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Sample records for bentonite deposit cabo

  1. Occurrence of Fe-Mg-rich smectites and corrensite in the Morron de Mateo bentonite deposit (Cabo de Gata region, Spain): A natural analogue of the bentonite barrier in a radwaste repository

    Energy Technology Data Exchange (ETDEWEB)

    Pelayo, M., E-mail: m.pelayo@ciemat.es [Departamento de Medio Ambiente, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Garcia-Romero, E. [Departamento de Cristalografia y Mineralogia, Facultad C.C. Geologicas, UCM, 28040 Madrid (Spain); Labajo, M.A.; Perez del Villar, L. [Departamento de Medio Ambiente, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain)

    2011-07-15

    Highlights: > A hydrothermal process transformed Fe-Mg smectites into corrensite. > This transformation was favoured by the intrusion of the Morron de Mateo dome. > The intrusion caused a temperature increased and a supply of Fe-Mg rich solutions. > The system can be a good natural analogue of bentonite barrier in a radwaste disposal. > Experimental studies of stability of bentonite are in agreement with the results. - Abstract: The Morron 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 hydrothermally altered pyroclastic (white tuffs) and epiclastic rocks (mass flow), located in the NE sector of the Morron de Mateo deposit are described. White tuffs have a high content of phyllosilicates, mainly composed of dioctahedral smectites, while mass flow have a higher proportion of inherited minerals, the neoformed phyllosilicates are dioctahedral smectites and an interlayer chlorite/smectite mineral of corrensite type. The chemical composition of smectites reflects the different nature of the parent rocks, in such a way that smectites from white tuffs have a quite homogeneous chemical composition and their structural formulae correspond to montmorillonite type, while smectites from mass flow show more chemical variability, higher Fe and Mg contents and a mean structural formulae corresponding to Fe-Mg-rich beidellite and/or to an intermediate smectite member between beidellite and saponite. In addition, chemical composition and textural features of corrensite-like clay minerals in relation to Fe-Mg-rich smectites in the samples have also been studied, suggesting

  2. Occurrence of Fe-Mg-rich smectites and corrensite in the Morron de Mateo bentonite deposit (Cabo de Gata region, Spain): A natural analogue of the bentonite barrier in a radwaste repository

    International Nuclear Information System (INIS)

    Pelayo, M.; Garcia-Romero, E.; Labajo, M.A.; Perez del Villar, L.

    2011-01-01

    Highlights: → A hydrothermal process transformed Fe-Mg smectites into corrensite. → This transformation was favoured by the intrusion of the Morron de Mateo dome. → The intrusion caused a temperature increased and a supply of Fe-Mg rich solutions. → The system can be a good natural analogue of bentonite barrier in a radwaste disposal. → Experimental studies of stability of bentonite are in agreement with the results. - Abstract: The Morron 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 hydrothermally altered pyroclastic (white tuffs) and epiclastic rocks (mass flow), located in the NE sector of the Morron de Mateo deposit are described. White tuffs have a high content of phyllosilicates, mainly composed of dioctahedral smectites, while mass flow have a higher proportion of inherited minerals, the neoformed phyllosilicates are dioctahedral smectites and an interlayer chlorite/smectite mineral of corrensite type. The chemical composition of smectites reflects the different nature of the parent rocks, in such a way that smectites from white tuffs have a quite homogeneous chemical composition and their structural formulae correspond to montmorillonite type, while smectites from mass flow show more chemical variability, higher Fe and Mg contents and a mean structural formulae corresponding to Fe-Mg-rich beidellite and/or to an intermediate smectite member between beidellite and saponite. In addition, chemical composition and textural features of corrensite-like clay minerals in relation to Fe-Mg-rich smectites in the samples have also been studied

  3. Chemical and Mineralogical Features of Smectite from the Morron de Mateo Bentonite Deposit (Cabo de Gata, Almeria) in Relation to the Parent Rocks and the Alteration Processes Occurred After the Bentonite Formation: Analogies and Implications for the Engineered Clayey Barrier of a Deep Geological Rad waste Repository

    International Nuclear Information System (INIS)

    Pelayo, M.; Labajo, M. A.; Garcia Romero, L.; Perez del Villar, L.

    2009-01-01

    The Morron de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on the clayey barrier of a Deep Geological Rad waste Repository (DGRR) after its closure, in relation to the radioactive decay of the fission products and the container corrosion. This bentonite deposit and their host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the bioclastic calcarenite beds close to the dome. Bentonite from the NE sector of the deposit have been chemically and mineralogically characterized. Pyroclastic rocks (white tuffs), epyclastic rocks (mass flow) and andesitic breccia all of them hydrothermally altered, have been studied at the site. Samples are composed of feldspars, quartz and amphybols, as inherited minerals, and phyllosilicates, zeolites, crystoballite and calcite, as new formed minerals. White tuffs have the highest phyllosilicate contents, mainly dioctahedral smectite of montmorillonite type. Epyclastic rocks and andesitic breccia have a highest proportion of inherited minerals, the new formed phillosilicates being di octahedral smectite of beidellite type and an ordered interlayer chlorite/smectite mineral, of corrensite type. Smectite from the epyclastic rocks have higher Fe and Mg contents and chemical variability, as a consequence of nature of their parent rocks. The presence of corrensite in the epyclastic rocks suggests that in the Morron de Mateo area a propilitic alteration process occurred after bentonite formation, which transformed Fe-Mg-rich smectite into corrensite. This transformation was probably favoured by the sub volcanic intrusion, which also produced a temperature increase in the geological media and a supply of Fe-Mg-rich solutions, which also were the responsible for the metasomatic transformations observed in the calcarenite beds. (Author) 57 refs

  4. 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)

  5. Chemical and Mineralogical Features of Smectite from the Morron de Mateo Bentonite Deposit (Cabo de Gata, Almeria) in Relation to the Parent Rocks and the Alteration Processes Occurred After the Bentonite Formation: Analogies and Implications for the Engineered Clayey Barrier of a Deep Geological Rad waste Repository; Naturaleza de las Esmectitas del Yacimiento de Morron de Mateo (Cabo de Gata, Almeria) en Relacion con la Roca Madre y con los Procesos Posteriores a la Bentonitizacion: Implicaciones Analogicas para la Barrera de Ingenieria de un Almacenamiento Geologico de Residuos Radiactivos

    Energy Technology Data Exchange (ETDEWEB)

    Pelayo, M; Labajo, M A; Garcia Romero, L; Perez del Villar, L

    2009-10-12

    The Morron de Mateo bentonite deposit is being studied as a natural analogue of the thermal and geochemical effects on the clayey barrier of a Deep Geological Rad waste Repository (DGRR) after its closure, in relation to the radioactive decay of the fission products and the container corrosion. This bentonite deposit and their host rocks were intruded by a rhyodacitic volcanic dome that induced a hydrothermal metasomatic process affecting the bioclastic calcarenite beds close to the dome. Bentonite from the NE sector of the deposit have been chemically and mineralogically characterized. Pyroclastic rocks (white tuffs), epyclastic rocks (mass flow) and andesitic breccia all of them hydrothermally altered, have been studied at the site. Samples are composed of feldspars, quartz and amphybols, as inherited minerals, and phyllosilicates, zeolites, crystoballite and calcite, as new formed minerals. White tuffs have the highest phyllosilicate contents, mainly dioctahedral smectite of montmorillonite type. Epyclastic rocks and andesitic breccia have a highest proportion of inherited minerals, the new formed phillosilicates being di octahedral smectite of beidellite type and an ordered interlayer chlorite/smectite mineral, of corrensite type. Smectite from the epyclastic rocks have higher Fe and Mg contents and chemical variability, as a consequence of nature of their parent rocks. The presence of corrensite in the epyclastic rocks suggests that in the Morron de Mateo area a propilitic alteration process occurred after bentonite formation, which transformed Fe-Mg-rich smectite into corrensite. This transformation was probably favoured by the sub volcanic intrusion, which also produced a temperature increase in the geological media and a supply of Fe-Mg-rich solutions, which also were the responsible for the metasomatic transformations observed in the calcarenite beds. (Author) 57 refs.

  6. 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

  7. 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.

  8. Sorption of strontium on bentonites from Slovak deposits

    International Nuclear Information System (INIS)

    Kufcakova, J.; Galambos, M.; Rajc, P.

    2005-01-01

    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 + , NH 4 + , Ca 2+ , Mg 2+ and Ba 2+ 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)

  9. DEPOSITS AND MINING POTENTIAL OF BENTONITE IN CROATIA

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    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.

  10. Maps showing characteristics of the Cabo Rojo West offshore sand deposit, southwestern Puerto Rico

    Science.gov (United States)

    Trumbull, James V.A.; Trias, Juan L.

    1982-01-01

    This report presents detailed information on a deposit of well-sorted coarse calcareous sand in water depths of 10-20 m in an area between 1 and 6 km west and southwest fo the promontory of Cabo Rojo, the southwesternmost corner of Puerto Rico. 

  11. Possibilities of reducing radiocesium transfer to hen eggs. II. Using bentonite from Polish geological deposits

    International Nuclear Information System (INIS)

    Rachubik, J.; Kowalski, B.

    2000-01-01

    The decontamination effectiveness of bentonite from Polish geological deposits in reducing the radiocesium transfer to hen eggs was examined. The egg white radiocesium concentration was higher than that in egg yolk. The highest decontamination efficacy in all egg components was noticed in animals treated with bentonite from the first day of radionuclide administration. Generally, the radioactivity concentration in hens treated simultaneously with 137CsCl and a cesium binder were lower by 50% than those in the controls. The decontamination efficiency lowered with the delayed bentonite treatment. In Poland bentonite seems to be an alternative to other decontamination agents. (author)

  12. Backfilling of deposition tunnels: Use of bentonite pellets

    International Nuclear Information System (INIS)

    Dixon, David; Sanden, Torbjoern; Jonsson, Esther; Hansen, Johanna

    2011-02-01

    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

  13. 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

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

    International Nuclear Information System (INIS)

    Linares, J.; Linares Gonzalez, J.; Huertas Garcia, F.; Reyes Camacho.

    1993-01-01

    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

  15. Uncertainties in pore water chemistry of compacted bentonite from Rokle deposit

    International Nuclear Information System (INIS)

    Cervinka, R.; Vejsadu, J.; Vokal, A.

    2012-01-01

    Document available in extended abstract form only. The composition of compacted bentonite pore water influences a number of important processes occurring in a deep geological repository (DGR), e.g. corrosion of waste package materials, solubility of radionuclides, or diffusion and sorption of radionuclides. Its determination is not straightforward, because it is difficult to obtain (e.g. squeeze) the pore water from compacted bentonite without changing its properties. It is therefore necessary to combine experimentally obtained parameters and geochemical modelling to approach it compositions. This article describes the results achieved in investigation the composition of pore water of compacted Ca-Mg bentonite from Czech deposits, proposed in Czech DGR concept. Ca-Mg bentonite from the largest operating deposit Rokle (Tertiary neo-volcanic area, NW Bohemia) represents complex mixture of (Ca,Mg)-Fe-rich montmorillonite, micas, kaolinite and other mineral admixtures (mainly Ca, Mg, Fe carbonates, feldspars and iron oxides). For experimental investigations the homogenized and grind raw bentonite material obtained directly from the deposit and commercial product (partly Na-activated) from supplier were used. Geochemical characterization of Rokle bentonite included mineralogical composition analyzed by Xray diffraction, cation exchange capacity determined using Cu-trien method, surface complexation parameters determined by acid-base titrations and 'geochemical' porosity derived from diffusion experiments with tracers ( 3 H and 36 Cl). Soluble salts inventory was calculated on the base of results from aqueous extracts of bentonite in deionized water at different solid to liquid ratios (from 18.6 to 125 g/l) and high pressure squeezing of water saturated bentonite at different solid to liquid ratios (from 1:1 to 4:1 w/w). The geochemical model contained cation exchange in the interlayer space and protonization and de-protonization of surface hydroxyl groups on clay

  16. Properties of the bentonite from Lieskovec deposit and their possible environmental applications

    International Nuclear Information System (INIS)

    Andrejkovicova, S.

    2008-01-01

    The community increasingly focuses on broader uses of raw materials, occurring in relatively sufficient amounts. Among them, bentonite play very important role in the environmental applications. Results presented herein are related to the yet comprehensively unexplored Fe-rich bentonite from Lieskovec deposit, Central Slovakia. The objective of this study was complex investigation of Lieskovec bentonite deposit. This bentonite was developed from andesitic pyroclastics; the dominant mineral in all the samples is iron-rich montmorillonite, covering 29 to 56 mass % in the samples. The accessory minerals include kaolinite (5-17 mass %), quartz (3-28 mass %), muscovite/illite (3-16 mass %), volcanic glass (6-14 mass %), orthoclase (1-12 mass %), opal (1-8 mass %) and cristobalite (1-3 mass %). Structural Fe(III) is mainly in phyllosilicates accounting for 70 % to 90 % of the total Fe in the unfractionated samples; less than 5 % is Fe(II). The remainder of the Fe is present in oxide and/or oxyhydroxide phases dominated by poorly ordered goethite and hematite with possibly some maghemite. Basic properties of bentonites result from the structure of the smectites. Size fractionation did not lead to pure smectite. Kaolinite and mica were not successfully removed. Quartz and feldspars were dismantled effectively. Non-clay minerals contribution decreased. Smectite content increased after separation up to 75 mass %. Low cation exchange capacities between 35 and 61 meq/100 g are caused also by low magnesium content in the octahedral sheets of montmorillonite, suggesting lower isomorphic Mg for Al substitution in the octahedral sheets of smectite and thus its lower octahedral charge. The main factor influencing CECs is smectite content affecting dominantly also the geotechnical properties. Geotechnical properties of Lieskovec bentonite, such as liquid limit in range 64-80 % and water adsorption by Enslin test 123-265 % were insufficient for utilization in geo-synthetic clay

  17. Bentonite deposits as a natural analogue to long-term barriers in a final repository of nuclear waste

    International Nuclear Information System (INIS)

    Keto, P.

    2000-01-01

    The geology of bentonite occurrences in Almeria (Spain) and Wyoming (USA) were studied in order to find suitable natural analogue to the longterm mechanical behaviour of the bentonite barrier in the final nuclear waste disposal. The study is based on literature review over both occurrence areas and on fieldwork observations from Almeria, Spain. The deposit areas differ from each other by age, deposition environment, exchangeable cation chemistry, alteration condition, occurrence and deformational features. One of the most important deformational feature in Almeria bentonites was the existence of Tertiary (Middle and Upper Miocene, 6-15.5 Ma old) bentonite intrusion inside/over younger Quaternary (Pleistocene Superior, 0.01-0.72 Ma old) sediments. This was a result of the confining pressure of overlying volcanic rocks and sediments and the high plasticity behaviour of bentonites. According to this observation, the pressure effect in final nuclear waste repositories requires further investigations. The bentonites in Wyoming have survived weathering and shearing without losing their expandability or other properties typical of smectite-rich materials. (orig.)

  18. Predictive mapping using GIS to locate epithermal gold deposits at Cabo de Gata (Prov. of Almeria, Spain); Cartografia predictiva mediante SIG de depositos epitermales de oro en Cabo de Gata, Almeria, Espana

    Energy Technology Data Exchange (ETDEWEB)

    Rogol-Sanchez, J. P.; Chica-Olmo, M.; Rodriguez-Galiano, V.; Pardo-Iguzquiza, E.

    2011-07-01

    The main aim of mineral potential mapping is to generate predictive maps showing the spatial distribution of a numerical index of favour ability for the presence of a mineral deposit of the type sought. We have studied the mineral favorability for epithermal gold deposits in the Cabo de Gata volcanic field in the Province of Almeria in Spain. Predictive maps deriving from the models suggest the presence of several potentially favourable zones. The performance of predictive maps is similar in most cases. Nevertheless, data-driven methods are able to capture more readily the spatial distribution of known gold occurrences in the area. (Author) 32 refs.

  19. Chemical signature of two Permian volcanic ash deposits within a bentonite bed from Melo, Uruguay

    Directory of Open Access Journals (Sweden)

    Liane M. Calarge

    2006-09-01

    Full Text Available A Permian bentonite deposit at Melo, Uruguay is composed of a calcite-cemented sandstone containing clay pseudomorphs of glass shards (0-0.50 m overlying a pink massive clay deposit (0.50-2.10m. The massive bed is composed of two layers containing quartz and smectite or pure smectite respectively. The smectite is remarkably homogeneous throughout the profile: it is a complex mixed layer composed of three layer types whose expandability with ethylene glycol (2EG 1EG or 0EG sheets in the interlayer zone which correspond to low-, medium- and high-charge layers respectively varies with the cation saturating the interlayer zone. The smectite homogeneity through the profile is the signature of an early alteration process in a lagoonal water which was over saturated with respect to calcite. Compaction during burial has made the bentonite bed a K-depleted closed system in which diagenetic illitization was inhibited. Variations in major, REE and minor element abundances throughout the massive clay deposit suggest that it originated from two successive ash falls. The incompatible element abundances are consistent with that of a volcanic glass fractionated from a rhyolite magma formed in a subduction/collision geological context.Um depósito Permiano de bentonita em Melo, Uruguai,é composto por um arenito com cimento calcítico contendo pseudomorfos de argila sobre detritos vítreos(0-0.50 m superpostos a um deposito maciço de argila rosado (0.50-2.10 m. A camada maciça é composta por dois níveis contendo quartzo e esmectita ou esmectita pura, respectivamente. A homogeneidade de esmectita ao longo do perfil é notável: trata-se de um interestratificado composto de três tipos de camadas, cuja expansibilidade com etileno-glicol (folhas 2EG, 1EG ou 0EG na zona interfoliar correspondentes a camadas com baixa, média e alta carga, respectivamente variam com o tipo de cátion que satura a zona interfoliar. A homogeneidade da esmectita ao longo do perfil

  20. BENTONITE PROCESSING

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    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.

  1. Quantitative controls on location and architecture of carbonate depositional sequences: upper miocene, cabo de gata region, se Spain

    Science.gov (United States)

    Franseen, E.K.; Goldstein, R.H.; Farr, M.R.

    1998-01-01

    Sequence stratigraphy, pinning-point relative sea-level curves, and magnetostratigraphy provide the quantitative data necessary to understand how rates of sea-level change and different substrate paleoslopes are dominant controls on accumulation rate, carbonate depositional sequence location, and internal architecture. Five third-order (1-10 my) and fourth-order (0.1-1.0 my) upper Miocene carbonate depositional sequences (DS1A, DS1B, DS2, DS3, TCC) formed with superimposed higher-frequency sea-level cycles in an archipelago setting in SE Spain. Overall, our study indicates when areas of high substrate slope (> 15??) are in shallow water, independent of climate, the location and internal architecture of carbonate deposits are not directly linked to sea-level position but, instead, are controlled by location of gently sloping substrates and processes of bypass. In contrast, if carbonate sediments are generated where substrates of low slope ( 15.6 cm/ky to ??? 2 cm/ky and overall relative sea level rose at rates of 17-21.4 cm/ky. Higher frequency sea-level rates were about 111 to more than 260 cm/ky, producing onlapping, fining- (deepening-) upward cycles. Decreasing accumulation rates resulted from decreasing surface area for shallow-water sediment production, drowning of shallow-water substrates, and complex sediment dispersal related to the archipelago setting. Typical systems tract and parasequence development should not be expected in "bypass ramp" settings; facies of onlapping strata do not track base level and are likely to be significantly different compared to onlapping strata associated with coastal onlap. Basal and upper DS2 reef megabreccias (indicating the transition from cool to warmer climatic conditions) were eroded from steep upslope positions and redeposited downslope onto areas of gentle substrate during rapid sea-level falls (> 22.7 cm/ky) of short duration. Such rapid sea-level falls and presence of steep slopes are not conducive to formation of

  2. Roles of bentonite in radioactive waste disposal

    International Nuclear Information System (INIS)

    Suzuki, Keizo

    1995-01-01

    Bentonite is used in radioactive waste disposal from the following points; (1) properties (2) now utilization fields (3) how to use in radioactive waste disposal (4) how much consumption and deposits as source at the present time. Bentonite is produced as alteration products from pyroclastic rocks such as volcanic ash and ryolite, and is clay composed mainly smectite (montmorillonite in general). Therefore, special properties of bentonite such as swelling potential, rheological property, bonding ability, cation exchange capacity and absorption come mainly from properties of montmorillonite. Bentonite has numerous uses such as iron ore pelleizing, civil engineering, green sand molding, cat litter, agricultural chemicals and drilling mud. Consumption of bentonite is about 600-700 x 10 3 tons in Japan and about 10 x 10 6 tons in the world. Roles of bentonite to be expected in radioactive waste disposal are hydraulic conductivity, swelling potential, absorption, mechanical strength, ion diffusion capacity and long-term durability. These properties come from montmorillonite. (author)

  3. Cabo Verde - Private Sector Development

    Data.gov (United States)

    Millennium Challenge Corporation — The objective of the Private Sector Development Project activities of the 2005-2010 Cabo Verde Compact was to support Cabo Verde's long-term economic transformation...

  4. Dependencies of the speed of adsorption {sup 60}Co(II) from the time on the bentonite from a deposit Jelsovy potok; Zavislosti rychlosti adsorpcie {sup 60}Co(II) od casu na bentonite z lozska Jelsovy potok

    Energy Technology Data Exchange (ETDEWEB)

    Heglasova, K [Univerzita Komenskeho v Bratislave, Prirodovedecka fakulta, Katedra jadrovej chemie, 84215 Bratislava (Slovakia)

    2012-04-25

    Adsorption of cobalt on selected sorbents was studied by radioindicator method in a batch experimental arrangement. Distribution coefficients and adsorption percentage were determined for bentonite - cobalt system as a function of time mixing. For adsorption study there were selected bentonite from the alder creek area. Their main advantages are rapid ion exchange and low permeability. They are also considered as the most promising candidates in multi barrier system in repositories of radioactive waste and spent nuclear fuel. Cobalt solution at two concentrations was stirred from 15 min to 24 h. The experiment results showed that the adsorption is a time dependent process. Rapid adsorption of cobalt in the beginning and later very slow adsorption indicates two adsorption mechanisms, which are ion exchange and adsorption followed by a slow penetration of cobalt into the crystal grid of montmorillonite, the main component of bentonite. The time to reach the adsorption equilibrium was 4 hours. (authors)

  5. Earthquake induced rock shear through a deposition hole. Modelling of three model tests scaled 1:10. Verification of the bentonite material model and the calculation technique

    Energy Technology Data Exchange (ETDEWEB)

    Boergesson, Lennart (Clay Technology AB, Lund (Sweden)); Hernelind, Jan (5T Engineering AB, Vaesteraas (Sweden))

    2010-11-15

    Three model shear tests of very high quality simulating a horizontal rock shear through a deposition hole in the centre of a canister were performed 1986. The tests and the results are described by /Boergesson 1986/. The tests simulated a deposition hole in the scale 1:10 with reference density of the buffer, very stiff confinement simulating the rock, and a solid bar of copper simulating the canister. The three tests were almost identical with exception of the rate of shear, which was varied between 0.031 and 160 mm/s, i.e. with a factor of more than 5,000 and the density of the bentonite, which differed slightly. The tests were very well documented. Shear force, shear rate, total stress in the bentonite, strain in the copper and the movement of the top of the simulated canister were measured continuously during the shear. After finished shear the equipment was dismantled and careful sampling of the bentonite with measurement of water ratio and density were made. The deformed copper 'canister' was also carefully measured after the test. The tests have been modelled with the finite element code Abaqus with the same models and techniques that were used for the full scale scenarios in SR-Site. The results have been compared with the measured results, which has yielded very valuable information about the relevancy of the material models and the modelling technique. An elastic-plastic material model was used for the bentonite where the stress-strain relations have been derived from laboratory tests. The material model is made a function of both the density and the strain rate at shear. Since the shear is fast and takes place under undrained conditions, the density is not changed during the tests. However, strain rate varies largely with both the location of the elements and time. This can be taken into account in Abaqus by making the material model a function of the strain rate for each element. A similar model, based on tensile tests on the copper used in

  6. Selfinjection of highly compacted bentonite into rock joints

    International Nuclear Information System (INIS)

    Pusch, R.

    1978-02-01

    When radioactive waste is disposed in bore holes in rocks there will be some space between rock and canister. Other investigations have suggested that the space could be filled with highly compacted bentonite. In this report it is discussed if open joints formed or widened in the surrounding rock after the deposition will be sealed by self-injecting bentonite. Bentonite in contact with water will swell. The flow pattern and properties of the swelling bentonite, the permeability of the extruded bentonite and the viscosity of the extruded bentonite have been investigated. The following statements are done. In the narrow joints that can possibly be opened by various processes, the rate of bentonite extrusion will be very slow except for the first few centimeter move, which may take place in a few mounths. The swelling pressure of the extruded bentonite will decrease rapidly with the distance from the deposition hole. The loss of bentonite extruded through the narrow joints will be negligible. In the outer part of the bentonite zone there will be a successive transition to a very soft, dilute bentonite suspension. It will consist of fairly large particle aggregates which will be stuck where the joint width decreases

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

    International Nuclear Information System (INIS)

    López-Fernández, Margarita; Fernández-Sanfrancisco, Omar; Moreno-García, Alberto; Martín-Sánchez, Inés; Sánchez-Castro, Iván; Merroun, Mohamed Larbi

    2014-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    López-Fernández, Margarita; Fernández-Sanfrancisco, Omar; Moreno-García, Alberto; Martín-Sánchez, Inés; Sánchez-Castro, Iván; Merroun, Mohamed Larbi, E-mail: merroun@ugr.es

    2014-10-15

    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

  9. Study on the basic property of Gaomiaozi bentonite, inner mongolia

    International Nuclear Information System (INIS)

    Liu Yuemiao; Xu Guoqing; Liu Shufen; Chen Zhangru

    2001-01-01

    Buffer/backfill material layer is one of important engineered barriers in the HLW geological repository. The geologic setting of Gaomiaozi bentonite deposit is introduced, and the mineral composition, physical and chemical property, basic geotechnical property, swelling property and permeability of highly compacted bentonite of main ore bed has been studied. The study results show that montmorillonite content of Gaomiaozi bentonite is relatively high, physical and chemical property, geotechnical property and impermeability are good. So Gaomiaozi bentonite deposit could be regarded as supply base of buffer/backfill material for HLW geological repository

  10. Timing of Late Cretaceous Gulf Coast volcanism and chronostratigraphic constraints on deposition of the Ripley Formation from a newly recognized bentonite bed, Pontotoc County, Mississippi

    Science.gov (United States)

    Vitale, E. J.; Gifford, J.; Platt, B. F.

    2017-12-01

    The Upper Cretaceous Ripley Formation is present throughout the Mississippi (MS) Embayment and contains local bentonite lenses related to regional volcanism. The Pontotoc bentonite is such a lens located near the town of Pontotoc, MS, that was strip-mined and has not been accessible since reclamation of the land. Recent investigations in Pontotoc County south of the Pontotoc bentonite site resulted in the discovery of a previously unknown bentonite bed. Litho- and biostratigraphy indicate that the bentonite is younger than known volcanism from MS. The purposes of the present investigation are 1) to test whether the new bentonite bed is correlative to the Pontotoc bentonite & 2) to recover volcanogenic zircons for U-Pb dating to better constrain timing of volcanism and chronostratigraphy of the Ripley Fm. Outcrops in an active sand pit in the field area expose 2.5 m of fine sand, and an upper gradational contact with an overlying 2.5 m of sandy clay, containing the bentonite bed. Two trenches were excavated through the outcrop, and in each trench a stratigraphic section was measured and bulk samples collected for zircons. Sampling began in the lower bounding sand and continued upsection in 1 m intervals, corresponding to the gradational contact with the bentonite, and 2 locations within the bentonite. The Ripley Fm. consists of 73 m of fossiliferous clay, sand, and calcareous sand beds. Recent stratigraphic revisions of the lateral facies in MS recognize a lower transitional clay facies, a limestone, marl, and calcareous sand facies, a sandy upper Ripley facies, and the formally named Chiwapa Sandstone Member. Ammonite biostratigraphy places the contact between the Chiwapa and the overlying Owl Creek/Prairie Bluff at 68.5 Ma. Unlike the mined area north of Pontotoc where the bentonite is within the Chiwapa, the bed here is directly above the Chiwapa section and its upper contact represents the Ripley Fm. / Owl Creek Fm. contact. Where the bentonite is present, it

  11. Long-time stability following freezing and thawing of concrete and bentonite in deposition of low- and intermediate-level radioactive waste in SFR 1

    International Nuclear Information System (INIS)

    Emborg, Mats; Jonasson, Jan-Erik; Knutsson, Sven

    2007-10-01

    This document describes the effect of freezing on the concrete and bentonite barriers in SFR 1. The document constitutes one of the references describing the degradation of barriers in a long-time perspective and is used in the safety analysis SFR 1 SAR-08

  12. Corrosion of carbon steel in contact with bentonite

    International Nuclear Information System (INIS)

    Dobrev, D.; Vokal, A.; Bruha, P.

    2010-01-01

    Document available in extended abstract form only. Carbon steel canisters were chosen in a number of disposal concepts as reference material for disposal canisters. The corrosion rates of carbon steels in water solution both in aerobic and anaerobic conditions are well known, but only scarce data are available for corrosion behaviour of carbon steels in contact with bentonite. A special apparatus, which enables to measure corrosion rate of carbon steels under conditions simulating conditions in a repository, namely in contact with bentonite under high pressure and elevated temperatures was therefore prepared to study: - Corrosion rate of carbon steels in direct contact with bentonite in comparison with corrosion rate of carbon steels in synthetic bentonite pore water. - Influence of corrosion products on bentonite. The apparatus is composed of corrosion chamber containing a carbon steel disc in direct contact with compacted bentonite. Synthetic granitic water is above compacted bentonite under high pressure (50 - 100 bar) to simulate hydrostatic pressure in a repository. The experiments can be carried out under various temperatures. Bentonites used for experiments were Na-type of bentonite Volclay KWK 80 - 20 and Ca-Mg Czech bentonite from deposit Rokle. Before adding water into corrosion system the corrosion chamber was purged by nitrogen gas. The saturation of bentonite and corrosion rate were monitored by measuring consumption of water, pressure increase caused by swelling pressure of bentonite and by generation of hydrogen. Corrosion rate was also determined after corrosion experiments from weight loss of samples. The results of experiments show that the corrosion behaviour of carbon steels in contact with bentonite is very different from corrosion of carbon steels in water simulating bentonite pore water solution. The corrosion rates of carbon steel in contact with bentonite reached after 30 days of corrosion the values approaching 40 mm/yr contrary to values

  13. 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.

  14. Fabrication and handling of bentonite blocks

    International Nuclear Information System (INIS)

    1978-06-01

    In accordance with the project for the final storage of spent nuclear fuel, the waste will be encapsulated into copper canisters, which will be deposited in a final repository located in rock 500 m below ground level. The canisters will be placed in vertical holes in the bottoms of the tunnels, where the copper cylinders will be surrounded by blocks of highly compacted bentonite. When the blocks are saturated with water and expansion is essentially retained as in the actual case, a very high swelling pressure will arise. The bentonite will be extremely impermeable and thus it will form a barrier against transport of corrosive matters to the canister. The blocks are fabricated by means of cold isostatic pressing of bentonite powder. The base material in the form of powder is enclosed in flexible forms, which are introduced into pressure vessels where the forms are surrounded by oil or water. Thus the powder is compacted into rigid bodies with a bulk density of about 2.2 t/m 3 for ''air dry'' bentonite, which might be compared with a specific density of about 2.7 t/m 3 . The placing of a canister is preceded by piling up bentonite blocks to a level just below the canister lid position, after which the slot around the blocks is filled with bentonite powder. The rest of the blocks are mounted after filling bentonite powder into the inner slot around the canister as well. Finally the storage tunnels will be sealed by filling them with a mixture o02067NRM 0000181 45

  15. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.

    2007-01-01

    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 Ca 2+ exhibit higher effect on cesium sorption than the Na 2+ ions. Results indicate that the sorption of Sr 2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  16. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    International Nuclear Information System (INIS)

    Liu Xiaodong; Luo Taian; Zhu Guoping; Chen Qingchun

    2007-12-01

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  17. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Liu [East China Inst. of Technology, Fuzhou (China); [Key Laboratory of Nuclear Resources and Environment of Ministry of Education, Fuzhou (China); Taian, Luo; Guoping, Zhu; Qingchun, Chen [East China Inst. of Technology, Fuzhou (China)

    2007-12-15

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  18. Opportunity on 'Cabo Frio' (Simulated)

    Science.gov (United States)

    2006-01-01

    This image superimposes an artist's concept of the Mars Exploration Rover Opportunity atop the 'Cabo Frio' promontory on the rim of 'Victoria Crater' in the Meridiani Planum region of Mars. It is done to give a sense of scale. The underlying image was taken by Opportunity's panoramic camera during the rover's 952nd Martian day, or sol (Sept. 28, 2006). This synthetic image of NASA's Opportunity Mars Exploration Rover at Victoria Crater was produced using 'Virtual Presence in Space' technology. Developed at NASA's Jet Propulsion Laboratory, Pasadena, Calif., this technology combines visualization and image processing tools with Hollywood-style special effects. The image was created using a photorealistic model of the rover and an approximately full-color mosaic.

  19. Microstructure of bentonite in relation to its physical properties within nuclear waste repositories

    International Nuclear Information System (INIS)

    Laine, E.

    1998-01-01

    High-level nuclear waste in Finland is planned to be placed in bedrock at a depth of several hundred metres. The spent fuel containers in boreholes drilled in the floors of deposition tunnels will be surrounded by bentonite blocks. The upper parts of the tunnels will be filled with mixture of bentonite and crushed rock. The behaviour of the bentonite around the containers during several years after deposition of nuclear waste should be predicted. In the present report, a short literature study of the microstructure of bentonite is presented. The report concentrates on bentonite MX-80. The use of stochastic imaging of microstructure was tested by using the Boolean simulation. Using stochastic imaging, the effect of changes of bentonite microstructure on its physical properties can be evaluated and predicted. (orig.)

  20. Bentonite erosion - Laboratory studies

    International Nuclear Information System (INIS)

    Jansson, Mats

    2010-01-01

    Document available in extended abstract form only. Bentonite clay is proposed as buffer material in the KBS-3 concept of storing spent nuclear fuel. Since the clay is plastic it will protect the canisters containing the spent fuel from movements in the rock. Furthermore, the clay will expand when taking up water, become very compact and hence limit the transport of solutes to and from the canister to only diffusion. The chemical stability of the bentonite barrier is of vital importance. If much material would be lost the barrier will lose its functions. As a side effect, lots of colloids will be released which may facilitate radionuclide transport in case of a breach in the canister. There are scenarios where during an ice age fresh melt water may penetrate down to repository depths with relatively high flow rates and not mix with older waters of high salinity. Under such conditions bentonite colloids will be more stable and there is a possibility that the bentonite buffer would start to disperse and bentonite colloids be carried away by the passing water. This work is a part of a larger project called Bentonite Erosion, initiated and supported by SKB. In this work several minor experiments have been performed in order to investigate the influence of for instance di-valent cations, gravity, etc. on the dispersion behaviour of bentonite and/or montmorillonite. A bigger experiment where the real situation was simulated using an artificial fracture was conducted. Two Plexiglas slabs were placed on top of each other, separated by plastic spacers. Bentonite was placed in a container in contact with a fracture. The bentonite was water saturated before deionized water was pumped through the fracture. The evolution of the bentonite profile in the fracture was followed visually. The eluate was collected in five different slots at the outlet side and analyzed for colloid concentration employing Photon Correlation Spectroscopy (PCS) and a Single Particle Counter (SPC). Some

  1. Characterization of bentonite clay from Cubati, PB, Brazil

    International Nuclear Information System (INIS)

    Batista, A.P.; Marques, L.N.; Campos, L.A.; Neves, G.A.; Ferreira, H.C.; Menezes, R.R.

    2009-01-01

    The bentonite of the State of Paraiba are commercially used in numerous technological sectors, particularly in oil drilling muds. However, these bentonite deposits are becoming exhausted after decades of exploitation. Thus, the aim of this work was to characterize physically, mineralogically and technologically bentonite clays from Cubati city, PB. The samples were dried at 60 deg C and characterized through X-ray fluorescence, particle size distribution, X-ray diffraction, differential thermal and gravimetric analyzes and scanning electronic microscopy. The natural bentonite clays were transformed into sodium bentonite by Na_2CO_3 solution treatment. It was estimated the rheological properties of the suspensions: apparent and plastic viscosities and water loss. The results showed that the samples are polycationic bentonite clays, containing amounts of MgO, CaO and K_2O similar to those of bentonite from Boa Vista, PB, and are composed of smectite, kaolinite and quartz. The samples presented fractions of particles size under 2 μm of 30 and 32%. The rheological properties showed that the samples presented technological potential to be used in drilling muds. (author)

  2. 76 FR 24511 - Cabo Rojo National Wildlife Refuge, Cabo Rojo, Puerto Rico; Draft Comprehensive Conservation Plan...

    Science.gov (United States)

    2011-05-02

    ... DEPARTMENT OF THE INTERIOR Fish and Wildlife Service [FWS-R4-R-2010-N277; 40136-1265-0000-S3] Cabo Rojo National Wildlife Refuge, Cabo Rojo, Puerto Rico; Draft Comprehensive Conservation Plan and... draft comprehensive conservation plan and environmental assessment (Draft CCP/EA) for Cabo Rojo National...

  3. Porewater chemistry in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-03-01

    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 33 refs.

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

    International Nuclear Information System (INIS)

    Jacobsson, A.; Pusch, R.

    1978-06-01

    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

  5. Stability of bentonite gels in crystalline rock

    International Nuclear Information System (INIS)

    Pusch, R.

    1983-02-01

    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 10 6 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)

  6. The application of bentonite in the atomic energy field and some research results of the sorption of uranium on Vietnam bentonite

    International Nuclear Information System (INIS)

    Than Van Lien; Do Qui Son; Le Thi Kim Dung

    2008-01-01

    The properties of bentonite can be summarised as follows: low gas permeability, low hydraulic conductivity, high radionuclide retardation capacity, high swelling potential, that is why bentonite has been widely used in the atomic energy fields in many countries all over the world. Vietnam has bentonite deposits that is exploited and used in some fields. In order to use bentonite - available and abandon resources in our country for atomic energy many research activities on the field of bentonite applications have been carried out in Institute for Technology of Radioactive and Rare Elements and Dalat Nuclear Research Institute. In this content, this article introduces the application of bentonite in radioactive waste management and treatment fields (bentonite used as barrier in the deep repository for spent nuclear fuel, as barriers in landfills to prevent contamination of soil and groundwater by leachates containing radioactive, bentonite is also used as sorbent for nuclear reactor activation products (Co, Cr in the waste effluents). At the some time it is present some research results of the sorption of uranium on Vietnamese bentonite. (author)

  7. Application of HDTMA-intercalated bentonites in water waste treatment for U(VI) removal

    International Nuclear Information System (INIS)

    Krajnak, Adrian; Viglasova, Eva; Galambos, Michal; Krivosudsky, Lukas; Universitat Wien, Vienna

    2017-01-01

    Bentonite deposits in Slovakia are systematically investigated as potential adsorbents for wastewater and radioactive waste treatment applications. Herein, adsorption properties (isotherms, kinetics and thermodynamics) of raw and organo-modified bentonites towards uranium species in aqueous solutions were investigated. Organo-modified bentonites was prepared by practical and simple chemical modification method with hexadecyltrimethylammonium bromide (denoted as HDTMA-bentonites). The adsorption processes of U(VI) on HDTMA-bentonites were spontaneous and endothermic, and well simulated by pseudo-second-order model. The maximum adsorption capacity of U(VI) was calculated to be 31.45 mg/g at pH 8.5 and T = 298 K. Slovak bentonites Jelsovy potok and Kopernica, their natural and HDTMA-modified forms might be a promising sorbent for the treatment of U(VI) contaminants in aqueous solutions. (author)

  8. 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

  9. Gas Transport in Bentonite

    International Nuclear Information System (INIS)

    Villar, M. V.; Gutierrez-Rodrigo, V.; Martin, P. L.; Romero, F. J.; Barcala, J. M.

    2013-01-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm 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 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 remained

  10. Optimization of bentonite pellet properties

    International Nuclear Information System (INIS)

    Sanden, Torbjoern; Andersson, Linus; Jonsson, Esther; Fritzell, Anni

    2012-01-01

    Document available in extended abstract form only. SKB in Sweden is developing and implementing concepts for the final disposal of spent nuclear fuel. A KBS-3V repository consists of a deposition tunnel with copper canisters containing spent fuel placed in vertical deposition holes. The canisters are embedded in highly compacted bentonite. After emplacement of canisters and bentonite blocks, the tunnels will be backfilled and sealed with an in-situ cast plug at the entrance. The main concept for backfilling the deposition tunnels imply pre compacted blocks of bentonite stacked on a bed of bentonite pellet. The remaining slot between blocks and rock will be filled with bentonite pellets. The work described in this abstract is a part of the ASKAR-project which main goal is to make a system design based on the selected concept for backfilling. Immediately after starting the backfill installation, inflowing water from the rock will come in contact with the pellet filling and thereby influence the characteristics of the pellet filling. The pellet filling helps to increase the average density of the backfill, but one of the most important properties beside this is the water storing capacity which will prevent water from reaching the backfill front where it would disturb and influence the quality of the installation. If water flows through the pellet filling out to the backfilling front, there will be erosion of material which also will affect the quality of the installed backfill. In order to optimize the properties regarding water storing capacity and sensitivity for erosion a number of tests have been made with different pellet types. The tests were made in different scales and with equipment specially designed for the purpose. The performed tests can be divided in four parts: 1. Standard tests (determining water content and density of pellet fillings and individual pellets, compressibility of the pellet fillings and strength of the individual pellets); 2. Erosion

  11. 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.

  12. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

    2009-12-01

    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.

  13. 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

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

    International Nuclear Information System (INIS)

    Laine, H.; Karttunen, P.

    2010-07-01

    extensive 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.)

  15. Customized bentonite pellets. Manufacturing, performance and gap filling properties

    Energy Technology Data Exchange (ETDEWEB)

    Marjavaara, P.; Holt, E.; Sjoeblom, V. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-12-15

    The goal of this work was to provide knowledge about how to manufacture customized bentonite pellets and how customized bentonite pellets perform in practice during the nuclear repository construction process. The project was mainly focused on laboratory experimental tests to optimize the pellet filling by customizing the raw materials and pellet manufacturing. Bentonite pellets were made using both extrusion and roller compaction methods. The pellets were intended for use in gaps between compacted bentonite and the rock walls in both buffer deposition holes and tunnel backfilling. Performance of different types of custom-made pellets were evaluated with regard to their ease of manufacturing, density, crush strength, abrasion resistance, water holding capacity, free swelling and also their thermal conductivity. These evaluations were done in both Finland (by VTT) and Canada (by AECL). Over 50 different varieties of pellets were roller-compaction manufactured at AECL in Canada and 20 types of extrusion pellets at VTT in Finland. The parameters that were varied during manufacturing included: bentonite raw material type, water content, pellet sizes, bentonite compaction machine parameters, use of recycled pellets, and addition of two different types of filler (illite or granitic sand) at varying addition percentages. By examining the pellets produced with these methods and materials the performance and behaviour of the bentonite pellets were evaluated in laboratory with selected tests. The work done using extrusion pellets showed that it was possible to manufacture pellets with higher water contents, up to 21 % from MX-80. This water content value was higher than what was typically possible using roller-compaction method in this study. Higher water content values allow closer compatibility with the designed bentonite buffer water content. The extrusion tests also showed that the required production simulation runs could be made successfully with reference type of MX

  16. 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)

    Smellie, J.

    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

  17. 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

  18. Layers of 'Cabo Frio' in 'Victoria Crater'

    Science.gov (United States)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is an approximately true color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  19. Study of cesium and strontium adsorption on slovak bentonite

    International Nuclear Information System (INIS)

    Galambos, M.

    2010-01-01

    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 K d 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)

  20. Evolution of the east-central San Jose del Cabo basin, Baja California Sur, Mexico

    Science.gov (United States)

    McTeague, M. S.; Umhoefer, P. J.; Schwennicke, T.; Ingle, J. C.; Cortes Martinez, M.

