Eocene-aged bentonite deposits in Gonzalez (Texas, USA) carrfy scattered manganese oxide-rich pods where rare earth element (REE) concentrations as high as 7800 ppm have been detected — 10 times greater than in the already enriched bentonite. This study investigated the nature of the association between REEs and Mn oxides as well as REE modes of occurrence in these pods, in order to understand the processes that mobilize and accumulate REEs in the low-temperature depositional environment of the Texas coastal plain. Embedded, polished blocks of Mn pods were analyzed by Scanning Electron Microscopy (SEM); sections were then extracted by the FIB liftout technique from regions bearing REEs for further analysis by Transmission Electron Microscopy (TEM). The SEM and TEM results revealed the presence of abundant yttrium phosphate nanoparticles identified as xenotime, forming large globular aggregates that reach a few microns in diameter; these xenotime aggregates also host trace concentrations of Zr, Dy, Er, Yb, and Ce. Further, rhabdophane nanoparticles were detected that host predominantly light REEs and Y. The relative proportions of REEs in rhabdophane vary between particles and show decoupling of Ce from other light REEs, suggesting oxidation from Ce3+ to Ce4+. The REE enrichment of these Mn pods is due to extensive weathering along fractures cutting through the bentonite deposit that drove their remobilization and transport downward. At the base of the bentonite, where fractures terminate against the boundary with a cemented sandstone, changes in flow regime combined with gradual downward changes in fluid composition, prompted co-precipitation of Mn oxides and REE phosphates (xenotime and rhabdophane).

Study of the behavior of landfill lining materials (clays) in organic solvents is important because, in waste management, lining prevents groundwater contamination by the adsorption of various pollutants such as chemicals and organic solvents. Although scaling behavior and the self-association property of clays in water-alcohol binary solvents have been studied by many researchers, the anomalous behavior of Laponite XLG in binary solvents requires investigation as suggested by previous studies. In the present study, Laponite® RD, which is structurally similar to Laponite XLG, was used to gain further insight into the reasons for the anomalous viscosity, aggregation, and non-ergodic behavior of clay in a water–methanol binary solvent. Dynamic light scattering (DLS) revealed the emergence of the non-ergodic phase of 3% w/v Laponite® RD in the water–methanol binary solvent, which increased in the presence of a large methanol content as well as with aging time in the binary solvent. Viscosity measurements further indicated that aggregation was responsible for the non-ergodic behavior, and small-angle X-ray scattering (SAXS) revealed that a large methanol content enhanced the aggregation. Moreover, SAXS data also revealed that the surface charge was responsible for anomalous viscosity fluctuations in the binary solvent due to interparticle repulsion within aggregates. Rheological studies showed that the large methanol content in the binary solvent led to frequency-independent behavior of the storage modulus of Laponite® RD.

Phenol contaminants are highly biotoxic and have become a global problem threatening the environment and human health. The objective of the present study was to develop a very efficient and easily recyclable adsorbent to remove phenol. A magnetic montmorillonite composite with organic co-intercalation was fabricated by a simple one-step co-precipitation method and exhibited excellent phenol removal. Two surfactants, cetyltrimethylammonium bromide (CTAB) and erucic acid amide (EA), were successfully co-intercalated into the interlayer of Ca-montmorillonite, and Fe3O4 nanoparticles were simultaneously decorated to obtain Fe3O4-CTAB/EA-montmorillonite composite (Fe3O4-C/E-Mnt). The morphology and structure of Fe3O4-C/E-Mnt composite were explored by using different techniques such as X-ray diffraction, Fourier-Transform infrared spectroscopy, X-ray photoelectron microscopy and so on. The adsorption capacity of Fe3O4-C/E-Mnt for phenol was investigated under various conditions including temperature, pH, contact time, various phenol concentrations, and adsorbent dosage. The results showed that Fe3O4-C/E-Mnt retained a lamellar structure of Ca-Mnt with mesopores. Its interlayer space, surface area, and pore volume were increased. The Fe3O4-C/E-Mnt composite exhibited a good adsorption capacity (31.45 mg·g–1) for phenol with a removal efficiency of 85.46% at optimized conditions. Moreover, the adsorbent still maintained 78.32% of the adsorption capacity after five cycles. The adsorption test data of Fe3O4-C/E-Mnt followed the pseudo-second order kinetic model and the Langmuir model. The adsorption was a spontaneous, exothermic, entropy-decreasing process, and a possible adsorption mechanism of Fe3O4-C/E-Mnt was finally proposed.

