The structural stability of barrier layers is critical for the long-term effectiveness of landfill remediation projects, although leachate pumping and organic contamination can cause structural degradation, reduce remediation performance, and increase the risk of pollutant release. The objectives of this study were to determine the consolidation–rebound mechanisms of sand–bentonite mixtures through standardized tests and to analyze deformation under diesel contamination using multi-scale approaches, including pore-structure characterization, particle-size distribution, cation exchange capacity, and oil-blocking effects. The results revealed that uncontaminated soil (0.0 wt.% diesel) exhibited non-linear compression behavior, with an initial decrease and a subsequent increase with increasing sand content; when the consolidation pressure exceeded 400 kPa, the compression rate decreased markedly. The compression deformation of the contaminated soil increased and was positively correlated with the sand and diesel contents, with accelerated deformation at >4.0 wt.% diesel. The rebound capacity decreased under combined sand–diesel effects. Microstructural analysis indicated that initial compression was controlled by inter-aggregate pores, whereas mid- to late-stage compression was influenced by intra-aggregate pore evolution and particle breakage. Increased diesel content shifted aggregate breakage from single/secondary to tertiary patterns, altering later compression behavior. Coupled hydration reduction and enhanced oil-blocking suppressed rebound significantly, worsening with increasing diesel content. Technical–economic analysis revealed that pure bentonite (0% sand) was optimal under uncontaminated conditions and that a 10% sand mixture was best under contaminated conditions. The sand–bentonite barrier exhibited amplified consolidation–rebound deformation and reduced stability with increasing sand and diesel contents, providing a theoretical basis for long-term landfill remediation assessment.

Improving the thermal and rheological limitations of traditional natural hydrogels remains a key challenge for their medical use. Inorganic and organic elements were combined synergistically to develop natural hydrogels, and subsequently subjected to comprehensive thermal and rheological analysis for potential applications in physical medical treatments. The primary objective of this study was to optimize the technological, biopharmaceutical, and therapeutic properties of these innovative hydrogels, constituted by an inorganic framework of clay particles entrapping organic components from peat extracts. The hydrogels underwent thorough mineralogical and chemical characterization, confirming the pharmaceutical-grade quality of the clay component, which was predominantly composed of montmorillonite and saponite. Rheological evaluations revealed non-Newtonian viscoplastic behavior, with viscosity and thixotropy increasing significantly with higher clay concentrations and prolonged swelling durations. Thermal analyses demonstrated that the hydrogels possess adequate heat-transfer capabilities, ensuring effective maintenance of skin temperature during therapeutic application. Elemental analysis and cation exchange capacity determinations highlighted the substantial water retention and ion exchange properties of the hydrogels, contributing to their stability and functional performance. The integration of organic and inorganic constituents enhanced synergistically the mechanical strength, thermal stability, and therapeutic efficacy of the hydrogels. These advancements position the formulated hydrogels as promising candidates for innovative applications in physical medical treatments, offering enhanced mechanical and thermal properties essential for effective therapeutic outcomes.

One of the challenges in measuring the adsorption of metal cations is that they may form metal hydroxide compounds at certain pH ranges. This becomes problematic when adsorption is quantified in terms of measuring a decrease in metal ions in solution, because metal hydroxy complexes are removed from solution through precipitation, leading to erroneously high determinations of adsorption. Within this context, the present study aimed to analyze the pH-dependent adsorption behavior of Ni2+ ions onto sepiolite, a naturally occurring magnesium silicate clay mineral, while simultaneously accounting for the precipitation of nickel compounds during the process. For this purpose, zeta potential, ion exchange capacity, and the adsorption behavior of 2.5×10–3 mol L–1 nickel (II) sulfate hexahydrate onto relatively high-quality sepiolite were investigated. Kinetic studies and thermodynamic assessments were delineated to enhance the understanding of adsorption isotherms, both for future research and practical applications in environmental remediation. The results showed that the adsorption of Ni2+ ions onto sepiolite before the onset of precipitation is governed by an ion exchange process involving the release of Mg2+ ions from the sepiolite matrix and the uptake of Ni2+ ions from the solution. Above the threshold of pH ~8 where Ni-hydroxide complexes begin to form, ~97% of nickel ions were present in the forms of NiOH+, Ni(OH)2, and Ni(OH)3–. Isotherms for total Ni2+ removal were constructed to distinguish true adsorption from precipitation phenomena. The calculated and experimental values for true adsorption were found to be in good agreement.

