Search Results (979)

The occurrence of pharmaceutical residues in aquatic environments has become an important environmental challenge, encouraging the development of sustainable and low-cost treatment technologies. In this study, eggshell waste in the form of eggshell without membrane (ES) and eggshell with membrane (ESM) was investigated as a biosorbent for the removal of levomepromazine from aqueous solutions. The materials were characterized by XRD, FTIR, SEM–EDS, TGA, and pH_PZC analyses, confirming the predominance of calcite and the presence of functional groups potentially involved in adsorption. Batch adsorption experiments were conducted to evaluate the effects of pH, adsorbent dosage, contact time, initial levomepromazine concentration, and temperature. The adsorption capacity increased with increasing pH, reaching optimum performance under alkaline conditions, while equilibrium was attained within approximately 60 min. Kinetic data were best described by the pseudo-second-order model (R² > 0.99). Equilibrium studies showed that the Freundlich model provided the best fit to the experimental data, suggesting adsorption on heterogeneous surfaces. Regeneration experiments demonstrated that both adsorbents retained a substantial fraction of their adsorption performance after five adsorption–desorption cycles. FTIR analyses after adsorption and pH_PZC measurements suggest that electrostatic interactions and hydrogen bonding may contribute to levomepromazine uptake. Response surface methodology identified adsorbent dosage and initial concentration as the most influential operating parameters. Overall, the results demonstrate the potential of eggshell-derived materials as low-cost biosorbents for levomepromazine removal from aqueous media. Full article

Electrospun composite nanofibers represent an emerging strategy for the development of efficient fertilizer systems, as they enable modulation of the structural properties of the nanofibrous network and, consequently, the transport and release processes of nutrients. In this study, polyvinyl alcohol (PVA) nanofibers loaded with two different urea contents (0.09 g and 0.36 g) were fabricated and characterized to investigate how urea incorporation modifies the nanofiber morphology and influences urea release kinetics. SEM and EDS analyses confirmed that increasing urea content promotes surface roughnes and reduced nanofiber diameters, whereas XRD and FTIR demonstrated a decrease in crystallinity and the formation of hydrogen-bonded interactions between PVA chains and urea molecules, indicating that urea is incorporated within the PVA network rather than being superficially adsorbed on the nanofiber surface. These structural changes govern water retention and release kinetics: the 0.36 g formulation exhibited a 100-h induction period followed by multiphase diffusion, while the 0.09 g system displayed immediate release but lower final concentrations. Kinetic modeling revealed excellent fitting to the Higuchi and second-order models, confirming diffusion-controlled urea release modulated by internal interactions. The nanofiber network thus behaves as an active regulator of nitrogen mobility, overcoming the limitations of conventional coating-based fertilizers. These findings demonstrate the potential of PVA/urea nanofibers as scalable platforms for sustainable nitrogen delivery in agriculture, bridging morphology-driven polymer design with environmental performance. Full article

The long-term stability of biodegradable polymer coatings deposited by matrix-assisted pulsed laser evaporation (MAPLE) remains insufficiently understood, particularly under ultraviolet irradiation conditions where photochemical effects may accompany material transfer. In this work, thin films of poly(lactide-co-caprolactone)-block-poly(ethyleneglycol)-block-poly(lactide-co-caprolactone), also known as PLCL-PEG-PLCL, are deposited from chloroform solutions by UV-MAPLE using a nanosecond Nd:YAG laser operating at 266 nm over a wide laser fluence range (0.25–0.9 J/cm²). The effect of laser fluence on the morphological, structural, and chemical evolution of the coatings is investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), focused ion beam scanning electron microscopy (FIB-SEM), and X-ray diffraction (XRD). At low laser fluence, relatively homogeneous coatings are obtained while largely preserving the characteristic functional groups of the triblock copolymer. Increasing the laser fluence progressively induces surface restructuring phenomena, including droplets, wrinkles, and the appearance of highly symmetric faceted structures. These entities develop preferentially in samples deposited at elevated fluence and frequently appear only after prolonged aging under ambient conditions, revealing delayed recrystallization behaviour associated with metastable species generated during the deposition process. EDS analyses reveal localized chlorine enrichment within the faceted structures, while FIB-SEM investigations show porous internal morphologies. XRD confirms that the polymer matrix remains predominantly amorphous. The combined observations suggest that UV-MAPLE deposition from chloroform involves not only physical material transfer but also photochemical processes that promote decomposition, recombination, and delayed crystallization phenomena. A phenomenological model describing the successive stages of surface evolution, aging, and recrystallization is proposed. These results provide new insight into the long-term evolution of laser-deposited biodegradable polymer coatings and highlight the importance of solvent selection and processing conditions in determining their stability. Full article