Contamination of surface and groundwater with glyphosate, used widely on crops to control weeds, can cause severe environmental damage. Processes for glyphosate removal from water bodies have been developed, but few are effective and all are expensive. This objective of the present study was to investigate the use of a layered double oxide as a potentially effective and inexpensive material to remove glyphosate from water. Equilibrium, kinetics, and adsorption mechanisms were evaluated, in addition to the effects of competing anions and temperature on glyphosate adsorption. Up to 95% of glyphosate was removed from a synthetic solution in 50 min by Zn2Al-LDO (layered double oxide in Zn/Al ratio of 2:1) at pH 10. The adsorption isotherms were type L and the Langmuir model best fitted the experimental data, with a qmax value of 191.96 μg mg–1 at 25°C. The XRD pattern did not support the hypothesis of intercalation of glyphosate anions, whereas Fourier-transform infrared and solid-state 13C and 31P magic angle spinning nuclear magnetic resonance confirmed the adsorption of glyphosate anions on the Zn2Al-LDO surface, through carboxylate and phosphonate moiety interactions with end-on and side-on modes. The degree of removal of glyphosate increased with increasing temperature and decreased with increasing concentration of competing anions, with carbonate anions having the most prominent effect on the inhibition of glyphosate adsorption. The adsorption kinetics fitted a pseudo-first order law. Moreover, the intraparticle diffusion model suggested that the adsorption process depends on the formation and thickness of the film at the solution/solid interface.

Cis-1,4-polyisoprene latex (IRL) is the best alternative to natural rubber latex (NRL), and can help to avoid human allergic reactions caused by proteins in NRL. The mechanical properties of IRL are inferior to those of NRL, however. To address this issue, a novel strategy was developed using an in situ solution emulsification to prepare a latex composite incorporating sodium montmorillonite (Na-Mnt). The properties of the latex film prepared were investigated. The dispersion state of the Mnt in the latex composites and the morphology of the resulting composite films were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the mechanism of Mnt reinforcement of IRL is described comprehensively. The results showed that the Mnt/IRL latex composites prepared were stable and excellent films were formed, similar to those of NRL. The current research provided an effective method for preparing high-performance composite films suitable for use in high-end medical applications.

Mineralizable macronutrients (e.g. C, N, P, and S) are sorbed readily (i.e. adsorption and precipitation) in clays and clay minerals. Phosphorus (P) is one of the limiting macronutrients in soils because both phosphate and organic P undergo chemisorption in soil minerals. Furthermore, phosphatases that mineralize the organic P species tend to partition into soil minerals, suppressing the interactions between organic P and phosphatase. Adsorbed phosphatase on the mineral surfaces can regulate the enzyme activity and influence the biochemical properties of the enzyme (e.g. kinetics, conformation, and stability), affecting the P cycle in the terrestrial environment. Phosphatase–mineral interactions are widely reported to decrease the enzyme activity while enhancing the enzyme stability (e.g. thermal and proteolysis stability). Contradictory findings have also been reported. Specific enzymes, mineral characteristics, and reaction conditions are probably responsible for various reactivity (e.g. mineralization). The purpose of the present review was to summarize current and past investigations of acid and alkaline phosphatase sorption in clays and clay minerals and to examine phosphatase chemical properties (e.g. kinetic activity, thermal and proteolysis stability) and factors (e.g. pH, saturating cations of the mineral, enzyme structure, and mineral surface polarity) influencing the phosphatase-mineral interaction. Lastly, also reviewed is the application of phosphatase–mineral interactions with some expansion to other enzymes as an indication of potential future application for phosphatase and future research needs.