    2006-12-01

    The San Jose del Cabo basin at the southern tip of the Baja California peninsula records the early tectonic evolution of the west side of the Gulf of California. This study focused on the east central margin of the basin. The basal La Calera Formation unconformably overlies Cretaceous granite and consists of conglomerate, pebbly sandstone and conglomerate, and sandstone deposited in alluvial fans and fan-deltas. Deposition of the La Calera Formation was from ca. 9-14 Ma. The lower member of the Trinidad Formation was deposited beginning ca. 9-13 Ma and consists of sandstone, mudstone, and shelly mudstone deposited in nearshore and estuarine environments. These age estimates are based on sedimentation rates and foraminifera and coccoliths from the NN 11A nannozone (7.4 8.6 Ma, GTS 2004). The middle member of the Trinidad Formation consists of deeper water mudstones deposited by turbidity currents and suspension settling in a shelf to slope and conglomerates deposited by submarine debris flows on the shelf. The basin began earlier than previously thought. The oldest marine rocks are ca.9-13 Ma, while sedimentation on the east side began at ca. 9-14 Ma, synchronous with estimates of initiation of offset on the San Jose del Cabo fault. The Zapote fault is a down-to-the-east normal and sinistral-oblique fault that exposes a wedge of granite and older strata in the footwall to the west. The fault was active during sedimentation in the late Miocene and possibly later. The fault divides the study area into an eastern hanging wall subbasin and western footwall subbasin. The eastern subbasin formed an embayment in the eastern margin of the Cabo basin. A regional flooding surface (ca. 8 Ma) can be correlated across the fault that marks a major marine incursion. Depositional systems evolved rapidly from coarse-grained terrestrial systems to fine-grained marine and estuarine systems. The Cabo basin provides an excellent analogue for comparison with offshore basins, which are

  1. Antifungal activity of streptomycetes isolated bentonite clay

    Directory of Open Access Journals (Sweden)

    V. P. Shirobokov

    2016-12-01

    Full Text Available Aim. To investigate the biological activity of streptomycetes, isolated from Ukrainian bentonite clay. Methods. For identification of the investigated microorganisms there were used generally accepted methods for study of morpho-cultural and biochemical properties and sequencing of 16Ѕ rRNA producer. Antagonistic activity of the strain was determined by agar diffusion and agar block method using gram-positive, gram-negative microorganisms and fungi. Results. Research of autochthonous flora from bentonite clay of Ukrainian various deposits proved the existence of stable politaxonomic prokaryotic-eukaryotic consortia there. It was particularly interesting that the isolated microorganisms had demonstrated clearly expressed antagonistic properties against fungi. During bacteriological investigation this bacterial culture was identified like representative of the genus Streptomyces. Bentonite streptomycetes, named as Streptomyces SVP-71, inagar mediums (agar block method inhibited the growth of fungi (yeast and mold; zones of growth retardation constituted of 11-36 mm, and did not affect the growth of bacteria. There were investigated the inhibitory effects of supernatant culture fluid, ethanol and butanol extracts of biomass streptomycetes on museum and clinical strains of fungi that are pathogenic for humans (Candida albicans, C. krusei, C. utilis, C. parapsilosis, C. tropicalis, C. kefir, S. glabrata, C. lusitaniae, Aspergillus niger, Mucor pusillus, Fusarium sporotrichioides. It has been shown that research antifungal factor had 100% of inhibitory effect against all fungi used in experiments in vitro. In parallel, it was found that alcohol extracts hadn’t influence to the growth of gram-positive and gram-negative bacteria absolutely. It was shown that the cultural fluid supernatant and alcoholic extracts of biomass had the same antagonistic effect, but with different manifestation. This evidenced about identity of antifungal substances

  2. A new age model for the Late Ordovician bentonites in Oslo, Norway

    Science.gov (United States)

    Gottschalk Ballo, Eirik; Eivind Augland, Lars; Hammer, Øyvind; Svensen, Henrik

    2017-04-01

    During the Late Ordovician, explosive volcanic eruptions led to the deposition of worldwide bentonites. Some of the largest of these eruptions took place in the Sandbian and produced the Milbrig and Deicke K-bentonites of North America and the Kinnekulle K-bentonite of Scandinavia. We have studied the classic locality of Hagemann and Spjeldnæs (1955) - one of the most complete sections of Ordovician bentonites in Europe. The bentonites are present in the Arnestad Formation comprising dark shale with carbonate nodule beds grading into an increasingly more carbonate rich environment. Through a 50-meter interval we have identified 33 bentonites of which 10 have not previously been reported from this locality. The bentonites have an average thickness of 4.9 cm with a few exceptions such as the Kinnekulle K-bentonite (35 cm) and the Grimstorp B (13 cm). We have measured magnetic susceptibility of two 2-3 meter intervals with a sampling distance of 5 cm, using a handheld magnetic susceptibility meter in the field. These data show significant periodicity peaks that correlate well with Milankovitch cycles and are suggested to represent astronomically forced changes in sediment supply. This study further presents high-precision U-Pb zircon ages of five bentonites from the section, including the Kinnekulle K-bentonite and Grimstorp B. These two beds were previously dated by Svensen et al. (2015) from a locality south of Oslo. Our new data improves the precision of the ages of these two key beds, and constrain the duration of the entire interval and thus the onset and termination of the late Ordovician volcanic system that deposited these tephras. We conclude that the Oslo section provides a high-resolution age model to understand one of the most intense volcanic periods of the Paleozoic by combining radiometric and cyclostratigraphic data. BIBLIOGRAPHY Hagemann, F. and Spjeldnæs, N. (1955). "The Middle Ordovician of the Oslo region, Norway. 6. Notes on bentonites (K-bentonites

  3. Prediction for swelling characteristics of compacted bentonite

    International Nuclear Information System (INIS)

    Komine, H.; Ogata, N.

    1996-01-01

    Compacted bentonites are attracting greater attention as back-filling (buffer) materials for high-level nuclear waste repositories. For this purpose, it is very important to quantitatively evaluate the swelling characteristics of compacted bentonite. New equations for evaluating the relationship between the swelling deformation of compacted bentonite and the distance between two montmorillonite layers are derived. New equations for evaluating the ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of compacted bentonite, are proposed. Furthermore, a prediction method for the swelling characteristics of compacted bentonite is presented by combining the new equations with the well-known theoretical equations of repulsive and attractive forces between two montmorillonite layers. The applicability of this method was investigated by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites. (author) 31 refs., 8 tabs., 12 figs

  4. Purification of bentonite clays from the district of Cubati, PB, for other uses

    International Nuclear Information System (INIS)

    Costa, M.R.; Araujo, J.P.; Silva, I.A.; Cardoso, M.A.; Silva, C.D.; Neves, G.A.; Ferreira, H.C.

    2012-01-01

    The state of Paraiba is responsible for the increased production of crude bentonite in the country, coming from one of the largest mines of Brazil, located in Boa Vista, PB. Recently, in the regions of Cubati and Pedra Lavrada, PB, found new deposits of bentonite that could expand the state reserves. The paper aims at the characterization and development of clay purified using the techniques of screening and hydrocycloning, from bentonite clay recently discovered in the city of Cubati, PB, for various uses. The sample characterization was performed through techniques: granulometric analysis by laser diffraction, X-ray diffraction and chemical analysis by X-ray fluorescence and thermogravimetric and differential thermogravimetric analysis. The results showed that the samples are typical of bentonite clay, and that the purification process using only the hydrocycloning shows better results. (author)

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

    International Nuclear Information System (INIS)

    Cervinka, R.; Vejsada, J.

    2010-01-01

    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 CO 2 ), 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

  6. 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.

  7. Bentoniteiron interactions in natural occurrences and in laboratory. The effects of the interactions on the properties of bentonite. A literature survey

    Energy Technology Data Exchange (ETDEWEB)

    Marcos, N. [Helsinki University of Technology, Espoo (Finland)

    2003-10-15

    properties of the bentonite due to this change were not investigated. The physicochemical conditions of any bentonite deposit are hardly similar to the conditions in the nuclear waste repository after closure. However, the change of properties in bentonite as a result of interaction with iron and iron oxy-hydroxides could be investigated in natural analogues. Deposits of bentonite in Greece and Spain have been affected by iron-rich solutions coming from faults and other discontinuities. Feasibility studies could further clarify the suitability of these deposits as natural analogues to the behaviour of bentonite as a result of interaction with iron. (orig.)

  8. Adsorption of strontium ions on bentonites of slovak provenance - Influence of pH change of medium

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.; Paucova, V.

    2007-01-01

    Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for spent fuel and 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. Slovak republic disposes of many significant deposits of bentonites, e.g. Jelsovy potok, Kopernica, Lieskovec, Lastovce, etc. The bentonites present significant group of natural nanomaterials composed of microcrystallic particles of montmorillonite. Bentonite is characterized by a low hydraulic conductivity, low throughput and excellent sorption capacity for cationic fission products of 235 U (e.g. 89 Sr, 90 Sr, 137 Cs). Sorption of strontium on bentonite from various Slovak deposits was studied using batch technique. Distribution coefficients (K d ) were determined for bentonite-strontium solution system as a function of contact time, pH, sorbent and sorbate concentration. The data were interpreted in term of Langmuir isotherm. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The effect of pH, on the sorption of metal ions on bentonite was studied by varying the pH of the aqueous metal solutions. The sorption of this nuclide increased by increasing pH. The percentage sorption decreased with increasing metal concentrations. These results could be helpful for nuclear waste management, for waste water effluents containing low concentrations of strontium. (authors)

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

    International Nuclear Information System (INIS)

    Hultgren, Aa.

    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. Diffusion of uranium in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.

    1992-09-01

    In the study the diffusion of uranium dissolved from uranium oxide fuel was studied experimentally in compacted sodium bentonite (Wyoming bentonite MX-80). The experiments were carried out by the through-diffusion method. The parameters varied in the study were the density of bentonite, salt content of the solution and redox conditions. Uranium was dissolved under aerobic conditions in order to simulate oxic conditions possibly caused by radiolysis in the repository

  11. Bentonite Permeability at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Katherine A. Daniels

    2017-01-01

    Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.

  12. Structural characterization of bentonite clays for utilization as nanofillers in nanocomposites

    International Nuclear Information System (INIS)

    Oliveira, Carlos Ivan Ribeiro de; Rocha, Marisa Cristina Guimares; Vogas, Arthur Considera

    2014-01-01

    Clays of different composition have been used in the development of polymer nanocomposites. However, the utilization of bentonite clays has been emphasized in Brazil, mainly due to their availability.The best known and studied deposits of bentonite clays are located in the state of Paraiba. However, these deposits are becoming exhausted after decades of exploitation. In this context, the aim of this work is to proceed the physical-mineralogical characterization of bentonite clays recently discovered in Cubati, PB. In order to achieve this objective, the samples underwent a particle size classification step and were characterized by X-ray fluorescence, X-ray diffraction, infrared spectroscopy, thermal analysis and scanning electron microscopy. Results of X-ray diffraction showed that the samples are composed of smectite, and kaolinite and quartz. The characterization of the samples by FTIR confirmed these results. Results of chemical analysis showed that the clays have predominantly different exchangeable cations. (author)

  13. Bentonite erosion by dilute waters in initially saturated bentonite

    International Nuclear Information System (INIS)

    Olin, Markus; Seppaelae, Anniina; Laurila, Teemu; Koskinen, Kari

    2012-01-01

    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

  14. Adsorption of strontium on different sodium-enriched bentonites

    Directory of Open Access Journals (Sweden)

    Marinović Sanja R.

    2017-01-01

    Full Text Available Bentonites from three different deposits (Wyoming, TX, USA and Bogovina, Serbia with similar cation exchange capacities were sodium enriched and tested as adsorbents for Sr2+ in aqueous solutions. X-Ray diffraction analysis confirmed successful Na-exchange. The textural properties of the bentonite samples were determined using low-temperature the nitrogen physisorption method. Significant differences in the textural properties between the different sodium enriched bentonites were found. Adsorption was investigated with respect to adsorbent dosage, pH, contact time and the initial concentration of Sr2+. The adsorption capacity increased with pH. In the pH range from 4.0–8.5, the amount of adsorbed Sr2+ was almost constant but 2–3 times smaller than at pH ≈11. Further experiments were performed at the unadjusted pH since extreme alkaline conditions are environmentally hostile and inapplicable in real systems. The adsorption capacity of all the investigated adsorbents toward Sr2+ was similar under the investigated conditions, regardless of significant differences in the specific surface areas. It was shown and confirmed by the Dubinin–Radushkevich model that the cation exchange mechanism was the dominant mechanism of Sr2+ adsorption. Their developed microporous structures contributed to the Sr2+ adsorption process. The adsorption kinetics obeyed the pseudo-second-order model. The isotherm data were best fitted with the Langmuir isotherm model. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001

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

    International Nuclear Information System (INIS)

    Bengtsson, A.; Widen, H.

    1991-05-01

    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)

  16. The bentonite industry in North America

    International Nuclear Information System (INIS)

    Dixon, D.A.; Hnatiw, D.S.J.; Walker, B.T.

    1992-11-01

    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 10 5 Mg of used fuel would be emplaced. This would require 2.5 x 10 6 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 10 8 Mg, and vast supplies are known to exist but not yet proven. The Canadian conceptual disposal vault would require 6 x 10 4 Mg of sodium bentonite each year for 40 years. The bentonite industry of North America has an installed annual production capacity of 2 x 10 7 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.)

  17. Thermochemically induced transformations in Al-smectites: A Spanish natural analogue of the bentonite barrier behaviour in a radwaste disposal

    International Nuclear Information System (INIS)

    Perez del Villar, L.; Delgado, A.; Reyes, E.; Pelayo, M.; Fernandez-Soler, J.M.; Cozar, J.S.; Tsige, M.; Quejido, A.J.

    2005-01-01

    The thermal effect induced by the Morron de Mateo volcanic dome (Cabo de Gata volcanic region, Spain) on the adjacent bentonitised tuffaceous beds has been studied as a natural analogue of the thermal behaviour of the bentonite-engineered barrier of a geological radwaste repository. These bentonites consist mainly of Fe-rich smectites and were formed in equilibrium with seawater at temperatures between 75 and 95 o C, according to the δ 18 O and δD values. In contrast, bentonites from other localities in the region consist mainly of Al-smectites, formed in equilibrium with meteoric water below 25 deg. C. This investigation is focussed on the detection of the chemical differences between smectites from proximal and distal zones to the dome, as well as to test whether the temperatures calculated based on the O and H isotopic values correspond to their formation or transformation. The initial hypothesis was that the chosen smectites could be formed under marine conditions, being later transformed and isotopically re-equilibrated as a result of the intrusion. To check this hypothesis, a detailed mineralogical, chemical, geochemical and isotopic study has been performed on the smectitised tuffaceous materials and the overlaying biocalcarenites outcropping near and far from the dome. The results show that distal smectites are dioctahedral Al-smectites, similar to those from other deposits in the region, while proximal smectites are Fe- and Mg-rich smectites, showing two evolutionary trends on a Fe-Mg-Al ternary diagram. Similar features are observed when their structural formulae are plotted on the muscovite-celadonite-pyrophylite diagram. Thus, they plot in the smectite domain with interlayer charge less than 1, which is mainly due to octahedral substitution for distal smectites, while for proximal ones it is caused by both octahedral and tetrahedral substitutions. In this ternary diagram, the domains of both proximal and distal smectites are partially overlapped. The

  18. Magmatism and cenozoic tectonism in the Cabo Frio region, RJ, Brazil

    International Nuclear Information System (INIS)

    Mohriak, W.U.; Barros, A.Z.N. de; Fujita, A.

    1990-01-01

    The western portion of the Campos Basin is limited by a hinge line that bounds the deposition of pre-Aptian sediments in the offshore region. The Cabo Frio arch corresponds to a platform with smaller relative subsidence, where Tertiary sediments are deposited directly on shallow basement rocks. Towards the continental slope of the Cabo Frio region, tectonic activity is also observed in the post-Aptian sequence, particularly in the region between the Santos and Campos basins, where a very large graben trends parallel to the pre-Aptian limit of the basin, and is controlled by faults that-affect Upper Miocene rocks. Eastwards of this region, an array of antithetic faults trends in a NE direction. These faults, apparently detaching an the Aptian salt, show unique geometric patterns. The rupturing of Pangea in the Lower Cretaceous is marked by widespread outpouring of mafic magmas in Campos and Santos basins. Radiometric age determinations for this volcanism show a mean of about 139 M.a. After the rift phase, another volcanic episode is observed in the Cabo Frio region, with K/Ar radiometric dating of about 50 M.a. Volcanic mounds are observed within the Eocene sedimentary sequence. An Eocene volcanic episode is characterized by the presence of volcaniclassic rocks, including autoclastic, hydroclastic, epiclastic and pyroclastic sediments. This tectonic episode is also identified within other stratigraphic intervals in the sedimentary column. (author)

  19. Permeability of highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1980-12-01

    The object of the study was the water flow through the bentonite which is caused by hydraulic gradients. The study comprised laboratory tests and theoretical considerations. It was found that high bulk densities reduced the permeability to very low values. It was concluded that practically impervious conditions prevail when the gradients are low. Thus with a regional gradient of 10 -2 and a premeability of 10 -13 m/s the flow rate will not be higher than approximately 1 mm in 30 000 years. (G.B.)

  20. 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

  1. Strontium migration in a crystalline medium: effects of the presence of bentonite colloids.

    Science.gov (United States)

    Albarran, Nairoby; Missana, Tiziana; García-Gutiérrez, Miguel; Alonso, Ursula; Mingarro, Manuel

    2011-03-25

    The effects of bentonite colloids on strontium migration in fractured crystalline medium were investigated. We analyzed first the transport behaviour of bentonite colloids alone at different flow rates; then we compared the transport behaviour of strontium as solute and of strontium previously adsorbed onto stable bentonite colloids at a water velocity of approximately 7.1·10(-6)m/s-224m/yr. Experiments with bentonite colloids alone showed that - at the lowest water flow rate used in our experiments (7.1·10(-6)m/s) - approximately 70% of the initially injected colloids were retained in the fracture. Nevertheless, the mobile colloidal fraction, moved through the fracture without retardation, at any flow rate. Bentonite colloids deposited over the fracture surface were identified during post-mortem analyses. The breakthrough curve of strontium as a solute, presented a retardation factor, R(f)~6, in agreement with its sorption onto the granite fracture surface. The breakthrough curve of strontium in the presence of bentonite colloids was much more complex, suggesting additional contributions of colloids to strontium transport. A very small fraction of strontium adsorbed on mobile colloids moved un-retarded (R(f)=1) and this fraction was much lower than the expected, considering the quantity of strontium initially adsorbed onto colloids (90%). This behaviour suggests the hypothesis of strontium sorption reversibility from colloids. On the other hand, bentonite colloids retained within the granite fracture played a major role, contributing to a slower strontium transport in comparison with strontium as a solute. This was shown by a clear peak in the breakthrough curve corresponding to a retardation factor of approximately 20. Copyright © 2010 Elsevier B.V. All rights reserved.

  2. 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.

  3. Rheological Behavior of Bentonite-Polyester Dispersions

    Science.gov (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin

    2013-07-01

    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  4. Mechanical stability of bentonite buffer system for high level nuclear waste

    Energy Technology Data Exchange (ETDEWEB)

    Lempinen, A. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Theoretical and Applied Mechanics

    1998-05-01

    According to present plans, high level nuclear waste in Finland is going to be disposed of in bedrock at a depth of several hundred metres. The spent fuel containers will be placed in boreholes drilled in the floors of deposition tunnels with engineered clay buffer, which is made of bentonite blocks. The tunnels will be filled with a mixture of bentonite and crushed rock. For stability calculations a thermomechanical model for compressed bentonite is needed. In the study a thermomechanically consistent model for reversible processes for swelling clays is presented. Preliminary calculations were performed and they show that uncertainty in material parameter values causes significantly different results. Therefore, measurements that are consistent with the model are needed 12 refs.

  5. Mechanical stability of bentonite buffer system for high level nuclear waste

    International Nuclear Information System (INIS)

    Lempinen, A.

    1998-05-01

    According to present plans, high level nuclear waste in Finland is going to be disposed of in bedrock at a depth of several hundred metres. The spent fuel containers will be placed in boreholes drilled in the floors of deposition tunnels with engineered clay buffer, which is made of bentonite blocks. The tunnels will be filled with a mixture of bentonite and crushed rock. For stability calculations a thermomechanical model for compressed bentonite is needed. In the study a thermomechanically consistent model for reversible processes for swelling clays is presented. Preliminary calculations were performed and they show that uncertainty in material parameter values causes significantly different results. Therefore, measurements that are consistent with the model are needed

  6. Quality assurance of the bentonite material

    International Nuclear Information System (INIS)

    Ahonen, L.; Korkeakoski, P.; Tiljander, M.; Kivikoski, H.; Laaksonen, R.

    2008-05-01

    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.)

  7. Activation of wine bentonite with gamma rays

    International Nuclear Information System (INIS)

    Goranov, N.; Antonov, M.

    1997-01-01

    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/dm 3 . 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

  8. Purification of bentonitics of the city Cubati-PB to obtaining organoclays for use in oil-based drilling fluids

    International Nuclear Information System (INIS)

    Costa, J.M.R.; Vitorino, I.J.F.; Silva, I.A.; Neves, G.A.; Ferreira, H.C.

    2011-01-01

    In Boa Vista, PB, are located deposits of bentonite clays commonly used in the preparation of drilling fluids. The disorderly exploitation of the deposits of Boa Vista is causing the depletion of these clays, which will cause a very serious problem for the national oil industry. This work aims to characterize new deposits of bentonite clays Cubati, PB, for the development of organoclay from its refining using a hydrocyclone for use in oil based drilling fluids. The characterization of samples of the clays was performed through the techniques: AG, XRD, EDX, TGA and DTA. The characterization is typical of bentonite for the purification process was determined the best configuration of the hydrocyclone, and the environment organic diesel fuel, the best affinity was obtained with clays organophilizated with surfactant Praepagen WB. (author)

  9. Seafloor mapping of the southeast Iberian margin (from Cabo de Palos to Cabo de Gata)

    Science.gov (United States)

    Lastras, Galderic; Leon, César; Elvira, Elena; Pascual, Laura; Muñoz, Araceli; de Cárdenas, Enrique; Acosta, Juan; Canals, Miquel

    2014-05-01

    We present the multibeam bathymetry and derived maps of the southeast Iberian margin from Cabo de Palos to Cabo de Gata, 37º35'N to 35º45'N and 2º10'W to 0º20'E, from the coastline down to the Algero-Balearic abyssal plain at depths exceeding 2600 m. The edition of of the maps is carried out within the Complementary Action VALORPLAT ("Scientific valorisation of multibeam bathymetry data from the Spanish continental shelf and slope"), funded by the Spanish Ministry of Economy and Competitivity. The multibeam bathymetry data of the slope and abyssal plain were obtained during different surveys in 2004, 2006 and 2007 on board R/V Vizconde de Eza with a Simrad EM300 multibeam echo-sounder as part of the CAPESME Project, a collaboration between the Spanish Institute of Oceanography (IEO) and General Secretariat of Fisheries (SGP), primarily aiming at creating maps of the fishing grounds of the Mediterranean continental margins of Spain. Multibeam bathymetry data from the continental shelf were obtained within the ESPACE project, also in a cooperative frame between IEO and SGP. The map series is constituted by a general map at 1:400,000 scale and 14 detailed maps at 1:75,000 scale, which include inset maps on slope gradients and seafloor nature (rock or sediment type), the later obtained with rock dredges and Shipeck sediment dredges. Both the detailed maps and the general map are available in paper print, and the whole collection is also distributed in an edited USB. The geological features displayed in the different maps include the continental shelf, with abundant geomorphic features indicative of past sea-level changes, the continental slope carved by the Palos, Tiñoso, Cartagena Este, Cartagena Oeste, Águilas, Almanzora, Alias, Garrucha and Gata submarine canyons, the Mazarrón, Palomares and Al-Mansour escarpments, the Abubácer, Maimonides and Yusuf ridges, the Águilas and Al-Mansour seamounts, and the Algero-Balearic abyssal plain where prominent

  10. 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

  11. Mechanisms and models for bentonite erosion

    International Nuclear Information System (INIS)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis

    2009-12-01

    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

  12. Erosion of bentonite by flow and colloid diffusion

    International Nuclear Information System (INIS)

    Moreno, Luis; Liu, Longcheng; Neretnieks, Ivars

    2010-01-01

    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

  13. Organophilization and characterization of commercial bentonite clays

    International Nuclear Information System (INIS)

    Cunha, B.B. da; Lima, J.C.C.; Alves, A.M.; Araujo, E.M.; Melo, T.J.A. de

    2012-01-01

    Bentonite clay is a plastic changes resulting from volcanic ash, consisting mostly of montmorillonite. The state of Paraiba is a major source of bentonite clay from Brazil, where the main oil fields are located in Boa Vista and represents the largest national production of raw and beneficiated bentonite. Aimed at the commercial value of this type of clay and its high applicability in the polls, this article aims to make a comparison between two kinds of clay, a national (Brasgel) and other imported (Cloisite) from organophilization of two commercial bentonite, ionic surfactant with Praepagem WB, and characterize them by XRD, FTIR and TG / DTG. We observe that despite getting inferior properties, the clay presents national values very similar to those presented by imported clay. (author)

  14. Quality control and characterization of bentonite materials

    International Nuclear Information System (INIS)

    Kiviranta, L.; Kumpulainen, S.

    2011-12-01

    Before bentonite material is taken into use in performance testing, the quality of the material needs to be checked. Three high grade bentonite materials: two natural Nabentonites from Wyoming, and one natural Ca-bentonite from Milos, were characterized. Each material was characterized using duplicate or triplicate samples in order to study variability in material quality in batches. The procedure consisted of basic acceptance testing (water ratio, CEC, swelling index, liquid limit, and granule size distribution), advanced acceptance testing (exchangeable cations, chemical and mineralogical composition, density, swelling pressure and hydraulic conductivity) and complementary testing (herein surface area, water absorption capacity, montmorillonite composition, grain size distribution and plastic limit). All three materials qualified the requirements set for buffer bentonite for CEC, smectite content, swelling pressure, and hydraulic conductivity. Wyoming bentonites contained approximately 88 wt.% of smectite, and Milos bentonite 79 wt.% of smectite and 3 wt.% of illite. Precision of smectite analyses was ±2 %, and variances in composition of parallel samples within analytical errors, at least for Wyoming bentonites. Accuracy of quantitative analyses for trace minerals such as gypsum, pyrite or carbonates, was however low. As the concentrations of these trace minerals are important for Eh or pH buffering reactions or development of bentonite pore water composition, normative concentrations are recommended to be used instead of mineralogically determined concentrations. The swelling pressures and hydraulic conductivities of different materials were compared using EMDD. Swelling pressure was relatively higher for studied Cabentonite than for the studied Na-bentonites and the difference could not be explained with different smectite contents. Hydraulic conductivities seemed to be similar for all materials. The results of index tests correlated with the smectite content

  15. Calculation of saturated hydraulic conductivity of bentonite

    International Nuclear Information System (INIS)

    He Jun

    2006-01-01

    Hydraulic conductivity test has some defects such as weak repeatability, time-consuming. Taking bentonite as dual porous media, the calculation formula of the distance, d 2 , between montmorillonite in intraparticle pores is deduced. Improved calculated method of hydraulic conductivity is obtained using d 2 and Poiseuille law. The method is valid through the comparison with results of test and other methods. The method is very convenient to calculate hydraulic conductivity of bentonite of certain montmorillonite content and void ratio. (authors)

  16. Removal of oil from water by bentonite

    International Nuclear Information System (INIS)

    Moazed, H.; Viraraghavan, T.

    1999-01-01

    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

  17. Hydraulic conductivity of some bentonites in artificial seawater

    International Nuclear Information System (INIS)

    Komine, Hideo; Murakami, Satoshi; Yasuhara, Kazuya

    2011-01-01

    A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on hydraulic conductivity of three common sodium-types of bentonite and one calcium-type bentonite by the laboratory experiments. >From the results of laboratory experiment, this study discussed the influence of seawater on hydraulic conductivity of bentonites from the viewpoints of kinds of bentonite such as exchangeable-cation type and montmorillonite content and dry density of bentonite-based buffer. (author)

  18. Structural characterization of bentonite clays for utilization as nanofillers in nanocomposites; Caracterizacao estrutural de argilas bentoniticas para utilizacao como nanocargas

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Carlos Ivan Ribeiro de; Rocha, Marisa Cristina Guimares; Vogas, Arthur Considera, E-mail: carlosivanr@gmail.com [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico; Silva, Ana Lucia Nazareth da [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Instituto de Macromoleculas Professora Eloisa Mano; Bertolino, Luiz Carlos [Centro de Tecnologia Mineral (CETEM/MCTI), Rio de Janeiro, RJ (Brazil)

    2014-07-01

    Clays of different composition have been used in the development of polymer nanocomposites. However, the utilization of bentonite clays has been emphasized in Brazil, mainly due to their availability.The best known and studied deposits of bentonite clays are located in the state of Paraiba. However, these deposits are becoming exhausted after decades of exploitation. In this context, the aim of this work is to proceed the physical-mineralogical characterization of bentonite clays recently discovered in Cubati, PB. In order to achieve this objective, the samples underwent a particle size classification step and were characterized by X-ray fluorescence, X-ray diffraction, infrared spectroscopy, thermal analysis and scanning electron microscopy. Results of X-ray diffraction showed that the samples are composed of smectite, and kaolinite and quartz. The characterization of the samples by FTIR confirmed these results. Results of chemical analysis showed that the clays have predominantly different exchangeable cations. (author)

  19. Exchangeability of bentonite buffer and backfill materials

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D. [Savage Earth Associates Ltd, Bournemouth (United Kingdom); Arthur, R. [Intera Inc, Ottawa, ON, (Canada); Luukkonen, A.

    2012-08-15

    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

  20. 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.)

  1. Simulation of bentonite colloid migration through granite

    International Nuclear Information System (INIS)

    Rosicka, Dana; Hokr, Milan

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid

  2. Chemical interaction of fresh and saline waters with compacted bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.; Melamed, A.; Pitkaenen, P.

    1996-01-01

    The interaction of compacted sodium bentonite with fresh and saline ground-water simulant was studied. The parameters varied in the experiments were the compositions of the solutions and oxygen and carbon dioxide content in the surroundings. The main interests of the study were the chemical changes in the experimental solution, bentonite porewater and bentonite together with the microstructural properties of bentonite. The major processes with fresh water were the diffusion of sodium, potassium, sulphate, bicarbonate and chloride from bentonite to the solution, and the diffusion of calcium and magnesium from the solution into bentonite. The major processes in the experiments with saline water were the diffusion of the sodium, magnesium, sulphate and bicarbonate from bentonite into the solution, and the diffusion of calcium from the solution into bentonite

  3. Evaluation of gas migration characteristics of compacted bentonite and Ca-bentonite mixture

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2014-01-01

    In the current concept of subsurface disposal and near-surface pit disposal for low level radioactive waste, compacted bentonite and Ca-bentonite mixture will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides, respectively. Hydrogen gas can be generated inside the engineered barrier of subsurface disposal facilities mainly by anaerobic corrosion of metals used for containers, etc. Hydrogen gas can be also generated inside the engineered barrier of near-surface pit disposal facilities mainly by the chemical interaction between aluminum and the alkaline component of cement, or water. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the compacted bentonite and Ca-bentonite mixture, gas will accumulate in the void space inside of the compacted bentonite and Ca-bentonite mixture until breakthrough occurs. It is expected to be not easy for gas to entering into the compacted bentonite mixture as a discrete gaseous phase because the pore of the compacted bentonite and Ca-bentonite mixture is so minute. Therefore in this study, the gas migration characteristics and the effect of gas migration on the hydraulic conductivity of the compacted bentonite and Ca-bentonite mixture are investigated by the gas migration tests. The applicability of the two phase flow model without considering deformability of the specimen is investigated. The applicability of the model of two phase flow through deformable porous media, which was originally developed by CRIEPI, is also investigated. Results of this study imply that : (1) Gas migration mechanism of the compacted bentonite and Ca-bentonite mixture is revealed through gas migration test. (2) Hydraulic conductivity measured after the large gas breakthrough is substantially the same that measured before the gas migration test. (3) Stress change, pore-water pressure change and volume change of the specimen during the gas migration test can be reproduced by the numerical

  4. Dew contribution to the water balance in a semiarid coastal steppe ecosystem (Cabo de Gata, SE Spain)

    International Nuclear Information System (INIS)

    Moro, M. J.; Were, A.; Morillas, L.; Villagarcia, L.; Canton, Y.; Lazaro, R.; Serrano-Ortiz, P.; Kowalski, A. S.; Domingo, F.

    2009-01-01

    Dewfall deposition can be a significant source of moisture in arid and semiarid ecosystems, thus contribution to improve daily and annual water balances. Occurrence, frequency and amount of dewfall were measured in the Balsa Blanca site (Cabo de Gata, Almeria, Spain) from January 2007 to May 2008. this area has a sparse vegetation cover dominated by Stipa tenacissima combined with bare soil and biological soil crusts. (Author) 3 refs.

  5. Sorption behavior of cesium onto bentonite colloid

    International Nuclear Information System (INIS)

    Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

    2004-01-01

    It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

  6. Bentonite-amended soil special study

    International Nuclear Information System (INIS)

    1989-12-01

    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 CLAYMAX R , 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

  7. Analysis of the effect of vibrations on the bentonite buffer in the canister hole

    International Nuclear Information System (INIS)

    Jonsson, Martin; Hakami, Hossein; Ekneligoda, Thushan

    2009-09-01

    During the construction of a final repository for spent nuclear fuel in crystalline rock, blasting activities in certain deposition tunnels will occur at the same time as the deposition of canisters containing the waste is going on in another adjacent access tunnel. In fact, the deposition consists of several stages after the drilling of the deposition hole. The most vulnerable stage from a vibration point of view is when the bentonite buffer is placed in the deposition hole but the canister has not been placed yet. During this stage, a hollow column of bentonite blocks remains free to vibrate inside the deposition hole. The goal of this study was to investigate the displacement of the bentonite blocks when exposed to the highest vibration level that can be expected during the drill and blast operations. In order to investigate this, a three dimensional model in 3DEC, capable of capturing the dynamic behaviour of the bentonite buffer was set up. To define the vibration levels, which serve as input data for the 3DEC model, an extensive analysis of the recorded vibrations from the TASQ - tunnel was carried out. For this purpose, an upper expected vibration limit was defined. This was done outgoing from the fact that the planned charging for the construction of the geological repository will lie in the interval 2 to 4 kg. Furthermore, at the first stage for this study, it was decided that the vibration should be conservatively evaluated for 30 m distance. Using these data, it was concluded that the maximum vibration level that can be expected will be approximately 60 mm/s. After simplifying the vibration signal, a sinusoidal wave with the amplitude 60 mm/s was applied at the bottom of the column and it was assumed that the vibrations only affect the bentonite buffer in one direction (horizontal direction). From this simulation, it was concluded that hardly any displacements occurred. However, when applying the same sinusoidal wave both in the horizontal and the

  8. BaM bentonite and some of its properties

    International Nuclear Information System (INIS)

    Matal, Oldřich; Vávra Michal; Kachlík, Martin; Maca, Karel; Kotnour, Petr; Pospíšková, Ilona

    2018-01-01

    BaM bentonite is lime-magnesium bentonite of domestic origin. Its properties were measured experimentally with focus on the following parameters: composition, morphology and particle size distribution, powder bulk density, powder pressing parameters, shear strength, and water saturation. The findings will find use in nuclear safety assessments of engineered bentonite barriers in underground nuclear waste disposal facilities. (orig.)

  9. Bentonite-amended soils special study

    International Nuclear Information System (INIS)

    1990-10-01

    This report presents the results of a two-phased special study to evaluate the viability of soil amended with a high percentage of bentonite as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. Phase I of the study was initiated in order to examine the feasibility of using bentonite-amended soils as a cover component on sideslopes and topslopes. The Phase I objectives were to test a variety of materials to determine if low hydraulic conductivities were achievable in materials exhibiting sufficient strength and to select suitable materials for further testing. Phase II objectives were to (1) optimize designs -- test materials with various percentages of bentonite added; (2) provide design recommendations; (3) address constructibility concerns; and (4) evaluate long-term performance with respect to desiccation effects on the amended materials

  10. SAXS and TEM Investigation of Bentonite Structure

    International Nuclear Information System (INIS)

    Matusewicz, Michal; Liljestroem, Ville; Muurinen, Arto; Serimaa, Ritva

    2013-01-01

    A preliminary investigation of bentonite structure using Small-Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) is presented. Three types of clay were used: unchanged MX-80 bentonite and purified clays with sodium or calcium ions. Quantitative information in nano-scale - basal spacing, mean crystallite size - was obtained from SAXS, which was complemented by TEM to give qualitative information from micron to nanometre scale. SAXS seems to be a more reliable source of quantitative data than TEM. SAXS gives the averaged information about basal spacing. TEM in this study gives more qualitative information, but in a greater resolution range. The presented work is a starting point to combine more methods to obtain a better idea of bentonite structure. (authors)

  11. Equipment for deployment of canisters with spent nuclear fuel and bentonite buffer in horizontal holes

    International Nuclear Information System (INIS)

    Henttonen, V.; Suikki, M.

    1992-08-01

    The study presents the predesign of equipment for the deployment of canisters in long horizontal holes. The canisters are placed in the centre of the hole and are surrounded by a bentonite buffer. In thE study the canisters are assumed to have a diameter of 1.6 m and a length of 5.9 m, including the hemispherical ends. Their total weight is 60 tonnes. The bentonite buffer after homogenization is 400 mm thick, making a total package diameter of 2.4 m. The deployment system consists of four wagons for handling The canisters and the bentonite blocks. To ensure safe emplacement, every part is installed separately in its final position. This also makes it possible to use small clearances between the canisters and the bentonite blocks and between the blocks and the rock wall. With small clearances, backfilling can be avoided. Another basic design idea is that the wagons are equipped with wheels, which are in direct contact with the rock walls. Thus, rails, which have to be removed as the deployment progresses, are unnecessary. To minimize the time taken for deploying one canister, the wagons are designed so that only three trips from the service area to the deposit area are needed. Due to the radiation in the vicinity of the canisters, the wagons have to be teleoperated

  12. Equipment for deployment of canisters with spent nuclear fuel and bentonite buffer in horisontal holes

    International Nuclear Information System (INIS)

    Henttonen, V.; Suikki, M.

    1992-06-01

    This study presents the predesign of equipment for the deployment of canisters in long horizontal holes. The canisters are placed in the centre of the hole and are surrounded by a bentonite buffer. In this study the canisters are assumed to have a diameter of 1.6 m and a length of 5.9 m, including the hemispherical ends. Their total weight is 60 tonnes. The bentonite buffer after homogenization is 400 mm thick, making a total package diameter of 2.4 m. The deployment system consists of four wagons for handling the canisters and the bentonite blocks. To ensure safe emplacement, every part is installed separately in its final position. This also makes it possible to use small clearances between the canisters and the bentonite blocks and between the blocks and the rock wall. With small clearances, backfilling can be avoided. Another basic design idea is that the wagons are equipped with wheels, which are in direct contact with the rock walls. Thus, rails, which have to be removed as the deployment progresses, are unnecessary. To minimize the time taken for deploying one canister, the wagons are designed so that only three trips from the service area to the deposit area are needed. Due to the radiation in the vicinity of the canisters, the wagons have to be teleoperated. (au)

  13. Effect of pH on the sorption properties of bentonite Kopernica

    International Nuclear Information System (INIS)

    Galambos, M.; Paucova, V.

    2009-01-01

    In this work sorption of strontium-85 on Slovak bentonites was studied. Sorption experiments that were conducted at four different values of pH = 2, 4, 6 and 8 showed that by increasing of pH in the solution an increasing of values of percentage of sorption and of distribution relationships occur. Value approaching 99% was achieved during the sorption of strontium cations from the bentonite deposits Kopernica only at pH = 8. It can be concluded that in addition to the basic mechanism of sorption, which is ion exchange, complex-forming reactions with surface groups of bentonite take place there at higher values. The increase in value attributable to R 'hydrolytic' adsorption, because there is a reaction between Sr(OH) + and OH-groups and H + ion competition is stifled. At pH = 2 in the whole studied range of concentrations low values of sorption percent, distribution ratio and adsorbed amount of strontium were observed. It can be attributed to a significant competitive impact of hydrogen ions and disruption of the structure of bentonite.

  14. MANU. Purchase of Bentonite. Process Description

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    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.)

  15. Preparation and characterization of bentonite organo clay

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Almeida Neto, A.F.; Silva, M.G.C.

    2009-01-01

    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)

  16. Sorption of natural uranium by algerian bentonite

    International Nuclear Information System (INIS)

    Megouda, N.; Kadi, H.; Hamla, M.S.; Brahimi, H.

    2004-01-01

    Full text.Batch sorption experiments have been used to assess the sorption behaviour of uranium onto natural and drilling bentonites. The operating parameters (pH, aolis-liquid ratio, particle size, time and initial uranium concentration) influenced the rate of adsorption. The distribution coefficient (Kd) range values at equilibrium time are 45.95-1079.26 ml/g and 32.81-463053 ml/g for the drilling and natural bentonites respectively. The equilibrium isotherms show that the data correlate with both Freundlich and Langmuir models

  17. Effect of pH on-Sr adsorption on bentonite Lieskovec

    International Nuclear Information System (INIS)

    Galambos, M.

    2009-01-01

    Effect of changes in pH environment on the adsorption of Sr 2+ has been studied by radioisotope indications, using of radioisotope 85 Sr with energy γ-rays 0.514 MeV, in a static arrangement of the experiment, under aerobic conditions. The concentration range was 1 · 10 -5 - 5 · 10 -2 mol dm -3 . The samples of bentonite from Lieskovec deposit were tested which could be assigned into the Fe-montmorillonite group. (Author)

  18. Natural analogue studies of bentonite reaction under hyperalkaline conditions. Overview of ongoing work at the Zambales ophiolite, Philippines

    International Nuclear Information System (INIS)

    Fujii, N.; Yanakawa, M.; Arcilla, C.A.; Pascua, C.; Namiki, K.; Sato, T.; Shikazono, N.; Alexander, W.R.

    2011-01-01

    zeolites could have been produced as a product of smectite reaction in the hyperalkaline groundwaters. Although not included in this calculation to date, the CSH phases identified are completely consistent with reaction of clays with hyperalkaline groundwaters, as seen at other sites worldwide. At the Bigbiga site, an active hyperaline groundwater/bentonite reaction zone (at the base of the bentonite deposit) has recently been identified and a drilling campaign is planned for late autumn 2010. (author)

  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. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    Lehikoinen, J.

    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 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.)

  1. Layers of 'Cabo Frio' in 'Victoria Crater' (False Color)

    Science.gov (United States)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is an enhanced false color rendering of images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 750-nanometer, 530-nanometer and 430-nanometer filters.

  2. Layers of 'Cabo Frio' in 'Victoria Crater' (Stereo)

    Science.gov (United States)

    2006-01-01

    This view of 'Victoria crater' is looking southeast from 'Duck Bay' towards the dramatic promontory called 'Cabo Frio.' The small crater in the right foreground, informally known as 'Sputnik,' is about 20 meters (about 65 feet) away from the rover, the tip of the spectacular, layered, Cabo Frio promontory itself is about 200 meters (about 650 feet) away from the rover, and the exposed rock layers are about 15 meters (about 50 feet) tall. This is a red-blue stereo anaglyph generated from images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity during the rover's 952nd sol, or Martian day, (Sept. 28, 2006) using the camera's 430-nanometer filters.

  3. Cabo Verde telemedicine program: initial results of nationwide implementation.

    Science.gov (United States)

    Latifi, Rifat; Dasho, Erion; Merrell, Ronald C; Lopes, Miguel; Azevedo, Vanda; Bekteshi, Flamur; Osmani, Kalterina L; Qesteri, Orland; Kucani, Julian; Lecaj, Ismet

    2014-11-01

    Telemedicine and e-health have been suggested as one solution for closing the health disparity gap between the developed world and the developing world. Yet evidence is lacking from current successful programs in the developing world and, in particular, from sub-Saharan Africa. The primary objective of our study was to present the preliminary results of our efforts in building the Integrated Telemedicine and e-Health Program for Cabo Verde (ITeHP-CV), with an emphasis on initial utilization and results. This is a prospective study of data collected while we worked to establish a fully functional, integrated national telemedicine network and virtual education network in Cabo Verde. We used the International Virtual e-Hospital Foundation strategic approach known as "initiate-build-operate-transfer" over a 26-month period (November 2011-December 2013). We describe herein the five main pillars of this process that have been implemented: (1) capacity building; (2) network development and deployment of equipment; (3) implementation of clinical telemedicine; (4) implementation of activities related to continuing medical education, delivered from within the country and from abroad; and (5) establishment and use of the electronic virtual library. Based on comprehensive technical and medical assessment of the country's needs, 10 fully functional telemedicine centers in all nine inhabited islands of the Republic of Cabo Verde have been established. RESULTS are presented under the five main pillars of capacity building, network deployment, implementation of clinical telemedicine, implementation of continuing medical education activities, and establishment of the electronic virtual library. The ITeHP-CV has been successfully launched, and the initial results are encouraging. The continuity of the program and sustainability are primary goals once the program is transferred fully to the Ministry of Health of Cabo Verde. A long-term follow-up study is required in order to ensure

  4. Preparation and Characterization of Dabco (1,4-Diazabicyclo [2.2.2]octane) modified bentonite: Application for Congo red removal

    Science.gov (United States)

    Taher, Tarmizi; Rohendi, Dedi; Mohadi, Risfidian; Lesbani, Aldes

    2018-01-01

    Natural bentonite provided from Sarolangun deposit was modified with 1,4-Diazabicyclo[2.2.2]octane (Dabco) to form a new class of porous material. Prior further modification, the natural bentonite was cleaned up and activated by NaCl to remove the impurities and increase the bentonite nature. Dabco modified bentonite (Dabco-bent) was prepared by exchanging the inorganic cation placed in the interlayer space of the montmorillonite mineral structure with the 0.01 M Dabco1+ at pH 6. The modified bentonite products were characterized using X-Ray powder diffraction and FT-IR to monitor the change of the bentonite crystallinity and function group due to the modification process. The XRD result confirmed that during the modification process, the d(001) of smectite peak at 2q around 6° was shifted. After the modification, the d(001) reflection of the montmorillonite interlayer was shifted 0.36° to the left indicating that the interlayer space of the montmorillonite has been expanded during the modification process. The FTIR spectra of Dabco modified bentonite exhibit no significantly different with the host bentonite. However, the presence of the new band at the wavenumber around 3000 and 2800 cm-1 indicates that the Dabco molecule has been successfully inserted to the bentonite molecule. The Congo red adsorption experiment was performed onto Dabco-bent product by batch technique. The experiment data described that kinetic model for Congo red adsorption onto Dabco-bent was adequately followed the second-order kinetic model and well described by Freundlich adsorption isotherm model.

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

    International Nuclear Information System (INIS)

    Daemen, J.; Ran, Chongwei

    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

  6. 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.

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

    International Nuclear Information System (INIS)

    Ouyang, Shoung.

    1990-01-01

    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

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

    International Nuclear Information System (INIS)

    Santos, J.J.M.; Silva, B.L.; Araujo, I.J.C.; Medeiros, A.M.; Melo, J.D.D.; Paskocimas, C.A.

    2011-01-01

    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)

  9. Characterization of natural bentonite by NMR

    International Nuclear Information System (INIS)

    Leite, Sidnei Q.M.; Dieguez, Lidia C.; Menezes, Sonia M.C.; San Gil, Rosane A.S.

    1993-01-01

    Solid state NMR as well as several other instrumental chemical analysis techniques were used in order to characterize two natural occurring bentonite. The methodology is described. The NMR spectra, together with the other used techniques suggest that the observed differences are due to iron inclusions in tetrahedral and octahedral sites

  10. Pemanfaatan Bentonite sebagai Media Pembumian Elektroda Batang

    Directory of Open Access Journals (Sweden)

    Winanda Riga Tamma

    2017-03-01

    Full Text Available Sistem pentanahan merupakan suatu sistem yang bertujuan untuk mengamankan sistem tenaga listrik dari gangguan ke tanah maupun gangguan hubung singkat. Pada sistem pentanahan yang baik, resistansi pentanahan harus bernilai dibawah lima ohm. Resistansi pentanahan bergantung pada berbagai aspek antara lain yaitu struktur tanah, kelembapan tanah, dan kandungan yang ada dalam tanah itu sendiri. Dalam pengujian pada penelitian ini akan dilakukan perbaikan pada tanah dengan mencampurkan bentonite ke dalam tanah sebagai media pentanahan. Pencampuran bentonite bertujuan agar mendapatkan nilai resistansi pentanahan yang baik sesuai dengan standar sistem pentanahan. Pengujian dilakukan menggunakan elektroda batang dan alat earth resistance tester dengan metode tiga titik dimana elektroda utama atau elektroda pengukuran diberikan treatment sesuai dengan kondisi yang telah ditentukan. Diharapkan pada pengujian ini akan diketahui dampak dari bentonite terhadap penurunan nilai resistansi pentanahan. Hasil pengujian menunjukkan bahwa dengan mencampurkan bentonite pada media pentanahan, resistansi pentanahan menjadi lebih baik. Meskipun tidak terlalu signifikan, rata-rata penurunan dari setiap masing-masing treatment adalah sebesar 2 ohm.

