Search Results (1,580)

This paper presents the results of numerical and experimental studies of forced convection of water/EG-Al₂O₃ nanofluids through a horizontal stainless steel tube (8 mm inner diameter; 2000 mm length). As a base fluid, distilled water/EG mixture of three volume ratios (90:10, 80:20, and 60:40) is used. Nanoparticle mass concentrations are 0.1%, 1%, and 5%. The tested nanofluids are prepared by use of the two-step method. No dispersant is used to stabilize the suspension. Transition and turbulent flow regimes are tested. The commercial code Ansys Fluent 19.3 is used to conduct numerical simulations. A k-ε turbulence model with an expanded boundary layer function is adopted. A homogeneous nanofluid model is assumed, with thermophysical properties depending on the mean fluid temperature and nanoparticle concentration. The nanofluids are treated as incompressible Newtonian fluids. Both experimental and numerical studies showed an increase in the average Nusselt number with the addition of Al₂O₃ nanoparticles to each of the water/EG mixtures. However, the experimental results indicated that, at the maximum mass nanoparticle concentration of 5%, the Nusselt number increased by 42%, whereas the numerical simulations showed an increase of only 16% compared with the base fluid. Both experimental studies and numerical simulations show the flow resistance of the nanofluid increases with increasing nanoparticle concentration. Similarly to heat transfer, the numerical calculations predict lower pressure drops than those observed experimentally. For the maximum nanoparticle mass concentration of 5%, the experimental results indicate an increase in nanofluid flow resistance of about 95%, while numerical simulations predict an increase of about 50%, compared to the base liquid. The generalized correlation equations are proposed to calculate the average Nusselt number and the friction factor valid for the turbulent flow of water-based nanofluids and water/EG mixtures with a volumetric water fraction above 60% and a mass concentration of nanoparticles in the range of 0.1% ≤ φ_m ≤ 5%. Full article

Rice husk biomass was investigated under O₂/CO₂ oxy-fuel conditions using Thermogravimetric analysis (TG)-derivative thermogravimetry (DTG)-mass spectrometry (MS) experiments, iso-conversional kinetic analysis, and ReaxFF reactive molecular dynamics simulations. Oxy-fuel combustion significantly enhanced combustion performance compared with air combustion. At 10 °C·min⁻¹, the ignition and burnout temperatures decreased to 235 °C and 435 °C under 70%O₂/30%CO₂, while the maximum mass loss rate increased more than fivefold and the comprehensive combustion index increased markedly. Online MS analysis showed concentrated CO₂ formation and O₂ consumption within 280–330 °C, accompanied by markedly suppressed NO_x and SO₂ emissions. Kinetic analysis revealed high apparent activation energies (525–548 kJ·mol⁻¹) at α ≈ 0.5; these values are conversion-dependent and sensitive to the iso-conversional method employed and therefore reflect relative kinetic trends rather than intrinsic Arrhenius parameters, indicating a transition from chemical control to diffusion–structure-coupled control. Molecular dynamics simulations further confirmed that moderate oxygen enrichment promotes organic backbone cleavage, whereas excessive oxygen leads to a carbon-limited regime. These results provide mechanistic insights into biomass oxy-fuel combustion and its optimization for CO₂ capture applications. Full article

This work presents a study on the evaluation of the erosive wear behavior of laminated composites, manufactured using the vacuum-assisted resin infusion (VARI) method with a glass fiber-reinforced epoxy matrix modified with SiO₂ nanoparticles (0.0, 1.5, and 3.0 wt.%). Results indicate that nanoparticle concentration and dispersion state critically influence the mechanical and tribological performance. The composite FG-1.5-SiO₂ with 1.5 wt.% SiO₂ exhibited optimal nanoparticle distribution, as confirmed by FTIR, GIXRD, and SEM analyses, with the lowest surface roughness (Ra = 0.215 μm), highest hardness (35.58 HV), and highest elastic modulus (19.66 GPa). These enhancements contributed to a 38% improvement in erosion rate compared to the unmodified laminated composite, with the lowest total mass loss (0.0261 mg) and erosion rate (2.3360 × 10⁻⁵ mg/g). Profilometry and SEM results revealed shallower wear depths and reduced matrix removal, indicating stronger fiber–matrix interface integrity. In contrast, the 3.0 wt.% SiO₂ composite (FG-3-SiO₂) suffered from nanoparticle agglomeration, which increased surface roughness, diminished mechanical properties, and reduced erosion resistance to levels comparable to the unreinforced material. The results indicate that homogeneous dispersion at an optimal concentration (1.5 wt.%) is crucial for improving erosion resistance, while agglomeration at higher concentrations negates the potential benefits of nanoparticle incorporation. These findings highlight the need to optimize nanoparticle dispersion for the development of fiberglass/epoxy composites with greater durability and erosion resistance in demanding applications. Full article

