Na-montmorillonite Research Articles

Carbon Dioxide Adsorption on Iron (III) Oxide Pillarized Na-Montmorillonite

Iron (III) oxide (Fe2O3) pillarized Na-montmorillonite (NaMMT) was prepared by ion-exchanging and calcining three different concentrations (0.025, 0.05, and 0.075 M) of Fe(OH)3 with NaMMT. The obtained materials were then examined for its ability to capture carbon dioxide, using thermogravimetric methods. The structural, compositional, and textural changes caused by pillarization were also examined using XRD, XRF, FTIR, and BET-BJH. The results showed that NaMMT-0.025 (pillared using 0.025 M of Fe(OH)3) and NaMMT-0.075 exhibit superior adsorption capacity compared to NaMMT, with NaMMT-0.025 having the greatest capacity. By contrast, NaMMT-0.05 registers a decrease in the amount of CO2 adsorbed, compared to NaMMT. Using XRF, it was shown that the amount of Fe2O3 present in the samples correspond to the concentration of Fe(OH)3 used in ion-exchange. XRD results shows that the interlayer space of NaMMT barely changed after addition of Fe2O3. Using FTIR, successful pillarization of Fe2O3 is confirmed, and by combining it with BET-BJH, it shows that addition of Fe2O3 could enhance carbon capture by creating favourable pore structures. Overall, it shows that adding an appropriate amount of Fe2O3 to montmorillonite will enhance CO2 adsorption.

Developing cellulose nanofibrils/Na-montmorillonite composite air filter with efficient filtration ability for PM2.5 and adsorption of formaldehyde

Indoor and outdoor air treatment is one of the key issues that people focus on. However, developinggreen air filtration materials withhigh filtration efficiency (FE), low pressure drops (ΔP) and good mechanical propertiesis still intractable challenges. In this study, we designed a green compositeaerogel air filter with double filtration mechanism, where Na-montmorillonite (NMMT) was exploited in the adsorption ability for PM2.5 due to its unique layered structure, high specific surface area, and negative charge. In the system, cellulose nanofibrils (CNF) as the structure materials were mixed with HCl acidified modified Na-montmorillonite (HMMT) as the functional particles, followed by freeze-drying to obtainCNF/HMMT compositeaerogel air filter. The resultingaerogel air filter showed excellent capture ability to PM2.5 (up to 96.5 %) and adsorption performance for formaldehyde (81.97 mg/g). This was mainly due to both the mechanical interception of the three-dimensional network constructed by CNF and the surface electrostatic adsorption of HMMT.After hydrophobic modification with methyltrimethoxysilane (MTMS), the samples displayed good water resistance, recycling performance and mechanical properties. In view of its features of environment-friendly, wide source and low cost, the aerogel air filter has the possibility of wide application.

Intercalation of pyrazolone-based oxalamide metal complexes into Na-montmorillonite for catalytic liquid-phase oxidation of phenol using H2O2.

The intercalation of pyrazolone-based oxalamide metal complexes into Na-montmorillonite (Na-MMT) for catalytic liquid-phase oxidation of phenol using H2O2 was undertaken by a flexible ligand method using metal ions including Mn(II), Zn(II), and Sn(II). First, the metal ions were exchanged with the sodium ions of Na-MMT, and then these metal ions were complexed with a new pyrazolone-based oxalamide ligand. The intercalated metal complexes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental analysis, and thermogravimetric analysis. Phenol was successfully oxidized by heterogeneous catalysts based on Mn(II), Zn(II), and Sn(II) pyrazolone-based oxalamide complexes intercalated into Na-MMT. These heterogeneous catalysts catalyze the liquid-phase oxidation of phenol using H2O2 to catechol as the major product and hydroquinone and benzoquinone as the minor products. The Mn(II) and Zn(II) complexes intercalated into Na-MMT showed better activity than the Sn(II) complex intercalated into Na-MMT and the reaction without the catalyst. It has been shown that some metal ion complexes intercalated into Na-MMT are active catalysts for liquid-phase oxidation of phenol with hydrogen peroxide.

