Search Results (153)

Ultrasonic-assisted heterogeneous Fenton-like (UHEF) pretreatment is an emerging strategy that overcomes the limitations of traditional homogeneous Fenton systems while enhancing the efficiency of lignocellulosic biomass processing. In this study, we constructed a UHEF system employing iron-loaded zeolite as a heterogeneous catalyst to pretreat eucalyptus sawdust (ES). Process conditions were optimized using response surface methodology (RSM) with a central composite design (CCD), yielding a maximum reducing sugar production of 441.45 mg/g. We systematically investigated the mechanism by which UHEF pretreatment enhances the enzymatic hydrolysis of ES through compositional analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), cross-polarization magic-angle spinning carbon-13 nuclear magnetic resonance (CP/MAS ¹³C NMR), and scanning electron microscopy (SEM). Additionally, recovery and recycling experiments were conducted to evaluate the reusability of the iron-loaded zeolite. XRD, XPS, and ICP-OES were further used to verify the crystalline structure, surface Fe chemical states, and Fe loading of the catalyst, and Fe leaching was quantified for each reuse cycle. The results demonstrated that UHEF pretreatment effectively removed lignin and hemicellulose from ES, disrupted the cellulose crystalline structure, and generated numerous grooves on the substrate surface. These modifications increased the effective adsorption of cellulase and enhanced reducing sugar production to 4.32 times that of raw eucalyptus sawdust (RES). Although the recycling experiments indicated that the stability of the iron-loaded zeolite requires further improvement, the catalyst retained a certain degree of reusability over four consecutive cycles. These findings demonstrate that UHEF pretreatment is a promising approach with broad application prospects in lignocellulosic biorefinery, consistent with recent advances in advanced oxidation processes for biomass valorization. Full article

Two new nitropyridine amino N-oxide derivatives were synthesized and characterized: 3-N-methylamino-4-nitropyridine N-oxide (NOPCH₃) and [(4-nitropyridine-3-yl)amino]propanoic acid N-oxide (NOPCOOH)1. Their molecular and crystal structures were determined by single-crystal X-ray diffraction, and the intermolecular contact patterns were evaluated using Hirshfeld surface analysis. Vibrational properties were investigated by FT-IR and Raman spectroscopy and interpreted with the support of quantum-chemical calculations (DFT). Electronic absorption was examined by UV–Vis measurements, while photoluminescence spectra and decay profiles were recorded under femtosecond excitation and interpreted conservatively in terms of relaxed excited-state emission. Solid-state ¹³C CP-MAS and ¹H WPMLG NMR spectroscopy provided additional support for the chemical constitution of both derivatives, with ¹H spectra interpreted conservatively because of the limitations inherent to solid-state homonuclear-decoupled measurements. A comparative analysis shows that replacing the methyl substituent (NOPCH₃) with the carboxylic-acid side chain (NOPCOOH) modifies the hydrogen-bonding landscape and the local electronic environment of the NO₂ group, which is reflected in the positions and intensities of selected NO₂-related vibrational bands and in the near-UV electronic transitions. Overall, the combined structural and spectroscopic dataset provides a consistent structure–property picture for both N-oxide derivatives and a basis for further studies of their coordination and photophysical behavior. Full article

Wood is a sustainable material, but hygroscopicity can affect dimensional stability and mechanical durability. Recent research has increasingly focused on combining citric acid with various polyols as eco-friendly crosslinking systems to improve wood properties. Herein, a solvent-free and catalyst-free method was used to synthesize bio-based polyesters from citric acid and mannitol. In situ curing was carried out after vacuum-pressure impregnation of fast-growing poplar wood (Populus deltoides Marshall). Morphological characterization showed that the polyester filled the cell lumen and penetrated the cell wall structure. It was confirmed by Fourier Transform Infrared (FTIR) and cross-polarization/magic angle spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR) analysis that the polyester formed covalent ester bonds with wood hydroxyl groups, which indicated successful chemical grafting. The dimensional stability and mechanical properties of the modified wood were greatly improved. The parallel compressive strength of the grain reached 41.5 MPa, which was 41.7% higher than that of the untreated wood. This research adopted a citric acid–mannitol polyester, providing a sustainable, economical, and scalable approach for the development of high-performance, degradable wood composites for construction/furniture applications. Full article

