Interlayer Of Montmorillonite Research Articles

Sub-2 nm Ternary Metallic Alloy Encapsulated within Montmorillonite Interlayers for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Sub-2 nm Ternary Metallic Alloy Encapsulated within Montmorillonite Interlayers for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Osmotic absorption behaviors of imidazolium ILs in digestive system and their effective removal way

Considering the controversial safety and risk solutions of ionic liquids (ILs), more essential basic researches are required as their applied fields become broader and applied scale grows larger. Under this background, the permeation behaviors of six common imidazole ILs on porcine gastric and enteric membranes together with the feasibility of their removal by adsorption with montmorillonite were investigated in vitro. Through the single-factor investigation of different cations, anions and ionic liquid concentrations, the current results show that the IL of 1-ethyl-3-methylimidazolium bromide ([Emim]Br) has the strongest permeation capacity on the gastric membrane during the tests. The cumulative permeation amount of Qn can reach 0.72 mg/cm2, and the cumulative permeation percentage alsoreaches 95.77 %; the whole permeation process conforms to the Hixcon-Crowell model. As comparison, the maximum cumulative penetration percentage of [Emim]Br on enteric member was determined as 89.11 %, and related models was also compared. In order to remove the potential IL in digestive tract, montmorillonite was screened out from those popularily used antidotes in clinic and the adsorption of [Emim]Br in gastric fluid by montmorillonite has been proved more consistent with the second-order kinetics and Langmuir model. The results of molecular simulation, infrared spectrum (IR), X-ray diffraction (XRD) and thermogravimetric (TG) characterization exhibit that [Emim]Br has been successfully adsorbed into the interlayer of montmorillonite. As a whole, the study provided a scientific and effective way to diminish the hidden danger of ionic liquid entering the blood through the digestive system.

استخدام المجهر الألكتروني الماسح في تشخيص المعادن الطينية في بعض ترب الرز العراقية

The Middle Euphrates region, represented by the governorates of Diwaniyah and Al-Najaf, was chosen to conduct the current study. As the two governorates are famous for cultivating various varieties of rice crop. Two methods using to irrigated these soils during the growing season, and called locally wet and dry methods. The morphological features of clay minerals were studied using scanning electron microscope (SEM), to describe the changes that occurred to the mineralogical features of these minerals due to the influence of the irrigation patterns used during irrigation of these soils. The scanning electron microscope (SEM) results show that were many changes in morphological features occurs such as in size and shape of clay minerals, in particular to smectite minerals. The scanning electron microscope (SEM) figure of clays in Al-Najaf(dry) soil showed some of particles appeared as well-formed imperfect hexagonal shape, which revealed that these particles belong to the chlorite mineral. While the mica minerals were appeared in lath-shaped, and rounded flakes in clays of all studied soils. Whereas the montmorillonite particles appear as a thin, webby crust, and have a flat, perming morphology. The variation in the size of the montmorillonite particles was adopted as a basis for the occurrence of the Mg-hydroxide layer within the interlayers of montmorillonite.

Agricultural light-converting anti-icing superhydrophobic coating for plant growth promotion

Agricultural coatings play a crucial role in addressing the global food crisis by significantly improving the plant growth environment, accelerating plant development, and enhancing the biological quality of plants. Nevertheless, there exist constraints in the form of limited sunlight utilization, decreased light transmission caused by surface icing leading to diminished plant photosynthesis, and high cost. In this study, a cost-effective and readily scalable superhydrophobic photothermal light-conversion coating is suggested as a means to improve the light conditions necessary for optimal plant growth. By employing in situ growth of carbon dots (CDs) on the surface and interlayers of montmorillonite (MMT) and hydrolytic polymerization of fluorinated alkyl silane (FAS) on the surface of MMT, light-converting superhydrophobic materials (CDs/MMT) with a micro-nano structure were synthesized. These materials demonstrated broad-spectrum fluorescence emission suitable for utilization by plant photosynthesis. They were dispersed into an epoxy resin (ER) matrix to obtain an agricultural superhydrophobic coating (ER-CDs/MMT). The “light absorption-capture-conversion” effect confers exceptional passive anti-icing and active de-icing properties upon the coating. Furthermore, outdoor planting experiments have demonstrated its capacity to substantially enhance the light environment and enhance the biological quality of soybean and morning glory by leveraging light scattering and conversion characteristics. This underscores its considerable potential for application in the next generation of facility agriculture.

