Search Results (839)

2,5-bis(hydroxymethy)lfuran (BHMF), a renewable compound with extensive industrial applications, can be obtained by selective hydrogenation of the C=O group of 5-hydroxymethylfurfural (HMF), a platform molecule derived from lignocellulosic biomass. In this work, we perform kinetic modeling of the selective liquid-phase hydrogenation of HMF to BHMF over a Cu/SiO₂ catalyst prepared by precipitation–deposition (PD) at a constant pH. Physicochemical characterization, using different techniques, confirms that the Cu/SiO₂–PD catalyst is formed by copper metallic nanoparticles of 3–5 nm in size highly dispersed on the SiO₂ surface. Before the kinetic study, the Cu/SiO₂-PD catalyst was evaluated in three solvents: tetrahydrofuran (THF), 2-propanol (2-POH), and water. The pattern of catalytic activity and BHMF yield for the different solvents was THF > 2-POH > H₂O. In addition, selectivity to BHF was the highest in THF. Thus, THF was chosen for further kinetic study. Several experiments were carried out by varying the initial HMF concentration (C⁰_HMF) between 0.02 and 0.26 M and the hydrogen pressure (P_H2) between 200 and 1500 kPa. In all experiments, BHMF selectivity was 97–99%. By pseudo-homogeneous modeling, an apparent reaction order with respect to HFM close to 1 was estimated for a C⁰_HMF between 0.02 M and 0.065 M, while when higher than 0.065 M, the apparent reaction order changed to 0. The apparent reaction order with respect to H₂ was nearly 0 when C⁰_HMF = 0.13 M, while for C⁰_HMF = 0.04 M, it was close to 1. The reaction orders estimated suggest that HMF is strongly absorbed on the catalyst surface, and thus total active site coverage is reached when the C⁰_HMF is higher than 0.065 M. Several Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were proposed, tested against experimental data, and statistically compared. The best fitting of the experimental data was obtained with an LHHW model that considered non-competitive H₂ and HMF chemisorption and strong chemisorption of reactant and product molecules on copper metallic active sites. This model predicts both the catalytic performance of Cu/SiO₂-PD and its deactivation during liquid-phase HMF hydrogenation. Full article

The present study focuses on the effect of doping KH560-modified cellulose nanocrystals (CNCs) on the electro-optical characteristics of polymer-dispersed liquid crystals (PDLCs). PDLC films were fabricated through the polymerization-initiated phase separation (PIPS) process and doped with CNC nanoparticles at various concentrations. At low concentrations, the CNCs at the interface, by virtue of their unique chiral characteristics, induce an orderly arrangement of liquid crystal molecules. Meanwhile, the interaction between the film’s fiber structure and the liquid crystal droplets brings about an augmentation in the arrangement efficiency. The excellent dispersion of CNCs diminishes the random alignment of liquid crystal molecules and mitigates light scattering. Additionally, it aids in the deflection of the liquid crystal director, facilitating the lubrication of the liquid crystals’ movement. It is remarkable that within the range of relatively lower CNCs doping concentrations, specifically from 0.005 wt% to 0.05 wt%, the PDLC films exhibit lower threshold and saturation voltages, faster response, enhanced viewing angle performance and higher contrast. Full article

This study demonstrates the successful fabrication of high-performance reaction-bonded silicon carbide (RBSC) ceramics through an optimized liquid silicon infiltration (LSI) process employing multi-modal SiC particle gradation and nano-carbon black (0.6 µm) additives. By engineering porous preforms with hierarchical SiC distributions and tailored carbon sources, the resulting ceramics achieved a compressive strength of 2393 MPa and a flexural strength of 380 MPa, surpassing conventional RBSC systems. Microstructural analyses revealed homogeneous β-SiC formation and crack deflection mechanisms as key contributors to mechanical enhancement. Ultrafine SiC particles (0.5–2 µm) refined pore architectures and mediated capillary dynamics during infiltration, enabling nanoscale dispersion of residual silicon phases and minimizing interfacial defects. Compared to coarse-grained counterparts, the ultrafine SiC system exhibited a 23% increase in compressive strength, attributed to reduced sintering defects and enhanced load transfer efficiency. This work establishes a scalable strategy for designing RBSC ceramics for extreme mechanical environments, bridging material innovation with applications in high-stress structural components. Full article

