Search Results (590)

The present work investigates the effect of powdered lignocellulose from alfalfa straw obtained by a chemo-extrusion method, as well as its carboxymethylated derivative, on the physicomechanical properties and swelling behavior of vulcanizates based on nitrile butadiene rubber (NBR, BNKS-28 AMN grade). Carboxymethylation of lignocellulose was performed using microwave activation. The functional group composition of the modified lignocellulose was characterized by Fourier-transform infrared (FTIR) spectroscopy, which confirmed successful carboxymethylation and revealed a reduction in crystallinity. Thermogravimetric analysis (TGA) was used to determine the thermal stability of the swelling carboxymethylated fillers. The degree of crystallinity of the carboxymethylated swelling fillers was evaluated by X-ray diffraction (XRD). It was shown that the introduction of powdered lignocellulose and its carboxymethylated derivative into the rubber compounds lead to an increase in compound viscosity and prolong the optimum cure time, while having no effect on the scorch time, in a manner similar to that observed for the commercial product sodium carboxymethylcellulose (NaCMC). It has been shown that the introduction of powdered lignocellulose and its carboxymethylated derivative increases the tensile strength of the rubber and improves its resistance to the action of mineralized water compared with the samples containing NaCMC. It was also demonstrated that carboxymethylated lignocellulose exhibits enhanced sorption capacity comparable to that of NaCMC. Overall, carboxymethylation of lignocellulose derived from alfalfa straw significantly improves the stability and sorption characteristics of nitrile butadiene rubber composites. These findings indicate that carboxymethylated lignocellulose is a sustainable and effective alternative to industrial NaCMC for use as a functional filler in elastomeric materials. Full article

The use of white-rot fungi Pleurotus spp. and Trametes versicolor in continuous-flow fixed-bed systems has emerged as a promising and sustainable approach for the removal of different pollutants from aqueous media. This overview presents the most important design and operating parameters, the efficiency of fixed-bed systems using these fungi and their spent substrate, and the effect of operating parameters on changes in removal efficiency. After a literature screening based on the Scopus database, the overview focuses specifically on 55 studies that present the results of several hundred tests, meeting the criteria for continuous-flow fixed-bed systems, which include ensuring uninterrupted flow, constant adsorbent mass, and continuous interaction between the stationary and mobile phases. Results reported in the literature show the varying importance of biodegradation and biosorption processes in the removal of metals and organic pollutants (e.g., dyes, pharmaceuticals, pesticides, volatile compounds). The overview highlights the impact of operational parameters on removal efficiency, including bed depth, flow rate, type of polluted water, and initial concentration. It also determines that these fixed-bed systems using Pleurotus spp. and Trametes versicolor are primarily suitable for modelling the adsorption-based removal of given pollutants and the bioremediation of smaller amounts of municipal, industrial, or agricultural wastewater. Full article

Green chemistry, achieved by using water as a reaction medium, has several potential applications. In this work, a number of water-soluble Rh(III)–THP complexes, [Rh(III)Cl₃(OH)(THP)₂]⁻ (1), [Rh(III)Cl₂(OH)(THP)₃] (2), [Rh(III)Cl(OH)(THP)₄]⁺ (3), [Rh(III)Cl(OH)(en)(THP)₂]⁺ (4a), [Rh(I)(en)(THP)₂]⁺ (4b) and [Rh(III)(en)₂Cl₂]Cl (5) (where THP = P(CH₂OH)₃), were generated in aqueous media by controlling the reaction at different molar ratios of RhCl₃/THP/en (en: ethylenediamine). These complexes were fully characterized in situ by ³¹P NMR spectroscopy, base titration and by X-ray crystallography for the solid compound (4). The catalytic hydrogenation reactivities of freshly prepared complexes (1–5) were tested in situ with the selected substrate of 3,4-dimethoxystyrene under the same experimental conditions; the related catalytic reactivities are discussed in detail. Full article

