Sepiolite, a fibrous clay mineral, shows superior salt tolerance compared with layered clays, making it attractive for seawater-based drilling fluids. However, the specific ions responsible for rheological degradation in complex seawater environments remain unclear. The present study used a component-resolved approach to investigate the effects of five major seawater salts: NaCl, MgCl2, Na2SO4, CaCl2, and KCl, on the microstructure and rheology of 5 wt.% sepiolite dispersions. Zeta-potential measurements, cryogenic scanning electron microscopy (Cryo-SEM), and rheological tests revealed distinct ion-specific effects. Monovalent cations, Na+ and K+, mainly compressed the electrical double layer (EDL) and preserved relatively voluminous, reversible fiber networks, resulting in modest viscosity loss. In contrast, divalent cations, Mg2+ and Ca2+, caused stronger charge neutralization, probably through a combination of EDL compression and specific cation association with sepiolite surfaces, thereby promoting side-by-side fiber aggregation into bundles. This bundling reduced the number of effectively dispersed structural units and lowered the apparent aspect ratio, leading to pronounced apparent-viscosity reductions of 40% for MgCl2 and 27% for CaCl2. Mg2+ reduced the zeta potential to a near-neutral or slightly positive value (+0.20 mV). Although MgCl2 accounted for only 23% of the ionic strength of the simplified seawater system, its strong interfacial effect was closely associated with fiber bundling and rheological deterioration. The apparent viscosity in seawater (5.0 mPa·s) was closer to that in the divalent-cation systems than to a simple average of all single-salt systems, indicating that minority divalent cations exert a disproportionate influence on rheological degradation. These findings provide mechanistic guidance for optimizing sepiolite-based drilling fluids in high-salinity environments.

Clay minerals are key indicators of soil evolution and the building blocks of soil behavior. Long-term agronomic trials, in which soil samples have been collected and archived over several decades, provide a valuable opportunity to track the transformation of clay minerals over centennial timescales. To achieve this, the clay mineralogy of the archived soil samples must be characterized in great detail. In this context, the initial clay mineralogy of the <2 μm fraction of one of the world’s oldest experimental sites, the 42 plots of Versailles (France, 1929), was determined using an approach that coupled sequential fractionation with X-ray diffraction profile modeling of 00ℓ reflections. This analysis of the original clay mineralogy confirmed the great complexity of temperate soil clay mineralogy. Seven clay phases were identified, including two quasi-discrete kaolinite and illite phases, and five randomly mixed-layered minerals (MLMs), three of which had three different 2:1 layer types. Results showed that MLMs accounted for >70% of the clay phases, with their proportions increasing as particle sizes decreased. The widespread occurrence of kaolinite-illite MLMs and three 2:1 component MLMs in temperate loess soils was also assessed. Comparisons with previous descriptions of clay mineralogy in temperate soils demonstrated that despite their complex crystal structures, the three 2:1 MLMs exhibited similar relative contributions from their constituent layers, particularly the illite layers. The high proportions of such illitic clay phases quantified in the study suggested that they could serve as key markers in the study of pedogenesis in soils that have developed from sedimentary rocks or deposits under temperate climatic conditions.

In Brazil, the largest bentonite deposits, located in the Boa Vista region of Paraíba State, have been studied extensively. However, with the near depletion of high-quality varieties from this region, new deposits are being explored elsewhere in the Brazilian northeast. Among these, the Formosa deposit, in Maranhão State, stands out. In this study, the <0.1 μm clay fraction highly enriched in smectite from the Formosa deposit was characterized and compared with three commercial smectites (Bofe, Chocolate, and Verde Lodo) from the Boa Vista region. Analytical techniques included X-ray diffraction, infrared spectroscopy, transmission electron microscopy, and atomic absorption spectroscopy. Although previously described as montmorillonites, their crystal chemistry has not yet been elucidated fully. The present study therefore aimed to clarify the crystal chemistry of these smectites by resolving the distribution of layer charge between tetrahedral and octahedral sheets and evaluating its implications for swelling behavior. The results revealed that these Al-rich smectites also exhibit a significant tetrahedral layer charge. Indeed, they possess sufficient tetrahedral charge (~0.15 per half unit cell) to induce interlayer swelling after the Hofmann-Klemen effect, a value lower than that commonly reported for natural smectites. The structural and chemical similarities between Formosa and the three commercial smectites demonstrate that the Formosa deposit is a promising alternative source to the smectites from Boa Vista.

