Search Results (1,150)

Microbial contamination challenges have led to the development of active edible coatings for fruit preservation. Herein, a Konjac glucomannan (KGM) coating loaded with Ocimum gratissimum (OG) essential oil stabilized by pectin with superior resistance to air permeability, oxidation, and fungal, was prepared in situ on the surface of Mandarin oranges to enhance postharvest fruit quality. The results demonstrated that the KGM-pectin-OG (K-P-OG) 1.5 wt% coating exhibited good performance in terms of stability, adhesion, and wetting. Meanwhile, the coating had an ideal air permeability due to its compact and dense structure based on the good compatibility and interactions between the components. The oxygen permeability of the K-P-OG coating was 7.9 × (10⁻¹⁶ g·cm)/(cm²·s·Pa), which was six orders of magnitude lower than that of the KGM coating. The antioxidant, in vitro, and in vivo antifungal activities against Penicillium italicum of the coating were strengthened by the OG emulsion and mainly depended on its concentration. The storage results showed that the K-P-OG 1.5% coating extended the shelf life of Mandarin oranges by 8 days, reduced the weight loss rate by 13%, and increased the firmness and POD during storage by 24.14% and 100%, respectively, compared with the control group. These results demonstrate that K-P-OG can effectively maintain nutrient content and extend the storage time of Mandarin oranges by enhancing antioxidant capacity and inhibiting fruit respiration and microorganism growth. This study presents a strategy for developing edible coatings for postharvest fruit preservation. Full article

The adsorption of Fe(III) onto the surface of microplastics (MPs) enhances their toxicity and mobility in aquatic environments, posing a serious threat to human health and ecosystem balance. This study investigated the adsorption mechanism and influencing factors of Fe(III) on three types of MPs with varying particle sizes and aging degrees using batch experiments in freshwater and saltwater. Machine learning (ML) techniques were employed to predict the adsorption capacity and conduct attribution analysis. The results showed that Fe(III) adsorption in both freshwater and saltwater followed Pseudo-First-Order kinetics and Langmuir isotherms, indicating a monolayer homogeneous physical reaction driven by oxygen-containing functional groups, hydrogen bonds and aromatic rings on the MP surface. The adsorption capacity of MPs for Fe(III) was higher in freshwater than in saltwater, and was positively correlated with the aging degree and pH value, but negatively correlated with the particle size. Among the tested ML models, the Random Forest and Gaussian Process Regression models with Bayesian Optimization performed well in predicting adsorption capacity, with pH value and aging degree identified as key factors based on SHAP analysis. This study conducted a comprehensive investigation of the adsorption behavior between MPs and Fe(III) in water, providing valuable insights for the risk assessment and prevention of MP and Fe(III) pollution in aquatic environments. Full article

The acidification modification of coal seams is a significant technical measure for transforming coalbed methane reservoirs and enhancing the permeability of coal seams, thereby improving the extractability of coalbed methane. However, the acids currently used in fracturing fluids are predominantly inorganic acids, which are highly corrosive and can contaminate groundwater reservoirs. In contrast, organic acids are not only significantly less corrosive than inorganic acids but also readily bind with the coal matrix. Some organic acids even exhibit complexing and flocculating effects, thus avoiding groundwater contamination. This study focuses on the 1/3 coking coal from the Guqiao Coal Mine of Huainan Mining Group Co., Ltd., in China. It systematically investigates the fractal characteristics and chemical structure of coal samples before and after pore modification using four organic acids (acetic acid, glycolic acid, oxalic acid, and citric acid) and compares their effects with those of hydrochloric acid solutions at the same concentration. Following treatment with organic acids, the coal samples exhibit an increase in surface fractal dimension, a reduction in spatial fractal dimension, a decline in micropore volume proportion, and a rise in the proportions of transitional and mesopore volumes, and the structure of the hydroxyl group and oxygen-containing functional group decreased. This indicates that treating coal samples with organic acids enhances their pore structure and chemical structure. A comparative analysis reveals that hydrochloric acid is more effective than acetic acid in modifying coal pores, while oxalic acid and citric acid outperform hydrochloric acid, and citric acid shows the best results. The findings provide essential theoretical support for organic acidification modification technology in coalbed methane reservoirs and hydraulic fracturing techniques for coalbed methane extraction. Full article