Over efficient photocatalysts, CO₂ photoreduction typically converts CO₂ into low-carbon chemicals, which serve as raw materials for downstream synthesis processes. Here, an efficient composite photocatalyst heterojunction (Cu₂O-u/g-C₃N₄) has been fabricated to reduce CO₂. Graphitic carbon nitride (g-C₃N₄) was synthesized via thermal polymerization of urea at 550 °C, while pre-dispersed Cu₂O derived from urea pyrolysis (Cu₂O-u) was prepared by thermal reduction of urea and CuCl₂·2H₂O at 180 °C. The heterojunction Cu₂O-u/g-C₃N₄ was subsequently constructed through hydrothermal treatment at 180 °C. This heterojunction exhibited a bandgap of 2.10 eV, with dual optical absorption edges at 485 nm and above 800 nm, enabling efficient harvesting of solar light. Under 175 W mercury lamp irradiation, the heterojunction catalyzed liquid-phase CO₂ photoreduction to formic acid, acetic acid, and methanol. Its formic acid production activity surpassed that of pristine g-C₃N₄ by 3.14-fold and TiO₂ by 8.72-fold. Reaction media, hole scavengers, and reaction duration modulated product selectivity. In acetonitrile/isopropanol systems, formic acid and acetic acid production reached 579.4 and 582.8 μmol·h⁻¹·g_cat⁻¹. Conversely, in water/triethanolamine systems, methanol production reached 3061.6 μmol·h⁻¹·g_cat⁻¹, with 94.79% of the initial conversion retained after three cycles. Finally, this work ends with the conclusions of the CO₂ photocatalytic reduction to formic acid, acetic acid, and methanol, and recommends prospects for future research. Full article

Solid–liquid phase-change materials (PCMs) have attracted considerable attention in heat energy storage due to their appropriate phase-transition temperatures and high thermal storage density. The primary issues that need to be addressed in the wide application of traditional PCMs are easy leakage during solid–liquid phase transitions, low thermal conductivity, and poor energy conversion function. The heat transfer properties of PCMs can be improved by compounding with carbon materials. Carbon nanotubes (CNTs) are widely used in PCMs for heat storage because of their high thermal conductivity, strong electrical conductivity, and high chemical stability. This study investigates the thermal properties of 1-octadecanol (OD) modified with different diameters and amounts of CNTs using the melt blending method and the ultrasonic dispersion method. The aim is to enhance thermal conductivity while minimizing latent heat loss. The physical phase, microstructure, phase-change temperature, phase-transition enthalpy, thermal stability, and thermal conductivity of the OD/CNTs CPCMs were systematically studied using XRD, FTIR, SEM, DSC, and Hot Disk. Moreover, the heat charging and releasing performance of the OD/CNTs CPCMs was investigated through heat charging and releasing experiments, and the relationship among the composition–structure–performance of the CPCMs was established. Full article

