Search Results (8,440)

Chrysocolla, a hydrated copper silicate mineral, is notoriously difficult to recover by conventional froth flotation due to its microporous structure, low hydrophobicity, impurity substitutions, and poor response to traditional collectors. This study evaluates the performance and adsorption mechanism of benzohydroxamic acid (BHA) as a collector for chrysocolla flotation under varying pH conditions and collector dosages. Microflotation results showed that chrysocolla recovery increased with BHA concentration, with enhanced flotation occurring at alkaline pH (8–10), consistent with BHA dissociation behavior. Zeta potential measurements indicated selective adsorption of BHA on the chrysocolla surface, while quartz showed minimal interaction, confirming collector selectivity. X-ray photoelectron spectroscopy (XPS) revealed that BHA was chemisorbed through Cu–hydroxamate complex formation. Bench-scale flotation tests on a chrysocolla ore containing 3.7% Cu produced a concentrate grading 26.7% Cu with 35.3% recovery after initial sulfide flotation. Kinetic tests indicated rapid recovery of more floatable copper phases, while scanning electron microscopy (SEM) showed preferential flotation of finer particles. Overall, the results demonstrate that BHA can effectively promote chrysocolla flotation through selective chemisorption, although high collector dosages are required due to the mineral’s high specific surface area and structural complexity. Full article

In powder-based additive manufacturing (AM), thermal exposure during processing can modify powder surface chemistry and promote oxide growth, even under inert atmospheres from residual oxygen contamination. This study investigates the effect of thermal oxidation on the surface chemistry and triboelectric charging behavior of three AM metal alloy powders: AlSi10Mg, 316L stainless steel (SS 316L), and Ti6Al4V. The work examines the evolution of the oxide layer during baking at 100 and 300 °C using triboelectric charging corroborated by X-ray photoelectron spectroscopy (XPS), diffuse-reflectance spectroscopy, and work-function measurements. The results show that heating modifies the surface oxide state of all powders, with changes dependent on the alloy composition and baking temperature. For AlSi10Mg, heating modified the Al₂O₃-rich surface oxide, with changes consistent with increased oxide ordering and γ-Al₂O₃-like characteristics, with the work function increasing from 4.34 ± 0.01 eV in the as-received (AR) condition to 4.92 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.91 to 1.38. For SS 316L, transformation of Cr(OH)₃ to Cr₂O₃ reduced triboelectric charge accumulation, while the oxygen concentration increased from 49.92 to 54.87 at.% and the work function decreased from 5.74 ± 0.02 to 5.28 ± 0.04 eV after baking at 300 °C. This reflected a drop in the $n$-exponent from 0.82 for AR to 0.73 at 300 °C. For Ti6Al4V, charging variations were associated with titanium oxide evolution and surface modifications consistent with rutile-related titanium oxide characteristics, with the work function increasing from 5.33 ± 0.01 to 5.44 ± 0.03 eV after baking at 300 °C. The corresponding triboelectric $n$-exponent increased from 0.49 to 0.52. Overall, triboelectric charging is a sensitive approach for detecting thermally driven surface oxide modifications in additive manufacturing powders. Full article

In this study, a simple, cost-effective, and eco-friendly approach was developed for the synthesis of AgNPs using white (Muscat Ottonel, WGPE) and red (Cabernet Sauvignon, RGPE) grape pomace extracts. The AgNPs were characterized by SEM, AFM, DLS, UV–Vis, FTIR, and XPS techniques. Their formation was initially indicated by a color change from colorless to dark brown and confirmed by the appearance of an SPR peak at 445 nm. The AgNPs are predominantly spherical with varied sizes. FTIR and XPS analyses indicated the presence of oxygen- and nitrogen-containing functional groups on the nanoparticle surface, suggesting their involvement in the reduction of Ag⁺ ions and the stabilization of the synthesized AgNPs. The biological activity of AgNPs was assessed through wheat (Triticum aestivum L.) seed priming experiments. Treatment with 25 mg/L AgNPs (WGPE) significantly enhanced seedling growth and chlorophyll content, whereas exposure to 100 mg/L AgNPs (RGPE) induced oxidative stress and negatively affected growth parameters. Furthermore, the photocatalytic activity of both AgNPs was evaluated against MB degradation under visible light irradiation. AgNPs (WGPE) showed superior photocatalytic efficiency, achieving up to 77% dye removal within 240 min and a constant rate nearly three times higher than that of AgNPs (RGPE). The photodegradation process was mainly driven by ^•OH radicals. Our results highlight the potential of biosynthesized AgNPs for agricultural applications and wastewater remediation. Full article

