Layered Silicate Structure Research Articles

Influences of composition and reaction conditions on molecular structure, hygroscopicity, and swelling behavior of alkali-silica reaction gels

Alkali-silica reaction (ASR) gel, a product of the reactions between the dissolved silica from aggregate and the alkalis from cement, governs the destructiveness of ASR and concrete deterioration. The influences of chemical composition and reaction conditions of ASR gel on its structure and properties remain unclear. In this work, the correlations between the molecular structure, hygroscopicity, and swelling behavior of ASR products were uncovered by investigating six CaO–SiO2-M2O systems with varying alkali/Si and Ca/Si ratios under two reaction conditions. The results indicate that the low-alkali gels have a layered silicate structure dominated by Q1 and Q2 sites similar to calcium silicate hydrate (C–S–H), whereas the high-alkali gels showed coexistence of tobermorite-type C–S–H and alkali-silicate hydrates featured with Q3 polymerization. The 29Si nuclear magnetic resonance (NMR) results showed that the mean chain length (MCL) and degree of polymerization (DP) decrease with alkali/Si and Ca/Si ratios but increase with moisture. Under 97 % RH, decreased crystallinity and enhanced formation of ASH and Q3 sites are obtained along with increased polymerization and d-spacing. The moisture uptake and swelling of the high-alkali gels showed a reverse correlation with the Ca/Si ratio, which confirms the role of calcium in suppressing the formation of ASH and the dominant role of Q3 sites in determining the hygroscopicity of ASR products.

Incorporation of Fe(iii) into Bentonite and Study of its As3+ Adsorption Properties

Bentonite is montmorillonite type layered clay and has high cation exchange capacity (CEC) because of its typical layered silicate structure. The bentonite was treated with hydrochloric acid to obtain H-bentonite which was further modified by incorporating Fe(Ⅲ) into it. The modified Fe-bentonite was characterized by XRD and FTIR analyses. The specific surface area of the Fe-bentonite adsorbent was obtained from Methylene Blue Adsorption Method and was 598 m2/g. The adsorption of As3+ by Fe-bentonite adsorbent in aqueous environment was investigated by varying different experimental parameters such as pH, contact time and adsorption isotherm. The adsorption process was found to be best fitted to Langmuir adsorption isotherm model controlled by pseudo-second –order kinetics with the rate constant value 0.03723 g/(mg.min). The maximum arsenic adsorption was observed at pH 5 at room temperature. The time taken to reach equilibrium was 75 minutes. The maximum adsorption capacity for As3+ on Fe-bentonite was 101.01 mg/g. The value of ∆G (-21 kJ/mole) confirmed the adsorption process was favored by physiosorption. The slope of the linear plot of Qt vs t0.5 was linear but not passed through the origin, which indicated that, the intraparticle diffusion was not only rate controlling step.

Recent Advances in Kaolinite Nanoclay as Drug Carrier for Bioapplications: A Review.

Advanced functional two-dimensional (2D) nanomaterials offer unique advantages in drug delivery systems for disease treatment. Kaolinite (Kaol), a nanoclay mineral, is a natural 2D nanomaterial because of its layered silicate structure with nanoscale layer spacing. Recently, Kaolnanoclay is used as a carrier for controlled drug release and improved drug dissolution owing to its advantageous properties such as surface charge, strong biocompatibility, and naturally layered structure, making it an essential development direction for nanoclay-based drug carriers. This review outlines the main physicochemical characteristics of Kaol and the modification methods used for its application in biomedicine. The safety and biocompatibility of Kaol are addressed, and details of the application of Kaol as a drug delivery nanomaterial in antibacterial, anti-inflammatory, and anticancer treatment are discussed. Furthermore, the challenges and prospects of Kaol-based drug delivery nanomaterials in biomedicine are discussed. This review recommends directions for the further development of Kaol nanocarriers by improving their physicochemical properties and expanding the bioapplication range of Kaol.

