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Introduction: There is growing evidence from animal and clinical studies suggesting probiotics can positively affect type 2 diabetes (T2D). In a previous randomized clinical study, we found that administering a live multistrain probiotic and absorbent smectite once a day for eight weeks to patients with T2D could reduce chronic systemic inflammatory state, insulin resistance, waist circumference and improve the glycemic profile. However, there is a lack of evidence supporting the efficacy of probiotic co-supplementation with absorbent smectite on pancreatic b-cell function in T2D. Aim: This secondary analysis aimed to assess the effectiveness of an alive multistrain probiotic co-supplementation with absorbent smectite vs placebo on b-cell function in T2D patients. Material and Methods: We performed a secondary analysis on a previously published randomized controlled trial (NCT04293731, NCT03614039) involving 46 patients with T2D. The main inclusion criteria were the presence of b-cell dysfunction (%B<60%) and insulin therapy alone or combined with oral antidiabetic drugs. The primary outcome was assessing b-cell function as change Cpeptide and %B. Results: We observed only a tendency for improving b-cell function (44.22 ± 12.80 vs 55.69 ± 25.75; p=0.094). The effectiveness of the therapy probioticsmectite group was confirmed by fasting glycemia decreased by 14% (p=0.019), HbA1c - 5% (p=0.007), HOMA-2 - 17% (p=0.003) and increase of insulin sensitivity by 23% (p=0.005). Analysis of the cytokine profile showed that statistical differences after treatment were in the concentration of both proinflammatory cytokines: IL-1b (22.83 ± 9.04 vs 19.03 ± 5.57; p=0.045) and TNF-a (31.25 ± 11.32 vs 26.23 ± 10.13; p=0.041). Conclusion: Adding a live multistrain probiotic and absorbent smectite supplement slightly improved b-cell function and reduced glycemic-related parameters in patients with T2D. This suggests that adjusting the gut microbiota could be a promising treatment for diabetes and warrants further investigation through more extensive studies. [ABSTRACT FROM AUTHOR]

A novel and cost-effective heterogeneous catalyst for glycerol carbonate production through transesterification was developed by impregnating smectite clay with K2CO3. Comprehensive structural and chemical analyses, including X-ray diffraction Analysis (XRD), Scanning Electron Microscopy (SEM)-Electron Dispersion Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis measurements, were employed to characterize the catalysts. Among the various catalysts prepared, the one impregnated with 40 wt% K2CO3 on smectite and calcined at 550 °C exhibited the highest catalytic activity, primarily due to its superior basicity. To enhance the efficiency of the transesterification process, several reaction parameters were optimized, including the molar ratio between propylene carbonate and glycerol reactor loading of the catalyst and reaction temperature. The highest glycerol carbonate conversion rate, approximately 77.13% ± 1.2%, was achieved using the best catalyst under the following optimal conditions: 2 wt% reactor loading, 110 °C reaction temperature, 2:1 propylene carbonate to glycerol molar ratio, and 6h reaction duration. Furthermore, both the raw clay and the best calcined K2CO3-impregnated catalysts demonstrated remarkable stability, maintaining their high activity for up to four consecutive reaction cycles. Finally, a kinetic analysis was performed using kinetic data from several runs employing raw clay and the most active K2CO3-modified clay at different temperatures, observing that a simple reversible second-order potential kinetic model of the quasi-homogeneous type fits perfectly to such data in diverse temperature ranges. [ABSTRACT FROM AUTHOR]

To investigate the influence of organic matter conversion on the evolution of organic matter pores, fractional conversion (TRHI) and loss of TOC (TOCL) from the organic matter conversion of Middle Jurassic Dameigou Formation shale samples were calculated using petrographic analysis. The TRHI of organic matter varies from 0.30 to 0.88 and TOCL content ranges from 0.62% and 4.09%. Relative to samples of Type III organic matter in shales, type II samples exhibit higher TRHI and TOCL values. Petrographic calculations of TRHI reveal that the fractional conversion of different kerogens differs for the same thermal maturity level. The specific surface area (SBET) ranges between 1.25 and 6.63 m2/g and micropore surface area (Smic) ranges between 4.16 and 21.27 m2/g. Correlations between pore structure parameters and TOCL content are higher than those between pore structure parameters and TOC content. The original TOC content decreases with increasing maturity level owing to hydrocarbon generation from organic matter conversion. The development of organic matter pores depends mainly on organic matter conversion, which is influenced by the richness, organic maceral compositions, and thermal maturity of the organic matter. The contents of kaolinite, illite, and mixed-layer illite/smectite (I/S) in the studied shales are 17.83%–37.05%, 5.36%–11.31%, and 5.27%–14.36%, respectively. Pore structure parameters (SBET and Smic) exhibit moderate positive correlations with illite content and I/S content, and moderate negative correlations with kaolinite content, indicating that different clay minerals have differential effects on pore structure. [ABSTRACT FROM AUTHOR]

In the northern Patagonian region of Argentina, some of the largest bentonite deposits exist. Four bentonite samples (B1, B2, B3, and B4) from two deposits were thoroughly characterised and evaluated as potential adsorbents of anthocyanins extracted from red cabbage. Anthocyanins (ACys) are natural colourants obtained from fruits and plants and have shown excellent antioxidant properties that have promising applications in health. The adsorption of ACys onto bentonites enhances their stability relative to that observed in aqueous solutions. Material characterisation showed that three of the samples are soFdium bentonites (Na-bentonites: B2, B3, and B4), while the fourth exhibits a large quantity of magnesium and calcium in its interlayer, classifying it as a Mg-Ca-Na-bentonite (B1). Na-bentonites demonstrated higher ACy adsorption capacities, occurring through cation exchange, while Mg-Ca-Na-bentonite adsorption occurs by another type of interaction and a cooperative adsorption mechanism, resulting in the lowest ACy adsorption. The highest adsorption capacity was noted for B3, characterised by the highest smectite content, cation exchange capacity, and proportion of monovalent cations in its interlayer. Under the conditions studied, sodium smectites proved to be capable of retaining red cabbage ACys, thereby introducing a novel avenue for potential applications of regional materials with potential implications for health-related uses. [ABSTRACT FROM AUTHOR]