Nanostructured copper oxide (CuO) holds significant promise for optoelectronic, photocatalytic, and biomedical applications, yet its performance is critically dictated by its morphology, crystallite size, and surface chemistry. In this work, pure monoclinic CuO nanoparticles were successfully synthesized via a facile, kinetically controlled aqueous co-precipitation route using three distinct precursor salts: copper acetate (CO-Ac), copper sulfate (CO-S), and copper chloride (CO-Cl). To achieve precise architectural control, the synthesis was conducted near the thermodynamic solubility limit of the precursors combined with an abrupt NaOH injection, effectively decoupling the nucleation stage from crystal growth. Rietveld refinement of X-ray diffraction (XRD) data confirmed the structural integrity of the monoclinic lattice across all samples, χ² = 1.04 − 2.02, crystallinity 53–55%, while demonstrating that the precursor anion strongly governs the volume-averaged crystallite size, which expanded from 16 nm (CO-Ac) to 30 nm (CO-S) and 52 nm (CO-Cl). Morphological analyses revealed that acetate acts as a non-specific capping ligand, promoting isotropic, quasi-spherical nanoparticles that aggregate into high-surface-area (69.04 m²/g) “bead-chain” assemblies. Conversely, sulfate and chloride ions act as shape-directing agents via facet-selective adsorption on nucleation seeds, yielding two-dimensional plates and anisotropic acicular/needle-like architectures, respectively. X-ray photoelectron spectroscopy (XPS) and modified Auger parameter (α ~1851 eV) analyses confirmed the absolute dominance of Cu²⁺ states, with a minor fraction (~2.5 mol %) of lower-coordinated surface edge states. XPS further unveiled that the strongly alkaline environment (pH ~14) drives precursor-dependent surface chemistry: CO-Ac nanoparticles retain a clean, hydroxylated layer with minor acetate residues, whereas CO-S and CO-Cl samples develop a passive copper hydroxycarbonate (Cu₂(OH)₂CO₃) surface barrier that blocks active sites and reduces porosity. Optical properties analyzed via UV-vis diffuse reflectance revealed a pronounced, size-dependent blueshift relative to bulk CuO, with fundamental indirectly allowed bandgaps of 2.6 eV, 2.36 eV and 1.93 eV for CO-Ac, CO-S and CO-Cl samples, while the direct bandgaps shifted from 3.0 eV, 3.2 eV, and 3.57 eV for the mentioned samples. This behavior is attributed to quantum confinement governed by fine individual nanocrystals. These findings establish that precursor engineering offers a robust pathway to tailor the morphological, optical, and interfacial properties of CuO nanostructures for targeted functional devices. Full article

This study investigates the conditioning and deep dewatering of pyrite tailings slurry using a composite system comprising polyferric chloride (PFC), polydiallyldimethylammonium chloride (PDMDAAC), and fly ash as a skeleton builder. The synergistic application significantly enhanced solid–liquid separation, reducing the filter cake moisture content to 53.6% and the capillary suction time (CST) to 15.1 s. Based on settling and dewatering kinetics, the optimal dosages were established as 5 g/L PFC, 10 mL/L PDMDAAC, and 20 g/L fly ash. Characterization via SEM, XPS, and FTIR elucidated the underlying mechanisms: PDMDAAC facilitated fine particle aggregation through charge neutralization and adsorption bridging, while PFC hydrolysis products reinforced the floc architecture via hydroxyl complexation and sweep flocculation. Crucially, fly ash constructed a robust skeletal framework with efficient drainage channels within the filter cake, effectively mitigating pore clogging. This study provides a high-performance conditioning strategy facilitating the resource utilization of pyrite tailings. Full article

In our prior research (2022), a Fe₃O₄@PDA@Au@GO composite was reported as a surface-enhanced Raman scattering (SERS) substrate for phenanthrene detection, with a detection limit of 10⁻⁷ g/L. The current study is a mechanistic follow-up investigation, which aims to explore the enhancement and enrichment mechanisms of the same substrate. By integrating density functional theory (DFT) calculations, adsorption experiments, and spectroscopic analyses (Raman, FTIR, XPS) before and after adsorption, the surface enhancement mechanism of the Fe₃O₄-PDA-Au-GO composite substrate is investigated. Our findings suggest that Fe₃O₄ enables efficient magnetic separation. The polydopamine (PDA) modification layer appears to enhance the uniformity and stability of the substrate surface, which is beneficial for uniform loading of Au nanoparticles (Au NPs). Graphene oxide (GO) and PDA are found to contribute to the effective enrichment of phenanthrene. Au NPs (mostly in the metallic Au⁰ state) may provide electromagnetic enhancement through localized surface plasmon resonance, and may also contribute to chemical enhancement through possible interactions with phenanthrene. Overall, the stepwise comparison presented in this study is consistent with the proposed roles of Au and GO in enhancing the SERS performance, which collectively improve the detection sensitivity. Full article