Road dust is an important urban reservoir of potentially toxic elements (PTEs) and a relevant source of human exposure through resuspension and inhalation, particularly in large megacities. This study provides an integrated assessment of the seasonal variability, contamination levels, source identification, particle characteristics, lung bioaccessibility, and health risk of road dust in Mexico City, one of the world’s largest urban centers. A total of 74 road dust samples were collected during the dry and wet seasons, and V, Cr, Mn, Co, Ni, Cu, As, Cd, Sb, and Pb were analyzed by ICP–MS in the <20 µm fraction. Geochemical indices, spatial analysis, Pearson correlation, principal component analysis, SEM–EDS particle characterization, in vitro lung bioaccessibility (ALF), and human health risk models were applied. Sb, Cu, and Pb were identified as the most enriched elements, exceeded local background concentrations at all sampling sites. Spatial patterns revealed recurrent hotspots in the northern, northeastern, and central sectors of the city. SEM–EDS analyses showed that most particles belonged to the 2.5–5 µm equivalent-size class and included Fe-rich spherules, Pb-rich aggregates, silicate grains, and C-rich particles. Health risk assessment indicated acceptable risks for adults, whereas children exceeded the non-carcinogenic threshold (HI = 3.85–4.60) and slightly surpassed the upper acceptable carcinogenic risk level. Lung bioaccessibility results revealed low Pb solubility but high mobility of Ni and Cu, with some samples reaching complete dissolution under ALF conditions. These findings demonstrate that traffic-derived road dust represents a persistent urban exposure pathway in Mexico City and highlight the importance of integrating total concentrations, particle characteristics, and bioaccessibility data to improve environmental and health-risk assessments in urban environments. Full article

The contamination of aquatic environments by cadmium and other toxic heavy metals represents a major environmental concern requiring efficient and operationally sustainable remediation strategies. In this work, iron oxide materials were synthesized through a microwave-assisted hydrothermal method and evaluated for Cd(II) removal from aqueous systems. Different precursor compositions and organic additives were initially screened in order to identify the most suitable adsorbent formulation. The selected Fe-Tart material was characterized by FTIR, SEM-EDS, and XRD analyses, revealing hydroxylated and poorly crystalline iron oxide structures with heterogeneous surface organization. Batch adsorption experiments were performed under controlled conditions to investigate the influence of pH and equilibrium adsorption behavior, while adsorption data were analyzed using Langmuir and Freundlich isotherm models. Cd(II) uptake showed strong pH dependence, with adsorption progressively increasing from acidic to near-neutral conditions and reaching approximately 80% removal at pH 7–8. The Langmuir model provided the best fitting results (R² = 0.988), suggesting preferential occupation of energetically comparable surface sites with a maximum adsorption capacity of 6.51 mg g⁻¹. The adsorption behavior was interpreted within a pH-dependent surface complexation framework involving hydroxylated iron oxide surfaces. Although the adsorption capacity remained lower than that reported for some highly engineered adsorbents, the results indicate that microwave-assisted synthesis may provide a relatively simple and rapid route for preparing iron oxide-based materials potentially applicable to water remediation systems. Full article

