Properties Of Montmorillonite Research Articles

Structure and properties of montmorillonite containing Ca2+, Sr2+, and Ba2+ cations simultaneously

Most raw montmorillonites (MMT) used for radioactive waste disposal (HLW) contain Ca in the interlayer space. When HLW and MMT come into contact, various ions, such as Sr2+ and Ba2+, enter the mineral. Therefore, the article presents the results of modeling, based on molecular dynamics, for four different models for the replacement of part of Ca2+ with Sr2+ and Ba2+ ions in Ca-MMT.The general trend of MMT swelling does not change significantly after the introduction of Sr2+ and Ba2+ ions. The diffusion coefficient of water molecules increases with an increase in the number of H2O layers between mineral layers or the presence of a certain amount of large radius ions in the series Ca-MMT, Ca-Ba-MMT, Ca-Sr-MMT, Ca-Sr-Ba-MMT. It shown that in the state of single-layer clay hydration, all the studied cations form outer-sphere complexes. During two-layer clay hydration, Ca2+ tends to form outer-sphere complexes, while Sr2+ and Ba2+ ions predominantly form inner-sphere complexes. With a further increase in the number of water molecules, the interaction of Ca2+ with the basal surface of the MMT mineral layer increases.

Raw and Purified Clay Minerals for Drug Delivery Applications.

In this study, the aim was to prepare drug-releasing clay mineral particles using raw (CaMt) and purified (PMt) montmorillonite and to compare and determine the effects of purification on the properties of montmorillonite. Montmorillonite clay minerals are used in several pharmaceutical and cosmetic products due to their many favorable properties, such as cation exchange capacity, adsorption capability, high specific surface area, and biocompatibility. Recently, several types of clay minerals have been widely studied for drug delivery applications due to their unique properties. The purification of montmorillonite is considered as a potentially useful step which may decrease the toxicity of impurities but which may increase the adsorption capacity of the montmorillonite. However, the effects on the toxicity and drug-release properties of purified montmorillonite have never been compared to that of raw montmorillonite. Montmorillonite was purified through decomposition of carbonates, dissolution of hydroxides, oxidation of organic materials, dialysis, and sedimentation. The raw and the purified montmorillonite were characterized using XRD, FTIR, and cation exchange capacities. Then, the cytotoxicity of raw and purified montmorillonite on normal hFOB cells was investigated to assess their biocompatibility in vitro. Finally, the efficacy of montmorillonite as a drug-delivering agent was investigated in vitro using cytotoxicity assays with the MCF7 cell line. The antitumor drug doxorubicin was loaded onto particles through electrostatic forces at 97.99% for CaMt and 96.79% for PMt. The drug-loading efficiency and release behavior of both clay minerals were determined. Results showed that both raw and purified montmorillonite did not significantly reduce the viability of normal cells at low concentrations (<500 μg/mL). At high concentrations, both raw and purified montmorillonite showed significant toxicity and the effect of impurities on toxicity were also more pronounced. Although drug loading was successful for both clay minerals there were differences in their controlled drug-release behavior. Doxorubicin-loaded raw and purified clay minerals significantly reduced MCF7 cell viability similar to pure DOX.

Acid activation as a method to control the catalytic properties of montmorillonite in the synthesis of solketal from glycerol and acetone

The effect of acid activation using 0.125–0.5 mol/l Н2SO4, HCl and HNO3 on the physicochemical and catalytic properties of natural clay (95 % montmorillonite, Mukhartalinsk deposit) was investigated. The rate and selectivity of the solketal (2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane) synthesis from glycerol and acetone were shown to depend on the concentration and type of the acid. The reaction rate and the yield of solketal increase with increasing concentration of the acid, which is consistent with the growth in the amount of Broensted sites. As the surface acidity increases, the efficiency of the system increases in the series MM/HCl &gt; MM/HNO3 &gt; MM/H2SO4.

