Carbon foam composites containing hollow microspheres, reinforced by carbon nanotubes (CNTs) and montmorillonite (MMT), have been developed as the thermal insulation and EMI shielding layer. The effects of additive amounts of CNTs/ MMT on microstructure and properties of the carbon foam composites were investigated. Results showed that carbon foam composites had hierarchical porous structure, with CNTs and MMT being relatively uniformly dispersed in the composites. The addition of multiscale additives improved the mechanical, electromagnetic shielding effectiveness and thermal insulation properties of carbon foam composites. The composites containing 0.2 wt.% CNTs and 5 wt.% MMT, showed outstanding compressive strength, up to 8.54 MPa, increased by 116% to pure carbon foam. Their electromagnetic shielding effectiveness was as high as 65 dB, increased by 75%. Due to the hierarchical porous structure and MMT’s heat barrier effect, carbon foam composites presented remarkable thermal insulation properties. The minimum thermal conductivity was 0.45 W·m−1·K−1 at 800 °C. Their exceptional thermal protection can also be evidenced by ablation resistance under flame at 1000 °C. Therefore, such multifunctional carbon-based composites are ideal for use in thermal protection.

Chitosan powder is synthesized by a deasetylation process of chitin, obtained from processing of dried shrimp shell powder. Subsequently, chitosan (CS) membranes filled by montmorillonite (MMT) particles and phosphotungstic acid are prepared, and characterized by FT-IR and SEM. The morphology, obtained by SEM for the composite membrane, showed that MMT filler is successfully incorporated and relatively well dispersed in the chitosan polymer matrix. Water and methanol uptake for the CS/MMT composite membranes decrease with increasing MMT loadings, but IEC value increases. In all prepared CS/ MMT composite membranes, the CS membrane filled by 5 wt% MMT particles exhibits the best proton conductivity, while that with 10 wt% MMT loading exhibits the lowest methanol permeability; these values are 2.67 mS·cm−1 and 3.40 × 10−7 cm2·s−1, respectively. The best membrane selectivity is shown in the CS/MMT10 composite membrane; this shows that 10 wt% filled MMT is the optimum loading to improve the performance of the chitosan composite membrane. These characteristics make the developed chitosan composite membranes a promising electrolyte for direct methanol fuel cell (DMFC) application.

This paper presents the characteristics of gentamicin-loaded into cetyl trimethyl ammonium intercalated montmorillonite (GtM/CTMA/Mt) as a hybrid composite for a slow-released antibacterial delivery systems. The work describes the successful immobilization of gentamicin into the interlayers of surfactant-modified montmorillonite. Physicochemical characterization of the material is carried out by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The kinetics of the gentamicin release is investigated by in vitro study and analyzed based on UV–Vis spectrometry. In addition, antibacterial study is performed towards Klebsiella pneumoniae Staphylococcus aureus, Escherichia coli, and Streptococcus pyogenes. The results show that the gentamicin loading into CTMA/ Mt increases the effectiveness of the antibacterial activity, as shown by the higher inhibition zone for all tested bacteria, compared to gentamicin as a positive control. The kinetics study suggests that the gentamicin release obeys the modified Korsmeyer–Peppas model. The physicochemical study and activity test demonstrate the feasibility of the GtM/CTMA/Mt for practical applications.

Purpose: The interaction of methylene blue (MB) with Na-saturated clay from Maghnia deposit in aqueous suspension was investigated using visible absorption spectroscopy. Methods: The effect of the optical properties of dyes in aqueous solutions and adsorbed onto Na-saturated clay was assessed in terms of the absorption bands maxima and the removal rate as a function of pH. Results: The adsorption of MB dye onto Na-saturated clay surface leads to the methacromatic effect in the absorption spectrum of the dye. Formation of MB dimers and higher agglomerates depended sensitively on the potential of the layer charge density. MB agglomerates occurred predominantly in the Na-saturated clay with high charge density, even with low charge density. The redistribution of MB molecules over the surface of Na-saturated clay of lower charge density (high acidic medium) leads to a reduction of the dye aggregation, accompanied by a bathochromic shift of the band maximum of MB dye to the longer wavelengths. Conclusion: The methachromatic effect was analyzed by the R=A(MB+)/A(MB+)n parameter, which decreases with the charge density, owing to the increase in the pH solution. To explain the relationship between the layer charge density and the adsorption, so- colled model 2-pKa of surface complexation (SCM) was developed.

