Search Results (2,923)

HVOF coatings based on tungsten and chromium carbides are widely used in aerospace, energy, and oil and gas industries. However, the selection between the wear resistance of WC–Co and the corrosion resistance of Cr₃C₂–NiCr is often hindered by a lack of systematic data on the effect of powder particle size. In this study, WC–12Co and Cr₃C₂–NiCr coatings were deposited onto 12Kh18N10T stainless steel substrates by HVOF spraying using three particle size fractions: <20, 20–32, and 32–40 μm. Individual spray parameters were selected for each material to ensure high-quality deposition (standoff distance 350 mm, one pass for WC–12Co; 250 mm, two passes for Cr₃C₂–NiCr). The influence of powder particle size distribution on coating properties was investigated using a comprehensive set of methods, including scanning electron microscopy, X-ray diffraction with Rietveld quantitative phase analysis, microhardness testing, tribological testing, electrochemical measurements, and numerical modeling of particle in-flight motion. It was found that the 20–32 μm fraction is optimal for both materials. Different degradation mechanisms were identified: for WC–Co, decarburization of WC with the formation of W₂C and η-phases dominates (maximum for the <20 μm fraction); for Cr₃C₂–NiCr, oxidation and carbide dissociation prevail (in the <20 μm fraction—13.7% Cr₂O₃ and 38.6% Cr₇C₃), leading to low coating thickness (~16 μm) due to loss of ductility and wettability. Numerical modeling confirmed that the high velocity of fine Cr₃C₂–NiCr particles (~680–720 m/s) does not compensate for their overheating, whereas for WC–12Co all fractions have velocities above the critical threshold, but coarse particles (32–40 μm) give porosity up to 3.15% due to insufficient deformation. Corrosion tests showed that under spraying conditions optimized for each material, the Cr₃C₂–NiCr coatings (corrosion rate 0.066–0.102 mm/year) are an order of magnitude superior in corrosion resistance to WC–12Co coatings (corrosion rate 0.353–0.651 mm/year), owing to the passivation of the γ-Ni(Cr) matrix; for WC–Co, the main protective barrier is provided by the structural density. Full article

Historical paper collections held in archives and libraries represent an irreplaceable component of cultural heritage; yet, their systematic chemical assessment is often constrained by limited measurement datasets, heterogeneous material composition, and restricted access for sampling. This paper presents an extended version of the ARTEMISA framework (Intelligent Surface Assessment), a web-based decision-support application designed to assist conservators and archivists in assessing the chemical condition and degradation dynamics of paper-based materials under real-world constraints. The framework characterises the chemical state of paper through surface pH measurement—a non-destructive, practically accessible proxy for acidity-driven cellulose degradation. Rather than aiming at deterministic lifetime prediction, ARTEMISA emphasises chemically consistent segmentation of samples into homogeneous pH regimes, followed by regime-specific statistical modelling. For long-term trend exploration, the system integrates three regression approaches: log-transformed linear, polynomial, and exponential models. For short-term time-series analysis within restricted chemical regimes, an ARIMA model is applied. Model performance was evaluated using standard statistical metrics: Mean squared error (MSE), Root mean squared error (RMSE), Mean absolute error (MAE) and the coefficient of determination (R²). The framework was applied to a case study comprising twelve book titles from the Public Library in Trenčín (Slovak Republic), published between 1959 and 2016. Results indicate that log-transformed linear and exponential regression models provide physically consistent representations of long-term pH trends, while ARIMA modelling captures short-term dynamics directly actionable for conservation planning. Exponential regression achieved R² = 0.783, linear 0.826, polynomial 0.911; however, the polynomial model produced physically implausible extrapolations and is retained for comparative purposes only. The Arrhenius principle is incorporated as an interpretative component, contextualising pH-derived degradation trends within temperature-dependent reaction kinetics. ARTEMISA offers an accessible, open-architecture tool for the prioritisation of conversation interventions under conditions of data scarity. This is applicable to broader material degradation studies with limited measurements. Full article

