Montmorillonite In Bentonite Research Articles

Acoustic properties of composites materials based on bentonite and coconut or cactus (nopal) fibers

Materials made from natural fibers or waste have been studied to acquire a composite with good acoustical isolation properties, commercial materials used in this concern are polyurethane foam, fiberglass, Rockwool, and drywall. This work proposes using waste coconut and cactus ( Opuntia ficus-indica) fibers to synthesize bentonite composites and study their physicochemical and acoustic properties. Physicochemical properties of precursor and composites (75% wt. fiber) were determined by XRD, FTIR, N2 adsorption, optical, and SEM microscopies. The transmission, reflection, and absorption coefficients, 50 to 10,000 Hz, were obtained in an impedance tube and were compared with commercial materials. The composites were subjected to surface humidity and thermal (30, 50, and 70°C) tests to evaluate the stability of acoustic properties. The mechanical properties of the composites are improved with the addition of bentonite, hardness is increased by 6.7% and 0.9%, and the density is decreased by 73.6% and 45.5%, for coconut and nopal, respectively, porosity also changes. We corroborated the significant presence of montmorillonite in bentonite (XRD), while the nopal or coconut fibers are composed of hemicellulose, cellulose, and lignin (FTIR). Also, mucilage was identified in the nopal samples as adherent biopolymer that generates stability either thermally or in wetting conditions. Coconut fiber has a high absorption coefficient (similar to polyurethane), which is reduced with humidity. However, by adding bentonite, the reflection is more elevated, and transmission is lower than commercial materials. The bentonite and nopal (fiber and composite) presented stability in the acoustic coefficients as a function of humidity and temperature.

Interaction of diesel oil contaminants with laterite soil and bentonite treated by sawdust -landfill liner

ABSTRACT Landfill liners blended with industrial by-product seems to outperform the conventional liners. This paper presents the influence of sawdust (SD) admixed with bentonite and locally available lateritic soil on consistency limits, free swell index (FSI), compaction characteristics, unconfined compressive strength (UCS), hydraulic conductivity and leachate characteristics. SD content was varied as 10%, 15% and 20%. Diesel oil contaminants (DOC) and deionised water (DIW) were used as the test fluids. From the test results, consistency limits, FSI, maximum dry density, leachate concentration of heavy metals and UCS decreased, whereas optimum moisture content and hydraulic conductivity increased with increasing sawdust content. Furthermore, the energy-dispersive X-ray spectrometer revealed the absence of calcium in the blends which have resulted in poor cementation and decreased the UCS. X-ray diffraction showed that the presence of cellulose in sawdust and montmorillonite in bentonite adsorb the heavy metals in DOC. Based on the test results, 15% Saw dust content in the blends proves to be the optimum in retaining the heavy metal concentrations, improving the geotechnical properties and qualifying as a landfill liner material.

Molecular Dynamic (MD) Simulations of Organic Modified Montmorillonite

This study complements the knowledge about organobentonites, which are intended to be new binders in foundry technology. In the developed materials, acrylic polymers act as mineral modifying compounds. Modification of montmorillonite in bentonite was carried out in order to obtain a composite containing a polymer as a lustrous carbon precursor. The polymer undergoes thermal degradation during the casting process, which results in the formation of this specific carbon form, ensuring the appropriate quality of the casting surface without negative environmental impact. The present paper reports the results of computational simulation studies (LAMMPS software) aimed at broadening the knowledge of interactions of organic molecules in the form of acrylic acid and acrylate anions (from sodium acrylate) near the montmorillonite surface, which is a simplified model of bentonite/acrylic polymer systems. It has been proven that the –COOH group promotes the adsorption of acrylic acid (AA) to the mineral surface, while acrylate ions tend to be unpredictably scattered, which may be related to the electrostatic repulsion between anions and negatively charged clay surfaces. The simulation results are consistent with the results of structural tests carried out for actual organobentonites. It has been proven that the polymer mainly adsorbs on the mineral surface, although it also partially intercalates into the interlayer spaces of the montmorillonite. This comprehensive research approach is innovative in the engineering of foundry materials. Computer simulation methods have not been used in the production of new binding materials in molding sand technology so far.

Effect of Desiccation on the Hydraulic Conductivity of Compacted Bentonite–Sand Blocks

This study investigated the impact of drying cracks on the hydraulic conductivity of compacted bentonite–sand blocks to support the construction of buffer barriers in an underground research laboratory for the disposal of China’s high–level radioactive waste. The hydraulic conductivity of an air-dried block (the worst storage case) was measured in a flexible–wall permeameter in the directions parallel and perpendicular to the direction of compaction according to ASTM D5084. The results were compared with the hydraulic conductivity of fresh blocks. Computerized tomography (CT) images were used to visualize the internal cracks of the blocks, and the swell index was measured to represent the blocks’ swelling properties. The test results revealed that compared with fresh blocks, the drying cracks increased the hydraulic conductivity of the blocks by less than fourfold. As demonstrated by the CT images, the drying cracks were healed after permeation with distilled water. The swell index of the block was unaffected by air drying, and the swelling of montmorillonite in bentonite contributed to the healing of the drying cracks.