The Scalable and Expeditious Additive Manufacturing (SEAM) process is an advanced additive manufacturing (AM) technique that relies on the optimization of metal powder suspensions to achieve high-quality 3D-printed components. This study explores the critical role of dispersants in enhancing the performance of stainless steel (SS) 420 metal powder suspensions for the SEAM process by improving powder loading, recyclability, flowability, and consequent final part density. The addition of dispersant allows for increased powder contents while preserving stable rheological properties, thereby enabling higher powder loading without compromising the rheological characteristics required in the SEAM process. Previously, our team implemented a two-step printing strategy to address the segregation issues during printing. Nonetheless, the semi-cured layer was not recyclable after printing, resulting in a significant amount of waste in the SEAM process. This, in turn, leads to a considerable increase in material costs. On the other hand, the addition of a dispersant has been shown to enhance suspension stability, enabling multiple cycles of reuse. This novel approach has been demonstrated to reduce material waste and lower production costs. The enhanced flowability guarantees uniform suspension spreading, resulting in defect-free layer deposition and superior process control. Moreover, the dispersant’s ability to impede particle agglomeration and promote powder loading contributes to the attainment of a 99.33% relative density in the final sintered SS420 parts, thereby markedly enhancing their mechanical integrity. These findings demonstrate the pivotal role of dispersants in refining the SEAM process, enabling the production of high-density, cost-effective metal components with superior material utilization and process efficiency. Full article

The widespread discharge of industrial and urban waste has led to significant increases in the environmental concentrations of numerous chemical substances. This work presents the development of a simple and environmentally friendly dispersive liquid–liquid microextraction (DLLME) method based on a hydrophobic natural deep eutectic solvent (NADES) for the determination of selected compounds from benzotriazole, benzothiazole, paraben, and UV filter families in wastewater samples. Of the twelve NADES formulations evaluated, those composed of a 4:1 molar ratio of thymol and menthol presented the highest extraction efficiencies. The influence of key experimental variables such as the pH of the aqueous sample, the ratio of NADES phase to sample volume, and the extraction time on the extraction efficiency was investigated using a multivariate optimization. Under optimal conditions, relative standard deviations below 15% and recoveries for spiked wastewater samples ranged between 82 and 108%, demonstrating the suitability of the method for routine water-quality monitoring. The sustainability and practicality of the developed method was evaluated using the assessment tools ChlorTox, AGREEprep, AGRRE, and BAGI, obtaining scores of 0.005 g in the NADES-DLLME method, 0.70, 0.52, and 72.5, respectively, demonstrating that the method is green and reliable. Full article

The analysis of wastewater is essential in environmental chemistry, particularly for monitoring emerging contaminants and assessing ecological impacts. In this context, hyphenated chromatographic techniques are widely used, with liquid chromatography being one of the most common. However, gas chromatography coupled with mass spectrometry (GC-MS) remains a valuable tool in this field due to its sensitivity, selectivity, and widespread availability in most laboratories. This review examines the application of validated methods for wastewater analysis using GC-MS (MS), highlighting its relevance in identifying micropollutants such as pharmaceuticals, drugs of abuse, pesticides, hormones, and industrial by-products. The validation of analytical methods is crucial to ensuring the reliability and reproducibility of data and the accurate monitoring of contaminants. Key parameters, including sample volume, recovery efficiency, and detection and quantification limits, are discussed, evaluating different approaches to optimising the identification of different classes of contaminants. Additionally, this study explores advances in sample preparation techniques, such as solid-phase microextraction (SPME), dispersive liquid–liquid microextraction (DLLME), and solid-phase extraction (SPE), which enhance efficiency and minimise interferences in the analysis. Finally, future perspectives are discussed, including the integration of emerging technologies such as high-resolution mass spectrometry, the miniaturisation of GC systems, and the development of faster and more sustainable analytical methods. Full article

As a persistent organic pollutant, methoxychlor has drawn considerable environmental attention. Photocatalysis, recognized for its environmentally friendly characteristics, has been widely utilized for the degradation of contaminants. In this study, the photocatalytic material BiVO₄@diatomite was successfully synthesized via the liquid-phase precipitation method. The synthesized material was comprehensively characterized using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), and a Brunauer–Emmett–Teller (BET) analysis, providing robust evidence for the material’s stability and biocompatibility. The results confirmed the successful deposition of BiVO₄ onto the diatomite surface. Furthermore, the effects of various parameters, including the initial methoxychlor concentration, pH, light exposure duration, and illumination intensity, on the photocatalytic degradation efficiency of methoxychlor by BiVO₄@diatomite were systematically investigated to optimize degradation performance. The identification of optimal reaction conditions and the proposed degradation mechanism based on experimental findings will be valuable for guiding future studies and practical applications in environmental pollution control. The integration of BiVO₄ with diatomite in this study yields a novel composite system with significantly enhanced photocatalytic degradation performance, offering fresh insights into the design of efficient, stable, and eco-friendly materials for pollutant removal. Full article

