WorldWideScience

Sample records for application aux bentonites

  1. Comparative study of bentonite properties with respect to the application as geotechnical barrier in HLRW repositories

    International Nuclear Information System (INIS)

    In concepts for the storage of high level radioactive waste (HLRW) the application of bentonite as sealing material is envisaged. Relevant properties of bentonites are cation exchange capacity (retention of pollutants), swelling (sealing of cracks), and low hydraulic conductivity. These properties significantly vary with the type of counter ion which is dominant in the smectite (commonly montmorillonite) interlayers. However, the variability of bentonites - not depending on the type of counter ion - is frequently underestimated. Bentonites vary in the mineralogical and chemical composition, and the arrangement of all components (intergrowth and micro fabric). Additionally, the main component (smectite) varies with respect to the degree of structural order, particle size, crystallite size, chemical composition, morphology, and amount and location of negative charges. This variation, of course, strongly affects bentonite properties in almost all fields of industrial application. Measurable parameters only occasionally explain the different properties. The common approach, therefore, is to perform application tests. In this study an attempt is made to identify the variation of bentonite properties with respect to the application in HLRW repositories. The study is based on the comparative investigation of 30 different bentonites from important bentonite mining areas worldwide. The bentonites were characterized intensively by mineralogical, optical, and chemical methods: XRD, IR, SEM, CEC, XRF, granulometry, layer charge density. (authors)

  2. Simulation of Tracer Transport in Porous Media: Application to Bentonites

    International Nuclear Information System (INIS)

    We present a formal framework to describe tracer transport in heterogeneous media, such as porous media like bentonites. In these media, mean field approximation is not valid because there exist some geometrical constraints and the transport is anomalous. (Author)

  3. Application de la combustion catalytique aux turbines à gaz

    Science.gov (United States)

    Lebas, E.; Martin, G. H.

    2002-04-01

    La réduction des émissions d'oxydes d'azote sur turbines à gaz est obtenue par diminution de la température au sein de la chambre de combustion. Les techniques possibles comprennent l'injection d'eau ou de vapeur, la combustion pauvre et l'oxydation catalytique. Parmi celles-ci, la dernière est la plus prometteuse en terme de coûts et de performances, avec des émissions de NOx ramenées à un seul chiffre (typiquement inférieures à 3 ppm). L'IFP travaille depuis maintenant 10 ans sur l'adaptation de la combustion catalytique aux turbines à gaz. Les études ont été conduites au travers de projets européen tels que AGATA (Advance Gas Turbine for Automotive Application) et ULECAT (Ultra Low CATalytic combustor for dual fuel gas turbine). Le premier projet était destiné au développement de véhicules hybrides et le second à la combustion stationnaire de biogaz et de combustible Diesel. Les études en cours dans ce domaine portent sur le développement d'une unité de cogénération intégrant une microturbine à combustion catalytique. Les travaux menés à l'IFP concernent la mise au point de catalyseurs répondant aux exigences de la combustion catalytique en turbine à gaz et le développement de chambres de combustion permettant la mise en oeuvre de ces catalyseurs.

  4. 40 CFR 436.220 - Applicability; description of the bentonite subcategory.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Applicability; description of the bentonite subcategory. 436.220 Section 436.220 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS MINERAL MINING AND PROCESSING POINT SOURCE CATEGORY...

  5. BENTONITE PROCESSING

    Directory of Open Access Journals (Sweden)

    Anamarija Kutlić

    2012-07-01

    Full Text Available Bentonite has vide variety of uses. Special use of bentonite, where its absorbing properties are employed to provide water-tight sealing is for an underground repository in granites In this paper, bentonite processing and beneficiation are described.

  6. Ti1-xAux Alloys: Hard Biocompatible Metals and Their Possible Applications

    Science.gov (United States)

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevzi; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Morosan, Emilia

    2015-03-01

    The search for new hard materials is often challenging from both theoretical and experimental points of view. Furthermore, using materials for biomedical applications calls for alloys with high biocompatibility which are even more sparse. The Ti1-xAux (0 . 22 dental, and prosthetic applications, where they could be used as both permanent and temporary components. Additionally, the ability of Ti1-xAux alloys to adhere to ceramic parts could reduce the weight and cost of these components. The work at Rice was supported by NSF DMR 0847681 (E.M. and E.S.).

  7. Phytoplankton community responses in a shallow lake following lanthanum-bentonite application.

    Science.gov (United States)

    Lang, P; Meis, S; Procházková, L; Carvalho, L; Mackay, E B; Woods, H J; Pottie, J; Milne, I; Taylor, C; Maberly, S C; Spears, B M

    2016-06-15

    The release of phosphorus (P) from bed sediments to the overlying water can delay the recovery of lakes for decades following reductions in catchment contributions, preventing water quality targets being met within timeframes set out by environmental legislation (e.g. EU Water Framework Directive: WFD). Therefore supplementary solutions for restoring lakes have been explored, including the capping of sediment P sources using a lanthanum (La)-modified bentonite clay to reduce internal P loading and enhance the recovery process. Here we present results from Loch Flemington where the first long-term field trial documenting responses of phytoplankton community structure and abundance, and the UK WFD phytoplankton metric to a La-bentonite application was performed. A Before-After-Control-Impact (BACI) analysis was used to distinguish natural variability from treatment effect and confirmed significant reductions in the magnitude of summer cyanobacterial blooms in Loch Flemington, relative to the control site, following La-bentonite application. However this initial cyanobacterial response was not sustained beyond two years after application, which implied that the reduction in internal P loading was short-lived; several possible explanations for this are discussed. One reason is that this ecological quality indicator is sensitive to inter-annual variability in weather patterns, particularly summer rainfall and water temperature. Over the monitoring period, the phytoplankton community structure of Loch Flemington became less dominated by cyanobacteria and more functionally diverse. This resulted in continual improvements in the phytoplankton compositional and abundance metrics, which were not observed at the control site, and may suggest an ecological response to the sustained reduction in filterable reactive phosphorus (FRP) concentration following La-bentonite application. Overall, phytoplankton classification indicated that the lake moved from poor to moderate

  8. Bentonite porewater chemistry

    International Nuclear Information System (INIS)

    Porewater composition in a compacted bentonite is dependent on the composition of the surrounding groundwater, and on the characteristics of the bentonite itself. Two mechanisms through which bentonite influences the respective porewater composition are distinguished: surface chemical reactions (ion exchange, surface complexation) on smectite and dissolution of minerals and soluble impurities included in bentonite. This report provides the results of different activities related to the definition of porewater chemistry through the use of geochemical models: 1) review of thermodynamic model on ion exchange reaction, 2) modeling of bentonite-water interactions under aerobic conditions, 3) performance of sensitivity analyses of key parameters in the bentonite model, 4) model simulation of bentonite porewater chemistry in the engineered barrier system under repository conditions. Experimental information of bentonite-water interaction allowed the determination of soluble impurities in the bentonite, and the knowledge of these impurities is important for predictive modeling. For the impurities of Kunigel-V1, 0.38% of CaSO4, 0.0011% of NaCl and 0.0044% of KCl were determined. The sensitivity analyses resulted in that the presence of calcite, CaSO4 and pyrite strongly influences the pH in the compacted bentonite, and the pH in compacted bentonite is buffered by the acid/base equilibria at the Na-smectite surface as well. Through the model calculations, some remarks on the expected trends for the long term behavior can be made like that the pH in compacted bentonite is expected to increase with increasing number of water exchange cycles, as long as CaCO3 contributes to the pH buffering capacity, due to slow depletion of the soluble impurities in the bentonite. The pH of the porewater, however, lies in all cases (but in the presence of CaCo3) between 5.6 and 9.5. Based on the findings discussed above, a large number of calculations were carried out to support the definition

  9. Physico-chemical characterization of bentonite and its application for Mn2+ removal from water

    Directory of Open Access Journals (Sweden)

    Ranđelović Marjan S.

    2011-01-01

    Full Text Available Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.

  10. Applicability of low alkaline cement for construction and alteration of bentonite in the cement. 2

    International Nuclear Information System (INIS)

    This study consists of accelerating corrosion test of rebar in saline, automogeneous shrinkage test of HFSC, accelerating test for bentonite and rock, and summarizing rock and bentonite alteration. Corrosion of rebars in HFSC: Since sorption capacity of HFSC for Cl ion is slow due to low alkalinity, rate of corrosion of rebar in HFSC is very large. Cracking due to corrosion is generating in 4 years or 20 years, although service period is deferent in OPC amount. Automogenous shrinkage: Automogenous shrinkage of HFSC is larger than OPC in cement paste. It decreases corresponding to rise of fly ash content. The shrinkage in HFSC 226 is quite similar to OPC. The shrinkage in HFSC concrete is smaller than OPC concrete. 720 days alteration test of bentonite by solution of low alkaline cement: Ion exchange to Ca bentonite and calcite are observed in the solid phase. Thin plate of bentonite is disappeared and round shaped secondary mineral is generated. Dissolution of bentonite and generation of secondary minerals are limited in pH 11.0 or less, since pH of bentonite is about 10.0. 720 days alteration test of rock by solution of low alkaline cement: Calcite is generated in very test. Very small evidence is observed as generation of secondary minerals. Etched pits are observed in tuff A due to corrosion. (author)

  11. Hydraulic permeability of bentonite-polymer composites for application in landfill technology

    Science.gov (United States)

    Dehn, Hanna; Haase, Hanna; Schanz, Tom

    2015-04-01

    Bentonites are often used as barrier materials in landfill technology to prevent infiltration of leachates to the natural environment. Since decades, geoenvironmental engineering aims at improving the hydro-mechanical performance of landfill liners. Various studies on the permeability performance of geosynthetic clay liners (GCLs) show effects of non-standard liquids on behaviour of Na+-bentonite regarding its sealing capacity. With increasing concentration of chemical aggressive solutions the sealing capacity decreases (Shackelford et al. 2000). An opportunity to improve the hydraulic permeability of the bentonites is the addition of polymers. The changes in hydraulic permeability performance of polymer treated and untreated bentonites while adding chemical aggressive solutions were studied by several authors. Results obtained by Scalia et al. (2014) illustrate that an increase in permeability can be prevented by adding polymer to Na+-bentonite. On the other hand, Ashmawy et al. (2002) presented results on the incapability of several commercial bentonite-polymer-products. The objective of this study is to characterize the influence of polymer addition on hydraulic performance of Na+-bentonite systematically. Therefore, the influence of 1% polymer addition of cationic and anionic polyacrylamide on the swelling pressure and hydraulic permeability of MX 80 bentonite was investigated. Preparation of bentonite-polymer composites was conducted (1) in dry conditions and (2) using solution-intercalation method. Experiments on hydraulic permeability were carried out using distilled water as well as CaCl2-solution. References Ashmawy, A. K., El-Hajji, D., Sotelo, N. & Muhammad, N. (2002), `Hydraulic Performance of Untreated and Polymer-treated Bentonite in Inorganic Landfill Leachates', Clays and Clay Minerals 50(5), 546-552. Scalia, J., Benson, C., Bohnhoff, G., Edil, T. & Shackelford, C. (2014), 'Long-Term Hydraulic Conductivity of a Bentonite-Polymer Composite Permeated

  12. Approval condition in application of bentonite grouting to the radioactive waste disposal

    International Nuclear Information System (INIS)

    The purpose of this study is to understand the flow properties and the permeability of bentonite grout added NaCl by the laboratory tests, and to clarify the approval condition of bentonite as materials. The viscosity of the bentonite suspension was measured under the weight ratio of water and bentonite (W/B) is 6 to 20. The suspension of which W/B is smaller than 10 is difficult to inject into the rock joints, because the viscosity is higher than the thickest cement milk on dam grouting. When the necessary permeability of the clay grout is assumed to be 10-7 (cm/sec), the W/B becomes 10 or less. Then, when we add NaCl to the suspension of which W/B is 6, the viscosity decreases as the amount of NaCl increases. The injectable viscosity is achieved by adding NaCl as the proportion of water to NaCl is 1 to 40. Next, the permeability of the bentonite suspension that added NaCl was examined by the falling head permeability test. It was found that the initial permeability 10-6 (cm/sec) decreased to 10-8∼10-9 (cm/sec) by the test of the sample of 'B:W:NaCl=20:20:1' for 10 days. From these results, the suspension to inject into the rock joints can be made by adding NaCl. And it was clarified that the groundwater permeation to the suspension causes the decrease of the permeability. In addition, the bentonite is swelling according to the infiltration of underground water, the persistence in the suppression effect of diffusion and stability to erosion can be expected. (author)

  13. Development of numerical simulation method for gas migration through saturated dense bentonite. Modeling by two-phase flow through deformable porous media and its applicability

    International Nuclear Information System (INIS)

    In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the effect of gas pressure generation and gas migration on the engineered barrier, peripheral facilities and ground. In this study, a method for simulating gas migration through the compacted bentonite is proposed. The proposed method can analyze coupled hydrological-mechanical processes using the model of two-phase flow through deformable porous media. Validity of the proposed analytical method is examined by comparing existing gas migration test results with the calculated results, which revealed that the proposed method can simulate gas migration behavior through compacted bentonite with accuracy. Furthermore, considering that conventional two-phase flow model is widely used in engineering practice, a simplified method for correcting calculated results by conventional two-phase flow model for the deformation of bentonite specimens accompanied by application of gas pressure is proposed. (author)

  14. Application of thermo-mechanically treated drill cuttings as an alternative to bentonite in spud muds

    OpenAIRE

    Taghiyev, Farid

    2014-01-01

    Drill cuttings recovered after drilling with OBM today are treated and deposited at onshore facilities. The TWMA Company offers a new technology, which recovers drilled subsurface materials together with oil and water rests. Due to the similarity between subsurface rock mineralogy and conventional bentonite used in the drilling fluid industry an extended laboratory study was carried out to evaluate the possibility of spud mud development using thermo-mechanically treated drill cuttings. Pr...

  15. Mixing conditions in application of bentonite grouting to radioactive waste disposal

    International Nuclear Information System (INIS)

    The purpose of this study was to understand the flow properties and permeability of bentonite grout with NaCl added, using laboratory tests, and to clarify the mixing conditions of bentonite as a material. Given that the required permeability of clay grout is 10-9 (m/s), the combination of grout (W/B) becomes 6 or less. The viscosity of the grout was measured, and because the viscosity was higher than the thickest cement milk on dam grouting, it was found that grout with a W/B of less than 10 was difficult to inject into rock joints. We then added NaCl to grout with a W/B is 6, and its viscosity decreased as the amount of NaCl increased. A grout of viscosity able to be injected into rock joints was achieved by adding NaCl in a density higher than 'W:NaCl=40:1'. Next, the permeability of a bentonite suspension with NaCl was examined using the falling head permeability test. Testing the sample 'B:W:NaCl=20:20:1' for 10 days revealed that the initial permeability 10-8 (m/s) decreased to 10-10 - 10-11 (m/s). These results showed that a suspension to inject into rock joints could be made by adding NaCl, and clarified that permeation of groundwater into the suspension causes a decline in permeability. (author)

  16. Evaluation of crushed aggregate and sand-bentonite mixtures for application to sealing of the final repository for reactor waste

    International Nuclear Information System (INIS)

    The Industrial Power Company Ltd (TVO) is planning to dispose the low- and intermediate level waste from the reactors of the Olkiluoto Nuclear Power Station into the bedrock of Olkiluoto at a depth of approximately 50-100 meters. In the TVO concept the reactor waste is disposed in silo shaped rock caverns. The bituminized waste is packed into steel drums, which are laid into a concrete silo inside the rock cavern. In this study the properties of sands, crushed aggregate and their mixtures with bentonite are reviewed. The applicability of these materials for use as a buffer on the top of the concrete silo is evaluated. This study is based on earlier experimental studies of the materials mentioned before and available literature. Gas production in the silo after disposal is estimated. General concepts of gas conductivity and gas migration in saturated soil are reviewed. The results of this study suggest that crushed aggregate and sand-bentonite mixtures are possible sealing materials for the silo in concern. But the need for further experimental study of their physical and mechanical properties and the gas migration processes through the saturated barrier is emphasized. A program for testing of these properties is presented

  17. Polyester-Bentonite Clay Composite: Synthesis, Characterization and Application as Anticorrosive Agent

    Directory of Open Access Journals (Sweden)

    Subramanian Chitra

    2015-09-01

    Full Text Available New polyester-bentonite clay composite was prepared and characterized by FTIR, TGA, SEM& XRD. The XRD and SEM studies are quite supportive of well dispersed polymer clay composite formation. The thermal stability of the polymer was significantly improved as indicated by TGA. The composite was evaluated for its inhibition performance for mild steel corrosion in 1M H2SO4 by weight loss, polarization and electrochemical impedance techniques. The studies reveal that the clay composite was an excellent adsorption type inhibitor and obeys Langmuir adsorption isotherm. Electrochemical studies showed that the polymer composite was a mixed inhibitor retarding both anodic metal dissolution and cathodic hydrogen evolution.

  18. Evaluation of Chlorophyll Fluorescence and Biochemical Traits of Lettuce under Drought Stress and Super Absorbent or Bentonite Application

    Directory of Open Access Journals (Sweden)

    Akram Valizadeh Ghale Beig

    2014-03-01

    Full Text Available The effects of two superabsorbents (natural-bentonite and (synthetic-A 200 on the chlorophyll fluorescence index, proline accumulation, phenolic compounds, antioxidant activity and total carbohydrate in lettuce (Lactuca sativa L. was evaluated. For this purpose, a factorial experiment using completely randomized design with superabsorbents at 3 levels (0, 0.15, 0.30 w/w%, drought stress at 2 levels (60 and 100% of field capacity and 4 replicates was conducted. Results showed that photosystem photochemical efficiency (Fv/Fm II under drought stress (60% FC as well as lower levels of bentonite superabsorbent polymer reduced. The minimum and maximum proline content were obtained in 0.3% bentonite, 100% FC and 0 benetonite, 60% FC, respectively. The lowest and highest phenolic compounds was corresponded to the highest levels in both super absorbents and control respectively, so that the super absorbent and bentonite, reduced phenolic compounds by 62.65 and 66.21% compared to control. 0 and 0.15 wt % bentonite in high drought stress (60% FC showed the highest and 0.3 wt % bentonite and 100% FC attained the lowest level of antioxidant activity. Control bentonite treatment beds at 60% FC and beds containing 0.3 wt. % bentonite in 100% FC, showed the lowest and the highest total carbohydrate content respectively. Results of this study indicate that bentonite can reduce the negative effects of drought stress similar to artificial super absorbent.

  19. MRI profiles over very wide concentration ranges: Application to swelling of a bentonite clay

    Science.gov (United States)

    Dvinskikh, S. V.; Szutkowski, K.; Furó, I.

    2009-06-01

    In MRI investigation of soils, clays, and rocks, mainly mobile water is detected, similarly to that in biological and medical samples. However, the spin relaxation properties of water in these materials and/or low water concentration may make it difficult to use standard MRI approaches. Despite these limitations, one can combine MRI techniques developed for solid and liquid states and use independent information on relaxation properties of water, interacting with the material of interest, to obtain true images of both water and material content. We present procedures for obtaining such true density maps and demonstrate their use for studying the swelling of bentonite clay by water. A constant time imaging protocol provides 1D mapping of the clay distribution in regions with clay concentration above 10 vol%. T1 relaxation time imaging is employed to monitor the clay content down to 10 -3 vol%. Data provided by those two approaches are in good agreement in the overlapping range of concentrations. Covering five orders of magnitude of clay concentration, swelling of sodium-exchanged bentonite clays from pre-compacted pellets into a gel phase is followed in detail.

  20. Application of solar chargers to prospection instruments; Application des chargeurs solaires aux appareils de prospection

    Energy Technology Data Exchange (ETDEWEB)

    Caille, G. [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    The use of conventional batteries has certain disadvantages, and for this reason high-voltage batteries have been gradually replaced in all prospection instruments by transistor supply systems, using less cumbersome sources of energy. All the same low voltages are still necessary, and in hot or damp countries the use of these batteries leads to consumptions out of all proportion to the services rendered. This is why the use of solar energy possesses real advantages. After a brief review of the basic ideas on semiconductors, this article describes a selenium solar battery which was developed by the Westinghouse brakes and signals society. (author) [French] L'utilisation de piles classiques presente certains inconvenients. C'est pourquoi, dans tous les appareils de prospection, les piles fournissant des tensions elevees ont ete remplacees au fur et a mesure par des alimentations a base de transistors, utilisant des sources d'energie moins encombrantes. Toutefois, il faut tout de meme avoir des tensions faibles et l'utilisation de ces piles entraine dans les pays chauds ou humides une consommation disproportionnee par rapport aux services rendus. C'est pourquoi l'emploi de l'energie solaire presente de reels avantages. Cet expose decrit, apres un rappel de notion de base sur les semi-conducteurs, une batterie solaire a base de selenium qui a ete realisee par la Societe des freins et signaux Westinghouse. (auteur)

  1. Precise AuxPt1-x Alloy Nanoparticle Array of Tunable Composition for Catalytic Applications

    Science.gov (United States)

    Jahn, Sarah; Lechner, Sebastian J.; Freichels, Helene; Möller, Martin; Spatz, Joachim P.

    2016-02-01

    A 3-dimensional Block Copolymer Micellar nanoLithography (BCML) process was used to prepare AuxPt1-x alloy nanoparticles (NPs) monodisperse in size and composition, strongly anchored onto SiO2-particles (0.2 wt.% AuxPt1-x/SiO2). The particles possess a face-centered cubic (fcc) crystal structure and their size could be varied from 3-12 nm. We demonstrate the uniformity of the Au/Pt composition by analyzing individual NPs by energy-dispersive X-ray spectroscopy. The strongly bound AuxPt1-x NPs catalyzed the oxidation of CO with high activity. Thermal ageing experiments in pure CO2 as well as in ambient atmosphere demonstrated stability of the size distribution for times as long as 22 h.

  2. Properties of Bentonite Enhanced Loess and Laterite

    Institute of Scientific and Technical Information of China (English)

    刘阳生; 白庆中; 聂永丰

    2004-01-01

    Loess and laterite distributed widely in the northern and southern China cannot be directly used as the natural barrier to isolate the solid waste because of their high hydraulic conductivity. In this paper, they are enhanced by bentonite to improve their hydraulic performance. The impact of bentonite content and water content on compressive strength of the compacted soil was investigated. The effects of bentonite content, water content, dry density and hydraulic gradient on the hydraulic conductivity were studied in detail. For the laterite and the laterite with 8% of bentonite, the experimental results of hydraulic conductivity can be applied in the engineering design. However, for the loess and the bentonite enhanced loess, those of hydraulic conductivity can not be directly applied in the engineering design because their hydraulic performance does not comply with the Darcy's law. These experimental results have to be carefully modified before application.

  3. Design and emplacement of bentonite barriers

    International Nuclear Information System (INIS)

    Bentonite is a well known sealing and buffer material for waste disposals in hard rock conditions. Bentonite was also tested as a sealing material for rock salt formations. Under salt conditions the hydraulic conductivity is higher and the swelling pressure is lower then under freshwater conditions using the same bentonite dry density. Because rock salt conditions are more ambitious for bentonite, the new research results of material design and emplacement technology are very useful for applications under freshwater conditions. Commercial available bentonites were tested by measurements of hydraulic conductivity and swelling pressure at various dry densities. The result is the required emplacement dry density for each bentonite. Following an industrial production process for high compacted bentonite materials with low initial water content was developed. Bentonite blocks for drift sealings and compacts / granules for bulk mixtures for shaft sealings have been successful tested in large scale in situ tests in salt mines. Since 1998 about 500 t of bentonite blocks have been produced by the company Preiss-Daimler Industries GmbH - Feuerfestwerke Wetro. The blocks have a standard size of (250 x 125 x 62,5) mm. A proper fit of the blocks to the rock contour can be formed by sawing. The emplacement as dry brickwork is simple and reliable for the rough conditions in underground mines. The recent shaft sealing systems consist of a binary mixture of air dry compacted bentonite compacts and granules (moisture content 7 - 10 %). This material design and the production technology were developed in cooperation with the K and S Group. Both components of the bulk mixture (compacts and granules) are now produced at the plant 'Bergmannssegen-Hugo' (K and S Group). This material defines the actual best state of the art for bentonite sealing materials for long term stable shaft sealing systems, especially under difficult conditions like in salt mines. Since 2004 about 3000 t of

  4. Immobilization of methylene blue onto bentonite and its application in the extraction of mercury (II)

    International Nuclear Information System (INIS)

    Methylene blue was immobilized onto bentonite (BNT). The modified clay (MB-BNT) was used to extract Hg2+ at pH 6.0 yielding Hg-MB-BNT. BNT, MB-BNT and Hg-MB-BNT were characterized by X-ray diffractometry, infrared spectra, and elemental and thermogravimetric analyses. MB is suggested to be intercalated into the major phase of BNT; montmorillonite mineral (MMT), lying parallel to the aluminosilicate layers, with a capacity of 36 mequiv./100 g. MB-BNT shows good stability in 0.1-1 M hydrochloric or nitric acids, ammonium hydroxide, and concentrated Na+, K+ or NH4+ chlorides or iodides. It shows good selectivity towards Hg2+ with an extraction capacity of 37 mequiv./100 g in the presence of I- giving rise to a ratio of MB/Hg2+/I- 1:1:3 in the clay phase. Extracted Hg2+ could be quantitatively recovered by ammonia buffer at pH 8.5. MB-BNT was successfully applied to recover Hg2+ from spiked natural water and cinnabar mineral samples using the optimum conditions; pH 6.0, time of stirring 10 min and 10 mL of 0.05 M NH4Cl/NH4OH at pH 8.5 as eluent.

  5. Selection of bentonite deposits

    International Nuclear Information System (INIS)

    The selection of bentonite deposits is to offer a supply base of backfill/buffer materials for high-level radioactive waste repository in China. In this paper the comprehensive evaluation criteria were discussed first, then a comprehensive comment on bentonite deposits in China was given. The properties of geographic distribution, origin, reserves and ore quality of bentonite deposits were also discussed. The comprehensive comparison studies on 12 large-sized bentonite deposits was presented. Based on the results obtained Gaomiaozi bentonite deposit, Inner Mongolia, was recommended as the first choice of backfill/buffer materials for repository in China. (author)

  6. Evaluation on application of bentonite slurry grout for excavation disturbed zone in order to recover low permeable rock masses

    International Nuclear Information System (INIS)

    The purpose of this paper is to improve the technologies of the grouting for excavation disturbed zone in order to recover low permeable rock masses for research and development on geological disposal of high-level radioactive waste. In this study, experiments of grouting injection test are performed on bentonite slurry mixes with saline and ethanol in the laboratory. From the results of the tests, low viscous and high density bentonite slurry is found to be able to inject the concentrated bentonite slurry and to recover low permeable in the fine fractured aperture. In conclusion this bentonite slurry is able to be expected the grouting effects for excavation disturbed zone in order to recover low permeable rock masses. (author)

  7. Assessment of changes in potential nutrient limitation in an impounded river after application of lanthanum-modified bentonite.

    Science.gov (United States)

    Douglas, Grant B; Lurling, Miquel; Spears, Bryan M

    2016-06-15

    With the advent of phosphorus (P)-adsorbent materials and techniques to address eutrophication in aquatic systems, there is a need to develop interpretive techniques to rapidly assess changes in potential nutrient limitation. In a trial application of the P-adsorbent, lanthanum-modified bentonite (LMB) to an impounded section of the Canning River, Western Australia, a combination of potential P, nitrogen (N) and silicon (Si) nutrient limitation diagrams based on dissolved molar nutrient ratios and actual dissolved nutrient concentrations have been used to interpret trial outcomes. Application of LMB resulted in rapid and effective removal of filterable reactive P (FRP) from the water column and also effectively intercepted FRP released from bottom sediments until the advent of a major unseasonal flood event. A shift from potential N-limitation to potential P-limitation also occurred in surface waters. In the absence of other factors, the reduction in FRP was likely to be sufficient to induce actual nutrient limitation of phytoplankton growth. The outcomes of this experiment underpins the concept that, where possible in the short-term, in managing eutrophication the focus should not be on the limiting nutrient under eutrophic conditions (here N), but the one that can be made limiting most rapidly and cost-effectively (P). PMID:26879191

  8. Bentonite as a waste isolation pilot plant shaft sealing material

    Energy Technology Data Exchange (ETDEWEB)

    Daemen, J.; Ran, Chongwei [Univ. of Nevada, Reno, NV (United States)

    1996-12-01

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites.

  9. Bentonite as a waste isolation pilot plant shaft sealing material

    International Nuclear Information System (INIS)

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites

  10. Fabrification of electroreduced graphene oxide–bentonite sodium composite modified electrode and its sensing application for linezolid

    International Nuclear Information System (INIS)

    Graphene and its composites have attracted considerable attention in synthesis and electrochemical applications. In the present work, we have synthesized and characterized graphene oxide-bentonite composite (GO-BEN) and utilized it to fabricate an electrochemical sensor. For this, the solution of GO-BEN cast on glassy carbon electrode (GCE) was reduced electrochemically in phosphate buffer solution of pH 6 to obtain electrochemically reduced graphene oxide-bentonite composite (ERGO-BEN-GCE). This ERGO-BEN film was used for electrochemical investigation of an oxazolidinone class of antibiotic, linezolid (LIN) for the first time. The electrochemical sensor showed excellent enhancement and adsorptive ability towards the electrooxidation of LIN. LIN exhibited two each of oxidation and reduction peaks on ERGO-BEN film in phosphate buffer of pH 7.0. Effects of accumulation time, pH of solution and scan rate were studied and various electrochemical parameters were evaluated. The plot of pH versus Ep gave a slope of 26.2 mV/pH in the pH range of 4.2-8.0 indicating the participation of two electrons and one proton in the electrode process. An adsorptive stripping differential pulse voltammetric method (AdSDPV) was developed for the determination of LIN in bulk, pharmaceutical formulations and urine samples. Adsorptive stripping linear sweep voltammetric (AdSLSV) and differential pulse voltammetric (DPV) methods were also developed and the results were compared. LIN showed linear relationship between the current density and concentration in the range of 0.25 - 31.25 μM with a LOD of 0.0337 μM in AdSDPV method; 0.5 - 31.25 μM with a LOD of 0.100 μM in DPV method and 1.25 - 37.5 μM with a LOD of 0.5461 μM in AdSLSV method respectively. The proposed AdSDPV method was observed to be simple, fast and inexpensive and hence, could be readily adopted for quality control in pharmaceutical products

  11. Tolérance aux fautes dans les applications J2EE: Une solution scalable et générique

    OpenAIRE

    Bouchenak, Sara; Krakowiak, Sacha; De Plama, Noël

    2005-01-01

    La plate-forme J2EE définit un modèle pour développer des applications réparties dans une architecture multi-tiers, telles que les applications Web de commerce électronique. Avec la multiplication des couches logicielles et intergicielles, les applications Internet sont encore plus sujettes aux défaillances ; ces défaillances étant, pour la majorité, causées par des fautes logicielles ou des fautes de l'opérateur. Dans cet article, nous proposons un système de tolérance aux fautes qui traite ...

  12. Décompositions parcimonieuses et persistantes de signaux multicanaux. Applications aux signaux MEEG.

    OpenAIRE

    Kowalski, Matthieu; Torrésani, Bruno

    2009-01-01

    On considère le problème de la régression parcimonieuse de signaux multicanaux sur des repères temps-fréquences. Les signaux multicanaux sont décomposés sur un unique repère en utilisant des coefficients vectoriels (i.e. multi-canal). La parcimonie apparaît habituellement grâce à des approches type “basis pursuit denoising” : la régression s'effectue en minimisant une fonctionnel qui fait intervenir un terme d'attache aux données 2 , et une pénalité 1 sur les coefficients. Dans cette contribu...

  13. Nanocristaux d'amidon: Preparation et Application aux emballages flexibles et barrières

    OpenAIRE

    Le Corre, Déborah

    2011-01-01

    Ce travail examine la potentielle mise à l'échelle industrielle des procédés de préparation des nanocristaux d'amidon (SNCs). Une caractérisation approfondie (morphologie, viscosité, stabilité thermique et propriétés en nanocomposites) de 5 SNCs différents montre une faible influence de la source botanique, contrairement aux nanocristaux de cellulose. L'analyse du procédé de préparation actuel des SNCs a conduit à 3 nouvelles stratégies d'optimisation et à la définition d'une nouvelle générat...

  14. Validity of chalk and bentonite application in soil and water on reducing the absorption of ratio-strontium and radio-cerium by crop

    International Nuclear Information System (INIS)

    Effects of the chalk and bentonite application in soil and surface water respectively on reducing the absorption of 89Sr and 141Ce by crop (especially in the edible part of crop) were studied by using isotope tracer techniques. The results showed that the specific activity of 89Sr in the ryegrass and Chinese cabbage could be decreased significantly by chalk application in the soil. The reduced ratio of 89Sr absorption of Chinese cabbage and ryegrass reached 77.7% and 35.2% respectively with the chalk application of 20 g/kg soil. The specific activity of 89Sr in ryegrass and Chinese cabbage followed obvious negative linear correlation with the quantity of application chalk in the soil. The specific activity of 141Ce in surface water, chaff and brown rice decreased by application bentonite in the surface water, which led to the lower accumulation of 141Ce in paddy. However, the absorption and accumulation of 141Ce in root and straw could not be changed. The specific activity of 141Ce in soil followed a negative exponential relation with depth of soil profile

  15. Modelling the induced polarization of bentonite-sand mixtures

    OpenAIRE

    Leroy, Philippe; Ghorbani, Ahmad; Revil, André; Cosenza, P.; Okay, G.

    2014-01-01

    Spectral induced polarization (SIP) has become an increasingly popular geophysical method for hydrogeological and environmental applications. These applications include for instance the non-intrusive characterization of the textural and interfacial physicochemical properties of bentonites used as permeability barriers in landfills or to store various types of contaminants including radioactive wastes. Bentonites are mainly constituted of smectites, which have very high specific surface areas ...

  16. Mobilidade do zinco e do cobre em Argissolo com aplicação de argila bentonita Zinc and copper mobility in Argisol with application of bentonite clay

    Directory of Open Access Journals (Sweden)

    Gilvanise A. Tito

    2012-09-01

    Full Text Available A mobilidade dos metais pesados no solo é influenciada pelas características do solo, pela mineralogia das argilas e pelo teor do metal. Objetivando avaliar o efeito da bentonita na mobilidade do zinco e do cobre no solo, colunas de lixiviação preenchidas com um Argissolo foram submetidas a ensaios de mobilidade utilizando-se doses de bentonita (0, 30 e 60 t ha-1 e concentrações de zinco e cobre, de 50, 250 e 450 mg kg-1. As colunas de solo foram mantidas saturadas e sob fluxo de água permanente; em seguida foram determinados densidade, velocidade do fluxo, fator de retardamento, coeficiente de dispersão-difusão e número de Peclet. Os parâmetros de transporte foram definidos através do modelo computacional DISP. A incorporação de bentonita ao solo promoveu a retenção do zinco e do cobre pelo solo, principalmente deste último, diminuindo a concentração em solução lixiviada e os riscos de contaminação do meio ambiente. A aplicação de bentonita aumentou o fator de retardamento, mas reduziu o coeficiente de dispersão-difusão do solo.The mobility of heavy metals in the soil is influenced by the soil, the clay mineralogy and the amount of metal. Aiming to evaluate the effect of bentonite clay on zinc and copper mobility, leaching columns of soil, filled with an Argisol, utilising increasing doses of bentonite (0, 30 e 60 t ha-1 and concentrations of zinc and copper (50, 250 e 450 mg kg-1 were submitted to a saturated and steady flow. The flux density, velocity, transport retardation factor, dispersion-diffusion coefficient and breakthrough curves were obtained. The transport parameters were determined using the DISP computational model. The results allow to conclude that the application of bentonite clay to the soil promoted the retention of the zinc and copper, mainly the last one, decreasing the concentration in leachate and reducing potential contamination risks. The bentonite clay application increased the soil

  17. New quantitative methods for mineral and porosity mapping in clayey materials: application to the compacted bentonites of engineered barriers

    International Nuclear Information System (INIS)

    Clayey materials are well known for their non permeable properties and their textural changes between the dry and hydrated states. Their porous network is classically investigated in the dry state using bulk measurements. However, the relationship between porosity and mineral spatial heterogeneities in the hydrated state is poorly understood. The textural analysis limits induce some difficulties to understand the migration of solute species into compacted bentonites (as for nuclear waste repository). The goal of this work is to improve the analysis techniques for hydrated clayey materials in order to provide a multi-scale quantitative petrography. The bentonite samples are impregnated using a resin whose properties are close to water ones. The classical petrographic study reveals strong heterogeneities of spatial and size distributions of porosity and minerals. SEM images analysis allows a quantification and a simple mapping of pores and minerals into unaltered bentonites. Nevertheless, as alterations are suspected to happen in the repository context, two methods for the analysis of all types of materials have been also developed. Two specific softwares permits the treatments of autoradiographs and chemical element maps obtained using electron microprobe. The results are quantitative maps highlighting the spatial porosity heterogeneities from the decimetric to the micrometric scales. All pore sizes are taken into account including clay interlayer spaces. Moreover, an accurate mineral mapping is also supplied on millimetric areas with a spatial resolution close to the micrometer. In a widely point of view, this work provides new complementary tools for the textural analysis of fine grained materials and the improvement of migration modelling of solute species. (author)

  18. Dual swelling mechanism model for saturated and unsaturated compacted bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite-based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Since compacted bentonite swells when it is saturated, dry density of compacted bentonite will be redistributed and container of radioactive wastes will move during infiltration of underground water. Accurate evaluation of these events is effective in decreasing uncertainty in long term safety evaluation of radioactive waste facilities. However, sufficient evaluation is not conducted because behaviour of bentonite material during saturation process is not clarified sufficiently. Thus, stress-strain model of bentonite material during saturation process is proposed and applicability of the model is investigated. It is well known that compacted bentonite swells with large deformation by infiltration of water. Swelling behaviour of bentonite is mainly attributable to osmotic pressure caused by the difference between concentration of ions inside of montmorillonite flakes and that outside of montmorillonite flakes. Thus, swelling which is attributable to osmotic pressure is named 'swelling by osmotic pressure' here. By contrast, unsaturated ordinary clay swells or shrinks during infiltration of water without effect of osmotic pressure. Since this phenomenon is mainly attributable to reduction of suction during infiltration of water, it is reasonable to assume that unsaturated bentonite swells or shrinks during infiltration of water by reduction of suction. Thus, swelling which is attributable to reduction of suction is named 'swelling by reduction of suction' here. It is assumed in this paper that swelling by osmotic pressure occurs when bentonite is fully saturated, while swelling by reduction of suction occurs when bentonite is unsaturated. Swelling deformation under a constant vertical load is measured

  19. Responses in sediment phosphorus and lanthanum concentrations and composition across 10 lakes following applications of lanthanum modified bentonite

    DEFF Research Database (Denmark)

    Dithmer, Line; Nielsen, Ulla Gro; Lürling, Miquel;

    2016-01-01

    A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and...... were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the...

  20. Modification de la bentonite par un sel de diphosphonim – Applications à l’adsorption des colorants textiles (rouge, bleu et jaune Bemacide).

    OpenAIRE

    MEHDI, fatima

    2014-01-01

    L’objectif de notre étude est d’améliorer les propriétés de sorption de la bentonite vis-à-vis les colorants qui sont classés parmi les produits les plus toxiques et comparaison entre bentonite sodique et modifiée. La première partie du travail concerne la préparation et la caractérisation des bentonites modifiées avec un sel de diphosphonium(p-HpHBM). Les bentonites modifiées sont obtenues par échange cationique entre les cations inorganiques qui se trouvent dans les feuillets de...

  1. Copper/bentonite interaction

    International Nuclear Information System (INIS)

    The prediction of the processes and rate of corrosion of the KBS 2 copper canisters must be based on a proper scenario, which involves the physical state of the bentonite surrounding the canisters, and the chemical interaction between copper and bentonite. Literature data suggest slow Cu migration and Cu exchanging originally adsorbed cations. Two tests involving copper/bentonite contacts for 3 - 6 months in boreholes have yielded certain valuable information. Thus, Cu ion migration is indeed very slow and where it yields a sufficiently high concentration, it is associated with replacement of originally adsorbed Na ions, which should result in an increased permeability. In one of the tests the copper was separated from the bentonite by a partly air-filled slot. These conditions caused the formation of copper oxides and hydroxides which intermingled with the bentonite that expanded to fill the slot. Due to the low solubility of these copper compounds, the Cu ion concentration was too low to produce ion exchange during the time of observation. (Author)

  2. Sorption of metals on zeolites and bentonite

    International Nuclear Information System (INIS)

    This contribution presents the recently obtained results on the sorption of heavy metals by natural microporous materials (especially zeolites and bentonite) of different origin. The sorption of caesium and strontium from its aqueous solutions by ten clinoptilolite-mordenite-containing sedimentary materials from Slovakia, Bulgaria, Ukraine and Greece and bentonite was investigated a batch-type procedure and radiotracer techniques. The experimental results provide information on suitability of the individual materials for the treatment of radioactive waste and their application as backfills in potential nuclear waste repositories. Furthermore, the sorption of cadmium, mercury and zinc-ions by zeolites and bentonite was investigated using batch techniques and radioactive tracers. Uptake values and distribution coefficients were calculated in order to study the suitability of these materials for utilization in the environmental technology (i.g. treatment of industrial waste). (author)

  3. Porewater chemistry in compacted bentonite

    International Nuclear Information System (INIS)

    In this study, the porewater chemistry in compacted bentonite, considered as an engineered barrier in the repository of spent fuel, has been studied in interaction experiments. Many parameters, like the composition and density of bentonite, composition of the solution, bentonite-to-water ratio (B/W), surrounding conditions and experimental time have been varied in the experiments. At the end of the interaction the equilibrating solution, the porewaters squeezed out of the bentonite samples, and bentonites themselves were analyzed to give information for the interpretation and modelling of the interaction. Equilibrium modelling was performed with the HYDRAQL/CE computer code

  4. Scorpio : une Approche d'Adaptation Structurelle de Composants Logiciels - Application aux Environnements Ubiquitaires

    OpenAIRE

    Bastide, Gautier

    2007-01-01

    La réutilisation à grande échelle de composants logiciels se révèle être un challenge pour la conception de nouvelles applications. Dans la grande majorité des cas, pour être intégrés à une application, les composants disponibles ont besoin d'être adaptés afin de faire face à la multiplicité des environnements de déploiement dotés de caractéristiques variables. Ainsi, pour éviter le redéveloppement de nouveaux composants et favoriser la réutilisation, de nombreuses approches ont proposé des te...

  5. Matériaux solide conducteur thermodurcissable : Application aux plaques bipolaires pour pile à combustible

    OpenAIRE

    Dessertenne, Estelle

    2012-01-01

    Among the new technologies for energy for sustainable development, PEM fuel cells offer seducing aspects. However, in order to make this technology fit large scale application requirements, it has to comply with stringent cost, performance, and durability criteria. While metal bipolar plates are penalized by their corrosion resistance and those based on graphite by their mechanical properties and cost (due to machining phases of the channels), the composite bipolar plates appear attractive be...

  6. Enhanced shear strength of sodium bentonite using frictional additives

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, K.E. [GeoSyntec Consultants, Huntington Beach, CA (United States); Bowders, J.J.; Gilbert, R.B. [Univ. of Texas, Austin, TX (United States); Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States)

    1997-12-31

    One of the most important obstacles to using geosynthetic clay liners (GCLs) in landfill cover systems is the low shear strength provided by the bentonitic portion of the GCL. In this study, the authors propose that granular, frictional materials might be added to the bentonite to form an admixture that would have greater shear strength than the bentonite alone while still raining low hydraulic conductivity. Bentonite was mixed with two separate granular additives, expanded shale and recycled to form mixtures consisting of 20-70% bentonite by weight. In direct shear tests at normal stresses of 34.5-103.5 kPa, effective friction angles were measured as 45{degrees} for the expanded 36{degrees} for the recycled glass, and 7{degrees} for the hydrated granular bentonite. The strength of the expanded shale mixtures increased nearly linearly as the percentage shale in the mixture increased, to 44{degrees} for a bentonite mixture with 80% shale. The addition of recycled glass showed little effect on the shear strength of the mixtures of glass and bentonite. Hydraulic conductivity measurements for both types of mixtures indicated a linear increase with log(k) as the amount of granular additive increased. For applications involving geosynthetic clay liners for cover systems, a mixture of 40% expanded shale and 60% bentonite is recommended, although further testing must be done. The 40/60 mixture satisfies the hydraulic equivalency requirement, with k = 5.1X10{sup -9} cm/sec, while increasing the shear strength parameters of the bentonitic mixture to {phi}{prime} = 17{degrees} and c{prime} = 0.

  7. Localisation par vision multi-spectrale. Application aux systèmes embarqués

    OpenAIRE

    Gonzalez, Aurélien

    2013-01-01

    The SLAM (Simultaneous Localization and Mapping) problematic is widely studied from years at LAAS. The aimed application is the development of a helping rolling system for planes on airports. This system has to work under any visibility and weather conditions ("SART" project, funding by DGE, with FLIR Systems, Thalès and Latecoère). During some weather conditions (fog, rain, darkness), one only visible camera is not enough to complete this task of SLAM. Firstly, in this thesis, we will study ...

  8. Development of clay characterization methods for use in repository design with application to a natural Ca bentonite clay containing a redox front

    International Nuclear Information System (INIS)

    Natural smectite clays in the form of 'true' bentonites formed from volcanic ash, or resulting from in-situ weathering of rock, are suitable for a number of sealing options in repositories, both as tightening component of sand/clay backfills and as highly efficient buffer for embedment of canisters, as well as for fracture sealing. The price and quality, in terms of smectite content and type of smectite, vary considerably and an optimum choice of clay for use in repositories has to be based on quantitative quality data. This requires characterization of the clay material for which a test scheme has been worked out. It comprises determination of the granulometrical, chemical, and mineralogical compositions, as well as of certain physical properties. Recent research shows the importance of the type of smectite for the longevity of buffers in repository environment, beidellite being less favourable and saponite superior to montmorillonite, which is the most common smectite species. The test scheme hence includes means of distinguishing between various smectite minerals. The influence of accessory minerals on the chemical integrity of both the smectite and the canister material requires identification also of such minerals, for which the scheme is useful as well. The report summarizes the various test procedures and gives data from application of the scheme to samples from a natural Ca bentonite containing a redox front. This study suggests that a significant part of the iron in the clay fraction is in the form of Fe2+ in octahedral positions of the montmorillonite of unoxidized natural clay and that it is converted to Fe3+ on oxidation. Part of the iron is probably in the form of the Fe2+Fe3+ hydroxy compounds that give the unoxidized clay its bluish colour, while they can be assumed to be transformed to yellowish FeOOH forms on oxidation. (author)

  9. Application des ultrasons aux procédés de transformation des produits agroalimentaires

    OpenAIRE

    Pingret de Sousa, Daniella,

    2012-01-01

    L’utilisation des ultrasons dans l’industrie agro-alimentaire présente de nombreux avantages, tels que l’augmentation de la productivité et la diminution des coûts et des impacts environnementaux. Dans la première partie de ce travail, une brève introduction sur la théorie des ultrasons et ses applications en agro-alimentaire et l’utilisation de ces derniers pour l’extraction des polyphénols de marc de pomme en solution aqueuse seront présentés. Cette étude a été optimisée et présente d’excel...

  10. Gas Transport in Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gutierre-Rodrigo, V.; Martin, P. I.; Romero, F. J.; Barcala, J. M.

    2013-07-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm{sup 3} with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm{sup 3} for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others

  11. UO22+ sorption on bentonite

    International Nuclear Information System (INIS)

    The capacity of bentonite and purified bentonite to remove UO22+ ions from aqueous solutions has been investigated. The UO22+ uptake in these clays was determined for 0.2 and 0.002M uranyl nitrate solutions. It was found that under these conditions (0.2M) the maximum UO22+ uptake was 1.010±0.070 meq UO22+/g of bentonite and 0.787±0.020 meq UO22+/g of purified bentonite. In purified bentonite UO22+ sorption is irreversible up to 50 hours as no desorption was observed. Such is not the case in the natural bentonite. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The uranium content was determined by neutron activation analysis. (author)

  12. Electromigration : structure de zone frontière, application à la séparation d'espèces en solution et aux transferts interfaciaux

    OpenAIRE

    Londiche, Henry

    1982-01-01

    L'application d'un champ de forces externes à un milieu liquide contenant un ou plusieurs solutés permet d'agir sur sa composition en modifiant les conditions d'équilibre thermodynamique. En particulier surimposer un champ électrique aux transferts entre phases non miscibles conduit à rendre complètes l'extraction liquide liquide d'un soluté contenu dans une phase non polaire ou la dissolution d'un sel réputé insoluble. Le passage d'un courant électrique continu d'intensité. constante dans un...

  13. Simulation of Tracer Transport in Porous Media: Application to Bentonites; Simulacion del Transporte de Trazadores en Medios Porosos: Aplicacion al Caso de Arcillas

    Energy Technology Data Exchange (ETDEWEB)

    Bru, A.; Casero, D. [CIEMAT, Madrid (Spain)

    2001-07-01

    We present a formal framework to describe tracer transport in heterogeneous media, such as porous media like bentonites. In these media, mean field approximation is not valid because there exist some geometrical constraints and the transport is anomalous. (Author)

  14. Application of Greek lignite as an additive for controlling rheological and filtration properties of water-bentonite suspensions at high temperatures: A review

    Energy Technology Data Exchange (ETDEWEB)

    Kelessidis, Vassilios C.; Foscolos, Antonios [Department Mineral Resources Engineering, Technical University of Crete, 73100 Chania (Greece); Papanicolaou, Cassiani [Institute of Geology and Mineral Exploration (IGME) (Greece)

    2009-01-31

    This review paper presents the results of an extensive study investigating whether addition of 3% w/w Greek lignite to 6.42% w/w water-bentonite suspensions, after being exposed to high temperatures, can prevent gelation and control filtration characteristics. Two different bentonites and eight lignites from different Greek basins have been used while a commercial lignite product has been used as standard. The lignite-free bentonite suspensions heated to 177 C for 16 h (thermal aging) thicken considerably, increasing the yield stress and the yield point. Fluid consistency and flow behavior indices also change while no significant change is observed for plastic viscosity. Thermal aging of the suspensions results in unacceptably high fluid loss values. Addition of Greek lignite to water-bentonite suspensions, followed by thermal aging, provided the rheological stability of the suspensions by maintaining the low yield stress/point regardless of the type of bentonite. Some of the lignites performed as well as their commercial counterpart. No specific trends for rheological improvement have been identified with respect to various characteristics of lignites such as contents of humic, fulvic acids, humins and other parameters such as specific surface area and cation exchange capacity. Furthermore, addition of lignite in most cases provided very good filtration control of the water-bentonite suspensions after exposure to 177 C, with some Greek lignites being superior to the commercial product. The same lignite parameters examined for rheological control, were also examined to determine their effect on fluid loss of these suspensions for both bentonites. The content of humic and fulvic acids of two groups of lignites showed weak inverse correlations with the fluid loss volumes for both bentonites, while all other parameters did not seem to directly correlate with the effectiveness of the lignites. (author)

  15. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  16. Bentonite erosion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2009-12-15

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  17. Lake responses following lanthanum-modified bentonite clay (Phoslock®) application: an analysis of water column lanthanum data from 16 case study lakes.

    Science.gov (United States)

    Spears, Bryan M; Lürling, Miquel; Yasseri, Said; Castro-Castellon, Ana T; Gibbs, Max; Meis, Sebastian; McDonald, Claire; McIntosh, John; Sleep, Darren; Van Oosterhout, Frank

    2013-10-01

    Phoslock(®) is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock(®) across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) and filterable La (FLa) concentrations in surface and bottom waters were quantified over a period of up to 60 months following Phoslock(®) application. Both surface and bottom water TLa and FLa concentrations were 0.8 mEq L(-1)), but higher (up to 0.12 mg L(-1)) in lakes characterised by very low alkalinity. The effects of elevated La(3+) concentrations following Phoslock(®) applications in lakes of very low alkalinity requires further evaluation. The implications for the use of Phoslock(®) in eutrophication management are discussed. PMID:23911225

  18. Bentonite erosion. Laboratory studies

    International Nuclear Information System (INIS)

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain mostly

  19. Bentonite erosion. Laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats (Div. of Nuclear Chemistry, Royal Inst. of Technology, Stockholm (Sweden), School of Chemical Science and Engineering)

    2009-11-15

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain

  20. Results of bentonite grouting experiment

    International Nuclear Information System (INIS)

    The Bentonite grouting, which will not solidify, is mainly expected to reduce the hydraulic conductivity of underground water in the expected damage zone by filling the fractures or cracks, so the evaluation of the degree of hydraulic conductivity, stability and the improvement area becomes important. The study and basic experiments for sealing of the adits have been promoted, up to now, from the aspects of the characteristics and long term stability of candidate materials, and design and construction (Pusch et al., 1987; Tanai and Masuda, 1991). However, in Japan, the application examples of clay type materials for grouting are extremely few and is limited to the construction experience of the national oil underground storage at Kuji (Miyanaga and Ebara, 1993), with the exception of some test cases (Boergesson et al., 1991) from overseas. This report summarize basic characteristics of the clay type material relevant to the hydraulic conductivity, from the result of the clay grouting experiment conducted at the rock site. (author)

  1. Efficient removal of Eu(III) from aqueous solutions using super-adsorbent of bentonite-polyacrylamide composites

    International Nuclear Information System (INIS)

    The bentonite has been studied extensively to preconcentrate radionuclides from aqueous solutions, however, the low sorption capacity limits it application in real work. Herein, bentonite embedded in the polyacrylamide (PAAm) gels is synthesized and used as a novel adsorbent for the removal of Eu(III) from aqueous solutions. The bentonite-PAAm composites show much higher sorption capacity for Eu(III) preconcentration than bare bentonite. The bentonite-PAAm composites can be used as super-adsorbent for the removal of Eu(III) from aqueous solution in radioactive pollution cleanup. (author)

  2. The oolitization rate determination of bentonite moulding mixtures

    Directory of Open Access Journals (Sweden)

    F. Miksovsky

    2008-07-01

    Full Text Available Bentonite mixtures belong and will always belong among the most widespread sand mixtures for the “green sand” technology of castings production. This technology’s essential advantage is bentonite mixtures application reversibility in the closed circulation after composition modifications and circulation losses replenishment. After the casting of a mould, the surrounding sand mixture is strained by the solidifying casting heat and bentonite degradation occurs. In case of appropriate conditions the oolitization occurs. This phenomenon is specific only for bentonite-bonded mixtures. The oolitization of opening material silica grains brings a number of negative as well as positive features with it. It is not only a technological problem but economical and ecological as well because for minimization of mixture regeneration with a help of new sand it is necessary to know bentonite mixtures quality control tools even in term of the oolitization rate. This paper deals with the description of undemanding physical method of the oolitization rate evaluation with a help of powder density assessment and its examination with actual sand mixtures which were obtained from the Czech Republic foundry plants. There are foundry plants of heavier weight castings and in one case there was an operation where bentonite mixtures regeneration was applied. Moreover, the oolitization effect on metal penetration in test castings was verified.

  3. Borehole sealing with highly compactd Na bentonite

    International Nuclear Information System (INIS)

    This report describes the use of highly compacted Na bentonite for borehole plugging. Bentonites have an extremely low permeability and a low diffusivity, and a swelling ability which produces a nonleaching boundary between clay and rock if the initial bulk density of the bentonite is sufficiently high. The suggested technique, which is applicable to long vertical, and inclined, as well as horizontal boreholes, is based on the use of perforated copper pipes to insert elements of compacted bentonite. Such pipe segments are connected at the rock surface and successively inserted in the hole. When the hole is equipped, the clay takes up water spontaneously and swells through the perforation, and ultimately forms an almost completely homogenous clay core. It embeds the pipe which is left in the hole. Several tests were conducted in the laboratory and one field test was run in Stripa. They all showed that a gel soon fills the slot between the pipe and the confinement which had the form of metal pipes in the laboratory investigations. Subsequently, more clay migrates through the perforation and produces a stiff clay filling in the slot. The redistribution of minerals, leading ultimately to a high degree of homogeneity, can be described as a diffusion process. The rate of redistribution depends on the joint geometry and water flow pattern in the rock. In the rock with an average joint frequence of one per meter or higher, very good homogeneity and sealing ability of the clay are expected within a few months after the application of the plug. (author)

  4. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Science.gov (United States)

    Parolo, María E.; Pettinari, Gisela R.; Musso, Telma B.; Sánchez-Izquierdo, María P.; Fernández, Laura G.

    2014-11-01

    The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm-1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  5. Preparation of sol-gel TiO2/purified Na-bentonite composites and their photovoltaic application for natural dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Highlights: → Natural dye from red cabbage was successfully employed in DSSC. → A fast sol-gel method to produce TiO2/clay thin film was proposed. → The sol-gel-prepared TiO2/clay was applied as the scattering layer on top of TiO2 electrode. → Thicker sol-gel-prepared TiO2/clay electrode showed higher DSSC efficiency. - Abstract: The sol-gel TiO2/purified natural clay electrodes having Ti:Si molar ratios of 95:5 and 90:10 were initially prepared, sensitized with natural red cabbage dye, and compared to the sol-gel TiO2 electrode in terms of physicochemical characteristics and solar cell efficiency. The results showed that the increase in purified Na-bentonite content greatly increased the specific surface area and total pore volume of the prepared sol-gel TiO2/purified Na-bentonite composites because the clay platelets prevented TiO2 particle agglomeration. The sol-gel TiO2/5 mol% Si purified Na-bentonite and sol-gel TiO2/10 mol% Si purified Na-bentonite composites could increase the film thickness of solar cells without cracking when they were coated as a scattering layer on the TiO2 semiconductor-based film, leading to increasing the efficiency of the natural dye-sensitized solar cells in this work.

  6. Lake responses following lanthanum-modified bentonite clay (Phoslock) application: an analysis of water column lanthanum data from 16 case study lakes

    NARCIS (Netherlands)

    Spears, B.M.; Lürling, M.F.L.L.W.; Yasseri, S.; Castro-Castellon, A.T.; Gibbs, M.; Meis, S.; McDonald, C.; McIntosh, J.; Sleep, D.; Oosterhout, van F.

    2013-01-01

    Phoslock is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentr

  7. Studies of the coagulation flotation of bentonite and its application to the removal of Co2+ ions and fission products, Ce and Eu

    International Nuclear Information System (INIS)

    The regions of dispersion, coagulation precipitation, coagulation flotation, and redispersion were determined for aqueous bentonite-cationic surfactant and bentonite-cationic surfactant-polyacrylamide(PAA) systems. The region of coagulation flotation was markedly extended by the addition of PAA to both the lower and higher concentration regions of the cationic surfactant, hexadecyldimethylbenzylammonium chloride(HDBAC), and to the lower concentration region of bentonite. The phenomenon of coagulation flotation was investigated in detail and was applied to the removal of Co2+ ions and nuclear fission products, 144Ce and 155Eu, from an aqueous solution. The composition of the reagents for the maximum efficiency of bentonite flotation corresponded to that of the maximum efficiency of Co2+-ion flotation. The effect of the pH on the flotation efficiency was studied in particular. The maximum flotation efficiency of 96% was obtained at pH 11 for Co2+ ions, 86% at pH 9.7 for 144Ce, and 93% at pH 10.5 for 155Eu. These radioactive elements were almost completely adsorbed on the surface of bentonite particles and were floated with them in the pH region of the maximum flotation efficiency. It was confirmed that Co2+ ions could be floated also from an extremely low concentration (10-9 mol/l) of Co2+ ions with nearly the same efficiency of flotation and with the additives in the same condition. Co2+ ions could also be effectively removed by using the step-by-step flotation, showing as high a flotation efficiency as 99.8%. (auth.)

  8. Long-term stability of bentonite. A literature review

    International Nuclear Information System (INIS)

    for divalent cations and it is not as easily eroded or dissolved in case of diluted groundwater or in case of high pH. Although the information on cementation by thermal effects from natural bentonite occurrences may not be directly applicable to the repository conditions, they show that very high temperatures have affected the bentonites and for long periods of time and there is still unaltered montmorillonite in those deposits. Natural occurrences of bentonite and smectite provide information on the bentonite behaviour in varying conditions. How to adapt this information in the predicting the buffer behaviour is a challenging task. To be able to make a direct comparison between different natural occurrences and the buffer, more detailed information would be needed on density/compaction rate, saturation degrees, pressure conditions, chemical conditions, and duration of the thermal events for the natural bentonites as these are well known for the buffer. (orig.)

  9. Bentonite in the repository - Manufacture of bentonite blocks. A literature study; Bentonit i slutfoervaret - Tillverkning av bentonitblock. En litteraturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Hultgren, Aa. [NFC Konsult, Nykoeping (Sweden)

    1995-09-01

    Activities in nuclear power countries are reviewed, concerning developments in the use of bentonite for backfilling in nuclear waste repositories, in particular regarding manufacture of bentonite-blocks. Only one report was found which in detail describes the manufacture of highly compacted blocks of bentonite. Use of bentonite for sealing boreholes etc in the oil- and gas industry was also covered in the literature study. 19 refs, 3 tabs.

  10. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, Kd, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)

  11. Equilibria in saturated bentonite

    International Nuclear Information System (INIS)

    It has been proposed that smectite clays, the predominant minerals in bentonite, are metastable solid solutions whose compositional heterogeneity prevents strict adherence to fixed ion activities and activity ratios characterizing invariant equilibria among stoichiometric phases. This is analysis of exceptionally well-constrained experimental data using a solid solution model defined by the phase rule and estimated ideal site-mixing are approached among smectite solid solutions and coexist metastably with respect to aSiO2(aq). Irreducible uncertainties are generated in the model by analytical and conceptual deficiencies in understanding compositional variability in smectite. However, their estimated effects on smectite's stability are relatively small, and are comparable to the effects of experimental uncertainty in standard Gibbs energies on the stabilities of stoichiometric minerals. An alternate analysis of the data further confirms that smectite does not behave like a stoichiometric phase. Ion-exchange models for this clay mineral may therefore be thermodynamically ill defined because stoichiometric behavior is assumed implicitly under limiting conditions of fixed sites. Ion exchange is a pragmatic simplification enabling empirical analysis of some experimental data. However, its empirical, rather than thermodynamic, basis should not be overextended to conditions that are beyond an experimentally calibrated range

  12. Application of Continuous Thermodynamics to Natural-Gas Mixtures Application de la thermodynamique continue aux mélanges de gaz naturel

    Directory of Open Access Journals (Sweden)

    Prausnitz J. M.