Aromatic hydrocarbons are vital petrochemical feedstocks used in producing various materials, but these hydrocarbons often contain trace olefins that harm product quality. Modified bentonite-based structures serve as catalysts for the removal of olefins from aromatic compounds. To enhance the catalyst efficiency of this material, which is primarily found in montmorillonite, various modification methods can be employed. The objective of the present study was to develop a high-performance catalyst for the removal of olefins and to evaluate how the quality of water used during preparation influences the final performance of the catalyst. For this purpose, the effect of mass ratio of bentonite to acid on leaching was first investigated, and the optimal ratio was determined to be 0.8. Then, the combination of purification with sodium hexametaphosphate (NaHMP) and acid activation with sulfuric acid on Iranian bentonite was performed to acquire a highly active catalyst. The prepared catalysts were characterized using various analytical techniques, including nitrogen adsorption-desorption analysis (BET analysis), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and ammonia temperature-programmed desorption (NH3-TPD). In addition, the effect of urban and deionized water on the activity of the prepared samples was investigated. Analysis by XRD revealed that the sample purified with deionized water contained smaller amounts of impurity phases, such as quartz, dolomite, and calcium carbonate. Additionally, the catalytic performance of the samples was evaluated in the olefin-removal process at a temperature of 160°C and a pressure of 11 bar. According to the results, the sample purified and activated with deionized water displayed superior performance and greater stability compared with the unpurified and urban water-purified and activated bentonite. This catalyst maintained the bromine index of <20 mg per 100 g for 370 h, which indicates the stability and high performance of this catalyst in terms of olefin removal.

The rapid decomposition and uncontrolled release of chlorine dioxide (ClO2) hinder its practical application in an atmosphere of ClO2; if released at an appropriate rate, it will extend the shelf-life of fresh water fruit at least by 10 days. Montmorillonite (Mnt) microspheres with a hollow, mesoporous structure were prepared using a spray-drying approach, with Mnt as a raw material and sodium metasilicate as a structural binder. Characterization revealed that: (1) the walls of the microsphere consist of Mnt nanoparticles ranging from 2 to 20 nm, and mesopores with an average aperture of 3.0 nm; (2) the mesopores connect the interior cavity with exterior space of the microsphere; and (3) Si–O–Si bonds act as bridges to combine different Mnt particles to form the hollow mesoporous structure. The microspheres with a specific surface area of 40.1 m2 g–1 exhibit a tunable and slow-release property for ClO2 and this can be adjusted by the mass ratio of Mnt microspheres to the precursors of ClO2. The power of the microspheres to retain the freshness of seasonal water fruits was demonstrated, and the results show that the microspheres containing 20 wt.% of the precursors of ClO2 can release ClO2 stably over 20 days at a suitable concentration to ensure that the freshness of the fruit is retained. This represents a new use for Mnt.

