Search Results (494)

In recent years, synergistic effects between inorganic clay minerals (e.g., montmorillonite, sepiolite, kaolinite) and bio-based flame retardants (e.g., chitosan-based, lignin-based, phytate-based) have achieved certain progress in the area of polymer flame retardancy. The effects of bio-based flame retardants are exerted through mechanisms such as catalytic char generation and vapour-phase hindrance. However, they have limitations when used alone, including insufficient thermal stability and the need for a high dosage. Inorganic clays form physical barriers through their layered or tubular structures. The high thermal stability of these structures suppresses heat and mass transfer, thereby offsetting the shortcomings of bio-based flame retardants. This synergistic combination greatly improves the flame retardancy of polymer composites, often strengthening their mechanical performance in the process. It therefore offers great potential for the design of multifunctional, eco-friendly flame-retardant polymer composites. Nevertheless, a systematic review of the synergistic mechanisms, fabrication approaches and application progress of different inorganic clay minerals when combined with various bio-based flame retardants is still lacking. Therefore, this article offers a comprehensive review of the current developments of synergistic systems that incorporate various primary clays, such as sepiolite and montmorillonite, with bio-based flame retardants for usage in polymers. Before this, the synergistic flame-retardant mechanism and the key preparation techniques of the composite system were explained in detail. Finally, this article puts forward solutions to the current challenges and sets out prospects for innovation in the designing of flame-retardant materials and the optimisation of processes. The aim is to promote the sustainable growth of efficient, eco-friendly flame-retardant materials. Full article

Chiral pharmaceuticals (CPs) have gained growing attention in environmental studies regarding the differential behavior of individual enantiomers in racemic mixtures. This study investigates the stereoselectivity and efficiency of montmorillonite (MMT), a natural and low-cost adsorbent, for the removal of a wide group chiral pharmaceuticals and metabolites (atenolol, propranolol, metoprolol, fluoxetine, venlafaxine, norfluoxetine, and O-desmethylvenlafaxine). The effects of adsorption conditions including initial CP concentration, contact time, adsorbent dose, solution pH, and humic acid content were evaluated. In most adsorption experiments, no significant stereoselective behavior was observed, except for the case where a low adsorbent dose was applied. Interestingly, as the solution humic acid content increased (up to 40 mg/L), the adsorption capacity was increased for most of the target CPs. Isotherm studies revealed that the Freundlich model described the experimental data well and the process was favorable. Adsorption mechanism was interpreted by material characterization before and after adsorption. High removal efficiencies (88.0 to 99.8%) and the non-enantioselective behavior of MMT indicate that it can be used effectively for the simultaneous removal of both enantiomeric forms of various chiral pharmaceuticals from aqueous matrices. Full article

Polyvinylidene fluoride (PVDF)/clay nanocomposite membranes with different nanoclay loadings (0–5 wt%) were prepared via the non-solvent induced phase inversion method. Effects of organo-montmorillonite (OMMT) content on the morphology and performance were systematically investigated. Results showed that OMMT was uniformly exfoliated and dispersed in the PVDF matrix, while the nanocomposite membranes consistently maintained the β-crystalline phase of PVDF. The incorporation of nano-clay significantly enhanced membrane hydrophilicity, porosity, pure water flux, and protein rejection performance: when clay content increased to 5 wt%, the pure water flux improved from 89.8 L·m⁻²·h⁻¹ to 216.3 L·m⁻²·h⁻¹, with rejection rates of 98.6% for bovine serum albumin (BSA) and 95.1% for pepsin. Mechanical tests showed that 3 wt% was the optimal clay loading, at which the storage modulus of the membrane increased by 59.8% compared to neat PVDF membranes. Antifouling experiments revealed that the nanocomposite membranes exhibited significantly lower irreversible fouling resistance, substantially improved hydraulic cleaning flux recovery rates, and markedly enhanced antifouling properties. Furthermore, long-term stability, economic analysis, and environmental safety assessments confirmed the practical application potential of these nanocomposite membranes in water treatment. These findings provide theoretical support and technical references for the preparation and application of high-performance PVDF ultrafiltration membranes. Full article