Continuous alumina (Al₂O₃) fibers are critical reinforcement materials for ceramic matrix composites (CMCs) utilized in extreme high-temperature environments. While their baseline thermal and mechanical properties are well-documented, their long-term service reliability in complex, multi-field environments—specifically coupled thermal, hygral, and atmospheric conditions—remains insufficiently quantified. This study systematically investigates the degradation mechanisms of alumina ceramic fiber ropes subjected to simulated engine exhaust atmospheres and cyclic rain exposure. By integrating macroscopic tensile testing with rigorous multi-scale microstructural characterizations (SEM, XRD, TGA, and advanced surface chemical state analyses via EDS and XPS), a comprehensive degradation model is proposed. Our findings reveal a pronounced two-stage mechanical degradation behavior: an initial catastrophic strength collapse followed by a stabilization phase. We elucidate that the initial embrittlement is governed not merely by thermal damage, but fundamentally by the hydrothermal volatilization and depletion of the surface amorphous SiO₂ binder, which annihilates the inter-fiber cooperative load-sharing capability. Concurrently, quantitative XPS and XRD analyses strongly suggest that the internal amorphous grain-boundary films undergo rapid structural rearrangement and crystallization, effectively homogenizing the microstructure and shifting the fracture mechanics from energy-dissipative crack deflection to unhindered brittle cleavage. After the preferential depletion of the amorphous silicate phase, the exposed α-Al₂O₃ core dictates a stabilized mechanical response. This research provides critical theoretical frameworks and experimental evidence for the life-cycle assessment and microstructural optimization of advanced oxide ceramic fibers in next-generation aerospace applications. Full article

The growing application of nanotechnology in wood modification has led to significant improvements in the durability, fire resistance, and biological stability of wood-based building materials, such as glued laminated timber (GLT), as well as related chemical products, including fire retardants and anticorrosion preservatives. While numerous review papers have focused on material performance and functionalisation strategies, a comprehensive analysis of the research methodologies employed in this field remains limited. This review addresses this gap by systematically examining the experimental and analytical methods used in studies on nanomaterial-modified wood surface treatments. Scientific articles published and indexed in the Web of Science and Scopus databases within the last ten years were selected using keywords related to wood, nanotechnology, and surface applications simulating industrial timber treatment processes applied in factories and construction sites. Publications were screened according to predefined inclusion and exclusion criteria. The study selection process was conducted according to the PRISMA methodology, and 74 studies meeting the inclusion criteria were selected for the final analysis. Extracted methodological features were coded and analysed using frequency-based descriptive statistics. Considerable methodological heterogeneity was observed among the analysed studies. Softwood species, TiO₂- and ZnO-based nanomaterials, and brushing or immersion treatments represented the most frequently investigated research configurations. Scanning electron microscopy (SEM), often combined with EDS and XRD analyses, occupied a central role within the analytical framework of nanomodified wood research. In contrast, long-term durability assessments, biological resistance testing, and fire-performance evaluations were comparatively underrepresented. The review also revealed substantial variability in the use of testing standards and statistical methods. By linking research methodologies to normative requirements for construction materials, this work provides a methodological framework supporting future research, standardisation, certification, and commercial implementation of nanomaterial-based wood protection systems. Full article

Refractory metals are being studied as alternatives to Pd and its alloys for the separation of hydrogen in high-temperature processes. The development of a membrane reactor for the production of hydrogen via water splitting has required studying hydrogen permeability through Ta at temperatures above 1273 K, for which no data is available in the literature. A dedicated experimental setup has been realized for testing Ta tubes in the temperature range 673–1573 K. Despite the use of controlled atmospheres and ultra-pure gases (with oxygen content below a few ppm), the tests over 1473 K have involved the formation of oxide layers over the metal surfaces, as verified by SEM-EDS analyses. The presence of oxide layers significantly increases the energy barrier to permeation: in agreement with a modest surface oxidation, at lower temperatures (673–1273 K) the activation energy of 2679.8 K has been measured against the value of 30,691 K measured in the high-temperature tests (1473–1573 K). Full article

