Search Results (90)

The strength parameters of fault gouge are critical factors that influence sealing capacity and fault reactivation in underground gas storage reservoirs. This study investigates the shear characteristics of remolded fault gouge under varying hydro-mechanical conditions, focusing on the coupled influence of water content and cementation. Sixty fault gouge samples are prepared using a mineral mixture of quartz, montmorillonite, and kaolinite, with five levels of water content (10–30%) and three cementation degrees (0%, 1%, 3%). Direct shear tests are conducted under four normal stress levels (100–400 kPa), and microstructural characteristics are examined using SEM. The results show that shear strength and cohesion exhibit a non-monotonic trend with water content, increasing initially and then decreasing, while the internal friction angle decreases continuously. Higher cementation degrees not only enhance shear strength and reduce the softening effect caused by water but also shift the failure mode from ductile sliding to brittle, cliff-type rupture. Moreover, clay content is found to modulate the degree—but not the trend—of strength parameter responses to water and cementation variations. Based on the observed mechanical behavior, a semi-empirical shear strength prediction model is developed by extending the classical Mohr–Coulomb criterion with water–cementation coupling terms. The model accurately predicts cohesion and internal friction angle as functions of water content and cementation degree, achieving strong agreement with experimental results (R² = 0.8309 for training and R² = 0.8172 for testing). These findings provide a practical and interpretable framework for predicting the mechanical response of fault gouge under complex geological conditions. Full article

Background/Objectives: Denture hygiene is essential for the prevention of oral candidiasis, a condition frequently associated with Candida albicans colonization on denture surfaces. Cetylpyridinium chloride (CPC)-loaded montmorillonite (CPC-Mont) has demonstrated antimicrobial efficacy in tissue conditioners and demonstrates potential for use in antimicrobial coatings. In this study, we aimed to develop and characterize CPC-Mont-containing coating films for dentures, focusing on their physicochemical behaviors and antifungal efficacies. Methods: CPC was intercalated into sodium-type montmorillonite to prepare CPC-Mont; thereafter, films containing CPC-Mont were fabricated using emulsions of different polymer types (nonionic, cationic, and anionic). CPC loading, release, and recharging behaviors were assessed at various temperatures, and activation energies were calculated using Arrhenius plots. Antimicrobial efficacy against Candida albicans was evaluated for each film using standard microbial assays. Results: X-ray diffraction analysis confirmed the expansion of montmorillonite interlayer spacing by approximately 3 nm upon CPC loading. CPC-Mont showed temperature-dependent release and recharging behavior, with higher temperatures enhancing its performance. The activation energy for CPC release was 38 kJ/mol, while that for recharging was 26 kJ/mol. Nonionic emulsions supported uniform CPC-Mont dispersion and successful film formation, while cationic and anionic emulsions did not. CPC-Mont-containing coatings maintained antimicrobial activity against Candida albicans on dentures. Conclusions: CPC-Mont can be effectively incorporated into nonionic emulsion-based films to create antimicrobial coatings for denture applications. The films exhibited temperature-responsive, reversible CPC release and recharging behaviors, while maintaining antifungal efficacy, findings which suggest the potential utility of CPC-Mont-containing films as a practical strategy to prevent denture-related candidiasis. Full article

This study explores a series of eco-compatible, safe, inexpensive, and recyclable catalysts for the aza-Michael reaction, an essential transformation for constructing C-N bonds. In particular, we focus on hydrothermal carbons (HCB and HCC) prepared from chestnut cupule waste under mild, aqueous conditions, offering a sustainable alternative to traditional pyrolytic methods. These carbonaceous solids, thoroughly characterized by physicochemical techniques, exhibit notable catalytic activity, completing aza-Michael reactions in as little as 5–30 min for various model substrates. Their performance was benchmarked against Montmorillonite K10, [Cho][Pro] ionic liquid, and K10+[Cho][Pro], with the latter combination and [Cho][Pro] alone giving the fastest conversions. For example, the reaction of benzylamine with acrylonitrile reached complete conversion (typically 95% yield) in five minutes using [Cho][Pro], K10+[Cho][Pro], or likewise with HCB and HCC. Although the reactions catalyzed by hydrothermal carbons did not outperform in general those using K10-[Cho][Pro] or [Cho][Pro], they proceeded rapidly and afforded good to excellent yields. Furthermore, the HCC catalyst demonstrated excellent recyclability, maintaining its activity and yield over at least five cycles. These findings underscore the potential of hydrothermal carbons as efficient green heterogeneous catalysts, combining high surface area, porosity, and reusability with strong catalytic performance and scalability, in alignment with the principles of the circular economy. Full article