Coal-based humic acid waste residue is a solid waste generated during the production of humic acid products. The extraction of coal-based humin (NHM) from such residues presents an effective approach for solid waste resource recovery. In this study, a novel calcium-based humin (Ca-NHM) was synthesized via a low-temperature-assisted method. The material was characterized and its cadmium passivation mechanism was investigated using scanning electron microscopy (SEM), zeta potential analysis (Zeta), carbon nuclear magnetic resonance (¹³C-CPMAS-NMR), and X-ray photoelectron spectroscopy (XPS). Soil incubation experiments were conducted to determine the actual cadmium adsorption capacity of coal-based humin in soils and to evaluate the stability of cadmium passivation. Plant cultivation experiments were carried out to verify the effects of coal-based humin on migration and transformation in soil, as well as on cadmium bioefficiency. The results showed that Ca-NHM passivated soil cadmium through multiple mechanisms such as ion exchange, electrostatic adsorption, complexation reactions, and physical adsorption. Compared with NHM, Ca-NHM exhibited a 69.71% increase in passivation efficiency, and a 2.44% reduction in cadmium leaching concentration. In Ca-NHM treatments, the above- and below-ground biomass of pakchoi increased by 18.06%, and 80.95%, respectively, relative to the control group. Furthermore, Ca-NHM enhanced the cadmium resistance of pakchoi, reduced the enrichment coefficient, activity coefficient, and activity-to-stability ratio in the above-ground portion of pakchoi, and maintained a transfer coefficient below 1, thereby alleviating cadmium toxicity. In summary, this study provides a theoretical foundation for understanding the mechanisms by which coal-based humin mitigates cadmium toxicity in pakchoi. Full article

Organophilic acidic magadiites were prepared after an acidic magadiite (A-Mgd) reaction with cetyltrimethylammonium solutions containing different anions, such as cetyltrimethylammonium bromide (C16TMABr), cetyltrimethylammonium chloride (C16TMACl), and cetyltrimethylammonium hydroxide (C16TMAOH). The resulting materials were studied as adsorbents for Eosin Y removal from artificially contaminated solution. Successful preparation of oganophilic A-Mgd was achieved using C16TMAOH solution with an increased basal spacing from 1.21 nm to 3.15 nm and uptake C16TMA amount of 1.16 mmol/g. Meanwhile, no variation in the basal spacing of 1.20 nm occurred using C16TMACl and C16TMA Br solutions with an uptake mount of 0.07 to 0.09 mmol/g, respectively. Other techniques supported the behavior of the counteranion of surfactant solution on the synthesis of organophilic A-Mgd samples. 13C CP/MAS NMR data revealed that C16TMA cations displayed all-trans conformation comparable to C16TMABr solid, and ²⁹Si MAS NMR confirmed the stability of the host silicate layers during the reaction. The specific surface area of A-Mgd was reduced after the intercalation of C16TMA cations from 38 m²/g to 11 m²/g. The removal properties of organophilic samples were investigated under different conditions, including the Eosin Y pH solution, initial concentration, dosage mass, and content of C16TMA cations. The maximum removal amount was 70 mg/g at acidic pH and using A-Mgd prepared from C16TMAOH solution, while the other organophilic A-Mgds exhibited low removal amounts of 3 to 5 mg/g. The regeneration tests indicated that the efficiency was maintained after four reuse tests with a drop of 30 to 50% from the initial value after seven cycles. The adsorber batch design was employed to estimate theoretically the required masses of used samples to treat an effluent volume of 10 L at a removal percentage of 95% at a fixed initial concentration of 200 mg/L. In total, 20 g of organophilic prepared from A-Mgd and C16TMAOH solution was needed, while 243 g of sample prepared from C16TMABr solution was required. This study proposes the development of a cost-effective, sustainable solution for dye-contaminated wastewater treatment. Full article