Se sorption onto Ca-type montmorillonite purified from Bentonil-WRK—a new research bentonite introduced by Korea Atomic Energy Research Institute—was examined under ambient conditions (pH 4−9, pe 7−9, I = 0.01 M CaCl2, and T = 25°C). Se(IV) was identified as the oxidation state responsible for weak sorption (Kd < 22 L∙kg−1) by forming surface complexes with edge functional groups of the montmorillonite. Thermodynamic modeling, considering reaction mechanisms of outer-sphere complexation (≡AlOH2 + + HSeO3 − ⇌ ≡AlOH3SeO3, log K = 0.50 ± 0.21), inner-sphere complexation (2≡AlOH + H2SeO3(aq) ⇌ (≡Al)2SeO3 + 2H2O(l), log K = 7.89 ± 0.51), and Ca2+-involved ternary complexation (≡AlOH + Ca2+ + SeO3 2− ⇌ ≡AlOHCaSeO3, log K = 7.69 ± 0.28) between selenite and aluminol sites of montmorillonite, acceptably reproduced the batch sorption data. Outer- and inner-sphere complexes are predominant Se(IV) forms sorbed in acidic (pH ≈ 4) and near-acidic (pH ≈ 6) regions, respectively, whereas ternary complexation accounts for Se(IV) sorption at neutral pHs under the ambient conditions. The experimental and modeling data generally extend a material-specific sorption database of Bentonil-WRK, which is essential for assessing its radionuclide retention performance as a buffer candidate of deep geological disposal system for high-level radioactive waste.

Thermodynamic sorption modeling can enhance confidence in assessing and demonstrating the radionuclide sorption phenomena onto various mineral adsorbents. In this work, Ca-montmorillonite was successfully purified from Bentonil-WRK bentonite by performing the sequential physical and chemical treatments, and its geochemical properties were characterized using X-ray diffraction, Brunauer-Emmett-Teller analysis, cesium-saturation method, and controlled continuous acidbase titration. Further, batch experiments were conducted to evaluate the adsorption properties of Cs(I) and Sr(II) onto the homoionic Ca-montmorillonite under ambient conditions, and the diffuse double layer model-based inverse analysis of sorption data was performed to establish the relevant surface reaction models and obtain corresponding thermodynamic constants. Two types of surface reactions were identified as responsible for the sorption of Cs(I) and Sr(II) onto Ca-montmorillonite: cation exchange at interlayer site and complexation with edge silanol functionality. The thermodynamic sorption modeling provides acceptable representations of the experimental data, and the species distributions calculated using the resulting reaction constants accounts for the predominance of cation exchange mechanism of Cs(I) and Sr(II) under the ambient aqueous conditions. The surface complexation of cationic fission products with silanol group slightly facilitates their sorption at pH > 8.

Bentonite, primarily composed of montmorillonite, plays a crucial role as one of the engineering barrier materials in a deep geological repository (DGR). The advantageous properties of montmorillonite, such as its swelling capacity, low permeability, and low thermal conductivity, make it a key component as a buffer material for isolating high-level radioactive waste from the surrounding natural environment. It has been known that the stability of montmorillonite is influenced by a wide range of pressure-temperature-composition (P-T-X) conditions relevant to the DGR environment. When considering potential geological events, of notable concerns are its interactions with groundwater or seawater at elevated temperatures, leading to safety hazards within the system. In this study, therefore, we investigated the hydration and dehydration reactions of Ca-montmorillonite with saline fluids such as NaCl and KCl solutions at elevated pressures and temperatures by conducting in-situ X-ray diffraction experiments using both a capillary sample heating cell and a resistive-heated diamond anvil cell. As a result, we observed different hydration states of montmorillonite depending on the chemical composition of fluids, i.e., tri-hydrated layers in NaCl and bi-hydrated layers in KCl solutions, respectively. Furthermore, we identified that montmorillonite undergoes distinct stepwise dehydration with increasing temperature, and the dehydration temperature of montmorillonite significantly increases with increasing water pressure. Consequently, this study would provide insights into the stability of hydrated montmorillonite in a seawater-dominated fluid environment and its implications for the long-term safety of the disposal system.

