1/year, and 0.009/year, respectively, whereas b increased by 0.004/year. The selected aerosol properties were strongly correlated with particle number, mass, area and volume concentrations in the 200–800 nm mode. A decrease in SAE_450/700 implies a shift towards larger particle sizes, and evolutions in b and g suggest a higher backscattering portion to total scattering. The highest σsp and σbsp levels were observed in the cold seasons together with higher concentrations of air pollutants (carbonaceous aerosol, SO2 and NOx). This could be explained by enhanced emissions from human activities such as domestic heating combined with the higher stability of the atmosphere (poor atmospheric dispersion). In the summer, decreases in particle size and higher rates of backscatter fraction were attributed to secondary organic aerosol (SOA) formation. The accumulation mode showed the strongest aerosol scattering potential, with SAE_450/700 values < 2. Aerosol light scattering was significantly higher during overcast and foggy days compared to fine, cloudy, partly cloudy and no-fog days, possibly due to the particle hygroscopic growth under high relative humidity (shift of particle size towards larger sizes), which in turn can lead to a lower aerosol backscattering fraction. Source identification linked the changes in ASP to the synoptic situation over Europe rather than to specific sources of pollution.

Dispersal mediates trophic interactions and habitat connectivity to alter metacommunity composition.

Dispersal contributes vitally to metacommunity structure. However, interactions between dispersal and other key processes have rarely been explored, particularly in the context of multitrophic metacommunities. We investigated such a metacommunity in naturally fragmented habitats populated by butterfly species (whose dispersal capacities were previously assessed), flowering plants, and butterfly predators. Using data on butterfly species abundance, floral abundance, and predation (on experimentally placed clay butterfly models), we asked how dispersal ability mediates interactions with predators, mutualists, and the landscape matrix. In contrast to expectations, high densities of strong dispersers were found in more isolated sites and sites with low floral resource density, while intermediate dispersers maintained similar densities across isolation and floral gradients, and higher densities of poor dispersers were found in more connected sites and sites with higher floral density. These findings raise questions about how strong dispersers experience the landscape matrix and the quality of isolated and low-resource sites. Strong dispersers were able to escape habitat patches with high predation, while intermediate dispersers maintained similar densities along a predation gradient, and poor dispersers occurred at high densities in these patches, exposing them to interactions with predators. This work demonstrates that species that vary in dispersal capacities interact differently with predators and mutualist partners in a landscape context, shaping metacommunity composition.

DNA metabarcoding uncovers dispersal‐constrained arthropods in a highly fragmented restoration setting

Degraded areas are often restored through active revegetation; however, recolonization by animals is rarely engineered. Recolonization may be rapid for species with strong dispersal abilities. However, poor dispersers, such as many flightless arthropods, may struggle to recolonize newly restored sites. Actively reintroducing or “rewilding” arthropods may therefore be necessary to facilitate recolonization and restoration of arthropod communities and the ecological functions they perform. However, active interventions are rare. The purpose of this study was twofold. First, we asked whether potential source remnant arthropod communities were dispersal‐constrained and struggling to recolonize restoration sites. Second, we tested whether reintroducing entire arthropod communities from remnant populations would help dispersal‐constrained species establish during farmland ecological restoration in southern Australia. Rewilding was conducted in summer 2018 by transplanting leaf litter, soil, and entire communities contained within it from remnant source populations into geographically isolated restoration sites, which were paired with untreated controls (n = 6 remnant, rewilding transplant, and control sites). We collected leaf litter and extracted arthropod communities 19 months after the initial rewilding event, then sequenced mite, springtail, and insect communities using a metabarcoding approach. Within all groups, community similarity decreased with spatial distance between sites, suggesting significant dispersal barriers. However, only mite communities showed a strong response to rewilding, which was expressed as increased compositional similarity toward remnant sites and greater species richness relative to controls. Our results demonstrate that many arthropod species may struggle to recolonize geographically isolated restoration sites and that full community restoration requires active interventions via rewilding.