REY‐rich mud, consisting of deep‐sea sediments with high concentrations of rare‐earth elements and yttrium (REY), holds significant economic potential. Many studies have been conducted on biogenic apatite, ferromanganese micronodule, and phillipsite within these deposits to ascertain the REY enrichment mechanisms. However, the knowledge of clay minerals in REY‐rich mud, which is the predominant component of pelagic sediments, is still limited. In this study, two adjacent gravity cores (core GC02: REY‐rich mud; core GC03: typical sediments of equatorial Pacific) were collected from the Clarion‐Clipperton Fracture Zone (CCFZ) of the Eastern Pacific to study the role of different clay minerals in REY enrichment. The clay minerals in core GC03 and core GC02 are primarily illite (averaging 60%) and smectite (averaging 63%), respectively, and the smectite in core GC02 was mainly Fe‐rich, which was probably formed via the reaction between opal and FeOOH. Moreover, multiple studies have reported similar smectite enrichment in REY‐rich mud, suggesting that it is a common characteristic. The presumed hydrothermal or volcanic origination of smectite in REY‐rich layers of core GC02 indicates the essential role of hydrothermal and volcanic activities in REY‐rich mud formation during the Oligocene in the western CCFZ. Key Points: Smectite is likely to be commonly enriched in rare‐earth elements and yttrium (REY)‐rich mud of the PacificAuthigenic smectite probably originated from hydrothermal or volcanic activity and concentrated moderate amounts of REYThe REY‐rich mud of the western Clarion‐Clipperton Fracture Zone presumably formed through hydrothermal or volcanic activities during the Oligocene [ABSTRACT FROM AUTHOR]

A quantitative understanding of the molecular-scale mechanisms of radionuclide sorption on different clay minerals is crucial for the development and safe implementation of geological nuclear waste disposal technologies. We apply classical molecular dynamics (MD) computer simulations to study the adsorption of uranyl on the external basal surfaces of two typical clay models. In the illite model, negative charge is primarily localized in the tetrahedral sheets, while in the lower-charge smectite model, the isomorphic substitutions are introduced in the octahedral sheet. The comparison of atomic density distributions at the clay surfaces and adsorption-free energies profiles as a function of distance from these surfaces demonstrates that overall U behavior at the basal clay surface is quite similar for illite and smectite. Uranyl is sorbed as a mixture of outer-sphere aqua complexes [UO2(H2O)5]2+ and hydrolyzed aqua complexes [UO2(H2O)4–5OH]+ on both surfaces. The structural and compositional differences between the models do not greatly affect the uranyl's nearest coordination environment and are mainly reflected in the specific localization and orientation of the uranyl ions at both surfaces and in the magnitude of the adsorption-free energies. The observed quantitative characteristics of uranyl interactions with illite and smectite surfaces will help to better understand U behavior during the sorption process on clay minerals for the entire range of mixed-layer illite–smectite structures. A comparison of two versions of the ClayFF force field in the simulations made it possible to more accurately and quantitatively evaluate some subtle features of the uranyl–clay interactions and to obtain a more precise composition of uranyl complex with the modified ClayFF force field (ClayFF-MOH). [ABSTRACT FROM AUTHOR]

Catalytic degradation of tartrazine in the presence of Oxone® activated by a catalyst constituted of cobalt supported on a nanocomposite of smectite with chitosan-derived carbon was investigated. The catalyst was synthesized using cobalt impregnation followed by carbonization at 773 K in an inert atmosphere. The synthesized catalyst was previously fully characterized using appropriate characterization methods, including XRPD, XPS, FTIR, HRTEM, and low-temperature N2-physisorption analysis. The catalytic experiments were performed by varying different experimental parameters (dye concentration, Oxone® concentration, temperature, and initial pH of the reaction solution). The kinetic and thermodynamic parameters were estimated from the experimental results. The kinetics data showed the best fit with the pseudo-first-order kinetics model. The activation energy of the investigated degradation process was calculated according to the Arrhenius equation. The catalyst showed excellent performance at low temperatures even at 298 K, and in the wide range of pH values. [ABSTRACT FROM AUTHOR]

The mineralogical composition of Bobov Dol sub-bituminous coals from the lower part of the coal-bearing formation, was studied using optical microscopy, XRD and SEM-EDS analyses. Clay minerals (smectite, illite and kaolinite) and quartz, are the dominant minerals. Their characteristics indicate predominant terrigenous origin and argue for major detrital input from intermediate to mafic rocks. Accessory epigenetic barite-celestine mineralization, substituting almost completely oxidized siderite crystals and spheroidal aggregates, denotes circulation of meteoric aqueous solutions in the absence of other fracture-filing minerals. Finite glass spheres from the top of the coal seam I indicate synchronous volcanic activity, which did not influence peat formation. [ABSTRACT FROM AUTHOR]

Smectite-type porous materials having catalytically active metal cations in octahedral sheets are prepared from metal chloride and water glass with a hydrothermal method. The pore structure （surface area, pore volume and pore diameter） of the porous materials can be controlled by adjusting pH values and the addition of quaternary alkyl ammonium salts during the hydrothermal synthesis. In this manuscript, the synthesis of smectite-type porous materials is briefly described, and their catalysis and catalyst support properties for commercially important reactions are introduced. In the part of the catalysis, 1-butene isomerization, carbon dioxide insertion, and desulfurization activities of smectite-type porous materials having divalent cations （Ni2＋, Mg2＋, and Co2＋） and alkali cations （Li＋, Na＋ and K＋） are described. In the part of the support usage, n-butane hydrogenolysis over platinum metal particles supported on smectite-type porous materials having divalent cations （Ni2＋, Mg2＋, and Co2＋）, and hydrogenation of acrylonitrile-butadiene rubber in organic solvents over palladium metal particles supported on pore-size-controlled smectite-type porous materials. [ABSTRACT FROM AUTHOR]

The four smectite clays in the CSSJ reference samples have been examined using TEM/STEM imaging and energy dispersive X-ray spectroscopy (EDS) in SEM and STEM, to characterize their chemical compositions, grain sizes, impurity minerals, and other properties. Fine calcite particles were commonly found along with quartz in the Tsukinuno samples (JCSS-3101, 3101b), which serve as the primary source of calcium as reported in previous bulk analyses. Cristobalite, quartz, and feldspar are prevalent impurity minerals in the Mikawa sample (JCSS-3102), and the STEM-EDS analysis revealed that the composition of the smectite clay is definitely montmorillonite with subtle difference from the Tsukinuno montmorillonite. The synthetic saponite (JCSS-3501) displayed a wide range of crystal sizes. Sulfate and sodium ions are concentrated in the aggregates of very fine saponite crystallites compared to the saponite particles with larger sizes. [ABSTRACT FROM AUTHOR]

