• Title, Summary, Keyword: Bentonite

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Risk Evaluation of Monopotassium Phosphate (MKP) and Bentonite Application via the Mobility Reduction of Soil TNT and Heavy Metals (제일인산칼륨과 벤토나이트 처리를 통한 토양 내 TNT와 중금속 이동성 및 인체위해도 저감 기술)

  • Jung, Jae-Woong;Yu, Gihyeon;Nam, Kyoungphile
    • Journal of Soil and Groundwater Environment
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    • v.20 no.6
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    • pp.28-36
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    • 2015
  • Simultaneous mobility reduction of explosives and heavy metals in an operational range by monopotassium phosphate (MKP) and bentonite spreading technology was investigated. Potassium ion and phosphate ion in MKP act as explosives sorption enhancer and insoluble heavy metal phosphate formation, respectively, while bentonite acts as the explosives adsorbent. Then, the decrease in surface water concentration of the pollutants and resulting risk reduction for local residents of the operational range, by MKP/bentonite application was estimated. Under untreated scenario, the noncancer hazard index (HI) exceeded unity on February, July and August, mainly due to 2,4,6-trinitrotoluene (TNT); however, MKP/bentonite treatment was expected to lower the noncancer hazard index by decreasing the surface water concentration of explosives and heavy metals (especially TNT). For example, on July, estimated surface water concentration and HI of TNT were 0.01 mg/L and 1.1, respectively, meanwhile the sorption coefficient of TNT was 3.9 mg1−nkg−1Ln. However, by MKP/bentonite treatment, the TNT sorption coefficient increased to 113.8 mg1−nkg−1Ln and the surface water concentration and HI decreased to about 0.002 mg/L and 0.2, respectively. Based on the result, it can be concluded that MKP/bentonite spreading is a benign technology that can mitigate the risk posed by the pollutants migration from operational ranges.

Comparison of Some Physicochemical Properties and Adsorption of Organic Cations between Ca- and Na-bentonites (Ca-형 및 Na-형 벤토나이트의 제반 물성 및 유기양이온 흡착비교)

  • 고상모;김자영
    • Journal of the Mineralogical Society of Korea
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    • v.15 no.4
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    • pp.243-257
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    • 2002
  • Ca-type and Na-type bentonites show the great difference of some physicochemical properties. Na exchanged bentonite is mainly used for the foundry and construction materials in domestic utilization. This study tries to identify in detail the differences of some physicochemical properties and thermal properties between Ca-type and Na-type bentonites. Also the adsorption behavior and interlayer expansion for the HDTMA (Hexadecyltrimethylammonium) exchanged and CP (Cetylprydinium) exchanged Ca-type and Na-type bentonites were compared. Na-type bentonite shows the strong alkaline property, high viscosity and swelling compared to Ca-type bentonite. However, two types are very similar for the cation exchange capacity and MB (Methylene Blue) adsorption. The decomposition of adsorbed and interlayer water of Na-type bentonite is caused in the lower temperature than Ca-type bentonite. And Ca-type bentonite shows the decomposition of structural water in the lower temperature than Na-type bentonite. The interlayer expansion of montmorillonite resulted to the intercalation of HDTMA and CP into bentonite is so strongly caused from 12~15 $\AA$ to $40\AA$ (basal spacing). HDTMA-bentonite is almost expanded to $37~38\AA$ when 200% CEC equivalent amount of HDTMA is added, and CP-bentonite is fullly expanded to 40 $\AA$ in the 140% CEC equivalent amount of CP It means that CP causes the stronger interlayer expansion of montmorillonite and easier adsorption than HDTMA. Adsorption behaviors of CP into bentonite is so stable and continuously sorbed in the proportion to the treatment of amount until 200% of the CEC equivalents. CP-bentonite shows the same adsorption behavior regardless of Ca-type or Na-type montmorillonite.