Surface Coatings of Reinforcement Phases in Magnesium Matrix Composites: A Review.

Magnesium matrix composites have been extensively investigated due to their light weight and machinability. The interfaces are the most important part of these composites, and their properties determine the properties of composites to a large extent. However, there are still many problems with interface bonding. The reinforcements are faced with the dilemma of poor dispersion, bad interfacial reaction, and poor wettability, which limits further improvements in the mechanical properties. Surface coating treatment of reinforcements is considered to be one of the effective methods to protect reinforcements and modify the interface. This review presents an overview of different coating materials on various reinforcements. The major roles of coatings in the composites and the properties of the composites are discussed. Future directions and potential research areas in the field of magnesium matrix composites reinforced with coated reinforcements are also highlighted.

High erosion resistance thermoplastic polyurethanes composites fabricated via intercalation reinforced interfacial interaction

AbstractThe weak interface and poor dispersion of carbon nanofillers in polymer matrix composites lead to a significant decrease in their performance, restricting the development of polymer nanocomposites. In this work, a highly facile strategy has been developed to improve the interfacial adhesion performance between graphene nanoplates (GNP) and thermoplastic polyurethanes (TPU) matrix via self‐polymerization of dopamine. Then, single‐walled carbon nanotubes (CNT), as reinforcing agent, were introduced into surface modified GNP solution to prepare the corresponding ternary composites. Scanning electron microscope images show that GNP and CNT formed 3‐D interconnecting network‐like architecture. The sample modified with three layers of nonwoven fabric decorated with 1.0 mg/mL nanomaterial exhibit a tensile strength 35% higher than that of the virgin TPU. Consequently, compared with virgin TPU, the erosion resistance and thermal conductivity are enhanced by 78% and 45%, respectively.

Cryptic diversity and phylogeographic patterns of Deto echinata (Isopoda: Detonidae) in southern Africa

Recent phylogeographic studies of poorly-dispersing coastal invertebrates in highly biodiverse regions have led to the discovery of high levels of cryptic diversity and complex phylogeographic patterns that suggest isolation, geological, and ecological processes have shaped their biodiversity. Studies of southern African coastal invertebrates have uncovered cryptic diversity for various taxa and phylogeographic patterns that, although sharing some similarities across taxa, do differ. These findings underscore the need for additional studies to better understand the biodiversity levels, distributional patterns, and processes responsible for producing coastal biodiversity in that region. The coastal isopod Deto echinata is of particular interest, as its complex taxonomic history, poor dispersal capabilities, and broad geographic distribution suggest the potential for cryptic diversity. We use mitochondrial and nuclear sequences to characterize D. echinata individuals from localities ranging from northern Namibia to Glentana, about 2,500 km along the coastline on the south coast of South Africa. These are used to assess whether D. echinata harbors cryptic genetic diversity and whether phylogeographic distributional patterns correlate with those previously documented for other coastal isopods in the region. Analysis of mitochondrial and nuclear sequences revealed two deeply-divergent lineages that exhibit a distributional break in the Cape Peninsula region. These findings suggest D. echinata is a cryptic species complex in need of taxonomic revision and highlight the need for further taxonomic and phylogeographic studies of similarly poorly-dispersing coastal invertebrates in southern Africa.

Multiblock parallel high-order implicit residual smoothing time scheme for compressible Navier–Stokes equations

In direct and large eddy simulations, very small space steps are used close to the solid walls in order to resolve the boundary-layer structures. Due to the restrictive CFL stability criteria of explicit time-stepping schemes, the maximum allowable time step is also very small, leading to high computational costs, notably for converging flow statistics. The use of an implicit integration scheme may overcome this limitation at the price of an increased computational cost per step. Moreover, the most commonly used fully implicit schemes induce higher errors due to the necessary approximations and poor dispersion and dissipation properties. As a compromise, a fourth-order implicit residual smoothing scheme (IRS4), successfully validated for a finite volume solver in Cinnella nad Content (2016); Hoarau and Cinnella (2020), has been introduced in a multiblock high-order finite-difference solver. Several improvements are proposed to ensure better dissipation properties, a more efficient treatment of physical boundaries and an accurate and stable parallel multiblock implementation. For moderate CFL numbers, a similar accuracy as the explicit method is obtained with substantial savings in terms of computational time.