The Application of Mineral Kaolinite for Environment Decontamination: A Review

Kaolinite clay mineral with a layered silicate structure is an abundant resource in China. Due to its advantages of excellent stability, high specific surface area and environmental friendliness, kaolinite is widely used in environment decontamination. By using kaolinite as a carrier, the photocatalytic technology in pure photocatalysts of poor activities, narrow spectral responses, and limited electron transport can be overcome, and the nano-Ag disinfectant’s limitation of the growth and aggregation of nanoparticles is released. Moreover, pure kaolinite used as an adsorbent shows poor surface hydroxyl activity and low cation exchange, leading to the poor adsorption selectivity and easy desorption of heavy metals. Current modification methods including heat treatment, acid modification, metal modification, inorganic salt modification, and organic modification are carried out to obtain better adsorption performance. This review systematically summarizes the application of kaolinite-based nanomaterials in environmental decontamination, such as photocatalytic pollutant degradation and disinfection, nano silver (Ag) disinfection, and heavy metal adsorption. In addition, applications on gas phase pollutant, such as carbon dioxide (CO2), capture and the removal of volatile organic compounds (VOCs) are also discussed. This study is the first comprehensive summary of the application of kaolinite in the environmental field. The review also illustrates the efficiency and mechanisms of coupling naturally/modified kaolinite with nanomaterials, and the limitation of the current use of kaolinite.

The behavior of aluminum sites in H-[Al]-RUB-18 catalysts: A theoretical-experimental investigation

Functional acidic sites can be generated in the structure of layered silicates by the isomorphic substitution of silicon by aluminum atoms, leading to suitable heterogeneous catalysts. H-[Al]-RUB-18 samples were synthesized with Si/Al molar ratios of 15, 30, and 60. Experimental characterizations showed that two different aluminum sites were obtained: one tetrahedrally coordinated (framework-Al), very similar to those found in microporous zeolites; and the other octahedrally coordinated, analogous to silanol groups (hydrated aluminol sites). Computational simulations based on Density Functional Theory (DFT) were used to test the atomic positions of these aluminum sites and confirmed, in terms of electronic energies, the tetrahedral and octahedral positions already predicted in the experimental characterizations. In addition, ethanol dehydration reaction was used to probe the acidic sites and evaluate the performance of the different [Al]-RUB-18 samples. Although a widely known reaction for zeolites and other porous solids, the chemical analysis in this work indicated that the Al-substituted layered silicates are promising candidates to be used in heterogeneous catalysis. The experimental catalytic data showed that the presence of aluminum atoms improved the reaction conversion. Moreover, MEP calculations also presented, in each step of ethanol dehydration, Alframework sites with the lowest electronic energy barriers.

Preparation and Characterization of LCT/SPEEK Composite Membrane for PEMFC Application

AbstractA novel SPEEK‐based blends proton exchange membrane doping liquid crystal polymer intercalated montmorillonite (LCT) were prepared by solution casting technology. FT‐IR, XRD and POM proved that SPEEK contained sulfonic acid group and LCT which had liquid crystal intercalated into SPEEK matrix. LCT/SPEEK composite membrane with 1.0 wt% had higher swelling rate and proton conductivity than those membranes. It was also shown that the proton conductivity of LCT/SPEEK composite membrane decreased, but reached 0.137 S/cm when LCT was 1.0 wt%, and the swelling rate of SPEEK membrane was significantly decreased 6.19 % to 3.38 %. The layer silicate structure in LCT promotes its dimensional stability, and the sulfonic group forms hydrogen bond network in SPEEK matrix to promote proton transfer. These results propose the composite membranes as a potential candidate for PEMFC at 25 °C making SPEEK composite membrane.

Influence mechanism of Na2O on the network structure depolymerization of ZD coal ash silicate under high temperature

Na2O is the basic alkali metal oxide in Zhundong (ZD) coal, the content of Na2O directly affects the ash fusion temperatures (AFTs) of coal ash. Fourier transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulation were used to study the structural characteristics of synthetic coal ash under Na2O concentration of 1–13 mol%. Both FTIR experiments and MD simulation show that Na+ attacks the tri-coordinate oxygen (Ot) and the bridge oxygen (Ob) formed by [SiO4]4− and [AlO4]5− tetrahedron structure, generates more non-bridge oxygen (Onb), the shelf-like network structure(Q4) in fused coal ash is depolymerized to form layered silicate structure (Q3), chain or cyclic silicate structure (Q2, Q1). O(Al, Al, Si) and O(Al, Al, Al) in Ot decreased their trend by 3% each, Si–O–Si was reduced from 12% to 7%. Al–O–Si was reduced from 36% to 29%. The intricate structures are gradually depolymerized into plain structures, which leads to the decrease of AFTs.

