Concentrations Of Montmorillonite Research Articles

Linear and nonlinear optical parameters of biodegradable chitosan/polyvinyl alcohol/sodium montmorillonite nanocomposite films for potential optoelectronic applications

Innovations in sophisticated optoelectronic devices have increased interest in high-refractive index polymers. Herein, we report innovative nanocomposite films with high linear and nonlinear refractive indices prepared by casting chitosan (Cs) with polyvinyl alcohol (PVA) (50:50 wt%) along with different concentrations (10–50 wt%) of sodium montmorillonite (NaMMT) nanoclay. The refractive indices in addition to other optical parameters of homopolymers and hybrid materials were investigated by UV–Vis. spectroscopy and optical modeling to assess their potential applications in optics. Besides, the structure, morphology, and thermal stability of the prepared films were investigated by a multitude of experimental techniques including X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA/DTG). The ATR-FTIR, XRD, SEM, and AFM measurements confirmed the complete exfoliation of NaMMT nanolayers in the Cs/PVA matrix. The TGA/DTG revealed an increase in the thermal stability of Cs/PVA film with increasing clay content. The UV–Vis. measurements revealed a decrease in the optical energy gap (Eg) and a substantial increase in the linear (nD) and nonlinear (n2) refractive indices as clay content increased. Additionally, the nanohybrids displayed low UV transmission and reflected about 80 % of UV rays, making them excellent candidates for UV protection. For the first time, the dissipation factor (tanδ) in the UV/Vis. region has been calculated and fitted with the Drude-Lorentz model to predict the plasma frequency (ωp), resonance frequency (ω0), and electron lifetime (τ) of pristine polymers and nanocomposites.

Optimizing the Functional Properties of Starch-Based Biodegradable Films.

A definitive screening design was used in order to evaluate the effects of starch, glycerol and montmorillonite (MMT) concentrations, as well as the drying temperature, drying tray type and starch species, on packaging film's functional properties. Optimization showed that in order to obtain films with the minimum possible thickness, the maximum elongation at break, the maximum tensile strength, as well as reduced water vapor permeability and low opacity, a combination of factors should be used as follows: 5.5% wt starch concentration, 30% wt glycerol concentration on a dry starch basis, 10.5% wt MMT concentration on a dry starch basis, 45 °C drying temperature, chickpea as the starch species and plexiglass as the drying tray type. Based on these results, starch films were prepared, and fresh minced meat was stored in them for 3 days. It was shown that the incorporation of MMT at 10.5% wt on a dry starch basis in the packaging films led to a decreased mesophilic and psychrotrophic bacteria growth factor compared to commercial packaging. When assessed for their biodegradability, the starch films disintegrated after 10 days of thermophilic incubation under simulated composting conditions. Finally, to prove their handling capability during industrial production, the starch films were rewound in a paper cylinder using an industrial-scale rewinding machine.

Optimization of mechanical properties of carrageenan-based bioplastic as food packaging

Several types of plastic materials are widely used in food packaging because it has good mechanical and physical properties. However, the types of plastic used in food packaging, such as polyethylene (PE), polypropylene (PP), and polycarbonate (PC), are petroleum-based plastic that is not renewable, not biodegradable, and causes environmental pollution. One option to overcome this problem is to make bioplastic using renewable sources, one of which is carrageenan. Carrageenan is a polysaccharide used in bioplastic synthesis, but it has shortcomings in terms of mechanical properties. Thereby it needs additional supporting materials to improve its mechanical properties. This study aims to obtain optimal mechanical properties such as tensile strength, elongation, and modulus of elasticity. We optimized two variables in this study: glycerol concentration (1, 2, 3, 4, and 5%) and montmorillonite concentration (10, 20, and 30%). Optimization was carried out in two stages; the first stage was the optimization of glycerol concentrations, and the second stage was the optimization of montmorillonite concentrations. The optimum condition was obtained at 3% (v/v) glycerol and 20% (w/w) montmorillonite which gives a tensile strength value of 3.43 MPa, elongation of 47.01%, and Young Modulus of 7.31 MPa. Based on these optimization results, carrageenan-based bioplastic, especially on %EAB value, are comparable with other commercial plastic for food packaging.