    2006-11-01

    Full Text Available This work reviews recent progress in the application of continuous thermodynamics towards calculation of phase equilibria in natural-gas mixtures. In such mixtures, there may be too many components to identify each component individually. Continuous thermodynamics provides a theoretical framework for representing the composition of a portion of the natural-gas mixture by a continuous distribution function. Advances in continuous thermodynamics are discussed in three areas :(1 Characterization and representation of composition in a many-component mixture(2 Development and application of molecular-thermodynamic models for continuous mixtures, and(3 Implementation of efficient numerical techniques for solving material-balance and phase-equilibrium equations. While continuous thermodynamics provides a useful tool for calculation of phase equilibria in natural-gas mixtures, successful implementation requires better chemical-analytical characterization methods. Further, improved semi-theoretical techniques must be developed to relate experimental characterization information to physically significant parameters in molecular-thermodynamic models. Ce travail examine les récents développements de l'application de la thermodynamique continue au calcul des équilibres de phases de mélanges de gaz naturel. Dans ces mélanges, les composants sont souvent en trop grand nombre pour qu'on puisse les identifier individuellement. La thermodynamique continue fournit un schéma théorique permettant de représenter la composition d'une partie de mélange de gaz naturel par une fonction de distribution continue. Les progrès de la thermodynamique continue sont examinés dans les trois domaines suivants : 1 caractérisation et représentation de la composition d'un mélange de plusieurs produits; 2 mise au point et application des modèles de thermodynamique moléculaire aux mélanges continus; 3 mise en oeuvre de techniques numériques efficaces pour r

  13. A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (PHOSLOCK®)

    OpenAIRE

    Spears, Bryan M.; Mackay, Eleanor B.; Yasseri, Said; Gunn, Iain D.M.; Waters, Kate E.; Andrews, Christopher; Cole, Stephanie; de Ville, Mitzi; Kelly, Andrea; Meis, Sebastian; Moore, Alanna L.; Nurnberg, Gertrud K.; van Oosterhout, Frank; Pitt, Jo-Anne; Madgwick, Genevieve

    2015-01-01

    Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads...

  14. Decantation time of evaluation on bentonite clays fractionation

    International Nuclear Information System (INIS)

    Bentonite clays present a great number of industrial uses, from petroleum to pharmaceutics and cosmetic industry. The bentonite clay present particles with very fine particles that is responsible by the vast application of these materials. However, commercial clays present wide particle size distribution and a significant content of impurities, particularly quartz, in the form of silt and fine silt. So, the aim of this work is to analyze the effect of the stirring and decantation time in the deagglomeration, purification and size separation of the bentonite clay particles from Paraiba. The clays were characterized by X-ray diffraction and particle size distribution. Based on the results it was observed the decantation time give the elimination of the agglomerates formed by submicrometric particles. The uses of decantation column give separation of the fraction below 200nm. (author)

  15. Microcapillary flow behavior of magnetic nanofluids in the presence of plate shaped bentonite particles

    International Nuclear Information System (INIS)

    Plate shaped bentonite particles of size ∼600 nm and thickness ∼2 nm are dispersed in a magnetic nanofluid. Magnetic field dependent flow behavior of this composite suspension is studied using a horizontal microcapillary placed between the poles of an electromagnet. The plate shaped bentonite particle produces extra hindrance to the flow under the application of moderate magnetic field and produces an enhanced magnetoviscous effect. 75% volume concentration of bentonite produces eight times larger change in magnetic field dependent viscosity than does the pure magnetic nanofluid. Hindrance to the flow is due to the chain like structure of magnetic nanoparticles, tumbling and rotational motion of bentonite particles and interaction between magnetic and bentonite particles. The field-induced structures are also observed using an optical microscope. Results offer several advantages over the inverse MR effect as well as to study the motion of biological cells and tissues under the effect of magnetic field. -- Highlights: ► Dispersed plate shaped bentonite particles in magnetic fluids to study capillary viscosity. ► Increased viscosity is due to the hindrance to the rotation of the bentonite particles. ► Increase in viscosity is five times larger for bentonite particles than the pure magnetic fluids. ► This is a new kind of magnetoviscous effect, dispersing anisotropic particles in magnetic fluids

  16. Modelling the induced polarization of bentonite-sand mixtures. In : Proceedings of the 3rd International Workshop on Induced Polarization

    OpenAIRE

    Leroy, Philippe; Ghorbani, Ahmad; Revil, André; Cosenza, P.; Okay, G.

    2014-01-01

    Spectral induced polarization (SIP) has become an increasingly popular geophysical method for hydrogeological and environmental applications. These applications include for instance the non-intrusive characterization of the textural and interfacial physicochemical properties of bentonites used as permeability barriers in landfills or to store various types of contaminants including radioactive wastes. Bentonites are mainly constituted of smectites, which have very high specific surface areas ...

  17. Multiple scenarios of bentonite alteration

    International Nuclear Information System (INIS)

    Performance assessment for TRU waste repositories has shown that soluble and poorly sorbing nuclides such as I-129 and C-14 dominate the dose. These nuclides are expected to migrate with groundwater flow, hence hydraulic conditions and their evolution with time in the repository are key issues for repository safety. Cementitious material will be used for waste packaging, backfilling and structural material in a TRU waste repository. Bentonite is also expected to be used for some TRU wastes to provide the function of a hydraulic barrier in the disposal system. There is concern that the coexistence of cementitious material and bentonite cause the alteration of smectite due to interaction with hyperalkaline leachates and consequent deleterious perturbation of the function of bentonite as a hydraulic barrier. Many research studies have been performed to identify possible mechanisms of cement-bentonite interaction. However, uncertainties still exist in our understanding of the precise chemical scheme of bentonite alteration in highly alkaline conditions, especially the space and time variation of secondary mineral occurrences. In order to reflect this uncertainty, multiple scenarios of bentonite alteration were developed based on the possible mineralogical changes derived from knowledge of both experiments and observation of natural systems. It was focused that the mineral reaction involving hyperalkaline fluids would thermodynamically depend on the variable chemical condition in bentonite buffer and that kinetics would be important as well as thermodynamic stability in controlling their occurrence, i.e., the kinetic controls may operate to remain metastable minerals over the long term. The mineralogical consequences of the interaction between clays and alkaline fluids are summarized as follows. Clay → C-S-H gel and other solids which can rapidly precipitate. Clay and gel → illite. Clay and gel → metastable zeolite. Clay and gel → metastable zeolite → stable

  18. Study of aggregation in a micellar solution within bentonite clay by SANS

    International Nuclear Information System (INIS)

    Aggregation studies of surfactant solutions exposed to different surfaces are relevant to their applications as detergents, oil recovery agents etc. The infusion of SDS micellar solutions into the pores of compacted normal bentonite clay and the clay saturated with sodium at different concentrations viz. 1, 2 and 5 molar percentages, has been studied here by small angle neutron scattering and X-ray diffraction. In the sodium saturated bentonite, the Na+ ion (having a positive scattering length) is held in the interlayer of the clay and on account of this, the scattering length density difference (i.e. contrast) between the bentonite matrix and the inter-layer pores is lower than the bentonite which has less sodium. The average pore size in normal bentonite clay is 13 Å while in the clay saturated with 1M Na+ ions it is 20 Å . For a 10% SDS solution, the micelles are prolate ellipsoids having average semi major and minor axes of 22.5 Å and 16.7 Å, respectively with an effective charge of 30 e.u. and an aggregation number of 75. Both aggregation number and effective charge increase with concentration of SDS solution. Sodium is present in normal bentonite but is enhanced in concentration in the case of sodium saturated bentonite. Aggregation number and micellar separation are reduced for SDS loaded into raw bentonite clay and then into Na saturated clay. Likewise, there is a reduction of fractional charge on the micelle in going from raw to sodium bentonite caused by the Na+ ions present on the surface of the clay pores which would be attracted to the negative surface of each micelle thereby reducing its net charge. The effective attraction between micelles and Na+ ion concentration control the growth of aggregates, their volumes and aggregation numbers. Hence the sodium ion in the bentonite plays a vital role in the change of these parameters by effectively reducing charge on the micellar aggregates.

  19. Ion diffusion in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K{sub d}, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.) 45 refs.

  20. A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal

    Science.gov (United States)

    Dessirier, Benoît; Frampton, Andrew; Jarsjö, Jerker

    2015-11-01

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository. In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to

  1. Studies on dynamic compaction and hydraulic properties of Bentonite-based materials for geological disposal of radioactive wastes

    International Nuclear Information System (INIS)

    As the safe disposal method of high-level radioactive waste from nuclear power plants, there is the 'geological disposal' that buries the waste in the stable soil. For cushioning materials to be used for geological disposal, performances such as low permeability. self-sealing ability, and nuclide sorption ability are required, and bentonite has been picked up as a candidate for its main base material. This paper takes up granular bentonite and bentonite - silica sand mixed material as the bentonite-based materials used as cushioning materials for site application, and explains their dynamic compaction test and easy-to-use evaluation method. As for the granular bentonite, it was found that its compaction properties can be predicted from the plastic limit of pulverized sample of the original ore as a raw material for granular bentonite. As for bentonite - silica sand mixed material, the relationship between maximum dry density, optimum moisture content, and plastic limit showed a very good match between the measured results and calculated results. The permeability coefficient of granular bentonite can be predicted from the wet volume strain of montmorillonite, or the partial density of montmorillonite. As for the bentonite - silica sand mixed material, the permeability of Fe(III) type montmorillonite became significantly larger. (A.O.)

  2. Determination of a PWR key neutron parameters uncertainties and conformity studies applications; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustible et applications aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2002-07-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and lifetime. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimised. (author)

  3. Organophilic bentonites based on Argentinean and Brazilian bentonites: part 2: potential evaluation to obtain nanocomposites

    Directory of Open Access Journals (Sweden)

    L. B. Paiva

    2012-12-01

    Full Text Available This work describes the preparation of composites of polypropylene and organophilic bentonites based on Brazilian and Argentinean bentonites. During the processing of the samples in a twin screw microextruder, torque and pressures of the extruder were accompanied and the viscosity values were calculated. No significant changes in the torque, pressure and viscosity were found for composites prepared with different bentonites. The samples were characterized by XRD and TEM to evaluate the structure and dispersion of the organophilic bentonites. Composites with exfoliated, partially exfoliated and intercalated structures were obtained and correlations between the intrinsic properties of the sodium clays and organophilic bentonites and their influence on the composites were studied. The cation exchange capacity of the sodium bentonites and the swelling capacity of the organophilic bentonites were the most important properties to obtain exfoliated structures in composites. All bentonites showed the potential to obtain polymer nanocomposites, but the ones from Argentina displayed the best results.

  4. Conception and test of an integrated circuit (ASIC): application to multiwire chambers and photomultipliers of the GRAAL experience; Conception et test d`un circuit integre (ASIC): application aux chambres multifils et aux photomultiplicateurs de l`experience GRAAL

    Energy Technology Data Exchange (ETDEWEB)

    Bugnet, H.

    1995-11-21

    The nuclear physics project GRAAL (GRenoble Anneau Accelerateur Laser) located at the European Synchrotron Radiation Facility (ESRF) in Grenoble produces a high energy photon beam with a maximum energy of 1.5 GeV. This gamma beam is obtained by Compton backscattering and can be polarized easily. It permits to probe, in an original way, the structure of the nucleon. The associated detector system includes multiwire proportional chambers and scintillator hodoscopes. A kit of six ASICs (Application Specific Integrated Circuit) has been developed and used for the signal processing and data conditioning up to the level of the data acquisition. This integrated electronics can be mounted right on the detectors. Obvious advantages, due to the reduction of the length of the wires and the number of connections, are an improvement of the signal quality and an increase of the reliability. The Wire Processor (WP), ASIC designed and tested during this thesis, treats the signals from the chamber wires and the photomultipliers. In one chip, there are two identical channels permitting the amplification, the amplitude discrimination, the generation of a programmable delay and the writing in a two state memory in case of coincidence with an external strobe signal. The measurement of the multiwire chamber efficiency demonstrates the functioning of the WP, the data conditioning electronics, the data acquisition and the chamber itself. (author). 62 refs., 111 figs., 13 tabs.

  5. Bentonite in the repository - Manufacture of bentonite blocks. A literature study

    International Nuclear Information System (INIS)

    Activities in nuclear power countries are reviewed, concerning developments in the use of bentonite for backfilling in nuclear waste repositories, in particular regarding manufacture of bentonite-blocks. Only one report was found which in detail describes the manufacture of highly compacted blocks of bentonite. Use of bentonite for sealing boreholes etc in the oil- and gas industry was also covered in the literature study. 19 refs, 3 tabs

  6. Critère de fatigue polycyclique pour des matériaux anisotropes : application aux monocristaux

    Science.gov (United States)

    Cano, Florian; Constantinescu, Andrei; Maitournam, Habibou

    2004-02-01

    The high-cycle fatigue criteria based on a macroscopic-mesoscopic scale interpretation, initiated by Dang Van, were used essentially for polycrystalline materials. In the existing criteria the material isotropy at both mesoscopic and macroscopic scales plays a key role. The purpose of this paper is to revisit the macroscopic to mesoscopic fatigue approach taking into account the material anisotropy and some results obtained by Bui. The possible applications are some anisotropic steels or monocrystalline structures such as stitanium turbine blades. To cite this article: F. Cano et al., C. R. Mecanique 332 (2004).

  7. ANALYSE ET SYNTHESE D'UNE ARCHITECTURE COOPERATIVE POUR LA COMMANDE TOLERANTE AUX DEFAUTS - APPLICATION A UN SYSTEME AERONAUTIQUE

    OpenAIRE

    Cieslak, Jérôme

    2007-01-01

    This thesis discusses the design of an active Fault Tolerant Control (FTC) strategy for improvement of the operational control capability of the safety critical systems. The FTC strategy works in such a way that once a fault is detected by the Fault Detection and Isolation (FDI) unit, a compensation loop is activated for safe recovery. A key feature of the proposed strategy is that the design of the FTC loop is done independently of the nominal control law already in place. For a given applic...

  8. Decontamination characteristics of inorganic surface contaminated with Cs(134+137), Am241, Eu(154+155) and Ce144 radionuclides using bentonite decontamination agent

    International Nuclear Information System (INIS)

    The decontamination of the urban building surfaces, based on the covering of bentonite suspensions, has been studied. A bentonite suspension as a decontaminant has a lot of merits; chemically unharmful substance, low price, prevalence of raw material, nondestructive, applicable to large area, and simplicity of preparation and application. The cation converting conditions of bentonite suspensions were determined by the experiments of swelling and stability of suspension. Contaminated samples for test purpose were prepared by application of radioactive solution which was extracted from the soil of the Chernobyl Nuclear Power Plant. The results of this study showed that bentonite suspension technology is effective for decontamination of urban environment

  9. Hydration states of clays followed by water and hydroxyls vibrational analyses in the near infrared: application to saponite and bentonite systems

    International Nuclear Information System (INIS)

    The study of the feasibility of a deep geological disposal facility conducted by ANDRA - the French national radioactive waste management agency -, requires the knowledge of water status and water content in clays. Thanks to an original lab-built device coupling vibrational spectroscopies and water adsorption isotherms, adsorbed water and clay's structure are described quantitatively and qualitatively. A multidisciplinary approach allows the description of hydration mechanisms and water molecules network in the inter lamellar space of synthetic saponites. The effects of density and nature of inter-foliar cations and the influence of temperature on hydration are presented. Using mechanisms and important parameters established on saponites, hydration of bentonite MX80 is carried out. In order to describe and quantify simultaneously two different water states, a simple but relevant method of spectra analysis was developed. (author)

  10. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm−1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination

  11. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Energy Technology Data Exchange (ETDEWEB)

    Parolo, María E., E-mail: maria.parolo@fain.uncoma.edu.ar [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Pettinari, Gisela R. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Musso, Telma B. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); CONICET, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Sánchez-Izquierdo, María P.; Fernández, Laura G. [Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina)

    2014-11-30

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm{sup −1} with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  12. Application of response surface methodology for optimization of azocarmine B removal by heterogeneous photo-Fenton process using hydroxy-iron–aluminum pillared bentonite

    International Nuclear Information System (INIS)

    Hydroxy-iron–aluminum pillared bentonite (H-Fe–Al-B) was synthesized with ion exchange method, and its catalyst characteristics were analyzed by using X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS). The photo-Fenton catalytic activity of H-Fe–Al-B was tested under different reaction condition using azocarmine B (ACB) as model pollutant under ultraviolet light (UV) irradiation. The effects of three operating variables, initial dye concentration, initial pH value and H2O2 concentration on the decolorization efficiency of ACB were optimized by response surface methodology (RSM) based on Box–Behnken design. The results showed that hydroxy aluminum iron ions intercalated into the interlayer spaces of bentonite successfully and H-Fe–Al-B had high photocatalytic activity. Analysis of variance (ANOVA) indicated that the proposed quadratic model could be used to navigate the design space. The proposed model was approximately in accordance with the experimental case with correlation coefficients R2, Radj2 and Rpred2 correlation coefficients of 0.9996, 0.9991 and 0.9934, respectively. The optimum conditions for ACB decolorization were dye concentration of 143.7 mg/L, pH of 4.2 and H2O2 concentration of 17.7 mM, respectively. The predicted decolorization rate under the optimum conditions determined by the proposed model was 99.6%. Confirmatory tests were carried out under the optimum conditions and the decolorization rate of 99.5% was observed, which closely agreed with the predicted value.

  13. Methodological study of the diffusion of interacting cations through clays. Application: experimental tests and simulation of coupled chemistry-diffusion transport of alkaline ions through a synthetical bentonite

    International Nuclear Information System (INIS)

    The subject of this work deals with the project of underground disposal of radioactive wastes in deep geological formations. It concerns the study of the migration of radionuclides through clays. In these materials, the main transport mechanism is assumed to be diffusion under natural conditions. Therefore, some diffusion experiments are conducted. With interacting solutes which present a strong affinity for the material, the duration of these tests will be too long, for the range of concentrations of interest. An alternative is to determine on one hand the geochemical retention properties using batch tests and crushed rock samples and, on the other hand, to deduce the transport parameters from diffusion tests realised with a non-interacting tracer, tritiated water. These data are then used to simulate the migration of the reactive elements with a numerical code which can deal with coupled chemistry-diffusion equations. The validity of this approach is tested by comparing the numerical simulations with the results of diffusion experiments of cations through a clay. The subject is investigated in the case of the diffusion of cesium, lithium and sodium through a compacted sodium bentonite. The diffusion tests are realised with the through-diffusion method. The comparison between the experimental results and the simulations shows that the latter tends to under estimate the propagation of the considered species. The differences could be attributed to surface diffusion and to a decrease of the accessibility to the sites of fixation of the bentonite, from the conditions of clay suspensions in batch tests to the situation of compacted samples. The influence of the experimental apparatus used during the diffusion tests on the results of the measurement has also been tested. It showed that these apparatus have to be taken into consideration when the experimental data are interpreted. A specific model has been therefore developed with the numerical code CASTEM 2000. (author)

  14. Preparation of bentonites for laboratory investigations

    International Nuclear Information System (INIS)

    A project study on behalf of Nagra for high radioactive waste disposal in deep geological formations as well as literature studies have shown that bentonite could be a suitable filling and sealing material. The Institute for Foundation and Soil Mechanics of the Swiss Institute of Technology has been given a contract by Nagra to investigate different bentonites. The investigations concentrate on the Na-bentonite MX-80 from Wyoming, which is foreseen by the Swedes, and on the geographically more favorable Ca-bentonite Montigel from Bavaria. Montigel powder and granulate, which show certain manufacturing advantages, were investigated. The quality of the bentonites was examined especially to ascertain whether the bentonites were homogeneous with respect to composition and properties. Montmorillonite, carbonate, oxidizing substances and exchangeable ions were quality content criteria for bentonite. The investigations showed that these bentonites are typical Na- and Ca-bentonites. A representative sample of 500 kg weight (250 kg for Montigel K) was largely homogeneous. The samples were analysed by x-rays and thermoanalysis. Additionally grain size, carbonate content, methylene blue value, yield point, exchange capacity and exchangeable ions were determined. 5 refs., 2 figs., 2 tabs

  15. Pertechnetate diffusion in GMZ bentonite

    International Nuclear Information System (INIS)

    99Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO4-) can be reduced to immobility technetium(IV) hydrous oxides (TcO2 · nH2O) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for the HLW repository, which is contained some FeO. The diffusion behavior of 99Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient (De), the accessible porosity (εacc), apparent diffusion coefficient (Da) and distribution coefficient (Kd) were decreased with the increasing of dry density. The De values were (2.8 ± 0.2) x 10-11 m2/s and (3.5 ± 0.2) x 10-12 m2/s at dry density of 1,600 and 1,800 kg/m3, respectively. It was indicated that the dominating species was TcO4- during the diffusion processing. While, out-diffusion results showed that part of TcO4- may be reduced by Fe(II). The relationship of De and εacc could be described by Archie's law with exponent n = 2.4 for 99Tc diffusion in GMZ bentonite. Furthermore, the relationship between Da and dry density (ρ) was exponential. (author)

  16. Surface Modification of Bentonites. II. Modification of Montmorillonite with Cationic Poly(ethylene oxides)

    OpenAIRE

    Dau, Jörn; Lagaly, Gerhard

    1998-01-01

    Surface modification of clay minerals has become increasingly important for optimizing the practical application of bentonites, kaolins, and clays. We describe the reaction of montmorillonite, an important mineral in bentonites, with cationic poly(ethylene oxides). Poly(ethylene oxides), PEOs, with molecular masses between 1550 and 35000, were modified by substituting the OH end groups by bromine, then replacing Br by trimethylammonium (TMA) groups. Mono-endcapped PEOs were prepared from poly...

  17. Aux origines du monde

    CERN Multimedia

    2004-01-01

    "C'est l'histoire d'une aventure humaine, scientifique, international qui a vu le jour il y a cinquante ans, aux confins de la Suisse et du département de l'Ain. Le plus grand laboratoire de physique des particules du monde, le Cern, a été fondé en 1954. Les festivités organisées à l occasion de cet anniversaire connaîtront leur point d'orgue le 16 octobre prochain, avec portes-ouvertes, accueil de personallités et inauguration d'un monumnet spécifique, le Globe de l'innovation" (2 pages)

  18. Activation of a Ca-bentonite as buffer material

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Swelling behavior is an important criterion in achieving the low-permeability sealing function of buffer material. A potential buffer material may be used for radioactive waste repository in Taiwan is a locally available clayey material known as Zhisin clay, which has been identified as a Ca-bentonite. Due to its Ca-based origin, Zhisin was found to exhibit swelling capacity much lower than that of Na-bentonite. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder was introduced in this paper. The addition of Na2CO3 reagent to Zhisin clay, in a liquid phase, caused the precipitation of CaCO3 and thereby induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite. Characterization test conducted on Zhisin clay includes chemical analysis, cation exchange capacity, X-ray diffraction, and thermogravimetry (TG). Free-swelling test apparatus was developed according to International Society of Rock Mechanics recommendations. A series of free-swelling tests were conducted on untreated and activated specimens to characterize the effect of activation on the swelling capacity of Zhisin clay. Efforts were made to determine an optimum dosage for the activation, and to evaluate the aging effect. Also, the activated material was evaluated for its stability in various hydrothermal conditions for potential applications as buffer material in a repository. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Also, there exists an optimum amount of activator in terms of improvements in the swelling capacity. A distinct time-swell relationship was discovered for activated Zhisin clay. The corresponding mechanism refers to exchange of cations and breakdown of quasi-crystal, which results in ion exchange hysteresis of Ca-bentonite. Due to the ion exchange hysteresis, activated bentonite shows a post

  19. Activation of a Ca-bentonite as buffer material

    Science.gov (United States)

    Huang, Wei-Hsing; Chen, Wen-Chuan

    2016-04-01

    Swelling behavior is an important criterion in achieving the low-permeability sealing function of buffer material. A potential buffer material may be used for radioactive waste repository in Taiwan is a locally available clayey material known as Zhisin clay, which has been identified as a Ca-bentonite. Due to its Ca-based origin, Zhisin was found to exhibit swelling capacity much lower than that of Na-bentonite. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder was introduced in this paper. The addition of Na2CO3 reagent to Zhisin clay, in a liquid phase, caused the precipitation of CaCO3 and thereby induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite. Characterization test conducted on Zhisin clay includes chemical analysis, cation exchange capacity, X-ray diffraction, and thermogravimetry (TG). Free-swelling test apparatus was developed according to International Society of Rock Mechanics recommendations. A series of free-swelling tests were conducted on untreated and activated specimens to characterize the effect of activation on the swelling capacity of Zhisin clay. Efforts were made to determine an optimum dosage for the activation, and to evaluate the aging effect. Also, the activated material was evaluated for its stability in various hydrothermal conditions for potential applications as buffer material in a repository. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Also, there exists an optimum amount of activator in terms of improvements in the swelling capacity. A distinct time-swell relationship was discovered for activated Zhisin clay. The corresponding mechanism refers to exchange of cations and breakdown of quasi-crystal, which results in ion exchange hysteresis of Ca-bentonite. Due to the ion exchange hysteresis, activated bentonite shows a post-rise time-swell relationship different than the sigmoid

  20. Response surface optimisation for activation of bentonite with microwave irradiation

    Directory of Open Access Journals (Sweden)

    Rožić Ljiljana S.

    2011-01-01

    Full Text Available In this study, the statistical design of the experimental method was applied on the acid activation process of bentonite with microwave irradiation. The influence of activation parameters (time, acid normality and microwave heating power on the selected process response of the activated bentonite samples was studied. The specific surface area was chosen for the process response, because the chemical, surface and structural properties of the activated clay determine and limit its potential applications. The relationship of various process parameters with the specific surface area of bentonite was examined. A mathematical model was developed using a second-order response surface model (RSM with a central composite design incorporating the above mentioned process parameters. The mathematical model developed helped in predicting the variation in specific surface area of activated bentonite with time (5-21 min, acid normality (2-7 N and microwave heating power (63-172 W. The calculated regression models were found to be statistically significant at the required range and presented little variability. Furthermore, high values of R2 (0.957 and R2 (adjusted (0.914 indicate a high dependence and correlation between the observed and the predicted values of the response. These high values also indicate that about 96% of the result of the total variation can be explained by this model. In addition, the model shows that increasing the time and acid normality improves the textural properties of bentonites, resulting in increased specific surface area. This model also can be useful for setting an optimum value of the activation parameters for achieving the maximum specific surface area. An optimum specific surface area of 142 m2g-1 was achieved with an acid normality of 5.2 N, activation time of 7.38 min and microwave power of 117 W. Acid activation of bentonite was found to occur faster with microwave irradiation than with conventional heating. Microwave

  1. Modified bentonite as adsorbent and catalyst for purification of wastewaters containing dyes

    Directory of Open Access Journals (Sweden)

    Žunić Marija J.

    2010-01-01

    Full Text Available Modification and characterization of bentonite from location Bogovina, Serbia was performed in order to obtain material applicable in wastewater purification. The <75μm bentonite fraction was used in organobentonite synthesis while the <2μm bentonite fraction, obtained by hydroseparation was used in pillaring procedure. Organo-modification of bentonite was performed with (1-hexadecyltrimethylammonium bromide (HDTMA-Br. Pillared bentonite was obtained using standard procedure. Al3+ and Fe3+ ions were incorporated in pillars in 4:1 ratio and applied as catalyst in catalytic wet peroxide oxidation. Differences in structure of starting and modified bentonites were established by XRD analysis and nitrogen physisorption on -196 °C. The (001 smectite peak around 2θ = 6° shifts during the modification process. The Na-exchange process lowered d001 from 1.53 nm (2θ = 5.78° for starting clay to 1.28 nm (2θ = 6.92°, but the clay retained its swelling properties. The pillaring process increased and fixed the basal spacing to 1.74 nm. Intercalation of HDTMA ions into smectite structure increased d001 to 2.00 nm for organobentonite. Specific surface area, SBET, was affected by particle size and type of modification. The samples with finer bentonite fraction had higher SBET due to increased smectite content. Na-exchanged bentonite samples had higher SBET value than starting clay samples of same granulation. Organomodification caused dramatic decrease in SBET value, while the pillaring process lead to an increase of SBET value. Adsorptive and catalytic purification of wastewaters containing dyes was tested using Acid Yellow 99 as a model dye. Na-exchanged bentonite had greater adsorption affinity for dye adsorption than raw bentonite owing to higher SBET. By organomodification this affinity was enhanced more than 70 times due to transition of bentonite surface from hydrophilic to organophilic. Al,Fe pillared bentonite was proven to be efficient in

  2. Bentonite erosion by dilute waters in initially saturated bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. One scenario of interest for the long-term safety assessment of a spent nuclear fuel repository involves the loss of bentonite buffer material through contact with dilute groundwater at a transmissive fracture interface (SKB 2011, Posiva 2012a). The scenario is based on the stable colloids at low ionic strength: - the cohesive forces of bentonite decrease in low-salinity conditions, and colloids start to dominate and are able to leave the gel-like bentonite on the groundwater bentonite boundary; - after colloid formation, groundwater may carry away the only just released clay colloids; - low-salinity events are most probable during post-glacial conditions, when also pressure gradients are high, causing elevated flow velocity, which may enhance colloidal transport. Therefore, it is very important from the point of view of repository safety assessment to be able to estimate how much bentonite may be lost during a post-glacial event, when the groundwater salinity and velocity, as well as the duration of the event are fixed. It is possible that more than one event will hit the same canister and buffer, and that several canisters and buffers may be jeopardized. The results in the issue so far may be divided into modelling attempts and experimental work. The modelling has been based on two main guidelines: external (Birgersson et al., 2009) and internal friction models (Neretnieks et al., 2009). However, these models have not been validated for erosion, probably due to lack of suitable laboratory data. The latter approach is more ambitious due to lack of fitting parameters, though the internal friction model itself may be varied. The internal friction model has proven to be time-consuming to solve numerically. This work indicates that experiments carried out by Schatz et al. (2012) differ significantly from the predictions obtained from Neretnieks' model. We present our numerical modelling results based on a set of

  3. The bentonite industry in North America

    International Nuclear Information System (INIS)

    The Canadian Nuclear Fuel Waste Management Program is studying a concept for the disposal of nuclear fuel waste at a depth of 500 to 1000 m below the surface in stable crystalline rock of the Canadian Shield. The waste containers would be surrounded by a clay-based buffer material, composed of equal proportions of bentonite clay and silica sand. In the reference disposal concept, some 1.9 x 105 Mg of used fuel would be emplaced. This would require 2.5 x 106 Mg of bentonite. A review of the bentonite industry in North America was carried out to establish the availability of sufficient high-quality material. There are proven reserves of sodium bentonite clay in excess of 1.5 x 108 Mg, and vast supplies are known to exist but not yet proven. The Canadian conceptual disposal vault would require 6 x 104 Mg of sodium bentonite each year for 40 years. The bentonite industry of North America has an installed annual production capacity of 2 x 107 Mg. A disposal vault would therefore require approximately 2% of the industry capacity. A number of commercial products have been screened for potential suitability for use as a component of the buffer. Ten currently marketed bentonite products have been identified as meeting the initial quality standards for the buffer, and two non-commercial bentonites have been identified as having the potential for use in a disposal vault. (Author) (14 figs., 7 tabs., 18 refs.)

  4. Observation et diagnostic de processus industriels à modèle non linéaire : application aux machines électriques

    OpenAIRE

    Mahamoud, Ayan

    2010-01-01

    Cette thèse porte sur la définition d'une stratégie robuste pour le diagnostic des processus industriels à modèle non linéaire. La stratégie définie repose sur l'utilisation d'observateurs non linéaires non seulement pour le diagnostic mais aussi pour la commande de ces systèmes. L'objectif est triple. L'observateur synthétisé devra reconstruire les variables d'état, être sensible aux défauts pour le diagnostic tout en étant robuste aux perturbations et autres incertitudes paramétriques pour ...

  5. Monitoring of bentonite pore water with a probe based on solid-state microsensors

    International Nuclear Information System (INIS)

    Repositories for the disposal of radioactive waste generally rely on a multi-barrier system to isolate the waste from the biosphere. This multi-barrier system typically comprises Natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system (EBS). Bentonite is being studied as an appropriated porous material for an EBS to prevent or delay the release and transport of radionuclides towards biosphere. The study of pore water chemistry within bentonite barriers will permit to understand the transport phenomena of radionuclides and obtain a database of the bentonite-water interaction processes. In this work, the measurement of some chemical parameters in bentonite pore water using solid-state microsensors is proposed. Those sensors are well suited for this application since in situ measurements are feasible and they are robust enough for the long periods of time that monitoring is needed in an EBS. A probe containing an ISFET (ion sensitive field effect transistor) for measuring pH, and platinum microelectrodes for measuring conductivity and redox potential was developed, together with the required instrumentation, to study the chemical changes in a test cell with compacted bentonite. Response features of the sensors' probe and instrumentation performance in synthetic samples with compositions similar to those present in bentonite barriers are reported. Measurements of sensors stability in a test cell are also presented

  6. The influence of the addition of polymers on the physico-chemical properties of bentonite suspensions

    Directory of Open Access Journals (Sweden)

    Stojiljkovic S.

    2014-01-01

    Full Text Available Bentonite clays have many applications in industries ranging from construction to cosmetics. Addition of polymers can profoundly influence the properties of bentonite suspensions and we now describe the influence of a range of different polymers. Whereas polyvinyl pyrolidone and soy isolate only slightly influenced the pH and the electrical conductivity of bentonite polymers in suspension, Carbopol solution caused decreases in both pH and electrical conductivity. As expected, strong electrolytes like sodium chloride caused big changes in the electrical conductivity of the suspensions. When the temperature of the bentonite suspensions was increased, the pH was almost unchanged, but the electrical conductivity increased. Bentonite treated with polymer suspensions can be used in purifying polluted water; for example, our results suggest that high pH caused by phosphorous salts can be addressed using bentonite modified with Carbopol. [Projekat Ministarstva nauke Republike Srbije: Stanisa Stojiljkovic, Vojkan Miljkovic, Goran Nikolic, Ivana Savic and Ivan Savic, TR 34020, Danijela Kostic 172047 and Biljana Arsic 174007

  7. Bentonite mat demonstration. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Serrato, M.G.

    1994-12-30

    The Bentonite Mat Demonstration was developed to provide the Environmental Restoration Department with field performance characteristics and engineering data for an alternative closure cover system configuration. The demonstration was initiated in response to regulatory concerns regarding the use of an alternative cover system for future design configurations. These design considerations are in lieu of the US Environmental Protection Agency (EPA) Recommended Design for Closure Cover Systems and specifically a single compacted kaolin clay layer with a hydraulic conductivity of 1 {times} 10{sup {minus}7} cm/sec. This alternative configuration is a composite geosynthetic material hydraulic barrier consisting from bottom to top: 2 ft compacted sandy clay layer (typical local Savannah River Site soil type) that is covered by a bentonite mat--geosynthetic clay liner (GCL) and is overlaid by a 40 mil High Density Polyethylene (HDPE) geomembrane--flexible membrane liner. This effort was undertaken to obtain and document the necessary field performance/engineering data for future designs and meet regulatory technical requirements for an alternative cover system configuration. The composite geosynthetic materials hydraulic barrier is the recommended alternative cover system configuration for containment of hazardous and low level radiological waste layers that have a high potential of subsidence to be used at the Savannah River Site (SRS). This alternative configuration mitigates subsidence effects in providing a flexible, lightweight cover system to maintain the integrity of the closure. The composite geosynthetic materials hydraulic barrier is recommended for the Sanitary Landfill and Low Level Radiological Waste Disposal Facility (LLRWDF) Closures.

  8. Thermal stability of the thermoluminescence trap structure of bentonite

    International Nuclear Information System (INIS)

    This work reports about the thermal stability of the blue thermoluminescence (TL) of a well-characterised natural bentonite from Almeria (Spain). The main interest of this clay, mainly composed of montmorillonite, is because of its application in the field of high-level radioactive waste (HLW) repository in deep-lying rocks. As observed in other aluminosilicates, bentonite exhibits a very complex structure of the emission spectra based on a wide broad maximum peaked at ∼265 deg. C that can be associated to physico-chemical processes such as dehydroxylation processes, consecutive breaking linking of bonds, formation of hydrolysed ions and redox reactions. The thermal stability tests performed at different temperatures confirm a continuum in the distribution of traps. Hence, the glow curve analysis methods commonly used for synthetic materials based on single discrete traps cannot be applied for this material and the kinetic parameters were fitted assuming an exponential distribution of trapped electrons. (authors)

  9. Assessment Criteria of Bentonite Binding Properties

    Directory of Open Access Journals (Sweden)

    S. Żymankowska-Kumon

    2012-09-01

    Full Text Available The criteria, with which one should be guided at the assessment of the binding properties of bentonites used for moulding sands, areproposed in the paper. Apart from the standard parameter which is the active bentonite content, the unrestrained growth indicator should be taken into account since it seems to be more adequate in the estimation of the sand compression strength. The investigations performed for three kinds of bentonites, applied in the Polish foundry plants, subjected to a high temperature influences indicate, that the pathway of changes of the unrestrained growth indicator is very similar to the pathway of changes of the sand compression strength. Instead, the character of changes of the montmorillonite content in the sand in dependence of the temperature is quite different. The sand exhibits the significant active bentonite content, and the sand compression strength decreases rapidly. The montmorillonite content in bentonite samples was determined by the modern copper complex method of triethylenetetraamine (Cu(II-TET. Tests were performed for bentonites and for sands with those bentonites subjected to high temperatures influences in a range: 100-700ºC.

  10. Effectiveness of fracture sealing with bentonite grouting

    International Nuclear Information System (INIS)

    Bentonite is known to have an extremely low permeability and a self-healing ability. It has therefore been selected as a major sealing component in several repository concepts. Bentonite grouts have the following advantages, (1) small particle size, can be injected into small fractures or voids, (2) suitable water absorption properties, can produce gels at low concentrations, and (3) stable physical and chemical properties, may have considerable longevity. Bentonite fracture grouting tests are performed on a model made of circular acrylic plates with outer diameter of 30 cm and central injection hole of 2.5 cm diameter. Suspension with bentonite concentration of 15% to 31% have been injected into fractures with apertures of 9 to 90 microns under injection pressures less than 0.6 MPa. Grouting reduces the hydraulic conductivities of the fractures from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in more than 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studies. The physical stability or bleeding capacity of bentonite suspensions is determined. 122 refs., 56 figs., 10 tabs

  11. Quality assurance of the bentonite material

    International Nuclear Information System (INIS)

    This report describes a quality assurance chain for the bentonite material acquisition for a nuclear waste disposal repository. Chemical, mineralogical and geotechnical methods, which may be applied in quality control of bentonite are shortly reviewed. As a case study, many of the presented control studies were performed for six different bentonite samples. Chemical analysis is a very reliable research method to control material homogeneity, because the accuracy and repeatability of the study method is extremely good. Accurate mineralogical study of bentonite is a complicated task. X-ray diffractometry is the best method to identify smectite minerals, but quantitative analysis of smectite content remains uncertain. To obtain a better quantitative analysis, development of techniques based on automatic image analysis of SEM images is proposed. General characteristics of bentonite can be obtained by rapid indicator tests, which can be done on the place of reception. These tests are methylene blue test giving information on the cation exchange capacity, swelling index and determination of water absorption. Different methods were used in the determination of cation exchange capacity (CEC) of bentonite. The results indicated differences both between methodologies and between replicate determinations for the same material and method. Additional work should be done to improve the reliability and reproducibility of the methodology. Bentonite contains water in different modes. Thus, different determination methods are used in bentonite studies and they give somewhat dissimilar results. Clay research use frequently the so-called consistency tests (liquid limit, plastic limit and plasticity index). This study method does, however, not seem to be very practical in quality control of bentonite. Therefore, only the determination of liquid limit with fall-cone method is recommended for quality control. (orig.)

  12. Activation of wine bentonite with gamma rays

    International Nuclear Information System (INIS)

    The action of gamma rays on wine bentonite as well as influence of its adsorption and technologic qualities on the composition and stability of wines against protein darkening and precipitation has been studied. The experiments were carried out with wine bentonite produced in the firm Bentonite and irradiated with doses of 0.4, 0.6, 0.8 and 1.0 MR. White and red wines have been treated with irradiated bentonite under laboratory conditions at 1.0 g/dm3. All samples are treated at the same conditions. The flocculation rate of the sediment was determined visually. Samples have been taken 24 h later from the cleared wine layers. The following parameters have been determined: clarification, filtration rate, phenolic compounds, calcium, colour intensity, total extracted substances, etc. The volume of the sediment has been determined also. The control samples have been taken from the same unirradiated wines. The results showed better and faster clarification in on the third, the 20th and the 24th hours with using of gamma-irradiated at doses 0.8 and 1.0 MR. The sediment was the most compact and its volume - the smallest compared to the samples treated with bentonite irradiated with doses of 0.6 and 0.4 MR. This ensures a faster clarification and better filtration of treated wines. The bentonite activated with doses of 0.8 and 1.0 MR adsorbs the phenolic compounds and the complex protein-phenolic molecules better. In the same time it adsorbs less extracted substances compared to untreated bentonite and so preserves all organoleptic properties of wine. The irradiated bentonite adsorbs less the monomers of anthocyan compounds which ensures brighter natural colour of wine. The gamma-rays activation consolidates calcium in the crystal lattice of bentonite particles and in this way eliminates the formation of crystal precipitates

  13. Diffusion, sorption, and retardation processes of anions in bentonite and organo-bentonites for multibarrier systems

    Science.gov (United States)

    Schampera, Birgit; Dultz, Stefan

    2013-04-01

    The low permeability, high cation exchange capacity (CEC) and plasticity of bentonites favor their use in multibarrier systems of waste deposits [1]. Bentonites have a high CEC but their ability to sorb anions is very low. There is, however, need for retardation of anions and organic pollutants in many applications. Bentonites, modified with certain organic cations, have the capacity to sorb anions and non-polar organic compounds in addition to cations. Investigations on organically modified clays address a wide variety of applications including immobilization of pollutants in contaminated soils, waste water treatment and in situ placement for the protection of ground water [2]. Many experiments on anion and cation sorption of organo-clays were conducted in the batch mode which does not reflect solid-liquid ratios and material densities in barrier systems. Diffusion experiments on compacted clays allow the evaluation of transport processes and sorption of pollutants at conditions relevant for repositories. For organo-clays only few diffusion studies are published e.g. [3] measured the diffusion of tritium and [4] the diffusion of H2O in bentonite and organo-bentonites. The organic cation hexadecylpyridinium (HDPy) was added to Wyoming bentonite (MX-80) in amounts corresponding to 2-400 % of the CEC. The uptake of organic cations was determined by the C-content, XRD and IR-spectroscopy. Wettability was analyzed by the contact angle. Physical, chemical and mineralogical properties of clays were characterized. Diffusion experiments were carried out in situ in a cell attached to the ATR-unit of a FTIR-spectrometer. For H2O-diffusion the compacted organo-clays are saturated first with D2O, afterwards H2O is supplied to the surface at the top of the clay platelet. Anion-diffusion was conducted with NO3--solution instead of H2O only having characteristic IR band positions at 1350 cm-1. Three different concentrations (0.25M, 0.5M and 1M) were used. Additional batch

  14. ESTIMATION DES PERTES FER DANS LES MACHINES ELECTRIQUES.
    MODELE D'HYSTERESIS LOSS SURFACE ET APPLICATION AUX MACHINES SYNCHRONES A AIMANTS.

    OpenAIRE

    Gautreau, Thierry

    2005-01-01

    Suite aux directives européennes incitant les constructeurs de moteurs électriques à supprimerde leur offre, les moteurs à faible rendement, une politique de conception de moteurs à hautrendement est engagée. Toutefois, l'évaluation préalable, en simulation, de ce paramètre, etnotamment des pertes fer de la machine reste aujourd'hui un problème difficile. Dans cetteoptique, depuis quelques années, un modèle, nommé « Loss Surface », de calcul a posteriorides pertes fer sous le logiciel élément...

  15. Modelling Iron-Bentonite Interactions

    Science.gov (United States)

    Watson, C.; Savage, D.; Benbow, S.; Wilson, J.

    2009-04-01

    The presence of both iron canisters and bentonitic clay in some engineered barrier system (EBS) designs for the geological disposal of high-level radioactive wastes creates the potential for chemical interactions which may impact upon the long-term performance of the clay as a barrier to radionuclide migration. Flooding of potential radionuclide sorption sites on the clay by ferrous ions and conversion of clay to non-swelling sheet silicates (e.g. berthierine) are two possible outcomes deleterious to long-term performance. Laboratory experimental studies of the corrosion of iron in clay show that corrosion product layers are generally thin ( 250 °C) are dominated by chlorite, whereas lower temperatures produce berthierine, odinite, cronstedtite, or Fe-rich smectite. Unfortunately, the inevitable short-term nature of laboratory experimental studies introduces issues of metastability and kinetics. The sequential formation in time of minerals in natural systems often produces the formation of phases not predicted by equilibrium thermodynamics. Evidence from analogous natural systems suggests that the sequence of alteration of clay by Fe-rich fluids will proceed via an Ostwald step sequence. The computer code, QPAC, has been modified to incorporate processes of nucleation, growth, precursor cannibalisation, and Ostwald ripening to address the issues of the slow growth of bentonite alteration products. This, together with inclusion of processes of iron corrosion and diffusion, has enabled investigation of a representative model of the alteration of bentonite in a typical EBS environment. Simulations with fixed mineral surface areas show that berthierine dominates the solid product assemblage, with siderite replacing it at simulation times greater than 10 000 years. Simulations with time-dependent mineral surface areas show a sequence of solid alteration products, described by: magnetite -> cronstedtite -> berthierine -> chlorite. Using plausible estimates of mineral

  16. Segregation of bentonite components in order to achieve nano montmorillonite

    International Nuclear Information System (INIS)

    Nano technology makes the possibility to achieve specific properties for materials. In this process, by reducing the size of materials in the range of nano size, new noticeable behaviour for material can be observed. Such behaviour cannot be observed for larger particles from that material. Bentonite soils contain more than 76% montmorillonite and some other minerals. Pure montmorillonite with nano size has a vast industrial application in which its production is relatively costly and time consuming. This research is aimed to propose a method for segregation of bentonite components to reach nano montmorillonite. To achieve this objective, a mechanical method is proposed. Based on this method, a nano montmorillonite with micro and nano size is achieved. The segregation process is monitored with PSA, XRD, SSA and SEM experiments. The results of this research show that a nano montmorillonite with SSA of 522.58 m2/g and average diameter of 6.13 micron is attained. The achieved nano montmorillonite has larger purity in comparison to Cloisite Na+. In addition, it has lower average particle size than Cloisite Na+. Furthermore, according to the results of this research the extracted nano clay is free from carbonate and quartz particles. The SSA of this nano montmorillonite was 25% more than that of bentonite. The proposed method is relatively inexpensive. Moreover, since no chemical is used in its production process, it is a suitable sample for practical, research, and industrial projects.

  17. Gas migration through bentonite clay

    International Nuclear Information System (INIS)

    Hydrogen gas produced by irradiation of pore water in the highly compacted bentonite that surrounds the copper canisters according to the KBS 2 and 3 concepts, may escape from the clay/copper interface if the gas pressure is higher than the groundwater pressure. A reasonable physical model predicts that gas may penetrate wider capillary passages that actually exist in the very dense clay, although these passages are still of microscopic size. In the large majority of the clay voids, the capillary action is sufficient, however, to resist gas penetration, and this suggests that a possible mechanism of gas migration is that of a finger-like pattern of tortuous gas passages extending from the canisters if radiolysis takes place at all. Two series of experiments have been run at gas pressures up to about 10 MPa. Nitrogen as well as hydrogen were used in these tests which seem to confirm, in principle, the validity of the physical model. (authors)

  18. Effect of bentonites on fluorometric selenium determination

    International Nuclear Information System (INIS)

    Bentonites in feeds cause error in the analysis for Se by the AOAC (3.097-3.101) fluorometric method for Se in plants. The error apparently results from the binding of the piazselenol by insoluble residue from the bentonite. This effect is avoided by diluting digests to volume after reduction with HCl, centrifuging or allowing to stand, and analyzing a portion of the clear supernatant liquid. Insoluble residues present after digestion of plant materials do not appear to cause a similar error

  19. Thermal cycling: impact on bentonite permeability

    OpenAIRE

    Zihms, S.G.; Harrington, J. F.

    2015-01-01

    Due to its favourable properties, in particular, low permeability and swelling capacity, bentonite has been favoured as an engineered-barrier and backfill material for the geological storage of radioactive waste. To ensure its safe long-term performance it is important to understand any changes in these properties when the material is subject to heat-emitting waste. As such, this study investigates the hydraulic response of bentonite under multi-step thermal loading subject to a constant-volu...

  20. Diffusion of humic colloids in compacted bentonite

    International Nuclear Information System (INIS)

    In Sweden, as in many other countries, compacted bentonite will surround the encapsulated spent nuclear fuel in a deep bedrock repository. Bentonite gives mechanical support and minimizes the water flow over the deposition holes. The retardation for cationic radionuclides escaping a faulted canister is high in saturated compacted bentonite, since cationic radionuclides sorbs strongly on the bentonite surface, and the only plausible transport mechanism is diffusion. Sorption and diffusion of radionuclides in the bentonite barrier has been extensively studied, and sorption and diffusion coefficients are well established. There is a lack of knowledge as well as data for effects of colloids on radionuclide mobility and transport in the bentonite barrier. In a deep bedrock repository, colloids, particles in the size range of 1-1000 nm, will be present, however in very low concentrations. The colloids origin from eroded bedrock and filling material, mineral oxides, clay, degraded organic compounds and micro-organisms etc. The bentonite barrier is regarded to be an efficient filtering barrier for colloids. With the widely spread micro-structure with pores in between the montmorillonite flakes in the size range of nm, and the inter particle voids partly gel filled of sizes, colloid transport seems unlikely. In a Japanese diffusion study on gold colloids no breakthrough of the colloids was detected. However, to reject the possibility of enhancement of transport of radionuclides by colloids, more data from diffusion studies on other types of colloids in compacted bentonite are needed. Therefore diffusion experiments of Humic Colloids (HC), in the size range of 1-10 nm, were performed. (author)

  1. Methodological study of the diffusion of interacting cations through clays. Application: experimental tests and simulation of coupled chemistry-diffusion transport of alkaline ions through a synthetical bentonite; Etude methodologique de la diffusion de cations interagissants dans les argiles. Application: mise en oeuvre experimentale et modelisation du couplage chimie-diffusion d'alcalins dans une bentonite synthetique

    Energy Technology Data Exchange (ETDEWEB)

    Melkior, Th

    2000-07-01

    The subject of this work deals with the project of underground disposal of radioactive wastes in deep geological formations. It concerns the study of the migration of radionuclides through clays. In these materials, the main transport mechanism is assumed to be diffusion under natural conditions. Therefore, some diffusion experiments are conducted. With interacting solutes which present a strong affinity for the material, the duration of these tests will be too long, for the range of concentrations of interest. An alternative is to determine on one hand the geochemical retention properties using batch tests and crushed rock samples and, on the other hand, to deduce the transport parameters from diffusion tests realised with a non-interacting tracer, tritiated water. These data are then used to simulate the migration of the reactive elements with a numerical code which can deal with coupled chemistry-diffusion equations. The validity of this approach is tested by comparing the numerical simulations with the results of diffusion experiments of cations through a clay. The subject is investigated in the case of the diffusion of cesium, lithium and sodium through a compacted sodium bentonite. The diffusion tests are realised with the through-diffusion method. The comparison between the experimental results and the simulations shows that the latter tends to under estimate the propagation of the considered species. The differences could be attributed to surface diffusion and to a decrease of the accessibility to the sites of fixation of the bentonite, from the conditions of clay suspensions in batch tests to the situation of compacted samples. The influence of the experimental apparatus used during the diffusion tests on the results of the measurement has also been tested. It showed that these apparatus have to be taken into consideration when the experimental data are interpreted. A specific model has been therefore developed with the numerical code CASTEM 2000. (author)

  2. Removal of oil from water by bentonite

    International Nuclear Information System (INIS)

    Many materials, included activated carbon, peat, coal, fiberglass, polypropylene, organoclay and bentonite have been used for removing oils and grease from water. However, bentonite has been used only rarely for this purpose. In this study Na-bentonite was used to remove oil from oil-in-water emulsions of various kinds such as standard mineral oil, cutting oils, refinery effluent and produced water from production wells at Estevan, Saskatchewan. Removal efficiencies obtained were 85 to 96 per cent for cutting oils, 84 to 86 per cent for produced water and 54 to 87 per cent for refinery effluent. Bentonite proved to be more effective in the removal of oil from oil-in-water emulsions than from actual waste waters; up to 96 percent from oil-in-water emulsions to only 87 per cent from actual waste water. The percentage of oil removed was found to be a function of the amount of bentonite added and the adsorption time up to the equilibrium time. Result also showed that the Langmuir, Freundlich and BET isotherms are well suited to describe the adsorption of oil by bentonite from the various oily waters employed in this study. 15 refs

  3. Etude, analyse et modélisation physique de la production de la parole avec applications aux troubles liés à une surdité profonde

    OpenAIRE

    Delebecque, Louis

    2015-01-01

    L’apprentissage du langage parlé nécessite un contrôle musculaire très précis des différents organes intervenant dans la production de la parole. La production de sons voisés, qui résulte de l’auto-oscillation des cordes vocales, est notamment influencée par l’ensemble du système phonatoire, du diaphragme jusqu’aux lèvres. Les travaux réalisés dans le cadre de cette thèse s’inscrivent dans un contexte de modélisation physique de la parole. Les objectifs s’articulent autour de la compréhension...

  4. Détection et isolation de pannes basées sur la platitude différentielle. Application aux engins atmosphériques.

    OpenAIRE

    Zhang, Nan

    2010-01-01

    Ce travail de thèse aborde le problème de la détection et de l’isolation des pannes à base de modèle du système dynamique non linéaire. Les techniques de détection et d’identification de pannes sont déjà appliquées aux systèmes industriels et elles jouent un rôle important pour assurer les performances attendues des systèmes automatiques. Les différentes approches du diagnostic des systèmes dynamiques semblent être souvent le résultat de contextes différents notamment en ce qui concerne les a...

  5. Les déterminants du coût du capital des petites capitalisations : application aux segments B et C de la Bourse de Paris

    OpenAIRE

    Marrot, Olivier

    2008-01-01

    La spécificité des petites capitalisations (l’effet taille), est au centre des recherches en finance depuis de nombreuses années. Peu de travaux se sont cependant concentrés sur ce compartiment. Notre recherche porte sur les sociétés des listes B et C d’Euronext Paris sur la période 1994-2004. Le modèle APT avec utilisation d’attributs spécifiques comme sensibilité aux risques affectant la rentabilité des titres, palie la faible significativité des bêtas. Conformément à la littérature sur les...

  6. Contribution à la conception de circuits intégrés analogiques en technologie CMOS basse tension pour application aux instruments d'observation de la Terre

    OpenAIRE

    Standarovski, Denis

    2005-01-01

    Le présent mémoire de thèse s'inscrit dans la problématique d'intégration de chaînes pour traitement du signal vidéo issu d'un capteur CCD dédiées aux instruments d'observation de la Terre. La solution présentée à travers cette étude consiste à concevoir des circuits intégrés spécifiques (ASIC) analogiques avec des technologies CMOS sub-microniques basse-tension, principalement développées pour les circuits numériques complexes. Dans une première partie, nous présentons le contexte de l'étude...

  7. 0.25{mu}m radiation tolerant technology for space applications; Technology 0.25 {mu}m tolerante aux radiations pour les applications spatiales

    Energy Technology Data Exchange (ETDEWEB)

    Haddad, N.; Brady, F.; Scott, T.; Yoder, J. [Lockheed Martin Federal Systems, Manassas, VA (United States)

    1999-07-01

    Lockheed Martin federal systems has developed a state-of-the-art radiation tolerant 0,25 {mu}m CMOS capability that is compatible with commercial foundries as well as radiation hardened fabrication. A technology test chip was designed, fabricated and evaluated for performance, power and radiation hardness in order to validate the methodology and evaluate the technology. Testing results show that -) the active transistor threshold shift is negligible for 0.25 {mu}m CMOS, -) the hardened STI (shallow trench isolation) can support Mega-rad applications, and -) the holding voltage is well beyond the operating voltage of 2.5 V. This technology is intended to support high density, high performance and low power space applications.

  8. Application of Continuous Thermodynamics to Natural-Gas Mixtures Application de la thermodynamique continue aux mélanges de gaz naturel

    OpenAIRE

    Prausnitz J. M.; Cotterman R. L.

    2006-01-01

    This work reviews recent progress in the application of continuous thermodynamics towards calculation of phase equilibria in natural-gas mixtures. In such mixtures, there may be too many components to identify each component individually. Continuous thermodynamics provides a theoretical framework for representing the composition of a portion of the natural-gas mixture by a continuous distribution function. Advances in continuous thermodynamics are discussed in three areas :(1) Characterizatio...

  9. Exchangeability of bentonite buffer and backfill materials

    International Nuclear Information System (INIS)

    Clay-based buffer and tunnel backfill materials are important barriers in the KBS-3 repository concept for final disposal of spent nuclear fuel in Finland. One issue that is relevant to material properties is the degree to which different bentonite compositions can be regarded as interchangeable. In Posiva's current repository design, the reference bentonite composition is MX-80, a sodium montmorillonite dominated clay. Posiva would like to be able to use bentonite with Ca-montmorillonite as the dominant clay mineral. However, at this stage, it is not clear what supporting data need to be acquired/defined to be able to place the state of knowledge of Ca-bentonite at the same level as that of Na-bentonite. In this report, the concept of bentonite exchangeability has been evaluated through consideration of how bentonite behaviour may be affected in six key performance-relevant properties, namely (1) mineralogical composition and availability of materials, (2) hydraulic conductivity, (3) mechanical and rheological properties, (4) long-term alteration, (5) colloidal properties, and (6) swelling pressure. The report evaluates implications for both buffer and backfill. Summary conclusions are drawn from these sections to suggest how bentonite exchangeability may be addressed in regulatory assessments of engineered barrier design for a future geological repository for spent fuel in Finland. Some important conclusions are: (a) There are some fundamental differences between Ca- and Na-bentonites such as colloidal behaviour, pore structure and long-term alteration that could affect the exchangeability of these materials as buffer or backfill materials and which should be further evaluated; (b) Additional experimental data are desirable for some issues such as long-term alteration, hydraulic properties and swelling behaviour, (c) The minor mineral content of bentonites is very variable, both between different bentonites and within the same bentonite type, it is not clear

  10. Pore water chemistry of the febex bentonite

    International Nuclear Information System (INIS)

    The knowledge of pore water chemistry in the clay barrier is essential for performance assessment purposes in a nuclear waste repository, since the pore water composition controls the processes involved in the release and transport of the radionuclides. The methodology followed to define the representative composition of the FEBEX bentonite pore water is presented in this paper. A series of bentonite-water interaction tests have been performed with the aim of providing a database on the main chemical parameters of the bentonite. These tests were carried out both with high solid to liquid (s:l) ratios (squeezing tests) and low s:l ratios (aqueous extracts tests). The exchangeable cations have also been analyzed to determine the selectivity coefficient of the exchange reactions. To complete the data set, a physical and mineralogical characterization of the bentonite was made. The most significant bentonite-water interaction processes controlling the chemistry of the system was identified. The ion concentrations basically depend on the s:l ratio of the system, and the pore water composition is controlled by the dissolution of chlorides, dissolution/precipitation of carbonates and sulphates and the cation exchange reactions in the smectite. The bentonite/water system was modelled with the PHREEQC2 program to obtain the best possible estimation of the pore water composition for initial conditions of water content (=14%), after checking the conceptual model with the experimental results. The model predictions fitted satisfactorily with the experimental data at low s:l ratios. At high s:l ratios, the modelled results agree adequately, except for the sulphate content, which could be affected by the effective porosity, anion exclusion or stagnant zones not taken into account in the model. According to the model, the FEBEX bentonite pore water at 14% moisture is a sodium-chloride type, with an ionic strength of 0.25 M and pH of 7.78. Copyright (2001) Material Research

  11. Microbial activity in bentonite buffers. Literature study

    Energy Technology Data Exchange (ETDEWEB)

    Ratto, M.; Itavaara, M.

    2012-07-01

    The proposed disposal concept for high-level radioactive wastes involves storing the wastes underground in copper-iron containers embedded in buffer material of compacted bentonite. Hydrogen sulphide production by sulphate-reducing prokaryotes is a potential mechanism that could cause corrosion of waste containers in repository conditions. The prevailing conditions in compacted bentonite buffer will be harsh. The swelling pressure is 7-8 MPa, the amount of free water is low and the average pore and pore throat diameters are small. This literature study aims to assess the potential of microbial activity in bentonite buffers. Literature on the environmental limits of microbial life in extreme conditions and the occurrence of sulphatereducing prokaryotes in extreme environments is reviewed briefly and the results of published studies characterizing microbes and microbial processes in repository conditions or in relevant subsurface environments are presented. The presence of bacteria, including SRBs, has been confirmed in deep groundwater and bentonite-based materials. Sulphate reducers have been detected in various high-pressure environments, and sulphate-reduction based on hydrogen as an energy source is considered a major microbial process in deep subsurface environments. In bentonite, microbial activity is strongly suppressed, mainly due to the low amount of free water and small pores, which limit the transport of microbes and nutrients. Spore-forming bacteria have been shown to survive in compacted bentonite as dormant spores, and they are able to resume a metabolically active state after decompaction. Thus, microbial sulphide production may increase in repository conditions if the dry density of the bentonite buffer is locally reduced. (orig.)

  12. Microbial activity in bentonite buffers. Literature study

    International Nuclear Information System (INIS)

    The proposed disposal concept for high-level radioactive wastes involves storing the wastes underground in copper-iron containers embedded in buffer material of compacted bentonite. Hydrogen sulphide production by sulphate-reducing prokaryotes is a potential mechanism that could cause corrosion of waste containers in repository conditions. The prevailing conditions in compacted bentonite buffer will be harsh. The swelling pressure is 7-8 MPa, the amount of free water is low and the average pore and pore throat diameters are small. This literature study aims to assess the potential of microbial activity in bentonite buffers. Literature on the environmental limits of microbial life in extreme conditions and the occurrence of sulphatereducing prokaryotes in extreme environments is reviewed briefly and the results of published studies characterizing microbes and microbial processes in repository conditions or in relevant subsurface environments are presented. The presence of bacteria, including SRBs, has been confirmed in deep groundwater and bentonite-based materials. Sulphate reducers have been detected in various high-pressure environments, and sulphate-reduction based on hydrogen as an energy source is considered a major microbial process in deep subsurface environments. In bentonite, microbial activity is strongly suppressed, mainly due to the low amount of free water and small pores, which limit the transport of microbes and nutrients. Spore-forming bacteria have been shown to survive in compacted bentonite as dormant spores, and they are able to resume a metabolically active state after decompaction. Thus, microbial sulphide production may increase in repository conditions if the dry density of the bentonite buffer is locally reduced. (orig.)