Effect of Montmorillonite Layer Charge on the Thermal Stability of Bentonite

AbstractThe thermal stability of bentonite is vitally important for its application in the casting field and the layer charge of montmorillonite (Qm) is one of its central crystal-chemical parameters. As the main component of bentonite, the influence of Qm on montmorillonite properties and behavior needs to be considered if bentonite is to be used in high-temperature environments. The objective of the current study was to investigate the relationship between Qm and the thermal stability of Chinese bentonite samples collected from Wuhu, Anhui Province (marked as WH); Xinyang, Henan Province (marked as XY); and Santai, Sichuan Province (marked as ST) below. The values of Qm were obtained using the O (11) method, and the structural properties of the bentonite samples were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry-differential scanning calorimetry (TG-DSC), and field emission scanning electron microscopy (FESEM). The results showed that, in the samples investigated, Qm was inversely related to the thermal stability of bentonite. The Qm value (electrons per half unit cell, e/huc) was greatest for sample ST (0.725 e/huc), followed by sample XY (0.470 e/huc), and by sample WH (0.354 e/huc). The dehydroxylation temperature changed related to Qm; the sample with the largest Qm value was WH (701°C), followed by sample XY (684°C), and sample ST (630°C). After the samples were calcined at 600°C, sample WH had the best montmorillonite structural integrity with the greatest degree of reusability (78.21%); while the montmorillonite structures of samples XY and ST were destroyed, and their reusabilities were only 9.48 and 6.01%, respectively.

Novel high‐strength montmorillonite/polyvinyl alcohol composite film enhanced by chitin nanowhiskers

AbstractNanomaterials can be used as reinforcement phase to improve the performance of polymers. A simple method to prepare a composite film with super high tensile strength was used in this study. The properties of montmorillonite (MMT)/polyvinyl alcohol (PVA) films reinforced by chitin nanowhisker (CNW) have been evaluated. The structures and properties of films were analyzed by atomic force microscope (AFM), Fourier transforms infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile testing. The results of FTIR and XRD showed that no chemical interaction occurred among MMT, PVA, and CNW. The SEM and AFM images suggested that the obtained composite films with the three substances had a relatively uniform layered structure and relatively smooth. The temperature at the onset of decomposition of the composite films was increased from 262.0 to 282.3°C by the addition of CNW. The tensile strength of the MMT/PVA/CNW film was reached 263.5 MPa, which was increased approximately 382% compared with the MMT/PVA film. According to these results, the composite film could be potentially used in packaging materials.

Surface properties of chitosan/montmorillonite films for biomedical applications

In this study, we firstly investigated the surface and protein adsorption properties of montmorillonite (MMT)/chitosan (CS) composite films with various MMT/CS weight ratios for metallic implants coating applications. Bicinchoninic acid (BCA) protein assay results show that the neat CS film exhibits a high concentration of bovine serum albumin (BSA) protein adhesion because the abundant carbonyl and amide functional groups on the surface of the CS film easily form hydrogen bonds with the copious carboxylic acid groups on the surface of the BSA protein. The MMT/CS composite films with MMT/CS = 3, 5, 8, and 10 possess a much lower BSA adhesion concentration than that of the neat CS film, as some of the carbonyl and amide functional groups on the surface of the composite films are replaced by the –Si–O–Si and –Al–O–Al groups. Among these MMT/CS composite films, the film with MMT/CS = 5 exhibits the lowest BSA adsorption concentration because it possesses a higher MMT content than those with MMT/CS = 1 and 3 and a smoother and non-porous surface than those with MMT/CS = 8 and 10. According to our results, MMT/CS composite films with appropriate MMT/CS weight ratios exhibit better surface and protein adsorption properties than neat CS for biomedical applications.

Research of structure and sorption properties of montmorillonite modified with hexadecylthymethylammonium bromide

