Papers by Keyword: Montmorillonite

Abstract: The object of this study was bentonite clay from the Ilnytskyi deposit in the Transcarpathian region. The clay was enriched in montmorillonite by sedimentation to remove the coarse-dispersed phase. Complex thermal, X-ray diffractometric, and energy-dispersive spectral analyses showed that the enriched bentonite consists mainly of Ca, Mg-montmorillonite. The sorption of methylene blue dye by the enriched bentonite was found to occur through an ion-exchange mechanism. Modeling of the experimental sorption isotherm data using the Langmuir equation revealed the influence of medium pH on the sorption characteristics of bentonite. The spent sorbent is recommended for application in sorption technologies for landfill reclamation and land restoration.

Abstract: To improve the flame retardant and smoke suppression performance of fire retardant coatings. Aluminum hydroxide (ATH) and montmorillonite (MMT) were used as reinforced fillers to prepare intumescent fire-retardant coatings. The results showed that when ATH and MMT were combined with a mass ratio of 9:2, the flame retardant and smoke suppression performance was best. The maximum temperature on the back decreased by 47.1 °C, the heat release rate (HRR) decreased by 15.9%, the total smoke production (TSP) decreased by 23.5%, the peak carbon dioxide yield (PCDY) decreased by 39.4%, the maximum carbon residue was 50.59%. The main reason is that ATH reacts with phosphoric acid to form Al(H₂PO₄)₃, which binds each component together to increase the carbon residue. At high temperatures, ATH generates a large number of Mg-O-P and Si-O-P bonds and the mesh structure of MMT synergistically improves the thermal stability of the coating and absorbs flue gas particles. The oxides decomposed by ATH adhere to the surface of MMT and migrate to the surface of the charcoal layer to form a protective layer, which enhances the flame-retardant and smoke-suppressant properties of the coating. In this study, ATH/MMT was used as the flame retardant filler, and the optimal addition amount of ATH/MMT was obtained for the preparation of intumescent fire retardant coatings, which provides a theoretical basis for the selection of reinforcing fillers.

Abstract: The object of the study was the Ukrainian bentonite clays of the Cherkasy deposit (layer II of the Dashukivska area) and the Ilnytske deposit of the Transcarpathian region. Enrichment of clays with montmorillonite was carried out by the method of sedimentation of the coarsely dispersed phase. The natural type of montmorillonite and the nature of isomorphic substitutions in its structure were confirmed by X-ray diffractometric and complex thermal analyses. Activation of bentonite clay enriched with montmorillonite was carried out by the action of ultrasonic waves. The sorption capacity of activated and montmorillonite-enriched clays with respect to Cu²⁺ ions was assessed by the results of energy dispersive X-ray analysis. The ion exchange mechanism of sorption of Cu²⁺ ions was confirmed by the data of diffractometric X-ray analysis. The prospects for the use of enriched bentonite clays activated by ultrasonic waves are outlined.

Abstract: Natural montmorillonite (MMT) was facilely impregnated with a mixed solution of protonated chitosan (CS) and KNO₃, which was then subsequently impregnated with sodium tripolyphosphate (TPP) to ionically crosslink with chitosan, resulting in the MMT/xCS-20KNO3-TPP nanocomposites. The initial content of chitosan to MMT was varied from 2.5, 5 and 10 wt%, and while the TPP:chitosan weight ratio was kept at 1:5. The K⁺ and NO₃^- ions interacted ionically and were entrapped in the MMT basal spacing and the free volume of TPP crosslinked chitosan of the MMT/xCS-20KNO3-TPP nanocomposites. These nanocomposites were able to successfully prolong the K⁺ and NO₃^- releases, in which the cumulative released values (%R) ranging from 21 – 26 % for K⁺ and 0.37 – 0.65 % for NO₃^-. The presence of protonated amine in the chitosan played the dominant effect on the release profile of NO₃^- ion more than that of the K⁺ ion. The higher the chitosan content employed in the impregnation method, the more crosslinked chitosan structure in the MMT/xCS-20KNO3-TPP nanocomposites, resulting in decreased K⁺ and NO₃^- releases at each pre-determined soaking duration. The MMT/xCS-20KNO3-TPP nanocomposites have been considered as a promising choice for environmentally friendly fertilizers.