This study reports the analysis of diclofenac removal from aqueous solution using a novel adsorbent coating with amphoteric surface. This adsorbent coating was improved using a new amphoteric ratio to increase its performance for the removal of pharmaceuticals such as diclofenac. The adsorbent coating was formulated using acrylic polymer emulsion, smectite-based clay powder and epichlorohydrin-dimethylamine to obtain a layer form via the implementation of a facile synthesis method. In a previous study, this adsorbent coating was successful to remove cationic and anionic dyes. Therefore, this research aimed to further investigate and test its application in the removal of other emerging water pollutants like pharmaceuticals. SEM, EDX, and FTIR analyses were carried out for the characterization of this novel adsorbent. The effects of adsorbent composition, diclofenac concentration, temperature, and solution pH were studied and modeled. The best conditions to improve the diclofenac adsorption was 303 K and pH 3 where the adsorption capacity was 25.59 mg/g. Adsorption isotherms and kinetics were quantified and modeled, and the corresponding adsorption mechanism was also analyzed. Diclofenac adsorption with this novel material was exothermic and spontaneous. This alternative adsorbent is promising for diclofenac removal from industrial wastewater systems. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the most toxic transition metals for living organisms. Thus, effective measures to remediate Cd from water and soils need to be developed. Cd immobilization by alumina and mixtures of alumina and smectite have been analyzed experimentally and theoretically by sorption experiments and sorption modelling, respectively. Removal of aqueous Cd was dependent on pH and Cd concentration, being maximal for pH > 7.5. A two-site non-electrostatic sorption model for Cd sorption on alumina was developed and it successfully reproduced the experimental Cd immobilization on alumina. Cd sorption on mixtures of alumina and smectite were depending on pH, ionic strength, and alumina content in the mixture. Cd removal in mixtures increased with alumina content at high pH and ionic strength values. However, Cd sorption decreased with increasing alumina content under acidic conditions and low ionic strength. This effect was the result of alumina dissolution and the release of Al3+ into the suspension at low pH values. Modelling of Cd sorption on mixtures of alumina and smectite was performed by considering the individual Cd sorption models for alumina and smectite. It could be shown that the contributions of the individual sorption models were additive in the model for the mixtures when the competition of Al3+ with Cd2+ for cation exchange sites in smectite was included. [ABSTRACT FROM AUTHOR]

Bentonite is used in pharmacology and cosmetology for different applications, the chemical and mineralogical composition and characteristics of these materials are so important. Therefore, the aim of this work is to evaluate the suitability of application of Maghnia Bentonite (clay from Algeria) through different tests. Initially, it was performed the characterization by Xray Diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Swelling volum, Gel Formation, CEC and Surface area. The microbial content of natural bentonite and the activated one with 4% of Na2CO3 labelled (M4) are verified. The suspensions were characterized through tests of sedimentation rate, swelling volum and pH determination. The physical-chemical characterization of M4 indicated compatible characteristics with those of clean clay; it was observed smectite and quartz reflections as crystalline phases and in terms of chemical composition the major presence of Montmorillonite was verified. The microbiological evaluation showed that microbial content of M4 Bentonite presents acceptable limits, according to the Pharmacopeas. The pH of the sample M0 was close to neutral (7.75 ± 0.05), while the pH of the sample M4 (9.2). The results showed a possible application of M4 in pharmaceutical products. [ABSTRACT FROM AUTHOR]

Calcined clays are the most promising future supplementary cementitious material which are capable of replacing fly ashes and blast furnace slag on the long run due to their potential to achieve high cement replacement levels and their global availability. In the last decade most research has focused on calcined clays rich in the 1:1 kaolinite. Clay with less than 20 to 25 % kaolinite were seen as worthless. Even the content of 2:1 phyllosilicates in the kaolinitic clays was neglected and not even mentioned although especially these clays are dominant in areas like central and northern Europe. Here, highly kaolinitic clays are rare or used by other industries leading to high prices. This paper is based on published works and highlights whether information obtained for calcined 1:1 dominated clays can be applied for calcined 2:1 dominated clays or not and where further research is needed. [ABSTRACT FROM AUTHOR]

The nickel-bearing laterites of Noorabad area are seen in the high Zagros zone along with Kermanshah ophiolitic complex. The ophiolitic complex in the studied area includes serpentinized peridotites, isotropic gabbros, plagiogranite, sheeted dykes, basaltic lavas, andesite, and radiolarite. The peridotites of this ophiolitic complex include dunite, harzburgite, and lherzolite. The tectonic activities have caused tectonization in these rocks in such a way that it has facilitated their alteration process and created laterite zones. The alterations of peridotite rocks include serpentine, dolomite, hematite, and silicification. The laterite zone is layered and lens-shaped red horizon on peridotite rocks and is covered by Miocene limestones. Based on XRD analysis, mineralogy of the lateritic zone includes dolomite, quartz, smectite, and serpentine. The ratio of La/Y changes indicates that the studied laterites were formed in alkaline pH. According to the discrimination diagrams of the source rock, the studied laterites are karst bauxites with ultrabasic origin. Introduction Laterites are formed in areas with long tectonic stability and low erosion rates (Brand et al., 1998). Usually, the source rock of these laterites is serpentinites. Nickel is washed from the profile upper parts and concentrates in the lower parts, causing the enrichment and formation of nickel-bearing laterites. Most nickel-bearing laterite profiles have two ore types, an oxide component and a hydrous silicate or clay silicate component (Brand et al., 1998). The richest deposits of nickel-bearing laterite are formed where oxide-rich regoliths rise and nickel is washed down to the new silicates in saprolite (absolute accumulation) to be concentrated (Butt & Cluzel, 2013). This study tried to investigate the field geology, mineralogy, lateritization process, and geochemistry of Noorabad laterites (northwest of Lorestan province, Iran). Materials and methods The field operations were carried out in several rounds and led to the collection of 30 samples from serpentines and laterites of the studied area. Then, by preparing 25 thin and polished sections, the geological characteristics of ores, especially their texture and associated minerals, were discussed. Then three soil laterite samples, for mineralogical study by XRD method were sent to the central lab of Lorestan University and 10 rock and soil samples from the laterites of the studied area were sent to the Canadian SGS laboratory for determining the amount of major and minor elements by ICP-MS method. Results The peridotite rocks of Noorabad ophiolite complex in the northwest of Lorestan province include dunite, harzburgite, and lherzolite, which have been strongly affected by alteration. The tectonic activities have caused crushing in these rocks in a way that has facilitated their alteration process and created laterite areas. As a result of different alteration processes such as serpentinization, carbonation, hematitization, and silicification, primary minerals such as olivine, pyroxene, and spinel have been altered and secondary minerals such as serpentine, dolomite, quartz, hematite, and smectite have been formed. The laterite zone is a layered red horizon and in some areas is lenticular, which is located on peridotite rocks. In some areas it is covered by Miocene limestones. In some areas, the secondary fractures of laterites formed by tectonic and diagenesis activities are filled by dolomite and silica. According to XRD analysis, there are dolomite, quartz, hematite, smectite and serpentine group minerals in the laterite section. The chemical analysis of the studied samples shows the nickel content of 381-2660 ppm for Noorabad laterites. According to the discrimination diagrams of source rock, the studied laterites are derived from ultramafic rocks. Moreover, the investigations carried out on the La/Y ratio showed that the formation environment for the studied laterite samples is alkaline. Discussion The peridotite rocks of Kermanshah ophiolite are related to suprasubduction ophiolites (Kiani, 2011). Due to the multi-stage replacement mechanism, these types of peridotites undergo the most serpentine alteration, so that their severe crushing during replacement and their migration on the margins of the continents facilitate the intensity of the altered. The peridotites of northwestern of Lorestan province were altered into serpentine during these alterations in the initial stages, and then underwent carbonate, hematite, and silicification alterations. During these changes, the primary minerals of these peridotites, such as olivine, pyroxene, and spinel, have become secondary minerals. The serpentine minerals are the first group of secondary minerals that were formed. Then, the secondary minerals of the second stage replaced the serpentines in such a way that the minerals of the smectite group can directly replace the serpentine (Dixon, 1989; Nahon et al., 1989; Gaudin et al., 2005). Other minerals are formed by substitution and saturation of other elements and form minerals with simple chemical formula such as quartz, dolomite, and hematite. During the first stages of alteration of peridotite rocks, the main elements Si, Mg, Ca, Fe, and Al were washed from the rock and caused the formation of secondary minerals in the lateritic zone. A significant amount of silica is included in the structure of silicate minerals such as serpentine and smectite, and the rest is filled in fractures in the form of chert and chalcedony. During the weathering process, magnesium-bearing minerals are destroyed and Mg2+ is removed from them, so that some of the magnesium in the serpentine mineral are replaced by Ni2+ (Sagapoa et al., 2011) and nickel-bearing serpentine minerals. The Ca element is removed from the pyroxene group minerals during alteration and enters the structure of smectite minerals or forms dolomite mineral. The Ni element has a positive correlation with the Co, Mg, Cr, and Fe elements, and this correlation can be due to the substitution of nickel instead of these elements in the crystal network of secondary minerals or due to the surface absorption of the mentioned elements by the hematite mineral.