The removal of persistent dye pollutants from wastewater remains a major environmental challenge, particularly due to the limited efficiency, stability, and reusability of clay-based catalytic systems. The present study aimed to develop an environmentally friendly and magnetically recoverable biopolymer–clay composite catalyst with enhanced performance for dye decolorization via a heterogeneous Fenton-like process. A novel catalyst composed of xanthan gum (XG), kaolin, and CoFe2O4 was synthesized and designated as XG-CF-K. The composite exhibited a Brunauer–Emmett–Teller surface area of 58.55 m2 g–1 and a saturation magnetization of 27.2 emu g–1. The catalyst was applied for the decolorization of malachite green (M-GR). The effects of various operational parameters, including XG-CF-K dosage, H2O2 concentration, pH, initial dye concentration, reaction time, and the presence of salt, were investigated systematically. Under optimal conditions (1 g L–1 XG-CF-K dosage, 20 mg L–1 M-GR concentration, pH 6, 0.147 M H2O2, 25°C, and 20 min reaction time), a decolorization efficiency of 95.9% was achieved. The decolorization kinetics followed a pseudo-first order model and were well described by the Langmuir–Hinshelwood mechanism. In addition, the catalyst exhibited good stability and reusability, and a plausible degradation mechanism was proposed. Overall, the results demonstrate that XG-CF-K is an effective, sustainable, and reusable catalyst for the removal of dye pollutants, offering a promising approach for wastewater-treatment applications.

Cattle are primary livestock, but they burp methane, a potent greenhouse gas. This is caused by microbial fermentation in the rumen, a process known as methanogenesis. Ruminal archaea, bacteria, protozoa, fungi, and nematodes take part directly and indirectly in this process. Feed supplements have become a feasible way of inhibiting methanogenesis. Considering that cattle are naturally geophagic, clay minerals, particularly kaolin, are being added to those supplements with the expectation that they will reduce enteric methane. The present study characterized a halloysite-kaolinite mixed mineral sample collected from a prospective deposit in Western Australia. The clay was mixed into grass mash to formulate a cattle diet. An in vitro experiment was conducted using the ANKOM system and viable rumen fluid to simulate cattle rumen fermentation. Rumen parameters, such as dissolved oxygen, oxidation-reduction potential, pH, and volatile fatty acids, were measured. Methane was produced as a result of rumen function, and its kinetic concentrations were measured. Scanning electron microscopy (SEM) of the rumen sample revealed clusters of kaolin-associated nematodes. Microbial diversity and functional community analyses were performed using 16S rRNA sequencing. Post-fermentation changes in kaolin minerals were assessed using SEM and X-ray diffractometry (XRD). The inclusion of kaolin significantly reduced methane production by 22.5% (p < 0.05). This intervention did not affect the other fermentation parameters, microbial population, or clay composition. However, kaolin might reduce the mobility and survival of nematodes through physical attachment. Overall, these results indicate that raw halloysite-kaolinite mixed mineral can reduce enteric methane production without disrupting the measured ruminal fermentation parameters or the structural stability of the clay mineral. This study provides valuable insights into the inclusion of halloysite-kaolinite mixed mineral in specialized cattle feed additives.

Elevated levels of hexavalent chromium (Cr(VI)) in soil and water pose severe ecological and health risks, and clay–iron composites are promising natural reactive materials for contaminant immobilization. Yet, the combined effects of Fe loading and organic modification on Cr(VI) retention remain poorly understood. The present study aimed to clarify Cr(VI) adsorption behavior and interfacial mechanisms of montmorillonite–Fe(oxyhydr)oxide composites, and to evaluate the regulating roles of Fe/clay ratio and organic modification. Natural montmorillonite and organo-montmorillonite were composited with ferrihydrite to prepare a series of clay–iron assemblies, and their Cr(VI) adsorption performances were investigated systematically. The Fe/clay ratio dominated the adsorption capacity; the composite with the highest Fe loading exhibited optimal Cr(VI) retention performance due to favorable surface charge and abundant reactive sites. Organic modification introduced extra functional groups but reduced adsorption efficiency by occupying surface sites and altering surface physicochemical properties. The immobilization of Cr(VI) was primarily controlled by electrostatic interaction and inner-sphere complexation at Fe–OH surface sites. This work elucidates key structure–activity relationships of clay–iron composites, provides fundamental insights into Cr(VI) geochemical behavior, and offers a practical basis for developing low-cost clay-based amendments for Cr(VI) contamination remediation.