The object of research is a natural layered silicate – montmorillonite of the Cherkasy deposit (Ukraine) with the general formula (Ca,Na)(А1,Mg,Fe)2(OH)2[(Si,А1)4О10]×nH2O. The chemical composition of the mineral: SiO2 – 51.9 %, Аl2O3 – 17.10 %, Fe2O3 – 7.92 %, MgO – 1.18 %, Na2O, K2O and CaO up to 2 % and Н2О – 8.78 %. Montmorillonite is characterized by a significant dispersion of particles and the presence of a large number of sorption centers on its surface is capable of cation exchange. One of the most problematic places is that montmorillonite is practically incapable of removing pollutants present in water as anions. In order to obtain sorbents capable of removing heavy metal anions, the surface of montmorillonite was modified with the cationic surfactant hexadecyltrimethylammonium bromide.During the study, X-ray diffraction analysis, scanning electron microscopy, infrared spectroscopy, and thermal analysis were used to study the structure of the initial montmorillonite and its organomodified forms. The spectrophotocolorimetric method is used to study the sorption properties of composites.The work confirms that hexadecyltrimethylammonium bromide molecules are sorbed not only on the outer surface of the particles, but also migrate between the aluminosilicate packets of the layered structure of montmorillonite. Sorption studies have confirmed that the use of organomodified forms of montmorillonite has increased the degree of extraction of chromium (VI) ions from 32 % to 96 %. The resulting sorbents make it possible to purify contaminated water with a chromium (VI) concentration of 1 mg/dm3 to the maximum permissible concentrations. This is due to the fact that the organomodification of the surface of montmorillonite has a number of features and allows to change the structure of the original mineral, as well as recharge the clay surface from negative to positive. This makes it possible to use organoclay to remove inorganic toxicants in anionic forms. Compared with similar known ones, the obtained composites provide the removal of even trace amounts of heavy metal anions from aqueous media.

A modeling methodology to investigate the effect of interfacial adhesion on the yield strength of MMT reinforced nanocomposites

This article focuses on the effects of incomplete interfacial adhesion on the yield strength and interface/interphase properties of montmorillonite (MMT)/polymer nanocomposites (MPN). The minimum length of platelets necessary for efficient stress transfer from matrix to MMT (Lc) and the interfacial shear strength (τ) change the effective inverse aspect ratio (α=thickness/length) and the effective volume fraction of MMT in nanocomposites. These effective parameters are applied to express the yield strength and interface/interphase properties in MPN. It was found that large platelets, small “Lc” and high “τ” increased the yield strength of MPN and the high levels of “Lc” and “α” caused poor interface/interphase properties.

Kinetic and thermodynamic assessment on isoniazid/montmorillonite adsorption

Abstract The properties of montmorillonite (Mt) as a natural nanocarrier of drugs have been fully reported. Isoniazid (INH), a first-line tuberculostatic drug, was intercalated into this inorganic matrix and the equilibrium and thermodynamic aspects of the adsorption process were evaluated. Adsorption experiments were performed at different times and temperatures in aqueous medium. The overall adsorption process was the result of two simple processes: INH adsorption on the activated sites of Mt. followed by a slight precipitation phase of INH molecules over the adsorbed monolayer. Formation of the nanohybrid was spontaneous, exothermic and exoentropic, obtaining an increase in the thermodynamic stability of the system. The hybrid material (Mt-INH) was successfully prepared with high drug loading. Solid state characterization of the pure materials and the resulting nanohybrid was carried out. Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), differential scanning calorimetry (DSC), surface charge, X-ray powder diffraction (XRPD) and high resolution transmission electron microscopy (HRTEM) coupled with energy dispersive spectroscopy (XEDS) and elemental X-ray maps served to correctly resolve the structure of the nanohybrid and to assess the nature and degree of the drug-clay interactions.

The jamming mechanism of sand control screen for the montmorillonite inflation with the water

In the process of well completion with mechanical screen to control sand, once the water content of the reservoir increased, the montmorillonite in clay minerals would swell which combined with formation sand has an obvious effect on the plugging of screen pipe in production string. According to the prediction of water production of reservoir, shale expansion instrument was used to establish the relationship between the different water content and swelling properties of montmorillonites and combined with the clogging test of screen under different water content to evaluate the blocking effect of montmorillonite under different water content on the clogging of screen in the process of sand control. It can be found in the experiment that: (1) If the reservoir products water, the expansion height of two kinds of montmorillonites is similar when the water content of oil is less than 10% or more than 20%, the expansion height of montmorillonites is large of which expansion rate can reach to 188% when the water content is between 10 and 20%. (2) Through the simulation experiment of sand control, when the water content is 10 and 30%, the screen blocking is the fastest, and the productivity index per meter is the lowest, the blockage rate is increased by nearly three times when the water content of oil is 0. (3) The influence of concentration ratio of oil and water on the productivity index per meter of metal mesh screen is larger than the swelling of montmorillonites which is mainly reflected in the water content is close to 20–30%. The degree and speed of screen blocking can be reduced by reducing the water content of produced fluid.