  13. Enhancement of the bentonite sorption properties

    Energy Technology Data Exchange (ETDEWEB)

    Mockovciakova, Annamaria, E-mail: mocka@saske.sk [Institute of Geotechnics, Slovak Academy of Sciences Watsonova 45, 04354 Kosice (Slovakia); Orolinova, Zuzana [Institute of Geotechnics, Slovak Academy of Sciences Watsonova 45, 04354 Kosice (Slovakia); Skvarla, Jiri [Institute of Montaneous Sciences and Environmental Protection, Technical University in Kosice, Park Komenskeho 19, 04200 Kosice (Slovakia)

    2010-08-15

    The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 deg. C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Moessbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low.

  14. Migration behavior of iodine in compacted bentonite

    International Nuclear Information System (INIS)

    When the wastes that include I-129 dispose, compacted bentonite would be used as buffer material as well as for HLW disposal. Therefore in this study diffusion experiments were carried out to investigate the migration behavior of iodine in compacted bentonite. Bentonite used in this study consists of more than 95 % of sodium montmorillonite. Bentonite powder was compacted into a cylinder with a diameter of 10 mm and a height of 10 mm with a varied dry density. After saturated with water including 0.01 M of NaCl for one month, approximately 10 micro liters of tracer solution I- or IO3- were spiked on a surface of compacted bentonite respectively. The constant boundary concentrations and the diffusion coefficients of I- and IO3- were determined by the penetration method. Iodine profiles showed typical shape of error function complement. The constant boundary concentration of I- is several times larger than that of IO3-. This could be cause by geometrical limitation and/or anion exclusion of montmorillonite because IO3- is larger than I- and montmorillonite has negative surface charge. Apparent diffusion coefficients of I- and IO3- were obtained in the range of 27.0 to 192.9 μm2/s and 9.8 to 117.4 μm2/s, respectively. (author)

  15. Bentonite-amended soil special study

    International Nuclear Information System (INIS)

    This special study was conducted to assess the viability of soil with a high percentage of bentonite added as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. To achieve maximum concentration limits (MCLs) at several UMTRA Project sites, covers with a very low permeability are needed. If alternate concentration limits (ACLs) are the appropriate site groundwater compliance strategy, the US Department of Energy (DOE) is required to demonstrate, among other things, that the infiltration to the disposal cell is as low as reasonably achievable, and hence that the cover has a very low permeability. When the study discussed here was begun, the lowest permeability element available was CLAYMAXR, a manufactured liner material constructed of natural material (bentonite clay) between two geosynthetics.The strength of soil-bentonite mixes was measured to see if they could be placed on sideslopes and not pose stability problems. Also evaluated were the hydraulic conductivities of soil-bentonite mixes. If the strengths and permeabilities of soils with a high percentage of bentonite are favorable, the soils may be used as infiltration barriers in current cover designs without changing pile geometries. The scope of work for this study called for a literature review and a two-phased laboratory testing program. This report presents the results of the literature review and the first phase of the testing program

  16. Development of interface tracking method. Two-phase flows applications; Developpement d'une methode de suivi d'interface. Applications aux ecoulements diphasiques

    Energy Technology Data Exchange (ETDEWEB)

    Tanguy, S.

    2004-11-15

    Spray formation mechanisms study from a liquid-gas flow is a fundamental research subject, which industrial applications are large, especially in combustion and propulsion field. Numerical simulation of such flows appear as an essential complement to experimental and theoretical studies, for comprehension and accurate prediction of such physical processes. In this study we developed an numerical interface tracking technique with a Navier-Stokes solver to study accurately the liquid-gas interface dynamics. We describe Level Set method which has been used to track interface motion, and numerical methods for solving Navier-Stokes equations. Different numerical schemes have been tested to improve the computation accuracy. Ghost Fluid Method enables a robust and accurate treatment of discontinuities across the liquid-gas interface. The codes developed (2D, 3D, parallelization MPI) are then used to study droplets collisions. Comparisons with experimental results show that simulations are realistic and predictive. Next, feasibility studies are done on more complex configurations. Droplets spray formation from primary atomization of a liquid jet seems to be especially a promising investigation field for such simulations. Finally, reactive interfaces propagation, as liquid vaporization and premixed combustion have also been studied using Ghost Fluid Method to impose specific jump conditions. (author)

  17. CHARACTERIZATION OF BENTONITE FOR ENGINEERED BARRIER SYSTEMS IN RADIOACTIVE WASTE DISPOSAL SITES

    Directory of Open Access Journals (Sweden)

    Dubravko Domitrović

    2012-07-01

    Full Text Available Engineered barrier systems are used in radioactive waste disposal sites in order to provide better protection of humans and the environment from the potential hazards associated with the radioactive waste disposal. The engineered barrier systems usually contain cement or clay (bentonite because of their isolation properties and long term performance. Quality control tests of clays are the same for all engineering barrier systems. Differences may arise in the required criteria to be met due for different application. Prescribed clay properties depend also on the type of host rocks. This article presents radioactive waste management based on best international practice. Standard quality control procedures for bentonite used as a sealing barrier in radioactive waste disposal sites are described as some personal experiences and results of the index tests (free swelling index, water adsorption capacity, plasticity limits and hydraulic permeability of bentonite (the paper is published in Croatian.

  18. Eutrophication management in surface waters using lanthanum modified bentonite

    DEFF Research Database (Denmark)

    Copetti, Diego; Finsterle, Karin; Marziali, Laura;

    2016-01-01

    This paper reviews the scientific knowledge on the use of a lanthanum modified bentonite (LMB) to manage eutrophication in surface water. The LMB has been applied in around 200 environments worldwide and it has undergone extensive testing at laboratory, mesocosm, and whole lake scales. The...... alkalinity waters. To date there are no indications for long-term negative effects on LMB treated ecosystems, but issues related to La accumulation, increase of suspended solids and drastic resources depletion still need to be explored, in particular for sediment dwelling organisms. Application of LMB in...... saline waters need a careful risk evaluation due to potential lanthanum release....

  19. Sealing performance of bentonite and bentonite/crushed rock borehole plugs

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, S.; Daemen, J.J.K. [Arizona Univ., Tucson, AZ (United States). Dept. of Mining and Geological Engineering

    1992-07-01

    This study includes a systematic investigation of the sealing performance of bentonite and bentonite/crushed rock plugs. American Colloid C/S granular bentonite and crushed Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that a composition to yield a permeability lower than 5 {times} 10{sup {minus}8} cm/s would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no significant effect on the sealing performance within the test range from room temperature to 600{degree}C. Piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for samples with a bentonite content of 25 and 35%, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for plug design. A permeability model is developed for the prediction of permeability in clays, especially in view of the difficulties in obtaining this property experimentally. A piping model is derived based on plastic flow theory. This piping model permits the estimation of critical hydraulic gradients at which flow of bentonite takes place. The model can also be used to define the maximum allowable pore diameter of a protective filter layer.

  20. MANU. Purchase of Bentonite. Process Description

    International Nuclear Information System (INIS)

    The aim of this study is to describe the entire bentonite purchasing process accurately. This will enable efficient and focused use of information related to the purchasing phase and to each individual bentonite batch. This work continues from the work started in the report by Ahonen et al. (2008), Quality Assurance of the Bentonite Material, Posiva Working Report 2008-33. The current work includes a short enquiry for all relevant and at the time known producers or re-sellers of bentonite. Questions about relevant products suitable for civil engineering use, more specifically nuclear waste disposal site use, were asked together with test methods, typical test results and test standards. The following aspects and opinions have been processed from the results that were obtained during the project. Each seller/producer has a quality management system, QMS (typically ISO 9001), and ability to perform the basic tests, but there is not an established common set of properties to be tested. Some producers are willing to test according to customers' specifications. Posiva could arrange a network of capable laboratories to carry out tests according to its selected standards. This activity should then be accredited with a reasonable testing volume. Before starting the purchase of bentonite at a large scale, Posiva should go through negotiations and audits with each seller in order to make sure that both parties are testing with the same methods and both understand the range where the values of key parameters may lie. A database is needed for gathering statistically relevant information from the bentonite material parameters over the long run. This is needed for determining the limits within which the material parameters should remain in order to be acceptable. Posiva is encouraged to create a process to optimize the test types and the amount of tests should be identified for immediate and long term use. This process ensures the required quality and costs involved. (orig.)

  1. Erosion properties and dispersion-flocculation behavior of bentonite particles

    International Nuclear Information System (INIS)

    Experimental and theoretical studies have been performed to clarify the ability of flowing groundwater in contact with bentonite to generate bentonite colloidal particles and disperse such colloids. This information is required to determine (a) the long-term stability of bentonite as a buffer material for borehole disposal of radioactive wastes in deep geologic media and (b) the potential influence of bentonite colloidal particles on radionuclide transport, specifically for use in scenario analyses in the performance assessment of waste disposal. In this study, the minimum groundwater velocity required to erode particles of Na-bentonite or Ca-bentonite from a bentonite surface in contact with groundwater was derived from shear strengths of aqueous bentonite gel suspensions, as determined by viscometer tests. The shear strengths were used to estimate the corresponding shear force on bentonite particle-particle bonds, using an estimated value for the number of initial bentonite particle-particle bonds in the experimental systems studied. The derived shear force was converted to corresponding groundwater velocity by using Stokes' equation and simplifying assumptions. The results indicate that groundwater velocities in a range of about 10-5 to 10-4 m/s would be required to initiate bentonite erosion. This range is higher than the groundwater flow velocity generally found in deep geologic media in Japan. In addition, known groundwater electrolyte concentrations were compared with theoretical estimates of aqueous electrolyte concentrations required to flocculate colloidal bentonite particles (for example 1 x 10-3 mol/l Na+). The comparison indicates that, even if erosion of bentonite occurred, the colloidal bentonite particles formed would flocculate. As a result, this study has shown that the effect of bentonite colloids on radionuclide transport is likely to be negligible in the performance assessment of radioactive waste disposal in deep geologic media

  2. Preparation and characterization of bentonite organo clay

    International Nuclear Information System (INIS)

    Bentonite clays organically modified have great potential use for environmental remediation, especially in the separation of organic compounds from the water. The aim of this work was the preparation of organophilic clays from 'Verde-Lodo' bentonite clay with the quaternary ammonium salts cetyl-pyridinium chloride and benzalkonium chloride. The materials obtained were characterized by XRD, thermogravimetric analyses, Helium picnometry, SEM and energy dispersive X-ray techniques. The results show consistently successful synthesis of the organoclay through the increase in the basal spacing, as well as salt elimination picks and presence of carbon and chlorine in the modified clays; they are inexistent elements in the natural clay. (author)

  3. Retention of chromium by modified Al-Bentonite

    OpenAIRE

    Volzone C.; Garrido L. B.

    2002-01-01

    Retention of chromium (III) from a tanning wastewater by modified Al-bentonites was studied. One bentonite from San Juan province, Argentina, was used. Al-bentonite was prepared by contact of bentonite with hydrolyzed OH-Al solutions (0.10 M in Al) for 24 hours. The modified Al-bentonites were obtained by: a) treatment with 0.5 M sodium chloride; b) with 0.5 M sodium chloride adjusted at pH 8; and c) treatment with an hexametaphosphate solution after sodium addition. Then, the samples were dr...

  4. Effects of silica sol on bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Compacted bentonite will be used in Sweden as an engineered barrier in the disposal of nuclear waste, mainly due to bentonites sorption and swelling capacity, where the latter property is warranted in order to seal possible future intersecting fractures. However during the actual construction and deposition period other grouting agents must be used in order to seal already existing fractures. In Sweden Silica sol is currently being investigated in situ at Aespoe Hard Rock Laboratory as a fine fracture (< 100 μm) grouting agent by injection. During this period, there is a plausible risk of Silica sol coming into contact with bentonite. The effect of Silica sol, either in colloidal form or as a gel, on the chemical and physical properties of bentonite has not been properly addressed and has to be further investigated. The Silica sol (Meyco MP320, EKA Chemicals) consists of amorphous SiO2 particles, average size approximately 20 nm. Due to the small particle size Silica sol can penetrate and seal finer fractures than more coarse grouting agents commonly used. Upon injection NaCl (approx 0.3 M) is used as a gel accelerator, leading to a hydrological barrier in the form of a ductile gel after < 1 hour, which then hardens with time (months) increasing its strength significantly, depending on water content, ionic strength and temperature. Upon aggregation, either due to high ionic strength or drying, the silica colloids aggregate seemingly irreversible forming siloxane bonds by condensation of the silanol surface groups. These silanol groups can react at the montmorillonite edges in a similar way. In a worst case scenario the Silica sol would act as an inorganic glue, creating a pillared montmorillonite or modify the edges of the clay particles. Such effects would irreversibly reduce the overall swelling capacity of the affected bentonite. An experimental program has been developed to characterize the Silica sol

  5. Manufacture and homogeneity of highly dense bentonite samples

    International Nuclear Information System (INIS)

    A project study on behalf of Nagra for high radioactive waste disposal in deep geological formations as well as literature studies have shown that bentonite could be a suitable filling and sealing material. The Institute for Foundation and Soil Mechanics of the Swiss Institute of Technology is under contract by Nagra to investigate different bentonites. The investigations concentrate on the Na-bentonite MX-80 from Wyoming, which is foreseen by the Swedes, and on the geographically more favorable Ca-bentonite Montigel from Bavaria. Montigel powder and granulate, which show certain manufacturing advantages, were investigated. Numerous experiments, mostly for manufacturing of sample bodies for swelling experiments, were performed and evaluated with the aim to clarify the condensation properties of bentonites in a highly dense field. Especially the relationship between water content, pressure and attained dry density for the three bentonites: MX-80 (granulate), Montigel (powder) and Montigel K (granulate) were investigated. It was shown that the delivery water contents of the three bentonites favorably lie within the 8-10 % necessary to prepare high density samples with dry densities of about 2.0 Mg/m3. The comparison of the three bentonites shows that both bentonites in granular form allow lower pressures at condensation than the bentonite in powder form. Based on x-ray and pressure porosimetry investigations the high density bentonites are largely homogeneous sample bodies considering their density and pore radius distribution. 15 figs., 2 tabs

  6. Sealing performance assessments of bentonite and bentonite/crushed rock plugs

    International Nuclear Information System (INIS)

    Bentonite and mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. The materials have been used to form cap layers to reduce infiltration for mined waste tailings and can also be used to construct clay liners for municipal as well as industrial waste managements. American Colloid C/S granular dentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no negative effects on the sealing performance within the test range from room temperature to 60C. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for the plug design. A permeability model developed is useful for the prediction of permeability in clays. A piping model permits the estimation of critical hydraulic gradient allowed before the flow of bentonite takes place. It can also be used to define the maximum allowable pore diameter of a protective filter layer

  7. Ion-migration through bentonite/zeolite and bentonite/quartz sand mixture

    International Nuclear Information System (INIS)

    In the geological disposal system of the high level radioactive wastes radionuclides begin leaching from the waste form when the canister is degraded by corrosion. The buffer materials, as one of the engineered barriers can retard the migration of the radionuclides to the biosphere. In this study, the diffusivity of radionuclides has been obtained in the compacted clay materials, such as mixtures of bentonite-zeolite, and bentonite-quartz sand for buffer materials. For the bentonite and zeolite mixture, Kd-value for cesium has been increasing with zeolite contents. The increase in the Kd-value has also been obtained for strontium, though the inclination is found to be smaller than that for cesium. In the case of bentonite and quartz sand mixture, the Kd-value has increased with quartz content (up to 70%), though the increasing rate is smaller than that in the zeolite mixture. The purpose of the quartz sand mixing is to improve the thermal conductivity of the buffer materials. It is to be noted that the sorption capability of bentonite and quartz sand mixture is found to be a little bit larger than that of bentonite. As for cesium, the Kd-values obtained in diffusion experiment agree well with those from batch experiments within a factor of 2, while for strontium good agreement has not been obtained

  8. Ga migration through MX-80 bentonite

    International Nuclear Information System (INIS)

    Highly compacted bentonite is known to let gas ghrough at a very low rate but earlier invetigations have indicated the possible existence of a critical gas pressure at which the gas forms highly conductive passages through the clay. The present study was primarily aimed at testing the hypothesis of the critical pressure concept by measuring the gas pressure, and by trying to identify microstructural evidence of how gas percolates clay. Eight tests were run with MX-80 bentonite saturated with strongly brackish NAGRA water, the density of the water saturated bentonite ranging from 1.7 to somewhat more than 2.1 t/m3. In all the tests it was observed that gas break-through, manifested by largely increased conductivity, took place at a gas pressure of the same order of magnitude as the swelling pressure. One of the samples was analysed with respect to the microstructure and it revealed the existence of discrete gas-filled voids, some of which released gas when the trimmed clay specimen was placed into the embedding substance used for the microstructural analysis. This confirms that gas percolates through a number of narrow passages that are formed when the gas pressure is sufficiently high. In soft and medium-dense bentonite the 'capillary retention' is probably the major resistance to gas propagation, while in dense bentonite the penetrating gas has to make its way by displacing clay aggregates. In the latter case the critical gas pressure is therefore logically very high and close to the swelling pressure. (author)

  9. Fe-bentonite. Experiments and modelling of the interactions of bentonites with iron

    International Nuclear Information System (INIS)

    The main objectives of this study were to enhance the understanding of the interactions of bentonites with steel containers in the near field of a repository in salt formations and to determine missing experimental thermo-hydraulical-chemical and mineralogical data needed for the THC modelling of the interactions of bentonites with iron. At the beginning of this project a literature review helped to clarify the state of the art regarding the above mentioned objectives prior to the start of the experimental work. In the following experimental programme the hydraulic changes in the pore space of compacted MX80 bentonites containing metallic iron powder and in contact with three solutions of different ionic strength containing different concentrations of Fe2+ have been investigated. The alterations of MX80 and several other bentonites have been assessed in contact with the low ionic strength Opalinus Clay Pore Water (OCPW) and the saturated salt solutions NaCl solution and IP21 solution. Under repository relevant boundary conditions we determined on compacted MX80 samples with the raw density of 1.6 g/cm3 simultaneously interdependent properties like swelling pressures, hydraulic parameters (permeabilities and porosities), mineralogical data (changes of the smectite composition and iron corrosion products), transport parameters (diffusion coefficients) and thermal data (temperature dependent reaction progresses). The information and data resulting from the experiments have been used in geochemical modelling calculations and the existing possibilities and limitations to simulate these very complex near field processes were demonstrated. The main conclusion of this study is that the alteration of bentonites in contact with iron is accentuated and accelerated. Alterations in contact with solutions of different ionic strength identified by the authors in previous studies were found be much more intensive in contact with metallic iron and at elevated temperatures. The

  10. pH buffering in compacted bentonite

    International Nuclear Information System (INIS)

    In almost all high-level waste and spent fuel repository concepts, highly compacted bentonite in one form or another is the preferred material for backfilling and sealing. During re-saturation the bentonite swells and seals against the emplacement tunnels. The very low transmissivity to water movement and good sorption characteristics make compacted bentonite an extremely effective near-field diffusion barrier to the movement of radionuclides. The ability to give a chemically well founded pore water composition is essential since such knowledge is a pre-requisite for understanding sorption and diffusion processes, assessing the influence of long term groundwater-bentonite interactions and also predicting near-field solubilities and developing sorption data bases. In this context the pH of the pore water is of central importance, particularly for sorption. Almost invariably the compositions given for highly compacted bentonite pore waters are calculated values because reliable water samples are virtually impossible to obtain, even by squeezing under very high pressures. Assumptions and simplifications are made in the geochemical models used to perform such calculations and the predictions are seldom if ever tested. One of the main hypotheses in a recently proposed model for bentonite pore water was that the initial pH is determined by the state of the amphoteric surface hydroxy groups, ≡SOH type sites, and these buffer the pH of the pore water in to a value close to 8. Surface site types, site capacities and proto-lysis constants were obtained from previous montmorillonite titration measurements and were fixed in the calculations. The aim of this work was to test the Bradbury and Baeyens (2003) model in terms of its ability to the predict one of the most important parameters for any pore water, namely the pH. Tests against the real system are not practicable for the reasons mentioned above. Hence the experiments had to be indirect but nevertheless devised to

  11. Evaluation of factors affecting diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    The information available from the open literature and studies on exclusion, sorption and diffusion mechanisms of ionic and neutral species in bentonite has been compiled and re-examined in relation to the microstructure of bentonite. The emphasis is placed on a more thorough understanding of the diffusion processes taking place in compacted bentonite. Despite the scarcity of experiments performed with neutral diffusants, these imply that virtually all the pores in compacted bentonite are accessible to neutral species. Anion exclusion, induced by the overlap of electrical double layers, may render the accessible porosity for anions considerably less than the porosity obtained from the water content of the clay. On the basis of the compiled data, it is highly probable that surface diffusion plays a significant role in the transport of cations in bentonite clays. Moreover, easily soluble compounds in bentonite can affect the ionic strength of porewater and, consequently, exclusion, equilibrium between cations, and surface diffusion

  12. UV curable polyester polyol acrylate/bentonite nanocomposites: synthesis, characterization, and drug release.

    Science.gov (United States)

    Thatiparti, Thimma Reddy; Tammishetti, Shekharam; Nivasu, Muram V

    2010-01-01

    Polyesterpolyolacrylate/bentonite nanocomposites, capable of in situ photo polymerization, were synthesized and characterized. The organically modified bentonite clay was prepared by an ion exchange process, in which sodium ions were replaced by alkyl ammonium ions. Organo modification of bentonite was confirmed from X-ray diffraction and fourier transform-infrared data. Microstructures were characterized by XRD data and transmission electron microscopy (TEM). Both XRD data and TEM images of polyester polyol acrylate/organo modified bentonite nanocomposites indicated that most of silicate layers were intercalated into the acrylate matrix. The resulting nanocomposites were characterized by gel content, water equilibrium swell, tensile strength, and in vitro degradation. The results showed that water equilibrium swell and in vitro degradation of these nanocomposites decreased with increase in the clay content. The tensile strength of these nanocomposites also increased with increase in the clay content. Release of two model drugs namely sulfamethoxazole and diclofenac sodium (DS) from these nanocomposites was studied in phosphate buffer saline pH = 7.4 at 37 degrees C. The drug release studies showed that sulfamethoxazole released slower than DS from polyester polyol acrylate nanocomposites. Therefore, these materials may be useful for mucoadhesive drug carriers and other biomedical applications. PMID:19904735

  13. Geomechanical characterisation of unsaturated Kunigel V1 bentonite: swelling and shear strength

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The development and validation of hydro-geomechanical models for bentonite buffer are one of the important subjects to appropriately evaluate long term behaviour of EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one extension of the modified Cam- Clay model for unsaturated and expansive soil, has been developed and widely applied to several hydro-geomechanical problems by using the coupled THM code, Code-Bright. Some advantages of the model are that hydro-geomechanical characteristics of buffer materials under saturated and partially saturated conditions are taken into account as well as the swelling characteristics due to wetting. Applicability of the BBM to consolidation and swelling behaviour of unsaturated bentonite has already been confirmed. In this study swelling characteristics of unsaturated bentonite are further discussed based on results from controlled-suction odometer tests, and in addition shear strength depending on matric suction is discussed based on controlled-suction triaxial compression tests. Swelling tests of compacted bentonite (Kunigel V1, initial dry density: 1.0 Mg/m3) under constant confined vertical net stresses (20 and 100 kPa) were performed by using controlled-suction odometer cells. Matrice suction was stepwise reduced from 500 kPa to 0 kPa by 100 kPa. It is found that swelling is more dominant in latter step of the suction change (i.e., closer steps to saturation), especially the step from 100 kPa to 0 kPa. Swelling due to wetting, i.e. decrease in matric suction is defined in the BBM. Controlled-suction triaxial compression tests of compacted bentonite (Kunigel V1, initial dry density: 1.36 Mg/m3) under both constant matric suctions (0, 300, and 500 kPa) and constant confined lateral net stresses were performed to study dependency of shear strength on matric suction. It is found that the apparent cohesion linearly increases with increase in matric

  14. Iron content and reducing capacity of granites and bentonite

    International Nuclear Information System (INIS)

    The iron contents in various granites and in bentonite have been determined. For granites, the content is usually in the range 1-9% (weight) and 2.5-3% for bentonite. Most of the iron is divalent in the granites (70-90%); in bentonite the divalent fraction is 25-50%. A large part of the divalent iron in the granites appears to be accessible for the reduction of dissolved oxygen in an aqueous system. (author)

  15. Mechanical Properties of Plastic Concrete Containing Bentonite

    OpenAIRE

    Peng Zhang; Qiaoyan Guan; Qingfu Li

    2013-01-01

    Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable barrier (cut-off wall) for containment of contaminated sites or seepage control in highly permeable dam foundations. The effects of water to binder ratio and clay dosage on mechanical properties of plastic concrete were investigated. The results indicate that the water to binder ratio and clay dosage have great influenc...

  16. Bentonites in powder detergents: softness and perfum

    OpenAIRE

    Bernal, Cristóbal; Carrión Fité, Francisco Javier

    2011-01-01

    The sodium bentonite is a mineral composed by hydrated aluminium silicates with a great capacity for absorbing several types of substrates. In cotton articles, softeners are added after the washing process. Softeners are organic products which are absorbed within the last rinse. These types of softeners can present some disadvantages as the possible lack of biodegradability, solidity and higher hydrophobicity which might reduce the sensation of comfort in the clothes as water absorption is di...

  17. Stability of bentonite gels in crystalline rock

    International Nuclear Information System (INIS)

    The present, extended study comprises a derivation of a simple rock model as a basis for calculation of the penetration rate of bentonite and of the groundwater flow rate, which is a determinant of the erodibility of the protruding clay film. This model, which is representative of a gross permeability of about 10-8 - 10-9 m/s, implies a spectrum of slot-shaped joints with apertures ranging between 0.1 and 0.5 mm. It is concluded that less than 2percent of the highly compacted bentonite will be lost into traversing joints in 106 years. A closer analysis, in which also Poiseuille retardation and short-term experiments were taken into account, even suggests that the penetration into the considered joints will be less than that. The penetration rate is expected to be 1 decimeter in a few hundred years. The risk of erosion by flowing groundwater was estimated by comparing clay particle bond strength, evaluated from viscometer tests, and theoretically derived drag forces, the conclusion being that the maximum expected water flow rate in the widest joints of the rock model (4 times 10-4 m/s) is not sufficient to disrupt the gel front or the large individual clay flocs that may exist at this front. The experiments support the conclusion that erosion will not be a source of bentonite loss. A worst case scenario with a shear zone being developed across deposition holes is finally considered and in addition to this, the conditions in the fracture-rich tunnel floor at the upper end of the deposition holes are also analysed. This study shows that even if the rock is much more fractured than normal conditions would imply, the bentonite loss is expected to be very moderate and without substantial effect on the barrier functions of the remaining clay cores in the deposition holes. (author)

  18. Swelling characteristics of Gaomiaozi bentonite and its prediction

    Directory of Open Access Journals (Sweden)

    De'an Sun

    2014-04-01

    Full Text Available Gaomiaozi (GMZ bentonite has been chosen as a possible matrix material of buffers/backfills in the deep geological disposal to isolate the high-level radioactive waste (HLRW in China. In the Gaomiaozi deposit area, calcium bentonite in the near surface zone and sodium bentonite in the deeper zone are observed. The swelling characteristics of GMZ sodium and calcium bentonites and their mixtures with sand wetted with distilled water were studied in the present work. The test results show that the relationship between the void ratio and swelling pressure of compacted GMZ bentonite-sand mixtures at full saturation is independent of the initial conditions such as the initial dry density and water content, but dependent on the ratio of bentonite to sand. An empirical method was accordingly proposed allowing the prediction of the swelling deformation and swelling pressure with different initial densities and bentonite-sand ratios when in saturated conditions. Finally, the swelling capacities of GMZ Na- and Ca-bentonites and Kunigel Na-bentonite are compared.

  19. Removal of Phosphate from Aqueous Solution with Modified Bentonite

    Institute of Scientific and Technical Information of China (English)

    唐艳葵; 童张法; 魏光涛; 李仲民; 梁达文

    2006-01-01

    Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% of phosphate removal rate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.

  20. Analysis of corrosion products of carbon steel in wet bentonite

    International Nuclear Information System (INIS)

    As a part of evaluation of the long-term durability for the overpack containers for high-level radioactive waste, we have conducted corrosion tests for carbon steel in wet bentonite, a candidate buffer material. The corrosion rates were evaluated by weight difference of carbon steel and corrosion products were analyzed by Fourier transform infrared spectroscopy (FT-IR) and colorimetry. At 40degC, the corrosion rate of carbon steel in wet bentonite was smaller than that in pure water. At 95degC, however, the corrosion rate in wet bentonite was much higher than that in pure water. This high corrosion rate in wet bentonite at 95degC was considered to result from evaporation of moisture in bentonite in contact with the metal. This evaporation led to dryness and then to shrinkage of the bentonite, which generated ununiform contact of the metal with bentonite. Probably, this ununiform contact promoted the local corrosion. The locally corroded parts of specimen in wet bentonite at 95degC were analyzed by Fourier transform infrared microspectroscopy (micro-FT-IR), and lepidocrocite γ-FeO(OH) was found as well as goethite α-FeO(OH). In wet bentonite at 95degC, hematite α-Fe2O3 was identified by means of colorimetry. (author)

  1. Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

    Science.gov (United States)

    Sitompul, Johnner; Setyawan, Daru; Kim, Daniel Young Joon; Lee, Hyung Woo

    2016-04-01

    This paper concerns the synthesis of poly(D,L-lactic acid)/poly(L-lactic acid) bentonite nanocomposites. Poly (D,L-lactic acid) (PDLLA) was synthesized using lactic acid through the ZnO-catalyzed direct polycondensation method at vacuum pressure and poly(L-lactic acid) (PLLA) was synthesized with L-lactide by ring-opening polymerization method. The PDLLA/PLLA-bentonite nanocomposite films were synthesized using the solvent casting method. The nanoclay, bentonite, was prepared using the solution-intercalation method by dissolving the nanoparticles into chloroform before sonication. In this study, PDLLA/PLLA-bentonite nanocomposite films were produced using variable amounts of nanoclay and sonication times during the mixing of PDLLA/PLLA and bentonite. The properties of the PDLLA/PLLA nanocomposites were then characterized using the X-ray Diffraction (XRD), Universal Testing Machine (UTM), Water Vapor Permeability (WVP) tests, and the enzymatic biodegradability test. The XRD test was used to measure the intercalation of nanoclay layers in the PDLLA/PLLA matrix and the PDLLA/PLLA-bentonite intercalated nanocomposite films. It was found through these various tests that adding bentonite to the PDLLA/PLLA increases tensile strength to 56.76 MP. Furthermore, the biodegradability increases as well as the barrier properties of the polymers The different sonication time used during the mixing of the polymer solution with bentonite also affected the properties of the PDLLA/PLLA-bentonite nanocomposite films.

  2. KAJIAN ADSORPSI LINEAR ALKYL BENZENE SULPHONATE (LAS DENGAN BENTONIT-KITOSAN

    Directory of Open Access Journals (Sweden)

    Miftah Rifai

    2013-11-01

    Full Text Available Deterjen pada umumnya tersusun atas surfaktan anionik seperti LAS (Linear alkyl Benzene sulphonate. pada percobaan ini LAS dapat menyerap sinar pada daerahuv dengan panjang gelombang maksimumnya adalah 223,5 nm. LAS dalam perairan dapat menimbulkan potensi masalah pencemaran.Tujuan dari penelitian ini adalah sebagai salah satu alternatif penanganan masalah pencemaran limbah domestik dengan cara menguji kinerja bentonit alam dan bentonit termodifikasi kitosan dalam mengadsorpsi LAS. Untuk mengetahui bahwa kitosan telah bereaksi dengan bentonit maka diuji dengan FTIR dan XRD pada bentonit alam dan bentonit-kitosan. Kemudian ditentukan waktu kontak optimum antara LAS dengan bentonit alam dan bentonit-kitosan. Serta penentuan isoterm adsorpsi LAS dengan bentonit alam dan bentonit-kitosan dengan cara membuat variasi konsentrasi larutan LAS. Uji kinerja bentonit alam dan bentonit-kitosan dalam mengadsorpsi LAS dilakukan dengan menggunakan sistem batch. Didapat waktu kontak optimum antara LAS berinteraksi dengan bentonit alam adalah 15 menit dengan kapasitas adsorpsi sebesar 3,265 mg/g. Sedangkan Waktu kontak optimum interaksi LAS dengan bentonit-kitosan terjadi pada waktu 15 menit dengan kapasitas adsorpsi sebesar 1,7mg/g. Dari hasil yang didapat maka dapat terlihat bahwa bentonit alam memiliki kapasitas adsorpsi yang lebih besar dibandingkan bentonit hasil modifikasi dengan kitosan. Interaksi antara bentonit alam dan bentonit–kitosan dengan LAS terjadi secara fisik dengan energi adsorpsi bentonit alam dengan LAS adalah 19,31 KJ/mol dan energi adsorpsi bentonit-kitosan dengan LAS adalah 19,60 KJ/mol.

  3. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    The use of bentonite as backfilling and sealing material in the high level radioactive waste disposals has been treated in previous studies accomplished by different authors. However, the use of this clayey barrier needs the resolution of different problems so that its efficiency will be enhanced. between those could be cited the study of the actual capacity of sealing the space around the canister and the accommodation to the pressure of the rocky environment; the possible variations in plasticity; the diffusion and reaction processes that can be produced through the barrier by groundwater, the capacity of radionuclides adsorption, etc. These studies, show that the bentonites with high content in smectite fulfill satisfactorily with the physical and chemical conditions to be used as sealing material, but it is known that the smectite can be unstable in diagenetic conditions similar to those are given in a deep repository of radioactive wastes, being transformed into illite. A conclusion of immediate interest is deduced from this last study. The bentonites used as sealing material in radioactive waste repositories must no contain Na as interlayer cation since it is very easily exchangeable by K. It is better to select those smectites with Ca and Mg that detain the entry of K in the interlayer and as a consequence the transformation process of smectite into illite is made more difficult. (Author)

  4. Nuclear magnetic resonance properties of water-rich gels of Kunigel-V1 bentonite

    International Nuclear Information System (INIS)

    Kunigel-V1 bentonite was analyzed by proton nuclear magnetic resonance (NMR) spectroscopy over a wide range of water content and temperature at 0.47 T. Kunigel-V1 is a bentonite clay consisting of ∼50 wt% Na-rich montmorillonite from Yamagata, Japan, and represents a candidate for engineered barriers of underground nuclear waste disposal sites in Japan. The NMR-related properties of bentonite are also important with respect to application of the material as a mud in boreholes for NMR well logging in the geophysical exploration of disposal sites. The proton relaxation times, surface relaxivity of montmorillonite, and H2O self-diffusion coefficient, were determined in this study for water-rich gel samples of bentonite at 11.0 to 70.0degC and for bentonite weight fractions of 0 to 37.7 wt%. The proton relaxation times (T1 and T2) were measured by the inversion recovery method and Carr-Purcell-Meiboom-Gill method, respectively, and the self-diffusion coefficient of H2O molecules (D) was measured by the pulsed-gradient spin-echo method. The results showed that T1, T2, and D increased with increasing temperature, and decreased with increasing bentonite weight fraction (ω). The T1 and T2 surface-relaxivities were on the order of 10-7 m/s and also decreased with temperature. The activation energies of the T1 and T2 relaxation for the bentonite gels were significantly lower than those for bulk water (i.e., about 50 to 70%), whereas the activation energy of the diffusion process for the gels was nearly equal to that for bulk water. As a result, the normalized H2O self-diffusivity, D/D0, obeys a temperature-independent master curve described by ln(D/D0)=1.54[exp(-0.0377ω)-1], where D0 is D in bulk water and ω is in wt%. (author)

  5. Study on bentonite-based buffer material of radioactive waste disposal facility. Influence of cement leachate on bentonite impermeability

    International Nuclear Information System (INIS)

    Cementitious materials and bentonite are planned for use as engineered barriers for the disposal of TRU waste from nuclear fuel reprocessing. When groundwater penetrates cementitious material, hyperalkaline water containing Ca ions may leach out and change bentonite physicochemically, resulting in degradation of its barrier performance. Furthermore, ion concentration of groundwater may increase due to dissolution of nitrate salt in some wastes. To investigate the hydraulic characteristics of bentonite under the disposal environment, hydraulic conductivity tests were performed using hyperalkaline solutions that imitate cement leachate and sodium nitrate solution. It was shown that ion concentration of permeant solution and exchangeable cation type of smectite had a large impact on bentonite impermeability. (author)

  6. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick steel canister horizontally emplaced in a drift, and a backfill of highly compacted sodium bentonite. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. Solubility limits and speciation of important actinides and the fission product technetium in the bentonite pore water are then calculated. The model is based on available experimental data on the interaction of sodium bentonite and groundwater and represents means of extrapolation from laboratory data to repository conditions. The modelled composition of the pore water of compacted sodium bentonite, as well as the various compositions resulting from the long-term extrapolation, are used to estimate radionuclide solubilities in the near-field of a deep repository. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. Since the effect of calcium bentonite on the groundwater chemical composition will be considerably less marked than that of sodium bentonite, especially with respect to key parameters for the nuclide speciation like carbonate concentration and pH, the use of calcium bentonite instead of sodium bentonite will improve the reliability in the prediction of source terms for radionuclide transport in the geosphere. (author)

  7. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    Sorption on bentonite will play an important role in retarding the migration of radionuclides from a waste repository. Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by sorption. Bentonite is characterized by low permeability, water swelling capability and excellent sorption potential for cationic radionuclides. To correctly assess the sorption potential of radionuclides on bentonite is essential for the development of predictive migration models. The sorption of strontium on bentonite from different Slovak deposits - Jelsovy potok, Kopernica and Lieskovec has been investigated under various experimental conditions, such as contact time, sorbate concentrations, presence of complementary cation. Sorption was studied using the batch technique. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The instantaneous uptake may be due to adsorption and/or exchange of the metal with some ions on the surface of the adsorbent. The best sorption characteristics distinguish bentonite Kopernica, sorption capacity for Sr of the fraction under 45 mm is 0,48 mmol·g-1 for Sr. The highest values of distribution coefficient were reached for the bentonite Jelsovy potok. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites, which can be explained by the increase of specific surface of the bentonite samples. The presence of complementary cations depresses the sorption of Sr on bentonite. Cations Ca2+ exhibit higher effect on cesium sorption than the Na2+ ions. Results indicate that the sorption of Sr2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  8. Properties of zeolite a synthesized by natural bentonite

    International Nuclear Information System (INIS)

    Synthetic zeolite was prepared by using of natural bentonite from Kampo area and the application of detergent builder was investigated. The optimum synthetic condition was SiO2/Al2O3 = 2, Na2O/Al2O3 = 1, H2O/Al2O3 30 at 90 deg C for 3 hr and it was found by XRD analysis that the zeolite synthesized under this condition was type A. When the zeolite A synthesized under the optimum condition was contacted with 40 deg Dh CaCl2 solution at 30 deg C for 15 min, the cation exchange capacity was 264.9 mg CaO/g-zeolite. And the whiteness of the sample was 89% and the mean particle size was 9.95μm. (author)

  9. Evaluation of impact strength of polyamide 6/bentonite clay nanocomposites

    International Nuclear Information System (INIS)

    Nanocomposites of polymer/clay have had much attention in recent years, particularly those developed with layered silicates due to the need of engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in crystalline structure of polymer matrices has been studied and has been observed that they affect the crystalline behavior and the physical and mechanical properties. In this study, nanocomposites of polyamide 6 were obtained by the melt intercalation method, using a regional bentonite modified with a quaternary ammonium salt in an amount of 3% by weight. XRD results showed that incorporation of salt among the layers of clay, making it organophilic and obtaining exfoliated and/or partially exfoliated structures. The impact properties of the nanocomposites showed inferior in relation to pure polyamide, in other words, lost of toughness. (author)

  10. Estimation de l'état pour la surveillance des systèmes de grandes dimensions. Application aux réseaux électriques

    OpenAIRE

    Thabet, Assem

    2012-01-01

    This work deals with the state estimation and diagnosis of nonlinear systems with application to power systems. Dynamic modeling is performed using an index 1 property and decoupling techniques. New methods of state estimation, based on Extended Kalman Filter including a sliding window of measurements, are proposed to improve the robustness and accuracy. A new convergence study based on Lyapunov function and conditioning of the observability matrix is proposed to ensure the convergence of the...

  11. Etude électromécanique de nanofils piézoélectriques semi conducteurs. Application aux capteurs et recuperateurs d’énergie mecaniques

    OpenAIRE

    Hinchet, Ronan

    2014-01-01

    Smart systems are the combined result of different advances in microelectronics leading to an increase in computing power, lower energy consumption, the addition of new features, means of communication and especially its integration and application into our daily lives. The evolution of the field of smart systems is promising, and the expectations are high in many fields: Industry, transport, infrastructure and environment monitoring as well as housing, consumer electronics, health care servi...

  12. Decantation time of evaluation on bentonite clays fractionation; Avaliacao do tempo de decantacao no fracionamento de argilas bentonitas

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, J.; Menezes, R.R.; Neves, G.A.; Lira, H.L; Santana, L.N.L., E-mail: lisiane@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia de Materiais

    2009-07-01

    Bentonite clays present a great number of industrial uses, from petroleum to pharmaceutics and cosmetic industry. The bentonite clay present particles with very fine particles that is responsible by the vast application of these materials. However, commercial clays present wide particle size distribution and a significant content of impurities, particularly quartz, in the form of silt and fine silt. So, the aim of this work is to analyze the effect of the stirring and decantation time in the deagglomeration, purification and size separation of the bentonite clay particles from Paraiba. The clays were characterized by X-ray diffraction and particle size distribution. Based on the results it was observed the decantation time give the elimination of the agglomerates formed by submicrometric particles. The uses of decantation column give separation of the fraction below 200nm. (author)

  13. Aux marges du monde arabe

    Directory of Open Access Journals (Sweden)

    Hélène Thiollet

    2004-09-01

    Full Text Available L’étude des migrations contemporaines des Érythréens vers le Yémen au tournant des années quatre-vingt-dix permet d’observer les transformations des dynamiques régionales à l’œuvre dans le monde arabe. Les migrations sont un phénomène sensible aux différents aspects (politiques, économiques, culturels, géographiques de l’intégration régionale. Celle si est envisagée dans cet article à travers une approche doublement marginale : -la marginalité géographique de l’Érythrée arabo-africaine et du Yémen, économi­quement isolé dans la péninsule Arabique, -l’étude des migrations formelles et informelles, élément souvent marginal dans l’étude des institutions et des échanges qui constituent un système régional intégré. Cette étude est fondée sur une série d’entretiens menés au Yémen entre février et avril 2002 auprès des administrations yéménites et de la population érythréenne.

  14. Mineralogy and geochemistry of bauxite and bentonite deposits from Mozambique

    NARCIS (Netherlands)

    Dos Muchangos, A.C.

    2000-01-01

    Results of mineralogical and geochemical studies of bauxites, kaolinitic clays and bentoniteS from Mozambique are presented in this thesis. The bauxite and kaolinitic clay deposits in Penhalonga area (in the central western part of Mozambique) are associated with Precambrian magmatic rocks and the b

  15. Filtration behavior of organic substance through a compacted bentonite

    International Nuclear Information System (INIS)

    Filtration behavior of organic substance through a compacted bentonite was investigated. Na-type bentonite containing 30wt% of quartz sand was compacted in a column and the dry density was adjusted to be 1.6 g/cm3. Polyacrylic acid solution (including three types of polyacrylic acid, average molecular weight 2,100, 15,000 and 450,000) was prepared and was passed through the compacted bentonite. Molecular weight distributions of polyacrylic acid in the effluent solution were analysed by GPC (Gel Permeation Chromatography). A batch type experiment was also carried out in order to examine a sorption behavior of these organic substances onto the surfaces of grains of the bentonite. The results indicated that the smaller size polyacrylic acid (molecular weight < 100,000) was passed through the compacted bentonite. On the other hand, the larger size polyacrylic acid (molecular weight ≥100,000) was mostly filtrated by the compacted bentonite. The batch type sorption tests clarified that the polyacrylic acid did not sorb onto the surfaces of minerals constituting the bentonite. Therefore it was suggested that the larger size molecules (≥100,000) of organic substances could be predominantly filtrated by the microstructure of the compacted bentonite. (author)

  16. Diffusion behavior for Se and Zr in sodium-bentonite

    International Nuclear Information System (INIS)

    Apparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite, Kunigel V1 reg-sign containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400--1,800 kg/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted to be SeO32-, Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted to be Zr(OH)5- or HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0 m3/kg from batch experiments. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modeling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement

  17. Long-term Corrosion of Copper Container in Bentonite Buffer

    International Nuclear Information System (INIS)

    The experimental method for the evaluation of copper corrosion was discussed in this report. Especially, the corrosion behavior of a copper container in a compacted bentonite environment was reviewed in detail. Several previous studies on the copper corrosion in a bentonite environment were summarized and the applied methods were illustrated firstly. On the basis of the review, it is discussed how to execute long-term copper corrosion test as regarding korean disposal environment. The selection of bentonite medium and the composition of a medium such as bentonite-sand mixture or bentonite-sand double layer was mentioned in this report. The need for protection layer on copper surface was also discussed for reducing initial copper corrosion rate. As key aspects on the corrosion test, a measuring of corrosion rate, an observation of surface morphology, an analysis of corrosion product, and a measuring of corrosion potential were pointed out. For the purpose of a experimental consistency, the necessity of standard composition for a bentonite and a underground water might be confirmed before the test. Consequently, three experimental designs were derived for the corrosion test such as a corrosion testing design at creep condition, a simple corrosion design for the evaluation for other candidate materials, and lastly, a corrosion testing design in compacted bentonite. Through this survey and discussion for a copper corrosion in bentonite environment it would be very helpful for a high level radioactive waste disposal plan in the future

  18. Perception multisensorielle pour la localisation d'un robot mobile en environnement extérieur, application aux véhicules routiers

    OpenAIRE

    Laneurit, Jean

    2006-01-01

    This thesis report deals with precise and uncorrupted localisation of mobile robots within a road environment associated to a precise numerical map. Le sujet traité dans cette thèse concerne la localisation précise et intègre de robots mobiles ( de véhicules routiers en l'occurence) dans un environnement routier cartographié. Pour ceci, nous proposons une approche multisensorielle hybridant les capteurs classiquement utilisés dans ce genre d'application (un GPS naturel, un odomètre et un g...

  19. Une approche pour la composition autonome de services de communication orientés QoS. Application aux protocoles de transport configurables

    OpenAIRE

    Van Wambeke, Nicolas

    2009-01-01

    Les dernières évolutions de l’Internet se sont traduites par l’émergence de nouvelles applications distribuées et par la multiplication des technologies réseaux (sans fils, mobiles. . . ) ainsi que des services offerts par les opérateurs sur de nouveaux types de terminaux (portable, PDA. . . ). L’enjeu socio économique majeur de ces avancées est le futur Internet ambiant, à la fois ubiquitaire et intelligent, au travers duquel l’utilisateur pourra, quelle que soit sa localisation ...

  20. Bentonite electrical conductivity: a model based on series–parallel transport

    KAUST Repository

    Lima, Ana T.

    2010-01-30

    Bentonite has significant applications nowadays, among them as landfill liners, in concrete industry as a repairing material, and as drilling mud in oil well construction. The application of an electric field to such perimeters is under wide discussion, and subject of many studies. However, to understand the behaviour of such an expansive and plastic material under the influence of an electric field, the perception of its electrical properties is essential. This work serves to compare existing data of such electrical behaviour with new laboratorial results. Electrical conductivity is a pertinent parameter since it indicates how much a material is prone to conduct electricity. In the current study, total conductivity of a compacted porous medium was established to be dependent upon density of the bentonite plug. Therefore, surface conductivity was addressed and a series-parallel transport model used to quantify/predict the total conductivity of the system. © The Author(s) 2010.

  1. One-dimensional contaminant transport model for the design of soil-bentonite slurry walls

    International Nuclear Information System (INIS)

    A user oriented computer model (TRANS1D) was developed for application to the analysis and design of vertical soil-bentonite barriers. TRANS1D is a collection of analytical and numerical solutions to the one dimensional advective-dispersive-reactive (ADR) equation. The primary objective in developing TRANS1D was to enable the designer of a barrier system to evaluate the potential system performance with respect to contaminant transport, without performing difficult and time consuming field or laboratory experiments. Several issues related to model application are discussed, including identification of governing transport processes, specification of boundary conditions, and parameter estimation. Model predictions are compared with the results of laboratory column experiments conducted with soil bentonite barrier material under diffusion-dominated conditions. Good agreement between model calibrations and experimental results was noted, with calibrated diffusion coefficients for organic contaminants consistent with literature values

  2. Remediation of distilleries wastewater using chitosan immobilized Bentonite and Bentonite based organoclays.

    Science.gov (United States)

    El-Dib, F I; Tawfik, F M; Eshaq, Gh; Hefni, H H H; ElMetwally, A E

    2016-05-01

    Organic-inorganic nanocomposite, namely chitosan immobilized Bentonite (CIB) with chitosan content of 5% was synthesized in an acetic acid solution (2%). Organically modified CIB and Bentonite (mbent.) were prepared by intercalating cetyl trimethylammonium bromide (CTAB) as a cationic surfactant at doses equivalent to 1.5 and 3 times the cation exchange capacity (CEC) of clay. The prepared samples were characterized using FTIR, XRD and SEM to explore the interlayer structure and morphology of the resultant nanocomposites. The remediation of distilleries (vinasse) wastewater process was carried out using different adsorbents including CIB, modified CIB (mCIB), Bentonite (bent.), modified Bentonite (mbent.) and chitosan at different contact time. The results showed that the packing density of surfactant used in the synthesis of organoclays strongly affects the sorption capacity of the clay mineral and also showed that (mCIB)3 was found to be the most effective sorbent in the purification of distilleries wastewater with 83% chemical oxygen demand (COD) reduction and 78% color removal. PMID:26840179

  3. Effect of sulfuric acid concentration of bentonite and calcination time of pillared bentonite

    Science.gov (United States)

    Mara, Ady; Wijaya, Karna; Trisunaryati, Wega; Mudasir

    2016-04-01

    An activation of natural clay has been developed. Activation was applied by refluxing the natural bentonite in variation of the sulfuric acid concentration and calcination time of pillared bentonite (PLC). Calcination was applied using oven in microwave 2,45 GHz. Determination of acidity was applied by measuring the amount of adsorbed ammonia and pyridine. Morphological, functional groups and chrystanility characterizations were analyzed using SEM, TEM, FTIR and XRD. Porosity was analyzed using SSA. The results showed that the greater of the concentration of sulfuric acid and calcination time was, the greater the acidity of bentonite as well as the pore diameter were. FTIR spectra showed no fundamental changes in the structure of the natural bentonite, SEM, and TEM images were showing an increase in space or field due to pillarization while the XRD patterns showed a shift to a lower peak. Optimization was obtained at a concentration of 2 M of sulfuric acid and calcination time of 20 minutes, keggin ion of 2.2 and suspension of 10 mmol, respectively each amounted to 11.7490 mmol/gram of ammonia and 2.4437 mmol/gram of pyridine with 154.6391 m2/gram for surface area, 0.130470 m3/gram of pore volume and 3.37484 nm of pore diameter.

  4. Phytomass of beans and grain production as affected by zinc, copper and cadmium doses and bentonite application Fitomassa e produção do feijão afetadas pelas doses de zinco, cobre e cádmio e aplicação de bentonita

    Directory of Open Access Journals (Sweden)

    Gilvanise A. Tito

    2011-07-01

    Full Text Available The objective of this study was to determine the effect of zinc, copper and cadmium on phytomass and grain production and to evaluate indirectly the adsorbent effect of bentonite clay by determining the accumulation of these heavy metals in bean plants. The study consisted of three separate experiments (one for each cation with the application of three doses of bentonite (0, 30 and 60 t ha-1 in pots containing separately 50 mg of Zn; Cu and Cd kg-1 of soil, with three replicates. Thus, each experiment consisted of 9 experimental units. In each one, a bean plant was cultivated and after 65 days, samples of leaves, stems, roots and grains were collected. Afterwards, the samples were dried, weighed, grinded and the concentrations of Zn, Cu and Cd were determined. The phytomass of leaves of the plant growing on the soil with Zn, the Zn concentration in the whole plant and the Cd concentration in the leaves, stem and grains were significantly influenced by the bentonite application. Zn and Cd concentration in leaves, stem and grains decreased with the application of bentonite, indicating a positive effect of the clay application to the soil on the adsorption of these metals, decreasing the availability for plants. Zn was the most accumulated element in the plant, followed by Cd and Cu. The Zn, Cu and Cd accumulation in the plant obeyed the following sequence: stem > leaves > grains > roots; roots > stem > grains > leaves; roots > stem > leaves > grains, respectively.Objetivou-se, com este trabalho, estudar o efeito do cobre, zinco e cádmio em fitomassa e produção de grãos e avaliar indiretamente o efeito adsorvente da argila bentonita, determinando o acúmulo de metais pesados em plantas de feijão. O estudo consistiu de três experimentos separados (um para cada cátion, com a aplicação de três doses de bentonita (0, 30 e 60 t ha-1 em vasos contendo, separadamente, 50 mg de Zn, 50 mg de Cu e 50 mg de Cd kg-1 de solo, com três repeti

  5. Mineralogical investigations of Wyoming bentonite MX-80 and Montigel

    International Nuclear Information System (INIS)

    A project study for the final disposal of high-level radioactive wastes in deep geological formations, carried out on behalf of Nagra has shown that bentonite could serve as backfilling and sealing material for the final repository concept foreseen by Nagra. Subsequently, the Institute for Foundation and Ground Mechanics of the ETH-Zurich was charged by Nagra with the investigation of various bentonites. The investigations concentrated on the Na-bentonite MX-80 from Wyoming, which is favoured by the Swedes, and on the geographically more favourable Ca-bentonite Montigel from Bavaria. The mineral composition, surface, exchange capacity and exchangeable ions, charge distribution and density of both bentonites have been investigated

  6. Adsorption behavior of 239Pu by Gaomiaozi bentonite

    International Nuclear Information System (INIS)

    Adsorption behavior of 239Pu by Gaomiaozi bentonite as a function of the factors of aqueous phase pH value, 239Pu initial concentration and ionic species is studied by static adsorption experiments in this paper. The following results are obtained. Adsorption equilibrium time of 239Pu by Gaomiaozi bentonite samples is about 24 h, and the adsorption distribution ratio Kd value of 239Pu increases with the pH value, but decreases with increasing initial concentration of 239Pu. And adsorption of 239Pu by bentonite samples with different ionic species show that anions affect the most on adsorption of bentonite is CO32-, followed by HCO3- and SO42-, whereas Cl- and NO3- hardly have any influence on the adsorption of bentonite. (authors)

  7. Principe d'alimentation par convertisseurs multiniveaux à stockage intégré - Application aux accélérateurs de particules

    CERN Document Server

    Fahrni, Claude

    Facilities operating in cycles, such as particles accelerators, require pulsed power. Directly drawing this pulsed power from the industrial network is generally not acceptable. A system with a local energy storage system lessens the impact on the network. In this work, a power supply is proposed that allows pulsed operation of a proton synchrotron without disturbing the industrial network with large variations of active power. The context of this study is the search of a completely static replace ment of an existing inertial energy storage device. The application is the proton synchrotron of the CERN. Several solutions to store the energy needed by the proton synchrotron are studied, they include inertial energy storage, capacitive energy storage and magnetic energy storage. On this basis, the solution based on capacitive energy storage with interleaved multilevel converters is retained. The sizing of the storage elements and the filter is carried out. The control strategies are studied and designed. They ar...

  8. Corrosion monitoring of carbon steel in the bentonite in deep underground

    International Nuclear Information System (INIS)

    In previous study, a corrosion sensor has been developed and its applicability to monitoring of the corrosion behavior of carbon steel overpack has been confirmed. In this study, a simulated overpack was placed with buffer material composed mainly of bentonite in test tunnel of 350 m deep underground constructed at Horonobe underground research laboratory. The corrosion monitoring was performed by AC impedance method using the corrosion sensors embeded in the buffer material. (author)

  9. The effect of zeolite,bentonite and sepiolite minerals onheavy metal uptake by sunflower

    OpenAIRE

    N . Esmaeilpour Fard; J. Givi; S. Houshmand

    2015-01-01

    Mining, industrial and agricultural activities can result in considerable soil pollution by heavy metals (HMs). One of the methods to control this pollution is application of adsorbent minerals. The purpose of this study was to compare the effects of adsorbent minerals (bentonite, zeolite and sepiolite) on transfer of some heavy metals (i.e., Pb, Zn and Cd) from soil to tissues of sunflower (Heliantus annuus L.). Treatments included: Non-polluted soil, HM-polluted soil, polluted soil + benton...

  10. Les enjeux économiques et industriels liés au recours aux partenariats public-privédans le domaine spatialUne application : le contrat de Private Finance Initiative britannique Skynet V

    OpenAIRE

    Frédéric Marty

    2008-01-01

    Analyse économique du contrat de partenariat public-privé relatif aux satellites de télécommunications de défense Skynet V.Etude de la construction contractuelle et de sa renégociation : impact sur l'équilibre économique du contrat

  11. Les enjeux économiques et industriels liés au recours aux partenariats public-privé
    dans le domaine spatial
    Une application : le contrat de Private Finance Initiative britannique Skynet V

    OpenAIRE

    Marty, Frédéric

    2008-01-01

    Analyse économique du contrat de partenariat public-privé relatif aux satellites de télécommunications de défense Skynet V.Etude de la construction contractuelle et de sa renégociation : impact sur l'équilibre économique du contrat

  12. Vegetation mapping for tropical marine/coastal zone applications = Cartographie de la végétation, applications aux zones côtières et marines tropicales

    OpenAIRE

    Morgan, G A

    1992-01-01

    L'image multispectrale satellitaire appliquée aux zones tropicales, a été analysée afin de permettre une représentation pointue de la végétation par carte thématique jusqu'au 1/100 000 provenant d'une seule scène satellitaire. La clé du succès est dans le soin apporté au choix de la scène initiale et l'adoption d'une méthodologie basée sur une vérité terrain-botanique rigoureuse et fiable. Cette méthodologie utilisera un nombre adéquat de "caractérisations de parcelles" selon une surface cart...

  13. Sorption of Cadmium on Na-Bentonite

    International Nuclear Information System (INIS)

    The sorption of Cd radionuclide into Na-bentonite as candidate for buffer material in the radioactive waste disposal system has been performed. Cadmium was used for this study as a model for bivalence elements. Batch experiment was adopted to study sorption isotherm, influence of carbonate and influence of EDTA. In a simple media, pure water, Cd was retained with a high affinity. Two stages Freundlich sorption isotherm was shown, with high coefficient distribution and sorption capacities. It is shown that the presence of carbonate in solution was not affect significantly to the sorption. While the presence of EDTA, decrease the distribution coefficient value. (author)

  14. Control of Urea SCR Systems for US Diesel Applications Commande des systèmes de RCS à l’urée destinés aux applications Diesel US

    Directory of Open Access Journals (Sweden)

    van Nieuwstadt M.

    2011-09-01

    Full Text Available This paper sets out to qualify challenges in the control of urea selective catalytic reduction systems for NOx conversion in Diesel powertrains. We show the importance of ammonia storage control, and the difficulties in estimating it in the face of system uncertainties. The slow storage dynamics of the SCR catalyst are shown to be a major limiting factor on the performance of SCR systems in transient operation. Lastly we show the effect of sensor uncertainty on system performance and how NOx sensors can be used in conjunction with input correlation to distinguish NOx slip from ammonia slip. Cet article a pour objet de qualifier les défis en matière de commande des systèmes de réduction catalytique sélective (RCS dans une solution à base d’urée, pour la conversion des NOx au sein de groupes motopropulseurs Diesel. Nous montrons l’importance de la maîtrise du stockage d’ammoniac ainsi que les difficultés à l’estimer face aux incertitudes du système. Les dynamiques de stockage lentes du catalyseur de RCS s’avèrent constituer un facteur de limitation majeur quant aux performances des systèmes de RCS au cours d’un fonctionnement transitoire. Enfin, nous montrons l’effet de l’incertitude des capteurs sur les performances du système et comment les capteurs de NOx peuvent être utilisés en association avec une corrélation d’entrée pour distinguer une déviation de NOx d’un glissement d’ammoniac.

  15. Adsorption of aniline, phenol, and chlorophenols on pure and modified bentonite

    Science.gov (United States)

    Yildiz, A.; Gür, A.; Ceylan, H.

    2006-11-01

    In the present study, pure bentonite and bentonite modified by HNO3, EDTA, and HDTMA are adsorbents. The changes on the surfaces of bentonite samples are studied by IR spectroscopy. The adsorption of aniline, phenol, and phenol derivatives on these adsorbents is examined by means of gas chromatography. As the result of these examinations, it is seen that the adsorption capacities of clay-organic complexes (bentonite-EDTA and bentonite-HDTMA) are higher than those of bentonite-HNO3 and pure bentonite.

