• Title, Summary, Keyword: 벤토나이트

Search Result 387, Processing Time 0.048 seconds

An Experimental Study on the Erosion of a Compacted Calcium Bentonite Block (압축된 칼슘벤토나이트 블록의 침식에 대한 실험적 연구)

  • Baik Min-Hoon;Cho Won-Jin
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.3 no.4
    • /
    • pp.341-348
    • /
    • 2005
  • Bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste because of its low permeability, high sorption capacity, self sealing characteristics, and durability in nature. In this study, the potential for separation of bentonite particles caused by the groundwater erosion was studied experimentally for a Korean Ca-bentonite under the relevant repository conditions. Results showed that bentonite particles can be generated at the bentonite/granite interface and mobilized by the water flow although the intrusion of bentonite into fracture by swelling pressure was observed to be small. Different processes of mobilization of theses colloids from the compacted bentonite block have been identified in this study. The concentration of particles eluted in water was increased as the flow rate increased. Thus the result reveals that the erosion of the bentonite surface due to the groundwater flow together with intrusion processes is the main mechanism that can mobilize bentonite colloids in the fracture of the granite.

  • PDF

A study on the Evaluation of Permeability and Structure for Calcium Bentonite-Sand Mixtures (칼슘 벤토나이트-모래 혼합차수재의 투수 및 구조 특성에 관한 연구)

  • Yun, Seong Yeol;An, Hyeon Kyu;Oh, Minah;Lee, Jai-Young
    • Journal of the Korean Geosynthetics Society
    • /
    • v.18 no.2
    • /
    • pp.1-10
    • /
    • 2019
  • This study was intended to evaluate the water permeability and structure for calcium bentonite-sand mixtures to utilize calcium bentonite as a liner. This study conducted physico-chemical properties tests, compaction tests, permeability test and Scanning Electron Microscopy analysis (SEM) analysis. It was found the higher the ratio of calcium bentonite, the lower the dry density with coefficient of permeability, and the higher the optimum moisture content. In particular, SEM analysis was found the higher the ratio of calcium bentonite, the higher the area of the montmorillonite particles. In conclusion, the optimum coefficient of permeability that finds the landfill liner condition (must be less than $1{\times}10^{-7}cm/sec$) was obtained when the ratio of calcium bentonite was 40% or higher. These findings may improve the understanding of the calcium bentonite as a liner. Calcium bentonite shows a similar permeability to sodium bentonite 7% when mixed at 40% or more. Therefore, it is considered that calcium bentonite can be utilized as a liner.

Factors Affecting the Electrical Properties of Bentonite Slurry (벤토나이트 슬러리의 전기적 특성에 대한 영향인자 분석)

  • Yoo, Dong-Ju;Oh, Myoung-Hak;Kim, Yong-Sung;Park, Jun-Boum
    • Journal of the Korean Geotechnical Society
    • /
    • v.22 no.10
    • /
    • pp.21-32
    • /
    • 2006
  • Factors affecting the electrical properties of bentonite slurry were identified and electric conduction mechanism in slurry was examined. Electrical conductivity of bentonite and soil-bentonite slurry linearly increases with the bentonite content. Test result indicated that the change In electrical conductivity of slurry was mainly caused by dissolved cations from bentonite particles. The relationship between electrical conductivity and bentonite content was affected by the initial electrical conductivity of slurry solution and fine content in soil-bentonite mixture. Such influences were evaluated and the calibrated relationships were suggested. Based on the suggested relationship between electrical conductivity and bentonite content, bentonite content in various bentonite and soil-bentonite slurry can be quantitatively evaluated by using electrical conductivity measurement method.

A Correlation to Predict the Thermal Conductivity of Buffer and Backfill Material for a High-Level Waste Repository (고준위폐기물처분장 완충재 및 뒷채움재의 열전도도 예측을 위한 관계식)

  • Cho, Won-Jin;Lee, Jae-Owan;Kwon, Sang-Ki
    • Tunnel and Underground Space
    • /
    • v.20 no.4
    • /
    • pp.284-291
    • /
    • 2010
  • In the present design concept of a high-level waste repository, the bentonite and bentonite-sand mixture are considered as the buffer and backfill material. For the Kyungju bentonite which is a candidate material, the thermal conductivities of compacted bentonite and bentonite-sand mixture were measured. A correlation has been proposed to predict the thermal conductivity of the Kyungju bentonite and the bentonite-sand mixture as a function of the dry density, the water content and the sand fraction. The proposed correlation can predict the thermal conductivity with a difference less than 10% under the experimental conditions.