Modern agriculture relies heavily on chemical inputs to sustain productivity, yet their intensive use poses environmental and health risks. Sustainable strategies based on biostimulants have emerged as promising alternatives to reduce agrochemical dependence. Among these compounds, humic substances (HS) stand out for their ability to modulate plant growth and activate defense responses. This study aimed to evaluate the effects of HS from different sources—vermicompost (Vc) and peat (Pt)—on the salicylic acid (SA)-mediated defense pathway in tomato plants (Solanum lycopersicum cv. Micro-Tom) infected with Oidium sp. The HS were characterized by solid-state ¹³C CPMAS NMR to determine the relative distribution of carbon functional groups and structural domains, including alkyl, O-alkyl, aromatic, and carbonyl carbon fractions, as well as hydrophobicity-related indices. Enzymatic activities of lipoxygenase, peroxidase, phenylalanine ammonia lyase, and beta 1,3-glucanase were determined spectrophotometrically, and RT-qPCR quantified gene transcription levels involved in SA signaling and defense (MED25, MED16, MED14, NPR1, ICS, PAL, LOX1.1, MYC2, JAZ, jar1, CAT, POX, SOD, APX, ERF, PR-1, PR-2, PR-4 e PR-5). Both HS significantly reduced disease severity and activated key SA-related defense genes, including the regulatory gene NPR1 and the effector genes PR1, PR2 and PR5, with Pt providing greater protection. Notably, HS amplified defense-related gene expression and enzymatic activities specifically under infection, showing a stronger induction than in non-infected plants. These results demonstrate that structural differences among HS drive distinct and enhanced defense responses under pathogen challenge, highlighting their potential as sustainable tools for improving plant immunity in agricultural systems. Full article

Passion fruit (Passiflora edulis f. flavicarpa), commonly known as yellow passion fruit, is widely grown across tropical and subtropical regions worldwide, with Brazil as one of the top producers. Mexico also produces a significant amount of this variety, mainly for juices, jams, or flavoring in desserts. Since this fruit is highly perishable with a short shelf life, it needs to be consumed or used quickly. Although different preservation methods have been suggested, no structural analyses of the peel have been performed to improve these processes. This study aimed to analyze the structural and chemical properties of the peel’s cuticular matrix to better understand water loss. CPMAS ¹³C NMR analysis revealed a matrix containing polysaccharides, a small amount of aliphatics, and a notable group of aromatic signals that may indicate lignin presence. This was supported by alkaline hydrolysis, which achieved only 30% hydrolysis. Soluble compounds identified included hexoses, palmitic acid, stearic acid, and derivatives of ferulic and caffeic acids, the latter being parts of lignin monomers. MCL and SEM analyses showed features similar to cutans, including pores along the structures. The BET surface area measurement indicated that the insoluble cuticular material (ICM) has a significant specific surface area. The lignin in the yellow passion fruit peel gives the shell toughness, which, along with its pores, may contribute to dehydration and a short shelf life. Full article

Carmustine (BCNU) is a powerful alkylating agent primarily used in the chemotherapeutic treatment of malignant brain tumors. However, its clinical application faces significant constraints due to its lipophilicity, low thermal stability, and rapid degradation in physiological environments. To tackle these challenges, our research aimed at the development and detailed characterization of α-cyclodextrin (α-CD) inclusion complexes (ICs) with BCNU employing three different synthesis techniques: co-grinding, cryomilling, and co-precipitation. The selected synthetic methods displayed variations dependent on the technique used, affecting the efficiency, inclusion ratios, and drug-loading capacities, with co-precipitation achieving the most favorable complexation parameters. Structural elucidation through ¹H NMR chemical shifts analysis indicated that only partial inclusion of BCNU occurred within α-CD in ICs produced via co-grinding, while cryomilling and co-precipitation allowed for complete inclusion. Multimodal spectroscopic analyses (FT-IR, UV-Vis, ¹³C CP MAS NMR, and ESI-MS) further substantiated the effective encapsulation of BCNU within α-CD, and systematic solubility assessments via Job’s continuous variation and the Benesi-Hildebrand method revealed a 1:1 host-guest stoichiometry. The ICs obtained were evaluated for BCNU release in vitro at pH levels of 4, 5, 6.5, and 7.4. The mechanism of BCNU drug release was determined to be Fickian diffusion, with the highest cumulative release noted in the acidic microenvironment. These findings collectively validate the effectiveness of α-CD as a functional excipient for the modulation of BCNU’s physicochemical properties through non-covalent complexation. This strategy shows potential for increasing the stability and solubility of BCNU, which may enhance its therapeutic effectiveness in the treatment of brain tumors. Full article