The subject of the conducted study was primarily focused on the development of a new type of polymer blend modified with the use of nanosized fillers. The research concept involved the use of polycarbonate/polyethylene terephthalate glycol (PETG/PC) blends modified with the EBA-GMA impact modifier (ethylene–butylene–acrylonitrile copolymer) and three different types of nanofillers: montmorillonite (MMT), halloysite (HNT), and carbon nanotubes (CNT) of two types. The combination of PC, PETG, and EBA phases was used in order to achieve enhanced mechanical performance and stable processing properties. The results of the conducted study revealed that for the toughened PETG/PC/EBA blends, the impact resistance was strongly improved from the reference by 1.5 kJ/m² to 15 kJ/m². However, the results for the nanocomposites revealed that the MMT and HNT additions were limiting the impact strength. In contrast, the Charpy test results for CNT were again close to 15 kJ/m². The results of the thermal resistance measurements again revealed more favorable properties for CNT-modified PETG/PC/EBA blends. Full article

Cyanobacteria are a widespread group of photosynthesizing prokaryotes potentially relevant for space exploration, as they can produce both oxygen and organic matter. These organisms have been repeatedly proposed as tools for colonizing planetary bodies in the solar system. We used several Martian regolith simulants to support the growth of three widespread filamentous cyanobacteria (Desmonostoc muscorum UTAD N213, Anabaena cylindrica UTAD A212 and an uncharacterized Desmonostoc sp.). All cyanobacteria grew well on the surface of the commercial simulants MGS-1 and MMS-2 and in soluble extracts obtained from them, suggesting that these Martian regolith analogs contain everything necessary to sustain cyanobacterial growth, at least in the short term. We also evaluated the survival of the two Desmonostoc species under desiccation and UV-B radiation, using the same regolith simulants and two clays: Montmorillonite and nontronite. Desiccation hindered growth, but both cyanobacteria were able to recover in less than 30 days in all cases after desiccation. Short irradiation times (up to 1000 kJ/m²) did not consistently affect survival, but longer ones (24,000 kJ/m²) could fully sterilize some samples, although cyanobacteria within MGS-1, montmorillonite and nontronite showed signs of recovery in the long term (>70 days). Clays led to very fast recoveries, particularly montmorillonite. Full article

Highly toughened bio-based polylactic acid (PLA)/Eucommia ulmoides gum (EUG) blends were prepared using organic montmorillonite (OMMT) as a compatibilizer through melt-blending. Both the theoretically predicted values and the experimental results confirm that the majority of the OMMT’s nanolayers are selectively localized at the PLA/EUG interface. This localization leads to improved interfacial properties and a more refined morphology of the dispersed EUG phase. By increasing the OMMT content from 0 phr to 2 phr, the notched Izod impact strength of the PLA/EUG/OMMT (85/15/2) blend increases to a maximum value of 44.6 kJ/m². This is significantly higher than the values observed for neat PLA at 3.8 kJ/m² and the PLA/EUG (85/15) blend at 4.7 kJ/m². Moreover, compared to neat PLA and the PLA/EUG (85/15) blend, which exhibit poor tensile ductility, as indicated by their low elongation at break, the PLA/EUG/OMMT blend demonstrates a substantial improvement in its tensile ductility when an appropriate amount of OMMT is added. It is believed that the enhanced toughness of the PLA/EUG/OMMT blends can primarily be attributed to the refinement and more uniform dispersion of the EUG domains, which is caused by the incorporation of OMMT. In addition, the crystalline properties, thermal degradation behavior, and extrudate swell behavior of the PLA/EUG blends with and without OMMT were also evaluated in detail. Finally, the experimental results prove that the PLA/EUG (85/15) blend containing 2 phr of OMMT exhibits the highest impact toughness and tensile ductility, accompanied by improved thermal stability and extrusion stability. Full article

