Search Results (2,532)

This study presents a method for extracting lignin and hemicellulose from black liquor using organic acids (citric, malic, and acetic) in comparison to the traditional sulfuric acid method. We investigated and compared the influence of the acid type on the structural properties of the resulting precipitates in the context of their potential applications. The lignin fractions were characterized for their chemical structure (ATR-FTIR, NMR), thermal stability (TGA), morphology and surface elemental composition (SEM-EDS), bulk elemental composition (C, H, N, S), and molecular weight distribution (GPC). The hemicellulose fractions were analyzed for their molecular weight (GPC), surface elemental composition (EDS), and chemical structure (ATR-FTIR). These analyses revealed subtle differences in the properties of the individual materials depending on the extraction method. We showed that organic acids, particularly citric acid, can effectively precipitate lignin with yields comparable to the sulfuric acid method (47–60 g/dm³ vs. 50 g/dm³). Simultaneously, this method produces lignin with higher purity (regarding sulfur content) and an increased content of carboxyl groups. This latter aspect is of particular interest due to the enhanced potential of lignin’s adsorption functions towards metal ions. AAS analysis confirmed that lignin precipitated with citric acid showed better adsorption efficiency towards heavy metals compared to lignin precipitated with sulfuric acid, especially for Cu²⁺ ions (80% vs. 20%) and Cr³⁺ ions (46% vs. 2%). This enhanced adsorption efficiency of the isolated lignins, combined with the environmental benefits of using organic acids, opens a promising perspective for their application in water treatment and environmental remediation. Furthermore, the presented research on the valorization and reuse of paper industry by-products fully aligns with the fundamental principles of the Circular Economy. Full article

This study investigated the effect of mechanical activation on the physicochemical properties of lepidolite and the leaching behavior of mechanically activated samples in sulfuric acid (H₂SO₄). Lepidolite was mechanically activated using a high-energy planetary ball mill (PBM) at 400 RPM with a 20:1 ball-to-feed weight ratio (BFR, g:g) and the samples activated for different durations were characterized for amorphous phase content, particle size, and morphology using various solid analyses. X-ray diffraction (XRD) revealed the progressive amorphization of lepidolite, with the amorphous fraction increased from 34.1% (unactivated) to 81.4% after 60 min of mechanical activation. Scanning electron microscopy (SEM) showed that mechanically activated particles became fluffy and rounded, whereas unactivated particles retained lamellar and angular shapes. The reactivity of minerals after mechanical activation was evaluated through a 2 M H₂SO₄ leaching test at different leaching temperatures (25–80 °C) and time periods (30–180 min). Although the leaching efficiencies of Li and Al slightly improved at higher leaching temperatures and longer leaching times, the leaching of these metals was primarily governed by the mechanical activation time. The highest Li and Al leaching efficiencies—87.0% for Li and 79.4% for Al—were obtained from lepidolite that was mechanically activated for 60 min under leaching conditions of 80 °C and a 10% (w/v) solid/liquid (S/L) ratio for 30 min. The elemental mapping images of leaching feed and residue produced via energy dispersive spectroscopy (EDS) indicated that unactivated particles in the leaching residue had much higher metal content than mechanically activated particles. Kinetic analysis further suggested that leaching predominantly occurs at mechanically activated sites and the apparent activation energies calculated in this study (<3.1 kJ·mol⁻¹) indicate diffusion-controlled behavior with weak temperature dependence. This result confirmed that mechanical activation significantly improves reactivity and that the residual unleached fraction can be attributed to unactivated particles. Full article