Plastic pollution from polyethylene-based materials is a critical environmental concern due to their high persistence. Here, we report the first proof-of-concept application of a multitechnique analytical framework for quantifying linear low-density polyethylene (LLDPE) in Tenebrio molitor frass. Artificially enriched frass–LLDPE mixtures were analyzed using thermogravimetric analysis (TGA), TGA coupled with Fourier-Transform Infrared Spectroscopy (FTIR) and Mass Spectrometry (MS), TGA under inert atmosphere, and solid-state ¹³C nuclear magnetic resonance spectroscopy with Cross-Polarization and Magic Angle Spinning (CP-MAS NMR) ¹³C CP-MAS NMR combined with interval Partial Least Squares (iPLS) modeling. Thermal methods provided insight into decomposition pathways but showed reduced specificity at <1% w/w due to matrix interference. CP-MAS NMR offered matrix-independent quantification, with characteristic signals in the 10–45 ppm region and a calculated LOD and LOQ of 0.173% and 0.525% w/w, respectively. The LOQ lies within the reported ingestion range for T. molitor (0.8–3.2% w/w in frass), confirming biological relevance. This validated workflow establishes CP-MAS NMR as the most robust tool for quantifying polyethylene residues in complex matrices and provides a foundation for in vivo biodegradation studies and environmental monitoring. Full article

Two new long-chain N-alkyl imidazole derivatives, 2-(1-octadecyl-imidazol-2-yl)pyridine and 2-(furan-2-yl)-1-(octadecane-1-yl)-1H-imidazole, were synthesized via the Radziszewski reaction followed by N-alkylation. This is the first report of furan-imidazole obtained by this route using furfuraldehyde as a renewable biomass-derived precursor. FTIR, 1D/2D solution NMR, and HRMS confirmed the structural elucidation, while XRD and solid-state ¹³C CPMAS NMR corroborated the crystal structures of the precursors. Notably, previously misassigned ¹H and ¹³C chemical shifts reported in the literature for pyridine and furan-imidazole precursors were corrected. Furthermore, ¹³C CPMAS NMR spectra of those precursors are reported here for the first time. These findings expand the scope of the Radziszewski reaction and provide new insights into the structural characterization of imidazole-based systems. Full article

The growing demand for sustainable biorefinery approaches calls for efficient, environmentally benign strategies to valorize agricultural residues and ensure their complete utilization. This study explores the combination of deep eutectic solvents (DESs) and microwave heating technology as a greener process for the selective fractionation of agri-food waste residues in a zero-waste perspective. Within this framework, five representative biomasses were thoroughly investigated, namely brewer’s spent grain, raw and parboiled rice husks, rapeseed cakes, and hemp hurds. DES formulation was selected for its ability to solubilize and separate lignocellulosic components, enabling the recovery of a polysaccharide-rich fraction, lignin, and bioactive compounds. DES extraction was performed using both microwave heating and conventional batch heating, enabling a direct comparison of the two methods, the optimization of a more sustainable fractionation process, and the maximization of yields while preserving the functional integrity of the recovered fractions. A comprehensive characterization of the separated fractions was carried out, revealing that the two fractionation methods do not yield significant differences in the composition of the primary components. Moreover, a ¹³C CP-MAS NMR analysis of the recovered lignins demonstrates how this analytical technique is a real fingerprint for the biomass source. The results demonstrate the great potential of microwave DES-mediated fractionation as a mild, tunable, and sustainable alternative to conventional methods, aligning with green chemistry principles and opening new approaches for the full valorization of waste byproducts Full article

Leaf litter conservation practices in forests can contribute to increasing CO₂ storage in natural soils as organic matter; however, this process depends on the type of vegetation cover. This study, using different approaches, aimed to assess this process starting from the characteristics of three different types of litters and topsoil (0–5 cm depth) originating from chestnut, beech, and pine in various forest locations within the territory of Edolo (Camonica Valley, Central Italian Alps). Both labile (DOM) and recalcitrant (ROM) organic matter fractions were considered. Microbial degradation activity was strongly influenced by DOM (DOM vs. Respiration mg CO₂ g⁻¹ dry matter: r = 0.96), and NMR spectroscopy showed that aromatic C and polymethylene C in long-chain aliphatic structures (e.g., lipids, cutin) became more evident from litters to topsoils due to a concentration effect. Finally, chemometric elaboration of quantitative and qualitative data identified two principal component (PC) profiles, explaining 88% of the total variance, in which litter and the topsoil samples were spatially separated, indicating that significant changes occurred during the decomposition process. An Evolution Index (EI) calculated highlighted greater changes for chestnut (0.90) followed by pine (0.60) and beech (0.48), in agreement with chemical (degradation rates of 14.21%, 49.11%, and 48% for beech, chestnut, and pine litter, respectively) and spectroscopic data. Beech litter appears to be more efficient at conserving organic carbon. These findings underscore the importance of understanding litter characteristics for forest management, suggesting which species are most effective in promoting soil carbon storage. Full article