Hepatocellular carcinoma (HCC) incidence in Texas is 45% higher than the national average, with disproportionate burden among the Hispanic/Latino population. Despite significant health disparities, comprehensive evidence on HCC risk factors specific to this population remains limited. This scoping review of 20 primarily observational studies utilized PubMed, EbscoHost, and the PRISMA-ScR checklist to map risk factors in south Texas. Results show that metabolic dysfunction, specifically diabetes and obesity, increases advanced liver disease odds by 7- to 12-fold compared to non-Hispanic groups. Environmental exposures are also significant: aflatoxin was detected in 5.7 to 7.3% of Hispanic/Latino HCC tumors, and cases demonstrated 6-fold higher odds of aflatoxin biomarkers, while alcohol contributed to 3.0% of cancers. Furthermore, PNPLA3 genetic variants exerted synergistic effects with obesity and heavy alcohol consumption. Among four intervention studies, strategies included low-dose calcium montmorillonite clay for aflatoxin reduction, community-health-worker-integrated chronic care, and hospital-based hepatitis screening. However, critical research gaps remain regarding multirisk factor interactions, toxin dose–response characterization, dietary interventions, and longitudinal data. These findings underscore the urgent need for culturally tailored, community-engaged prevention programs and ethnicity-specific HCC guidelines for the Texas Hispanic/Latino population to effectively address these rising health disparities. Full article

Wheat straw is a plant-derived substrate rich in cellulose, hemicellulose, and lignin and represents a major carbon input to agricultural soils. Mineral-associated organic carbon (MAOC) is the most stable soil carbon pool, yet how mineral structure regulates the stability of straw-derived MAOC through microbial processing remains unclear. Here, straw-derived MAOC was formed in artificial soils containing five clay minerals (halloysite, kaolinite, illite, vermiculite, and montmorillonite) during a two-year incubation, followed by a 45-day incubation with a standardized microbial community to quantify CO₂ emission and net carbon balance. Mineral type regulated MAOC mineralization (38.54–54.48 mg C g⁻¹ MAOC). Vermiculite produced the highest CO₂ emission but maintained a positive net carbon balance, whereas illite showed net carbon loss (−0.53 g kg⁻¹). Kaolinite, halloysite, and montmorillonite exhibited lower mineralization and retained net carbon. The 2:1 clay minerals enhanced interlayer interactions and favored accumulation of C=O and aromatic compounds, reflecting stronger microbial transformation and residue retention. In contrast, 1:1 minerals stabilized carbon via edge hydroxyl bonding, which restricted substrate accessibility and slowed decomposition. Cumulative mineralization decreased with initial MAOC carbon but increased with dissolved organic carbon and bacterial abundance. Net carbon retention increased with N-acetylglucosaminidase activity and fungal abundance, indicating joint microbial control via nutrient acquisition and fungal processing. Two contrasting stabilization regimes were observed: high turnover driven by vermiculite and halloysite, and strong protection dominated by montmorillonite and kaolinite. These differences indicate that MAOC stability is jointly constrained by mineral-regulated accessibility and microbial transformation processes. Full article

The growing environmental plastic pollution triggered research for biodegradable and safe materials, among which biopolymer-based films stand as the most promising. Among these, chitosan has gained significant attention due to its biocompatibility, film-forming ability, and inherent antimicrobial properties. In this context, the use of fillers to design chitosan nanocomposite films has been shown to enhance the mechanical, barrier, thermal, optical, and antimicrobial properties of the resulting bioplastics. However, the fate and destiny of these fillers, as well as their impact on the biological properties and biodegradability of chitosan films, remain underexplored. We herein report a more comprehensive screening of a set of fillers, encompassing three clay variants (montmorillonite, sepiolite, and halloysite) and microcrystalline chitin. The films were systematically characterized to assess their antibacterial performance, cytocompatibility, hemocompatibility, and biodegradability. The highest antibacterial activity was observed for CS@MMT-f film towards Staphylococcus aureus and Escherichia coli. Importantly, all developed films demonstrated negligible hemolytic activity and low cytotoxicity, indicating their safety for potential biomedical or food-contact applications. Moreover, the selected films completely degrade within four to six weeks under soil burial conditions, demonstrating their potential as environmentally friendly packaging materials. Full article