The green transformation of the shipping industry urgently requires zero-carbon power, and hydrogen-powered ships such as hydrogen fuel cell ships face bottlenecks in in situ hydrogen production and storage and transportation. Methanol steam reforming (MSR) online hydrogen production is suitable for ship scenarios, reducing costs and increasing efficiency while helping achieve zero carbon throughout the entire lifecycle, which has important practical significance. The key technology for MSR technology is the performance of the catalyst. A series of Cu_1−xMn_xAl₂O₄ catalysts were successfully synthesized and applied for hydrogen production in this study. The catalyst structure was characterized using physicochemical techniques including XRD, SEM, and EDS. Hydrogen production performance was evaluated in a fixed-bed reactor under the following conditions: a liquid hourly space velocity (LHSV) of 20 h⁻¹, a water-to-methanol molar ratio of 3:1, and a reaction temperature range of 275 °C–350 °C. The results demonstrate that A-site Mn substitution significantly enhanced the catalytic performance. In addition, XRD analysis revealed that Mn incorporation effectively suppressed the formation of segregated CuO phases. However, excessive substitution (x is 0.9) led to the generation of an MnAl₂O₄ impurity phase. Finally, the Cu_0.7Mn_0.3Al₂O₄ catalyst achieved a methanol conversion of 68.336% at 325 °C, with a hydrogen production rate of 5.611 mmol/min/g_cat, and maintained CO selectivity below 1%. The results demonstrate that the hydrogen production catalyst developed in this study is a promising material for meeting the requirements of online hydrogen sources for ships. Full article

Heavy metals are major toxic anthropogenic contaminants released into the environment mainly through wastewater discharges. Adsorption is one of the most effective and widely applied methods for their removal from aqueous systems. However, although activated carbon is commonly used, its high cost and limited regenerability motivate the search for cheaper and more environmentally friendly alternatives. In this study, selected natural and waste-derived materials were evaluated for Cu²⁺ removal from both model solutions and atypical textile wastewater. Coffee grounds, chestnut seeds, acorns, potato peels, eggshells, marine shells, and poultry bones were tested and compared with commercial activated carbon. Their structural and functional properties were characterised using specific surface area measurements, optical microscopy, SEM-EDS, and FTIR analyses. Two adsorption isotherm models (Langmuir and Freundlich) were used to analyse the experimental data for the selected adsorbents, and model parameters were determined by linear regression. Based on model solution tests, two materials showed the highest Cu²⁺ sorption potential: coarse poultry bones (97.0% at 24 h) and fine cockle shells (96.2% at 24 h). When applied to real textile wastewater, the bone-derived material achieved the highest Cu²⁺ removal efficiency (79.4%). Although this efficiency is lower than typical values obtained in laboratory solutions, it demonstrates the feasibility of waste-derived materials as low-cost adsorbents and suggests that further optimisation could further improve their performance. Full article

The increasing presence of pharmaceutical residues such as ibuprofen in aquatic environments represents a growing concern due to their persistence and limited biodegradability. In this study, selenium-doped tin oxide (SnO₂:Se) nanoparticles covered with glycerol were synthesized via a microwave-assisted method to evaluate their photocatalytic performance in the degradation of ibuprofen under ultraviolet (UV) and visible light. Optimal synthesis parameters were determined at pH 7.5–8.0 and 130 °C, yielding stable, dark-brown colloidal suspensions. HRTEM analysis revealed a coexistence of one-dimensional (1D) nanowires and zero-dimensional (0D) quantum dots, confirming nanoscale morphology with crystallite sizes between 8 and 100 nm. EDS analysis confirmed the presence of Sn, O, and trace Se (0.1 wt%), indicating Se incorporation as a dopant. UV–Vis spectroscopy showed strong absorption near 324 nm and slight band-gap narrowing in the Se-doped samples, suggesting enhanced visible-light responsiveness. Photocatalytic experiments demonstrated an ibuprofen degradation efficiency of ~60% under visible light and 80% under UV irradiation with aeration, compared to only 5% removal using commercial SnO₂. The enhanced performance was attributed to Se-induced band-gap modulation, effective charge-carrier separation, and singlet oxygen generation. Full article

Background: Depression and eating disorders (EDs) represent significant and often multiple public health concerns. Healthcare workers, including medical residents, were affected by several stressors that the COVID-19 pandemic has engendered and amplified, potentially exacerbating mental health issues. Despite this, limited evidence is available regarding the association between depressive symptoms and possible EDs among Public Health Residents (PHRs). Methods: A nationwide cross-sectional study, the ‘Public Health Residents Anonymous Survey in Italy (PHRASI),’ was conducted between June and July 2022. A total of 379 PHRs participated in this study, filling in a self-administered questionnaire which included the PHQ-9 for assessing depressive symptoms and the SCOFF (Sick, Control, One, Fat, Food) test as a screening tool for possible EDs. Multivariable logistic regression evaluated associations between sociodemographic and training/work-related factors, depressive symptoms, and EDs. Results: Overall, 40.6% of respondents screened positive for possible EDs. Depressive symptoms had a positive association with possible EDs (aOR = 2.76; 95% CI = 1.55–4.93). Other factors associated with higher ED odds included region of residence (aOR = 1.92; 95% CI = 1.06–3.47), intention to repeat the test for another postgraduate course (aOR = 3.22; 95% CI = 1.25–8.3), and working more than 40 h per week (aOR = 1.91; 95% CI = 1.19–3.07). Conversely, having more than one child (aOR = 0.32; 95% CI = 0.13–0.78) was associated with lower odds. Conclusions: The findings highlight a significant association between depressive symptoms and positive screening for possible EDs, underscoring the need for integrated mental health support and preventive interventions within medical residency programmes, especially in the context of public health crises. Full article