Mechanical, thermal, and morphological properties of low-density polyethylene nanocomposites reinforced with montmorillonite: Fabrication and characterizations

Nanoparticle incorporation in polymeric matrices to generate polymer nanocomposite with the intention of maximizing the “nano-effect” derived from the nanoparticles and minimizing the drawbacks of the polymer is an emerging field of research. In this study, low-density polyethylene (LDPE) was mixed with varying concentrations of montmorillonite (MMT) nanoclays to create a polymer nanocomposite with desirable characteristics. Composite sheets with nanoclays contents of (0, 1, 2, 3, and 4 wt%) were prepared for hardness, tensile-fractography, thermal conductivity, and tensile testing (elongation and stress-at-break). The results showed that, according to scanning electron microscope (SEM) study, LDPE has a low flexibility temperature and is prone to corrosion. For larger MMT filler loadings (>3% wt), tensile-fractography showed nanoclays particle micro-aggregation. The pure LDPE sample fracture’s tensile-fractography showed plastic deformation. MMT/LDPE samples with 3% wt hard MMT filler have brittle fractures without appreciable plastic deformation. Thermal conductivity test results show that LDPE/MMT composite thermal conductivity decreased with increasing clay concentration. The thermal conductivity values were reduced from a value of 0.13 W/m.K to a value of 0.039 W/m.K when reinforced with 0% wt to 3% wt filler loading, respectively. With 4% wt filler loading, LDPE/MMT composites had the highest shore hardness at 47.4. Yet, tensile tests indicated that increasing clay content improved the composite’s characteristics. At modest loading percentages (1–2 wt%), tensile results were excellent. Furthermore, the elongation at break of the unadulterated LDPE was reduced by 20% and 30% after introducing 1% wt and 2% wt of MMT as reinforcement additives, respectively. Hence, MMT clay can improve the mechanical properties and thermal insulation of LDPE polymer matrix.

Protein–Mineral Composite Particles with Logarithmic Dependence of Anticancer Cytotoxicity on Concentration of Montmorillonite Nanoplates with Adsorbed Cytochrome c

Montmorillonite (MM) colloid nanoplates have high adsorption capacity due to their large size/thickness ratio, which allows them to be used as carriers for drug delivery. Upon adsorption of the mitochondrial protein cytochrome c (cytC) onto MM plates, the composite cytC-MM particles acquire anticancer properties because of the ability of cancer cells to phagocytize submicron particles (in contrast to the normal cells). In this way, exogenous cytC can be introduced into tumor cells, thereby triggering apoptosis-an irreversible cascade of biochemical reactions leading to cell death. In the present study, we investigated the physicochemical properties of cytC-MM particles as a function of the cytC concentration in the suspension, namely, the electrophoretic mobility, the mass increment of MM monoplates upon cytC adsorption, the ratio of the adsorbed to the free cytC in the bulk, the protein density on the MM's surface, the number of cytC globules adsorbed on an MM monoplate, the concentration of cytC-MM composite particles in the suspension, and the dependence of cytotoxicity on the cytC-MM particle concentration. For this purpose, we used microelectrophoresis, static and electric light scattering, and a colon cancer cell culture to test the cytotoxic effects of the cytC-MM suspensions. The results show that the cytotoxicity depends linearly on the logarithm of the particle concentration in the cytC-MM suspension reaching 97%.

Fade resistance of propylene-ethylene copolymer. Effect of low concentration of organophilic montmorillonite

Propylene-ethylene copolymer (PEC) is an important material used in the production of a large diversity of plastic goods. However, its low polarity and lack of functional groups make PEC challenging for dye coloring. A method to obtain colored PEC using the cationic dye Rhodamine 6G (RA) was investigated. It involves modification with very low concentrations of organophilic montmorillonite (o-Mt) and a propylene copolymer grafted with maleic anhydride by producing nanocomposites having very thin clay tactoids. Mixing was performed in molten state in a batch mixer considering 0.1 wt% of dye and up to 3 wt% of clay. FT-IR, XRD, SEM and rheology were used to analyze the effect of clay and dye on composite morphology while fade resistance to solvent and UV-radiation was analyzed by UV–visible spectroscopy and colorimetry. Neither structure nor properties of polymeric systems are affected by addition of RA. In fact, the degree of oxidation reached by the polymeric material after UV irradiation as well as its fade resistance is determined by clay concentration. The addition of just 1 wt% of o-Mt reduces in about one eighth the exposure time at which the polymer reaches a given value of total color difference, ∆E*.

