Minerals Montmorillonite Research Articles

Effect of mineralized solution on protective properties of clays in radioactive waste isolation

In this paper there were studied the mineral composition and sorption properties as well as filtration properties of natural clay samples from “Gorodnoe” deposit of Brest region and “Markovskoe” deposit of Gomel region. It was determined that clay mineral montmorillonite of the samples contains illite phase in the structure, which is 4,8 wt.% in “Gorodnoe” sample and 3,6 wt.% in “Markovskoe” sample. The illite phase was shown to contain highly selective sorption sites for 137Cs. 85Sr sorption mostly takes place on montmorillonite. It was determined that model mineralized solution (the solution imitating chemical composition of water solution if water penetrates a radioactive waste disposal and consequently passes through concrete, Na-bentonite and again concrete layers) doesn’t affect 137Cs sorption, but significantly affects 85Sr sorption. Distribution coefficients (Kd ) of 137Cs sorption on studied clay samples are higher than 103 dm3 /kg, indicating high sorption properties of the clays towards 137Cs. Kd 85Sr for sorption on the clay samples in the model mineralized solution is 30 times lower than Kd 137Cs mostly because of competition between strontium and calcium ions. It was determined that filtration coefficient values of clays from “Gorodnoe” and “Markovskoe” deposits are 2,4 and 1,3 times higher after being treated with the model mineralized solution than the filtration coefficient values for raw clay samples. Hence, the clay from “Markovskoe” deposit is more resistant to the influence of the model mineralized solution than the clay from “Gorodnoe” deposit. The overall results of the research state that the clay from “Markovskoe” deposit can be used in the underlying layer of low- and medium-level radioactive waste disposal facility at NPP.

Agronomic Evaluation Study: Use of Caiapônia Shale as Magnesium Supplementation for Soybean (Glycine max) and Maize (Zea mays) Cultivation

The soil of the cerrado is acidic, with high levels of iron and aluminum, and has low fertility due to weathering, which removes elements such as magnesium. To increase the availability of magnesium, essential for various plant processes, an alternative is the use of agrominerals rich in this element. The objective of this work was the agronomic evaluation of the use of Caiapônia shale as magnesium supplementation for soybean and corn crops. It is characterized as Magnesium Silicate containing 18% Magnesium Oxide (MgO) in its composition, in addition to the minerals Montmorillonite, Albite and Ilite. The product was screened to 0.425 mm in sieve no. 40. The study was conducted at the School of Agronomy of the Federal University of Goiás, located in the municipality of Goiânia, Goiás, in a greenhouse in two soils: Red Latosol (LV) and Yellow Latosol (LA). The treatments of Caiapônia Shale (CS) were increasing doses (0, 50, 100, 200 and 400 kg. ha-1 of MgO), in addition to the reference agrominerals, Dianutri (SiMg) and Ibar (MgO) and Wollastonite, source of Ca, with addition of MgO. The experimental design was completely randomized, with eight treatments conducted in quadruplicate. The variables analyzed were magnesium and calcium content and pH in the soil. The Caiapônia Shale (CS) released Mg+2, increasing the availability of magnesium, especially in LV in the first year of soybean and residual in corn in the second year, while in LA it was efficient in the first year.

Swelling characteristics of montmorillonite mineral particles in Gaomiaozi bentonite

Highly compacted bentonite is an ideal back-filling (buffer) material for the deep geological disposal of high-level radioactive waste. Montmorillonite is the main constituent mineral of it. The nanoscopic swelling characteristic of montmorillonite mineral particles greatly influences the macroscopic buffering performance of highly compacted bentonite blocks. Firstly, the montmorillonite suspension liquid was exfoliated by freeze-thaw cycles, the appropriate mineral particles were selected by atomic force microscope (AFM) for making colloidal probes. Then, the swelling pressure between mineral particles was measured by AFM, investigating the effects of interlayer distance, layer number, temperature, and interlayer cation type on the nanoscale swelling pressure. The experimental results showed that the swelling pressure of montmorillonite mineral particles peaks at about 0.7–0.8 nm interlayer distance. The swelling pressure of mineral particles with more layers is smaller. The higher the ambient temperature, the greater the swelling pressure. The swelling pressure of Ca-montmorillonite is significantly larger than that of Na-montmorillonite. The Laird model has a relatively good applicability with the interlayer distance of 0.6–1.2 nm; the DLVO theory has a good applicability with the interlayer distance greater than 1.5 nm. Finally, a predictive model was developed for the swelling pressure of nanoscopic mineral particles considering the effect of layer number. The research results provide data support and theoretical support for swelling pressure generation and cross-scale transmission mechanism of highly compacted bentonite hydration.