Utjecaj mineralogije gline na nedreniranu posmičnu čvrstoću pomoću pokusa s padajućim šiljkom

Consistency limits are the basic parameters used as standard inputs for any soil investigation program to evaluate the geotechnical properties of fine-grained soils. The primary objective of this study is to investigate the variations in the undrained shear strength of clays with different plasticity properties based on the fine content, clay mineralogy, and water absorption capacity. To achieve this objective, 33 Fall cone tests were conducted on low-, high-, and very high-plastic clay mixtures. Various blends of different plasticity were ensured by preparing mixtures of Na-montmorillonite (NaM)/Ca-montmorillonite (CaM), Na-montmorillonite (NaM)/Kaolinite (K), and Na-montmorillonite (NaM)/Sepiolite (S). According to the experimental results, the highest liquid limit (LL) was obtained in 100 % NaM clay at 255.07 %, whereas the lowest LL was obtained in 100 % S clay at 33.55 %. Similarly, the highest undrained shear strength was obtained at 160 kPa at 30 % water content in the 100 % NaM clay, whereas the lowest undrained shear strength was obtained at 10 kPa in the 100 % S clay at the same water content. Consequently, based on an experimental framework, empirical equations were obtained which could be used to establish the relationships among cone penetration-water content, liquid limit-clay content, and undrained shear strength-cone penetration.

Preparation of clay-supported sodium benzoate and its effect on the rheology, crystallization and foaming of long chain branched polypropylene

The foaming of PP has encountered challenges because of its low melt strength and semi-crystalline characteristics. Introducing long chain branching (LCB) onto the PP backbone and the addition of particles as cell nucleating agent are the commonly used methods to improve the cell structure of PP foams. In this paper, clay-supported sodium benzoate (NaB-OMMT) was prepared from Na-montmorillonite (Na-MMT) via the partial ion exchange reaction with surfactant and subsequent reaction with benzoic acid. The as prepared NaB-OMMTs were then applied to prepare LCBPP/NaB-OMMT nanocomposites and their foams. The dispersion state of clay, crystallization behaviors and rheological properties of the nanocomposites, as well as the cell structure and compression properties of the foams were investigated. The results show that clay layers are mostly exfoliated in the nanocomposites with low NaB-OMMT content, while intercalated layers dominant with the content reaches 2% or higher. The melting temperature of the nanocomposites decreases and the crystallinity increases, while the spherulite size decreases compared to LCBPP. The melt viscosity and elasticity of nanocomposites increase significantly when the content of NaB-OMMT reaches 2% or higher. LCBPP/NaB-OMMT nanocomposites foams exhibit higher cell density, smaller cell size and its standard deviation. Therein, the foam with 1% of NaB-OMMT shows the maximum cell density and the minimum cell size. It is concluded that the cell structure of the foam is highly dependent on the content, dispersion state and structure of the cell nucleating agent. When NaB is supported on well dispersed and exfoliated clay layers, the cell nucleation efficiency is significantly enhanced. The compression properties of the foams depend on their cell structures and exhibit the similar variation trend with the latter with the content of NaB-OMMT increasing.

Organo-Montmorillonite Modified by Gemini Quaternary Ammonium Surfactants with Different Counterions for Adsorption toward Phenol

The discharge of industrial phenol pollutants causes great harm to the natural environment and human health. In this study, phenol removal from water was studied via the adsorption of Na-montmorillonite (Na-Mt) modified by a series of Gemini quaternary ammonium surfactants with different counterions [(C11H23CONH(CH2)2N+ (CH3)2(CH2)2 N+(CH3)2 (CH2)2NHCOC11H23·2Y-, Y = CH3CO3-, C6H5COO- and Br-, 12-2-12·2Y-]. The results of the phenol adsorption indicated that MMt-12-2-12·2Br-, MMt-12-2-12·2CH3CO3- and MMt-12-2-12·2C6H5COO- reached the optimum adsorption capacity, which was 115.110 mg/g, 100.834 mg/g and 99.985 mg/g, respectively, under the conditions of the saturated intercalation concentration at 2.0 times that of the cation exchange capacity (CEC) of the original Na-Mt, 0.04 g of adsorbent and a pH = 10. The adsorption kinetics of all adsorption processes were in good agreement with the pseudo-second-order kinetics model, and the adsorption isotherm was better modeled by Freundlich isotherm. Thermodynamic parameters revealed that the adsorption of phenol was a physical, spontaneous and exothermic process. The results also showed that the counterions of the surfactant had a certain influence on the adsorption performance of MMt for phenol, especially the rigid structure, hydrophobicity, and hydration of the counterions.

