This study aimed to control capsaicin release from montmorillonite (MMT) to extend its half-life and improve stability in simulated gastric fluid. MMT was beneficiated from bentonite and modified with cetyltrimethylammonium bromide (CTAB) at various concentrations to determine the optimal modification ratio. Based on preliminary characterization, the sample modified with CTAB at 50% of its cation exchange capacity (50% CEC-CTAB) was selected for drug loading. Capsaicin was loaded onto beneficiated MMT (F1) and CTAB-modified MMT (F2). In vitro release tests revealed that F2 significantly retarded the release rate compared to F1 (maximum release of 93.3% at 240 min vs 98.3% at 300 min), exhibiting a controlled release profile consistent with the Higuchi kinetic model. Characterization via XRD, FT-IR, SEM, particle size analysis, and Zeta Potential (ζ) confirmed the successful intercalation of surfactant and loading of capsaicin. Preliminary (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT screening using Caco-2 human colorectal adenocarcinoma cells indicated concentration-dependent cytotoxicity, with F2 showing a lower IC50 than blank 50-M-MMT. These findings suggest that CTAB-modified MMT is a promising organoclay-based carrier for the controlled delivery of hydrophobic drugs.
Although the interest in Moroccan clay ghassoul (GHA) has already shifted decades ago from geology and mineralogy to practical applications, e.g. adsorption, ceramics or advanced functional composites, the question of the mineralogical composition of GHA is still not fully answered. The currently accepted opinion that GHA is primarily stevensite cannot be a complete picture of reality due to the detection of fluorine in this clay (in units of mass%). The presence of hectorite explaining the fluorine in GHA has been questioned in the past based on lithium and aluminum content, leading to a preference for other clays, particularly stevensite. However, fluorine was completely omitted, and no explanation for its presence was provided. In this study, ∼2.5 and ∼ 3.6 mass% of fluorine in GHA was confirmed by X-ray fluorescence spectroscopy (XRFS) and X-ray photoelectron spectroscopy (XPS), respectively. For fluorine detection by XRFS, pelletized samples must be used without polyethylene film covering the sample holder. X-ray powder diffraction (XRPD) analysis did not demonstrate fluorides as significant sources of fluorine. XPS analyses ruled out organic substances as the source of fluorine, and demonstrated fluorine as a component of magnesium silicate structure. XRPD analysis of GHA saturated by ethylene glycol revealed the presence of an expanding phase in GHA. This phase is minor and expands like hectorite. The fluorine-rich trioctahedral magnesium smectite appears to be a natural component of GHA. Using exploratory modeling, its amount was estimated to be in the range of 25–40 mass%.
Clay minerals and polyoxometalates (POMs) cannot be effectively combined at the molecular level due to their intrinsic anionic nature. Herein, to fabricate stable high-performance clay-POM composite proton-conducting materials, we first introduced phosphotungstic acid (PW12) to intercalate and exfoliate montmorillonite (Mt), followed by the addition of protonated ethylenediamine (EDA) as a bridging agent to connect Mt nanosheets and PW clusters through proposed Al/Si/Mg–O–NH2+– covalent linkages and N–H‧‧‧O–W hydrogen bonds. As a result, the Mt-EDA-PW composite exhibits high reliability across a wide range of operating conditions, delivering proton conductivities of 1.54 × 10−4–5.65 × 10−4 S cm−1 under 35–95% relative humidities (RHs) at 25 °C, and 2.51 × 10−4–1.46 × 10−3 S cm−1 within 25–120 °C (95% RH). This performance is 10 to 100 times higher than that of pristine Mt, and more stable than that of pure PW, which is attributed to the highly continuous and stable hydrogen-bond network formed by the synergistic integration of Mt nanosheets (with high thermal stability and water-retention capacity) and PW clusters. This work demonstrates the considerable potential of protonated-EDA stabilized clay-POM composites for the optimization of proton conductors.