This study analyzes the mineralogical and geochemical composition of 38 surface sediment samples from the northwest African continental shelf between Cap Boujdour (26.5° N) and Cap Blanc (20.5° N). Using a multiproxy approach, sediment characteristics were assessed through grain size, calcium carbonate (CaCO₃), and organic carbon (Corg) measurements, along with X-ray diffraction (XRD) and X-ray fluorescence (XRF) for geochemical analysis. Bottom water properties, including temperature, salinity, and dissolved oxygen, were measured at various stations using a Conductivity, Temperature, and Depth (CTD) sensor. The results reveal that the inner shelf sediments are primarily mud, with high concentrations of terrigenous elements such as iron (Fe), silicon (Si), rubidium (Rb), and potassium (K), with Fe and Si concentrations ranging from 2.1 to 4.3 wt%. The middle and outer shelf sediments are dominated by biogenic carbonates, with CaCO₃ levels approaching 65%, and elevated calcium (Ca) and strontium (Sr) content. These areas also exhibit the highest bottom water temperatures (up to 16 °C), salinity (36%), and moderate oxygen levels (2–4 mL/L). Slope sediments are enriched with mud and montmorillonite, and aeolian contributions are more pronounced south of Dakhla, as indicated by elevated quartz levels (up to 20%) and the presence of illite, aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃). This study provides valuable new insights into sedimentary processes on the northwest African shelf, offering implications for regional environmental management and resource exploration. Full article

The current investigation aims to offer fundamental, molecular- to microscopic-level descriptions of methane gas inside natural source clay minerals. Texas montmorillonite (STx-1), Georgia kaolinite (KGa-2), and Ca²⁺-saturated Texas montmorillonite (Ca-STx-1, Ca-bentonite) were utilized as subsurface model clay minerals for elucidating nano-confinement behaviors of ¹³C-labeled methane gas. High-pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) was used to describe the interactions between methane and the clays by varying temperature and pressure. Proton-decoupled ¹³C-NMR spectra were acquired at 28.2 bar at 307 K, 32.6 bar at 346 K, 56.4 bar at 307 K, 65.1 bar at 346 K, 112.7 bar at 307 K, and 130.3 bar at 346 K. In the pure state, no significant thermal effect on the behavior of methane was observed. However, there was a perceptible variation in the chemical shift position of confined methane in the mixtures with the clays up to 346 K. Conversely, the ¹³C-NMR chemical shift of methane altered by varying pressure in a pure state, and the mixtures with clays, attributed to the interaction of methane with the clay surfaces or the nanopore network of the clay–silica mixed phase. Pressure-induced shifts in methane peak positions were observed: 0.25 ppm (28.2–56.4 bar) and 0.47 ppm (56.4–112.3 bar) at 307 K. For methane in a montmorillonite mixture, shifts were 0.32 ppm for bulk-like methane and 0.20 ppm for confined methane under similar conditions. At 346 K, increasing pressure from 65.1 to 130.3 bar caused shifts exceeding 0.50 ppm, with bulk-like methane showing a 0.64 ppm shift and confined methane a 0.57 ppm shift. There was only one ¹³C-NMR methane peak in the mixture with either kaolinite (KGa-2) or Ca-bentonite with line broadening compared to that of pure methane. Still, two peaks were observed in the mixture with STx-1, explained by the imbibition and mobility of methane in the pore network. Full article

Glycerol is a biogenic waste that is generated in both the biodiesel and oleo-chemical industries. The value addition of surplus glycerol is of utmost importance for making these industries economically profitable. In line with this, glycerol is converted into glycerol carbonate, a potential candidate for the industrial production of polymers and biobased non-isocyanate polyurethanes. In addition, glycerol can also be converted into solketal, which is the protected form of glycerol with a primary hydroxyl functional group. In this contribution, we developed a microwave-assisted solvent and catalyst-free method for converting solketal into solketal carbonate. Under conventional heating conditions, the reaction of solketal with dimethyl carbonate resulted in 70% solketal carbonate in 48 h. However, under microwave heating, 90% solketal carbonate was obtained in just 30 min. From the perspective of sustainability and green chemistry, biomass-derived heterogeneous catalysts are gaining importance. Therefore, in this project, several green catalysts, such as molecular sieves (MS, 4Å), Hβ-Zeolite, Montmorillonite K-10 clay, activated carbon from groundnut shell (Arachis hypogaea), biochar prepared from the pyrolysis of sawdust, and silica gel, were successfully used for the carbonyl transfer reaction. The obtained solketal carbonate was thoroughly characterized by ¹H NMR, ¹³C NMR, IR, and MS. The method presented here is facile, clean, and environmentally benign, as it eliminates the use of complicated procedures, toxic solvents, and toxic catalysts. Full article