Bismuth oxybromide (BiOBr), a layered semiconductor with good photogenerated carrier separation, is valuable for visible-light organic pollutant degradation. However, traditional hydrolysis-synthesized BiOBr has uneven particles, agglomeration, and insufficient active sites, limiting performance. This study used a microwave–hydrothermal method (adjusting time, temperature, power, pH) to prepare nanosheet-assembled BiOBr, characterized via XRD, SEM, Raman, and XPS. Under light irradiation, BiOBr primarily degrades Rhodamine B through direct oxidation by highly oxidative photogenerated holes, supplemented by the auxiliary oxidation of superoxide radicals. While maintaining a consistent catalyst loading, the optimal experimental conditions were applied (140 °C, 400 W, 10 min); 50–60 nm thick BiOBr achieved 95.4% RhB degradation (k = 0.03174 min⁻¹) in 100 min, far better than traditional BiOBr (61.16%, k = 0.00917 min⁻¹). This proves the method optimizes BiOBr performance. Full article

W-modified TiAlN coatings were developed as hydrogen permeation barrier coatings for magnetic materials. TiAlN and TiAlN-W coatings with comparable thicknesses of approximately 1.5 μm were deposited on Fe and NdFeB substrates by physical vapor deposition. GIXRD and SEM results showed that W modification was associated with a change from weakly crystalline, columnar TiAlN to a more compact, low-crystallinity W-modified Ti–Al–N coating with amorphous/nanocrystalline features inferred from the broad diffraction response. XPS analysis identified low-valence W-related species, such as W–N/Wⁿ⁺-related bonding, together with overlapping Ti 3p/W–O_x contributions and surface oxide/oxynitride species, indicating a modified surface and near-surface chemical environment. Electrochemical hydrogen permeation tests on Fe substrates showed that TiAlN reduced the steady-state current density from 2.54 ± 0.86 to 0.55 ± 0.08 μA cm⁻², corresponding to a permeation reduction factor of 4.68 ± 0.16. In contrast, TiAlN-W showed no obvious hydrogen breakthrough during the 15,000 s test period, and the current density remained below the practical detection limit of 0.01 μA cm⁻², giving a lower-bound permeation reduction factor of >250. In high-pressure H₂ exposure tests, the TiAlN-W-coated NdFeB sample remained macroscopically intact after exposure to 5 MPa H₂ at 23 °C for 24 h, whereas the uncoated and TiAlN-coated samples were pulverized. The markedly improved hydrogen permeation resistance is associated primarily with the more compact cross-sectional morphology and W-modified coating structure. Full article

This study investigated microbiologically influenced corrosion (MIC) and passive-film degradation of a Ti-15Mo-3Al-2.7Nb-0.25Si β titanium alloy exposed to Pseudomonas aeruginosa. The alloy comprised a continuous β-Ti matrix with dispersed α-Ti precipitates, and this α/β dual-phase microstructure provided a potential microstructural basis for spatial variations in passivation behavior among different microregions. During immersion, P. aeruginosa formed a heterogeneous biofilm of bacterial cells and extracellular polymeric substances, altering interfacial mass transfer, oxygen distribution, and local chemistry. Relative to the sterile control, the inoculated group showed increases in maximum pit depth from 2.4 to 4.1 μm and corrosion current density from 8.72 to 17.2 nA cm⁻², while the charge-transfer resistance decreased to 4.32 MΩ cm² after 14 d, confirming enhanced localized corrosion. Mott-Schottky and XPS analyses showed that the donor density increased from 1.07 × 10¹⁹ to 1.29 × 10¹⁹ cm⁻³ and the Ti⁴⁺ fraction decreased from 72.29% to 66.74% and the relative Ti⁰ fraction increased from 7.01% to 17.59%, reflecting increased defect accumulation within the film, impaired passive-film integrity, and reduced local protective capability. P. aeruginosa therefore increases the MIC susceptibility of this β titanium alloy by biofilm-induced interfacial microenvironmental heterogeneity. These findings support MIC assessment and integrated antifouling-anticorrosion surface design for marine β titanium alloys. Full article