A sensitive method was developed for detecting diazepam residues in aquatic products using magnetic dispersive solid-phase extraction (MDSPE) coupled with ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). Samples extracted with 1% ammonia–acetonitrile were purified using synthesized Fe₃O₄@SiO₂-PSA nanoparticles via MDSPE before UPLC-MS/MS analysis. Separation was performed on a C₁₈ column with gradient elution using 0.1% formic acid–2 mM ammonium acetate/methanol. Detection employed positive electrospray ionization (ESI⁺) in multiple reaction monitoring (MRM) mode. Characterization confirmed Fe₃O₄@SiO₂-PSA’s mesoporous structure with excellent adsorption capacity and magnetic properties. The method showed good linearity (0.1–10 μg/L, r > 0.99) with an LOD and LOQ of 0.20 μg/kg and 0.50 μg/kg, respectively. Recoveries at 0.5–15.0 µg/kg spiking levels were 74.9–109% (RSDs 1.24–11.6%). This approach provides rapid, accurate, and high-precision analysis of diazepam in aquatic products, meeting regulatory requirements. Full article

The application of fluidized bed reactors to biomass fast pyrolysis is regarded as a promising technology for enabling high-value utilization of biomass. This work established a three-dimensional numerical model of an industrial-scale fluidized bed reactor for biomass catalytic pyrolysis, employing the multiphase particle-in-cell method (MP-PIC) and coupling catalytic pyrolysis kinetics. Primary gas flow rate and biomass–catalyst injection modes were optimized to further improve the performance of the reactor. The model received additional validation from experimental data, primarily to ensure prediction accuracy. The results revealed that an optimal primary gas flow rate of 4 kg/s achieved a peak catalytic efficiency of 71.3%. Using maximum high-quality liquid fuels and adopting a relatively dispersed inlet mode with opposite jetting for biomass and catalyst promoted uniform particle distribution and thermal homogeneity in the dense phase zone, further increasing the catalytic efficiency to 75.6%. With the integration of the multiphase particle-in-cell (MP-PIC) method with catalytic pyrolysis kinetics at the industrial-scale, this work could provide theoretical guidance for designing fluidized bed catalytic pyrolysis reactors and optimizing biomass catalytic pyrolysis processes. Full article

In high-pressure thermal power systems, corrosion-induced wall thinning in steam pipelines poses a significant threat to operational safety and efficiency. This study investigates the effects of gas–liquid two-phase flow on corrosion-induced wall thinning in pipe bends of high-pressure heaters in power plants, with particular emphasis on the mechanisms of void fraction and inner wall surface roughness. Research reveals that an increased void fraction significantly enhances flow turbulence and centrifugal effects, resulting in elevated pressure and Discrete Phase Model (DPM) concentration at the bend, thereby intensifying erosion phenomena. Simultaneously, the turbulence generated by bubble collapse at the bend promotes the accumulation and detachment of corrosion products, maintaining a cyclic process of erosion and corrosion that accelerates wall thinning. Furthermore, the increased surface roughness of the inner bend wall exacerbates the corrosion process. The rough surface alters local flow characteristics, leading to changes in pressure distribution and DPM concentration accumulation points, subsequently accelerating corrosion progression. Energy-Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) analyses reveal changes in the chemical composition and microstructural characteristics of corrosion products. The results indicate that the porous structure of oxide films fails to effectively protect against corrosive media, while bubble impact forces damage the oxide films, exposing fresh metal surfaces and further accelerating the corrosion process. Comprehensive analysis demonstrates that the interaction between void fraction and surface roughness significantly intensifies wall thinning, particularly under conditions of high void fraction and high roughness, where pressure and DPM concentration at the bend may reach extreme values, further increasing corrosion risk. Therefore, optimization of void fraction and surface roughness, along with the application of corrosion-resistant materials and surface treatment technologies, should be considered in pipeline design and operation to mitigate corrosion risks. Full article