Impact of the Salt Concentration and Biophysical Cohesion on the Settling Behavior of Bentonites

The flocculation behavior of clay minerals in aquatic environments is an important process in estuarine and riverine dynamics, where strong gradients in salinity can locally occur. Various contradicting observations have been reported in the literature on the impact of salt concentration on the settling process of cohesive sediments. To address this issue in a systematic manner, we investigate the settling behavior of clay minerals as a function of the salt concentration of the ambient water. Specifically, we focus on montmorillonite as a prototype clay mineral with a high cation exchange capacity (CEC). To this end, we study suspensions of Wyoming bentonite (Volclay SPV) as a very important constituent for many constructional and industrial purposes. We perform an experimental campaign to study the settling behavior of moderately turbid montmorillonite concentrations in monovalent salt solutions with different salinities (sodium chloride) to represent different environments ranging from deionized to ocean water, respectively. The subsequent settling process was monitored by taking pictures by a camera in regular time intervals over a total observation time up to 48 h. In addition, a modified hydrometer analysis is conducted to determine the grain size distribution (in terms of an equivalent diameter) of the flocculated clay suspension in salt water. Despite the rather high cation exchange capacity of the investigated clay (CEC=88.1), our results show that the settling speed drastically increases within a range of 0.6–1.0 PSU and stays approximately constant for higher salinities. This critical salt concentration is defined here as the critical coagulation concentration (CCC) and lies well below the salinity of natural open water bodies. The hydrometer analysis revealed that 60% of the agglomerates exceed the equivalent grain size of 20 μm. Finally, the findings of this study are supplemented with experiments studying the effect of Extracellular Polymeric Substances (EPS) on the flocculation behavior of bentonite in salt water. Our results demonstrate that salinity is the original trigger for flocculation, whereas EPS allows for even larger floc size but it does not play a significant role for the settling processes of bentonite in estuarine environments.

Effects of the NaCl Concentration and Montmorillonite Content on Formation Kinetics of Methane Hydrate

Most resources of natural gas hydrate (NGH) exist in marine sediments where salts and sea mud are involved. It is of great importance to investigate the effects of salts and sea mud on NGH formation kinetics. In this study, the mixture of silica sand and montmorillonite was used to mimic sea mud. The effects of the NaCl concentration of pore water and montmorillonite content on methane hydrate formation were studied. A low NaCl concentration of 0.2 mol/L and a low montmorillonite content range of 10–25 wt% is beneficial to reduce the induction time of hydrate formation. The high NaCl concentration and high content of montmorillonite will significantly increase the induction time. The average induction time for the experiments with the NaCl concentrations of 0, 0.2, 0.6, and 1.2 mol/L is 20.99, 8.11, 15.74, and 30.88 h, respectively. In the pure silica sand, the NaCl concentration of 0.2 mol/L can improve the final water conversion. In the experiments with pure water, the water conversion increases with the increase of the montmorillonite content due to the improvement of the dispersion of montmorillonite to water. The water conversion of the experiments in pure water with the montmorillonite contents of 0, 10, 25 and 40 wt% is 12.14% (±1.06%), 24.68% (±1.49%), 29.59% (±2.30%), and 32.57% (±1.64%), respectively. In the case of both montmorillonite and NaCl existing, there is a complicated change in the water conversion. In general, the increase of the NaCl concentration enhances the inhibition of hydrate formation and reduces the final water conversion, which is the key factor affecting the final water conversion. The average water conversion of the experiments under the NaCl concentrations of 0, 0.2, 0.6 and 1.2 mol/L is 24.74, 15.14, 8.85, and 5.74%, respectively.