  11. Mineralogy and sealing properties of various bentonites and smectite-rich clay materials

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, Ola; Olsson, Siv; Nilsson, Ulf (Clay Technology AB (SE))

    2006-12-15

    The present work includes a coherent study of Wyoming bentonite with respect to the most relevant properties for use in a repository, and a parallel study of other potential buffer and tunnel backfilling materials. The reason for this is twofold; to quantify the effect of mineralogical variations on the various important sealing properties of bentonite, and to verify that there are alternative potential sources of bentonite. The latter is motivated by the fact that Sweden alone plans to deposit at least 6,000 copper canisters which include approximately 130,000 metric tones bentonite buffer material and several times more as tunnel backfill material. Different types of sealing clay materials may also be relevant to use, since the demands on the clay will be different at the various locations in a repository. Alternative sources of bentonite would consequently be valuable in order to secure quality, supply, and price. Important aspects on buffer and tunnel backfilling materials may be summarized as: Original sealing properties. Hazardous substances in any respect. Short-term effects of ground-water chemistry. Long-term stability, i.e. effects of temperature and ground-water chemistry. Availability. Costs. The focus in this study is on the first three items. The long-term stability is indirectly considered in that mineralogical composition is determined. The availability is only considered in such a way that most of the analyzed materials represent huge clay formations, which contain much more material than needed for a repository. The cost aspects have not been included, mainly because the present day price is not relevant due to the time frame of the construction of a repository

  12. Functioning of blocks of compacted bentonite in a repository for spent nuclear fuels

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Kalbantner, P.; Sjoeblom, R.

    2001-12-01

    The main purpose of the presented work is to provide The Swedish Nuclear Fuel and Waste Management Company (SKB) with a proposed set of requirements regarding the functioning of the blocks of compacted bentonite. These blocks are intended to constitute the bentonite envelope which after uptake of water will form the buffer between the canister and the rock. The purpose is also to provide a basis for SKB for their direction of the continued development work for the selection of a reference technology and for creating a quality system for the buffer material. No attempts are made in the report to derive the functional requirements. Instead, such requirements are postulated based on realistic scenarios regarding the chain of processes from excavation - transport - preparation of press powder - compaction - handling and emplacement in the deposition hole. It is the strategy of SKB to use a natural material which after the above-mentioned processes forms a buffer with properties which closely resemble those of the original material. This implies that all process steps must be designed in such a way that the properties of the bentonite do not change to any significant degree with respect to the disposal function. The main results in the report are as follows: A set of functional requirements are compiled and presented. These concord with the different descriptions given on the process steps. The requirements are generic and are assessed to be relatively invariant for various operational requirements and process controls. The process chain comprising excavation of bentonite - transport - preparation of press powder - compaction - handling and emplacement are explained. The presentations of functional requirements and processes are foreseen to constitute a basis for a comparison between uniaxial and isostatic compaction and can be an important basis for SKB's quality work. The development of cracks in the bentonite blocks has been identified as an important aspect for the

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

    Energy Technology Data Exchange (ETDEWEB)

    Herbert, Horst-Juergen; Xie, Mingliang [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany); Kasbohm, Joern; Lan, Nguyen T. [Greifswald Univ. (Germany); Hoang Thi Minh Thao [Hanoi Univ. of Science (Viet Nam)

    2011-11-15

    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 Fe{sup 2+} 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/cm{sup 3} 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

  14. Modeling early in situ wetting of a compacted bentonite buffer installed in low permeable crystalline bedrock

    Science.gov (United States)

    Dessirier, B.; Frampton, A.; Fransson, À.; Jarsjö, J.

    2016-08-01

    The repository concept for geological disposal of spent nuclear fuel in Sweden and Finland is planned to be constructed in sparsely fractured crystalline bedrock and with an engineered bentonite buffer to embed the waste canisters. An important stage in such a deep repository is the postclosure phase following the deposition and the backfilling operations when the initially unsaturated buffer material gets hydrated by the groundwater delivered by the natural bedrock. We use numerical simulations to interpret observations on buffer wetting gathered during an in situ campaign, the Bentonite Rock Interaction Experiment, in which unsaturated bentonite columns were introduced into deposition holes in the floor of a 417 m deep tunnel at the Äspö Hard Rock Laboratory in Sweden. Our objectives are to assess the performance of state-of-the-art flow models in reproducing the buffer wetting process and to investigate to which extent dependable predictions of buffer wetting times and saturation patterns can be made based on information collected prior to buffer insertion. This would be important for preventing insertion into unsuitable bedrock environments. Field data and modeling results indicate the development of a de-saturated zone in the rock and show that in most cases, the presence or absence of fractures and flow heterogeneity are more important factors for correct wetting predictions than the total inflow. For instance, for an equal open-hole inflow value, homogeneous inflow yields much more rapid buffer wetting than cases where fractures are represented explicitly thus creating heterogeneous inflow distributions.

  15. Water uptake, migration and swelling characteristics of unsaturated and saturated, highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1980-09-01

    The report presents the results of a number of laboratory tests and field observations to form the basis of a physical and mathematical model that can be used for predicting water uptake and swelling in highly compacted bentonite components of an actual deposition plant. The clay buffer masses have been suggested as barriers in the Swedish KBS concepts. Two commercially available bentonites were used for the production of samples. The rate of water uptake suggests a mathematical model based on a simple diffusion equation. The rate is determined by the access of water and thousands of years may pass before saturation is obtained. The rate of swelling is governed by the negative pore pressure and the permeability. There is reasonable agreement with field observations. The observed swelling potential of old smectite-rich clays has offered the evidence. (G.B.)

  16. STUDY OF THERMAL AND ACID STABILITY OF BENTONITE CLAY

    Directory of Open Access Journals (Sweden)

    Karna Wijaya

    2010-06-01

    Full Text Available The thermal and acid stability of the bentonite clays (Na- and Ca-bentonite have been tested. The thermal stability testing has been carried out by heating 5 gram of the clays  for five hours at 200, 300 and 500 °C respectively, meanwhile acid stability testing was performed by immersing 5 gram clays into 100 mL sulphuric acid 1M, 2M and 3M for 24 hours. The tested clays, then were characterized by means of X-Ray difractometry and IR-spectroscopy methods. The characterization results showed that upon heating, both Ca- and Na-bentonites indicated same thermal stability. However, upon acid treatment, Na-bentonite was found relatively stabiler and more resistance then Ca-bentonite.   Keywords: bentonite, clay, thermal stability, acid stability.

  17. Bentonite. Geotechnical barrier and source for microbial life

    Energy Technology Data Exchange (ETDEWEB)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HZDR Young Investigator Group; Steglich, Jennifer

    2017-06-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N{sub 2}/CO{sub 2}-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  18. Bentonite. Geotechnical barrier and source for microbial life

    International Nuclear Information System (INIS)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea; Steglich, Jennifer

    2017-01-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N_2/CO_2-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  19. FEBEX bentonite colloid stability in ground water

    Energy Technology Data Exchange (ETDEWEB)

    Seher, H.; Schaefer, T.; Geckeis, H. [Inst. fuer Nukleare Entsorgung (INE), Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)]. e-mail: holger.seher@ine.fzk .de; Fanghaenel, T. [Ruprecht-Karls-Univ. Heidelberg, Physikalisch-Chemisches In st., D-69120 Heidelberg (Germany)

    2007-06-15

    Coagulation experiments are accomplished to identify the geochemical conditions for the stability of Febex bentonite colloids in granite ground water. The experiments are carried out by varying pH, ionic strength and type of electrolyte. The dynamic light scattering technique (photon correlation spectroscopy) is used to measure the size evolution of the colloids with time. Agglomeration rates are higher in MgCl{sub 2} and CaCl{sub 2} than in NaCl solution. Relative agglomeration rates follow approximately the Schulze-Hardy rule. Increasing agglomeration rates at pH>8 are observed in experiments with MgCl{sub 2} and CaCl{sub 2} which are, however, caused by coprecipitation phenomena. Bentonite colloid stability fields derived from the colloid agglomeration experiments predict low colloid stabilization in granite ground water taken from Aespoe, Sweden, and relatively high colloid stability in Grimsel ground water (Switzerland)

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

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

    International Nuclear Information System (INIS)

    Osada, Kazuo; Nagano, Tetsushi; Nakayama, Shinichi; Muraoka, Susumu

    1992-02-01

    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-Fe 2 O 3 was identified by means of colorimetry. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Sitompul, Johnner, E-mail: sitompul@che.itb.ac.id; Setyawan, Daru, E-mail: daru.setyawan@gmail.com; Kim, Daniel Young Joon, E-mail: daniel.kim12321@gmail.com [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Lee, Hyung Woo, E-mail: leehw@che.itb.ac.id [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Research and Business Foundation, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi, 440-746 (Korea, Republic of)

    2016-04-19

    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.

  3. Immobilization of spent Bentonite by using cement matrix

    International Nuclear Information System (INIS)

    Isman MT; Endro-Kismolo

    1996-01-01

    Investigation of spent bentonite immobilization by using cement was done. The purpose of the investigation was to know the performance of cement in binding bentonite waste. The investigation was done by adding cement, water, and bentonite waste into a container and string until the mixture became homogenous. The mixture was put into a polyethylene tube (3.5 cm in diameter and 4 cm high) and it was cured up to 28 days. The specific weight of the monolith block was then calculated, and the compressive strength and the leaching rate in ground water and sea water was tested. The mass ratio of water to cement was 0.4. The variable investigated was the mass ratio of bentonite to cement. The immobilized bentonite waste was natural bentonite waste and activated bentonite waste. The result of the investigation showed that cement was good for binding bentonite waste. The maximum binding mass ratio of bentonite to cement was 0.4. In this condition the specific weight of the monolith block was 2.177 gram/cm 3 , its compressive strength was 22.6 N/mm 2 , and the leaching rate for 90 days in ground water and sea water was 5.7 x 10 -4 gram cm -2 day -1

  4. Borehole sealing with highly compactd Na bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1981-12-01

    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)

  5. Using bentonite for NPP liquid waste treatment

    International Nuclear Information System (INIS)

    Bui Dang Hanh

    2015-01-01

    During operation, nuclear power plants (NPPs) release a large quantity of water waste containing radionuclides required treatment for protection of the radiation workers and the environment. This paper introduces processes used to treat water waste from Paks NPP in Hungary and it also presents the results of a study on the use of Vietnamese bentonite to remove radioactive Caesium from a simulated water waste containing Cs. (author)

  6. Thermal characteristics of highly compressed bentonite

    International Nuclear Information System (INIS)

    Sueoka, Tooru; Kobayashi, Atsushi; Imamura, S.; Ogawa, Terushige; Murata, Shigemi.

    1990-01-01

    In the disposal of high level radioactive wastes in strata, it is planned to protect the canisters enclosing wastes with buffer materials such as overpacks and clay, therefore, the examination of artificial barrier materials is an important problem. The concept of the disposal in strata and the soil mechanics characteristics of highly compressed bentonite as an artificial barrier material were already reported. In this study, the basic experiment on the thermal characteristics of highly compressed bentonite was carried out, therefore, it is reported. The thermal conductivity of buffer materials is important because the possibility that it determines the temperature of solidified bodies and canisters is high, and the buffer materials may cause the thermal degeneration due to high temperature. Thermophysical properties are roughly divided into thermodynamic property, transport property and optical property. The basic principle of measured thermal conductivity and thermal diffusivity, the kinds of the measuring method and so on are explained. As for the measurement of the thermal conductivity of highly compressed bentonite, the experimental setup, the procedure, samples and the results are reported. (K.I.)

  7. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    Linares Gonzalez, J.; Barahona Fernandez, E.; Huertas Garcia, F.; Caballero Mesa, E.; Cuadros Ojeda, J.

    1996-01-01

    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)

  8. Sorption properties of bentonite clays towards Pu(IV), U(VI), Np(V) and Cs: experimental and surface complexation study

    Energy Technology Data Exchange (ETDEWEB)

    Sabodina, M.N. [Institute of Physical Chemistry of Russian Academy of Science, Moscow 119192 (Russian Federation); Kalmykov, St.N.; Sapozhnikov, Yu.A. [Radiochemistry div., Chemistry dept., Lomonosov Moscow State University, Moscow 119992, (Russian Federation); Gupalo, T.A.; Beigul, V.P. [VNIPI Promtechnology, Moscow (Russian Federation)

    2005-07-01

    Full text of publication follows: Sorption of radionuclides, their diffusion in bentonite as well as its solubility are the major factors that define bentonite as a geochemical barrier. Sorption of cations by bentonite could be governed by two mechanisms including ion exchange with interlayer cations and formation of surface complexes with either silanol or aluminol groups. The aim of this work was to study mechanisms of {sup 137}Cs, Pu(IV), Np(V) and U(VI) sorption by bentonite and their solubility in bentonite pore waters. Bentonite (Khakassiya deposit) used in the experiments was taken in Na-form and characterized by powder X-ray diffraction, scanning electron microscopy, potentiometric titration. The cation exchange capacities of bentonite at pH=6 were measured by isotopic exchange with {sup 22}Na{sup +} and Cs{sup +} saturation. Sorption experiments were performed in N{sub 2} atmosphere in plastic vials. Bentonite samples were left in the working solutions to swell for few days before sorption experiments were performed. After the desired concentration of radionuclide ({sup 137}Cs, {sup 238}Pu, {sup 239}Pu, {sup 237}Np, {sup 239}Np, {sup 238}U) was added to the suspension, the required pH values are established and samples were left until the equilibrium was reached. Separation of solution after the sorption was performed using micro- and ultrafiltration techniques. The sorption of Pu(IV), U(VI) and Np(V) was highly pH dependent that indicates predominant surface complexation mechanism of sorption. For {sup 137}Cs the pH dependence of sorption was less pronounced and significant decrease of sorption occurs at pH<1.7 that indicate the ion exchange as the major mechanism. The equilibrium constant of Na{sup +}/Cs{sup +} exchange was calculated form sorption isotherms and pH dependence of sorption. It is established using micro- and ultra-filtrations, that sorption of radionuclides onto bentonite nano colloids is essential. Surface complexation modeling exercises

  9. A comparison of nano bentonite and some nano chemical additives to improve drilling fluid using local clay and commercial bentonites

    Directory of Open Access Journals (Sweden)

    Nada S. Al-Zubaidi

    2017-09-01

    In the second part, a commercial bentonite was used and mixed with nano commercial bentonite and nano chemical materials (MgO, TiO2, and graphene at 0.005, 0.01, 0.05, 0.1, 0.2 and 0.4 wt% concentrations. The results showed that nano commercial bentonite gives the same filtration behavior of graphene, whereas, the plastic viscosity, yield point and apparent viscosity were the same when using nano commercial bentonite, TiO2 and graphene. The best results were obtained with MgO addition, whereby the filter loss decreased to 35% with a higher value of yield point.

  10. Biological and oceanographic upwelling indicators at Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Gleyci A. O. Moser

    1997-01-01

    Full Text Available Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ, Southeast Brazil, during summer (December 29 to 31, 1991 and winter (June 27 to 30, 1992. Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW, found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.A biomassa fitoplanctônica, parâmetros químicos e hidrologia foram estudadas em um transecto de 101,6 Km ao largo de Cabo Frio, (RJ Brasil, durante o verão (Dezembro 29 a 31, 1991 e inverno (Junho 27 a 30, 1992. Nesta área, eventos de ressurgência induzidos pelo vento são comuns durante o verão, tornando-se mais raros durante o inverno. Durante o período de verão uma floração de fitoplâncton foi observada na superfície próximo ao continente, apresentando um máximo de clorofila-a igual a 25,55 mg Cl-a m'3 desacoplado das águas frias e ricas em nutrientes da Água Central do Atlântico Sul (ACAS, presente abaixo de 40 m. Durante o inverno, a ACAS alcançou a superflcie em frente a Cabo Frio, caracterizando um evento de ressurgência. Entretanto, apesar das altas concentrações de nitrato na superf

  11. Estudo da rigidez efetiva do cabo de pontes estaiadas

    OpenAIRE

    Alexandre Magno Lima Cardoso

    2013-01-01

    As pontes estaiadas vêm sendo cada vez mais utilizadas no país, seja pela competitividade alcançada em função do domínio da tecnologia por parte dos empreiteiros e calculistas, seja pelo apelo estético. Os cabos, principais componentes deste sistema estrutural, que conferem o caráter altamente hiperestático e o comportamento não linear da estrutura são, em muitos modelos, numericamente simulados como um elemento de treliça, com a sua rigidez calculada em função da geometria e nível de carrega...

  12. 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

    dimensions and relatively even surfaces. The blocks could readily be produced to desirable void ratio and density. The bentonite blocks produced had a high homogeneity. No fractures could be observed visually. Microcracks could be identified on strong magnification, as might be expected. The mechanical properties recorded were good and the spread in the values low for all blocks. No special difficulty was encountered which was related to the complex shape of the blocks (beaker-like). The complex shape influenced the design of the bag and filling system, as well as the procedure for filling. The method of machining presently used at Ifoe Ceramics AB for their ordinary production works excellently for compacted bentonite as well. A coarse estimate indicates that the machining of the blocks for one entire deposition hole may take on the order of a small number of hours. The production went very well for all the combinations of production parameters used. Variation of production parameters might be utilised to adjust some of the properties of the blocks. It should be noted that in the processes, no substances are introduced into the bentonite other than pure water. No limitations have been identified regarding the proportions of the blocks manufactured (e.g.diameter/height ratio). Although very positive conclusions are drawn on essentially all points above, further development work is necessary before a process for full scale operation can be established.

  13. MANU. Handling of bentonite prior buffer block manufacturing

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The aim of this study is to describe the entire bentonite handling process starting from freight from harbour to storage facility and ending up to the manufacturing filling process of the bentonite block moulds. This work describes the bentonite handling prior to the process in which bentonite blocks are manufactured in great quantities. This work included a study of relevant Nordic and international well documented cases of storage, processing and techniques involving bentonite material. Information about storage and handling processes from producers or re-sellers of bentonite was collected while keeping in mind the requirements coming from the Posiva side. Also a limited experiment was made for humidification of different material types. This work includes a detailed description of methods and equipment needed for bentonite storage and processing. Posiva Oy used Jauhetekniikka Oy as a consultant to prepare handling process flow charts for bentonite. Jauhetekniikka Oy also evaluated the content of this report. The handling of bentonite was based on the assumption that bentonite process work is done in one factory for 11 months of work time while the weekly volume is around 41-45 tons. Storage space needed in this case is about 300 tons of bentonite which equals about seven weeks of raw material consumption. This work concluded several things to be carefully considered: sampling at various phases of the process, the air quality at the production/storage facilities (humidity and temperature), the level of automation/process control of the manufacturing process and the means of producing/saving data from different phases of the process. (orig.)

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

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    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)

  15. LOT A2 Test, THC-modelling of bentonite buffer in a final repository of spent nuclear fuel

    International Nuclear Information System (INIS)

    Itaelae, A.; Olin, M.; Rasilainen, K.; Pulkkanen, V.M.

    2010-01-01

    Document available in extended abstract form only. The Finnish spent nuclear fuel disposal is planned to be based on the KBS-3V repository concept. Within this concept, the role of the bentonite buffer is considered to be central. The aim of this study was to model the evolution of the buffer during the thermal phase (heat-generating period of spent fuel), when the bentonite is only partially saturated initially, and the surrounding rock matrix is assumed to be fully saturated. It is essential to study how temperature will affect saturation and also how both of these affect the chemistry of bentonite. In order to make the modeling more concrete, an example experimental case was considered: Long Term Test of Buffer Materials (LOT) A2-parcel test at the Aespoe Hard Rock Laboratory (HRL) in Sweden. In the A2-parcel the MX-80 bentonite was exposed to adverse (120-150 deg. C) temperature conditions and high temperature gradients. The test parcel diameter was smaller than in the actual KBS-3V deposition hole to speed up the saturation. The chemical behaviour of minerals causes their redistribution inside the bentonite. For example, according to the laboratory tests, gypsum dissolves and anhydrite precipitates near the heater-bentonite interface. Also, incoming groundwater affects the bentonite pore water and its properties. These changes may, in turn, influence the mechanical properties of the bentonite. A coupled Thermo-Hydro-Chemical (THC) model was applied, which means that all mechanical effects were ignored. The purpose of the model was first to achieve a satisfactory match between the model and experimental results, and, therefore, the time frame was limited to ten years (LOT A-2 parcel test lasted approximately 6 years). The system was simplified to 1-D in order to reduce the computational work, which can be very significant due to complex chemical calculations. The 1-D model results are reported in Itaelae (2009). The aim is to extend the calculations to 2-D

  16. Verification of substitution of bentonites by montmorillonitic clays summary report on Czech montmorillonitic clays

    International Nuclear Information System (INIS)

    Carlson, L.; Keto, P.

    2006-10-01

    Czech bentonites and smectite-rich clays were characterised in order to study if they could be used as buffer and backfill materials instead of non-Czech commercial bentonites. The characterisation work was orgnized by RAWRA (the Czech Radioactive Waste Repository Authority) and the main part of the work was performed in the Czech Republic at Charles University and at Czech Technical University. Parallel and complementary characterisation was conducted in Finland in Sweden. This report was compiled with the aim to summarise the results, and to compare the methods and results gained in different testing laboratories. The characterisation included mineralogical, chemical and geotechnical investigations and experiments on thermal stability and sorption. There were some variations between the results gained in different laboratories. This was mainly due to differences between the testing methods used but also due to heterogeneity of the samples. The Czech bentonite-clays from Rokle and Strance clay deposits contained relatively high amount of swelling minerals and thus can be considered as potential buffer and backfill materials. (orig.)

  17. Sorption of uranium anionic species from aqueous solutions on HDTMA-bentonite Jelsovy potok

    International Nuclear Information System (INIS)

    Krajnak, A.; Viglasova, E.; Galambos, M.; Rosskopfova, O.

    2014-01-01

    Bentonite deposit Jelsovy potok in Slovakia has great potential for use as a engineering barrier in the multi-barrier system of deep geological repository. In this paper, HDTMA-modified bentonite J15m from Slovak bentonite Jelsovy potok was prepared and its sorption properties (sorption isotherms, kinetics) towards anionic uranium species was investigated. The removal of uranium anionic species from aqueous solutions (initial concentration: 10-1,000 mg/L) by J15m was studied in the absence of background electrolytes at initial pH range (pH init ) 8.5; 9.5; 10.5. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake capacity observed was 31.35 (mg/g) at 298 K. Experimental results were analysed by the Langmuir, Freundlich Dubinin-Redushkevich and Tempkin isotherm. The kinetics of adsorption of U(VI) ions was also discussed using the pseudo-first-order and the pseudo-second-order at three different temperatures. The activation energy of the sorption for J15m was calculated as 23.534 kJ·mol -1 . (authors)

  18. Filtration behavior of organic substance through a compacted bentonite

    International Nuclear Information System (INIS)

    Kanaji, Mariko; Kuno, Yoshio; Yui, Mikazu

    1999-07-01

    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/cm 3 . 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)

  19. A comparative study of the flow enhancing properties of bentonite ...

    African Journals Online (AJOL)

    A comparative study of granule flow enhancing property of bentonite, magnesium stearate, talc and microcrystalline cellulose (MCC) was undertaken. Bentonite was processed into fine powder. A 10 %w/w of starch granules was prepared and separated into different sizes (˂180, 180-500, 500-710 and 710-850 μm).

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

    International Nuclear Information System (INIS)

    Sato, Haruo; Yui, Mikazu; Yoshikawa, Hideki

    1995-01-01

    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/m 3 . Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N 2 atmospheric condition (O 2 : 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 SeO 3 2- , 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 HZrO 3 - . Distribution coefficient measured for Zr on the bentonite was about 1.0 m 3 /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

  1. Surface coatings on quartz grains in bentonites and their relevance to human health

    International Nuclear Information System (INIS)

    Wendlandt, Richard F.; Harrison, Wendy J.; Vaughan, David J.

    2007-01-01

    The cytotoxicity of quartz in the human lung is recognized to be dependent on both the inherent properties of the silica dust and external factors related to the history of the dust and including the presence of surface contamination. In this study, the physical and chemical surface properties of quartz grains in commercial bentonite deposits from the western (South Dakota) and southern (Alabama) USA were investigated. Measured quartz contents of bentonites range from 1.9 to 8.5 wt% with the <10 μm size fraction comprising 6-45% of this total. Trace element contents (Fe-Ti-Al) of quartz grains from any given bentonite are similar, indicating a single origin for the quartz with little if any contamination from other sources. Surface coatings are pervasive on all quartz grains and resist removal by repeated vigorous washings and reaction with HCl. Textural attributes and XPS and EDS analyses of these coatings are consistent with most being montmorillonite and, less frequently, mixtures of montmorillonite and opaline silica. Opaline silica (opal-A and opal-CT) occurs in two texturally distinct generations: an early massive grain-coating event and as later lepispheres. Montmorillonite coating thicknesses range from <1 μm to more than 10 μm thick. Surfaces of plagioclase, K-feldspar, and biotite grains are conspicuously devoid of montmorillonite coatings, but may show sparse distributions of opal-CT lepispheres. HRTEM has not confirmed a topotactic relationship or atomic structural concordance between montmorillonite coatings and underlying quartz grains. Alternatively, a precursor volcanic glass phase that coats the quartz surfaces during volcanic eruption and/or preferential early precipitation of opaline silica on quartz may provide substrates for development of montmorillonite coatings. Estimations of montmorillonite biodurability under pulmonary pH conditions suggest possible prolonged sequestration of respired bentonite quartz grains from contact with lung

  2. General corrosion of Ti in hot water and water saturated bentonite clay

    International Nuclear Information System (INIS)

    Mattsson, H.; Olefjord, I.

    1984-12-01

    Titanium has been proposed as one of the candidates for canister materials for storing spent nuclear fuel in the Swedish bed-rock. The deposition milieu was simulated on a laboratory scale by embedding titanium in compacted bentonite and the general corrosion rate was investigated. More fundamental studies were also performed where titanium was exposed to water in which special attention was paid to the NaCl content and oxygen content. In reaction cells designed according to high vacuum principles it was possible to reduce the oxygen content to very low values. The exposure time ranged between 1 min. and 6 months. Analysis of the corrosion products was performed mainly with ESCA. In water at 95 degrees C the oxide growth follows a direct logarithmic law: y equals 8.7 + 3.65 ln t. Oxygen and salt do not influence the rate of the oxide growth significantly. The general corrosion rate is approximately the same as the oxide growth rate since the dissolution of Ti into the water-solution is very low. The oxide consists of an outer layer of TiO 2 and a few atomic layers of suboxide close to the oxide/metal interface. Transmission electron microscopy studies of the water-formed oxides indicate that these are amorphous. The oxides formed on Ti exposed in bentonite is 70-100 Aa thick for exposure times ranging between 4 months and 2 years. It is shown, that montmorillonite - the main constituent in bentonite - is absorbed in the TiO 2 formed on these samples. If it is assumed that a logarithmic growth law is valid even for long-term exposure in bentonite, the growth law which will give the highest growth rate is y equals 5.5 ln t. An oxide thickness of 160 Aa is obtained if this law is extrapolated to 100.000 years exposure. (Author)

  3. Gas migration characteristics of highly compacted bentonite ore

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2010-01-01

    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 dissolved gas 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. Gas migration characteristics of highly compacted powdered bentonite are already reported by CRIEPI. In this report, gas migration characteristics of bentonite ore, which is a candidate for construction material of repository for radioactive waste, is investigated. The following conclusions are obtained through the results of the gas migration tests which are conducted in this study: 1) When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. By increasing the gas pressure more, gas breakthrough, which defined as a sudden and sharp increase in gas flow rate out of the specimen, occurs. Therefore gas migration mechanism of compacted bentonite ore is basically identical to that of compacted powdered bentonite. 2) Hydraulic conductivity measured after the gas breakthrough is somewhat smaller than that measured before the gas migration test. This fact means that it might be possible to neglect decline of the function of bentonite as engineered barrier caused by the gas breakthrough. These characteristics of compacted bentonite ore are identical to those of

  4. Removal of cobalt from lubricant oil by the use of bentonite: equilibrium, kinetic and adsorption preliminary studies

    Energy Technology Data Exchange (ETDEWEB)

    Cuccia, Valeria; Seles, Sandro R.N.; Ladeira, Ana Cláudia Queiroz, E-mail: vc@cdtn.br, E-mail: seless@cdtn.br, E-mail: acql@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-11-01

    Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator's facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Bentonite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system's kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assumption that the adsorption is due to chemisorption. Batch sorption tests were conducted and the results fitted to Langmuir and Freundlich sorption models. Both isotherm models chosen for this work did not fit to the experimental data. Thus, these are preliminary results and the studies must be repeated to evaluate data variability and better statistical inference. Other isotherm models must be evaluated to choose the best fitted one and describe the sorption of cobalt on bentonite in oil matrix. Even though, bentonite has considerable potential as sorbent for the removal of cobalt from lubricant oil. Finally, the results might be extended to other kinds of radioactive oils and radioactive organic wastes. (author)

  5. Enhanced shear strength of sodium bentonite using frictional additives

    International Nuclear Information System (INIS)

    Schmitt, K.E.; Bowders, J.J.; Gilbert, R.B.; Daniel, D.E.

    1997-01-01

    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 -9 cm/sec, while increasing the shear strength parameters of the bentonitic mixture to φ' = 17 degrees and c' = 0

  6. Influence factors of sand-bentonite mixtures on hydraulic conductivity

    International Nuclear Information System (INIS)

    Chen Yonggui; Ye Weimin; Chen Bao; Wan Min; Wang Qiong

    2008-01-01

    Buffer material is a very important part of the engineering barrier for geological disposal of high-level radioactive nuclear waste. Compacted bentonite is attracting greater attention as buffer and backfill material because it offer impermeability and swelling properties, but the pure compacted bentonite strength decreases with increasing hydration and these will reduce the buffer capability. To solve this problem, sand is often used to form compacted sand-bentonite mixtures (SBMs) providing high thermal conductivity, excellent compaction capacity, long-time stability, and low engineering cost. As to SBMs, hydraulic conductivity is a important index for evaluation barrier capability. Based on the review of research results, the factors affecting the hydraulic conductivity of SBMs were put forward including bentonite content, grain size distribution, moisture content, dry density, compacting method and energy, and bentonite type. The studies show that the hydraulic conductivity of SBMs is controlled by the hydraulic conductivity of the bentonite, it also decreases as dry density and bentonite content increase, but when the bentonite content reach a critical point, the influence of increasing bentonite to decrease the hydraulic conductivity is limited. A fine and well-graded SBMs is likely to have a lower hydraulic conductivity than a coarse and poorly graded material. The internal erosion or erodibility based on the grain size distribution of the SBMs has a negative effect on the final hydraulic conductivity. The lowest hydraulic conductivity is gained when the mixtures are compacted close to optimum moisture content. Also, the mixtures compacted at moisture contents slightly above optimum values give lower hydraulic conductivity than when compacted at slightly under the optimum moisture content. Finally, discussion was brought to importance of compaction method, compacting energy, and bentonite type to the hydraulic conductivity of SBMs. (authors)

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

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    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. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. The model is based on available experimental data and describes the basic reactions between bentonite and groundwater 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. The long-term situation is modelled by the assumption that the near-field of a deep repository behaves like a mixing tank. It is found that sodium bentonite will slowly be converted to calcium bentonite. The modelled composition of the pore water of compacted sodium bentonite is used to estimate radionuclide solubilities in the near-field of a deep repository. The elements considered are: uranium, neptunium, plutonium, thorium, americium, and technetium. The redox potential in the near-field is assumed to be controlled by the corrosion products of the iron canister. Except for uranium and neptunium, radionuclide solubilities turn out to be lower under the modelled near-field conditions than in the groundwater of the surrounding granitic host rock. Uranium and neptunium solubility might be higher by orders of magnitude in the near-field than in the far-field. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. 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)

  8. Impact of the changes in the chemical composition of pore water on chemical and physical stability of natural clays. A review of natural cases and related laboratory experiments and the ideas on natural analogues for bentonite erosion/non-erosion

    Energy Technology Data Exchange (ETDEWEB)

    Puura, Erik (Eridicon OUe, Tartu (Estonia)); Kirsimaee, Kalle (Univ. of Tartu, Inst. of Ecology and Earth Sciences, Tartu (Estonia))

    2010-01-15

    is the geological changes that have occurred in bentonites over geological time scales. The bentonite erosion project has to provide the scenarios for approximately 100,000 years, but the geological deposits have been changed and subjected to various conditions, many of those uncertain, during tens and hundreds of millions of years. The field studies of weathering of the historical K-bentonite deposits could provide interesting and new information, but the relevance related to the bentonite erosion project is questionable

  9. Impact of the changes in the chemical composition of pore water on chemical and physical stability of natural clays. A review of natural cases and related laboratory experiments and the ideas on natural analogues for bentonite erosion/non-erosion

    International Nuclear Information System (INIS)

    Puura, Erik; Kirsimaee, Kalle

    2010-01-01

    geological changes that have occurred in bentonites over geological time scales. The bentonite erosion project has to provide the scenarios for approximately 100,000 years, but the geological deposits have been changed and subjected to various conditions, many of those uncertain, during tens and hundreds of millions of years. The field studies of weathering of the historical K-bentonite deposits could provide interesting and new information, but the relevance related to the bentonite erosion project is questionable

  10. Effect of pH to adsorption behavior of Pu on bentonite in aqueous environment

    International Nuclear Information System (INIS)

    Wang Xiaoqiang; Tuo Xianguo; Li Pingchuan; Leng Yangchun; Su Jilong; Yueping

    2013-01-01

    The effects of pH to the adsorption behavior of Pu in GMZ-bentonite, Lingshou Ca-bentonite, Na-bentonite and bleaching earth were tested by static adsorption experiments in aqueous environment. The results show that the adsorption equilibrium time of Pu is four days in GMZ-bentonite and 5-6 days in bleaching earth, Ca-bentonite and Na-bentonite. In aqueous environment, the adsorption capacity of bentonite to Pu increases with pH in water phase, and it is weak in acidic aqueous environment and strong in alkaline aqueous environment extremely. (authors)

  11. Modelling of erosion of bentonite gel by gel/sol flow

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-11-15

    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. Diffusion of a counterion, sodium, 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. 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 size was selected sufficiently large to ensure that the water velocity, near the distant 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 by the slowly flowing fluid was found to be proportional to the square root of the seeping water velocity for the rectangular geometry. For the cylindrical geometry, the dependence is somewhat lower (exponent about 0.4) since the length of the gel/water interface decreases with increasing water flow rate. The penetration depth of the gel/water interface decreases with increasing water flow rate. For water velocity of the

  12. Modelling of erosion of bentonite gel by gel/sol flow

    International Nuclear Information System (INIS)

    Moreno, Luis; Neretnieks, Ivars; Longcheng Liu

    2010-11-01

    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. Diffusion of a counterion, sodium, 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. 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 size was selected sufficiently large to ensure that the water velocity, near the distant 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 by the slowly flowing fluid was found to be proportional to the square root of the seeping water velocity for the rectangular geometry. For the cylindrical geometry, the dependence is somewhat lower (exponent about 0.4) since the length of the gel/water interface decreases with increasing water flow rate. The penetration depth of the gel/water interface decreases with increasing water flow rate. For water velocity of the

  13. 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.

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

    International Nuclear Information System (INIS)

    Bell, J.C. Le

    1978-03-01

    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

  15. Optimizing soil and water management in dryland farming systems in Cabo Verde

    NARCIS (Netherlands)

    Santos Baptista Costa, Dos I.

    2016-01-01

    “Optimizing Soil and Water Management in Dryland Farming Systems in Cabo Verde”

    Isaurinda Baptista

    Summary

    Soil and land degradation poses a great challenge for sustainable development worldwide and, in Cabo Verde, has strongly affected both

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

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    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

  17. 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)

    Dixon, D.A.; Miller, S.H.

    1995-11-01

    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

  18. Bentonite chemical modification for use in industrial effluents

    International Nuclear Information System (INIS)

    Laranjeira, E.; Pinto, M.R.O.; Rodrigues, D.P.; Costa, B.P.; Guimaraes, P.L.F.

    2010-01-01

    The present work aims at synthesizing organoclays using a layered silicate of regional importance, bentonite clay, for the treatment of industrial effluents. The choice of clay to be organophilized was based on cation exchange capacity (CEC). Bentonite with higher CTC was called AN 35 (92 meq/100 g), and therefore was the one that suffered the chemical modification with salt cetyl trimethyl ammonium Cetremide, provided by Vetec.The unmodified and modified clays were characterized by FTIR and XDR. The data obtained through the characterizations confirmed the acquisition of bentonite organoclay thus suggesting its subsequent application in the treatment of industrial effluents. (author)

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

    International Nuclear Information System (INIS)

    Dixon, D.A.; Wan, A.W-L.; Gray, M.N.; Miller, S.H.

    1996-10-01

    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

  20. Mercury speciation in plankton from the Cabo Frio Bay, SE--Brazil.

    Science.gov (United States)

    Silva-Filho, Emmanoel V; Kütter, Vinicius T; Figueiredo, Thiago S; Tessier, Emmanuel; Rezende, Carlos E; Teixeira, Daniel C; Silva, Carlos A; Donard, Olivier F X

    2014-12-01

    Mercury (Hg) is considered a global pollutant, and the scientific community has shown great concern about its toxicity as it may affect the biota of entire systems, through bioaccumulation and bioamplification processes of its organic form, methylmercury (MeHg), along food web. However, few research studies deal with bioaccumulation of Hg from marine primary producers and the first-order consumers. So, this study aims to determine Hg distribution and concentration levels in phytoplankton and zooplankton in the Cabo Frio Bay, Brazil, a site influenced by coastal upwelling. The results from Hg speciation analyses show that inorganic mercury Hg(II) was the predominant specie in plankton from this bay. The annual Hg species distribution in plankton shown mean concentration of 2.00 ± 1.28 ng Hg(II) g(-1) and 0.15 ± 0.08 ng MeHg g(-1) wet weight (phytoplankton) and 2.5 ± 2.03 ng Hg(II) g(-1) and 0.25 ± 0.09 ng MeHg g(-1) wet weight (zooplankton). Therefore, upwelling zones should be considered in the Hg biogeochemical cycle models as a process that enhances Hg(II) bioaccumulation in plankton, raising its bioavailability and shelf deposition.

  1. Comparison between uniaxially and isostatically compacted bentonite

    International Nuclear Information System (INIS)

    Kalbantner, P.; Sjoeblom, R.; Boergesson, Lennart

    2001-12-01

    The purpose of the present report is to provide the Swedish Nuclear Fuel and Waste Management Company (SKB) with the knowledge base needed for their selection of reference method for manufacturing of bentonite blocks. The purpose is also to provide support for the direction of the further development work. Three types of blocks are compared in the present report: uniaxially compacted medium high blocks, isostatically compacted medium high blocks, isostatically compacted high blocks. The analyses is based on three process systems relating to the sequence of excavation of bentonite-transport-powder preparation-compaction-handling and emplacement of bentonite blocks. The need for further knowledge has been identified and documented in conjunction with these analyses. The comparison is primarily made with regard to the criteria safety/risk, quality/ technique and economy. It is carried out through identification of issues of significance and subsequent analysis and evaluation as well as more formally in a simplified AHP (AHP = Analytical Hierarchic Process). The result of the analyses is that the isostatic technique is applicable for the production of high as well as medium size blocks. The pressed blocks are assessed to fulfil the basic requirements with a very large margin. The result of the analyses is also that the uniaxial technique is applicable for the preparation of medium size blocks, which are assessed to fulfil the basic requirements with a large margin. The need for development and process control is assessed to be somewhat higher for the uniaxial technique. One example is the friction against the walls of the die during the compaction, including the significance of this friction for the development of stresses and discontinuities in the block. These results support a selection of the isostatic technique as the reference technique as it provides flexibility in the choice of block height. The uniaxial technique can form a second alternative if medium high

  2. On the presence of upper paleocene rocks in the foreland succession at Cabo Nariz, Tierra del Fuego, Chile: Geology and new palynological and U-Pb data

    International Nuclear Information System (INIS)

    Sanchez, Alejandro; Pavlishina, Polina; Godoy, Estanislao; Herve, Francisco; Fanning, C.Mark

    2010-01-01

    On the west coast of Tierra del Fuego, south of Cabo Nariz, in Chile, Upper Cretaceous to Paleocene sedimentary successions of the Magallanes foreland basin crop out. The presence of dinoflagellate cysts, as well as radiometric U-Pb SHPJMP dating of detrital zircons, indicate that this succession ranges from the Campanian to Thanetian (Late Paleocene) in age. The base of the exposed sedimentary succession comprises siltstones of external platform facies (Cerro Cuchilla Formation), which are thrust over the Cabo Nariz Beds. The latter fonnation is divided into two members: a lower siltstone-dominated turbidite facies member and an upper member of sandstone-dominated turbidites, with sandstone and conglomerate channel facies. The presence of dinocysts in the Cerro Cuchilla Formation suggests a late Campanian to early Danian age. The fossil content in the Cabo Nariz Beds indicate a Selandian (Middle Paleocene) depositional age in accordance with the detrital zircon ages which provide a maximum possible Campanian age (76.5±0.7 Ma), and very close to the Thanetian (Late Paleocene) (57.6±1 Ma) depositional ages for the lower and upper member, respectively. The sedimentary succession of Cabo Nariz Beds, is interpreted as a north-northwest prograding submarine fan of middle to Late Paleocene age. It is considered to represent the deposition of detritus derived from an uplifting orogen located to the south. The detrital zircon age spectra suggest that there was a period of low intensity of magmatic activity in the source area around the K-T boundary

  3. Current status of mechanical erosion studies of bentonite buffer

    International Nuclear Information System (INIS)

    Sane, P.; Olin, M.; Koskinen, K.

    2013-08-01

    The performance of the bentonite buffer in KBS-3-type nuclear waste repository concept relies to a great extent on the buffer surrounding the canister having sufficient dry density. Loss of buffer material caused by erosion remains as the most significant process reducing the density of the buffer. The mechanical erosion, or pre-saturation erosion, is the process where flowing groundwater transports buffer material away from the deposition hole towards the deposition tunnel. This process reduces the overall buffer density and potentially creates localized regions of low density. In the worst case the process is assumed to last as long as the free volume between the pellets in the pellets filled regions is filled with groundwater. With fixed environmental and material parameters a set of experiments was performed, testing the erosive properties of different buffer and backfill materials (MX-80 and Friedland Clay) in different groundwater conditions. The method used was a pinhole erosion test using two sizescales; 100 mm and 400 mm of cell length. The purpose of the pinhole tests was to test the scenario where piping channel is formed in the buffer and water flows through a single channel. The erosion data was produced with two methods, firstly the time-related erosion rates measured in-situ during the measurement and secondly the overall mass loss in the sample cell measured after dismantling of the test. It was observed that erosion in piping channels decreases rapidly (∼24 h) and irreversibly to a level that is an order of magnitude lower than the peak values. (orig.)

  4. Polypropylene–clay composite prepared from Indian bentonite

    Indian Academy of Sciences (India)

    WINTEC

    composites have recently found applications in packaging, automotive ... process using xylene as the solvent. Solvent ... Particle size distribution curve for clay, bentonite. Table 2. .... greater probability of debonding due to the poor interfa-.

  5. Small-scale bentonite injection test on rock

    International Nuclear Information System (INIS)

    Pusch, R.

    1978-03-01

    When radiactive waste is disposed a sealing of the rock is very valuable since it reduces the rate of water percolation and diffusion. In an earlier report injection of bentonite gels by means of over-pressure and subsequent electrophoresis has been suggested. The present report describes a rock test series where bentonite injection was applied. For the test an approximately cubical block of about 1 m 3 was selected. The rock type was diorite with a fairly high frequency of quartz denses. The block was kept in a basin during the test in order to maintain the water saturation. Holes were bored in the block. A bentonite slurry with 1000 percent water content was injected. It was shown that the bentonite had a sealing effect but the depth of extrusion into rock joints was not large because of gelation. Electro-Kinetic injection of montmorillonite was found to be a more promising technique for rock lightening

  6. Effects of polyethyleneimine adsorption on rheology of bentonite ...

    Indian Academy of Sciences (India)

    Unknown

    XRD, zeta potential and adsorption studies were done together with rheological .... trokinetics experiments on Balikesir bentonite samples. For this reason, the ... rence between apparent and true adsorption rates, and hence swelling of clays ...

  7. Immobilization of industrial waste in cement–bentonite clay matrix

    Indian Academy of Sciences (India)

    Unknown

    Immobilization of industrial waste in cement–bentonite clay matrix. I B PLECAS* and S ... high structural integrity and minimizing the risk of escape by leaching. ..... Radioactive Waste Management and Nuclear Fuel Cycle 14. 195. Plecas I ...

  8. Diffusion of Fission Product Elements in Compacted Bentonite

    International Nuclear Information System (INIS)

    Pratomo-Budiman-Sastrowardoyo; Dewi-Susilowati; Dadang-Suganda

    2000-01-01

    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)

  9. bentonite-sand mixture as new backfill/buffer material

    International Nuclear Information System (INIS)

    Cui Suli; Liu Jisheng; Zhang Huyuan; Liang Jian

    2008-01-01

    The mixture of bentonite and quartz sand is suggested as a new backfill/buffer material for geological disposal of HLW. To improve the further design of underground laboratory and in-situ industrial construction test, the optimization of sand addition to bentonite is focused at present research stage. Based on summarizing the research results abroad, laboratory tests were conducted on the mixture of GMZ001 bentonite and quartz sand, such as compaction test and swelling tests etc. Test data shows that GMZ bentonite-sand mixture exhibits a favorite compaction with a 30% sand addition, a highest swelling pressure with a 20% sand addition, and a decreasing plasticity with increases in sand addition and pore liquid concentration. (authors)

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

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.

    2001-01-01

    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)

  11. Migration study of actinides and lanthanides in compacted bentonite

    International Nuclear Information System (INIS)

    Sastrowardoyo, P.B.; Susilowati, D.; Suganda, D.

    1998-01-01

    Migration study of actinide and lanthanide elements in compacted bentonite has been conducted. Data of these elements mobilities have been shown, and it is showed that the diffusion coefficient was varied as the function of solution phase condition as well as the origin/composition of bentonite. It is 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 the difference of diffusion coefficient was related to the variation of pH and redox condition, as well as the presence of complexant in solution phase. The Lower diffusion coefficient could give the higher retardation factor, which is a favourable factor to retard the radionuclides release from a disposal facility to geosphere. (author)

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

    International Nuclear Information System (INIS)

    Tello, C.C.O. de.