This study investigated the use of Marine Recyclable Aggregate (MRA), synthesized from Recycled Particles from Paste (RPPs) obtained from construction waste, seawater, and alkali activator (Na₂O∙3.3SiO₂, NS), for reinforcing marine soft clay. RPP is a laboratory-prepared material used to simulate construction waste. The physicochemical properties of MRA were characterized using X-ray diffraction (XRD), thermal field emission scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA). The results revealed that the key hydration products in MRA are Friedel’s salt (3CaO·Al₂O₃·CaCl₂·10H₂O, FS), xCaO·SiO₂·nH₂O (C-S-H), and CaO·Al₂O₃·2SiO₂·4H₂O (C-A-S-H). The formation of these hydration products enables MRA to maintain stability in marine environments. The deformation characteristics of MRA-reinforced soft clay under various conditions were investigated by integrating X-ray computed tomography with triaxial compression tests, allowing for the three-dimensional visualization and reconstruction of the failure process. The application of MRA for soft clay reinforcement in seawater environments enhances the bearing capacity of the clay and provided significant environmental benefits. Full article

Observed rainfall erosivity risk (ORE) index is defined as the erosivity risk in the event of extreme rainfall events. ORE measures the kinetic energy of raindrops generated during a period of maximum precipitation intensity with the formula $\mathrm{O}\mathrm{R}\mathrm{E}=\left(\mathrm{E}\mathrm{D}·\mathrm{T}\mathrm{E}\mathrm{I}\right)/10$, where ED = erosivity density, TEI = total erosivity index, and ORE is measured in MJ mm ha⁻¹ h⁻¹ yr⁻¹. The goal of this study is to model ORE, estimate its spatiotemporal variability, and predict (PRE) and simulate ORE for the state of Sinaloa (1969–2018). Five indices of rainfall erosivity were calculated: the modified Fournier index, precipitation concentration index, ED, TEI, and rainfall erosivity factor. The nonparametric trend in ORE was calculated. Using multiple nonlinear regressions (MNR), PRE (dependent variable) was calculated as a function of cumulative annual, annual average, seasonal average, and seasonal cumulative rainfall (independent variables). To simulate PRE, cumulative distribution functions, adjusted return periods (ARPs), and the 99th percentile were used. ORE ranged from 51.39 MJ mm ha⁻¹ h⁻¹ yr⁻¹ in 1970 (Culiacán) to 92679.40 MJ mm ha⁻¹ h⁻¹ yr⁻¹ in 1998 (Sta. C. de Alaya). The only year that had very high ORE at all nine stations was 1998. The only significant trend was ORE = 34.64 MJ mm ha⁻¹ h⁻¹ yr⁻¹ (Culiacán). The nine PRE models were significantly predictive (Spearman correlation > 0.280). Guatenipa, Rosario, and Siqueros registered very high PRE, since one to eight extreme erosivity events per century are predicted on average. A new methodology is proposed for calculating ORE and PRE, which can be used to develop alternatives for managing and protecting agricultural land in the state considered “the breadbasket of Mexico”. Full article