Montmorillonite, a versatile clay mineral with a wide range of industrial applications, is often found in natural deposits with impurities that limit its effectiveness. This study investigates the use of column froth flotation as an innovative technique to improve the purity of montmorillonite by selectively removing impurities without affecting its essential properties. Column froth flotation, a well-established mineral separation method, is adapted to address the specific challenges associated with enhancing montmorillonite purity. The process involves conditioning raw montmorillonite with carefully chosen reagents to selectively separate impurities, including quartz, feldspar, and other minerals commonly found alongside montmorillonite in natural deposits. Experimental results confirm the effectiveness of column froth flotation in significantly enhancing the purity of montmorillonite. This method allows for efficient impurity removal while preserving the essential properties of montmorillonite, making it suitable for various industrial applications. The study also explores the optimal conditions and reagent choices to maximize the purification process. In conclusion, column froth flotation offers a promising avenue for enhancing montmorillonite purity without compromising its fundamental properties. This study provides valuable insights into optimizing the process for large-scale industrial applications, facilitating the development of highquality montmorillonite products tailored to specific industrial needs.

The permanent disposal of discharged spent nuclear fuel (SNF) and contaminated radioactive waste generated from the subsequent chemical treatments of SNF has become a serious pending issue in many countries that operate the nuclear power plants. Among the diverse engineering solutions proposed for the disposal of high-level radioactive waste (HLW), deep geological disposal (DGD) has been considered as the most proven and safe option to prevent any significant release of radionuclides into the biosphere and to predictably ensure the long-term performance of disposal system. The DGD system consists of multiple structural components; the bentonite clay-based buffer and tunnel backfills are designed to perform the primary hydrogeochemical functions of 1) inhibiting the ingress of groundwater and reactive substances that could compromise the integrity of canister and 2) retarding the migration of released radionuclides into biosphere by providing the sufficient chemisorption sites. Montmorillonite, which is a 2:1 phyllosilicate mineral belonging to smectite group, constitutes the majority of bentonite, and it mainly predominate the swelling and chemisorption capacities of the clay material. Thus, it is essentially required to thoroughly understand the chemical interactions of major radionuclides and other important substances with montmorillonite in advance to accurately evaluate the long-term retention performance of engineered barriers and to reduce the uncertainties in the safety assessment of a deep geological repository (DGR) ultimately. Thus far, sorption of dissolved species onto mineral adsorbents has been generally described and quantified using the simple sorption-desorption distribution coefficient (Kd) concept; since any specific reaction mechanisms are not considered and reflected in the Kd concept, an empirical Kd value is intrinsically dependent on the aqueous conditions under which it was measured. In this framework, substantial scientific efforts have been made to develop a robust basis for geochemically parametrizing the sorption phenomena more reliably, and the application of thermodynamic sorption modeling (TSM), which is based on the chemical principle of mass action laws, has been studied with the aim of improving overall confidence in the description of radionuclide migration under a wide range of aquatic conditions. The disposal performance demonstration R&D division of KAERI introduced a new reference Ca-bentonite clay called Bentonil-WRK (Clariant Korea) for HLW disposal research in 2021 as the domestic Ca-bentonite sources have being depleted. We successfully separated and purified Ca-montmorillonite from the Bentonil-WRK clay, and its geochemical characteristics were meticulously studied by means of XRD, BET, CEC, FT-IR analyses and controlled acid-base titration. In this work, chemical sorption behaviors of aqueous iodide and benzoate, which are a major fission product in HLW and a model ligand of complex natural organic matters present in the deep geological environment, onto the purified Camontmorillonite were assessed under ambient conditions of S/L = 5 g/L, I = 0.01 M CaCl2, pH = 4- 9, pCO2 = 10-3.4 atm, and T = 25°C. Further, their unique adsorption envelopes and corresponding thermodynamic reaction constants refined from the diffuse double layer model (DDLM)-based inverse modeling of experimental sorption data were discussed.