The shortage of analytical data on bentonite from the Michaľany-Lastovce deposit was the motivation for the current study. The main goal was to characterize the bentonite deposit by providing new data that could shed light on the geological conditions that contributed to the formation of similar bentonites. Twenty-two samples from the surface and boreholes were analyzed. Most of the samples were composed of Ca-montmorillonite and opaline polymorphs (mainly opal-CT). Feldspars, quartz, micas, kaolinite, and clinoptilolite were also present. The cation exchange capacity (CEC) values for bulk and clay fraction of bentonites were 35–58 and 45–80 meq per 100 g, respectively. The BET specific surface areas for bulk and clay fraction samples were 50–73 and 69–101 m2 g–1, respectively. Most samples exhibited the presence of both cis- and trans-vacant varieties of montmorillonite. The observed distribution of rare earth elements was almost in agreement with silicic explosive volcaniclastic units in the Hungarian Tokaj Mts. The results of the Bertaut-Warren-Averbach method along with microscopic and electron probe microanalysis studies of thin sections, pyrite sulfur isotope, and X-ray micro-computed tomography suggested that the Michaľany-Lastovce bentonite-like deposit probably originated from acidic pyroclastic material during diagenesis. Occasional increases in Fe content observed in whole-rock chemical analyses and in the montmorillonite structure might suggest a partial influence of andesitic rocks from the surrounding area. Despite the relatively small smectite content (<40 wt.%), the Michaľany-Lastovce deposit remains commercially exploited and its potential application as supplementary cementitious material needs to be re-evaluated.

When exposed to chemically aggressive permeants, bentonite-polymer composites often exhibit progressive increases in hydraulic conductivity (k) due to polymer elution, thereby compromising their long-term barrier performance in waste-containment systems. In situ polymerized bentonites (IPBs) synthesized with a crosslinker-based polymer formulation have been developed to improve chemical compatibility and mitigate polymer elution. However, the mechanisms governing their sustained low k and non-eluting behavior under aggressive chemical environments are not well understood. The present study investigated the mechanisms responsible for the long-term superior hydraulic performance of IPBs through integrated macro- and micro-scale analyses. The IPBs containing different polymer dosages were permeated with AlCl3 solutions over a wide concentration range, with comparative assessments performed using identical concentrations of NaCl and CaCl2 solutions. The role of the crosslinker-based polymer formulation in governing clay–polymer interactions, pore structure evolution, and hydraulic response was assessed through advanced characterization and microstructural analyses. Results showed that the IPBs consistently maintained low k values, up to three orders of magnitude below the regulatory threshold limit of 1×10–9 m s–1, without exhibiting polymer elution during long-term permeation. The enhanced chemical resilience and non-eluting behavior of IPBs were attributed to the formation of a stable three-dimensional crosslinked polymer network, which strengthened clay-polymer bonding and restricted polymer mobility. The polymer interacted with clay through surface adsorption, without inducing intercalation into the clay lattice. The infrared absorption spectra confirmed a dual binding mechanism involving esterification and hydrogen bonding. Morphological analyses revealed heterogeneous microstructural evolution driven by variations in polymer dosage and pore-fluid chemistry. Based on the microstructural evidence, a multiscale mechanistic framework involving pore-clogging, polymer bridging, and encapsulation was established. The findings of the study provided new mechanistic insights for designing chemically resilient, sustainable, low-k barrier materials to ensure long-term environmental protection.