To clarify the anomalous corrosion behavior in Cu-containing CoCrNi-based medium-entropy alloys, in which an enhanced corrosion driving force is accompanied by a reduced overall corrosion rate, the phase constitution, microstructure, electrochemical behavior, post-corrosion morphology, and surface chemical states of CoCrNi, CoCrNiCu, and CoCrNiCuFe alloys were systematically compared. The results show that Cu addition induces pronounced phase separation in the CoCrNi matrix, leading to the formation of a Cu-depleted FCC1 phase, a continuous Cu-rich FCC2 intergranular network, and dispersed nanoscale Cu-rich precipitates, with an FCC2 area fraction of about 0.145. In 3.5 wt.% NaCl solution, CoCrNiCu exhibits a stronger thermodynamic tendency for corrosion, whereas its overall corrosion rate does not increase, but instead shows the lowest corrosion current density and higher impedance, indicating an anomalous electrochemical response. Post-corrosion SEM morphology, EDS elemental mapping, and XPS valence-state analyses further reveal that corrosion is mainly concentrated in the Cu-rich phases and their adjacent narrow regions, while the Cu-rich phases themselves remain relatively stable as non-sacrificial cathodes. Semi-quantitative thermodynamic and mass-transport calculations indicate that although Cu-induced phase separation enhances the micro-galvanic corrosion driving force, with an estimated interphase potential difference of about 0.337 V, the overall corrosion rate remains constrained by the oxygen diffusion supply during cathodic oxygen reduction on the Cu-rich regions. Therefore, the anomalous corrosion response of CoCrNiCu can be attributed to the synergistic effect of the enhanced micro-galvanic corrosion driving force caused by Cu-induced phase separation and the restricted cathodic oxygen supply. Full article

Titanium alloys are among the most important biomaterials due to their good biocompatibility, high corrosion resistance and favourable mechanical properties. Particular interest is directed towards β-Ti alloys, whose properties can be tailored by adding β-stabilisers such as molybdenum and chromium, with the aim of developing materials suitable for biomedical applications. This paper investigates the influence of chemical composition on the phase composition, microstructure, microhardness and corrosion properties of experimental Ti-Mo-Cr alloys produced by casting. Phase composition was determined by X-ray diffraction analysis (XRD), while microstructural characteristics were analysed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that increasing the molybdenum and chromium content contributes to the stabilisation of the β-phase and reduces the proportion of α and α″ martensite. Complete stabilisation of the β-phase was achieved in the Ti-10Mo-30Cr alloy, while the Ti-10Mo-10Cr alloy showed a dominant presence of α″ martensite. EDS analysis confirmed the segregation of alloying elements during solidification. Microhardness measurements showed an increase in hardness with increasing total alloying element content, with the highest hardness measured in the Ti-20Mo-20Cr alloy. Corrosion properties were tested using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and Tafel polarisation methods in 0.9% NaCl (sodium chloride) medium. Among the alloys investigated, Ti-20Mo-20Cr showed a favourable overall balance of electrochemical properties, while Ti-10Mo-30Cr exhibited the lowest corrosion rate. The results suggest that a balanced ratio of molybdenum and chromium plays a key role in optimising the microstructure, mechanical properties, and corrosion performance of Ti-Mo-Cr alloys. Full article