An efficient method to improve the dispersion and biocompatibility of ZnO nanoparticles

As an important inorganic antibacterial nanomaterial, zinc oxide nanoparticles (ZnO NPs) have been widely used in biomedical fields. However, the poor dispersion and potential toxicity greatly limit its application. Surface modification is an effective method to improve the dispersion and biocompatibility of ZnO NPs. In this work, ε-polylysine (ε-PL) was grafted on the surface of ZnO NPs via the combination of mussel inspired method and “Michael addition” reaction. The results showed that the ε-PL grafted ZnO (ZnO@ε-PL) could disperse stably in water more than 72 h, demonstrating ε-PL greatly improves the dispersion of ZnO NPs. Furthermore, the cells viability of ZnO@ε-PL at high concentrations (500 μg/mL) was 143.05 ± 12.63%, indicating that the biocompatibility of ZnO@ε-PL is much better than that of ZnO NPs. This study proposed a feasible and effective strategy to improve the dispersion and biocompatibility of ZnO NPs, which may expand the application of ZnO NPs in the biological field.

Dispersion stability and tribological behavior of nanocomposite supramolecular gel lubricants and molecular dynamic simulation

The poor dispersion stability of nanoparticles in oils limited their application. To address this problem, diverse of nanoparticles were introduced to supramolecular gels to fabricate a new lubricant (Nano-Gel). The results of molecular dynamics simulation show that gelators adsorbed onto the surface of nanoparticles at the non-covalent interaction. Besides, the intricate networks of supramolecular gels show spatial confinement to nanoparticles, which improved the dispersion stability of nanoparticles. Compared with supramolecular gels lubricant, Nano-Gel shows good anti-friction and anti-wear properties. The excellent tribological properties would be contributed to the self-repairing and tribo-film formed by nanoparticles and gelators. The Nano-Gels provide effective solution to the application of nanoparticles in lubricating oil, which have great values to prolong the life of mechanisms.

Self-sensing properties of alkali-activated materials prepared with different precursors

The development of smart concretes with self-sensing properties has gained increasing attention recently. In this study, the effect of different precursors, including blast furnace slag, fly ash, silica fume, and metakaolin, on the electrical conductivity and piezoresistive properties of alkali-activated materials (AAMs) with and without carbon fiber (CF) was investigated. The experimental results revealed that the electrical and self-sensing properties of AAMs were significantly influenced by the raw materials, both with and without carbon fiber. However, distinct trends were observed. The use of silica fume (25 wt%) was beneficial to the self-sensing property of CF-AAM mortars. Mixtures containing fly ash and pure slag exhibited higher sensitivity but with reduced repeatability of the piezoresistivity. Due to the poor dispersion of carbon fibers, as well as the porous microstructure, mixtures with metakaolin had poorer conductivity and piezoresistivity. AAM mortars had evident piezoresistivity under cyclic loading, but their stability was inferior to that of AAM with carbon fibers. The pore size distribution and gel pore quantity of the binder phase were important factors determining the conductive and piezoresistive properties of CF-AAM mortars.