Potential Alendronate Sodium drug carrier by preparation and characterization of sodium alginate cross-linked Montmorillonite

In drug therapy, it is important to provide therapeutic levels of drug to the site of action and maintain them during the treatment. This work describes the in vitro release of alendronate from sodium alginate cross-linked Montmorillonite (MMT) composite beads. Effect of crosslinking cation, concentration of montmorillonite and media on encapsulation efficiencies, and release profiles of alendronate were studied. Beads were characterized using equilibrium swelling ability study, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Energy-dispersive x-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Results indicate that addition of montmorillonite increases the encapsulation efficiencies and slows down the release rates significantly.

Morphology, Dielectric and EMI Shielding Characteristics of Graphene Nanoplatelets, Montmorillonite Nanoclay and Titanium Dioxide Nanoparticles Reinforced Polyvinylidenefluoride Nanocomposites

Herein, flexible polyvinylidenefluoride (PVDF) nanocomposite films reinforced with different concentrations of graphene nanoplatelets (GNPs), montmorillonite (MMT) nanoclay and titanium dioxide (TiO2) nanoparticles (NPs) were prepared using a simple and low-cost solution casting method. The surface morphology of PVDF/GNPs/TiO2/MMT nanocomposites and the interaction between PVDF, GNPs, TiO2 NPs and MMT nanofillers was examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The dielectric properties of the prepared nanocomposite films were evaluated using a frequency response impedance analyzer in the frequency range from 50 Hz to 20 MHz at various temperatures. The electromagnetic interference (EMI) shielding effectiveness (SE) of PVDF/GNPs/TiO2/MMT nanocomposites was measured in the Ku-band region (12–18 GHz) and the maximum SE of 12.6 dB was obtained for nanocomposites with GNPs-2.5%, MMT-1% and TiO2-11.5%. Considering the excellent EMI shielding performance, these nanocomposites can have promising applications in smart electronics and flexible devices.

Barrier and structural properties of polyethylene terephthalate film coated with poly(acrylic acid)/montmorillonite nanocomposites

Food packaging is one of the most important parts of the food industry, and polyethylene‐based polymers have been widely used as food packaging films. In this study, corona‐treated polyethylene terephthalate (PET) films were used to increase adhesion to the barrier coating solution for multilayered film formation and various concentrations of montmorillonite (MMT; 0, 1, 3, and 5 wt.%) were used to improve the barrier properties of PET films for food packaging after different treatments of MMT including ultrasonication with bath or probe and 100‐W or 300‐W microwave to evenly disperse MMT. Among them, a 300‐W microwave treatment was most effective for size reduction of MMT particles. Even though 5 wt.% MMT was used to coat PET films with polyacrylic acid (PAA), good transmittance in the visible region (500 nm) was obtained, with a value similar to that of the neat PET film. The dispersion of MMT and binding of PAA/MMT nanocomposites were confirmed by field‐emission scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy analyses. The water vapor and oxygen barrier properties of PET films were enhanced by PAA coating. Moreover, the oxygen permeability of PET films decreased via coating by PAA blended with 1 and 3 wt.% MMT. Based on these results, the PET film coated with PAA/MMT nanocomposites could be applied as food packaging films that require high gas barrier properties for oxygen‐sensitive food.

Barrier Properties of PVA/TiO2/MMT Mixed-Matrix Membranes for Food Packaging

One of the important challenges in food industries is to achieve sufficient gas barrier properties for packaging films. Films made of polyvinyl alcohol (PVA) are commonly used for food packaging and are sometimes used with embedded nanoparticles. In this investigation, PVA nanocomposite films were prepared using solution-casting method with different concentrations of montmorillonite (MMT) and titanium oxide (TiO2) nanoparticles. A response surface methodology (RSM), based on three-level factorial design, was implemented to model and optimize the effect of the concentrations of the nanofillers on the barrier properties of thin nanocomposite films. The viscosity of the polymer-forming solution increased when nanoparticles were incorporated in the polymer matrix. SEM micrographs showed a good distribution of nanofillers at low concentration whereas some aggregation was observed at higher nanofiller loadings. Transparency of PVA-based thin films decreased with an increase of TiO2/MMT loading. A significant increase in the Young s modulus occurred with an increase in the loading of nanoparticles whereas the tensile strength and elongation at the breakpoint both decreased. Results for PVA/MMT/TiO2 nanocomposite films showed a decrease in the oxygen transmission rate and water vapor permeability compared to a neat PVA membrane. The particle loading leading to optimum barrier properties for nanocomposite films was a combined loading of 1 wt% TiO2 and 4 wt% MMT.