    1988-01-01

    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) [pt

  13. Comparative Analysis on Chemical Composition of Bentonite Clays ...

    African Journals Online (AJOL)

    2017-09-12

    Sep 12, 2017 ... Comparative Analysis on Chemical Composition of Bentonite Clays. Obtained from Ashaka and ... versatile material for geotechnical engineering and as well as their demand for ..... A PhD thesis submitted to the Chemical ...

  14. Physico-chemical properties of water in bentonite

    International Nuclear Information System (INIS)

    Torikai, Yuji; Sato, Seichi; Ohashi, Hiroshi

    1994-01-01

    As a part of safety analysis on ground layer disposal, in order to estimate nuclides migration behavior from engineering shielding materials, it is required to modelize migration process of nuclides in bentonite and chemical species relating to corrosion, to estimate solubility and to specify application condition of geochemical calculation code. In this study, as a part of elucidation of nuclide migration process, physico-chemical properties of water in bentonite and montmorillonite using steam pressure method were determined. As a result, following items were found: (1) Even if 1/3 of water in bentonite is near free water, it is far from a region dealable with dilute solution in the electrolyte solution theory. And, (2) the water in bentonite has generally small activity in comparison with dilute solution, then has smaller solubility than estimation value of calculation code. (G.K.)

  15. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    Masuda, Ryoichi; Asano, Hidekazu; Toguri, Satohito; Mori, Takuo; Shimura, Tomoyuki; Matsuda, Takeshi; Uyama, Masao; Noda, Masaru

    2007-01-01

    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/m 3 , 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)

  16. Thermally modified bentonite clay for copper removal

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Kleinübing, S.J.; Silva, M.G.C.

    2011-01-01

    Bentonite clay coming from Pernambuco was thermally modified in order to increase its affinity and capacity in the copper removal in porous bed. The application of this procedure is justified by the low cost of clay, their abundance and affinity for various metal ions. Thermally treatment modifies the clay adsorption properties enables its use in porous bed system, with the increase in surface area and mechanical strength. The material was characterized by x-ray diffraction, thermogravimetric analysis and N_2 physisorption. Then tests were carried out for adsorption of copper in various experimental conditions and evaluated the mass transfer zone, useful and total adsorbed removal amounts and total copper removal percentage. The results showed that the clay treated at higher temperature showed higher copper removal. (author)

  17. Experimental Setup to Characterize Bentonite Hydration Processes

    International Nuclear Information System (INIS)

    Bru, A.; Casero, D.; Pastor, J. M.

    2001-01-01

    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

  18. Modelling of long term geochemical evolution and study of mechanical perturbation of bentonite buffer of a KBS-3 repository

    Energy Technology Data Exchange (ETDEWEB)

    Marsal, Francois; Pellegrini, Delphine; Deleruyelle, Frederic; Serres, Christophe (French Institute for Radiological Protection and Nuclear Safety (IRSN) (FR)); Windt, Laurent de (Paris School of Mines (ENSMP) (FR))

    2008-03-15

    The Swedish Nuclear Fuel and Waste Management Co. (SKB) has recently completed a safety assessment project named SR-Can, related to the KBS-3 disposal concept. In this concept, the waste packages are surrounded by a buffer made of either MX-80 or Deponit CA-N bentonite. Interactions between the buffer and groundwater may modify the buffer composition and thus its containment properties. The Swedish Radiation Protection Authorities (SSI) requested the French Institute for Radiological Protection and Nuclear Safety (IRSN) to perform the present study in support of SSI review of the SR-Can report. The purpose is to assess the geochemical evolution of both potential buffer materials due to the intrusion of different types of groundwater, with a similar modelling layout to that reported in SR-Can. Three main categories of water inflows via a fracture intersecting a deposition hole are considered: the Forsmark reference groundwater, a high-salinity groundwater to account for up-rise of deep-seated brines and a diluted water representing ice-melting derived groundwater. In addition to this, the redox buffering capacity of Deponit CA-N bentonite and the thermal effect on MX-80 bentonite geochemistry have been assessed. This modelling work has been performed using the reactive transport modelling code HYTEC. The main outcome of the present study is that the intrusion of the considered groundwaters should not affect drastically the geochemistry of neither the Deponit CA-N nor the MX-80 bentonite on the long-term (100,000 y). Bentonite pH may reach high values (up to 10.5) in some cases but does not reach SKB criterion value related to bentonite chemical stability. Dissolution-precipitation of accessory minerals is not significant enough to induce important porosity changes (rise by maximum 2 %). Globally, the montmorillonite exchanger undergoes Na by Ca partial replacement, which may decrease the swelling pressure of the bentonite. The simulated intrusion of oxidizing waters

  19. Modelling of long term geochemical evolution and study of mechanical perturbation of bentonite buffer of a KBS-3 repository

    International Nuclear Information System (INIS)

    Marsal, Francois; Pellegrini, Delphine; Deleruyelle, Frederic; Serres, Chris tophe; Windt, Laurent de

    2008-03-01

    The Swedish Nuclear Fuel and Waste Management Co. (SKB) has recently completed a safety assessment project named SR-Can, related to the KBS-3 disposal concept. In this concept, the waste packages are surrounded by a buffer made of either MX-80 or Deponit CA-N bentonite. Interactions between the buffer and groundwater may modify the buffer composition and thus its containment properties. The Swedish Radiation Protection Authorities (SSI) requested the French Institute for Radiological Protection and Nuclear Safety (IRSN) to perform the present study in support of SSI review of the SR-Can report. The purpose is to assess the geochemical evolution of both potential buffer materials due to the intrusion of different types of groundwater, with a similar modelling layout to that reported in SR-Can. Three main categories of water inflows via a fracture intersecting a deposition hole are considered: the Forsmark reference groundwater, a high-salinity groundwater to account for up-rise of deep-seated brines and a diluted water representing ice-melting derived groundwater. In addition to this, the redox buffering capacity of Deponit CA-N bentonite and the thermal effect on MX-80 bentonite geochemistry have been assessed. This modelling work has been performed using the reactive transport modelling code HYTEC. The main outcome of the present study is that the intrusion of the considered groundwaters should not affect drastically the geochemistry of neither the Deponit CA-N nor the MX-80 bentonite on the long-term (100,000 y). Bentonite pH may reach high values (up to 10.5) in some cases but does not reach SKB criterion value related to bentonite chemical stability. Dissolution-precipitation of accessory minerals is not significant enough to induce important porosity changes (rise by maximum 2 %). Globally, the montmorillonite exchanger undergoes Na by Ca partial replacement, which may decrease the swelling pressure of the bentonite. The simulated intrusion of oxidizing waters

  20. Adsorption behavior of 99Tc in Ca-bentonite

    International Nuclear Information System (INIS)

    Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

    2004-01-01

    The adsorption behaviors of 99 Tc in bentonite were studied with batch methods under aerobic and anoxic conditions. The adsorption ratios is about 1.47 mL/g under aerobic conditions. The adsorption ratio of 99 Tc in bentonite is not affected by pH in the range of 5-12 and the CO 3 2- , Fe 3+ concentrations in the range of 10 -8 -10 -2 mol/L in the solution. The adsorption ratio of Tc in bentonite increases with the increase of the mass percent of Fe 2 O 3 and Fe 3 O 4 and the Fe 2+ concentration in the range of 10 -8 -10 -2 mol/L. Tc exists ainly in the form of Tc(VII) after the adsorption equilibriums. The adsorption ratio of Tc in bentonite increase with the increase of the mass percent of Fe and Tc exists mainly in the form of Tc(VII) after the adsorption equilibriums. The adsorption ratio of Tc in bentonite is about 84.84 mL/g under anoxic conditions. The adsorption ratios of 99 Tc in bentonite decreases with the increase of pH in the range of 5-12 and the CO 3 2- concentration in the range of 10 -8 -10 -2 mol/L in the solution. The adsorption ratio of Tc in bentonite increases with the increase of the Fe 3+ , Fe 2+ concentration in the range of 10 -8 -10 -2 mol/L and the mass percent of Fe, Fe 2 O 3 and Fe 3 O 4 . Tc exists mainly in the form of Tc(IV) after the adsorption equilibriums. The adsorption isotherms of TcO 4 - in bentonite are all in fairly agree with the Freundlich's equation under aerobic and anoxic conditions. (authors)

  1. Bentonite as a backfill material for shallow land repositories

    International Nuclear Information System (INIS)

    Yalmali, V.S.; Deshingkar, D.S.

    2001-01-01

    Two commercially available indigenous bentonite samples were evaluated for their cesium and strontium sorption properties in distilled water and surface water. By converting them into sodium form, the distribution coefficients for both cesium (I) and strontium (II) increased. Sodium bentonite was recommended because of high sorption capacity for Cs(I), Mg(II) and Sr(II) for use as backfill material in shallow land repositories where cement waste form containing Cs, Sr and Be wastes are disposed. (author)

  2. Saturation of bentonite dependent upon temperature

    International Nuclear Information System (INIS)

    Hausmannova, Lucie; Vasicek, Radek

    2010-01-01

    Document available in extended abstract form only. The fundamental idea behind the long-term safe operation of a deep repository is the use of the Multi-barrier system principle. Barriers may well differ according to the type of host rock in which the repository is located. It is assumed that the buffer in the granitic host rock environment will consist of swelling clays which boast the ideal properties for such a function i.e. low permeability, high swelling pressure, self-healing ability etc. all of which are affected primarily by mineralogy and dry density. Water content plays a crucial role in the activation of swelling pressure as well as, subsequently, in the potential self healing of the various contact areas of the numerous buffer components made from bentonite. In the case of a deep repository, a change in water content is not only connected with the possible intake of water from the host rock, but also with its redistribution owing to changes in temperature after the insertion of the heat source (disposal waste package containing spent fuel) into the repository 'nest'. The principal reason for the experimental testing of this high dry density material is the uncertainty with regard to its saturation ability (final water content or the degree of saturation) at higher temperatures. The results of the Mock-Up-CZ experiment showed that when the barrier is constantly supplied with a saturation medium over a long time period the water content in the barrier as well as the degree of saturation settle independently of temperature. The Mock-Up-CZ experiment was performed at temperatures of 30 deg. - 90 deg. C in the barrier; therefore it was decided to experimentally verify this behaviour by means of targeted laboratory tests. A temperature of 110 deg. C was added to the set of experimental temperatures resulting in samples being tested at 25 deg. C, 95 deg. C and 110 deg. C. The degree of saturation is defined as the ratio of pore water volume to pore

  3. Development of polypropylene (PP)/bentonite organoclay nanocomposites; Desenvolvimento de nanocompositos de polipropileno/argila bentonitica organofilica

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Carlos Ivan Ribeiro de; Rocha, Marisa Cristina Guimaraes; Verly, Jessica, E-mail: carlosivanr@gmail.com [Universidade do Estado do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil). Instituto Politecnico; Silva, Ana Lucia Nazareth da [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Instituto de Macromoleculas Professora Eloisa Mano; Bertolino, Luiz Carlos [Centro de Tecnologia Mineral (CETEM), Rio de Janeiro, RJ (Brazil)

    2016-07-01

    In recent years, a significant number of studies on polymer/clay nanocomposites has been developed due to the improved properties these materials have compared to those of the conventional composites. Among the various clays used for preparing nanocomposites, the bentonite clays have been the most widely used. In this context, the aim of this work is to develop polypropylene/organoclay nanocomposites based on deposits of bentonite clays recently discovered in Cubati, PB. The composites were prepared in a twin screw extruder. The structural characterization of the produced materials indicated a possible intercalation of the polymer chains between the layers of the organoclay. The results of impact strength showed that the addition of clay as well as the initial addition of clay and compatibilizer decreased the impact strength of polypropylene. The Young's modulus and tensile strength of the polymer were not significantly affected by the filler addition. However, an increase of the elongation at break was observed. (author)

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

    International Nuclear Information System (INIS)

    Hunter, Fiona; Bate, Fiona; Heath, Tim; Hoch, Andrew

    2007-09-01

    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

  5. Behaviour of bentonite accessory minerals during the thermal stage

    International Nuclear Information System (INIS)

    Arcos, David; Bruno, Jordi; Benbow, Steven; Takase, Hiro

    2000-03-01

    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 4 (aq) is the predominant aqueous species, then anhydrite dissolves at the initial groundwater migration times through bentonite. However, if Ca 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, Fiona; Bate, Fiona; Heath, Tim; Hoch, Andrew [Serco Assurance, Harwe ll (United Kingdom)

    2007-09-15

    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

  7. Review of the interactions between bentonite and cement

    International Nuclear Information System (INIS)

    Duerden, S.L.

    1992-01-01

    Properties of bentonite may be significantly affected by reaction with cement. This report reviews the literature to identify the reactions that may occur and considers their effects on the performance of bentonite in these applications. The dominant reactions expected under alkaline conditions prevalent in an underground repository where cement is used extensively are zeolitization, beidellitization, and ion exchange. Zeolitisation will occur at high temperatures (200 o C) or after long periods (500-1000 years) when the pH is high (pH>9). Beidellitization may occur at high pH (pH>9). The silica may reprecipitate in situ due to low hydraulic conductivity or in regions of low pH or temperature. This may result in reduced porosity/permeability and plasticity. Ion exchange reactions are virtually instantaneous. The rate of the reaction depends on the concentration and rate of access of ground water. Substitution of Ca 2+ ions from cement for Na + ions in sodium-bentonites will result in reduced swelling pressure and plasticity, and increased hydraulic conductivity of the bentonite. The effect of Na-bentonite on the properties of cement is the formation of an Al-substituted 11A tobermorite, which results in improved Cs + sorption. In cements reacted with Calcium-bentonite the main product was found to be a hydroxyapatite layer on the cement surface. (author)

  8. Diffusive transport of strontium-85 in sand-bentonite mixtures

    International Nuclear Information System (INIS)

    Gillham, R.W.; Robin, M.J.L.; Dytynyshyn, D.J.

    1983-06-01

    Diffusion experiments have been used to determine the transport of 85 Sr in sand-bentonite mixtures. The diffusion experiments were performed on one natural soil (Chalk River sand) and on seven mixtures of bentonite and silica sand, containing from 0 percent to 100 percent bentonite. Two non-reactive solutes ( 36 Cl and 3 H) and one reactive solute ( 85 Sr) were used in the study. The experiments with non-reactive solutes yielded estimates of tortuosity factors. Retardation factors were obtained from experimental porosities, experimental bulk densities, and from batch distribution coefficients (Ksub(d)). These Ksub(d) values are a simple way of describing the solute/medium reaction, and are based on the assumption that the cation-exchange reaction may be described by a linear adsorption isotherm passing through the origin. The results demonstrate that, for practical purposes and for our experimental conditions, the use of the distribution coefficient provides a convenient means of calculating the effective diffusion coefficient for 85 Sr. The porosity and bulk density were also found to have a considerable influence on the effective diffusion coefficient, through the retardation factor. Mixtures containing 5-10 percent bentonite were found to be more effective in retarding 85 Sr than either sand alone, or mixtures containing more bentonite. In the soils of higher bentonite content, the effect of increased cation-exchange capacity was balanced by a decreasing ratio of bulk density to porosity

  9. Chitosan/bentonite bionanocomposites: morphology and mechanical behavior

    International Nuclear Information System (INIS)

    Braga, C.R.C.; Melo, F.M.A. de; Vitorino, I.F.; Fook, M.V.L.; Silva, S.M.L.

    2010-01-01

    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)

  10. Evaluation of permeability and swelling pressure of compacted bentonite using a calcium hydroxide solution

    International Nuclear Information System (INIS)

    Aoyagi, Takayoshi; Maeda, Munehiro; Mihara, Morihiro; Tanaka, Masuhiro

    1998-12-01

    Tests to determine the swelling pressure, permeability, compressive strength and elastic modulus of Ca-Na exchanged bentonite, Na-bentonite and Ca-bentonite at the Power Reactor and Nuclear Fuel Development Corporation have mainly used distilled water. However, disposal facilities for TRU waste will use cementateous material for packaging, backfill as well as structural support. In this case, a large amount of calcium will dissolve in groundwater flowing through the cementateous material. Therefore, it is important to investigate the mechanical properties of bentonite in calcium-rich water as part of the disposal research program for TRU waste. In order to understand the effect of the chemical composition of water on the basic mechanical properties of bentonite - part of evaluating the disposal concepts for TRU waste disposal - we tested the permeability of compacted bentonite under saturated conditions using a calcium hydroxide solution. The aqueous solution represents water dominated by the calcium component. Na-bentonite, Ca-Na exchanged bentonite and Ca-bentonite were used for swelling pressure measurement tests and permeability testing. Measures of the maximum and equilibrium swelling pressure as well as permeability we obtained. The dry density of bentonite was varied between tests. Results show that swelling pressure and permeability are dependent on dry density. In separate tests using Ca-bentonite, the bentonite-mixing rate was varied as an independent parameter. Results show that there is little change in the swelling pressure and permeability between tests using calcium hydroxide solution and distilled water for all bentonite types. (author)

  11. 24 CFR 200.926e - Supplemental information for use with the CABO One and Two Family Dwelling Code.

    Science.gov (United States)

    2010-04-01

    ... with the CABO One and Two Family Dwelling Code. 200.926e Section 200.926e Housing and Urban Development... PROGRAMS Minimum Property Standards § 200.926e Supplemental information for use with the CABO One and Two... Criteria of the CABO One and Two Family Dwelling Code. (a) Roof live loads. Roof slope 3 in 12 or less: 20...

  12. Quality characterization and evaluation of bentonites from the provinces of San Juan and Río Negro (Argentina) for their use in the oil and ceramics industries

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo, N.; Senese, A.; Cano, E.; Sarquis, P.

    2016-07-01

    The aim of this research work is to characterize bentonites, both physically and chemically, as well as mineralogically, from deposits located in the Argentine provinces of San Juan and Rio Negro. The study is completed with technological assays to evaluate the quality of the samples under study so as to determine possible industrial uses and/or applications for this material. To carry out this work, four samples of bentonite, identified as M1, M3, and M4, from the province of San Juan, and another, identified as M2, from the province of Rio Negro were used. Physical characterization consisted of determining: swelling, density, moisture, pH and specific gravity of the bentonite samples through application of a number of techniques. Chemical characterization of major components was carried out by using wet methods through acid attack, whilst ICP was used to characterize minor components. Mineralogical characterization was carried out by using an infrared spectrometer. The technological assays for evaluating the quality of the bentonite were carried out following the method indicated by the API and SEGEMAR standards, among others, in order to determine possible uses and/or applications, mainly in the oil and ceramics industries It was found that the M2 bentonite is the most suitable to be used as a drilling mud as it meets the requirements specified by the API standards. The M3 bentonite, due to its physico-chemical characteristics such as low rheology, swelling, low iron content, amongst others, is the most suitable for the ceramics industry. (Author)

  13. Petrology of an eclogite- and pyrigarnite-bearing polymetamorphic rock complex at Cabo Ortegal, NW Spain

    NARCIS (Netherlands)

    Vogel, D.E.

    1967-01-01

    At Cabo Ortegal, paragneisses are found in association with amphibolites, metagabbros, amphibolized eclogites, amphibolized (plagio) pyrigarnites, and serpentinized ultrabasic rocks. On the basis of petrographical and chemical evidence, their geological history was reconstructed as follows:

  14. HLA polymorphisms in Cabo Verde and Guiné-Bissau inferred from sequence-based typing.

    Science.gov (United States)

    Spínola, Hélder; Bruges-Armas, Jácome; Middleton, Derek; Brehm, António

    2005-10-01

    Human leukocyte antigen (HLA)-A, -B, and -DRB1 polymorphisms were examined in the Cabo Verde and Guiné-Bissau populations. The data were obtained at high-resolution level, using sequence-based typing. The most frequent alleles in each locus was: A*020101 (16.7% in Guiné-Bissau and 13.5% in Cabo Verde), B*350101 (14.4% in Guiné-Bissau and 13.2% in Cabo Verde), DRB1*1304 (19.6% in Guiné-Bissau), and DRB1*1101 (10.1% in Cabo Verde). The predominant three loci haplotype in Guiné-Bissau was A*2301-B*1503-DRB1*1101 (4.6%) and in Cabo Verde was A*3002-B*350101-DRB1*1001 (2.8%), exclusive to northwestern islands (5.6%) and absent in Guiné-Bissau. The present study corroborates historic sources and other genetic studies that say Cabo Verde were populated not only by Africans but also by Europeans. Haplotypes and dendrogram analysis shows a Caucasian genetic influence in today's gene pool of Cabo Verdeans. Haplotypes and allele frequencies present a differential distribution between southeastern and northwestern Cabo Verde islands, which could be the result of different genetic influences, founder effect, or bottlenecks. Dendrograms and principal coordinates analysis show that Guineans are more similar to North Africans than other HLA-studied sub-Saharans, probably from ancient and recent genetic contacts with other peoples, namely East Africans.

  15. Diffusion in crushed rock and in bentonite clay

    International Nuclear Information System (INIS)

    Olin, M.

    1994-04-01

    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 m 2 /s and 6.0*10 -12 m 2 /s, respectively, but these values are questionable, as experimental results good enough for fitting are not available. (orig.). (74 refs., 27 figs., 12 tabs.)

  16. Thermal properties of bentonite under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Vasicek, R. [Czech Technical Univ., Centre of Experimental Geotechnics, Faculty of Civil Engineering, Prague (Czech Republic)

    2005-07-01

    Centre of Experimental Geotechnics (CEG) deals with the research of the behaviour of bentonite and clays. The measurement of thermal properties is not so frequent test in geotechnical laboratory but in relation to deep repository it is a part which should not be overlooked. The reason is the heat generated by canister with spent nuclear fuel and possible influence of the heat on the materials of the engineered barrier. In the initial stages following the burial of canister with the waste the barrier materials will be exposed to elevated temperature. According to existing information, these temperatures should not exceed 90 C. That heat can induce a creation of cracks and opening of joint between highly compacted blocks. It will predispose the bentonite barrier to penetration of water from surrounding towards to canister. Therefore easy removal of heat through the barrier is required. It is essential that the tests aimed at determining the real values of measured parameters are carried out in conditions identical with those anticipated in a future disposal system. These relatively complicated thermophysical tests are logical continuation of the simple ones, carried out under laboratory temperature and on not fully saturated samples without possibility to measure the swelling pressure. Thermophysical properties and swelling pressure are dominantly influenced by water content (which is influenced by temperature). Therefore is important to realize the tests under different moisture and thermal conditions. These tests are running at the APT-PO1 Analyser, designed to fulfill mentioned requirements - it allows measurement of thermal properties under temperature up to 200 C and swelling pressure up to 20 MPa. The device is capable to register the evolution of temperature, swelling and vapor pressure. The measurement of thermal conductivity and volume heat capacity is realized by the dynamic impulse method with point source of heat. Four types of tests are possible: at

  17. Lake restoration with aluminium, bentonite and Phoslock: the effect on sediment stability and light attenuation

    DEFF Research Database (Denmark)

    Egemose, Sara; Reitzel, Kasper; Flindt, Mogens

    treatments on aluminium mobility, sediment stability or light climate. A laboratory flume experiment including three shallow Danish lakes was conducted. We measured the effects of aluminium, Phoslock (a commercial product), bentonite, and a combination of bentonite/aluminium. Each treatment caused a varying...... consolidation of the sediment. The largest consolidation occurred using Phoslock- and bentonite-addition followed by bentonite/aluminium-addition, whereas aluminium alone had no effect. Sediment stability thresholds were measured before and after addition. Especially Phoslock, but also bentonite and bentonite....../aluminium increased sediment erosion threshold, with respectively 200%, 43% and 57%. Aluminium, bentonite/aluminium, and Phoslock improved the light conditions in the water phase, with respectively 60%, 57% and 50%, whereas bentonite created higher turbidity. Conclusively aluminium improved the light conditions...

  18. Effect of seawater and high-temperature history on swelling characteristics of bentonite

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Nakamura, Kunihiko

    2005-01-01

    In the case of construction of repository for nuclear waste near the coastal area, the effect of seawater on swelling characteristics of bentonite as an engineering as an engineering barrier should be considered. Effects of high-temperature history on swelling characteristics of bentonite should also be considered because nuclear waste generates heat. Thus, in this study, swelling characteristics of bentonite on the conditions of high temperature history and seawater are investigated. The results of this study imply that : (1) Swelling strain of sodium bentonite or transformed sodium bentonite decrease as the salinity of water increases, whereas those of calcium bentonite are not affected by salinity of the water. (2) Quantitative evaluation method for swelling strain and swelling pressure of several kinds of bentonites under brine is proposed. (3) Using distilled water, swelling strain and swelling pressure of sodium bentonite with high-temperature history is less than those without high-temperature history. (author)

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

    International Nuclear Information System (INIS)

    Kukaniev, M.A.; Badalov, A.B.; Sharopov, F.S.

    2004-01-01

    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

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

    International Nuclear Information System (INIS)

    Motoyuki Asada; Hitoshi Nakashima; Takashi Ishii; Sumio Horiuchi

    2006-01-01

    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)

  1. Aespoe Hard Rock Laboratory. The use of focused ion beams for structural characterisation of bentonite. A feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Wegden, Marie; Kristiansson, Per (Division of Nuclear Physics, Lund Inst. of Technology (Sweden)); Svensson, Daniel; Sjoeland, Anders (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

    2009-07-01

    Bentonite clay is planned to be used in the KBS-3 concept for future nuclear high level waste (HLW) repository in Sweden. In the concept the spent nuclear fuel is placed in an iron insert, which is encapsulated in a copper canister. The copper canister is embedded in compacted bentonite and deposited at 500 m depth in granite bedrock. The compacted bentonite will act as a buffer material, giving mechanical support for the copper canister, reducing water movements and capturing potentially escaping radionuclides. Bentonite contains high amounts of smectite minerals (most common is montmorillonite), which are swelling clay minerals. The smectite minerals are layered and have the ability to store water in its structure. This is done by intercalating water between the layers and expanding the interlayer distance. The exceptional swelling capacity makes bentonite a suitable buffer material that works as a sealant and barrier. Heterogeneity in the material, compaction and in swelling may result in porosity, both on the nano- and micrometre scale. This may affect the permeability of the clay and may mediate the transport of radionuclides, cations and corrosion products. The aim of this work is to investigate the feasibility of using common ion beam techniques for structural characterisation of bentonite, including studying the mineral composition and the coarse porosity. The analytical techniques used were scanning transmission ion microscopy (STIM), particle-induced X-ray emission (PIXE) and elastic p-p scattering, performed at the Lund Nuclear Microprobe. On-axis STIM analysis was performed in order to measure and map the areal mass density of the sample. Since it was impossible to differentiate an increase in thickness from an area of higher mass density, as well as discerning depth variations, the STIM analysis was also performed in tomographic mode, in an attempt to obtain 3D structural information. The tomographic reconstruction showed that the bentonite had an

  2. Aespoe Hard Rock Laboratory. The use of focused ion beams for structural characterisation of bentonite. A feasibility study

    International Nuclear Information System (INIS)

    Wegden, Marie; Kristiansson, Per; Svensson, Daniel; Sjoeland, Anders

    2009-01-01

    Bentonite clay is planned to be used in the KBS-3 concept for future nuclear high level waste (HLW) repository in Sweden. In the concept the spent nuclear fuel is placed in an iron insert, which is encapsulated in a copper canister. The copper canister is embedded in compacted bentonite and deposited at 500 m depth in granite bedrock. The compacted bentonite will act as a buffer material, giving mechanical support for the copper canister, reducing water movements and capturing potentially escaping radionuclides. Bentonite contains high amounts of smectite minerals (most common is montmorillonite), which are swelling clay minerals. The smectite minerals are layered and have the ability to store water in its structure. This is done by intercalating water between the layers and expanding the interlayer distance. The exceptional swelling capacity makes bentonite a suitable buffer material that works as a sealant and barrier. Heterogeneity in the material, compaction and in swelling may result in porosity, both on the nano- and micrometre scale. This may affect the permeability of the clay and may mediate the transport of radionuclides, cations and corrosion products. The aim of this work is to investigate the feasibility of using common ion beam techniques for structural characterisation of bentonite, including studying the mineral composition and the coarse porosity. The analytical techniques used were scanning transmission ion microscopy (STIM), particle-induced X-ray emission (PIXE) and elastic p-p scattering, performed at the Lund Nuclear Microprobe. On-axis STIM analysis was performed in order to measure and map the areal mass density of the sample. Since it was impossible to differentiate an increase in thickness from an area of higher mass density, as well as discerning depth variations, the STIM analysis was also performed in tomographic mode, in an attempt to obtain 3D structural information. The tomographic reconstruction showed that the bentonite had an

  3. Observations of bentonite-hyper-alkaline fluid and bentonite-cement interactions by the X-ray computed tomography

    International Nuclear Information System (INIS)

    Nakabayashi, R.; Chino, D.; Kawaragi, C.; Sato, T.; Yoneda, T.; Kaneko, K.; Shibata, S.; Sakamoto, H.

    2010-01-01

    Document available in extended abstract form only. Bentonite-hyper-alkaline fluid interaction has been a key research issue in the performance assessment of radioactive waste disposal. It has therefore been investigated based on the dissolution rate of smectite (main constituent mineral of bentonite) under such hyper-alkaline condition. Generally, the dissolution rate has been obtained from batch and flow-through experiments under the conditions with high fluid/solid weight rations. These previous studies have provided a contribution to kinetic model of smectite dissolution. Some of them in particularly showed some equations explaining the effect of different factors such as pH of reactive fluid, temperature and deviation from equilibrium on smectite dissolution rate. However, the experimental conditions in such studies were completely different from the conditions in actual radioactive waste disposal system. For quantitative understanding, dissolution experiments for the compacted bentonite have also been conducted. These studies showed that the dissolution rate of compacted bentonite was different from that of batch and flow-through experiments. However, the difference has not been understood in details. On the other hand, the interface between bentonite and cement has also been investigated by experiments in laboratories and field sites, via reaction transport modelling. Despite the very few in numbers of experimental results as function of time, there are many long-term modelling works intended for bentonite-cement interaction. The models developed by many authors should be verified by comparing results of the model calculations with experimental observations. The experimental results with different conditions are therefore necessary for verifications and comparisons. Even in the experimental works done previously, the alteration process at the interface has mainly been observed by EPMA. EPMA is a destructive analysis with lower time resolution for 2D images

  4. Radioassay of vitamin B-12 employing bentonite

    International Nuclear Information System (INIS)

    Lewin, N.; Fries, J.E.; Richards, C.S.

    1976-01-01

    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

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

    International Nuclear Information System (INIS)

    Osada, K.; Nagano, T.; Kozai, N.; Nakashima, S.; Nakayama, S.; Muraoka, S.

    1991-01-01

    The following conclusions were obtained; (1) At 40degC, the average corrosion rate of SS41 carbon steel in wet bentonite was 0.025 mm/y. This is smaller than the value of 0.042 mm/y obtained in pure water at 40degC. However, at 95degC, the corrosion rate of SS41 carbon steel in wet bentonite was 0.27 mm/y, which is much larger than that in pure water at 95degC. (2) At 95degC, γ-FeO(OH) (lepidocrocite) was formed only in wet bentonite, and it was absent in pure water. Evaporation of moisture resulted in the formation of partial covering of bentonite, which promoted local corrosion. Consequently, γ-FeO(OH) was considered to be formed. (3) In wet bentonite at 95degC, α-Fe 2 O 3 (hematite) can be identified by means of colorimetry. The color of corrosion products is orangish, indicating the contribution of α-Fe 2 O 3 in iron hydroxides. (author)

  6. Tracer diffusion in compacted, water-saturated bentonite

    International Nuclear Information System (INIS)

    Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.

    2005-01-01

    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

  7. Iodine sorption of bentonite - radiometric and polarographic study

    International Nuclear Information System (INIS)

    Konirova, R.; Vinsova, H.; Koudelkova, M.; Ernestova, M.; Jedinakova-Krizova, V.

    2003-01-01

    The experiments focused on kinetics of iodine retardation on bentonite, influence of aqueous phase pH, buffering properties of bentonite, etc. were carried out by batch method. Distribution coefficient KD was the criterion applied for evaluation of iodine interaction with solid phase. High sorption potential of bentonite to cationic forms of various radionuclides, resulting from relatively high cation exchange capacity, is generally known. On the other hand the inorganic anions are not adsorbed strongly to mineral surface of clays thus uptake of iodine (occurring mainly at iodide (I - ) or iodate (IO 3 - ) form under oxoic conditions) is limited. The distribution coefficients of iodine anions' sorption on bentonite R reach order of magnitude 10 -1 mL/g. In order to increase the sorption capacity of the solid phase, several additives were added to bentonite. Most of them didn't provide satisfactory results except of the addition of activated carbon, which has high surface area. Electromigration and polarographic methods were used for investigation of the redox state of iodine in aqueous phase and determination of KD values as well. Acquired results were compared with data obtained by radiometric measurements. (authors)

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

    International Nuclear Information System (INIS)

    Leguey Jimenez, S.; Cuevas Rodriguez, J.; Ramirez Martin, S.; Vigil de la villa Mencia, R.; Martin Barca, M.

    2002-01-01

    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)

  9. Influence of material and solution composition on the extrusion/erosion behaviour of compacted bentonite

    International Nuclear Information System (INIS)

    Schatz, Timothy; Martikainen, Jari; Koskinen, Kari

    2010-01-01

    Document available in extended abstract form only. In principle, in a KBS-3 type repository, the volume of a deposition hole is fixed and the bentonite buffer mass accordingly balanced to lead to the development of a suitable swelling pressure upon saturation. However, fractures intersecting the deposition holes give rise to the possibility that volume constrained conditions do not universally exist. Such fractures may provide pathways for the continued, localised, free swelling of bentonite buffer material. Loss of mass from the deposition hole by extrusion into intersecting fractures may compromise the long-term safety and performance of the buffer component of the engineered barrier system. Furthermore, the continued hydration and expansion of extruded bentonite in these fracture environments could lead to the separation of colloid-sized (or larger) particles by diffusion or shear which may have to be accounted for in possible radionuclide migration scenarios. Geochemical conditions, with respect to both solution and material composition, are considered to play important roles regarding the fracture extrusion/erosion of bentonite buffer material. For example, calcium-montmorillonite exhibits limited free swelling relative to sodium-montmorillonite and the colloidal and rheological properties of montmorillonite dispersions are sensitive to the presence of electrolytes. Insofar as both the buffer material composition (due to ion exchange) and groundwater composition (dilution resulting from infiltration of glacial melt water) are expected to evolve with time, so too might the potential for fracture extrusion/erosion of buffer material vary over time. The hydraulic characteristics of the intersecting fracture are expected to influence the extrusion/erosion process as well. To evaluate the effect of material and solution composition on the potential for extrusion of buffer mass into intersecting fractures, a series of batch experiments were performed. In these

  10. Potential impact of Andrassy bentonite microbial diversity in the long-term performance of a deep nuclear waste repository

    Science.gov (United States)

    Tadza, M. Y. Mohd; Tadza, M. A. Mohd; Bag, R.; Harith, N. S. H.

    2018-01-01

    Copper and steel canning and bentonite buffer are normally forseen as the primary containment component of a deep nuclear waste repository. Distribution of microbes in subsurface environments have been found to be extensive and directly or indirectly may exert influence on waste canister corrosion and the mobility of radionuclides. The understanding of clays and microbial interaction with radionuclides will be useful in predicting the microbial impacts on the performance of the waste repositories. The present work characterizes the culture-dependent microbial diversity of Andrassy bentonite recovered from Tawau clay deposits. The evaluation of microbial populations shows the presence of a number of cultivable microbes (e.g. Staphylococcus, Micrococcus, Achromobacter, Bacillus, Paecilomyces, Trichoderma, and Fusarium). Additionally, a pigmented yeast strain Rhodotorula mucilaginosa was also recovered from the formation. Both Bacillus and Rhodotorula mucilaginosa have high tolerance towards U radiation and toxicity. The presence of Rhodotorula mucilaginosa in Andrassy bentonite might be able to change the speciation of radionuclides (e.g. uranium) in a future deep repository. However, concern over the presence of Fe (III) reduction microbes such as Bacillus also found in the formation could lead to corrosion of copper steel canister and affect the overall performance of the containment system.

  11. Crystallite size distribution of clay minerals from selected Serbian clay deposits

    Directory of Open Access Journals (Sweden)

    Simić Vladimir

    2006-01-01

    Full Text Available The BWA (Bertaut-Warren-Averbach technique for the measurement of the mean crystallite thickness and thickness distributions of phyllosilicates was applied to a set of kaolin and bentonite minerals. Six samples of kaolinitic clays, one sample of halloysite, and five bentonite samples from selected Serbian deposits were analyzed. These clays are of sedimentary volcano-sedimentary (diagenetic, and hydrothermal origin. Two different types of shape of thickness distribution were found - lognormal, typical for bentonite and halloysite, and polymodal, typical for kaolinite. The mean crystallite thickness (T BWA seams to be influenced by the genetic type of the clay sample.

  12. Evaluation for swelling characteristics of buffer and backfill materials for high-level nuclear waste disposal. Influence of sand-bentonite content and cation compositions in bentonite

    International Nuclear Information System (INIS)

    Komine, Hideo; Ogata, Nobuhide

    1999-01-01

    Compacted bentonite and sand-bentonite mixture are attracting greater attention as buffer and backfill materials for disposal pits and access tunnels in the underground facilities for repositories of high-level nuclear waste. Buffer and backfill materials must have the swelling characteristics and are expected to fill up the space between these materials and surrounding ground by swelling. This role is called as 'Self-sealing'. To design the specifications, such as dry density, bentonite content and size, of buffer and backfill materials for the disposal facilities of high-level nuclear wastes described above, we must evaluate the swelling characteristics of compacted bentonite and sand-bentonite mixtures. For this purpose, this study proposed the evaluation formula for swelling characteristics of buffer and backfill materials containing bentonite. This study derived new equations for evaluating the relationship between the swelling deformation of compacted bentonite and sand-bentonite mixtures, and the swelling behavior of montmorillonite minerals, which are swelling clay minerals. This study also proposed new equations for evaluating the ion compositions of bentonite, ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of buffer and backfill materials. The evaluation formula proposed in this study is presented by combining the above-mentioned new equations with theoretical equations, of which are the Gouy-Chapman diffuse double layer theory and the van der Waals force, of repulsive and attractive forces of montmorillonite minerals. (author)

  13. Electrochemical behavior of H3PW12O40/ acid-activated bentonite powders

    Directory of Open Access Journals (Sweden)

    Mojović Zorica

    2012-01-01

    Full Text Available Electrochemical behavior of 12-tungstophosphoric acid (HPW/acid-activated bentonite (AAB powders with various loadings of HPW was investigated. The physicochemical properties of the prepared powders were examined by X-ray powder diffraction, nitrogen adsorption-desorption isotherms, atomic force microscopy and cyclic voltammetry measurements. The results indicated that the prepared powders are composed mainly of oriented domains of large rock blocks, probably resulting from a preferable deposition of bentonite particles having a face-to-face interaction. The particles had a mainly disordered mesoporous structure with a pore volume that varied according to the pore size in the range of 2-50 nm. In addition, the particles had crystallite size between 4.9 and 9.0 nm. The electrocatalytic activities of prepared HPW/Aelectrodes were studied in the oxidation of NO2-ions and the results revealed that the electrodes possessed relatively higher nitrite oxidation currents than Aelectrode. The best electroactivity was observed for HPW3/Aelectrode (AAB+20 wt. % HPW and the limit of detection (3σ was determined as 8 μM.

  14. Sorption of uranium cationic species from aqueous solutions on Slovak bentonite Jelsovy potok

    Energy Technology Data Exchange (ETDEWEB)

    Krajnak, A.; Viglasova, E.; Galambos, M.; Rosskopfova, O. [Comenius University in Bratislava, Faculty of Natural Sciences, Department of Nuclear Chemistry, 842 15 Bratislava (Slovakia)

    2013-04-16

    Bentonite deposit Jelsovy potok in Slovakia has great potential for use as a engineering barrier in the multi-barrier system of deep geological repository for high level radioactive waste and spent nuclear fuel. In this study, the adsorption equilibrium and kinetics of U(VI) ions on Slovak bentonite Jelsovy potok (J15) was examined. The removal of uranium cationic species from aqueous solutions (initial concentration: 10-1,000 mg/L) by J15 was studied in the absence of background electrolytes at initial pH (pH{sub init}) 2.5. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake capacity observed was 30.15 (mg/g) at 298 K. Experimental results were analysed by the Langmuir, Freundlich and Dubinin-Redushkevich isotherm. The kinetics of adsorption of U(VI) ions was also discussed using the pseudo-first-order and the pseudo-second-order at three different temperatures. The experimental data fitted very well the pseudo-second-order kinetic model. The activation energy of the sorption was calculated as 11.316 kJ.mol{sup -}1 for J15. (authors)

  15. The tectonic significance of the Cabo Frio Tectonic Domain in the SE Brazilian margin: a Paleoproterozoic through Cretaceous saga of a reworked continental margin

    Directory of Open Access Journals (Sweden)

    Renata da Silva Schmitt

    Full Text Available ABSTRACT: The Cabo Frio Tectonic Domain is composed of a Paleoproterozoic basement tectonically interleaved with Neoproterozoic supracrustal rocks (Buzios-Palmital successions. It is in contact with the Neoproterozoic-Cambrian Ribeira Orogen along the SE Brazilian coast. The basement was part of at least three continental margins: (a 1.97 Ga; (b 0.59 - 0.53 Ga; (c 0.14 Ga to today. It consists of continental magmatic arc rocks of 1.99 to 1.94 Ga. Zircon cores show a 2.5 - 2.6 Ga inheritance from the ancient margin of the Congo Craton. During the Ediacaran, this domain was thinned and intruded by tholeiitic mafic dykes during the development of an oceanic basin at ca. 0.59 Ma. After the tectonic inversion, these basin deposits reached high P-T metamorphic conditions, by subduction of the oceanic lithosphere, and were later exhumed as nappes over the basement. The Cabo Frio Tectonic Domain collided with the arc domain of the Ribeira Orogen at ca. 0.54 Ga. It is not an exotic block, but the eastern transition between this orogen and the Congo Craton. Almost 400 m.y. later, the South Atlantic rift zone followed roughly this suture, not coincidently. It shows how the Cabo Frio Tectonic Domain was reactivated as a continental margin in successive extensional and convergent events through geological time.

  16. Evaluation of bentonite alteration due to interactions with iron. Sensitivity analyses to identify the important factors for the bentonite alteration

    International Nuclear Information System (INIS)

    Sasamoto, Hiroshi; Wilson, James; Sato, Tsutomu

    2013-01-01

    Performance assessment of geological disposal systems for high-level radioactive waste requires a consideration of long-term systems behaviour. It is possible that the alteration of swelling clay present in bentonite buffers might have an impact on buffer functions. In the present study, iron (as a candidate overpack material)-bentonite (I-B) interactions were evaluated as the main buffer alteration scenario. Existing knowledge on alteration of bentonite during I-B interactions was first reviewed, then the evaluation methodology was developed considering modeling techniques previously used overseas. A conceptual model for smectite alteration during I-B interactions was produced. The following reactions and processes were selected: 1) release of Fe 2+ due to overpack corrosion; 2) diffusion of Fe 2+ in compacted bentonite; 3) sorption of Fe 2+ on smectite edge and ion exchange in interlayers; 4) dissolution of primary phases and formation of alteration products. Sensitivity analyses were performed to identify the most important factors for the alteration of bentonite by I-B interactions. (author)

  17. Migration Behaviour of Strontium in Czech Bentonite Clay

    Directory of Open Access Journals (Sweden)

    Lucie Baborova

    2016-09-01

    Full Text Available The study deals with sorption and diffusion behaviour of strontium in Czech bentonite B75. The study is a part of a research on reactive transport of radioactive contaminants in barrier materials of a deep geological repository of radioactive waste in the Czech Republic. Series of sorption and diffusion experiments with Sr and non-activated Ca bentonite B75 produced in the Czech Republic were performed in two background solutions (CaCl2 and NaCl. On the basis of sorption batch experiments the kinetics of strontium sorption on bentonite was assessed and the sorption isotherms for various experimental conditions were obtained. As a result of performed diffusion experiments the parameters of diffusion (i.e. effective diffusion coefficient De and apparent diffusion coefficient Da were determined. The observed discrepancies between sorption characteristics obtained from the sorption and diffusion experiments are discussed.

  18. Decantation time of evaluation on bentonite clays fractionation

    International Nuclear Information System (INIS)

    Gomes, J.; Menezes, R.R.; Neves, G.A.; Lira, H.L; Santana, L.N.L.

    2009-01-01

    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)

  19. Effect of organic matter on 125I diffusion in bentonite

    International Nuclear Information System (INIS)

    Tao Wu; Qing Zheng

    2015-01-01

    Through-diffusion method was conducted to investigate the diffusion behavior of 125 I in bentonite in present of organic matter, such as polyaminopolycarboxylate EDTA, oxalic acid, hydrazine and humic acid HA. The effective diffusion coefficient D e value and rock capacity factor α were (2.32.6) × 10 -11 m 2 /s and 0.040-0.052, respectively. The small difference showed that iodine was preferentially associated with silicoaluminate mineral as an inorganic form. In present of HA, the D a value of 125 I was almost two orders of magnitude higher than that of HA and humic substances HS. The D e and α derived from the experiments were used to simulate its diffusion in the designed bentonite obstacle of high-level radioactive waste repository and the results showed that 125 I can be transported from 30 to 50 cm thickness of bentonite to the far-field of repository in several years. (author)

  20. Organophilization process of Brazilian bentonite for preparation of polymeric nanocomposites

    International Nuclear Information System (INIS)

    Oliveira, Carlos I.R. de; Rocha, Marisa C.G.; Ferreira, Joao L.A.N.G.

    2015-01-01

    Bentonite clay from the municipality of Cubati, PB, was used for the preparation of an organophilic clay. First, the clay was treated with sodium chloride to obtain the homo-ionic sodium clay. The organoclay was, then, obtained from the reaction of homo-ionic clay with the quaternary ammonium salt, cetyltrimethyl ammonium chloride. The natural clay and the modified clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The chemical analysis showed a decrease in the concentration of the majority of the metallic oxides when the bentonite was organophilizated. This result is characteristic of the metal cation exchange process by organic salt molecules. The X-ray diffraction confirmed the intercalation among the layers of the clay. The results obtained by FTIR showed the presence of the characteristic groups of the salt in the clay, thus confirming the obtaining of organophilic bentonite. (author)

  1. Database on gas migration tests through bentonite buffer material

    International Nuclear Information System (INIS)

    Tanai, Kenji

    2009-02-01

    Carbon steel is a candidate material for an overpack for geological disposal of high-level radioactive waste in Japan. The corrosion of the carbon steel overpack in aqueous solution under anoxic conditions will cause the generation of hydrogen gas, which may affect hydrological and mechanical properties of the bentonite buffer. To evaluate such an effect of gas generation, it is necessary to develop a model of gas migration through bentonite buffer material taking account of data obtained from experiments. The gas migration experiments under both unsaturated and saturated conditions have been carried out to clarify the fundamental characteristics of bentonite for gas migration. This report compiles the experimental data obtained from gas migration tests for buffer material which has been conducted by JAEA until December, 2007. A CD-ROM is attached as an appendix. (author)

  2. Coupled behaviour of bentonite buffer results of PUSKURI project

    International Nuclear Information System (INIS)

    Olin, M.; Rasilainen, K.; Itaelae, A.