The development of bilayered geopolymer-concrete composites represents a pivotal stride toward sustainable construction, yet their performance is critically governed by the interfacial bond. While the water-to-binder (W/B) ratio of concrete and the alkali equivalent (AE) of metakaolin-based geopolymer are known to individually affect material properties, their synergistic role in defining the interfacial bond remains unexplored. This study systematically investigates this synergy in simultaneously cast bilayered metakaolin-based geopolymer-concrete composites. The experimental results reveal that increasing the AE from 24% to 32% consistently enhanced interfacial shear strength and modulus, primarily through alkali migration that optimized geopolymerization at the interface and fostered the formation of cohesive C-A-S-H/N-A-S-H gels. In contrast, the W/B ratio exhibits a non-linear effect, with an optimum at 0.3–0.35 for a high AE but at 0.4 for a low AE. This may be a game outcome from the balanced moisture for ion transport against the risks of dilution and segregation. Through further chemical characterization upon the bilayered composites with varying W/B ratios at 28% AE, the enhanced polymerization degree was corroborated at the optimal interface. Moreover, an experimentally validated model was developed to predict the interfacial shear strength of bilayered metakaolin-based geopolymer-concrete composites. Based on the investigated ranges of concrete W/B ratio (0.2–0.6) and geopolymer AE content (20%–40%). Within this calibrated framework, the model identified a potential optimal formulation, corresponding to a W/B ratio of 0.25–0.31 and an AE content of 34.8%–38.4%.
The construction sector is one of the main contributors to global energy consumption and CO2 emissions, largely due to the extensive use of Ordinary Portland Cement (OPC). In response, increasing attention has been given to alternative materials such as geopolymers, which are inorganic materials and offer a more sustainable approach while maintaining adequate mechanical and durability performance. This study investigates the possibility of incorporating Portuguese mine tailings into metakaolin-based geopolymers as a strategy for reducing environmental problems associated with abandoned mines and promoting a circular economy. Kaolin from São Vicente de Pereira was calcined to produce metakaolin, while tailings were collected from the abandoned Moncorvo, Tinoca, and Lousal mines. Raw materials and resulting geopolymers were characterized through X-ray diffraction, X-ray fluorescence, compressive strength, water absorption, and durability tests under sodium chloride, sulfate, acidic conditions, and an accelerated ageing chamber.The results showed that geopolymers with Moncorvo tailings achieved compressive strengths comparable to the reference geopolymer (100% metakaolin), reaching approximately 40 MPa after 90 days of curing. Geopolymers incorporating hematite and quartz demonstrated satisfactory mechanical performance, while formulations containing sulfate generally exhibited lower strength values. Durability tests revealed low mass variation, with some formulations showing mass losses below 0.5% and others presenting slight mass gains. Compressive strength losses after chemical exposure ranged between 3% and 25%, remaining significantly lower than values typically reported for OPC-based materials. The results demonstrate that selected tailings can be successfully valorized in geopolymer production.
Efficient extraction of coalbed methane (CBM) is crucial for optimizing energy structures and ensuring coal mine safety. Flushing medium plays a crucial role in the construction of CBM extraction boreholes. However, conventional drilling fluids frequently suffer from inadequate rheological stability, poor fracture plugging, and loose filter cake structures, which trigger borehole instability in soft coal seams. This study proposes a novel micro-nano CaCO3 particle-enhanced clay-based solid-liquid two-phase fluid (Ca-CBSLTPF) to tackle these challenges. Through macro-micro experiments and numerical simulations, the borehole damage evolution, mud cakes and fluid performance, and wall-healing mechanisms were systematically evaluated. The results indicate that the Ca-CBSLTPF is able to heal the borehole wall and form a stable deposit layer to support the borehole. Compared to CBSLTPF, Ca-CBSLTPF forms a denser filter cake, with an average thickness approximately twice as thick and a strength more than three times greater. XRD and FTIR analyses suggest high-density spatial intercalation of rigid particles and the formation of a dense intermolecular hydrogen-bonding network within the clay-polymer matrix. The Ca-CBSLTPF exhibits superior water retention and rheological properties, whose thixotropic structure recovery rate reaches 115%, and it maintains a water retention capacity of over 90% even under high-temperature conditions. Based on the results of the CT 3D reconstruction, the Ca-CBSLTPF effectively suppresses the development of peri-borehole fractures. SEM-EDS mappings show calcium-rich regions associated with the treated fracture surfaces, a phenomenon possibly linked to CaCO3 bridging and sealing. The water seepage simulation reveals that Ca-CBSLTPF effectively inhibits fluid permeation, reducing the pathways. This study aims to develop a new technology to improve the stability control of coal seam boreholes.