Mineralogical Characteristics and Genetic Environment of Zeolitic Bentonite in Yeongil Area (영일 지역 제올라이트질 벤토나이트의 광물특성 및 생성환경)

  • 노진환;고상모
    • Journal of the Mineralogical Society of Korea
    • /
    • v.17 no.2
    • /
    • pp.135-145
    • /
    • 2004
  • A zeolitic bentonite, which exhibits whitish appearance and contains considerable amounts (nearly 〉 5%) of zeolites, frequently occurs as thin beds less than 1 m in Yeongil area. The bentonites are mostly found in closely association with zeolite beds in the Nuldaeri Tuff and Coal-bearing formations of the Janggi Croup. A discordant occurrence of the bentonite against the bedding plane is also locally found. Montmorillonite, the major mineral constituent of the bentonite, is mostly associated with clinoptilolite as a zeolite. However, instead of clinoptilolite, mordenite is sometimes included in the case of more silicic bentonite, and heulandite in the less silicic one. It is characteristic that the mordenite is accompanied by lots of opal-CT in the silicic bentonite. SEM observations characteristically indicate that these authigenic phases, especially the montmorillonite and zeolite, nearly coexist as mixtures not forming a fine-scale zoning. The zeolitic bentonite seems to be formed in the comparatively silicic pore fluid at the alkaline condition accompanying pH fluctuation Compared to the zeolite-free normal bentonite, the zeolitic types exhibit somewhat higher REE abundance. These chemical characteristics, together with modes of occurrences and authigenic mineral associations, may suggest that the zeolitic bentonite is not merely diagenetic products and a possible hydrothermal alteration could not be excluded in the bentonite genesis.

Anion Adsorption Properties of Organobentonites Modified by Cationic Polymers (양이온 폴리머를 이용한 유기벤토나이트의 음이온 흡착특성)

  • 윤지해;황진연;이효민;고상모;유장한
    • Journal of the Mineralogical Society of Korea
    • /
    • v.17 no.2
    • /
    • pp.147-155
    • /
    • 2004
  • Anion adsorption properties of organobentonites modified by two cationic polymers, hexadecyltrimmethylammonium (HDTMA) and cetylpyridinum (CP), were investigated. The organobentonites showed the significant expansion of basal spacing to 42.0 $\AA$ at room temperature. The adsorption experiments were conducted for the 0.2 g of organobentonites with 40 mL solutions of various concentrations of anions such as nitrate, sulfate and phosphate. As a result, the organobentonites showed excellent adsorption capacities for those anions whereas untreated bentonite showed very low adsorption capacity. Adsorption rate of HDTMA-bentonite was about 90% for 100 mg/L solutions of nitrate and phosphate, and that of CP-bentonite was 97% for 100 mg/L solution of nitrate. Adsorption behaviors were slightly different for the different organobentonites and anions. Both organobentonites showed relatively higher adsorption rate for nitrate and phosphate than sulfate. Therefore, these organobentonites showing high anion adsorption capacities can be used far the removal of deleterious anions in the treatment of environmental pollution.

Penetration of Compacted Bentonite into the Discontinuity in the Excavation Damaged Zone of Deposition Hole in the Geological Repository (심층처분장 처분공 주변 굴착손상영역에 존재하는 불연속면으로의 압축 벤토나이트 침투)

  • Lee, Changsoo;Cho, Won-Jin;Kim, Jin-Seop;Kim, Geon-Young
    • Tunnel and Underground Space
    • /
    • v.30 no.3
    • /
    • pp.193-213
    • /
    • 2020
  • A mathematical model to simulate more realistically the penetration of compacted bentonite buffer installed in the deposition hole into the discontinuity in the excavation damaged zone formed at the inner wall of the deposition hole in the geological repository for spent fuel is developed. In this model, the penetration of compacted bentonite is assumed to be the flow of Bingham fluid through the parallel planar rock fracture. The penetration of compacted bentonite is analyzed using the developed model. The results show that the maximum penetration depth of compacted bentonite into the rock fracture is proportioned to the swelling pressure of saturated compacted bentonite and the aperture of rock fracture. However, it is in inverse proportion to the yield strength of compacted bentonite. The viscosity of compacted bentonite dominates the penetration rate of compacted bentonite, but has no influence to the maximum penetration depth.