Parent material and topography are among the soil-forming factors that affect soil evolution by influencing different parameters. This study was conducted to compare the effect of marl and calcareous parent materials in different slope positions, including the summit, shoulder, foot-, and toe-slopes on soil clay mineralogy in the Karoon 3 Basin, east of Khuzestan Province. Four soil profiles in each of the two topo-sequences were dug. They were sampled based on their genetic horizons and some physical, chemical properties, and clay mineralogy were measured. The results showed that the type and abundance of clay minerals identified for both parent materials were more affected by topo-sequence position. The composition of minerals identified in the topo-sequence with marl parent materials included kaolinite, palygorskite, smectite, chlorite, mica, and quartz, and in the topo-sequence with calcareous parent materials, palygorskite, smectite, chlorite, mica minerals, and quartz, and most of the identified minerals were also observed in all positions in the C horizon. However, in marl parent materials kaolinite, and calcareous parent materials, smectite seems to have been formed pedogenically. The result of the association between Weaver and Beck indicated that most of the clay minerals are in the equilibrium of Palygorskite.

Abstract REY‐rich mud, consisting of deep‐sea sediments with high concentrations of rare‐earth elements and yttrium (REY), holds significant economic potential. Many studies have been conducted on biogenic apatite, ferromanganese micronodule, and phillipsite within these deposits to ascertain the REY enrichment mechanisms. However, the knowledge of clay minerals in REY‐rich mud, which is the predominant component of pelagic sediments, is still limited. In this study, two adjacent gravity cores (core GC02: REY‐rich mud; core GC03: typical sediments of equatorial Pacific) were collected from the Clarion‐Clipperton Fracture Zone (CCFZ) of the Eastern Pacific to study the role of different clay minerals in REY enrichment. The clay minerals in core GC03 and core GC02 are primarily illite (averaging 60%) and smectite (averaging 63%), respectively, and the smectite in core GC02 was mainly Fe‐rich, which was probably formed via the reaction between opal and FeOOH. Moreover, multiple studies have reported similar smectite enrichment in REY‐rich mud, suggesting that it is a common characteristic. The presumed hydrothermal or volcanic origination of smectite in REY‐rich layers of core GC02 indicates the essential role of hydrothermal and volcanic activities in REY‐rich mud formation during the Oligocene in the western CCFZ.

IntroductionThere is growing evidence from animal and clinical studies suggesting probiotics can positively affect type 2 diabetes (T2D). In a previous randomized clinical study, we found that administering a live multistrain probiotic and absorbent smectite once a day for eight weeks to patients with T2D could reduce chronic systemic inflammatory state, insulin resistance, waist circumference and improve the glycemic profile. However, there is a lack of evidence supporting the efficacy of probiotic co-supplementation with absorbent smectite on pancreatic β-cell function in T2D.AimThis secondary analysis aimed to assess the effectiveness of an alive multistrain probiotic co-supplementation with absorbent smectite vs placebo on β-cell function in T2D patients.Material and methodsWe performed a secondary analysis on a previously published randomized controlled trial (NCT04293731, NCT03614039) involving 46 patients with T2D. The main inclusion criteria were the presence of β-cell dysfunction (%B

The association between clay minerals and organic carbon is pivotal for understanding transport, burial, and preservation processes of sedimentary organic carbon. However, fine-scale microscopic studies are still limited in assessing the effect of diverse clay mineral structures and properties on organic carbon sequestration. In this study, we employed X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy coupled with energy dispersive spectroscopy and electron energy loss spectroscopy analyses to investigate the nanoscale interaction between clay minerals and organic carbon of two typical fluvial sediment samples with contrasting clay mineral compositions and organic carbon origins. Sample from Taiwan shows abundant illite and chlorite with petrogenic organic carbon, while sample from Luzon has significant smectite with pedogenic organic carbon. We observed that the nanostructure of the clay minerals controls the distribution of organic carbon. In the Luzon sample, the organic carbon is tightly associated with smectite, occupying expandable interlayer spaces. In the Taiwan sample, however, the organic carbon is primarily confined on the surface and edge of illite. These findings offer valuable insights into the selective association of organic carbon with clay minerals and underscore the role of clay mineral nanolayer structures in governing the occurrence and preservation of organic carbon in sediments. A comprehensive understanding of these interactions is crucial for accurate assessments of carbon cycling and sequestration in the natural environment.