In radioactive waste disposal facilities, the coupled mechanical–chemical phenomena, specifically the effects of alkaline alteration on the mechanical properties of compacted bentonite, must be evaluated in the context of long-term cement–bentonite interaction. This study investigated the tensile strength of compacted Ca-bentonite immersed in 5 mmol/L Ca(OH)2 at 40 °C for up to 704 days, focusing on the development of interparticle cementation through secondary-product precipitation. During immersion, changes in Si and Ca concentrations in the solution indicated the dissolution of primary minerals such as SiO2 followed by precipitation of secondary products. Splitting tensile strength increased from approximately 0.07 MN/m2 before alteration to 0.28 MN/m2 after 704 days of immersion, while the axial strain at failure decreased. Calcite or aragonite was identified by both X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses in the specimens immersed for 511 days or longer. In the NH4Cl leaching test, a slight increase in the leachable Ca suggested a slight increase in the proportion of exchangeable Ca ions after immersion, whereas the increase in leachable Si suggested dissolution of Si-bearing secondary products formed during immersion. Both the slight increase in the proportion of exchangeable Ca ions and the precipitation of secondary products may have contributed to the development of cementation and the increase in tensile strength of compacted bentonite. These findings provide insight into the coupled mechanical–chemical evolution of bentonite under alkaline conditions and contribute to the assessment of the long-term performance of engineered barriers.
The urgent need for efficient antibiotic degradation is underscored by persistent detection of elevated concentrations in wastewater. While metal-organic frameworks (MOFs) hold photocatalytic promise due to structural tunability, their bulk forms suffer from limited active site exposure. To overcome this, we develop sepiolite-doped MOF composites via in-situ solvothermal synthesis, implementing crystal facet engineering to regulate photocatalytic behavior. The abundant Si-OH and Si-O-Si groups in sepiolite preferentially coordinate with Fe3+, directing facet orientation to induce morphological transformation. This multi-level regulation narrows the bandgap for enhanced light harvesting, suppresses carrier recombination via increased active sites, and weakens FeO bonds to facilitate H2O coordination-enabling efficient hole-mediated ·OH generation. These synergies drive 99% ofloxacin degradation within 50 min, representing a 50-fold rate enhancement over pristine Fe-MOF. This work establishes facet engineering as a transformative strategy for environmental remediation and provides a mineral-mediated design blueprint for high-performance MOF photocatalysts.
The composition of the amorphous phase in aluminosilicates is recognized as a key factor influencing the degree of geopolymerization. This research aims to examine the impact of thermal activation on the characteristics of the amorphous phase changes, and reactivity of iron and aluminum-rich lateritic soils, two compositional end-members of the laterite weathering. The effects of calcination temperature on phase evolution, amorphous phase development and elemental distribution were evaluated through dissolution behavior in alkaline solution, chemical, calorimetry and microstructural analyses. The thermodynamic modelling of the energy input has also been carried out to evaluate the impact of mineralogy on the energy demand for thermal activation of laterite. The maximum amorphous SiO2 and Al2O3 contents in both laterites are obtained at 600 °C. Meanwhile, goethite-rich laterite reaches its highest level of amorphous iron at 700 °C, which helps improve binding properties within cementitious matrices. Thermal activation within the 500–600 °C range achieves an optimal balance of energy efficiency, formation of reactive phases, and strength development. Both gibbsite and kaolinite influence the energy requirement. However, the kaolinite content predominantly controls strength enhancement, while gibbsite transformation into γ-Al2O3 decreases the reactivity and reveals lower strength. An increase in metakaolinite and reactive iron content promotes the formation of iron-rich geopolymers, resulting in elevated compressive strength (45 MPa). Overall, these insights provide a scientific basis for adapting calcination protocols to maximize the reactivity and structural contribution of the two types of lateritic soil, ultimately enabling the production of geopolymer with enhanced compressive strength and microstructural integrity.