Developing efficient, low-resource adsorbents from solid wastes is critical for heavy-metal wastewater treatment. Here, solid-waste-based geopolymer adsorbents were prepared from ground granulated blast-furnace slag (GGBFS) and carbide slag (CS) at a CS:GGBFS mass ratio of 15:85, with 0–30 wt% rice husk biochar (BC) as a functional modifier. The effects of pH, contact time, adsorbent dosage, and initial Cu²⁺ concentration on adsorption were evaluated. The BC-2% adsorbent achieved a maximum adsorption capacity of 208.85 mg/g at pH 4, an adsorbent dosage of 1 g/L, and an initial Cu²⁺ concentration of 300 mg/L, 48.65% higher than the BC-free control; equilibrium was reached within approximately 80 min. Low BC contents (≤5 wt%) improved adsorption capacity and initial adsorption rate, whereas excessive BC (≥10 wt%) reduced performance. Kinetic and isotherm analyses revealed that Cu²⁺ uptake followed pseudo-first-order behavior and was better described by the Langmuir and Dubinin–Radushkevich models, indicating a physically dominated process controlled by finite surface sites, pore filling, and multiple mass-transfer steps. Brunauer–Emmett–Teller (BET) and Fourier transform infrared spectroscopy (FTIR) analyses showed that low BC addition increased the specific surface area and enriched hydroxyl and amino groups, thereby improving site accessibility and surface affinity, whereas high BC contents weakened these structural and interfacial advantages. This study offers a practical route for converting industrial and agricultural wastes into low-cost Cu²⁺ adsorbents. Full article

Benzophenone-3 (BP-3), an organic UV filter extensively applied in sunscreens, cosmetics and daily plastic products, is classified as a typical emerging endocrine-disrupting micropollutant. This compound is highly susceptible to bioaccumulation in aquatic organisms, triggers coral bleaching, and incurs oxidative damage to algae, fish and invertebrates. Conventional wastewater treatment processes cannot efficiently eliminate BP-3 from aqueous media, thereby imposing severe ecological risks on freshwater and marine ecosystems. In this study, iron-impregnated biochar (Fe-BC) was synthesized via an impregnation–pyrolysis route using powder of cultivated Chlorella pyrenoidosa (green microalga) as raw feedstock. Batch adsorption experiments revealed that iron impregnation remarkably enhanced the removal efficiency of BP-3. The maximum Langmuir saturated adsorption capacity of Fe-BC reached 91.7 mg/g, considerably exceeding the value of 51.5 mg/g for pristine biochar. Kinetic data exhibited favorable fitting with the pseudo-first-order kinetic model, demonstrating that Fe-BC rapidly captures BP-3 and achieves adsorption equilibrium within 120 min. Solution pH exerted a prominent influence on adsorption performance: the material maintained high BP-3 adsorption capacity at pH 7–10, whereas adsorption capacity declined drastically under strongly acidic (pH < 5) and extreme alkaline conditions (pH > 10.5). Fourier-transform infrared spectroscopy (FTIR) validated the successful loading of iron species onto the biochar surface, as well as the binding of BP-3 onto Fe-BC. Combined with pH-controlled experimental results, hydrogen bonding, hydrophobic interactions, and pore-filling effects are inferred as the dominant adsorption mechanisms for BP-3 removal. Furthermore, Fe-BC retained favorable BP-3 removal performance in simulated seawater matrices, endowing it with preliminary potential for wastewater treatment in coastal zones and tourist scenic areas. This work offers basic laboratory insights into BP-3 adsorption, while further verification concerning environmental low-concentration conditions, authentic water matrices, material reusability and stability is essential for its practical application. Full article