Study on the Effect of Clay Minerals on CO<sub>2</sub> Hydrate Formation

With the massive emission of greenhouse gases, global warming has become an important challenge for human beings at present. Storing carbon dioxide in the form of solid hydrates in the ocean is an effective strategy to mitigate climate warming. Clay in the ocean may have an effect on hydrate formation and CO<sub>2</sub> storage. In this study, montmorillonite and kaolinite were selected as clay minerals, and the effects of clay particles on CO<sub>2</sub> hydrate formation in suspensions with different mass fractions were experimentally analyzed. The results showed that the clay particles were able to promote hydrate nucleation and shorten the induction time, but the final amount of hydrate was reduced, which was related to the bound water. CO<sub>2</sub> hydrate storage in clay minerals with different water contents was investigated. The amount of CO<sub>2</sub> storage in montmorillonite minerals first decreased and then increased with the increase of water content, while the amount of storage in kaolinite minerals increased. The reason was that the amount of bound water on the surfaces of montmorillonite and kaolinite was different, and the stronger bound water was difficult to form hydrates. The results revealed the effect of clay particles on CO<sub>2</sub> hydrate formation and provided some experimental support for the CO<sub>2</sub> storage by hydrate method in the ocean.

Changes of Temperature and Moisture Distribution over Time by Thermo-Hydro-Chemical (T-H-C)-Coupled Analysis in Buffer Material Focusing on Montmorillonite Content

Bentonite is used as a buffer material in engineered barriers for the geological disposal of high-level radioactive waste. The buffer material will be made of bentonite, a natural clay, mixed with silica sand. The buffer material is affected by decay heat from high-level radioactive waste, infiltration of groundwater, and swelling of the buffer material. The analysis of these factors requires coupled analysis of heat transfer, moisture transfer, and groundwater chemistry. The purpose of this study is to develop a model to evaluate bentonite types and silica sand content in a unified manner for thermo-hydro-chemical (T-H-C)-coupled analysis in buffer materials. We focused on the content of the clay mineral montmorillonite, which is the main component of bentonite, and developed a model to derive the moisture diffusion coefficient of liquid water and water vapor based on Philip and de Vries, and Kozeny–Carman. The evolutions of the temperature and moisture distribution in the buffer material were analyzed, and the validity of each distribution was confirmed by comparison with the measured data obtained from an in situ experiment at 350 m in depth at the Horonobe Underground Research Center, Hokkaido, Japan.

A Study of the Effect of Addition of Nano SiO2 and Polyamide Fiber toward Swelling Potential Expansive Clay

Expansive clay with great swelling potential requires improvement or stabilization of the soil. It can be successfully done by mechanical and chemical stabilization techniques. This study aims to determine the effect of adding Polyamide (PA) fibre as the material for mechanical stabilization and nano SiO2 as the material for chemical stabilization. The expansive clay used in this study deployed a sample of clay containing mineral montmorillonite with the USCS classification in the high plasticity (CH) category. The mixed materials used include PA fibre with variations of 0.5%, 0.75% and 1% by weight of dry soil and nano SiO2 with variations of 1%, 2% and 3% by dry soil weight. To prove the effectiveness of using nano SiO2, this study compares the treatment with the use of micro SiO2 materials under the same comparison variations. This result indicates that the expansive clay that has been stabilized using PA fibre and nano SiO2 is capable of preventing the swelling potential.