    2011-08-01

    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.)

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

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.

    1995-04-01

    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.)

  4. Thermal conductivity tests on buffermasses of bentonite/silt

    International Nuclear Information System (INIS)

    Knutsson, S.

    1977-09-01

    The investigation concerns the thermal conductivity of the bentonite/quartz buffer mass suggested as embedding substance for radioactive canisters. The first part presents the theoretical relationships associated with the various heat transfer mechanisms in moist granular materials. Chapter 3 describes the author's experimental determination of the thermal conductivity of the buffer mass. The tested mass consisted of 10 percent (by weight) bentonite and 90 percent natural silt. Four tests were made with different water content values and degree of water saturation. A comparison between the measured and calculated thermal conductivities is given. It is shown that the conductivity can be calculated with an accuracy of +-20 percent. (author)

  5. Structure and forces in bentonite MX-80

    International Nuclear Information System (INIS)

    Joensson, Bo; Aakesson, Torbjoern; Joensson, Bengt; Meehdi, Segad; Janiak, John; Wallenberg, Reine

    2009-03-01

    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 Ca 2+ 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

  6. Strength and Compaction Analysis of Sand-Bentonite-Coal Ash Mixes

    Science.gov (United States)

    Sobti, Jaskiran; Singh, Sanjay Kumar

    2017-08-01

    This paper deals with the strength and compaction characteristics of sand-bentonite-coal ash mixes prepared by varying percentages of sand, bentonite and coal ash to be used in cutoff walls and as a liner or cover material in landfills. The maximum dry density (MDD) and optimum moisture content (OMC) of sand-bentonite mixes and sand-bentonite-coal ash mixes were determined by conducting the standard proctor test. Also, the strength and stiffness characteristics of soil mixes were furnished using unconfined compressive strength test. The results of the study reveal influence of varying percentages of coal ash and bentonite on the compaction characteristics of the sand-bentonite-coal ash mixes. Also, validation of a statistical analysis of the correlations between maximum dry density (MDD), optimum moisture content (OMC) and Specific Gravity (G) was done using the experimental results. The experimental results obtained for sand-bentonite, sand-bentonite-ash and coal ash-bentonite mixes very well satisfied the statistical relations between MDD, OMC and G with a maximum error in the estimate of MDD being within ±1 kN/m3. The coefficient of determination (R2) ranged from 0.95 to 0.967 in case of sand-bentonite-ash mixes. However, for sand-bentonite mixes, the R2 values are low and varied from 0.48 to 0.56.

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

    International Nuclear Information System (INIS)

    Jacobsen, J.S.; Carnahan, C.L.

    1987-12-01

    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

  8. Modelling of long term geochemical evolution and study of mechanical perturbation of bentonite buffer of a KBS-3 repository

    Energy Technology Data Exchange (ETDEWEB)

    Marsal, Francois; Pellegrini, Delphine; Deleruyelle, Frederic; Serres, Christophe (French Inst. for Radiological Protection and Nuclear Safety (IRSN), Fontenay-aux-Roses (FR)); Windt, Laurent de (Ecole des Mines de Paris, Paris (FR))

    2008-03-15

    PART I: The Swedish Nuclear Fuel and Waste Management Co. (SKB) has recently completed a safety assessment project named SR-Can, related to the KBS-3 disposal concept. In this concept, the waste packages are surrounded by a buffer made of either MX-80 or Deponit CA-N bentonite. Interactions between the buffer and groundwater may modify the buffer composition and thus its containment properties. The Swedish Radiation Protection Authorities (SSI) requested the French Institute for Radiological Protection and Nuclear Safety (IRSN) to perform the present study in support of SSI review of the SR-Can report. The purpose is to assess the geochemical evolution of both potential buffer materials due to the intrusion of different types of groundwater, with a similar modelling layout to that reported in SR-Can and detailed in Arcos et al. Three main categories of water inflows via a fracture intersecting a deposition hole are considered: the Forsmark reference groundwater, a high-salinity groundwater to account for up-rise of deep-seated brines and a diluted water representing ice-melting derived-groundwater. In addition to this, the redox buffering capacity of Deponit CA-N bentonite and the thermal effect on MX-80 bentonite geochemistry have been assessed. This modelling work has been performed using the reactive transport modelling code HYTEC. The main outcome of the present study is that the intrusion of the considered groundwaters should not affect drastically the geochemistry of neither the Deponit CA-N nor the MX-80 bentonite on the longterm (100,000 y). Bentonite pH may reach high values (up to 10.5) in some cases but does not reach SKB criterion value related to bentonite chemical stability. Dissolution-precipitation of accessory minerals is not significant enough to induce important porosity changes (rise by maximum 2 %). Globally, the montmorillonite exchanger undergoes Na by Ca partial replacement, which may decrease the swelling pressure of the bentonite. The

  9. Erosion of bentonite buffer in a KBS-3 repository

    International Nuclear Information System (INIS)

    Neretnieks, Ivars; Liu, Loncheng; Moreno, Luis

    2010-01-01

    Document available in extended abstract form only. 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, MRI. The model also predicted the gel expansion through filters with very narrow pores well. In addition the model predicts the CCC fairly well, order to orders of magnitude better than the conventional DLVO theory. 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. The viscosity model uses experimental data to obtain the necessary fitting parameters but is otherwise based on established theories of suspension viscosity. These models form the core of the erosion model. Both show a strong dependence on the ionic strength of the pore water. 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. The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses from the compacted bentonite into and through the expanding gel towards the gel/water interface and further out into the seeping water. Mass transfer resistance for ions as well as smectite particles in the seeping water is

  10. Synthesis and characterization of organophilic clay from Cuban Chiqui Gomez bentonite

    International Nuclear Information System (INIS)

    Cortes, Guillermo R. Martin; Hennies, Wildor T.; Valera, Ticiane S.; Esper, Fabio J.; Diaz, Francisco R. Valenzuela

    2009-01-01

    Smectite are clay minerals with a layered structure and nanometric thickness, high specific area and a huge variety of uses. Consisting on stacked layers of about 1nm thickness, including two silica tetrahedral and one octahedral sheet. Properties of natural Smectite can be enhanced by organic modification, due to the substitution of the exchangeable cations in the interlayer area. In fact, the properties of the modified smectite (organophilic clay) are related to its modified chemical composition and structural parameters. The interaction of smectite clays with surfactants has an important interest in the fields of drilling fluids, paints, cosmetic, ceramic industries and others. Recent applications are: remediation of contaminated areas and polymer/clay nanocomposites. The aim of this paper is to obtain organophilic clays using a bentonite from the Chiqui Gomez deposit in Central Cuba. The raw and organophilic clays were analyzed by DRX, SEM, swelling capacity in organic solvents and others. (author)

  11. Complejo de restauración del atún rojo en Cabo de Palos : CRARCP

    OpenAIRE

    Denchev Torlakov, Ivaylo

    2016-01-01

    El proyecto pretende por una parte poner en valor el producto del atún rojo promocionando los nuevos valores de la cocina (I+D+I) y convertirlo en símbolo de identidad para el municipio de Cabo de Palos y la Región de Murcia. Por otra parte se busca la reactivación y definición de un borde urbano en Cabo de Palos. Para ello se definen los siguientes objetivos: - Analizar el entorno urbano existente, evaluarlo y proponer soluciones que permitan mejorar las condiciones del mismo, impulsando la ...

  12. The carbohydrate sequence markup language (CabosML): an XML description of carbohydrate structures.

    Science.gov (United States)

    Kikuchi, Norihiro; Kameyama, Akihiko; Nakaya, Shuuichi; Ito, Hiromi; Sato, Takashi; Shikanai, Toshihide; Takahashi, Yoriko; Narimatsu, Hisashi

    2005-04-15

    Bioinformatics resources for glycomics are very poor as compared with those for genomics and proteomics. The complexity of carbohydrate sequences makes it difficult to define a common language to represent them, and the development of bioinformatics tools for glycomics has not progressed. In this study, we developed a carbohydrate sequence markup language (CabosML), an XML description of carbohydrate structures. The language definition (XML Schema) and an experimental database of carbohydrate structures using an XML database management system are available at http://www.phoenix.hydra.mki.co.jp/CabosDemo.html kikuchi@hydra.mki.co.jp.

  13. Glucose Oxidase Immobilization on TMAH-Modified Bentonite

    Directory of Open Access Journals (Sweden)

    Ruth Chrisnasari

    2015-03-01

    Full Text Available The influence of bentonite modification by tetramethyl ammonium hydroxide (TMAH on its capability to immobilize glucose oxidase (GOX was studied. Modification of bentonite was conducted by the adding of 0-5% (v/v TMAH. The observed results show that the different concentrations of TMAH affect the percentage of immobilized enzyme. The results of this study show that the best concentration of TMAH is 5% (v/v which can immobilize up to 84.71% of GOX. X-ray diffraction (XRD and Fourier Transforms Infrared Spectroscopy (FTIR studies have been carried out to observe the structural changes in bentonite due to TMAH modification. The obtained immobilized GOX show the optimum catalytic activity on reaction temperature of 40-50 °C and pH of 7. The immobilized GOX kinetics at the optimum conditions determined the Km and Vmax value to be 4.96x10-2 mM and 4.99x10-3 mM.min-1 respectively. In addition, the immobilized GOX on TMAH-modified bentonite is stable enough so it could be re-used six times before its activity decreased by 39.44%.

  14. Magnesium incorporated bentonite clay for defluoridation of drinking water.

    Science.gov (United States)

    Thakre, Dilip; Rayalu, Sadhana; Kawade, Raju; Meshram, Siddharth; Subrt, J; Labhsetwar, Nitin

    2010-08-15

    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 mgg(-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 ( approximately 97%) using 1M 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. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Magnesium incorporated bentonite clay for defluoridation of drinking water

    International Nuclear Information System (INIS)

    Thakre, Dilip; Rayalu, Sadhana; Kawade, Raju; Meshram, Siddharth; Subrt, J.; Labhsetwar, Nitin

    2010-01-01

    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.

  16. The biological costs of not reclaiming bentonite mine spoils

    Science.gov (United States)

    Carolyn Hull Sieg; Daniel W. Uresk; Richard M. Hansen

    1982-01-01

    Bentonite clay has been mined in the northern Great Plains for more than 80 years. Until the late 1960's, mine spoil materials were left in steep piles and no effort was made to restore biological productivity to these disturbed sites. As a result, unreclaimed spoils are barren and eroded. The biological costs of not reclaiming these spoils are examined in this...

  17. Mineralogical behaviour of bentonites in open and closed systems

    International Nuclear Information System (INIS)

    Herbert, H.J.; Kasbohm, J.

    2004-01-01

    Mineralogical and chemical changes of bentonites were investigated in a natural analogue study and in laboratory experiments. As a working hypothesis we assumed that in geological, i.e. open systems, bentonites may be penetrated over geological time scales by larger water volumes than high compacted bentonites used as technical barriers in repositories in salt formations. Under this assumption open geological systems are characterised by low solid/liquid ratios and closed repository systems by high solid/liquid ratios. Consequently in laboratory experiments the mineralogical changes were investigated under different solid/liquid ratios and compared with results of a natural analogue study. In the natural analogue study in deep boreholes in the East Slovakian Basin the expandability of montmorillonite and the degree of transformation in illite-smectite (IS) mixed layer structures was found to be dependent not only on depth and temperature but also on the salinity of the pore waters. In this open geological system with a comparatively low solid/liquid ratio the observed changes in the montmorillonite were significantly different than those observed in the laboratory study on compacted MX-80 bentonite. (authors)

  18. Behaviour of humic-bentonite aggregates in diluted suspensions ...

    African Journals Online (AJOL)

    Formation and disaggregation of micron-size aggregates in a diluted suspension made up of HSs and bentonite (B) were studied by tracing distribution of aggregate sizes and their counts in freshly prepared and aged suspensions, and at high (10 000) and low (1.0) [HS]/[B] ratios. Diluted HSB suspensions are unstable ...

  19. Magnesium incorporated bentonite clay for defluoridation of drinking water

    Czech Academy of Sciences Publication Activity Database

    Thakre, D.; Rayalu, S.; Kawade, R.; Meshram, S.; Šubrt, Jan; Labhsetwar, N.

    2010-01-01

    Roč. 180, 1-3 (2010), s. 122-130 ISSN 0304-3894 Institutional research plan: CEZ:AV0Z40320502 Keywords : adsorption * bentonite * fluoride removal Subject RIV: CA - Inorganic Chemistry Impact factor: 3.723, year: 2010

  20. Synthesis of MCM-41 nanomaterial from Algerian bentonite ...

    African Journals Online (AJOL)

    Mesoporous materials of the MCM-41 type were synthesized from Algerian bentonite as an aluminosilicate source without the addition of pure silica and aluminum reagents. The samples were synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. The influence of initial ...

  1. Vitrification and neomineralisation of bentonitic and kaolinitic clays ...

    African Journals Online (AJOL)

    ... metamorphic and/or igneous rocks. Resultant fired mineral phases depicted mineral compositions of ceramic bodies, and the study suggested that these clays could be gainfully utilized in the making of ceramic wares, subject to selected beneficiation processes. Keywords: kaolin, bentonite, vitrification, neomineralization, ...

  2. Diffusion of anions and cations in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.

    1994-02-01

    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 Sr 2+ 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 Sr 2+ 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.)

  3. Effects of polyethyleneimine adsorption on rheology of bentonite ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... 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 ...

  4. characterization of geotechnical properties of lateritic soil-bentonite

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... cilities should ensure minimum fluid flow through or into the repository ... were evaluated using the rigid wall permeameter un- der falling ... cell pressure [22]. 3. Results .... them to retain a portion of water (double layer water) that may ... water in the pore space. ... The effect of bentonite content on volumetric.

  5. Performance of Mn2+-modified Bentonite Clay for the Removal

    African Journals Online (AJOL)

    NICOLAAS

    Clay minerals are promising materials for defluoridation of ... edge of the bentonite sheet. ... surface area analyzer (Autosorb-iQ & Quadrasorb SI, USA). .... used to describe chemisorption, as well as cation exchange reac- tions.14 t q. 1. K q. 1.

  6. Bentonite Modification with Manganese Oxides and Its Characterization

    Czech Academy of Sciences Publication Activity Database

    Dolinská, S.; Schütz, T.; Znamenáčková, I.; Lovás, M.; Vaculíková, Lenka

    2015-01-01

    Roč. 35, č. 1 (2015), s. 213-218 ISSN 1640-4920 Institutional support: RVO:68145535 Keywords : bentonite * natrification * manganese oxide Subject RIV: CB - Analytical Chemistry, Separation http://www.potopk.com.pl/ Full _text/2015_full/IM%202-2015-a35.pdf

  7. The removal of chromium from wastewaters by activated bentonite

    International Nuclear Information System (INIS)

    Mellah, A.; Chegrouche, S.; Ait Ghezala, H.; Douar, L.

    1994-12-01

    The adsorption of chromium onto activated bentonite has been investigated. Adsorption isotherms were analysed to obtain the Langmuir and freundlich constants. The operating parameters (i.e pH, contact time, solid/liquid ratio, temperatureand initial chromium concentration) influenced the rate of adsorption have been studied

  8. Thermal loading of bentonite. Impact on hydromechanics and permeability

    Energy Technology Data Exchange (ETDEWEB)

    Zihms, Stephanie G.; Harrington, Jon [British Geological Survey, Nickerhill Keyworth (United Kingdom)

    2015-07-01

    Due to its favorable properties, in particular, low permeability and swelling capacity, bentonite has been favored as an engineered barrier and backfill material for the geological storage of radioactive waste. To ensure 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 will investigate the hydro-mechanical response of bentonite under multi-step thermal loading subject to a constant volume boundary condition. The experimental set up allows continuous measurements of hydraulic and mechanical response during each phase of the thermal cycle. The constant volume cell was placed inside an oven and connected to a hydraulic system with the water reservoir located externally. A pressure gradient of 4 MPa was placed across the sample for the duration of the test in order to map the evolution of permeability. After initial hydration of the bentonite, in this case signified by reaching the asymptote in total stress, the temperature was raised in 20 C increments from 20 to 80 C followed by a final 10 C step to reach 90 C. Each temperature was held constant for at least 7-10 days to allow the stresses and hydraulic transients to equilibrate. This data set will provide an insight into the hydromechanical behavior of the bentonite and the evolution of its permeability when exposed to elevated temperatures.

  9. 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

  10. Gas migration mechanism of saturated dense bentonite and its modeling

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko; Kudo, Koji

    2007-01-01

    In the current concept of repository for nuclear 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 following subjects: a) Effect of the accumulated gas pressure on surrounding objects such as concrete lining, rock mass. b) Effect of gas breakthrough on the barrier function of bentonite. c) Revealing and modeling gas migration mechanism for overcoming the scale effects in laboratory specimen test. Therefore in this study, gas migration tests for compacted and saturated bentonite to investigate and to model the mechanism of gas migration phenomenon. Firstly, the following conclusions were obtained through by the results of the gas migration tests which are conducted in this study: 1) Bubbles appear in the semitransparent drainage tube at first when the total gas is equal to the initial total axial stress or somewhat smaller. By increasing the gas pressure more, breakthrough of gas migration, which is defined as a sudden increase of amount of emission gas, occurred. When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. 2) Effective gas conductivity after breakthrough of gas migration is times larger than that

  11. 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

  12. Alteration of bentonite when contacted with supercritical CO2

    Science.gov (United States)

    Jinseok, K.; Jo, H. Y.; Yun, S. T.

    2014-12-01

    Deep saline formations overlaid by impermeable caprocks with a high sealing capacity are attractive CO2 storage reservoirs. Shales, which consist of mainly clay minerals, are potential caprocks for the CO2 storage reservoirs. The properties of clay minerals in shales may affect the sealing capacity of shales. In this study, changes in clay minerals' properties when contacted with supercritical (SC) CO2 at various conditions were investigated. Bentonite, whichis composed of primarily montmorillonite, was used as the clay material in this study. Batch reactor tests on wet bentonite samples in the presence of SC CO2 with or without aqueous phases were conducted at high pressure (12 MPa) and moderate temperature (50 oC) conditions for a week. Results show that the bentonite samples obtained from the tests with SC CO2 had less change in porosity than those obtained from the tests without SC CO2 (vacuum-drying) at a given reaction time, indicating that the bentonite samples dried in the presence of SC CO2 maintained their structure. These results suggest that CO2 molecules can diffuse into interlayer of montmorillonite, which is a primary mineral of bentonite, and form a single CO2 molecule layer or double CO2 molecule layers. The CO2 molecules can displace water molecules in the interlayer, resulting in maintaining the interlayer spacing when dehydration occurs. Noticeable changes in reacted bentonite samples obtained from the tests with an aqueous phase (NaCl, CaCl2, or sea water) are decreases in the fraction of plagioclase and pyrite and formation of carbonate minerals (i.e., calcite and dolomite) and halite. In addition, no significant exchanges of Na or Ca on the exchangeable complex of the montmorillonite in the presence of SC CO2 occurred, resulting in no significant changes in the swelling capacity of bentonite samples after reacting with SC CO2 in the presence of aqueous phases. These results might be attributed by the CO2 molecule layer, which prevents

  13. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, O. [Clay Technology AB, Lund (Sweden)

    1997-12-01

    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 5 refs, 48 figs, 11 tabs

  15. Thermodynamic understanding on swelling pressure of bentonite buffer

    International Nuclear Information System (INIS)

    Sato, Haruo

    2007-01-01

    Smectite (montmorillonite) is a major clay mineral constituent of the bentonite buffer and backfilling materials to be used for the geological disposal of high-level radioactive waste. Swelling pressure of the bentonite buffer occurring in the permeation process of moisture was estimated based on thermodynamic theory and the thermodynamic data of interlayer water in smectite in this study. The relative partial molar Gibbs free energies (ΔG H2O ) of water on the smectite surface were measured as a function of water content (0-83%) in a dry density range of 0.6-0.9 Mg/m 3 . Purified Na-smectite of which interlayer cations were exchanged with Na + ions and soluble salts were completely removed, was used in this study. Obtained ΔG H2O decreased with an increase of water content in the range of water content lower than about 40%, and similar trends were obtained to data of Kunipia-F bentonite (Na-bentonite) of which smectite content was approximately 100 wt.%. From the specific surface area of smectite (ca. 800 m 2 /g) and the correlation between ΔG H2O and water content, water affected from the surface of smectite was estimated to be up to approximately 2 water layers. Swelling pressure versus smectite partial density (montmorillonite partial density) was estimated based on ΔG H2O from the chemical potential balance of water in equilibrium between the free water and moisturized smectite, and compared to data measured for various kinds of bentonites of which smectite contents were respectively different. The estimated swelling pressures were in good agreement with the measured data. (author)

  16. assessment of invasive fruit fly fruit infestation and damage in cabo

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    039o50.352' E and 246 masl), where B. invadensis widespread and well established (Cugala et al.,. 2011). Niuje and Koma-koma are well organised fruit production areas and Mahipa is a major mango and cashew production area in Cabo Delgado. Province. The choice of these host species was due to their abundance, ...

  17. The catazonal poly-metamorphic rocks of Cabo Ortegal (NW Spain), a structural and petrofabric study

    NARCIS (Netherlands)

    Engels, J.P.

    1972-01-01

    The petrological study of the southern part of the Cabo Ortegal area is a complement of Vogel’s (1967) investigation of the northern half. The present investigations include a structural as well as a petrofabric study. The rocks belong to an eugeosynclinal sequence which during the Precambrian

  18. Excursions in the catazonal rock complexes of the polyorogenic terrain of Cabo Ortegal (NW Spain)

    NARCIS (Netherlands)

    Vogel, D.E.

    1967-01-01

    This excursion program anticipates the publication of a PhD. thesis (Vogel, in preparation) in this periodical and is intended as a guide to those points at Cabo Ortegal, that are readily accessible, well exposed and of general petrological interest. The described localities are indicated on a small

  19. Advances in nuclear medicine and in radiopharmaceuticals, International meeting in Cabo Frio. Program and abstracts

    International Nuclear Information System (INIS)

    2002-01-01

    The meeting of Advances in Nuclear Medicine and in Radiopharmaceuticals, held in Cabo Frio, Rio de Janeiro State, Brazil, in September 26-28, 2002, has provided an excellent opportunity for the presentation and the discussion of the latest achievements and new trends of nuclear medicine techniques and radiopharmaceuticals for the clinical evaluation of inflammation, infection, oncology and therapy of diseases with radionuclides

  20. Etnobotânica na Reserva Extrativista Marinha de Arraial do Cabo, RJ, Brasil Ethnobotany of Arraial do Cabo Marine Extractive Reserve, Rio de Janeiro, Brazil

    Directory of Open Access Journals (Sweden)

    Viviane Stern da Fonseca-Kruel

    2004-03-01

    Full Text Available A Reserva Extrativista Marinha de Arraial do Cabo (RESEX localiza-se no município de Arraial do Cabo, região de Cabo Frio. É uma unidade de conservação de interesse ecológico-social e visa proteger o sustento dos pescadores artesanais, a flora e a fauna locais. O clima da região é tropical seco e a vegetação é de restinga. Este estudo objetivou inventariar as espécies vegetais usadas na faixa terrestre da RESEX, associando este conhecimento às tradições locais. As informações etnobotânicas foram obtidas através de observação participante e entrevistas estruturadas com pescadores artesanais. Das 444 citações de uso, catalogou-se 68 espécies, 61 gêneros e 42 famílias. As categorias de uso foram: alimentar (45,6%, medicinal (39,7%, tecnológica (29,4%, lenha (10,2%, construção (8,8% e ornamental (2,9%. Utilizou-se o Índice de Shannon para análise da diversidade de espécies resultando: 1,78 (base 10 e 4,10 (base e, denotando que os pescadores possuem bom conhecimento da biodiversidade local, quando comparado a outros estudos da costa brasileira. Os dados obtidos nesta pesquisa possibilitarão a formulação de estratégias de uso sustentável dos recursos naturais, considerando a percepção ambiental da população, baseado nos sistemas cognitivos desenvolvidos ao longo do convívio do homem com a natureza.The Arraial do Cabo Marine Extractive Reserve (RESEX, is located on Arraial do Cabo Municipality, Cabo Frio region. It is a conservation unit with social and ecological interest, that intends to protect the livelihood of traditional fishermen, local flora and fauna. The climate is tropical dry and the vegetation classified as sandy-coastal-plain vegetation. This study goal was to survey useful species on the land part of RESEX, and associate this knowledge to local traditions. The ethnobotanical data was obtained by observer participation and structured interviews with traditional fishermen. From the 444 use

  1. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-01-01

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  2. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  3. Sequential use of bentonites and solar photocatalysis to treat winery wastewater.

    Science.gov (United States)

    Rodríguez, Eva; Márquez, Gracia; Carpintero, Juan Carlos; Beltrán, Fernando J; Alvarez, Pedro

    2008-12-24

    The sequential use of low-cost adsorbent bentonites and solar photocatalysis to treat winery wastewater has been studied. Three commercial sodium-bentonites (MB-M, MB-G, and MB-P) and one calcium-bentonite (Bengel) were characterized and used in this study. These clay materials were useful to totally remove turbidity (90-100%) and, to a lesser extent, color, polyphenols (PPh), and soluble chemical oxygen demand (CODS) from winery wastewater. Both surface area and cation exchange capacity (CEC) of bentonite had a positive impact on treatment efficiency. The effect of pH on turbidity removal by bentonites was studied in the 3.5-12 pH range. The bentonites were capable of greatly removing turbidity from winery wastewater at pH 3.5-5.5, but removal efficiency decreased with pH increase beyond this range. Settling characteristics (i.e., sludge volume index (SVI) and settling rate) of bentonites were also studied. Best settling properties were observed for bentonite doses around 0.5 g/L. The reuse of bentonite for winery wastewater treatment was found not to be advisable as the turbidity and PPh removal efficiencies decreased with successive uses. The resulting wastewater after bentonite treatment was exposed to solar radiation at oxic conditions in the presence of Fe(III) and Fe(III)/H2O2 catalysts. Significant reductions of COD, total organic carbon (TOC), and PPh were achieved by these solar photocatalytic processes.

  4. Diffusion of strongly sorbing cations (60Co and 152Eu) in compacted Febex bentonite

    International Nuclear Information System (INIS)

    Garcia-Gutierrez, M.; Missana, T.; Alonso, U.; Mingarro, M.; Cormenzana, J.L.

    2010-01-01

    Document available in extended abstract form only. Compacted bentonite is used as an engineered barrier in high-level radioactive waste (HLRW) repositories because is a swelling clay of very low permeability and high sorption capability for many solutes. The transport of radionuclides through compacted bentonite is a diffusion-controlled process retarded by sorption. Performance assessment calculations of a repository need diffusion coefficients data of relevant radionuclides. Several studies on diffusion behaviour of neutral, anionic and weakly sorbing elements on clay exist while very few studies are available for moderately sorbing elements, and almost no studies for Eu, a highly sorbing element are reported. In this study, diffusion experiments with strongly sorbing radionuclides, as 60 Co and 152 Eu, have been performed through compacted FEBEX bentonite. Diffusion essays with these strongly sorbing radionuclides are not straightforward to carry out because they are very time consuming essays, but also because sorption on the diffusion cells, tubing, filters and reservoirs, typically used in the classical through-diffusion or in-diffusion methods make hard the interpretation of the experimental results and the calculation of the diffusion coefficients. FEBEX bentonite was selected as Spanish reference buffer materials, and used in many national and international projects. The clay comes from the Cortijo de Archidona deposit (Almeria, Spain), and has a smectite content greater than 90% (93 ± 2%), with quartz (2 ± 1%), plagioclase (3 ± 1%), cristobalite (2 ± 1%), potassic feldspar, calcite, and trydimite as accessory minerals. The specific weight of the FEBEX bentonite is 2.7 g/cm 3 . Diffusion experiments were performed using the instantaneous plane source method. In this setup, a paper filter tagged with a tracer is introduced between two compacted tablets, avoiding contact between the tracer and the experimental vessels. The tracer can diffuse into both

  5. Mineralogical and geological study of quaternary deposits and weathering profiles

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Gi Young; Lee, Bong Ho [Andong National Univ., Andong (Korea, Republic of)

    2004-01-15

    Movement history of a quaternary reverse fault cutting marine terrace deposit and tertiary bentonite in the Yangnammyon, Gyoungju city was studied by the mineralogical and microtextural analysis of the fault clays and weathered terrace deposits. Two types of fault clays were identified as greenish gray before the deposition of the marine terrace deposits and reddish brown after deposition. Greenish gray fault clay is composed mostly of smectite probably powdered from bentonite showing at least two events of movement from microtextures. After the bentonite was covered by quaternary marine gravel deposits, the reverse fault was reactivated cutting marine gravel deposits to form open spaces along the fault plane which allowed the hydrological infiltration of soil particles and deposition of clays in deep subsurface. The reddish brown 'fault' clays enclosed the fragments of dark brown ultrafine varved clay, proving two events of faulting, and slicken sides bisecting reddish brown clays suggest another faulting event in the final stage. Mineralogical and microtextural analysis of the fault clay show total five events of faulting, which had not been recognized even by thorough conventional paleoseismological investigation using trench, highlighting the importance of microtextural and mineralogical analysis in paleoseismology.

  6. Alteration behavior of bentonite barrier of radioactive waste disposal by alkaline solutions. Part 2. Effect of type of alkaline solution on permeability of compacted bentonite-sand mixture

    International Nuclear Information System (INIS)

    Yokoyama, Shingo; Nakamura, Kunihiko; Tanaka, Yukihisa; Hironaga, Michihiko

    2011-01-01

    Permeability tests were carried out using compacted bentonite-sand mixture with initial dry density of 1.55 Mg/m 3 and alkaline solutions at 50degC for about two years to estimate the alteration behavior and the change in the permeability. Bentonite-sand mixtures which contain bentonites of 15wt% were made using Na-bentonite or Ca-exchanged bentonite. 0.3M-NaOH solution with pH 13.3 and 5mM-Ca(OH) 2 solution with pH 12.0 were used to the permeability tests of Na-bentonite-sand mixture and of Ca-exchanged bentonite-sand mixture, respectively. In the case of the permeability test conducted using NaOH solution, montmorillonite and other associated minerals were dissolved, and consequently, the dry density and effective montmorillonite density of Na-bentonite-sand mixture were decreased. Furthermore, the mineralogical feature of montmorillonite was changed (i.e. beidellitization and an increase in the layer charge). The permeability of Na-bentonite-sand mixture was increased 5.6 times by the end of permeability test as a result of above alteration. In the case of the permeability test conducted using Ca(OH) 2 solution, montmorillonite and other associated minerals were dissolved, and calcium silicate hydrate (C-S-H) was precipitated. Consequently, the dry density of Ca-exchanged bentonite-sand mixture was increased, while the effective montmorillonite density was decreased. The mineralogical feature of montmorillonite was changed (i.e. beidellitization and an increase in the layer charge). The permeability of Ca-exchange bentonite-sand mixture was decreased by more than two orders of magnitude due to fill the pore of Ca-exchange bentonite-sand mixture by the precipitation of C-S-H. From above results, the type of alkaline solution affects the mineralogical alteration behavior of the compacted bentonite-sand mixture, and consequently, affects the changing trend of permeability. In conclusion, it is important not only to consider the dissolution of montmorillonite, but

  7. O golfe e os rumos do Cabo Verde independente = Golfing and the independent Cape Verde directions = El golf y los caminos del Cabo Verde independiente

    Directory of Open Access Journals (Sweden)

    Melo, Victor Andrade de

    2016-01-01

    Full Text Available Em função de uma série de peculiaridades, o golfe tem desempenhado um importante papel na história de Cabo Verde. A prática, que tem uma longa trajetória no arquipélago, em diversas ocasiões foi mobilizada a fim de materializar a ideia de que o cabo-verdiano era portador de um alto padrão civilizacional. No período colonial, essa foi uma das estratégias pelos nativos usada para lidar com o jugo da metrópole, argumento utilizado para requisitar maior respeito às especificidades e atenção às necessidades locais. O que terá mudado nas considerações sobre esse esporte quando chegou a independência (1975? Que diferenças podem ser sentidas nas décadas seguintes? Neste artigo, argumentamos que os discursos sobre a modalidade nos ajudam a lançar um olhar sobre os debates acerca dos rumos do país insular nos últimos 40 anos

  8. Compaction of bentonite blocks. Development of techniques for production of blocks with different shapes and sizes

    International Nuclear Information System (INIS)

    Johannesson, Lars-Erik; Boergesson, Lennart

    1998-09-01

    In this report useful techniques for producing both smaller blocks manageable by man (10-15 kg) and larger blocks which need special equipment for handling (weight up to 600 kg) are described. Tests for producing blocks with a weight of approximately 10 kg were carried out at Hoeganaes Bjuf AB in Bjuv. This industry is normally producing refractory bricks and other refractory products. The plant has facilities for handling large volumes of clay. It also has machines suitable for producing uniaxially compacted blocks. Tests performed at the plant show that it is possible to compact blocks with good quality. The best quality was reached with a coarsely ground bentonite at a water ratio of 17 %. The compaction rate was high and performed with lubricated form and stepwise loading. Tests, in order to find a technique for producing larger blocks with a diameter of the same size as a deposition hole (about 1.65 m), were also made. The technique was developed in a smaller scale (250 mm). Ring-shaped blocks with the same outer diameter and with an inner diameter of about 156 mm were also compacted. The compaction was made with vacuum in the form. The outer surface of the form was conical and most of the tests were performed with a lubricated form. Tests were performed with different water ratios of the bentonite. All the blocks had a good quality. In consequence of the good test results a form with a 1000 mm diameter was constructed and a number of compaction tests were performed. The same technique was used as for the smaller blocks. The compaction pressure in most tests was 100 MPa (maximum compaction load 80.000 kN). The tests were performed at HYDROWELD in Ystad in a press with a maximum capacity of 300.000 kN. All tests were performed with MX-80. Most of the blocks had a good quality. A small damage close to the upper surface of all blocks was observed but is considered to be of no importance for the possibility to handle the blocks and is not affecting the properties

  9. Compaction of bentonite blocks. Development of techniques for production of blocks with different shapes and sizes

    Energy Technology Data Exchange (ETDEWEB)

    Johannesson, Lars-Erik; Boergesson, Lennart [Clay Technology AB, Lund (Sweden)

    1998-09-01

    In this report useful techniques for producing both smaller blocks manageable by man (10-15 kg) and larger blocks which need special equipment for handling (weight up to 600 kg) are described. Tests for producing blocks with a weight of approximately 10 kg were carried out at Hoeganaes Bjuf AB in Bjuv. This industry is normally producing refractory bricks and other refractory products. The plant has facilities for handling large volumes of clay. It also has machines suitable for producing uniaxially compacted blocks. Tests performed at the plant show that it is possible to compact blocks with good quality. The best quality was reached with a coarsely ground bentonite at a water ratio of 17 %. The compaction rate was high and performed with lubricated form and stepwise loading. Tests, in order to find a technique for producing larger blocks with a diameter of the same size as a deposition hole (about 1.65 m), were also made. The technique was developed in a smaller scale (250 mm). Ring-shaped blocks with the same outer diameter and with an inner diameter of about 156 mm were also compacted. The compaction was made with vacuum in the form. The outer surface of the form was conical and most of the tests were performed with a lubricated form. Tests were performed with different water ratios of the bentonite. All the blocks had a good quality. In consequence of the good test results a form with a 1000 mm diameter was constructed and a number of compaction tests were performed. The same technique was used as for the smaller blocks. The compaction pressure in most tests was 100 MPa (maximum compaction load 80.000 kN). The tests were performed at HYDROWELD in Ystad in a press with a maximum capacity of 300.000 kN. All tests were performed with MX-80. Most of the blocks had a good quality. A small damage close to the upper surface of all blocks was observed but is considered to be of no importance for the possibility to handle the blocks and is not affecting the properties

  10. O arquipélago “literopintado”: escritura literária de autoria feminina em Cabo Verde

    Directory of Open Access Journals (Sweden)

    Simone Caputo Gomes

    2010-12-01

    Full Text Available Este artigo tem por objetivo estudar a representação de Cabo Verde pela literatura de autoria feminina, que retrata – lê, pinta, desenha, esculpe, escreve, imagina – suas belas paisagens, seu cotidiano popular, seus perfis de mulher, sua riqueza cultural.Palavras-chave: Literatura feminina; Cabo Verde; Representação cultural.

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

    International Nuclear Information System (INIS)

    Ye Weimin; Zheng Zhenji; Chen Bao; Chen Yonggui

    2011-01-01

    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)

  12. Optimization of acid-activated bentonites on bleaching of cotton oil

    International Nuclear Information System (INIS)

    Lacin, O.; Sayan, E.; Kirali, E.G.

    2013-01-01

    Bentonites are commonly used adsorbent on bleaching cotton oil to produce edible oil products. Bleaching capacities of neutralized cotton oil were investigated with acid-activated Arguvan and Kursunlu bentonites. Two models for acid activation of the bentonites were developed by using a full factorial experimental design and central composite design. The parameters used to develop these models were contact time, solid to liquid ratio, acid concentration and moisture of bentonite. By using a constrained optimization program, the maximum bleaching capacities of neutralized cotton oil were determined as 99.99% and 48.5% for Arguvan and Kursunlu, respectively. Optimum results showed that Turkish bentonites (especially Arguvan bentonite) have high bleaching ability and they can be used efficiently to bleach neutralized cotton oil by considering the favorable volume weight, capacity of oil adsorbed and filtration rate. (author)

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

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Nakamura, Kunihiko; Kudo, Kohji; Hironaga, Michihiko; Nakagami, Motonori; Niwase, Kazuhito; Komatsu, Shin-ichi

    2007-01-01

    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)

  14. Investigations of the changes in the bentonite structure caused by the different treatments

    OpenAIRE

    Stojiljković S.; Stamenković M.; Kostić D.; Miljković M.; Arsić B.; Savić I.; Savić I.

    2015-01-01

    The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. ...

  15. Migration behaviour of Pu released from Pu-doped glass in compacted bentonite

    International Nuclear Information System (INIS)

    Ashida, T.; Kohara, Y.; Yui, M.

    1994-01-01

    In order to investigate the coupled behavior of Pu release from the waste glass and transport in bentonite, a migration experiment with compacted sodium-type bentonite saturated with distilled water was carried out at room temperature, in which Pu-doped borosilicate glass was sandwiched. Under these conditions, leaching of Pu from the glass, diffusion and sorption of Pu in the compacted bentonite occur simultaneously. (orig.)

  16. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2006-01-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  17. Investigation on the effect of seawater to hydraulic property and wetting process of bentonite

    International Nuclear Information System (INIS)

    Hasegawa, Takuma

    2004-01-01

    On high-level waste disposal, bentonite is one of the most promising material for buffer and backfill material. The hydraulic properties and wetting process of bentonite are important not only for barrier performance assessment but also for prediction of waste disposal environment, such as resaturation time and thermal distribution. In Japan, we should consider the effect of seawater for bentonite, because radioactive waste will be disposed of in coastal area and in marine sediment where seawater remained. However, it is not enough to understand the effect of seawater. Therefore, experimental study was conducted to investigate the effect of seawater on the hydraulic conductivity and wetting process of bentonite. The effect of seawater on hydraulic conductivity is significant for Na-bentonite, the hydraulic conductivity of Na-bentonite in seawater is one order to magnitude higher than that in distilled water. On the other hand, the hydraulic conductivity of Ca-bentonite is not influenced by seawater. The hydraulic conductivity of bentonite decreases as effective montmorillonite density increases. The effective montmorillonite density is ratio between the weight of montmorillonite and volume of porosity and montmorillonite. The hydraulic conductivity of bentonite is close related to swelling property since the hydraulic conductivity decrease as the swelling pressure increase. Wetting process of compacted bentonite could be evaluated by diffusion phenomena since infiltration rate and change of saturation rate and represented by diffusion equation. The effect of seawater on water diffusivity is significant for Na-type bentonite with low effective montmorillonite density. Except for that condition, the water diffusivity of bentonite is almost constant and is not influenced by effective montmorillonite density and seawater. (author)

  18. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2005-03-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  19. Physical and chemical stability of the bentonite buffer

    Energy Technology Data Exchange (ETDEWEB)

    Jinsong Liu; Neretnieks, Ivars [Chemical Engineering and Technology, Royal I nstitute of Technology, Stockholm (Sweden)

    2007-12-15

    A literature study was made on previous work on clay erosion and on the fundamental processes that govern the stability of clay gels. Mechanical erosion has been studied earlier and models devised to estimate the tendency to erode. We have used a different approach that we deem is fundamentally more correct. Chemical erosion processes have not been found to be studied previously and we have approached the problem by applying simple but fundamental mass balances and transport processes to the problem. The physical and chemical processes that govern the repulsive and cohesive forces in clay are well understood in principle but cannot yet be applied quantitatively to predict the gel/sol behaviour of the bentonite clay. It was necessary to rely directly on laboratory measurements for information on swelling and gel/sol properties. The backfill bentonite clay acts as a Bingham fluid over a wide range of clay density. To mobilise the clay a shear stress larger than the Bingham yield stress must be applied to the gel. The Bingham yield stress has been measured to be larger than 1 Pa (N/m{sup 2}) although it cannot be ruled out that lower values can be found under different experimental conditions than those reported. Shear stresses exerted by the water flowing in the fractures that intersect the deposition holes with the clay backfill have been estimated for a wide range of fracture transmissivities, apertures and hydraulic gradients that could exist under repository conditions. This includes the extremely high gradients that could exist during some periods during an ice age. For fracture transmissivities ranging from 10{sup -9} to 10{sup -6} m{sup 2}/s, fracture apertures from 0.1 to 2 mm and the hydraulic gradients from 0.01 to 1 mH{sub 2}O/m, the largest local shear stress found in this range was about 0.1 Pa. To investigate a 'what if' situation where the shear stress exceeds the yield stress simple models were devised. They were used to assess the rate of

  20. Physical and chemical stability of the bentonite buffer

    International Nuclear Information System (INIS)

    Jinsong Liu; Neretnieks, Ivars

    2007-12-01

    A literature study was made on previous work on clay erosion and on the fundamental processes that govern the stability of clay gels. Mechanical erosion has been studied earlier and models devised to estimate the tendency to erode. We have used a different approach that we deem is fundamentally more correct. Chemical erosion processes have not been found to be studied previously and we have approached the problem by applying simple but fundamental mass balances and transport processes to the problem. The physical and chemical processes that govern the repulsive and cohesive forces in clay are well understood in principle but cannot yet be applied quantitatively to predict the gel/sol behaviour of the bentonite clay. It was necessary to rely directly on laboratory measurements for information on swelling and gel/sol properties. The backfill bentonite clay acts as a Bingham fluid over a wide range of clay density. To mobilise the clay a shear stress larger than the Bingham yield stress must be applied to the gel. The Bingham yield stress has been measured to be larger than 1 Pa (N/m 2 ) although it cannot be ruled out that lower values can be found under different experimental conditions than those reported. Shear stresses exerted by the water flowing in the fractures that intersect the deposition holes with the clay backfill have been estimated for a wide range of fracture transmissivities, apertures and hydraulic gradients that could exist under repository conditions. This includes the extremely high gradients that could exist during some periods during an ice age. For fracture transmissivities ranging from 10 -9 to 10 -6 m 2 /s, fracture apertures from 0.1 to 2 mm and the hydraulic gradients from 0.01 to 1 mH 2 O/m, the largest local shear stress found in this range was about 0.1 Pa. To investigate a 'what if' situation where the shear stress exceeds the yield stress simple models were devised. They were used to assess the rate of erosion by the groundwater. In

  1. Rheological characterization of nanocomposites Nylon 6/bentonite clay

    International Nuclear Information System (INIS)

    Silva, T.R.G.; Fernandes, P.C.; Oliveira, S.V.; Araujo, E.M.; Melo, T.J.A.

    2010-01-01

    Polymer nanocomposites are a class of materials that have been widely used in various applications. Among them, has been emphasizing the preparation of polymer films with barrier properties for applications in polymer membranes. In this work, nanocomposites of nylon 6/bentonite clay were obtained from a Homogenizer, in the ratios of 1, 3 and 5 wt% clay. The Brasgel PA bentonite clay was treated organically with Praepagen HY salt, to make it organophilic. By X-ray diffraction (XRD), it was showed that the efficiency of the incorporation of salt in the clay. The rheological curves showed that for the AST clay the torque did not change when compared with the pure nylon 6, while for the clay ACT, the torque increased gradually with the percentage of clay. (author)

  2. 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 .

  3. Retention of Cs on zeolite, bentonite and their mixtures

    International Nuclear Information System (INIS)

    Atun, G.

    2002-01-01

    The sorption behavior of cesium on zeolite and bentonite minerals and their mixtures was studied by means of a batch method and a tracer technique. All experiments were carried out in the presence of CsCl spiked with 137 Cs and NaCl as a supporting electrolyte in varying concentrations. The distribution coefficients (K D ) did not show significant differences at low Cs + loadings while they decreased in the high loading region. Freundlich and D-R isotherms were applied to the adsorption data of zeolite and bentonite. Adsorption capacities and mean energies calculated from D-R isotherm parameters decreased by increasing ionic strength on both minerals. The identification of the specific uptake sites was attempted on the basis of the Freundlich isotherm. Experimentally observed distribution coefficients of Cs on two mineral mixtures were smaller than theoretically calculated values, except at the highest NaCl concentration. (author)

  4. Sedimentation Characteristics of Kaolin and Bentonite in Concentrated Solutions

    Directory of Open Access Journals (Sweden)

    Abdulah Obut

    2005-11-01

    Full Text Available The sedimentation characteristics of two clays, namely kaolinite and bentonite, were determinated at high clay (5 % wt/vol and electrolyte (1 N concentrations using various inorganic-organic compounds. It was observed that the settling behaviour of kaolinite (1:1 clay and montmorillonite (2:1 clay is quite different due to the structural differences between these minerals. Although, similar initial settling rates and final sediment volumes were obtained after 24 hours of settling time for kaolin suspensions, the corresponding rates and volumes for bentonite suspensions varied greatly with the used chemical compound. According to the experimental results, a further intensive theoretical and experimental investigation is needed to reveal the mechanism underlying the sedimentation characteristics of clay minerals at high clay and electrolyte concentrations.