Organomontmorillonite-type (O-Mnt) antibacterial agents are less susceptible to development of resistance by bacteria. The aim of the present study was to test the effects of O-Mnt samples, which were reported to be effective against Staphlococcus aureus and Streptococcus mutans in previous studies and to act as a scavenger for opportunistic pathogenic microorganisms, Actinomyces viscosus and Bacteroides fragilis, which cause severe infections such as periodontal diseases, endocarditis, and lung infections. O-Mnt samples with single and mixed surfactant layers, namely benzethonium montmorillonite (Mnt-BZT) and cetylpyridinium and N-lauroyl sarcosinate montmorillonite (Mnt-CP-SR), were subjected to X-ray diffraction, thermogravimetric analysis, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and zeta potential analyses to determine some key structural properties. Within the scope of the present study, detailed X-ray photoelectron spectroscopy (XPS) analyses were performed to elucidate the external surface structures, which are important in explaining their antibacterial properties. There have been few studies on XPS analysis in terms of types of surfactants used in O-Mnt preparation. These analyses made it possible to estimate the interaction between the surfactants on the external surface and the bacterial cell wall leading to lysis. A. viscosus, a facultative anaerobe, and B. fragilis, a strict anaerobe, required specific culture conditions, and their antibacterial susceptibility testing was conducted with caution due to challenges in isolation and antimicrobial resistance. Antibacterial susceptibility tests including the agar well diffusion test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) determinations and time-kill assay showed that both OMnt samples were effective against the bacteria used. The XPS analyses of the exterior surface structure of O-Mnt revealed that contact killing was the mechanism of antibacterial effect. In vitro cytotoxicity and in vivo animal studies indicated that both O-Mnt samples can be used safely as antibacterial agents in oral and topical applications.

Aflatoxins (AFs) are contaminants of several agricultural crops, and aflatoxin B1 (AFB1) is the most toxic AF and a known carcinogen to humans and animals. A practical solution for decontamination of animal feed contaminated with AFB1 is to use bentonite, a natural raw material consisting primarily of the mineral montmorillonite (dioctahedral 2:1 layer aluminosilicate of the smectite group). The aims of this research were to compare mineralogical, structural, chemical, and physico-chemical characteristics of three bentonites from the Balkan region (Beretnica clay from Serbia (B-Clay), Yellow clay (Y-Clay) and Gray clay (G-Clay) from Bosnia) with the characteristics of a commercial pharmaceutical-grade bentonite (P-Clay), and to study the behavior of the bentonites in phosphate buffer at pH 3 and 7 with and without AFB1. AFB1 adsorption by bentonites followed non-linear isotherms with maximum amounts adsorbed from 75.43 mg g–1 at pH 3 and 62.91 mg g–1 at pH 7 for the P-Clay to 100.25 mg g–1 at pH 3 and 78.58 mg g–1 at pH 7 for the B-Clay. The Ca-bentonites (B-Clay-cis-vacant, 83% montmorillonite; Y-Clay-cis/trans-vacant, 98% montmorillonite; and G-Clay-trans-vacant, 88% montmorillonite) were efficient adsorbents of AFB1, with the greater adsorption observed at pH 3. The P-Clay (Na/Ca bentonite, cis-vacant, 63% montmorillonite), exhibited the lowest AFB1 adsorption at both pH values. The behavior of bentonites in buffers, in the presence of AFB1, indicated that ion exchange and AFB1 adsorption by montmorillonite occurred simultaneously. Cations with larger hydrated radii (Mg2+ and Ca2+) represented the primary active sites for AFB1 adsorption. The position of OH– groups in cis-montmorillonites at the same side of the octahedral site enhanced AFB1 adsorption, making them more available for protonation of edge sites and subsequent interaction with AFB1. Specific characteristics of the montmorillonite in bentonites play an important role in AFB1 adsorption, although the buffer composition also affects the adsorption process significantly.