Insight into the water–rock interaction process and purification mechanism of mine water in underground reservoir of Daliuta coal mine in China

The water quality of mine water is obviously improved after being stored in underground reservoir, but the process of water-rock interaction and the purification mechanism of mine water quality are not clear. In this study, the water samples and rock samples collected in the underground reservoir of Daliuta coal mine were taken as the research object. Based on the analysis of the hydrochemical characteristics of the reservoir water samples and the characterization of the rock samples, combined with PHREEQC analysis, the mechanism of water quality purification of mine water was discussed. The results showed that the rocks in the underground reservoir had layered silicate structure and flaky kaolinite structure, with some irregular edges and microcracks, and higher specific surface area and total pore volume. These characteristics made the rocks have a certain adsorption and removal capacity for heavy metal ions and other pollutants in the mine water. The water-rock interaction, such as the dissolution of albite and halite, the precipitation of gypsum and kaolinite, and the cation exchange, resulted in the increase of the concentration of Na+ and the decrease of the concentration of Ca2+, Mg2+, and TDS in the outlet water, and the hydrochemical type changed from SO42--Cl-/Ca2+ type to SO42--Cl-/Na+ type. Moreover, this study shows that PHREEQC analysis can be used to analyze the water-rock interaction of coal mine underground reservoir and can obtain more detailed information; therefore, it may have the potential ability to help assess the migration and transformation of pollutants during the storage process of mine water in underground reservoirs.

A local green composite study: the effect of edible oil on the morphological and mechanical properties of PBS/bentonite composite

Abstract Composites of a biodegradable thermoplastic aliphatic polyester, polybutylene succinate (PBS), with bentonite were investigated for morphological and mechanical properties. The bentonite was modified with soybean oil (SBO) and lard oil (LO) (2:98 clay:oil % by weight) by mechanical stirring and ultrasonication. The PBS/modified bentonite composite was prepared by using an internal mixer and processed by compression molding. Under bentonite modification conditions, XRD and SEM showed that the bentonite layers were broken into small layers, and the d-spacing between the layers was increased by edible oil molecules. A small plate like structure of modified bentonite composite was observed by SEM micrograph, which revealed short and long layer silicate structure non-directionally throughout the matrix phase. The mechanical properties of PBS were reinforced by this structure. The tensile modulus and elongation at break seem to depend on its directional bentonite. Interestingly, considerable improvement in impact strength was observed at over 2 wt% of clay. The impact strengths of PBS, PBS/modified BTN with SBO composite, and PBS/modified BTN with LO composite were increased from 1 to 1.5 and 2 kJ/m2, respectively. Comparatively, using LO modified bentonite had a better performance for increased interlayer and resulted in higher impact strength of the composite than that of SBO composite. The results demonstrated that PBS/modified bentonite using edible oil could be a potential alternative low cost, eco-friendly material with superior impact properties useful for further applications.

Impact of high temperatures on aluminoceladonite studied by M\xf6ssbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

Robust nickel silicate catalysts with high Ni loading for CO2 methanation.

CO2 is the main component of greenhouse gases and also an important carbon source. The hydrogenation of CO2 to methane using Ni-based catalysts can not only alleviate CO2 emissions but also obtain useful fuels. However, Ni-based catalysts face one major problem of the sintering of Ni nanoparticles in the process of CO2 methanation. Thus, this work has synthesized a series of efficient and robust nickel silicate catalysts (NiPS-X) with different nickel content derived from nickel phyllosilicate by the hydrothermal method. It was found that the Ni loading plays a critical role in the structure and catalytic performance of the NiPS-X catalysts. The catalytic performance gradually increases with the increase of Ni loading. In particular, the highly dispersed NiPS-1.6 catalyst with a high Ni loading of 34.3 wt% could obtain the CO2 conversion greater than 80%, and the methane selectivity was close to 100% for 48 h at 330 °C and the GHSV of 40,000 mL g-1 h-1 . The excellent catalytic property can be assigned to the high dispersion of Ni nanoparticles and the strong interaction between the active component and the carrier, which is derived from a unique layered silicate structure with lots of nickel phyllosilicate and a large number of Lewis acid sites.