Insights into conjugative transfer of antibiotic resistance genes affected by soil minerals

AbstractWidespread antibiotic resistance genes (ARGs) have caused critical threats to public health on a global scale. Soil, composed mainly of minerals, acts as a source of resistance determinants, playing a considerable role in the development and dissemination of ARGs. The great abundance of ARGs in the soil environment raises concern about the effect of minerals on the spread of ARGs. Herein, the horizontal transfer of a model plasmid pMP2463 containing ARGs from Escherichia coli S17‐1 to Pseudomonas putida KT2440 was monitored following exposure to four common soil minerals, namely, kaolinite, montmorillonite, goethite and birnessite. Birnessite resulted in concentration‐dependent increases in conjugative transfer of plasmid pMP2463 by 1.3–4.3 fold, compared with that in the control group. However, no obvious laws were found in the change of conjugative transfer rate at different concentrations of kaolinite and montmorillonite. As for goethite, the conjugative transfer rate increased firstly and then decreased as the concentration increased. The possible mechanisms underlying birnessite‐induced conjugative transfer of plasmid were explored; birnessite is capable of initiating intracellular reactive oxygen species (ROS) formation, inducing the oxidative stress response. Additionally, birnessite notably facilitated the mRNA expression of the outer membrane protein genes, which contributed to cellular membrane pore formation and horizontal gene transfer, and altered the mRNA expression of conjugative‐related genes that are responsible for conjugative transfer of mobile genetic elements between bacteria. This study triggers questions regarding the potential role of soil minerals in the global dissemination of antimicrobial resistance and provides insights into the interactions between bacteria and minerals in the natural soil environment.Highlights The effect of soil minerals on conjugative transfer of ARGs was explored. Birnessite induced the concentration‐dependent increase of conjugative transfer. Mechanisms underlying ROS formation, membrane permeability increase, gene expression alteration were revealed. Our results provide evidence for the effect of birnessite on antibiotic resistance dissemination.

Caracterização de filmes de polietileno de baixa densidade incorporados com diferentes concentrações de montmorilonita

This work aimed to evaluate the effect of incorporating different concentrations of montmorillonite in low-density polyethylene films. The incorporation Cloisite® 10A nanocomposite in the films was carried out using a single screw extruder modular. After the incorporation of six concentrations of organophilic montmorillonite clay (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%, w/w) to the films, their optical, mechanical (tensile strength, elongation and Young modulus), and gas barrier (CO2) properties were investigated. The degree of exfoliation was evaluated through the analysis of X-ray diffraction. The incorporation of nanoparticles from montmorillonite increased the opacity of the films. Regarding their mechanical properties, the incorporated films with montmorillonite presented reductions in tensile strength and elongation values, whereas the modulus of elasticity did not show any significant difference. They also showed an increase in the permeability of CO2. The analysis of X-ray diffraction showed no formation of nanocomposites. It was observed, therefore, that the properties of the films were affected by the incorporation of montmorillonite clay.

Montmorillonite-based polyacrylamide hydrogel rings for controlled vaginal drug delivery.