  5. Removal of uranium from water media by bentonite and zeolite

    International Nuclear Information System (INIS)

    Viglasova, E.; Krajnak, A.; Galambos, M.; Rosskopfova, O.

    2014-01-01

    The removal and recovery of uranium from contaminated surface, environment and ground water, as result of nuclear industries, has attracted more and more attentions. Several methods are available for removing of uranium, but adsorption among the others, is the most attractive. In case of management of radioactive waste, the adsorption of radionuclides plays significant role. Among the natural sorbents applied to the adsorption of uranium zeolites and bentonites offer a number of advantages. The main aims of this work are investigations of adsorption properties of Greek zeolite Metaxades and Greek bentonite Kimolos during adsorption of uranium from water solutions, comparison of their adsorption characteristics, fitting with isotherms (Freundlich, Langmuir and DR isotherm) and its behaviour during kinetics process influenced by temperature. (authors)

  6. Investigation of alteration behaviour of compacted bentonite contracted with carbon steel for 10 years

    International Nuclear Information System (INIS)

    Suyama, Tadahiro; Ueno, Kenichi; Sasamoto, Hiroshi

    2008-03-01

    To evaluate long term behavior of corrosion for carbon steel in compacted bentonite, and to evaluate long term stability of bentonite, corrosion experiments were conducted using synthetic sea water and synthetic groundwater at 50 and 80degC for 10 years under anaerobic atmosphere. In the present study, the samples of compacted bentonite after experiments were investigated to understand the alteration behavior of bentonite by iron-bentonite interactions. Results were summarized below. Iron generated by corrosion of carbon steel was migrated into compacted bentonite further in the synthetic seawater case than in the synthetic groundwater case. Result of TEM observation for the sample of synthetic sea water case at 80degC showed that the original layer structure for clay minerals was maintained and the layer distance was about 12[A] which was similar to the layer distance of normal 2:1 smectite. Thus, it was suggested that there was no change in smectite before and after experiments. Iron generated by corrosion of carbon steel was migrated into compacted bentonite in anaerobic condition case but scarcely migrated in aerobic condition case. Results of EPMA analysis indicated that the maximum migration depth of iron in compacted bentonite was about 0.2 mm for sample in synthetic sea water at 80degC under anaerobic condition. Results of XRD analysis for the sample in which iron migration in compacted bentonite was observed showed that there was no corrosion product in compacted bentonite and the structure of clay mineral in bentonite was di-octahedral. Furthermore, the result of XRD analysis under relative humidity controlled condition suggested that the swelling property of sample after experiment was similar to that of initial Na-type smectite. Therefore, it was supposed that the initial Na-type smectite did not change during the experiment. Batch type experiments with different temperature, solutions and duration have been conducted to understand the alteration

  7. Investigations of the changes in the bentonite structure caused by the different treatments

    Directory of Open Access Journals (Sweden)

    Stojiljković S.

    2015-01-01

    Full Text Available The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. By thermal activation of bentonite clay in the temperature range 100-1100 0C, samples of desired porosity were acquired. [Projekat Ministarstva nauke Republike Srbije, br. 174007i br. TR 34020

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

    International Nuclear Information System (INIS)

    Suryantoro; Arimuladi, S.P.; Sastrowardoyo, P.B.

    1998-01-01

    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)

  9. Study of the Properties of Bentonites for their use in Clay Geo synthetic Barriers

    International Nuclear Information System (INIS)

    Leiro Lopez, A.; Mateo Sanz, B.; Garcia Cidoncha, H.; Blanco Fernandez, M.

    2014-01-01

    Bentonites used for the production of clay geo synthetic barriers need to meet some properties so that they can be a waterproofing system. among the bentonites used in industry, sodium bentonite has the lowest permeability due to its high water absorption capacity in the inter-laminar space, causing it to swell and form a barrier to water flow. this paper provides the study of the properties of four bentonite to evaluate their quality the study of the properties of four bentonite to evaluate their quality. For this study, the main properties have been tested: water absorption, swelling index, fluid loss, cation exchange capacity and montmorillonite content. In order to optimize the procedure for the characterization of bentonites, correlations between different tests have been done, to identify the most suitable ones. Finally, a compatibility test has been carried out to study the performance of bentonites in water containing a high amount of sales, because in this case, an ion exchange between the interlayer sodium ions of bentonite and cations dissolved in the water can take, resulting in a decrease swell of the bentonite. (Author)

  10. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Science.gov (United States)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-07-01

    Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  11. 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.

  12. Soil-bentonite design mix for slurry cutoff walls used as containment barriers

    International Nuclear Information System (INIS)

    Rad, N.S.; Bachus, R.C.; Jacobson, B.D.

    1995-01-01

    In recent years, soil-bentonite slurry cutoff walls have been increasingly used as containment barriers around contaminated soils to impede or, in some cases, nearly eliminate the off-site migration of contaminated ground water or other potentially hazardous liquids. The paper presents the procedures used and the results obtained during an extensive laboratory testing program performed to select varying soil-bentonite slurry mix components for a soil-bentonite slurry cutoff wall constructed around an old landfill at a former oil refinery. The landfill is underlain to varying depths by a coarse granular soils that has been exposed to oil-products. Compatibility of three commercially available bentonite products with the free oil-products and the oil-contaminated ground water found at some locations in the landfill was initially investigated. Based on the test results, one of the bentonite products was selected for use in the soil-bentonite slurry testing program. A clayey soil from a borrow source, potable water from the site, and subsurface soils from the proposed soil-bentonite slurry wall alignment were used to form different soil-bentonite slurry mixes. Slump tests were performed to evaluate the workability of the mixes. Based on the test results, a single mix was selected for further study, including permeability/compatibility testing. The results of the compatibility testing program are presented and discussed in the paper. A specific design mix methodology for evaluating the chemical compatibility of soil-bentonite slurry mixes with permeants is proposed

  13. One-dimensional self-sealing ability of bentonites in artificial seawater

    International Nuclear Information System (INIS)

    Komine, Hideo; Yasuhara, Kazuya; Murakami, Satoshi

    2009-01-01

    A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on self-sealing ability of three common sodium-types of bentonite by the laboratory experiment and chemical analysis. From the results of laboratory experiment, suitable specifications were defined for a bentonite-based buffer that can withstand the effects of seawater. Furthermore, mechanism on filtration of seawater components in highly compacted bentonite was discussed by the results of chemical analysis. (author)

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

    International Nuclear Information System (INIS)

    Valenzuela Diaz, Francisco R.; Souza Santos, Persio de

    1995-01-01

    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)

  15. Removal of zinc from aqueous solutions by natural bentonite

    International Nuclear Information System (INIS)

    Mellah, A.; Chegrouche, S.

    1994-01-01

    The equilibrium isotherms of zinc adsorption onto natural bentonite show that the data correlate well with freundlich and Langmuir's models and that the adsorption is physical in nature. The operating parameters (agitation speed, solid/liquid ratio temperature, particle size and initial zinc concentration) influenced the rate of adsorption. The maximum monomolecular capacity (Q 0 ) according to the Langmuir model is 52.91 mg. g-1 for an initial zinc concentration of 300 mg. litre-1, At 20 0 C

  16. Leaching of rare earth elements from bentonite clay

    OpenAIRE

    van der Watt, J.G; Waanders, F.B

    2012-01-01

    Due to increasing concerns of global rare earth element shortfalls in the near future, possible alternative sources of rare earth elements have recently become of economic interest. One such alternative is decanting acid mine water originating primarily from abandoned old mines in the Witwatersrand region of the Republic of South Africa. In this study, a novel way of rare earth element removal from the acid mine drainage was employed, making use of bentonite clay, which has very good adsorben...

  17. Water uptake and motion in highly densified bentonite

    International Nuclear Information System (INIS)

    Kahr, G.; Mueller-Vonmoos, F.; Kraehenbuehl, F.; Stoeckli, H.F.

    1986-07-01

    Water uptake by the bentonites MX-80 and Montigel was investigated according to the classical method of determination of the heat immersion and the adsorption-desorption isotherms. In addition, the layer expansion of the montmorillonite was measured as a function of the water content. The evaluation of the adsorption isotherms according to Dubinin-Radushkevich and the stratification distances determined by x-ray confirmed gradual water uptake. Up to 10% water content, the water is adsorbed as a monolayer, up to 20%, as a bimolecular layer around the interlayer cations. The partial specific entropy could be determined from the approximative calculation of the partial specific enthalpy from the heats of immersion and the free enthalpy from the adsorption isotherms. From this it is evident that the interlayer water shows a high degree of order. In this condition, the mobility of the water molecules is considerably lower than in free water. From the adsorption isotherm and the layer expansion observed, it can be assumed that water can appear in the pore space only from approximately 25% water content. The spaces outwith the interlayer space and the surfaces of the montmorillonite particles are considered as pore space. If free swelling is prevented and with dry densities greater than 1.8 Mg/m/sup 3/ for the highly compacted bentonites, water uptake causes a drastic reduction of the original pore space so that practically all the water is in the interlayer space. Calculation of the swelling pressure from the adsorption isotherms gives a good approximation of the measured swelling pressures. A montmorillonite surface of ca. 750 m/sup 2//g for both bentonites can be derived from a Dubinin-Radushkevich analysis of the adsorption isotherm. Water uptake into the compacted unsaturated bentonites can be described as diffusion with a diffusion coefficient of the order of magnitude of 3.10/sup -10/ m/sup 2//s. (author)

  18. Preparation and performance of Ecobras/bentonite biodegrading films

    International Nuclear Information System (INIS)

    Costa, Ana Nery M.; Melo, Nadja M.C.; Canedo, Eduardo L.; Carvalho, Laura H.; Araujo, Arthur R.A.

    2011-01-01

    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)

  19. Diffusion and sorption properties of radionuclides in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Yu Ji-Wei; Neretnieks, I. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Engineering and Technology

    1997-07-01

    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{sup -10} m{sup 2}/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{sup -12} m{sup 2}/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{sup -8} m{sup 2}/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. 99 refs.

  20. Advanced study of transport analysis in bentonite (2)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2004-03-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation first we improved the interatomic potential model for the smectitic clays. Then the behaviors of hydrated Na-beidellite and its substitution products by Cs and Ca were calculated. Not only the swelling behaviors of the beidellite minerals but also the diffusion characteristics of cations in the interlayer space are calculated. A microscopic image is important to specify micro/macro behavior of bentonite. Last year we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). Based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption characteristics at the edges of clay minerals. (author)

  1. Advanced study of transport analysis in bentonite (3)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2005-02-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization analysis (HA) method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation we precisely simulated the molecular behaviors of cations and H 2 O in the neighborhood of a clay mineral. In FY2002 the swelling property and diffusivity of interlayer cations, Cs and Ca, were calculated. In FY2003 the interatomic potential model was improved, and the diffusivity of several interlayer cations were calculated. In FY2004 the interatomic potential model was further improved, and the swelling and diffusive properties became more realistic. Then the coordination number of cations were calculated. A microscopic image is important to specify micro/macro behavior of bentonite. In FY2002 we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). In FY2003 based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption

  2. X-chromosome STR markers data in a Cabo Verde immigrant population of Lisboa.

    Science.gov (United States)

    Afonso Costa, Heloísa; Morais, Paulo; Vieira da Silva, Cláudia; Matos, Sara; Marques Santos, Rodolfo; Espinheira, Rosa; Costa Santos, Jorge; Amorim, António

    2014-01-01

    Population genetic data of 12 X chromosomal short tandem repeats markers (DXS10074, DXS10079, DXS10101, DXS10103, DXS10134, DXS10135, DXS10146, DXS10148, DXS7132, DXS7423, DXS8378 and HPRTB) were analysed in 54 females and 95 males of an immigrant population from Cabo Verde living in Lisboa. The obtained results for forensic statistical parameters such as observed heterozigosity, polymorphism information content, power of discrimination and mean exclusion chance, based on single allele frequencies, reveal that this multiplex system is highly informative and can represent an important tool for genetic identification purposes in the immigrant population of Cabo Verde. Since the studied short tandem repeats genetic markers are distributed on four linkage groups, that can provide independent genotype information, we studied those groups as haploytes. The forensic efficiency parameters for the linked groups were all higher than 0.97, with linkage group I being the most polymorphic and linkage group III the less informative.

  3. Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation.

    Science.gov (United States)

    Calado, Leandro; Camargo Rodríguez, Orlando; Codato, Gabriel; Contrera Xavier, Fabio

    2018-03-01

    This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment.

  4. Diffusion of radionuclides in concrete/bentonite systems

    International Nuclear Information System (INIS)

    Albinsson, Y.; Boerjesson, S.; Andersson, K.; Allard, B.

    1993-02-01

    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

  5. Swelling pressure in compacted bentonite below 0°C

    International Nuclear Information System (INIS)

    Birgersson, Martin; Karnland, Ola; Nilsson, Ulf

    2010-01-01

    Document available in extended abstract form only. Bentonite is a common component in many concepts for underground storage of high level radioactive waste. During its lifetime, an underground 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 investigate and understand the behavior of bentonite below 0 deg. C. 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 - +25 deg. C. The swelling pressure response has been recorded continuously. The samples have been varied with respect to bentonite type (e.g. calcium or sodium dominated), smectite content and density. The general observation is that the pressure of the bentonite lowers in a temperature range between 0 deg. C and a specific (negative) temperature T c , which is strongly correlated to the swelling pressure measured above 0 deg. C. Consequently, Tc decreases (i.e. becomes more negative) with increased density or smectite content. At T c , swelling pressure is completely lost. Furthermore, a very weak pressure dependence is observed at temperatures above 0 deg. C. This dependence is however strictly dependent on sample density. For any type of bentonite at high enough densities above 0 deg. C, the slope of the P-T curve is negative and becomes more negative with increasing density. For Na-dominated bentonites at lower densities, on the other hand, the slope is positive. An important observation is that no pressure increase was observed for any of the tested bentonite samples as the transition to temperatures below 0 deg. C was made. Since water expands as it freezes, this observation indicates that no ice is formed in compacted bentonite as the 0 deg. C level is passed. The observed swelling

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

    International Nuclear Information System (INIS)

    Sun Wenjing; Sun De'an; Fang Lei

    2012-01-01

    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/cm 3 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. Bentonite as a colloid source in groundwaters at Olkiluoto

    International Nuclear Information System (INIS)

    Vuorinen, U.; Hirvonen, H.

    2005-02-01

    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 μm filters before entering the glove-box, because only colloids smaller than 0.45 μm 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 μm, 300kD and 10kD). The ultrafiltrations produced the colloid-containing concentrate fractions and the soluble substances-containing filtrate fractions. In

  8. Modelling Ni diffusion in bentonite using different sorption models

    International Nuclear Information System (INIS)

    Pfingsten, W.; Baeyens, B.; Bradbury, M.

    2010-01-01

    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

  9. Ageing effects on swelling behaviour of compacted GMZ01 bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Ye, W.M., E-mail: ye_tju@tongji.edu.cn [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); United Research Center for Urban Environment and Sustainable Development, the Ministry of Education, China, Shanghai 200092 (China); Lai, X.L.; Liu, Y. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Chen, Y.G. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); United Research Center for Urban Environment and Sustainable Development, the Ministry of Education, China, Shanghai 200092 (China); Cui, Y.J. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Ecole des Ponts Paris Tech, UR Navier/CERMES (France)

    2013-12-15

    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 K{sub 0} 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 K{sub 0} 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.

  10. Cabo Verde: Democracia, Cultura Política e Esfera Pública

    Directory of Open Access Journals (Sweden)

    Nataniel Andrade Monteiro

    2016-07-01

    Full Text Available O artigo procura contribuir para se compreender e descrever aquilo que, no meu entender, constitui a nova abordagem da discussão acerca da cultura política e da esfera pública em Cabo Verde. A pobreza, o desemprego, a justiça social e a segurança, entre outros assuntos, têm sido alvos de atenção por parte da sociedade civil cabo-verdiana, sobretudo a partir da década de noventa, com o advento da democracia. O que me incita a pensar sobre novas tendências no que se refere à cultura política dos cabo-verdianos, particularmente na afirmação e configuração de uma esfera pública que prima pela prática do debate e respeito pela opinião pública, capaz de influenciar as acções do sistema político. O ano de 2015 tem sido marcado por debates de repercussão nacional e internacional, como é o caso mediático do Estatuto de Titulares de Cargos Políticos (ETCP. Este acontecimento, ao que tudo indica, possibilita uma nova configuração da esfera pública cabo-verdiana, corroborada numa cultura política participativa, de modo que sirva, não apenas para os períodos eleitorais, mas igualmente como instrumento para a consolidação do sistema político.

  11. Epidemiology of the Zika Virus Outbreak in the Cabo Verde Islands, West Africa.

    Science.gov (United States)

    Lourenço, José; de Lourdes Monteiro, Maria; Valdez, Tomás; Monteiro Rodrigues, Júlio; Pybus, Oliver; Rodrigues Faria, Nuno

    2018-03-15

    The Zika virus (ZIKV) outbreak in the island nation of Cabo Verde was of unprecedented magnitude in Africa and the first to be associated with microcephaly in the continent. Using a simple mathematical framework we present a first epidemiological assessment of attack and observation rates from 7,580 ZIKV notified cases and 18 microcephaly reports between July 2015 and May 2016. In line with observations from the Americas and elsewhere, the single-wave Cabo Verdean ZIKV epidemic was characterized by a basic reproductive number of 1.85 (95% CI, 1.5 - 2.2), with overall the attack rate of 51.1% (range 42.1 - 61.1) and observation rate of 2.7% (range 2.29 - 3.33). Current herd-immunity may not be sufficient to prevent future small-to-medium epidemics in Cabo Verde. Together with a small observation rate, these results highlight the need for rapid and integrated epidemiological, molecular and genomic surveillance to tackle forthcoming outbreaks of ZIKV and other arboviruses.

  12. 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

  13. Phylogenetic relationships of cone snails endemic to Cabo Verde based on mitochondrial genomes.

    Science.gov (United States)

    Abalde, Samuel; Tenorio, Manuel J; Afonso, Carlos M L; Uribe, Juan E; Echeverry, Ana M; Zardoya, Rafael

    2017-11-25

    Due to their great species and ecological diversity as well as their capacity to produce hundreds of different toxins, cone snails are of interest to evolutionary biologists, pharmacologists and amateur naturalists alike. Taxonomic identification of cone snails still relies mostly on the shape, color, and banding patterns of the shell. However, these phenotypic traits are prone to homoplasy. Therefore, the consistent use of genetic data for species delimitation and phylogenetic inference in this apparently hyperdiverse group is largely wanting. Here, we reconstruct the phylogeny of the cones endemic to Cabo Verde archipelago, a well-known radiation of the group, using mitochondrial (mt) genomes. The reconstructed phylogeny grouped the analyzed species into two main clades, one including Kalloconus from West Africa sister to Trovaoconus from Cabo Verde and the other with a paraphyletic Lautoconus due to the sister group relationship of Africonus from Cabo Verde and Lautoconus ventricosus from Mediterranean Sea and neighboring Atlantic Ocean to the exclusion of Lautoconus endemic to Senegal (plus Lautoconus guanche from Mauritania, Morocco, and Canary Islands). Within Trovaoconus, up to three main lineages could be distinguished. The clade of Africonus included four main lineages (named I to IV), each further subdivided into two monophyletic groups. The reconstructed phylogeny allowed inferring the evolution of the radula in the studied lineages as well as biogeographic patterns. The number of cone species endemic to Cabo Verde was revised under the light of sequence divergence data and the inferred phylogenetic relationships. The sequence divergence between continental members of the genus Kalloconus and island endemics ascribed to the genus Trovaoconus is low, prompting for synonymization of the latter. The genus Lautoconus is paraphyletic. Lautoconus ventricosus is the closest living sister group of genus Africonus. Diversification of Africonus was in allopatry

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

    International Nuclear Information System (INIS)

    Muurinen, A.; Tournassat, C.; Hadi, J.; Greneche, J.-M.

    2014-02-01

    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 ( 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

  15. 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

  16. THE RESULTS OF PHYSICO-CHEMICAL STUDIES OF BENTONITE OF DASHUKOVSKІУ FIELD

    Directory of Open Access Journals (Sweden)

    Е. M. Nikipelova

    2015-04-01

    Full Text Available Thus, the basic physical and chemical properties ( moisture content (57,19 %, unit weight (1,31, shear stress (821,59 Pa, stickiness (1839,81 Pa, debris particles with a diameter of more than 250 mkm (0,34 %, specific heat (2,75 kG/(kg · K bentonite deposits Dashukovskoho Cherkasy region meets the eligibility criteria of the Therapeutic muds (peloids. The chemical composition of the aqueous extract of clay deposits Dashukovskoho refers to magnesium sulphate-bicarbonate-calcium-sodium type or complex cation composition with mineralization of 0,26 g/dm3. pH of the extract of clay is 7,95 m. pH is characterized by slightly alkaline reaction. Positive values oxidation -reduction potential of the extract of clay (+ 465 mV indicate the presence of oxidative processes. This is because the clay extraction in the preparation of the latter was in contact with oxygen. It should be noted that the calculation of the structural formulabentonite is great information because it allows to introduce the character of isomorphic substitutions in the structure, efficiently detect the composition of exchange cations, which makes it possible to predict the behavior of the sample during its processing technology.

  17. Formula of Moulding Sand, Bentonite and Portland Cement toImprove The Quality of Al-Si Cast Alloy

    OpenAIRE

    Andoko Andoko; Poppy Puspitasari; Avita Ayu Permanasari; Didin Zakaria Lubis

    2017-01-01

    A binder is any material used to strengthen the bonding of moulding sand grains. The primary function of the binder is to hold the moulding sand and other materialstogether to produce high-quality casts. In this study, there were four binder compositions being tested, i.e. 5% bentonite + 5% Portland cement, 4% bentonite + 6% Portland cement, 6% bentonite + 4% Portland cement, and 7% bentonite + 3% Portland cement. Each specimen was measured for its compressive strength, shear strength, tensil...

  18. Early age sealing of buffer-rock gap by artificial wetting to induce bentonite swelling

    International Nuclear Information System (INIS)

    Holt, Erika; Marjavaara, Pieti

    2012-01-01

    Document available in extended abstract form only. The aim of this work is to study the homogeneous and rapid swelling of bentonite in the gap between the buffer blocks and the rock wall of the Olkiluoto disposal facility by artificial wetting. The focus was on the construction period of the deposition hole and buffer, and thus only the very early ages of the first weeks. In practice it is desirable that the bentonite material has a volume increase sufficient enough to prevent rock scaling while lowering the risks of bentonite piping and erosion due to potential water flow. This initial study was done in a small-scale mock-up in laboratory conditions. The small-scale steel mock-up had dimensions of 39 cm in height by 36 cm in diameter and included 12 pressure sensors, two displacement transducers, thermal couples, and pore water pressure measurements. The radial and axial pressure development was typically measured over a two week period to assess the rate and magnitude of sealing. A steel confining lid was used for simulating overpressure, though in some cases a plexiglass lid was used to take video images of the gap sealing. The buffer blocks were produced by isostatic compression of 100 MPa. The material was MX-80 Wyoming bentonite having a water content of approximately 13% and a dry density of 1890 kg/m 3 . The testing samples were dry sawn and core drilled from the large block and machined to their final dimensions. These were typically 30 x 30 cm, either as a solid block or three disks of 10 cm height each. The diameter was sometimes varied to allow for a change of gap width between 25 to 50 mm The study included various scenarios, such as: eccentric aligned blocks with gap sizes of 5 and 45 mm, free upward swelling or confinement, different types of pellet and granular gap filling, addition of water at varying rates, and longer term test duration. The samples were typically disassembled after two weeks. At this ending point, material assessments were done

  19. Deep repository - engineered barrier systems. Assessment of backfill materials and methods for deposition tunnels

    International Nuclear Information System (INIS)

    Gunnarsson, D.; Moren, L.; Sellin, P; Keto, P.

    2007-09-01

    The main objectives of this report are to: (1) present density criteria considering deposition tunnels for the investigated backfill materials, (2) evaluate what densities can be achieved with the suggested backfill methods, (3) compare the density criteria to achievable densities, (4) based on this comparison evaluate the safety margin for the combinations of backfill materials and methods and, (5) make recommendations for further investigations and development work. The backfilling methods considered in this report are compaction of backfill material in situ in the tunnel and placement of pre-compacted blocks and pellets. The materials investigated in the second phase of the SKB-Posiva backfilling programme can be divided into three main categories: (1) Bentonite clays: two high-grade Na-bentonites from Wyoming (MX-80 and SPV200), one low-grade bentonite from Kutch (India Asha 2 0), and one high- and one low-grade Ca-bentonite from Milos (Deponite CA-N and Milos backfill). The highgrade bentonites are used in different bentonite-ballast mixtures. (2) Smectite-rich mixed-layer clays: one from Dnesice-Plzensko Jih (DPJ) located in the Czech Republic and one from Northern Germany (Friedland clay). (3) Mixtures of bentonite and ballast: Mixtures consisting of high-grade bentonite (30, 40 and 50 w-%) and crushed rock with different type of grain size distribution or sand. The general conclusion from the comparison between estimated achievable densities and the density criteria is that placing pre-compacted blocks of swelling clay or 50/50 mixture and pellets in the tunnel results in the highest safety margin. (orig.)

  20. BENTONITE-QUARTZ SAND AS THE BACKFILL MATERIALS ON THE RADIOACTIVE WASTE REPOSITORY

    Directory of Open Access Journals (Sweden)

    Raharjo Raharjo

    2010-06-01

    Full Text Available An investigation of the contribution of quartz sand in the bentonite mixture as the backfill materials on the shallow land burial of radioactive waste has been done. The experiment objective is to determine the effect of quartz sand in a bentonite mixture with bentonite particle sizes of -20+40, -40+60, and -60+80 mesh on the retardation factor and the uranium dispersion in the simulation of uranium migration in the backfill materials. The experiment was carried out by the fixed bed method in the column filled by the bentonite mixture with a bentonite-to-quartz sand weight percent ratio of 0/100, 25/75, 50/50, 75/25, and 100/0 on the water saturated condition flown by uranyl nitrate solution at concentration (Co of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, retardation factor (R and dispersivity ( were determined. The experiment data showed that the bentonite of -60+80 mesh and the quartz sand of -20+40 mesh on bentonite-to-quartz sand with weight percent ratio of 50/50 gave the highest retardation factor and dispersivity of 18.37 and 0.0363 cm, respectively.   Keywords: bentonite, quartz sand, backfill materials, radioactive waste

  1. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. 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.

  3. Study on the saturating and swelling behavior of an engineering bentonite barrier using a test model

    International Nuclear Information System (INIS)

    Nakajima, Makoto; Kobayashi, Ichizo; Toida, Masaru; Fujisaki, Katsutoshi

    2007-01-01

    The conceptual design of a disposal facility with additional buffer depth for radioactive waste is mainly constituted from the multi-barrier system that is constructed around the waste form so that it prevents radionuclide transfer to the biosphere. The engineered bentonite barrier is one of the elements of the multi-barrier system and is constructed with homogeneous bentonite-containing material compacted to a high density so that there are no voids. Due to the swelling characteristics of the bentonite material, the self-sealing function which is an important function of the bentonite barrier can work, but at the same time it mechanically affects the neighboring structures. Therefore, an experimental study was implemented in order to evaluate the mechanical effect of the bentonite swelling behavior throughout the construction, emplacement operations and closure re-saturation phase. In this article, the results of swelling tests to obtain the mechanical properties of the bentonite and three types of test model experiments performed for the event observations in the different saturation processes are described. As a result, the effects of a seepage pattern of ground water and a variation in the density produced by construction on the swelling pressure distribution of the bentonite barrier could be reproduced and validated. It is thought that they will be important events when ground water permeates the bentonite layer of a multiple barrier system. (author)

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

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.; Pusch, R.

    1994-12-01

    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.)

  5. Electrochemical and radiochemical material transport examinations in humate-containing montmorillonite a bentonite thin layers

    International Nuclear Information System (INIS)

    Antal, K.; Joo, P.

    1999-01-01

    Various humate-containing H-bentonite layers were investigated using 137 Cs ion transport and radio absorption measuring method. These processes can model radioactive contamination migration in soils exposed to acid rains. Experiment using montmorillonite and bentonite layers are discussed, and the results obtained with electrochemical and radioisotope absorption techniques are presented. (R.P.)

  6. Removal of nitrate by zero-valent iron and pillared bentonite

    International Nuclear Information System (INIS)

    Li Jianfa; Li Yimin; Meng Qingling

    2010-01-01

    The pillared bentonite prepared by intercalating poly(hydroxo Al(III)) cations into bentonite interlayers was used together with Fe(0) for removing nitrate in column experiments. The obvious synergetic effect on nitrate removal was exhibited through uniformly mixing the pillared bentonite with Fe(0). In such a mixing manner, the nitrate was 100% removed, and the removal efficiency was much higher than the simple summation of adsorption by the pillared bentonite and reduction by Fe(0). The influencing factors such as bentonite type, amount of the pillared bentonite and initial pH of nitrate solutions were investigated. In this uniform mixture, the pillared bentonite could adsorb nitrate ions, and facilitated the mass transfer of nitrate onto Fe(0) surface, then accelerated the nitrate reduction. The pillared bentonite could also act as the proton-donor, and helped to keep the complete nitrate removal for at least 10 h even when the nitrate solution was fed at nearly neutral pH.

  7. Geochemical modelling of hydrogen gas migration in an unsaturated bentonite buffer

    NARCIS (Netherlands)

    Sedighi, M.; Thomas, H.R.; Al Masum, S.; Vardon, P.J.; Nicholson, D.; Chen, Q.

    2014-01-01

    This paper presents an investigation of the transport and fate of hydrogen gas through compacted bentonite buffer. Various geochemical reactions that may occur in the multiphase and multicomponent system of the unsaturated bentonite buffer are considered. A reactive gas transport model, developed

  8. Effect of calcium bentonite on lipid parameters in Wistar albino rat ...

    African Journals Online (AJOL)

    The in vivo effect of Nigerian calcium bentonite clay on rat plasma cholesterol and triglyceride levels of Wistar albino rats was investigated. The rats were fed for a period of four weeks with varying concentrations of the bentonite clay, and the cholesterol and triglyceride levels determined using spectrophotometric methods.

  9. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Koudelkova, M.; Vinsova, H.; Konirova, R.; Ernestova, M.; Jedinakova-Krizova, V.; Tereesha, M.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing condition. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ ) with bentonite, the effect of solid: aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. The 8 days kinetics of the perrhenate and pertechnetate sorption on bentonite was described mathematically with a tendency to predict long-term behavior of studied systems. (authors)

  10. Theory and calculation of water distribution in bentonite in a thermal field

    International Nuclear Information System (INIS)

    Carnahan, C.L.

    1988-09-01

    Highly compacted bentonite is under consideration for use as a buffer material in geological repositories for high-level radioactive wastes. To assess the suitability of bentonite for this use, it is necessary to be able to predict the rate and spatial extent of water uptake and water distribution in highly compacted bentonite in the presence of thermal gradients. The ''Buffer Mass Test'' (BMT) was conducted by workers in Sweden as part of the Stripa Project. The BMT measured uptake and spatial distributions of water infiltrating annuli of compacted MX-80 sodium bentonite heated from within and surrounded by granite rock; the measurements provided a body of data very valuable for comparison to results of theoretical calculations. Results of experiments on adsorption of water by highly compacted MX-80 bentonite have been reported by workers in Switzerland. The experiments included measurements of heats of immersion and adsorption-desorption isotherms. These measurements provide the basis for prediction of water vapor pressures in equilibrium with bentonite having specified adsorbed water contents at various temperatures. The present work offers a phenomenological description of the processes influencing movement of water in compacted bentonite in the presence of a variable thermal field. The theory is applied to the bentonite buffer-water system in an assumed steady state of heat and mass transport, using critical data derived from the experimental work done in Switzerland. Results of the theory are compared to distributions of absorbed water in buffers observed in the Swedish BMT experiments. 9 refs., 2 figs

  11. Natural analogue study for interaction between alkaline groundwater and bentonite at Mangatarem region in the Philippines

    International Nuclear Information System (INIS)

    Tsukada, Y.; Fujita, K.; Nakabayashi, R.; Sato, T.; Yoneda, T.; Yamakawa, M.; Fujii, N.; Namiki, K.; Kasama, T.; Alexander, R.; Arcilla, C.; Pascua, C.

    2012-01-01

    Document available in extended abstract form only. Alteration of bentonite by alkaline leachate from cement/concrete in geological repositories for TRU radioactive waste is deleterious to bentonite performance as a buffer material. Although there have been many laboratory studies on high pH fluid-bentonite interaction for longer term understanding of the behavior of bentonites as buffer materials, different time scales between laboratory experiments and real disposal conditions impede its proper assessment. Thus, a natural analogue study can play an important role in (a) bridging the timescale gaps between laboratory experiments and real disposal conditions and (b) verifying the modeling studies of bentonite stability. Previous natural analogue studies on the cement-bentonite interaction are relatively few. Therefore, this study focuses on the process of serpentinization in ophiolitic rocks which resemble the process of leaching high pH ground waters from cement materials and report the results of study about alkaline water-bentonite interaction in Mangatarem, Philippines. In Mangatarem, in west central Luzon Island in the northern Philippines, there are bentonite quarries in the Aksitero Formation, which is part of the Zambales Ophiolite. Several alkaline hot springs derived from ongoing serpentinization of the ophiolite can be found in close proximity to the bentonite.Through a site characterization (including a foot survey, a series of boreholes and trench excavation in the Saile quarry in Mangatarem, the interface between the bentonite and the pillow lava of the upper ophiolite was confirmed, and chrysotile, a low temperature type of serpentine, was observed in the fault filling by XRD analysis. In the pillow lava, serpentine was also observed inside the fault that cut across both the bentonite and the pillow lava. From these facts, low temperature high pH fluids appears to have passed through the faults and came into contact with the bentonite. In order to

  12. Use of Bentonite in residual waters of tanneries for the removal of Cr(III)

    International Nuclear Information System (INIS)

    Echavarria Isaza, Adriana; Moreno Casaf, Monica; Ramirez Ochoa, Claudia; Tamayo Martinez, Claudia; Saldarriaga Molina, Carlos

    1998-01-01

    An efficient procedure is reported for Cr(III) removal from tannery waste waters by means of natural and chemically treated bentonites. The best result was obtained using 20 mL of effluent with 7.5 grams of Bentonite. With this quantity it was removed the total amount of chromium III present in the sample

  13. Coupled transport/reaction model of the properties of bentonite buffer in a repository

    International Nuclear Information System (INIS)

    Liu, Jinsong; Neretnieks, I.

    1996-11-01

    Two mechanisms that can affect the long-term properties of the bentonite buffer surrounding the canister in a final repository of spent nuclear fuel are studied. The two mechanisms are the oxidation of reducing minerals in the buffer by radiolytically generated oxidant, and the low-temperature alteration of Na-montmorillonite in the bentonite buffer to illite. A coupled mass transport with geochemical reaction model is used. Four cases have been considered, which differ in the assumptions of whether the radiolytically generated oxidant first oxidizes uraninite in the spent fuel, or it is directly transported to the bentonite to oxidize the pyrite. The cases also differ in the assumptions of varying initial concentrations of pyrite in the bentonite buffer. The modelling results show that, at low temperatures, the sodium montmorillonite in the bentonite buffer is chemically stable with respect to the chemical conditions of the near field. Alteration to illite and thus an increase in hydraulic conductivity and loss of swelling ability is not likely to occur. The radiolytically generated oxidant can possibly oxidize the reducing minerals in the bentonite buffer. A redox front can be generated. In all the cases considered in this study, the modelling results indicate that slightly less than 1% by weight of pyrite in the bentonite buffer will be able to ensure that the redox front does not penetrate through the bentonite buffer within 1 million years. 31 refs

  14. Effects of bentonite on plasma urea and creatinine of wistar albino rats.

    African Journals Online (AJOL)

    The in vivo effect of Nigerian calcium bentonite clay on wistar albino rat plasma urea and creatinine levels were investigated. The rats were fed for a period of four weeks with varying concentrations of the bentonite clay, and the urea and creatinine levels determined using spectrophotometric methods. Test results showed ...

  15. Backfilling of deposition tunnels, block alternative

    International Nuclear Information System (INIS)

    Keto, P.; Roennqvist, P.-E.

    2007-03-01

    This report presents a preliminary process description of backfilling the deposition tunnels with pre-compacted blocks consisting of a mixture of bentonite and ballast (30:70). The process was modified for the Finnish KBS-3V type repository assuming that the amount of spent fuel canisters disposed of yearly is 40. Backfilling blocks (400 x 300 x 300 mm) are prepared in a block production plant with a hydraulic press with an estimated production capacity of 840 blocks per day. Some of the blocks are modified further to fit the profile of the tunnel roof. Prior to the installation of the blocks, the deposition tunnel floor is levelled with a mixture of bentonite and ballast (15:85). The blocks are placed in the tunnel with a modified reach truck. Centrifugal pellet throwing equipment is used to fill the gap between the blocks and the rock surface with bentonite pellets. Based on a preliminary assessment, the average dry density achieved with block backfill is sufficient to fulfil the criteria set for the backfill in order to ensure long-term safety and radiation protection. However, there are uncertainties concerning saturation, homogenisation, erosion, piping and self-healing of the block backfill that need to be studied further with laboratory and field tests. In addition, development efforts and testing concerning block manufacturing and installation are required to verify the technical feasibility of the concept. (orig.)

  16. 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

  17. Constraining controls on carbonate sequences with high-resolution chronostratigraphy: Upper Miocene, Cabo de Gata region, SE Spain

    Science.gov (United States)

    Montgomery, P.; Farr, M.R.; Franseen, E.K.; Goldstein, R.H.

    2001-01-01

    A high-resolution chronostratigraphy has been developed for Miocene shallow-water carbonate strata in the Cabo de Gata region of SE Spain for evaluation of local, regional and global factors that controlled platform architecture prior to and during the Messinian salinity crisis. Paleomagnetic data were collected from strata at three localities. Mean natural remanent magnetization (NRM) ranges between 1.53 ?? 10-8 and 5.2 ?? 10-3 Am2/kg. Incremental thermal and alternating field demagnetization isolated the characteristic remanent magnetization (ChRM). Rock magnetic studies show that the dominant magnetic mineral is magnetite, but mixtures of magnetite and hematite occur. A composite chronostratigraphy was derived from five stratigraphic sections. Regional stratigraphic data, biostratigraphic data, and an 40Ar/39Ar date of 8.5 ?? 0.1 Ma, for an interbedded volcanic flow, place the strata in geomagnetic polarity Chrons C4r to C3r. Sequence-stratigraphic and diagenetic evidence indicate a major unconformity at the base of depositional sequence (DS)3 that contains a prograding reef complex, suggesting that approximately 250 000 yr of record (Subchrons C3Br.2r to 3Br.1r) are missing near the Messinian-Tortonian boundary. Correlation to the GPTS shows that the studied strata represent five third- to fourth-order DSs. Basal units are temperate to subtropical ramps (DS1A, DS1B, DS2); these are overlain by subtropical to tropical reefal platforms (DS3), which are capped by subtropical to tropical cyclic carbonates (Terminal Carbonate Complex, TCC). Correlation of the Cabo de Gata record to the Melilla area of Morocco, and the Sorbas basin of Spain indicate that early - Late Tortonian ramp strata from these areas are partially time-equivalent. Similar strata are extensively developed in the Western Mediterranean and likely were influenced by a cool climate or influx of nutrients during an overall rise in global sea-level. After ramp deposition, a sequence boundary (SB3) in

  18. Preliminary Study on Benzoic Acid Adsorption from Crude Active Coals and Bentonite

    Directory of Open Access Journals (Sweden)

    Abbes Boucheta

    2016-04-01

    Full Text Available We studied the adsorption of pollutant benzoic acid by the modified bentonite of Maghnia (west of Algeria, and coal (Coal from the mines, southwest of Algeria, Bechar area under three forms, crude and activated. Kinetic data show that the balance of bentonite (as amended adsorbs organic acids better than activated and raw coal. Indeed, the intercalation of bentonite with benzoic acid causes an improvement in the texture of porous material, which allows its use in the adsorption of organic compounds. The adsorption isotherms (Langmuir and Freundlich indicate that the adsorption of benzoic acid by the coal and bentonite yielded results favorably. The results obtained showed the practical value of using the activated coal and bentonite (as amended in the field of remediation of water contaminated with organic pollutants

  19. A study of the condition for the passivation of carbon steel in bentonite

    International Nuclear Information System (INIS)

    Taniguchi, Naoki; Morimoto, Masataka; Honda, Akira

    1999-01-01

    It is important to study the corrosion behavior of materials to be used for overpack for high-level radioactive waste disposal. Carbon steel is one of the candidate materials. The type of corrosion on carbon steel depends on whether the carbon steel is passivated or not. In this study, the condition for the passivation of carbon steel was studied using bentonite as the buffer material. Anodic polarization in bentonite and the measurements of pH of porewater in bentonite was measured. The results of these experiments showed that the possibility of passivation is small in highly compacted bentonite in groundwater in Japan. Therefore, localized corrosion on carbon steel due to the breakdown of passive film is unlikely in bentonite. In other words, general corrosion seems to be the most probable type of corrosion under repository condition in Japan. (author)

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

    International Nuclear Information System (INIS)

    Yeon, Jae-Won; Ha, Young-Kyoung; Choi, In-Kyu; Chun, Kwan-Sik

    1996-01-01

    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)

  1. 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. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Mobility of U, Np, Pu, Am and Cm from spent nuclear fuel into bentonite clay

    International Nuclear Information System (INIS)

    Ramebaeck, H.; Skaalberg, M.; Eklund, U.B.; Kjellberg, L.; Werme, L.

    1998-01-01

    The mobility of uranium, neptunium, plutonium, americium and curium from spent nuclear fuel (UO 2 ) into compacted bentonite was studied. Pieces of spent BWR UO 2 fuel was embedded in a compacted bentonite clay/low saline synthetic groundwater system. After a contact time of six years the bentonite was sliced into 0.1 mm thick slices and analysed for its content of actinides. Radiometric as well as inductively coupled plasma mass spectrometry (ICP-MS) were used for the analysis. The influence on the mobility by the addition of metallic iron, metallic copper and vivianite (Fe(II)-mineral) to the bentonite clay was investigated. The results show a low mobility of actinides in bentonite clay. Except for uranium the mobility of the other actinides could, after six years of diffusion time, only be detected less than 1 mm from the spent fuel. (orig.)

  3. Review on cation exchange selectivity coefficients for MX-80 bentonite

    International Nuclear Information System (INIS)

    Domenech, C.; Arcos, D.; Duro, L.; Sellin, P.

    2005-01-01

    Full text of publication follows: Bentonite is considered as engineered barrier in the near field of a nuclear waste repository due to its low permeability, what impedes groundwater flow to the nuclear waste, and its high retention capacity (sorption) of radionuclides in the eventuality of groundwater intrusion. One of the main retention processes occurring at the bentonite surface is ion exchange. This process may exert a strong control on the mobility of major pore water cations. Changes in major cation concentration, especially calcium, can affect the dissolution-precipitation of calcite, which in turn controls one of the key parameters in the system: pH. The cation exchange process is usually described according to the Gaines-Thomas convention: Ca 2+ + 2 NaX = CaX 2 + 2 Na + , K Ca = (N Ca x a 2 Na + )/(N 2 Na x a Ca 2+ ) where K Ca is the selectivity coefficient for the Ca by Na exchange, ai is the activity of cation 'i' in solution and NJ the equivalent fractional occupancy of cation 'J' in bentonite. Parameters such as solid to liquid (S:L) ratio and dry density of the solid have an important influence on the value of selectivity coefficients (K ex ). Although in most geochemical modelling works, K ex values are directly taken from experiments conducted at low S:L ratios and low dry densities, the expected conditions in a deep geological nuclear waste repository are higher S:L and higher bentonite density (1.6 g.cm -3 in the SKB design to obtain a fully water saturated density of around 2.0 g.cm -3 ). Experiments focused at obtaining selectivity coefficients under the conditions of interest face the difficulty of achieving a proper extraction and analyses of pore water without disturbing the system by the sampling method itself. In this work we have conducted a complete analyses of published data on MX-80 bentonite cationic exchange in order to assess the effect of the S:L ratio and dry density on the value of the selectivity coefficients determined so far

  4. Draft genome sequence of Halorubrum tropicale strain V5, a novel halophilic archaeon isolated from the solar salterns of Cabo Rojo, Puerto Rico.

    Science.gov (United States)

    Sánchez-Nieves, Rubén; Facciotti, Marc T; Saavedra-Collado, Sofía; Dávila-Santiago, Lizbeth; Rodríguez-Carrero, Roy; Montalvo-Rodríguez, Rafael

    2016-03-01

    The genus Halorubrum is a member of the family Halobacteriaceae which currently has the highest number of described species (31) of all the haloarchaea. Here we report the draft genome sequence of strain V5, a new species within this genus that was isolated from the solar salterns of Cabo Rojo, Puerto Rico. Assembly was performed and rendered the genome into 17 contigs (N50 = 515,834 bp), the largest of which contains 1,031,026 bp. The genome consists of 3.57 MB in length with G + C content of 67.6%. In general, the genome includes 4 rRNAs, 52 tRNAs, and 3246 protein-coding sequences. The NCBI accession number for this genome is LIST00000000 and the strain deposit number is CECT9000.

  5. Behavior of plutonium interacting with bentonite and sulfate-reducing anaerobic bacteria

    International Nuclear Information System (INIS)

    Kudo, A.; Zheng, J.; Cayer, I.; Fujikawa, Y.; Yoshikawa, H.; Ito, M.

    1997-01-01

    The interactions between sulfate reducing anaerobic bacteria and plutonium, with or without bentonite present, were investigated using distribution coefficients [Kd (ml/g)] as an index of the radionuclide behavior. Plutonium Kds for living bacteria varied within a large range, from 1,804 to 112,952, depending on the pH, while the Kds ranged from 1,180 to 5,931 for dead bacteria. In general, living bacteria had higher plutonium Kds than dead bacteria. Furthermore, the higher Kd values of 39,677 to 106,915 for living bacteria were obtained for a pH range between 6.83 and 8.25, while no visible pH effect was observed for dead bacteria. These Kd values were obtained using tracers for both 236 Pu and 239 Pu, which can check the experimental procedures and mass balance. Another comparison was conducted for plutonium Kd values of mixtures of living bacteria with bentonite and sterilized bacteria with bentonite. The range of Kd values for the non-sterilized bacteria with bentonite were 1,194 to 83,648 while Kd values for the sterilized bacteria with bentonite were from 624 to 17,236. Again, the Kd values for the living bacteria with bentonite were higher than those of sterilized bacteria with bentonite. In other words, the presence of living anaerobic bacteria with bentonite increased, by roughly 50 times, the Kd values of 239 Pu when compared to the mixture of dead bacteria with bentonite. The results indicate that the effects of anaerobic bacteria within the engineered barrier system (in this case bentonite) will play a significant role in the behavior of plutonium in geologic repositories

  6. The advantages of a salt/bentonite backfill for Waste Isolation Pilot Plant disposal rooms

    International Nuclear Information System (INIS)

    Butcher, B.M.; Novak, C.F.; Jercinovic, M.