Pesticide use in agriculture can have negative collateral effects on the environment. In this study, two groups of treatments (G1 and G2) based on active substances (ASs) with different mobility were evaluated in order to determine pesticide residues in the soil and their impact on soil microbial populations in two vineyards located in two Denominations of Origin (D.O.). Soil samples were collected in July, October, and the following March over two consecutive years. Pesticide residues were analyzed by liquid chromatography–tandem mass spectrometry (LC-MS/MS) after QuEChERS extraction. Microbial genera were identified by the amplification of the fungal ITS regions with the universal primers ITS86F and ITS4R, and the bacterial 16S rRNA gene (V4 region) with primers 515F and 806R. Although G1 consistently showed higher residues, primarily attributable to azoxystrobin, no significant differences were observed between the two pesticide groups in the total pesticide residues or diversity of microbial communities. The factors D.O., campaign, and sampling month influenced the concentration of residues. Several ASs exhibited different dissipation dynamics depending on the D.O. Azoxystrobin and metrafenone were the most persistent in soil. The LEfSe analysis associated four beneficial fungal genera with the G2 group. The judicious selection of ASs can help to minimize the pesticide residues in soil and their harmful effects on beneficial genera. Full article

Reducing nitrous oxide (N₂O) emissions from biological wastewater treatment is critical for achieving low-carbon environmental goals. In this study, a Chlamydomonas reinhardtii -driven algal–bacterial granular sludge system was successfully established in a photo-sequencing batch reactor to enhance nitrogen removal while suppressing N₂O generation. Compact granules formed within 48 days, exhibiting good settling ability (SVI₅/SVI₃₀ = 1.0), an average diameter of 0.5 mm, and a mixed-liquor suspended solid concentration of 2.1 g/L. Algal enrichment was confirmed by an increase in chlorophyll-a to 6.6 mg/g-VSS and substantial accumulation of protein-rich extracellular polymeric substances, which improved granule stability and mass transfer. The system achieved efficient pollutant removal when treating synthetic municipal wastewater, maintaining a chemical oxygen demand removal efficiency of approximately 90% and total nitrogen removal of up to 69.4%, with effluent NH₄⁺-N consistently below 1.6 mg/L. Notably, the N₂O emission factor decreased from 4.2 to 0.4 g N₂O-N/kg N-removed, which is lower than that of conventional activated sludge processes. These results demonstrate the potential of microalgae-driven granulation as a promising low-carbon biotechnology for sustainable wastewater treatment. Full article

Photobioreactor-based microalgae cultivation offers an integrated approach for nutrient-rich wastewater treatment while producing valuable biomass. One of the main microalgae components is proteins, making them a biotechnological target. In this work, to develop efficient and greener extraction methodologies, aqueous two-phase systems (ATPSs) based on natural deep eutectic solvents (NADESs) were evaluated for one-step protein extraction from microalgae cultivated in swine wastewater. Six ATPSs combining two NADES—betaine:levulinic acid (Bet:2LA) and choline chloride:urea (ChCl:2Urea)—and their individual components (Bet or ChCl) with phosphate salts were compared. Systems {NADES + K₃PO₄ + water} were characterized and reported for the first time. Protein recovery yield (PRY) and selectivity (protein-to-carbohydrate mass ratio, R) were assessed for three extraction times and at room temperature. The ATPS {Bet:2LA + K₃PO₄ + H₂O} achieved a PRY of 16.4% and remarkable selectivity after 30 min (R = 2.17 g·g⁻¹), with proteins concentrated in the NADES-rich phase, and negligible recovery in the salt-rich phase. Although the maximum PRY (18.2% at 120 min) was achieved with the precursor betaine, the ATPS with Bet:2LA at 30 min offered an optimal balance between efficiency and process time. With a water content of up to 50%, these systems underscore the potential of NADES-based ATPSs as sustainable platforms for protein recovery. Full article