This article studies the geological structure, mineralogical composition, genesis, and sorption properties of Khonguruu zeolite deposit (Republic of Sakha, Russia). Although it is one of the largest developed deposits in Russia, detailed studies of the mineral composition and physicochemical properties have not been conducted previously, which limits its industrial potential. Zeolites were studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), X-ray fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) and cation exchange capacity (CEC) analyses. Experiments on the sorption of radioactive cesium were also carried out. Zeolites formed four beds with an average content of 50–85%. The main focus of this study is on the detailed investigation of its mineral composition. These data, together with the analyses of ion-exchange complexes and color, provided an opportunity to distinguish between different types of zeolites. The zeolite minerals are represented by heulandite-1, heulandite-2 and, to a lesser extent, clinoptilolite. For the first time, a significant presence of amorphous silica was demonstrated in zeolite samples and used for correction of the crystallochemical formula of zeolites. On the basis of exchangeable cations composition, two main types of zeolites were found at the deposit: alkaline and alkaline-earth. The CEC of the zeolites ranged from 139 to 214 cmolc kg–1 and high 137Cs sorption. The zeolites have a volcanogenic-sedimentary genesis and were formed from ash material of basic and acidic composition in coastal sea waters with alternating conditions of low and high salinity. Based on the data obtained, it can be concluded that the alkaline raw material can be used as a sorbent for wastewater treatment.

Smectite- and zeolite-dominated assemblages occur at different depths within the same volcanic tuff sequence at the study site, indicating variability in post-depositional alteration conditions. The present study investigated the geological and environmental factors associated with the vertical mineralogical differences using outcrop and core samples from Pohang, South Korea. Mineralogical, geochemical, thermal, spectroscopic, and microbial analyses were conducted on representative samples. The outcrop samples contain Ca-smectite, cristobalite, and amorphous aluminosilicates, whereas the core samples contain zeolite (clinoptilolite and mordenite), quartz, and feldspar. (Na,Ca)-smectite occurs only at specific depths within the core. Major- and trace-element geochemistry indicates that the outcrop and core samples were derived from rhyolitic and andesitic precursors, respectively. Chondrite-normalized rare earth element patterns show no evidence of hydrothermal enrichment or depletion, suggesting diagenesis as the dominant alteration process. Bacterial community compositions, used as environmental indicators, indicate contrasting formation environments: the outcrop samples represent anaerobic, freshwater conditions, whereas the core samples reflect aerobic and saline conditions. Mössbauer spectra independently support these redox differences, showing structurally bound Fe within smectite in the outcrop sample and hematite-magnetite assemblages in the core samples. These results indicate that variations in precursor composition, salinity, and redox conditions were closely associated with the development of contrasting smectite- and zeolite-bearing assemblages within the same volcanic sequence.

The interaction between iron released from corroded steel canisters and bentonite is a key process influencing the long-term performance of nuclear waste repositories. In particular, the migration of Fe²⁺ into montmorillonite (Mnt) interlayers may alter its hydration, swelling, and ion-transport properties. In the present study, molecular dynamics simulations were performed to investigate the hydration behavior, structural response, and transport properties of Fe-exchanged montmorillonite (Fe-Mnt) under varying hydration states. The simulations focus on short- to intermediate-time-scale Fe2+ and Fe3+ interlayer exchange and hydration effects, and do not consider long-term structural substitution, Fe-bearing clay phase stabilization, or secondary iron mineral precipitation. Systems containing Na+-, Fe2+-, and Fe3+-Mnt were examined using both periodic and edge-exposed configurations to evaluate interlayer structure, ion exchange, and free energy of Fe intercalation. The results show that Fe ions influence the interlayer spacing primarily at low water contents (<1 bilayer), where Fe-Mnt exhibits a d-spacing 1–2 Å larger than Na-Mnt due to stronger hydration. The calculated hydration energies follow the order Fe2+<Fe3+<Na+. Both water and ion diffusion coefficients decrease upon Fe ion intercalation, with Fe2+ ions diffusing an order of magnitude more slowly than those of Na+. Free energy profiles further confirm that Fe2+ and Fe3+ ions are thermodynamically favored in the interlayer, with Fe3+ being the most stable. These findings provide molecular-scale insights into the mechanisms of Fe–Na exchange and their implications for bentonite alteration in repository environments.

Halloysite nanotubes (HNTs), naturally abundant clay minerals with unique tubular structures and biocompatibility, offer significant potential as an enzyme immobilization matrix. Conventional functionalization methods often involve energy-intensive processes or compromise enzyme activity, however. The study offers an approach to functionalizing HNTs via alkali activation and polydopamine (PDA) coating for efficient immobilization of β-glucosidase (BG). Alkali treatment enhanced surface hydroxyl density and defect sites, while PDA deposition through mild oxidative polymerization provided a reactive interface for covalent enzyme conjugation mediated by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) crosslinking. Structural characterization (XRD, FTIR, SEM-EDS) confirmed successful PDA coating and enzyme binding while preserving the crystalline integrity of HNTs. At an optimal loading of 167 mg g–1support, the immobilization efficiency was 83% with retained activity. The immobilized BG not only exhibited optimal catalytic performance at pH 6.0 and 60°C but also enhanced stability against pH/temperature fluctuations through immobilization. Kinetic analysis revealed a 39% increase in Vmax (4.73 vs 3.40 mM L–1 min–1) and sustained substrate affinity (Km=10.4 mM L–1). The biocatalyst retained ≥84% activity after 30 days of storage at 4°C and 53% activity over six re-use cycles, attributed to the rigid enzyme conformation stabilized by covalent PDA coupling and HNTs confinement. The research results presented are expected to broaden the application scope of halloysite in the field of enzyme catalysis and provide a feasible solution for improving the catalytic stability of β-glucosidase.