Improving the uptake of PAHs by the ornamental plant Sedum spectabile using nano-SiO2 and nano-CeO2

Polycyclic aromatic hydrocarbons (PAHs) pollution is a global ecological soil problem. Screening and establishing an efficient phytoremediation system would be beneficial for alleviating this problem. The ornamental plant Sedum spectabile was selected as the remediation plant to study the removal efficiencies of PAHs after adding different concentrations of nano-SiO2, nano-CeO2, and traditional Na-montmorillonite (Na-MMT). The results demonstrated that shoot biomass was increased and photosynthesis was enhanced by the nanomaterial amendments. The uptake of 16 PAHs by S. spectabile was remarkably increased. Moreover, the two highest shoot concentrations were 7.61 (Phe) and 12.03 (Flo) times that of the control, and the two highest translocation factors were 31 (BbF) and 28 (BaP) times that of the control. Furthermore, 16S rRNA gene sequencing showed that the addition of nano-SiO2 increased the abundance of Acidobacteria, and the genera related to PAH degradation was higher under nanomaterial treatments. The very high Si concentration in the shoots of S. spectabile had a significant linear correlation with the concentration of PAHs. In conclusion, the S. spectabile remediation system assisted by two nanomaterials was effective for the removal of PAHs from soil, and the transfer of PAHs to easily harvested aboveground plant parts was especially worthy of attention.

Ca2+-Facilitated Adhesion of Bacteria on the Na-Montmorillonite Surface.

The adhesion of bacteria on clay surfaces strongly affected their migration and distribution in soil and water. Bacterial adhesion experiments on the Na-montmorillonite (Na-MMT) surface were conducted to determine the role of Na-MMT in the bacterial adhesion process and to prove the validity of the isotherm and kinetic theory for the bacterial surface adhesion in the presence of Ca2+ ions. Batch adhesion experiments with bacteria on the Na-MMT surface were carried out with varying time frames, temperatures, bacterial concentrations, and Ca2+ ion concentrations. The adhesion capacity of Na-MMT significantly correlated with the Ca2+ ion concentration, temperature, time frame, and bacterial concentration when Ca2+ ions were present. The adhesion morphology of the bacteria onto the Na-MMT surface, observed through the zeta-potential and atomic force microscopy (AFM), additionally demonstrated that the bacterial adhesion onto the Na-MMT surface was dominated by the nonelectrostatic force.

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

In a nuclear waste repository, the corrosion of metals and the degradation of the organic material in the waste matrix can generate significant amounts of gases. These gases should be able to migrate through the multibarrier system to prevent a potential pressure build-up that could lead to a loss of barrier integrity. Smectite mineral particles form a tortuous pore network consisting of larger interparticle pores and narrow interlayer pores between the platelets of the smectite minerals. These pores are normally saturated with water, so one of the most important mechanisms for the transport of gases is diffusion. The diffusion of gases through the interparticle porosity depends on the distribution of gas molecules in the water-rich phase, their self-diffusion coefficients, and the tortuosity of the pore space. Classical molecular dynamics simulations were applied to study the mobility of gases (CO2, H2, CH4, He, and Ar) in Na-montmorillonite (Na-MMT) under saturated conditions. The simulations were used to estimate the gas diffusion coefficient (D) in saturated Na-MMT as a function of nanopore size and temperature. The temperature dependence of the diffusion coefficient was expressed by the Arrhenius equation for the activation energy (Ea). The predicted D values of gases were found to be sensitive to the pore size as the D values gradually increase with increasing pore size and asymptotically converge to the gas diffusion coefficient in bulk water. This behavior is also observed in the self-diffusion coefficients of water in Na-MMT. In general, H2 and He exhibit higher D values than Ar, CO2, and CH4. The predicted Ea values indicate that the confinement affects the activation energy. This effect is due to the structuring of the water molecules near the clay surface, which is more pronounced in the first two layers of water near the surface and decreases thereafter. Atomic density profiles and radial distribution functions obtained from the simulations show that the interaction of the gas with the liquid and the clay surface influences mobility. The obtained diffusion coefficient for different gases and slit pore size were parameterized with a single empirical relationship, which can be applied to macroscopic simulations of gas transport.