  16. Backfilling of deposition tunnels: Use of bentonite pellets

    International Nuclear Information System (INIS)

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  17. Backfilling of deposition tunnels: Use of bentonite pellets

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David (Atomic Energy of Canada Limited (Canada)); Sanden, Torbjoern (Clay Technology AB (Sweden)); Jonsson, Esther (Swedish Nuclear Fuel and Waste Mangaement Co. (Sweden)); Hansen, Johanna (Posiva Oy (Finland))

    2011-02-15

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  18. Isostatic compaction of beaker shaped bentonite blocks on the scale 1:4

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik [Clay Technology AB, Lund (Sweden); Nord, Sven [Ifoe Ceramics AB, Bromoella (Sweden ); Pusch, Roland [Geodevelopment AB, Lund (Sweden); Sjoeblom, Rolf [AaF-Energikonsult AB, Stockholm (Sweden)

    2000-09-01

    The purpose of the present work is to test, on a scale of 1:4, the feasibility of manufacturing bentonite blocks by isostatic compaction for application as a buffer material in a repository for spent nuclear fuel. In order for the tests to be sensitive to any weaknesses of the method, the blocks were shaped as beakers. The scope included the following: 1. Preparation of powder: a. mixing of the bentonite and addition of water in predetermined amounts, b. sieving to remove any lumps generated; 2. Isostatic compaction: a. establishment of a separate laboratory for the handling of bentonite powder (weighing, mixing, filling, sampling and machining), b. development and design of equipment and procedures for compaction of bentonite to beaker-shaped specimens, c. compaction process operation, d. visual inspection; 3. Sampling and characterisation: a. extraction of samples from the blocks made, b. determination of water content, c. determination of density, d. determination of strain at maximum stress by means of bending tests, e. determination of tensile strength by means of bending tests, f. determination of geometries of the blocks prepared; 4. Post-treatment by means of machining: a. machining of blocks made, b. visual inspection; 5. Evaluation. The work went very smoothly. No significant obstacles or unexpected events were encountered. The conclusions are as follows: The conclusions drawn in this report from work on the (linear)scale of one to four are very relevant to the full scale. Mixing of bentonite powder as well as moistening can be carried out on a pilot scale with a good homogeneity and with maintained good quality of the press powder. The compaction of bentonite can be carried out in a similar manner to the present operation at Ifoe Ceramics AB. This implies a very efficient handling as well as a very efficient use of the time in the press which may account for a large proportion of the total cost. The blocks could readily be produced to reproducible

  19. Catalytic Polymerization of Acrylonitrile by Khulays Bentonite

    Directory of Open Access Journals (Sweden)

    Matar M. Al-Esaimi

    2007-04-01

    Full Text Available The aqueous polymerization of acrylonitrile (AN catalyzed with exchanged Khulays bentonite . The influence of various polymerization parameters ( e.g., concentrations of Potassium Persulfate (K2S2O8 and monomer , various of organic solvents, and different temperature has been investigated. It was found that the rate of polymerization of AN was found to be dependent on monomer concentration, initiator and temperature. The activation energy of polymerization was calculated .Thermal properties of the polymer were studied by TGA and DSC techniques. © 2007 CREC UNDIP. All rights reserved.Received: 5 February 2007; Received in revised: 19 April 2007; Accepted: 7 May 2007[How to Cite: M. M. Al-Esaimi. (2007. Catalytic Polymerization of Acrylonitrile by Khulays Bentonite. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3: 32-36.  doi:10.9767/bcrec.2.1.4.6-10][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.2.1.4.6-10 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/4] 

  20. An Evaluation of Models of Bentonite Pore Water Evolution

    International Nuclear Information System (INIS)

    The determination of a bentonite pore water composition and understanding its evolution of with time underpins many radioactive waste disposal issues, such as buffer erosion, canister corrosion, and radionuclide solubility, sorption, and diffusion, inter alia. The usual approach to modelling clay pore fluids is based primarily around assumed chemical equilibrium between Na+, K+, Ca2+, and Mg2+ aqueous species and ion exchange sites on montmorillonite, but also includes protonation- deprotonation of clay edge surface sites, and dissolution-precipitation of the trace mineral constituents, calcite and gypsum. An essential feature of this modelling approach is that clay hydrolysis reactions (i.e. dissolution of the aluminosilicate octahedral and tetrahedral sheets of montmorillonite) are ignored. A consequence of the omission of clay hydrolysis reactions from bentonite pore fluid models is that montmorillonite is preserved indefinitely in the near-field system, even over million-year timescales. Here, we investigate the applicability of an alternative clay pore fluid model, one that incorporates clay hydrolysis reactions as an integral component and test it against well-characterised laboratory experimental data, where key geochemical parameters, Eh and pH, have been measured directly in compacted bentonite. Simulations have been conducted using a range of computer codes to test the applicability of this alternative model. Thermodynamic data for MX-80 smectite used in the calculations were estimated using two different methods. Simulations of 'end-point' pH measurements in batch bentonite-water slurry experiments showed different pH values according to the complexity of the system studied. The most complete system investigated revealed pH values were a strong function of partial pressure of carbon dioxide, with pH increasing with decreasing PCO2 (log PCO2 values ranging from -3.5 to -7.5 bars produced pH values ranging from 7.9 to 9.6). A second set of calculations

  1. Sorption of Uranium(VI) and Thorium(IV) by Jordanian Bentonite

    OpenAIRE

    Fawwaz I. Khalili; Salameh, Najla'a H.; Mona M. Shaybe

    2013-01-01

    Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature,...

  2. Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum

    Directory of Open Access Journals (Sweden)

    Kumar Sujeet

    2014-12-01

    Full Text Available Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

  3. Colloid chemical aspects of the ''confined bentonite concept''

    International Nuclear Information System (INIS)

    Measurements of the amount of particles released from a bentonite gel by light scattering and visual inspection show that while particles are released in distilled water, the gel will be coagulated if in contact with ground water and consequently the release of particles is negligibly small. Studies of sedimentation volumes by ultracentrifugation also clearly indicate that the bentonite in contact with ground water under the repository pressure will form a completely stable coagulated gel. The swelling of confined bentonite was studied in an ''artificial crack'' of width 0.5 mm. The bentonite flowed readily into this crack and into the much narrower crack formed when the cell was broken. The swelling properties of the bentonite at the repository depth are discussed. It is argued that the gel, if sufficient volume is available, will swell spontaneously to a volume that is approximately 30 % larger than the initial one and then form a stable, coagulated gel containing 30-35 % water in equilibrium with the ground water. Investigations of the diffusion of colloidal matter (sodium lignosulphonate molecules of mean diameter 6 nm) and calcium ions into a dilute bentonite gel show that colloidal matter very probably will have a negligible rate of diffusion while the calcium ions diffuse rapidly. This implies that the initial bentonite gel which is partially in its sodium form will be completely exchanged to its calcium form when brought into contact with ground water which ensures that it will remain coagulated even in its swollen state

  4. Study on adsorption of 237Np on bentonite

    International Nuclear Information System (INIS)

    The performance of adsorbing 237Np for bentonite as buffer/backfill material was investigated. The adsorption coefficients of 237Np were determined for three kinds of bentonite under atmosphere and anoxic atmosphere. Further, it was studied that Kd values were affected by pH and CO32-. The results are shown as follows: (1) Distribution coefficients Kd under atmosphere: for mixed-bentonite is 47.3 mL/g, for Mg-bentonite 52.0 mL/g and for Ca-bentonite 42.4 mL/g; and the corresponding Kd under anoxic atmosphere: 89.3 mL/g, 38.8 mL/g and 29.0 mL/g, respectively. (2) When pH was lower than 9.2, Kd of the mixed-bentonite increased with the increase of pH and the maxi-mumt Kd value appeared at pH 9.2. (3) Kd of the mixed-bentonite got lower in high carbonate concentration when the total neptunium concentration was smaller than the solubility of NaNpO2CO3. (author)

  5. Synthesis of polycationic bentonite-ionene complexes and their benzene adsorption capacity

    Directory of Open Access Journals (Sweden)

    Valquíria Campos

    2015-04-01

    Full Text Available The purpose of this work was to structurally modify clays in order to incorporate water-insoluble molecules, such as petroleum hydrocarbons. The potential for ion exchange of quaternary ammonium salts was studied, which revealed their ability to interact with anions on the cationic surface, for environmental applications of the material. Ionenes, also known as polycations, have many potential uses in environmental applications. In this work, cationic aliphatic ammonium polyionenes, specifically 3,6-ionene and 3,6-dodecylionene, were prepared for incorporation into clay to form bentonite-ionene complexes. The intercalation of bentonite with ionene polymers resulted in an increase in the basal spacing of 3,6-dodecylionene from 1.5-3.5 nm. The higher d001 spacing of 3,6-dodecylionene samples than that of 3,6-ionene samples may be attributed to their longer tail length. The behavior of the TG/DTG curves and the activation energy values suggest that 3,6-dodecylionene (E = 174.85 kJ mol–1 is thermally more stable than 3,6 ionene (E = 115.52 kJ mol–1 complexes. The adsorption of benzene by 3,6-ionene and 3,6-dodecylionene was also investigated. The increase in benzene concentrations resulted in increased benzene adsorption by the sorbents tested in this work. The sorption capacity of benzene on ionene-modified bentonite was in the order of 3,6-dodecylionene > 3,6-ionene.

  6. Comptabilité environnementale et mondialisation. Quels défis ? Quels modèles pour y répondre ? Application d'un modèle Economie-Environnement-Impacts à l'évaluation des impacts environnementaux en Chine induits par l'Europe, et aux taxes carbone aux frontières de l'UE

    OpenAIRE

    Friot, Damien

    2009-01-01

    Cette thèse traite de l'intégration des contraintes liées à la mondialisation dans les méthodes de comptabilité environnementales. Nous proposons tout d'abord une analyse de la capacité des principales méthodes actuelles à répondre aux attentes sociétales et à relever les défis liés à la mondialisation. Nous développons à cette fin le premier cadre analytique spécifique à ces méthodes. Nous développons ensuite un modèle intégrant certaines des contraintes liées à la mondialisation. Ce modèle ...

  7. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick steel canister horizontally emplaced in a drift, and a backfill of highly compacted sodium bentonite. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. Solubility limits and speciation of important actinides and the fission product technetium in the bentonite pore water are then calculated. The model is based on available experimental data on the interaction of sodium bentonite and groundwater and represents means of extrapolation from laboratory data to repository conditions. The basic reactions between sodium bentonite and groundwater are described by an ion-exchange model for sodium, potassium, magnesium, and calcium. The model assumes equilibrium with calcite as long as sufficient carbonates remain in the bentonite, as well as quartz saturation. It is calculated that the pore water of compacted sodium bentonite saturated with Swiss Reference Groundwater will have a pH value of 9.7 and a free carbonate activity of 8x10-4 M. The long-term situation is modelled by the assumption that the near-field of a deep repository behaves like a mixing tank. In this way, an attempt is made to account for the continuous water exchange between the near-field and the host rock. It is found that sodium bentonite will be slowly converted to calcium bentonite. This conversion is roughly estimated to be completed after 2 million years

  8. Effects of polyethyleneimine adsorption on rheology of bentonite suspensions

    Indian Academy of Sciences (India)

    A Alemdar; N Öztekin; F B Erim; Ö I Ece; N Güngör

    2005-06-01

    The influence of the cationic polymer, polyethyleneimine polymer (PEI) on the flow behaviour of bentonite suspensions (2%, w/w), was studied. XRD, zeta potential and adsorption studies were done together with rheological measurements. The addition of PEI at concentration ranges of 10-5–4.5 g/l and their rheological properties and stability of bentonite suspensions were studied. The adsorption rates for the bentonite suspensions are very fast. The XRD results showed that the PEG molecules did not intercalate into the layers of the clay.

  9. Diffusion of chloride and uranium in compacted sodium bentonite

    International Nuclear Information System (INIS)

    The authors discuss the measurement of sorption and diffusion of chloride (Cl-36) and uranium in compacted sodium bentonite MX-80. No sorption was observed in the sorption tests, however, in the diffusion tests slight sorption of uranium was noticed. The diffusivities of Cl-36 were found to be strongly dependent on the compaction of bentonite and on the salt concentration of the solution. Ion-exclusion can propably explain these phenomena. The diffusivities of uranium were also strongly dependent on the compaction of bentonite. Uranium shows features of both ion-exclusion and sorption

  10. Gas transport through saturated bentonite and interfaces

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The aim of this investigation was the determination of the gas transport properties of saturated compacted bentonite and its interfaces. The bentonite used was the Spanish FEBEX bentonite, which is mainly composed of montmorillonite (more than 90%). For a dry density of 1.6 g/cm3 the saturated permeability of the bentonite is about 5.10-14 m/s, with deionised water used as percolating fluid. The saturated swelling pressure for the same dry density has a value of about 6 MPa. To perform the gas breakthrough tests a series of stainless steel cells were designed and manufactured. The cells consisted of a body, in which the cylindrical sample was inserted, pistons with o-rings at both ends of the samples and threaded caps. The samples, of 3.8 and 5.0 cm in diameter and 2.5 or 5.0 in height, were obtained by uniaxial compaction of the bentonite with its hygroscopic water content directly inside the cell body. Saturation with deionised water was accomplished by applying injection pressures of between 2 and 10 bar. The water content of the bentonite after saturation was higher than 27% for all the dry densities. Once the samples saturated, the filters on top and bottom of the samples were replaced by dry ones, the cells were again closed, and they were connected to a setup specially designed to measure breakthrough pressure. It consisted of two stainless steel deposits connected to the ends of the cell. One of the deposits was pressurised with nitrogen at 2 bar, whereas vacuum was applied to the other one. The pressures were measured by means of pressure transmitters. If no changes in pressure were recorded during 24 h, the injection pressure in the upstream deposit was increased by 2 bar and kept constant for 24 h. The process was repeated until gas started to flow through the sample. The time required for the completion of a particular experiment was determined by the conditions of the sample being studied. Although

  11. Water uptake and stress development in bentonites and bentonite-sand buffer materials

    International Nuclear Information System (INIS)

    The development of swelling pressure and the transfer of pore water pressures through dense bentonite and bentonite-sand materials are examined in this report. This report focuses on the swelling pressure and total pressure developed in initially unsaturated specimens allowed access to free water on one end. The bentonite in this wetted region rapidly develops its full swelling pressure and this pressure is transferred upwards through the specimen. Hence, the bentonite plug will exert a pressure approximately equivalent to the swelling pressure even though only a small region of the plug is actually saturated. A number of specimens were tested with total pressure sensors mounted normal and parallel to the axis of compaction. Lateral pressures developed long before the wetting front reached sensor locations, suggesting stress transfer through the unsaturated portions of these specimens. On achieving saturation, specimens were found to have similar swelling pressures both normal to and parallel to the axis of compaction. This indicates that there is little or no specimen anisotropy induced by the compaction process. Tests were conducted on specimens allowed only to take on a limited quantity of water and it was found that density anisotropy was induced as the result of the swelling pressures generated by the buffer. The wetted skin of buffer developed a considerable pressure and compressed a region of buffer immediately above the wetted region. The results suggest that the buffer material placed in a disposal vault will rapidly develop and transfer swelling pressures as a result of the saturation of a limited region or 'skin' within the emplacement site. The total pressure ultimately present on the container surface should be the sum of the swelling and hydraulic components. (author). 14 refs., 4 tabs., 8 figs

  12. A formula for determination of swelling characteristics of buffer material containing bentonite and evaluation of self-sealing performance

    International Nuclear Information System (INIS)

    High level radioactive waste disposal facility is planned to construct in a rock board deeper than some hundreds meter at underground, it is necessary to develop a material to refill the gap between waste container and its circumferential rock board. For this material it is required to have high water sealing and swellability, and bentonite is expected to use such application. Production of soil buffer materials containing bentonite is difficult to obtain required dry density by solidifying due to in situ roll-pressing, so it is, at present, thought to be an effective method to carry a block produced in a factory to a pit for disposal to settle. When supposing to produce and settle such buffer material, a gap forming between the buffer material and circumferential rock board or waste container has a large possibility to make a water path when remaining without treating it. Therefore, the buffer material is required to have a function to fill gap portion by swelling deformation and to proof water. In this study, in order to evaluated self-sealing of bentonite, due to a theoretical examination and a laboratory experiment on swelling behavior of soil materials containing bentonite, a swelling evaluation equation of the buffer materials was proposed. And, an application example for outlined design of an actual high level radioactive waste disposal facility was introduced. (G.K.)

  13. Development of mechanistic sorption model and treatment of uncertainties for Ni sorption on montmorillonite/bentonite

    International Nuclear Information System (INIS)

    Sorption and diffusion of radionuclides in buffer materials (bentonite) are the key processes in the safe geological disposal of radioactive waste, because migration of radionuclides in this barrier is expected to be diffusion-controlled and retarded by sorption processes. It is therefore necessary to understand the detailed/coupled processes of sorption and diffusion in compacted bentonite and develop mechanistic /predictive models, so that reliable parameters can be set under a variety of geochemical conditions relevant to performance assessment (PA). For this purpose, JAEA has developed the integrated sorption and diffusion (ISD) model/database in montmorillonite/bentonite systems. The main goal of the mechanistic model/database development is to provide a tool for a consistent explanation, prediction, and uncertainty assessment of Kd as well as diffusion parameters needed for the quantification of radionuclide transport. The present report focuses on developing the thermodynamic sorption model (TSM) and on the quantification and handling of model uncertainties in applications, based on illustrating by example of Ni sorption on montmorillonite/bentonite. This includes 1) a summary of the present state of the art of thermodynamic sorption modeling, 2) a discussion of the selection of surface species and model design appropriate for the present purpose, 3) possible sources and representations of TSM uncertainties, and 4) details of modeling, testing and uncertainty evaluation for Ni sorption. Two fundamentally different approaches are presented and compared for representing TSM uncertainties: 1) TSM parameter uncertainties calculated by FITEQL optimization routines and some statistical procedure, 2) overall error estimated by direct comparison of modeled and experimental Kd values. The overall error in Kd is viewed as the best representation of model uncertainty in ISD model/database development. (author)

  14. Bentonite THM behaviour mock-up studies

    International Nuclear Information System (INIS)

    Nuclear waste disposal rely on multi-barrier system. Engineered Barrier Systems make use of swelling clay buffer set in place unsaturated in deposition hole. After waste emplacement, buffer hydrates and swells, being submitted to the heat from nuclear waste decay. In order to characterize the THM behaviour of swelling clays under temperatures exceeding 100 C, Andra has gathered research laboratories, CEA/LECBA, Eurogeomat and EDF/CPM to conduct experimental a d modelling studies. The analysis of the state of art led to the definition of mock-up tests to evaluate effects of high temperatures and high thermal gradients on the heat and mass transfer, and the stress-strain behaviour of initially unsaturated MX80 bentonite during a thermal loading at constant volume for both closed and opened system. This paper presents the first mock-up tests and their experimental result. (authors)

  15. Experimental Setup to Characterize Bentonite Hydration Processes

    International Nuclear Information System (INIS)

    We present an experimental setup to follow-up the hydration process of a bentonite. Clay samples, of 2 cm x 12 cm x 12 cm, were made and introduced in a Hele-Shaw cell with two PMM windows and two steel frames. In hydration experiments, a fluid enters by an orifice in the frame, located both at the top and the bottom of the cell, to perform hydration in both senses. To get a uniform hydration we place a diffuser near the orifice. Volume influxes in hydration cells are registered in time. The evolution of the developed interface was recorded on a videotape. The video cameras was fixed to a holder so that the vertical direction in the monitor was the same as the direction of the larger extension of the cell. (Author) 6 refs

  16. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    Buffer construction using bentonite pellets as filling material is a promising technology for enhancing the ease of repository operation. In this study, a test of such technology was conducted in a full-scale simulated disposal drift, using a filling system which utilizes a screw conveyor system. The simulated drift, which contained two dummy overpacks, was configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m. The average dry density of the buffer obtained in the test was 1.29 Mg/m3, with an angle of repose of 35 to 40 degrees. These test results indicate that buffer construction using a screw conveyor system for pellet emplacement in a waste disposal drift is a promising technology for repositories for high level radioactive wastes. (author)

  17. Influence of seawater on swelling characteristics of bentonite buffer material

    International Nuclear Information System (INIS)

    High-level-radioactive-waste disposal facility can be built on the coastal area. One reason is that transportation of the wastes is easy. Groundwater in the coastal zone which flows into disposal pit contains large amount of seawater salts. So, it is important to investigate the influence of seawater on bentonite buffer material which is one of the Barrier materials in the nuclear disposal facility. The purpose of this study is to investigate the influence of artificial seawater on swelling pressure and swelling deformation characteristics of five typical kinds of bentonites. Various factors, such as density, montmorillonite contents, sort of exchangeable-cation of the bentonite have been investigated. This experimental works clarified the some factors for which the influence of artificial sea water on swelling characteristics of bentonite depends. Based on experimental results, a specification for the buffer material which can overcome the influence of seawater was defined. (author)

  18. Diffusion of Fission Product Elements in Compacted Bentonite

    International Nuclear Information System (INIS)

    Study on diffusion of fission product in compacted bentonite has been conducted. The information about mobilities of these elements have been obtained from the studies resulted in many countries. It is presented that the diffusion coefficient was varied by the function of solution phase condition as well as the nature of bentonite. It is also showed that the diffusion coefficient decreased by the increasing of density, as well as the increasing of montmorillonite content in bentonite. The ratio of bentonite/silica-sand used, was related to the increasing of elements mobility. In many case variation of diffusion coefficient was related to the variation of pH, redox condition, and the presence of complex ant in solution phase. The lower diffusion coefficient could give the higher retardation factor, which is a favorable factor to retard the radionuclides release from a disposal facility to geosphere. (author)

  19. A study on the thermal conductivity of compacted bentonites

    CERN Document Server

    Tang, Anh-Minh; Le, Trung Tinh; 10.1016/j.clay.2007.11.001

    2008-01-01

    Thermal conductivity of compacted bentonite is one of the most important properties in the design of high-level radioactive waste repositories where this material is proposed for use as a buffer. In the work described here, a thermal probe based on the hot wire method was used to measure the thermal conductivity of compacted bentonite specimens. The experimental results were analyzed to observe the effects of various factors (i.e. dry density, water content, hysteresis, degree of saturation and volumetric fraction of soil constituents) on the thermal conductivity. A linear correlation was proposed to predict the thermal conductivity of compacted bentonite based on experimentally observed relationship between the volumetric fraction of air and the thermal conductivity. The relevance of this correlation was finally analyzed together with others existing methods using experimental data on several compacted bentonites.

  20. Modified Ponorogo bentonite for the removal of ampicillin from wastewater.

    Science.gov (United States)

    Rahardjo, Andi Kurniawan; Susanto, Maria Josephine Jeannette; Kurniawan, Alfin; Indraswati, Nani; Ismadji, Suryadi

    2011-06-15

    The adsorption of ampicillin onto natural and organo-bentonite was studied. Organo-bentonite was obtained by modifying the natural bentonite obtained from Ponorogo, Indonesia, using CTAB surfactant by microwave heating. The temperature dependent form of the Langmuir, Freundlich, Sips and Toth equations was employed to correlate equilibrium data. Based on the evaluation of the physical meaning of fitted isotherm parameters of each model, it is clear that Toth equation can represent the equilibrium data better than other models. The adsorption performance of natural and organo-bentonite for the removal of ampicillin from pharmaceutical company wastewater was also studied. In real wastewater, both adsorbents could not completely remove the ampicillin due to the sorption competition with other substances which also present in the wastewater. PMID:21550716

  1. Long term mineralogical properties of bentonite/quartz buffer substance

    International Nuclear Information System (INIS)

    This report shows results from investigations concerning properties in bentonitebased buffersubstances which are suggested to be used when high level radioactive wastes from nuclear powerplants are to be stored finally. Recommended material characteristica of the bentonite to be used are summerized. In an attempt to find geological evidence for bentonite to loose its desireable properties there were no such findings at the temperatures, groundwater situations and pressures which are to be expected at the actual depositing depth (500 m) for a considerable period of time. Concerning biological activity and then specially the mobility and activity of bacteria the conclusion is that there will be little or no influence from them either there is bentonite-sand or compacted pure bentonite in the buffer mass

  2. Evaluation of brazilian bentonites as additive in the radwaste cementation

    International Nuclear Information System (INIS)

    The behavior of some Brazilian bentonites has been evaluated, concerning to their use as additive in the radwaste cementation. The purpose of the bentonite is to retain the radioelements in the final product in leaching process. Experiments to determine properties such as compressive strenght, viscosity, set time leaching and cesium sorption have been carried out to this evaluation. After one-year test, the results show that the bentonites greatly reduce the cesium release. A literature survey about cementation process and plants and about the cement product characteristics has been made in order to obtain a reliable final product, able to be transported and storaged. Some leaching test methods and mathematical models, that could be applied in the evaluation of cement products with bentonite have been evaluated. (author)

  3. LABORATORY TESTING OF BENTONITE CLAYS FOR LANDFILL DESIGN AND CONSTRUCTION

    OpenAIRE

    Biljana Kovačević Zelić; Dubravko Domitrović; Želimir Veinović

    2007-01-01

    Top and bottom liners are one of the key construction elements in every landfill. They are usually made as compacted clay liners (CCLs) composed of several layers of compacted clay with strictly defined properties or by the use of alternative materials such as: GCL – geosynthetic clay liner, BES – bentonite enhanced soils or bentonite/polymer mixtures. Following the state of the art experiences in the world, GCLs are used in Croatian landfills for several years, as well. Depending upon the lo...

  4. The Effect of Bentonite on External Corrosion of Well Casings

    OpenAIRE

    Orayith, Mohammed

    2012-01-01

    ABSTRACTThe overall goal of this research is concerned with understanding the effects of bentonite on the external corrosion of bare mild steel well casing. Na-bentonite is mainly used in enormous amounts in drilling processes, so it used as the main electrochemical environment surrounding the casing at different condition. The major part of the current study was divided into 3 stages; the first stage is constant current cathodic protection (CP) with a range of 0.0 (Open Circuit Potential) to...

  5. The interaction of bentonite and glass with aqueous media

    International Nuclear Information System (INIS)

    It has been demonstrated that Si(OH)4 is an important constituent of bentonite. In bentonites natural state the Si(OH)4 in the bentonite is permeable to the diffusible components of the aqeous medium in contact with it. As a consequence, the pH of the medium is a sensitive function of its ionic strength. Permeability of the Si(OH)4 to salt is lost, however, by pretreatment of the bentonite with dilute acid to protonate fully the Si(OH)4. The pH-producing property of the Si(OH)4 then is associated with its surface properties. The glasses (ABS-39 and ABS-Y Marcoule) studied in this research program also contain hydroxylated oxide as an important constituent. These materials, however, are not observed to exhibit gel-like (three-dimensional) properties prior to or after acid pretreatment. Instead they function always as a surface (two-dimensional) and are impermeable to the diffusible components of the aqueous media that come in contact with them. As a result, the pH of the medium is depentdent on ionic strength only so far as it affects the counter-ion screening efficiency of the charged surface. In both systems, bentonite and glass, the pH of the medium is affected by the presence of CO2. The lowering of medium pH by CO2 dissolution results in the neutralization of Si(OH)4 in the untreated bentonite gel phase or in the surface of the acid pretreated bentonite or glass in contact with the medium. If glass and bentonite are in contact the action of CO2 at their interface results in both systems striving to reach different equilibria. The result is enhanced chemical reactivity at the interface. To minimize such reactivity CO2 must be excluded from the atmosphere in contact with the solid-liquid phases. (author)

  6. Unified theory for swelling deformation and swelling pressure of bentonite

    International Nuclear Information System (INIS)

    The correlation of the water volume to vertical overburden pressure (p) is obtained as Vw/ Vm=KÞDs-3 for bentonite with fractal-textured surface. The maximum swelling strain is predicted according to the correlation of the water volume to vertical overburden pressure. The predictions of the maximum swelling strain and swelling pressure are in satisfactory agreement with the experimental data of Tsukinuno and Wyoming bentonite. (authors)

  7. Sorption of strontium on bentonites from Slovak deposits

    International Nuclear Information System (INIS)

    Sorption on bentonite from different Slovak deposits / Jelsovy potok, Kopernica and Lieskove has been investigated under various experimental conditions, such as contact time, pH, sorbate concentrations, presence of complementary cation. The sorption of strontium from aqueous solutions was investigated using a radiometric determination of distribution coefficient, Kd. The individual solutions were labelled with radiotracer. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites /tab.l/ , which can be explained by the increase of specific surface and change of solubility of the irradiated samples of bentonite. The presence of complementary cations, Na+, K+, NH4+, Ca2+, Mg2+ and Ba2+ depresses the sorption of Sr on bentonite. In the case of bentonite Kopernica the effectiveness in reducing the sorption of strontium by cations followed the order K+ 4+ + 2+ 2+ 2+. Results indicate that the sorption of Sr+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water effluents. (author)

  8. Effect of activation on swelling property in Ca-bentonite

    International Nuclear Information System (INIS)

    Compacted bentonite is attracting greater attention as buffer material for deep geological repository of high-level radioactive waste under current design concept. Swelling behavior is a significant property in achieving the low-permeability sealing function. The potential buffer material used is a locally available clayey material known as Zhisin clay in Taiwan. Zhisin clay is a Ca-type bentonite. Experimental data indicated that the swelling potential of Zhisin clay is much lower than that of Na-bentonite due to its exchangeable cation type and capacity. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder is introduced in this research. Addition of Na2CO3 reagent to Zhisin clay caused precipitation of CaCO3 to occur and induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite in liquid phase. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Due to the ion exchange hysteresis, activated bentonite shows different type of time-swell curve from traditional sigmoid-shaped curve. The optimal amount of Na2CO3 addition is found to be 1%, and the maximum swelling strain was found to be 3 times as much as that of untreated Zhisin clay. The Na2CO3 -activated Zhisin clay exhibited improved resistance to thermal environments and behaved similar to the Na-type bentonites under different hydrothermal temperatures. (authors)

  9. Lot A2 test, THC modelling of the bentonite buffer

    Science.gov (United States)

    Itälä, Aku; Olin, Markus; Lehikoinen, Jarmo

    Finnish spent nuclear fuel is planned to be disposed of deep in the crystalline bedrock of the Olkiluoto island. In such a repository, the role of the bentonite buffer is considered to be central. The initially unsaturated bentonite emplaced around a spent-fuel canister will become fully saturated by the groundwater from the host rock. In order to assess the long-term safety of a deep repository, it is essential to determine how temperature influences the chemical stability of bentonite. The aim of this study was to achieve an improved understanding of the factors governing the thermo-hydro-chemical evolution of the bentonite buffer subject to heat generation from the disposed fuel and in contact with a highly permeable rock fracture intersecting a canister deposition hole. TOUGHREACT was used to model a test known as the long-term test of buffer material adverse-2, which was conducted at the Äspö hard rock laboratory in Sweden. The results on the evolution of cation-exchange equilibria, bentonite porewater chemistry, mineralogy, and saturation of the buffer are presented and discussed. The calculated model results show similarity to the experimental results. In particular, the spatial differences in the saturation and porewater chemistry of the bentonite buffer were clearly visible in the model.

  10. Lot A2 test, THC modelling of the bentonite buffer

    International Nuclear Information System (INIS)

    Finnish spent nuclear fuel is planned to be disposed of deep in the crystalline bedrock of the Olkiluoto island. In such a repository, the role of the bentonite buffer is considered to be central. The initially unsaturated bentonite emplaced around a spent-fuel canister will become fully saturated by the groundwater from the host rock. In order to assess the long-term safety of a deep repository, it is essential to determine how temperature influences the chemical stability of bentonite. The aim of this study was to achieve an improved understanding of the factors governing the thermo-hydro-chemical evolution of the bentonite buffer subject to heat generation from the disposed fuel and in contact with a highly permeable rock fracture intersecting a canister deposition hole. TOUGHREACT was used to model a test known as the long-term test of buffer material adverse-2, which was conducted at the Aespoe hard rock laboratory in Sweden. The results on the evolution of cation-exchange equilibria, bentonite pore water chemistry, mineralogy, and saturation of the buffer are presented and discussed. The calculated model results show similarity to the experimental results. In particular, the spatial differences in the saturation and pore water chemistry of the bentonite buffer were clearly visible in the model. (authors)

  11. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior

    International Nuclear Information System (INIS)

    This study chitosan/bentonite bionanocomposite films were prepared by solution intercalation process, seeking to investigate the effect of the chitosan/bentonite ratio (5/1 e 10/1) on the morphology and mechanical behavior of the bionanocomposites. It was used as nanophase, Argel sodium bentonite (AN), was provided by Bentonit Uniao Nordeste-BUN (Campina Grande, Brazil) and as biopolymer matrix the chitosan of low molecular weight and degree of deacetylation of 86,7% was supplied by Polymar (Fortaleza, Brazil). The bionanocomposites was investigated by X-ray diffraction and tensile properties. According to the results, the morphology and the mechanical behavior of the bionanocomposite was affected by the ratio of chitosan/bentonite. The chitosan/bentonite ratio (5/1 and 10/1) indicated the formation of an intercalated nanostructure and of the predominantly exfoliated nanostructure, respectively. And the considerable increases in the resistance to the traction were observed mainly for the bionanocomposite with predominantly exfoliated morphology. (author)

  12. Behaviour of bentonite accessory minerals during the thermal stage

    Energy Technology Data Exchange (ETDEWEB)

    Arcos, David; Bruno, Jordi [Enviros-QuantiSci, Barcelona (Spain); Benbow, Steven; Takase, Hiro [Quintessa Limited, Henley-on-Thames (United Kingdom)

    2000-03-15

    This report discusses in a quantitative manner the evolution of the accessory minerals in the bentonite as a result of the thermal event exerted by the spent fuel in the near field. Three different modelling approaches have been used and the results compared between them. The three different approaches have been calculated using two Differential Algebraic Equation (DAE) solver: DYLAN (Model-1) and the Nag DAE solver, d02ngf (Model-2) and the third approach (Model-3) using the last version of PHREEQC. The results from these calculations indicate the feasibility of the modelling approach to model the migration of bentonite accessory minerals and relevant aqueous species throughout the thermal gradient. These calculations indicate that the migration of quartz and quartz polymorphs is a lesser problem. The aqueous speciation of Ca in the bentonite pore water is fundamental in order to define the potential migration of anhydrite during the thermal stage. If CaSO{sub 4}(aq) is the predominant aqueous species, then anhydrite dissolves at the initial groundwater migration times through bentonite. However, if Ca{sup 2+} is considered to be the dominant Ca species at the bentonite pore water, then anhydrite migrates towards the clay/granite interface. This is the main difference in the chemical systems considered in the three model approaches used in this work. The main process affecting the trace mineral behaviour in bentonite is cation exchange. This process controls the concentration of calcium, which results in a direct control of the calcite precipitation-dissolution.

  13. Reconstruction of Petroleum Feedstocks by Entropy Maximization. Application to FCC Gasolines Reconstruction de coupes pétrolières par maximisation d’entropie. Application aux essences de FCC

    Directory of Open Access Journals (Sweden)

    Hudebine D.

    2011-06-01

    pétrolier, les coupes sont généralement des mélanges complexes de plusieurs centaines à plusieurs millions d’espèces chimiques différentes. De ce fait, les outils analytiques, même les plus performants, ne permettent pas de séparer et d’identifier l’ensemble des composés présents. Les fractions pétrolières sont donc actuellement caractérisées soit via des descripteurs macroscopiques moyens (densité, analyse élémentaire, résonance magnétique nucléaire, etc., soit à l’aide de techniques séparatives (distillation, chromatographie gaz ou liquide, spectrométrie de masse, etc. qui ne quantifient cependant que quelques grandes familles de molécules. Les méthodes de reconstruction de coupes pétrolières sont des approches informatiques qui permettent d’évoluer vers un détail plus moléculaire en se basant sur le principe suivant : définir des mélanges simplifiés mais cohérents de composés chimiques à partir de données analytiques parcellaires et de connaissances expertes du procédé étudié. Ainsi, la méthode de reconstruction par maximisation d’entropie, proposée dans cet article, est une technique récente et puissante permettant de déterminer les fractions molaires d’un mélange préétabli de composés chimiques en maximisant un critère entropique et en respectant les contraintes analytiques fixées par le modélisateur. L’utilisation de cette méthodologie permet de réduire le nombre de degrés de liberté du système de quelques milliers (correspondant aux fractions molaires des composés à quelques dizaines (correspondant aux paramètres de Lagrange associés aux contraintes analytiques et ainsi de diminuer fortement le temps de calcul nécessaire à la résolution du problème. Cette approche a été appliquée avec succès à la reconstruction d’essences de FCC en prédisant précisément la composition moléculaire de ce type de coupes pétrolières à partir d’une distillation simulée et d

  14. Enhanced sonocatalysis of textile wastewater using bentonite-supported ZnO nanoparticles: Response surface methodological approach.

    Science.gov (United States)

    Darvishi Cheshmeh Soltani, Reza; Jorfi, Sahand; Safari, Mahdi; Rajaei, Mohammad-Sadegh

    2016-09-01

    The scope of this study was the use of bentonite as the carrier of ZnO nanoparticles for enhancing the sonocatalytic decolorization of Basic Red 46 (BR46) in the aqueous phase. The results demonstrated the higher sonocatalytic activity of bentonite-supported ZnO nanoparticles (BSZNs) in comparison with the suspended ZnO nanoparticles (SZNs). The particle size of BSZNs (5-40 nm) was lower than that of SZNs (20-120 nm). Due to the immobilization of ZnO nanoparticles, a specific surface area of 80.6 m(2)/g was obtained for the BSZNs, which was higher than the specific surface area of the raw bentonite (42.2 m(2)/g). Optimization of the process via response surface methodology (RSM) based on central composite design (CCD) showed the maximum sonocatalytic decolorization efficiency (%) of 89.92% in which the initial dye concentration, the ZnO/bentonite ratio, the sonocatalyst dosage, and the initial pH were 6 mg/L, 0.3, 2.5 g/L and 9, respectively. The byproducts generated during the sonocatalysis of BR46 over BSZNs were identified using gas chromatography-mass spectrometry (GC-MS) analysis. From an application viewpoint, the sonocatalysis of real textile wastewater resulted in a COD removal efficiency (%) of about 44% within a reaction time of 150 min. PMID:27173890

  15. Study on Preparation and Properties of Grease Based on Ultraifne Bentonite Powder

    Institute of Scientific and Technical Information of China (English)

    Wang Jing; Guo Xiaochuan; Jiang Mingjun; He Yan

    2016-01-01

    The feasibility for preparation of ultraifne bentonite powder by different milling methods was studied. And the comparison of comprehensive performance between ultraifne bentonite grease and traditional bentonite grease was also investigated. The results indicated that the statistic Z-average size of ultraifne bentonite prepared by sand milling was 250 nm with a narrow size distribution and the lattice structure of ultraifne bentonite maintained good character despite a slight distortion occasioned. The mechanical stability, colloid stability, antiwear ability and friction-reducing property of ultraifne bentonite grease were superior to the traditional one.

  16. Safety Training: Sensibilisation aux gestes et postures de travail

    CERN Multimedia

    Laetitia Laddada

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt.Nous vous proposons un nouveau cours de sécurité lié aux manutentions manuelles (durée 1 jour) : Sensibilisation aux gestes et postures de travail. Si vous êtes amené à manipuler régulièrement des charges lourdes ou volumineuses, cette formation peut vous aider à prévenir les lésions musculaires ou dorsales. A l'issue de cette formation, vous serez capable d'adopter et d'appliquer les principes de base de sécurité physique et d'&e...

  17. Geochemical investigation of iron transport into bentonite as steel corrodes

    International Nuclear Information System (INIS)

    In Sweden and Finland, it is proposed that spent nuclear fuel will be encapsulated in sealed cylindrical canisters, for disposal in a geologic repository, either in vertical boreholes (KBS-3V) or in long horizontal boreholes (KBS-3H). The canisters will consist of a thick cast iron insert and a copper outer container, and each canister will be surrounded by a compacted bentonite clay buffer. It is important to investigate the possible consequences if a failure of these physical barriers was to occur. For instance, if mechanical failure of the copper outer container were to occur then groundwater could enter the annulus and reach the cast iron insert. This would result in anaerobically corroded iron from the cast iron insert interacting with the bentonite surrounding the canisters. The presence of anaerobically corroded iron in groundwater raises the question of how the bentonite will be affected by this process. In the case of the KBS-3H concept, mechanical failure of the copper outer container could lead to interaction between anaerobically corroded iron and bentonite, as above. However, direct contact between anaerobically corroding carbon steel and bentonite is also likely because of the presence of perforated carbon steel support structures in the long horizontal boreholes. As part of the NF-PRO project, an extensive experimental programme has been carried out over several years to study the interactions between anaerobically corroding carbon steel or cast iron and bentonite. The purpose of this report is to describe the modelling work that has been carried out, and the conclusions that have been reached. The experimental programme has carried out a series of long term experiments looking at anaerobic corrosion of carbon steel or cast iron in compacted MX80 bentonite at 30 deg C or 50 deg C. In the bentonite the concentration of iron decreased with increasing distance away from the iron-bentonite interface, with local iron concentrations as high as 20 wt % in

  18. Reactive-transport model analyses of bentonite alteration behavior at alkaline condition generated by cement-water interaction in a TRU wastes repository

    International Nuclear Information System (INIS)

    The maximum dose of ionizing radiation from the geological disposal of TRU wastes will likely be controlled by poorly sorbing soluble radionuclides, such as I-129. Proposed repository designs for the geological disposal of TRU wastes envisage the use of an engineered barrier composed of a bentonite buffer to limit the migration of such radionuclides by impeding groundwater flow. Cementitious materials will inevitably be used for waste packaging, infilling and adding structural integrity to the repository. Using cementitious materials, however, is problematic because they produce highly alkaline leachates which have the potential to cause a complex series of coupled changes in the porewater chemistry, mineralogy and, ultimately, the mass transport properties of the bentonite buffer. To elucidate the consequences of these coupled changes, reactive-transport model analyses have been conducted for bentonite alteration test cases with the use of different combinations of secondary minerals that will likely form in the bentonite buffer. A dissolution rate equation of smectite (a key component of bentonite) applicable to pH 7-13 and 25-80degC was proposed and used in the reactive-transport model analyses. It was found that the amount of dissolved smectite at the center of the bentonite buffer was smaller and those in the vicinity of the cement interface was larger when thermodynamically metastable secondary minerals mainly precipitated as compared with the precipitation of stable phases. The calculated temporal and spatial changes of kinetic smectite dissolution were interpreted as a consequence of the changes in Gibbs free energy and porewater chemistry. Furthermore, the bentonite porewater chemistry was also affected by the stoichiometry and thermodynamic stability of the secondary minerals and the kinetics of smectite dissolution. Except in the close proximity of the cement interface, it was found that regardless of the choice of secondary minerals, the effective

  19. Mechanisms and models for bentonite erosion

    Energy Technology Data Exchange (ETDEWEB)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis (Dept. of Chemical Engineering and Technology, School of Chemical Science and Engineering, Royal Inst. of Technology, KTH, Stockholm (Sweden))

    2009-12-15

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  20. Mechanisms and models for bentonite erosion

    International Nuclear Information System (INIS)

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  1. Modification of bentonite with cationic surfactant for the enhanced retention of bisphenol A from landfill leachate.

    Science.gov (United States)

    Li, Yi; Jin, Fenglai; Wang, Chao; Chen, Yunxiao; Wang, Qing; Zhang, Wenlong; Wang, Dawei

    2015-06-01

    Bentonite was modified with cationic surfactant hexadecyl trimethyl ammonium bromide (HTAB) as landfill liner to retard the transportation of bisphenol A (BPA) for the first time. The modification was confirmed to form a lateral bi-layer in the interlayer space of bentonite by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. The introduction of HTAB into the internal position of bentonite led to an increased interlayer space of bentonite from 15.0 to 20.9 Å and a higher sorption affinity for BPA (10.449 mg/g of HTAB-bentonite and 3.413 mg/g of raw bentonite). According to the Freundlich model, the maximum adsorption capacity of the HTAB-bentonite was found to be 0.410 mg/g. The sorption capacity of raw bentonite and HTAB-bentonite both decreased at alkaline conditions. Although the hydraulic conductivity of HTAB-bentonite was higher than that of raw bentonite, results of laboratory permeability and column tests indicated that HTAB-bentonite obviously extended the BPA breakthrough time by 43.4 %. The properties of the HTAB-bentonite revealed its notable advantages as components of landfill liners material to retain BPA in leachate. PMID:25874420

  2. Diffusion in crushed rock and in bentonite clay

    International Nuclear Information System (INIS)

    Diffusion theories for porous media with sorption are reviewed to serve as a basis for considering diffusion in simple systems like sand of crushed rock. A Fickian diffusion and linear sorption model is solved both by analytical Laplance transform and Green's function methods and by numerical methods, and then applied to small-scale experiments for Finnish low- and medium-level operating waste repositories. The main properties of bentonite are reviewed. The hydraulic conductivity of compacted bentonite is so low that the major transport mechanism is diffusion. A Fickian diffusion and linear sorption model is applied to bentonite. The main component of bentonite, montmorillonite, has a high ion-exchange capacity and thus, transport in bentonite consists of interactive chemical and diffusion phenomena. A chemical equilibrium model, CHEQ, is developed for ion-exchange reactions in bentonite water systems. CHEQ is applied to some bentonite experiments with success, especially for monovalent ions. The fitted log-binding constants for sodium exchange with potassium, magnesium, and calcium were 0.27, 1.50, and 2.10, respectively. A coupled chemical and diffusion model, CHEQDIFF, is developed to take account of diffusion in pore water, surface diffusion and ion-exchange reactions. The model is applied to the same experiments as CHEQ, and validation is partly successful. In the diffusion case, the above-mentioned values for binding constants are used. The apparent diffusion (both anions and cations) and surface diffusion (only for cations) constants used are 3.0*10-11 m2/s and 6.0*10-12 m2/s, respectively, but these values are questionable, as experimental results good enough for fitting are not available. (orig.). (74 refs., 27 figs., 12 tabs.)

  3. Adsorption of cesium and strontium on natrified bentonites

    International Nuclear Information System (INIS)

    The influence of chemical activation-natrification of bentonites on adsorption of Cs and Sr was studied with regards to utilization of bentonites for depositing high-level radioactive waste and spent nuclear fuel. Bentonite samples from three Slovak deposits in three different grain-size (15, 45 and 250 μm), natural and natrified forms (Na-bentonites); under various experimental conditions, such as contact time, adsorbent and adsorbate concentration have been studied. When comparing the Na-bentonites and their natural analogues, the highest adsorbed Cs and Sr amounts were reached on the natrified samples. After the Sr adsorption a drop in the pH equilibrium value was observed together with the increase of the initial Sr concentration. A disadvantage of the natrified bentonite forms is formation of colloid particles. After 2 h of phase mixing a gentle turbidity was observed as well as formation of a gel-like form. The above findings were confirmed by observing the particle distribution in dry and wet dispersion and centrifugation at two different speeds. Natrification as a technological process of bentonite quality improvement cannot be applied when constructing a long-term repository for high-level radioactive waste and spent nuclear fuel. The main problem of natrification is a technological process which leads to a significant pH increase. Alkaline environment in combination with the K presence and increased temperature in the vicinity of radio-active waste can lead to a rapid illitization of smectite and loss of the original adsorption qualities. Moreover, sodium additions are a significant point of uncertainty since it is not possible to state what amount of Na enters the interlayer space and what amount stays in the inter-partition space. (author)

  4. How Molecular Evolution Technologies can Provide Bespoke Industrial Enzymes: Application to Biofuels Comment les technologies d’évolution moléculaire peuvent fournir des enzymes industrielles sur mesure : application aux biocarburants

    Directory of Open Access Journals (Sweden)

    Fourage L.

    2013-08-01

    est l’un des principaux goulets d’étranglement dans le développement de la conversion biologique de la biomasse lignocellulosique en biocarburants. L’un des organismes les plus efficaces pour la production d’enzymes cellulolytiques est le champignon Trichoderma reesei, principalement grâce à sa capacité importante de sécrétion. La conversion de la cellulose en glucose implique trois types de cellulases travaillant en synergie : les endoglucanases (EC 3.2.1.4 clivant de façon aléatoire les liaisons glycosidiques en (3-1,4, les cellobiohydrolases (EC 3.2.1.91 attaquant la chaîne de cellulose aux deux extrémités afin de produire le cellobiose, dimère qui sera converti en glucose par l’action des (3-glucosidases (EC 3.2.1.21. De façon inattendue, la quantité de 3-glucosidase (BGL1 sécrétée par les souches de T. reesei représente un très faible pourcentage de la quantité totale des protéines sécrétées qui en fait donc une activité limitante du cocktail. Cette faible activité limite d’autant plus les performances du cocktail que le cellobiose représente le principal inhibiteur de la réaction cellulolyse par les cellobiohydrolases. Ce goulot d’étranglement peut être atténué soit par une surexpression de la (3-glucosidase chez T. reesei, soit par une amélioration de son activité spécifique. Après un bref aperçu des principales technologies existantes, cet exemple sera utilisé dans cette revue pour illustrer le potentiel des technologies d’évolution dirigée pour développer des enzymes répondant aux besoins de l’industrie des biotechnologies. Nous décrivons comment la mise en oeuvre d’une stratégie d’évolution dirigée par le L-ShufflingTM avec trois gènes parentaux provenant de la biodiversité microbienne permet d’obtenir des activités (3-glucosidases très améliorées par rapport à la Cel3a (3-glucosidase de T. reesei (activité spécifique 242 fois plus élevée pour le substrat pNPGIc. Cette am

  5. Evaluation of impact strength of polyamide 6/bentonite clay nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Paz, Rene Anisio; Araujo, Edcleide Maria; Tomas Jeferson Alves; Amanda Damiao; Medeiros, Vanessa da Nobrega [Federal University of Campina Grande (CCT/UFCG), Campina Grande, PB (Brazil). Centro de Ciencias e Tecnologia; Pessan, Luiz Antonio [Federal University of Sao Carlos (DEMa/UFSCar), SP (Brazil). Materials Engineering Department

    2012-07-15

    Nanocomposites of polymer/clay have had much attention in recent years, particularly those developed with layered silicates due to the need of engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in crystalline structure of polymer matrices has been studied and has been observed that it affects the crystalline behavior and the physical and mechanical properties. In this study, nanocomposites of polyamide 6 were obtained by the melt intercalation method, using a Brazilian bentonite modified with a quaternary ammonium salt. X-Ray Diffraction (XRD) results showed the incorporation of salt among the layers of clay, making it organophilic and that the nanocomposites presented exfoliated and/or partially exfoliated structures and confirmed by transmission electron microscopy (TEM). By thermogravimetry (TG), the results indicated that the presence of clay increased the thermal stability of polyamide 6. The impact properties of the nanocomposites showed inferior values in relation to the pure polyamide, in other words, decrease the toughness. (author)

  6. Evaluation of impact strength of polyamide 6/bentonite clay nanocomposites

    Directory of Open Access Journals (Sweden)

    Rene Anisio Paz

    2012-08-01

    Full Text Available Nanocomposites of polymer/clay have had much attention in recent years, particularly those developed with layered silicates due to the need of engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in crystalline structure of polymer matrices has been studied and has been observed that it affects the crystalline behavior and the physical and mechanical properties. In this study, nanocomposites of polyamide 6 were obtained by the melt intercalation method, using a Brazilian bentonite modified with a quaternary ammonium salt. X-Ray Diffraction (XRD results showed the incorporation of salt among the layers of clay, making it organophilic and that the nanocomposites presented exfoliated and/or partially exfoliated structures and confirmed by transmission electron microscopy (TEM. By thermogravimetry (TG, the results indicated that the presence of clay increased the thermal stability of polyamide 6. The impact properties of the nanocomposites showed inferior values in relation to the pure polyamide, in other words, decrease the toughness.

  7. Field test of ethanol/bentonite slurry grouting into rock fracture

    International Nuclear Information System (INIS)

    Crystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction. Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material. (author)

  8. Performance characteristics of EZhou bentonite of Hubei province and its modification

    Institute of Scientific and Technical Information of China (English)

    Long Wei; Fan Zitian; Hu Xueting

    2009-01-01

    Both the chemical compositions and performance characteristics of the bentonite raw ores in Ezhou area of Hubei province and Honghuoshan area of Liaoning province were compared and analyzed. The properties of these two kinds of bentonites were tested before and after Na+- and Li+-modification. The results show that the Ezhou bentonite ore possesses higher montmorillonite content than the Honghuoshan bentonite ore, but the Ezhou Na-bentonite has weaker castability (e.g. Wet compression strength and hot wet tensile strength) than the Honghuoshan Na-bentonite, while the performance of Ezhou Li-bentonite, such as colloid index, swelling value, swelling volume and mould coating performance, is equivalent to that of the Honghuoshan Na-bentonite.

  9. Thermic and thermodynamic properties of desorption process of essential oil of Hyssopus seravshanicus from bentonite clays

    International Nuclear Information System (INIS)

    It shown, that desorption process of essential oil of Hyssopus seravshanicus from bentonite clays include by four parts (lines) and the nature between essential oil of Hyssopus seravshanicus from bentonite clays is physical and chemical sorption

  10. Evaluation of uncertainties of key neutron parameters of PWR-type reactors with slab fuel, application to neutronic conformity; Determination des incertitudes liees aux grandeurs neutroniques d'interet des reacteurs a eau pressurisee a plaques combustibles et application aux etudes de conformite

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, D

    2001-12-01

    The aim of this thesis was to evaluate uncertainties of key neutron parameters of slab reactors. Uncertainties sources have many origins, technologic origin for parameters of fabrication and physical origin for nuclear data. First, each contribution of uncertainties is calculated and finally, a factor of uncertainties is associated to key slab parameter like reactivity, isotherm reactivity coefficient, control rod efficiency, power form factor before irradiation and life-time. This factors of uncertainties were computed by Generalized Perturbations Theory in case of step 0 and by directs calculations in case of irradiation problems. One of neutronic conformity applications was about fabrication and nuclear data targets precision adjustments. Statistic (uncertainties) and deterministic (deviations) approaches were studied. Then, neutronics key slab parameters uncertainties were reduced and so nuclear performances were optimized. (author)

  11. Comparison of the mineralogical composition, physical, swelling and hydraulic properties of untreated sodium bentonites from Canada, the United States and Japan

    International Nuclear Information System (INIS)

    A large variety of commercial grade sodium bentonite products are available from suppliers in North America and Japan. This report generally characterizes the products available for environmental engineering applications. A compilation of the swelling capacity and hydraulic properties of the available products, together with their basic mineralogical composition, physical and engineering properties is presented. This report identifies the range of materials available commercially and documents the basic physical properties of these products. The geological origins and locations of bentonite-ore deposits are discussed with reference to the availability and variability of this material. The hydraulic and swelling characteristics of 17 different bentonite products from 9 different producers were compared. Considerable variation was noted in the free-swell capacity of these clays but this was not reflected in the swelling pressure or hydraulic conductivity of densely compacted specimens. The density -hydraulic conductivity relationship was found to be independent of product for untreated sodium bentonite clays with hydraulic conductivity decreasing with increasing clay density (for materials tested at high (>500) hydraulic gradients). A large body of hydraulic conductivity data was obtained from the literature to supplement the data generated by this study. The literature values further supported the results of this study. Hydraulic conductivity and swelling pressure performance at high density are consistent when sodium bentonites of similar quality are densely compacted prior to use. (author) 27 refs., 5 tabs., 17 figs

  12. Geochemical discrimination of the Upper Ordovician Kinnekulle Bentonite in the Billegrav-2 drill core section, Bornholm, Denmark

    Directory of Open Access Journals (Sweden)

    Tarmo Kiipli

    2014-12-01

    Full Text Available The content of the trace elements Ti, Nb, Zr and Th has been analysed in 34 Upper Ordovician bentonites from the Billegrav-2 drill core, Bornholm, Denmark. The section contains two 80–90 cm thick bentonites, which potentially may represent the Kinnekulle Bentonite, as well as several rather thick but composite bentonite layers with thin terrigenous shale interbeds. Comparison of the four immobile trace elements with data from the Kinnekulle Bentonite reported from other locations in Baltoscandia indicate that the 80 cm thick bentonite between 88.30 and 89.10 m in the Billegrav-2 core represents this marker bed. The other thick (90 cm bentonite in the Billegrav-2 core, exceeding the thickness of the Kinnekulle Bentonite, belongs to the Sinsen or uppermost Grefsen Series bentonites. Bentonites in the Grefsen Series frequently contain much higher concentrations of trace elements than the Kinnekulle Bentonite.

  13. Development of an analytical technique for the detection of alteration minerals formed in bentonite by reaction with alkaline solutions

    Science.gov (United States)

    Sakamoto, H.; Shibata, M.; Owada, H.; Kaneko, M.; Kuno, Y.; Asano, H.

    and 50.1°, Cu Kα) of the C-S-H gel, which could not be distinguished before the heavy liquid separation, were clearly identified by XRD after separation. The result of the analyses of the light density fraction indicates highest recovery of C-S-H gel and least inclusion of bentonite for separation using heavy liquid with a specific gravity of 2.10 g/cm 3. The traces of bentonite minerals included in the suspension were identified to be montmorillonite, quartz, clinoptilolite, and calcite. The separation technique was also tested for Ca-bentonite prepared by passing a calcium hydroxide solution through a bentonite (Kunigel V1)-silica sand mixture. The results indicated that the technique would also be applicable to separation of C-S-H gel from Ca-bentonite.

  14. Radioassay of vitamin B-12 employing bentonite

    International Nuclear Information System (INIS)

    Radioassay for vitamin B-12 using the unknown quantity of non-radioactive vitamin B-12 released from serum mixed with the radioactivity of a known quantity of radioactive vitamin B-12 tracer. A solution of intrinsic factor having a binding capacity less than the quantity of serum vitamin B-12 and radioactive vitamin B-12 is used to bind a portion of the vitamin B-12 mixture. The vitamin B-12 not bound to intrinsic factor is removed by addition of a bentonite-containing tablet. The quantity of radioactive vitamin B-12 bound to intrinsic factor is compared with standard values and the unknown serum vitamin B-12 obtained. In the steps of the procedure the acid assay medium is pre-combined with the radioactive tracer so that the radioactive vitamin B-12 tracer receives the same treatment as serum vitamin B-12. Certain of the other reagent solutions are pre-combined and the concentration of the components adjusted so that the volume used of each of these other reagent solutions is the same in different assay steps. Thus, fewer pipetting steps are necessary. 7 claims, 1 drawing figure

  15. Measurement of pH of the Compacted Bentonite under the Reducing Condition

    OpenAIRE

    Nessa, Syeda Afsarun; Idemitsu, Kazuya; Yamasaki, Yosuke; Inagaki, Yaohiro; Arima, Tatsumi

    2007-01-01

    Compacted bentonite and carbon steel have been considered as the good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95wt% of montmorillonite. It has a high cation-exchange capacity and a high specific surface area, and its properties determine the behavior of bentonite. The pH of the pore water in compacted bentonite is an extremely important parameter because of its influence on radionuclide sol...

  16. Hydrothermal alkaline stability of bentonite barrier by concrete interstitial wastes

    International Nuclear Information System (INIS)

    At present, the main source of High Level radioactive Waste (HLW) is the electrical energy production during all the steps of developing. In almost all the countries with nuclear programs, the option for the final management of HLW is the Deep Geological Repository (DGR) based on the concept of multi barrier. According to this concept, the waste is isolated from biosphere by the interposition of confinement barriers. Two of the engineering barriers in the Spanish design of DGR in granitic rock are compacted bentonite and concrete. The bentonite barrier is the backfilling and sealing material for the repository gallery, because of its mechanical and physico-chemical properties. The main qualities of concrete as a component of a multi barrier system are its low permeability, mechanical resistance and chemical properties. With regard to chemical composition of concrete, the alkaline nature of cement pore water lowers the solubility of many radioactive elements. However, structural transformation in smectite, dissolution or precipitation of minerals and, consequently, changes in the bentonite properties could occurs in the alkaline conditions generated by the cement degradation. The main objective of the present work is to evaluate the effect of concrete in the stability of Spanish reference bentonite (La Serrata of Nijar, Almeria, Spain) in conditions similar to those estimated in a DGR in granitic rock. Because of the main role of bentonite barrier in the global performance of the repository, the present study is essential to guarantee its security. (Author)

  17. ADSORPTION FROM AQUEOUS SOLUTION ONTO NATURAL AND ACID ACTIVATED BENTONITE

    Directory of Open Access Journals (Sweden)

    Laila Al-Khatib

    2012-01-01

    Full Text Available Dyes have long been used in dyeing, paper and pulp, textiles, plastics, leather, paint, cosmetics and food industries. Nowadays, more than 100,000 commercial dyes are available with a total production of 700,000 tones manufactured all over the world annually. About 10-15% of dyes are being disposed off as a waste into the environment after dyeing process. This poses certain hazards and environmental problems. The objective of this study is to investigate the adsorption behavior of Methylene Blue (MB from aqueous solution onto natural and acid activated Jordanian bentonite. Both bentonites are firstly characterized using XRD, FTIR and SEM techniques. Then batch adsorption experiments were conducted to investigate the effect of initial MB concentration, contact time, pH and temperature. It was found that the percentage of dye removal was improved from 75.8% for natural bentonite to reach 99.6% for acid treated bentonite. The rate of MB removal followed the pseudo second order model with a high correlation factor. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The Langmuir isotherm model was found more representative. The results indicate that bentonite could be employed as a low cost adsorbent in wastewater treatment for the removal of colour and dyes.

  18. Tracer diffusion in compacted, water-saturated bentonite

    International Nuclear Information System (INIS)

    Compacted Na-bentonite clay barriers, widely used in the isolation of solid-waste landfills and other contaminated sites, have been proposed for a similar use in the disposal of high-level radioactive waste. Molecular diffusion through the pore space in these barriers plays a key role in their performance, thus motivating recent measurements of the apparent diffusion coefficient tensor of water tracers in compacted, water-saturated Na-bentonites. In the present study, we introduce a conceptual model in which the pore space of water-saturated bentonite is divided into 'macropore' and 'interlayer nanopore' compartments. With this model we determine quantitatively the relative contributions of pore-network geometry (expressed as a geometric factor) and of the diffusive behavior of water molecules near montmorillonite basal surfaces(expressed as a contrastivity factor) to the apparent diffusion coefficient tensor. Our model predicts, in agreement with experiment, that the mean principal value of the apparent diffusion coefficient tensor follows a single relationship when plotted against the partial montmorillonite dry density (mass of montmorillonite per combined volume of montmorillonite and pore space). Using a single fitted parameter, the mean principal geometric factor, our model successfully describes this relationship for a broad range of bentonite-water system, from dilute gel to highly-compacted bentonite with 80 percent of its pore water in interlayer nanopores

  19. Utilization of locally available bentonites for water purification by activation

    International Nuclear Information System (INIS)

    Acid activation of commercial bentonite was conducted and tested for adsorption of impurities in water and industrial products. The properties of adsorption/absorption of bentonite are also used to remove impurities for the processing of edible oils and fats, as well as for the purification of products like honey and alcohol. The design of various experiments in order to assess and simulate the effects of acid activation of commercial bentonite on the adsorption capacity of methylene blue dye is described in this paper. The key parameters of the acid activation, namely acid concentration, contact time, temperature and type of acid, were established. The results indicated effects of these variables on the effectiveness of adsorption. The Swelling Index value of activated bentonite was 20 ml per 2 gram in deionized water as compared to 8 ml per 2 gm in unactivated samples. The acid concentration exerts a predominant individual effect as compared to other parameters. Bentonite activated by 5N HCl has more adsorption capacity than 40% HSO. Excessive 2 4 activation is discussed in terms of loss in both porosity and acid strength. (author)

  20. pH measuring of the interstitial water in high-density bentonite (2). Resin insertion method under controlled atmosphere (Progress report)

    Energy Technology Data Exchange (ETDEWEB)

    Oda, H.; Sato, K; Shibata, Masahiro [Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (Japan). Tokai Works; Isogai, T.