코발트는 합금산업에서 발생되는 산업 폐기물과 산성광산배수로 자연에 유입될 수 있으며 또한 고준위 방사성 폐기물을 구성하는 방사성 핵종(60Co)기도 하다. 스멕타이트는 이들을 흡착 격리하는데 유용하게 사용될 수 있는 광물이다. 본 연구에서는 기존에 특성이 잘 알려진 스멕타이트 중 The Clay Mineral Society (CMS)의 source clay인 Cheto-type montmorillonite (Cheto-MM)를 사용하여 가열에 의한 탈수 전후 광물의 층간수 존재 여 부에 따른 흡착 자리가 코발트 흡착에 미치는 영향을 평가하고, 흡착 속도 및 등온흡착식 모델을 적용하여 Cheto- MM의 코발트에 대한 흡착 기작을 연구하였다. 본 연구 결과 탈수 및 이에 따른 층간 수축에 의해 흡착 특성이 달 라지는 것을 확인할 수 있었으며, 코발트는 Cheto-MM의 층 모서리 자리에서의 흡착이 약 38%, 층간 내부에서의 흡착이 약 62%를 차지하는 것으로 확인되었고 Cheto-MM의 코발트 흡착은 층간 내부에 의한 영향이 큰 것으로 판 단된다. 이러한 흡착에 있어 흡착 속도 모델을 적용한 결과, Cheto-MM의 코발트 흡착 속도는 pseudo-second-order 모델로 설명되며 농도에 따른 흡착은 Langmuir 등온흡착 모델로 가장 잘 설명되었다. 본 연구는 몬모릴로나이트 의 흡착 자리에 따른 코발트의 흡착 양상에 대한 기본지식을 제공하고, 추후 고준위 방사성 폐기물 처분장에서의 스멕타이트의 흡착 거동을 예측하는데 유용하게 사용될 수 있을 것으로 생각된다.

In the deep geological repository, a considerable quantity of cementitious materials is generally used for structural stability of subcomponents such as grout and concrete plug of disposition tunnel. Strong alkaline leachates (pH>13) are produced after cement is dissolved by groundwater inflow from bedrock. When the leachates are transported to bentonite porewater (e.g. buffer and backfill) and thereby water exchange occurs, the physical properties of bentonite such as swelling capacity and hydraulic conductivity are changed, which eventually affects the safety function and long-term stability of engineered barrier system (EBS). Thus, in this paper, we reviewed the performance assessment methodology for cement-bentonite interaction in the operating license application for the Finnish deep geological repository, and suggested what to prepare for the analysis on the domestic disposal facility. In Finland, thermal-hydraulic-chemical analysis for dissolution of montmorillonite by alkaline leachates resulting from cement degradation during the saturation of bentonite was carried out using PRECIP code. From this analysis, it was confirmed that effect on pH was considered to be more significant than that on temperature and bentonite saturation. As a result of this analysis, it was predicted that all primary minerals (including montmorillonite, quartz, and calcite) were dissolved and some secondary minerals (e.g. chalcedony and celadonite) was precipitated by alkaline cement leachates transported to the bentonite. In addition, it was shown that silica was preferentially released while the montmorillonite was dissolved, thus cementation of the bentonite was occurred. Through this phenomenon, the swelling capacity of bentonite is reduced and the hydraulic conductivity of bentonite is increased, which have a significant impact on the performance of the buffer and backfill. Considering this, study on spreading of alkaline leachates, which is a condition for dissolution of montmorillonite, is necessary for the performance assessment of the domestic deep geological repository. However, this requires the site-specific data for the following in the disposal site: (a) distribution in fractured bedrock and pore structure (e.g. porosity, pore size distribution and pore morphology) in the bedrock, (b) hydraulic gradient and salinity concentration of groundwater, and (c) flux and velocity of groundwater. Results of this study is considered to be directly utilized to the conceptual design and performance assessment of the deep geological repository in Korea, provided that additional data on microbiological properties of groundwater are obtained for the site selected.