Intercalation of Cocamide Diethanolamine into Swellable Clay by Solid-State Process

Coconut fatty acid diethanolamine (cocamide-DEA (CDEA)), CH3(CH2)16CON(CH2CH2OH)2 was intercalated into montmorillonite using both solution and solid-state reaction methods. In a typical solution process, the CDEA aqueous solution was mixed with a montmorillonite (Kunipia-F) aqueous suspension, which resulted in a CDEA–montmorillonite layer complex with a basal spacing of 13.8 Å. A CDEA–montmorillonite complex was also easily prepared by the solid–solid reaction method. A mixture of CDEA and Na–montmorillonite was ground at ambient temperature. The basal spacing of the mixture increased to approximately 44 Å after grinding for 30 min. Upon washing, the basal spacing decreased to approximately 10 Å, which was close to that of pristine Na–montmorillonite owing to the deintercalation of the CDEA molecules. The basal spacing of the CDEA–montmorillonite composite starting from protonated montmorillonite decreased to 13.5 Å upon washing, indicating the parallel monolayer arrangement of CDEA molecules between the silicate layers. This finding strongly suggests that acid–base intralayer complexation is responsible for the solid-state intercalation reaction.

Comparative Analysis of Atterberg Limits, Liquidity Index, Flow Index and Undrained Shear Strength Behavior in Binary Clay Mixtures

In geotechnical engineering applications, it is very important to obtain the undrained shear strength of remolded soils accurately and reliably. This study aims to obtain a trustworthy solution to determine the undrained shear strength of remolded clay mixtures using Atterberg limit test results in various states of consistency. An experimental study was carried out involving a wide range of clay mixtures of varying plasticity and geological origin. In the analyses, the variation in the undrained shear strength of remolded soil depending on the cone penetration depth, water content, flow index, liquidity index and log liquidity index was investigated. In the study, the highest undrained shear strength of 100% Na-montmorillonite (NaM) was obtained at 171.89 kPa and 56.60% water content, while the lowest undrained shear strength was obtained for 100% Sepiolite (S) at 9.28 kPa and 31.65% water content. The results of this study revealed that the shear strength is significantly affected by soil conditions, rather than dominant clay mineral. Moreover, it was observed that the undrained shear strength at the plastic limit was approximately 30–35 times greater than that at the liquid limit. Equations for liquid limit–flow index and plasticity index–flow index were proposed. It was concluded that the interdependence between undrained shear strength, liquidity index, log liquidity index and flow index is not unique due to the different physical and chemical properties of clays.

Molecular dynamics simulation and experimental study of micro‐structure and gel properties of single chain alkyl ammonium intercalated Na‐montmorillonite

AbstractThe synergistic effect of layer charge density of Na‐montmorillonite (Na‐MT), the carbon chain length and the dosage of alkyl ammonium on the micro‐structure and gel properties of single chain alkyl ammonium intercalated Na‐MT was systematically studied by using X‐ray diffraction (XRD), molecular dynamics simulation and small‐scale experiment. The results of Z‐axis density distribution and radial distribution function (RDF) shows that with the increase of the dosage of alkyl ammonium, the distribution pattern is gradually changed from layered to inclined winding and stacking distribution. The results of the self‐diffusion coefficient show that the higher the layer charge density of Na‐MT, the shorter the length of alkyl ammonium carbon chain, the lower the diffusivity of each component in the inter‐layer. With the increase of the dosage of alkyl ammonium, the diffusivity of alkyl ammonium in the inter‐layer increases firstly and then decreases. The results of gel properties show that with the increase of the dosage of alkyl ammonium, the colloidal ratio of the alkyl ammonium/Na‐MT in xylene gradually increases, while the apparent viscosity in xylene‐ethanol increases firstly and then decreases. Furthermore, the longer the carbon chain of alkyl ammonium, the lower the layer charge density of MT, the better the gel properties of the prepared alkyl ammonium/Na‐MT.