Research progress on the flame retardation and modification of polypropylene by montmorillonite

Montmorillonite can be used to achieve nano-dispersion level by forming peel or intercalation structure in polypropylene body, so as to improve the mechanical properties of the material. In addition, montmorillonite plays the role of nucleating agent during the crystallization of polypropylene, which improves the crystallization efficiency of polypropylene. After the organic modification of montmorillonite, the spacing between crystal surfaces can be enlarged to form organic montmorillonite, which makes the molecular chains of polypropylene more easily dispersed to the interlayer of organic montmorillonite, forming a dense surface layer in the process of thermal decomposition, so as to improve the thermal stability of polypropylene and enhance the flame retardant property of polypropylene. Many previous studies have shown that montmorillonite plays a significant role in improving the mechanical strength and crystallization effect of polypropylene, as well as the flame retardant properties of nanocomposites.

Interlayer and surface characteristics of carboxymethyl cellulose and tetramethylammonium modified bentonite

This study aims to evaluate interlayer and surface characteristics of carboxymethylcellulose (CMC) and tetramethylammonium (TMA) modified bentonite, named as TCMB, as a potential material in contamination containment systems. The study employed a variety of experimental methods, including zeta-potential, scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscopy, and Fourier transform infrared spectroscopy (FTIR), along with molecular dynamics (MD) simulations. Zeta potential results revealed increased electronegativity in TCMB compared to the conventional bentonite. By forming three-dimensional hydrogel networks capable of filling inter clusters pore spaces, CMC effectively maintained the low hydraulic conductivity of TCMB. XRD results confirmed the presence of TMA in the interlayer of montmorillonite. MD simulations and FTIR analyses validated the successful adsorption of CMC and TMA, which can be jointly attributed to hydrogen bonds between hydroxyl groups in CMC and the surface oxygen of montmorillonite, and electrostatic attraction between TMA and montmorillonite. The comparatively weak bonding between CMC and montmorillonite may facilitate CMC elution in the TCMB exposed to aggressive permeants. Furthermore, the electrical double layer thickness of TCMB and CB was estimated as 31.54 Å and 18.76 Å, respectively. Overall, the CMC and TMA treatments effectively enhance the suitability of bentonite for contamination containment applications.

Optimization of preparation conditions of Bi-doped TiO2/montmorillonite composites and its photodegradation of Rhodamine B

In order to improve the photocatalytic degradation performance of titanium intercalated montmorillonite composites, the sol-gel method was used to intercalate bismuth/titanium polymerized hydroxyl cations into the interlayer of sodium-based montmorillonite (Na-MMT). The optimum synthesis conditions of Bi-doped TiO2/montmorillonite composite photocatalytic material (Bi/Ti-MMT) were investigated. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and UV–vis diffusion reflectance spectrum (UV-Vis DRS) had been used to study the formation of Bi/Ti-MMT. Under the conditions of Bi/Ti molar ratio of 7 %, montmorillonite suspension mass fraction of 2 %, calcination temperature of 600 ℃ and calcination time of 3 h, the Bi/Ti-MMT had the highest photocatalytic activity, the degradation rate of Rhodamine B (RhB) was 88.16 %. In Bi/Ti-MMT composites, TiO2 existed in anatase phase. Bi3+ replaced Ti4+ and was doped into the TiO2 lattice, which can inhibit the growth of TiO2 crystals and reduce the band gap. The photoresponse range of the composite material was broadened to visible light, which improved the utilization of light.

Montmorillonite-Silica-Graphene oxide composite incorporating with chiral thiourea for the Strecker reaction

The present study has successfully intercalated graphene oxide (GO) nanosheets and silica into the montmorillonite (MMT) interlayer and deposited them onto its external surface to make montmorillonite, silica, and graphene oxide composite (MMT-silica-GO). The as-prepared composite demonstrates improved thermal stability compared to neat MMT and GO. It was followed by incorporating chiral thiourea (CTU) scaffold into MMT-silica-GO-based composite to establish chiral MMT-silica-GO-CTU-based heterogeneous system and tested over Strecker reaction, revealing high activity and selectivity. FTIR, Raman spectroscopy, powder X-ray diffraction, SAXS, XPS, BET, SEM, EDAX, and thermogravimetric analysis were used to characterize the samples. It was credited to the synergistic effect between the composite components that enhanced access to active sites and dispersion of catalyst. Across the board, the chiral MMT-silica-GO-CTU-based heterogeneous system appears to be a promising candidate for the Strecker reaction.