Optimisation of the tensile strength of thermoplastic polymer-matrix composites remains a scientific as well as technological challenge for 3D printing technology due to the mass application of composite materials. Inadequate mechanical properties are due to the mismatch in the surface energies of the polymer and fillers. In this study, an additively manufactured composite was 3D-printed and tested. The composite consisted of a linear low-density polyethylene matrix filled with glass fibres. Composite filaments were extruded from neat and plasma-treated polymer powders. Plasma was sustained in oxygen at 100 Pa by a pulsed microwave discharge, and 250 g of polymer powder of average diameter 150 µm was placed into a dish and stirred during the plasma treatment. The O-atom density at the position of the dish containing polymer powder was about 2 × 10²¹ m⁻³, and the treatment time was varied up to 30 min. A gradual improvement in the composites’ tensile and flexural strength was observed at the plasma treatment time up to about 10 min, and the mechanical properties remained unchanged with prolonged treatment time. The tensile strength of composites prepared from plasma-treated polymer increased by one-third compared to those based on untreated powder. However, reinforcing the modified polyethylene with plasma-treated glass fibres did not result in further significant mechanical improvement compared to untreated fibres. In contrast, strength values doubled using glass fibres with silane sizing in combination with plasma-modified matrix. The results were explained by the increased surface energy of the polymer powder due to functionalisation with polar functional groups during plasma treatment. Full article

The proton exchange membrane fuel cell (PEMFC) is a promising energy conversion technology. The synthesis route of the cathode oxygen reduction catalyst electrode is an important factor affecting the development of the battery. In traditional technology, Pt shows low utilization of oxygen reduction activity due to poor contact between catalyst nanoparticles (NP), the electrolyte, and oxygen. In this work, an effective electrochemical method for the preparation of a Pt/C catalyst electrode was proposed. The carbon paper (CP) substrate was electrochemically activated by HNO₃, and then, Pt nanoparticles were prepared on CP by one-step electrodeposition. Secondly, a Density Functional Theory (DFT) investigation was carried out to elucidate that the N-doped catalyst facilitates the desorption of intermediates from the catalyst surface and promotes the oxygen reduction reaction. Thirdly, the effects of acid activation voltage were discussed. The result shows that increasing the voltage significantly increases the concentration of C–N groups and decreases the particle size of Pt. The effects of acidification concentration were investigated at an optimal activation voltage of 1.6 V. When the activation concentration was 0.1 mol, Pt⁰ reached an optimal value, and therefore obtained an equilibrium between the adsorption of oxygen on Pt and the desorption of the intermediates. Pt/0.1CP_1.6 exhibits better performance than commercial catalysts in oxygen reduction reactions. After 5000 testing cycles, the catalyst showed a constant durability with only a 3.0 mV·dec⁻¹ increase of the Tafel slope and just a 6.7 m²·g_Pt⁻¹ decline of the ECSA. Full article

Humin, as the most stable fraction in soil organic matter, determines possibility of sustainable environmental development by influencing, among other things, the binding and migration of different chemicals in soil. The aim of this paper was to determine changes in the properties of humins after interaction with three selected active substances of herbicides differing in structure and chemical properties (pendimethalin, metazachlor, and flufenacet) and two different commercial products. In accordance with OECD 106 guidelines, humins isolated from eight different soils were saturated with herbicide compounds under study. As humin is a non-hydrolyzable organic carbon fraction, solid state research techniques (elemental analysis, NMR, FTIR, EPR, and UV-Vis) were applied. The results clearly showed that the interaction between humin and herbicides increases the concentration of oxygen-containing groups and the internal oxidation (ω) in humin. For all investigated humins, a reduction in radical concentration was observed. Radicals in humins were not completely quenched; a certain concentration of radicals with unchanged structure always remained in the samples. Other spectroscopic analyses showed no significant changes in the structure of pesticide-saturated and non-saturated humins. This suggests that sorption of the studied compounds occurs on the humins only as a result of the interaction of physical forces on the surface of the studied organic matter fraction. Thus, interaction with the studied herbicides occurs as a surface phenomenon, and the inner core remains protected by the condensed structure and/or strong binding to the clay minerals. Full article