The aim of this study was to investigate the effect of PEG functionalization of hydrothermal carbon (HTC) on quercetin adsorption and desorption kinetics and, through that, evaluate the potential of functionalized HTC as a carrier for quercetin. Hydrothermal carbon (HTC) was synthesized using fructose as a precursor at a temperature of 160 °C. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy (SEM) confirmed an amorphous carbon structure and microspherical particles with an average size of 5.6 µm. X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FT-IR) spectroscopy characterization revealed a surface enriched with hydroxyl and carboxyl groups, which facilitated successful PEG modification. Surface modification was further corroborated by a zeta potential shift from –26.4 mV to –16.4 mV. Cytotoxicity assays in MRC-5 and HeLa cell lines confirmed high biocompatibility, with cell viability remaining above 70%. Quercetin binding experiments showed that PEG functionalization increased binding capacity up to 14%, reaching 19.50 mg/g for PEG-functionalized fructose-derived carbon. Desorption kinetics followed a pseudo-second-order model, with the PEG-modified sample exhibiting significantly slower rates than the unmodified sample. These findings indicate that PEG functionalization can improve the adsorption/desorption properties of HTC compared with the pristine material, highlighting its potential as a promising, environmentally friendly, and efficient delivery system for quercetin. Full article

Biosurfactants are environmentally friendly surface-active compounds with promising applications in environmental remediation. In this study, a biosurfactant-producing bacterium, Bacillus (B.) velezensis SHB.28, was isolated from heavy metal-contaminated soil and evaluated for its ability to produce biosurfactants using date syrup as a low-cost agro-industrial substrate. Screening assays including drop-collapse (DC), oil spreading (OS), and emulsification index after 24 h E₂₄ (%) confirmed strong biosurfactant production. Culture conditions were optimized, revealing that 30 °C, pH 6, and a C/N ratio between 10% and 20% provided optimal production. Under optimized conditions, the crude biosurfactant extract yield reached 2.16 g/L within 24 h, accompanied by a reduction in surface tension from 69 to 29.1 dyn/cm and high emulsification activity. Kinetic modeling showed that emulsification activity followed an exponential growth model (R² = 0.985), whereas surface tension dynamics were well described by a spike decay–plateau model (R² = 0.998). Structural characterization using Fourier-transform infrared spectroscopy (FTIR), electrospray ionization–mass spectrometry (ESI–MS), and nuclear magnetic resonance (NMR) spectroscopy revealed that the biosurfactants are surfactin- and iturin-like cyclic lipopeptides composed of a β-hydroxy fatty acid chain (C₁₃–C₁₅) linked to a cyclic peptide moiety. The biosurfactant exhibited a critical micelle concentration of 100 mg/L and an anionic character with a pH_pzc of 5.7. Furthermore, it demonstrated high efficiency in removing heavy metals, achieving removal efficiencies of 99.88% for Fe²⁺, 99.69% for Pb²⁺, and 94.72% for Cu²⁺, outperforming conventional surfactants such as SDS and Tween 80. These findings highlight the potential of date syrup-derived surfactin and iturin from B. velezensis SHB.28 as sustainable and efficient biosurfactants for environmental remediation and heavy metal removal applications. Full article

A magnetite–eggshell nanocomposite (Fe₃O₄@eggshell NC) was synthesized by green coprecipitation and evaluated for Cr(VI) removal from water. Passiflora ligularis peel extract, evaluated using a 2³ factorial design, served as the biogenic medium, while eggshell waste acted as the support. Characterization included X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM and TEM), Brunauer–Emmett–Teller (BET) analysis, zeta potential measurements, thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. The NC preserved Fe₃O₄ and CaCO₃ crystalline phases, contained nanoparticles averaging 18 nm, and exhibited oxygenated surface functionalities, a BET surface area of 134.93 m²/g, amphoteric behavior, and a predominantly superparamagnetic response suitable for magnetic recovery. Under conditions of pH 4, 180 rpm, 60 min, 0.15 g NC, and 50 mg/L Cr(VI), removal reached 75.98%. Kinetic data followed the pseudo-first-order model, whereas equilibrium data were well described by the Sips isotherm, with an estimated capacity of 50.81 mg/g. At the investigated initial concentration of 50 mg/L, adsorption was exothermic and favored at temperatures up to 308 K, and the material retained moderate reusability during the first three alkaline-regeneration cycles. Overall, Fe₃O₄@eggshell NC is a waste-derived, magnetically recoverable adsorbent with favorable Cr(VI) uptake under moderately acidic conditions. Full article