    1991-04-01

    A 70/30 wt% salt/bentonite mixture is shown to be preferable to pure crushed salt as backfill for disposal rooms in the Waste Isolation Pilot Plant (WIPP). This report discusses several selection criteria used to arrive at this conclusion: the need for low permeability and porosity after closure, chemical stability with the surroundings, adequate strength to avoid shear erosion from human intrusion, ease of emplacement, and sorption potential for brine and radionuclides. Both salt and salt/bentonite are expected to consolidate to a final state of impermeability (i.e., ≤ 10 -18 m 2 ) adequate for satisfying federal nuclear regulations. Any advantage of the salt/bentonite mixture is dependent upon bentonite's potential for sorbing brine and radionuclides. Estimates suggest that bentonite's sorption potential for water in brine is much less than for pure water. While no credit is presently taken for brine sorption in salt/bentonite backfill, the possibility that some amount of inflowing brine would be chemically bound is considered likely. Bentonite may also sorb much of the plutonium, americium, and neptunium within the disposal room inventory. Sorption would be effective only if a major portion of the backfill is in contact with radioactive brine. Brine flow from the waste out through highly localized channels in the backfill would negate sorption effectiveness. Although the sorption potentials of bentonite for both brine and radionuclides are not ideal, they are distinctly beneficial. Furthermore, no detrimental aspects of adding bentonite to the salt as a backfill have been identified. These two observations are the major reasons for selecting salt/bentonite as a backfill within the WIPP. 39 refs., 16 figs., 6 tabs

  7. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Vinsova, H.; Koudelkova, M.; Konirova, R.; Vecernik, P.; Jedinakova-Krizova, V.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. It is generally known that bentonite materials show an excellent cation-exchange capacity and, on the other hand, a poor uptake of anions. Technetium occurs under aerobic conditions in its most stable oxidation state (+VII) as pertechnetate, which makes a question of its sorption on bentonite more complex when compared with e.g. Cs + or Sr 2+ . To increase the K d values for technetium sorption on bentonite, it is necessary to carry out the experiments under anaerobic conditions in the presence of reducing agent, which is capable to lower the oxidation state of technetium which enables its successful immobilization. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing conditions. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ , Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. (authors)

  8. Electrical resistivity and rheological properties of sensing bentonite drilling muds modified with lightweight polymer

    Directory of Open Access Journals (Sweden)

    Ahmed S. Mohammed

    2018-03-01

    Full Text Available In this study, the electrical resistivity and rheological properties of a water-based bentonite clay drilling mud modified with the lightweight polymer (guar gum under various temperature were investigated. Based on the experimental and analytical study, the electrical resistivity was identified as the sensing property of the bentonite drilling mud so that the changes in the properties can be monitored in real-time during the construction. The bentonite contents in the drilling muds were varied up to 8% by the weight of water and temperature was varied from 25 °C to 85 °C. The guar gum content (GG% was varied between 0% and 1% by the weight of the drilling mud to modify the rheological properties and enhance the sensing electrical resistivity of the drilling mud. The guar gum and bentonite clay were characterized using thermal gravimetric analysis (TGA. The total weight loss at 800 °C for the bentonite decreased from 12.96% to 0.7%, about 95% reduction, when the bentonite was mixed with 1% of guar gum. The results also showed that 1% guar gum decreased the electrical resistivity of the drilling mud from 50% to 90% based on the bentonite content and the temperature of the drilling mud. The guar gum modification increased the yield point (YP and plastic viscosity (PV by 58% to 230% and 44% to 77% respectively based on the bentonite content and temperature of the drilling mud. The rheological properties of the drilling muds have been correlated to the electrical resistivity of the drilling mud using nonlinear power and hyperbolic relationships. The model predictions agreed well with the experimental results. Hence the performance of the bentonite drilling muds with and without guar gum can be characterized based on the electrical resistivity which can be monitored real-time in the field. Keywords: Bentonite, Polymer (Guar gum, Electrical resistivity, Rheological properties, Temperature, Modeling

  9. ENOTURISMO Y DESARROLLO ECONÓMICO. UN ESTUDIO DE CASO EN CABO VERDE (ÁFRICA)

    OpenAIRE

    Ana Mª Castillo Canalejo; Tomás López Guzmán

    2011-01-01

    El turismo del vino se está desarrollando significativamente en algunas regiones vitivinícolas del mundo satisfaciendo una demanda de viajeros que buscan unos destinos que supongan la experimentación de nuevas sensaciones que tengan que ver con la cultura local. En esta línea, el objetivo de este artículo es explorar las posibilidades del enoturismo en la isla de Fogo (Cabo Verde). Para alcanzar dicho objetivo se analizan los principales recursos turísticos de esta zona para fomentar este tip...

  10. TURISMO DE SOL Y PLAYA. ANÁLISIS DE LA DEMANDA EN BOAVISTA (CABO VERDE)

    OpenAIRE

    Castillo-Canalejonio, Ana María; Sánchez Cañizares, Sandra Mª

    2015-01-01

    El turismo de sol y playa ha jugado un papel destacado en el desarrollo socioeconómico de muchos países y las islas siempre han atraído a un gran número de visitantes seducidos por lo exótico. Paralelamente, la demanda de los turistas desde hace unos años, manifiesta una tendencia a buscar nuevas satisfacciones y así aparecen nuevos destinos turísticos. En esta línea el objetivo de este artículo es explorar las posibilidades de desarrollar un turismo sostenible en la isla de Boavista (Cabo Ve...

  11. A narrativa seriada televisiva: O seriado Mandrake produzido para a TV a cabo HBO

    Directory of Open Access Journals (Sweden)

    Lílian Fontes Moreira

    2007-10-01

    Full Text Available O presente artigo pretende abordar a investigação que se baseia na construção deum seriado produzido exclusivamente para uma TV a cabo, mais especificamente aHBO, baseado num personagem da literatura brasileira que surgiu na década de 60, opersonagem  Mandrake  criado pelo escritor Rubem Fonseca. Faremos, portanto, umtrajeto abordando a televisão como dispositivo audiovisual, seu papel na sociedadecontemporânea, as questões relativas à recepção e as características da narrativa seriadaaplicadas ao seriado em estudo.

  12. O pict?rico na poesia cabo-verdiana: dos claridosos a Kiki Lima

    OpenAIRE

    Oliveira Junior, Jos? Leite de

    2008-01-01

    A rela??o entre literatura e pintura vem instigando fil?sofos desde a antiguidade greco-latina. Atualmente desenvolvem-se novos ramos na Semiotiko com esse prop?sito. Esta pesquisa se baseia sobre a teoria semi?tica de Jean-Marie Floch ou, mais precisamente, sobre a adapta??o da teoria deste ? cultura brasileira feita por Antonio Vicente Pietroforte. Para objeto de pesquisa escolheu-se a pintura e a poesia de Cabo Verde, objetivando-se esclarecer a seguinte quest?o: A obra pict...

  13. In Search of Saint John: Reinventing Tradition for Migrants and Tourists in Cabo Verde

    Directory of Open Access Journals (Sweden)

    Isabel P.B. Fêo Rodrigues

    2016-11-01

    Full Text Available Following the revitalization of a popular feasts such as San Jon in Cabo Verde, this article highlights how this traditional feast is co-produced by those who left their rural villages in search of a better life in the USA and those who stay hoping to enhance the emigrant’s desire to return. These collective events not only help to sustain a relationship with a homeland, they also contribute to the flows of emigrant remittances and a transnational flow of gift exchange. In between departing and returning, migrants revitalize traditions, contribute to the wellbeing of rural lifestyles, and become agents of economic and cultural investment in their homeland.

  14. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm 3 to 1.8 g/cm 3 . The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm 3 to 1.8 g/cm 3 are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs

  15. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3}. The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3} are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs.

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

    International Nuclear Information System (INIS)

    Yonggui Chen; Changsha University of Science and Technology, Changsha; Chunming Zhu; Weimin Ye; Yanhong Sun; Huiying Duan; Dongbei Wu

    2012-01-01

    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)

  17. High Temperature Thermal Properties of Bentonite Foundry Sand

    Directory of Open Access Journals (Sweden)

    Krajewski P.K.

    2015-06-01

    Full Text Available The paper presents results of measuring thermal conductivity and heat capacity of bentonite foundry sand in temperature range ambient - 900­­°C. During the experiments a technical purity Cu plate was cast into the green-sand moulds. Basing on measurements of the mould temperature field during the solidification of the casting, the temperature relationships of the measured properties were evaluated. It was confirmed that water vaporization strongly influences thermal conductivity of the moulding sand in the first period of the mould heating by the poured casting.

  18. Morphology study of polyamide 6/bentonite clay nanocomposites

    International Nuclear Information System (INIS)

    Paz, Rene A.; Araujo, Edcleide M.; Melo, Tomas J.A.; Leite, Amanda M.D.; Medeiros, Vanessa Nobrega; Pessan, Luiz A.; Passador, Fabio R.

    2011-01-01

    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)

  19. Development of polymer nanocomposites with regional bentonite clay

    International Nuclear Information System (INIS)

    Araujo, Edcleide M.; Leite, Amanda M.D.; Paz, Rene A. da; Medeiros, Keila M. de; Melo, Tomas J.A.; Barbosa, Josiane D.V.; Barbosa, Renata

    2011-01-01

    nanocomposites with regional bentonite clay were prepared by melt intercalation technique. The clays were studied without modification and modified with four quaternary ammonium salts. It was evidenced by X-ray diffraction that salts were incorporated into the clay structure thus confirming its organophilization. The nanocomposites were evaluated by means of thermal mechanic and flammability tests where presented properties significantly improved their pure polymers. The process of biodegradation of obtained bio nanocomposites was accelerated by the presence of clay. The produced membranes from nanocomposites have potential in the oil-water separation. (author)

  20. Characterization of natural organic matter in bentonite clays for potential use in deep geological repositories for used nuclear fuel

    International Nuclear Information System (INIS)

    Marshall, Michaela H.M.; McKelvie, Jennifer R.; Simpson, André J.; Simpson, Myrna J.

    2015-01-01

    extracts from contemporary soils and sediments as well as the lack of amino acids suggests that the material corresponding to the aromatic signal is not composed of lignin or proteins but may be derived from another source such as black carbon or some other non-extractable aromatic-rich NOM. The aliphatic signal appears to correspond to long-chain compounds with little side branching based on the results of the one-dimensional (1D) and two-dimensional (2D) solution-state 1 H NMR analyses. Overall, the organic geochemical analyses suggest that the NOM is composed mainly of plant-derived waxes and highly aromatic carbon with low contributions from small molecules. The compounds identified by the molecular-level analysis of NOM in the clay samples are hypothesized to be recalcitrant but future studies should examine if these compounds may serve as a microbial substrate to further test the observations of this study. Furthermore, our study suggests that the NOM has undergone diagenesis and that marine NOM signatures are no longer recognizable or detectable. As such, future work may also examine the diagenesis of these deposits to further understand the NOM geochemistry and paleoenvironmental conditions in bentonite deposits

  1. Yearly variation of bacterial production in the Arraial do Cabo protection area (Cabo Frio upwelling region): an evidence of anthropogenic pressure.

    Science.gov (United States)

    Coelho-Souza, Sérgio A; Pereira, Gilberto C; Coutinho, Ricardo; Guimarães, Jean R D

    2013-12-01

    Arraial do Cabo is where upwelling occurs more intensively on the Brazilian coast. Although it is a protection area it suffers anthropogenic pressure such as harbor activities and sporadic sewage emissions. Short-time studies showed a high variability of bacterial production (BP) in this region but none of them evaluated BP during long periods in a large spatial scale including stations under different natural (upwelling and cold fronts) and anthropogenic pressures. During 2006, we sampled surface waters 10 times (5 in upwelling and 5 in subsidence periods) in 8 stations and we measured BP, temperature as well as the concentrations of inorganic nutrients, pigments and particulate organic matter (POM). BP was up to 400 times higher when sewage emissions were observed visually and it had a positive correlation with ammonia concentrations. Therefore, in 2007, we did two samples (each during upwelling and subsidence periods) during sewage emissions in five stations under different anthropogenic pressure and we also measured particles abundance by flow cytometry. The 12 samples in the most impacted area confirmed that BP was highest when ammonia was higher than 2 μM, also reporting the highest concentrations of chlorophyll a and suspended particles. However, considering all measured variables, upwelling was the main disturbing factor but the pressure of fronts should not be neglected since it had consequences in the auto-heterotrophic coupling, increasing the concentrations of non fluorescent particles and POM. Stations clustered in function of natural and anthropogenic pressures degrees and both determined the temporal-spatial variability.

  2. Bacterial and Archaeal Communities Variability Associated with Upwelling and Anthropogenic Pressures in the Protection Area of Arraial do Cabo (Cabo Frio region - RJ).

    Science.gov (United States)

    Coelho-Souza, Sergio A; Araújo, Fábio V; Cury, Juliano C; Jesus, Hugo E; Pereira, Gilberto C; Guimarães, Jean R D; Peixoto, Raquel S; Dávila, Alberto M R; Rosado, Alexandre S

    2015-09-01

    Upwelling systems contain a high diversity of pelagic microorganisms and their composition and activity are defined by factors like temperature and nutrient concentration. Denaturing gradient gel electrophoresis (DGGE) technique was used to verify the spatial and temporal genetic variability of Bacteria and Archaea in two stations of the Arraial do Cabo coastal region, one under upwelling pressure and another under anthropogenic pressure. In addition, biotic and abiotic variables were measured in surface and deep waters from three other stations between these stations. Six samplings were done during a year and adequately represented the degrees of upwelling and anthropogenic pressures to the system. Principal Component Analysis (PCA) showed negative correlations between the concentrations of ammonia and phosphorous with prokaryotic secondary production and the total heterotrophic bacteria. PCA also showed negative correlation between temperature and the abundance of prokaryotic cells. Bacterial and archaeal compositions were changeable as were the oceanographic conditions, and upwelling had a regional pressure while anthropogenic pressure was punctual. We suggest that the measurement of prokaryotic secondary production was associated with both Bacteria and Archaea activities, and that substrate availability and temperature determine nutrients cycling.

  3. Process and machinery description of equipment for deposition of canisters in medium-long deposition holes

    International Nuclear Information System (INIS)

    Kalbantner, P.

    2001-08-01

    In this report twelve methods are presented to deposit a canister with spent nuclear fuel in a horizontal hole, several canisters per hole (MLH). These methods are part of the KBS-3 system. They have been developed successively, after an analysis of weak points and strong points in previously described methods. In conformance with the guidelines for Project JADE, a choices of system has been considered during the development work. This is whether canister and bentonite buffer should be deposited 'in parts', i.e. at different occasions, but shortly after each other or 'in a package', i.e. together in a single package. The other choice in the guidelines for the JADE project, whether the canister should be placed in a radiation shield or not during transport in the secondary tunnels, was not relevant to MLR. The basic technical problem is depositing heavy objects, the canister and the buffer components, in an horizontal hole which is approximately 200 m deep. Two methods for depositing of the bentonite barrier and the canisters in separate processes have been studied. For depositing of the bentonite barrier and the canister 'in a package', four alternative techniques have been studied: a metallic sleeve around the package, a loading scoop that is rotated, a fork carriage and rails. The repeated transports in a hole, a consequence of depositing several canisters in the same hole, could lead to the rock being crushed. The mutual impact of machines, load and rock wall has therefore been particularly considered. In several methods, the use of a gangway has been proposed (steel plates or layer of ice). A failure mode and effect analysis has been performed for one of the twelve methods. When comparing with a method to deposit one canister per hole using the same technique, the need for equipment and resources is far larger for this MLH method if incidents should occur during depositing. The development work reported here has not yet yielded a definitive method for placing

  4. An observational study of the evolution of the atmospheric boundary-layer over Cabo Frio, Brazil

    Directory of Open Access Journals (Sweden)

    S. H. Franchito

    2007-08-01

    Full Text Available The effect of coastal upwelling on the evolution of the atmospheric boundary layer (ABL in Cabo Frio (Brazil is investigated. For this purpose, radiosounding data collected in two experiments made during the austral summer (upwelling case and austral winter (no upwelling case are analysed. The results show that during the austral summer, cold waters that crop up near the Cabo Frio coast favour the formation of an atmospheric stable layer, which persists during the upwelling episode. Due to the low SSTs, the descending branch of the sea-breeze circulation is located close to the coast, inhibiting the development of a mixed layer mainly during the day. At night, with the reduction of the land-sea thermal contrast the descending motion is weaker, allowing a vertical mixing. The stable ABL favours the formation of a low level jet, which may also contribute to the development of a nocturnal atmospheric mixed layer. During the austral winter, due to the higher SSTs observed near the coast, the ABL is less stable compared with that in the austral summer. Due to warming, a mixed layer is observed during the day. The observed vertical profiles of the zonal winds show that the easterlies at low levels are stronger in the austral summer, indicating that the upwelling modulates the sea-breeze signal, thus confirming model simulations.

  5. Evaluation of the mineralogical characterization of several smectite clay deposits of the state of Paraiba, Brazil using statistical analysis of variance

    International Nuclear Information System (INIS)

    Gama, A.J.A.; Menezes, R.R.; Neves, G.A.; Brito, A.L.F. de

    2015-01-01

    Currently over 80% of industrialized bentonite clay produced in Brazil in sodium form for use in various industrial applications come from the deposits in Boa Vista - PB. Recently they were discovered new bentonite deposits situated in the municipalities of Cubati - PB, Drawn Stone - PB, Sossego - PB, and last in olive groves - PB, requiring systematic studies to develop all its industrial potential. Therefore, this study aimed to evaluate chemical characterization several deposits of smectite clays from various regions of the state of Paraíba through the analysis of statistical variance. Chemical analysis form determined by fluorescence x-ray (EDX). Then analyzes were carried out of variance statistics and Tukey test using the statistical soft MINITAB® 17.0. The results showed that the chemical composition of bentonite clay of new deposits showed different amounts of silica, aluminum, magnesium and calcium in relation clays in Boa Vista, and clays imported. (author)

  6. 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 availa......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 available data underline a high efficiency for phosphorus binding. This efficiency can be limited by the presence of humic substances and competing oxyanions. Lanthanum concentrations detected during a LMB application are generally below acute toxicological threshold of different organisms, except in low...... 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...

  7. Investigation of Erosion of Cement-Bentonite via Piping

    Directory of Open Access Journals (Sweden)

    Zijun Wang

    2017-01-01

    Full Text Available Cement-bentonite is one of the main materials used in the seepage barriers to protect earth dams and levees from water erosion. However, the current understanding of the erodibility of the cementitious materials and the interactions between cracked seepage barriers and the water flow is inadequate. Based on the laboratory pinhole erosion test, we first investigated the impacts of cement-bentonite treatments by using the ground granulated blast-furnace slag (GGBS as replacement on the erosion characteristics, compared with the original mixtures; the inclusion of GGBS highlighted a potential advantage against water erosion. In addition, we proposed to calculate the erosion percentage and establish the mathematical relationships between the erosion percentage and different regimes, that is, different curing period, erosion time, and sizes of initial holes. Results showed that enough curing period was critical to avoid the increases of hydraulic conductivity in the macrofabric of the barrier; meanwhile, the materials were eroded quickly at the beginning and slowed down with the erosion time, where the enlargement of the initial creaks would be stabilised at some point in time. Moreover, the sizes of initial holes may affect the erosion situation varying from the sample curing periods.

  8. 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)

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

    International Nuclear Information System (INIS)

    Pusch, R.

    1983-05-01

    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)

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

    International Nuclear Information System (INIS)

    Iriya, K.; Fujii, K.; Kubo, H.

    2002-02-01

    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)

  11. Bentonite analogue research related to geological disposal of radioactive waste: current status and future outlook

    Energy Technology Data Exchange (ETDEWEB)

    Reijonen, H.M. [Saanio and Rickkola Oy, Helsinki (Finland); Russel, A.W. [Bedrock Geosciences, Auenstein (Switzerland)

    2015-06-15

    The practice of utilising natural analogues in assessing the long-term behaviour of various components of geological repositories for radioactive waste is already well established in most disposal programmes. Numerous studies on bentonites, focussing on bentonite interaction with other components of the engineered barrier system and a range of host rock environments, are present in the literature. In this article, recent bentonite natural analogue studies are briefly reviewed, and gaps in the current literature identified, with the aim of (1) suggesting where relevant new information could be obtained by data mining published bentonite natural analogue studies with a new focus on current safety case requirements, (2) collecting relevant information by revisiting known bentonite analogue sites and conducting investigations with more appropriate analytical techniques, and (3) identifying novel study sites where, for example, bentonite longevity in very dilute to highly saline groundwater conditions can be studied. It must be noted that the use of natural analogues in safety case development is likely to be site and repository design-specific in nature and thus emphasis is placed on the appropriate use of relevant natural analogue data on bentonite longevity. (authors)

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

    International Nuclear Information System (INIS)

    Iriya, Keishiro; Fujii, Kensuke; Tajima, Takatoshi; Takeda, N.; Kubo, Hiroshi

    2003-02-01

    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)

  13. Bentonite analogue research related to geological disposal of radioactive waste: current status and future outlook

    International Nuclear Information System (INIS)

    Reijonen, H.M.; Russel, A.W.

    2015-01-01

    The practice of utilising natural analogues in assessing the long-term behaviour of various components of geological repositories for radioactive waste is already well established in most disposal programmes. Numerous studies on bentonites, focussing on bentonite interaction with other components of the engineered barrier system and a range of host rock environments, are present in the literature. In this article, recent bentonite natural analogue studies are briefly reviewed, and gaps in the current literature identified, with the aim of (1) suggesting where relevant new information could be obtained by data mining published bentonite natural analogue studies with a new focus on current safety case requirements, (2) collecting relevant information by revisiting known bentonite analogue sites and conducting investigations with more appropriate analytical techniques, and (3) identifying novel study sites where, for example, bentonite longevity in very dilute to highly saline groundwater conditions can be studied. It must be noted that the use of natural analogues in safety case development is likely to be site and repository design-specific in nature and thus emphasis is placed on the appropriate use of relevant natural analogue data on bentonite longevity. (authors)

  14. Low-temperature pyrolysis of oily sludge: roles of Fe/Al-pillared bentonites

    Directory of Open Access Journals (Sweden)

    Jia Hanzhong

    2017-09-01

    Full Text Available Pyrolysis is potentially an effective treatment of oily sludge for oil recovery, and the addition of a catalyst is expected to affect its pyrolysis behavior. In the present study, Fe/Al-pillared bentonite with various Fe/Al ratios as pyrolysis catalyst is prepared and characterized by XRD, N2 adsorption, and NH3-TPD. The integration of Al and Fe in the bentonite interlayers to form pillared clay is evidenced by increase in the basal spacing. As a result, a critical ratio of Fe/Al exists in the Fe/Al-pillared bentonite catalytic pyrolysis for oil recovery from the sludge. The oil yield increases with respect to increase in Fe/Al ratio of catalysts, then decreases with further increasing of Fe/Al ratio. The optimum oil yield using 2.0 wt% of Fe/Al 0.5-pillared bentonite as catalyst attains to 52.46% compared to 29.23% without catalyst addition in the present study. In addition, the addition of Fe/Al-pillared bentonite catalyst also improves the quality of pyrolysis-produced oil and promotes the formation of CH4. Fe/Al-pillared bentonite provides acid center in the inner surface, which is beneficial to the cracking reaction of oil molecules in pyrolysis process. The present work implies that Fe/Al-pillared bentonite as addictive holds great potential in industrial pyrolysis of oily sludge.

  15. Evolution of the bentonite barrier under glacial meltwater intrusion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, T.; Bouby, M. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. for Nuclear Waste Disposal (INE); Blechschmidt, I. [NAGRA National Cooperation Disposal Radioactive Waste, Wettingen (Switzerland); and others

    2015-07-01

    Recent safety assessments for repository concepts that combine a clay engineered barrier system (EBS) with a fractured rock have shown that melt water intrusion may have a direct impact on the EBS barrier function in two aspects: - Generation of colloids may degrade the engineered barrier - Colloid transport of radionuclides may reduce the efficiency of the natural barrier The studies presented here are performed in the framework of the Federal Ministry of Economic Affairs and Energy (BMWi) KIT/GRS project KOLLORADO-e, the EU collaborative project CP BELBaR (www.skb.se/belbar) and especially within the Colloid Formation and Migration (CFM) project at the Grimsel Test Site, GTS (www.grimsel.com). Key research areas are (a) the erosion of the bentonite buffer, (b) clay colloid stability and (c) colloid-radionuclide- host rock surface interactions. Concerning bentonite buffer integrity parameters like the bentonite type, Na-/Ca-exchangeable cation ratio, compaction density, role of accessory minerals, the fracture aperture size and groundwater chemistry and flow velocity are investigated in order to identify controlling factors, understand the main mechanisms of erosion from the bentonite surface and to quantify the extent of the possible erosion under these different conditions. Clay colloid stability studies are performed under different geochemical conditions. The main objective is to answer the question if colloids formed at the near/far field interface would be stable only if favourable conditions exist and therefore their relevance for radionuclide transport will be strongly dependent on the local geochemical conditions (inorganic cations Na{sup +}, Ca{sup 2+}, Mg{sup 2+}, Al{sup 3+} and organic complexing agents). Finally, the interaction between colloids and radionuclides and the host rock is intensively investigated in order to answer the question, how colloid mobility may be affected by the composition of the host rock, surface roughness and the mechanism of

  16. Experimental study of the transport of HTO, {sup 3}6Cl and {sup 1}37Cs through barriers of bentonite and granite; Estudio experimental del transporte de HTO, {sup 3}6Cl y {sup 1}37Cs a traves de barreras de bentonita y granito

    Energy Technology Data Exchange (ETDEWEB)

    Mingarro, M.; Garcia-Gutierrez, M.; Morejon, J.; Missana, T.; Gil, P.

    2013-07-01

    The evaluation of the behavior of the engineered (bentonite) and natural (granite) barrier of a deep geological repository of high level radioactive waste, needs the knowledge of radionuclide migration and retention processes under conditions as similar as possible to the real ones. In CIEMAT a large-scale experiment has been designed with the objective of studying diffusive transport at the bentonite/granite interface of a geological repository in crystalline rock. The diffusion of three tracers has been analyzed: HTO (as conservative and neural element); Cl (as conservative anionic element) and Cs (as conservative cationic element). It was observed that cesium disappeared very fast from the water deposit, due to its strong retention on bentonite. On the other hand, HTO and Cl, disappeared much slower and could be finally detected in the granite at several centimeters from the original source.

  17. 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.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  19. 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)

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

    International Nuclear Information System (INIS)

    Escribano, A.; Turrero, M.J.; Torres, E.; Martin, P.L.

    2008-01-01

    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)

  1. Brazilian bentonite study: use in Goiania; Estudo das bentonitas nacionais: utilizacao em Goiania

    Energy Technology Data Exchange (ETDEWEB)

    Tello, Cledola Cassia Oliveira de [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil)

    1997-12-31

    The evaluation of the bentonite effect in the waste cementation process and in the final solidified product properties is presented. The research showed that bentonite amounts until 15% in the product improves the caesium retention without jeopardizing the other product properties. These results were very useful in the treatment of the wastes from the radiological accident occurred in Goiania in 1987, when a caesium sources was broken. Paste, mortar and grout with bentonite were used to solidify and immobilize these wastes. (author) 20 refs., 1 fig., 6 tabs.; e-mail: tellocc at urano.cdtn.br

  2. Evidence of ammonium ion-exchange properties of natural bentonite and application to ammonium detection.

    Science.gov (United States)

    Zazoua, A; Kazane, I; Khedimallah, N; Dernane, C; Errachid, A; Jaffrezic-Renault, N

    2013-12-01

    Ammonium exchange with hybrid PVC-bentonite (mineral montmorillonite clay) thin film was revealed using FTIR spectroscopy, EDX, cyclic voltammetry and electrochemical impedance spectroscopy. The effect of ammonium exchange on the charge transfer resistance of PVC-bentonite hybrid thin film was attributed to a modification of the intersheet distance and hydration of bentonite crystals. The obtained impedimetric ammonium sensor shows a linear range of detection from 10(-4)M to 1M and a detection limit around 10(-6)M. © 2013.

  3. Studies on mechanical behavior of bentonite for development of the constitutive model

    International Nuclear Information System (INIS)

    Sasakura, Tsuyoshi; Kuroyanagi, Mikio; Okamoto, Michitaka

    2002-02-01

    To integrate the system for evaluation of long-term hydraulic condition in near field of TRU waste disposal, series of laboratory tests were conducted to investigate the effect of (1) cation exchange of Na-bentonite for Ca ion, and (2) the swelling behavior of bentonite, on its mechanical and hydraulic properties. For the purpose of this study, same lot of bentonite was used in a series of tests to obtain consistent data. A constitutive model of clayey materials, called Cam-clay model, was expanded conceptually to express the effects mentioned above. The research results of this year are summarized below; 1) Some basic properties such as cation exchange capacity, particle density, grain size distribution, compaction-characteristics and water content were obtained. To examine the effect of previous swelling history of bentonite on its swelling characteristics and hydraulic and mechanical properties, specimens, which generated swelling deformation to various volumetric strain levels, were specially prepared and used in the following tests. Swelling pressure tests, swelling deformation tests, permeability tests were conducted to observe one dimensional swelling characteristics and hydraulic properties of Na-bentonite and Ca-bentonite. High-pressured triaxial consolidated-undrained (CU) compression tests and high-pressured consolidation tests were also carried out to investigate the compression, swelling, and shearing behavior of each type of bentonite. 2) As indicated in previous studies, two important phenomena (1) bentonite possesses remarkable swelling capacity, (2) cation exchange of Na-bentonite for Ca-ion lead increasing of hydraulic conductivity, were confirmed in the test results. From the swelling deformation test results and published data, it was found that swelling capacity of bentonite has no dependency on previous swelling history and it could be easily expressed as a function of void ratio e. It was also confirmed that swelling pressure and water

  4. 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

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

    International Nuclear Information System (INIS)

    Sena, Clara; Salas, Joaquin; Arcos, David

    2010-12-01

    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

  6. 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

  7. Physical changes in MX-80 bentonite saturated under thermal gradient

    International Nuclear Information System (INIS)

    Villar, Maria Victoria; Gomez-Espina, Roberto; Gutierrez-Nebot, Luis; Campos, Rocio; Barrios, Iciar

    2012-01-01

    Document available in extended abstract form only. This study was developed in the framework of the Temperature Buffer Test (TBT project), which was a full-scale test for HLW disposal that aimed at improving the understanding of the thermo-hydro-mechanical (THM) behaviour of buffers with a temperature around and above 100 deg. C during the water saturation transient. The French organisation ANDRA run this test at the Aespoe HRL in cooperation with SKB (Svensk Kaernbraenslehantering AB 2005). To simulate the conditions of the field test in the laboratory, 20-cm high columns of MX80 bentonite compacted at dry density 1.70 g/cm 3 with an initial water content of 16 percent were submitted in thermo-hydraulic cells to heating and hydration by opposite ends for different periods of time (TH test). The temperature at the bottom of the columns was set at 140 deg. C and on top at 30 C, and deionised water was injected on top at a pressure of 0.01 MPa. The tests were running for 337, 496 and 1510 days. Upon dismantling water content, dry density, specific surface area, porosity and basal spacings, among others, were determined in different positions along the bentonite columns. The strong gradients developed are remarkable. In the shorter tests the water content decreased below the initial value in the 7 cm closest to the heater, whereas in the longer test the decrease below the initial value took place only in the 5 cm closest to the heater. In the remaining part of the columns the water content increased with respect to the initial value, particularly so in the longest test. The dry density along the bentonite changed accordingly, decreasing in the hydrated areas below the initial value and increasing near the heater. The decrease in dry density is due to the swelling of the bentonite upon saturation, while the dry density increase results from the combination of two processes: the compression of the dry areas exerted by the hydrated bentonite, and the shrinkage due to the

  8. Sr isotope zoning in plagioclase from andesites at Cabo De Gata, Spai

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Tørnqvist, Jakob

    2018-01-01

    Plagioclase crystals in andesites from the Cabo De Gata region show generally radiogenic Sr isotope compositions and consistent core to rim increases in 87Sr/86Sr that are indicative of open system processes in the lithosphere and crustal contamination during crystallization. High-grade metamorphic...... rocks of the Alpujárride and Nevado-Filábride complexes represent the most likely crustal contaminants. The plagioclases are characterized by subtly zoned and resorbed calcic cores (An73-86). These cores also have radiogenic 87Sr/86Sr (0.7127-0.7129), although less radiogenic than plagioclase rims......, groundmass plagioclase and whole rock compositions (up to 87Sr/86Sr = 0.7135). These cores are interpreted to represent early crystallization of plagioclase from hydrous melts emplaced into the lower crust. The parental melts to these andesites must therefore have already inherited their radiogenic Sr...

  9. Assessment of groundwater salinization mechanisms in Santiago Island - Cabo Verde: An environmental isotopic approach

    International Nuclear Information System (INIS)

    Carreira, P.M.; Nunes, D.; Marques, J.M.; Pina, A.; Mota Gomes, A.; Almeida, E.; Goncalves, R.; Monteiro Santos, F.

    2007-01-01

    Two sampling campaigns were carried out at Santiago Island - Cabo Verde under the scope of an isotopic and geochemical research study. An evaluation of the groundwater systems was carried out through the application of environmental isotopes and geochemical data in order to answer questions such as: origin and mechanisms of groundwater recharge; relation between the hydrochemical evolution of the groundwater systems with the geological matrix (minerals dissolution) or mixture with seawater and aerosol marine influence; identification of seawater intrusion mechanisms and, determination of the apparent groundwater 'age'. The results obtained so far are not conclusive on the identification of the process responsible for the increase of salinity. In general, all the data obtained seems to indicate that the waters have the same isotopic history but different geochemical evolution, which depends on the weathering and permeability of the rocks. (author)

  10. Reposicionamiento para destinos turísticos consolidados: el caso de Los Cabos, México

    Directory of Open Access Journals (Sweden)

    Angélica Montaño Armendáriz

    2014-01-01

    Full Text Available Los Cabos es un destino internacional, en fase de madurez, sustentado en tres ventajas: localización, naturaleza e infraestructura turística. En este documento se revisan los conceptos y estudios relacionados con los destinos de sol y playa; se contextualiza la problemática y se esbozan las perspectivas de esta actividad, ya que de continuar el actual modelo la competitividad del destino se ve amenazada. La aplicación de la teoría del «Ciclo de vida de los destinos turísticos», como modelo descriptivo-predictivo, ayuda a plantear algunas propuestas para un posible replanteamiento del modelo.

  11. Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

    International Nuclear Information System (INIS)

    Santiago, Denise Ester O.; Pajarito, Bryan B.; Mangaccat, Winna Faye F.; Tigue, Maelyn Rose M.; Tipton, Monica T.

    2016-01-01

    The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

  12. Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

    Science.gov (United States)

    Santiago, Denise Ester O.; Pajarito, Bryan B.; Mangaccat, Winna Faye F.; Tigue, Maelyn Rose M.; Tipton, Monica T.

    2016-05-01

    The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

  13. Effects of bentonite kinds and dry density on the amount of settlement of overpack

    International Nuclear Information System (INIS)

    Nakamura, Kunihiko; Tanaka, Yukihisa

    2009-01-01

    The effects of bentonite kinds and dry density on the settlement behavior of overpack for high level radioactive waste disposal were investigated using both experimental (i.e. centrifuge) and analytical approaches. The nonlinear elastic analysis using a tangent modulus of elasticity obtained from the diffuse double layer theory was carried out to explain the settlement behavior from centrifuge experiments. The difference of properties between bentonites can be considered by this analysis. The results of nonlinear elastic analysis agreed with experimental results. The amount of settlement was decreased with an increase in the dry density and was exponentially decreased with an increase in the swelling pressure. Furthermore, no difference of the amount of settlement was observed if swelling pressure of each bentonite is same. When swelling pressure is more than 1 MPa, the amount of settlement of model overpack into bentonite with 400 mm thickness was less than 10 mm. (author)

  14. Textural properties of poly(glycidyl methacrylate) : acid-modified bentonite nanocomposites

    NARCIS (Netherlands)

    Zunic, M.; Milutinovic-Nikolic, A.; Nastasovic, A.; Vukovic, Z.; Loncarevic, D.; Vukovic, I.; Loos, K.; ten Brinke, G.; Jovanovic, D.; Sharma, Bhaskar; Ubaghs, Luc; Keul, Helmut; Höcker, Hartwig; Loontjens, Ton; Benthem, Rolf van; Žunić, M.; Milutinović-Nikolić, A.; Nastasović, A.; Vuković, Z.; Lončarević, D.; Vuković, I.; Jovanović, D.

    The aim of this study was to obtain enhanced textural properties of macroporous crosslinked copolymer poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) by synthesizing nanocomposites with acid-modified bentonite. Nanocomposites were obtained by introducing various amounts of

  15. Effect of anionic polyelectrolytes on the flow of activated sodium bentonite drilling mud

    Directory of Open Access Journals (Sweden)

    Chalah Kaci

    2018-01-01

    Full Text Available Bentonite is often used in water-based drilling fluids. The xanthan gum is widely used as to increase the viscosity of the bentonite suspension. For the stabilization of the drilled layers, we use filtrate reducers: sodium carboxymethylcellulose low viscosity and cellulose polyanionic low viscosity. The objective of this work is to explain the effect of the polymers on the rheological behavior of the 5% bentonite suspensions. These results will provide practical recommendations for the rational use of different types of additives in water-based drilling muds. Our work is based on rheological trials on a viscometer. The results obtained on the bentonite 5%-xanthane suspension show a rheofluidifying behavior with yield stress conform to the Herschel-bulckly modal. While increasing the concentration of filtrate reducer decreases the yield stress and reduces the viscosity. The effect of CMC LV is more pronounced than PAC L.

  16. 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...

  17. Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Santiago, Denise Ester O. [Polymer Research Laboratory, Department of Chemical Engineering, University of the Philippines, Diliman, Quezon City 1101 Philippines (Philippines); Department of Chemical Engineering, University of the Philippines, Los Baños, College, Laguna 4031 Philippines (Philippines); Pajarito, Bryan B.; Mangaccat, Winna Faye F.; Tigue, Maelyn Rose M.; Tipton, Monica T. [Polymer Research Laboratory, Department of Chemical Engineering, University of the Philippines, Diliman, Quezon City 1101 Philippines (Philippines)

    2016-05-18

    The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

  18. An optimum silica flour-bentonite mixture for an engineered barrier

    International Nuclear Information System (INIS)

    Walker, J.N.; Daffern, D.D.; Emer, D.F.

    1991-01-01

    To dispose of low-level and mixed wastes (MAR) by burial, it is necessary to design an impermeable closure, which limits water infiltration through the waste. Bentonite has very low permeability to water but can be subject to volume alterations. Over time, these alterations can lead to channeling and subsequent permeability increases. The fluid conductivity and bulk properties of silica flour and bentonite mixtures were tested to find a mixture that would retain the low conductivity of the bentonite while maintaining volumetric stability. Silica flour was chosen for its small grain size and spherical shape, and its similarity to silty soil. Test results indicate that a 90% silica flour and 10% bentonite mixture will provide the optimum properties for this application. 5 refs., 2 figs., 2 tabs

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

    International Nuclear Information System (INIS)

    Lee, J.O.; Cho, W.J.; Kang, C.H.; Chun, K.S.

    2001-01-01

    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/cm 2 to 190.2 Kg/cm 2 , 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/m 3 . They increased with increasing temperature in the range of 20 deg. C to 150 deg. C. (author)

  20. 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.

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

    International Nuclear Information System (INIS)

    Carlsson, T.; Muurinen, A.

    2008-12-01

    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. On-Going Bentonite Pore Water Studies by NMR and SAXS

    International Nuclear Information System (INIS)

    Carlsson, Torbjoern; Muurinen, Arto; Root, Andrew

    2013-01-01

    Compacted water-saturated MX-80 bentonite is presently being studied by SAXS and NMR in order to quantify the major pore water phases in the bentonite. The SAXS and NMR measurements gave very similar results indicating that the pore water is mainly distributed between two major phases (interlayer and non-interlayer water) and also indicate how these phases depend on the bentonite dry density. The results from the SAXS and NMR studies at VTT indicate the same thing: - The pore water in water-saturated compacted (?dry = 0.7-1.6 g/cm 3 ) bentonite is divided into two main phases: interlayer water and non-interlayer water. - The amounts of these pore water phases can be determined quantitatively with the above methods. (authors)

  3. Efficiency of ball milled South African bentonite clay for remediation of acid mine drainage

    CSIR Research Space (South Africa)

    Masindi, Vhahangwele

    2015-12-01

    Full Text Available The feasibility of using vibratory ball milled South African bentonite clay for neutralization and attenuation of inorganic contaminants from acidic and metalliferous mine effluents has been evaluated. Treatment of acid mine drainage (AMD...

  4. Evaluation of The Use of Bentonite, Kaolin and Feldspar For Immobilizing The Uranium Radionuclide Slugdewaste

    International Nuclear Information System (INIS)

    Prayitno

    2006-01-01

    The experimental investigation on the mixture of bentonite, kaolin, feldspar, sludge waste and with the ratio of bentonite, kaolin, feldspar for evaluating its effectiveness has been done. Experimentally, this investigation is the preliminary study of the use of bentonite, kaolin, feldspar as a material for the immobilization of sludge waste containing material element especially uranium. This investigation was conducted by mixing waste (2,5; 5; 7.5; 10; 12.5 and 15 %) of total weight sludge waste and bentonite, kaolin, feldspar with of 800, 900 and 1000 o C temperature. The obtained the process condition in which the uranium fraction immobilized could be kept in the limit of safety standard for the sludge waste. Therefore, it could be concluded that the addition of hay ash as an additive in the formation of block monolith tend to minimize the leached sludge waste in the leaching media. (author)

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

    International Nuclear Information System (INIS)

    Rodrigues, Andre W.B.; Agrawal, Pankaj; Araujo, Edcleide M.; Melo, Tomas J.A.; Ueki, Marcelo M.

    2009-01-01

    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)

  6. Hydrothermal stability of bentonite-based buffer materials

    International Nuclear Information System (INIS)

    Johnston, R.M.; Miller, H.G.

    1985-02-01

    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

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

    International Nuclear Information System (INIS)

    Paz, Rene A.; Leite, Amanda M.D.; Medeirosa, Vanessa da N.; Araujo, Edcleide M.; Melo, Tomas J.A.; Pessan, Luiz A.

    2010-01-01

    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)

  8. Evaluation on elution feature of bentonite buffer materials

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Hirohisa; Kanno, Takeshi; Matsumoto, Kazuhiro

    1997-09-01

    In order to evaluate long term physical stability of artificial barrier in land disposal of high level radioactive wastes, it is necessary to know quantitatively elution behavior of buffering materials from disposal road (or cavity) to circumferential rock crack. When elution of the buffer material occurs on large scale, amount of bentonite in the disposal road (or cavity) reduces and reduction of various functions expected to the buffer materials is presumed. According to specification examples of road transverse arrangement and disposal vertical arrangement systems, evaluation on elution amount of the buffer materials at disposal environment was conducted. Opening width of rock crack in the disposal environment was supposed to be 0.5 mm. As a result, obtained mass elution ratios of the buffer materials due to extrusion phenomenon were 0.04 to 0.2% after 10,000 year and 2 to 12% after 1,000,000 years. (G.K.)

  9. Synthesis of mullite nanometers microwave from bentonite delaminated

    International Nuclear Information System (INIS)

    Gomes, J.; Azevedo, N.A.; Vieira, D.A.; Neves, G.A.; Santana, L.N.L.; Menezes, R.R.

    2011-01-01

    The smectite clays present as lamellar structure is formed by two layers of silica tetrahedrons and one layer of aluminum octahedra, which can be individually delaminated, reaching a thickness of about 1mm. Mullite is the only thermodynamically stable crystalline phase of SiO 2 and Al2O 3 system and can be synthesized from minerals that exhibit these oxides in its composition. The microwave synthesis offers advantages over conventional methods, the heating is rapid and uniform, avoiding an undesirable grain growth. This study aims to obtain nanometric mullite from bentonites delamined subjected to microwave heating. The samples were initially treated, then rehydrated, frozen and deagglomeration in a ball mill for 4 and 8 hours. Subsequently subjected to centrifugation, drying and microwave heating. The results showed that nano-mullite was obtained for samples subjected to longer heating and dispersions. (author)

  10. Retention of redox sensitive waste elements in compacted bentonite

    International Nuclear Information System (INIS)

    Torstenfelt, B.; Allard, B.

    1984-01-01

    The diffusion of technetium, iodine, uranium and neptunium in compacted bentonite has been studied. The possible reduction of the transport rate of these elements (i.e. redoxsensitive elements) by mixing the clay with metallic iron (for technetium, uranium and neptunium) or by adding a chemisorbent (for iodine) to the clay is reported. Technetium has an apparent diffusivity about 5 times higher in the heptavalent state (TcO 4 - ) than in the tetravalent state (TcO(OH) 2 or TcO 2 ), uranium and neptunium in their higher oxidation state (VI and V) have apparent diffusivities about 6 and 50 times higher, respectively, than in the tetravalent state. Iodine, as I - (or IO 3 - ), has a transport rate more than one order of magnitude lower than TcO 4 - . 10 references, 5 figures, 3 tables

  11. Characterization of LDPE/PBAT/PLA and organophilic bentonite nanocomposites

    International Nuclear Information System (INIS)

    Figueredo, Daniela Casimiro de; Viana, Hamilton; Rosa, Derval dos Santos; Poveda, Patricia Negrini Siqueira

    2011-01-01

    Due to the ascension of Green chemistry in the 90's, it has been a demand for the production of biodegradable materials which cause minimal impacts to environment. Some nanocomposites are in this material class. In this context, six formulations containing low density polyethylene (LDPE), a compatibilized commercial poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) blend under the trademark Ecovio and organophilic bentonite were processed by extrusion to make films which were characterized by X-ray diffraction, melt flow index (MFI) and mechanical tests. X- ray pattern revealed that the nano clay was composed predominantly of montmorillonite, quartz and kaolinite and it could promote formation of intercalated or exfoliated composites. Nano clay also affected the fluidity of composites with variations in module up to 4%, as evidenced by melt flow index. Mechanical tests demonstrated that there was no uniformity in mechanical behavior of the nanocomposites. (author)

  12. Sorption behaviour of caesium on a bentonite sample

    International Nuclear Information System (INIS)

    Hurel, C.; Marmier, N.; Fromage, F.; Seby, F.; Bourg, A.C.M.; Giffaut, E.