Growing environmental concern over plastic pollution has increased the need to address the persistence of PET-derived monomers, such as bis(2-hydroxyethyl) terephthalate (BHET) and terephthalic acid (TPA). This work examines the use of excimer radiation lamps combined with hydrogen peroxide (H₂O₂) to enhance advanced oxidation processes (AOPs) for their degradation. This approach stands out for its high selectivity, absence of mercury, and lower production of toxic byproducts. Experimental tests assessed how different operational factors affect pollutant degradation, such as the initial pollutant concentration (50–200 mg/L), the reaction volume (125–500 mL), and the H₂O₂:monomer mass ratio (0:1–6:1 for BHET and 0:1–4:1 for TPA). For BHET, the best results occurred with a 5:1 mass ratio, while TPA degraded optimally with a 3:1 ratio, with a 250 mL reaction volume and a 100 mg/L initial concentration for both compounds. Under these conditions, total degradation of the initial monomers was achieved in around 30 and 80 min for BHET and TPA, respectively, and at the end of the reaction, COD decreased by 46% and 32% relative to their initial values. In both cases, hydrogen peroxide was crucial since UV radiation alone led to much lower degradation efficiency. These results emphasize the need to optimize operational conditions for greater efficiency and establish a starting point for future use of excimer technology in the treatment of wastewater contaminated with PET and its derivatives. Additionally, the degradation data closely matched a pseudo-first-order kinetic model (R² ≈ 1), confirming its reliability for predictive analysis, which is of high importance for the simulation and optimization of the process. Full article

Coffee silverskin (CS) is an abundant leftover of the coffee roasting process known to contain significant concentrations of bioactive molecules, including polyphenols and flavonoids, with established antioxidant properties and potential applications in nutraceutical and functional-food formulations. This study systematically optimized extraction conditions to maximize the recovery of phenolics and antioxidants from CS by evaluating the effects of solvent type, temperature, and sonication time. Ethanol extraction at 20 °C for 30 min yielded the most enriched polyphenolic fraction, with the highest total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity across 2,2-diphenyl-1-picrylhydrazyl (DPPH), trolox equivalent antioxidant capacity (TEAC), and ferric reducing antioxidant power (FRAP) assays. Comprehensive chemical characterization via high-performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC-MS) identified key phenolics (chlorogenic acid, hyperoside, quercetin), alongside abundant caffeine, tocopherols, and phytosterols. The biological relevance of the optimized extract was assessed for the first time in RT4-D6P2T Schwann-like cells, demonstrating significant cytoprotective and antioxidant effects against H₂O₂- and lipopolysaccharide-induced oxidative stress, thereby establishing a previously unreported neuroprotective potential. Full article

In this study, an electrochemical valorization strategy on liquid byproducts from hazelnut shell gasification was developed to couple waste remediation with energy-efficient hydrogen production. The aqueous phase, rich in organic compounds, is processed in an anion exchange membrane (AEM) cell, where pure hydrogen evolved at the cathode while organic pollutants are oxidized at the anode. First, the feedstock is thoroughly characterized using gas chromatography–mass spectrometry (GC-MS), identifying a complex matrix of water-soluble aromatic compounds such as phenols, catechols, and other aromatics compounds, with concentrations reaching up to 2.9 g/kg for catechols. Then, the electro-reforming process is optimized using Nickel oxide–hydroxide (Ni(O)OH) electrodes with a loading of 0.75 mg/cm². This methodology relies on the favorable thermodynamics of organic oxidation, which requires a lower onset potential (0.4 V) compared to the oxygen evolution reaction (OER) observed in the alkaline control (0.52 V), and the low overpotential of the Nickel oxide–hydroxide electrode towards the oxidized species. Consequently, the organic load undergoes progressive oxidation into hydrophilic and less bioaccumulating species and carbon dioxide, allowing for the simultaneous generation of pure hydrogen at the cathode at a reduced cell voltage. Elevated stability was observed, with a substantial abatement—78% of the initial organic load—of organic compounds achieved over 80 h at a fixed cell voltage of 0.5 V, and a specific energy consumption for hydrogen production of $38.5 \mathrm{M}\mathrm{J}\cdot {\mathrm{k}\mathrm{g}}_{{\mathrm{H}}_2}^{-1}$. This represents a step forward in the development of technologies that reduce the energy intensity of hydrogen generation while valorizing biomass gasification residues. Full article