Highly transparent thin films that exhibit circularly polarized luminescence (CPL) and which can be prepared by simple, water-based processes are important for advanced optical devices. However, most reported CPL-active thin films contain luminophores that were carefully designed to be strongly emissive and CPL-active in the solid state. Consequently, there is a need for water-based processes that can take luminophores that are essentially non-emissive as neat solids and use their CPL in the solution state to prepare transparent CPL-active films. In the present study, clay mineral-organic cation hybrids were prepared as CPL-active materials. Hybrid films of a synthetic saponite, Sumecton SA (SSA), and a chiral binaphthyl ammonium salt, (R)- or (S)-4,4-dibutyl-2,6-bis(3,4,5-trifluorophenyl)-4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]azepinium bromide (CBNC), that shows CPL in aqueous solutions, were prepared. Aqueous dispersions of SSA-CBNC hybrids were vacuum filtered to obtain optically transparent films containing CBNC molecules. Whereas CBNC was almost non-emissive as a solid powder, the hybrid films displayed fluorescence and clear CPL signals. The dissymmetry factor (|g| value), which represents the CPL efficiency of CBNC in the hybrid films was enhanced compared with that in aqueous solution. The enhancement was estimated to originate from clay-induced changes in the molecular conformation (e.g. a change in the binaphthyl dihedral angle). These results demonstrate that clay mineral-organic cation hybrids provide a simple, water-based route to transparent CPL-active thin films. Furthermore, clay interlayers may potentially be used to control the chiroptical properties of organic luminophores without covalent modification.

Understanding the long-term fate of radioactive cesium (137Cs) following nuclear accidents requires mechanistic knowledge of its adsorption on soil minerals. Although todorokite is a major tectomanganate, the mechanisms governing Cs+ adsorption at the trace levels typical of environmental contamination remain poorly understood. This study examined the concentration-dependent adsorption mechanisms of Cs+ on todorokite through molecular dynamics (MD) simulations. Selectivity-coefficient calculations based on potential of mean force (PMF) profiles showed that sodium ions (Na+) were energetically favored on external (100) and (010) todorokite surfaces, whereas this selectivity was reversed dramatically in favor of Cs+ within tunnel nanopores. Na+ encountered no significant kinetic barriers upon tunnel entry, but the interior was thermodynamically unfavorable; in contrast, Cs+ faced high entry barriers but gained strong interior binding, resulting in slow desorption and high retention. Thus, the exceptional Cs+ selectivity of todorokite arises from the contrasting energetic landscapes. Isotherm modeling of published experimental data, constrained by MD-derived equilibrium adsorption constants, suggested a concentration-dependent shift in dominant uptake sites, with intra-tunnel sites governing high-affinity adsorption at low Cs+ concentrations, whereas external surfaces (where both inner- and outer-sphere complexes form) become dominant at higher Cs+ concentrations.

Despite extensive research on asbestos mineralogy and health impacts, comprehensive multi-analytical characterization of naturally occurring asbestos (NOA) in ophiolitic mélanges of central Türkiye is still lacking. The present study examines asbestos-form minerals within the ophiolitic mélange northeast of Kıraman village (Karaman, Türkiye), with a focus on chrysotile, tremolite, and talc. These minerals were formed through intensive alteration processes, including serpentinization, talc formation, listwanitization, chloritization, carbonation, and silicification. The main objective was to characterize the mineralogical, morphological, and chemical features of asbestos-form serpentine and amphibole minerals and to evaluate their potential environmental and health implications. Analytical techniques such as optical microscopy, X-ray diffraction (XRD), differential thermal analysis–thermogravimetry (DTA–TG), Fourier-transform infrared (FTIR) and Raman spectroscopy, as well as scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX, TEM–EDX), were employed. The results confirmed the presence of nearly pure chrysotile, talc, and tremolite. Thermal and vibrational analyses revealed characteristic dehydroxylation reactions and diagnostic spectral bands. The SEM and TEM imaging displayed fibrous and acicular morphologies, while TEM–EDX confirmed typical chemical compositions, including minor Fe content (3–5%). Both chrysotile and tremolite fibers exhibited dimensions within the respirable range and elemental characteristics that are commonly associated with increased toxicity in asbestos minerals. The co-existence of Fe-bearing chrysotile and respirable-size tremolite fibers indicates a potential for asbestos-related health risks under conditions of environmental disturbance or exposure. These findings underscore the need for environmental monitoring and suggest the regional geological formations are a potential public health concern.