The safe disposal of high-level radioactive waste (HLW), including the discharged spent nuclear fuel (SNF) and contaminated by-products produced from relevant chemical treatments, has become a serious pending problem for numerous countries that operate the nuclear power plants. The deep geological disposal (DGD) has thus far been considered the most proven and viable solution for isolation of the HLW and preventing any significant release of radionuclides into the biosphere. The DGD system consists of the multiple engineered and natural barrier components. Among them, the montmorillonite-based buffer and tunnel backfills are designed to perform the two major geochemical functions: 1) preventing the ingress of groundwater and any chemicals that compromise the safety of waste canister and 2) retarding the migration of released radionuclides by providing sufficient chemisorption sites. Therefore, it is essential to investigate the sorption mechanism of radionuclides onto montmorillonite and develop a thermodynamic reaction model in advance in order to accurately predict the long-term performance of engineered barriers and to reduce the uncertainties in the safety assessment of a deep geological repository (DGR) ultimately; thus far, sorption of chemical species onto mineral adsorbents has been widely described based on the concept of sorption-desorption distribution coefficient (Kd), the value of which is intrinsically conditional, and active scientific efforts have been made to develop robust thermodynamic sorption models which offer the potential to improve confidence in demonstration of radionuclide migration under a wide range of geochemical conditions. The natural montmorillonites are generally classified into Na-type or Ca-type according to its exchangeable cation, and the Ca-montmorillonite containing clays are being considered as candidate materials for the engineered barriers of DGR in several countries; they generally have advantages of higher thermal conductivity and lower price than the Na-montmorillonite based clays, but their sorption capacities are still comparable. In this framework, we aimed to investigate the chemical interactions of Ca-montmorillonite with selenite [Se(IV)], which is a major oxyanionic species in terms of HLW disposal, and develop a reliable thermodynamic sorption model (TSM). The present work summarizes the characterization of Ca-montmorillonite separated from the newly adopted reference bentonite (Bentonil-WRK) by means of XRD, BET, FTIR, CEC measurement, and acid-base titration. Further, its sorption behaviors with aqueous selenite species under aqueous conditions of S/L = 5 g/L, I = 0.01-0.1 m CaCl2, pH = 4.5-8.5, pCO2 = 10-3.5 atm, and T = 25°C were examined, and the resulting thermodynamic data are discussed as well.

Bentonite is a potential buffer material of multi-barrier systems in high-level radioactive wastes repository. Montmorillonite, the main constituent of the bentonite, is 2:1 type aluminosilicate clay mineral with high swelling capacity and low permeability. Montmorillonite alteration under alkaline and saline conditions may affect the physico-chemical properties of the bentonite buffer. In this study, montmorillonite alteration by interaction with synthetic alkaline and saline solution and its retention capacity for cesium and iodide were investigated. The experiments were performed in three different batches (Milli-Q water, alkaline water, and saline water) doped with cesium and iodide for 7 days. Alteration characteristics and nuclide retention capacity of original- and reacted bentonite was analyzed by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), Nuclear Magnetic Resonance (NMR) and Cation Exchange Capacity (CEC) analysis. From the results, cesium retention occurred differently depending on the presence of competing ions such as K, Na, and Mg ions in synthetic solutions, while iodide was negligibly removed by bentonite. Montmorillonite alteration mainly occurred as cation exchange and zeolite minerals such as merlinoite and mordenite were new-formed during alkaline alteration of the montmorillonite. CEC value of reacted bentonite increased by formation of the zeolite minerals under alkaline conditions.

Bentonite, which mostly consists of montmorillonite, is considered as a suitable buffer material for disposal of high-level radioactive wastes in deep geological repository due to its high swelling capacity, low permeability, and strong retention capacity of radionuclide migration. Alkaline and saline solutions originated from degradation of cementitious material and seawater intrusion, respectively, may cause the changes in mineralogical and chemical properties of montmorillonite with various processes such as cation exchange within the interlayer, dissolution of montmorillonite, and precipitation of second minerals. In this study, montmorillonite alteration under alkaline and saline environments and its influences on retention of cesium and iodide by bentonite buffer were investigated. The reactions of bentonite (Bentonil-WRK) with alkaline solutions (0.1 M KOH and NaOH) and simulated saline solution were performed for 7 days in batch experiments at 25°C. After the experiments, reacted bentonite samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Short Wavelength Infrared (SWIR) spectrometry. The concentrations of cesium and iodide dissolved in the solutions were analyzed using an inductively coupled plasma mass spectrometer (ICP–MS). The XRD patterns showed significant decrease in the interlayer space of montmorillonite after the reaction with alkaline solution due to cation exchange and change in hydration status at the interlayer. The retention of cesium and iodide in alkaline and saline solutions were affected by montmorillonite alteration and ion competition. Therefore, the montmorillonite alteration affecting the nuclide retention capacity and long-term stability of bentonite buffer should be considered in the safety assessment of long-term geological disposal performance.