Anthracene and tetraphenylsilane based conjugated porous polymer nanoparticles for sensitive detection of nitroaromatics in water

Conjugated porous polymers (CPPs) are a kind of promising sensing materials for the detection of nitroaromatic compounds, but their sensing applications in aqueous media are limited because of their poor dispersity or solubility in water. In this study, we prepared anthracene and tetraphenylsilane based CPPs named PSiAn by conventional Suzuki coupling and Suzuki-miniemulsion polymerization, respectively. The structure, morphology and porosity of the CPPs were characterized by Fourier Transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), transmission electron microscope (TEM) and N2 sorption isotherm, respectively. Both of the CPPs have porous structure which is beneficial for the adsorption and diffusion of the analytes within them. The particle size of PSiAn nanoparticles prepared by Suzuki-miniemulsion polymerization is 10–40 nm from the TEM image, which facilitates the dispersion in the aqueous phase. Combined with the porosity and nanoparticle morphology, PSiAn nanoparticles realized the efficient photoluminescence (PL) sensing of nitroaromatic explosives in aqueous phase. The limit of detection (LOD) and limit of quantitation (LOQ) of PSiAn nanoparticles for 2,4,6-trinitrophenol (TNP) detection in the pure aqueous phase are 0.33 μM and 1.11 μM, respectively. Meanwhile, the good selectivity and anti-interference in presence of other nitro-compounds were observed. Furthermore, the spike/recovery test for the TNP detection in real water samples by PL sensing based on PSiAn nanoparticles indicates the quantitative recovery of TNP from 100.74 % to 101.00 %. The electrochemical test, ultraviolet–visible absorption spectra, excitation and emission spectra, and time-resolved PL spectra were investigated to explore the PL sensing mechanism. As a result, it is found that the fluorescence inner filter effect might be the predominant quenching mechanism during the detection of nitrophenolic compounds such as TNP and 4-nitrophenol (4-NP).

Development of pea protein isolate-based complexes as a novel delivery system for capsaicin

The application of capsaicin (CAP) is limited by poor water dispersibility and low bioaccessibility. Herein, we used pH-driven method to fabricate the CAP-loaded protein-rhamnolipid (Rha) complexes to overcome these disadvantages. The complexes with good physicochemical properties were prepared by regulating the mass ratio between pea protein isolate (PPI)/whey protein isolate (WPI) and CAP. The PPI-CAP-Rha complex with a highest encapsulation efficiency of 96.3% in the PPI-based complexes group was prepared at the PPI-CAP mass ratio of 30 : 1. The WPI-CAP-Rha complex with a highest encapsulation efficiency of 91.7% in the WPI-based complexes group was prepared at the WPI-CAP mass ratio of 50 : 1. In contrast to the WPI-CAP-Rha 50 : 1 complex, the PPI-CAP-Rha 30 : 1 complex had better physical and thermal stability. The CAP encapsulated within the PPI-Rha complex had better water dispersibility and could be more effectively delay-released. Moreover, the bioaccessibility of encapsulated CAP was improved.

Facile fabrication of low-content surface-assembled MXene in silicone rubber foam materials with lightweight, wide-temperature mechanical flexibility, improved flame resistance and exceptional smoke suppression

Silicone rubber foam (SiRF) is a promising porous material that is widely applied in various fields. However, its intrinsic flammability nature remains a significant challenge. One of the simplest and the most economical solutions is to incorporate high content flame-retardant fillers. Unfortunately, such approach is limited by several drawbacks, including poor filler dispersion, difficulty in processing and negative effect on mechanical flexibility. Herein, we report a green and facile strategy for surface-assembling ultralow content of MXene sheets bonded onto the pore surface of SiRF via the effective foaming reaction process. The as-prepared MSiRF-0.2 composite at 0.2 wt% MXene exhibited lightweight characteristic, wide-temperature mechanical flexibility, UL94-V0 grade, limited oxygen index of > 27 %, and exceptional smoke suppression (reduction by 88.24 %). Furthermore, flame-retardant mechanism was discussed based on the char structure observation. This study provides a novel approach for fabricating mechanically flexible and flame-retardant SiRF via in-situ reactive assembly of low content MXene sheets.