Role of Na-Montmorillonite on Microbially Induced Calcium Carbonate Precipitation.

The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO3 crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO3 precipitate was obtained. Moreover, the reaction of Ca2+ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO3 precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO3 changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated.

A diffusion model for the swelling of compacted Na–montmorillonite in water

A diffusion model, which considers the hydration force, is presented to predict Na–montmorillonite swelling in water. The swelling originates from the growth of the layer–to–layer distance in the montmorillonite layered structure. The hydration force controls the swelling when the montmorillonite has a layer–to–layer distance less than 100 Å. The layer separation increases because of the diffusion motion of the layers in water. The motion is controlled by a viscous drag force of liquids and four interaction forces between the layers, including hydration, van der Waals, repulsive electrostatic double–layer, and repulsive entropic forces. Based on the model, a diffusivity is defined for the compacted Na–montmorillonite over a wide concentration range of montmorillonite. The model predicted the volume fraction of the montmorillonite in the swelling process and agreed with the published experimental results from 60% to 0.001% volume fraction. Besides that, the result revealed that hydration force, repulsive electrostatic double–layer force, and repulsive entropic force, dominate crystalline swelling, osmotic swelling, and Brownian swelling respectively. The result explained the coexistence phenomenon of dense dispersion, concentrated dispersion, and dilute dispersion in the swelling process.

Effects of salinity and shear stress on clay deformation: A molecular dynamics study

The deformation of clay minerals is an important phenomenon that is relevant to many problems, particularly those that occur in subsurface geological formations. The salinity of the formations and external shear stress applied to them are two important factors that contribute to the deformation of such porous media. To gain a deeper understanding of such phenomena, we have carried out extensive molecular dynamics simulations using the Na-montmorillonite (Na-MMT) structure as the model of clay minerals and have studied the effect of salt concentration on its swelling. As the NaCl concentration increases, so also does the basal spacing. We demonstrate the effect of the coupling between the applied shear stress and NaCl salinity on the swelling behavior of Na-MMT, namely, deformation of the interlayer space that results in swelling. According to the results, the extent of Na-MMT deformation depends on both the brine salinity and the shear rate.

Molecular Dynamics Simulation of the Mechanical Behavior of Mixed-Layer Clay upon Hydration

A proper understanding of the the mechanical behavior of clay minerals is of crucial importance in earth sciences, soil mechanics, and geotechnical engineering. Although more than seventy percent of all clays are of mixed layer types, the vast majority of the previous studies are devoted to pure clays, which make the hydraulic and mechanical properties of the widespread mixed-layer clay (MLC) and its role in soils are little understood, especially the most common illite-montmorillonite (I-M) mixed-layer clay (MLC). This research reports on a molecular dynamics (MD) study of the differences in mechanical behavior between I-M MLC containing mixed K+ and Na+ and Na-montmorillonite (Na-MMT). The variations of key components in stiffness matrix with hydration have been analyzed. It is found that the stiffness tensor of two types of clay could be split into two groups: the in-plane coefficients (C11, C12, C22, and C66) and the out-of-plane coefficients (C13, C23, C33, C44, and C55). Due to the different forms of the support force of the clay layered structure in the two directions, they exhibit significantly different hydration mechanisms. Moreover, the I-M MLC is more difficult to hydrate and swell due to the asymmetric I-M interlayer and the existence of K+, and its ability to resist deformation is stronger than Na-MMT. This work offers insight into the molecular mechanism for initial swelling and mechanical behavior in widespread MLC. This will help to decipher its specific role in soils and controlling clay swelling.