Illite, a clay mineral, is used in diverse fields such as agriculture, cosmetics, and the food-related industry due to its many advantages, including biocompatibility, UV protection, antibacterial activity, high adsorption capacity for hazardous substances, and cost-effectiveness. However, its relatively large size, broad size distribution, and irregular morphology limit its broader applications. This study investigated the control of particle size and distribution during wet ball milling (WBM) using five media—acetone, ethanol, water, aqueous NaCl solution, and aqueous phosphoric acid solution—over milling times of 2–10 h. Prolonged milling progressively reduced particle size and narrowed the size distribution. Acetone and ethanol exhibited notably superior size-reduction performance compared with the aqueous systems, among which phosphoric acid solution showed the least effectiveness, likely attributed to variations in their physicochemical properties, including viscosity (η) and surface tension (σ), and in their interfacial interactions with illite. Optimal milling in acetone for 10 h resulted in the smallest particles (~700 nm), the narrowest distribution, the largest specific surface area, and the highest moisture retention. Overall, these findings demonstrate that the physicochemical properties of the milling medium, which govern WBM efficiency through fluid dynamics and particle–medium interactions, thereby determine the size and distribution of milled particles. Full article

The article presents a comprehensive comparative performance evaluation and validation of composite adsorbents based on the Se-derivative of 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide for U (VI) recovery from complex multicomponent aqueous media. Our results indicate the composite materials to be comparable to, and in some cases to surpass, existing adsorbents in recovery efficiency. Under static sorption conditions for trace U (VI) from real multicomponent solutions (tap, river, and sea water), the sorption efficiency reached 80–98%, while the distribution coefficients ranged from 10⁴ to 10⁶ cm³ g⁻¹. The sorption-selectivity properties of the materials were evaluated in the presence of competing ions (EDTA and oxalate ions), which possess a high chelating capacity and a strong tendency to form complexes with uranium. The dependence of sorption efficiency on the concentration of these ions and the solution pH was investigated. The possibility of reusing the materials over multiple sorption-desorption cycles was assessed. An optimal regenerating eluent agent was identified (NaHCO₃/NH₄NO₃), providing a desorption efficiency of >95% without degrading the material’s sorption properties over repeated cycles. Using a combination of physicochemical methods, including sorption techniques, the mechanism of uranium sorption and its dependence on the material structure were determined. The efficiency of uranium recovery from multicomponent natural waters was also investigated under dynamic conditions over repeated sorption-desorption cycles. The results demonstrate through comparative analysis that the developed composites exhibit a high sorption capacity and possess a high practical potential for the concentration and recovery of uranium from high-salinity solutions with complex composition. Full article

Lost circulation in oil-based drilling fluids (OBDFs) remains difficult to mitigate because particulate lost circulation materials depend on bridging/packing and gel systems for aqueous media often lack OBDF compatibility and controllable in situ sealing. A dual-precursor oil–water biphasic metal–organic supramolecular gel enables rapid in situ sealing in OBDF loss zones. The optimized formulation uses an oil-phase to aqueous gelling-solution volume ratio of 10:3, with 2.0 wt% Span 85, 12.5 wt% TXP-4, and 5.0 wt% NaAlO₂. Apparent-viscosity measurements and ATR–FTIR analysis were used to evaluate the effects of temperature, time, pH, and shear on MOSG gelation. Furthermore, the structural characteristics and performances of MOSGs were systematically investigated by combining microstructural characterization, thermogravimetric analysis, rheological tests, simulated fracture-plugging experiments, and anti-shear evaluations. The results indicate that elevated temperatures (30–70 °C) and mildly alkaline conditions in the aqueous gelling solution (pH ≈ 8.10–8.30) promote P–O–Al coordination and strengthen hydrogen bonding, thereby facilitating the formation of a three-dimensional network. In contrast, strong shear disrupts the nascent network and delays gelation. The optimized MOSGs rapidly exhibit pronounced viscoelasticity and thermal resistance (~193 °C); under high shear (380 rpm), the viscosity retention exceeds 60% and the viscosity recovery exceeds 70%. In plugging tests, MOSG forms a dense sealing layer, achieving a pressure-bearing gradient of 2.27 MPa/m in simulated permeable formations and markedly improving the fracture pressure-bearing capacity in simulated fractured formations. Full article