The pyranoside-into-furanoside (PIF) rearrangement is an uncommon but important process in carbohydrate chemistry. The quantum chemical investigation of the driving force of the recently discovered TfOH-catalyzed ring contraction revealed that it stemmed from the π–π interactions of the phenyl rings in benzoyl-protecting groups. In this study, we focused on the kinetic aspects, which included preliminary 2-O-benzoyl group rotation followed by the protonation of the endo-cyclic O5 atom. Using a combination of DFT and DLPNO-CCSDT methods, we found that in some cases, DFT may not produce adequate energies at the rate-limiting stage of the pyranoside ring opening, presumably due to inadequate modeling of Van der Waals interactions. Predicted rate constants for the PIF rearrangement of the β-O-methyl and β-S-ethyl galactosides were in agreement with NMR kinetic experiments, as the latter reacts significantly slower. The estimated constant for the β-O-phenyl galactoside supports its inability to undergo ring contraction and suggests temperatures of over 400 K for such transformation. The proposed mechanism was additionally confirmed by substituting the triflic acid with the much weaker trifluoroacetic one, which led to a drastic decrease of the reaction rate both in computations and in the experiment. Full article

This structured critical narrative review evaluates the bacterial transformation of six selected organophosphate pesticides—chlorpyrifos, methyl parathion, parathion, diazinon, malathion, and phosalone—in relation to chemical, mechanistic, and environmental evidence. Peer-reviewed literature was searched in Scopus and PubMed for the period from 1 January 2020 to 26 August 2026 and was supplemented by backward-reference screening and forward citation tracking of foundational studies. Evidence was assessed across eight domains spanning association, tolerance, controlled dissipation, product-resolved transformation, mechanistic attribution, non-sterile-soil validation, detoxification or ecological recovery, and field readiness. The selected compounds reveal substantial differences in pathway resolution: chlorpyrifos has the most developed parent–product evidence base, methyl parathion and parathion are comparatively well characterized at the hydrolytic and enzyme levels, diazinon and malathion retain important downstream uncertainties, and phosalone remains an unresolved evidence-gap comparator. The synthesis shows that credible soil bioremediation requires convergence among parent–product kinetics, catalytic attribution, transformation-product turnover, performance beyond natural attenuation, toxicity reduction, and recovery of relevant soil or plant functions. Full article

Photocatalytic CO₂ reduction to CH₄ with H₂O is hindered by rapid charge recombination and sluggish multielectron/proton-coupled hydrogenation kinetics. Herein, we show that Mn doping induces charge-carrier redistribution within Co₃O₄, thereby enhancing CO₂ photoreduction to CH₄ under sacrificial-agent-free conditions. The optimized Mn5–Co₃O₄ achieves CH₄ and CO production rates of 16.9 and 9.8 μmol g⁻¹ h⁻¹, respectively, with its CH₄ production rate reaching 10.6 times that of pristine Co₃O₄. Mechanistic investigations indicate that Mn doping modulates carrier dynamics and surface-intermediate hydrogenation. Photoelectrochemical and photoluminescence measurements demonstrate that Mn incorporation promotes charge-carrier separation, with Mn5–Co₃O₄ exhibiting the most favorable separation efficiency, as reflected in an extended average photoluminescence lifetime of 23.17 ns compared with 9.95 ns for pristine Co₃O₄. In situ irradiated X-ray photoelectron spectroscopy shows shifts of the Mn and Co signals toward lower and higher binding energies, respectively, indicating electron enrichment at Mn sites and hole accumulation at Co sites. In situ Fourier-transform infrared spectroscopy further reveals enhanced bands tentatively assigned to *COOH, *CHO, and *CH₃O intermediates, supporting their progressive hydrogenation toward CH₄. These findings provide a mechanistic framework for coordinating charge redistribution with surface hydrogenation during multielectron/proton-coupled CO₂ conversion with H₂O. Full article