    1999-03-01

    To measure the pH value of the interstitial water in the bentonite under the saturated pressure, a resin (adsorbent particles impregnated with pH indicator) was put between semi-permeable cellulose protection sheets and inserted into the bentonite and pH was measured using its color reaction. pH values (7-9) thus measured were found to depend on the pressure, the density at dried conditions and also on chemical constituents. The method was found to be applicable to rough estimate of elemental composition. (S. Ohno)

  1. Commande multi-modèles tolérante aux défauts : Application au contrôle de la dynamique d'un véhicule automobile.

    OpenAIRE

    Oudghiri, Mohammed

    2008-01-01

    Cette thèse traite la synthèse de lois de commande tolérantes aux défauts (FTC) pour le contrôle de la dynamique du châssis du véhicule automobile. L'étude est basée sur l'approche multimodèle avec la formulation et la résolution des problèmes de synthèse de lois de commande en utilisant les techniques LMI (Inégalités Matricielles Linéaires).La première partie consacrée à la FTC passive comporte trois chapitres. La première concerne la synthèse d'une loi de commande multimodèle par retour d'é...

  2. Systèmes d'Information Scientifique : des modèles conceptuels aux annotations sémantiques Application au domaine de l'archéologie et des sciences du vivant

    OpenAIRE

    Savonnet, Marinette

    2013-01-01

    Les Systèmes d'Information Scientifique (SIS) sont des Systèmes d'Information (SI) dont le but est de produire de la connaissance et non pas de gérer ou contrôler une activité de production de biens ou de services comme les SI d'entreprise. Les SIS se caractérisent par des domaines de recherche fortement collaboratifs impliquant des équipes pluridisciplinaires et le plus souvent géographiquement éloignées, ils manipulent des données aux structures très variables dans le temps qui vont au-delà...

  3. Modélisation du procédé de soudage hybride Arc / Laser par une approche level set application aux toles d'aciers de fortes épaisseurs

    OpenAIRE

    Desmaison, Olivier; Bellet, Michel; Guillemot, Gildas

    2013-01-01

    Le procédé de soudage hybride Arc/Laser est une solution aux assemblages difficiles de tôles de fortes épaisseurs. Ce procédé innovant associe deux sources de chaleur : un arc électrique produit par une torche MIG et une source laser placée en amont. Ce couplage améliore le rendement du procédé, la qualité du cordon et les déformations finales. La modélisation de ce procédé par une approche Level Set permet une prédiction du développement du cordon et du champ de température associé. La simul...

  4. Transitions des exploitations agricoles vers l'agriculture biologique dans un territoire : approche par les interactions entre systèmes techniques et de commercialisation : Application aux aires d'alimentation de captages en Île-de-France

    OpenAIRE

    Petit, Caroline

    2013-01-01

    En réponse aux réglementations environnementales récentes incitant à une gestion préventive de la qualité de l’eau, l’agriculture biologique (AB) constitue une des solutions globales préconisée pour cette gestion préventive. L’objectif de cette thèse est d’étudier les transitions des exploitations agricoles vers l’AB dans les territoires, en prenant les aires d’alimentation de captages (AAC) en Île-de-France comme cas d’étude. En nous inscrivant en agronomie des territoires, nous développons ...

  5. Coupled behaviour of bentonite buffer results of PUSKURI project

    International Nuclear Information System (INIS)

    In the report main results form a KYT2010 programme's project Coupled behaviour of bentonite buffer (PUSKURI) are presented. In THC modelling, Aku Itaelae made and published his Master of Science Thesis. Itaelae was able to successfully model the LOT-experiment. Additionally, he also listed problems and development proposals for THC-modelling of bentonite buffer. VTT and Numerola created in collaboration a model coupling saturation, diffusion and cation exchange; the model was implemented and tested in Numerrin, COMSOL and TOUGHREACT. Petri Jussila's PhD THM-model was implemented into COMSOL to facilitate further development. At GTK, the mineralogical characterisation of bentonite was planned. The previous THM model (Jussila's model) including only small deformations was successfully generalized to finite deformations in way at least formally preserving the original formalism. It appears that the theory allows also a possibility to include finite plastic deformations in the theory. In order to measure the relevant mechanical properties of compacted bentonite, two different experiments, namely hydrostatic compression experiment and one-dimensional compression experiment were designed. In the hydrostatic compression experiment, a cylindrical sample of compacted bentonite covered with liquid rubber coating is placed in the sample chamber equipped with a piston. The same device was also used in one-dimensional compression experiment. X-ray microtomographic techniques were used in order to study the basic mechanisms of water transport in bentonite. The preliminary results indicate that in the present experimental set-up, water transport is dominated by a dispersive mechanism such as diffusion of vapour in gas phase or diffusion of water in solid phase. (orig.)

  6. Structure and forces in bentonite MX-80

    International Nuclear Information System (INIS)

    Wyoming bentonite (MX-80) and its ion exchanged forms, Na and Ca montmorillonite, have been studied experimentally and theoretically. A variety of experimental techniques have been used in order to gain insight into the structural conditions in dry clay as well as clay in equilibrium with a bulk solution of given ionic composition. The main objective has been the swelling behaviour and osmotic pressure of montmorillonite clay when the bulk solution contains a mix of monovalent sodium and divalent calcium ions. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is predicted with an aqueous layer between the clay lamellaes of about 1 nm. This latter result is in excellent agreement with small angle x-ray scattering data, but in disagreement with dialysis experiments, which gives a significantly larger swelling for Ca montmorillonite in pure water. Obviously, there is one lamellar swelling and a second 'extra-lamellar' swelling, which could be the result of a phase separation in the clay. Montmorillonite in contact with a salt reservoir with both Na+ and Ca2+ counterions will only show a modest swelling unless the sodium concentration in the bulk is several orders of magnitude larger than the calcium concentration. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which reduce the entropic repulsion as well as give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favour divalent counterions in a situation where we have a competition with monovalent ones. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes nonmonotonic, which indicates the possibility of a phase separation into a concentrated and a dilute clay phase. This phenomenon could explain the

  7. Thermodynamic Aspects of Supercritical Fluids Processing: Applications of Polymers and Wastes Treatment Aspects thermodynamiques des procédés mettant en oeuvre des fluides supercritiques : applications aux traitements des polymères et des déchets

    Directory of Open Access Journals (Sweden)

    Beslin P.

    2006-11-01

    Full Text Available Supercritical fluid processes are of increasing interest for many fields : in supercritical fluid separation (petroleum-chemistry separation and purification, food industry and supercritical fluid chromatography (analytical and preparative separation, determination of physicochemical properties; as reaction media with continuously adjustable properties from gas to liquid (low-density polyethylene, waste destruction, polymer recycling; in geology and mineralogy (volcanoes, geothermal energy, hydrothermal synthesis; in particle, fibber and substrate formations (pharmaceuticals, explosives, coatings; in drying materials (gels. This paper presents the unusual physicochemical properties of supercritical fluids in relation to their engineering applications. After a short report of fundamental concepts of critical behavior in pure fluids, we develop in more details the tunable physicochemical properties of fluid in the supercritical domain. The second part of this paper describes the engineering applications of supercritical fluids relevant of chemical reactions and polymer processing. Each application presentation is divided in two parts : the first one recalls the basic concepts including general background, physicochemical properties and the second one develops the engineering applications relevant of the advocated domain. La mise en Suvre des fluides supercritiques est d'un intérêt croissant dans de nombreux domaines : pour la séparation (séparation et purification en pétrochimie, industrie alimentaire et la chromatographie par fluides supercritiques (séparation analytique et préparatoire, détermination des propriétés physicochimiques, comme milieux réactifs aux propriétés continûment ajustables allant du gaz au liquide (polyéthylène de faible densité, élimination des déchets, recyclage des polymères, en géologie et en minéralogie (volcanologie, énergie géothermique, synthèse hydrothermique, dans la formation des particules

  8. Characterization of bentonite clay from “Greda” deposit

    Directory of Open Access Journals (Sweden)

    Nadežda Stanković

    2011-06-01

    Full Text Available Based on mineralogical and technological investigations of the deposit “Greda” important characteristics of bentonite clay were determined. Representative samples of the deposit were characterized with X-ray diffraction, low-temperature nitrogen adsorption, chemical analysis, differential thermal analysis and scanning electron microscopy. It was determined that the main mineral is montmorillonite and in subordinate quantities kaolinite, quartz and pyrite. The chemical composition generally shows high silica and alumina contents in all samples and small quantities of Fe3+, Ca2+ and Mg2+ cations. Based on technological and mineralogical research, bentonite from this deposit is a high-quality raw material for use in the ceramic industry.

  9. Evaluation of phenomena affecting diffusion of cations in compacted bentonite

    International Nuclear Information System (INIS)

    In a number of diffusion studies, contradictions between the apparent diffusivities of cations and their distribution coefficients in bentonite have been found. Two principal reasons have been offered as explanations for this discrepancy; diffusion of the sorbed cations, often called surface diffusion, and the decrease of sorption in compacted clay compared to a sorption value obtained from a batch experiment. In the study the information available from the literature on sorption-diffusion mechanisms of cations in bentonite has been compiled and re-interpreted in order to improve the understanding of the diffusion process. (103 refs., 23 figs., 8 tabs.)

  10. Pore water chemistry of Rokle Bentonite (Czech Republic)

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. With inflowing the groundwater to Deep Geological Repository (DGR), the interaction of this water with engineering barrier materials will alter both, barrier materials and also the groundwater. One of the most important alterations represents the formation of bentonite pore water that will affect a number of important processes, e.g. corrosion of waste package materials, solubility of radionuclides, diffusion and sorption of radionuclides. The composition of bentonite pore water is influenced primarily by the composition of solid phase (bentonite), liquid phase (inflowing groundwater), the gaseous phase (partial pressure of CO2), bentonite compaction and the rate of groundwater species diffusion through bentonite. Also following processes have to be taken into account: dissolution of admixtures present in the bentonite (particularly well soluble salts, e.g. KCl, NaCl, gypsum), ion exchange process and protonation and deprotonation of surface hydroxyl groups on clay minerals. Long-term stability of mineral phases and possible mineral transformation should not be neglected as well. In the Czech Republic, DGR concept takes local bentonite into account as material for both buffer and backfill. The candidate bentonite comes from the Rokle deposit (NW Bohemia) and represents complex mixture of (Ca,Mg)-Fe-rich montmorillonite, micas, kaolinite and other mineral admixtures (mainly Ca, Mg, Fe carbonates, feldspars and iron oxides). The mineralogical and chemical characteristics were published previously. This bentonite is different in composition and properties from worldwide studied Na-bentonite (e.g. MX-80, Volclay) or Na-Ca bentonite (e.g. Febex). This fact leads to the need of investigation of Rokle bentonite in greater detail to verify its suitability as a buffer and backfill in DGR. Presented task is focused on the study of pore water evolution. Our approach for this study consists in modeling the pore water using

  11. Study of the integration of distributed generation systems in the grid: application in micro-grids; Etude de structures d'integration des systemes de generation decentralisee: application aux microreseaux

    Energy Technology Data Exchange (ETDEWEB)

    Gaztanaga Arantzamendi, H

    2006-12-15

    The present PhD deals with an original micro-grid concept and its application as a Renewable Energy Source's (RES) grid integration scheme. This micro-grid is composed of RES generators as well as support systems that incorporate additional functionalities in order to improve RES integration into the grid. According to this concept, two practical micro-grid applications have been studied in detail: a residential micro-grid and a wind farm supported by DFACTS systems (STATCOM and DVR). In both applications, the control structures which are implemented at different levels and applied to the different micro-grid elements have been developed, analyzed by means of off-line simulations and finally validated in real-time conditions with physical reduced-scale prototypes. (author)

  12. Notes de voyage aux Iles Baleares

    Directory of Open Access Journals (Sweden)

    Maurice LOUIS

    2009-10-01

    Full Text Available Les excursions du 1Vº Cours de Préhistoire et d'Archéologie, organisé en 1950 par l'Université de Barcelone en collaboratión avec l'Institut de Prehistoire méditerranéenne du Consejo Superior de Investigaciones Científicas d'Espagne, on conduit les participants aux Iles Baléares afin d'étudier sur place la civilisation dite "des talayots" de Majorque et de Minorque.

  13. Study on long-term performance of bentonite layer in radioactive waste repository

    International Nuclear Information System (INIS)

    It is important to appropriately evaluate the long-term performance of the bentonite layer in a radioactive waste repository because it can considerably affect the repository function for containment and delay of nuclides. Thus far, limited knowledge has been available on alkali alteration phenomena of highly compacted bentonite and their effect on its physical properties. In this study, we developed an apparatus for testing alkali alteration phenomena of highly compacted bentonite and its physical properties. Through studies conducted using the apparatus, we concluded that the alkali dissolution rate of montmorillonite in highly compacted bentonite is less than 9.7 x 10-13 mol/m2/sec and that the hydraulic conductivity of the bentonite layer is affected by the pore structure, which can be refined by the effect of dissolution and precipitation of minerals in bentonite, as well as by the density of the bentonite layer and the electrolyte concentration of pore solution. (author)

  14. Numerical simulation of alteration of sodium bentonite by diffusion of ionic groundwater components

    International Nuclear Information System (INIS)

    Experiments measuring the movement of trace amounts of radionuclides through compacted bentonite have typically used unaltered bentonite. Models based on experiments such as these may not lead to accurate predictions of the migration through altered or partially altered bentonite of radionuclides that undergo ion exchange. To address this problem, we have modified an existing transport code to include ion exchange and aqueous complexation reactions. The code is thus able to simulate the diffusion of major ionic groundwater components through bentonite and reactions between the bentonite and groundwater. Numerical simulations have been made to investigate the conversion of sodium bentonite to calcium bentonite for a reference groundwater characteristic of deep granitic formations. 20 refs., 2 figs., 2 tabs

  15. The effect of zeolite,bentonite and sepiolite minerals onheavy metal uptake by sunflower

    Directory of Open Access Journals (Sweden)

    N . Esmaeilpour Fard

    2015-06-01

    Full Text Available Mining, industrial and agricultural activities can result in considerable soil pollution by heavy metals (HMs. One of the methods to control this pollution is application of adsorbent minerals. The purpose of this study was to compare the effects of adsorbent minerals (bentonite, zeolite and sepiolite on transfer of some heavy metals (i.e., Pb, Zn and Cd from soil to tissues of sunflower (Heliantus annuus L.. Treatments included: Non-polluted soil, HM-polluted soil, polluted soil + bentonite, polluted soil + zeolite, and polluted soil + sepiolite. Sunflower seeds were planted in different pots containing the above treated soils. After 70 days of growth, plants were harvested and HMs content was measured. Results revealed that the uptake of HMs from non-polluted soil was lower than that of other treatments. In the polluted soil + sepiolite treatment, the added sepiolite increased plant Cd and Zn uptake by 0.37 and 7.17 mg/kg, respectively. However, the differences in HMs uptake were not significant for other treatments. Zeolite addition decreased plant uptake of Zn and Cd by about 12 and 0.21 mg/kg, respectively, while bentonite addition reduced Pb uptake by about 3.05 mg/kg, without any significant difference for the other treatments. Zn uptake was higher by about 12.2 mg/kg in plant shoots as compared to plant roots. On the contrary, the roots took up higher amounts of Cd and Pb, as compared to the shoots. Despite high concentration of the HMs in the polluted soils, considerable tendency of sunflower for uptake, and a high adsorption capacity of the applied minerals, the HMs uptake by sunflower and surface adsorption by the minerals were very low, probably due to HMs precipitation in the soil.

  16. Spray Atomization Models in Engine Applications, from Correlations to Direct Numerical Simulations Modèles de spray dans les applications moteur, des corrélations aux simulations numériques directes

    Directory of Open Access Journals (Sweden)

    Dos Santos F.

    2011-09-01

    Full Text Available Sprays are among the very main factors of mixture formation and combustion quality in almost every (IC engine. They are of great importance in pollutant formation and energy efficiency although adequate modeling is still on development. For many applications, validation and calibration of models are still an open question. Therefore, we present an overview of existing models and propose some trends of improvement. Models are classified in zero dimensional and dimensional classes ranging from simple formulations aimed at close-to-real-time applications to complete detailed description of early atomization stages. Les sprays sont parmi les principaux facteurs de qualite, dans la formation du melange et la combustion, dans un grand nombre de moteurs (a combustion interne. Ils sont de toute premiere importance dans la formation de polluants et l’efficacite energetique, bien qu’une modelisation adequate soit encore en developpement. Pour un grand nombre d’applications, la validation et la calibration de ces modeles demeurent une question ouverte. Aussi, presentons-nous un apercu des modeles existants et proposons quelques voies d’amelioration. Les modeles sont classes en nondimensionnels et dimensionnels allant de formules simples dediees a des applications proches du temps reel a des descriptions detaillees des premiers stades de l’atomisation.

  17. Influence of environmental factors on the phosphorus adsorption of lanthanum-modified bentonite in eutrophic water and sediment.

    Science.gov (United States)

    Liu, SheJiang; Li, Jie; Yang, YongKui; Wang, Juan; Ding, Hui

    2016-02-01

    Lanthanum-modified bentonite has potential for wide application in eutrophication control. We investigated P adsorption on a lanthanum-modified bentonite by analysis of adsorption kinetics, equilibrium, and the effect of environmental factors. P adsorption closely followed the pseudo-second-order kinetic model, and the isotherm was well described by the Langmuir model. This adsorbent could effectively immobilize P into the sediment, but the adsorption process was strongly dependent on pH, anions, and low molecular weight organic acids (LMWOAs). P adsorption increased with increasing pH from 0.52 mg P/g at pH 3.0 to 0.93 mg P/g at pH 7.0 with no adsorption at pH 11. P adsorption was strongly inhibited in the presence of anions and three LMWOAs, with P even re-released at high concentrations. These environmental factors should be given significant attention when considering the application of lanthanum-modified bentonite in eutrophication control. PMID:26423284

  18. Structure and forces in bentonite MX-80

    Energy Technology Data Exchange (ETDEWEB)

    Joensson, Bo; Aakesson, Torbjoern; Joensson, Bengt; Meehdi, Segad; Janiak, John; Wallenberg, Reine (Theoretical Chemistry, Chemical Center, Lund Univ., Lund (Sweden))

    2009-03-15

    Wyoming bentonite (MX-80) and its ion exchanged forms, Na and Ca montmorillonite, have been studied experimentally and theoretically. A variety of experimental techniques have been used in order to gain insight into the structural conditions in dry clay as well as clay in equilibrium with a bulk solution of given ionic composition. The main objective has been the swelling behaviour and osmotic pressure of montmorillonite clay when the bulk solution contains a mix of monovalent sodium and divalent calcium ions. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is predicted with an aqueous layer between the clay lamellaes of about 1 nm. This latter result is in excellent agreement with small angle x-ray scattering data, but in disagreement with dialysis experiments, which gives a significantly larger swelling for Ca montmorillonite in pure water. Obviously, there is one lamellar swelling and a second 'extra-lamellar' swelling, which could be the result of a phase separation in the clay. Montmorillonite in contact with a salt reservoir with both Na+ and Ca2+ counterions will only show a modest swelling unless the sodium concentration in the bulk is several orders of magnitude larger than the calcium concentration. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which reduce the entropic repulsion as well as give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favour divalent counterions in a situation where we have a competition with monovalent ones. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes nonmonotonic, which indicates the possibility of a phase separation into a concentrated and a dilute clay phase. This phenomenon could

  19. Magnesium incorporated bentonite clay for defluoridation of drinking water

    International Nuclear Information System (INIS)

    Low cost bentonite clay was chemically modified using magnesium chloride in order to enhance its fluoride removal capacity. The magnesium incorporated bentonite (MB) was characterized by using XRD and SEM techniques. Batch adsorption experiments were conducted to study and optimize various operational parameters such as adsorbent dose, contact time, pH, effect of co-ions and initial fluoride concentration. It was observed that the MB works effectively over wide range of pH and showed a maximum fluoride removal capacity of 2.26 mg g-1 at an initial fluoride concentration of 5 mg L-1, which is much better than the unmodified bentonite. The experimental data fitted well into Langmuir adsorption isotherm and follows pseudo-first-order kinetics. Thermodynamic study suggests that fluoride adsorption on MB is reasonably spontaneous and an endothermic process. MB showed significantly high fluoride removal in synthetic water as compared to field water. Desorption study of MB suggest that almost all the loaded fluoride was desorbed (∼97%) using 1 M NaOH solution however maximum fluoride removal decreases from 95.47 to 73 (%) after regeneration. From the experimental results, it may be inferred that chemical modification enhances the fluoride removal efficiency of bentonite and it works as an effective adsorbent for defluoridation of water.

  20. A review of porosity and diffusion in bentonite

    International Nuclear Information System (INIS)

    Porosity in bentonite can be subdivided in free porewater, diffuse double layer (DDL) water, and interlayer water in montmorillonite, the most important mineral of bentonite. The proportions of these water types can be calculated from the internal and external specific surface area of montmorillonite and the width of interlayer- and DDL-water. Stacking of the TOT layers in montmorillonite in the c-direction is the master variable that determines the specific internal and external surface areas. The thickness of the water layers depends on the ionic strength and the composition of the free porewater, and on the packing density of the bentonite. When the proportions of the water types change, the diffusion of cations, anions and neutral molecules is affected in different ways since the diffusional properties vary. Diffusive fluxes are proportional with accessible porosity, chemical potential gradient, and diffusion coefficient, but not with concentration as has been proposed often in diffusion models. The equations for calculating the diffusive flux through interlayer water are derived. The potential gradient here is given by the gradient of the equivalent (or molar) fraction of the cation in the cation exchange capacity. The latter is expressed as concentration in the interlayer water. An example calculation illustrates that the flux in interlayer water can be dominant and opposite to the one in free porewater. Retardation by ion exchange is an important process in bentonite that can be modeled if the concentrations of major ions are known. Unfortunately, the analyses are almost never done in diffusion experiments.(orig.)

  1. Sodium Bentonite-Based Fire Retardant Coatings Containing Starch

    Science.gov (United States)

    Sodium bentonite (SB) gel and foam coatings were tested for their ability to suppress the rate of heat increase at the surface of commercial lap siding. Starch was added to some treatments to determine whether it stabilized the coating and prevented vertical slumping. A commercial fire protection ge...

  2. Experimental study on bentonite gel migration from a deposition hole

    International Nuclear Information System (INIS)

    The experimental study on bentonite gel migration from a deposition hole into a surrounding joint has been performed by using a transparent acrylic resin cell with a slot. Cylindrical blocks of pure bentonite and a bentonite-sand mixture have been used as the buffer material, and the slot width simulating the joint aperture is set between 0.3 to 1.5 mm. The time-dependence displacement of migrating gel fronts in the slots and the swelling pressure of the sample in the core, which simulate a deposition hole, have been measured. It has been observed that the migrating gel front separates two distinct zones, and the displacement of the front is proportional to the square-root of time before the separation. With wider slots, the swelling pressure of the sample in the core has rapidly decreased. Applying theoretical models to the experimental results, the viscosity of the migrating gel in the slot (ca. 200 MPa·s) and the diffusion coefficient of bentonite clay (ca. 3 x 10-11m2/s) have been obtained. (author)

  3. Diffusion of anions and cations in compacted sodium bentonite

    International Nuclear Information System (INIS)

    The thesis presents the results of studies on the diffusion mechanisms of anions and cations in compacted sodium bentonite, which is planned to be used as a buffer material in nuclear waste disposal in Finland. The diffusivities and sorption factors were determined by tracer experiments. The pore volume accessible to chloride, here defined as effective porosity, was determined as a function of bentonite density and electrolyte concentration in water, and the Stern-Gouy double-layer model was used to explain the observed anion exclusion. The sorption of Cs+ and Sr2+ was studied in loose and compacted bentonite samples as a function of the electrolyte concentration in solution. In order to obtain evidence of the diffusion of exchangeable cations, defined as surface diffusion, the diffusivities of Cs+ and Sr2+ in compacted bentonite were studied as a function of the sorption factor, which was varied by electrolyte concentration in solution. The measurements were performed both by a non-steady state method and by a through-diffusion method. (89 refs., 35 fig., 4 tab.)

  4. DEPOSITS AND MINING POTENTIAL OF BENTONITE IN CROATIA

    Directory of Open Access Journals (Sweden)

    Mario Klanfar

    2012-07-01

    Full Text Available Bentonite is one of the materials that is planed to be used for buffering and backfilling in spent nuclear fuel repositories, within deep crystalline rock. There are several locations in Croatia that bentonite deposits and occurrences are found on. Some were exploited in past, and others were more or less explored. This paper presents overview of bentonite deposits, basic properties and potential resources, and mining practices in Croatia. Largest exploited deposits are found in area of Poljanska luka, Gornja Jelenska and Bednja. Surface and underground methods (drift and fill, sublevel caving were used during exploitation. In the area of Svilaja and Lika are found potentially valuable deposits that were never exploited. Montmorilonite content ranges form 20-50% to 57-89%. Most deposits contain bentonite beds with thickness 0,4-1,6 m, and have plunge 10°-30°. Few exceptions are nearly horizontal and thick more than 5 m and even 12 m. One is declined at 70° and up to 40m thick. Proven reserves are about 2,3 Mt with some level of uncertainty. Average production per mine during exploitation period can be assumed to be several thousands t/y.

  5. Polypropylene–clay composite prepared from Indian bentonite

    Indian Academy of Sciences (India)

    Madhuchhanda Sarkar; Kausik Dana; Sankar Ghatak; Amarnath Banerjee

    2008-02-01

    In the present work, a set of experimental polypropylene (PP) clay composites containing pristine bentonite clay of Indian origin has been prepared and then characterized. The polymer clay composites are processed by solution mixing of polypropylene with bentonite clay using a solvent xylene and high speed electric stirrer at a temperature around 130°C and then by compression molding at 170°C. The mechanical properties of PP–clay composites like tensile strength, hardness and impact resistance have been investigated. Microstructural studies were carried out using scanning electron microscope and transmission electron microscope and the thermal properties were studied using differential scanning calorimeter. Mechanical properties of the prepared composites showed highest reinforcing and toughening effects of the clay filler at a loading of only 5 mass % in PP matrix. Tensile strength was observed to be highest in case of 5 mass % of clay loading and it was more than 14% of that of the neat PP, while toughness increased by more than 80%. Bentonite clay–PP composite (5 mass %) also showed 60% increase in impact energy value. However, no significant change was observed in case of hardness and tensile modulus. Higher percentages of bentonite clay did not further improve the properties with respect to pristine polypropylene. The study of the microstructure of the prepared polymer layered silicate clay composites showed a mixed morphology with multiple stacks of clay layers and tactoids of different thicknesses.

  6. Spray Atomization Models in Engine Applications, from Correlations to Direct Numerical Simulations Modèles de spray dans les applications moteur, des corrélations aux simulations numériques directes

    OpenAIRE

    Dos Santos F.; Le Moyne L.

    2011-01-01

    Sprays are among the very main factors of mixture formation and combustion quality in almost every (IC) engine. They are of great importance in pollutant formation and energy efficiency although adequate modeling is still on development. For many applications, validation and calibration of models are still an open question. Therefore, we present an overview of existing models and propose some trends of improvement. Models are classified in zero dimensional and dimensional classes ranging from...

  7. Development and applications of coherent imaging with improved temporal and spatial resolution; Developpement et applications de l'imagerie coherente aux rayons X a tres haute resolution spatiale et temporelle

    Energy Technology Data Exchange (ETDEWEB)

    Mokso, Rajmund

    2006-07-01

    This work has 2 purposes: the improvement of both temporal and spatial resolution of X-ray tomography. The first part is devoted to the technical aspects of the tomographic technique, particularly at the ESRF (European Synchrotron Radiation Facility) beamline ID19, and the application of the new acquisition scheme to the imaging of liquid foams. We have improved the temporal resolution and field of view of the setup, which allowed to obtain for the first time experimental data with good statistics on three dimensional liquid foams. In the second part of the thesis we have described the Kirkpatrick-Baez focusing system and its first applications. In terms of stability and image quality the developments presented in this part of the thesis provide valuable evidence for the feasibility of phase contrast tomography in magnifying geometry. Since the ultimate goal of this research is to improve the spatial resolution in tomography for applications, four different contributions are important for the characterization of the imaging system: 1) the thermal stability and mechanical imperfections, 2) effects of distortion induced by mirror imperfections, 3) effects of refraction on sample borders, and 4) phase propagation effects with the influence of the magnification. Each of these factors has been studied.

  8. Effects of the injection grout Silica sol on bentonite

    International Nuclear Information System (INIS)

    Silica sol, i.e., colloidal SiO2, may be used as a low-pH injection grout for very fine fractures in the construction of deep geological repositories for radioactive waste in Sweden and in Finland. If the bentonite barrier encounters SiO2-colloid particles under conditions favorable for aggregation, there is concern that it will modify the bentonite barrier at the bentonite/bedrock interface. In this study qualitative experiments were performed with mixed dispersions of SiO2-colloids and bentonite or homo-ionic Na/Ca-montmorillonite. Samples were prepared at different colloid concentrations and treated under various conditions such as low and high ionic strength (0.3 M NaCl), as well as dehydration and re-dispersing. Free swelling and settling experiments were performed in order to qualitatively compare the conditions in which SiO2-colloids affect the bulk/macro properties of bentonite. In order to study specific SiO2-colloid/montmorillonite interactions and preferred type of initial aggregation, dilute dispersions of homo-ionic montmorillonite dispersions mixed with varying concentrations of SiO2-colloids were prepared and selected samples were characterized by PCS, SEM/EDS, AFM and PXRD. The results from this study show that bentonite and montmorillonite particles can be modified by SiO2-colloids when mixed in comparable amounts, due to dehydration or high ionic strength. Some indications for increased colloidal stability for the SiO2-colloid modified clay particles were also found. From the AFM investigation it was found that initial attachment of the SiO2-colloids in Na+ dominated samples seemed to occur on the edges of the montmorillonite layers. In Ca2+ dominated samples not subjected to excess NaCl, SiO2-colloid sorption onto the faces of the montmorillonite layers was also found. In all, contact between the bentonite barrier and un-gelled Silica sol should preferably be avoided. (authors)

  9. Colloids: a review of current knowledge with a view to application to phenomena of transportation within PWR; Colloides: point de vue sur les connaissances actuelles en vue d`une application aux phenomenes de transport dans les REP

    Energy Technology Data Exchange (ETDEWEB)

    Guinard, L.

    1996-12-31

    In an attempt to minimise dosimetry within the primary circuit of PWR units, research is being carried out into understanding the phenomena of transportation and deposition of corrosion products. It is therefore desirable to known the form of these corrosion products and the laws governing this form. It is generally considered that they are in soluble or particulate form. A third starts with a general presentation of colloids and goes on to define points which are useful, both on a theoretical and experimental level, in terms of application to phenomena of transportation within PWRs. (author). 69 refs., 30 figs., 6 tabs., 3 appends.

  10. Study of cesium and strontium adsorption on slovak bentonite

    International Nuclear Information System (INIS)

    Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level radioactive waste and spent nuclear fuel. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by adsorption. Slovak Republic avails of many significant deposits of bentonite. Adsorption of Cs and Sr on five Slovak bentonite of deposits (Jelsovy potok, Kopernica, Lieskovec, Lastovce and Dolna Ves) and montmorillonite K10 (Sigma-Aldrich) has been studied with the using batch of radiometric techniques. Natural, irradiated and natrified samples, in three different kinds of grain size: 15, 45 and 250 μm have been used in the experiments. The adsorptions of Cs and Sr on bentonite under various experimental conditions, such as contact time, adsorbent and adsorbate concentrations, pH after adsorption and effect of pH change, chemical modification, competitive ions and organic agents on the adsorption have been studied. The Kd have been determined for adsorbent-Cs/Sr solution system as a function of contact time and adsorbate and adsorbent concentration. The data have been interpreted in terms of Langmuir isotherm. The adsorption of Cs and Sr has increased with increasing metal concentrations. Adsorption of Cs and Sr has been suppressed by presence of organic agents; and of bivalent cations more than univalent cations. By adsorption on natrified samples colloidal particles and pH value increase have been formed. Adsorption experiments carried out show that the most suitable materials intended for use as barriers surrounding a canister of spent nuclear fuel are bentonite of the Jelsovy potok and Kopernica deposits. (author)

  11. Evaluation of the outflow characteristic of bentonite buffer material. 2

    International Nuclear Information System (INIS)

    The outflow behaviour of bentonite buffer material was experiment to assess the physical stability in the geological disposal system, the parameters of experiment are the dry density of bentonite, mixtures ratio silica sand, fracture width, and flow velocity. The outflow phenomena were identified as extrusion and erosion, and the experimental results are as follows; 1) Extrusion: The proportional coefficient obtained from the relation between time and extrusion distance was arranged by the relation with effective clay density. The experimental equation of the proportional coefficient is as follows; A = 6.7587x10-7∼ exp(5.7261d)∼ exp((6.1598+(-0.5398d)+(-0.9272d2))∼ Pb). By model experiment, the density distribution into fracture was measured. The density distribution of an extrusion region obtained 0.8-0.2 Mgm-3. The average dry density into fracture of bentonite gel was about 0.4 Mgm-3 below. The influence of density of bentonite/sand mixtures material (30 wt%, 1.6 Mgm-3) by the extrusion phenomenon was calculated. It was assumed that the average fracture density is about eight fractures parameter. The reduction in density of the bentonite/sand mixtures material is about 4.5% (1.527 Mgm-3) of the initial value after 10,000 years. 2) Erosion: The colloid concentration and the particle size in drainage liquid were measured as parameter of flow velocity into fracture. The result of measurement, colloid concentration decreased with the increase in the flow velocity. Moreover, the particle size of colloid became large. In the case of average flow velocity 1E-5 ms-1, the colloid was generated in drainage liquid. Therefore, the flow velocity for occurrence of erosion was suggested smaller than 1E-5 ms-1. (author)

  12. Cement/bentonite interaction. Results from 16 month laboratory tests

    International Nuclear Information System (INIS)

    The work concerns possible bentonite clay mineral alteration in constructions with bentonite in close contact with cement, and the effect of such changes on bentonite buffer properties. The investigation comprises a 16 months laboratory test series with hydrothermal cell tests, percolation tests and diffusion tests. MX-80 Wyoming bentonite was used in all tests. Two types of artificial cement pore water solutions were used in the percolation and diffusion tests. The swelling pressure and the hydraulic conductivity were measured continuously in the percolation tests. After termination, the clay was analyzed with respect to changes in element distribution, mineralogy and shear strength. The water solutions were analyzed with respect to pH, cations and major anions. The results concerning chemical and mineralogical changes are in summary: Ion exchange in the montmorillonite until equilibrium with cement pore-water ions was reached; Increase in cation exchange capacity; Dissolution of original cristobalite; Increase in quartz content; Minor increase in illite content; Minor formation of chlorite; Formation of CSH(I); Wash away of CSH-gel into surrounding water. A large decrease in swelling pressure and a moderate increase in hydraulic conductivity were recorded in the samples percolated by SULFACEM pore-water solution. The mineralogical alterations only concerned a minor part of the total bentonite mass and the changes in physical properties were therefore most likely due to the replacement of the original charge balancing cation by cement pore-water cations. Comparisons between the current test result and results from 4 month tests indicate that the rates of illite and chlorite formation were reduced during the tests. The presence of zeolites in the clay could not be ensured. However, the discovery of CSH material is important since CSH is expected to precede the formation of zeolites

  13. Experimental Investigation of Near-Borehole Crack Plugging with Bentonite

    Science.gov (United States)

    Upadhyay, R. A.; Islam, M. N.; Bunger, A.

    2015-12-01

    The success of the disposal of nuclear waste in a deep borehole (DBH) is determined by the integrity of the components of the borehole plug. Bentonite clay has been proposed as a key plugging material, and its effectiveness depends upon its penetration into near-borehole cracks associated with the drilling process. Here we present research aimed at understanding and maximizing the ability of clay materials to plug near-borehole cracks. A device was constructed such that the borehole is represented by a cylindrical chamber, and a near-borehole crack is represented by a slot adjacent to the center chamber. The experiments consist of placing bentonite clay pellets into the center chamber and filling the entire cavity with distilled water so that the pellets hydrate and swell, intruding into the slot because the cell prohibits swelling in the vertical direction along the borehole. Results indicate that the bentonite clay pellets do not fully plug the slot. We propose a model where the penetration is limited by (1) the free swelling potential intrinsic to the system comprised of the bentonite pellets and the hydrating fluid and (2) resisting shear force along the walls of the slot. Narrow slots have a smaller volume for the clay to fill than wider slots, but wider slots present less resistive force to clay intrusion. These two limiting factors work against each other, leading to a non-monotonic relationship between slot width and intrusion length. Further experimental results indicate that the free swelling potential of bentonite clay pellets depends on pellet diameter, "container" geometry, and solution salinity. Smaller diameter pellets possess more relative volumetric expansion than larger diameter pellets. The relative expansion of the clay also appears to decrease with the container size, which we understand to be due to the increased resistive force provided by the container walls. Increasing the salinity of the solution leads to a dramatic decrease in the clay

  14. Modeling of the thermal transfer inside a porous environment: application to nuclear reactors in accident situation; Modelisation du transfert thermique dans un milieu poreux: application aux reacteurs nucleaires en situation accidentelle

    Energy Technology Data Exchange (ETDEWEB)

    Rubiolo, P.R

    2000-03-01

    The purpose of this report is to simulate heat exchanges occurring by conduction, by convection and by radiating in a porous medium made up of opaque particles in a semi-transparent fluid. Usually the determination of the macroscopic equations is based on homogenization techniques, but in the case of a major accident, the complexity of the problem is so overwhelming that semi-empirical methods are used to determine macroscopic coefficients. The author develops a new method to determine these coefficients, this method is based on the calculation of different tensors: the equivalent conductivity tensor, the radiative conductivity tensor, the thermal conductivity tensor and the heat exchange coefficient (h{sub sf}) between the solid phase and the fluid one. The first chapter briefly describes energy, impulse and mass balances. In the case of the energy balance the solid phase is not supposed to be in thermal equilibrium with the liquid phase. The second chapter presents an application of the porous media method to a one-dimensional and stationary problem, this application to a simple problem gives an idea of the performance of the method. The model allowing the calculation of h{sub sf} is developed, it is a wide range model. The second chapter ends with the presentation of the model allowing the computing of the effective conductivity of fuel rods. A comparison between results given by this new method and other numeric calculations or experimental data coming from benchmarks is presented in the third chapter. This chapter ends with the simulation of a reactor core in accidental situation, 2 cases are presented: with and without the presence of water steam. (A.C.)

  15. Transport of Iodide Ion in Compacted Bentonite Containing Ag2O - 12111

    International Nuclear Information System (INIS)

    Observations of the transport of iodide through compacted bentonite containing Ag2O as additive and that without additive were made. Compacted bentonite samples with densities of 1.41 g/cm3 and 1.60 g/cm3 were used in the experiment. The amount of Ag2O added to the compacted bentonite was in the range of 0.0064 ∼ 0.0468 wt/wt%. Two diffusion solutions were used: one in which iodide ion was dissolved in demineralized water (pure iodide solution), and one in which iodide ion was dissolved in 0.1 M NaCl solution (0.1 M NaCl-iodide solution). Experimental results confirmed that iodide ion was transported by the diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. The time-lag of diffusion of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the time-lag of diffusion was observed in pure iodide ion solution as well as in 0.1 M NaCl-iodide solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O was smaller than in the compacted bentonite without Ag2O. The effective diffusion coefficient decreased as the amount of Ag2O in the compacted bentonite increased. (authors)

  16. An Investigation of Diffusion of Iodide Ion in Compacted Bentonite Containing Ag2O

    International Nuclear Information System (INIS)

    In the compacted bentonite containing Ag2O, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing Ag2O as well as in the compacted bentonite without Ag2O. However, the lag-time of iodide ion in the compacted bentonite containing Ag2O is larger than that in the compacted bentonite without Ag2O. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing Ag2O has lower value than that in the compacted bentonite without Ag2O. The effect of Ag2O on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing Ag2O while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without Ag2O obtained in this study were similar to those in the compacted bentonite reported in the literature

  17. Direct torque control of an asynchronous machine: observation structures: application to multi-machine/multi-converter systems; Commande directe en couple d'une machine asynchrone: structures d'observations: application aux systemes multimachines-multiconvertisseurs

    Energy Technology Data Exchange (ETDEWEB)

    Belhadj, J.

    2001-07-15

    The aim of this work is the development of an observation structure of the direct torque control (DTC) variables of an asynchronous machine. This structure has to solve the dilemma between its robustness and a minimum calculation time. The control law obtained will be used for the control of multi-machine/multi-converter systems. The new control laws based on direct stator flux control and electromagnetic torque control are studied first, in particular the DTC and the principles of flux and torque adjustment and the associated switching logic. Then, three observation structures are developed: the full order state observer, the sliding mode observer, and the decoupled observer. A comparative study between these three structures and the classical estimator shows that the decoupled observer is an interesting structure which answers the problem of very low-speed operation. In the case of the multi-machine application, two systems are studied: the single inverter/dual-machine system and the dual-inverter/dual-machine system. The control is performed with the DTC and the vectorial control. The DTC gives interesting results for the control of multi-machine systems. In the last part, an architecture is defined for the mono- and multi-machine validation. It consists in a pseudo-experimental validation of the control law associated to the observation structure developed. This validation is performed with a mixed analog/numerical simulation. (J.S.)

  18. Macroscopic models for single-phase flows in fractured porous medium: application to well tests; Modeles macroscopiques pour les ecoulements monophasiques en milieu poreux fracture: application aux tests de puits

    Energy Technology Data Exchange (ETDEWEB)

    Landereau, P.

    2000-12-01

    We consider pressure diffusion in fractured media, with application to well test interpretation. Using the volume averaging theory of Quintard and Whitaker, the local problem is replaced by a double-porosity large scale description. The parameters of the latter may be computed solving small scale closure problems on a representative volume. Using suitable numerical methods, we have performed a systematic study of these parameters as a function of the topology of the fracture network and matrix to fracture permeability contrast. We find that the matrix permeability plays a significant role near a percolation threshold. Next, we studied the exchange coefficient parameter, by unifying the different definitions of the literature in a single framework using a Fourier analysis. Finally, we applied our technique to well-test interpretation in fractured media by comparing large scale solutions to high resolution direct simulations. We find that at short time scale, very fine grid blocks are needed to get good accuracy. In that case, a good agreement is observed between large scale averaged results and reference simulations. (author)

  19. Cryo magnetic separation adaptation to environment technologies: application to industrial effluents; Adaptation de la separation cryomagnetique aux technologies de l`environnement: application a l`epuration d`effluents liquides industriels

    Energy Technology Data Exchange (ETDEWEB)

    Bureau, V.

    1993-12-20

    Cryomagnetic separation adaptation to environment technologies application to industrial liquid effluents. The performance, obtained by superconducting high filed - high gradient magnetic separation, permitted to foresee the magnetic treatment of heavy metals in rinse waters, derived from the surface finishing industry. The paramagnetic ions, precipitated in basic media as hydroxides, present a very hydrated amorphous structure, which masks their subjacent magnetic properties. Coprecipitation of a `magnetic carrier`, jointly with the heavy metals, has been studied: ferric chloride forms in basic media, an hydrated iron oxide. Its structure is of the goethite type, and it stabilizes as hematite. The magnetic susceptibility of the obtained product is still weak and its crystalline structure is not enough affirmative to utilize magnetic filtration with efficiency. Mixture of ferrous sulphate and ferric chloride forms, in a basic media, an hydrated magnetite. Initial ideal ratio between divalent iron and trivalent iron, varies between 0,5 and 1,2. This mixture, coprecipitated with the heavy metals, permits to optimize the magnetic cleaning of the fluids in a high field - high gradient filter. (author)

  20. Coupled thermo-hydro-chemical models of swelling bentonites

    Science.gov (United States)

    Samper, Javier; Mon, Alba; Zheng, Liange; Montenegro, Luis; Naves, Acacia; Pisani, Bruno

    2014-05-01

    The disposal of radioactive waste in deep geological repositories is based on the multibarrier concept of retention of the waste by a combination of engineered and geological barriers. The engineered barrier system (EBS) includes the solid conditioned waste-form, the waste container, the buffer made of materials such as clay, grout or crushed rock that separate the waste package from the host rock and the tunnel linings and supports. The geological barrier supports the engineered system and provides stability over the long term during which time radioactive decay reduces the levels of radioactivity. The strong interplays among thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration, thermal and solute transport stages of the engineered barrier system (EBS) of a radioactive waste repository call for coupled THMC models for the metallic overpack, the unsaturated compacted bentonite and the concrete liner. Conceptual and numerical coupled THMC models of the EBS have been developed, which have been implemented in INVERSE-FADES-CORE. Chemical reactions are coupled to the hydrodynamic processes through chemical osmosis (C-H coupling) while bentonite swelling affects solute transport via changes in bentonite porosity changes (M-H coupling). Here we present THMC models of heating and hydration laboratory experiments performed by CIEMAT (Madrid, Spain) on compacted FEBEX bentonite and numerical models for the long-term evolution of the EBS for 1 Ma. The changes in porosity caused by swelling are more important than those produced by the chemical reactions during the early evolution of the EBS (t < 100 years). For longer times, however, the changes in porosity induced by the dissolution/precipitation reactions are more relevant due to: 1) The effect of iron mineral phases (corrosion products) released by the corrosion of the carbon steel canister; and 2) The hyper alkaline plume produced by the concrete liner. Numerical results show that

  1. Experimental indications of effects of surface deprotonation on Na-bentonite pore water chemistry in a geological repository

    International Nuclear Information System (INIS)

    Bentonite-water interaction was studied using a simple equilibrium model based on experimental measurements in order to describe bentonite porewater chemistry. Direct pH measurements for highly compacted bentonite and batch-type bentonite-water interaction experiments were performed under anaerobic conditions. In the direct pH measurements, resin particles doped with a pH indicator were sandwiched between a pair of bentonite columns immersed in a test solution. The experimental results showed that the solution compositions in equilibrium with bentonite depended on the bentonite to liquid ratio (B/L) and the initial solution composition. An equilibrium model assuming only fast equilibration processes between the bentonite minerals and the solution could be used to calculate the trends of pH and other ion concentrations with B/L. This study indicates that the surface deprotonation of smectite is a very important factor influencing the porewater chemistry in highly compacted bentonite. Copyright (2001) Material Research Society

  2. Application of the simplified J-estimation scheme Aramis to mismatching welds in CCP; Application du concept d`integrale J dans l`outil Aramis aux effets de mismatch sur des eprouvettes CCP

    Energy Technology Data Exchange (ETDEWEB)

    Eripret, C.; Franco, C.; Gilles, P.

    1995-12-31

    The J-based criteria give reasonable predictions of the failure behaviour of ductile cracked metallic structures, even if the material characterization may be sensitive to the size of the specimens. However in cracked welds, this phenomenon due to stress triaxiality effects could be enhanced. Furthermore, the application of conventional methods of toughness measurement (ESIS or ASTM standard) have evidenced a strong influence of the portion of the weld metal in the specimen. Several authors have shown the inadequacy of the simplified J-estimation methods developed for homogeneous materials. These heterogeneity effects mainly related to the mismatch ratio (ratio of weld metal yield strength upon base metal yield strength) as well as to the geometrical parameter h/W-a (weld width upon ligament size). In order to make decisive progress in this field, the Atomic Energy Commission (CEA), the PWR manufacturer FRAMATOME, and the French utility (EDF) have launched a large research program on cracked piping welds behaviour. As part of this program, a new J-estimation scheme, so called ARAMIS, has been developed to account for the influence of both materials, i.e. base metal and weld metal, on the structural resistance of cracked welds. It has been shown that, when the mismatch is high, and when the ligament size is small compared to the weld width, a classical J-based method using the softer material properties is very conservative. On the opposite the ARAMIS method provides a good estimate of J, because it predicts pretty well the shift of the cracked weld limit load, due to the presence of the weld. the influence of geometrical parameters such as crack size, weld width, or specimen length is property accounted for. (authors). 23 refs., 8 figs., 1 tab., 1 appendix.

  3. Application of neural networks to measurement methods based on radiation interactions with matter; Application des reseaux de neurones aux methodes de mesure basees sur l'interaction rayonnement matiere

    Energy Technology Data Exchange (ETDEWEB)

    Pilato, V

    1999-07-01

    The possibility of improving by neuronal techniques the preparation and interpretation of nuclear measurements was investigated. A general methodology was developed and applied to various problems in this field. Whatever the problem to be treated, to solve it comes to determine the relation which binds the inputs to the outputs. Neural networks based on supervised training, like the multilayer Perceptron, have the capability to calculate any relation between a set of input and output data. On the other hand, the training phase is often a long and delicate operation whose difficulties grow with the size of the network:it is thus interesting to reduce it by introducing knowledge a priori and/or by reducing the number of inputs in order to extract the relevant information. If the correlations between the inputs are linear, the Principal Components Analysis (PCA) and its neuronal equivalents make it possible to obtain by orthogonal projection a reduced number of input components while preserving the maximum of initial information. If the correlations are nonlinear, the Curvilinear Components Analysis (CCA) allows, by a unsupervised training, to carry out a nonlinear projection of the inputs in a space of reduced size. Besides, it is noticed that when the dimension of the input space is equal to the intrinsic dimension of the problem, this last is practically solved by CCA. We propose a general method which consists in characterizing as well as possible the problem by its inputs and then to extract and classify the information contained in those by projection in a space of reduced size. Association between the projected data and the problem outputs is then carried out by a supervised training network. Certain results having to be provided with their associated uncertainty, a statistical method based on the bootstrap algorithm is proposed. Potential applications other that those treated are considered. (author)

  4. Global dynamics of shaft lines of turbo-machineries coupled to surrounding fluids: application to the case of fluid sheets; Dynamique globale des lignes d'arbres de turbomachines couplees aux fluides environnants: application au cas des lames fluides

    Energy Technology Data Exchange (ETDEWEB)

    Lornage, D.

    2001-12-15

    Shaft lines of turbo-machineries have to stand increasing reliability, efficiency and safety requirements. A precise modeling of the rotating parts with all possible coupling has become necessary. In this context, this work aims to develop a global modeling of rotating wheel/shaft system inside a surrounding fluid in order to foresee its dynamical behaviour. The use and advantage of Eulerian, Lagrangian and mixed (arbitrary Lagrangian Eulerian - ALE) formulations is recalled first. A bibliographic synthesis of the classical techniques used in structure mechanics and of coupling techniques for rotating machines is presented. The coupling technique retained is presented. It uses fluid and structure models independently developed and validated. The structure domain is discretized by the finite-element method. The fluid domain is discretized by the finite-difference method taking into consideration the hypotheses linked with thin films. A modal base projection combined with a mesh at the fluid-structure interface allows an efficient, adaptable and evolutive coupling. Finally, the method is applied to 3 test-cases. The first two ones comprise a shaft/disc system coupled to a fluid sheet between the disc and the casing and to an hydrodynamic bearing. Both cases allow a first validation of the coupling method. The third case aims to study a structure closer to a real system made of a shaft and a wheel coupled to a fluid sheet between a flange and a casing. These three applications allow to show the trends linked with the fluid effects and the coupling between the flexible sub-parts of the structure. (J.S.)

  5. Introduction aux études historiques

    OpenAIRE

    Langlois, Charles-Victor; Seignobos, Charles; Noiriel, Gérard

    2014-01-01

    L’Introduction aux études historiques constitue le texte de référence de ce qu’on a appelé « l’école méthodique historique » française. Ce manuel cherche à définir les règles de la méthode historique afin de contribuer à asseoir la scientificité d’une discipline, l’histoire, dans le contexte de sa professionnalisation universitaire. Le texte affirme le primat des archives comme preuves et sources du récit historique, et revient sur les différentes étapes du travail sur archives, de la localis...

  6. Near infrared thermography by CCD cameras and application to first wall components of Tore Supra tokamak; Thermographie proche infrarouge par cameras CCD et application aux composants de premiere paroi du tokamak Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, F.

    1996-06-07

    In the Tokamak TORE-SUPRA, the plasma facing components absorbs and evacuate (active cooling) high power fluxes (up to 10 MW/m{sup 2}). Their thermal behavior study is essential for the success of controlled thermonuclear fusion line. The first part is devoted to the study of power deposition on the TORE-SUPRA actively cooled limiters. A model of power deposition on one of the limiters is developed. It takes into account the magnetic topology and a description of the plasma edge. The model is validated with experimental calorimetric data obtained during a series of shots. This will allow to compare the surface temperature measurements with the predicted ones. The main purpose of this thesis was to evaluate and develop a new temperature measurement system. It works in the near infrared range (890 nm) and is designed to complete the existing thermographic diagnostic of TORE-SUPRA. By using the radiation laws (for a blackbody and the plasma) and the laboratory calibration one can estimate the surface temperature of the observed object. We evaluate the performances and limits of such a device in the harsh conditions encountered in a Tokamak environment. On the one hand, in a quasi ideal situation, this analysis shows that the range of measurements is 600 deg. C to 2500 deg. C. On the other hand, when one takes into account of the plasma radiation (with an averaged central plasma density of 6.10{sup 19} m{sup -3}), we find that the minimum surface temperature rise to 900 deg. C instead of 700 deg. C. In the near future, according to the development of IR-CCD cameras working in the near infrared range up to 2 micrometers, we will be able to keep the good spatial resolution with an improved lower limit for the temperature down to 150 deg. C. The last section deals with a number of computer tools to process the images obtained from experiments on TORE-SUPRA. A pattern recognition application was developed to detect a complex plasma iso-intensity structure. 87 refs.

  7. Evaluation of permeability of compacted bentonite ground considering heterogeneity by geostatistics

    International Nuclear Information System (INIS)

    The permeability of the bentonite ground as an engineered barrier is possibly designed to the value which is lower than that determined in terms of required performance because of heterogeneous distribution of permeability in the ground, which might be considerable when the ground is created by the compaction method. The effect of heterogeneity in the ground on the permeability of the bentonite ground should be evaluated by overall permeability of the ground, whereas in practice, the effect is evaluated by the distribution of permeability in the ground. Thus, in this study, overall permeability of the bentonite ground is evaluated from the permeability of the bentonite ground is evaluated from the permeability distribution determined using the geostatistical method with the dry density data as well as permeability data of the undisturbed sample recovered from the bentonite ground. Consequently, it was proved through this study that possibility of overestimation of permeability of the bentonite ground can be reduced if the overall permeability is used. (author)

  8. Synthesis, characterization and antimicrobial activity of alkaline ion-exchanged ZnO/bentonite nanocomposites

    Institute of Scientific and Technical Information of China (English)

    Hamideh Pouraboulghasem; Mohammad Ghorbanpour; Razieh Shayegh; Samaneh Lotfiman

    2016-01-01

    Nanocomposites of zinc/bentonite clay were synthesized for use as an antibacterial material by a quick and simple alkaline ion exchange method. The synthesis of zinc doped bentonite nanocomposite was accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The complexes were characterized by XRD, SEM and DRS. XRD analyses and SEM observations confirmed the diffusion of zinc to the clay surfaces. Antibacterial activity tests againstEscherichia coli showed that bentonite did not present any antibacterial properties, but after alkaline ion exchange treatment, inhibition was noted. The highest antibacterial activity was observed with ZnO/bentonite composite alkaline ion exchange for 60 and 90 min. Interestingly, the leaching test indicated that ZnO/bentonite did not present any risk for drinking water treatment.

  9. Characteristics of thermally-enhanced bentonite grouts for geothermal heat exchanger in South Korea

    Institute of Scientific and Technical Information of China (English)

    Chulho; LEE; Kangja; LEE; Hangseok; CHOI; Hyo-Pum; CHOI

    2010-01-01

    The thermal conductivity and viscosity of bentonite grouts have been evaluated and compared each other to determine the suitability of these materials for backfilling vertical boreholes of ground heat exchangers.Seven bentonite grouts from different product sources were considered in this paper.Two additives,silica sand and graphite were added in bentonite grouts to enhance thermal performance.The bentonite grouts indicate that both the thermal conductivity and the viscosity increase with the content of silica sand and graphite.Therefore,it is recommended to select cautiously the amount of silica sand and graphite considering not only thermal conductivity but also viscosity for the optimum condition of backfilling.Finally,the effect of salinity in the pore water on the change of swelling potential of the bentonite-based grouts has been quantitatively evaluated to show the feasibility of bentonite grouts in the coastal area.

  10. Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

    International Nuclear Information System (INIS)

    Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments, the effects of alkaline cation and alkaline solution on mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite are emphasized in this paper, temperature, pH values and concentration are discussed as main affecting factors. When bentonite is exposed to alkaline cation or alkaline solution, microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals, which results in the decrease of swelling pressure. The amount of the reduction of swelling pressure depends on the concentration of alkaline solution. Temperature, polyvalent cation, salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions. Therefore, future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values. (authors)

  11. Bentonite-like material sealing to high-level radioactive wastes storage

    International Nuclear Information System (INIS)

    Among the most used materials for sealing of radioactive waste storage, bentonite shows a high number of advantages because of its plasticity, thermal and hydraulic conductivity, etc. The paper makes a review on different Spanish deposits of bentonite and their stability. Most of studies are focussed on the volcanic region at Cabo de Gata (Almeria). That area offers the most productive hydrothermal bentonite deposits in Spain

  12. Empirical Calibration for Dolomite Stoichiometry Calculation: Application on Triassic Muschelkalk- Lettenkohle Carbonates (French Jura Calibration empirique pour le calcul de la stoechiométrie de la dolomite : application aux carbonates triasiques du Muschelkalk-Lettenkohle (Jura français

    Directory of Open Access Journals (Sweden)

    Turpin M.

    2012-02-01

    Full Text Available This study concerns an approach for dolomite quantification and stoichiometry calculation by using X-ray diffractometry coupled with cell and Rietveld refinements and equipped with a newly substantial database of dolomite composition. A greater accuracy and precision are obtained for quantifying dolomite as well as other mineral phases and calculating dolomite stoichiometry compared to the classical “Lumsden line” and previous methods. The applicability of this approach is verified on dolomite reference material (Eugui and on Triassic (Upper Muschelkalk-Lettenkohle carbonates from the French Jura. The approach shown here is applicable to bulk dolostones as well as to specific dolomite cements and was combined with petrographical and isotopic analyses. Upper Muschelkalk dolomites were formed during burial dolomitization under fluids characterized by increased temperature and variable isotopic composition through burial. This is clear from their Ca content in dolomites which gradually approaches an ideal stoichiometry (from 53.16% to 51.19% through increasing dolomitization. Lettenkohle dolostones consist of near-ideal stoichiometric (51.06%Ca and well-ordered dolomites associated with anhydrite relicts. They originated through both sabkha and burial dolomitization. This contribution gives an improved method for the characterization of different dolomite types and their distinct traits in sedimentary rocks, which allows a better evaluation of their reservoir potential. Cette étude propose une approche pour la quantification de la dolomite et le calcul de sa stoechiométrie grâce à l’utilisation de la diffraction des rayons X couplée aux affinements de maille et de Rietveld et complétée par de nombreuses données issues de la littérature. Elle permet d’obtenir une meilleure justesse et précision pour la quantification de la dolomite (et des autres phases minérales ainsi que pour le calcul de sa stoechiométrie par rapport à l

  13. Sorption of Lithium on Bentonite, Kaolin and Zeolite

    OpenAIRE

    Mandy Hoyer; Nicolai-Alexeji Kummer; Broder Merkel

    2015-01-01

    Li sorption was studied on natural bentonite, kaolin and zeolite in batch experiments at variable Li and Na concentrations (0, 1.5, 15, 150, 750 mM LiCl and 0.01, 0.1, 1, 3, 5 M NaCl). The solid-to-solution ratio was 1:4 and pH ranged from 2 to 10. Maximum Li sorption was determined at 0.01 M NaCl and 750 mM LiCl concentration in solution. It was 3800 ± 380 ppm, 1300 ± 130 ppm and 3900 ± 390 ppm on bentonite, kaolin and zeolite, respectively, which is in the average to upper range typical fo...

  14. LABORATORY TESTING OF BENTONITE CLAYS FOR LANDFILL DESIGN AND CONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Biljana Kovačević Zelić

    2007-12-01

    Full Text Available Top and bottom liners are one of the key construction elements in every landfill. They are usually made as compacted clay liners (CCLs composed of several layers of compacted clay with strictly defined properties or by the use of alternative materials such as: GCL – geosynthetic clay liner, BES – bentonite enhanced soils or bentonite/polymer mixtures. Following the state of the art experiences in the world, GCLs are used in Croatian landfills for several years, as well. Depending upon the location and the obeying function, GCLs have to fulfill certain conditions. A legislated compatibility criterion has to be proven by various laboratory tests. In the paper are presented the results of direct shear and chemical compatibility tests of GCLs as well as the results of permeability measurement of kaolin clay (the paper is published in Croatian .

  15. Preparation and performance of Ecobras/bentonite biodegrading films

    International Nuclear Information System (INIS)

    Compounds based on the biodegradable polymer Ecobras and bentonite clay in its pristine, sonicated, and organically modified with a quaternary ammonium salt forms were prepared as flat films. Clays and compounds were characterized by x-ray diffraction and scanning electron microscopy. Mechanical properties of the films were determined according to pertinent ASTM standards. Reasonable properties, higher than those of the matrix, were obtained with compounds prepared with purified clays and organoclays, particularly for low clay loading. (author)

  16. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface; (ii) to compare the sorption of cesium, in two different systems, a simple one ( Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then; (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. This study is one part of a work supported by ANDRA on the retention properties of bentonite materials. (author)

  17. Soil-Bentonite Cutoff Walls: Hydraulic Conductivity and Contaminant Transport

    OpenAIRE

    Britton, Jeremy Paul

    2001-01-01

    ABSTRACT Soil-bentonite cutoff walls are commonly used to contain contaminants in the subsurface. A key property in determining the effectiveness of a cutoff wall is its hydraulic conductivity. There are important difficulties and uncertainties regarding the accuracy of commonly used methods of measuring the hydraulic conductivity of cutoff walls. When predicting contaminant transport through cutoff walls, common practice is to use the average hydraulic conductivity of the wall. ...