The Karlovassi basin at Samos Island, East Aegean, Greece, hosts Li-rich volcanosedimentary rocks of Upper Miocene age. The parent materials were deposited and altered in an alkaline lake. The bulk sedimentary rocks contain up to 1200 ppm Li. The Li-occurrences are typical clay-type ones, with the main Li-mineral being trioctahedral, smectite, having characteristics of hectorite with minor stevensite. Most Li-rich outcrops contain mixtures of trioctahedral and dioctahedral smectites, and few Li-rich sedimentary rocks host Li in swinefordite-type smectite (dioctahedral smectite with trioctahedral domains) and dioctahedral illite. At least two generations of smectite have been recognized according to the smectite chemical characteristics. Except for the trioctahedral smectite, the alkaline environment of the lake is evidenced by the presence of Mg‑carbonates, namely dolomite and magnesite, borates (colemanite and ulexite), sulphates (gypsum, celestine), alkaline zeolites (HEU-type and analcime) authigenic illite and authigenic K-feldspar. The relative abundances of the authigenic phases, which are distributed in alteration zones, depend on local variations of alkalinity, salinity, pH and αSiO2 of lake water. The source of Li to form the occurrences is hydrothermal, linked to a magma chamber, located underneath or at the E-SE margins of the basin, with the hydrothermal fluids circulating along NW-SE trending fault lines crosscutting the basin. Surface runoff was vital for the supply of Mg2+ and controlling alkalinity.
Bentonite clay is widely used in engineered barriers, such as geosynthetic clay liners (GCLs), to safely contain wastes and chemicals. In addition to low hydraulic conductivity and diffusion coefficients, bentonite has been shown to exhibit membrane behavior (anion restriction) which can enhance long term containment performance. However, prior experimental studies on GCLs and other clay barriers have primarily focused on membrane behavior for chloride-based solutions. This study investigated diffusion and membrane behavior for two different anions (sulfate and chloride) through GCLs for a range of solution concentrations. Significant membrane behavior was observed for both KCl and K2SO4 solutions, with measured membrane efficiency coefficients (ω) as high as 0.75. These results provide the first direct evidence of the significance of membrane behavior in GCLs for sulfate. Further, ω values were higher for sulfate than for chloride, aligning with existing conceptual models of ion restriction in clay membranes. The findings suggest that membrane effects in bentonite barriers containing solutions with anions with greater hydrated radii than chloride may be more significant than anticipated based on existing experimental literature. The results have important implications for understanding anion transport through bentonite, and support advancements in coupled transport modeling and performance-based design of containment systems.
Layered aluminosilicate minerals are promising precursors for alkali-activated materials, but their stable lamellar structures can restrict dissolution and gel formation. This study investigated the effects of mechanochemical activation (MCA) on muscovite, kaolinite, and an equal-mass muscovite–kaolinite mixture, focusing on structural evolution, alkaline reaction behavior, gel formation, and mechanical performance. Under identical milling conditions, muscovite underwent more pronounced structural disordering and exhibited faster ionic release and more sustained late-stage polymerization than kaolinite. Accordingly, the muscovite-derived geopolymer achieved the highest 28 d compressive strength of 22.22 MPa. Fourier transform infrared (FTIR) spectral deconvolution showed that the Q4/(Q3 + Q4) area ratio reached 42.3% in the muscovite-derived geopolymer, compared with 29.9% and 28.4% in the mixture- and kaolinite-derived systems, respectively, indicating a greater contribution from highly connected SiOT environments. Point-based backscattered electron imaging coupled with energy-dispersive X-ray spectroscopy (BSE–EDS) further showed that 67% of the analyzed points in the muscovite-derived geopolymer fell within the Al/(Na + K) <1. The equal-mass mixture showed no synergistic enhancement, exhibiting weaker dissolution–polymerization coupling and lower strength than the muscovite-derived system. The amorphous fraction determined by X-ray diffraction (XRD) cannot be directly equated with reacted gel content because it includes both newly formed products and mechanically disordered precursors. These findings highlight the importance of mineral-specific structural disordering and reaction competition in MCA-activated clay geopolymers.
Traditional wound dressings lack antibacterial properties and may cause wound damage during dressing changes, impairing healing. Therefore, single-function dressings cannot meet the multifaceted requirements of modern wound healing processes. This study successfully prepared a Cu2O/PDA-MMT by loading cuprous oxide nanoparticles (Cu2O NPs) onto polydopamine (PDA)-modified montmorillonite (MMT), which was then incorporated with chitosan (CS)/polyvinyl alcohol (PVA) via a one-step blending method to fabricate CS/PVA/Cu2O/PDA-MMT hydrogels. Characterization techniques including XRD, FTIR, TG, and SEM confirmed the successful preparation of the material, while systematic evaluation demonstrated its physicochemical properties such as gel fraction, porosity, and mechanical performance. Antimicrobial experiments, cell compatibility tests, mouse tail-amputation hemorrhage models, and full-thickness skin wound infection models demonstrated that the 1% CS/PVA/Cu2O/PDA-MMT hydrogel not only exhibited over 95% antimicrobial inhibition rates against both test bacterial strains but also possessed excellent biocompatibility. It significantly reduced blood loss in rat tail hemorrhage models. When treating full-thickness skin wounds, this hydrogel effectively controlled infection, accelerated healing, achieved a wound healing rate exceeding 97% by day 12, and promoted tissue regeneration. These outstanding properties position it as a wound dressing material with significant clinical application potential.