Water interacting with clay minerals—such as kaolinite, montmorillonite, and pyrophyllite—fundamentally governs their geotechnical and environmental functions, thereby influencing parameters such as retention, transport, and stability. Understanding the effects of temperature on water behavior within clay mineral interlayers is critical for predicting the performance of clay–water systems under dynamic environmental conditions. This study performed molecular dynamics simulations to investigate the structural, dynamical, and mechanical properties of interlayer water in three representative clay minerals over a temperature range of 298.15–363.15 K. Our analyses focused on mean squared displacement (MSD), density profiles, hydrogen bond dynamics, and stress distributions, thereby revealing the interaction between water structuring and thermal fluctuations. Results indicated distinct temperature-dependent changes in water diffusion and hydrogen bond stability, with montmorillonite consistently exhibiting enhanced water retention and steadier hydrogen bonding networks across the studied temperature spectrum. Density profiles highlighted pronounced confinement effects at lower temperatures that gradually diminish with increasing thermal energy. Concurrently, the stress distributions revealed the mechanical responses of clay–water interfaces, highlighting the interplay between thermal motion of water molecules and their interactions with the clay surfaces. These findings offer valuable insights into how temperature regulates water behavior in clay mineral interlayers and provide a foundation for advancing predictive modeling and the design of engineered systems in water-rich, thermally variable environments. Full article

To propel the development of a robust methylmercury immobilisation technology, CH₃Hg⁺ adsorption on montmorillonite surfaces was simulated herein using density functional theory. This study involved a thorough molecular-level analysis, including factors such as electron potential energy, molecular orbital configurations, stable adsorption configurations, adsorption energies, charge distributions, and density of states. The principal findings are summarised as follows: (1) CH₃Hg⁺ adsorption on the (001) surface was characterised by an adsorption energy ranging from −27 to −51.7 kJ/mol. In this case, Hg was attracted to the involved silicon–oxygen ring cavities. Meanwhile, on the (010) surface, CH₃Hg⁺ exhibited an adsorption energy ranging between −119.4 and −154.3 kJ/mol. In this case, Hg was attracted to hydroxyl groups such as ≡Al(OH)(OH₂) and ≡Si(OH), forming a covalent bond with the oxygen atom of these groups. (2) Comparative analysis revealed that the adsorption energy of CH₃Hg⁺ on the (010) surface surpassed that on the (001) surface. On the (001) surface, electrostatic interactions were the predominant factor influencing adsorption, while on the (010) surface, electrostatic and covalent bonding interactions were important. Notably, the strength of electrostatic interactions was greater on the (001) surface than on the (010) surface. (3) The formation of covalent bonds between CH₃Hg⁺ and the (010) surface was primarily attributed to the overlap of electron cloud between Hg and surface O atoms. In particular, the interaction between the s orbital of Hg and the p orbital of O facilitated the formation of a σ bond. Overall, these findings provide a theoretical framework for the advancement of efficient in situ immobilisation technologies for methylmercury. Full article

Although a lot of recent research revealed advantages of novel biopolymers’ implementation as active food packaging polymers, there is not an equivalent effort from industry to use such films, probably because of the required cost to change the supply chain and the equipment. This study investigates the use of two natural abundant nanoclays, laponite (Lap) and montmorillonite (Mt), as eugenol slow-release carriers for enhancing the functionality of low-density polyethylene (LDPE) active packaging films. The target is to combine the spirit of the circular economy with the existent technology and the broadly used materials to develop a novel attractive product for active food packaging applications. Utilizing a vacuum-assisted adsorption method, eugenol was successfully intercalated into Lap and Mt nanoclays, forming EG@Lap and EG@Mt nanohybrids. Testing results confirmed effective integration and dispersion of the nanohybrids within the LDPE matrix. The most promising final film seems to be the LDPE with 15% w/w EG@Lap nanohybrid which exhibited a higher release rate (k₂ = 5.29 × 10⁻⁴ s⁻¹) for temperatures ≤70 °C, similar mechanical properties, a significantly improved water barrier (D_wv = 11.7 × 10⁻⁵ cm²·s⁻¹), and a slightly improved oxygen barrier (Pe_O2 = 2.03 × 10⁻⁸ cm²·s⁻¹) compared with neat LDPE. Antimicrobial and sensory tests on fresh minced pork showed two days’ shelf-life extension compared to pure LDPE and one more day compared to LDPE with 15% w/w EG@Mt nanohybrid. Full article