Clay minerals have great potentials in pinpointing sediment provenance for large depositional systems. However, source identification using clay minerals for small floodplain lakes is not well known. Situated in the North China Plain, the Dongping Lake receives sediments from both the Yellow River and the Dawen River, thereby representing an ideal site for testing the utility of this method. Here we use clay minerals in conjunction with the Bayesian end-member modeling analysis (BEMMA) to quantify the riverine contribution to modern sediments in the Dongping Lake. Results showed that modern sediments of the Dongping Lake are characterized by four primary clay minerals: illite, smectite, kaolinite, and chlorite, with average contents of 60.53%, 11.37%, 12.70%, and 15.40%, respectively. Clay minerals in modern sediments of the Dongping Lake are mainly delivered by the Yellow River, accounting for approximately 58.99–72.33%; whereas those originating from the Dawen River only account for 27.67–41.01%. It is also found that clay mineral from these rivers have a marked spatial variability. For example, source materials from the Yellow River are widely distributed across the lake, while those from the Dawen River only occur at the estuary of the river and slightly spread out in all directions under the action of water flow. [ABSTRACT FROM AUTHOR]

The Ni-laterite deposit at the San Felipe plateau, located 30 km northwest of Camagüey, in central Cuba, is the best example of a clay-type deposit in the Caribbean region. San Felipe resulted from the weathering of mantle peridotites of the Cretaceous Camagüey ophiolites. In this study, a geochemical and mineralogical characterization of two profiles (83 and 84) from the San Felipe deposit has been performed by XRF, ICP-MS, quantitative XRPD, oriented aggregate mount XRD, SEM, FE-SEM, and EMPA. Core 83, with a length of 23 m and drilled in the central part of the plateau, presents a notable concentration of cryptocrystalline quartz fragments and a rather poor content of NiO, averaging 0.87 wt.%. Core 84, which is 12 m long and drilled at the border of the plateau, lacks silica fragments and presents a higher NiO content, averaging 1.79 wt.%. The smectite structural formulae reveal that they evolve from trioctahedral to dioctahedral towards the top of the laterite profiles. Quantitative XRD analyses indicate that smectite is a dominant Ni-bearing phase, accompanied by serpentine and minor chlorite. Serpentine, as smectite, is enriched in the less soluble elements Fe3+, Al, and Ni towards the top of the profiles. Core 83 seems to have been affected by collapses and replenishments, whereas core 84 may have remained undisturbed. [ABSTRACT FROM AUTHOR]

In this study, atomistic simulations were carried out to study the difference in the adsorption process between two similar molecules, diazepam and oxazepam, on Na+-montmorillonite. Kinetic and XRD measurements showed a contrasting adsorption mechanism of these two molecules, differing only by the presence/absence of methyl and hydroxyl groups, with a larger adsorption amount and intercalation for the oxazepam. The structural characterization of these molecules was investigated through DFT calculations and showed the vicinity of hydroxyl and carbonyl groups for only the chair conformation of oxazepam compared to the boat conformation. Classical molecular dynamics simulations of diazepam and the two forms of oxazepam on the external surface of Na+-montmorillonite highlighted the better coordination of the oxazepam-chair conformation, compared to its boat counterpart and diazepam. This has been confirmed through DFT calculations, from which a coordination energy that is greater by 10 kcal·mol−1 is observed. This strongly suggests that the experimentally observed intercalation of oxazepam occurs only in the chair form because of the strong coordination with the Na+ cation present in the Na-Mt interlayer. Classical MD simulations of the intercalated oxazepam chair molecule in the Na-Mt interlayer allowed the evaluation of the interlayer spacing d001, which was in very good agreement with the experimental XRD measurement. [ABSTRACT FROM AUTHOR]

The paper reports a detailed coal-petrographic and mineralogical–geochemical study of humic coals and coaly rocks in the Upper Devonian Sargaevo deposits in North Timan (Sula River), which are an example of the burial of the oldest coal-forming plants. The following types of organic rocks are identified in the section: "jet-like" coal, liptobiolitic silty–argillaceous coal, and silty–argillaceous–coaly mixtolites. The studied coals and coaly rocks are mainly composed of humic organic components represented by vitrinite and liptinite macerals, with subordinate inertinite group. The vitrinite macerals include gelinite, collotelinite, and telinite (xylenite); the liptinite macerals include sporinite, cutinite, liptodetrinite, bituminite, alginite, and resinite, and the inertinite macerals include inertodetrinite, semifusinite, fusinite, and funginite. The vitrinite reflectance (RV, %) 0.45–0.55% corresponds to the insignificant organic maturity from proto- to meso-catagenesis (rank PC3–MС1). The mineral component of mixtolites and high-ash coals consists of kaolinite, chlorite/smectite (with a predominance of the chlorite component), and quartz. [ABSTRACT FROM AUTHOR]

Samples from Garmiyan located in Kurdistan region of Iraq were collected and investigated concerning their physical, chemical, and mineralogical properties. Eight samples from five different locations have been taken based on the experience of villagers who used these materials for bathing to soften their hair as an alternative to shampoo. Some of these materials are locally termed “Gllasar”, meaning “head mud”. The samples were analyzed by XRD, XRF, FTIR, STA, CEC, and concerning their C- and S-content. The results show that some of the materials can be classified as bentonites because they are predominantly composed of smectite with minor contents of carbonates, quartz, dolomite, kaolinite, plagioclase, chlorite, and feldspar. Three out of the eight samples showed smectite contents higher than 60 mass% and hence can be considered promising raw materials. Future work will be devoted to investigation of reserves in the deposit and application tests. [ABSTRACT FROM AUTHOR]

Smectite clay minerals have an outsize impact on the response of clay-rich media to common stimuli, such as hydration and ion exchange, motivating extensive effort to understand behaviors resulting from these processes such as swelling and exfoliation. Smectites are common and historic systems for investigating colloidal and interfacial phenomena, with two swelling regimes commonly identified across myriad clays: osmotic swelling at high water activity and crystalline swelling at low water activity. However, no current swelling model seamlessly spans the full ranges of water, salt and clay content encountered in natural or engineered settings. Here, we show that structures previously rationalized as either osmotic or crystalline coexist as a rich array of distinct colloidal phases that differ by water content, layer stacking thickness, and curvature. We present an analytical model for intermolecular potentials among water, salt and clay in both mono- and divalent electrolytes that predicts swelling pressures across high and low water activities. Our results indicate that all clay swelling is osmotic swelling, but that the osmotic pressure of charged mineral interfaces becomes attractive and dominates that of the electrolyte at high clay activities. Global energy minima are often not reached on experimental timescales due to many local energy minima that promote long-lived intermediate states with vast differences in clay, ion, and water mobilities, leading to hyperdiffusive layer dynamics driven by variable hydration-mediated interfacial charge. Teaser Distinct colloidal phases of swelling clays emerge via ion (de)hydration at mineral interfaces that drives hyperdiffusive layer dynamics as metastable smectites approach equilibrium. [ABSTRACT FROM AUTHOR]