Biodiesel, which is a blend of fatty acid methyl esters (FAME), has garnered significant attention as a promising alternative to petroleum-based diesel fuel. Nevertheless, the commercial production of biodiesel faces challenges due to the high costs associated with feedstock and the non-recyclable homogeneous catalyst system. To address these issues, a solid catalyst derived from construction industry waste cement was synthesized and utilized for biodiesel production from waste cooking oil (WCO). The catalyst’s surface and physical characteristics were analyzed through various techniques, including Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier Transform Infrared Spectroscopy (FTIR). The waste-cement catalyst demonstrated remarkable catalytic performance and reusability in the transesterification of WCO with methanol for biodiesel synthesis. A maximum biodiesel yield of 98.1% was obtained under the optimal reaction conditions of reaction temperature 65 °C; methanol/WCO molar ratio 16:1; calcined cement dosage 3 g; and reaction time 8 h. The apparent activation energy (Ea) from the reaction kinetic study is 35.78 KJ·mol⁻¹, suggesting that the transesterification reaction is governed by kinetic control rather than diffusion. The biodiesel produced exhibited high-quality properties and can be utilized in existing diesel engines without any modifications. This research presents a scalable, environmentally benign pathway for WCO transesterification, thereby contributing significantly to the economic viability and long-term sustainability of the global biodiesel industry. Full article

P-cresol, indole and indole-3-acetic acid (IAA) are catabolites of amino acids, formed by the gut microbiome. Most of these aromatic hydrocarbon derivatives are excreted by the colon before reentering the body to form “exogenous” protein-bound uremic toxins (PBUTs), which aggravate chronic kidney disease (CKD). Removal efficiencies of these PBUT precursors from model phosphate-buffered saline solutions by three different surface-modified nanoporous carbon adsorbents (PCs) were studied. PCs were produced by physicochemical and/or acid base activation of carbonized rice husk waste. Removal rates achieved values of 32–96% within a 3 h contact time. High micro/mesoporosity and surface chemistry of the N- and P-doped biochars were established by N₂ adsorption studies, SEM/EDS analysis, XPS and FT-IR-spectroscopy. The ammoxidized PC-N1 had the highest adsorption capacity (1.97 mmol/g for IAA, 2.43 mmol/g for p-cresol and 2.42 mmol/g for indole), followed by “urea-nitrified” PC-N2, whilst the phosphorylated PC-P demonstrated the lowest adsorption capacity for these solutes. These results do not correlate with the total pore volume values for PC-N2 (0.91 cm³/g) < PC-P (1.56 cm³/g) < PC-N1 (1.84 cm³/g), suggesting that other parameters such as the micropore volume (PC-N1 > PC-N2 > PC-P) and the interaction of surface chemical functional groups with the solutes play key roles in the adsorption mechanism. N-doped PC-N1 and PC-N2 have basic functional groups with higher affinity with acidic IAA and p-cresol. The ion-exchange mechanism of phenolic and indolic compound chemisorption by nanoporous carbon adsorbents, modified with surface N- and P-containing functional groups, has been proposed. Full article

This research investigates the micro-mechanisms and process control associated with the recovery of platinum group metals (PGMs) from spent automotive catalysts (SACs) through iron capturing. High-temperature smelting experiments, complemented by SEM-EDS and XRD analyses, demonstrate that PGMs spontaneously migrate from the slag phase to the iron phase, driven by interfacial energy, where they are captured to form alloy droplets with a PGM content exceeding 4 wt.%. The composite flux (CaO/H₃BO₃) markedly diminishes slag viscosity and enhances the density differential between slag and metal. This facilitates the aggregation, sedimentation, and separation of alloy droplets in accordance with Stokes’ law, thereby lowering the effective capture temperature from 1700 °C to 1500 °C and reducing energy consumption. Additionally, the flux inhibits the formation of detrimental Fe-Si alloys. PGMs form substitutional solid solutions that are uniformly dispersed within the iron matrix. This study provides both the theoretical and technical foundations necessary for the development of efficient, low-energy processes aimed at capturing and recovering Fe-PGMs alloys. Full article