Perfluorooctanoic acid (PFOA), an emerging organic contaminant frequently detected in wastewater, inhibits biological nitrogen removal processes, posing challenges to sustainable wastewater treatment. Mitigating the adverse effects of PFOA while enhancing total nitrogen (TN) removal efficiency remains a critical concern. In this study, three sequencing batch biofilm reactors (SBBRs) were operated under low-oxygen conditions with a C/N ratio of 4.0 to investigate enhanced nitrogen removal under PFOA stress using biochar. Compared to the 78.1% TN removal efficiency in the control reactor (SBBR-0) with an initial TN concentration of 50 mg/L, the addition of PFOA decreased TN removal by 2.3% in SBBR-1, while the combined addition of PFOA and biochar increased it by 3.2% in SBBR-2. Biochar, acting through its electron-donating surface functional groups, mitigated PFOA-induced reactive oxygen species accumulation and increased adenosine triphosphate production. These effects promoted the generation of quorum sensing (QS) signaling molecules, facilitating microbial communication and cooperation. Consequently, the relative abundance of key nitrogen-removing bacteria, such as Thauera (from 7.90% to 9.92%) and Nitrosomonas (from 1.42% to 5.75%), increased, leading to enhanced nitrogen removal efficiency. A metagenomic analysis revealed that biochar significantly reduced the production of antibiotic resistance genes without promoting their dissemination. These findings provide new insights into mitigating the negative effects of PFOA and improving TN removal through QS promotion, offering a potential approach for enhancing the sustainability of wastewater treatment systems. Full article

The oxygen evolution reaction (OER) has, in recent years, attracted great interest from scientists because of its prime role in a number of renewable energy technologies. It is one of the reactions that occurs during hydrogen production through water splitting, is used in rechargeable metal–air batteries, and plays a fundamental role in regenerative fuel cells. Therefore, there is an emerging need to develop new, active, stable, and cost-effective materials for OER. This review presents the latest research on various groups of materials, showing their potential to be used as OER electrocatalysts, as well as their shortcomings. Particular attention has been paid to metal–organic frameworks (MOFs) and their derivatives, as those materials offer coordinatively unsaturated sites, high density of transition metals, adjustable pore size, developed surface area, and the possibility to be modified and combined with other materials. Full article

Microplastics (MPs) and hexavalent chromium (Cr(VI)) are typical environmental pollutants, yet their interactions in aquatic systems remain poorly understood. This study investigates the mutual influence between Cr(VI) and both virgin and aged polystyrene microplastics (PS-MPs) under light conditions. Concentration kinetics revealed that the total chromium concentration remained stable across all systems, while Cr(VI) concentrations decreased over time, indicating that PS-MPs accelerate the reduction of Cr(VI) to Cr(III). Conversely, it had been found that Cr(VI) promoted the aging of PS-MPs, and this was evidenced by an increase in surface roughness and the generation of oxygen-containing functional groups. Cr(VI) led to a rise in the O/C ratio and carbonyl index, providing additional evidence for the aging of PS. Two-dimensional correlation spectroscopy (2D-COS) elucidated that under Cr(VI) exposure, the order of functional group alterations in PS and aged PS exhibited an opposite trend. Additionally, three-dimensional fluorescence spectroscopy revealed distinct changes in the fluorescence characteristics of leached substances from aged and pristine PS, both with and without Cr(VI), under light and dark conditions. These results furnish innovative understandings of environmental behavior and risks associated with the co-occurrence of MPs and heavy metals, highlighting the complex interplay between Cr(VI) and PS-MPs in aquatic environments. Full article

The development of carbonaceous materials such as biochar has triggered a hot spot in materials application. In this study, a new type of char carbon was developed from raw cigarette filter rods (CFRs) via a carbonization process under moderate conditions (T = 550 °C; t_res = 1 h) (CFR char carbon). The produced char was characterized by ATR-FTIR (Attenuated total reflectance—Fourier-transform infrared) spectroscopy, XRD (X-ray diffraction) analysis, GC-MS (Gas Chromatography–Mass Spectrometry), FESEM-EDS (Field-Emission Scanning Electron Microscopy—Energy-dispersive X-ray spectroscopy) technique, XPS (X-ray photoelectron spectroscopy), and N₂ adsorption/desorption (BET) measurements. The obtained carbon material is rich in oxygen-containing functional groups (i.e., C=O, C–O, –C(=O)–CH₃, C–O–C, C–OH, and O=C–O, with chemisorbed oxygen), containing significant amounts of calcium (that originates from CaCO₃) and silicon (Si), generated by reduction of SiO₂. It was found that the formation of char(C)/n-alkane composite material makes that CFR char have a high compressive strength improvement. Moderate carbonization has contributed to the creation of such material that has a fairly high specific surface area (320.93 m²/g), exhibiting a complex hierarchical structure that was characterized by composite Type I/IV(a) isotherm, associated with micro-/mesoporous carbon material. In addition, more directional extensions of this research for future work were proposed, including the implementation of electrochemical research. Full article