Iron-exchanged bentonites derived from a natural montmorillonite-rich clay (Taganskoe deposit, Kazakhstan) were prepared through a simple aqueous ion-exchange route using Fe(II) or Fe(III) inorganic salt precursors, yielding final Fe contents of ca. 5–7 wt.%, while preserving the smectite layered framework. A mild thermal treatment under air was applied to tune iron coordination without triggering major structural collapse. The resulting materials were characterized by ED-XRF, PXRD, FE-SEM/EDX, DLS/ζ-potential and DR UV–Vis–NIR spectroscopy, revealing predominantly exchanged Fe species with a limited fraction of surface iron-oxide clusters, whose contribution increases after activation. Structure–reactivity relationships were probed under mild conditions in liquid-phase ethyl acetate using dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethyl sulfide (2-CEES) as organophosphorus and organosulfur hazardous chemicals and chemical warfare agent simulants, respectively. Fe(III)-bentonite enabled very fast DMMP removal (ca. 93% within 0.5 h) with a remarkable improved performance with respect to Fe(II)-bentonite and the pristine mineral clay. For 2-CEES, the presence of H₂O₂ markedly enhanced oxidation on Fe-containing clays, reaching quantitative abatement within 24 h (up to >90%), with strong retention of oxidized sulfur products by the clay matrix. These results highlight Fe-exchanged natural bentonites as robust, cheap and multifunctional adsorption/catalytic solids for decontamination and water-treatment applications. Full article

The adsorption and desorption behavior of the azo dye Orange II (OII) was investigated using composite beads prepared from shrimp shell–derived chitosan (50 wt%) and montmorillonite-rich clay. The structural and morphological properties of the synthesized beads were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR (Fourier Transform Infrared Spectroscopy). Batch adsorption experiments were performed to evaluate the removal efficiency of OII from aqueous solutions under various conditions, revealing that a low adsorbent dosage (0.5 g L⁻¹) and an acidic medium (pH 4) provided optimal adsorption performance. Adsorption kinetics and equilibrium isotherms were analyzed to elucidate the adsorption mechanism. Thermodynamic parameters indicated that the adsorption process was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0). Equilibrium data were fitted to both Langmuir and Freundlich isotherm models, with the Freundlich model providing the best correlation (R² = 0.99), suggesting multilayer adsorption on a heterogeneous surface. The adsorption capacity increased significantly with temperature, rising from 98.35 mg g⁻¹ at 298 K to 182.57 mg g⁻¹ at 318 K, further confirming the endothermic nature of the process. Kinetic analysis revealed relatively rapid adsorption, with maximum adsorption capacities increasing from approximately 100 mg g⁻¹ at 25 °C to 123 mg g⁻¹ at 45 °C. Regeneration and reusability tests demonstrated that the composite beads could be reused through adsorption–desorption cycles; however, a gradual decline in removal efficiency was observed, decreasing from 97% in the first cycle to 25% after the fifth cycle. This decrease is likely associated with partial structural degradation or the detachment of bead components during repeated regeneration. Overall, the results highlight the potential of chitosan–clay composite beads as promising and sustainable adsorbents for the removal of azo dyes from aqueous media. Full article

Clay minerals in coal play a key role in controlling mineralogical composition, geochemical signatures, and the industrial behavior of coal and its combustion residues. This study investigates the occurrence, provenance, and potential applications of clay minerals in Carboniferous ash-rich coals from the Bogatyr, Lenin, and Saradyr coal mines in northeastern Kazakhstan. A total of 60 coal samples were analyzed using XRD, SEM–EDS/BSE, XRF, and ICP-OES following acid leaching. Based on ash yield, 52 samples were classified as coal (<50% ash), while 8 samples were classified as carbonaceous shale or mudstone (>50% ash). Mineralogical assemblages show clear variability among the studied mines. Saradyr samples are strongly quartz-dominated with lower clay proportions, Bogatyr samples exhibit highly heterogeneous quartz–clay–mica assemblages, whereas Lenin samples are relatively more clay-rich and dominated by kaolinite and illite-group minerals. Across all samples, kaolinite is the dominant clay mineral (16.6–46 wt.%), occurring mainly as authigenic pore- and cell-filling aggregates. Minor phases include illite–muscovite (7.1–29.9 wt.%), illite–smectite (up to 7.6 wt.% in Bogatyr), and smectite–montmorillonite (0.4–0.7 wt.%). Clay minerals occur as discrete particles, coatings, and pore fillings, contributing to ash formation; however, their correlation with ash yield is weak (R = 0.03–0.05), reflecting heterogeneous mineral inputs and diagenetic overprinting. All geochemical data are reported on a high-temperature coal ash (HTA) basis (815 °C). Geochemical indices (CIA, CIW, CIX) and Al₂O₃/TiO₂ ratios (1.8–17.4) indicate variable provenance and moderate to high weathering intensity, reflecting mixed mafic to intermediate source rocks. A total of 23 trace elements were identified. Au occurs at trace levels (up to 0.02 ppm), while selected rare earth elements (REE: Ce, Dy, Eu, La, Nd, Sm, Y, Yb) average 0.2–0.3 ppm, indicating negligible economic recovery potential. REEs show a strong positive correlation with clay minerals (r = 0.93), indicating adsorption and minor structural incorporation. In contrast, Au correlates with As, V, Zn, Cu, Ni, and Nb, suggesting sulfide association. HTA is enriched in SiO₂–Al₂O₃ phases dominated by kaolinite and quartz, indicating strong potential for cement, geopolymer, ceramic, and zeolite applications. Full article