Stripping Mechanism of Surfactant System Based on Residual Oil on the Surface of Sand-Conglomerate Rocks with Different Grain Size Mineral Compositions.

During the development of a sand-conglomerate reservoir, there is a huge variation in rock grain size and different åmineral compositions of different-sized sand grains. The mineral composition and microstructure of the rock both have an impact on the characteristics of the remaining oil in the reservoir. The stripping mechanism of a surfactant system on sand-conglomerate surface crude oil with varied grain size minerals was explored in this paper. Sand-conglomerate was classified and analyzed to determine their wettability and stripping oil effects. The optimization of the surfactant solution system and molecular dynamics simulation revealed the surfactant stripping mechanism on crude oil on distinct sandstone minerals. The results of the study showed that montmorillonite minerals are more readily adsorbed by surfactants. The crude oil within them is more likely to compete for adsorption and to be stripped off, and then extracted with the recovery fluid. The surfactant solution system can increase the hydrophilicity of the rock surface, make the crude oil on the rock surface shrink and gather, and enhance the transportation ability of the displacement fluid. And the emulsification seals part of the pore in the reservoir, increases the displacement pressure, and improves the overall wave volume. The results of this paper are of great significance for the efficient development of sand-conglomerate reservoirs.

Self-Assembly of Silicon Nanotubes Driven by a Biphasic Transition from the Natural Mineral Montmorillonite in Molten Salt Electrolysis.

Silicon nanotubes (SNTs) have been considered as promising anode materials for lithium-ion batteries (LIBs). However, the reported strategies for preparing SNTs generally have special requirements for either expensive templates or complex catalysts. It is necessary to explore a cost-effective and efficient approach for the preparation of high-performance SNTs. In this work, a biphasic transformation strategy involving "solid-state reduction" and "dissolution-deposition" in molten salts is developed to prepare SNTs using montmorillonite as a precursor. The rod-like intermediate of silicon-aluminum-calcium is initially reduced in solid state, which then triggers the continuous dissolution and deposition of calcium silicate in the inner space of the intermediate to form a hollow structure during the subsequent reduction process. The transition from solid to liquid is crucial for improving the kinetics of deoxygenation and induces the self-assembly of SNTs during electrolysis. When the obtained SNTs is used as anode materials for LIBs, they exhibit a high capacity of 2791mAhg-1 at 0.2Ag-1, excellent rate capability of 1427mAhg-1 at 2Ag-1, and stable cycling performance with a capacity of 2045mAhg-1 after 200 cycles at 0.5Ag-1. This work provides a self-assembling, controllable, and cost-effective approach for fabricating SNTs.

Clay minerals/sodium alginate/polyethylene hydrogel adsorbents control the selective adsorption and reduction of uranium: Experimental optimization and Monte Carlo simulation study

Clay minerals formations are potential geological barrier (host rocks) for the long-rerm storage of uranium tailing in deep geological repositories. However, there are still obstacles to the efficient retardation of uranium because of the competition between negatively charged regions at the clay minerals end face, surface and between layers, as well as low mineralization capacity. Herein, employing a simple method, we used sodium alginate (SA), an inexpensive natural polymer material, polyethylene (PE), and the natural clay minerals montmorillonite (Mt), nontronite (Nt), and beidellite (Bd) to prepare three hydrogel adsorbents, (denoted as Mt/PE-@SA, Nt/PE-@SA, and Bd/PE-@SA), respectively. The application of obtained hydrogel adsorbents further extends to uranium(VI) removal from aqueous. Due to the synergistic action of SA group and PE group, hydrogel adsorbents showed select adsorption and mineralization effect on uranium(VI), among which the maximum uranium(VI) adsorption capacity of Nt/PE-@SA was 133.3 mg·g-1 and Mt/PE-@SA exhibited strong selectivity for uranium(VI) in the presence of coexisting metal ions. Cyclic voltammetry studies indicated the mitigation and immobilization of uranium species onto adsorbents by both reduction and mineralization. Besides, the synergistic adsorption of SA and PE on clay minerals was hypothesized, and the idea was supported by structure optimizations results from Monte Carlo dynamics simulation (MCD). Three obtained hydrogel adsorbents structural model was constructed based on its physicochemical characterization, the low energy adsorption sites and adsorption energies are investigated using MCD simulation. The simulation results show that obtained hydrogel adsorbents have a strong interaction with uranium(VI), which ensures the high adsorption capacity of those materials. Most importantly, this work demonstrates a new strategy for preparing mineral-based hydrogel adsorbents with enough stability and provides a new perspective for uranium(VI) removal in complex environment.