The Dolná Ves K-bentonite deposit is one of a few known economic accumulations of illite-smectite in the world. Several studies have been done on the illite-smectitic component isolated from the Dolná Ves K-bentonite, but there is a shortage of analytical data on the K-bentonite itself. The main goal of the present study was to perform mineralogical and physico-chemical characterizations of various technological types of K-bentonites from the Dolná Ves deposit to better understand the relationships between the various qualitative types and their properties. The type I (high-grade) K-bentonite contains 88–91 wt.% of illite-smectite. The type II (low-grade) K-bentonite contained substantially less illite-smectite, ranging from 37 to 63 wt.%. The illite-smectites isolated from the type I K-bentonites displayed greater expandability, contained more octahedral Mg and less octahedral Fe, had greater cation exchange capacity (CEC), smaller thickness of fundamental particles, and thinner illite-smectite crystals in comparison with illite-smectites from the type II K-bentonites. The LOI (loss-on-ignition) and Al2O3 content increased with increasing amount of illite-smectite. The increase in the expandability by 10% corresponded to an increase in CEC by ~10 meq/100 g. The type I K-bentonites had much greater mass loss at <250°C due to greater expandability. The best tilemaking performance was expected for the type I K-bentonite. This raw material could also be potentially valuable for the pharmaceutical, cosmetic and food industries. Overall, the results showed that the studied technological types of K-bentonites from the Dolná Ves deposit differ not only in terms of illite-smectite contents but also in terms of the nature of the illite-smectites.

Catalysts are very important in the use of cellulose, the main component of biomass, as a raw material for the large-scale production of liquid fuels and chemicals. 5-Hydroxymethylfurfural (HMF) is an extremely important intermediate in the fine chemical industry. HMF can be synthesized by acid-catalyzed dehydration of fructose, glucose, cellulose, or sucrose. The conversion of cellulose to HMF is challenging due to its chemical structure. The objective of the present study was to devise a more facile synthesis method using transition metal-doped montmorillonite catalysts (10Cr-Mnt, 10Cu-Mnt, 10Fe-Mnt, and 10Zn-Mnt) by wet impregnation. Samples were characterized by X-ray powder diffraction, specific surface area, and NH3-TPD analyses. The synthesized catalysts were used for the conversion of cellulose to 5-HMF in an aqueous medium. Among the metals studied, Cr showed the greatest catalytic activity. With the use of this catalyst, efficient conversion of cellulose to 5-HMF was achieved, affording a conversion yield of 93.47% and 5-HMF yield of 9.07% within 6 h at 200°C. The study described here could be useful for the efficient conversion of cellulose into 5-HMF, as well as into other biomass-derived chemicals.

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.

The present study describes research carried out to evaluate the mineralogical, geochemical and technological properties of indurated shale-quarry wastes and assess the suitability of these low-cost and locally available quarry wastes generated from crushed indurated shales for possible use as alternatives to fresh raw materials in the manufacture of roofing-tile products. Firstly, the mineralogical and chemical properties of the indurated shales were investigated by X-ray diffraction (XRD) and X-ray fluorescence, while their physical properties were identified by grain-size distribution, Atterberg limits, and clay activity. Samples of indurated shale-quarry wastes (ISQWs) were subjected to heat treatment at elevated firing temperatures to provide the required strength and durability and their ceramics properties (linear shrinkage, weight loss, water absorption, bulk density, and flexural strength) were determined. From the results, the ISQWs were composed predominantly of fine particles with medium plasticity and clay activity with values generally >0.75. The mineralogy revealed a predominance of aluminosilicates (illite-kaolinite-smectite-chlorite) with large quartz contents and variable percentages of carbonate and feldspar. The oxides were dominated by SiO2 and Al2O3, small amounts of ferromagnesian minerals, and considerable amounts of alkalis (K2O and Na2O) which act as fluxes. The CaO concentrations were variable and related to carbonate contents. Characterizations based on compositional ternary (total clay mineral-carbonate-quartz + feldspar) systems, Casagrande clay workability charts, and Winkler and McNally diagrams revealed their suitability for ceramics applications as the majority of ISQW samples fell within the specifications for roofing tiles. The ISQWs fired at a high temperature of 1000°C revealed considerable weight loss, reduction in both linear shrinkage and water absorption with insignificant increase in flexural strength. In order to achieve excellent ceramics properties and further reduce sintering temperature for their suitability as raw materials in the production of roofing tiles, beneficiations of ISQWs are highly recommended.