Chitosan (CS) and carboxymethyl chitosan (CMCS) are polysaccharides valued for their biocompatibility, reactivity, and film-forming capabilities. This study compares the surface characteristics and stability of CS and CMCS thin films crosslinked with citric acid (CTA), polyethylene glycol diglycidyl ether (PEGDE), and glutaraldehyde (G). Flow behavior was assessed using steady-shear measurements, while film structure, morphology, and physical properties were analyzed by infrared spectroscopy, SEM, AFM, mechanical testing, and swelling experiments. Crosslinking generated new chemical bonds in both CS and CMCS films; however, interactions in CMCS did not result in stable cross-links and were comparatively weaker. These structural modifications influenced swelling behavior and enhanced stability, particularly in CS-based systems. Before neutralization, CS/PEGDE films exhibited the lowest swelling (67% ± 19) relative to unmodified CS (118% ± 25) and crosslinked samples such as CS/G2 (185% ± 30), CS/G1 (475% ± 88), and CS/CTA (520% ± 90). After neutralization, CS/G1 and CS/CTA maintained the highest swelling capacity. In contrast, CMCS films crosslinked with CTA and G1 dissolved rapidly in aqueous media due to high water uptake, while PEGDE- and G2-modified CMCS films demonstrated stability comparable to CS. Overall, the results highlight the superior stability and tunable surface properties of CS-based films, underscoring their potential for biomedical and packaging applications. Full article

Perfluorooctane sulfonate (PFOS), a persistent and bioaccumulative perfluoroalkyl substance, poses significant environmental and human health risks due to the extraordinary stability of its C–F bonds. Conventional remediation strategies largely fail to achieve mineralization, instead transferring contamination or producing secondary waste streams. In this study, we investigate neutron irradiation as a potential destructive approach for PFOS remediation in both solid and aqueous matrices. Samples were exposed to thermal neutrons (flux: 3.2 × 10⁹ n·cm⁻²·s⁻¹, 0.0025 eV) at the Argonauta reactor for 6 h. Raman and FTIR spectroscopy revealed that PFOS in powder form remained largely resistant to degradation, with only minor structural perturbations observed. In contrast, aqueous PFOS solutions exhibited pronounced spectral changes, including attenuation of C–F and S–O vibrational signatures, the emergence of carboxylate and carbonyl functionalities, and enhanced O–H stretching, consistent with radiolytic oxidation and partial defluorination. Notably, clear peak shifts were predominantly observed for PFOS in aqueous solution after irradiation (overall displacement toward higher wavenumbers), whereas in powdered PFOS the main spectral signature of irradiation was the attenuation of CF₂ and S–O related bands with comparatively limited band relocation. To evaluate the biological relevance of these structural alterations, cell viability assays (MTT) were performed using human umbilical vein endothelial cells. Non-irradiated PFOS induced marked cytotoxicity at 100 and 50 μg/mL (p < 0.0001), whereas neutron-irradiated PFOS no longer exhibited significant toxicity, with cell viability comparable to the control. These findings indicate a matrix-dependent response: neutron scattering in solids yields negligible molecular breakdown, whereas radiolysis-driven pathways in water facilitate measurable PFOS transformation. The cytotoxicity assay demonstrates that neutron irradiation promotes sufficient molecular degradation of PFOS in aqueous media to suppress its cytotoxic effects. Although complete mineralization was not achieved under the tested conditions, the combined spectroscopic and biological evidence supports neutron-induced radiolysis as a promising pathway for perfluoroalkyl detoxification. Future optimization of neutron flux, irradiation duration, and synergistic catalytic systems may enhance mineralization efficiency. Because PFOS concentration, fluoride release (F⁻), and TOC were not quantified in this study, remediation was assessed through spectroscopic fingerprints of transformation and the suppression of cytotoxicity, rather than by mass-balance mineralization metrics. This study highlights neutron irradiation as a promising strategy for perfluoroalkyl destruction in contaminated water sources. Full article