Background: In this study, two cocrystals of diclofenac acid (DCA) with the coformers theophylline (THEO) and isonicotinamide (ISNT) were prepared. Subsequently, nanococrystals were generated from these cocrystals using a top-down wet media milling approach. Methods: Critical process parameters such as milling time, milling volume, drug loading percentage, bead volume, and dispersion media were optimized to achieve the desired particle size distribution. The nanococrystals were characterized using dynamic light scattering (DLS), polarized light microscopy (PLM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results: In vitro dissolution studies revealed that nanococrystals of DCA-ISNT (DE_0–120 = 22.5% at pH 1.2 and DE_0–120 = 58.7% at pH 4.5) and DCA-THEO (DE_0–120 = 18.5% at pH 1.2 and DE_0–120 = 48.2% at pH 4.5) exhibited superior dissolution performance compared to DCA nanocrystals (DE_0–120 = 12.5% at pH 1.2 and DE_0–120 = 39.0% at pH 4.5), with the dissolution advantage decreasing as the pH of the medium increased. The improved dissolution behaviour was a complex interplay of factors including particle size distribution, surface wetting kinetics, exposure of hydrophilic/hydrophobic functional groups during dissolution, nanococrystal microenvironmental pH, DCA’s ionization behaviour, lattice energy, and intermolecular interaction strengths. Additionally, nanococrystals exhibited a significantly higher flux rate in simultaneous gastric transfer dissolution and flux studies compared with DCA, likely due to higher apparent solubility and superior diffusion through the unstirred water layer (UWL). Pharmacokinetic studies confirmed that nanococrystals DCA-ISNT NCC (AUC_0–∞ = 3062.65 ± 526.91 ng/mL·h) outperformed DCA nanocrystals (AUC_0–∞ = 2352.53 ± 537.78 ng/mL·h), DCA-THEO NCC (AUC_0–∞ = 2222.96 ± 151.19 ng/mL·h) and the cocrystals in terms of pharmacokinetic performance. Conclusions: The findings indicate that DCA-ISNT NCC exhibited superior pharmacokinetic performance and, together with the enhanced dissolution and flux properties of the nanococrystals, demonstrates their potential for enhanced therapeutic efficacy. Full article

Transforming agricultural residues into functional porous materials provides a sustainable strategy for wastewater remediation. Herein, cellulose was separated from cotton stalks via formic acid-assisted hemicellulose extraction and sodium chlorite delignification, and then sulfuric acid hydrolysis. Chitosan-assisted hydrothermally treated cellulose (CC) was prepared via hydrothermal treatment in the presence of chitosan. Anisotropic CC/chitosan composite aerogels were prepared via glutaraldehyde crosslinking and unidirectional freeze-drying. The hydrophilic CC/CS aerogel exhibited an oriented porous structure, a low density of 0.03 g cm⁻³, and a porosity of 85.33%. For Congo red (CR) adsorption, the equilibrium data were described well by the pseudo-second-order kinetic and Langmuir isotherm models, with a calculated maximum adsorption capacity of 483.09 mg g⁻¹. Electrostatic attraction, hydrogen bonding, and pore-mediated retention jointly contributed to CR uptake. To realize oil–water separation, methyltrimethoxysilane (MTMS) vapor modification was applied to prepare hydrophobic aerogel (M-CC/CS). M-CC/CS presented an initial water contact angle (WCA) of around 134°, and the WCA remained above 115° after 600 s of water droplet exposure. The aerogel showed absorption capacities of 16.22–40.13 g g⁻¹ toward various oils and organic solvents. Under gravity, M-CC/CS separated immiscible oil/water mixtures at a flux of 565.47 L m⁻² h⁻¹ and several water-in-oil (W/O) emulsions with efficiencies above 99.9% while maintaining high separation efficiency over 10 cycles. This work demonstrates a cotton-stalk-derived aerogel platform whose hydrophilic and hydrophobically modified forms can be used for dye adsorption and oily water treatment, respectively. Full article

Zn₂SnO₄ is a promising anode for lithium-ion batteries owing to its high theoretical capacity, yet its practical utilization is severely limited by sluggish reaction kinetics, large volume expansion, and unstable electrode/electrolyte interfaces. Here, we introduce a dimensionality-reduction strategy that simultaneously boosts capacity and cycling stability. Through surfactant-directed crystal growth, acid-etching reconstruction, and hydrothermal carbon coating, compact Zn₂SnO₄ octahedra are controllably transformed into sheet-assembled structures and finally into a core–shell composite with a continuous carbon layer (C@M-Zn₂SnO₄ (H⁺)). The continuous structural evolution shortens Li⁺ diffusion paths, buffers mechanical stress, and stabilizes the solid–electrolyte interface without altering the intrinsic lithium-storage mechanism of Zn₂SnO₄. As a result, the optimized C@M-Zn₂SnO₄ (H⁺) electrode delivers a reversible capacity of 650 mAh g⁻¹ after activation and retains 620 mAh g⁻¹ after 600 cycles at 200 mA g⁻¹, with Coulombic efficiency approaching 100% throughout. This work demonstrates that dimensionality-reduction-assisted structural engineering is an effective strategy for developing high-capacity, long-cycle-life anode materials. Full article