  18. Post examination of copper ER sensors exposed to bentonite

    International Nuclear Information System (INIS)

    Highlights: • Copper sensors were used for monitoring corrosion in bentonite during 4.2-y exposure. • Corrosion rates were estimated by applying three different methods. • Average corrosion rates for copper in bentonite are several µm/year. - Abstract: Copper corrosion in saline solutions under oxic conditions is one of concerns for the early periods of disposal of spent nuclear fuel in deep geological repositories. The main aim of the study was to investigate the corrosion behaviour of copper during this oxic period. The corrosion rate of pure copper was measured by means of thin electrical resistance (ER) sensors that were placed in a test package containing an oxic bentonite/saline groundwater environment at room temperature for a period of four years. Additionally, the corrosion rate was monitored by electrochemical impedance spectroscopy (EIS) measurements that were performed on the same ER sensors. By the end of the exposure period the corrosion rate, as estimated by both methods, had dropped to approximately 1.0 μm/year. The corrosion rate was also estimated by the examination of metallographic cross sections. The post examination tests which were used to determine the type and extent of corrosion products included different spectroscopic techniques (XRD and Raman analysis). It was confirmed that the corrosion rate obtained by means of physical (ER) and electrochemical techniques (EIS) was consistent with that estimated from the metallographic cross section analysis. The corrosion products consisted of cuprous oxide and paratacamite, which was very abundant. From the types of attack it can be concluded that the investigated samples of copper in bentonite underwent uneven general corrosion

  19. Sorption of Lithium on Bentonite, Kaolin and Zeolite

    Directory of Open Access Journals (Sweden)

    Mandy Hoyer

    2015-04-01

    Full Text Available Li sorption was studied on natural bentonite, kaolin and zeolite in batch experiments at variable Li and Na concentrations (0, 1.5, 15, 150, 750 mM LiCl and 0.01, 0.1, 1, 3, 5 M NaCl. The solid-to-solution ratio was 1:4 and pH ranged from 2 to 10. Maximum Li sorption was determined at 0.01 M NaCl and 750 mM LiCl concentration in solution. It was 3800 ± 380 ppm, 1300 ± 130 ppm and 3900 ± 390 ppm on bentonite, kaolin and zeolite, respectively, which is in the average to upper range typical for clay minerals. Under these conditions, kaolin was saturated with Li, whereas Li in bentonite and zeolite occupied only about 55%–79% and 9%–26% of the typical cation exchange capacity (CEC of smectites and zeolites, respectively. This is explained by differences in the way Li is bound in the materials studied. Li sorption on bentonite was independent of pH due to strong pH buffering. Above pH 5, kaolin was transformed to gibbsite, which completely changed its Li sorption capabilities. Extremely low as well as extremely high pH destabilized the crystal lattice of zeolite. All in all it was shown that, under the studied conditions, Li sorption on the studied materials occurs in detectable quantities. So, clay minerals and zeolites can act as a sink for Li if Li concentrations in solution are sufficiently high.

  20. Bentonite-cement interaction. Preliminary results from model calculations

    International Nuclear Information System (INIS)

    The interaction between the bentonite buffer and alkaline plume from degrading cementitious material used in the construction and operation of the repository is envisaged to constitute a risk to the long-term chemical stability of bentonite. In this report, first model calculations to shed light on the possible extent of mineralogical alteration of bentonite due to the plume have been carried out. A common feature of the model outcome for every case is the clogging of the pore space at the interface between the buffer and the rock fracture carrying the plume. Depending on the pH considered in the calculations for the plume (12.17, 11.60 and 9.70), this clogging will occur after 10, 18 and 5,900 years after the onset on interaction, respectively. For each case, the heavily altered zone in bentonite is confined very close to the interface. There are uncertainties related to the present calculations, the greatest ones pertaining to the poor knowledge of mineral dissolution/precipitation kinetics and to constraining the set of secondary minerals possible to form. The effects of the latter were clearly illustrated in two model cases (pH 11.60 and 9.70), where initially supersaturated secondary mineral phases were omitted; the pore clogging did not take place at the fracture-buffer interface and the buffer was continuously exposed to the alkaline plume. According to the present model calculations, it seems that the evolution of the interfacial porosity in the model system with pH 12.17 is not very sensitive to the selection of the secondary minerals as the pore space was clogged regardless. (orig.)

  1. Post examination of copper ER sensors exposed to bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Kosec, Tadeja, E-mail: tadeja.kosec@zag.si [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia); Kranjc, Andrej [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia); Rosborg, Bo [Royal Institute of Technology, Div. Surface and Corrosion Science, Drottning Kristinas väg 51, SE-100 44 Stockholm (Sweden); Legat, Andraž [Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana (Slovenia)

    2015-04-15

    Highlights: • Copper sensors were used for monitoring corrosion in bentonite during 4.2-y exposure. • Corrosion rates were estimated by applying three different methods. • Average corrosion rates for copper in bentonite are several µm/year. - Abstract: Copper corrosion in saline solutions under oxic conditions is one of concerns for the early periods of disposal of spent nuclear fuel in deep geological repositories. The main aim of the study was to investigate the corrosion behaviour of copper during this oxic period. The corrosion rate of pure copper was measured by means of thin electrical resistance (ER) sensors that were placed in a test package containing an oxic bentonite/saline groundwater environment at room temperature for a period of four years. Additionally, the corrosion rate was monitored by electrochemical impedance spectroscopy (EIS) measurements that were performed on the same ER sensors. By the end of the exposure period the corrosion rate, as estimated by both methods, had dropped to approximately 1.0 μm/year. The corrosion rate was also estimated by the examination of metallographic cross sections. The post examination tests which were used to determine the type and extent of corrosion products included different spectroscopic techniques (XRD and Raman analysis). It was confirmed that the corrosion rate obtained by means of physical (ER) and electrochemical techniques (EIS) was consistent with that estimated from the metallographic cross section analysis. The corrosion products consisted of cuprous oxide and paratacamite, which was very abundant. From the types of attack it can be concluded that the investigated samples of copper in bentonite underwent uneven general corrosion.

  2. Diffusion and sorption properties of radionuclides in compacted bentonite

    International Nuclear Information System (INIS)

    In this report, recent studies on sorption and diffusion of radionuclides in compacted bentonite have been reviewed. The sorption distribution coefficient and diffusion coefficient data obtained from experiments in the literature have been compiled. Based on these experimental data and the report SKB-TR--91-16 (Brandberg and Skagius, 1991), this report proposes a set of sorption distribution coefficient and diffusion coefficient values for modelling purpose for safety analysis of nuclear waste repositories. The variability and uncertainty of the diffusivity data span somewhat more than an order or magnitude up and down. Most of the nuclides have an effective diffusivity in around 10-10 m2/s. Ion exclusion effects are observed for C, Cl and for Tc in oxidizing waters. Effective diffusivities are nearly tow orders of magnitude lower for these elements and of the order of 10-12 m2/s. Surface diffusion effects are found for Cs, Ni, Pa, Pb, Ra, Sn, Sr and Zr. Effective diffusivities for these elements are of the order of 10-8 m2/s. The surface diffusion effect should decrease in saline waters which is seen for Cs and Sr where there are data available. It is also deemed that Ra will have this effect because of its similarity with Sr. The other nuclides should also show this decrease but no data is available. Sorption and diffusion mechanisms in compacted bentonite are discussed in the report. In highly compacted bentonite, sorption and hence its distribution coefficient is not well defined, and a pore diffusion coefficient or a surface diffusion coefficient is not well defined either. Therefore, an apparent diffusion coefficient and a total concentration gradient should be more relevant in describing the diffusion process in compacted bentonite

  3. Production of smectite organophylic clays from three commercial sodium bentonite

    International Nuclear Information System (INIS)

    Laboratory cationic exchange procedures using Brazilian's commercial quaternary ammonium salt and three samples of commercial sodium bentonites (two Brazilian's and one from Wyoming (US) are described. Swelling values in some liquid organic media are shown for the organophilic clays and for a Brazilian's commercial organophilic clay. Organophilic clays with larger swelling values than the commercial organophilic clay in kerosene, Varsol, toluene and soya bean oil were obtained. (author)

  4. The sorption of aniline on organically modified bentonites

    Czech Academy of Sciences Publication Activity Database

    Plevová, Eva; Vaculíková, Lenka; Vítámvásová, E.; Valovičová, Věra

    Ostrava: VŠB TUO, 2015. s. 47-47. ISBN 978-80-248-3745-1. [Nanomaterials and Nanotechnology Meeting, Nano Ostrava 2015 /4./. 18.05.2015-21.05.2015, Ostrava] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : bentonites * alkylammonium cations * sorption * aniline Subject RIV: JI - Composite Materials

  5. Characteristics study of bentonite as candidate of buffer materials for radioactive waste disposal system

    International Nuclear Information System (INIS)

    Literature studies on bentonite characteristic of, as candidate for radioactive waste disposal system, have been conducted. Several information have been obtained from references, which would be contributed on performance assessment of engineered barrier. The functions bentonite includes the buffering of chemical and physical behavior, i.e. swelling property, self sealing, hydraulic conductivities and gas permeability. This paper also presented long-term stability of bentonite in natural condition related to the illitisazation, which could change its buffering capacities. These information, showed that bentonite was satisfied to be used for candidate of buffer materials in radioactive waste disposal system. (author)

  6. Compression characteristics and permeability of saturated Gaomiaozi ca-bentonite

    International Nuclear Information System (INIS)

    The compression characteristics and permeability of compacted Gaomiaozi Ca-bentonite saturated by the water uptake tests are studied by conducting a series of one-dimension compression tests. The permeability coefficient can be calculated by the Terzaghi's one-dimensional consolidation theory after the consolidation coefficient is obtained by the square root of time method. It is found that the compression curves of compacted specimens saturated by the water uptake tests tend to be consistent in the relatively high stress range. The compression indexes show a linear decrease with increasing dry density and the swelling index is a constant. The permeability coefficient decreases with increasing compression stress, and they show the linear relationship in double logarithmic coordinates. Meanwhile, the permeability coefficient shows a linear decrease with decreasing void ratio, which has no relationship with initial states, stress states and stress paths. The permeability coefficient k of GMZ Ca-bentonite at dry density Pd of 1.75 g/cm3 can be calculated as 2.0 × 10-11 cm/s by the linear relationship between Pd and log k. It is closed to the permeability coefficient of GMZ Ca-bentonite with the same dry density published in literature, which testifies that the method calculating the permeability coefficient is feasible from the consolidation coefficient obtained by the consolidation test. (authors)

  7. Ageing effects on swelling behaviour of compacted GMZ01 bentonite

    International Nuclear Information System (INIS)

    Highlights: • Ageing effects on compacted GMZ01 bentonite are investigated. • Swelling property decreases with ageing and influenced by initial conditions. • Ageing effects are mainly attributed to the bonding effects and the hydration of smectites. - Abstract: Ageing effects on the swelling properties of compacted GMZ01 bentonite are investigated in this paper. Samples were compacted to prescribed dry densities and water contents and kept for ageing under constant volume and K0 confined conditions for target days of 0, 1, 7, 15, 30 and 90. Then, swelling deformation and swelling pressure tests were performed on the aged samples. Results indicate that both the swelling deformation and swelling pressure decrease with ageing time, with a more significant decrease at the first few days of ageing. Ageing effects are more pronounced for samples with large dry density and high water content. At the same initial dry density and water content, samples aged under constant volume conditions show much smaller decrease of swelling pressure compared to that of samples aged under K0 confined conditions. The decrease of swelling potential of samples with ageing days is mainly attributed to the bonding effects and the internal redistribution of water within the bentonite, which was confirmed by the changes of microstructure of samples with ageing

  8. Phenol determination on HDTMA-bentonite-based electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mojovic, Z., E-mail: zoricam@nanosys.ihtm.bg.ac.rs [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia); Jovic-Jovicic, N.; Milutinovic-Nikolic, A.; Bankovic, P.; Rabi-Stankovic, A. Abu; Jovanovic, D. [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoseva 12, 11000 Belgrade (Serbia)

    2011-10-30

    Highlights: {yields} HDTMA-modified bentonites were tested as electrode materials in the electro-oxidation of phenol. {yields} The influences of the surfactant loading and pH of the supporting electrolyte were investigated. {yields} Rapid deactivation of electrodes occurred in an acidic environment. {yields} Good stability of the investigated electrodes was obtained in alkaline medium. {yields} The sensitivity toward phenol and stability of the electrodes was markedly improved with increasing HDTMA loading. - Abstract: The partial and complete substitution of cations in the interlayer region of clay with different amounts of hexadecyl trimethylammonium bromide (HDTMABr) was performed. The aim was to synthesize organo-bentonites to be used as constituents of porous electrodes for the electrooxidation of phenol. Domestic clay from Bogovina was subjected to a common procedure of the production of organo-bentonites. It included the following steps: grinding, sieving, Na-exchange, cation exchange and drying. The samples were characterized by X-ray diffraction (XRD) analysis, while the textural properties were evaluated by nitrogen physisorption. The multisweep cyclic voltammetry was applied to analyze the behavior of the clay modified glassy carbon electrode. The influences of the surfactant loading and pH of the support electrolyte were investigated. Rapid deactivation of electrodes occurred in an acidic environment, while good stability of the investigated electrodes was obtained in alkaline medium.

  9. Study on model for bentonite buffer intrusion. 2

    International Nuclear Information System (INIS)

    Modelling study on the extrusion phenomenon of the bentonite in a geological repository for the high-level radioactive is performed to enhance the reliability of latest model studied on fiscal year 2003 (H14), on the matter of density distribution of extruded bentonite gel. In this study, the model is reconsidered and revised based on the result of comparison between experimental and calculated results. The numerical analyses for BENTFLOW type experiments and model experiments on extrusion in a pipe are performed using the revised model. The analyses for the BENTFLOW about distribution of extrusion density reproduce the experimental results tolerably. The agreement between the calculated and experimental results of the model experiments are not good. Our model is originated in solid diffusion model of swelling clay proposed by Nakano et al. To enhance the reliability of our model, the latest model is reviewed by experts. At last, the numerical analyses for H12 type repository are performed by revised model to evaluate the long-term reduction of bentonite density for the extrusion phenomenon. The analytical results are compared with the results described in H12 report. (author)

  10. Study on model for bentonite buffer intrusion phenomenon

    International Nuclear Information System (INIS)

    Modelling study on the extrusion phenomenon in a geological repository for the high-level radioactive is performed to enhance the reliability of existing model described in H12 report. Main conclusions of this study are as follows: (1) The methods and physical interpretation of bentonite gel viscosity measurements are clarified and input data of the viscosity for the solid diffusivity are obtained. (2) The input data of the swelling pressure and hydraulic conductivity of bentonite in the low- density region necessary for the solid diffusivity are determined. (3) The consolidation-type model proposed by Ahn et al. is surveyed and compared with that used in this study. The consolidation-type model is thought to be equivalent to the solid diffusion model used in this study. (4) The numerical analyses for BENTFLOW experiments and model experiments on extrusion in a pipe are performed. The analyses for the BENTFLOW reproduce the experimental results better than the past studies. The agreement between the calculated and experimental results of the model experiments is not good. Thus further study is required for the evaluation of density distribution in extruding bentonite gel. (author)

  11. The sealing performance of bentonite/crushed basalt borehole plugs

    International Nuclear Information System (INIS)

    Mixtures of crushed rock and bentonite are considered for backfilling and sealing high-level nuclear waste repositories. Many variables affect the hydraulic conductivity of such mixtures, including the size and shape of the rock particles, method of mixing and emplacement, water content and density of the clay, and the weight ratio of rock to clay. Mixtures of crushed basalt and bentonite have been tested in two types of permeameters, 20 cm diameter stainless steel permeameters and 10 cm diameter PVC permeameters. Plugs were installed as a single lift or in many lifts; the water content of the clay ranged from air-dry to as high as 200%. Preliminary results show that a mixture of 75% crushed basalt and 25% bentonite has a hydraulic conductivity between 1 x 10-9 cm/s and 2.5 x 10-8 cm/s. In some cases, preferential flow paths have developed (possibly as a result of the montmorillonite washing out of the crushed rock matrix), giving hydraulic conductivities as high as 1 x 10-4 cm/s. Other ratios of rock to clay have similar bimodal results. The probability of failure is decreased by including a higher percentage of clay in the plug, crushing the rock finer, and evenly mixing the crushed rock and clay. 136 refs., 50 figs., 7 tabs

  12. Transient nuclide release through the bentonite barrier -SKB 91

    International Nuclear Information System (INIS)

    A study of near-field radionuclide migration is presented. The study has been performed in the context of the SKB91 study which is a comprehensive performance assessment of disposal of spent fuel. The objective of the present study has been to enable the assessment of which nuclides can be screened out because they decay to insignificant levels already in the near-field of the repository. A numerical model has been used which describes the transient transport of radionuclides through a small hole in a HLW canister imbedded in bentonite clay into a fracture in the rock outside the bentonite. Calculations for more than twenty nuclides, nuclides with both high and low solubility have been made. The effect of sorption in the bentonite backfill is included. The size of the penetration hole was assumed to be constant up to time when the calculations were terminated, 500000 year after the deposition. The mass transport rate is controlled by diffusion. The model is three dimensional. The report describes the geometry of the modelled system, the assumptions concerning the transport resistances at the boundary conditions, the handling of the source term and obtained release curves. (au)

  13. Bentonite as a colloid source in groundwaters at Olkiluoto

    Energy Technology Data Exchange (ETDEWEB)

    Vuorinen, U. [VTT Processes, Espoo (Finland); Hirvonen, H.

    2005-02-15

    In this work bentonite was studied as a potential source of colloids in Olkiluoto groundwaters. Samples were collected at two groundwater stations, PVA1 at 37.5 m dept and PVA3 at 95.6 m depth, in the VLJ-tunnel. The deeper groundwater at PVA3 was more saline (2.6g/L of Cl-) than the shallow at PVA1 (0.8g/L of Cl-). A bentonite source had been assembled at each groundwater station so that two sample lines were available for water samples; one for collecting a sample before and the other for collecting a sample after interaction with bentonite. Before starting the actual colloid sampling groundwaters from both sample lines at both stations were analysed. Only minor alterations, mostly within the uncertainty limits of the analysis methods, were brought about in the water chemistries after interaction with the bentonite sources. The only clear changes were seen in the concentration of iron which decreased after interaction with bentonite in the groundwaters at both stations. After groundwater sampling the actual colloid sampling was performed. The water samples were collected and treated inside a movable nitrogen filled glove-box. The samples could be collected from each sampling line directly in the glove-box via two quick-couplings that had been assembled on the front face of the box. The sample lines had been assembled with 0.45 {mu}m filters before entering the glove-box, because only colloids smaller than 0.45 {mu}m were of interest, as they are not prone to sedimentation in slow groundwater flows and therefore could act as potential radionuclide carriers. Colloid samples were collected and treated similarly from both sampling lines at both groundwater stations. For estimating the colloid content the groundwater samples were filtered with centrifugal ultrafiltration tubes of different cut-off values (0.3 {mu}m, 300kD and 10kD). The ultrafiltrations produced the colloid-containing concentrate fractions and the soluble substances-containing filtrate fractions. In

  14. Preparation and thermal properties of chitosan/bentonite composite beads

    Directory of Open Access Journals (Sweden)

    Teofilović Vesna

    2014-01-01

    Full Text Available Due to their biodegradable and nontoxic nature, biopolymer composites are often used as remarkable adsorbents in treatment of wastewater. In this study chitosan/bentonite composite beads were obtained by addition of clay into the polymer using solution process. Before the composite preparation, bentonite was modified with surfactant cetyltrimethyl ammonium bromide (CTAB. The morphology of beads was examined by scanning electron microscopy (SEM. Thermal properties of the composite beads were studied by simultaneous thermogravimetry coupled with differential scanning calorimetry (SDT and differential scanning calorimetry (DSC. TG results showed that the complex decomposition mechanism of the composites depends on the preparation procedure. It was observed that the concentration of NaOH used for composites precipitation affects the final structure of beads. The influence of preparation procedure on the glass transition temperature Tg of chitosan/bentonite samples was not found (Tg values for all samples were about 144 °C. [Projekat Ministarstva nauke Republike Srbije, br. III45022 and ON172014 and Provincial Secretariat of Vojvodina for Science and Technological Development 114-451-2396/2011-01.

  15. Diffusion of radionuclides in concrete/bentonite systems

    International Nuclear Information System (INIS)

    In a repository for nuclear waste, different construction materials will be used. Two important materials among these are concrete and bentonite clay. These will act as mechanical barriers, preventing convective water flow and also retard transport due to diffusion of dissolved radionuclides by a combination of mechanical constraints and chemical interactions with the solid. An important issue is the possible change of the initial sodium bentonite into the calcium form due to ion exchange with calcium from the cement. The initial leaching of the concrete has been studied using radioactive spiked concrete in contact with compacted bentonite. The diffusion of Cs, Am and Pu into 5 different types of concrete in contact with porewater have been measured. The measured diffusivity for Cs agrees reasonable well with data found in literature. For Am and Pu no movement could be measured (less than 0.2 mm) even though the contact times were extremely long (2.5 y and 5 y, respectively). This report gives also a summary of the previously published results about sorption and diffusion of radionuclides in cement performed in Prav/KBS/SKB projects 1980-1990. 25 refs

  16. Modelling Ni diffusion in bentonite using different sorption models

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. An important component of the multi barrier disposal concept for a radioactive waste repository is the bentonite backfill surrounding the canisters containing vitrified high-level waste and spent fuel located in the tunnels deep within the chosen host rock. The effectiveness of the compacted bentonite barrier is such that calculations have indicated that many radionuclides have decayed to insignificant levels before having diffused through the thickness of bentonite. These calculations are performed using the simple Kd sorption concept in which the values are taken from batch type experiments performed on dispersed systems performed for a single metal at a time, usually at trace concentrations. However, in such complex systems many radionuclides, inactive metal contaminants/ground water components may be simultaneously present in the aqueous phase at a range of concentrations varying with time during the temporal evolution of the repository system. An important aspect influencing the sorption of any radioactive metal under a set of given geochemical conditions is its competition with other metals present, and how this may vary as a function of concentration. Competitive sorption effects are not currently included in safety assessments and are thus an issue which needs to be addressed. Here we provide some first estimates of the potential influence of competitive sorption effects on the migration of radioactive metals through compacted bentonite as a function of their concentration and the concentration of competing metals. Ni(II) and Fe(II) were chosen as possible competing cations since their concentration levels are expected to have values greater than trace levels and effects might be maximal and canister corrosion represents a permanent Fe source at the bentonite interface which could influence bivalent radionuclide diffusion. The modelling of the Ni(II) diffusion/sorption has been carried out using three

  17. Purification of Sardinella sp., Oil: Centrifugation and Bentonite Adsorbent

    Directory of Open Access Journals (Sweden)

    S.H. Suseno

    2014-01-01

    Full Text Available Centrifugation and purification using adsorbents is one example of a fish oil refining techniques applied to reduce impurities of fish oil. The study aimed to determine the sardine oil quality before treatment, to determine yield of fish oil after centrifugation treatment and to determine the influence of centrifugation speed and bentonite concentration on sardine oil quality. Factorial design with two factors was used in this study. Level of free fatty acid and peroxide value before purification was 35.53% and 170 mEq/kg. Yield of fish oil after centrifugation treatment has been ranged from 17.42±3.56 to 76.33±0.21%. The best treatment which could reduce the peroxide value and total oxidation was a treatment with centrifugation speed at 6500 rpm and bentonite concentration at 3%. Peroxide value and total oxidation of its treatment was 25.00±0.00 and 51.43±0.01 mEq/kg. The lowest value of p-anisidine was 1.29±0.05 mEq/kg and its value could be found in a treatment with centrifugation speed at 4500 rpm and bentonite concentration at 5%. The level of free fatty acid after purification process was ranged from 27.35 to 34.69%. Oil clarity tended to increase with the increase of centrifugation speed and adsorbent concentration.

  18. Hexacyanoferrates and bentonite as binders of radiocaesium for reindeer

    International Nuclear Information System (INIS)

    The effects of varying doses of caesium binders (Bentonite and several forms of iron-hexacyanoferrates) on radiocaesium accumulation in red blood cells and on radiocaesium transfer to urine and faeces were studied in feeding experiments with reindeer calves. The caesium binders were added to a ration of lichen (containing 9.5 kBq of 134Cs+137Cs originating from the Chernobyl accident) and fed together with a pelleted reindeer feed (RF-71) for 42 days. A 50% reduction in red blood cell radiocaesium concentration was obtained with a daily dose of 1 mg/kg body weigth of ammoniumironhexacyanoferrate (AFCF) and with 500 mg/kg of bentonite. Three mg/kg of AFCF or 2 g/kg of bentonite reduced both urinary excretion and RBC concentrations with more than 80%. It is concluded that iron-hexacyanoferrates, as a result of their high caesium binding capacity, are particularly useful as caesium binders for free ranging ruminants like the reindeer. (author)

  19. Comments regarding the bentonite barrier - SR 97 Post-closure safety

    International Nuclear Information System (INIS)

    This review only deals with the role of the bentonite for ensuring the integrity of the canister from the start and throughout the lifetime of the repository. It seems as the technical reports in question deliver convincing data and answers to most of the questions that can be raised concerning the bentonite and the interplay between the different processes at hand. However, there is one area where further analysis and discussions seem inevitable. This area is related to the thermo-hydrological behavior of the bentonite, especially during the first phase of the repository. This is discussed in some detail below. The bentonite is compacted to a high density before installation and has a degree of saturation of about 80 % when it is placed in the bedrock and around the canister. The bentonite is then expected to gradually increase its water content by uptake of water from the surrounding bedrock. Thereby, the bentonite will swell and completely fill the gap between the canister and the bentonite and between the bentonite and the bedrock as well as exert radial pressure on the canister itself. It is well known that the hydraulic conductivity and the heat conductivity of the bentonite to a large extent depend on the degree of saturation. In the reports it is obvious that the pore pressure in the surrounding bedrock is expected to be large, close to 500 kPa. This high pressure, together with the suction in the bentonite, is expected to result in a rather quick saturation of the bentonite around the canister. The same processes are expected to rather quickly saturate the backfill, consisting of a mixture of crushed bedrock and bentonite in the tunnels above the deposition holes. These processes have been analyzed by means of finite element analysis. The time required is comparatively short and the resulting temperatures in the bentonite close to the canister will be acceptable. Questions can, however, be raised regarding the boundary conditions assumed for the pressures

  20. Generation and stability of bentonite colloids at the bentonite/granite interface of a deep geological radioactive waste repository

    Science.gov (United States)

    Missana, Tiziana; Alonso, Úrsula; Turrero, Maria Jesús

    2003-03-01

    The possible mechanisms of colloid generation at the near field/far field interface of a radioactive repository have been investigated by means of novel column experiments simulating the granite/bentonite boundary, both in dynamic and in quasi-static water flow conditions. It has been shown that solid particles and colloids can be detached from the bulk and mobilised by the water flow. The higher the flow rate, the higher the concentration of particles found in the water, according to an erosion process. However, the gel formation and the intrinsic tactoid structure of the clay play an important role in the submicron particle generation even in the compacted clay and in a confined system. In fact, once a bentonite gel is formed, in the regions where the clay is contacted with water, clay colloids can be formed even in quasi-static flow conditions. The potential relevance of these colloids in radionuclide transport has been studied by evaluating their stability in different chemical environments. The coagulation kinetics of natural bentonite colloids was experimentally studied as a function of the ionic strength and pH, by means of time-resolved light scattering techniques. It has been shown that these colloids are very stable in low saline (˜1×10 -3 M) and alkaline (pH≥8) waters.

  1. Sorption and diffusion of FE(II) in bentonite

    International Nuclear Information System (INIS)

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope (55Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements. Qualitatively

  2. Sorption and diffusion of FE(II) in bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Tournassat, C.; Hadi, J. [BRGM, Orleans (France); Greneche, J.-M. [LPCE, Le Mans (France)

    2014-02-15

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ({sup 55}Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

  3. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Kaufhold, Stephan, E-mail: s.kaufhold@bgr.de [BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover (Germany); Hassel, Achim Walter [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf (Germany); Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz (Austria); Sanders, Daniel [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, D-40237 Düsseldorf (Germany); Dohrmann, Reiner [BGR, Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover (Germany); LBEG, Landesamt für Bergbau, Energie und Geologie, Stilleweg 2, D-30655 Hannover (Germany)

    2015-03-21

    Graphical abstract: Corrosion at the bentonite iron interface proceeds unaerobically with formation of an 1:1 Fe silicate mineral. A series of exposure tests with different types of bentonites showed that Na–bentonites are slightly less corrosive than Ca–bentonites and highly charges smectites are less corrosive compared to low charged ones. The formation of a patina was observed in some cases and has to be investigated further. - Highlights: • At the iron bentonite interface a 1:1 Fe layer silicate forms upon corrosion. • A series of iron–bentonite corrosion products showed slightly less corrosion for Na-rich and high-charged bentonites. • In some tests the formation of a patina was observed consisting of Fe–silicate, which has to be investigated further. - Abstract: Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na–bentonites compared to the Ca–bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe

  4. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite

    International Nuclear Information System (INIS)

    Graphical abstract: Corrosion at the bentonite iron interface proceeds unaerobically with formation of an 1:1 Fe silicate mineral. A series of exposure tests with different types of bentonites showed that Na–bentonites are slightly less corrosive than Ca–bentonites and highly charges smectites are less corrosive compared to low charged ones. The formation of a patina was observed in some cases and has to be investigated further. - Highlights: • At the iron bentonite interface a 1:1 Fe layer silicate forms upon corrosion. • A series of iron–bentonite corrosion products showed slightly less corrosion for Na-rich and high-charged bentonites. • In some tests the formation of a patina was observed consisting of Fe–silicate, which has to be investigated further. - Abstract: Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na–bentonites compared to the Ca–bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe

  5. Study of caesium sorption on Na and Ca-Mg bentonites using batch and diffusion experiments

    International Nuclear Information System (INIS)

    In most deep geological repository concepts sorption of radionuclides on bentonite represents a very important process in retarding radionuclide migration into geosphere. Despite a huge amount of studies concerning caesium sorption on bentonites, there are still some problems requiring deeper clarification. One of the most important issues is the difference between distribution coefficients (Kd) obtained using batch and diffusion experiments. The results of a comprehensive study of caesium sorption on Na bentonite (industrial sorbent Volclay KWK 20-80, Suedchemie, Germany) and Ca-Mg bentonite (raw bentonite, Rokle deposit, Czech Republic) using both of these methods suggest that the reasons of this difference can originate from different sources connected with conditions of experiments and the ways of their evaluation. The main uncertainties of caesium sorption on two different bentonites using the batch method were described and the influence on sorption has been demonstrated. Detailed mineralogical and chemical analysis of bentonite samples confirmed the differences in mineral composition and physical-chemical properties of selected bentonite types. These data are necessary for better understanding of their sorption behaviour and for sorption results evaluation. The results suggest that caesium-selective minerals present in bentonites as admixtures can govern the sorption behaviour of caesium on different bentonites at its trace concentrations. At higher concentrations, the ion exchange on non-selective sites dominates the sorption and can be well-described using sorption isotherms and ion-exchange models. It also follows from the performed experiments that the caesium sorption on studied bentonites cannot be described using the simple Kd method that is often used to evaluate distribution coefficients from diffusion experiments. The uncertainties of evaluation of sorption coefficients from diffusion experiments can also be connected with the way of diffusion

  6. A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (Phoslock(®)).

    Science.gov (United States)

    Spears, Bryan M; Mackay, Eleanor B; Yasseri, Said; Gunn, Iain D M; Waters, Kate E; Andrews, Christopher; Cole, Stephanie; De Ville, Mitzi; Kelly, Andrea; Meis, Sebastian; Moore, Alanna L; Nürnberg, Gertrud K; van Oosterhout, Frank; Pitt, Jo-Anne; Madgwick, Genevieve; Woods, Helen J; Lürling, Miquel

    2016-06-15

    Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads: 1.4-6.7 tonnes ha(-1)) in concentrations of surface water total phosphorus (TP; data available from 15 lakes), soluble reactive phosphorus (SRP; 14 lakes), and chlorophyll a (15 lakes), and in Secchi disk depths (15 lakes), aquatic macrophyte species numbers (6 lakes) and aquatic macrophyte maximum colonisation depths (4 lakes) across the treated lakes. Data availability varied across the lakes and variables, and in general monitoring was more frequent closer to the application dates. Median annual TP concentrations decreased significantly across the lakes, following the La-bentonite applications (from 0.08 mg L(-1) in the 24 months pre-application to 0.03 mg L(-1) in the 24 months post-application), particularly in autumn (0.08 mg L(-1) to 0.03 mg L(-1)) and winter (0.08 mg L(-1) to 0.02 mg L(-1)). Significant decreases in SRP concentrations over annual (0.019 mg L(-1) to 0.005 mg L(-1)), summer (0.018 mg L(-1) to 0.004 mg L(-1)), autumn (0.019 mg L(-1) to 0.005 mg L(-1)) and winter (0.033 mg L(-1) to 0.005 mg L(-1)) periods were also reported. P concentrations following La-bentonite application varied across the lakes and were correlated positively with dissolved organic carbon concentrations. Relatively weak, but significant responses were reported for summer chlorophyll a concentrations and Secchi disk depths following La-bentonite applications, the 75th percentile values decreasing from 119 μg L(-1) to 74 μg L(-1) and increasing from

  7. Physical and hydraulic characteristics of bentonite-amended soil from Area 5, Nevada Test Site

    International Nuclear Information System (INIS)

    Radioactive waste requires significant isolation from the biosphere. Shallow land burial using low-permeability covers are often used to prevent the release of impounded material. This report details the characterization of a soil mixture intended for use as the low-permeability component of a radioactive waste disposal site. The addition of 6.5 percent bentonite to the sandy soils of the site reduced the value of saturated hydraulic conductivity (Ks) by more than two orders of magnitude to 7.6 x 10-8 cm/sec. Characterization of the soil mixture included measurements of grain density, grain size distribution, compaction, porosity, dry bulk density, shear strength, desiccation shrinkage, Ks, vapor conductivity, air permeability, the characteristic water retention function, and unsaturated hydraulic conductivity by both experimental and numerical estimation methods. The ability of the soil layer to limit infiltration in a simulated application was estimated in a one-dimensional model of a landfill cover

  8. Adsorption of Bezanyl Red and Nylomine Green from aqueous solutions by natural and acid-activated bentonite

    OpenAIRE

    BENGUELLA, B.; YACOUTA-NOUR, A.

    2009-01-01

    The adsorption of two acid dyes, namely, Red Bezanyl and Green Nylomine, onto natural bentonite and acid activated bentonite from aqueous solutions were studied in a batch system. The kinetic data show that at the equilibrium, the acid-activated bentonite fixes more Bezanyl Red and Nylomine Green than the natural bentonite. Adsorption equilibrium was reached within 2 h. The results also showed that the kinetics of adsorption is best descibed by a pseudo second-order expression than a first or...

  9. Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation – interpretation of volcanic source regions

    OpenAIRE

    Tarmo Kiipli; Sigitas Radzevičius; Toivo Kallaste

    2014-01-01

    Integrated correlation of bentonites (altered volcanic ashes) and graptolite biozonation is presented. Detailed study of two Lithuanian drill core sections extended previous knowledge of the occurrence and composition of bentonites to the south. Identification of graptolite species allowed bentonites to be assigned their proper stratigraphical position. Silurian bentonites in Lithuania are mostly characterized by wide and very wide XRD 201 reflections of the main component of sanidine phenocr...

  10. Aux limites de la physique les paradoxes quantiques

    CERN Document Server

    Rothen, François

    2012-01-01

    Dans l’esprit des pères fondateurs de la science moderne, les phénomènes matériels se déroulent selon un schéma unique. La cause précède nécessairement l’effet, et la connaissance de l’effet permet de remonter à la cause. Sur la scène de la nature, le hasard n’occupe qu’une place congrue. On ne fait appel à lui que pour pallier notre ignorance. Dans les années 1920, la révolution quantique bouleverse ce cadre rigide. Elle accorde une place de choix au hasard, si malmené jusqu’alors, puis elle met en scène une constellation de phénomènes inexplicables aux yeux de la science dite classique. Après une courte introduction historique, l’auteur met ses lecteurs au contact de certains de ces phénomènes si contraires à l’intuition. Refusant l’aide du langage mathématique, il les convie à pénétrer dans un monde quantique qui déconcerte le novice avant de l’éblouir par sa nouveauté et sa cohérence. Un accent particulier est mis sur une application nouvelle de la physiqu...

  11. Cellular uptake and cytotoxic potential of respirable bentonite particles with different quartz contents and chemical modifications in human lung fibroblasts.

    Science.gov (United States)

    Geh, Stefan; Yücel, Raif; Duffin, Rodger; Albrecht, Catrin; Borm, Paul J A; Armbruster, Lorenz; Raulf-Heimsoth, Monika; Brüning, Thomas; Hoffmann, Eik; Rettenmeier, Albert W; Dopp, Elke

    2006-02-01

    Considering the biological reactivity of pure quartz in lung cells, there is a strong interest to clarify the cellular effects of respirable siliceous dusts, like bentonites. In the present study, we investigated the cellular uptake and the cytotoxic potential of bentonite particles (Øbentonite samples were tested for endotoxins with the in vitro-Pyrogen test and were found to be negative. Cellular uptake of particles by IMR90-cells was studied by transmission electron microscopy (TEM). Cytotoxicity was analyzed in IMR90-cells by determination of viable cells using flow cytometry and by measuring of the cell respiratory activity. Induced apoptotic cells were detected by AnnexinV/Propidiumiodide-staining and gel electrophoresis. Our results demonstrate that activated bentonite particles are better taken up by IMR90-cells than untreated (native) bentonite particles. Also, activated bentonite particles with a quartz content of 5-6% were more cytotoxic than untreated bentonites or bentonites with a quartz content lower than 4%. The bentonite samples induced necrotic as well as apoptotic cell death. In general, bentonites showed a high membrane-damaging potential shown as hemolytic activity in human erythrocytes. We conclude that cellular effects of bentonite particles in human lung cells are enhanced after chemical treatment of the particles. The cytotoxic potential of the different bentonites is primarily characterized by a strong lysis of the cell membrane. PMID:16059726

  12. Freezing of bentonite. Experimental studies and theoretical considerations

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2010-01-15

    During its lifetime, a KBS-3 repository will be subject to various ambient temperatures. Backfilled tunnels, shafts and investigation bore holes closest to ground level will experience periods of temperature below 0 deg C. From a safety assessment perspective, it is therefore essential to understand the behavior of compacted bentonite below 0 deg C. A theoretical framework for predicting the pressure response in compacted water saturated bentonite due to temperature changes has been developed based on thermodynamics and a single pore-type. This model predicts an approximately linear temperature dependence of swelling pressure P{sub s}(w,DELTAT) = P{sub s}(w,0 deg C) + DELTAs(w)DELTAT/nu{sub clay}(w) where DELTAT denotes a temperature difference from 0 deg C, DELTAs(w) is the difference in partial molar entropy between clay water and bulk water, nu{sub clay} (w) is the partial molar volume of the clay water and w denotes the water/solid mass ratio of the clay. As bulk water changes phase at 0 deg C, DELTAs(w) has a different value dependent on whether DELTAT is negative or positive. Above 0 deg C DELTAs(w) is a small value for all relevant densities which means that the pressure response due to temperature changes is small. A further consequence of this fact is that DELTAs(w) is a large positive number below 0 deg C when the external water phase is transformed to ice. Consequently, the model predicts a large drop of swelling pressure with temperature below 0 deg C, in the order of 1.2 MPa/deg C. Specifically, the swelling pressure is zero at a certain (negative) temperature T{sub C}. T{sub C} also quantifies the freezing point of the bentonite sample under consideration, as ice formation in the bentonite does not occur until swelling pressure is lost. A large set of laboratory tests have been performed where fully water saturated samples of bentonites have been exposed to temperatures in the range -10 deg C to +25 deg C. The swelling pressure response has been

  13. Freezing of bentonite. Experimental studies and theoretical considerations

    International Nuclear Information System (INIS)

    During its lifetime, a KBS-3 repository will be subject to various ambient temperatures. Backfilled tunnels, shafts and investigation bore holes closest to ground level will experience periods of temperature below 0 deg C. From a safety assessment perspective, it is therefore essential to understand the behavior of compacted bentonite below 0 deg C. A theoretical framework for predicting the pressure response in compacted water saturated bentonite due to temperature changes has been developed based on thermodynamics and a single pore-type. This model predicts an approximately linear temperature dependence of swelling pressure Ps(w,ΔT) = Ps(w,0 deg C) + Δs(w)*ΔT/νclay(w) where ΔT denotes a temperature difference from 0 deg C, Δs(w) is the difference in partial molar entropy between clay water and bulk water, νclay (w) is the partial molar volume of the clay water and w denotes the water/solid mass ratio of the clay. As bulk water changes phase at 0 deg C, Δs(w) has a different value dependent on whether ΔT is negative or positive. Above 0 deg C Δs(w) is a small value for all relevant densities which means that the pressure response due to temperature changes is small. A further consequence of this fact is that Δs(w) is a large positive number below 0 deg C when the external water phase is transformed to ice. Consequently, the model predicts a large drop of swelling pressure with temperature below 0 deg C, in the order of 1.2 MPa/deg C. Specifically, the swelling pressure is zero at a certain (negative) temperature TC. TC also quantifies the freezing point of the bentonite sample under consideration, as ice formation in the bentonite does not occur until swelling pressure is lost. A large set of laboratory tests have been performed where fully water saturated samples of bentonites have been exposed to temperatures in the range -10 deg C to +25 deg C. The swelling pressure response has been recorded continuously. The samples have been varied with respect to

  14. Morphology study of polyamide 6/bentonite clay nanocomposites; Estudo da morfologia de nanocompositos de poliamida 6/argila bentonitica

    Energy Technology Data Exchange (ETDEWEB)

    Paz, Rene A.; Araujo, Edcleide M.; Melo, Tomas J.A.; Leite, Amanda M.D.; Medeiros, Vanessa Nobrega, E-mail: rene@cct.ufcg.edu.br [Universidade Federal de Campina Grande- UFCG, Campina Grande, PB (Brazil); Pessan, Luiz A.; Passador, Fabio R. [Universidade Federal de Sao Carlos - UFSCar - Sao Carlos, SP (Brazil)

    2011-07-01

    Polymer/clay nanocomposites have had much attention in recent years, especially those developed with layered silicates, due to the need for engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in the crystalline structure of polymer matrices has been studied and it has been observed that it affects the behavior of crystalline and therefore the mechanical and physical properties. In this study, polyamide 6 nanocomposites were obtained by the melt intercalation technique, using regional bentonite clay modified with a quaternary ammonium salt in an amount of 3% by weight. XRD and TEM tests showed obtaining nanocomposites with exfoliated structures (author)

  15. Corrosion of high-level radioactive waste iron-canisters in contact with bentonite.

    Science.gov (United States)

    Kaufhold, Stephan; Hassel, Achim Walter; Sanders, Daniel; Dohrmann, Reiner

    2015-03-21

    Several countries favor the encapsulation of high-level radioactive waste (HLRW) in iron or steel canisters surrounded by highly compacted bentonite. In the present study the corrosion of iron in contact with different bentonites was investigated. The corrosion product was a 1:1 Fe layer silicate already described in literature (sometimes referred to as berthierine). Seven exposition test series (60 °C, 5 months) showed slightly less corrosion for the Na-bentonites compared to the Ca-bentonites. Two independent exposition tests with iron pellets and 38 different bentonites clearly proved the role of the layer charge density of the swelling clay minerals (smectites). Bentonites with high charged smectites are less corrosive than bentonites dominated by low charged ones. The type of counterion is additionally important because it determines the density of the gel and hence the solid/liquid ratio at the contact to the canister. The present study proves that the integrity of the multibarrier-system is seriously affected by the choice of the bentonite buffer encasing the metal canisters in most of the concepts. In some tests the formation of a patina was observed consisting of Fe-silicate. Up to now it is not clear why and how the patina formed. It, however, may be relevant as a corrosion inhibitor. PMID:25536393

  16. Synthesis and characterization of poly(sodium acrylate)/ bentonite superabsorbent composite

    International Nuclear Information System (INIS)

    Poly(sodium acrylate)/bentonite superabsorbent composite with water absorbency 1562 g·g−1 was synthesized by inverse suspension polymerization. The introduction of bentonite improves the water absorbency and facilitates the particle size even distribution of the composite. The network structure in the superabsorbent hydrogel is confirmed.

  17. Facile synthesis of carbon nanotube/natural bentonite composites as a stable catalyst for styrene synthesis.

    Science.gov (United States)

    Rinaldi, Ali; Zhang, Jian; Mizera, Jan; Girgsdies, Frank; Wang, Ning; Hamid, Sharifah Bee Abd; Schlögl, Robert; Su, Dang Sheng

    2008-12-28

    Natural bentonite mineral, without any wet chemical treatment, was used directly to catalyze the growth of multi-wall CNTs and the produced CNTs/bentonite as an integrated composite stably catalyzed the oxidative dehydrogenation reaction over a long period of time; this concept provides a highly economical way for large-scale synthesis of nanocarbons and manufacture of styrene synthesis catalysts. PMID:19057768

  18. Characterization of Cr/Bentonite and HZSM-5 Zeolite as Catalysts for Ethanol Conversion to Biogasoline

    Directory of Open Access Journals (Sweden)

    Robert Ronal Widjaya

    2012-04-01

    Full Text Available In this research it has been done characterization on Cr/Bentonit and Zeolit HZSM-5 catalysts for ethanol catalytic process to biogasoline (equal to gasoline. Cr/Bentonit has high acidity and resistant to a lot of moisture, so in addition to being able to processing feed which a lot of moisture (>15% from ethanol-water mixture, also it is not easy deactivated. Cr/Bentonit which is then used as the catalyst material on the process of ethanol conversion to be biogasoline and the result was compared with catalyst HZSM-5 zeolite. Several characterization methods: X-ray diffraction, Brunauer Emmett Teller (BET, thermogravimetry analysis (TGA, and catalyst activity tests using catalytic Muffler instrument and gas chromatography-mass spectrometry (GC-MS for product analysis were performed on both catalysts. From acidity measurement, it is known that acidity level of Cr/Bentonit is the highest and also from XRD result, it is known there is shift for 2theta in Cr/Bentonit, which indicates that Cr-pillar in the Bentonite can have interaction. It is also supported by BET data that shows the addition of specific surface are in Cr/Bentonite compared with natural Bentonite before pillarization. Futhermore catalyst activity test produced the results, analyzed by GC-MS, identified as butanol and also possibly formed hexanol, decane, dodecane, undecane, which are all included in gasoline range (C4 until C12.

  19. Literature study on the microstructure of bentonite and its effect on diffusion

    International Nuclear Information System (INIS)

    In the study the available information from the literature on the microstructural properties of bentonite and its main component montmorillonite have been compiled, together with different phenomena which have been found to participate in the diffusion process in bentonite. (167 refs., 36 figs., 6 tabs.)

  20. Iron and organo-bentonite for the reduction and sorption of trichloroethylene.

    Science.gov (United States)

    Cho, Hyun-Hee; Lee, Taeyoon; Hwang, Sun-Jin; Park, Jae-Woo

    2005-01-01

    Hybrid barriers using dechlorination and immobilization were studied to remove trichloroethylene (TCE) in this study. Hybrid barriers of iron filings and organo (hexadecyltrimethylammonium, HDTMA)-bentonite were simulated in columns to assess the performance of the hybrid barriers. TCE reduction rate for the mixture of zero valent iron (ZVI) and HDTMA-bentonite was approximately seven times higher than that for ZVI, suggesting the reduction of TCE was accelerated when HDTMA-bentonite was mixed with ZVI. For the column of two separate layers of iron and HDTMA-bentonite, TCE reduction rate was nearly similar to that for ZVI alone, but the partition coefficient (Kd) was 4.5 times higher than that for ZVI only. TCE was immobilized in the first layer with HDTMA-bentonite due to sorption, and then dechlorinated in the second layer with iron filings due to reduction. The HDTMA-bentonite and minimally-desorbed HDTMA from the organo-bentonite are believed to contribute the increase in TCE concentration on iron surface so that more TCE could be available for reduction. Therefore, the incorporation of HDTMA-bentonite into ZVI not only can effectively retard the transport of chlorinated organic contaminants from landfill leachate or oil shock in subsurface environment, also can expedite the reduction rate of TCE. PMID:15522338

  1. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Smellie, J. [Conterra AB (Sweden)

    2001-12-01

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  2. Bentonite barriers. New experiments and state of the art. Bentonite as barrier material for the sealing of underground disposal sites. Final report

    International Nuclear Information System (INIS)

    Bentonite is intensively investigated from many institutes for its properties and feasibility as engineering barrier material for many environmental facilities like landfill, underground landfill for chemotoxic waste and also HLW repositories. A summary of the current state of knowledge regarding the origin of bentonites and different processes through bentonite is provided together with the potential further research and development needs. Diffusion experiments with gas (CO2, H2, CH4 and SF6) and heavy metals Pb, Cd and Cs in highly saline solution (50 % and 90 % NaCl solutions, 90 % IP21 solution) at room temperature and atmosphere pressure conditions through compacted MX-80 bentonite with three different bulk dry densities (1,400 kg/m3,1,600 kg/m3 and/or 1,800 kg/m3) were performed. Numerical simulations of some experiments were undertaken.

  3. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    International Nuclear Information System (INIS)

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  4. Preparation, characterization and thermal stability of bentonite modified with bis-imidazolium salts

    Energy Technology Data Exchange (ETDEWEB)

    Makhoukhi, B., E-mail: benamarmakh@yahoo.fr [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria); Villemin, D. [Laboratoire de Chimie Moléculaire et Thio-organique, UMR CNRS 6507, INC3M, FR 3038, ENSICAEN and Université de Caen, 14050 Caen (France); Didi, M.A. [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria)

    2013-02-15

    Sodium bentonite was modified with several organic bis-imidazolium salts. Organoclays with water soluble surfactants were prepared by the traditional cation exchange reaction. The bis-imidazolium-bentonites were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (PXRD) and thermogravimetric analysis (TGA). The effect of chemical composition and molecular weight of the salts on the thermal stability and basal spacing were evaluated. The bis-imidazolium-bentonites showed enhanced thermal stability (300–400 °C) and may be potentially useful materials for melt processing of polymer/layered silicates nanocomposites. - Highlights: ► Geometry and volume of the molecule influence on interlayer spacing of modified bentonites. ► The intercalation increases with molecule length. ► The modified bentonites have an appreciably higher thermal stability.

  5. Corrosion behavior of carbon steel in wet Na-bentonite medium

    International Nuclear Information System (INIS)

    Corrosion behaviors of carbon steel in wet Na-bentonite medium were studied. Corrosion rate of carbon steel in wet bentonite was measured to be 20 μm/yr at 25 deg C using the AC impedance technique. This value is agreed with that obtained by weight loss at 40 deg C for 1 year. The effect of bicarbonate ion on the corrosion of carbon steel in wet bentonite was also evaluated. The carbon steels in wet bentonite having 0.001, 0.01, and 0.1 M concentration of bicarbonate ion gave corrosion rates of 20, 8, and 0.2 μm/yr, respectively. Corrosion potentials of specimens were also measured and compared with the AC impedance results. Both results indicated that bicarbonate ion could effectively reduce the corrosion rate of carbon steels in bentonite due to the formation of protective layer on the carbon steel. (author)

  6. Cytotoxicity and mechanical behavior of chitin-bentonite clay based polyurethane bio-nanocomposites.

    Science.gov (United States)

    Zia, Khalid Mahmood; Zuber, Mohammad; Barikani, Mehdi; Hussain, Rizwan; Jamil, Tahir; Anjum, Sohail

    2011-12-01

    Chitin based polyurethane bio-nanocomposites (PUBNC) were prepared using chitin, Delite HPS bentonite nanoclay enriched in montmorillonite (MMT), 4,4'-diphenylmethane diisocyanate (MDI) and polycaprolactone polyol CAPA 231 (3000 g/mol(-1)). The prepolymers having different concentration of Delite HPS bentonite nanoclay were extended with 2 moles of chitin. The structures of the resulted polymers were determined by FT-IR technique. The effect of nanoclay contents on mechanical properties and in vitro biocompatibility was investigated. The mechanical properties of the synthesized materials were improved with increase in the Delite HPS bentonite nanoclay contents. Optimum mechanical properties were obtained from the PU bio-nanocomposite samples having 4% Delite HPS bentonite nanoclay. The results revealed that the final PU bio-nanocomposite having 2% Delite HPS bentonite nanoclay contents is ideal contenders for surgical threads with on going investigations into their in vitro biocompatibility, non-toxicity, and mechanical properties. PMID:21945787

  7. The Bentonite Barrier: Microstructural properties and the influence of γ-radiation

    International Nuclear Information System (INIS)

    The main objectives of this work were to investigate three different topics relevant for the bentonite barrier, namely: - The microstructural properties of compacted bentonite, by i) testing the possibility of colloid transport and ii) by determining the interparticle and interlayer porosity, i.e. the free porosity in the saturated compacted bentonite by a basal spacing analysis (Paper I and II, respectively). - Potential γ-radiation-induced effects on i) montmorillonite colloid stability and changes in sol/gel properties, ii) the structural Fe(II)/Fe(III) ratio in montmorillonite and its effect on the montmorillonites reactivity towards one of the major oxidants formed upon water radiolysis, H2O2, and iii) radionuclide retention in compacted bentonite (Paper III-V, respectively). - Potential interactions of bentonite particles with Silica sol, i.e. the SiO2-colloids that are planned to be used as an injection grout during construction of the repository (Paper VI)

  8. Erosion of bentonite by flow and colloid diffusion

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Bentonite intrusion into a fracture intersecting the canister deposition hole is modelled. The model describes the expansion of the bentonite within the fracture. It accounts for the repulsive electrostatic double-layer forces, the attractive van der Waals forces and friction forces between the particles and the water. The model also takes into account the diffusion of the colloid particles in the smectite sol. The buffer contains sodium in the pore water in much higher concentrations than the approaching seeping groundwater in the fracture has. Diffusion of sodium outward in the expanding gel is accounted for as this strongly influences the double layer force and the viscosity of the gel/sol. The gel/ sol is considered to be a fluid with a varying viscosity that is strongly dependent on the bentonite volume fraction in the gel and the sodium concentration in the water. Two different geometries were modelled; a rectangular and a cylindrical showing the flow in a fracture intersecting the deposition hole with the canister. The rectangular geometry was used to gain experience with the processes and mechanisms and how they interact since the cylindrical geometry was somewhat less stable numerically and more time consuming. In the rectangular geometry a fracture 1 metre long in the flow direction was modelled. In both geometries the fracture depth (extent from the deposition hole) was selected sufficiently large to ensure that the water velocity, near this border was nearly the same as the approaching water velocity and that the smectite concentration there was vanishingly small. It was found that the velocity of the fluid drops considerably where the bentonite volume fraction is larger than 1-2%. This is due to the strong increase in viscosity with increasing bentonite volume fraction. The loss of smectite as it is carried away by the slowly flowing fluid was found to be proportional to the square root of the seeping

  9. Effects of A200 superabsorbent, bentonite and water stress on physiological traits and vitamin C of lettuce under greenhouse cultivation

    Directory of Open Access Journals (Sweden)

    2015-06-01

    Full Text Available Water stress is a global crisis and is considered a serious threat for agriculture. Superabsorbent polymers, through improving soil physical conditions, prevent moisture stress in arid and semi-arid areas. To evaluate the effects of a natural superabsorbent (bentonite and a synthetic superabsorbent (A200 on growth of lettuce, a factorial experiment in a completely randomized design with four replications was conducted. The amount of each superabsorbent at 3 levels (0, 0.15 and 0.3% w/w and 2 levels of water stress (60 and 100% of field capacity were tested. The results showed that in 100% of field capacity treatment, leaf relative water content, chlorophyll index and stomatal conductance were more than 60% of field capacity treatment. Electrolyte leakage, vitamin C, total soluble solids and chlorophyll b were higher in 60% of field capacity treatment. Application of 0.3% bentonite decreased electrolyte leakage, vitamin C and soluble solids by 74, 19 and 31 percent, respectively, and increased relative water content, chlorophyll index, stomatal conductance and total chlorophyll content by 3, 2, 22 and 8 percent, respectively, relative to the control. While, application of 0.3% of superabsorbent A200 decreased electrolyte leakage, vitamin C and soluble solids by 28, 18 and 37 percent, respectively, and increased relative water content, chlorophyll index, stomatal conductance and total chlorophyll content by 6, 32, 25 and 42 percent, respectively, as compared to the control treatment. These results indicated that bentonite can reduce the negative impacts of drought stress as much as artificial superabsorbent.

  10. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface, (ii) to compare the sorption of cesium, in two different systems, a simple one (Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. (author)

  11. Interactions between copper corrosion products and MX-80 bentonite

    International Nuclear Information System (INIS)

    The report presents results from a study of the possible interaction between copper corrosion products and MX-80 bentonite under conditions that might occur in a final repository for spent nuclear fuel in Finland. The first part of the report describes the results from a literature survey, the objective of which was to identify some relevant corrosion products that might form when copper corrodes in wet MX-80 bentonite. On the basis of the literature survey, atacamite and a green copper corrosion product produced in-house were used for experimental studies. Experiments were performed with both soft and compacted MX-80. The soft samples consisted of water-saturated MX-80 mixed with CuCl2 solutions of various concentrations. The samples were kept under anaerobic conditions at ambient room temperature or at 75 deg C for 330 days. Porewater samples were then squeezed from the samples and analysed. Compacted MX-80 samples were stored under anaerobic conditions and kept in contact with an NaCl solution. The samples were kept at room temperature and 75 deg C for 2.9 years and then analysed. The presence of either atacamite or the green copper corrosion product on the plates did not have any notable effects on the porewater chemistry. However, the Cu concentration profiles indicated that the corrosion products did dissolve, and then diffused into the surrounding bentonite. Concentration profiles were found to be roughly the same, irrespective of whether the samples had been stored at room temperature or at 75 deg C. (orig.)

  12. Influence of dry density on HTO diffusion in GMZ bentonite

    International Nuclear Information System (INIS)

    With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion coefficient (De) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient (FDP) was used for the experimental data processing and theoretical modeling. The De and ε values were (5.2-11.2) x 10-11 m2/s and 0.35-0.50 at dry density from 1,800 to 2,000 kg/m3, respectively. The De values at 1,800 kg/m3 was a little higher than that of at 2,000 kg/m3, whereas the D e value at 1,600 kg/m3 was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m3. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry density exceeding 1,300 kg/m3). 1,800 and 2,000 kg/m3 probably had similar interlayer space, whereas 1,600 kg/m3 had more. Both De and ε values decreased with increasing dry density. For compacted bentonite, the relationship of De and ε could be described by Archie's law with exponent n = 4.5 ± 1.0. (author)

  13. Performance of bentonite/crushed tuff seals for nuclear waste repositories

    International Nuclear Information System (INIS)

    Mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. To allow for overall repository performance assessments, evaluations of the sealing performance under diverse conditions are needed. American Colloid c/s granular bentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. The sealing performance of bentonite/crushed rock mixtures can be enhanced by increasing the amount of bentonite to 35%. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite takes place are deemed critical. The pressure required to generate a critical gradient probably is related to the yield stress of the bentonite in the mixture. A difference up to one or two orders of magnitude has been observed between the vertical and horizontal permeabilities. The high horizontal permeability results from the uneven bentonite distribution in the pores between the crushed rock particles due to particle segregation. Temperature seems to have no negative effects on the sealing performance within the test range from room temperature to 60. Recommendations for future research are included. 15 refs., 5 figs., 1 tab

  14. Effective diffusivities of iodine, chlorine, and carbon in bentonite buffer material

    International Nuclear Information System (INIS)

    Effective diffusivities of iodine, chlorine, and carbon in mixtures of bentonite and sand were determined by measuring the effective diffusivities of common chemical compounds labeled with radioactive isotopes of these elements. For carbon, both inorganic and organic carbon compounds were used in order to consider the variety of chemical forms of carbon possible in a radioactive waste repository. The bentonite content and dry density of the bentonite-sand mixture were varied. Two chemically different aqueous solutions, representing concrete pore water and bentonite pore water, were used to represent different conditions that could affect diffusivity in bentonite buffer material in a hypothetical radioactive waste disposal situation. The effective diffusivities of iodine, chlorine, and carbon tended to decrease with increasing bentonite content and dry density of the mixture. In the presence of simulated concrete pore water, the effective diffusivities for iodine, chlorine, and carbon in the bentonite mixtures were not higher than those obtained when simulated bentonite pore water was used. Except for some organic compounds, the measured effective diffusivities were lower than that of tritiated water under the same experimental conditions. This was attributed primarily to exclusion of anions from the bentonite pores. The effective diffusivity of carbon depended on its chemical form. The effective diffusivity of the anionic forms of organic carbon tested (carboxylic acids) was as low as that of inorganic anionic carbon. Measured effective diffusivities were compared with those calculated using a model based on electrical double layer theory. The theory was applied to calculate distributions of electrolyte ions and diffusion ions in the bentonite pores. The calculated effective diffusivities showed good agreement with the measured values

  15. Adsorption of La(III) onto GMZ bentonite. Effect of contact time, bentonite content, pH value and ionic strength

    International Nuclear Information System (INIS)

    Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (III) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g-1 under the given experimental conditions. (author)

  16. ADSORPTION STUDY OF RHODAMIN B DYE ON IRAQI BENTONITE AND MODIFIED BENTONITE BY NANOCOMPOUNDS TIO2, ZNO, AL2O3 AND SODIUM DODECYL SULFATE

    Directory of Open Access Journals (Sweden)

    Iqbal Salman AL-Jobouri

    2013-01-01

    Full Text Available The adsorption of Rhodamin B on Iraqi bentonite at the concentration range from 50 to 250 μg mL-1 was studied, Nano compounds; ZnO, TiO2, Al2O3 m and SDS in different amounts 0.01-0.1 g 10-1 g of Bentonite were used to modified the adsorption capacity of bentonite to remove the Rhodamin B from aqueous solutions. The study indicated that using 0.05 g and 0.1 of Sodium Dodecyl Sulfate (SDS lead to increase the percentage removal (%R from 79.3% for pure bentonite to 99.3%. While using 0.05 g TiO2 lead to increase the %R to 98.9%, 0.05 of ZnO to 98.6%. The other amount additives and Al2O3 using was not success to increase the %R for the Rhodamin B on bentonite surface. SEM measurement was achieved to discover the Nanoparticl exists in the bentonite surfaces.