Chemiresistive sensors integrated with functionalized conductive polymers have emerged as promising candidates for wearable applications, offering adequate protection against highly toxic and widely prevalent organophosphate compounds, due to their high sensitivity, room-temperature operation, and straightforward fabrication process. However, these chemiresistive sensors exhibit poor resistance to water vapor due to the intrinsic properties of these conducting polymers, likely leading to false sensor alarms. In this study, we engineered a series of water-vapor-resistant, yet organophosphate-sensitive, conducting polymers by electro-copolymerizing hexafluoroisopropanol (HFIP)-grafted 3,4-ethylenedioxythiophene (EDOT-HFIP) with EDOT comonomers bearing hydrophobic alkyl groups of varying lengths (ethyl, butyl, and hexyl). The typical results indicated that increasing the alkyl length and alkyl-bearing EDOT comonomer composition significantly enhanced the water resistance of the EDOT-HFIP copolymers and the copolymer-integrated chemiresistive sensor, but this improvement came at the unacceptable cost of compromising the organophosphate sensitivity. To address this issue, we developed a surface-driven phase-segregation strategy to enrich the alkyl chains on the surface while concentrating the HFIP groups beneath it by treating the silica substrates using oxygen plasma before polymer spin coating, thus decoupling and optimizing the two mutually competing characteristics. Finally, the chemiresistive sensor integrated with the EDOT-HFIP copolymer containing 10% hexyl-grafted EDOT comonomer exhibited an organophosphate (DMMP) resistive response 657 times higher than that to water vapor, and more than two times that of a PEDOT-HFIP sensor, while preserving the original specific sensitivity of the PEDOT-HFIP sensor. Furthermore, it demonstrated a markedly improved shelf storage stability, being directly exposed to air for 14 days without any special protection. We envision that this surface-driven phase-segregation strategy could offer a promising solution to the significant challenge of air moisture interference in highly sensitive polymer sensors, promoting their practical use in real-world applications. Full article

An in-depth investigation of the adsorption and diffusion mechanism of hydrogen in low-rank coals is of great significance for optimizing the technical path of geological hydrogen storage and improving the efficiency of hydrogen storage. Two kinds of coal samples with a low metamorphic degree from Foran Coal Mine and Sihe Coal Mine were used as adsorbents, and the metamorphic degree and molecular structure of the coal samples were determined experimentally, and the adsorption and diffusion mechanism of H₂ molecules in the structure of low metamorphic coal was analyzed from the atomic level based on numerical simulation. It was found that the aliphatic carbon in the low-rank coal mainly links the aromatic ring in the form of a branched chain and exists as an aliphatic ring, side chain, or bridging carbon, and the lower the deterioration degree of the coal, the longer the length of the alkane side chain in the molecular structure. The branched structure present in the aliphatic carbon and the polybenzene ring structure present in the aromatic carbon can provide more effective adsorption sites and enhance the adsorption of H₂ by the low-rank coal structure. High specific surface area and porosity will enhance the adsorption of H₂ from coal samples, while the presence of oxygen-containing functional groups in low-rank coals will strengthen the interaction between the microporous structure and H₂. These findings provide theoretical support for the application of low-rank coals in geological hydrogen storage. Full article