A Review on Measurement Techniques and Constitutive Models of Suction in Unsaturated Bentonite Buffer (불포화 벤토나이트 완충재의 수분흡입력 측정기술 및 구성모델 고찰)

  • Lee, Jae Owan;Yoon, Seok;Kim, Geon Young
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.17 no.3
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    • pp.329-338
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    • 2019
  • Suction of unsaturated bentonite buffers is a very important input parameter for hydro-mechanical performance assessment and design of an engineered barrier system. This study analyzed suction measurement techniques and constitutive models of unsaturated porous media reported in the literature, and suggested suction measurement techniques and constitutive models suitable for bentonite buffer in an HLW repository. The literature review showed the suction of bentonite buffer to be much higher than that of soil, as measured by total suction including matric suction and osmotic suction. The measurement methods (RH-Cell, RH-Cell/Sensor) using a relative humidity sensor were suitable for suction measurement of the bentonite buffer; the RH-Cell /Sensor method was more preferred in consideration of the temperature change due to radioactive decay heat and measurement time. Various water retention models of bentonite buffers have been proposed through experiments, but the van Genuchten model is mainly used as a constitutive model of hydro-mechanical performance assessment of unsaturated buffers. The water characteristic curve of bentonite buffers showed different tendencies according to bentonite type, dry density, temperature, salinity, sample state and hysteresis. Selection of water retention models and determination of model input parameters should consider the effects of these controlling factors so as to improve overall reliability.

Physical Characteristics and Germination of Pelleted Tobacco Seeds Depending on Moulding Materials (성형재료에 따른 담배 펠렛 종자의 물리적 틀성과 발아율)

  • 민태기;박민숙;이석순
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.41 no.5
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    • pp.535-541
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    • 1996
  • A seed pelleting technique was developed for easy handling of small tobacco seeds (variety, NC82) and for direct seeding in temperary planting bed or in field. The mixture of pelleting material, binder and seeds were moulded in cylindrical holes sized 2 mm diameter and 2 mm height in a plastic plate. Bentonite and cellulose powder were good materials to make pellets with CMC as binder, and bentonite formed the hardest pelleted seeds among the materials. The number of the pelleted seeds made with the same weight of the materials was different with materials used and the number of seeds contained in a pelleted seed could be controlled by mixture ratio of materials and seeds. The seedless pellets ranged 6.9 to 16.0% at the ratio of pelleting material and seed for 2~3 seeds in a pellet. The moisture absorption rate at 100% RH and $25^{\circ}C$ was greater in the order of clay < bentonite < cellulose. Germination rates of pelleted seeds with bentonite and cellulose were similar to that of usual seed, but it was significantly lower with clay pelleted seeds.

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A Study on the Stability of the Ca-Bentonite Colloids Using a Dynamic Light Scattering Method (동적광산란 방법을 이용한 칼슘벤토나이트 콜로이드의 안정성에 대한 연구)

  • Baik Min-Hoon;Park Jong-Hoon;Cho Won-Jin
    • Journal of Soil and Groundwater Environment
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    • v.11 no.3
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    • pp.12-19
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    • 2006
  • In this study, the stability of Ca-bentonite colloids from Gyeongju area was studied by investigating the changes in the size of the bentonite colloids using a dynamic light scattering method depending on the geochemical conditions such as pH and ionic strength. Kinetic and equilibrium coagulation behavior of the bentonite colloids was investigated by changing the pH and ionic strength of the bentonite suspensions. The results showed that the stability of the bentonite colloids strongly depended upon contact time, pH, and ionic strength. It was also shown that the bentonite colloids were unstable at higher ionic strength greater than 0.01 M $NaClO_4$ at whole pH values considered. In addition, the stability ratio Wand the critical coagulation concentration (CCC) were also calculated using the data from the kinetic coagulation experiments. The stability ratio W was decreased as the ionic strength increased and varied with pH depending on the ionic strength. The CCC of the Ca-bentonite colloids was about 0.05 M $NaClO_4$ around pH 7.