Only a few studies have been published investigating the use of carbon-doped clays as supercapacitor electrode materials, despite the many potential advantages of using clays, such as their very large specific surface area, reservoir porosity, surface conductivity, vacant crystallographic sites, layered and disrupted structure, hydrophilicity, and abundant availability worldwide. The present study is an attempt to utilize clays in supercapacitors for electrical energy storage. Furthermore, calcination and/or acid activation of kaolinitic, illitic, and smectitic clays was applied with the aim of introducing additional faradaic charge-storage mechanisms and thereby increasing the total capacitance of the clay–carbon black composite beyond the double-layer capacitance. After doping the clay with carbon black, symmetrical supercapacitors were prepared from the clay–carbon composite. Three different electrolyte solutions (H2SO4, KOH, and KCl) were used. Cyclic voltammetry measurements indicated the presence of double-layer capacitance, which may vary depending on the clay minerals, their treatment, and the electrolyte used. For smectitic clay, additional anodic currents were observed in the presence of a KCl electrolyte. Carbon-doped smectitic clay electrodes in KCl electrolyte achieved capacitance values only slightly lower than those of pure carbon black electrodes, despite containing ~1.9 times less carbon. The greatest capacitance of 5.11 F cm–3 was achieved for kaolinitic clay with H2SO4 electrolyte, and an electrode thickness of 2.5 mm.

This study demonstrated that supercapacitors based on clay–carbon black composites are feasible; however, additional research is required to better understand the interactions between carbon and clay particles.

Cronstedtite from the Salsigne mine, France, has long been known to mineralogists and collectors but has not been characterized previously. The current study is the first thorough investigation of cronstedtite from this locality, using electron microprobe analysis, laser ablation inductively coupled plasma mass spectroscopy, Mössbauer spectroscopy, scanning electron microscopy, and single crystal X-ray diffraction. The chemical and structural features of cronstedtite from Salsigne were compared with those of cronstedtites from other localities. The results showed that the chemical/structural signature of cronstedtite from Salsigne could help to distinguish it from cronstedtites found elsewhere. All analyzed polytypes from Salsigne belong to the subfamily A and are mostly 1M and 3T polytypes showing various degrees of disorder. The only exception is the 1T polytype (subfamily C), which was found not as an isolated crystal but allotwinned with a 3T crystal. Other allotwins were also observed in this study: 3T + 1M, 3T + 2M1, 3T + 6T2, and 2M1 + 6T2. Chemical data indicate that cronstedtite from Salsigne contains the most iron in the tetrahedral sites (x = 0.73–0.90) of any known cronstedtite, although previous studies reported that the iron in tetrahedral coordination is greater in polytypes of subfamily D. The octahedral sites are not fully occupied, and the Mössbauer results suggest the presence of a small amount of vacancies. Although the Salsigne mine is known for the extraction of Au and other metals (Ag, Cu, As, Bi, Pb), no traces of these were detected. Traces of Cl and S are present, which seems to be a common feature for cronstedtite.