The flow behavior of montmorillonite (MMT) slurries with a volume fraction of $6.6\times {10}^{-4}$ to $1.6\times {10}^{-3}$, coagulated in 1.0 M NaCl, was investigated across laminar, transitional and turbulent regions using a closed-loop circular pipeline system equipped with dual pressure transducers and a flow meter. In the laminar region, the linearized approximation of the Bingham model was applied to extract yield stress and plastic viscosity, which were subsequently used to estimate friction losses as a function of the Reynolds number. The predicted friction loss calculated using the Hedström number and the Bingham model showed excellent agreement with experimental data. Furthermore, the critical Reynolds number indicating the transition from laminar to turbulent flow was confirmed to increase with increasing yield stress. This trend is qualitatively consistent with flow stability predictions. Notably, the plastic viscosity obtained by this method was significantly lower than values estimated from sediment volume fractions using conventional viscosity correlations based on an effective volume fraction of flocs. These insights into the flow resistance of coagulated clay suspensions are useful for improving the design and operation of water purification, slurry transport, and solid–liquid separation processes. Full article

This article examines the interaction of clay minerals with iron ore concentrate in the context of the efficient use of composite mineral resources. The role of the adsorption properties of mineral additives in the formation of interparticle bonds in green pellets is analyzed. Using X-ray diffraction (XRD) and infrared spectroscopy, the dehydration processes of Na- and Ca-montmorillonite were investigated, and the influence of the cation type on the minerals’ ability to retain water was established. The high thermal stability of the structural OH groups of montmorillonite from the IV-layer clay of the Cherkasy deposit was confirmed, which is an important factor during high-temperature processing of mineral raw materials. Electron microscopy results showed that the fourth-layer clay forms an optimal porous composite microstructure, which contributes to increased water-holding capacity and gas permeability of the pellets. A direct correlation between the adsorption capacity of mineral additives and the strength of raw and dried pellets was experimentally confirmed. Montmorillonite with palygorskite from Layer IV, characterized by high adsorption capacity and prolonged dehydration processes, was identified as the most effective composite binding additive. The results obtained deepen scientific understanding of the mechanisms underlying pellet strength formation and have practical significance for the rational and resource-efficient use of mineral resources in the production of iron ore pellets. The results also demonstrate the potential for improving resource efficiency in pellet production through reduced consumption of traditional binder materials. Full article

The volcanic island of Fuerteventura (Canary Islands, Spain) offers the opportunity to investigate aqueous alteration in Mars-like environments. As on Mars, landscapes on Fuerteventura are typified by mafic volcanic landforms, minimal precipitation, strong winds, and minimal or absent vegetation. In this study, we perform reflectance spectral and geochemical analysis of near-surface basaltic materials from Fuerteventura’s Gairía caldera, as well as samples from a nearby arroyo. Tephra, outcrop rock, and soil-like material exhibit variations in color, spectral properties, mineralogy, and major oxides. Visible/near-infrared (VNIR) spectra of orange/light-brown materials have higher reflectance values and much stronger features attributed to phyllosilicates (including H₂O and Al-OH bands near 1.41–1.45, 1.91–1.92, 2.21, and 2.76 µm characteristic of montmorillonite in caldera and arroyo samples, plus shoulder features near 1.38 and 2.17 µm and a band at 2.70 µm indicative of kaolinite/halloysite in arroyo samples) compared to black/brown materials. Additionally, several of the highly altered samples contain spectral bands due to calcite at 2.33, 2.53, 3.36, 3.47, and 3.97 µm. Major oxide data reveal similar distinctions between lighter orange/tan (altered) versus darker (unaltered) samples. Lighter and orange-colored samples show elevated Al₂O₃ and depleted Fe₂O_3T, MgO, CaO, and Na₂O, as well as higher chemical index of alteration (CIA) values, overall characteristic of water-soluble cation release (and secondary clay formation) during incipient-to-intermediate chemical weathering of basalt. Gairía weathering trends inform phyllosilicate formation in arid volcanic settings broadly. Of particular interest is the chemical alteration of basalt to montmorillonite and kaolinite/halloysite taking place in warm but water-limited desert conditions, suggesting the potential for clay formation in analogous (warm but relatively dry) paleoenvironments on early Mars. Full article