The total concentrations of rare-earth elements (REE) in the mined kaolin (0.02–0.06 wt.%), kaolin mine tailings (0.03–1.9 wt.%), and the kaolin-associated Marion Member sand lithology (0.03–4.6 wt.%) opened questions regarding the modes of occurrence of the REE and the role(s) of chemical weathering and secondary processes to explain the presence of REE in these materials. The REE were hosted primarily by phosphate minerals (monazite, xenotime) based on mineralogic analyses (scanning electron microscopy, X-ray diffraction). Enrichments in the light rare-earth elements (LREE: La–Gd) and the high correlation coefficient values were noted between P and the total REE concentrations (r2 = 0.99) for the sands and the mine tailings. Lower correlation coefficient values were noted between total REE concentrations and Zr (r2 = 0.31). The coarse fractions of the mined kaolins were enriched in the heavy rare-earth elements (HREE: Y, Tb–Lu) relative to the kaolin-associated sand lithologies. The REE inventory cannot be explained solely by mineral inheritance within the mined kaolins. Lower correlation coefficient values between P and total REE, positive Eu/Eu* anomalies, and the presence of xenotime overgrowths on zircon showed the importance of the role of chemical weathering of the detrital minerals during post-depositional processes (such as diagenesis) leading to redistributed and fractionated REE within the mined kaolin. The possibility of adsorption of the REE to kaolin mineral surfaces in the fine fraction of the mined kaolins remains open and permits further study to characterize fully the multi-modal fractionation of REE possible in the Georgia kaolin deposits.

Fired bricks were valued as essential building materials in the central tradition of Byzantine architecture in Constantinople (İstanbul), Anatolia, and the Balkans. In this study, Byzantine bricks from three construction periods, covering nearly nine centuries (fifth–fourteenth centuries), of Anaia Church (Kadıkalesi) in Western Anatolia were investigated to determine their characteristics, raw material properties, and production technologies. The characteristics of the bricks were evaluated and compared in order to identify similarities and differences between the periods and to investigate the continuity of the tradition of brick production over centuries. Basic physical and colorimetric properties, chemical and mineralogical compositions, thermal behavior, and microstructural and mechanical properties of bricks were determined by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM–EDS), Fourier-transform infrared spectrometry (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and mechanical tests. The results indicated that all the bricks in the Anaia Church were brown-beige colored, highly porous, low-density materials with low mechanical strength. They were produced from Ca-rich clays, probably obtained from two different sources used during all construction periods. The mineralogical composition and thermal properties revealed that the bricks from the first and second periods were fired at between 800 and 900°C and the bricks from the third period were fired at < 850°C. Greater calcium content and firing temperatures were found to reduce the total porosity and the number of small pores (< 10 μm) and increase the mechanical strength of the bricks. The results of the study revealed no significant differences in the production of bricks, including raw material sources and kiln conditions, for the different construction periods of the church.