The discharge of metal-containing effluents into aquatic systems remains a major environmental concern because metal ions can persist in water bodies and accumulate in biological systems, potentially affecting ecosystem and human health. Among these contaminants, Cr(III) is frequently encountered in waste streams generated by industrial activities, making its removal an important objective in water quality management. This study investigated the adsorption behavior of Cr(III) using lignocellulosic biosorbents obtained from tamarind shell (Tamarindus indica) after water, H₂O₂, and HCl pretreatments, with particular emphasis on equilibrium behavior, thermodynamic characteristics, and pretreatment-induced physicochemical modifications. Batch adsorption experiments were conducted to evaluate equilibrium behavior. The highest adsorption capacity (41.6 mg g⁻¹) was obtained with the water-treated biosorbent at 60 °C. The equilibrium data were best represented by the Sips model, suggesting that Cr(III) adsorption occurred on surfaces containing adsorption sites with different energetic characteristics. Thermodynamic analysis revealed that the adsorption process was spontaneous, while the enthalpy changes indicated predominantly endothermic behavior for the pretreated biosorbents. ATR-FTIR, SEM, EDS, and XRD analyses were performed to characterize the biosorbents before and after adsorption. The characterization results indicated that oxygen-containing functional groups, particularly hydroxyl and carbonyl functionalities, were associated with the adsorption process. SEM images showed morphological changes associated with pore occupation, while EDS confirmed chromium adsorption and suggested possible ion-exchange mechanisms. XRD patterns indicated a mainly amorphous structure. The results demonstrated that pretreatment-induced modifications strongly influenced the adsorption performance of tamarind shell. Water pretreatment produced the most favorable adsorption behavior, yielding the highest adsorption capacity among the evaluated biosorbents. The combined interpretation of equilibrium, thermodynamic, and characterization results revealed a close relationship between surface properties and Cr(III) uptake. Full article

This study investigates the use of mussel shells (MSs), a biogenic by-product of the food industry, as a partial replacement for ground granulated blast furnace slag (GBFS) in alkali-activated mortars. Given their high CaCO₃ content, MSs represent a sustainable secondary raw material that reduces both waste disposal burden and reliance on natural resources, while offering a low-carbon alternative to conventional cement-based binders. Alkali-activated mussel shell/slag mortars (AAMSs) were produced with MS replacement ratios of 0%, 5%, 10%, 15%, and 20% by mass of GBFS. Sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) were used as alkaline activators. Fresh specimens were cured at 60 °C for 48 h. The experimental program included workability, compressive and flexural strength, water absorption, porosity, density, capillarity, ultrasonic pulse velocity (UPV), and freeze–thaw (F-T) resistance tests. Increasing MS content slightly reduced flowability and mechanical strength, while increasing water absorption, porosity, and capillarity. The M0 series achieved the highest 28-day compressive strength (54.06 MPa), while M15 exhibited the highest flexural strength (5.23 MPa). Following F-T cycling, the 5% and 10% MS series demonstrated the best compressive strength (30 MPa). The 10% MS exhibits a relatively balanced overall performance, providing the best balance between mechanical performance, F-T resistance, and microstructural stability, as confirmed by scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) analyses showing elevated Ca/Si ratios and the formation of Ca-rich crystalline phases. Full article

This study comparatively evaluated Raydent (here interpreted as a standard black chrome-type industrial condition in the present specimen context), DLC, and SiO₂ coatings for high-precision LM-guide applications as an application-oriented initial screening study. The emphasis was placed on dimensional preservation, surface integrity, and mechanical surface response rather than on complete coating-mechanism validation. Cross-sectional FE-SEM, EDS, Vickers hardness testing, surface profilometry, AFM, and SEM analyses were conducted to compare coating thickness, composite surface hardness, roughness, and morphology, and the influence of plasma pretreatment on the SiO₂ system was additionally investigated. Among the investigated coatings, SiO₂ exhibited the smallest thickness (1.03 μm), highest composite surface hardness (719.8 HV), and lowest average roughness (213.5 nm), suggesting favorable dimensional compatibility and surface integrity under the tested conditions. Plasma pretreatment increased the EDS-detected Si signal from 0.77 to 2.81 wt% and improved the composite surface hardness from 580 to 720 HV, suggesting an altered near-surface response and improvement in coating formation during pretreatment-assisted processing. AFM and SEM observations further indicated that the SiO₂ coating provided a more uniform and flatter surface morphology on the coupon specimens, whereas the DLC specimen prepared under the present commercial condition showed localized protrusions that may be associated with initial local contact disturbance. The comparative results suggest that SiO₂ coatings provide a favorable balance of thickness control, surface uniformity, composite surface hardness, and roughness for precision LM-guide applications. Although additional rolling-contact durability, adhesion, wear, friction-coefficient, and rolling-contact-fatigue studies are still required, the present findings should be interpreted as an initial screening result indicating that SiO₂ is a candidate coating condition for further engineering consideration in precision motion-guide systems, rather than as a direct validation of full tribological or long-term durability performance. Full article