Microbially induced formation and transformation of clay minerals are known to be ubiquitous in nature. This work investigated the smectite-to-kaolinite transformation by Bacillus mucilaginosus, a kind of silicate-weathering bacterium. Results showed that the microbe-smectite system doubled protein production compared with the abiotic controls and enhanced dissolved 1.6% of total Si and 0.9% of total Al from smectite after the 25 days experiment. The formation of kaolinite was verified through its distinguished d(001)-spacing of 0.710 nm revealed by synchrotron radiation X-ray difrac-tion (SR-XRD) and high-resolution transmission electron microscope (HR-TEM). HR-TEM analysis indicated some mixed layers of smectite and kaolinite appeared in the form of a super-lattice structure. Moreover, the compositional and morphological changes of the solids suggested the emergence of kaolinite was associated with the formation of amorphous SiO2 and fragmented clay particles with lower Si/Al ratio and exposed crystal edge. Based on the detection of –C=O species on the smectite surface and the decrease of pH from 8.5 to 6.5, we inferred the organic ligands secreted by Bacillus mucilaginosus complexed with cations, especially for Si, which stripped the tetrahedral sheets and promoted the kaolinization of smectite. To our knowledge, this is the first report of microbially induced smectite-to-kaolinite transformation under ambient conditions in a highly-efficient way. This work could shed light on a novel pathway of microbe-promoted weathering of smectite to kaolinite at the Earth surface conditions. Such a robust and eficient transformation from expansive smectite to non-expansive clays as kaolinite may be of great potential in enhancing oil recovery in reservoirs. [ABSTRACT FROM AUTHOR]

Smectitic clay minerals are unique indicators of paleoenvironmental conditions and exhibit a unique reactivity in the mineral world. Smectites may exhibit tetrahedral substitutions (Al3+, and sometimes Fe3+, can substitute for Si4+ in tetrahedral sites), resulting in a layer-charge increase, thereby impacting their properties (e.g. swelling and sorption capacities, catalytic properties, expandable abilities). The objective of the present study was to determine the influence of pH conditions on the hydrothermal production of smectite end-members exhibiting tetrahedral Al substitutions (saponite, beidellite, and nontronite), using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) methods. The results of a series of syntheses conducted at various pH values allowed discussion of the crystallization pathways of these smectites from a mechanistic point of view. Altogether, the present study provided easily reproducible protocols for the hydrothermal production of pure saponite, nontronite, or beidellite (i.e. with no other mineral). The successful synthesis of pure saponite was achieved by exposing the starting gels to 230°C for 4 days in solutions at pH ranging from 5.5 to 14. The successful synthesis of pure beidellite was achieved by exposing the starting gels to 230°C for 9 days in a solution at pH 12. The successful synthesis of pure nontronite was achieved by exposing the starting gels to 150°C for 2.5 days in a solution at pH 12.5. Although extrapolating experimental results to natural settings remains difficult, the results of the present study may be of great help to constrain better the geochemical conditions existing or having existed on extraterrestrial planetary bodies. [ABSTRACT FROM AUTHOR]

The employment of clay minerals in the transport of water, nutrients, and contaminants depends on a few factors, including permeability, hydration behavior, ion-exchange efficiency, and more. With the application of external stress, it is still difficult to understand how clay particles swell and collapse, how water is retained, how hydration heterogeneities are formed within crystallites, and how interlamellar space is organized. The present work studied the link between geochemical, thermal, kinetic constraints (established at the laboratory scale), and intrinsic clay features by exchanging Na-rich montmorillonite (SWy2) with Ni2+, Mg2+, or Zn2+ cations. By comparing the experimental 00l reflections with the calculated reflections obtained from the structural models, quantitative X-ray diffraction (XRD) analysis has enabled the building of a theoretical profile describing the layer stacking mode (LSM) and allowed the description of interlayer space (IS) configuration along the c* axis. Regardless of the type of the exchangeable cations (EC), XRD modeling revealed that all samples exhibited interstratified hydration behavior within the crystallite size, which probably indicates partial or incomplete saturation of the IS. This theoretical result was defined by the appearance of two hydration states (1W and 2W), which were unrelated to the strain strength creating a higher degree of structural heterogeneity. Using the theoretical decomposition of the observed XRD patterns, the identification of all distinct layer populations and their stacking mode was achieved. The segregated LSM are, therefore, obviously superior as a function of stress strength. [ABSTRACT FROM AUTHOR]

The results of investigations of the behavior of analcime-containing rocks of Timan (Komi Republic) at high temperatures (1200 – 1280°C) are brought forward. The mineral composition and physical characteristics of the resulting ceramics were determined: apparent density, water absorption, open porosity, and thermal conductivity. The influence of the mineral composition of the initial analcime-containing rocks on the foaming capacity and physical characteristics of fired ceramics is demonstrated. Porous materials with low apparent density (0.37 – 0.39 kg/m3), water absorption (up to 4.3%), and thermal conductivity (0.09 – 0.10W/(m · K)) have been obtained. The results show the prospects of using analcime-containing rocks of a certain mineral composition for the production of heat-insulating foam materials. [ABSTRACT FROM AUTHOR]

A new concept of the formation of glauconite from the Paleocene deposits of the sedimentary cover of the southwestern part of the Near-Volga monocline is presented. It was formed as a result of halmyrolysis of ash material in lake conditions. Glauconitization is confined to the Paleogene thermal maximum and the periphery of active volcanism along the entire mobile belt. In this connection, it is widely distributed in the Paleogene deposits. Structural and crystal-chemical features of glauconite, stages of crystallization of its aggregates, paragenetic associations with smectite, kaolinite, and zeolite, as well as the presence of ore minerals indicate its authigenic origin. The authigenic origin is confined to the formations of temporary, episodically submerging shallow marine basins. An applied scheme of discrimination of glauconites by their crystallochemical features has been developed. The discrimination diagram can be used to determine the specific conditions of the sedimentation basin, which are expressed in the progradation cycles of glauconite accumulation. The cycles were controlled by induced depressions within the Russian plate. [ABSTRACT FROM AUTHOR]