  17. Microbial communities in bentonite formations and their interactions with uranium

    International Nuclear Information System (INIS)

    Highlights: • Microbial diversity of Spanish bentonites was studied. • High number of aerobe and facultative anaerobe microbes were isolated from bentonites. • Natural bentonite microbes are able to tolerate high U concentrations. • U is immobilized by the cells of the strain Rhodotorula mucilaginosa BII-R8 as U(VI) phosphates. - Abstract: A reliable performance assessment of deep geological disposal of nuclear waste depends on better knowledge of radionuclide interactions with natural microbes of geological formations (granitic rock, clay, salts) used to host these disposal systems. In Spain, clay deposits from Cabo de Gata region, Almeria, are investigated for this purpose. The present work characterizes the culture-dependent microbial diversity of two bentonite samples (BI and BII) recovered from Spanish clay deposits. The evaluation of aerobe and facultative anaerobe microbial populations shows the presence of a high number of cultivable bacteria (e.g. Stenotrophomonas, Micrococcus, Arthrobacter, Kocuria, Sphingomonas, Bacillus, Pseudomonas, etc.) affiliated to three phyla Proteobacteria, Actinobacteria, and Firmicutes. In addition, a pigmented yeast strain BII-R8 related to Rhodotorula mucilaginosa was also recovered from these formations. The minimal inhibitory concentrations of uranium for the growth of these natural isolates were found to range from 4 to 10.0 mM. For instance, strain R. mucilaginosa BII-R8 was shown to tolerate up to 8 mM of U. Flow cytometry studies indicated that the high U tolerance of this yeast isolate is a biologically mediated process. Microscopically dense intracellular and cell wall-bound precipitates were observed by Scanning Transmission Electron Microscopy-High-Angle Annular Dark-Field (STEM-HAADF). Energy Dispersive X-ray (EDX) element-distribution maps showed the presence of U and P within these accumulates, indicating the ability of cells to precipitate U as U(VI) phosphate minerals. Fundamental understanding of the

  18. Swelling characteristics of immersed sand-bentonite mixtures

    Institute of Scientific and Technical Information of China (English)

    丰土根; 崔红斌; 孙德安; 杜冰

    2008-01-01

    A laboratory one-dimensional consolidation apparatus was employed to research the swelling stress and volume of the sand-bentonite mixture under immersed conditions. The stress-strain characteristics of mixtures under varied mixing ratios and loading statuses were analyzed. Based on the results of tests, the mechanism of mixture swelling and collapsing was further discussed. The results show that mixtures with low sand ratios are suitable as hydraulic barrier or containment barriers of general landfills, geological repository and other hydraulic infrastructure works.

  19. Problems of bentonite rebonding of synthetic system sands in turbine mixers

    Directory of Open Access Journals (Sweden)

    A. Fedoryszyn

    2008-12-01

    Full Text Available Turbine (rotor mixers are widely used in foundries for bentonite rebonding of synthetic system sands. They form basic equipment in modern sand processing plants. Their major advantage is the short time of the rebond mixing cycle.Until now, no complete theoretical description of the process of mixing in turbine mixers has been offered. Neither does it seem reasonable to try to adapt the theoretical backgrounds of the mixing process carried out in mixers of other types, for example, rooler mixers [1], to the description of operation of the turbine mixers. Truly one can risk the statement that the individual fundamental operations of mixing in rooler mixers, like kneading, grinding, mixing and thinning, are also performed in turbine mixers. Yet, even if so, in turbine mixers these processes are proceeding at a rate and intensity different than in the roller mixers. The fact should also be recalled that the theoretical backgrounds usually relate to the preparation of sand mixtures from new components, and this considerably restricts the field of application of these descriptions when referred to rebond mixing of the system sand. The fundamentals of the process of the synthetic sand rebonding with bentonite require determination and description of operations, like disaggregation, even distribution of binder and water within the entire volume of the rebonded sand batch, sand grains coating, binder activation and aeration.This study presents the scope of research on the sand rebonding process carried out in turbine mixers. The aim has been to determine the range and specific values of the designing and operating parameters to get optimum properties of the rebonded sand as well as energy input in the process.

  20. Retention of chromium by modified Al-Bentonite Retenção de cromo por Al-bentonita modificada

    OpenAIRE

    C. Volzone; L.B. Garrido

    2002-01-01

    Retention of chromium (III) from a tanning wastewater by modified Al-bentonites was studied. One bentonite from San Juan province, Argentina, was used. Al-bentonite was prepared by contact of bentonite with hydrolyzed OH-Al solutions (0.10 M in Al) for 24 hours. The modified Al-bentonites were obtained by: a) treatment with 0.5 M sodium chloride; b) with 0.5 M sodium chloride adjusted at pH 8; and c) treatment with an hexametaphosphate solution after sodium addition. Then, the samples were dr...

  1. Modification of bentonite clay and application on polypropylene nano composites

    International Nuclear Information System (INIS)

    This work consisted on the modification of Brasgel PA clay with ionic surfactant Praepagen WB and its incorporation into polypropylene. The results of infrared and DR-X was showed that the intercalation of surfactant in the clay and the incorporation of organoclay in PP matrix resulted in the formation of an intercalated structure. The impact strength of PP increased with the incorporation of organoclay. (author)

  2. SYSTEME ACRYLAMIDE/4VP/BENTONITE,PROPRIETES ET APPLICATIONS.

    OpenAIRE

    BENZEMRA, NASSIBA

    2015-01-01

    nous avons réalisé la polymérisation radicalaire de l’acrylamide en solution aqueuse dans les conditions adiabatiques ,en utilisant le persulfate d'ammonium comme initiateur .Centre technique de polymérisation nous permet d'obtenir des polymères de trais grandes masses moléculaires .les produits obtenus ont été caractérisés . l'hydrolyse basique du polyamide en solution a 60°C est étudiée .les superpolyamides hydrolysés sont caractérisés par spectroscopie Infra-Rouge a transformée de fourr...

  3. Stress/strain/time properties of highly compacted bentonite

    International Nuclear Information System (INIS)

    In this paper, a recently developed creep theory based on statistical mechanics has been used to analyze a number of experimental creep curves, the conclusion being that the creep behavior of dense MX-80 bentonite is in agreement with the physical model, and that the average bond strength is within the hydrogen bond region. The latter conclusion thus indicates that interparticle displacements leading to macroscopic creep takes place in interparticle and intraparticle water lattices. These findings were taken as a justification to apply the creep theory to a prediction of the settlement over a one million year period. It gave an estimated settlement of 1 cm at maximum, which is of no practical significance. The thixotropic and viscous properties of highly compacted bentonite present certain difficulties in the determination and evaluation of the stress/strain/time parameters that are required for ordinary elastic and elasto-plastic analyses. Still, these parameters could be sufficiently well identified to allow for a preliminary estimation of the stresses induced in the metal canisters by slight rock displacements. The analysis, suggests that a 1 cm rapid shear perpendicular to the axes of the canisters can take place without harming them. (author)

  4. Adsorption behaviour of bivalent ions onto Febex bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Missana, T.; Garcia-Gutierrez, M. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Dpt. de Impacto Ambiental de la Energia Madrid (Spain)

    2005-07-01

    The sorption and transport properties of radionuclides in the near and far field barriers of a deep geological radioactive waste repository are amongst the principal aspects to be evaluated for the performance assessment (PA) of such a kind of disposal. The study of the clayey materials is crucial because the backfill material is constituted by compacted clay in most countries design; in addition, argillaceous formations are particularly suitable as host rock formations. It is widely recognised that, to acquire predictive modelling capability, a theoretical effort is needed for a mechanistic understanding of sorption processes, as they greatly influence the transport of radionuclides in clay porous structures. In this work, an exhaustive experimental study of the Co(II), Sr (II) and Ca(II) sorption behaviour on a Spanish bentonite was carried out. The clay used for these experiments is the FEBEX bentonite, which is basically formed by smectite (93 {+-} 2%) with small percentages of quartz (2 {+-} 1 %), plagioclase (3 {+-} 1 %), cristobalite (2 {+-} 1 %) and traces of minerals such as K-feldspar and calcite. (authors)

  5. Buffer construction technique by means of granular bentonite

    International Nuclear Information System (INIS)

    Buffer construction technology using bentonite pellets as filling material is one of the promising technologies for enhancing the ease of buffer construction. In this study, a bentonite pellet filling test was conducted, using a filling system equipped with a screw conveyor system, in a full-scale simulated disposal drift. A simulated waste disposal drift configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m was constructed for the test, and two dummy overpacks were placed in the drift. The filling test was conducted in two phases. The average dry density of the buffer fill was 1.29 Mg/m3, which was close to the target value. The angle of repose was approximately 40 degrees. The test results indicate that the buffer construction technology using screw conveyor system for pellet conveyance in a waste disposal drift is a promising technology of the disposal of high level radioactive wastes. (author)

  6. Electrophysical characteristics of polyurethane/organo-bentonite nano composites

    International Nuclear Information System (INIS)

    Modification of the Egyptian Bentonite (EB) was carried out using organo-modifier namely; octadecylamine ODA. Before the modification, the cation exchange capacity (CEC) of the EB was measured, also it was purified from different impurities using HCl and distilled water. The Organo-bentonite OB was characterized using IR, XRD, and TEM. PU/ODA-B nano composites were prepared by in situ polymerization then characterized by XRD and TEM. An amount of ODA-B ranging from 0.25% up to 5% by weight was added to the polyol component of the resin before mixing with toluene diisocynate TDI. TEM showed that the nano composites achieved good dispersion in the polyurethane matrix. The mechanical, swelling and electrical properties of the nano composites were measured. The results indicate that the tensile strength of all the nano composites enhanced with the addition of OB compared with the pure PU. The crosslink density of the nano composites increases with increasing the content of OB. The Pool-Frenckel conduction mechanism predominates for all the nano composite samples and the blank one

  7. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions

    International Nuclear Information System (INIS)

    The chemical conditions of TRU waste repository were estimated as alkaline conditions effected by cementitious materials. And, some TRU wastes include soluble nitrate salt, we have to consider the repository conditions might be high ionic strength condition leaching of nitrate salt. In this study, experimental studies were carried out to evaluate hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions. The followings results were obtained for bentonite. 1) In the immersion experiments of bentonite in hyper alkaline fluids with and without nitrate, the disappearance of montmorillonite of bentonite was observed and CSH formation was found after 30 days. In hyper alkaline fluid with nitrate, minerals at θ=37 nm by XRD was identified. 2) Significant effects of hyper alkaline on hydraulic conductivity of compacted bentonite were not observed. However, hydraulic conductivities of hyper alkaline fluid with nitrate and ion exchanged bentonite increased. In hyper alkaline with nitrate, more higher hydraulic conductivities of exchanged bentonite were measured. The followings results were obtained for rock. 1) In the immersion experiments of crushed tuff in hyper alkaline fluids with and without nitrate, CSH and CASH phases were observed. 2) The hydraulic conductivity of tuff in hyper alkaline fluids decreased gradually. Finally, hyper alkaline flow in tuff stopped after 2 months and hyper alkaline flow with nitrate stopped shorter than without nitrate. In the results of analysis of tuff after experiment, we could identified secondary minerals, but we couldn't find the clogging evidence of pores in tuff by secondary minerals. (author)

  8. Research on bed layer made from bentonite for system of radioactive waste storage

    International Nuclear Information System (INIS)

    Nowadays, bentonite is widely used in many different fields such as environment, building, nanocomposite material and so on. Vietnam has huge reserve of bentonite. Montmorillonite of bentonite deposit in BinhThuan and Lam Dong ore ranges from 25 to 45 %. This project presents the results of research on the bed layer made from bentonite for system of radioactive waste storage. Our project has also researched the absorption capability of UO22+, Th4+ and heavy metals such as Pb2+ and Cd2+ on BinhThuan and Lam Dong bentonite in different conditions such as absorption time, pH of solution, concentration, amount of absorbent, etc. The swelling characteristic, the endosmosis of BinhThuan and Lam Dong bentonite have been identified. Our experiments showed that the bed layer made from BinhThuan and Lam Dong bentonite with size: (100 x 100 x 10) mm, additives Na2SiO3 is widely used for system of radioactive waste storage. (author)

  9. Project Caesium - An ion exchange model for the prediction of distribution coefficients of caesium in bentonite

    International Nuclear Information System (INIS)

    A surface chemical model is established to thermodynamically describe caesium sorption on bentonite. Caesium sorption is studied on Wyoming bentonite MX-80 in solutions of NaCl, KCl, MgCl2, CaCl2, NaNO3 and Ca(NO3)2 of concentrations varying between 0.025M and 1M, as well as in the weakly saline Allard groundwater and the strongly saline Aespoe groundwater. Based on these experiments it is shown that the sorption behaviour of caesium on bentonite can be described, within the experimental and model uncertainties, in terms of a one-site ion exchange model. The ion exchange constant for the replacement of Na+ on montmorillonite by Cs+ is logKex degrees = 1.6. The model predictions compare well with sorption data published in the open literature on both Wyoming bentonite MX-80 and other types of bentonite. For the analysis of diffusion experiments in compacted bentonite, the apparent diffusivity of tritiated water, HTO, is used as an analogue to estimate the pore diffusivity of Cs+. Since insufficient information is available at present to estimate the porosity actually available for diffusion in compacted bentonite, it is assumed that the diffusion porosity can be approximated by using the value of the bulk porosity. Under these circumstances, the cation ex change capacity (CEC) found to be available for the diffusing species in compacted bentonite corresponds to about 12% of the total CEC of bentonite. It is recognised that the errors made in the estimation of the pore diffusivity and of the diffusion porosity are contained in the reduction factor of the CEC. A discussion of the factors affecting the diffusivities of radionuclides and the problem of establishing consistent sets of diffusivity data is given in the Appendix. 33 refs, 7 figs, 12 tabs

  10. Na-smectite s in the Cala de Tomate bentonite deposit (Spain): a natural analogue of the salinity effect on the bentonite barrier of a rad waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Perez del Villar, L.; Pelayo, M.; Fernandez, A.M.; Cozar, J.S. [CIEMAT - Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT/DIRE/CEAGP), Madrid (Spain); Delgado, A.; Reyes, E. [Ciencias de la Tierra y Quimica Ambiental Estacion Experimental del Zaidin Dpt., Granada (Spain); Fernandez-Soler, J.M. [Granada Univ., Dpt. de Mineralogia y Petrologia (Spain); Tsige, M. [Facultad de Ciencias Geologicas, Dpt. de Geodinamica, Madrid (Spain)

    2005-07-01

    Within the framework of the ENRESA programme for the assessment of the long-term behaviour of the bentonite-engineered barrier for a deep radwaste geological repository, analogue studies on several bentonite deposits are conducted at CIEMAT. Among these analogue studies, the thermal effect induced by volcanic intrusions on bentonite deposits is highlighted. In the Cabo de Gata volcanic region, there are several analogue scenarios where these studies have been performed, such as the Cala de Tomate bentonite deposit that was intruded by a pyroxene andesite volcanic dome. However, geological, mineralogical, physicochemical, geochemical and stable isotopic data obtained from the smectites do not allow to establish any analogy with the thermal effect expected on the bentonite-engineered barrier of a deep geological repository after burial. Thus, the bentonitisation processes took place after the intrusion of the dome, as a result of meteoric diagenesis intensively developed on faulting zone affecting the parent pyroclastic acid tuffs. This faulting process occurred after the dome intrusion. However, the physicochemical characteristics of these smectites, specially the exchangeable cations, allow to consider this bentonite deposit as a natural analogue of the saline effect on the clayey barrier. This analogy has been established because Na-smectites are present in this deposit and, up to our present knowledge, it is the first time that these smectites occur naturally in the Cabo de Gata-La Serrata de Nijar volcanic region. As a consequence, the main objectives of this work are: i) to characterise these smectites; ii) to establish their genesis and processes affecting them after their formation and iii) to identify the effects on the bentonite-engineered barrier should it were affected by a Na-rich saline waterfront. (authors)

  11. Oxydes transparents conducteurs et convertisseurs de photons pour des applications photovoltaïques : les cas de l'oxyde de zinc et de l'oxyde de cérium dopés aux terres rares

    OpenAIRE

    Balestrieri, Matteo

    2014-01-01

    The objective of this thesis was to investigate the photon converting properties of rare earths (RE) ions embedded in transparent oxide hosts in view of potential application on silicon solar cells. In particular, the goal was to functionalize thin films that are already used in solar cells such as anti-Reflection coatings or transparent conductive oxides.Two host materials (ZnO and CeO2) have been selected, which are compatible with silicon solar cells.This work shows that RE-Doped transpare...

  12. Concrete/Febex Bentonite Interaction: Results On Short-Term Column Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Escribano, A.; Turrero, M.J.; Torres, E.; Martin, P.L. [CIEMAT, Environmental Department, Avda. Complutense, 22, 28040 Madrid (Spain)

    2008-07-01

    Interaction between the alkaline pore fluids from the concrete engineered barriers and the bentonite at the repository conditions may generate products that can diffuse through the porous structure of the bentonite affecting their properties. A comprehensive study based on series of short term experiments is being performed to provide experimental evidences on the physical, chemical and mineralogical changes during the concrete-compacted bentonite interaction. Samples were analyzed by XRD, SEM-EDS and FTIR. Measurements of swelling capacity, specific surface area and chemical analysis for cation exchange capacity and soluble salts analyses were also performed. (authors)

  13. Long-term dissolution behavior of spent fuel in compacted bentonite and synthetic granitic groundwater

    International Nuclear Information System (INIS)

    This contribution describes experimental work which aims to get the information on corrosion behaviour of Spent Fuel, and to obtain the release rate of radionuclides from the fuel within domestic bentonite and synthetic granitic ground water. Specimens of fuel with burn-up up to 39 GWd/tU, with and without bentonite, have been subjected to leaching. The effects of bentonite on the dissolution rate, and of structural materials, copper and stainless steel on caesium release have been identified and are reported. (author)

  14. The study on bentonite slurry grout with ethanol for fractured rock masses

    International Nuclear Information System (INIS)

    The purpose of this paper is to propose the grouting material and method for fractured rock masses. So experimental study is executed in order to grasp that the properties of grouting material is stable and impermeable. In this study, experiments of hydraulic test and grouting injection test are performed on bentonite slurry mixes in the laboratory. From the results of the tests, a mixer of ethanol and bentonite is found to be very suitable for a grouting material. Also, dynamic grouting method is able to inject the concentrated bentonite slurry in the fractured aperture. (author)

  15. NBR/ORGANOMODIFIED BENTONITE INTERCALATED HYBRIDS AND THEIR EFFECTS ON THE TOUGHNESS OF PVC

    Institute of Scientific and Technical Information of China (English)

    Chang-jiang You; De-min Jia; Zeng-yong Zhen; Kui Ding; Song Xi; Hai-lin Mo; Yong-hua Zhang

    2003-01-01

    Hybrids of intercalative nitrile-butadiene rubber/organomodified bentonite (NBR/OMB) were prepared by the latex intercalation technique. Investigation of their mechanical properties and the microstructure of NBR/OMB showed that the organomodified bentonite is an effective toughener for NBR. Transmission electronic microscopy (TEM) and X-ray diffraction (XRD) tests showed that the NBR macromolecule could be intercalated into the galleries of bentonite.Incorporation of NBR/OMB hybrids as tougheners into poly(vinyl chloride) (PVC) results in a substantial increase in the impact strength of PVC, but little decrease in its tensile strength and flexural strength, compared to the unmodified PVC.

  16. Concrete/Febex Bentonite Interaction: Results On Short-Term Column Experiments

    International Nuclear Information System (INIS)

    Interaction between the alkaline pore fluids from the concrete engineered barriers and the bentonite at the repository conditions may generate products that can diffuse through the porous structure of the bentonite affecting their properties. A comprehensive study based on series of short term experiments is being performed to provide experimental evidences on the physical, chemical and mineralogical changes during the concrete-compacted bentonite interaction. Samples were analyzed by XRD, SEM-EDS and FTIR. Measurements of swelling capacity, specific surface area and chemical analysis for cation exchange capacity and soluble salts analyses were also performed. (authors)

  17. Study of Interaction between Fly Ash-cement and Bentonite Matrices

    Directory of Open Access Journals (Sweden)

    Daněk Tomáš

    2015-01-01

    Full Text Available Among the important factors characterizing the quality of sealing mixtures is strength, durability, compatibility and permeability. Experimental work was therefore conducted to assess the use of cement, fly ash, gravel and bentonite in the form of artificial self-hardening sealing mixture. The results of the work show a good compatibility between the bentonite and cement during its fly ash replacement. Compactness of the structure was confirmed by studying of permeability and SEM microscopy, which in the system of ash-cement-bentonite matrix allowed assessing successive microstructure development of hydrating gel.

  18. Removal of natural uranium from water produced in the oil industry using Algerian bentonite

    International Nuclear Information System (INIS)

    Batch sorption experiments have been carried out to remove natural uranium (NORM) from water obtained together with crude oil and natural gas, using Algerian bentonites. The effect of some important factors such as S/L ratio, pH, initial concentration, particle size was evaluated and a kinetic study performed. The value of the distribution coefficient (Kd) at equilibrium for natural uranium varied from 30 to 600 cm3 x g-1 and 50 to 1100 cm3 x g-1 (∼ 10% margin error) using natural bentonite and drilling bentonite, respectively. The isotherms showed that the data are consistent with both Freundlich and Langmuir models. (author)

  19. Experimental study on self-healing of bentonite/sand mixtures in hydraulic permeability

    International Nuclear Information System (INIS)

    Effects of gas permeation on the impervious characteristics of bentonite/sand mixtures were studied experimentally by conducting permeability tests with various fluids and microscopic observations. In this test, hydraulic permeabilities were measured before/after helium gas was applied to permeate through the mixtures. It was found that gas formed preferential paths to migrate through the mixtures, and that the bentonite/sand mixtures never deteriorated in impervious capacity because the paths were-filled with swelling bentonite in re-saturation. (author)

  20. Bentonite-stabilized CDA/CTA membranes for seawater desalination. Pt. 2

    International Nuclear Information System (INIS)

    The bentonite-stabilized seawater desalination membranes developed at GKSS were characterized by two transport coefficients. Both the hydrodynamic permeability as well as the electro-mechanical coefficient were significantly changed after 2000 hours RO rest runs. Their alterations were interpreted - applying the fively-porous membrane model - as an increase of the diffusion potential and a decrease of the streaming potential. The salt diffusion coefficient was analysed to be diminished by about 10%. The lowest performance changes of the membranes with 1000 ppm bentonite dope, support the experimental findings of flux-stabilization of bentonite-containing CDA/CTA membranes, published previously. (orig.)

  1. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Sena, Clara; Salas, Joaquin; Arcos, David (Amphos 21 Consulting S.L., Barcelona (Spain))

    2010-12-15

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  2. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    International Nuclear Information System (INIS)

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  3. Application of native knowledge in EIA: Inuit, eiders and Hudson Bay oil. Les connaissances des autochtones appliquees aux etudes d'impact environnemental: Les Inuit, les eiders et le petrole de la baie d'Hudson

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, D.J.

    1990-09-01

    Environmental baseline data, essential for environmental impact assessment of petroleum development, is scarce or nonexistent for much of the Arctic. It is proposed that environmental assessment in Arctic regions can benefit substantially from Inuit environmental knowledge, in the form of a formal integration of Inuit expertise into the environmental assessment process. To assess the soundness of this proposition, environmental data from Inuit of 3 communities in southeastern Hudson Bay are examined. These data pertain to the biogeography and ecology of the Hudson Bay eider (Somateria mollissima sedentaria), a large seaduck of interest because of its extreme vulnerability to oil pollution. Information on this bird was collected by means of semi-directive interviews with Inuit hunters. This information reveals an extensive knowledge of the dramatic seasonal changes in the distribution and habitat use of the eider, and their winter mortality. The applications of this knowledge to environmental impact assessment is discussed. 16 refs., 5 figs.

  4. PREVISION QUANTITATIVE DES PRECIPITATIONS : ADAPTATION PROBABILISTE PAR RECHERCHE D'ANALOGUES.Utilisation des Réanalyses NCEP / NCAR et application aux précipitations du Sud-Est de la France

    OpenAIRE

    Bontron, Guillaume

    2004-01-01

    Ce mémoire étudie l'application du principe d'analogie à la prévision et à la simulation des précipitations. A partir de la caractérisation d'une situation météorologique cible, cette approche consiste à rechercher, dans une archive météorologique, les situations passées similaires. Les précipitations observées lors de ces situations analogues permettent ensuite de donner une estimation probabiliste des précipitations attendues pour la situation cible.Après avoir défini les critères et les sc...

  5. Magnetotransport in CeCu6-xAux

    International Nuclear Information System (INIS)

    We report on a comparative study of the low-temperature magnetoresistance ρxx(B) and Hall resistance ρxy(B) of CeCu6-xAux for 0=xx(B), and of the anomalous Hall effect and bandstructure effects of the heavy-quasiparticle bands affecting ρxy(B)

  6. A study on long term stability of bentonite. The preliminary study on the bentonite stability in the groundwater influenced by cementitious material

    International Nuclear Information System (INIS)

    In the geological disposal concept of radioactive wastes, a kind of clay with sorption ability and low permeability, called bentonite, is envisaged as an engineered barrier system in the geological repository. Also, the cementitious material is envisaged as the backfill material in the vaults and the structure material of the vaults. The groundwater in contact with the cementitious material will promote hyperalkaline conditions in the repository environment and these conditions will affect the performance of the bentonite. Therefore, it is necessary to investigate the interaction between the cementitious material and the bentonite for the evaluation of long term stability of the disposal system. In this study, for the identification and the investigation of the secondary minerals, the batch immersion experiments of the powder bentonite were carried out using synthetic cement leachates (pH=7, 12.5, 14) at 200degC. As the results, it was confirmed that Na as exchangeable cations in the bentonite can exchange relatively easily with Ca in the solution from the experiment results. And the ratio of cation exchange was estimated to be about 25% based on the amount of exchangeable cations Ca2+ between layers. Furthermore, it was concretely shown that the generation of analcime might be affected by the Na concentration from results of the solution analyses and a stability analysis of analcime using the chemical equilibrium model, in addition to the pH in the solution. (author)

  7. Monte Carlo simulations for thermodynamical properties calculations of plasmas at thermodynamical equilibrium. Applications to opacity and equation of state calculations; Apport d'un code de simulation Monte Carlo pour l'etude des proprietes thermodynamiques d'un plasma a l'equilibre et application au calcul de l'elargissement des profils de raies ioniques emises dans les plasmas denses, aux opacites spectrales et aux equations d'etat de systemes fluides

    Energy Technology Data Exchange (ETDEWEB)

    Gilles, D

    2005-07-01

    This report is devoted to illustrate the power of a Monte Carlo (MC) simulation code to study the thermodynamical properties of a plasma, composed of classical point particles at thermodynamical equilibrium. Such simulations can help us to manage successfully the challenge of taking into account 'exactly' all classical correlations between particles due to density effects, unlike analytical or semi-analytical approaches, often restricted to low dense plasmas. MC simulations results allow to cover, for laser or astrophysical applications, a wide range of thermodynamical conditions from more dense (and correlated) to less dense ones (where potentials are long ranged type). Therefore Yukawa potentials, with a Thomas-Fermi temperature- and density-dependent screening length, are used to describe the effective ion-ion potentials. In this report we present two MC codes ('PDE' and 'PUCE') and applications performed with these codes in different fields (spectroscopy, opacity, equation of state). Some examples of them are discussed and illustrated at the end of the report. (author)

  8. The effect of treating pastures with bentonite on the transfer of 137Cs from grazed herbage to sheep

    International Nuclear Information System (INIS)

    The persistence of high levels of 134Cs + 137Cs in vegetation of certain upland areas of the United Kingdom has prompted investigations into possible methods of reducing levels in sheep tissues. The introduction of the clay mineral, bentonite, into the diet of ruminants has been shown to reduce the uptake of caesium from the gut. The effects of treating pasture with bentonite at two rates (single or repeated application of 80 g m-2) on the intake and transfer of 137Cs to sheep tissues was investigated. Whilst there were reductions in the radiocaesium activity concentrations of tissues of sheep grazing pasture treated at both rates, transfer coefficients were only affected for sheep on the repeated treatment. However, ewes grazing the repeatedly treated pasture experienced a loss in body weight (18%) associated with a decrease in herbage intake (39%). Considerable variation in the herbage intake by individual ewes and lambs, both between and within treatments, showed the need for direct intake measurements in order to determine relevant transfer coefficients in field experiments. Transfer coefficients for 137Cs of 0.33 d kg-1 and 1.61 d kg-1 were obtained for muscle of control ewes and lambs respectively. (author)

  9. Patient doses in medical imaging including interventional Radiology International actions: ICRP recommendations and practices in Spain; Doses delivrees aux patients en imagerie medicale: recommandations de la CIPR et leur application en Espagne

    Energy Technology Data Exchange (ETDEWEB)

    Vano, Eliseo [Departement de radiologie, Univ. Complutense, Avenida Complutense, 28040 Madrid (Spain); Service de physique medicale, Hopital Universitaire San Carlos (Spain)

    2011-07-15

    The ICRP recommends that justification and optimization criteria be applied to medical exposures and that diagnostic reference levels (DRLs) be used in medical imaging including interventional radiology. For fluoroscopic guided interventional procedures, the relative 'complexity' of the procedure should be taken into account when establishing DRLs. The ICRP recommendations on patient dose management for different imaging modalities are summarized, especially for interventional procedures, digital radiology and computed tomography. Reference is also being made to the new publication on 'Education and Training in Radiological Protection for Diagnostic and Interventional Procedures' and the working documents on 'Radiological Protection in Paediatric Diagnostic and Interventional Radiology', 'Avoiding adverse radiation effects to doctors and patients in fluoroscopic guided procedures - practical guidelines' and 'Patient and staff Radiation Protection in Cardiology'. The second part of the paper deals with the application of the ICRP recommendations and the European Directive on Medical Exposures in medical imaging, in Spain. The requirements on RP training for medical professionals are described, including the mandatory 'second level' of training in RP for interventional radiology. The support and involvement of the medical physics experts in medical imaging are also discussed, together with the role of the Health Authority and the Nuclear Regulatory Authority. In Spain, a quality assurance program, including patient dose measurements, has been mandatory since 1999 and some hospitals have promoted pilot experiences to collect and process patient dose values in real time. As a conclusion and considering the global demand for 'safer medicine', it is suggested that the management of patient doses in imaging come first on the agenda, that automatic registration of patient doses in the X-ray systems be

  10. Nanocomposites of PP and bentonite clay modified with different surfactants

    International Nuclear Information System (INIS)

    The aim of this work was the development of nano composites of polypropylene (PP) and national bentonite clay modified with different surfactants. The results of X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) showed that the organophilization process was effective. The surfactants led to a significant increase in the basal spacing of Brasgel PA clay. XRD results of the mixture PP/Brasgel PA clay modified with Praepagem WB surfactant indicated that a nanocomposite with intercalated structure was formed. When the Brasgel PA clay was modified with Praepagem HY surfactant, DRX results indicated that a micro composite was formed. Screw speed, clay content and PP viscosity had no influence on the XRD pattern of the obtained materials. (author)

  11. Sorption behaviour of caesium on a bentonite sample

    International Nuclear Information System (INIS)

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  12. Sorption behaviour of caesium on a bentonite sample

    Energy Technology Data Exchange (ETDEWEB)

    Hurel, C. [Lab. de Chimie Analytique Bio-Inorganique et Environnement, UMR CNRS 5034, Univ. de Pau et des Pays de l' Adour, Helioparc Pau Pyrenees, Pau (France); GRECI, Univ. de Reims Champagne-Ardenne, Moulin de la Housse, Reims (France); Marmier, N.; Fromage, F. [GRECI, Univ. de Reims Champagne-Ardenne, Moulin de la Housse, Reims (France); Seby, F.; Bourg, A.C.M. [Lab. de Chimie Analytique Bio-Inorganique et Environnement, UMR CNRS 5034, Univ. de Pau et des Pays de l' Adour, Helioparc Pau Pyrenees, Pau (France); Giffaut, E. [ANDRA, Agence Nationale pour la Gestion des Dechets Radioactifs, Chatenay-Malabry (France)

    2002-07-01

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  13. Effect of freezing and thawing on compacted bentonite buffer performance

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Over the time scale of the lifecycle of the spent nuclear fuel repository at Olkiluoto, local conditions involving both permafrost and glacial climactic phases, possibly repeatedly, cannot be excluded. Permafrost typically occurs when cold and dry climate conditions prevail with no ice-sheet formation or during glaciation as sub-glacial permafrost. Permafrost is generally defined as ground (soil or rock) that remains at or below 0 deg. C for at least two consecutive years. The growth and development of permafrost to some depth of the geologic subsurface depends on a complex heat exchange process across the atmosphere/ground interface and on the geothermal heat flow. Due to the potential impact on hydraulic, mechanical, and chemical subsurface properties and conditions, permafrost penetration is of interest for the performance and safety assessment of a deep, geologic repository. Deleterious effects on porous soil material, resulting from freezing and thawing, are generally ascribed to the occurrence of ice formation. Of course exposure to permafrost does not necessarily imply the presence of ice in the affected material. Indeed the primary consequence of the confinement of water in small pores is a depression to lower temperature of the melting transition. However, when ice forms in porous material, there is a corresponding increase in volume and/or pressure depending on the particular confining stresses at hand and the permeability to water migration. If ice is not formed in the fully saturated buffer system, no increase in volume and/or pressure need be considered. If, on the other hand, ice does form, increased stress from the buffer on the canister and host rock will need to be taken into account. In order to evaluate the effect of freezing and thawing on compacted bentonite buffer performance a series of experiments were conducted using constant-volume swelling pressure cells as follows: - Pre- and post

  14. Hydrothermal stability of bentonite-based buffer materials

    International Nuclear Information System (INIS)

    The reactions expected in bentonite-based buffer materials under conditions typical of a nuclear fuel waste disposal include mineral transformations (e.g. smectite to illite; smectite to zeolite) and a range of low-temperature cementation reactions. The probable extent and significance of these reactions are reviewed, and other reactions involving proposed filler sands are also examined briefly. The effects of mineral transformations on buffer performance will be insignificant if disposal vault temperatures do not exceed 100-120 degrees C and pH remains in the range 4 to 8. At pH > 9, zeolitization and silica dissolution may occur and buffer stability cannot be assured. The effects of cementation reactions may be significant, but are difficult to predict and require further investigation

  15. Behaviour of bentonite/montmorillonite gel at low ionic strength

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. In the Swedish KBS-3 concept for a geological deep storage of spent nuclear fuel, bentonite of high montmorillonite content is proposed to serve as a buffer surrounding copper canisters containing the spent fuel. Montmorillonite has an exceptional affinity for water which results in the build-up of a swelling pressure when bentonite is placed in a confined volume. There may be fractures intersecting the deposition hole and at those fractures the bentonite is not restricted but can continue to swell until a steady state is reached. Under present day Swedish groundwater conditions the swelling into fractures will be limited because the montmorillonite at the swelling front will coagulate. However, at the end of a glaciation one cannot exclude that glacial meltwater of low ionic strength will permeate the bedrock. This could cause erosion of the bentonite, due to colloidal sol formation at the swelling front. A homo-ionic Ca-montmorillonite would not pose any problem because it has limited swelling due to attraction forces caused by ion correlations. In homo-ionic Na-montmorillonite, on the other hand, the correlation interactions are weak and cannot prevent the sol formation in case the montmorillonite is contacted with water of low ionic strength. Under repository conditions the montmorillonite is not homo-ionic, but contains a variety of counterions, both mono- and divalent. It was demonstrated earlier that for mixed Ca/Na-montmorillonite the sol-formation ability is much more sensitive to the ionic strength of the electrolyte than homo-ionic Na-montmorillonite. In deionized water sol formation occurs unless the equivalent charge fraction of Ca2+ is 90% or higher. However in electrolyte solution it was found that the sol is unstable if the ionic strength is above 4 mM. The investigated cases indicate that this condition holds even if the charge fraction of Ca2+ in the interlayer is as low as 20%. In this work it is

  16. Characterization of Unye bentonite after treatment with sulfuric acid

    Directory of Open Access Journals (Sweden)

    Bulent Caglar

    2013-01-01

    Full Text Available Unye bentonite was found to consist predominantly of a dioctahedral smectite along with quartz, tridymite, cristobalite, and minor fractions of feldspar and anatase. A considerable amount of Al was retained as a constituent in acid-resistant impurities following the decomposition of the montmorillonite via acid treatment at an acid/clay ratio of 0.4. These impurities were mesoporous with a maximum surface area of 303.9±0.4 m² g-1. A sharp decrease in the d001 lattice spacing of the montmorillonite to 15.33 Å reflected the reduction of the crystallinity in the activated products. In addition, the increase in the ease with which newly formed hydroxyl groups were lost paralleled the severity of the acid treatment.

  17. Preparation and characterization of bentonite clay for formation of nanocomposites

    International Nuclear Information System (INIS)

    This study we used the linear medium density polyethylene (PELMD) as polymer matrix and introduced, as reinforcement to increase the mechanical and thermal properties, the green bentonite deposit of Boa Vista/PB, rich montmorillonite (MMT), previously characterized by XRD, that passed by three stages of purification. The first stage was to clean by washing and filtering for removal of coarse material (sand and organic matter), followed by an acid attack. In the second, we used the quaternary ammonium surfactant, in order to increase the distance between the layers of MMT, and the third was removed from the wastewater, using absolute ethanol, finishing the purification of process. Then, the clay was introduced into the polymer matrix by polymerization in solution by intercalation and characterized by XRD. The results showed a partial exfoliation, satisfying the increasing properties. (author)

  18. Decontamination effectiveness of bentonite in pigs and sheep repeatedly contaminated with radiocesium

    International Nuclear Information System (INIS)

    The investigations were conducted on 10 pigs and 10 sheep contaminated daily for 21 days with 137CsCl and fed twice a day a normal diet or the same diet supplemented with 10% of bentonite. The animals were killed at days 7, 14 and 21 of radiocesium administration and after cessation of the administration. The abomasum, liver, kidneys, lung, spleen, brain, heart, muscles, tongue and skin were sampled for radiometric determinations. The animals fed a bentonite-supplemented diet revealed substantially lower contents of Cs-137 as compared to the controls. The radioactivities of pig and sheep organs after 21 d Cs-137 administration were lower by about 67.5 and 81.3%, respectively, compared to the controls. The cessation of Cs-137 administration decreased organ radioactivities in bentonite-fed sheep and pigs by about 74.5 and 64.1%, respectively, compared to those in animals without bentonite. (author). 12 refs, 2 tabs

  19. EVALUATION OF THE BENTONITE CONTENT IN SPENT FOUNDRY SANDS AS A FUNCTION OF HYDRAULIC CONDUCTIVITY COEFFICIENT

    Directory of Open Access Journals (Sweden)

    Schirlene Chegatti

    2013-06-01

    Full Text Available This study evaluates the relationship of the bentonite content and hydraulic conductivity coefficient (k of waste foundry sands in tests of hydraulic conductivity in a flexible wall permeameter. The test samples had concentrations of activated sodium bentonite and natural sodium bentonite between 4% and 15%. It was also analyzed chemically the liquid leachate (aluminum, barium, chromium, cadmium, lead, phenols, iron, fluoride, and manganese, following de standard tests of Standard Methods 3111 B e D for the determination of this components in liquid samples. The experiments were supplemented with cation exchange capacity analysis. The results indicate that the values of are is related to the content of bentonite in waste foundry sand and the percolation from this waste disposal.

  20. Swelling and hydraulic properties of Ca-bentonite for the buffer of a waste repository

    International Nuclear Information System (INIS)

    Swelling and hydraulic tests were carried out to provide the information for the selection of buffer material in a radioactive waste repository. Ca-bentonite and de-ionized water were used for the tests. The swelling pressures of compacted bentonite were in the wide range of 0.7 Kg/cm2 to 190.2 Kg/cm2, and they largely increased with an increase in the dry density and bentonite content. However, the swelling pressures decreased with increasing the initial water content and beyond about 12 wt.% of the initial water content, leveled off to a nearly constant value. The hydraulic conductivities were lower than 10-11 m/s for the compacted bentonite with the dry density higher than 1.4 Mg/m3. They increased with increasing temperature in the range of 20 deg. C to 150 deg. C. (author)

  1. Practical and theoretical basis for performing redox-measurements in compacted bentonite. A literature survey

    International Nuclear Information System (INIS)

    This report reviews the state-of-the-art with regard to redox measurements, especially in compacted water saturated bentonite, but also in natural systems like sediments and ground waters. Both theoretical and practical aspects of redox measurements are discussed, as well as some basic concepts like terminal electron-accepting processes (TEAPs) and oxidative capacity (OXC). The problems associated with the interpretation of measured electrode potentials are treated. Despite many practical and theoretical difficulties, redox measurements continue to be carried out by researchers all over the world. The over-all conclusion from the literature survey is that fruitful redox-measurements can be performed in compacted bentonite. Irrespective of whether the measured redox potentials are absolute or not, the use of electrodes provide a valuable tool for studying, e.g., long-term changes in the pore water of compacted bentonite and/or the diffusion of oxygen into a bentonite. (orig.)

  2. Temperature effects on geotechnical and hydraulic properties of bentonite hydrated with inorganic salt solutions

    DEFF Research Database (Denmark)

    Rashid, H. M. A.; Kawamoto, K.; Saito, T.;

    2015-01-01

    © 2015, International Journal of GEOMATE. This study investigated the combined effect of temperature and single-species salt solutions on geotechnical properties (swell index and liquid limit) and hydraulic conductivity of bentonite applying different cation types, concentrations, and temperatures...

  3. RECEIVING FUNCTIONAL FEED ADDITIVE ON THE BASIS OF BENTONITE CLAYS AND CAROTENE CONTAINING RAW MATERIALS

    Directory of Open Access Journals (Sweden)

    Zholobova I. S.

    2014-02-01

    Full Text Available In this article we have shown the results of studying of biologically active connections in bentonite clays, carotene containing raw materials for the purpose of receiving functional feed additive for agricultural birds

  4. Safety Training: Sensibilisation aux gestes et postures de travail

    CERN Multimedia

    Laetitia Laddada

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Nous vous proposons un nouveau cours de sécurité lié aux manutentions manuelles (durée 1 jour) : Sensibilisation aux gestes et postures de travail. Si vous êtes amené à manipuler régulièrement des charges lourdes ou volumineuses, cette formation peut vous aider à prévenir les lésions musculaires ou dorsales. A l'issue de cette formation, vous serez capable d'adopter et d'appliquer les principes de base de sécurité physique et d'économie d'efforts dans les manipulations...

  5. Highly compacted bentonite: a self-healing substance for nuclear waste isolation

    International Nuclear Information System (INIS)

    Granular Na bentonite acquires considerable microstructural homogeneity through water and particle redistribution processes. This yields a very low permeability and thus excellent barrier functions in repositories. This self-healing property also means that large bentonite volumes tend to reach a homogeneous condition. Thus, local voids or inhomogeneities produced, for instance, by minor displacement of the surrounding rock will be healed. The swelling potential also means that a perfect contact is established between the clay barrier and the rock

  6. Removal of formaldehyde from aqueous solution by adsorption on kaolin and bentonite: a comparative study

    OpenAIRE

    Salman, Muhammad; Athar, Makshoof; SHAFIQUE, Umer; Rehman, Rabia

    2012-01-01

    The adsorption of formaldehyde on bentonite and kaolin was studied in batch mode. Parameters like adsorbent dose, pH, contact time and agitation speed were investigated. Langmuir, Freundlich and Temkin isotherms were employed for describing adsorption equilibrium. The maximum amounts of formaldehyde adsorbed (qmax), as evaluated by Langmuir isotherm, were 3.41 and 5.03 milligrams per gram of ground kaolin and bentonite, respectively. The study results led to the conclusion that kaol...

  7. An investigation on physical properties of polyethylene composite with bentonite, kaolin and calcium carbonate additives

    OpenAIRE

    Karabeyoğlu, Sencer S.; , Nurşen Öntürk

    2014-01-01

    Bentonite, Kaolin, Calcium carbonate easily obtained in nature as mineral products are widely used in plastics industry for additive materials. In this study, Bentonite, Kaolin, and Calcium carbonate minerals were compounded with polyethylene matrix used in specific rates. Prepared compounds melted in sheet metal molds and cooled down under appropriate conditions. Thus, production of composite material was achieved. Hardness, water absorption, and physical properties of manufactured composite...

  8. Adsorption of and acidic dye from aqueous solution by surfactant modified bentonite

    International Nuclear Information System (INIS)

    The aim of this paper is to study the adsorption of an acidic dye S. Y. 4 GL (i.e: Supranol yellow 4GL) from aqueous solution on inorgano-organo clay. Bentonite is a kind of natural clay with good exchanging ability. By exchanging its inter lamellar cations with Cetyltrimethylammonium bromide (CTAB) and hydroxy aluminic or chromium poly cations, the properties of natural bentonite can be greatly improved. (Author)

  9. Research program to study the gamma radiation effects in Spanish bentonites

    International Nuclear Information System (INIS)

    The engineering barrier of a radioactive waste underground disposal facility, placed in a granitic host rock, will consist of a backfill of compacted bentonite blocks. At first, this material will be subjected to a gamma radiation field, from the waste canister, and heat from the spent fuel inside the canister. Moreover, any groundwater that reaches the repository will saturate the bentonite. For these reasons the performance of the engineered barrier must be carefully assessed in laboratory experiments. (Author)

  10. The effect of pore structural factors on diffusion in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Four kinds of diffusion experiments; (1) through-diffusion (T-D) experiments for diffusion direction dependency to compacted direction, (2) in-diffusion (I-D) experiments for composition dependency of silica sand in bentonite, (3) I-D experiments for initial bentonite grain size dependency, and (4) I-D experiments for the effect of a single fracture developed in bentonite, were carried out using tritiated water (HTO) to evaluate the effect of pore structural factors on diffusion. For (1), effective diffusivities (De) in Na-bentonites, Kunigel-V1 and Kunipia-F, were measured for densities of 1.0 and 1.5 Mg.m-3 in the axial and perpendicular directions to compacted one. Although De values in Kunigel-V1 for both directions were similar over the density, De values for perpendicular direction to compacted one in Kunipia-F were higher than those for the same direction as compacted one. For (2), apparent diffusivities (Da) in Kunigel-V1 with silica sand were measured for densities of 0.8 to 1.8 Mg.m-3. No significant effect of the mixture of silica sand was found. For (3), Da values for densities of 0.8 to 1.8 Mg.m-3 were measured for a granulated Na-bentonite, OT-9607. However, no effect of initial bentonite grain size was found. For (4), Da values in Kunigel-V1, in which a single fracture was artificially reproduced and immersed in distilled water, were measured. No effect of the fracture on Da was found. Based on this, it may be said that the composition of smectite in bentonite affects the orientation property of clay particle and also affects diffusion. Furthermore, a penetrated fracture formed in bentonite is restored for a short while and does not affect diffusion. Copyright (2001) Material Research Society

  11. From chemical mapping to pressure temperature deformation micro-cartography: mineralogical evolution and mass transport in thermo-mechanic disequilibrium systems: application to meta-pelites and confinement nuclear waste materials; De l'imagerie chimique a la micro-cartographie Pression-Temperature-Deformation: evolution mineralogique et transport de matiere dans des systemes en desequilibre thermomecanique. Applications aux metapelites et aux materiaux de stockage de dechets radioactifs

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, V. de

    2006-03-15

    The mineralogical composition of metamorphic rocks or industrial materials evolves when they are submitted to thermomechanical disequilibria, i.e. a spatial or temporal pressure and temperature evolution, or chemical disequilibria as variations in redox conditions, pH... For example, during low temperature metamorphic processes, rocks re-equilibrate only partially, and thus record locally thermodynamic equilibria increasing so the spatial chemical heterogeneities. Understanding the P-T evolution of such systems and deciphering modalities of their mineralogical transformation imply to recognize and characterize the size of these local 'paleo-equilibria', and so to have a spatial chemical information at least in 2 dimensions. In order to get this information, microprobe X-ray fluorescence maps have been used. Computer codes have been developed with Matlab to quantify these maps in view of thermo-barometric estimations. In this way, P-T maps of mineral crystallisation were produced using the multi-equilibria thermodynamic technique. Applications on two meta-pelites from the Sambagawa blue-schist belt (Japan) and from the Caledonian eclogitic zone in Spitsbergen, show that quantitative chemical maps are a powerful tool to retrieve the metamorphic history of rocks. From these chemical maps have been derived maps of P-T-time-redox-deformation that allow to characterize P-T conditions of minerals formation, and so, the P-T path of the sample, the oxidation state of iron in the chlorite phase. As a result, we underline the relation between deformation and crystallisation, and propose a relative chronology of minerals crystallisation and deformations. The Fe{sup 3+} content map in chlorite calculated by thermodynamic has also been validated by a {mu}-XANES mapping at the iron K-edge measured at the ESRF (ID24) using an innovative method. Another application relates to an experimental study of clay materials, main components of an analogical model of a nuclear

  12. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior; Bionanocompositos quitosana/bentonita: morfologia e comportamento mecanico

    Energy Technology Data Exchange (ETDEWEB)

    Braga, C.R.C.; Melo, F.M.A. de [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-graduacao em Ciencia e Engenharia de Materiais; Vitorino, I.F. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Ciencia e Engenharia de Materiais; Fook, M.V.L.; Silva, S.M.L., E-mail: suedina@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

    2010-07-01

    This study chitosan/bentonite bionanocomposite films were prepared by solution intercalation process, seeking to investigate the effect of the chitosan/bentonite ratio (5/1 e 10/1) on the morphology and mechanical behavior of the bionanocomposites. It was used as nanophase, Argel sodium bentonite (AN), was provided by Bentonit Uniao Nordeste-BUN (Campina Grande, Brazil) and as biopolymer matrix the chitosan of low molecular weight and degree of deacetylation of 86,7% was supplied by Polymar (Fortaleza, Brazil). The bionanocomposites was investigated by X-ray diffraction and tensile properties. According to the results, the morphology and the mechanical behavior of the bionanocomposite was affected by the ratio of chitosan/bentonite. The chitosan/bentonite ratio (5/1 and 10/1) indicated the formation of an intercalated nanostructure and of the predominantly exfoliated nanostructure, respectively. And the considerable increases in the resistance to the traction were observed mainly for the bionanocomposite with predominantly exfoliated morphology. (author)

  13. Investigation of Co(II) sorption on GMZ bentonite from aqueous solutions by batch experiments

    International Nuclear Information System (INIS)

    In this study, a local bentonite from Gaomiaozi county (Inner Mongolia, China) was converted to Na-bentonite and was characterized by FTIR and XRD to determine its chemical constituents and micro-structure. The removal of cobalt from aqueous solutions by Na-bentonite was investigated as a function of contact time, pH, ionic strength, foreign ions and temperature by batch technique under ambient conditions. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Co(II) at the temperatures of 293.15, 313.15 and 333.15 K, respectively. The thermodynamic parameters (ΔG0, ΔS0, ΔH0) of Co(II) sorption on GMZ bentonite calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on GMZ bentonite was an exothermic and spontaneous process. The Na-bentonite is a suitable material for the preconcentration and solidification of Co(II) from aqueous solutions. (author)

  14. Study of combined effect of proteins and bentonite fining on the wine aroma loss.

    Science.gov (United States)

    Vincenzi, Simone; Panighel, Annarita; Gazzola, Diana; Flamini, Riccardo; Curioni, Andrea

    2015-03-01

    The wine aroma loss as a consequence of treatments with bentonite is due to the occurrence of multiple interaction mechanisms. In addition to a direct effect of bentonite, the removal of aroma compounds bound to protein components adsorbed by the clay has been hypothesized but never demonstrated. We studied the effect of bentonite addition on total wine aroma compounds (extracted from Moscato wine) in a model solution in the absence and presence of total and purified (thaumatin-like proteins and chitinase) wine proteins. The results showed that in general bentonite alone has a low effect on the loss of terpenes but removed ethyl esters and fatty acids. The presence of wine proteins in the solution treated with bentonite tended to increase the loss of esters with the longest carbon chains (from ethyl octanoate to ethyl decanoate), and this was significant when the purified proteins were used. The results here reported suggest that hydrophobicity can be one of the driving forces involved in the interaction of aromas with both bentonite and proteins. PMID:25665100

  15. Adsorption of dye from wastewater using chitosan-CTAB modified bentonites.

    Science.gov (United States)

    Guo, Jianzhong; Chen, Shunwei; Liu, Li; Li, Bing; Yang, Ping; Zhang, Lijun; Feng, Yanlong

    2012-09-15

    Dyeing wastewater removal is important for the water treatment, and adsorption is an efficient treatment process. In this study, three modified bentonites, chitosan modified bentonite (CTS-Bent), hexadecyl trimethyl ammonium bromide (CTAB) modified bentonite (CTAB-Bent), and both chitosan and hexadecyl trimethyl ammonium bromide modified bentonite (CTS-CTAB-Bent) were prepared and characterized by FTIR and XRD analysis. Batch experiments were conducted to evaluate the adsorptive removal of weak acid scarlet from aqueous phase using modified bentonites under different conditions. The results show that the adsorption capacity of weak acid scarlet onto natural bentonite was low (4.9%), but higher for 1CTS-Bent and 1CTS-10CTAB-Bent. The optimal conditions for weak acid scarlet adsorption were 1% chitosan, 10% CTAB, at 80°C and reaction time 2.5h. The best removal efficiency was ∼85%, and the adsorption capacity of weak acid scarlet was around 102.0mg g(-1), much higher than that of commercial activated carbon (27.2mg g(-1)). These results suggest that 1CTS-10CTAB-Bent is an excellent adsorbent for effective weak acid scarlet removal from water. The adsorption isotherms of weak acid scarlet were investigated. It was found that Langmuir and Temkin models fitted the data very well (R(2)>0.99). PMID:22738850

  16. EFFECT OF BENTONITE ON SKIN WOUND HEALING: EXPERIMENTAL STUDY IN THE RAT MODEL

    Directory of Open Access Journals (Sweden)

    S. H. Emami-Razavi

    2006-08-01

    Full Text Available Wound healing in the skin depends upon the availability of appropriate trace metals as enzyme cofactors and structural components in tissue repair. The present study is a part of a series of experimental investigations to examine the influence of Bentonite on skin wound healing. Surgically induced skin wounds in 48 young adult male rats were exposed topically to Bentonite (12 round wound and 12 incisional wound and control wounds (12 round wound and 12 incisional wound received de-ionized water only. Skin wounds (round and incisional treated with Bentonite exhibited no significant difference in margins with erythema and edematous changes. Scab and wound debris was more extensive and persisted for at least 7 days after surgery in control group (P < 0.05. Skin wounds exposed to Bentonite exhibited a mild retarded re-epithelialization, the treatment wounds were characterized by a prominent central mass of inflammatory cells, cell debris and wound exudate. The intense infiltrate of lymphocytes, macrophages, monocytes and fibroblasts extended from the wound margin into the region of the panniculus carnosus muscle and hypodermis. Vascular dilatation and dermal oedema were prominent features of these wounds. External utilization of Bentonite for wound healing is safe and feasible, and we finalized that macroscopic healing of wound that treated by Bentonite was superior versus control group.

  17. Anti-fouling effect of bentonite suspension in ultrafiltration of oil/water emulsion.

    Science.gov (United States)

    Panpanit, S; Visvanathan, C; Muttamara, S

    2002-03-01

    The effect on membrane fouling resistance during ultrafilration of oil/water emulsion with the presence of bentonite suspension is experimentally evaluated. The fouling resistance was analyzed as a function of different membrane types and bentonite concentration. The total membrane fouling was categorized into reversible and irreversible, by adopting an appropriate chemical cleaning technique. The results revealed a 40% flux augmentation with the increase of bentonite concentration up to an optimum value of 300 mg l(-1) for cellulose acetate membrane. Further increase of bentonite concentration led to particle deposition on the membrane surface and reduced the flux. The polysulfone membrane did not show a similar flux improvement. This could be due to its high hydrophobicity. The absorption of oil/water emulsion on bentonite increased TOC removal rate from 65% to 80%, and this effect was the major cause of reduction in gel layer formation on the membrane surface. The extent of irreversible fouling of the hydrophilic cellulose acetate membrane was much smaller than that of the polysulfone membrane. These experiments demonstrated that, presence of bentonite could induce transformation of irreversible fouling caused by oil emulsion to reversible fouling, which could be periodically chemically cleaned. PMID:11999987

  18. Fundamental study on anisotropy of diffusion and migration pathway in compacted bentonite

    International Nuclear Information System (INIS)

    SEM observations for micropore structure in compacted bentonite and through-diffusion experiments for non-sorptive tritiated water (HTO) were conducted to evaluate the anisotropy of diffusive pathway in compacted bentonite used as a buffer material in the geological disposal of high-level radioactive waste. The SEM observations and thorough-diffusion experiments were conducted for axial and perpendicular directions to the compacted direction of bentonite as a function of bentonite's dry density. Two types of Na-bentonites, Kunigel-V1 and Kunipia-F with different smectite contents were used in both experiments. No orientation of clay particles was found for low-smectite content Kunigel-V1, while layers of clay particles orientated in the perpendicular direction to compacted direction were observed for Kunipia-F with approximately 100 wt% smectite content. This tendency is in good agreement with that for HTO's effective diffusivities obtained from diffusion experiments, indicating that smectite content in bentonite affects the orientation properties of clay particles and diffusive pathway. (author)

  19. [Study on performance of double mineral base liner using modified bentonite as active material].

    Science.gov (United States)

    Qu, Zhi-Hui; Zhao, Yong-Sheng; Wang, Tie-Jun; Ren, He-Jun; Zhou, Rui; Hua, Fei; Wang, Bing; Hou, Yin-Ting; Dai, Yun

    2009-06-15

    The absorbing capacity of clay,roasting bentonites by 450 degrees C and dual-cation organobentonites of the pollutions in landfill leachate was compared through static experiment, and investigations were conducted into availability of controlling the permeating of landfill leachate and feasibility of removing the main pollutants in leachate on the double mineral base liners of clay/roasting bentonites by 450 degrees C and clay/dual-cation organobentonites by using nice landfill leachate as the filter fluid. Experiment indicated that the adsorption equilibrium time of landfill leachate in clay, roasting bentonites by 450 degrees C and dual-cation organobentonites was 24 h; the absorbing capacity of roasting bentonites by 450 degrees C and dual-cation organobentonites was larger than that of clay. Simultaneous the penetration coefficients of the two liners were respective 1.31 x 10(-8) cm x s(-1) and 2.80 x 10(-8) cm x s(-1); Double mineral base liners of clay/roasting bentonites by 450 degrees C owned larger absorbing capacity of NH4+, however, double mineral base liners of clay/dual-cation organobentonites had strong absorbing capacity of organic pollutants and the attenuation rate of COD was 33.82% higher than the other. Conclusion was drawn that different types of modified bentonite should be chosen as "the active layer" according to different styles of landfill pollutants. PMID:19662882

  20. Salt content impact on the unsaturated property of bentonite-sand buffer backfilling materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ming [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Zhang Huyuan, E-mail: p1314lvp@yahoo.com.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Jia Lingyan; Cui Suli [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer SWCC and infiltration process of bentonite-sand mixtures is researched. Black-Right-Pointing-Pointer The k{sub u} of bentonite-sand mixtures was evaluated as the buffer backfilling materials. Black-Right-Pointing-Pointer Salt content impacting on the unsaturated property of bentonite-sand materials is small. - Abstract: Bentonite mixed with sand is often considered as possible engineered barrier in deep high-level radioactive waste disposal in China. In the present work, the vapor transfer technique and water infiltration apparatus were used to measure the soil water characteristic curve (SWCC) and unsaturated hydraulic conductivity (k{sub u}) of bentonite-sand mixtures (B/S) effected by salt content. Results show, the water-holding capacity and k{sub u} increase slightly with the concentration of Na{sup +} in pore liquid increasing from 0 g/L to 12 g/L, similar with the solution concentration of Beishan groundwater in China. Salt content in the laboratory produced only one order of magnitude increase in k{sub u}, which is the 'safe' value. The different pore liquid concentrations used in this study led to small differences in thickness of diffuse double layer of bentonite in mixtures, this might explain why some differences have been found in final values of k{sub u}.

  1. Influence of Water Salinity on the Hydraulic Conductivity of Compacted Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Kim, Jin Seop; Choi, Jong Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-12-15

    The influence of water salinity on the hydraulic conductivities of compacted bentonite with several dry densities were studied. The hydraulic conductivity increases with increasing salinity only when the dry density of bentonite is relatively low. The degree of increase becomes more remarkable at a lower dry density of bentonite. For bentonite with the density of 1.0 Mg/m{sup 3} and 1.2 Mg/m{sup 3}, the hydraulic conductivity of the 0.4 M NaCl solution increases up to about 7 times and 3 times, respectively higher than that of freshwater. However, for the bentonite with a dry density higher than 1.4 Mg/m{sup 3}, the salinity has an insignificant effect on the hydraulic conductivity, and the hydraulic conductivity is nearly constant within the salinity range of 0.04 to 0.4 M NaCl. The pre-saturation of the bentonite specimen with freshwater has no significant influence on the hydraulic conductivity.

  2. Occurrence of Fe–Mg-rich smectites and corrensite in the Morrón de Mateo bentonite deposit (Cabo de Gata region, Spain): A natural analogue of the bentonite barrier in a radwaste repository

    OpenAIRE

    Pelayo Bayón, Marta; García Romero, Emilia; Labajo Rodillana, Miguel A.; Pérez del Villar Guillén, L.

    2011-01-01

    The Morrón de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on a bentonite barrier in a deep geological repository of high level radioactive wastes. This bentonite deposit and its host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the biocalcarenite beds close to the dome. In this work, the mineralogical and chemical features of the clay minerals of the hydrotherm...