The efficient recovery of rare earth elements (REEs) from low-concentration mine tailwater is crucial for resource sustainability. In this study, a novel composite adsorbent, sesame stalk biochar-supported zirconium phosphate (sBC/ZrP), was synthesized for the selective adsorption and recovery of La³⁺ as a representative REE. The material was characterized using SEM-EDS, BET, XRD, FTIR, and XPS. Batch adsorption experiments were conducted to evaluate the effects of pH, coexisting ions, and the adsorption kinetics and thermodynamics. The results showed that sBC/ZrP exhibited a high adsorption capacity (up to 185.83 mg/g at 35 °C for 4 h) and strong selectivity for La³⁺, particularly in the presence of common competing cations, although Al³⁺ demonstrated significant interference. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, indicating monolayer chemisorption, and was determined to be spontaneous and endothermic. The material maintained over 90% adsorption efficiency after five consecutive adsorption–desorption cycles. The mechanism primarily involved complexation of La³⁺ with the P-OH and Zr-O groups on the composite. This work demonstrates that sBC/ZrP is a highly efficient, stable, and reusable adsorbent with significant potential for the recovery of REEs from mining tailwater. Full article

This work used activated carbon material obtained by chemical activation of abundantly available agricultural sunflower waste residues to remove metol (4-(methylamino) phenol sulfate, MTL) from aqueous solutions. The adsorbent structure was characterized using SEM-EDS and FT-IR spectroscopy. A modified screen-printed carbon electrode (SPCE) with gold nanoparticles synthesized using the Laser Ablation Synthesis in Solution (LASIS) method was used to detect MTL. The successful LASIS formation of gold nanoparticles was confirmed by the specific dark burgundy–red color. TEM measurements showed uniform pseudo-spherical particles with an average diameter of 7.9 ± 0.2 nm. The modified electrode showed improved electrochemical activity, which was confirmed by comparing it with an unmodified electrode using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode was subsequently used to optimize the MTL detection conditions. UV–Vis spectroscopy was used to optimize the adsorption conditions, with the optimal values for pH and contact time found to be 8 and 120 min, respectively. The electrochemical detection of MTL was performed using differential pulse voltammetry, and the linear calibration range was established for concentrations ranging from 0.73–49.35 µM. The obtained limits of detection (LOD) and quantification (LOQ) were 0.06 µM and 0.2 µM, respectively. The efficiency of MTL removal was 100% after a contact time of 1 min and remained at 100% after 120 min. Full article

The Electro-Fenton (EF) process is a promising technology for the sustainable remediation of organic contaminants in complex wastewater. In this study, a weak magnetic field (~150 G) was applied to enhance the performance of an EF system using magnetite (Fe₃O₄) synthesized by a controlled co-precipitation route as a recyclable solid iron source. The magnetite was characterized by FTIR, SEM/EDS, and XPS, confirming the coexistence of Fe²⁺/Fe³⁺ species essential for in situ Fenton-like reactions. Under the selected operating conditions (90 min reaction time), magnetic-field assistance improved methylene blue decolorization from 14.2% to 46.0% at pH 3. FeSO₄ was used only as a homogeneous benchmark, whereas the magnetite-based system operated without soluble iron addition, minimizing sludge formation and secondary contamination. These results demonstrate the potential of magnetite-assisted and magnetically enhanced EF systems as a low-cost, sustainable alternative for the treatment of dye-containing industrial wastewater and other complex effluents. Full article

In this study, the influence of the electrochemical oxidation process on Ti-Grad 23 alloy (Ti6Al4V ELI) in 1 M H₃PO₄, under applied voltages between 200 and 275 V, at a constant time of 1 min, is analyzed. The structural, morphological, and wettability properties of the TiO₂ anodic layers obtained were investigated by X-ray diffraction (XRD), energy dispersive electron microscopy (SEM-EDS), contact angle measurements, and chemical corrosion. XRD analysis showed the development and intensification of anatase and brookite phases, with increased crystallite size after electrochemical oxidation. SEM/EDS characterization confirmed the formation of an inhomogeneous porous TiO₂ layer, with pore diameters ranging from 98 to 139 nm and a significant increase in oxygen content. Contact angle measurements demonstrate enhanced hydrophilicity for all oxidized samples, with progressively lower values as the applied voltage increased. Chemical corrosion tests in Ringer solution and Ringer + 40 g/L H₂O₂ indicated that oxidized surfaces maintain structural stability in physiological media, whereas exposure to oxidizing environments induces partial pore closure and crack formation due to localized corrosion. The optimal anodizing condition was identified at 200 V for 1 min, yielding a uniform distribution of pores and improved morpho-functional characteristics suitable for biomedical applications. The optimal electrochemical oxidation conditions were identified at 200 V for 1 min, ensuring a uniform pore distribution. Full article