Relation between Usages of Bentonite and Properties of Montmorillonite

Relation between Usages of Bentonite and Properties of Montmorillonite

Effects of Surface Properties of Montmorillonite for their Cytocompatibility

We modified the surface of organically modified montmorillonite (OMMT) with the carboxyl group using the silane coupling reaction and assessed its characteristics and cytocompatibility. Scanning electron microscope observations show that while the size and morphology of the obtained OMMT (OMMT-COOH) was unchanged, the surface of OMMT-COOH was coarser than that of OMMT. Fourier transform infrared spectra showed characteristic strong peaks at 1210 and 1630 cm−1, corresponding to the peaks of the carboxyl group. X-ray diffraction analysis showed that the diffraction peak of OMMT-COOH corresponding to the (001) reflection was located at higher a 2θ value than that of OMMT. Results of the proliferation ratio and cell viability measurements indicated that the OMMT-COOH cytocompatibility is higher than that of OMMT. Based on these results, we conclude that cytocompatibility of montmorillonite would be improved by tuning the properties of the surface.

Effect of Bacillus mucilaginosus D4B1 on the structure and soil-conservation-related properties of montmorillonite

Bacillus mucilaginosus is one of the common soil bacteria and is widely used as a microbial fertilizer to release potassium from K-rich soil minerals. But few researchers have discussed possible effects that the bacteria may have on montmorillonite. This study investigated the effect of B. mucilaginosus strain on the capability of montmorillonite to retain water/cations. After 20days of interaction with B. mucilaginosus D4B1, the expansion ratios of montmorillonite samples decreased from 83.2% to 76.7%, and the cation exchange capacities (CEC) decreased from 80.8 mmol/100g to 67.8 mmol/100g, suggesting the durative interaction with the bacteria may reduce the capabilities of incorporating water molecules and nutrient into the interlayer space of montmorillonite. Morphological changes of discrete layers and etch pits were observed with scanning electron microscope (SEM). In the synchrotron radiation X-ray diffraction (SR-XRD) profiles, the full-width at half maximum (FWHM) of 001 reflection increased to 0.24nm as compared to the abiotic sample (0.19nm), indicating a decreased structural order in bacteria-treated montmorillonite. Also, a new band at 1540cm−1 assigned to asymmetric stretching vibrations of carboxylate was detected by micro fourier-transform infrared spectroscopy (FTIR) in bacteria-treated samples, suggesting the alteration in the mineral structure of montmorillonite was possibly triggered by the organic acids produced by bacteria. Moreover, in bacteria involved dispersion, a significant decrease of the pH value was coupled with a consecutive increase of total protein concentration, indicating the continuous activities of the bacteria during 20days of interaction. Above all, the decreased water-holding or cations-exchange capacity of montmorillonite was related to the partial alteration in the mineral structure of montmorillonite by B. mucilaginosus D4B1. Such a durable interaction on structural alteration of soil clays would have detrimental impact on long-term sustainability of soil resources.

The equilibrium benzene vapor adsorption on alkylammonium montmorillonites

Changes in the surface properties and porous structure of montmorillonite have been studied upon substitution of exchangeable Na+ ions by methylammonium and ethylammonium cations. It has been found that the modification significantly affects adsorption properties of montmorillonite with respect to benzene. Based on measured isosteres of benzene adsorption/desorption by dehydrated samples of montmorillonite in Na+, CH3NH+3, and C2H5NH+3 forms, the heats of adsorption and desorption have been determined as functions of the amount of adsorbed substance.

Materials, preparation, and characterization of PVA/MMT nanocomposite hydrogels: A review

This article presents a review of studies on materials, preparation, properties, and characterization of polyvinyl alcohol (PVA) nanocomposite hydrogels. The structure and properties of Montmorillonite, the nanoclay used in the manufacture of PVA nanocomposites and techniques for making PVA nanocomposite hydrogels have been reviewed. The characterization techniques such as Fourier transform infrared spectroscopy (FT‐IR), Differential scanning calorimetry (DSC), Dynamic mechanical analysis (DMA), Scanning electron microscopy, Transmission electron microscopy (TEM), X‐ray diffraction (XRD) are also studied. The XRD patterns and TEM images have proven the intercalated and exfoliated structures of PVA nanocomposite hydrogels that is due to the presence of nanoclay layers. Investigation of FT‐IR spectra shows the bonding formation between OH and silanol groups of PVA and Montmorillonite. Also, the results of DSC and DMA indicated a decrease in crystallinity and the glass transition temperature of PVA by the incorporation of nanoclay, while the loss modulus is increased compared to that of pure PVA. POLYM. COMPOS., 38:1086–1102, 2017. © 2015 Society of Plastics Engineers