  3. Study of Japanese and Serbia bentonite on the fraction of 137Cs from cement-ion exchange resins-bentonite clay mixture

    International Nuclear Information System (INIS)

    Leaching tests in cement-ion exchange resins-bentonite matrix, were carried out in accordance with a method recommended by IAEA. The cement specimens were prepared from construction cement which is basically a standard Portland cement. The cement was mixed with saturated wet cation exchange resins, (100 g. of dry resins +100 g. of water containing 137Cs) and two bentonite clay, from Serbia, and another from Japan. After each leaching period the radioactivity in the leachant was measured. All results exhibit practically the same general characteristics. An enhanced initial period of leaching occurs during the first 25-30 days or so, followed by a distinct reduction in the leach rate which is broadly maintained up to the long period of leaching. The leach behaviour of cement-mortar materials can be explained as a combination of two processes: surface wash-off, which is not diffusion controlled, followed by a static diffusion stage. Enhanced initial period of leaching can be explained in terms of a rapid equilibrium being established between spaces present in the surface pores of the Portland cement and ions in solution in the leachant; hence the term wash-off. It is the second stage which is controlled by diffusion that dominates the long-term leaching behaviour of the material. We also prove that increasing amount of bentonite causes a significant reduction in the leaching rate, because of bentonite good sorption characteristics and ion selectivity. We showed that the bentonite from Serbia can successfully be used for the immobilisation of radioactive waste with same quality as Japanese bentonite

  4. Effect of pH, ionic strength and fulvic acid on the sorption and desorption of cobalt to bentonite

    International Nuclear Information System (INIS)

    Humic substances and bentonite have attracted great interest in radioactive waste management. Here the sorption of cobalt on bentonite in the presence and absence of fulvic acid (FA) under ambient conditions was studied. The effects of pH, ionic strength, FA and solution concentrations on cobalt sorption to bentonite were also investigated using batch techniques. The results indicate that the sorption of cobalt is strongly dependent on pH and is independent of ionic strength under our experimental conditions. Surface complexation is considered the main mechanism of cobalt sorption to bentonite. In the presence of FA, little effect of FA on cobalt sorption was found at pH8. The addition sequences of FA/Co2+ to the bentonite suspension on the sorption of cobalt to FA-coated bentonite were also studied. The results indicated that the sorption is not influenced by the addition sequences. Some possible mechanisms are discussed

  5. The Optimization of Aniline Adsorption from Aqueous Solutions by Raw Bentonite and Bentonite Modified with Cationic Surfactants Using the Taguchi Model

    Directory of Open Access Journals (Sweden)

    F. Taherkhani

    2015-04-01

    Full Text Available Introduction & Objectives: Aniline is an organic compound widely used in various industries. The release of this compound has had various environmental impacts. Thus, the assessment of efficient and practical methods for the removal of aniline from wastewater of these industries is remarkable. Taguchi model is a model for the analysis of experiments, that predicts both the effects of each factors and the optimum level of them using a certain number of experiment. The purpose of this study was the optimization of aniline adsorption on the raw and modified bentonite with a cationic surfactant using Taguchi model. Materials & Methods: In this experimental study, the raw bentonite and modified bentonite was prepared in a few steps. Then, 4 main factors (i.e. pollutant concentration, contact time, pH, and adsorbent dosage on 4 levels were selected by Matrix L16 trials and the experiments were conducted in this matrix. The factors were also ranked based on the R-value. Then , the data were analyzed with Minitab 17 software. Finally, the adsorption of aniline on raw and modified bentonite was determined in optimal conditions. Results: The optimization of adsorption process using Taguchi model showed that the factors of importance for optimizing respectively were: contact time of 360 minutes, pH =10 pH, ani-line initial concentration of 300 mg/L and adsorbent dosages of 40 g/L. The maximum ad-sorption of aniline onto raw bentonite and modified bentonite with cationic surfactant in op-timal conditions were determined 81.86 and 8.75, respectively. The results revealed that Freundlich isotherm and pseudo-second-order kinetic model provided a better ?t to the ex-perimental data. Conclusion: The results showed that the bentonite modified with cationic surfactant is efficient in the removal of aniline. At the same time, since bentonite is cheap and easily accessible ,it is considered a desirable adsorbant. (Sci J Hamadan Univ Med Sci 2015; 22 (1:55-64

  6. Modélisation du procédé de soudage hybride Arc / Laser par une approche level set application aux toles d'aciers de fortes épaisseurs A level-set approach for the modelling of hybrid arc/laser welding process application for high thickness steel sheets joining

    OpenAIRE

    Desmaison Olivier; Bellet Michel; Guillemot Gildas

    2013-01-01

    Le procédé de soudage hybride Arc/Laser est une solution aux assemblages difficiles de tôles de fortes épaisseurs. Ce procédé innovant associe deux sources de chaleur : un arc électrique produit par une torche MIG et une source laser placée en amont. Ce couplage améliore le rendement du procédé, la qualité du cordon et les déformations finales. La modélisation de ce procédé par une approche Level Set permet une prédiction du développement du cordon et du champ de température associé. La simul...

  7. Experimental study on self-healing of bentonite/sand mixtures and its impact on hydraulic permeability

    International Nuclear Information System (INIS)

    The effects of gas permeation on the hydraulic permeability of bentonite/sand mixtures were studied experimentally by conducting permeability tests with various fluids and by microscopic observations. In these tests, hydraulic permeabilities were measured before and after helium gas was applied to permeate the mixtures. Although gas formed preferential migration paths through the mixtures, the imperviousness of the bentonite/sand mixtures to the tested fluids never deteriorated because the paths became filled by swelling bentonite on re-saturation

  8. Modélisation du procédé de soudage hybride Arc / Laser par une approche level set application aux toles d'aciers de fortes épaisseurs A level-set approach for the modelling of hybrid arc/laser welding process application for high thickness steel sheets joining

    Directory of Open Access Journals (Sweden)

    Desmaison Olivier

    2013-11-01

    Full Text Available Le procédé de soudage hybride Arc/Laser est une solution aux assemblages difficiles de tôles de fortes épaisseurs. Ce procédé innovant associe deux sources de chaleur : un arc électrique produit par une torche MIG et une source laser placée en amont. Ce couplage améliore le rendement du procédé, la qualité du cordon et les déformations finales. La modélisation de ce procédé par une approche Level Set permet une prédiction du développement du cordon et du champ de température associé. La simulation du soudage multi-passes d'une nuance d'acier 18MnNiMo5 est présentée ici et les résultats sont comparés aux observations expérimentales. The hybrid arc/laser welding process has been developed in order to overcome the difficulties encountered for joining high thickness steel sheets. This innovative process gathers two heat sources: an arc source developed by a MIG torch and a pre-located laser source. This coupling improves the efficiency of the process, the weld bead quality and the final deformations. The Level-Set approach for the modelling of this process enables the prediction of the weld bead development and the temperature field evolution. The simulation of the multi-passes welding of a 18MnNiMo5 steel grade is detailed and the results are compared to the experimental observations.

  9. Mineral alteration in a 4.5 years concrete-bentonite interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Chemical processes occurring in the concrete-bentonite interface can affect the feasibility of the clay barriers implemented for the isolation of nuclear wastes. During the concrete degradation, highly alkaline waters from the concrete will diffuse through the clay barrier. This may produce geochemical and microstructural transformations in the bentonite. Particularly, the studies carried out with the FEBEX bentonite in contact with concrete showed montmorillonite dissolution, precipitation of zeolites, Mg-smectite, CSH gels and brucite. These studies focused mainly in a highly reactive alteration environment (pH>13). During the NF-PRO integrated project the concrete-compacted bentonite interaction was also studied containing the materials and conditions as close as possible to real ones, with simultaneous heating and hydration. Several experimental cells were designed and mounted at a time in CIEMAT, starting in 2006. Presently, in the context of the PEBS project a long-term cell has been dismounted after 4.5 years. The tests were performed in cells especially designed in CIEMAT for the experiments. Blocks of FEBEX bentonite were compacted with its hygroscopic water content at a dry density of 1.65 g/cm3. At the bottom of the cell, the bentonite block was inserted just in contact with the heater. On top of this, a 30-mm thick concrete block was placed. The hydration occurred through the concrete block. In a few days after the beginning of the test the sensor placed at the concrete/bentonite interface recorded stable relative humidities of 100% and temperatures of 45 deg. C. The 4.5 years cell was dismantled with the aim to preserve the concrete/bentonite interface. Then, a detailed sampling of the concrete/bentonite interface and the cement matrix of the concrete was performed for mineralogical, microscopy, and geochemical characterization. The water injected to hydrate the concrete/bentonite cells is synthetic

  10. Evaluation of long-term interaction between cement and bentonite for geological disposal (2) XAFS analysis of calcium silicate hydrate precipitates at cementitious and bentonite material interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Numerical analyses of the long-term alteration of the engineered barriers used for the disposal of TRU waste predicted precipitation of C-S-H minerals at the interface between the cementitious materials and the bentonite-based buffer. When the C-S-H precipitates at this interface, the diffusion coefficient in the engineered barriers will decrease, resulting in reduced mass transport, which feeds back to reduce the rate of subsequent alteration. The C-S-H predicted to form at the cement-bentonite interface could not be identified directly using conventional analytical tools, including XRD, due to its low crystallinity. The authors propose that XAFS analysis, which provides spectra sensitive to the valency and coordination of the element of interest regardless of its crystallinity, would be capable of characterizing the C-S-H. The presence of the C-S-H precipitated as a secondary mineral has already been confirmed by applying chemical and XAFS analyses to bentonite specimens collected from the compacted bentonite-cement interface. However, because of the limitations on the width of specimens that can be collected by cutting from block samples, i.e. approximately 1 mm, detailed concentration profiles could not be obtained for this secondary C-S-H. In this study, XAFS spectra of thin specimens were measured using an X-ray detector in order to obtain detailed concentration profiles for the C-S-H formed at the interface between the cementitious material and the bentonite-based buffer. The X-ray detector used in the XAFS analysis consists of 1024 photodiodes arranged in line with a 0.025 mm pitch (photodiode array; PDA). Ca-K-edge XAFS measurements were conducted at the Photon Factory of the KEK. The synchrotron was operated in top-up mode with 450 mA during the measurements. Specimens were taken from a contact sample of compacted bentonite (Kunigel V1; dry density of 1.6 g/cm3) and hardened OPC (w/c = 0.6) immersed in

  11. The adsorption characteristics and porous structure of bentonite adsorbents as determined from the adsorption isotherms of benzene vapor

    Directory of Open Access Journals (Sweden)

    LEPA STOJANOVSKA

    2004-02-01

    Full Text Available The adsorption of benzene vapor on natural and acid activated bentonites was treated by the theory of volume filling of micropores. The micropore volume and characteristic values of the free energy of adsorption were determined from the adsorption isotherms. The Dubinin–Radushkevish–Stoeckli and Dubinin–Astakhov equations were used for this purpose. The results showed that natural bentonite has a more homogeneous micropore structure than the acid activated ones. The characteristic values of the free energy of adsorption for the natural bentonite were higher than those of the acid activated bentonite. This is due to differences in its structure and the pore size.

  12. Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation – interpretation of volcanic source regions

    Directory of Open Access Journals (Sweden)

    Tarmo Kiipli

    2014-02-01

    Full Text Available Integrated correlation of bentonites (altered volcanic ashes and graptolite biozonation is presented. Detailed study of two Lithuanian drill core sections extended previous knowledge of the occurrence and composition of bentonites to the south. Identification of graptolite species allowed bentonites to be assigned their proper stratigraphical position. Silurian bentonites in Lithuania are mostly characterized by wide and very wide XRD 201 reflections of the main component of sanidine phenocrysts. Only fourteen of the 69 samples studied contained sanidine with a sharp reflection, which gave the best correlation potential. In the Lithuanian sections one bentonite was found in the Rhuddanian, five bentonites were recognized in the Aeronian, 17 bentonites in the Telychian, 26 in the Sheinwoodian, 10 in the Homerian and six in the Ludlow. All bentonites found in Lithuania are characterized by the main component of sanidine. A large number of Lithuanian bentonites are not known in Latvia and Estonia, indicating that volcanic ashes reached the East Baltic area from two source regions – the Central European and Norwegian Caledonides.

  13. Conditions de contrat applicables aux travaux de construction

    CERN Document Server

    1999-01-01

    Conditions of Contract for Construction, which are recommended for building or engineering works designed by the Employer or by his representative, the Engineer. Under the usual arrangements for this type of contract, the Contractor constructs the works in accordance with a design provided by the Employer. However, the works may include some elements of Contractor-designed civil, mechanical, electrical and/or construction works.

  14. Soja MON 87701 Résistant Aux Insectes

    OpenAIRE

    Canada, Publié par la Direction des aliments de Santé

    2014-01-01

    Santé Canada a avisé Monsanto Canada Inc. qu’il ne s’oppose pas à l’utilisation alimentaire du soja MON 87701 résistant aux insectes. Le Ministère a réalisé une évaluation approfondie de cette lignée de soja conformément aux Lignes directrices sur l’évaluation de l’innocuité des aliments nouveaux. Ces lignes directrices sont fondées sur les principes admis internationalement de l’établissement de l’innocuité d’aliments comportant des caractères nouveaux. Le texte qu...

  15. Des arbres et des herbes aux marges du Sahara

    OpenAIRE

    Bernus, Edmond

    1992-01-01

    Le Sahara possède une végétation qui est d'autant plus précieuse pour ses habitants qu'elle est rare. Les herbes, prairies d'"éphémères" dans les zones aux pluies les plus aléatoires, ou vivaces et annuelles plus régulières, fournissent un fourrage très recherché. Dans les marges méridionales des herbes permettent des ramassages de graines qui donnent aux nomades des nourritures appréciées. Mil, sorgho et riz poussent à l'état spontané : les deux premiers ont été domestiqués dans cette région...

  16. Sensibilisation aux gestes et postures de travail - French version only

    CERN Multimedia

    2004-01-01

    Nous vous proposons un nouveau cours de sécurité lié aux manutentions manuelles (durée 1 jour) : Sensibilisation aux gestes et postures de travail. Si vous êtes amené à manipuler régulièrement des charges lourdes ou volumineuses, cette formation peut vous aider à prévenir les lésions musculaires ou dorsales. A l'issue de cette formation, vous serez capable d'adopter et d'appliquer les principes de base de sécurité physique et d'économie d'efforts dans les manipulations d'objets. Les cours sont pris en charge par la Commission de Sécurité. L'inscription EDH est obligatoire. Pour plus d'information, veuillez consulter les pages Formation & Développement (Groupe Sécurité)

  17. Développement d'une approche innovante de modélisation de la cinétique de décomposition thermique des matériaux solides en espaces confinés sous-ventilés. Application aux incendies en tunnel

    OpenAIRE

    Hermouet, Fabien

    2015-01-01

    Les incendies de tunnels sont des phénomènes violents, à l’évolution rapide qui engendrent la plupart du temps des dommages importants aux personnes et aux biens. La sécurité incendie dans les tunnels routiers est basée sur l’utilisation de modèles empiriques très simplifiés de description de l’évolution de la cinétique de développement de l’incendie. Ces modèles ne prennent cependant pas en compte le type de combustible impliqués dans le phénomène, tels que les polymères constitutifs des env...

  18. Modified swelling pressure apparatus using vapor pressure technique for compacted bentonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. bentonite. The compacted bentonite is found in unsaturated conditions before applying of swelling due to absorption. The behaviour of compacted bentonite is not consistent with the principle and concepts of classical, saturated soil mechanics. An unsaturated soil theoretical framework using soil water characteristic curve has been fairly established over the past several decades. The soil-water characteristic curve is a relationship between soil moisture and soil suction obtained by the axis translation technique, vapor pressure technique or osmotic suction control which is a key feature in unsaturated soil mechanics. The soil-water characteristic curve can be used for prediction of the shear strength, volume change and hydraulic conductivity. Cui et al. 2002 indicated soil-water characteristic curve of expansive clay soil in high soil suction ranges using osmotic suction technique. Tripathy et al. 2010 described the soil-water characteristic curve both using the axis translation technique and vapor pressure technique in the entire soil suction ranges. Nishimura and Koseki 2011 measured suction of bentonite applied high soil suction due vapor pressure using a chilled mirror dew point potentiometer (WP4-T of DECAGON Device). The bentonite with gravimetric water content of 18 % indicated soil suction of 2.8 MPa at least. It is predicted that suction efforts to swelling pressure and shear strength of unsaturated compacted bentonite. This study focuses on the influence of suction on both swelling pressure and shear strength of compacted bentonite. The soil-water characteristic curve (SWCC) tests were conducted for compacted bentonite using both axis-translation technique and vapor pressure technique. The SWCC had a range from 0 kPa to 296 MPa in suction. The compacted bentonite having two different soil suctions were prepared for swelling pressure tests. Newly swelling pressure testing apparatus was developed in order

  19. Modelling bentonite pore waters for the Swiss high-level radioactive waste repository

    International Nuclear Information System (INIS)

    The main objective of this investigation is to contribute to definition of representative compositions of bentonite pore waters in the near-field of the Swiss repository for high-level radioactive waste. Such compositions are necessary for determining the solubility limits of radionuclides for the safety analysis KRISTALLIN I. The model developed here is based on the premise, supported by experimental data, that the composition of bentonite pore waters is largely controlled by the dissolution or precipitation of reactive trace solids in bentonite. Selectivity constants for the exchange equilibria among Na-K, Na-Ca, and Ca-Mg were derived from water-bentonite interaction experiments performed for NAGRA by the British Geological Survey (BGS). An important parameter for the prediction of radionuclide solubilities is the oxidation potential of the bentonite water. Since the BGS experiments yielded no information on this, the oxidation potential had to be estimated from model assumptions. Bentonite pore waters were defined by computer simulation with the geochemical code MINEQL. They have been modelled in a closed system, i.e. assuming the bentonite, once it has reacted with a fixed volume of groundwater, does not exchange further chemical species with an external reservoir. No attempt was made to model the evolution of the pore water by simulating diffusive exchange processes. It can be anticipated that uncertainties in the concentrations of some major elements (e.g. Al, Si) will not significantly affect the calculated radionuclide solubilities. The latter will depend primarily on the concentrations of a few major ligands (OH-, Cl- and CO3-2) and, for multivalent elements, also on the oxidation potential of the solution. (author) 10 figs., 22 tabs., 40 refs

  20. Adsorption properties and porous structure of sulfuric acid treated bentonites determined - SHORT COMMUNICATION

    Directory of Open Access Journals (Sweden)

    SNEZANA BREZOVSKA

    2005-02-01

    Full Text Available In a previous paper adsorption isotherms of benzene vapor on natural bentonite from Ginovci, Macedonia, and forms acid activated with 10 % and 15 % solutions of hydrochloric were interpreted by means of the Dubinin–Radushkevich–Stoeckli and Dubinin–Astakhov equations; the investigation has been continued with bentonites acid activated with 10 % and 15 % solutions of sulfuric acid where X-ray analysis indicates smaller structural changes. Using the above equations, the heterogeneity of the micropores and the energetic heterogeneity of the bentonites were determined from the differential distribution of the micropore volume with respect to the structural parameter of the equations characterizing the microporous structure and to the molar free energy of adsorption. Activated bentonites obtain bigger pores but also a certain quantity of new small pores appear during acid activation with the higher concentration of acid. The micropore volumes, determined from the adsorption of benzene vapor, of bentonites activated with 10 % and 15 % solution of hydrochloric acid (144.60 cm3 kg-1 and 110.06 cm3 kg-1, respectively, decrease in comparison with that of natural bentonite (162.55 cm3 kgv.1 In contrast, the values of the micropore volume for bentonities treated with 10 % and 15 % solutions of sulfuric acids increase (169.19 cm3 kg-1 and 227.74 cm3 kg-1. That is due to the difference in the structural changes occurring during activation with hydrochloric and sulfuric acids. The values of the free energy of adsorption of benzene vapor for natural bentonite are higher than those of the acid acitivated bentonities, what is in accordance with the structural and porosity changes.

  1. Na + and HTO diffusion in compacted bentonite: Effect of surface chemistry and related texture

    Science.gov (United States)

    Melkior, T.; Gaucher, E. C.; Brouard, C.; Yahiaoui, S.; Thoby, D.; Clinard, Ch.; Ferrage, E.; Guyonnet, D.; Tournassat, C.; Coelho, D.

    2009-05-01

    SummaryIn underground repository concepts for radioactive waste, bentonite is studied as a reference swelling material to be used as an engineered barrier. Under the changing geochemical conditions prevailing within the barrier (saturation with the fluid coming from the host formation, diffusion of various chemical plumes caused by the degradation of some constituents of the barrier-system, etc.), the surface chemistry of the clay particles could evolve. This work aims to characterize the effects of these changes on (i) the microstructure of compacted bentonite samples and (ii) the diffusion properties of HTO and Na in these samples. For this purpose, bentonite sets were equilibrated with different solutions: NaCl, CaCl 2, CsCl solutions as well as an artificial clayey porewater solution. The microstructure of the different samples was characterized by HRTEM and XRD, in a water saturated state. In parallel, effective diffusion coefficients of both HTO and 22Na were measured for the different samples. The density of the bentonite in the diffusion tests and in the HRTEM observations was set at 1.6 Mg m -3. From the microstructural observations and the results of diffusion tests, it is deduced that one key parameter is the occurrence of a gel phase in the material, which is found to depend strongly on the bentonite set: the gel phase dominates in Na-bentonite, while it is lacking in Cs-bentonite. The HTO diffusion coefficients are found to be lower in the samples with high gel phase content. Sodium diffusion does not follow the same trend: when compared with HTO, Na diffuses faster when the gel phase content is high. The latter result could indicate that the "accelerated diffusion mechanism" of cations, already mentioned in the literature, is enhanced in clayey materials that contain a gel phase.

  2. Engineered barrier experiments and analytical studies on coupled thermal - hydraulic - chemical processes in bentonite buffer material

    International Nuclear Information System (INIS)

    It is anticipated that thermal - hydraulic - mechanical - chemical (THMC) processes will be coupled in the bentonite buffer material of a high-level radioactive waste repository. The main contributors to these processes are heat arising from the radioactive decay of the vitrified waste, infiltration of groundwater from the host rock and/or leachate from the cementitious component of the repository, and the consequent increase in swelling pressure and chemical reactions. In order to evaluate these coupled processes in the bentonite buffer material, it is necessary to take steps towards the development of a credible and robust THMC model. The current paper describes the measured data of an engineering-scale coupled THC process experiment and the calculated results of a THC model undergoing development. The coupled experiment used an electric heater, bentonite blocks and a mortar block, subjected to infiltrating water to simulate a high-alkaline porewater derived from the concrete tunnel support seeping into the bentonite buffer material under a thermal gradient provided by the vitrified waste. Temperature and water content of the bentonite buffer material were measured by several sensors continuously for several months. After this time, the buffer material was sampled. The results of mineral analysis of the samples suggested that the precipitate of amorphous hydrate with silica was found in the buffer material in contact with the mortar. The developing THC model simulated C-S-H gel precipitation as a secondary mineral in the exact same locality because of the solution being saturated with respect to portlandite and chalcedony, thereby providing some confidence in the chemical feature of the developing THC model. Some important issues in the future development of the model were also identified, including the concentration of porewater being influenced by vapor movement in the bentonite buffer material due to heating from the vitrified waste and geochemical reactions

  3. Sorption of Uranium(VI and Thorium(IV by Jordanian Bentonite

    Directory of Open Access Journals (Sweden)

    Fawwaz I. Khalili

    2013-01-01

    Full Text Available Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0∘C and . The highest rate of metal ions uptake was observed after 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at . Bentonite has shown high metal ion uptake capacity toward uranium(VI than thorium(IV. Sorption data were evaluated according to the pseudo- second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0∘C, 35.0∘C, and 45.0∘C. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI and thorium(IV. Recovery of uranium(VI and thorium(IV ions after sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. The best percent recovery for uranium(VI and thorium(IV was obtained when 1.0 M HNO3 was used.

  4. Decontamination of cesium, strontium, and cobalt from aqueous solutions by bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Khan, M.A. [Univ. of the Punjab, Lahore (Pakistan); Khan, S.A. [Government F.C. College, Lahore (Pakistan)

    1996-12-31

    Sorption studies of cesium, strontium, and cobalt (Cs, Sr, and Co) on bentonite under various experimental conditions, such as contact time, pH, sorbent and sorbate concentration, and temperature, have been performed. The sorption data for all these metals have been interpreted in terms of Freundlich, Langmuir, and Dubinin-Radushkevich equations. Thermodynamics parameters, such as heat of sorption {Delta}H{degrees}, free energy change {Delta}G{degrees}, and entropy change {Delta}S{degrees}, for the sorption of these metals on bentonite have been calculated. The value of {Delta}H{degrees} shows that the sorption of Cs was exothermic, while the sorption of Sr and Co on bentonite were endothermic in nature. The value of {Delta}G{degrees} for their sorption was negative, showing the spontaneity of the process. The maximum loading capacity of Cs, Sr, and Co were 75.5, 22, and 27.5 meq, respectively, for 100 g of bentonite. The mean free energy E of Cs, Sr, and Co sorption on bentonite was 14.5, 9, and 7.7 kJ/mol, respectively. The value of E indicates that ion exchange may be the predominant mode of sorption for these radionuclides. The desorption studies with 0.01 M CaCl{sub 2} and groundwater at low-metal loading on bentonite showed that about 95% of Cs, 85-90% of Sr, and 97% of Co were irreversibly sorbed. Bentonite could be effectively used for the decontamination of wastewater effluent containing low concentrations of radioactive nuclides of Cs, Sr, and Co. 16 refs., 7 figs., 3 tabs.

  5. Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy

    Science.gov (United States)

    Dobryden, I.; Potapova, E.; Holmgren, A.; Weber, H.; Hedlund, J.; Almqvist, N.

    2015-04-01

    Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle-particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite-magnetite, bentonite-magnetite, silica-bentonite, and silica-magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite-magnetite and bentonite-silica systems and slightly increased for the magnetite-bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite-silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.

  6. Effect of Different Levels of Kaolin, Bentonite and Zeolite on Broilers Performance

    Directory of Open Access Journals (Sweden)

    M. Safaei Katouli

    2010-01-01

    Full Text Available An experiment was conducted to study the effects of different levels of kaolin, bentonite and zeolite on broiler performance in 6 weeks. Four hundred and forty eight day-old broilers of male Ross 308 strain were allocated to 7 treatments with four replications and 16 broilers in each. The experiment was carried out in a completely randomized design. Treatments were control and 1.5, 3% of kaolin, bentonite and zeolite. Treatments with 3% zeolite and bentonite was significantly (p<0.05 increased weight gain during the 1st and 6th weeks, 1.5% kaolin and zeolite, significantly (p<0.05 increased weight gain in 5th and 6th weeks compared to the control, respectively. Treatments 1.5% bentonite in 4th and 5th weeks and 1.5% zeolite and 3% bentonite in 5th week was significantly (p<0.05 increased feed intake compared to the control. Feed conversion ratio in diets with 3% kaolin in the 1st and 2nd weeks and 3% zeolite in the 1st week was significantly (p<0.05 improved compared to the control. There was no significant (p>0.05 differences in internal organs and fecal pH between trial groups and control. Fecal moisture in treatments with 1.5% kaolin, 3% bentonite and zeolite was significantly (p<0.05 different from control. Growth rate in treats containing 3% kaolin at 0-3 week and 1.5% zeolite, 1.5% kaolin and 3% kaolin, bentonite and zeolite at 0-6 week was more than control (p<0.05. The results demonstrated that adding silicate minerals in diet, improve performance of broiler chickens.

  7. Introduction aux modèles espace état et au filtre de Kalman

    OpenAIRE

    Lemoine, Matthieu; Pelgrin, Florian

    2003-01-01

    Nous détaillons ici les principaux concepts et problèmes liés aux modèles espace-état, ainsi que leurs applications. Nous présentons d'abord ces modèles dans leur généralité. Ensuite, nous explicitons les algorithmes utilisés afin de procéder à l'estimation par le maximum de vraisemblance, c'est-à-dire fondamentalement le filtre de Kalman et l'algorithme EM. Nous considérons enfin quatre applications : les décompositions tendance-cycle, l'extraction d'indicateurs coïncidents d'activité, l'est...

  8. Synthesis and characterization of gold nanoparticles incorporated bentonite clay for electrocatalytic sensing of arsenic(III)

    Indian Academy of Sciences (India)

    Pankaj Kumar Rastogi; Dharmendra Kumar Yadav; Shruti Pandey; Vellaichamy Ganesan; Piyush Kumar Sonkar; Rupali Gupta

    2016-03-01

    In the present manuscript, a simple and easy route to synthesize bentonite (bt) clay-supported goldnanoparticles (Au NPs) is reported (represented as Au-bt).Application of this new environmentally benignmaterial in electrocatalytic determination of arsenite (As(III)) was studied. The successful synthesis and incorporation of Au NPs into the bt clay is supported by spectroscopic, microscopic and electrochemical methods.The synthesized Au-bt material was used to modify glassy carbon electrode (GC) by the evaporation of Au-btaqueous suspension dropped on the surface of the GC (GC/Au-bt).Cyclic voltammetry and chronoamperometry studies of As(III) solutions were performed with this GC/Au-bt electrode which act as efficient platform forthe electro-oxidation of As(III) to As(V) at a very low overpotential. Kinetic parameters were evaluated for theoxidation of As(III) at the GC/Au-bt platforms.A wide linear calibration range for the determination of As(III)from 1 to 1700 μM was obtained with high reproducibility and stability. A limit of detection, 0.1 μM wasachieved with high sensitivity.Additionally, it showed a good selectivity for the determination of As(III) in thepresence of copper(II) and other interfering ions suggesting a promising new route for trace level determinationof As(III) in neutral conditions.

  9. Internal stratification of two thick Ordovician bentonites of Estonia: deciphering primary magmatic, sedimentary, environmental and diagenetic signatures

    Directory of Open Access Journals (Sweden)

    Sven Siir

    2015-05-01

    Full Text Available Twenty-six samples from two major altered volcanic ash beds, Kinnekulle and BII Bentonite of the Kuressaare core section (K-3, Saaremaa Island, were explored to record the geochemical and mineralogical heterogeneity of beds. Signs of ash transport fractionation, redeposition of volcanic ash and diagenetic redistribution of material are described and interpreted. In authigenic mineralogy of the Kinnekulle Bentonite illite–smectite dominates with addition of K-feldspar at the margins. The BII Bentonite is composed of chlorite–smectite and illite–smectite. The stability of phenocryst compositions, including that of sanidine and biotite, indicates that both bentonites originate from a single eruption. The observed rather stable pyroclastic sanidine compositions in the cross section of bentonites confirm the reliability of sanidine-based fingerprinting of altered volcanic ash beds. Trace element distribution in bentonites and host rocks indicates that Zr, Ga, Rb, Nb, Ti and Th stayed largely immobile during volcanic ash alteration and reflect primary ash composition. However, some redistribution of Nb and Ti as well as Y has probably occurred near the contacts of bentonite with the host rock. More scattered grain size distribution and immobile element patterns of the Kinnekulle Bentonite support the idea that the primary ash bed had a heterogeneous composition and it was one of the biggest bentonites of the Phanerozoic and most likely records an extended volcanic event. Significant geochemical variations, including a high S content, near the upper and lower contacts of the Kinnekulle Bentonite and elevated Ca and P in host rocks of both bentonites suggest that the studied large ash-falls caused notable perturbations in shallow marine and early post-sedimentary environment.

  10. Review of the properties and uses of bentonite as a buffer and backfill material

    International Nuclear Information System (INIS)

    Research carried out by SKB on the use and behaviour of bentonite as a buffer and backfill material in a radioactive waste repository has been reviewed. The following research areas have been evaluated: mechanical properties; hydraulic and other transport properties; geochemical properties; thermal properties and resaturation; gas migration; manufacturing and emplacement procedures. This review has shown that SKB has carried out much pioneering and world-leading research on bentonite, particularly with regard to analogue studies, microtextural work and practical manufacturing and emplacement procedures. However, there are a number of subject areas which appear less well addressed than others which require further attention: The extrapolation of experimental results of the mechanical properties of bentonite to repository timescales and repository conditions should be investigated further. There is a need for detailed microstructural analysis of materials as part of experimental programmes. This would enable SKB to build confidence in the interpretations of results and reveal whether the mechanical processes occurring during experimentation truly reflect expectations of the performance of the repository. The large amount of experimental, theoretical, empirical datasets and computer models of the mechanical properties of bentonite need to be collated to form a database which is assessable and relevant to those involved in performance assessment calculations. At present, the valuable results of many excellent research projects on mechanical properties of bentonite buffer are not readily available. There seems to be a relatively poor understanding of the mechanisms of radionuclide diffusion through compacted bentonite. Other international work suggests that diffusion coefficients are much lower than those applied by SKB in its PA work. The importance of surface diffusion to describe diffusion in bentonite for certain chemical species ascribed by SKB is not reflected in

  11. Review of the properties and uses of bentonite as a buffer and backfill material

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D.; Lind, A. [QuantiSci Ltd., Melton Mowbray (United Kingdom); Arthur, R.C. [QuantiSci lnc., Denver, CO (United States)

    1999-05-01

    Research carried out by SKB on the use and behaviour of bentonite as a buffer and backfill material in a radioactive waste repository has been reviewed. The following research areas have been evaluated: mechanical properties; hydraulic and other transport properties; geochemical properties; thermal properties and resaturation; gas migration; manufacturing and emplacement procedures. This review has shown that SKB has carried out much pioneering and world-leading research on bentonite, particularly with regard to analogue studies, microtextural work and practical manufacturing and emplacement procedures. However, there are a number of subject areas which appear less well addressed than others which require further attention: The extrapolation of experimental results of the mechanical properties of bentonite to repository timescales and repository conditions should be investigated further. There is a need for detailed microstructural analysis of materials as part of experimental programmes. This would enable SKB to build confidence in the interpretations of results and reveal whether the mechanical processes occurring during experimentation truly reflect expectations of the performance of the repository. The large amount of experimental, theoretical, empirical datasets and computer models of the mechanical properties of bentonite need to be collated to form a database which is assessable and relevant to those involved in performance assessment calculations. At present, the valuable results of many excellent research projects on mechanical properties of bentonite buffer are not readily available. There seems to be a relatively poor understanding of the mechanisms of radionuclide diffusion through compacted bentonite. Other international work suggests that diffusion coefficients are much lower than those applied by SKB in its PA work. The importance of surface diffusion to describe diffusion in bentonite for certain chemical species ascribed by SKB is not reflected in

  12. Experimental Study on Volume Change Indices of Bentonite Soils

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper reports experimental results regarding statically compacted clay specimens to study the volume change behavior of bentonites. The volume change indices such as the coefficients of compressibility, volume compressibility, and consolidation ( i. e.av , mv and cv respectively) and the saturated coefficient of permeability k at different surcharge pressures were determined with the commonly adopted procedures. The swell potentials, swelling pressures, different phases of the swollen specimens were analyzed for the volume change behavior during compression. Experimental results revealed that the swell potential is dependent on the initial dry density, the initial water content and the vertical pressure at which the clay specimens were allowed to swell. The swelling pressure was found to be similar for the specimens with varying water content, showing strong dependency on the initial void ratio. The compression indices ( viz. mv and av) of saturated specimens decreased with an increase in the vertical pressure. About 80% to 90% of the volume change occurred in the primary compression phase under any given vertical pressure. The coefficient of consolidation cv and the saturated coefficient of permeability k decreased with an increase in the vertical pressure.

  13. Thermal detoxification and bloating of chromium(VI) with bentonite

    International Nuclear Information System (INIS)

    This study stabilizes and bloats Cr(VI)-sorbed bentonite by heating at high temperature. Cr leaching decreases with increasing temperatures. Heating the sample at 1100 oC results in a non-detectable Cr concentration in the leachate, equivalent to a Cr leaching percent less than 0.001% (i.e., Cr TCLP concentration -1 of leachate). Morphology observed with a scanning electron microscopy indicates the occurrence of sintering of the sample heated at 1100 oC. The heated samples also show the occurrence of a vesicant process at 1100 oC. X-ray absorption spectroscopy results indicate that heating at 500 oC for 4 h can convert approximately 87% Cr(VI) into Cr(III) that is negligibly toxic; Cr2O3 was detected to be the most abundant Cr species. After heating at higher temperatures, namely 900-1100 oC, almost all doped Cr(VI) is reduced to Cr(III) as inferred from the height of the pre-edge peak of XANES spectra and/or from XANES simulation.

  14. Modelling the in situ performance of bentonite-sand buffer

    International Nuclear Information System (INIS)

    In the Canadian nuclear fuel waste management concept, a number of engineered barriers, such as the bentonite-sand buffer which surrounds the waste container in the emplacement boreholes, are used to inhibit the transport of radionuclides. The buffer material is also required to effectively conduct heat from the fuel-waste containers to the surrounding rock. To a large extent, in situ buffer performance will depend on the degree of moisture within the buffer. The moisture content will in turn depend on temperature, temperature gradients, and buffer initial and moisture flux boundary conditions. Modelling of coupled heat and moisture transport in the buffer before resaturation is necessary to assess in situ buffer performance. This paper describes the results of a parametric study using the Philip and de Vries coupled heat and moisture transport model to assess the effects of variations in the moisture diffusivity parameters and the boundary conditions on buffer performance. The results show that the thermal performance of the buffer is affected by heat-induced moisture movement. In particular, the thermal vapor diffusivity, DTvap, has the most significant effect on thermal drying in a closed system. Work is currently underway to improve capability to model coupled heat and moisture transport in buffer. Laboratory experiments are in progress to more accurately define the moisture diffusivity parameters and the model is being modified to include the effects of boundary moisture fluxes and pressure potentials so that the resaturation process may be modelled

  15. Adsorption Properties of Bentonite with In Situ Immobilized Polyaniline Towards Anionic Forms of Cr(VI), Mo(VI), W(VI), V(V)

    OpenAIRE

    Kateryna RYABCHENKO; Elina YANOVSKA; Mariya MELNYK; Dariusz STERNIK; Olga KYCHKIRUK; Valentun TERTYKH

    2016-01-01

    A new composite material bentonite-PANI was synthesized by in situ immobilization of polyaniline (PANI) on the surface of natural mineral bentonite. It was established as a result of the modification of bentonite a surface area and an interlayer distance of mineral decrease and particles of bentonite transformed of irregular shape with different porosity on irregularly shaped particles of smaller size. It has been found that the total Cr(VI) ions extraction took place under the acid condition...

  16. Rational Formulation of Alternative Fuels using QSPR Methods: Application to Jet Fuels Développement d’un outil d’aide à la formulation des carburants alternatifs utilisant des méthodes QSPR (Quantitative Structure Property Relationship: application aux carburéacteurs

    Directory of Open Access Journals (Sweden)

    Saldana D.A.

    2013-06-01

    éveloppement et l’application de méthodes QSPR (Quantitative Structure Property Relationship permettant de relier la structure aux propriétés d’une molécule. Les produits étudiés sont les hydrocarbures (normal et iso-paraffines, naphtènes, aromatiques, etc. et les oxygénés du type alcools et esters. Les propriétés ciblées sont celles figurant dans les spécifications carburants telles que le point d’éclair, l’indice de cétane, la masse volumique et la viscosité. Les modèles prédictifs des propriétés des corps purs ont été établis à partir de données expérimentales de référence provenant en grande partie de la littérature. L’utilité de tels modèles dans la sélection de composés d’intérêt peut être montrée par exemple pour trouver le meilleur compromis pour satisfaire les critères de tenue à froid et de masse volumique des paraffines. Ainsi, si la chaîne carbonée est trop longue alors le critère de tenue à froid risque de ne pas être satisfait. Il est alors nécessaire de favoriser la ramification ou d’ajouter des bases ayant une bonne tenue à froid comme certains naphtènes ou monoaromatiques alkylés. Cependant, cela entraîne bien souvent une masse volumique trop basse par rapport à la spécification. Là encore l’ajout de naphtènes ou de monoaromatiques alkylés issus de la biomasse peut être intéressant.

  17. Adsorption behavior of a textile dye of Reactive Blue 19 from aqueous solutions onto modified bentonite

    International Nuclear Information System (INIS)

    The aim of this study is to evaluate adsorption kinetics, isotherms and thermodynamic parameters of Reactive Blue 19 (RB19) onto modified bentonite from aqueous solutions. The effects of pH, contact time, initial dye concentration and temperature were investigated in the experimentally. Natural bentonite was modified by using 1,6-diamino hexane (DAH) as a modifying agent. The characterization of modified bentonite (DAH-bentonite) was accomplished by using FTIR, TGA, BET and elemental analysis techniques. The optimum pH value for the adsorption experiments was found to be 1.5 and all the experiments were carried out at this pH value. The pseudo-second-order kinetic model agrees very well with the experimental results. Equilibrium data were also fitted well to the Langmuir isotherm model in the studied concentration range of RB19 at 20 deg. C. The results indicate that DAH-modified bentonite is a suitable adsorbent for the adsorption of textile dyes.

  18. Effect of bentonite on muscle radioactivity in pigs and sheep contaminated repeatedly with radiocesium

    International Nuclear Information System (INIS)

    Twelve pigs and twelve sheep were contaminated daily with Cs-137 for 21 days. The animal feed was fortified with a 10% supplement of bentonite. Control and bentonite-fed animals were slaughtered 7, 14 and 21 days after contamination and 7 and 14 days after contamination ceased. Samples (1 g) collected from 6 various parts of muscles (joint, jam, sirloin, chuck, heart and tongue) were measured radiometrically. Pigs fed bentonite showed muscle Cs-137 levels reduced by 70.3, 70.9 and 71.6% after 7, 14 and 21 days, respectively, as compared to those in the controls. Sheep fed bentonite showed Cs-137 radioactivity decreased by 83.7, 88.9% after 7 and 14 days, respectively. When the contamination ceased the Cs-137 levels were reduced by about 80.4% and 83.7% after 7 and 14 days, respectively, compared to those in the controls. The marked reduction of radiocesium from pig and sheep tissues emphasized, from an economic point of view, the importance of bentonite use. (author)

  19. FACTORS AFFECTING THE HYDRAULIC BARRIER PERFORMANCE OF SOIL-BENTONITE MIXTURE CUT-OFF WALL

    Science.gov (United States)

    Takai, Atsushi; Inui, Toru; Katsumi, Takeshi; Kamon, Masashi; Araki, Susumu

    Containment technique using cut-off walls is a valid method against contaminants in subsurface soil and/or groundwater. This paper states laboratory testing results on hydraulic barrier performance of Soil-Bentonite (SB), which is made by mixing bentonite with in-situ soil. Since the bentonite swelling is sensitive to chemicals, chemical compatibility is important for the hydraulic barrier performance of SB. Hydraulic conductivity tests using flexible-wall permeameter were conducted on SB specimens with various types and concentrations of chemicals in the pore water and/or in the permeant and with various bentonite powder contents. As a result, hydraulic barrier performance of SB was influenced by the chemical concentration in the pore water of original soil and bentonite powder content. In the case that SB specimens have damage parallel to the permeating direction, no significant leakage in the SB occurs by the self-sealing property of SB. In addition, the hydraulic conductivity values of SB have excellent correlation with their plastic indexes and swelling pr essures, thus these properties of SB have some possibility to be indicators for estimation of the hydraulic barrier performance of SB.

  20. Photodegradation of Methylene Blue by TiO2-Fe3O4-Bentonite Magnetic Nanocomposite

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2015-01-01

    Full Text Available Fe3O4-bentonite nanoparticles have been prepared by a coprecipitation technique under a nitrogen atmosphere. An aqueous suspension of bentonite was first modified with FeCl2 and FeCl3. TiO2 was then loaded onto the surface of the Fe3O4-bentonite by a sol-gel method. After sufficient drying, the colloidal solution was placed in a muffle furnace at 773 K to obtain the TiO2-Fe3O4-bentonite composite. The material has been characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD analysis, and vibrating sample magnetometry (VSM. Morphological observation showed that Fe3O4 and TiO2 nanoparticles had been adsorbed on the surface of bentonite nanoneedles. The material was then applied for the photodegradation of the azo dye methylene blue (MB. It was found that the removal efficiency of MB exceeded 90% under UV illumination, and that only a 20% mass loss was incurred after six cycles. The composite material thus showed good photocatalytic performance and recycling properties.

  1. Modeling cation diffusion in compacted water-saturated Na-bentonite at low ionic strength

    International Nuclear Information System (INIS)

    Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm-3 (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.2 kg dm-3

  2. Microbial incidence on copper and titanium embedded in compacted bentonite clay

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Joergen; Lydmark, Sara; Edlund, Johanna; Paeaejaervi, Anna; Pedersen, Karsten (Microbial Analytics Sweden AB (Sweden))

    2011-10-15

    The incidence of bacteria on metal surfaces was examined in an experimental setting simulating conditions of the proposed Swedish concept for disposal of spent nuclear fuel. Titanium and copper rods were embedded in compacted bentonite clay saturated with groundwater collected at a depth of 450 m. Bentonite blocks were exposed to an external flux of groundwater with or without added lactate or H{sub 2} for up to 203 days. Bacterial accumulation on metal rods and in the surrounding bentonite was analyzed using real-time quantitative PCR (qPCR), with genetic markers for overall bacterial presence (16S rDNA) as well as specific for sulfate-reducing bacteria (apsA). Clay species composition was analyzed by cloning and sequencing 16S rDNA extracted from the clay. Results suggest limited bacterial accumulation on metal surfaces, amounting to a maximum of approximately 106 apsA copies cm-2, corresponding to a 3.7% coverage of metal surfaces. Bacterial species composition appeared to be a mix of species originating from the bentonite clay and from the added groundwater, including an apparently high proportion of sulfate-reducing bacteria. While titanium surfaces exhibited higher bacterial presence than did copper surfaces, neither the degree of bentonite compaction nor the addition of lactate or H{sub 2} appeared to have any effect on the bacterial incidence on metal surfaces

  3. THE IMPACT OF LABORATORY AIR TEMPERATURE AND RELATIVE HUMIDITY ON BENTONITE WATER ABSORPTION CAPACITY

    Directory of Open Access Journals (Sweden)

    Helena Strgar

    2011-12-01

    Full Text Available Bentonite, which is a mineral component of geosynthetic clay liners, has important physical and chemical properties that ensure very small hydraulic permeability. The main component of bentonite is a clay mineral called sodium montmorillonite whose very low permeability is due to its ability to swell. The deposits of bentonite are spread all over the world, however, only a very small number of those deposits satisfies all the quality and durability demands that must be met if the bentonite is to be used in the sealing barriers. Depending on the location of installation and their purpose, geosynthetic clay liners must meet certain requirements. Their compatibility with the prescribed criterion is confirmed through various laboratory procedures. Amongst them are tests examining the index indicators (free swell index, fluid loss index, and water absorption capacity. This paper presents results regarding the impact of laboratory air temperature and relative humidity of the testing area on the water absorption capacity. This is one of the criteria that bentonite must satisfy during the quality and durability control of the mineral component of geosynthetic clay liner (the paper is published in Croatian.

  4. Heat and Radiation Effects on Iodide Sorption by Surfactant Modified Bentonite (SMB)

    International Nuclear Information System (INIS)

    Radioactive waste repository is designed using multiple barriers to prevent the release of radionuclides to environments. Bentonite has been used as engineering barrier in many countries. Although the bentonite is an effective sorbent for cationic radionuclides, it is not good for anions such as 129-I and 99-Tc because of negative surface charges over the pH. Radioactive iodine exists usually as anions such as iodate (IO3-) and iodide (I-) as stable iodine species in groundwater environments. Therefore, the iodine is one of the most difficult elements for its transport through engineering barrier (i. e., bentonite) to be controlled by sorption processes in the geological repository. We modified the bentonite using a cationic surfactant to enhance iodine sorption capability. The goal of this study is addressed to evaluate the effects of sorption of high heat and radiation on iodide sorption to surfactant modified bentonite (SMB) which can be used as engineering barrier in the repository. The iodide sorption on the SMBs was significantly affected by temperature conditions rather than radiation. As temperature increases, the iodide sorption decreases. Considering the similar sorption abilities between 100 and 200% SMBs, the 100% SMB is economical sorbent to apply for engineering barrier in a geological repository

  5. Polypropylene Fiber Amendments to Alleviate Initiation and Evolution of Desiccation Cracks in Bentonite Liners

    Science.gov (United States)

    Tuller, M.; Gebrenegus, T. B.

    2009-12-01

    Sodium saturated bentonite is a major constituent of compacted and geosynthetic liners and covers for hydraulic isolation of hazardous waste, playing a crucial role in protecting groundwater and other environmental resources from harmful landfill leachates. Due to favorable hydraulic properties (i.e., low permeability), large surface area and associated adsorption capacity for particular contaminants, and relative abundance and low cost, bentonite is the material of choice in many modern waste containment systems. However, long-term interactions between bentonite and waste leachate and exposure of bentonite to desiccative conditions may significantly deteriorate liner or cover performance and ultimately lead to failure of containment systems. In the presented study, the potential usefulness of polypropylene fiber amendments for preventing initiation and evolution of desiccation cracks, while maintaining acceptably low permeability under saturated conditions was investigated. Well-controlled desiccation experiments were conducted using initially saturated bentonite-sand mixtures that contained varying amounts of polypropylene fibers. Initiation and evolution of surface cracks were observed by means of X-Ray Computed Tomography (CT). Advanced image analysis techniques were employed to characterize and quantify 2-D and 3-D features of the evolving crack networks. Potential negative effects of employed additives on saturated hydraulic conductivity were determined with fully-automated Flexible Wall Permeametry (FWP).

  6. Modeling cation diffusion in compacted water-saturated sodium bentonite at low ionic strength.

    Science.gov (United States)

    Bourg, Ian C; Sposito, Garrison; Bourg, Alain C M

    2007-12-01

    Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the "macropore/nanopore" model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the "surface diffusion" model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm(-3) (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.3 kg dm(-3). PMID:18186346

  7. Role of bentonite colloids on europium and plutonium migration in a granite fracture

    International Nuclear Information System (INIS)

    To establish when the presence of colloids can favour contaminant migration is a critical task for the performance assessment of a high level radioactive waste repository. In this study, the effects of the presence of bentonite colloids on the migration of highly sorbing elements, such as Eu and Pu, in a granite environment were investigated. Special efforts were made to quantify the filtration of bentonite colloids in this medium and to determine the experimental uncertainties that could bias the interpretation of the results. The migration of bentonite colloids in a granite fracture was studied in the laboratory by dynamic column experiments under low water flow rates (4-11 mL/h). The breakthrough curves of bentonite colloids always showed a peak in a similar position to conservative tracers, but the colloids recovery critically depended on their initial concentration and on the water flow rate. In the presence of colloids, the breakthrough curves of Eu and Pu always showed a peak in the same position as conservative tracers, thus indicating the migration of these radionuclides to be mostly colloid-driven. The recovery of Pu adsorbed onto the colloids was approximately that expected when the experimentally determined bentonite colloid filtration in the column was accounting for but the Eu recovery was always significantly lower

  8. Swelling deformation characteristics of Gaomiaozi bentonite-sand mixture inundated in water

    International Nuclear Information System (INIS)

    A bentonite from Gaomiaozi, Xinghe County, Inner Mongolia, has been regarded as the first choice for using as buffer/backfill materials in the high-level waste geological disposal in China. In this paper, one-dimensional swelling deformation tests, collapse tests and swelling pressure tests due to wetting were carried out on Gaomiaozi sodium bentonite by using oedometer, for analyzing the swelling and collapse deformation characteristics of mixtures of bentonite and quartz sand in different sand additions. Based on the concept of the montmorillonite void ratio, the de- formation characteristics of bentonite-sand mixtures at saturation were consistently identified. Test results indicated that when the content of sand in the mixture is small, the relationship between the montmorillonite void ratio and vertical pressure at saturation is a straight line in the log scales. For different kinds of bentonites, the relationship is different; Test results of the mixture with high sand fractions were analyzed by using the sand skeleton void ratio, which can predict whether the sand skeleton forms and the vertical pressure when the sand skeleton begins to form. (authors)

  9. Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

    International Nuclear Information System (INIS)

    The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs

  10. Transport of heavy metals and chemical compatibility of hydraulic conductivity of a compacted sand-bentonite mixture

    Directory of Open Access Journals (Sweden)

    Nanthanit Charoenthaisong

    2008-03-01

    Full Text Available Clayey soils are usually used as barrier material in landfill liners because of its low hydraulic conductivity and high sorption capacity. Bentonite, which consists mainly of montmorillonite, has a high cation exchange capacity resulting in a high retention capacity of heavy metals. Sand is a permeable material but its hydraulic conductivity decreases significantly when mixed with bentonite. However, using a sand-bentonite mixture as landfill liners is questionable, because the hydraulic conductivity of the sand-bentonite mixture may increase when permeated with heavy metal solutions, which are normally found in landfill leachates. In this paper, transport of heavy metals through a compacted sand-bentonite mixture and its chemical compatibility were studied through the batch adsorption test, the column test, and the hydraulic conductivity test.Experimental results indicate that the sorption capacity of the bentonite, ranked in descending order, was Cr3+, Pb2+, Cd2+, Zn2+, and Ni2+, respectively. The diffusion coefficients of the sand-bentonite mixture were in the order of 10-5 cm2/s and the retardation factors were 130, 115, 111, and 90 for Pb2+, Ni2+, Zn2+, and Cd2+, respectively. The hydraulic conductivity of thesand-bentonite mixture was only compatible with a chromium solution having a concentration not greater than 0.001 M.

  11. Model for diffusion and porewater chemistry in compacted bentonite. Experimental arrangements and preliminary results of the porewater chemistry studies

    International Nuclear Information System (INIS)

    This report describes the progress of the experimental research on the porewater chemistry in bentonite. The research is part of the project Microstructural and chemical parameters of bentonite as determinants of waste isolation efficiency within the Nuclear Fission Safety Program organized by The Commission of the European Communities. The study was started by a literature overview on the properties of bentonite, porewater-sampling methods and obtained results. On the basis of the literature study, porewater extraction by squeezing seemed the most promising method for further development. The apparatus developed in this study consists of a pressing apparatus, which is used to create the necessary long-term compression, and of the compaction cell where porewater is separated from bentonite and collected in a syringe. The constant log-term force is maintained by a strong spring. An experimental study of solution-bentonite interactions was initiated. The parameters varied are the bentonite density, bentonite-water ratio, composition of the solutions, and the composition of bentonite. The report presents the experimental arrangements, the preliminary results for studying the evolution of water chemistry and the results of pre-modelling. (orig.) (27 refs.)

  12. CRIEPI's research results (2006-2011) and clarified future issues on alteration behavior of bentonite barrier by alkaline solutions

    International Nuclear Information System (INIS)

    In radioactive waste disposal facilities, bentonite barrier would be altered by alkaline solutions which arise by leaching of cementitious materials. Consequently suitable properties of the bentonite barrier would be degraded for a long time period. In CRIEPI, the investigation on the alteration of the bentonite under alkaline conditions was started in 2006, and several CRIEPI reports have been published. Specifically, we have investigated the kinetics of montmorillonite dissolution, the mineralogical alteration of compacted bentonite (with high- and low-dry density) and the change of permeability of the compacted bentonite (with high- and low-dry density) during alteration under the alkaline conditions. Furthermore, stability of saponite, which has similar physical properties to the bentonite, under the alkaline conditions was also examined. In this report, we show the outline of those research results, and lay out the clarified future issues extracted from our results. Ten clarified future issues were divided three categories as follows: 1) the estimation of the alteration behavior of the bentonite by alkaline solutions, 2) the elucidation of the mechanism of physical properties (e.g., permeability, swelling properties and mechanistic properties) change of the compacted bentonites during alteration, and 3) the development of the model building and simulation technology concerning the change in physical properties during alteration under alkaline conditions. (author)

  13. A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, L.; Samper, J.; Montenegro, L.

    2011-04-01

    The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collected after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO{sub 2}(g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO{sub 3}{sup -} and pH data cannot be explained solely by solute transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions.

  14. Thermodynamic modelling of bentonite-groundwater interaction and implications for near field chemistry in a repository for spent fuel

    International Nuclear Information System (INIS)

    Predictions of near field geochemistry are made using a thermodynamic model for bentonite/ground interaction. This model is a refinement and extension of the model developed by the senior author. It is based on recent experiments performed at high solid/water ratio and adapted to the Swedish type of HLW repository design. Thus, from the obtained experimental results on solution composition, the model includes chemical reactions resulting from both the impurities and the main clay fraction within the bentonite. Ion exchange reactions are treated both with and without the contribution of edge sites. Due to its thermodynamic basis, the model exhibits prediction capability over a wide range of conditions in terms of solid/water ratio. The modelling of repository conditions implies, due to the lack of experimental information, simplifications with regard to thermodynamic properties of the bentonite. This mainly involves the non-consideration of the temperature effects and of the acid/base properties of the solid. Nevertheless, our results yield insight into important processes affecting porewater chemistry. Thus, the model suggests that proton exchange reactions may exert a strong control on calcite dissolution within highly compacted bentonite. Estimations of chemical changes over time in the bentonite were done in the basis of a mixing tank model. These results indicate transformation of Na-bentonite to Ca-bentonite over time. The extent of this process, however, critically depends on the amount of carbonate present in the bentonite. (authors) (34 refs.)

  15. Report on Thermo-Hydro-Mechanical Laboratory Tests Performed by CIEMAT on Febex Bentonite 2004-2008

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gomez-Espina, R.

    2009-11-25

    The results of the laboratory studies performed by CIEMAT with the FEBEX bentonite in the context of WP3.2 of the NF-PRO Project and of the Agreement ENRESA-CIEMAT Anexo V are presented and analysed in this report. They refer to the effect of the hydraulic gradient on the permeability of bentonite, the effect of the thermal gradient on the hydration kinetics of bentonite, and the repercussion of temperature on the hydro-mechanical properties of bentonite (swelling, permeability and water retention capacity). In all the cases the bentonite has been used compacted to densities expected in the engineered barrier of a high-level radioactive waste repository. The existence of threshold and critical hydraulic gradients has been observed, both of them dependent on bentonite density and water pressures. After more than seven years of hydration, the 40-cm high bentonite columns are far from full saturation, the thermal gradient additionally delaying the process, which is very slow. Temperatures below 100 degree centigrade slightly decrease the swelling and the water retention capacity of the bentonite and increase its permeability. The information obtained improves the knowledge on the behaviour of expansive clay and will help the development of constitutive models and the interpretation of the results obtained in the mock-up and the in situ tests. (Author) 35 refs.

  16. Time evolution of the general characteristics and Cu retention capacity in an acid soil amended with a bentonite winery waste

    DEFF Research Database (Denmark)

    Fernandez Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula;

    2015-01-01

    The effect of bentonite waste added to a "poor" soil on its general characteristic and copper adsorption capacity was assessed. The soil was amended with different bentonite waste concentrations (0, 10, 20, 40 and 80Mgha-1) in laboratory pots, and different times of incubation of samples were...

  17. MX-80 Bentonite. Thermal-Hydro-Mechanical Characterisation Performed at CIEMAT in the Context of the Prototype Project

    International Nuclear Information System (INIS)

    This document details the results of the thermo-hydro-mechanical (THM) characterisation of the commercial MX-80 bentonite performed by CIEMAT from 2001 to 2004 in the context of a project carried out at the AEspoe Hard Rock Laboratory (Sweden), the Prototype Repository. The swelling pressure and the permeability of the bentonite compacted to different dry densities has been determined, as well as the influence of the permeant salinity on hydraulic conductivity. The influence of salinity on the retention capacity of the compacted bentonite has been studied. For that, a new methodology has been designed. Water retention curves have been determined at temperatures of 20 and 600C. Suction controlled odometer tests have been performed at 20oC. Finally, the behaviour of the MX-80 bentonite has been compared to that of the Spanish FEBEX bentonite. (Author) 13 refs

  18. Leachability of bentonite/cement for medium-level waste immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Hamlat, M.S.; Rabia, N. [Centre de Radioprotection et de Surete, Alger-Gare (Algeria)

    1998-12-31

    The release of radionuclides from Algerian bentonite/cement matrix has been measured experimentally using static and dynamic testing procedures. The waste forms were cement/sand and bentonite/cement matrices contaminated with Cs-137. To characterise radionuclide/waste form combination, two parameters, diffusion (D) and distribution coefficients ({alpha}) were used. (D) is an effective diffusion coefficient that describes the kinetic behaviour and is most easily determined using Soxhlet test, whereas, ({alpha}) describes the distribution of radionuclide between aqueous and solid phases at equilibrium and is best measured in static test. Leach rates obtained being very low. Distribution coefficient values have showed that the bentonite has relatively a high degree of fixation. It was concluded that the matrix under study seems play a role for the immobilisation. (orig.)

  19. Diffusion of Radionuclides in Bentonite Clay - Laboratory and in situ Studies

    International Nuclear Information System (INIS)

    This thesis deals with the diffusion of ions in compacted bentonite clay. Laboratory experiments were performed to examine in detail different processes that affect the diffusion. To demonstrate that the results obtained from the laboratory investigations are valid under in situ conditions, two different kinds of in situ experiments were performed. Laboratory experiments were performed to better understand the impact of ionic strength on the diffusion of S2+ and Cs+ ions, which sorb to mineral surfaces primarily by ion exchange. Furthermore, surface related diffusion was examined and demonstrated to take place for Sr2+ and Cs+ but not for Co2+, which sorbs on mineral surfaces by complexation. The diffusion of anions in bentonite clay compacted to different dry densities was also investigated. The results indicate that anion diffusion in bentonite clay consists of two processes, one fast and another slower. We ascribe the fast diffusive process to intralayer diffusion and the slow process to diffusion in interparticle water, where anions are to some extent sorbed to edge sites of the montmorillonite. Two different types of in situ experiments were performed, CHEMLAB and LOT. CHEMLAB is a borehole laboratory, where cation (Cs+, Sr2+ and Co2+) and anion (I- and TcO4-) diffusion experiments were performed using groundwater from a fracture in the borehole. In the LOT experiments cylindrical bentonite blocks surrounding a central copper rod were placed in a 4 m deep vertical borehole. The borehole was then sealed and the blocks are left for 1, 5 or >> 5 years. When the bentonite was water saturated the central copper rod is heated to simulate the temperature increase due to radioactive decay of the spent fuel. Bentonite doped with radioactive Cs and Co was placed in one of the lower blocks. Interestingly, the redox-sensitive pertechnetate ion (TcO4-) which thermodynamically should be reduced and precipitate as TcO2 n H2O, travelled unreduced through the bentonite

  20. Rebounding process of moulding sands-thermal degradation of bentonite binding qualities

    Directory of Open Access Journals (Sweden)

    R. Dańko

    2010-01-01

    Full Text Available Problems related to a gradual degradation of binding qualities of montmorillonite, the main component of foundry bentonites, are presented in the paper. This degradation is caused by high temperatures originated from liquid metal influencing moulding sands. Laboratory measurements of an active binding agent content in classic moulding sands prepared with two types of bentonite and subjected to a controlled heating to high temperatures – were performed. These laboratory examinations were compared to industrial tests, in which a temperature distribution was being determined in several places in the thickness of the casting ingot mould for 24 hours from the moment of pouring liquid metal. On the basis of the performed examinations, the method allowing to determine optimal additions in the rebounding process of the tested bentonites was developed.