Formation mechanism of a novel core–shell with tetradecyl dimethyl benzyl ammonium–modified montmorillonite interlayer nanofibrous membrane and its antimicrobial properties

A novel core–shell with a tetradecyl dimethyl benzyl ammonium chloride–modified montmorillonite (TDMBA/MMT) interlayer silk fibroin (SF)/poly(lactic acid) (PLLA) nanofibrous membrane was fabricated using a simple conventional electrospinning method. Scanning electron microscopy and pore size analyses revealed that this core–shell with TDMBA/MMT interlayer maintained its nanofibrous morphology and larger pore structure more successfully than SF/PLLA nanofibrous membranes after treatment with 75% ethanol vapor. Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses testified that the SF/PLLA–TDMBA/MMT nanofibers exhibited a core–shell with an interlayer structure, with SF/PLLA in the core–shell layer and TDMBA/MMT in the interlayer. The formation of a core–shell with interlayer nanofibers was primarily attributed to the uniform dispersion of TDMBA/MMT nanosheets in a solution owing to its exfoliation using hexafluoroisopropanol and then preparing a stable spinning solution similar to an emulsion. Compared to SF/PLLA nanofibrous membranes, the core–shell structure with TDMBA/MMT interlayers of SF/PLLA nanofibrous membranes exhibited enhanced hydrophilicity, thermal stability, mechanical properties as well as improved and long-lasting antimicrobial performance against Escherichia coli and Staphylococcus aureus without cytotoxicity.

A comparative study on the Cs adsorption/desorption and structural changes in different clay minerals.

We investigated the structural changes in clay minerals after Cs adsorption and understood their low desorption efficiency using an ion-exchanger. We focused on the role of interlayers in Cs adsorption and desorption in 2:1 clay minerals, namely illite, hydrobiotite, and montmorillonite, using batch experiments and XRD and EXAFS analyses. The adsorption characteristics of the clay minerals were analyzed using cation exchange capacity (CEC), maximum adsorption isotherms (Qmax), and radiocesium interception potential (RIP) experiments. Although illite showed a low CEC value, it exhibited high selectivity for Cs with a relatively high RIP/CEC ratio. The Cs desorption efficiency after treatment with a NaCl ion exchanger was the highest for illite (74.3%), followed by hydrobiotite (45.5%) and montmorillonite (30.3%); thus, Cs adsorbed onto planar sites, rather than on interlayers or frayed edge sites (FESs), is easily desorbed. After NaCl treatment, XRD analysis showed that the low desorption efficiency was due to the collapse of the interlayer-fixed Cs, which tightly narrowed the interlayers' hydrobiotite due to the ion exchange of divalent cations (Mg2+ or Ca2+) into the monovalent cation (Na+). Moreover, EXAFS analysis showed that hydrobiotite formed inner-sphere structures after NaCl desorption, indicating that it was difficult to remove Cs from NaCl desorption due to the collapsed hydrobiotite and montmorillonite interlayers as well as the strong bonding in FESs of illite. In contrast, chelation desorption using oxalic acid effectively dissolved the narrowed interlayers of hydrobiotite (98%) and montmorillonite (85.26%), enhancing the desorption efficiency. Therefore, low desorption efficiency for Cs clays using an ion exchanger was caused by the collapsed interlayer due to the exchange between monovalent cation and divalent cation.

Molecular dynamics simulation of dodecyl dimethyl benzyl ammonium cation-intercalated montmorillonite

Abstract Dodecyl dimethyl benzyl ammonium (DDBA) is a novel cation surfactant used to modify clay minerals. DDBA-intercalated montmorillonite is formed by the ion exchange between DDBA cations in the solution and cations in the montmorillonite interlayers. By using molecular dynamics simulations, we investigated the basal spacings, interlayer structures and dynamics of DDBA-montmorillonites. The results showed that the calculated basal spacings agreed well with experimental values and that the layering behaviours of DDBA had been revealed. The ammonium groups of DDBA ions preferred staying close to the centre of Si–O six-member rings. The benzyl group and lauryl group were oriented in parallel in the monolayer state, whereas they were tilted in other states. DDBA ions have very low mobility in the interlayer region, indicating that the negatively charged montmorillonite surfaces can effectively fix this positively charged surfactant. The microscopic structures and dynamics obtained in the present study provide atomic-scale insights into the properties of DDBA-intercalated clay minerals.