Developing stable, surfactant-free formulations for food, pharmaceutical, and cosmetic applications remains a challenge due to the high environmental impact and toxicity risks associated with synthetic surfactants. While solid particles offer an eco-friendly alternative for establishing kinetic stability in Pickering emulsions, the performance of natural, unmodified aluminosilicate clays remains highly variable and poorly optimized. This study aimed to solve this limitation by systematically mapping the stabilization performance of raw bentonite and kaolin using targeted mechanical milling and ionic-strength adjustments without relying on chemical surface modifications. The mineral matrices were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, and electron microscopy to link structural amorphization to interfacial performance. Oil-in-water formulations were prepared via high-shear homogenization by systematically adjusting clay content, oil volume fraction, and phase salinity, utilizing a central composite design and response surface methodology to model system stability. The experimental results demonstrated that mechanical processing yielded optimized particle-size distributions capable of organizing rigid interparticle networks at the oil–water interface. Rheological modeling confirmed solid-sphere behavior and thixotropy under optimal concentrations, proving that physical processing and electrolyte control are sufficient to engineer highly stable, green Pickering systems tailored for targeted industrial applications.

Smectite‑group minerals have a wide range of industrial applications; their properties vary depending on isomorphic substitutions in the crystal structure, while the specific arrangement of OH groups affects their stability under thermochemical treatments. The present study investigated how the silica source, duration of synthesis, pressure, and synthesis temperature influence the structural characteristics of the smectites synthesized. The samples were analyzed using X‑ray diffraction, infrared spectroscopy, thermal analysis, and cation exchange capacity determination. An increase in synthesis temperature was found to lead to an increase in the proportion of isomorphic substitutions in the tetrahedral sheet of smectite. The formation of cis‑ and trans‑vacant smectites was found to depend on the composition of the octahedral sheet; in the presence of magnesium in the octahedral sheet, a trans‑vacant variety of smectite was observed. At the same time, changes in temperature and pressure did not affect significantly the preferential formation of either cis‑ or trans‑vacant montmorillonite. It was also noted that trans‑vacant smectite forms during the first days of synthesis, followed predominantly by the formation of cis‑vacant smectite.

Polymer composites with tunable thermal stability and surface morphology have attracted significant attention in terms of advanced engineering applications. Enhanced thermal resistance ensures long-term durability and safety under demanding conditions, while controlled surface morphology influences interfacial interactions, wettability, adhesion, barrier properties, and overall material performance. In the present study, polystyrene (PS) composite films containing 40 wt.% microspherical silica (average diameter ≈0.5 μm) or halloysite nanotubes (HNT) were fabricated to investigate morphology-driven structure–property relationships at identical filler loadings. Fourier transform infrared (FTIR) spectroscopy confirmed successful filler incorporation through characteristic Si–O–Si vibrations for silica and O–H and aluminosilicate bands for HNT, without evidence of new covalent bonding, indicating physical dispersion within the PS matrix. Thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses revealed clear morphology-dependent degradation behavior. PS–SiO₂ composites showed delayed degradation onset and higher mid-conversion degradation temperatures (Tinitial and T50), consistent with an effective barrier effect that limits volatile and oxygen diffusion. In contrast, PS–HNT composites exhibited the highest peak degradation temperature (Tmax), suggesting enhanced thermal stability during the main degradation stage, probably due to confinement and char-forming effects associated with the tubular morphology. DTG analysis further indicated slight shifts in peak-degradation temperatures, confirming the influence of filler geometry on decomposition behavior. A minor early mass-loss event observed for HNT-containing films was attributed to hydroxyl-rich surfaces and adsorbed moisture. Atomic force microscopy (AFM) demonstrated that filler geometry governs surface topology to a significant extent. PS–SiO2 films retained a relatively smooth surface, whereas PS–HNT films exhibited pronounced roughening and anisotropic features arising from nanotube-rich regions. Overall, the results identify filler morphology as a key parameter controlling thermal degradation pathways and surface architecture in PS composites, providing valuable insights for the morphology-guided design of advanced polymer nanocomposites.