Highly accurate quantitative detection of heavy metals is crucial for preventing environmental pollution and safeguarding public health. To address the demand for sensitive and specific detection of Cu²⁺ ions, we have developed carbon dots using a simple hydrothermal process. The synthesized carbon dots are highly stable in aqueous media, environmentally friendly, and exhibit strong blue photoluminescence at 440 nm when excited at 352 nm, with a quantum yield of 5.73%. Additionally, the size distribution of the carbon dots ranges from 2.0 to 20 nm, and they feature excitation-dependent emission. They retain consistent optical properties across a wide pH range and under high ionic strength. The photoluminescent probes are selectively quenched by Cu²⁺ ions, with no interference observed from other metal cations such as Ag⁺, Ca²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Hg²⁺, K⁺, Mg²⁺, Sn²⁺, Pb²⁺, Sr²⁺, and Zn²⁺. The emission of carbon dots exhibits a strong linear correlation with Cu²⁺ concentration in the range of 0–14 μM via a static quenching mechanism, with a detection limit (LOD) of 4.77 μM in water. The proposed carbon dot sensor is low cost and has been successfully tested for detecting Cu²⁺ ions in general water samples collected from rivers in Taiwan. Full article

Incorporating hydrophobic flavonoids such as naringenin into food systems is challenging due to their poor water solubility and instability. Effective delivery systems are essential to improve solubility, dispersibility, and controlled release during digestion. This study developed a food-grade encapsulation system using basil seed gum water-soluble extract (BSG-WSE) combined with proteins, sodium caseinate (NaCas) and whey protein isolate (WPI), via pH-driven and mild heat treatments in aqueous media, without the use of organic solvents, to ensure safety and sustainability. BSG-WSE and NaCas were tested at mass ratios of 1:1, 1:3, and 1:5 under pH conditions of 4, 5, and 7, followed by heat treatments at 60 °C or 80 °C for 30 min. The total biopolymer concentrations were 0.15%, 0.3%, and 0.45% (w/v). The most stable colloidal system was obtained at a 1:1 ratio, pH 4, and 60 °C, which was further evaluated for two additional flavonoids (rutin and quercetin) and with WPI as an alternative protein source. The highest loading capacity (11.18 ± 0.17%) and encapsulation efficiency (72.50 ± 0.85%) were achieved for naringenin under these conditions. Quercetin exhibited superior performance, with a loading capacity of 14.1 ± 3.12% and an encapsulation efficiency of 94.36 ± 5.81%, indicating a stronger affinity for the delivery system. WPI showed lower encapsulation efficiency than NaCas. Ternary systems (BSG-WSE, NaCas, and naringenin) formed under different pH and heat treatments displayed distinct morphologies and interactions. The pH 4 system demonstrated good dispersion and pH-responsive release of naringenin, highlighting its potential as a delivery vehicle for hydrophobic flavonoids. BSG-WSE significantly improved the stability of protein-based complexes formed via pH-driven assembly. Physicochemical characterization, rheological analysis, and release studies suggest that this system is particularly suitable for semi-solid food products such as yogurt or emulsions, supporting its application in functional food development. Full article

Poly(acrylic acid)/polyvinylpyrrolidone (PAA/PVP) hydrogen-bonded complexes are of growing interest as functional materials for biomedical applications. However, the influence of polyhydroxyl additives, such as polyols and sugars, on complex formation and material performance remains insufficiently understood. This study aimed to elucidate how polyhydroxyl compounds affect the physical properties of PAA/PVP complexes. Dried PAA films were brought into contact with aqueous PVP solutions containing various additives (glycerol, sugar alcohols, or sugars), and the resulting hydrogels were dried to form films. Their swelling behavior in water and PBS, thermal stability, and mechanical properties were comparatively evaluated. Sugar alcohols markedly improved swelling and flexibility, whereas sugars showed limited effects. Glucitol exhibited intermediate performance due to a high tendency toward intramolecular hydrogen bonding in aqueous media. Mechanistic analysis suggested that sugar alcohols act in a chaperone-like manner during complex formation, promoting microphase-separated structures composed of hydrogen-bonded domains and free segment regions. These findings provide new molecular insight into designing PAA/PVP-based materials with additives for biomedical applications. Full article