Effect of alkali-treated bamboo fibers on the properties of asphalt mixture

ABSTRACT Bamboo fiber is a natural fiber that is ecologically beneficial and one of the best materials to replace lignin fiber for roads, which is still difficult to utilize properly in asphalt mixtures owing to its poor adherence, dispersion, and hydrophilicity. Previous research has discovered that alkali treatment, as an effective treatment approach, may effectively lower the hydrophilicity of plant fibers and improve their compatibility with the matrix. As a result, it is vital to investigate the effect of alkali treatment on bamboo fibers used in asphalt mixtures. The composition and microstructure of bamboo fibers treated with alkali were investigated using SEM and FTIR methods, while the adhesion between the bamboo fiber and asphalt before and after alkali treatment was tested using the fiber pull-out test. In addition, the dispersion rate of bamboo fibers in asphalt mixture was determined by developing a connection equation using the Schellenberg binder drainage test. The performance of bamboo fiber asphalt mixtures was then evaluated using rutting tests, beam bending tests, immersion Marshall tests, freeze-thaw splitting tests, and cyclic fatigue testing. The results showed that the alkali treatment successfully eliminated impurities in the outer layer of the bamboo fibers and reduced their hydrophilicity, which enhanced the asphalt-bamboo fiber interactions as well as the asphalt mixture’s water damage resistance, specifically manifested as the residual stability of ABM was enhanced by 7.8% and the splitting tensile strength of ABM was raised by 12.2%. Furthermore, the surface polarity of the bamboo fibers was reduced, which weakened the agglomeration phenomenon and increases the dispersion rate of bamboo fibers in the mixture by 9%, efficiently improving the low-temperature cracking resistance and fatigue performance of asphalt mixtures.

A machine learning approach for assessing the compressive strength of cementitious composites reinforced by graphene derivatives

The potential reinforcement effect of graphene derivatives (GDs) on cementitious composites (CCs) has attracted significant attention. Previous studies, however, have produced varied results regarding the impact of GDs on CCs. This can be attributed to differences in the properties of GDs and the fabrication details of CCs reinforced by GDs. Experiments to explore these factors are both time-consuming and cost-ineffective. Additionally, no predictive model currently exists for assessing the influence of GDs on the compressive strength of CCs. In terms of Machine Learning (ML), most existing models focus on continuous parameters, including mixture design properties of CCs and reinforcing filler content, but ignore discontinuous parameters such as dispersion technique of GDs in CCs, curing type, and type of GDs.Compiling a unique dataset, this study tailors ML models to comprehensively explore the effect of GDs inclusion on the compressive strength of CCs, considering continuous and discontinuous parameters, including GD properties, fabrication details, and mixture design properties. The most used dispersion techniques and types of GDs were divided into different categories in this study. Moreover, the dataset included cement strength grade and fineness modules to distinguish between the effect of cement types' variety and GDs. Finally, the backwards elimination technique confirmed the necessity of such a customized dataset for trustworthy predictions.Artificial neural networks (ANN), decision trees, and support vector regressors could successfully investigate the impact of GDs' inclusion on the compressive strength of CCs, with ANN demonstrating superior prediction performance. Among the GDs properties, sensitivity analysis revealed that lateral size had the highest effect. Among the fabrication conditions, the dispersion technique had the greatest effect. Considering all investigated parameters, the water-to-cement ratio was considered the most influential, followed by lateral size and curing time. A low w/c significantly reduces the strength growth rate due to poor dispersion of GDs.

Well-Dispersed Graphene Enhanced Lithium Complex Grease Toward High-Efficient Lubrication

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the influence of graphene dispersion on the thickening effect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modified graphene ([P66614][DEHP]-G). Then lithium complex grease was prepared by saponification with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefin (PAO20) as base oil and the modified-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modified-graphene lithium complex grease offered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefficient and wear volume up to 18.84% and 67.34%, respectively. With base oil overflow and afflux, well-dispersed [P66614][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition film. The synergy of deposited graphene-film, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.