Halloysite nanotubes (HNTs) can be used as stable support materials for gold and silver nanoparticles (Au/Ag-NPs) without distinction given to the morphology of the tubular HNTs, i.e. polygonal prismatic or cylindrical. The present study aimed to use direct visualization techniques to observe and compare the adsorption sites and behaviors of the two tubular morphologies with both Au- and Ag-NPs. Au/Ag-NPs were surface engineered with methyl-, carboxylate-, or phosphonate-terminated linker groups and reacted with halloysite nanotubes with two different morphologies, forming composite materials HNTs@Au-NPs and HNTs@Ag-NPs. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy were used to investigate the sorption reactions. Au-NPs disperse well into individual particles while the Ag-NPs show a tendency to agglomerate, making them less suitable probes for adsorption onto HNTs. The results also indicate that polygonal prismatic HNTs show greater sorption than cylindrical HNTs, where NPs were detected on the external walls of the nanotubes. This sorption is suggested to occur at the steps and edges of the particles, at the termini of the tubes, and in the hollow inner lumina. For the varying linker groups, carboxylate- and phosphonate-derivatized Au-NPs show similar sorption behavior on HNTs, while no surface sorption was observed for the methyl-terminated linkers. This justifies the hypothesis that the carboxylate and phosphonate moieties chemisorb to the hydroxyls of the aluminol groups at the edge sites, steps, and lumina of polygonal prismatic HNTs, identifying these as key anion bonding sites on HNTs, while non-ionic, methyl-terminated Au-NPs do not adsorb. Identification of these specific anionic bonding sites on two different HNT morphologies highlights the importance of HNT morphology in their use as stable support materials in applications such as catalysis, anion sorption, and drug delivery, amongst others.

The abuse of antibiotics as feed additives in the poultry-farming industry has led to problems such as bacterial resistance and drug residues, posing significant threats to food safety, human health, and ecological safety. Consequently, many countries have issued regulations to prohibit or restrict in-feed antibiotics, underscoring the urgency of developing and evaluating viable alternative feed additives. In this study, a green and safe antibacterial composite material was reported by synthesizing grape pip/skin extract with natural mineral material palygorskite. The composite materials were thoroughly characterized using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The sustained-release profiles of the plant extracts from the composite material were also investigated. The antibacterial performance of the composite material was evaluated by measuring the inhibition zone against Staphylococcus aureus. The resulting composite materials exhibited superior thermal stability and considerable sustained-release capabilities while maintaining excellent antibacterial activity equivalent to the original extracts. The successful combination of natural antibacterial ingredients with inorganic mineral material has laid the foundation for the exploration of potential alternatives to antibiotic additives in feed.

Glauconite-bearing sediments and glauconite-based mineral materials may interact with waters of contrasting pH, but the response of intact glauconite globules under static water-mineral conditions remains poorly constrained. The present study evaluated whether pH-driven interaction modifies the layered structure, crystal chemistry, and near-surface texture of natural glauconite globules while preserving their natural granular morphology. Natural glauconite was reacted with distilled water-based solutions at pH 2, 3, 4, 6, 7, 8, 9, and 10 for 1, 3, 7, 14, 30, and 60 days under static conditions. The mineral fractions were examined by X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and Fourier-transform infrared spectroscopy. The results show that the 10 Å layered TOT structure of glauconite was preserved in all experimental series. Under acidic conditions (pH 2–4), a slight, steady decrease in d001 was observed. This decrease was accompanied by peak broadening and reduced intensity of basal reflections, signifying increased structural disorder without structural destruction. The diagnostic (060) reflection was preserved in all samples (d060 = 1.508–1.514 Å), confirming the stability of the dioctahedral octahedral framework. Crystal-chemical data showed a distinct pH- and time-dependent adaptive response in the interlayer and tetrahedral domains. In acidic solutions, interlayer K decreased by ~25–45% relative to the initial composition, with maximum deviations noted after 14 days of interaction. These changes were accompanied by an increase in Al in the tetrahedral sheet (up to +0.05–0.32 a.p.f.u.) relative to the initial state. In contrast, structural and crystal-chemical changes were minimal under neutral plus alkaline conditions. Morphological changes of glauconite globules were mainly confined to near-surface zones. Overall, the results indicate that glauconite globules show high structural stability in static aqueous environments, with only limited pH-dependent structural, chemical, and near-surface modifications.