Density Functional Theory Simulation of Iron-Montmorillonite as Carbon Dioxide Adsorber

Carbon dioxide (CO2) is a greenhouse gas that naturally keep the Earth^s surface temperature warm but currently the levels cause environmental problem such as climate change. Carbon capture and storage (CCS) technology is built to reduce CO2 gas emissions by binding carbon dioxide molecules and then storing them or utilising them as more useful products. In this study, simulations were carried out for the addition of iron (Fe) impurities as additional cation in montmorillonite to see the increase in the ability to bind carbon gas. Density Functional Theory calculations were carried out using additional corrections such as Van der Waals (vdW) and Hubbard-U. Here we got that Fe cation can help CO2 adsorbtion compare with other site without Fe atom by adding acid cite condition. But to adsorb CO2, the structure need initial process to swell the montmorillonite interlayer to certain optimum distance.

Insights on adsorption of pyocyanin in montmorillonite using molecular dynamics simulation.

Pyocyanin is an important virulence factor in the resistance of Pseudomonas aeruginosa to antibiotics. Pyocyanin is a planar three ring aromatic molecule that occurs as zwitterionic (PYO) or protonated species (PYOH+). Our earlier studies have shown that montmorillonite, through adsorption and transformation, can inactivate both PYO and PYOH+ in the interlayer space. The objective of this study was to elucidate the interaction mechanisms between montmorillonite and the adsorbed pyocyanin and to characterize the structure of the pyocyanin-montmorillonite complex via molecular dynamics (MD) simulations. The MD simulations were performed for the complexes of hydrated Na-montmorillonite (HM) with (i) neutral pyocyanin (HMP) and (ii) protonated pyocyanin (HMPH); and dehydrated Na-montmorillonite (DM) with (iii) neutral pyocyanin (DMP) and (iv) protonated pyocyanin (DMPH). The simulations indicated that in dry conditions, both PYO and PYOH+ were well-ordered in the midplane of the interlayer of montmorillonite, with the three aromatic rings almost parallel to the basal surface and sandwiched in-between basal surface-adsorbed Na+ planes. In humid conditions, the pyocyanin and Na+ were solvated in the interlayer space and the pyocyanin was less ordered compared to dehydrated models. Ion-dipole interaction (Na-O) was the dominant interaction for the dehydrated complexes DMPH and DMP but the interaction was stronger in the latter. The Na-O ion-dipole interaction remained the dominant interaction in hydrated HMP while in HMPH, water outcompeted PYOH+ for Na+ resulting in water-Na interaction being the dominant interaction. These results revealed the arrangement of the two species of pyocyanin in the interlayer spaces of montmorillonite and the mechanism of interaction between the pyocyanin and montmorillonite.

Cotransport of fullerene nanoparticles and montmorillonite colloids in porous media: Critical role of divalent cations of montmorillonite

While the cotransport of carbon nanoparticles (CNPs) and clay colloids in porous media has been widely studied, the influence of the cation exchange capacity (CEC) of clay colloids on the transport process remains unclear. In this study, batch adsorption and column transport experiments were conducted to investigate the fate and transport of CNPs and clay colloids in quartz sand, with respect to the effect of monovalent-cation exchange capacity (mono-CEC), divalent-cation exchange capacity (di-CEC) and total CEC of clays. Fullerene nanoparticles (nC60) and six types of montmorillonite (ML) with different CEC were selected as modeled CNPs and clay colloids, respectively. Transport behavior of nC60 and ML was characterized using breakthrough curves (BTCs) and fitted with two-kinetic-sites colloid transport model. Results of the adsorption experiments showed a good linear correlation between the deposition of nC60 on the sand surface and the di-CEC of ML. Transport of ML and nC60 was inhibited by each other. The calculated mass recovery of nC60, as well as the fitted maximum deposition capacity and attachment rate coefficients of nC60 exhibited a strong linear relationship with the di-CEC of ML. These results indicate that divalent cations in ML interlayers play a significant role in aggregation between nC60 and ML and their cotransport. Through measurements of the particle size and zeta potentials of sole nC60 and mixtures of ML and nC60, FTIR and XPS analysis of nC60 under different conditions, and a release experiment of nC60 in a sand column, it demonstrated cation bridging (Ca2+-π) between nC60 and ML mediated by the divalent cations in ML interlayers. The study highlighted the potential of using di-CEC of clays as an indicator to predict the mobility of nC60 in clay-containing porous media and added insights to the transport behavior of CNPs in porous media.