The presence of abundant water vapor in industrial organic waste gases greatly reduces the selective adsorption of volatile organic pollutants (VOCs). The polarity of the adsorbent and VOC molecules plays an important role in the adsorption process, especially in the presence of water vapor. In this paper, commercial coconut shell activated carbon (CSC) was modified by a thermal reduction treatment to obtain heat-treated coconut shell activated carbon (HCSC). CSC and HCSC exhibited similar pore structure characteristics but differed significantly in surface oxygen content (10.97% and 7.55%, respectively). Dynamic adsorption breakthrough experiments were conducted to determine the dynamic adsorption capacities of toluene on both adsorbents under varying relative humidity levels. HCSC demonstrated superior toluene/water vapor adsorption selectivity. Further analyses of toluene adsorption kinetics, activation energy, and water vapor adsorption isotherms revealed that the lower surface oxygen functional group content of HCSC resulted in a weaker surface polarity, facilitating the adsorption of weakly polar toluene. This was attributed to stronger toluene–HCSC interactions and weaker water–HCSC interactions. The dynamic adsorption capacities of three VOCs with varying polarities were also tested on HCSC. The observed VOC/water vapor adsorption selectivity had the following order: toluene > n-heptane > 1,2-dichloroethane. Grand Canonical Monte Carlo (GCMC) simulations were employed to quantify the relationship between the adsorption selectivity of eight VOCs with varying polarities and their molecular polarity. The results indicated a decrease in adsorption selectivity with increasing VOC polarity. A mechanistic analysis suggests that more polar VOCs prefer to adsorb polar oxygen-containing functional groups, competing with water molecules for adsorption sites. Under high humidity, hydrogen bonding leads to the formation of water clusters, exacerbating this competition. This research holds significant implications for the efficient selective adsorption of VOCs with varying polarities in humid industrial conditions. Full article

This study investigates the activation mechanisms of hydrogen peroxide (H₂O₂) using iron-activated carbon (Fe²⁺/H₂O₂/AC) for the efficient degradation of amoxicillin (AM) in wastewater. The system achieved a high degradation efficiency of 90% under alkaline conditions (pH 9), with singlet oxygen (¹O₂) and hydroxyl radicals (^•OH) identified as the dominant reactive species through scavenger experiments. High-performance liquid chromatography–mass spectrometry (HPLC-MS) analysis revealed degradation by-products and proposed reaction pathways, including the loss of amine groups, ring-opening oxidation, and bond cleavage. The structural and morphological properties of Fe²⁺/H₂O₂/AC were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis. The BET surface area of Fe²⁺/H₂O₂/AC was determined to be 128.36 m²/g, with a mesoporous structure facilitating efficient mass transfer and adsorption. The system was systematically evaluated under varying conditions, including H₂O₂ concentration (25–250 mg/L), catalyst dosage (0.05–1.0 mg/L), and pH (3–10). Kinetic analysis revealed that the degradation process follows pseudo-second-order kinetics (R² = 0.966), while adsorption isotherms were best described by the Langmuir model (R² = 0.98). Ecotoxicity tests indicated that the degradation products are less harmful to aquatic organisms. The system demonstrated excellent stability over three consecutive cycles, highlighting its potential for long-term application in treating pharmaceutical-contaminated wastewater. Full article

A growing interest in novel noble metal-free electrocatalysts is fuelled by the pressing need to overcome the drastic demand for sustainable energy sources. To this end, the oxygen evolution reaction (OER) utilising transition metal oxide–carbon composites in alkaline media is considered a robust technology. In many such systems, carbon is used as a conductive additive or support, and the interactions between carbon support materials and the active phase affect the efficiency of the electrocatalyst. Cobalt forms some of the most active and stable electrocatalysts for OER. In carbon-supported systems, the dispersion of the cobalt phase on the carbon surface is a key factor in influencing the catalyst activity in water-splitting reactions. In this study, a low-temperature plasma treatment is used to boost the efficiency of the cobalt active phase by functionalising the carbon support with various oxygen groups. We used a simple deposition–precipitation method to obtain cobalt hydroxide active phase over graphene nanoparticles. The activation of graphene nanoparticles with oxygen plasma allowed us to obtain a catalyst that showed only 317 mV@10 mA·cm⁻². More importantly, in the series of plasma-activated samples, the OER activity was very high in a range of cobalt phase loadings, yielding a material with 2.4 wt.% of cobalt and an overpotential of only 327 mV@10 mA·cm⁻². The results indicate that plasma activation of GNP support maximises the usage of the transition metal active phase, which allows for an improvement in area-normalised and a dramatic improvement in the mass-normalised OER electrocatalytic activity. Full article