    2002-01-01

    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. The coupled process laboratory test of highly compacted bentonite

    International Nuclear Information System (INIS)

    Shen Zhenyao; Li Guoding; Li Shushen; Wang Chengzu

    2004-01-01

    Highly compacted bentonite blocks have been heated and hydrated in the laboratory in order to simulate the thermo-hydro-mechanical (THM) coupled processes of buffer material in a high-level radioactive waste (HLW) repository. The experiment facility, which is composed of experiment barrel, heated system, high pressure water input system, temperature measure system, water content measure system and swelling stress system, is introduced in this paper. The steps of the THM coupled experiment are also given out in detail. There are total 10 highly compacted bentonite blocks used in this test. Experimental number 1-4 are the tests with the heater and the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 5-8 are the tests with the heater and without the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 9-10 are the tests with the heater and the hydrated process, which temperature distribution vs. time, final moisture distribution and the swelling stress distribution at some typical points vs. time are measured. The maximum test time is nearly 20 days and the minimum test time is only 8 hours. The results show that the temperature field is little affected by hydration process and stress condition, but moisture transport and stress distribution are a little affected by the thermal gradient. The results also show that the water head difference is the mainly driving force of hydration process and the swelling stress is mainly from hydration process. It will great help to understand better about heat and mass transfer in porous media and the THM coupled process in actual HLW disposal. (author)

  14. Origins of chirality in Nature: a reassessment of the postulated role of bentonite

    International Nuclear Information System (INIS)

    Youatt, J.B.; Brown, R.D.

    1981-01-01

    Bondy and Harrington have proposed that selective binding of L isomers of amino acids and D isomers of sugars to bentonite is the mechanism by which the chirality of molecules in living cells was originally established. Further experiments indicate that the observations of Bondy and Harrington are better explained in terms of the effects of the binding to bentonite of the products of radiochemical decomposition. 1 table

  15. Microwave-acid treated bentonite as adsorbent for removal of radiocobalt from liquid radioactive waste

    International Nuclear Information System (INIS)

    Egamediev, S.; Nurbaeva, D.; Saidova, Z.; Khujaev, S.

    2014-01-01

    Full text : Development of new sorbents and study of its sorption properties is an important task for nuclear waste management. In this study it was examined the ability of modified bentonite clays to sorb 60Co radionuclide with aim to evaluate the possibility of using them as sorbents for treatment of radioactively contaminated solutions. The radioactive tracer technique was used for determination of distribution coefficients and to monitor the modification processes of bentonite

  16. Research program to study the gamma radiation effects in Spanish bentonites

    International Nuclear Information System (INIS)

    Dies, J.; Tarrasa, F.; Cuevas de las, C.; Miralles, L.; Pueyo, J. J.

    2000-01-01

    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)

  17. Oxygen and hydrogen isotope geochemistry of Cretaceous bentonites and shales from the Disturbed Belt, Montana

    International Nuclear Information System (INIS)

    Eslinger, E.V.; Yeh Hsuehwen

    1986-01-01

    The mineralogy, deltaO 18 , and deltaD of the 18 of the 18 of 18 , data for the 18 of bulk bentonite is 1 to 3 per mille more negative than the deltaO 18 of the 18 of several size fractions of clay-sized quartz separated from the bentonite varies from +11 per mille to +24 per mille. Results are presented and discussed. (author)

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

    International Nuclear Information System (INIS)

    Bouberka, Z.; Khenifi, A.; Belkaid, N.; Ait Mahamed, H.; Haddou, B.; Derriche, Z.

    2009-01-01

    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)

  19. Photophysical and adsorption properties of pyronin B in natural bentonite clay dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Rostami, Mohammad Reza [Department of Chemistry, Faculty of Sciences, Atatürk University, 25240, Erzurum (Turkey); Kaya, Mehmet [Recep Tayyip Erdoğan University, Faculty of Arts and Sciences, 53100 Rize (Turkey); Gür, Bahri; Onganer, Yavuz [Department of Chemistry, Faculty of Sciences, Atatürk University, 25240, Erzurum (Turkey); Meral, Kadem, E-mail: kademm@atauni.edu.tr [Department of Chemistry, Faculty of Sciences, Atatürk University, 25240, Erzurum (Turkey)

    2015-12-30

    Graphical abstract: The molecular aggregation of PyB in bentonite aqueous dispersion is observed by using molecular absorption spectrum. - Highlights: • Molecular behavior of PyB adsorbed on bentonite was spectroscopically followed. • H-aggregates of PyB in bentonite aqueous dispersion were formed. • The adsorption characteristics of PyB on bentonite particles were determined. - Abstract: The present study focused on the adsorption and photophysical properties of pyronin B (PyB) in bentonite aqueous dispersion. The photophysical properties of PyB in the aqueous dispersion were studied by using UV–vis absorption, steady-state and time-resolved fluorescence spectroscopy techniques. In this concept, the interaction of the dye with bentonite particles in the aqueous dispersion was spectroscopically followed depending on certain parameters such as interaction time, pH and the dye concentration. Obtained spectral data revealed that the aggregate structures (H-type) of PyB in the aqueous dispersion were formed in the dye concentration range studied. The non-fluorescence nature of H-aggregates and the clay minerals governed the fluorescence property of PyB. The mentioned non-radiative processes caused the fluorescence lifetime of the dye to decrease compared to that in water. The adsorption process of PyB on bentonite was examined depending on contact time and initial adsorbate concentration. An adsorption isotherm was good-fitted by the Freundlich model with a linear regression correlation value of 0.999. The adsorption of PyB on bentonite particles was in agreement with pseudo second-order kinetics.

  20. Modelos analíticos no estudo do comportamento estrutural de tubos flexíveis e cabos umbilicais.

    OpenAIRE

    Roberto Ramos Junior

    2001-01-01

    Tubos flexíveis e cabos umbilicais têm sido bastante utilizados pela indústria petrolífera em aplicações offshore nos últimos anos. Os primeiros consistem num tipo de tubulação usada para o transporte de vários tipos de fluidos, geralmente trabalhando a alta pressão. Já os cabos umbilicais são usados para permitir o controle e a comunicação entre equipamentos submersos e de superfície. Quanto à concepção estrutural, os dois tipos de produto são muito semelhantes, apresentando diversas camadas...

  1. Study of genetic markers of CODIS and ESS systems in a population of individuals from Cabo Verde living in Lisboa.

    Science.gov (United States)

    Resende, Ana; Amorim, António; da Silva, Cláudia Vieira; Ribeiro, Teresa; Porto, Maria João; Costa Santos, Jorge; Afonso Costa, Heloísa

    2017-01-01

    Twenty-two autosomal short tandem repeats included in the PowerPlex® Fusion System Amplification kit (Promega Corporation) were genotyped in a population sample of 500 unrelated individuals from Cabo Verde living in Lisboa. Allelic frequency data and forensic and statistical parameters were calculated and evaluated in this work. The genetic relationship among immigrant population from Cabo Verde living in Lisboa and other populations, such as Brazilian and Angola immigrants living in Lisboa; Afro-Americans, Caucasians, Hispanics and Asians living in the USA and the population from Lisboa was assessed, and a multidimensional scaling plot was drown to show these results.

  2. Synthesis of H/Bentonite and Ni/Al2O3-bentonite and its application to produce biogasoline from nyamplung seed (Calophyllum inophillum Linn) oil by catalytic hydrocracking

    Science.gov (United States)

    Marini, A. T.; Wijaya, K.; Sasongko, N. A.

    2018-03-01

    Hydrocracking process of Nyamplung (Calophyllum inophillum Linn) seed oil to produce biogasoline using H/bentonite and Ni/Al2O3-bentonite that pillared by Al2O3 as catalyst had been conducted. Bentonite was activated by acidification using HF 1% and H2SO4 0.5 M. Ni metal was impregnated into bentonite with two steps reaction; therewas intercalation with Al2O3kegging ion and Ni metal impregnation using NiCl2 metal salt. Catalysts were characterized by infrared spectrophotometer (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET, TEM and ammonia adsorption. Hydrocracking reaction was variated by Ni/Al2O3-bentonite and H/bentonite with ratio catalyst/oil 1:100. Biocrude was prepared by extraction by using ethanol 96%. Hydrocracking oil products were further analyzed by GC-MS. The results show that the acidity of bentonite by activation using HF 1% and H2SO4 0.5 M has been increased from 62.58 to 64.62 mmol/g. Impregnation process also increased the acidity of bentonite from 62.58 to 64.89 mmol/g. Activation using HF 1% and H2SO4 0.5 M, intercalation by Al2O3 and impregnation by Ni metal were increasing the crystallinity, surface area, total volume pore and average pore size of bentonite. These techniques were also causeddealumination of bentonite. The hydrocracking process successfully synthesized hydrocarbons with a number of carbon chain between C5-C20 which include bio-gasoline group compounds. Moreover, catalytic processes by H/bentonite and Ni/Al2O3-bentonite also successfully produced 39.83% and 60.37% of biogasoline yields, respectively.

  3. New evidence of cenozoic tectonism in the southeastern region of Brazil: the Barra de Sao Joao graben in Cabo Frio platform

    International Nuclear Information System (INIS)

    Mohriak, W.U.

    1990-01-01

    The western portion of the Campos Basin is limited by a hinge line that limits the deposition of pre-Aptian sediments in the offshore region. The Cabo Frio arch corresponds to a platform with smaller relative subsidence, where Tertiary sediments are deposited directly on shallow basement rocks. A conspicuous asymmetric graben occurs in the offshore region between Buzios and Macae. This rhomb-graben measures 20 km by 40 km, with the longer axis trending NE. The geological and geophysical characteristics of the Barra de Sao Joao graben supports a genetic affiliation with the onshore Taubate, Resende and Volta Redonda basins, rather than with the Campos Basin. The latter basin was formed in the Neocomian by rupturing of the Pangea, while the radiometric age determination of ankaramitic lavas near Volta Redonda suggests that the onshore basins were formed during the Eocene or Early Oligocene. A better understanding of the crustal geometry and the postulation of geodynamic models for these sedimentary basins will result from the integration of the onshore geology with the subsurface data presented in this paper. (author)

  4. 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}.

  5. 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

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

    International Nuclear Information System (INIS)

    Orozco, Jahir; Baldi, Antoni; Martin, Pedro L.; Bratov, Andrei; Jimenez, Cecilia

    2006-01-01

    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

  7. 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)

  8. Effect on physical properties of laterite soil with difference percentage of sodium bentonite

    Science.gov (United States)

    Kasim, Nur Aisyah; Azmi, Nor Azizah Che; Mukri, Mazidah; Noor, Siti Nur Aishah Mohd

    2017-08-01

    This research was carried out in an attempt to know the physical properties of laterite soil with the appearance of difference percentage of sodium bentonite. Lateritic soils usually develop in tropical and other regions with similar hot and humid climate, where heavy rainfall, warm temperature and well drainage lead to the formation of thick horizons of reddish lateritic soil profiles rich in iron and aluminium. When sodium predominates, a large amount of water can be absorbed in the interlayer, resulting in the remarkable swelling properties observed with hydrating sodium bentonite. There are some basic physical properties test conducted in this research which are Specific Gravity Test, pH Test, Sieve Analysis, Hydrometer Test, Shrinkage Limit and Atterberg Limit. The test will be conducted with 0%, 5%, 10%, 15% and 20% of sodium bentonite. Each test will be repeated three times for the accuracy of the result. From the physical properties test the soil properties characteristic react with the sodium bentonite can be determine. Therefore the best percentage of sodium bentonite admixture can be determined for laterite soil. The outcomes of this study give positive results due to the potential of sodium bentonite to improve the laterite soil particle.

  9. γ-radiation induced corrosion of copper in bentonite-water systems under anaerobic conditions

    Science.gov (United States)

    Karin Norrfors, K.; Björkbacka, Åsa; Kessler, Amanda; Wold, Susanna; Jonsson, Mats

    2018-03-01

    In this work we have experimentally studied the impact of bentonite clay on the process of radiation-induced copper corrosion in anoxic water. The motivation for this is to further develop our understanding of radiation-driven processes occurring in deep geological repositories for spent nuclear fuel where copper canisters containing the spent nuclear fuel will be embedded in compacted bentonite. Experiments on radiation-induced corrosion in the presence and absence of bentonite were performed along with experiments elucidating the impact irradiation on the Cu2+ adsorption capacity of bentonite. The experiments presented in this work show that the presence of bentonite clay has no or very little effect on the magnitude of radiation-induced corrosion of copper in anoxic aqueous systems. The absence of a protective effect similar to that observed for radiation-induced dissolution of UO2 is attributed to differences in the corrosion mechanism. This provides further support for the previously proposed mechanism where the hydroxyl radical is the key radiolytic oxidant responsible for the corrosion of copper. The radiation effect on the bentonite sorption capacity of Cu2+ (reduced capacity) is in line with what has previously been reported for other cations. The reduced cation sorption capacity is partly attributed to a loss of Al-OH sites upon irradiation.

  10. Development of spraying methods for high density bentonite barriers. Part 3. Field investigation of spraying methods

    International Nuclear Information System (INIS)

    Tanaka, Toshiyuki; Nakajima, Makoto; Kobayashi, Ichizo; Toida, Masaru; Fukuda, Katsumi; Sato, Tatsuro; Nonaka, Katsumi; Gozu, Keisuke

    2007-01-01

    The authors have developed a new method of constructing high density bentonite barriers by means of a wet spraying method. Using this method, backfill material can be placed in narrow upper and side parts in a low-level radioactive waste disposal facility. Using a new supplying machine for bentonite, spraying tests were conducted to investigate the conditions during construction. On the basis of the test results, the various parameters for the spraying method were investigated. The test results are summarized as follows: 1. The new machine supplied about twice the weight of material supplied by a screw conveyor. A dry density of spraying bentonite 0.05 Mg/m 3 higher than that of a screw conveyor with the same water content could be achieved. 2. The dry density of sprayed bentonite at a boundary with concrete was the same as that at the center of the cross section. 3. The variation in densities of bentonite sprayed in the vertical downward and horizontal directions was small. Also, density reduction due to rebound during spraying was not seen. 4. Bentonite controlled by water content could be sprayed smoothly in the horizontal direction by a small machine. Also rebound could be collected by a machine conveying air. (author)

  11. Stabilization of heavy metals in soil using two organo-bentonites.

    Science.gov (United States)

    Yu, Kai; Xu, Jian; Jiang, Xiaohong; Liu, Cun; McCall, Wesley; Lu, Jinlong

    2017-10-01

    Stabilization of Cu, Zn, Cd, Hg, Cr and As in soil using tetramethylammonium (TMA) and dodecyltrimethylammonium (DTMA) modified bentonites (T-Bents and D-Bents) as amendments was investigated. Toxicity characteristic leaching procedure (TCLP) was used to quantify the metal mobility after soil treatment. The structural parameters of modified bentonites, including the BET surface area, basal spacing and zeta potential were obtained as a function of the TMA and DTMA loading at 40, 80, 120, 160 and 200% of the bentonite's cation exchange capacity, respectively. The results indicated that the characteristics of the organo-bentonites fundamentally varied depending on the species and concentration of modifiers loaded on bentonite. T-Bents and D-Bents manifested distinct immobilization effectiveness towards various metals. In association with the organo-bentonite characteristics, the main interactive mechanisms for Cu, Zn and Cd proceeded via cation exchange, Hg proceeded via physical adsorption and partitioning, Cr and As proceeded via specific adsorption and electrostatic attraction, respectively. This study provided operational and mechanistic basis for optimizing the organic clay synthesis and selecting as the appropriate amendment for remediation of heavy metal contaminated soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. The Use of Modified Bentonite for Removal of Aromatic Organics from Contaminated Soil.

    Science.gov (United States)

    Gitipour; Bowers; Bodocsi

    1997-12-15

    This study investigates the clay-aromatic interactions with a view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and o-xylene (BTEX compounds) in contaminated soils. BTEX compounds are the most toxic aromatic constituents of gasoline present in many underground storage tanks. Modified (organophilic) and ordinary bentonites are used to remove these organics. The organophilic bentonites are prepared by replacing the exchangeable inorganic cations present in bentonite particles with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in enhancing the cement-based solidification/stabilization (S/S) of BTEX contaminated soils. Toxicity characteristics leaching procedure (TCLP) tests were performed on soil samples to evaluate the leaching of the organics. In addition, X-ray diffraction analyses were conducted to assess the changes in the basal spacing of the clays as a result of their interaction with BTEX compounds. The findings of this study reveal that organophilic bentonite can act as a successful adsorbent for removing the aromatic organics from contaminated soil. Thus, this material is viable for enhancing the performance of cement-based S/S processes, as an adsorbent for petroleum spills, and for landfill liners and slurry walls. Copyright 1997 Academic Press.

  13. The use of modified bentonite for removal of aromatic organics from contaminated soil

    International Nuclear Information System (INIS)

    Gitipour, S.; Bowers, M.T.; Bodocsi, A.

    1997-01-01

    This study investigates the clay-aromatic interactions with a view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and o-xylene (BTEX compounds) in contaminated soils. BTEX compounds are the most toxic aromatic constituents of gasoline present in many underground storage tanks. Modified (organophilic) and ordinary bentonites are used to remove these organics. The organophilic bentonites are prepared by replacing the exchangeable inorganic cations present in bentonite particles with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in enhancing the cement-based solidification/stabilization (S/S) of BTEX contaminated soils. Toxicity characteristics leaching procedure (TCLP) tests were performed on soil samples to evaluate the leaching of the organics. In addition, X-ray diffraction analyses were conducted to assess the changes in the basal spacing of the clays as a result of their interaction with BTEX compounds. The findings of this study reveal that organophilic bentonite can act as a successful adsorbent for removing the aromatic organics from contaminated soil. Thus, this material is viable for enhancing the performance of cement-based S/S processes, as an adsorbent for petroleum spills, and for landfill liners and slurry walls

  14. Modeling hydraulic conductivity and swelling pressure of several kinds of bentonites affected by concentration of saline water

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hasegawa, Takuma; Nakamura, Kunihiko

    2007-01-01

    In case of construction of repository for radioactive waste near the coastal area, the effect of brine on hydraulic conductivity of bentonite as an engineering barrier should be considered because it is known that the hydraulic conductivity of bentonite increases with increasing in salt concentration of water. Thus, the effect of salinity of water on hydraulic conductivity of bentonite has been conducted experimentally. However, it is necessary to elucidate and to model the mechanism of the phenomenon because various kinds of bentonites may possibly be placed in various salinity of salt water. In this study, a model for evaluating permeability of compacted bentonite is proposed considering a) increase in number of sheets of montomorillonite crystal because of cohesion, b) decrease in viscosity of water in interlayer between sheets of montmorillonite crystal. Quantitative evaluation method for permeability of several kinds of bentonite under brine is proposed based on the model mentioned above. (author)

  15. Study of Cadmium adsorption of Nickel and Zinc on a natural bentonite and homo ionic of sodium

    International Nuclear Information System (INIS)

    Silva Giraldo, German Dario; Pinzon Bello, Jorge Alejo

    1999-01-01

    It was studied the adsorption of cadmium, nickel and zinc in aqueous solution at 25oC over a bentonite from the Cauca Valley, in its native state as well as in its sodium homo ionic form. The Langmuir isotherm adequately describes the adsorption of these metal ions over both bentonites, and the thermodynamic distribution coefficient, Kdm, which allow quantifying the degree of adsorption, can be calculated. Baeyens-bradbury model correlates well the adsorption of the metal ions over both bentonites but Kdm cannot be calculated from it. The adsorption data do not adjust to freundlich isotherm or B.E.T. As well as they do to the previously mentioned models. The sodium homo ionic bentonite adsorbs nickel and zinc better than the native bentonite, whereas there are not significant differences in cadmium adsorption. The order of adsorption over both bentonites, Cadmium > Zinc > Nickel, follow the HSAB principle

  16. Effect of pH, ionic strength and fulvic acid on the sorption and desorption of cobalt to bentonite

    International Nuclear Information System (INIS)

    Yu, Sh.M.; Ren, A.P.; Chen, Ch.L.; Chen, Y.X.; Wang, X.

    2006-01-01

    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 pH 8. The addition sequences of FA/Co 2+ 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

  17. Swelling pressure and water absorption property of compacted granular bentonite during water absorption

    International Nuclear Information System (INIS)

    Oyamada, T.; Komine, H.; Murakami, S.; Sekiguchi, T.; Sekine, I.

    2012-01-01

    Document available in extended abstract form only. Bentonite is currently planned to be used as buffer materials in engineered barrier of radioactive waste disposal. Granular bentonites are expected as the materials used in constructions as buffer materials by in-situ compaction methods. After applying these buffer materials, it is expected that the condition of the buffer area changes in long-term by the seepage of groundwater into buffer area. Therefore, it is important to understand water movement and swelling behavior of the buffer materials for evaluating the performance of engineered barrier. In this study, we investigated water absorption property and swelling pressure of compacted granular bentonite. Specifically, the process of swelling pressure and amount of water absorption of granular bentonite-GX (Kunigel-GX, produced at the Tsukinuno mine in Japan) were observed by laboratory tests. To discuss the influence of maximum grain size of bentonite particle on swelling pressure and water absorption property, two types of samples were used. One is granular sample which is Bentonite-GX controlled under 2 mm the maximum grain size, the other is milled sample which is Bentonite-GX with the maximum grain size under 0.18 mm by milling with the agate mortar. In addition, the mechanism on the swelling pressure of compacted granular bentonite was considered and discussed. In the cases of granular sample, swelling pressure increases rapidly, then gradually continues to increase up to maximum value. In the cases of milled sample, swelling pressure also increases rapidly at first. However, then its value decreases before progressing of gradual increase continues. Especially, this trend was clearly observed at a relatively low dry density. At the peaks of these curves, the swelling pressure of granular samples is lower than that of milled samples. In addition, the increasing of swelling pressure by the time the peak observed during the process of swelling pressure from

  18. La zaratita de Cabo Ortegal (A Coruña: historia de su descubrimiento y caracterización actual

    Directory of Open Access Journals (Sweden)

    La Iglesia, A.

    2014-06-01

    Full Text Available Zaratite, Ni3CO3(OH4.4H2O is one of the few minerals discovered in Spain. Taking into account that it is an amorphous compound with variable chemical composition depending on the ore deposits, the International Mineralogical Association (IMA currently considers zaratita in the Q status (Questionable. In this article we analyze first the nearly simultaneous discoveries of the Spanish zaratite and other material called “Emerald of Nickel” from Texas, Lancaster County, Pennsylvania (USA, of similar chemical composition. Both led to the current zaratite, where the Spanish mineral provides the name and the American one, the chemical composition anc physical properties. In addition, here we also include an experimental characterization of the zaratite historical specimen from Ortegal Cape, by electron microprobe, scanning electron microscopy, X-ray diffraction, differential thermal and thermo-gravimetric analyses, micro-Raman, infrared transmission spectroscopy and spectral cathodoluminescence together with a discussion of the analytical results.La zaratita, Ni3CO3(OH4.4H2O es uno de los pocos minerales descubiertos en España. Por ser una fase de baja cristalinidad y presentar una composición química variable según los diferentes yacimientos, la International Mineralogical Association (IMA actualmente la considera con status Q (questioned. En este artículo se analizan en primer lugar los descubrimientos, casi simultáneos, del mineral español y del llamado “Emerald of Nickel” de Texas, Lancaster County, Pennsilvania (USA, de similar composición química, que dieron lugar a la actual zaratita, donde el mineral español aportó el nombre y el americano la composición química y la descripción de las propiedades físicas. En segundo lugar, se presenta una nueva caracterización de la muestra histórica de zaratita de Cabo Ortegal, por microsonda electrónica, microscopia electrónica de barrido, difracción de rayos-X, análisis termo

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

    Energy Technology Data Exchange (ETDEWEB)

    Geh, Stefan; Rettenmeier, Albert W.; Dopp, Elke [University Hospital, Institute of Hygiene and Occupational Medicine, Essen (Germany); Yuecel, Raif [University Hospital, Institute of Cell Biology (Cancer Research), Essen (Germany); Duffin, Rodger [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); University of Edinburgh, ELEGI COLT Lab, Scotland (United Kingdom); Albrecht, Catrin; Borm, Paul J.A. [Institute of Environmental Health Research (IUF), Duesseldorf (Germany); Armbruster, Lorenz [Verein fuer Technische Sicherheit und Umweltschutz e.V., Gotha (Germany); Raulf-Heimsoth, Monika; Bruening, Thomas [Research Institute for Occupational Medicine of the Institutions for Statutory Accident Insurance and Prevention (BGFA), Bochum (Germany); Hoffmann, Eik [University of Rostock, Institute of Biology, Department of Cell Biology and Biosystems Technology, Rostock (Germany)

    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 (Oe< 10 {mu}m) with an {alpha}-quartz content of up to 6% and different chemical modifications (activation: alkaline, acidic, organic) in human lung fibroblasts (IMR90). Additionally, the ability of the particles to induce apoptosis in IMR90-cells and the hemolytic activity was tested. All bentonite 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. (orig.)

  20. Numerical simulation of cesium and strontium migration through sodium bentonite altered by cation exchange with groundwater components

    International Nuclear Information System (INIS)

    Jacobsen, J.S.; Carnahan, C.L.

    1988-10-01

    Numerical simulations have been used to investigate how spatial and temporal changes in the ion exchange properties of bentonite affect the migration of cationic fission products from high-level waste. Simulations in which fission products compete for exchange sites with ions present in groundwater diffusing into the bentonite are compared to simulations in which the exchange properties of bentonite are constant. 12 refs., 3 figs., 2 tabs

  1. Model shear tests of canisters with smectite clay envelopes in deposition holes

    International Nuclear Information System (INIS)

    Boergesson, L.

    1986-01-01

    The consequences of rock displacement across a deposition hole has been investigated by some model tests. The model was scaled 1:10 to a real deposition hole. It was filled with a canister made of solid copper surrounded by highly compacted water saturated MX-80 bentonite. Before shear the swelling pressure was measured by six transducers in order to follow the water uptake process. During shear, pressure, strain, force and deformation were measured in altogether 18 points. The shearing was made at different rates in the various tests. An extensive sampling after shear was made through which the density, water content, degree of saturation, homogenization and the effect of shear on the bentonite and canister could be studied. One important conlusion from these tests was that the rate dependence is about 10% increased shear resistance per decade increased rate of shear. This resulted also in a very clear increase in strain in the canister with increased rate. The results also showed that the saturated bentonite has excellent stress distributing properties and that there is no risk of destroying the canister if the rock displacement is smaller than the thickness of the bentonite cover. The high density of the clay makes the bentonite produce such a high swelling pressure that the material will be very stiff. In the case of a larger shear deformation corresponding to ≅ 50% of the bentonite thickness the result will be a rather large deformation of the canister. A lower density would be preferable if it can be accepted with respect to other required isolating properties. The results also showed that three-dimensional FEM calculation using non-linear material properties is necessary to simulate the shear process. The rate dependence may be taken into account by adapting the properties to the actual rate of shear but might in a later stage be included in the model by giving the material viscous properties. (orig./HP)

  2. Rare earth elements in pore waters from Cabo Friós western boundary upwelling system

    Science.gov (United States)

    Smoak, J. M.; Silva-Filho, E. V.; Rousseau, T.; Albuquerque, A. L.; Caldeira, P. P.; Moreira, M.

    2015-12-01

    Rare earth elements (REE) are a group of reactive trace elements in aqueous media, they have a coherent chemical behavior with however a subtle and gradual shift in physicochemical properties allowing their use as tracers of sources and processes. Uncertainties on their oceanic inputs and outputs still remains [Arsouze et al., 2009; Siddall et al., 2008; Tachikawa et al., 2003]. The water-sediment interface were early on identified as a relevant REE source due to the high distribution coefficient between sediments and pore waters [Elderfield and Sholkovitz, 1987] and substantially higher concentration then the water column [Abbott et al., 2015; Haley et al., 2004; Sholkovitz et al., 1989; Soyol-Erdene and Huh, 2013]. Here we present a cross shelf transect of 4 short pore waters REE profiles on a 680 km2 mud bank located in the region of Cabo Frio, Brazil. This study reveals similar trends at the four sites: a REE production zone reflected by a maximum in concentration at the top of the sediment evolving with depth toward a REE consumption zone reflected by a minimum in REE concentrations. PAAS normalized patterns shows 1) a progressive depletion in LREE with depth with HREE/LREE ratios comprised between 1.1 and 1.6 in the 2 first centimeters evolving gradually to ratios comprised between 2.8 and 4.7 above 7 cm 2) A sharp gradient in negative Ce anomaly with Ce/Ce* values reaching 0.3. With maximum Nd concentrations comprised between 780 and 1200 pmol.kg and considering that seawater Nd concentrations of Brazilian shelf bottom waters are comprised between 24 and 50 pmol.Kg-1 we apply the Fick´s First Law of diffusion and estimate that 340 +/- 90 nmol. m-2 Y-1 of Nd is released in the Cabo frio´s mudbank. This flux is in the same order of magnitude of recent estimates by [Abbott et al., 2015] in the slope of Oregon´s margin. Unraveling processes responsible for the REE production zone will help to refine the global REE fluxes estimates.

  3. Mercury speciation in fish of the Cabo Frio upwelling region, SE-Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Alberto da Silva

    2011-09-01

    Full Text Available Mercury distribution in the oceans is controlled by complex biogeochemical cycles, resulting in retention of trace amounts of this metal in marine biota. The impact of upwelling processes in this metal behavior has been overlooked. Data from literature are insufficient to evaluate the risks associated with the presence of mercury in the fish collected in upwelling areas and its consumers. Therefore, the aim of the present work was to perform a study of mercury speciation in four fish species belonging to different trophic levels from Cabo Frio-Brazil upwelling region. The total mercury content vary of 53 ng g-1 (Sardinella brasiliensis -sardine to 1215 ng g-1 (Cynoscion striatus -striped weakfish and, with exception of the planktivorous fish, methylmercury levels reaches circa 90% of total mercury concentration.A distribuição de Mercúrio nos oceanos é controlada por um complexo ciclo biogeoquímico, resultando na retenção de pequenas quantidades na biota marinha. O impacto dos processos de ressurgência costeira no comportamento desse metal tem sido negligenciado. Dados da literatura são insuficientes para elucidar o risco associado com a presença de mercúrio em peixes capturados em áreas de ressurgência e seus consumidores. Portanto o objetivo do presente trabalho foi realizar um estudo de especiação de mercúrio em quatro espécies de peixes pertencentes a diferentes níveis tróficos da região de ressurgência de Cabo Frio-Brasil. O conteúdo total de mercúrio variou de 53 ng g-1 (Sardinella brasiliensis -sardinha to 1215 ng g-1 (Cynoscion striatus -pescada e, com exceção da espécie planctivora, os níveis de metilmercúrio atingem cerca de 90% da concentração total de mercúrio.

  4. Susceptibility profile of Aedes aegypti from Santiago Island, Cabo Verde, to insecticides.

    Science.gov (United States)

    Rocha, Hélio Daniel Ribeiro; Paiva, Marcelo Henrique Santos; Silva, Norma Machado; de Araújo, Ana Paula; Camacho, Denise Dos Reis da Rosa de Azevedo; Moura, Aires Januário Fernandes da; Gómez, Lara Ferrero; Ayres, Constância Flávia Junqueira; Santos, Maria Alice Varjal de Melo

    2015-12-01

    In 2009, Cabo Verde diagnosed the first dengue cases, with 21,137 cases reported and Aedes aegypti was identified as the vector. Since the outbreak, chemical insecticides and source reduction were used to control the mosquito population. This study aimed to assess the susceptibility of A. aegypti populations from Santiago, Cabo Verde to insecticides and identify the mechanisms of resistance. Samples of A. aegypti eggs were obtained at two different time periods (2012 and 2014), using ovitraps in different locations in Santiago Island to establish the parental population. F1 larvae were exposed to different concentrations of insecticides (Bacillus thuringiensis var israelensis (Bti), diflubenzuron and temephos) to estimate the lethal concentrations (LC90) and calculate the respective rate of resistance (RR90). Semi-field tests using temephos-ABATE(®) were performed to evaluate the persistence of the product. Bottle tests using female mosquitoes were carried out to determine the susceptibility to the adulticides malathion, cypermethrin and deltamethrin. Biochemical and molecular tests were performed to investigate the presence of metabolic resistance mechanisms, associated with the enzymes glutathione S-transferases (GSTs), esterases and mixed-function oxidases (MFO) and to detect mutations or alterations in the sodium channel and acetylcholinesterase genes. A. aegypti mosquitoes from Santiago exhibited resistance to deltamethrin, cypermethrin (mortality<80%) and temephos (RR90=4.4) but susceptibility to malathion (mortality≥98%), Bti and diflubenzuron. The low level of resistance to temephos did not affect the effectiveness of Abate(®). The enzymatic analysis conducted in 2012 revealed slight changes in the activities of GST (25%), MFO (18%), α-esterase (19%) and β-esterase (17%), but no significant changes in 2014. Target site resistance mutations were not detected. Our results suggest that the A. aegypti population from Santiago is resistant to two major

  5. Urogenital schistosomiasis in Cabo Delgado, northern Mozambique: baseline findings from the SCORE study.

    Science.gov (United States)

    Phillips, Anna E; Gazzinelli-Guimarães, Pedro H; Aurelio, Herminio O; Dhanani, Neerav; Ferro, Josefo; Nala, Rassul; Deol, Arminder; Fenwick, Alan

    2018-01-10

    The results presented here are part of a five-year cluster-randomised intervention trial that was implemented to understand how best to gain and sustain control of schistosomiasis through different preventive chemotherapy strategies. This paper presents baseline data that were collected in ten districts of Cabo Delgado province, northern Mozambique, before treatment. A cross-sectional study of 19,039 individuals was sampled from 144 villages from May to September 2011. In each village prevalence and intensity of S. haematobium were investigated in 100 children first-year students (aged 5-8 years), 100 school children aged 9-12 years (from classes 2 to 7) and 50 adults (20-55 years). Prevalence and intensity of S. haematobium infection were evaluated microscopically by two filtrations, each of 10 ml, from a single urine specimen. Given that individual and community perceptions of schistosomiasis influence control efforts, community knowledge and environmental risk factors were collected using a face-to-face interview. Data were entered onto mobile phones using EpiCollect. Data summary was made using descriptive statistics. Chi-square and logistic regression were used to determine the association between dependent and independent variables. The overall prevalence of urogenital schistosomiasis was 60.4% with an arithmetic mean intensity of infection of 55.8 eggs/10 ml of urine. Heavy infections were detected in 17.7%, of which 235 individuals (6.97%) had an egg count of 1000 eggs/10 ml or more. There was a significantly higher likelihood of males being infected than females across all ages (62% vs 58%; P Cabo Delgado. In addition, poor community knowledge about the causes of schistosomiasis and how to prevent it increases the significant public health challenge for the national control program. This was the first study in Mozambique that examined infection levels among adults, where results showed that S. haematobium infection was also extremely high. Given

  6. Techniques for freeing deposited canisters. Final report

    International Nuclear Information System (INIS)

    Kalbantner, P.; Sjoeblom, R.

    2000-06-01

    Four different techniques for removal of the bentonite buffer around a deposited canister have been identified, studied and evaluated: mechanical, hydrodynamical, thermal, and electrical techniques. Different techniques to determine the position of the canister in the buffer have also been studied: mechanical, electromagnetic, thermal and acoustic techniques. The mechanical techniques studied are full-face boring, milling and core-drilling. It is expected that the bentonite can be machined relatively easily. It is assessed that cooling by means of flushing water over the outer surfaces of the tools is not feasible in view of the tendency of bentonite to form a gel. The mechanical techniques are characterized by the potential of damaging the canister, a high degree of complexity, and high requirements of energy/power input. The generated byproduct is solid and cannot be removed by means of flushing. Removal is assessed to be simplest in conjunction with full-face boring and most difficult when coredrilling is applied. The hydrodynamical techniques comprise high-pressure hydrodynamic techniques, where pressures above and below 100 bar, and low pressure hydrodynamical techniques (< 10 bar) are separated. At pressures above 100 bar, a water jet with a diameter of approximately a millimetre cuts through the material. If desired, sand can be added to the jet. At pressures below 100 bar the jet has a diameter of one or a few centimetres. The liquid contains a few percent of salt, which is essential for the efficiency of the process. The flushing is important not only because it removes the modified bentonite but also because it frees previously unaffected bentonite and thereby makes it accessible to chemical modification. All of the hydrodynamical techniques are applicable for freeing the end surface as well as the mantle surface. The degree of complexity and the requirement on energy/power decrease with a decrease in pressure. A significant potential for damaging the

  7. 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.

  8. 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.

  9. Alteration behavior of bentonite barrier of radioactive waste disposal by alkaline solutions. Part 1. Permeability change of compacted bentonite immersed in alkaline solutions

    International Nuclear Information System (INIS)

    Yokoyama, Shingo; Nakamura, Kunihiko

    2010-01-01

    Permeability tests using the compacted bentonites and alkaline solutions were carried out to estimate of alteration behavior and the change of permeability during the alteration reaction. The permeability tests of the compacted bentonites were carried out at 23degC for one week after they were immersed in alkaline solution at 60degC for four weeks (immersing test). After permeability tests, the compacted bentonites were repeatedly tested as the same procedure (i.e. repetition of permeability test and immersing test) at 11 cycles. The compacted bentonites with initial dry density of 1.6 Mg/m 3 were reacted with the different type of the alkaline solutions (deionized water, NaOH (pH=12 and 14), KOH (pH=12 and 14) and Ca(OH) 2 (pH=12)) in each experiments. In the case of deionized water and alkaline solutions of pH12, the mineral compositions of altered bentonite were similar to original bentonite while the exchangeable cations of altered bentonites were changed. No changes of the mineralogical features of montmorillonite in altered bentonites (i.e. illitization, baideritization and increasing of layer charge) were observed in the case of deionized water, pH12-NaOH and pH12-Ca(OH) 2 . The montmorillonite was changed to the illite/smectite interstratified mineral containing about 40% illite like component during the reaction with pH12-KOH. In the case of alkaline solutions with pH14, the component minerals of bentonite (e.g. montmorillonite, quartz and clinoptilolite) were dissolved, consequently secondly minerals (e.g. analcime and phillipsite) were crystallized during experiments. Furthermore, the mineralogical features of montmorillonite were changed as illitization (pH14-KOH), beidellitization (pH14-NaOH and pH14-KOH) and increasing of layer charge (pH14-NaOH and pH14-KOH). No increasing of permeability were observed during the experiment using pH12-NaOH and pH12-Ca(OH) 2 as well as the case of deionized water. In the case of pH12-KOH, the permeability continually

  10. Evaluation of the mineralogical characterization of several smectite clay deposits of the state of Paraiba, Brazil using statistical analysis of variance; Avaliacao da caracterizacao mineralogica de diversos depositos de argilas esmectiticas do estado da Paraiba utilizando analise estatistica de variancia

    Energy Technology Data Exchange (ETDEWEB)

    Gama, A.J.A.; Menezes, R.R.; Neves, G.A.; Brito, A.L.F. de, E-mail: agama@reitoria.ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2015-07-01

    Currently over 80% of industrialized bentonite clay produced in Brazil in sodium form for use in various industrial applications come from the deposits in Boa Vista - PB. Recently they were discovered new bentonite deposits situated in the municipalities of Cubati - PB, Drawn Stone - PB, Sossego - PB, and last in olive groves - PB, requiring systematic studies to develop all its industrial potential. Therefore, this study aimed to evaluate chemical characterization several deposits of smectite clays from various regions of the state of Paraíba through the analysis of statistical variance. Chemical analysis form determined by fluorescence x-ray (EDX). Then analyzes were carried out of variance statistics and Tukey test using the statistical soft MINITAB® 17.0. The results showed that the chemical composition of bentonite clay of new deposits showed different amounts of silica, aluminum, magnesium and calcium in relation clays in Boa Vista, and clays imported. (author)

  11. Development and validation of mechanical model for saturated/unsaturated bentonite buffer

    International Nuclear Information System (INIS)

    Yamamoto, S.; Komine, H.; Kato, S.

    2010-01-01

    Document available in extended abstract form only. Development and validation of mechanical models for bentonite buffer and backfill materials are one of important subjects to appropriately evaluate long term behaviour or condition of the EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one of extensions of the modified Cam-Clay model for unsaturated and expansive soil, has been developed and widely applied to several problems by using the coupled THM code, Code B right. Advantage of the model is that mechanical characteristics of buffer and backfill materials under not only saturated condition but also unsaturated one are taken account as well as swelling characteristics due to wetting. In this study the BBM is compared with already existing experimental data and already developed another model in terms of swelling characteristics of Japanese bentonite Kunigel-V1, and is validated in terms of consolidation characteristics based on newly performed controlled-suction oedometer tests for the Kunigel-V1 bentonite. Komine et al. (2003) have proposed a model (set of equations) for predicting swelling characteristics based on the diffuse double layer concept and the van der Waals force concept etc. They performed a lot of swelling deformation tests of bentonite and sand-bentonite mixture to confirm the applicability of the model. The BBM well agrees with the model proposed by Komine et al. and the experimental data in terms of swelling characteristics. Compression index and swelling index depending on suction are introduced in the BBM. Controlled-suction consolidation tests (oedometer tests) were performed to confirm the applicability of the suction dependent indexes to unsaturated bentonite. Compacted bentonite with initial dry density of 1.0 Mg/m 3 was tested. Constant suction, 80 kPa, 280 kPa and 480 kPa was applied and kept during the consolidation tests. Applicability of the BBM to consolidation and swelling behaviour of saturated and

  12. USE OF PHOSPHOLIPID FATTY ACID PROFILES TO STUDY THE MICROBIAL COMPOSITION OF CYANOBACTERIAL MATS IN CABO ROJO SOLAR SALTERNS

    Science.gov (United States)

    The Cabo Rojo Saltern located in the West side of Puerto Rico is a hypersaline ecosystem that consists of crystallizer ponds surrounded by series of cyanobacterial mats. Although this ecosystem harbors a variety of microorganisms not much is known about their identity and relati...

  13. Secondary forest succession and tree planting at the Laguna Cartagena and Cabo Rojo wildlife refuges in southwestern Puerto Rico

    Science.gov (United States)

    P.L. Weaver; J.J. Schwagerl

    2008-01-01

    Secondary forest succession and tree planting are contributing to the recovery of the Cabo Rojo refuge (Headquarters and Salinas tracts) and Laguna Cartagena refuge (Lagoon and Tinaja tracts) of the Fish and Wildlife Service in southwestern Puerto Rico. About 80 species, mainly natives, have been planted on 44 ha during the past 25 y in an effort to reduce the threat...

  14. Experimental investigations of piping phenomena in bentonite based buffer material

    International Nuclear Information System (INIS)

    Suzuki, K.; Asano, H.; Kobayashi, I.; Sellin, P.; Svemar, C.; Holmqvist, M.

    2012-01-01

    Document available in extended abstract form only. Formation of channels in a clay based buffer material is often referred to as 'piping'. Piping is likely to occur in bentonite based buffer materials in a fractured host rock during the early evolution of the repository when strong hydraulic gradients are present. After water saturation of the repository and reestablishment of the hydraulic gradients piping will not be an issue. However, piping in the early phase may still have implications for long-term performance: 1. if the pipes fail to close there may be remaining conductive pathways in the engineered barrier, and 2. piping may lead to erosion or redistribution of material which needs to be taken into account in the long-term performance assessment. This means that the piping process may affect requirements on rock characterization, water inflow and water management during the installation phase, buffer material properties and buffer installation methodology. As a part of the 'Bentonite re-saturation' program, RWMC has initiated and performed studies of the piping process. The main objectives of the studies are to answer: 1. Under what conditions can pipes form? 2. How do pipes evolve with time? 3. When and how do pipes close/reseal? 4. How does piping affect the buffer properties? 5. How much mass can be lost by erosion? The answers will be used in the development of the requirements stated above as well as input to long term performance assessments. overview of the experiment Test apparatuses were manufactured for investigation of the piping phenomena, see Figure 1. The apparatuses have drainage gutter to prevent clogging to take place with eroded material, and to keep an advection field around specimens. There is also a storage chamber for eroded material on the apparatuses. In the investigation, specimens of bentonite block and pellets were used. The block specimen consisted of a mixture of Japanese Na type bentonite, termed Kunigel V1, and 30 wt% silica

  15. Sorption-desorption of samarium in Febex bentonite

    International Nuclear Information System (INIS)

    Ramirez-Guinart, O.; Rigol, A.; Vidal, M.; Fernandez-Poyatos, P.; Alba, M. D.

    2012-01-01

    Document available in extended abstract form only. The chemical and physical nature of the clay is a key issue in the design of engineered barriers. The FEBEX bentonite is one of the clays candidates to be used in engineered barriers in deep geology repositories (DGR). Here, its performance was tested with respect to the sorption-desorption of samarium, which is a lanthanide that, besides being considered as a natural analogue of actinides, may also be present in high level radioactive waste in the form of the radioactive isotope 151 Sm. FEBEX bentonite was used in this study. This is a di-octahedral smectite, with isomorphic substitutions in tetrahedral and octahedral sheets. Its theoretical cation exchange capacity value is 1500 meq kg -1 . Sorption isotherms were obtained for Sm in the range of initial concentrations of 0.01 and 9 meq l -1 . Tests were carried out in deionized water and in a medium simulating the composition of interstitial water. Sorption tests were performed equilibrating 30 ml of the Sm solution with 0.2 g of clay. After a contact time of 24 hours, supernatants were decanted off after centrifugation. The quantification of the concentration of Sm in the initial and final solutions allowed us to quantify the Sm equilibrium concentration (C eq ), the fraction sorbed in the FEBEX bentonite (C sorb ) and to derive the sorption K d data. Desorption tests were applied to determine the desorption K d and the percentage of Sm reversibly sorbed. Desorption tests were performed with the bentonite residue from the sorption step, under the same experimental conditions, but without Sm. Powder X-ray diffractograms were obtained from 3 to 70 deg. 2θ with a step of 0.05 deg. and a counting time of 3 s. The crystalline phases were identified using the computer program X'Pert HighScore. The morphology of the samples was analyzed by SEM at 20 kV. An EDX system was fitted to the SEM equipment to perform chemical analyses of the samples using a Si/Li detector

  16. Physical and chemical properties for sandstone and bentonites

    International Nuclear Information System (INIS)

    Sato, Haruo

    2004-01-01

    Physical and chemical properties such as porosity, pore-size distribution, dry density, solid density, mineralogy and chemical composition, which are important parameters for the understanding and analysis of the diffusion phenomena of radionuclides and ions in bentonite and in the geosphere, were measured. The measurements were performed for sandstone, of which fundamental data and information are limited. For bentonite, 3 kinds of <