Background: Innovative training strategies aimed at improving physiological efficiency are of growing interest in kinesiology and sports performance. Elevation training masks (ETMs) offer a practical means of inducing hypoxia-like stress. However, evidence of their effectiveness in recreationally active populations remains limited. This pilot study examined the efficiency of a five-week progressive ETM protocol combined with high-intensity interval training (HIIT) in eliciting physiological, hematological, and body-composition adaptations relevant to endurance performance. Methods: Nine recreationally active men completed a five-week intervention consisting of three treadmill-based sessions per week: one weekly incremental Conconi test and two structured aerobic–anaerobic HIIT sessions performed with an ETM. Mask resistance was progressively increased to simulate altitudes of approximately 900–3600 m. Hematological variables (erythrocytes, hemoglobin, hematocrit, erythrocyte indices, leukocytes, and platelets), body composition, maximal heart rate (HRmax), and peripheral oxygen saturation (SpO₂) were assessed pre- and post intervention. Data were analyzed using paired-sample t-tests and repeated-measures ANOVA, with effect sizes reported (Cohen’s d, ω²). Results: A significant main effect of time on SpO₂ was observed (F(1, 8) = 130.61, p < 0.001, ω² = 0.69), along with a significant effect of training week (F(4, 32) = 17.41, p < 0.001, ω² = 0.43), and a significant Time × Week interaction (F(4, 32) = 15.20, p < 0.001, ω² = 0.42), indicating progressively greater post-exercise oxygen desaturation with increasing simulated altitude. Significant post-intervention increases were found in erythrocyte count, hemoglobin concentration, and hematocrit (p ≤ 0.009, d = 1.15–1.55), alongside increases in mean corpuscular volume and mean corpuscular hemoglobin. Platelet count increased significantly (p = 0.001, d = 1.68), while leukocyte values remained unchanged (p > 0.05). Body mass index (p = 0.049, d = 0.77) and body fat percentage (p = 0.012, d = 1.08) decreased following the intervention. HRmax tended to be lower at higher simulated altitudes. Conclusions: A five-week progressive ETM-HIIT protocol efficiently induced hematological and body-composition adaptations associated with improved oxygen transport and metabolic efficiency in recreationally active men. These findings support ETM-based training as an accessible strategy for enhancing physiological efficiency in endurance-oriented kinesiology practice, warranting confirmation in larger randomized controlled studies. Full article

Titanium dioxide (TiO₂) nano- and submicrometric particles’ widespread use in different sectors raised concerns about human and environmental exposure. The validation of analytical methods is essential to ensure reliability in risk assessment studies. In this study, a single-particle inductively coupled plasma mass spectrometry (spICP-MS) method was validated for the detection, quantification, and dimensional characterization of TiO₂ particles in biological tissues. Tissue samples collected after exposure to TiO₂ particles underwent mild acidic digestion using a HNO₃/H₂O₂ mixture to achieve complete matrix decomposition while preserving particle integrity. The resulting digests were analyzed by ICP-MS operated in single-particle mode to quantify and size TiO₂ particles. Method validation was conducted according to ISO/IEC 17025:2017 and included linearity, repeatability, recovery, and detection limit assessments. The limit of detection for TiO₂ particles was 0.04 µg/g, and 55.7 nm was the size the detection limit. Repeatability was within 0.5–11.5% for both TiO₂ mass concentrations and particle size determination. The validated method was applied to tissues from inhalation-exposed subjects, showing TiO₂ levels of 80 ± 20 µg TiO₂/g and particle number concentrations of 5.0 × 10⁵ ± 1.2 × 10⁵ part. TiO₂/mg. Detected TiO₂ particles’ mean diameter ranged from 230 to 330 nm. The developed and validated spICP-MS method provides robust and sensitive quantification of TiO₂ particles in biological matrices, supporting its use in human biomonitoring and exposure assessment studies. Full article

To investigate the treatment performance of a CuTiO₃ photocatalytic system for organic peroxide production wastewater under visible light, CuTiO₃ powder prepared through the hydrothermal method was used for this experiment. The light absorption properties of the CuTiO₃ catalyst were analyzed using Uv-Vis diffuse reflectance spectroscopy (Uv-Vis DRS). The effects of the initial pH, photocatalyst dosage, light intensity, and reaction duration on the photocatalytic reaction were examined. Before and after the reaction, the changes in pollutant components in water were characterized via three-dimensional excitation–emission matrix fluorescence spectrometry (3D-EEM) and gas chromatography–mass spectrometry (GC-MS); the changes in the concentrations of some pollutants were analyzed via wavelength scanning. The results indicated that CuTiO₃ has a good response to visible light. Under the optimized conditions (initial pH = 5, CuTiO₃ dosage = 1.2 g/L, light intensity = 1300 W/m², duration = 4 h), the COD removal rate reached 58%, and the B/C (BOD₅/COD) ratio of wastewater increased from 0.112 to 0.221, demonstrating a good pretreatment effect. GC-MS analysis demonstrated significant degradation effects on amide and hydride substances. Radical capture experiments verified hydroxyl radicals as the dominant species in CuTiO₃ photocatalysis. Visible-light photocatalysis using CuTiO₃ provides an efficient pretreatment pathway for organic peroxide production wastewater. Full article