РЕСТАВРАЦІЯ ТА ХІМІКО-ТЕХНОЛОГІЧНІ ДОСЛІДЖЕННЯ КАМ’ЯНОЇ СКУЛЬПТУРИ СВ. ЯНА НЕПОМУЦЬКОГО З СЕЛА ЧАБАРІВКА ВАСИЛЬКІВСЬКОГО Р-НУ ТЕРНОПІЛЬСЬКОЇ ОБЛ.

The sculptural composition originates from the village of Chabarivka, Vasylkiv district, Ternopil region (since 2015). On the map of 1779-1783 by Friedrich von Mieg, the sculpture of St. John of Nepomuk is marked with a red cross, located in the eastern part of the village stretched along the road, opposite the manor. The road from Kopychyntsi to Husiatyn passed to the north of the settlement. On the map of the late nineteenth century the figure of St. John of Nepomuk is recorded on the south side of the street, in the eastern part of Chabarivka. Instead, the manor no longer exists, and the existing church does not yet exist. It is probable that in the first half of the 19th century the village community changed the location of the roadside sculptural composition. Since there is a carved coat of arms of Pilava on the stone pedestal of the figure, it is logical to say that the founder of the composition was a representative of the Potocki magnate family. Since the owner of Husiatyn and its environs during 1729-1732 was Stanislav Vladyslav Potocki, we can assume that it was at this time that the sculptural composition of St. John of Nepomuk was made. As a result of thermal studies, it was found that the samples taken from the surface of the figure and the pedestal contain organic surface contaminants. A sample taken from the surface of the pedestal revealed a significant amount of clay contaminants introduced to the surface of the stone by dust deposits. The results of thermal analysis are confirmed by X-ray fluorescence analysis. In the samples taken from the surface layer of the pedestal and the figure, the presence of elements Si, Al, Mg, K, Fe, which are part of the structure of layered silicates, was detected. The relative content of elements present in the structure of clay minerals is determined by the ratio of the areas of the bands of electronic transitions, which are manifested on the spectrum of samples at the corresponding characteristic energies. Based on these data, it can be argued that the surface layer of the pedestal contains more clay contaminants. Based on chemical and technological research, it can be argued that the surface layer of the pedestal contains more clay contaminants than the sculpture. Taking into account the results of historical, art and chemical-technological research, a program of restoration of the monument has been developed: Carrying out a visual and field inspection of the work; Execution of photofixation before completion of restoration works; Study of analogues of the image of St. John of Nepomuk; Execution of mechanical clearing; Extraction of salts from the structure of the stone by applying a compress of cellulose and distilled water; Carrying out of structural strengthening of a stone by the KSE300 Remmers preparation; Production of the lost lower part of a plinth from limestone, its installation on stainless steel cores and epoxy glue; Gluing of the reflected and saved parts to a sculpture on proper places. Gluing the saved left hand with epoxy glue; Making a plasticine model of the saint's head according to the proportions and collected analogues. Execution of a lump plaster form and formation of a head from an artificial stone; Mounting the head using a stainless steel anchor and polyester glue; Gradual addition of lost elements on the sculpture and pedestal with mineral restoration solution with the addition of pigments; Modeling of the neck and collar of St. John of Nepomuk with mineral solution; Execution of structural strengthening of a stone by an alcoholic solution of nanovap; Execution of structural strengthening of a stone by the KSE300 Remmers preparation; Coating the monument with a long-acting biocidal solution from Remmers; Double plastering of the monument with a solution of historical translucent azure and water water repellent by Remmers with the addition of pigments for stone tinting; Execution of final photofixation of a monument after the carried-out restoration actions. Chemical-technological studies confirm what was revealed by visual examination and microscope. During the restoration, a full range of measures was taken to stabilize the material structure of the sculptural composition. Remains of blue and red paints were found during the work. According to the results of X-ray fluorescence analysis, it was found that the staining was done in the XIX century. Instead, the primary staining was not detected. The performed chemical-technological researches have formulated a restoration map, will allow in the following works to define more precisely mineral composition of a stone and the author's color decision of a work of art. After the completion of the restoration works, the sculptural composition acquired artistic integrity and received a sacred meaning. Similar works of art located on the territory of Ukraine need to be preserved and restored, as they form a valuable cultural landscape of historical settlements.