Adsorption characteristics and mechanisms of water-soluble polymers (PVP and PEG) on kaolin and montmorillonite minerals

The excessive use and accumulation of water-soluble polymers (WSPs, known as “liquid plastics”) in the environment can pose potential risks to both ecosystems and human health, but the environmental fate of WSPs remains unclear. Here, the adsorption behavior of WSPs with different molecular weight on kaolinite (Kaol) and montmorillonite (Mt) were examined. The results showed that the adsorption of PEG and PVP on minerals were controlled by hydrogen bond and van der Waals force. The Fourier transform infrared (FTIR) spectra and two-dimensional correlation spectroscopy (2D-COS) analysis revealed that there were interactions between the Al-O and Si-O groups of the minerals and the polar O- or N-containing functional groups as well as the alkyl groups of PEG and PVP. The adsorption characteristics of WSPs were closely related to their molecular weight and the pore size of minerals. Due to the relatively large mesopore size of Kaol, both PEG and PVP were absorbed into inner spaces, for which the adsorption capacity increased with molecular weight of the polymers. For Mt, all types of PEG could enter its micropores, while PVP with larger molecular weights appeared to be confined externally, leading to a decrease in the adsorption capacity of PVP with increasing molecular weight. The findings of this study provide a theoretical basis for scientific evaluation of environmental processes of WSPs.

Ultrasonic Activation of Mineral Sorbents

Introduction. Medical clays are polymineral sorbents with a predominance of the underlying clay mineral, the concentration of which determines the quality of mineral raw materials and its adsorption activity. One of the methods of improving the quality of mineral raw materials is its activation by means of ultrasonic treatment.Aim. To study the effect of ultrasound on the activation and adsorption activity of mineral sorbents.Materials and methods. Clinoptilolite mineral raw materials of the Kholinsky deposit, montmorillonite mineral raw materials of the Belgorod deposit and kaolinite mineral raw materials of the Eleninsky deposit were used as objects of research. A high-frequency UZDN-1 unit was used for ultrasonic treatment. Determination of adsorption activity was carried out by methylene blue.Results and discussion. The effect of ultrasound on the activation of mineral sorbents at an ultrasonic wave frequency of 40 kHz for five minutes has been studied. It was found that the average content of Clinoptilolite, taking into account all fractions in the clay of the Kholinsky deposit, increases by 20 %, the average content of Montmorillonite, taking into account all fractions in the clay of the Belgorod deposit, increases by 14 %, the average content of Kaolinite, taking into account all fractions in the clay of the Eleninsky deposit, increases by 18 %. The effect of ultrasound on the adsorption activity of mineral sorbents has been investigated. The use of ultrasonic treatment increases the adsorption activity of mineral sorbents by 12–19 %.Conclusion. The developed method of activation of mineral sorbents by ultrasonic treatment can be used to activate mineral sorbents by increasing the concentration of the underlying mineral (Clinoptilolite, Montmorillonite, Kaolinite), as well as increasing their adsorption activity.

Adsorption Performance and Mechanisms of Tetracycline on Clay Minerals in Estuaries and Nearby Coastal Areas.