Montmorillonite plays a key role in engineered barrier systems in the high-level radioactive waste repository because of its large sorption capacity and high swelling pressure. However, the sorption capacity of montmorillonite can be largely varied dependent on the surrounding environments. This study conducted the batch simulation for U(VI) sorption on Na-montmorillonite by utilizing the cation exchange and surface complexation coupled (2SP-NE-SC/CE) model and evaluated the effects of physicochemical properties (i.e., pH, temperature, competing cations, U(VI) concentration, and carbonate species) on U(VI) sorption. The simulation demonstrated that the U(VI) sorption was affected by physicochemical properties: the pH and temperature relate to aqueous U(VI) speciation, the competing cations relate to the cation exchange process and selectivity, the U(VI) concentration relates to saturation at sorption sites. For example, the Kd (L kg−1) of Na-montmorillonite represented the largest values of 2.7×105 L kg−1 at neutral pH condition and had significantly decreased at acidic pH<3, showing non-linear and diverse U(VI) sorption at the ranged pH from 2 to 11. Additionally, the U(VI) sorption on montmorillonite significantly decreased in presence of carbonate species. The U(VI) sorption for long-term in actual porewater chemistry and temperature of high-level radioactive waste repository represented that the sorption capacity of Na-montmorillonite was affected by various external properties such as concentration of competing cation, temperature, pH, and carbonate species. These results indicate that geochemical sorption capacity of bentonite should be evaluated by considering both geological and aquifer environments in the high-level radioactive waste repository.

The sorption behavior of Se(IV) on montmorillonite clay, a promising buffer and backfill material, was investigated in the presence of aquatic fulvic acid. Selenium-79 is one of the major radioactive nuclides which are long-lived and highly mobile in subsurface environments. Moreover, it is highly toxic even in small amounts, so the selenium quantity in soil and groundwater should be assessed. Although natural organic matters such as humic and fulvic acids are present in the environment, the influence of natural organic matters on Se(IV) migration has not yet been extensively studied. The batch sorption experiments were performed under oxic conditions. Suwannee River III standard aquatic fulvic acid (International Humic Substances Society) was used to build an organicrich environment. The N2 – BET surface area of the montmorillonite (Clay Minerals Society) was 97 ± 5 m2·g−1. The montmorillonite suspensions with/without fulvic acid were equilibrated with air before adding Na2SeO3. The solid-to-liquid ratio was 5 g·L−1, the ionic medium was 0.1 M NaCl, fulvic acid concentration was 50 mg·L−1, and the final pH was 3. The horizontal vial roller was used to prevent the clay from sinking. After 7 days of sorption at room temperature, the suspensions were centrifuged at 10,600 g for 15 min and filtered through 0.2 μm PTFE filters. The colloidal fulvic selenide and free Se(IV) concentrations were entirely measured by inductively coupled plasma–mass spectrometry (ICP-MS). The sorption results were fitted with Langmuir and Freundlich models. At concentrations lower than 20 μM, the distribution coefficients (Kd) were 50 ± 9 L·kg−1 without fulvic acid, and 36 ± 5 L·kg−1 with 50 mg·L−1 fulvic acid. For the concentrations between 20 and 100 μM, the Kd values without and with fulvic acid were 16 ± 7 L·kg−1 and 10 ± 1 L·kg−1, respectively. As a result, it turned out that fulvic acid interferes with the sorption of Se(IV) on montmorillonite in competition with the selenite anion. This indicates that such organic matter may facilitate the migration of selenium in deep geological groundwaters.

Bentonite is considered as buffer of engineered barrier for retardation of radionuclide migration. Bentonite has low permeability, high swelling and high sorption capacity for radioactive nuclides. Properties have been widely investigated under various geochemical conditions simulating deep geological environments. The chemical stability of bentonite is an important factor in evaluating the long-term stability of the bentonite buffer. However, the presence of impurities in bentonite clays can reduce the retention capacity for retardation of radionuclide migration value of bentonite. Therefore, the bentonite purification is necessary. In the present study, grade improvement of montmorillonite was conducted using ultrasonic and froth flotation methods. As a result of confirming the grade of montmorillonite according to the optimal ultrasonic intensity for ultrasonic irradiation is 1.0 kHz of bentonite in Gyeongju (KJ-II) increased from 60% to 78%. In case of froth flotation method using PSS (0.1 mM) as a reagent, the grade of montmorillonite increased up to 90%.