Abstract: Clay from the Khmelnytskyi region was enriched in montmorillonite by separation of a fraction with a particle size  0.5 ∙ 10^-6 m. The X-ray diffraction and thermal analyses suggest that the enriched clay composition is close to mono-mineral, that is, represented by ferric-type montmorillonite in the form of Ca and Mg. The mineral interlayer spacings are partially filled with natural organic matter. An exchange capacity of montmorillonite is 0.78 mmol/g as shown by the photocolorimetry studies of the adsorption of the cationic methylene blue (MB) dye. It is recommended that studied clay be used as an effective natural adsorbent for wastewater treatment and for the arrangement of geochemical barriers to prevent harmful substances from entering the environment.

Abstract: The microcapsules with inorganic/organic composites as capsule wall were prepared to optimize the performance of microcapsules. The MMT stabilized Pickering emulsion was used as template in the interfacial polymerization. TDI and EDA were polymerized at the oil-water interface to form MMT/PU composite as the capsule wall to encapsulate clove oil. Under the process condition of the dosage ratio of clove oil to TDI 5:1, the content of MMT 2%, and the reaction temperature 70 °C, the embedding rate of microcapsule could reach 92.31%. The average volume diameter of microcapsules was 49.4 μm. The microcapsules were regular and basically spherical shape, smooth surface and high elasticity. TGA showed that the thermal stability of essential oil was improved. The retention rates of clove oil in microcapsules after 40 days storage at 4 °C and 25 °C were more than 80%, indicating that clove oil microcapsules were relatively stable. The relative content of eugenol, the main component in clove oil decreased after storage, while the relative content of secondary components increased.

Abstract: The influence of hydrophilic electrochemically exfoliated graphite (EEG) and hydrophobic reduced EEG (rEEG) on the electrical conductivity, dielectric properties, and high-frequency dielectric losses of epoxy-based composites with montmorillonite was described. It was confirmed, that the addition of EEG changes the low-temperature conduction mechanism. The electrical conductivity in composite with EEG and montmorillonite was described by correlated barrier hopping model, whereas for composites with montmorillonite and rEEG two models were used: non-overlapping small polaron tunneling and correlated barrier hopping. The addition of EEG drastically changes the activation energy of charge carriers motions from 2.68 to 0.83 eV, whereas the addition of rEEG only to 2.43 eV. Also composite with EEG was characterized by highest high-frequency dielectric losses.

Abstract: The synthesis of polyphenylene sulfide in the presence of catalytic systems based on montmorillonite and various lithium salts has been studied, and conditions have been identified that accelerate the process and obtain a polymer with a given microstructure. The rheological, thermal, and physicomechanical.

Abstract: Acid activation is the most commonly used method to enhance the chemical and physical properties of clay minerals. Porous structure formation behavior depends on the crystal structure of clay minerals. Within the same structure of clay minerals, their resistance to acid also varies. Acid leaching has been used to increase the surface area of clay minerals and obtain solids with high porosity and many acidic sites. This paper is focused on the results of acid leaching of Mongolian clay minerals (montmorillonite and muscovite). Both clay minerals belong to a group of phyllosilicates with the 2:1 crystal structure. The influence of acid concentration and leaching time on the porous properties of silica was studied. Initially, the montmorillonite was pre-treated by a simple physical purification methods. The montmorillonite and muscovite were acid leached by a 10% hydrochloric acid solution in an autoclave at 120°C for 10h. X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and the surface area used for characterization of the raw and leached samples. The surface area of leached montmorillonite increased up to 77% and muscovite up to 63%. Clay mineral’s swelling character and isomorphic substitution of the octahedral layer show the main influence on porous structure formation.

Abstract: The work is focused on obtaining hybrid pigments by adsorption of anionic dyes on positively charged montmorillonite. Modification of the sodium form of montmorillonite by chromium hydroxocomplexes was provided to ensure effective adsorption of anionic dyes on the surface of mineral particles. A high level of adsorption of anionic dyes as a result of steric factor was revealed. It was shown that the adsorption of dyes depended on the pH of the medium and was characterized by a maximum level at pH 4.5 – 6.0. The scheme of obtaining hybrid pigments, which were characterized by good сovering ability, resistance to stratification, especially saturated and intense colour was proposed.