Clay minerals in sediments have strong adsorption capacities for pollutants, but their role in the distribution of antibiotics in estuaries and nearby coastal areas is unclear. We evaluated the clay mineral montmorillonite (SWy-2) adsorption capacity for tetracycline (TC). We assessed the adsorption capacity of SWy-2 for TC by measuring the removal percentage of 30 mg/L TC over time. The effects of pH and ionic strength on the TC adsorption onto SWy-2 were investigated. We analyzed the kinetics of TC adsorption using a pseudo-second-order model and determined the adsorption isotherm using the Langmuir equation. SWy-2 particles were characterized using zeta potential, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analyses before and after TC adsorption. The removal percentage of 30 mg/L TC by SWy-2 reached 70.76% within 0.25 h and gradually increased to 78.64% at 6 h. TC adsorption was influenced by pH and ionic strength, where low pH enhanced and high ionic strength reduced the adsorption. The kinetics of TC adsorption followed a pseudo-second-order model, and the adsorption isotherm adhered to the Langmuir equation. The saturated adsorption capacity (qmax) of SWy-2 for TC was 227.27 mg/g. Zeta potential, FTIR, and XRD analyses confirmed that electrostatic interactions and chemical bonds played a significant role in the TC adsorption by SWy-2. SWy-2 clay mineral exhibits a substantial adsorption capacity for TC, indicating its potential as an effective sorbent to mitigate antibiotic contamination in estuaries and nearby coastal areas. The observed effects of pH and ionic strength on TC adsorption have implications for the environmental fate and transport of antibiotics. The pseudo-second-order kinetic model and Langmuir isotherm equation provide valuable insights into the adsorption behavior and capacity of TC on SWy-2. Characterization analyses support the involvement of electrostatic interactions and chemical bonds in the SWy-2-TC adsorption mechanism.

Influence of carbon sequestration in natural clay on engineering properties of cement-lime stabilized soil mortars

Carbon sequestration in natural soil, and using it for manufacturing of stablized earth-based materials can be an effective pathway for low embodied carbon constructions. This research demonstrates a possibility of sequestering carbon dioxide in clayey-soil, comprising of kaolinite and montmorillonite minerals, and examines its influence on rheological properties, hydration, mechanical strength and shrinkage of cement-lime-soil mortars. Carbon sequestration reduces the specific surface area, pore volume and lime reactivity of carbonated soil (CS). This leads to higher availability of unconsumed lime in cement-soil mixes, resulting in faster hydration, higher yield stress and plastic viscosity of cement-lime mixes with CS than control (with natural soil). Higher precipitation of binder gel due to addition of CS result in better stabilization, higher wet strength-to-dry strength ratio and up to 18% lower drying shrinkage than control. Depending on clay content and type of soil (S or CS), 40–58% of drying shrinkage can be reversed.

The Effect of High-Energy Ball Milling of Montmorillonite for Adsorptive Removal of Cesium, Strontium, and Uranium Ions from Aqueous Solution

Clay minerals are widely used to treat groundwater and surface water containing radionuclides. In our study, the method of mechanochemical activation for increasing the sorption capacity of the natural clay mineral montmorillonite was used. By adjusting the grinding time, the increasing sorption parameters of mechanochemically activated montmorillonite were determined. X-ray diffraction method, scanning electron microscopy, and the determination of the specific surface by low-temperature adsorption–desorption of nitrogen to characterize the natural and mechanochemical-activated montmorillonites were used. It was established that the maximal sorption of uranium, strontium, and cesium is found for montmorillonite after mechanochemical treatment for 2 h. It is shown that the filling of the surface of montmorillonite with ions of different natures occurs in various ways during different times of mechanochemical treatment. The appropriateness of the Langmuir and Freundlich models for the sorption parameters of uranium, strontium, and cesium ions on montmorillonite after its mechanochemical activation was established. The effect of natural organic substances—humic acids—on the efficiency of water purification from uranium on mechanoactivated montmorillonite was studied. The obtained sorbents can be effectively used for the removal of trace amounts of radionuclides of different chemical natures (uranium, cesium, and strontium) from polluted surface and ground waters.