Magnetic polymer nanocomposites (MPNCs) have attracted considerable attention as advanced multifunctional materials for water purification due to their high adsorption capacity, magnetic recoverability, and excellent reusability. This review presents a comprehensive overview of recent developments in the synthesis, characterization, and environmental applications of MPNCs for wastewater treatment. Particular emphasis is placed on the principal synthesis strategies, including in situ and ex situ approaches, and their influence on nanoparticle dispersion, interfacial interactions, and the physicochemical properties of the resulting nanocomposites. The review covers the most widely investigated magnetic nanomaterials, such as Fe₃O₄, γ-Fe₂O₃, CoFe₂O₄, ZnFe₂O₄, and other ferrites, incorporated into natural and synthetic polymer matrices including chitosan, cellulose, alginate, polyaniline, polypyrrole, poly(vinyl alcohol), and polystyrene. Advanced characterization techniques, including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and superconducting quantum interference device (SQUID) measurements, are discussed to evaluate the structural, chemical, thermal, and magnetic properties of these hybrid materials. The adsorption performance and underlying mechanisms of MPNCs for the removal of heavy metals, dyes, pharmaceutical compounds, organic pollutants, and oil contaminants are critically analyzed, highlighting the roles of polymer functionalization, nanocomposite architecture, and magnetic separation in enhancing treatment efficiency and reusability. In addition, the contribution of density functional theory (DFT) to understanding adsorption mechanisms and guiding the rational design of high-performance adsorbents is reviewed. Finally, current challenges and future perspectives, including green synthesis, multifunctional and stimuli-responsive materials, scalable manufacturing, and industrial implementation, are discussed. This review provides a comprehensive framework for the design and development of next-generation magnetic polymer nanocomposites for sustainable water remediation applications. Full article

This study proposes a process combining alkali-activated potassium feldspar, acid leaching, and sol–gel coupling with supercritical drying to prepare high-performance silica–alumina composite aerogel. The optimal parameters for potassium feldspar alkali-melt activation are a calcination temperature of 350 °C, mass ratio of potassium feldspar to sodium hydroxide of 1:1.2, and calcination time of 120 min, achieving an acid-leaching efficiency of 97.3% for the activated potassium feldspar. The acid leachate, using propylene oxide as a gelling promoter, was processed through aging, solvent exchange, and supercritical drying to yield SiO₂-Al₂O₃ aerogel with typical three-dimensional nanoporous network structure. EDS spectroscopy revealed that the spatial distributions of aluminum and silicon elements were highly coincident and uniformly dispersed. XPS and FTIR further confirmed the formation of Si-O-Al bonds, indicating that aluminum atoms were successfully incorporated into the silico-aluminate tetrahedral network, constructing silicon–aluminum composite framework. The SiO₂-Al₂O₃ aerogel exhibits specific surface area of 660.841 m²/g and a pore volume of 1.321 cm³/g. Its mass loss within the 0–1000 °C range is only 9.55%, far lower than the 28% mass loss of pure aluminum oxide aerogel, indicating that the silicon–aluminum composite structure effectively suppresses high-temperature phase transitions and framework collapse. Full article

Selective catalytic reduction (NH₃-SCR) technology is the predominant technique for industrial flue gas denitrification, with its improvement dependent on the development of highly efficient catalysts. As the most widely employed support for vanadium-based DeNO_x catalysts, TiO₂ exerts significant influences on the dispersion state of active species and the catalytic performance through its physicochemical properties. In this work, three VMoO_x@TiO₂ catalysts were prepared using three different Ti precursors. Multiple characterization techniques were employed to systematically investigate the effects of different support origins on the surface morphology, acid-base properties, and redox performance of the catalysts. The results revealed that the tetrabutyl titanate-derived support possesses the largest specific surface area and most abundant mesoporous structure, facilitating highly dispersed V and Mo species. XPS analysis demonstrated that V⁴⁺ proportion increased from 38.9% to 56.6% and Mo⁶⁺ proportion increased from 50.2% to 78.9% from Catalyst A to C, attributed to enhanced V–O–Mo bridge bond electron transfer. DFT calculations confirmed that the electron transfer driving force on Catalyst C was the largest, and the NH₃ adsorption energy at Lewis acid sites reached −102.4 kJ/mol, significantly exceeding those of Catalysts A and B. The potential energy surface analysis revealed that the rate-determining step exhibited the lowest energy barrier on Catalyst C, consistent with its superior DeNO_x activity: it reaches complete NO conversion at 350 °C and displays optimal sulfur resistance. This study integrates experimental characterization with theoretical computation to establish the structure–activity relationship between TiO₂ support properties and the DeNO_x performance of vanadium-molybdenum catalysts, providing both theoretical guidance and a scientific basis for the rational design of high-performance SCR DeNO_x catalysts. Full article