The heat transfer and flow characteristics of TiO₂/R123 nano-organic working fluid are investigated and compared with that of R123. A three-dimensional numerical model of the smooth circular tube with a diameter of 10 mm and a length of 1 m is established, and the thermodynamic properties of the nano-organic working fluids are rectified with the volume of fluid model. The grid independence validation is conducted, and the simulation results from three models (the k-ε model, the realizable k-ε model, and the Reynolds Stress Model) are evaluated against experimental data. When using the TiO₂/R123 nano-organic working fluid, the error between the simulation and experimental results is 6.1%. The flow field distribution is examined, and the effect of mass flux on heat transfer coefficient and pressure drop is discussed. Results demonstrated that the inclusion of TiO₂ nanoparticles significantly enhances heat transfer performance. At a 0.1 wt% nanoparticle concentration, the heat transfer coefficient increases by 23.2%, reaching a range of 1430.11 to 2647.25 W/(m²·K), compared to pure R123. However, this improvement in heat transfer performance is accompanied by an increase in flow resistance, with the flow resistance coefficient rising from 0.0353 to 0.0571. Additionally, pressure drops increase by up to 18.7%. Full article

Port wine production involves the addition of grape spirit to halt fermentation and retain natural sweetness. This spirit, produced by distilling wine and its by-products, must comply with legal standards, including a mandatory sensory assessment. Because grape spirit influences Port wine’s volatile composition, this study investigated the odour-active compounds present in several grape spirits intended for fortification. Volatile compounds were extracted by liquid–liquid extraction, concentrated, and analysed using gas chromatography–olfactometry (GC-O) and gas chromatography–mass spectrometry (GC-MS). In GC-O, based on frequency detection, a panel of assessors sniffed the extracts to determine the presence of aroma compounds. The results revealed a wide range of odour-active compounds in grape spirits, belonging to several chemical families such as esters, alcohols, terpenic compounds and acids. These compounds exhibited both pleasant aromas, such as fruity, floral and caramel notes as well as undesirable ones like cheese and foot odour. Most of these compounds originate from the fermentation process and are also found in other unaged distilled beverages, including young Cognac, Calvados and fruit spirits. This research highlights the aromatic complexity of grape spirits and, for the first time, determined the aroma thresholds for 25 of 36 the compounds studied at an ethanol content of 20%. Full article

The adsorption of methylene blue (MB) on poly(vinylidene fluoride) (PVDF) and PVDF/titanium dioxide(TiO₂) membranes with 1.5 wt% dosage was examined through batch adsorption and dynamic cross-flow filtration experiments. The effects of pH, temperature, and initial MB concentration on adsorption performance were evaluated via batch experiments. The Thomas model was applied to analyze the membrane filtration process, while kinetic, isothermal, and thermodynamic models were integrated to elucidate the adsorption mechanisms. Results demonstrated that low temperature and high initial MB concentration significantly improved MB adsorption on both membranes. Under neutral pH conditions (pH = 7), the maximum adsorption capacities of PVDF and PVDF/TiO₂ membranes reached 1.518 ± 0.025 mg/g and 0.189 ± 0.008 mg/g, respectively. The adsorption processes on both membranes conformed to the pseudo-second-order kinetic model, with optimal fitting to the Langmuir isotherm model. Thermodynamic analysis revealed physical adsorption mechanisms, as evidenced by adsorption free energy (E) calculated via the Dubinin–Radushrevich model Notably, PVDF membrane exhibited a more pronounced mass transfer zone height (h_Z = 2.3 ± 0.1 cm) and achieved higher adsorption capacity (2.1 ± 0.09 mg/g) than PVDF/TiO₂ membranes (0.25 ± 0.01 mg/g). The TiO₂ incorporation reduced hybrid membrane adsorption capacity and significantly mitigated membrane fouling caused by adsorption, with PVDF/TiO₂ membranes showing a 32 ± 2.5% lower flux decline rate than PVDF membranes with less MB into the pores. This study provides fundamental data supporting the combined application of “adsorption–subsequent oxidation” using PVDF-based membranes in dye wastewater treatment. Full article