Effect of montmorillonite K10 clay on RNA structure and function

One of the earliest living systems was likely based on RNA (“the RNA world”). Mineral surfaces have been postulated to be an important environment for the prebiotic chemistry of RNA. In addition to adsorbing RNA and thus potentially reducing the chance of parasitic takeover through limited diffusion, minerals have been shown to promote a range of processes related to the emergence of life, including RNA polymerization, peptide bond formation, and self-assembly of vesicles. In addition, self-cleaving ribozymes have been shown to retain activity when adsorbed to the clay mineral montmorillonite. However, simulation studies suggest that adsorption to minerals is likely to interfere with RNA folding and, thus, function. To further evaluate the plausibility of a mineral-adsorbed RNA world, here we studied the effect of the synthetic clay montmorillonite K10 on the malachite green RNA aptamer, including binding of the clay to malachite green and RNA, as well as on the formation of secondary structures in model RNA and DNA oligonucleotides. We evaluated the fluorescence of the aptamer complex, adsorption to the mineral, melting curves, Förster resonance energy transfer interactions, and 1H-NMR signals to study the folding and functionality of these nucleic acids. Our results indicate that while some base pairings are unperturbed, the overall folding and binding of the malachite green aptamer are substantially disrupted by montmorillonite. These findings suggest that minerals would constrain the structures, and possibly the functions, available to an adsorbed RNA world.

Surfactant Modified Bentonite Characterization: Effects and Comparative Analysis

Extensive soils can be found all over the world. The clay mineral montmorillonite is predominantly responsible for soil expansion. Because of their ability to shrink and swell with seasonal changes in moisture content, these expansive soils can cause significant damage to engineering construction. To stabilize the effects of swelling soil various ground improvement techniques, incorporate mineralogical modification of clays. The application of nanotechnology increased in past few years to deal with clay minerals as it possesses the same dimensional properties. To understand the behaviour of Nano modified clay, bentonite was selected as it represents the montmorillonite clay mineral. The characterization of surface-treated bentonite by nanomaterial was carried out. The study of physio-chemical properties and textural properties of surface-modified bentonite clay was carried out. Swelling pressure was evaluated by a consolidometer test. With the advanced nanotechnology instrumentation technique, particle size analysis, zeta potential, wettability, contact angle, infra-red spectroscopy, rheological properties, BET surface area, pH values, XRD, TGA, etc was carried out for treated and untreated soil, to understand the comparative behaviour of surface modification. It was found that by using Nano surfactant, liquid limit and shrinkage limit were reduced considerably. The increase in the quantity of surfactant increases the d-spacing. Thermal stability and particle size increase after surface treatment of bentonite clay. Soil reaches a visco-elastic state and BET surface area decreased after surface modification.