This study aimed to synthesize a magnetic biochar@ZIF-8 composite derived from almond shell biomass for the adsorption of fluoroquinolones (FQs) from aqueous media. The biochar was prepared under different pyrolysis conditions using a central composite design (CCD) based on temperature and residence time, with biochar yield (%) and ofloxacin adsorption capacity selected as the response variables. Subsequently, the composite was obtained by combining KOH-activated biochar with ZIF-8 and magnetic particles, producing a hierarchically porous material with enhanced surface area and functional groups favorable for adsorption. The physicochemical and morphological properties of the composite were characterized by SEM–EDS, FTIR, BET, TGA, and XRD analyses, confirming the successful incorporation of ZIF-8 and magnetic phases onto the biochar surface. The adsorption performance was systematically evaluated by studying the effects of pH and contact time. The kinetic data fitted well to the pseudo-second-order model, suggesting that chemisorption predominates through π–π stacking, hydrogen bonding, and coordination interactions between FQ molecules and the active sites of the composite. Furthermore, the material exhibited high reusability, maintaining over 84% of its adsorption capacity after four cycles, with efficient magnetic recovery without the need for filtration or centrifugation. Overall, the magnetic biochar@ZIF-8 composite demonstrates a sustainable, cost-effective, and magnetically separable adsorbent for water remediation, transforming almond shell waste into a high-value material within the framework of circular economy principles. Full article

Oil spills are a significant environmental issue for marine wildlife and coastal communities. Cellulose derived from citrus peel industrial waste is an interesting, economical, and eco-friendly advantageous material that was used for the first time with the aim of developing a low-cost and sustainable sorbent for water purification. Citrus peel cellulose was grafted with methyl acrylate to enhance hydrophobicity and favor the oil adsorption in aqueous media. Grafting copolymerization was performed in a simple manner, and the conditions were optimized in terms of monomer concentration, amount of catalyst, time, and temperature. The modified cellulose polymer was obtained in different grafting percentages, with a maximum of 93% grafting. Fourier transform infrared spectroscopy (FTIR), ¹H NMR, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. Finally, the oil adsorption capacity of selected copolymers from freshwater, artificial seawater, and seawater samples was tested in a continuous-flow system. The results showed promising performance retaining diesel in seawater (4.01 g oil/g cellulose), demonstrating the use of agri-food waste as a natural sorbent in oil removal. Full article

Antibiotics are increasingly detected in aquatic environments, raising environmental and public health concerns due to their persistence and contribution to antimicrobial resistance. This study examines copper sulfide (CuS) nanostructures as potential materials for sustainable water remediation. CuS nanoparticles were synthesized in aqueous media using thioglycolic acid (TGA) as a stabilizing ligand and characterized by UV–Vis, FTIR, XRD, TEM, SEM, and EDS. An optimized Cu:TGA molar ratio of 1:6 yielded stable nanoparticles with a distinct excitonic absorption at 312 nm, strong ligand coordination, and a covellite-type hexagonal crystalline phase. These nanoparticles were subsequently immobilized within calcium–alginate hydrogel beads of two controlled size regimes, producing structurally uniform and recoverable composites. SEM imaging revealed qualitative increases in surface texturing following CuS incorporation, while bead diameter analyses indicated minimal changes in morphology. Overall, the results confirm the successful synthesis, stabilization, and immobilization of CuS nanoparticles within alginate beads and establish a robust materials platform with potential for future adsorption and photocatalytic applications targeting antibiotic contaminants in water. Full article

The photocatalytic reduction of CO₂ in aqueous media offers a sustainable route for solar-to-fuel conversion, yet remains challenged by CO₂’s thermodynamic stability and kinetic inertness, low solubility, and competitive hydrogen evolution. Here, we investigate the interplay between ionic liquids (ILs), photocatalyst supports, and additive composition in directing product selectivity among CO, CH₄, and H₂. Using imidazolium acetate as a benchmark, we demonstrate that ILs not only pre-activate CO₂ but can also undergo decomposition pathways under illumination, notably Kolbe-type reactions leading to methane formation from acetate rather than from CO₂. Comparative studies of Pd-decorated TiO₂ and g-C₃N₄ nanosheets reveal distinct behaviors driven by their interfacial interactions with the imidazolim-based ionic liquid: weak interaction with TiO₂ strongly promotes hydrogen evolution, whereas strong coupling with g-C₃N₄ synergizes with C₁C₄ImOAc to trigger acetate-derived Kolbe reactivity. The systematic evaluation of alternative salts confirms the determinant role of anion basicity and medium-pH-basic anions facilitate CO₂ activation, whereas weakly basic or non-coordinating anions favor water splitting. Overall, these results clarify the dual role of ionic liquids as both CO₂ activators and sacrificial agents, and highlight design principles for improving product selectivity and efficiency in aqueous CO₂ photoreduction systems. Full article