Extraction of Potassium from Biotite by Sr2+/K+ Exchange Method and Electrochemical Properties of Hydrated Sr-Mica

Soluble potassium has been successfully extracted from biotite by Sr2+/K+ ion exchange. The hydrated Sr-mica after ion exchange has better electrochemical properties. The potassium extraction rate, mica silicate structure and electrochemical properties (charge-discharge and cycling properties) before and after ion exchange were characterized by X-ray fluorescence spectroscopy, powder X-ray diffraction, Fourier Transform Infrared spectrometer and constant current charge-discharge cycle technology. The results show that after 10 hours of strontium ion exchange, the layered silicate structure is not destroyed. The maximum potassium extraction rate is 98%. The biotite gradually transforms into vermiculite strontium mica to form strontium mica, and the basal (001) spacing expands from 1.001 nm to 1.517 nm. The electrochemical properties of hydrated Sr-mica obtained after exchange have been improved.

Extraction of Potassium from Biotite by Lithium Ion Exchange and Its Electrochemical Properties

In order to solve the problem of shortage of potassium resources in China, the technology of extracting soluble potassium from insoluble potassium minerals needs to be further studied. Biotite with relatively high potassium content was used as the research object to extract soluble potassium elements from biotite by lithium ion exchange method, and the electrochemical properties of biotite were tested after potassium extraction. After 80°C hydrothermal reaction for hours, potassium and lithium ion exchanged with each other, and soluble potassium were obtained from the filtrate by filtering the reaction liquid. The efficiency of potassium extraction and the structure of mica changed after the oxidation reaction was determined by XRF and XRD, respectively. The results showed that the layered silicate structure of mica after the reaction was not destroyed, and the potassium extraction rate for 8h was up to 92.3%. The discharge capacitance was 1.32F/g, and the coulomb efficiency was 64% in 0.6C.

Extraction of Potassium from Biotite by Ca2+/K+ Ion Exchange and the Structural Transformation

In order to alleviate the contradiction between supply and demand of potassium resources in China, we extracted potassium from biotite by Ca2+/K+ ion exchange. Soluble potassium salts were obtained from the filtrate by hydrothermal reaction of biotite with oxidant, ion exchanger and other reagents at 80 ℃. The extraction rate of potassium and the structure change of biotite during the process of potassium exchange were determined by atomic absorption spectrophotometer and X-ray diffraction. The results showed that the layered silicate structure of biotite after ion exchange had not been destroyed, the base-plane spacing has expanded from 1.012 nm to 1.4288 nm, and most of the interlayer potassium ions have been extracted after 24 hours. The potassium extraction rate is 89%.

Structure and Properties of Syntetic Layered Lithium-Containing Silicates

A crystallochemical analysis of synthetic layered lithium-containing silicates has been performed. It is shown that these compounds have unique properties and structural characteristics. According to the X-ray diffraction data, the initial material possess a layered structure. After filling the material with ethylene glycol, the intensity of the reflection corresponding to the interplanar spacing d001 = 12.3 A significantly decreased, and two additional peaks arose: strong (d = 16.8 A) and weak (d = 14.7 A), which indicates possible presence of three layered phases with different sorption properties in the sample. The samples easily absorb moisture from air. The range of stretching vibrations of OH groups in the IR spectra of synthesized samples corresponds to the spectrum of adsorbed water.

Structuring of composite hydrogel bioadhesives and its effect on properties and bonding mechanism.