Al-Cu-Fe quasicrystalline coatings were deposited on AISI 321 stainless steel substrates by high-velocity oxy-fuel (HVOF) spraying at oxygen pressures of 3.0, 3.5, and 4.0 bar. The influence of oxygen pressure on the phase composition, microstructure, porosity, corrosion behavior, thermal stability, and microhardness of the coatings was investigated using X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), ImageJ porosity analysis, electrochemical corrosion testing in 3.5 wt.% NaCl solution, simultaneous thermal analysis (TGA/DSC), and microhardness measurements. XRD analysis revealed the formation of quasicrystalline-related intermetallic phases together with Al, Fe₃Al₁₃, FeAl, Fe₃O₄, CuFe₂O₄, Cu₂O, and CuO phases. The coating deposited at 3.5 bar exhibited the lowest porosity (5.37%), the most homogeneous microstructure, and the largest residual coating thickness after corrosion testing. SEM and EDS analyses indicated that corrosion preferentially initiated at pores, splat boundaries, and phase interfaces, while the coating produced at 3.5 bar demonstrated the most stable surface condition after exposure to a 3.5 wt.% NaCl solution. Thermal analysis showed that all coatings remained stable up to 900 °C. Sample (a) exhibited the lowest mass loss and the highest thermal stability, whereas sample (b) demonstrated the most favorable combination of structural integrity, phase ordering, coating density, corrosion-related performance, and thermal stability. Microhardness values of the coatings ranged from 754 to 778 HV, significantly exceeding that of the AISI 321 substrate. The results demonstrate that oxygen pressure is a critical parameter controlling the microstructure and functional properties of HVOF-sprayed Al-Cu-Fe coatings, with 3.5 bar providing the most balanced set of properties. Full article

A biogenic ZnO/Ag photoelectrode treated with atmospheric-pressure plasma was evaluated as an anode in a photo-assisted electroflotation system for the transformation of chromophoric pollutants in real industrial wastewater. ZnO was synthesized from Azadirachta indica leaf extract and plasma-treated for 10 min (M2) and 15 min (M3), with an untreated reference (M1). XRD, SEM-EDS, Raman, FTIR, EPR, and XPS analyses showed that the plasma preserved the wurtzite structure, relaxed the bulk, and modified the surface by removing residues, deoxygenating it, and activating oxygen vacancies (V_O). Although M3 reached the highest deoxygenation, M2 showed the most favorable response; thus, the performance did not depend only on the total amount of V_O. Under dark conditions, M2 showed a 14.86 percent decrease in COD compared to the control in a single batch and had the most negative ORP value. However, only ORP came close to statistical significance after multiplicity correction, with p_adj = 0.055. Under illumination, it showed the strongest photoinduced changes in conductivity and total suspended solids. The light–dark differences (ΔL−O) showed sign reversals in COD, conductivity, and pH, which identified three functional regimes and indicated that the electronic coupling of the surface V_O, rather than its amount, controlled the performance. ΔL−O was proposed as an operational test to distinguish these regimes, with the plasma exposure time as a key control variable. Because the effluent responses were single determinations, they are considered exploratory; the mechanism is primarily based on structural and spectroscopic characterization and supported by photoelectrochemical tests. Full article