Vaginal drug delivery is regarded as a promising route against women-related health issues such as unwanted pregnancies and sexually transmitted infections. However, only a very few studies have been reported on the use of hydrogel rings with low cytotoxicity for vaginal drug delivery applications. Moreover, the effect of nanoparticles on hydrogel vaginal rings has not been clearly evaluated. To overcome these challenges, we hereby developed nanocomposite hydrogel rings based on polyacrylamide-sodium carboxymethyl cellulose-montmorillonite nanoparticles in the ring-shaped aluminum mold for controlled drug delivery. The hydrogel rings were synthesized by using N,N'-methylene bisacrylamide, N,N,N',N'-tetramethyl ethylene diamine, and ammonium persulfate, as a crosslinker, accelerator, and initiator, respectively. The obtained rings were 5.5cm in diameters and 0.5cm in rims. Chemical structures of the nanocomposite rings were confirmed by Fourier transform infrared, and Nuclear Magnetic Resonance spectroscopies. Additionally, the swelling ratio of hydrogels was appeared to be adjusted by the introduction of nanoparticles. In vitro release experiment of methylene blue, as a hydrophilic model drug, revealed that the nanocomposite rings could not only reduce burst effect (almost more than twice), but also achieve prolonged release for 15days in the vaginal fluid simulant which mimic the vaginal conditions at pH of almost 4.2, and a temperature of 37°C. Importantly, the resultant hydrogel rings with or without various concentrations of montmorillonite showed low cytotoxicity toward human skin fibroblasts. Furthermore, different antibacterial activities against Escherichia coli were observed for various concentrations of montmorillonite in hydrogels. These results suggest the great potential of montmorillonite-based hydrogel rings for vaginal drug delivery.

Clay minerals as sorbents for mycotoxins in lactating goat’s diets: Intake, digestibility, blood chemistry, ruminal fermentation, milk yield and composition, and milk aflatoxin M1 content

We assessed the effect of bentonite and montmorillonite, as sorbents, on feed utilization, lactation performance, and mycotoxin concentrations in milk. During the first week of lactation, fifteen lactating crossbred (Nubian × Baladi) goats weighing 20.5 ± 0.5 kg were randomly assigned to three treatments (five does each) in a complete randomized design for a 90-day trial with repeated measures. Goats were stratified according to parity and expected average milk yield to be fed daily with one of three diets: a basal diet containing 600 g concentrates and 400 g berseem hay (Control treatment), or the control diet supplemented with bentonite clay at 20 g/kg dry matter (DM) concentrate (Bentonite treatment), or the control diet supplemented with montmorillonite clay at 20 g/kg DM concentrate (Montmorillonite treatment). The basal diet used in all treatments was naturally contaminated with aflatoxin B1 (AFB1) at 56.7 μg/kg and zearalenone (ZEN) at 112.5 μg/kg. Additives had no effect on nutrient intake but increased (P < 0.05) the digestibility of DM, organic matter, crude protein, ether extract, non-fibre carbohydrates and neutral detergent fibre. The montmorillonite diet had a greater (P < 0.05) nutritive value than the bentonite and control diets. Does that received the bentonite treatment had greater (P < 0.001) ruminal ammonia-N concentration at 6 h after feeding than those received the control or the montmorillonite treatment. Feeding the bentonite and montmorillonite diets increased (P < 0.001) the total N concentration in the rumen. Moreover, montmorillonite treatment increased (P < 0.01) ruminal total volatile fatty acid concentrations at 3 and 6 h after feeding, however, AFB1 and ZEN concentrations were decreased (P < 0.05) in the rumens of the montmorillonite does compared with the control does. Additives increased (P < 0.01) the concentrations of plasma glucose compared with the control diet. Without affecting the daily yields of milk or energy-corrected milk, additives increased (P < 0.05) the concentrations of total solids, solids-non-fat, protein, lactose and energy in milk. Despite an increased concentration of faecal AFB1 (P < 0.001), montmorillonite and bentonite treatments decreased the concentrations of aflatoxin M1(AFM1) in milk (P < 0.001) and ZEN in faeces. It was concluded that the addition of bentonite or montmorillonite at 20 g/kg DM concentrate (equal to 1.2% of total diet DM) in the diets of lactating does enhanced nutrient digestibility and milk composition and decreased the content of AFM1 in milk, resulting in improving the health benefit of milk for consumers.