In situ growth of MoS2@AuNRs nanoparticles with synergistically enhanced NIR response for controlled drug release

MoS2 nanosheets have received a lot of favor in biomedical applications due to their outstanding near-infrared (NIR) responsiveness. However, the poor aqueous dispersibility of MoS2 limits their biomedical application. In this paper, in-situ growth method was applied to integrate gold nanorods (AuNRs) with MoS2, and then MoS2 @AuNRs/HAP/PDA (denoted as MAHP) was prepared by introducing hydroxyapatite (HAP) and polydopamine (PDA) into MoS2 @AuNRs (MA) via self-assembly approach. In-situ grown MA inhibited the aggregation of MoS2 due to the insertion of AuNRs between MoS2 nanolayers. Therefore, MA revealed excellent aqueous dispersibility and synergistically enhanced NIR photothermal responsiveness (42.16% of photothermal conversion efficiency). In addition, MAHP exhibited outstanding DOX loading capacity (80%) and distinct pH-/NIR- dual responsive drug release properties, owing to the structural collapse of HAP in acidic medium and the excellent NIR responsiveness of MA. In vitro cell viability results revealed that MAHP could effectively kill MCF-7 cells under the dual effect of NIR laser irradiation and acidic medium. This paper presents a feasible process to prepare MoS2-based nanoparticles with NIR/pH dual-responsive release properties, which shows great potential in controlled photothermal therapy field.

Magnetite nanoparticles decorated on cellulose aerogel for p-nitrophenol Fenton degradation: Effects of the active phase loading, cross-linker agent and preparation method

Magnetite nanoparticles (Fe3O4 NPs) are among the most effective Fenton-Like heterogeneous catalysts for degrading environmental contaminants. However, Fe3O4 NPs aggregate easily and have poor dispersion stability because of their magnetic properties, which seriously decrease their catalytic efficiency. In this study, a novel environmentally friendly method for synthesising Fe3O4@CA was proposed. Fe3O4 NPs were immobilized on the 3D cellulose aerogels (CAs) in order to augment the degradation efficiency of p-nitrophenol (PNP) treatment and make the separation of the catalyst accessible by vacuum filtration method. Besides, CAs were fabricated from a cellulose source extracted from water hyacinth by using different cross-linking agents, such as kymene (KM) and polyvinyl alcohol–glutaraldehyde system (PVA–GA), and other drying methods, including vacuum thermal drying and freeze drying, were evaluated in the synthesis process. As-synthesized samples were analysed by various methods, including Powder X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis and Brunauer–Emmett–Teller. Then, using ultraviolet–visible spectroscopy, the difference in the degradability of PNP of the obtained material samples was also investigated to determine their potential applications. Results highlighted that the Fe3O4-3@CA-KF catalyst with an Fe3O4 loading of 0.40 g/gCA used KM as a cross-linker and the freeze-drying method demonstrated the highest PNP removal efficiency (92.5 %) in all Fe3O4@CA samples with a H2O2 content of 5 g/L. The degradation kinetics and well-fitted pseudo-first-order model were investigated. Notably, after five successive PNP degradation experiments, this catalyst retained ∼80 % of the ability to degrade PNP, indicating its outstanding reusability. In environmental remediation, this study provides valuable insights into the development of simply separated and high-efficiency catalysts for heterogeneous catalytic reactions.

Supercritical hydrothermal synthesis of copper nanoparticles: Experimental and kinetic study

Copper nanoparticles are widely used in electronics, catalysis, energy storage and other fields. But the traditional preparation technology has the defects of high cost, low yield, and poor product dispersion, which prevent industrialization and application. Supercritical hydrothermal synthesis (SCHS) technology is a green frontier technology for the preparation of nanomaterials, which can overcome the deficiencies of the existing technology and achieve industrialization. In this paper, the material system of SCHS of copper nanoparticles is optimized, and the effects of precursor, reductant, reductant dosage and PVP dosage on the particle size and morphology of the products are investigated, and the influence mechanism is analyzed. In addition, the effect of PVP dosage on the antioxidant capacity of copper nanoparticles was investigated in the context of the oxidation kinetics of copper nanoparticles. The optimal material system for the synthesis of antioxidant copper nanoparticles was finally obtained.