Water-based perovskite solar cells (W-PSCs) provide a promising route toward reducing the use of hazardous organic solvents during perovskite fabrication. However, their development remains limited by sluggish precursor conversion, incomplete phase transformation, and poor control over film morphology. This review summarizes recent progress in W-PSCs, with particular emphasis on aqueous lead precursors and the subsequent conversion from precursor films to perovskite absorbers. The selection criteria for aqueous lead sources are first discussed in terms of water solubility, anion-Pb²⁺ interactions, precursor-solution stability, and ion-exchange behavior. Thermodynamic and kinetic considerations, including nucleation, crystal growth, reaction–diffusion coupling, and ion transport, are then discussed to provide a framework for understanding the conversion of aqueous precursor films into perovskites. Strategies for improving film formation are further classified into precursor-film and substrate engineering, conversion-process regulation, and ionic/compositional engineering. Particular attention is given to the role of precursor-film microstructure in regulating organic ammonium salt transport and conversion completeness. The photovoltaic performance of regular and inverted W-PSCs is subsequently compared, and the possible origins of their performance differences are discussed from the perspectives of precursor-film formation, perovskite conversion, film morphology, and interfacial properties. Finally, future opportunities in substrate-interface regulation, scalable aqueous processing, precursor and additive design, and life-cycle assessment are outlined. This review provides a reaction-diffusion-based perspective for understanding and improving water-based perovskite photovoltaics. Full article

For nearly a century, flotation kinetics has relied on deterministic first-order rate equations treating the cell as a homogeneous reactor, a paradigm that faces significant limitations for heterogeneous ores, especially coal, whose organic macerals, porosity, and oxidation susceptibility defy a single rate constant. While more advanced distributed-k, mixed-order, and population-balance models can account for certain types of particle heterogeneity (e.g., size or liberation), they still assume that the floatability distribution remains invariant during flotation, an assumption that fails when surface chemistry evolves concurrently with the separation process. Breaking from chronological cataloguing, this review proposes a three-dimensional taxonomy based on physical scale, inherent material heterogeneity, and epistemic certainty. We demonstrate that critical industrial prediction failures arise from structural mismatches between model physics and particle surface chemistry, notably time-dependent oxidation deactivation and selective maceral recovery. Six fundamental failure modes are identified, from neglected time-dependence of rate constants to the absence of a thermodynamic deactivation term, corroborated by experimental evidence from coal and base-metal flotation. Advanced microfluidic, automated mineralogical, surface-sensitive spectromicroscopic, CFD-DEM, and physics-informed machine learning tools are dismantling the black box of the flotation rate constant “k”. We introduce the Distributed Reactive Surface Kinetics (DRSK) framework, which embeds particle-scale heterogeneity into a population balance via an adaptive surface-sensitive selection function and treats kinetic uncertainty through stochastic differential equations. A comprehensive comparison table facilitates the transition from conventional models to the DRSK paradigm. We conclude with a roadmap for flotation kinetics 4.0, where digital twins, real-time froth analytics, and self-calibrating hybrid models transform this empirical discipline into a truly predictive engineering science. Quantitative validation against published coal and copper flotation data demonstrates that DRSK reduces prediction error by 60%–75% compared to conventional first-order and distributed-k models, while providing probabilistic uncertainty bounds essential for risk-based decision-making. The framework is elaborated for coal and conventional minerals, underscoring why coal demands its own dedicated kinetic theory and how these lessons can revolutionize the processing of increasingly complex, low-grade ores and secondary resources. Full article