Polyester Yarns Reinforced by Nanoclays

In the present study, poly(ethylene terephthalate)-clay nanocomposite multifilament yarns were prepared using two commercial and four nanoclays synthesized from Resadiye Na-montmorillonite (Na-MMT). Two type multifilament yarns, i.e., fully drawn yarn (FDY) and partially oriented yarn (POY), were melt spun. The FDY yarns were prepared using pilot type Buschaert SpinBoy II CC melt spinning machine with a masterbatch feeding ratio of 4–5% in order to meet industrial machine requirements. The POY spinning was made on the Barmag industrial machine, and the POY yarn was subsequently texturized. All multifilament yarns were prepared via the masterbatch approach, similarly used for the preparation of colored dope dyed yarns. The mechanical properties, flame retardancy, thermal stability, and morphology of produced yarns on melt spinning experiments were analyzed and discussed along with the effect of nanoclay properties such as thermal stability, polymer-clay compatibility, and particle size distribution.

Swelling pressure of montmorillonite with multiple water layers at elevated temperatures and water pressures: A molecular dynamics study

The swelling of clay at high temperature and pressure is important for applications including nuclear waste storage but is not well understood. A molecular dynamics study of the swelling of Na montmorillonite in water at several temperatures (T = 298, 400, and 500 K) and water environment pressures (Pe = 5 and 100 MPa) is reported here. Adopting a rarely used setup that enables swelling pressure to be resolved with an accuracy of ~1 MPa, the swelling pressure was computed at basal spacings 1.6–2.6 nm (or 2–5 water layers between neighboring clay sheets), which has not been widely studied before. At T = 298 K and Pe = 5 MPa, swelling pressure Ps oscillates at d-spacing d smaller than 2.2 nm and decays monotonically as d increases. Increasing T to 500 K but keeping Pe at 5 MPa, Ps remains oscillatory at small d, but its repulsive peak at d = 2.2 nm shifts to ~2.0 nm and Ps at different d-spacings can grow more attractive or repulsive. At d > 2.0 nm, Ps is weakened greatly. Keeping T at 500 K and increasing Pe to 100 MPa, Ps recovers toward that at T = 298 K and Pe = 5 MPa, however, the repulsive peak at d = 2.0 nm remains the same. The opposite effects of increasing temperature and pressure on the density and dielectric screening of water, which control ion correlations and thus double layer repulsion, are essential for understanding the observed swelling pressure at elevated temperatures and its response to environment pressures.

Evaluation of a robust Gel System for Water Shutoff in Large Aperture Fractures

Polymer gels for water shutoff usually base on high concentration and high molecular weight of hydrolyzed polyacrylamide (HPAM). It would lead to a high injection pressure during blocking the large aperture fractures in tight reservoirs. The in-situ polymerization of monomer gel (IPMG) has been investigated in this study. The properties of high strength and long-term thermal stability could greatly extend gel conformance control duration. The gelation time of IPMG can up to 24 hours at the temperature of 65°C. In addition, the gel strength with formulations based on Na montmorillonite (Na-MMT) was much better than that without it. The flooding experiments have shown that the robust gel has a high rupture pressure when blocking the fractures. Another benefit of the gel is a long-lasting decrease permeability of the fracture even after experiencing long time flooding.

Zinc supported on acid-activated montmorillonite for aromatization reactions

AbstractA Na-montmorillonite (Na-MMT) was activated with HNO3 (20 wt.%) solution at various temperatures and times to obtain acid-activated MMT (Acid-MMT). Zinc (4 wt.%) was supported on Acid-MMT via the impregnation method using Zn(NO3)2⋅6H2O as a precursor. The catalytic performance of the Zn/Acid-MMT for the aromatization of heptane was investigated. The amount and distribution of acidity of Acid-MMT, which could be adjusted by changing the acid activation time and temperature, significantly affected the heptane conversion and aromatics content. As a result, an efficient Zn/Acid-MMT catalyst for the aromatization reaction was obtained by optimizing the acid-treatment conditions of Na-MMT.