Numerous previous investigations have exploited single-component aluminum hydroxide, silica, or phosphorus-containing organic agents to improve the fire resistance of epoxy resin. Existing literature confirms that ATH relies on endothermic dehydration and inorganic barrier layers to suppress combustion, while phosphorus organics exert radical quenching effects in the gas phase. However, separate use of these fillers generally requires high loading to achieve satisfactory flame retardancy, which inevitably weakens the mechanical properties of the epoxy matrix; few studies integrate N, P, and Si elements into ATH via chemical grafting to realize synergistic flame retardancy at low filler dosage, and the dual heat-transfer regulation effect of formed SiO₂-Al₂O₃ inorganic residues has rarely been systematically discussed in prior reports. This study presents an organic–inorganic hybrid flame retardant, SPDP-PTMS@ATH, synthesized by grafting N,P,Si-containing organic groups onto Al(OH)₃. The modified ATH retained its layered structure, as confirmed by FTIR, XPS, SEM, and XRD. At only 5 wt.% loading in epoxy, the additive significantly enhanced flame retardancy and smoke suppression: LOI increased to 33.5% (34% higher than pure EP), UL-94 reached V-0 rating, and peak HRR, THR, COPR, TSR, CO2PR, and SPR are reduced by 30.2%, 30.8%, 33.1%, 26.9%, 25.86%, and 15%, respectively. Char analysis revealed a denser, more graphitized structure with fewer defects. Moreover, tensile strength and elongation at break improved by 22.0% and 47.5%, respectively. This work demonstrates that low-loading SPDP-PTMS@ATH simultaneously boosts fire safety, smoke suppression, and mechanical performance, offering a cost-effective and sustainable route to high-performance epoxy composites. Full article

In this work, we report the synthesis of a photocatalytic system based on impregnating g-C₃N₄ quantum dots (CNQDs) onto the surface of exfoliated graphitic carbon nitride (CN). The CNQDs were prepared using a top-down strategy via a hydrothermal route and then grafted onto exfoliated g-C₃N₄ under solvothermal conditions. The prepared CNQDs/CN composites were characterized using several techniques, including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and nitrogen physisorption. According to XPS analysis, a slight increase in the O 1s signal in the 1-CNQDs/CN sample could indicate a higher amount of adsorbed hydroxyl groups, which would favor the dispersion of the powder material in the aqueous medium. The photocatalytic degradation of the antibiotic levofloxacin (LEVO) was assessed using the CNQDs/CN samples, with the sample impregnated with 1 wt.% of CNQDs demonstrating the highest photocatalytic performance under UV-vis radiation conditions. Likewise, the 1-CNQDs/CN sample also exhibited the lowest photoluminescence emission (λ_exc = 315 nm), indicating that the presence of g- C₃N₄ quantum dots contributed to the decrease in the recombination rate of the photogenerated electron–hole pairs in the photoexcited graphitic carbon nitride. The stability tests revealed a modest performance reduction of 21% over three cycles. From the photocatalytic tests using scavenger agents, it was determined that hydroxyl (·OH) and superoxide (·O₂⁻) radicals are the reactive species that govern the levofloxacin photodegradation under experimental conditions. Consequently, we determined a photocatalytic mechanism consistent with the results. Full article

The scientific literature on plasma methods for modifying the surface properties of non-woven polypropylene (NWPP) fabrics is reviewed. The scientific background of the observations reported by different teams is explained, and the technological limits are highlighted. Plasma treatment usually modifies the surface layer, which is beneficial for some applications, such as grafting functional coatings onto the fibers in the surface film of NWPP fabrics. The water contact angle of NWPP fabrics treated by plasmas sustained by the classical dielectric barrier discharges at atmospheric pressure and low-pressure discharges in the range of about 10 to a few 100 Pa rarely drops below 90°, which is explained by the inability to modify fibers deep in the fabrics due to the limited penetration depth of such plasmas. The super-hydrophilic finish can be achieved either by using nanosecond-pulsed atmospheric-pressure discharges or by weakly ionized plasma with a relatively high electron temperature, sustained at a pressure of a few Pa or below. Such plasmas modify the fibers deep in the fabric, which is particularly useful for applications in respiratory masks where the fibers should be coated with ultra-thin films of virucidal substance. The energy efficiency of the latter plasmas is better because practically no gas-phase loss of reactive species occurs, and so is their scalability, making them the most suitable for modifying NWPP fabrics at an industrial scale. While most authors reported only increased wettability with increasing treatment intensity, over-treatment has been reported and is attributed to thermal effects. The range of optimal intensity has yet to be systematically quantified. Full article