Broad lateral size and thickness distributions impede the application of hexagonal boron nitride nanosheets (BNNSs) as friction modifiers in base oil, although they possess remarkable potential for lubrication performance promotion. In this work, a cascade centrifugation-assisted liquid-phase exfoliation approach was presented to prepare BNNSs from hexagonal boron nitride (h-BN) efficiently and scalably. Subsequently, they were ultrasonically dispersed into gas-to-liquid (GTL) base oil, and their lubrication performance promotion was evaluated by a four-ball tribotester. Tribological tests demonstrated that BNNS possesses excellent friction-reducing and anti-wear properties in GTL. Furthermore, the findings indicate that at a BNNS content of 0.8 wt.%, the system displayed the lowest COF and WSD. Particularly, with an addition of 0.8 wt.% BNNS into GTL, the AFC and WSD are reduced significantly by 40.1% and 35.4% compared to pure base oil, respectively, and the surface roughness, wear depth, and wear volume were effectively reduced by 91.0%, 68.5%, and 76.8% compared to GTL base oil, respectively. Raman, SEM-EDS, and XPS results proved that the outstanding friction-reducing and anti-wear properties of BNNS can mainly be ascribed to the presence of physical adsorption film and tribo-chemical film, which were composed of FeOOH, FeO, Fe₃O₄, and B₂O₃. Full article

This study investigated the solid-state reduction characteristics of natural chromite ore and the effect of iron powder on the solid-state reduction characteristics of natural chromite ore under isothermal conditions below 1200 °C. The enhancement mechanism of iron powder on the solid-state reduction of natural chromite ore was revealed using optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS). The iron metallization rate of chromite ore exhibited a trend of increasing first and then decreasing with the addition of iron powder, and the optimal iron powder addition was determined to be 30%. The multi-step reaction gradually transforms into a single-step reaction with the increase in the dosage of iron powder. Iron powder facilitates the generation of a low-melting Fe-C alloy liquid phase and accelerates the speed of the solid-state reduction reaction of chromite ore and the disintegration of chromite spinel particles. When the iron powder dosage exceeds 30%, most of the multi-step reduction reaction of chromite ore is transformed into the single-step reduction reaction, which reduces the disintegration of chromite spinel particles and weakens the enhancement effect of iron powder on the solid-state reduction of chromite ore. Full article

In this study, graphene production via liquid-phase exfoliation assisted by sonication was evaluated using deionized water as a solvent and two graphite sources: one recovered from spent lithium-ion batteries (LIBs) and a commercial counterpart. A 750 W, 20 kHz ultrasonic processor was used, with sonication amplitudes ranging from 50% to 80% for two hours while maintaining a constant temperature of 45 °C. The resulting dispersions were left undisturbed for 24 h at ambient temperature to allow natural phase separation between decanted and dispersed fractions. These fractions were subsequently dried and weighed to determine exfoliation yield. High-quality graphene was successfully obtained via direct liquid-phase exfoliation of graphite recovered from LIBs, assisted by sonication in deionized water. Graphene formation was confirmed in both suspended and decanted fractions after two hours of sonication at 80% amplitude through complementary characterization techniques, including UV-Vis, Raman spectroscopy, HRTEM, and XRD. Comparative experiments using thermally pretreated battery graphite and commercial graphite revealed that graphene dispersions derived from untreated LIB-derived graphite exhibited greater long-term stability than those obtained from commercial or thermally pretreated battery graphite before sonication. Full article