Effect of Irrigation Regime on Mineralogical Properties of Clay Fraction in some Iraqi Rice Soils

Five soil pedons were chosen from two sites in Najaf and Diwaniyah, governorates, represent some of the soils of Middle Euphrates area. The soils are exploited by rice crop, and irrigated by two methods (flooded and dry) during the growing season. The mineralogical composition of < 2μm fractions for two depths (0-30 and 31-60 cm) in all studied soils were examined by X-ray diffractions. Results showed the presence of Mica, Smectite, Real chlorite and Kaolinite minerals in clay fraction of soils irrigated by the wet method. Results also, showed the precipitation of Brucite layer into Montmorillonite interlayers and caused to shifting Montmorillonite towards Chlorite mineral in soils irrigated by the dry method, and this was attributed to creation a suitable conditions from continuous wet-dry cycling, which encouraged a chloritization phenomenon to occur in these soils.. While, the continuous waterlogging process did not affect much on the weathering of mica minerals, and transformed it towards of expandable 2:1 minerals in these soils.

Migration of nanocolloid-carrying antibiotics in paddy red soil during the organic fertilization process

Soil nanocolloids are highly mobile and can act as carriers for the transport of antibiotics to a wider and deeper range of soils; however, the inherent behavior and mechanism of nanocolloid-carrying antibiotics in soil remain unclear. In this study, we conducted a comprehensive investigation of the migration of antibiotics in paddy red soil during the organic fertilization process using four common soil nanocolloids: kaolin (KL), montmorillonite (MT), hematite (HT), and humic acid (HA). The results showed that nanocolloid carriers promoted the intra-medium (from soil surface to the bottom) and inter-medium transfer (from organic fertilizers to soil) of antibiotics. The migration mechanisms of antibiotics carried by the nanocolloids differed: the phenolic hydroxyl and carboxyl groups of HA esterified with the carboxyl groups of quinolones and phenolic hydroxyl groups of tetracyclines, respectively, while the oxygen atoms of HT formed stabilizing complexes with the soil, which could further adsorb antibiotics using their functional group-rich complexes. Smaller antibiotic compounds were adsorbed in the metal oxide interlayer of MT via cation exchange, whereas KL adsorbed antibiotics on its metal oxide surface layer in the same way but were susceptible to desorption. Additionally, nanocolloids changed the adsorption capacity of soil for antibiotics and influenced the enrichment of dominant/functional bacteria (e.g., Burkholderiaceae) and thus varied the vertical distribution of antibiotics in soil. These findings enhance our understanding of the migration behavior and mechanism of nanocolloid-carrying antibiotics in red paddy soil and provide a theoretical foundation for preventing and controlling antibiotic pollution in arable systems.

Regulating interlayer and surface properties of montmorillonite by dodecyl dimethyl betaine for enhanced lead ion capture

Developing low-cost and high-performance adsorbents is of great significance for the treatment of wastewater containing heavy metal ions. Herein, dodecyl dimethyl betaine modified Na-based montmorillonite (BS-MMT) is successfully prepared by a facile wet method for enhanced lead ion (Pb2+) adsorption. The interlamellar spacing of Na-MMT is effectively regulated ranges from 1.25 to 1.79 nm by changing the ratio of BS-12 content from 5% to 150% (vs. MMT). The Pb2+ capacity adsorption of BS-MMT could reach up to 255.36 mg/g when the usage of BS-12 is 15%. Pb2+ adsorption process on BS-MMT follows the Langmuir model and is endothermic. Mechanism analysis suggests that the main Pb2+ adsorption pathways on BS-MMT include ion exchange, functional group complexation, electrostatic attraction and precipitation by CO32−. Moreover, the modification of BS-12 could not only brings carboxyl and amine functional groups to trap of Pb2+ on the surface and interlayer of MMT, but also optimize the layer spacing of MMT since its long carbon chain. This work provides a feasible strategy to optimize the adsorption capacity of organic modified MMT for heavy metals.