A common design of a high-level radioactive waste (HLW) disposal system consists of the waste canisters emplaced in tunnels or shafts, with the space between the heat-emitting canisters and the surrounding rock filled with a bentonite-based material. Understanding the behavior of this barrier, in particular the effect of prolonged heating on its properties, is important to assess the barrier’s long-term performance. The objective of the present study was to add to this understanding and to supply experimental data about the state of bentonite hydrated and heated for a long period of time. To that end, a 50 cm long column of Wyoming-type bentonite pellets was heated at its base at 140 °C (simulating the waste canister) while a synthetic sodium-chloride-rich groundwater including sulfate, calcium, and magnesium was supplied through its upper surface for almost 10 y. At the end of the experiment the upper half of the column was saturated, but in the lower half the water content decreased sharply toward the heater, where it was close to 0%. No relevant mineralogical changes occurred, and the main component of the bentonite continued to be a predominantly sodium montmorillonite with no structural changes with respect to the initial one. In the area where the temperatures were >60°C and the material very dry, however, the smectite was not able to completely develop the 1-layer hydrate after 48 h of stabilization at RH 55%, although its expandability was fully recovered when the smectite was hydrated with liquid water. The ions solubilized as a result of the water-content increase were transported toward the heater and concentrated in two distinct areas: sodium and calcium chlorides closer to the heater than calcium and sodium sulfates. At the heater contact, the bentonite microstructure was of dense packets with carbon and Na-S-coated cavities. Precipitation of calcite and calcium sulfates and possibly dissolution of silica minerals also took place close to the heater.

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.

In the search for rare earth and other critical elements in coal measures, the coals are emphasized with lesser consideration for the accompanying rocks. In this investigation, the focus is on a lanthanide-rich, 315–317 Ma (after Machlus et al., Chemical Geology, 539, art. no. 119485, 2020) volcanic ash-fall trachyandesite to trachyte tonstein which occurs in association with the Middle Pennsylvanian Duckmantian-age Fire Clay coal in eastern Kentucky. The tonstein was deposited largely during peat accumulation, although it is known to occur at the base of the coal or within the underclay. The mineralogy is dominated by kaolinite with illite and quartz as minor to major minerals. A number of accessory minerals, as detected by X-ray diffraction + Siroquant XRD software and scanning and transmission electron microscopy (S/TEM), include REE-bearing phosphates (apatite, crandallite, florencite, monazite), and Y-bearing zircon. The highest rare earth element + Y concentrations occur in the weathered tonsteins, probably due to the concentration of these minerals after weathering of kaolinite from the rock.

Muscovite has been used increasingly as a substrate in flexible electronics and fillers in high-performance nanocomposites. Muscovite-based interfacial interactions play a crucial rule in material fabrication. Hansen solubility parameters (HSPs) have proven useful in characterizing molecular interactions within/between condensed phases. The present study aimed to determine the HSPs of raw muscovite (RM) and to investigate solvent dispersion mechanisms of RM. To achieve this, the solubilities of RM in 17 solvents were evaluated by dispersion tests, and the HSPs of RM were calculated as the center of the optimal solubility rotated-ellipsoid in HSP space, which included all good solvents, had the smallest number of outliers, and had the smallest volume. The resulting dispersion, polar, and hydrogen bonding components of RM were 18.301, 2.366, and 3.727 MPa1/2, respectively. By considering the HSPs and Kamlet-Taft's solvatochromic parameters of solvents, we concluded that the low polarity of RM is due to hindered K+/H+ exchange on the RM surface, resulting from limited water/moisture contact. For solvent dispersion of RM, essential conditions include strong dispersion forces and weak polar forces, finely tuned to match the surface property of RM at a certain hydration level. The HSPs of RM determined from dispersion tests were restricted to predicting/characterizing RM-based interfacial phenomena in an environment with strictly controlled water/moisture content. The HSP calculation method proposed herein was applicable to any clay mineral.

Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitutions in the structure, from vacancies in the octahedral sheet and from unsatisfied bonds at the edges of the crystals. It is of particular interest in the case of smectites because it affects important properties of this mineral. Several methods have been proposed for determining the layer charge of smectites, namely the structural formula method (SFM), the alkylammonium method (AAM), the NH4-method, the K-saturation method, and the O-D method. Most of these methods have been used extensively in the past and they all have advantages and shortcomings. The SFM and the AAM are based on different principles and are considered as primary methods. They have been used for a long time but they are time consuming and they provide contrasting layer charge values, with the AAM yielding consistently lower layer charge values than the SFM, especially for low-charge smectites. The remaining methods have been developed more recently and have been calibrated over their primary counterparts. They are applied easily and are capable of producing a large amount of data within a short time. In this sense they can be used both for geological interpretations and for assessment of bentonite deposits at an industrial scale.