We measured the water pore diffusion coefficient of a sample from the Toarcian formation at the Tournemire Underground Research Laboratory at 4 temperatures (10, 30, 50 and 70 °C), corresponding to the range of temperatures expected during the thermal phase of a high level nuclear waste storage.Using a fast NMR based technique, diffusion coefficients could be obtained in about 20 h for each temperature with high accuracy. Effective diffusion coefficients at 20 °C (2.7 × 10−11 m2/s) agree with existing data on similar claystones and tracer measurements on similar samples. Using an Arrhenius model an activation energy of 22.9 kJ/mol is found in the temperature range 30–70 °C, a value larger than those found by other authors in other claystones (17 to 21 kJ/mol). From NMR T2 relaxation time data, the activation energy of surface diffusion is evaluated at 9.6 kJ/mol. When considering all data points in the range 10–70 °C, we propose a power law model already used for bulk water to represent the observed non-Arrhenius behavior. The model allows estimating a tortuosity value of 4.1 for the sample considered around 100 °C. We attribute the low diffusion coefficient observed at low temperatures to a balance between surface and volume diffusion, where surface diffusion becomes more dominant at lower temperatures.
Methane (CH4) is a potent greenhouse gas and an important target for near-term climate mitigation. This study investigated the CH4 capture potential of two Australian halloysite-rich kaolin variants, an iron-poor sample (Hal) and an iron-bearing sample (HalFe), in their raw form and after modification by mechanical activation, calcination, and solvent-free biocomposite formation with locust bean gum (LBG) and quillaja saponin (SPN). CH4 adsorption isotherms were measured over environmentally relevant pressures and temperatures (1–5 bar at 15 and 25 °C). All materials showed gradual pressure-dependent CH4 uptake consistent with physisorption, with generally higher adsorption at 15 °C than at 25 °C. However, the overall uptake values were low, remaining below 0.40 mg/g under all tested conditions. Among the modification strategies, biocomposite formation produced the most pronounced enhancement. Hal/SPN and HalFe/SPN showed the highest uptake at 15 °C (0.38 mg/g), while HalFe/SPN remained the best-performing sample at 25 °C (0.37 mg/g). Mechanical activation produced composition- and temperature-dependent effects, whereas calcination at 800 °C consistently reduced CH4 adsorption, with calcined Hal (CHal) showing the lowest uptake. Comparison with previously reported carbon dioxide (CO2) adsorption results showed that CH4 uptake was substantially lower and appeared to be governed more strongly by accessible pore structure and physical confinement than by surface chemistry.
Acute and chronic wounds present a major clinical burden, where uncontrolled bleeding and bacterial infection significantly impede healing. This study presents a comprehensive evaluation of a nanocomposite hydrogel, comprising oxidized bacterial cellulose (oxBC), gelatin, and halloysite nanotubes (Hal), for in vitro hemostatic and antibacterial properties. Rheological analysis confirms its suitability for conforming to irregular wounds. The oxBC/Gel/Hal nanocomposite exhibited an accelerated clotting time of 3.8 ± 0.1 min and a significantly lower blood clotting index of 8.1 ± 1.8% at 5 min, demonstrating effectiveness in controlling bleeding. Using vancomycin as a model antibiotic, Hal enabled sustained drug release over 42 days with 74% release, protecting against premature degradation and prolonging antibacterial efficacy against Staphylococcus spp. Biocompatibility, with cell viability >85% across three human cell lines, and hemocompatibility, with near-zero hemolysis, further validate its safety profile. Collectively, this work establishes the oxBC/Gel/Hal nanocomposite as a multifunctional platform that synergistically provides immediate hemostasis and sustained antibacterial action for potential wound care applications.