Alkali activation of Mercia mudstone offers a pathway to developing low-cement-content construction materials, but early-age reaction pathways and strength development are highly sensitive to water availability, calcium supply, and carbonation. The present study explored whether press mud, a Ca/Fe-bearing by-product of sugar refining, can be used as a co-activatable precursor to guide these processes deliberately. Clay was blended with 10–45 wt.% press mud and activated at an activator-to-press-mud (A/P) mass ratio of 0.22–0.28, then cured either sealed (non-carbonated) or under intermittent CO₂ exposure (carbonated) for 3, 7, and 21 days. Time-resolved diffuse reflectance infrared Fourier transform spectroscopy, X-ray diffraction, and scanning electron microscopy were used to track phase evolution and relate it to unconfined compression behavior at elastic, peak, and post-peak strain states. Early curing was governed by surface silication and Fe(III) hydrolysis introduced by press mud; increasing A/P raised alkalinity and dissolved silicate, delayed goethite crystallization, and stabilized ferrihydrite skins, extending the alkaline window for early calcium silicate hydrate and sodium aluminosilicate hydrate formation. At intermediate press mud content (~25 wt.%), Fe-oxyhydroxide pellets disrupted Si-O-Al and Si-O-Si networks, producing a transient reduction in strength. Single-point total suction values, inferred from chilled-mirror dew point psychrometry provided direct water-budget evidence. This showed a suction maximum at 25 wt.% press mud at comparable water contents. Observations were consistent with transient sequestration of pore water by hydrophilic organo-Ca(II) complexes and zeolitic phases and explained the observed strength minimum near ~25 wt.% press mud. Carbonation generally increased strength; however, baseline-corrected carbonate formation was consistently lower at high press mud contents, which gives direct evidence for slowed carbonation kinetics when siliceous and Fe-rich surface coatings limited CO₂ access.

Expansive soils, characterized by large montmorillonite (Mnt) contents, exhibit significant swelling-shrinkage behavior, posing engineering challenges in regions with alternating wet and dry seasons, such as southern China. Recent studies have explored the possible use of microbes to control or modify the swelling-shrinkage behavior. This study has evaluated microbial influence on the swelling-shrinkage behaviors of expansive soils. A combination of aqueous phase characterization through inductively coupled plasma-optical emission spectroscopy (ICP-OES) and solid phase analyses including X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) was adopted to elucidate the variations in system parameters. Results showed that Si, Al, K, and Mg concentrations in the supernatant increased with prolonged interaction, with K concentration peaking at 14 days and decreasing to 27.5 mg L−1 at 42 days, indicating K+ uptake by Mnt interlayers. The Si–O bonds in tetrahedral sheets, Al–O bonds in octahedral structures, and –OH bonds in water molecules were disrupted by Paenibacillus mucilaginosus, accelerating the montmorillonite to illite (Mnt-to-Ilt) transformation. An Ilt-Mnt interstratification peak appeared near 9.88°2θ after 14 days, and an Ilt peak emerged at 48.07°2θ after 28 days. The Mnt content decreased by 37.28%, while the Ilt content increased by 104.01% after 42 days, as calculated by the K-value method. Analysis of swelling-shrinkage properties revealed that reduced Mnt content led to a 69.01% decrease in the free swell index and a 24.04% decrease in the swell ratio under load. The linear and volumetric shrinkage ratios decreased by 32.90% and 30.98%, respectively. Microorganisms can promote the weathering and phase transformation of Mnt into non-expansive minerals, thereby reducing the amount of it and thus reducing the swelling-shrinkage potential in expansive soils.

Mannitol (C6H14O6) is a soluble sugar-alcohol that chelates alkali metals and is commonly used to remove adsorbed boron from mineral surfaces before isotopic analysis. Boron (B) and lithium (Li) are both light incompatible elements that substitute in clay minerals; therefore, the potential for mannitol to extract surface adsorbed Li was studied. Lithium was adsorbed on <2 μm kaolinite (KGa-1) and smectite (SWy-1) clays, and on <20 μm quartz, from 1.0 M LiCl and LiOH solutions. Differences in surface attraction for Li+ result from the mineral point of zero charge (PZC) and solution pH. Various concentrations of mannitol (0.1 M, 0.5 M, 1.0 M) were tested for Li-extraction. Efficient Li-extraction requires mannitol concentrations approximating molar amounts of adsorbed Li. Mannitol molecules (>5 nm) cannot enter clay interlayers easily, but nonetheless extracted large amounts of soluble interlayer Li. Smectite adsorbed the most Li (2.2 wt.%) from LiOH, and >99% of it was removed using 0.5 M mannitol at 25°C in 24 h. Lithium bound in the interlayers can then be retrieved for isotopic analysis using NH4Cl cation exchange. This methodological framework for isolating different reservoirs of Li in clay provides a tool for tracking fluid δ7Li evolution during clay alteration. It opens new possibilities for evaluating fluid δ7Li evolution in asteroidal clays. Structural Li records fluid δ7Li at temperatures of neoformation, while interlayer-bound Li preserves the δ7Li of most recent fluids. Overall, this study demonstrates that mannitol is an efficient and environmentally benign alternative to harsh acid extractions for ore-grade Li adsorbed in clays.