The sustainable management of groundwater in the Jimma area is complicated by a lack of comprehensive studies on its chemical makeup and the geochemical processes influencing its hydrochemistry. This research aims to fill that gap by examining 51 groundwater samples from various sources, including deep groundwaters, shallow groundwaters, hand-dug well groundwaters, surface waters, and springs within the area primarily consisting of complex volcanic rocks. The goal is to describe the hydrogeochemical characteristics and determine the key processes affecting groundwater composition in this volcanic area. The study identifies clear patterns in cation and anion concentrations. For deep groundwaters, the average cation concentration is ranked as Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, while shallow groundwaters, hand-dug well groundwaters, surface waters, and springs show a ranking of Ca²⁺ > Na⁺ > Mg²⁺ > K⁺. The major anions are typically ordered as HCO₃⁻ > NO₃⁻ > Cl⁻ > SO₄²⁻. The quantitative hydrogeochemical analysis indicates that the freshwater types in the region are primarily Ca-HCO₃ and Ca-Mg-HCO₃, with some highly mineralized Na-HCO₃ waters also detected. The weathering of silicate minerals mainly drives the geochemical processes affecting groundwater chemistry. An increase in mineralization, suggested by saturation indices, points to a longer residence time underground, with deep groundwaters exhibiting the highest saturation levels and springs the lowest. This mineralization is especially significant for Mg-silicates and carbonates. Stability diagrams for feldspar minerals further demonstrate groundwater evolution along flow paths, revealing that shallow systems are in equilibrium with minerals like gibbsite, whereas deeper systems achieve stability with albite, Ca-montmorillonite, and microcline. Higher CO₂ levels (10^−1.5 to 10^0.5 atm), likely from mantle-magma degassing, add more HCO₃⁻ to the deeper aquifers. This study offers the first thorough characterization of the groundwater composition in the Jimma area and provides important insights into the Jimma area’s hydrogeochemical development, establishing a basis for enhanced groundwater management within this intricate volcanic aquifer system. Full article

CO₂–water–rock interactions have an important impact on the stability and integrity of the caprock in CO₂ geological storage projects. The injected CO₂ in the reservoir enters the caprock via different mechanisms, leading to either the dissolution or precipitation of minerals. The mineral alterations change the porosity, permeability, and mechanical properties of the caprock, affecting its sealing capability. To evaluate the sealing effectiveness of overlying caprock and identify the influencing factors, numerical simulations and experiments were carried out on the mudstone Dongying Formation in Dezhou, China. Based on high-temperature and high-pressure autoclave experiments, batch reaction simulations were performed to obtain some key kinetic parameters for mineral dissolution/precipitation. Then, they were applied to the following simulation. The simulation results indicate that gaseous CO₂ has migrated 7 m in the caprock, while dissolved CO₂ migrated to the top of the caprock. Calcite is the dominant mineral within 1 m of the bottom of the caprock. The dissolution of calcite increases the porosity from 0.0625 to 0.4, but the overall porosity of the caprock decreases, with a minimum of 0.054, mainly due to the precipitation of montmorillonite and K-feldspar. A sensitivity analysis of the factors affecting the sealing performance of the caprock considered the changes in sealing performance under different reservoir sealing conditions. Sensitivity analysis of the factors affecting the sealing performance of the caprock indicates that the difference in pressure between reservoir and caprock affects the range of CO₂ transport and the degree of mineral reaction, and the sealing of the caprock increases with the difference in pressure. Increasing the initial reservoir gas saturation can weaken the caprock’s self-sealing behavior but shorten the migration distance of CO₂ within the caprock. When the content is lower than 2%, the presence of chlorite improves the sealing performance of the caprock and does not increase with further chlorite content. This study elucidates the factors that affect the sealing ability of the caprock, providing a theoretical basis for the selection and safety evaluation of CO₂ geological storage sites. Full article

The development of eco-friendly elastomeric materials has become an important issue in recent years. In this work, thermoplastic elastomer samples of an ethylene–norbornene copolymer (EN) with coffee and tea biofillers mixed with typical fillers such as montmorillonite (MMT), silica (SiO₂), and cellulose were investigated. The aim of this research was to determine the effect of fillers on the properties of the materials and to assess their degradability after two ultraviolet (UV) aging cycles (200, 400 h). The scientific novelty of this work is the assessment of the anti-aging effect of simultaneous biofillers–stabilizers based on coffee and tea waste. The surfaces of the obtained polymer compositions were examined using infrared spectroscopy (FTIR-ATR). Contact angles were determined, and surface energy was calculated. The mechanical properties were tested, and the influence of plant fillers and aging on the color change in the materials was analyzed. The combination of coffee with silica, MMT, and cellulose fillers limited the migration of fatty acids and other compounds from the biofiller to the EN surface (FTIR analysis). Based on the aging coefficients K, it was shown that all coffee- and tea-based fillers stabilized the polymer compositions during UV aging (400 h). The results allowed the authors to determine the importance and impact of waste plant fillers on the degradability of the synthetic EN. Full article