The structure and composition of short-range ordered aluminosilicates (SROAS) may control their affinity for organic acids with potential effects on soil organic matter stabilization. Adsorption mechanisms of model organic acids were studied to resolve the effect of Si incorporation. Adsorption of oxalic, salicylic, and octanoic acid on Al-rich (Al:Si = 3.7) and Si-rich (Al:Si = 1.4) SROAS was quantified by analyses of dissolved organic carbon using catalytic high-temperature combustion. The initial pH of 5 and 6.5 increased to 6.3–8.2 during adsorption of oxalic and salicylic acid, demonstrating hydroxyl release by ligand exchange. Minor changes in pH indicated weak interactions of octanoic acid with both SROAS. Adsorbates were characterized by Fourier-transform infrared spectroscopy. Asymmetric stretching of carboxylate groups at 1720 and 1700 cm–1, and symmetric stretching at 1430 cm–1 evinced the formation of chelate complexes for oxalic acid. An absorption band centered at 1545 cm–1 indicated partial inner-sphere binding of salicylic acid on both SROAS. Silicon-rich SROAS adsorbed 80–90% less than Al-rich SROAS, suggesting that adsorption of oxalic and salicylic acid was controlled by surface aluminol groups. Fast kinetics of oxalate adsorption on Al sites was studied by a conductivity-based stopped-flow technique. Ligand exchange proceeded at a rate constant of 3.5 s–1 (25°C), similar to solute Al complexation, with an activation energy of up to 34.1 kJ mol–1. A slow process with a rate constant of 0.13 s–1 (25°C) was attributed to diffusion of oxalate at the surface or into SROAS particles. As supported by structural characterization of Si-rich SROAS, the much lower susceptibility of Si-rich SROAS to ligand exchange relates to Al speciation. The formation of tetrahedral Al precludes its complexation by carboxyl groups.

Strong gas-mineral interactions or slow adsorption kinetics require a molecular-level understanding of both adsorption and diffusion for these interactions to be properly described in transport models. In this combined molecular simulation and experimental study, noble gas adsorption and mobility is investigated in two naturally abundant zeolites whose pores are similar in size (clinoptilolite) and greater than (mordenite) the gas diameters. Simulated adsorption isotherms obtained from grand canonical Monte Carlo simulations indicate that both zeolites can accommodate even the largest gas (Rn). However, gas mobility in clinoptilolite is significantly hindered at pore-limiting window sites, as seen from molecular dynamics simulations in both bulk and slab zeolite models. Experimental gas adsorption isotherms for clinoptilolite confirm the presence of a kinetic barrier to Xe uptake, resulting in the unusual property of reverse Kr/Xe selectivity. Finally, a kinetic model is used to fit the simulated gas loading profiles, allowing a comparison of trends in gas diffusivity in the zeolite pores.

The modification of montmorillonite with metallic species affects directly its crystalline structure, texture, porosity, and surface. The interaction of the metallic molecules with the clay matrix, derived from the modification pathway and the characteristics of the adsorbate, modifies the physicochemical properties of montmorillonite, enabling the creation of materials with varied characteristics to be used both as catalysts and adsorbents. Small amounts of metallic species can confer various structural and physicochemical characteristics on the same montmorillonite matrix, depending on the metal incorporated. The objective of the present study was to create an acid-base catalyst based on montmorillonite K10 (K10 Mnt), modified with Ti, Ce, and Ni, for the catalytic esterification of acetic acid and penta-1-ol. K10-Mnt was modified using particles of Ti and of Ti modified with Ce and Ni. The effect of the inclusion of Ti and modified Ti species on the transformation of the physicochemical properties of the K10 Mnt and their contributions to the catalytic esterification syntheses were investigated. Samples were characterized by scanning electron microscopy coupled to an energy-dispersive X-ray spectroscopy system (SEM-EDS), powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N2 at 77 K (BET and BJH), and thermogravimetric analysis (TGA-DTGA). Finally, the original and modified K10 Mnt samples were tested for their catalytic esterification of acetic acid and penta-1-ol in the liquid phase.