Aflatoxins can cause intoxication and poisoning in animals and humans. Among these molecules, aflatoxin B1 (AFB1) is the most dangerous because of its carcinogenic and mutagenic properties. To mitigate these effects, clay adsorbents are commonly included in the diet of animals to adsorb the carcinogens and prevent their absorption in the gastrointestinal tract. In this study, four clays, three smectites (C-1, C-2, and C-3), and one zeolite (C-4), were compared as adsorbents of AFB1 and trace inorganic nutrients using an in vitro gastrointestinal model for poultry. Characterization of the clays using Fourier transform infrared spectroscopy revealed characteristic bands of smectites in C-1, C-2, and C-3 (stretching vibrations of Si-O, Al-O-Si, and Si-O-Si). The C-4 presented bands related to the bending vibration of structural units (Si-O-Si and Al-O-Si). X-ray diffraction analysis showed that C-1 is a montmorillonite, C-2 is a beidellite, C-3 is a beidellite-Ca-montmorillonite, and C-4 is a clinoptilolite. The elemental compositions of the clays showed alumina, silica, iron, calcium, and sodium contents. The cation exchange capacity was higher in C-3 clay (60.2 cmol(+)/kg) in contrast with the other clays. The AFB1 adsorption of C-1 was the highest (98%; p ˂ 0.001), followed by C-2 (94%). However, all the clays also sequestered trace inorganic nutrients (Fe, Mn, Zn, and Se). Both smectites, montmorillonite and beidellite, were the most suitable for use as adsorbents of AFB1. [ABSTRACT FROM AUTHOR]

Exploring reservoir stratum sensitivity is an important basic work for oil and gas exploration and exploitation, in which the degree of water sensitivity damage is often affected by the clay mineral content and microscopic pore throat structure of illite/montmorillonite mixed clay minerals. To reveal the distribution law and the main controlling factors of illite/montmorillonite mixed layers, the diagenesis, regional distribution law, and main controlling factors of illite/montmorillonite mixed layers in the reservoir stratum of the Upper Wuerhe Formation in the study area were analyzed by high-resolution testing techniques such as scanning electron microscopy (SEM) and Advanced Mineral Identification and Characterization System. Diagenesis was the main cause of illite/montmorillonite mixed layers in the study area, and the occurrence state under SEM was mostly flaky, silky, and flocculent filling in intragranular dissolved pores or intergranular pores. The mass fraction of illite/montmorillonite mixed layers increased with the increase in depth in the longitudinal direction, which was closely related to the sedimentary microfacies and the hydrodynamic environment in the plane. Results show that potash feldspar is the material basis for the formation of illite/montmorillonite mixed layers, and the strength of the hydrodynamic environment is the main controlling factor for the quality distribution characteristics of such mixed layers. This study provides a new technical method and research idea for understanding the reservoir sensitivity characteristics, which has good guiding significance for the blocks with strong reservoir sensitivity. The original pore structure of the reservoir can also be protected against destruction by various sensitivity factors in the developmental stage caused by the unclear understanding of the spatial distribution characteristics of clay minerals affecting the yield in oil and gas field development. [ABSTRACT FROM AUTHOR]

Bentonites are proposed to be used as buffers in high-level radioactive waste repositories. The elevated temperatures in repositories may, however, affect bentonites’ desired properties. For instance, heating under dry conditions can cause cation fixation, potentially affecting swelling properties. The kinetics of mineral dissolution and precipitation reactions will equally be influenced by temperature. Redistributions of Ca-sulphates and -carbonates have been observed, as well as illitization of smectite. Illitization, however, has only been observed in laboratory experiments at large solution/solid ratios, whereas it has not yet been unambiguously identified in large scale experiments. In many large-scale tests, cation exchange is the first observable geochemical reaction. In addition, an enrichment of Mg close to the heater is found in many such tests. The thermal gradient and (incongruent) smectite dissolution are suspected to play a role with respect to the Mg enrichment, but the underlying mechanism has not been unravelled so far. To predict the longterm performance of a bentonite buffer, numerical modelling is required in order to be able to simulate the reactions of all accompanying mineral phases. Smectites, which dominate the bentonite composition, are therefore particularly difficult to characterise, as their dissolution is often observed to be non-stoichiometric. Various model approaches exist to simulate smectite reactions, mostly based on kinetic rate reactions, ideally considering the effect of pH (congruent or incongruent dissolution), temperature and the degree of saturation of the solution. Reassessing and improving the thermodynamic/kinetic data of smectites are prerequisites for improving long-term buffer performance assessment. [ABSTRACT FROM AUTHOR]

Synchrotron powder diffraction data is presented for a series of relatively phase-pure smectite clay mineral standards obtained from the Clay Minerals Society. Rietveld refinement using a model for turbostratic disorder was performed to estimate the lattice parameters and mineral impurities in the smectite standards. Bragg reflection lists and raw data have been provided for inclusion in the Powder Diffraction File. [ABSTRACT FROM AUTHOR]

The aim of this work was to compare the adsorption efficiency of two clay materials, namely activated smectite (SMT) and laterite clay (ALT). The comparison was focused on the removal of indigo carmine (IC) dye from aqueous solution. The characterizations showed that the initial materials were mainly mesoporous for effective adsorption. Batch adsorption studies were investigated to optimize the operating parameters such as adsorbent dose, contact time, solution pH, and initial concentration. The pH of point of zero charge (pHpzc) was found to be 2.5, and the optimal adsorption pH obtained was 2 for laterite clay (ALT) and activated smectite (SMT) adsorbents with adsorption capacities of 1.64 mg/g and 1.37 mg/g, respectively, and 10 min as contact time. Surface heterogeneity of both adsorbents was proportional to the amount of IC adsorbed. Freundlich, Langmuir, Dubinin–Kaganer–Radushkevich (D–K–R), and Temkin isotherm models clearly described the retention of the IC on these mesoporous materials. The values of adsorption energies located between 2.23 and 2.54 kJ/mol demonstrated the physisorption of the process. The adsorption capacities obtained by Langmuir model were 4.08 and 4.38 mg/g for ALT and SMT, respectively. The pseudo-second-order kinetic model has been approvingly fitted with complete curves derived from experimental data of both adsorbents. ALT was found to be more effective in the removal of IC compared to SMT. Activated smectite and laterite clay appear to be tenable and profit-making materials for the clean-up of indigo carmine from wastewater. [ABSTRACT FROM AUTHOR]

Artificial soil mixtures were prepared with 10–40% of either kaolinite or bentonite clay, plus Sphagnum moss, and clean sand. Mixtures were placed in plastic containers in the field, and let mature for six months (in a tropical climate). They were then contaminated with 3% of either light, medium or heavy crude oil, and let weather for another six months. Afterward, compaction was measured in the field, and core samples were taken for laboratory determinations. No correlation was found between soil density and compaction, and it appeared that some of the density determinations were unreliable due to interferences from the petroleum. Compaction was low (< 0.5 MPa) for smectite-based soil, but much higher (up to 1.24 MPa) in kaolinite-based soil, especially with higher clay levels contaminated with heavy crude. Water repellency for kaolinite-based soil was low to null (especially for 30 and 40% clay), but repellency for smectite-based soil was three orders of magnitude higher, in the severe to extreme range. However, it is uncertain whether these laboratory determinations on smectite-based soils could be applied to the field. Regional, smectite-rich soils tend to be moist and low-lying in the landscape, unlikely to manifest water repellency, even during the dry season. Field capacity in smectite-based soil showed low impacts (reductions of 0–1% of moisture content with higher amounts of clay), but kaolinite-based soil showed considerable reduction, especially at 30% clay (being 15% less). The importance of these results for contamination, characterization and remediation of regional soils is discussed, as well as recommendations for future research. [ABSTRACT FROM AUTHOR]