Study of Iodide Adsorption on Organobentonite using X-ray Absorption Spectroscopy (X-선 흡수분광기를 이용한 유기벤토나이트의 요오드 흡착연구)

  • Yoon, Ji-Hae;Ha, Ju-Young;Hwang, Jin-Yeon;Hwang, Byoung-Hoon;Gordon E. Brown, Jr.
    • Journal of the Mineralogical Society of Korea
    • /
    • v.22 no.1
    • /
    • pp.23-34
    • /
    • 2009
  • The adsorption of iodide on untreated bentonite and bentonites modified with organic cation (i.e., hexadecylpyridinium chloride monohydrate ($HDP^+$)) was investigated, and the organobentonites were characterized using uptake measurements, ${\mu}$-XRD, and electrophoretic mobilities measurement. Uptake measurements indicate that bentonite has a high affinity for $HDP^+$. Our ${\mu}$-XRD study indicates that organobentonites significantly expanded in basal spacing and organic cations were substantially intercalated into the interlayer spaces of bentonite. The electrophoretic mobility indicates that organobentonite tht is modified with organic cations in excess of the CEC of bentonite is completely different from untreated bentonite in the surface charge distribution. We found significant differences in adsorption capacities of iodide depending on the bentonite properties as follows: iodide adsorption capacities were 439 mmol/kg for the bentonite modified with $HDP^+$ at an equivalent amount corresponding to 200% of the CEC of bentonite whereas no adsorption of iodide was observed for the untreated bentonite. The molecular environments of iodine adsorbed on organobentonites were further studied using I K-edge and $L_{III}$-edge x-ray absorption spectroscopy (XAS). The X-ray absorption near-edge structure (XANES) of iodine spectra from organobentonites was similar to that of KI reference solution. Linear combination fitting of EXAFS data suggests the fraction of iodine reacted with the organic compound increased with increasing loading of the organic compound on organobentonites. In this study, we observed significant differences in the adsorption environments of iodide depending on the modified property of bentonite and suggest that an organobentonite has potential as reactive barrier material around a nuclear waste repository containing anionic radioactive iodide.

Effects of the Water Quality on the Dispersion Properties of Bentonites Used for Drilling Fluid (시추이수용 벤토나이트의 분산 특성에 미치는 수질의 영향)

  • Akther, Shamima;Hwang, Jin-Yeon;Lee, Hyo-Min
    • Journal of the Mineralogical Society of Korea
    • /
    • v.20 no.1
    • /
    • pp.21-33
    • /
    • 2007
  • The dispersion/flocculation behavior of bentonite is a major concern in performance of drilling fluid. We studied the dispersion/flocculation characteristics of three commercial bentonites [two CMC (carboxymethyl cellulose) treated and one untreated] in waters of different pHs and salt concentrations. We also examined changes in the viscosity of bentonite suspensions in such waters as a major rheological property of drilling fluid. The dispersion/flocculation behaviors of bentonites were measured by two methods: colorimetric and light scattering method. Light scattering method allows estimating the floc diameter and flocculation rate. The dispersion and flocculation behaviors were diverse with the different bentonites and water qualities. In distilled water, all the bentonites were well dispersed up to first 10 minutes. After that, the CMC-bearing bentonites were flocculated. In salt waters, all the samples were flocculated and the flocculation rate is varied with salt concentration and polymer content. The volume of settled flocs decreased with increasing salt concentration. The flocculation rate and floc diameter increased with decreasing pH of solutions, whereas the volume of settled flocs increased with increasing pH of solutions. The bentonites of fast flocculation behavior had low viscosity. The results of the present study will be helpful in applying bentonites to drilling fluids in diverse environments.

Thermal Conductivity of Compacted Bentonite and Bentonite-Sand Mixture (압축 벤토나이트 및 벤토나이트-모래 혼합물의 열전도도)

  • Cho, Won-Jin;Lee, Jae-Owan;Kwon, Sang-Ki
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.6 no.2
    • /
    • pp.101-109
    • /
    • 2008
  • For the Kyungju bentonite which is considered as a candidate material for the buffer and backfill in the high-level waste repository, the thermal conductivities of compacted bentonite and a bentonite-sand mixture were measured. The thermal conductivities of the compacted bentonites with a dry density of 1.2 to $1.8\;Mg/m^3$ and the bentonite-sand mixture with a dry density of 1.6 and $1.8\;Mg/m^3$ were measured within the gravimetric water content range of 10wt% to 20wt% and the sand fraction range of 10 to 30wt%. The thermal conductivity of compacted bentonite and a bentonite-sand mixture increases with increasing dry density and sand weight fraction in the case of constant water weight fraction, and increases with increasing water weight fraction and sand weight fraction in the case of constant dry density. The empirical correlations to describe the thermal conductivity of compacted bentonite and a bentonite-sand mixture as a function of water fraction at each dry density were suggested. These correlations can predict the thermal conductivities of bentonite and a bentonite-sand mixture with a difference below 10%.

  • PDF