Effect of heating on the behaviour of bentonite in the presence of salt solution

Due to its high swelling tendency, layers of compacted bentonite is provided as a buffer materials at the nuclear waste repository site around the world. The development of the diffuse double layer (DDL) by the mineral montmorillonite, which is present in bentonite, provides the bentonite its swelling characteristics when permeated with water. The basic engineering properties, hydraulic conductivity and swelling behaviour of different bentonitehave been investigated by many of the researchers. However, when the bentonite is exposed to a higher temperature, it may undergo a transformation in its mineralogical composition and severely loses its tendency to develop the DDL. This in turn will impact the bentonite’s swelling and hydraulic characteristics. Therefore, it is essential to investigate the influence of temperature on the swelling and hydraulic characteristics of bentonite.
 Most of the earlier studies were mainly conducted on oven dried soil at room temperature in the presence of deionized (DI) water as the pore fluid. Considering that the an extremely large storage period and generation of high temperature caused by the decay of radionuclide’s, the bentonite’s functionality under complex thermal and chemical conditions must be ensured.
 Previous studies [1, 2, 3] have shown a reduction in the swelling and liquid limit with an increase in the temperature. Similarly, previous studies [4] have indicated a substantial impact of salt solution on swelling, hydraulic and consolidation tendency of bentonite.
 From the previous sinvestigatios it can be concluded that the temperature and salt have a definite impact on the behaviour of bentonite. However, no studies have been performed to investigate the collective influence of salt solution and temperature on the bentonite. Hence, the primary objective of this present study to investigate the combined impact of temperature on swelling and hydraulic behaviour of the bentonite.
 Materials and Methods
 Bentonite investigated in this research is in powdered form obtained from local source. Since an initial temperature of 2500C was observed in the Yuca mountain repository site [5], a temperature of 3000C was selected for study. Furthermore at higher temperature such as 5000C the montmorillonite undergoes a significant change in its swelling behaviour [6], the study was also performed at 5000C. Since most of the waste contains ions like Na+ and Ca2+, solutions of NaCl and CaCl2 were selected for this study.
 After pre-heating the bentonite at 300 and 5000C for 24 hours in a muffle furnace, various experiments were performed as per relevant ASTM standards.
 Results and Discussions
 The data in Table 1 compares the liquid limit, plastic limit and free swelling of pre-heated bentonites in the presence of 0 N, 0.1 N NaCl and 0.1 N CaCl2 solution. The data shows that the liquid limit, plastic limit and free swelling of bentonite decreases due to increase in the temperature. The data also shows that the heating has less effect on liquid limit, plastic limit and free swelling for the bentonite in the presence of NaCl and CaCl2 salt solution. The data also indicates that with the rise in the temperature from 3000C to 5000C, the salt has minimal impact on the behaviour of bentonite. By pre-heating the bentonite, the plasticity behaviour alters due to reduction of interlamellar water and the influence of the DDL becomes negligible. Therefore, the variation in the liquid limit with the salt was minimal for the bentonite pre-heated at 5000C. However, as the DDL is dominant for the bentonite at 250C, the variation in the liquid limit was higher due to a change in the salt.
 The plot in Fig. 1 indicates the influence of heating on the swelling potential and swelling pressure of bentonite in the presence 0.1 N of NaCl and CaCl2 solution. The plot also shows that the swelling potential and swelling pressure decreases with increase in the temperature and salt. However when permeated with the salt, the bentonite pre-heated at a higher temperature shows a neglible impact due to presence of salt on its swelling behaviour.
 Conclusions
 The study was perfomed to investigate the impact of pre-heating on the behaviour of bentonite in the presence of salt solution. The study concluded that the swelling and plasticity behaviour of bentonite decreases due to pre-heating at a higher temperature. The result also concluded that the bentonite pre-heated at a higher temperature undergoes a marginal change in its behaviour due to the exposure of salt solution.