For the safe disposal of high-level radioactive waste using Engineered Barrier Systems (EBS), bentonite buffer is used by its high swelling capability and low hydraulic conductivity. When the bentonite buffer is contacted to heated pore water containing ions by radioactive decay, chemical alterations of minerals such as illitization reaction occur. Illitization of bentonite indicates the alteration of expandable smectite into non-expandable illite, which threatens the stability and integrity of EBS. This study intends to provide a thorough review on the information underlying in the illitization of bentonite, by covering basic clay mineralogy, smectite expansion, mechanisms and observation of illitization, and illitization in EBS. Since understanding of smectite illitization is crucial for securing the safety and integrity of nuclear waste disposal systems using bentonite buffer, this thorough review study is expected to provide essential and concise information for the preventive EBS design.

Iron(II)-bearing trioctahedral smectites (saponites) form during anoxic alteration of basaltic rock. They are predicted to have been widespread on the early Earth and are observed in the oceanic subsurface today. Smectite structures, including the occupancy of sites in the octahedral sheet, affect iron redox behavior but the rates and products of trioctahedral smectite oxidation have been largely unexplored to date. In this study we synthesized two Fe(II)-bearing trioctahedral smectites, one moderate (22 wt% Fe) and one high (27 wt% Fe) in iron content. We then examined the rate, extent, and products of their oxidation by dissolved oxygen, nitrite, and hydrogen peroxide. Dissolved oxygen caused partial oxidation of Fe(II) in the smectites with 14 to 43% of Fe(II) unoxidized after 20 to 30 days of exposure. The rate and extent of oxidation correlated with the dissolved oxygen concentration and the Fe(II) content of the clay. The incomplete oxidation in these experiments is consistent with the mixed-valent trioctahedral smectites observed in oxidized natural samples but contrasts with the complete reoxidation by oxygen shown by chemically- or microbially-reduced dioctahedral smectites. Oxidation of structural Fe(II) by 5 mmol L−1 nitrite was negligible for the moderate-iron smectite and yielded only ∼17% oxidation after 54 days of reaction for the high-iron smectite. Hydrogen peroxide caused rapid and near-complete oxidation of both clays. Powder X-ray diffraction, variable-temperature Mössbauer spectroscopy, and extended X-ray absorption fine structure spectroscopy together detected no crystalline or short-range-ordered secondary phases and show that oxidized iron remained in the trioctahedral smectite structure. The recalcitrant Fe(II) pool in oxidized trioctahedral smectites exists in less distorted sites than Fe(II) in the initial clays. Its unreactive nature at prolonged reaction times indicates an elevated redox potential generated by the local coordination environment. Slower oxidation rates create a larger recalcitrant Fe(II) pool, suggesting kinetic competition between oxidation and a process involved in redox stabilization, such as electron exchange between octahedral iron sites or deprotonation of hydroxyl groups in the structure. The resistance to complete oxidation of trioctahedral ferrous smectites and their full retention of iron demonstrates that transitions from anoxic to oxic conditions generate mixed-valence smectites rather than a mixture of new phases. Identifying the diagenetic products of mixed-valent trioctahedral smectites may provide an indicator in the rock record of past redox cycling. Substantial portions of structural Fe(II) in trioctahedral smectites display slow abiotic oxidation kinetics and represent potential electron donors for both microaerophilic iron oxidizing and nitrate-reducing, iron-oxidizing microorganisms in altered mafic rocks and related settings. [ABSTRACT FROM AUTHOR]

Using the through diffusion method at room temperature, the migration of radionuclides (3H, 99Tc, 137Cs, 233U) in compacted samples of clay materials was studied through pore diffusion from a model leachates of phosphate matrix of radioactive waste with a total salt content of about 400 mg/L. The effective diffusion coefficients and sorption distribution coefficients of radionuclides for the studied clay barrier materials were determined based on the experimental results. The patterns of diffusion transfer of tritium, cesium and uranium were revealed depending on the structure, mineral composition of clay materials and the content of radionuclides in the pore solution. Numerical solutions are proposed for calculating the effective pore diffusion coefficients of these radionuclides. There are not yet enough data to analyze the factors influencing the diffusion of technetium. [ABSTRACT FROM AUTHOR]

Volcanic glass and its mixture with smectite are commonly observed in shallow parts of subduction zones. As volcanic glass layers often act as glide planes in submarine landslides, and because its alteration product, smectite, is one of the frictionally weakest geological materials, the frictional characteristics of volcanic glass‐smectite mixtures are important for fault slip behavior in shallow parts of subduction zones. We performed a series of friction experiments on volcanic glass‐smectite mixtures with different smectite contents from 0% to 100% at various velocity conditions from 10 μm/s to 1 m/s under an effective normal stress of 5 MPa and pore pressure of 10 MPa. In general, apparent friction coefficients negatively depend on the smectite content at any velocity tested. We found that samples with smectite contents of 15%–30% showed a drastic slip‐weakening behavior at intermediate velocities of 1–3 mm/s. Finite element method modeling shows that thermal pressurization does not contribute to the observed weakening behavior. The critical nucleation length estimated from the slip‐weakening behavior is approximately 1–10 km, which is large enough to prevent the slip to accelerate to seismic slip velocity. Therefore, gouges with minor amount of clay, such as subducting volcanic ash layers, may contribute to the occurrence of the slow earthquakes at shallow depths in subduction zones. Plain Language Summary: Materials erupted from volcanoes deposit on the seafloor and subduct at the trench. One such material, volcanic glass, easily alters into mechanically weak clay minerals such as smectite that can cause an enormous slip during an earthquake in subduction zones. In this study, we experimentally examined the frictional properties of mixtures of volcanic glass and smectite to elucidate fault slip behavior at shallow depths of subduction zones. Experiments with varying smectite content showed that a drastic reduction in fault frictional strength was induced when a small amount of smectite was present at moderately high velocity conditions. This behavior may induce slow earthquakes in shallow subduction zones. Key Points: Small amount of clay minerals in volcanic glass induces a drastic slip‐weakening at ∼1 mm/sThermal processes do not contribute to the weakening behaviorSlip weakening and large critical nucleation length at intermediate slip velocities might cause slow earthquakes [ABSTRACT FROM AUTHOR]