Removal of Humic Acid by Organo-Montmorillonites: Influence of Surfactant Loading and Chain Length of Alkylammonium Cations

In this study, the characterization and adsorption properties of montmorillonite (MMT) and organomontmorillonites with different surfactant/cationic exchange capacity (CEC) ratios (1 and 2) of tetradecyl trimethylammonium (TDTMA+) and hexadecyl trimethylammonium (HDTMA+) cations were evaluated. The particle apparent diameter, determined by laser and scanning electron microscopy showed aggregate formation, which varied with loading and cation length of the surfactant used. X-ray diffraction analysis revealed the formation of a pseudotrilayer arrangement of both surfactants in the interlayer space, FTIR showed the characteristic bands of the surfactants and micelle formations, and zeta potential determinations indicated neutral or negative surface charge values, except for sample obtained with one CEC concentration exchanged with HDTMA+ (HDTMA1-MMT) where a charge reversal to positive was found. Higher adsorption amounts of humic acid (HA) were found for HDTMA1-MMT and TDTMA1-MMT samples than for MMT sample, while the increase in the loading of both surfactants decreased the amounts of HA adsorbed could be assigned to a higher micelle formation and different packing density of alkyl chain, in the external surface. The correlation found between the total surface area and negative zeta potential values and the HA adsorption rate, within each surfactant, indicated the strong influence that these properties have on HA adsorption.

Effect of Lithium Absorption at Tetrahedral Site and Isomorphic Substitution on Montmorillonite Properties: A Density Functional Theory Study

This study deals with the effect of the isomorphic substitution on the sorption of two Li atoms on montmorillonite using density functional theory (DFT). The isomorphic substitution is carried out by modifying the atomic composition of the upper tetrahedral layer of the montmorillonite by replacing one Si atom with one Al atom on the said position. Note that in the conventional structure, Si atom is located at the upper tetrahedral layer of montmorillonite. Results show that one Li atom is likely to be situated in the vacant tetrahedral site and the other one is in the vacant octahedral site, for both of the two montmorillonite systems (isomorphic substitution and conventional structure). The sorption energy was found to be -6.31 eV at the most stable configuration, that is for the isomorphic substitution.

Effect of Lithium Absorption at Tetrahedral Site and Isomorphic Substitution on Montmorillonite Properties: A Density Functional Theory Study

Effect of Lithium Absorption at Tetrahedral Site and Isomorphic Substitution on Montmorillonite Properties: A Density Functional Theory Study

Molecular Simulation on Modification of Structure and Thermodynamic Properties of Montmorillonite

Modification of structure and thermodynamic properties of montmorillonite is studied by molecular dynamics simulation. The simulation results show that the pure montmorillonite system is unstable in nature, while the structure of doping-modified montmorillonite is more stable. In simulation process, the activity between the molecule and impurity ions maintains strong synergistic effect, and the configuration of the analog system is energetically most stable.

The characterizations of rheological, electrokinetical and structural properties of ODTABr/MMT and HDTABr/MMT organoclays

In the present paper, we have investigated as a function of surfactant concentration the rheological (yield value, plastic viscosity) and electrokinetic (mobility, zeta potential) properties of montmorillonite (MMT) dispersions. The influence of surfactants (Octadeccyltrimethylammonium bromide, ODTABr and Hexadecyltrimethylammonium bromide, HDTABr) on dispersions of Na-activated bentonite was evaluated by rheological and electrokinetic measurements, and X-ray diffraction (XRD) studies. The interactions between clay minerals and surfactants in water-based Na-activated MMT dispersions (2 wt.%) were examined in detail using rheologic parameters, such as viscosity, yield point, apparent and plastic viscosity, hysteresis area, and electrokinetic parameters of mobility and zeta potentials, and XRD also analyses helped to determine swelling properties of d-spacings. MMT and organoclay dispersions showed Bingham Plastic flow behavior. The zeta potential measurements displayed that the surfactant molecules hold on the clay particle surfaces and the XRD analyses displayed that they get into the basal layers.