The degradation of modern and ancient permafrost-affected soils and organic-rich sediments and the release of relict soil organic matter from the frozen state are critical for understanding the global carbon cycle in a changing climate. The molecular structure of humic acids isolated from modern Cryosols and paleosoils from the Ice Complex deposits in the Batagay megaslump area was investigated. The elemental composition analysis was performed using a CHN analyzer, and molecular composition analysis was determined by CP/MAS ¹³C-NMR spectroscopy. Analysis of the molecular structure of humic acids showed that MIS 5e paleosoils are characterized by a relatively high content of aliphatic structural fragments (C,H-AL—29–36%) and a low content of aromatic structural fragments (AR/AL—0.49–0.43), which reveals low humification rates in this time period. The composition of humic acids from MIS 7 paleosoils shows a relatively high content of aromatic structural fragments compared to modern soils (AR/AL—0.47) and MIS 5e deposits (AR/AL—0.67–0.54), indicating a longer humification process in heterogenic conditions (warm and cold periods). The results indicate that the molecular structure of humic acids is a dynamic parameter of the environment that reflects the local conditions of pedogenesis and organic matter formation. Permafrost thawing leads to the release of organic matter (including matter that is relatively weakly resistant to biodegradation where aliphatic structural fragments dominate the composition of humic acids) that may strengthen the emission of climate-active gases into the atmosphere and boost climate change. Full article

In this study, supramolecular inclusion complexes composed of komecosanol (Ko), a lipophilic compound derived from rice bran, and α-cyclodextrin (αCD) were prepared using a solvent-free three-dimensional (3D) ball milling method. Their physicochemical properties were examined using various techniques. Powder X-ray diffraction analysis of the ground mixture at a Ko/αCD ratio of 1/8 revealed the disappearance of diffraction peaks characteristic of Ko and the emergence of new peaks, indicating the formation of a distinct crystalline phase. Moreover, differential scanning calorimetry analysis showed the disappearance of the endothermic peaks corresponding to Ko, indicating molecular-level interactions with αCD. Near-infrared spectroscopy results suggested the formation of hydrogen bonds between the C–H groups of Ko and the O–H groups of αCD. Solid-state ¹³C CP/MAS NMR and T₁ relaxation time measurements indicated the formation of a pseudopolyrotaxane structure, while scanning electron microscopy images confirmed distinct morphological changes consistent with complex formation. These findings demonstrate that 3D ball milling facilitates the formation of Ko/αCD inclusion complexes with a supramolecular architecture, providing a novel approach to improve the formulation and bioavailability of poorly water-soluble lipophilic compounds. Full article

This study aims to evaluate eco-innovative solutions in the fertilizer industry that allow for waste valorization in the context of a resource-efficient circular economy. A comprehensive reuse strategy was developed for low-rank peat and post-cultivation horticultural mineral wool, involving the extraction of valuable humic substances from peat and residual nutrients from used mineral wool, followed by the use of both post-extraction residues to produce organic–mineral substrates. The resulting products/semifinished products were characterized in terms of their composition and properties, which met the requirements necessary to obtain the admission of this type of product to the market in accordance with the Regulation of the Minister for Agriculture and Rural Development of 18 June 2008 on the implementation of certain provisions of the Act on fertilizers and fertilization (Journal of Laws No 119, item 765). Elemental analysis, FTIR spectroscopy, and solid-state CP-MAS ¹³C NMR spectroscopy suggest that post-extraction peat has a relatively condensed structure with a high C content (47.4%) and a reduced O/C atomic ratio and is rich in alkyl-like matter (63.2%) but devoid of some functional groups in favor of extracted fulvic acids. Therefore, it remains a valuable organic biowaste, which, in combination with post-extraction waste mineral wool in a ratio of 60:40 and possibly the addition of mineral nutrients, allows us to obtain a completely new substrate with a bulk density of 264 g/m³, a salinity of 7.8 g/dm³ and a pH of 5.3, with an appropriate content of heavy metals and with no impurities, meeting the requirements of this type of product. A liquid fertilizer based on an extract containing previously recovered nutrients also meets the criteria in terms of quality and content of impurities and can potentially be used as a fertilizing product suitable for agricultural crops. This study demonstrates a feasible pathway for transforming specific waste streams into valuable agricultural inputs, contributing to environmental protection and sustainable production. The production of a new liquid fertilizer using nutrients recovered from post-cultivation mineral wool and the preparation of an organic–mineral substrate using post-extraction solid residue is a rational strategy for recycling hard-to-biodegrade end-of-life products. Full article