Experimental evidence for abiotic formation of low-temperature proto-dolomite facilitated by clay minerals

Abstract The origin of sedimentary dolomite is a subject of long-standing enigma that still awaits resolution. Previous studies have shown that room temperature synthesis of abiotic dolomite is rarely achieved and primary (proto-)dolomite precipitation is closely associated with microbial activities. In this study, we demonstrate through laboratory carbonation experiments that highly negative-charged clay minerals (as indicated by the values of zetal potential) such as illite and montmorillonite can aid the precipitation of abiotic proto-dolomite under ambient conditions, whereas nearly-neutral charged kaolinite exerts negligible influence on such process. In comparison to montmorillonite, illite has higher surface-charge density, thus is more effective in catalyzing proto-dolomite precipitation. Furthermore, the signal of proto-dolomite in carbonate neoformations is enhanced with increasing concentrations of illite or montmorillonite. On the basis of these results, we suggest that clay minerals catalyze dolomite formation perhaps via electrostatic binding of Mg2+ and Ca2+ ions and simultaneous desolvation of these strongly hydrated cations, a crucial step for dolomite crystallization. The resulting proto-dolomites display the morphologies, textures, and structures similar to those of biogenic dolomite reported before, which are considered precursors of ordered sedimentary dolomite. Therefore, our results offer a possible route to authigenic dolomite found in sedimentary environments.

Electrospun polyimide/organic montmorillonite composite nanofibrous membranes with enhanced mechanical properties and flame retardancy

Polyimide/organic montmorillonite nanofibrous membranes were fabricated through electrospinning of polyamic acid/organic montmorillonite precursors followed by a thermal imidization process. Scanning electron microscopy micrographs showed small amounts of organic montmorillonite addition (&lt;3%) and increase in the diameter of polyimide nanofibers. However, higher organic montmorillonite fraction generated microspheres due to the aggregation of clay nanoplatelets. Transmission electron microscopy images indicated that both exfoliated and intercalated organic montmorillonites existed in polyimide nanofibers when low quantity of clay was loaded (&lt;3%). As the clay amount increased, exfoliated structure disappeared and stacked clay layers were observed. The optimum concentration of organic montmorillonite is 3%. By incorporating 3% clay, the tensile strength and modulus of membrane increased by 92.1 and 48.6%, respectively. Moreover, the limiting oxygen index value arose from 29.2 to 30.4%. Higher thermal stability was also achieved because of the heat barrier effect of clay layers. The onset decomposition temperature increased by 17℃ by adding 5% clay. These results demonstrate that tiny organic montmorillonite incorporation is relatively effective for improving the mechanical properties as well as flame retardancy of polyimide nanofibrous membrane.

Preparation of Zirconium Pillared Montmorillonite Composites

Zr-pillared montmorillonite (Zr-pmt) was obtained from which ZrOCl2.8H2O cross-linked Na-mt through Sol-gel means. Several important parameters of the preparation of Zr-pmt, such as the initial concentration of montmorillonite (mt), Zr/mt, aging time of the pillaring agent and cross-linking reaction time were investigated in detail to evaluate performances of Zr-pmt. Under the conditions of the montmorillonite initial concentration of 4%, Zr/mt of 7.5 mmol/g, aging time of the pillaring agent for 3 h and cross-linking reaction time of 6 h, the maximum basal spacing (d001) of Zr-pmt is 2.06 nm. Zr-pmt material is expected to be used for adsorption of wastewater.

Biodegradable grafting cellulose/clay composites for metal ions removal

Biodegradable bi-functional cellulose derivatives were synthesized to remove widespread underground water cations such as; Ca2+, Mg2+, Fe2+, Pb2+, and Cu2+. Firstly, graft copolymerization of cellulose with binary monomers such as acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) with acrylamide (Am) were achieved using potassium persulfate as initiator. Then, cellulose/clay composites were prepared by graft copolymerization of cellulose using different montmorillonite concentrations such as 3, 6 and 9% weight/cellulose weight. The obtained Biodegradable grafted cellulose and their composites were used as adsorbents for the removal of Ca, Mg, Fe, Pb, and Cu ions individually from aqueous solutions. A possible reaction mechanism was deduced and the products were characterized by Fourier transfer infrared (FT-IR), scanning electron microscopy (SEM) and thermal degradation by thermogravimetric analysis (TGA). The results obtained from this study revealed that as the content of clay increases, the uptake of cations increasing and the removal order of the composites were Pb2+ > Mg2+ > Fe2+ > Cu2+ > Ca2+. The biodegradability of grafted cellulose was increased by the addition of clay.