The current manuscript focuses on novel bioadhesives, based on natural polymers and loaded with hemostatic agents with a layered silicate structure, in order to improve the sealing ability in hemorrhagic environment. Such composite bioadhesives have not been developed and studied before. The effect of the adhesive's components on its mechanical strength was studied by three different methods, as well as the physical properties and structural features. Thorough understanding of these unique biomaterials resulted in a qualitative model which describes the effect of the bioadhesive's parameters on the cohesive and adhesive strength. Thus, structure-property-function relationships are presented. Structuring of the composite bioadhesives and its effect of the properties and bonding mechanism, are expected to be of high interest to Acta readership.

A Novel Approach to Improve the Barrier Properties of PET/Clay Nanocomposites

An investigation of oleic acid-modified clay versus plain clay with regard to the physical and barrier properties of PET/clay nanocomposites was performed. Montmorillonite (MMT) and Cloisite 30B nanoclays were modified by long-chain oleic acid and identified as ol-MMT and ol-30B, respectively. Fourier Transformed Infrared Spectroscopy and X-ray diffraction (XRD) results revealed that the fatty acid was associated with the clay surface and that the gallery spacing of the layered silicates was expanded. In the case of ol-MMT, a disordered structure of layered silicates was achieved. TGA results indicated that ol-MMT showed thermal stability and could survive PET processing temperature. The degradation of ol-30B, however, increased after modification because of the presence of oleic acid. PET/clay nanocomposites were prepared with modified ol-MMT and modified ol-30B by using a twin screw extruder. XRD indicated that there was a significant improvement on the dispersion of nanoclays modified with long-chain oleic acid into the PET matrix, and an exfoliated structure was achieved. DSC data also revealed that crystallization behaviors of nanocomposites prepared with oleic acid-modified clays are similar to that of extruded PET. Significant improvements in the mechanical and barrier properties of stretched PET/clay nanocomposites were also achieved.

Long- and Short-Range Constraints for the Structure Determination of Layered Silicates with Stacking Disorder

Layered silicates have important applications as host materials, supports for catalysis, and zeolite precursors. However, their local structures are often challenging to establish due to disorder of the sheet assemblies. We present a new protocol that combines long- and short-range structural constraints from diffraction and solid-state NMR techniques, respectively, to determine the molecular structure of layered silicates in the presence of various extents of stacking disorder. Solid-state 29Si NMR data are largely insensitive to the incomplete extent of three-dimensional (3D) crystallinity that limits the interpretation of diffraction data alone to the identification of possible unit cells and space groups. State-of-the-art NMR crystallography techniques consequently provide a simplified view of materials from which candidate framework structures can be built and evaluated based on local structural constraints, including interatomic distances, Si site numbers and multiplicities, and Si–O–Si connectivities, and refined using density functional theory. This protocol was applied to a new layered silicate material named CLS-1, of composition [Si5O11H][C9N2H15]·1.9(H2O), synthesized by using a fluoride-based protocol and cationic alkylaminopyridinium as a structure-directing agent (SDA). Despite the intrinsic complexity and partial ordering of the intersheet arrangements and organic–inorganic interactions, this led to the identification of a single space group that is compatible with both NMR and diffraction data, from which the silicate framework structure could be established,. The remarkable similarities between the layered framework structures of CLS-1, HUS-2 (Tsunoji et al. J. Mater. Chem. 2012, 22, 13682), and another layered silicate material with a radically different morphology and extent of stacking order and interlayer dynamics, established by using a similar approach (Brouwer et al. J. Am. Chem. Soc. 2013, 135, 5641), point to the remarkable robustness of this previously unknown silicate framework type.

Polymer-Nanoclay Mixed Matrix Membranes for CO<sub>2</sub>/CH<sub>4</sub> Separation: A Review

Mixed matrix membrane (MMM) has shown significant progress towards gas separation. Rigid polymers are suitable materials for MMM fabrication but adhesion problems with filler need to be addressed. A variety of inorganic fillers have been studied for CO2 separation but clay minerals were not considered much in this class. The layered silicate structure of nanoclay such as montmorillonite provides excellent opportunity to manipulate its properties, leading towards better dispersion and adhesion towards the polymer matrix. This paper reviews the potential of polymer-nanoclay MMM for CO2/CH4 separation.