Temperature Effects on Atterberg Limits

This study aims to investigate the effects of temperature on Atterberg limits of fine-grained soils with different mineralogies using fall cone tests. It is found in the literature that Atterberg limits are dependent on the clay mineralogy [1, 2] and are subjected to change upon an increase in temperature [3-5]. Measurements of liquid limit at different temperatures reveal sodium smectite is more sensitive to temperature than kaolinite. This observation is justified by relating the evolution of liquid limit to the initial changes of total specific surface areas associated with the physicochemical activity and inter-particle contacts [6]. Measurement of Atterberg limits using the conventional methods of Casagrande’s cup and threading is not very practical when the impact of temperature on these parameters is investigated. The trial and error associated with this method and the time they take may hinder a robust estimation of the liquid and plastic limit. Various studies have shown that Atterberg limits measured using Cone Penetration Test are less subjective and more consistent compared to traditional ways [7-9]. For these reasons, utilizing a Fall Cone Test apparatus and a temperature control unit facilitates the investigation of the impact of temperature on Atterberg limits. In this study, first, the liquid limits measured at room temperature by Fall Cone and Casagrande’s method are compared, and then Cone Penetration is utilized to investigate the evolution of liquid limit with temperature.
 Rhassoul Clay (29.4% Illite, 0.10% Kaolinite, 70.5% montmorillonite) and Illite Clay are considered in this study. The measured penetration values of the cone against moisture content at room temperature for these two clays are plotted in Figure 1. The liquid limit is the water content at which the cone penetrates 20mm into the soil in the cup [10]. Accordingly, Table 1 lists the determined liquid fall cone test and their deviation for the measured Atterberg limits using Casagrande’s cup. This comparison was performed to ensure that the difference between these two methods is not significant and the utilized device was accurate enough.
 To determine the Atterberg limits at higher temperatures (40 °C and 50 °C) and lower temperatures (10 °C), a temperature control unit is used to maintain the temperature of the soil sample during fall cone testing. For this purpose, first, the cup was filled with soil and then wrapped to avoid moisture migration in and out of the sample. The sample was then placed inside the temperature controller for an hour at the desired temperature. After one hour, the sample was swiftly unwrapped, and Cone Penetration test was performed. After the penetration a thermometer was used to measure the temperature at the center of the cup. This measurement showed that the alteration of temperature during the whole process is less than 1°C. Next, more water was added to the batch and then the same steps were followed until enough data points were obtained to estimate the liquid limit. The result of these tests allows for an assessment of temperature effects on Atterberg limits, which would be helpful in the understanding of the influence of temperature on different shear strength parameters of fine-grained soil with regards to their mineralogy.
 Table 2 lists the measured liquid limit values for Rhassoul Clay and Illite clay at different temperatures. The results suggest that the liquid limit of Illite is temperature independent. On the other hand, Rhassoul clay liquid limits was more sensitive to elevated temperatures and did not change with cooling. As mentioned earlier, the liquid limit is directly associated with clay mineralogy and the thermal alteration of soil characteristics [11, 12]. Therefore, the observed thermally-induced change in liquid limit should be discussed with respect to mineralogy. According to Table 1, the Illite liquid limit is temperature independent. Furthermore, Rhassoul clay comprises 70.5% montmorillonite minerals and 29.4% Illite. Providing this and the observed sensitivity of Rhassoul clay to temperature change can be attributed to the montmorillonite constituent. This argument can be further supported by testing more clays with different percentages of montmorillonite and illite.

Recent Advances in Antibacterial Metallic Species Supported on Montmorillonite Clay Mineral: A Review

This review provides information on the latest advances in inorganic materials with antimicrobial properties based on a metallic species immobilized on the clay mineral montmorillonite realized between the years 2015 and 2023. This class has shown many promising results compared to certain organic agents. Montmorillonite in natural and/or modified forms is a good platform for the storage and release of metallic species, and several researchers have worked on this mineral owing to its cation exchange capacity, low cost, biocompatibility, and local availability. The preparation methods and the properties such as the antibacterial, antifungal, and toxicological activities of this mineral are discussed. The main characteristics of this antibacterial class for the elimination of pathogenic bacteria were examined and the known weak points of its antimicrobial application are discussed, leading to suggestions for further research.

Properties of sepiolite clay soil as a natural material (Iran’s sources clay)

ABSTRACT Sepiolite is a fibrous clay mineral, which is mostly associated with a semi-arid to arid climate, with characteristics intermediate between kaolinite and montmorillonite minerals. An experimental study was conducted, with the goal of creating a substantial database of physical, microstructural, and geotechnical characteristics of sepiolite to develop its applications as a natural resource that is explored as the main deposit of Iran. It has been found that sepiolite soils were lightweight, porous, and cohesive with negligible settlement and swelling properties and almost high UCS values. Various analysis were performed to characterise the macroscopic behaviour (Atterberg limit, physical, and compressibility tests), microstructural, chemical, and mineralogical characterisations by chemical analysis, X-Ray diffraction, and Scanning Electron Microscopy. At first glance, sepiolite soils showed high liquid limits with medium to high plastic indices which can result in problems including creation of up and down movements in foundations. After mixing with silt and fine sand to decrease high liquid limit and optimum moisture amounts, sepiolite is suitable candidate for engineering applications (including clay liners, clay cores, etc.) due to its compressibility and strength characteristics. In conclusion, sepiolite soils are strongly recommended for geo-environmental structures due to their adsorption capacity, low permeability coefficient, and suitable strengths.