Comparison of methylene blue adsorption on bentonite measured using the spot and colorimetric methods

The maximum amount of methylene blue (MB) adsorbed on montmorillonite in bentonite can be determined using a spot or colorimetric method to evaluate the quality of bentonite. The spot method differs from the colorimetric method in terms of the procedure used to add MB solution to a bentonite dispersion and the procedure to determine the maximum amount of MB. In the spot method, MB solution is added in a step-by-step process and the maximum amount is determined by observing a spot of MB and bentonite on filter paper. In the colorimetric method, MB is added only once and the maximum amount is determined using a spectrophotometer. This study revealed that the maximum amount of MB adsorbed onto bentonite measured using the spot method differs from that measured using the colorimetric method. The maximum amount measured using the colorimetric method can be estimated by multiplying the amount measured using the spot method by 0.937. To ascertain why the maximum amounts measured using the two methods differ, we examined bentonites using a newly proposed method (a step-by-step colorimetric method), in which MB is added in a step-by-step manner and the maximum amount is determined using a spectrophotometer. The maximum amount measured using the step-by-step colorimetric method showed that step-by-step addition of MB decreases the maximum amount. The decrease can be explained by the re-flocculation of montmorillonite particles in bentonite.

Application of montmorillonite in bentonite as a pharmaceutical excipient in drug delivery systems

Montmorillonite is a multifunctional clay mineral and a major component of bentonite. Montmorillonite has been used in various industrial and pharmaceutical fields due to its unique characteristics, which include swelling and adsorption. The high adsorption capacity of montmorillonite contributes to increase drug entrapment and sustained-release of drugs. Montmorillonite generally sustains drug release in many formulations by strongly adsorbing to the drug. In addition, montmorillonite enhances the dissolution rate and bioavailability of hydrophobic drugs. Moreover, montmorillonite was applied to form composites with other polymer-based delivery systems. Thus, montmorillonite could be applied to formulate diverse drug delivery systems to control and/or improve the pharmaceutical properties of drugs, including solubility, dissolution rate, and absorption. In this review, perspectives of applying montmorillonite as a pharmaceutical excipient in drug delivery systems are discussed.

Quantification of Exchangeable Cations in Interlayer of Tsukinuno Sodium-Montmorillonite

AbstractIn this study, the cation exchange capacity (CEC) and leached exchangeable cations (LC) of montmorillonite purified from bentonite produced in the Tsukinuno bentonite mine, Yamagata, Japan, were measured, and the exchangeable cations in the interlayer of the montmorillonite were discussed. A montmorillonite, in which the soluble minerals were completely removed, was prepared. Kunipia-F and Kunipia-P, for which both bentonites originally contain approximately 100 wt.% montmorillonite, were used as the initial material. All of the measurements were carried out in a N2 atmosphere-controlled glove-box.The CEC values of montmorillonites for both bentonites (100-110 meq/100g) were similar to data conventionally reported, and the sum of LC was also approximately in good agreement with the CEC values. The share of Na+ in the interlayer of montmorillonite calculated from the LC was about 3/4 of the sum of the LC (≍ CEC), and Mg2+ and Ca2+ occupied about 7 and 19 %, respectively. Although montmorillonite in bentonite produced in the Tsukinuno bentonite mine is known as a Na type, the sum of Ca2+ and Mg2+ occupied about 26 % of all exchangeable cations in the interlayer. Based on these data, the ion exchange reaction constant between Na+ and H+ in the interlayer of montmorillonite was calculated to be -0.07. This is nearly 2 orders of magnitude lower than data that are usually adopted.

Theoretical Equations on Hydraulic Conductivities of Bentonite-Based Buffer and Backfill for Underground Disposal of Radioactive Wastes

Compacted bentonite and sand-bentonite mixtures are sought as buffer and backfill materials for high-level radioactive waste disposal facilities because they have very low permeability. To establish specifications such as the dry density and sand-bentonite mass ratio for buffer and backfill materials, we must quantitatively evaluate a material’s hydraulic conductivities. This study presents theoretical new equations for evaluating the hydraulic conductivity of compacted bentonites and sand-bentonite mixtures. New equations are proposed for evaluating the flow velocity of interlayer water between two montmorillonite parallel-plate layers considering the swelling behaviors of montmorillonite. Furthermore, a prediction method for hydraulic conductivity of compacted bentonite and sand-bentonite mixtures is presented by combining new equations with previous equations for evaluating swelling behavior of montmorillonite in bentonite. The applicability of this method is clarified by comparing predicted results wi...

Thermodynamic Properties of Water in Compacted Bentonite Under External Pressure-free Conditions

AbstractIn an attempt to determine the thermodynamic properties of water in bentonite, the vapor pressure of water in compacted bentonite was measured as functions of water content and temperature, under external pressure-free conditions. The relative partial molar Gibbs free energy ΔGH2O, enthalpy ΔHH2Oand entropy ΔSH2O of tne waler in bentonite were determined at temperature of 298.15K. The interlayer distance of montmorillonite in bentonite was also measured by X-ray diffraction.It is probable that one fourth of the total water included in the bentonite at water content of 20.3wt% and dry density of 1.76 × 103kg/m3 is nearly free water; the water is not regarded as dilute electrolytic solution but the solution with higher ionic strength. Another one fourth of the water in the bentonite at the water content is bound water; the partial molar entropy of the bound water referred to pure water is from a half to whole of solidification entropy of pure water. The remainder is regarded as intermediately bound water.