To mitigate health hazards from pathogenic bacteria (Escherichia coli, Staphylococcus aureus) and fungi (Aspergillus niger) as well as the coating mildew issue in high-humidity indoor environments, and to overcome the challenges of particle agglomeration and non-uniform distribution in conventional benzalkonium chloride (BAC)-clay composites, this study proposes a wet chemical strategy to prepare BAC-hectorite antimicrobial composites using synthetic hectorite as a high-performance carrier, which is superior to natural clays such as montmorillonite and kaolin in structural uniformity, ion-exchange efficiency, and dispersion stability. Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis confirmed the successful intercalation of BAC cations into the hectorite interlayers through ion exchange. This resulted in a significant expansion of the interlayer spacing from 1.0–1.2 nm to 1.5–1.8 nm, a marked alleviation of particle agglomeration, and an optimized pore structure. A clear structure–activity relationship between preparation conditions, microstructure regulation, and antimicrobial performance is systematically established. Antibacterial tests revealed superior efficacy against Gram-positive bacteria; the composite exhibited an inhibition zone of 13.31 mm and a minimum inhibitory concentration (MIC) of 4 μg/mL against S. aureus, compared to 11.62 mm and 32 μg/mL against E. coli. Practical application tests demonstrated that at an ultralow addition level of 0.4%, incorporating this composite into latex paint achieved an antibacterial rate exceeding 99.9% against both pathogens. When added to putty powder, it yielded Grade 0 mold resistance with no observable growth. Furthermore, compounding with polypropylene (PP) increased the elongation at break to approximately 600%, simultaneously realizing antibacterial, antifungal, and toughening functions, thereby not only conferring antibacterial functionality but also significantly enhancing toughness—resolving the typical polymer embrittlement caused by traditional inorganic antibacterial fillers. Short-term evaluations confirm that this composite offers a stable structure, high-efficiency antimicrobial properties, and improved substrate mechanics at low loading levels. These findings provide technical support and experimental guidance for the functional upgrading of indoor decorative coatings, putties, and polymer materials used in high-humidity scenarios such as kitchens and bathrooms. Full article

The effects of exchangeable cations on bisphenol A adsorption and degradation were investigated in montmorillonite-catalyzed ozonation and compared to the parent bentonite. Total BPA removal (100%) can be achieved after only 5 min adsorption on NaMt and by 15 min ozonation with all clay catalysts but without complete mineralization. The BPA degradation level was found to correlate to the ecotoxicity of the ozonized BPA mixtures, using the aquatic plant Lemna minor as a bioindicator species. Liquid chromatography revealed that BPA adsorption contributes to the ozonation process and that BPA degradation rates and ecotoxicity strongly depend on the exchangeable cation and the particle size of the clay catalyst. These factors also appear to govern the ozonation and adsorption process through catalyst dispersion in the liquid medium, with direct effects on the toxicity towards the living species. The results of the present work allow envisaging clay-based oxidative water treatments with advanced BPA removal that drastically reduce the amounts of persistent derivatives. Full article

Understanding the hydration dynamics of montmorillonite clay minerals is critical for predicting their behavior in geotechnical and environmental applications. However, prior ESEM studies have employed separate measurement techniques and lack synchronized multi-scale observations linking microscale aggregate morphology to nanoscale interlayer spacing, with kinetic timescales for clay equilibration remaining unknown. This study employs in situ environmental scanning electron microscopy (ESEM) combined with synchronized X-ray diffraction (XRD) to directly observe and quantify the hydration and dehydration processes of montmorillonite SWy-1 under controlled pressure and temperature conditions on the same sample. ESEM enabled direct visualization of water–clay interactions by precisely controlling chamber pressure (4–5.3 Torr), while synchronized XRD measured basal spacing (d₀₀₁) changes. Key findings reveal: single water-layer hydration (1W) produces ~19% aggregate swelling and two-layer hydration (2W) yields ~32% swelling; rapid dehydration occurs within 3 min with complete equilibration by 15 min; hydration exhibits steeper pressure dependency (slope = 2.7249) compared to dehydration (slope = 1.6702), indicating thermodynamically driven water uptake but kinetically limited desorption; and water-adsorption isotherms exhibited type-H3 hysteresis. This dual-scale integration establishes practical timescales for clay equilibration and provides critical mechanistic insights for predicting clay behavior in geotechnical engineering and engineered barrier design. Full article