Effects of iron corrosion products on the degradation of bentonite structure and properties

Bentonite is a key material for engineering barriers to prevent groundwater and nuclide migration in the multi-barrier system of high-level radioactive waste (HLW) geological disposal. However, its barrier property will be degraded under the action of iron corrosion products of steel disposal containers. In this paper, the effects of iron corrosion products on the degradation of bentonite structure and properties were investigated in the simulated environments for HLW geological disposal. The results showed that Fe2+/Fe3+ dissolved from iron powder could enter montmorillonite (Mt) interlayer and substituted part of Na+, which caused the decrease of the volume and interlayer spacing of Mt, and the structural integrity of Mt was destroyed. Macroscopically, the water absorption and swelling property of bentonite were significantly decreased. The degradation mechanism of Mt structure was mainly that Fe2+/Fe3+ generated by iron corrosion entered the interlayer domain of Mt to compensate for the interlayer charge deficit.

Lacustrine Shale Diagenesis—A Case Study of the Second Member of the Funing Formation in the Subei Basin

Shale diagenesis differs from that of sandstone and carbonate rocks with regard to the type, evolution stage, and evolution mode. The quality of shale reservoirs is closely linked to the extent of diagenetic evolution. This study identifies the types and characteristics of shale diagenesis using thin sections and scanning electron microscopy (SEM) observations. The stages of shale diagenesis are determined by analyzing organic matter evolution and clay mineral transformation and establishing a diagenetic evolution sequence. This paper describes the comprehensive diagenetic evolution of organic matter, clay minerals, clastic particles, and carbonate minerals to determine the diagenesis types, diagenetic sequences, and pore evolution occurring during diagenetic evolution. The results show that the diagenesis types of shale in the second member of the Funing Formation include compaction, dissolution, cementation, metasomatism, dolomitization, syneresis, and transformation of clay minerals, as well as thermal evolution of organic matter. The middle diagenetic A stage is prevalent, with some areas in the early and middle diagenetic B stages. The shale underwent a diagenetic evolution sequence, including the collapse and shrinkage of montmorillonite interlayers in the early stage; the rapid formation and transformation of illite and smectite mixed layers, massive hydrocarbon generation of organic matters, and dissolution of unstable components in the middle stage; and the occurrence of fractures filled with gypsum, quartz, ferrocalcite, or other authigenic minerals in the later stage. Dissolution pores and fractures are the dominant shale reservoirs of the second member of the Funing Formation in the Subei Basin. The results provide new insights into understanding the formation and evolution of reservoir spaces during shale diagenesis and information for the exploration and development of lacustrine shale oil and gas.

Adsorption and characterization of exopolysaccharides from Rhizobium tropici on clay minerals

Exopolysaccharides (EPS) are extracellular macromolecular carbohydrate polymers secreted by microorganisms. EPS significantly improves soil structure, fertility and decreases erosion. Montmorillonite and kaolinite are two major clay minerals in soil. Interaction of EPS with clay minerals is important for understanding mechanisms of soil microaggregate and maintaining soil nutrients. The objectives of this study were to investigate mechanisms of EPS from Rhizobium tropici interaction with these clays and their adsorption capacity. Results show that EPS adsorption on clays were better described with Langmuir than Freundlich models, but kinetics followed the parabolic diffusion model. This suggested that EPS adsorption occurred on both surface and interlayers of montmorillonite as controlled by diffusion processes. The maximum adsorption capacity of EPS on montmorillonite and kaolinite were 236.4 mg/g and 168.6 mg/g, respectively. After initial adsorption of EPS on montmorillonite, the d-spacing was slightly increased, but further increase in EPS adsorption significantly decreased the d-spacing. This indicated the partial entrance of EPS into interlayers of montmorillonite, but high EPS presence possibly dehydrated metal ions within interlayers, shrinking montmorillonite. Thus, the current study provides an insight understanding of mechanisms of EPS from Rhizobium tropici interaction with clay minerals.