Assessment of the Hydraulic Conductivity of the Furnace Slag Coated with the Mixture of Bentonite-sepiolite-guargum under Sea Water Condition (벤토나이트-해포석-구아검 혼합물질이 코팅된 제강슬래그의 해수에 대한 투수성 평가)

  • Cheong, Eui-Seok;Rhee, Sung-Su;Woo, Hee-Soo;Park, Jun-Boum
    • Journal of Soil and Groundwater Environment
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    • v.16 no.4
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    • pp.1-9
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    • 2011
  • Bentonite has been generally used as vertical cutoff barrier material and reported to have several problems regarding its low workability, drying shrinkage cracking by particle cohesion, and ineffective waterproof ability under sea water condition. In this study, the particle sealant, the furnace slag coated by the mixture of bentonite, sepiolite and guargum, was developed to compensate these weak points and the hydraulic conductivity of the particle sealant was evaluated. Drying shrinkage cracking and swelling index was estimated to find the optimal mixing ratio of bentonite, sepiolite and guargum. The hydraulic conductivity of the particle sealants having different amount of sealant (bentonite-sepioliteguargum mixture) coating the furnace slag was estimated using the rigid wall permeameter and flexible wall permeameter. The results showed that drying shrinkage cracking was not found in the bentonite-sepiolite mixture with 20% sepiolite contents and the results from free swelling tests for the sealant having 1 : 0.025, 1 : 0.05 and 1 : 0.075 of weight ratios of bentonite-sepiolite mixture and guargum under simulated sea water condition were higher than those for the bentonitesepiolite mixture without guargum under tap water condition. These three sealants were coated on the furnace slag with 50% and 60% of sealant in the particle sealant and the hydraulic conductivity was estimated. In the cases of the particle sealants having 20% sepiolite in the bentonite-sepiolite mixture and 1 : 0.075 weight ratio of the bentonite-sepiolite mixture and guargum, the hydraulic conductivity from the rigid wall permeameter was below $1.0{\times}10^{-7}$ cm/sec under simulated sea water condition. The hydraulic conductivity of the particle sealant having $1.0{\times}10^{-6}$~$1.0{\times}10^{-7}$ cm/sec by the rigid wall permeameter was estimated using the flexible wall permeameter and found to be below $1.0{\times}10^{-7}$ cm/sec.

An Experimental Study on the Sorption Properties of Uranium(VI) onto Bentonite Colloids (벤토나이트 콜로이드에 대한 우라늄(VI) 수착특성에 대한 실험적 연구)

  • Baik Min-Hoon;Cho Won-Jin;Hahn Pil-Soo
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.239-247
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    • 2005
  • In this study, an experimental study on the sorption properties of uranium(VI) onto bentonite colloids generated from a domestic calcium bentonite (called as Gyeongju bentonite). Gyeongju bentonite has been considered as a potential candidate buffer material in the Korean disposal concept for high-level radioactive wastes. The size and concentration of the bentonite colloids used in the sorption experiment were measured by a filtration method. The result showed that the concentration of the synthesized bentonite colloid suspension was 5100ppm and the size of the most of bentonite colloids(over $98\%$) was in the range of 200-450nm in diameter. The amount of uranium lost by the sorption onto bottle walls, by precipitation, and by ultrafiltration or colloid formation was analyzed by carrying out some blank tests. The loss of uranium by the ultrafiltration was significant in the lower ionic strength(i.e., in the case of 0.001M $NaClO_4$) due to the cationic sorption effect onto the ultrafilter by a surface charge reversion. The distribution coefficient (or pseudo-colloid formation constant) for the sorption of uranium(VI) onto bentonite colloids was $10^4^{\sim}10^6$ mL/g depending upon pH and the distribution coefficient was highest in the neutral pH around 6.5.

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Development of Bentonite Composite Liners for Waste Landfill Sites (폐기물매립지 침출수 누출방지용 벤토나이트 복합라이너 개발)

  • Choi, Woo-Zin;Jin, Sung-Ki;Ha, Hun-Jung
    • Journal of the Korean Geoenvironmental Society
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    • v.1 no.1
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    • pp.65-70
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    • 2000
  • Recently, soil-bentonite mixtures are frequently used as impervious liners for waste disposal sites. In the present work, bentonite composite liner systems have been developed by utilizing Korean zeolitic bentonites. The geomechanical properties of the liner systems, such as strength hydraulic conductivity, etc. have also been studied. The laboratory and field test results showed that uniaxial strengths of the system were improved by addition of bentonite and CaO-based additive to the upper and lower layer of the liner systems, respectively. Hydraulic conductivity values measured on field liner systems showed less $1{\times}10^{-3}cm/s$, which is considered to be minimum regulation requirement for waste disposal sites.

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