A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, L.; Samper, J.; Montenegro, L.

2010-05-01

Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed onmore » a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous extract data occur for dissolved SO{sub 4}{sup 2-} which is underpredicted by the model. There are uncertainties on the amount of gypsum available for dissolution and its dissolution mechanism (kinetics or local equilibrium).« less

Illitization within bentonite engineered barrier system in clay repositories for nuclear waste and its effect on the swelling stress: a coupled THMC modeling study

NASA Astrophysics Data System (ADS)

Zheng, L.; Rutqvist, J.; Birkholzer, J. T.; Liu, H. H.

2014-12-01

Geological repositories for disposal of high-level nuclear waste generally rely on a multi-barrier system to isolate radioactive waste from the biosphere. An engineered barrier system (EBS), which comprises in many design concepts a bentonite backfill, is widely used. Clay formations have been considered as a host rock throughout the world. Illitization, the transformation of smectite to illite, could compromise some beneficiary features of EBS bentonite and clay host rock such as sorption and swelling capacity. It is the major determining factor to establish the maximum design temperature of the repositories because it is believed that illitization could be greatly enhanced at temperatures higher than 100 oC. However, existing experimental and modeling studies on the occurrence of illitization and related performance impacts are not conclusive, in part because the relevant couplings between the thermal, hydrological, chemical, and mechanical (THMC) processes have not been fully represented in the models. Here we present a fully coupled THMC simulation study of a generic nuclear waste repository in a clay formation with a bentonite-backfilled EBS. Two scenarios were simulated for comparison: a case in which the temperature in the bentonite near the waste canister can reach about 200 oC and a case in which the temperature in the bentonite near the waste canister peaks at about 100 oC. The model simulations demonstrate that illitization is in general more significant under higher temperature. However, the quantity of illitization is affected by many chemical factors and therefore varies a great deal. The most important chemical factors are the concentration of K in the pore water as well as the abundance and dissolution rate of K-feldspar. For the particular case and bentonite properties studied, the reduction in swelling stress as a result of chemical changes vary from 2% up to 70% depending on chemical and temperature conditions, and key mechanical parameters. The modeling work is illustrative in light of the relative importance of different processes occurring in EBS bentonite and clay host rock at higher than 100 oC conditions, and could be of greater use when site specific data are available.

The effect of iron on montmorillonite stability. (I) Background and thermodynamic considerations

NASA Astrophysics Data System (ADS)

Wilson, James; Savage, David; Cuadros, Javier; Shibata, Masahiro; Ragnarsdottir, K. Vala

2006-01-01

It is envisaged that high-level nuclear waste (HLW) will be disposed of in underground repositories. Many proposed repository designs include steel waste canisters and bentonite backfill. Natural analogues and experimental data indicate that the montmorillonite component of the backfill could react with steel corrosion products to produce non-swelling Fe-rich phyllosilicates such as chamosite, berthierine, or Fe-rich smectite. In K-bearing systems, the alteration of montmorillonite to illite/glauconite could also be envisaged. If montmorillonite were altered to non-swelling minerals, the swelling capacity and self-healing properties of the bentonite backfill could be reduced, thereby diminishing backfill performance. The main aim of this paper was to investigate Fe-rich phyllosilicate mineral stability at the canister-backfill interface using thermodynamic modelling. Estimates of thermodynamic properties were made for Fe-rich clay minerals in order to construct approximate phase-relations for end-member/simplified mineral compositions in logarithmic activity space. Logarithmic activity diagrams (for the system Al 2O 3-FeO-Fe 2O 3-MgO-Na 2O-SiO 2-H 2O) suggest that if pore waters are supersaturated with respect to magnetite in HLW repositories, Fe(II)-rich saponite is the most likely montmorillonite alteration product (if f values are significantly lower than magnetite-hematite equilibrium). Therefore, the alteration of montmorillonite may not be detrimental to nuclear waste repositories that include Fe, as long as the swelling behaviour of the Fe-rich smectite produced is maintained. If f exceeds magnetite-hematite equilibrium, and solutions are saturated with respect to magnetite in HLW repositories, berthierine is likely to be more stable than smectite minerals. The alteration of montmorillonite to berthierine could be detrimental to the performance of HLW repositories.

Air and groundwater flow at the interface between fractured host rock and a bentonite buffer

NASA Astrophysics Data System (ADS)

Dessirier, B.; Jarsjo, J.; Frampton, A.

2014-12-01

Designs of deep geological repositories for spent nuclear fuel include several levels of confinement. The Swedish and Finnish concept KBS-3 targets for example sparsely fractured crystalline bedrock as host formation and would have the waste canisters embedded in an engineered buffer of compacted MX-80 bentonite. The host rock is a highly heterogeneous dual porosity material containing fractures and a rock matrix. Bentonite is a complex expansive porous material. Its water content and mechanical properties are interdependent. Beyond the specific physics of unsaturated flow and transport in each medium, the interface between them is critical. Detailed knowledge of the transitory two-phase flow regime, induced by the insertion of the unsaturated buffer in a saturated rock environment, is necessary to assess the performance of planned KBS-3 deposition holes. A set of numerical simulations based on the equations of two-phase flow for water and air in porous media were conducted to investigate the dynamics of air and groundwater flow near the rock/bentonite interface in the period following installation of the unsaturated bentonite buffer. We assume state of the two-phase flow parameter values for bentonite from laboratory water uptake tests and typical fracture and rock properties from the Äspö Hard rock laboratory (Sweden) gathered under several field characterization campaigns. The results point to desaturation of the rock domain as far as 10 cm away from the interface into matrix-dominated regions for up to 160 days. Similar observations were made during the Bentonite Rock Interaction Experiment (BRIE) at the Äspö HRL, with a desaturation sustained for even longer times. More than the mere time to mechanical and hydraulic equilibrium, the occurrence of sustained unsaturated conditions opens the possibility for biogeochemical processes that could be critical in the safety assessment of the planned repository.

Investigation of Coupled Processes and Impact of High Temperature Limits in Argillite Rock: FY17 Progress. Predecisional Draft

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Liange; Rutqvist, Jonny; Xu, Hao

The focus of research within the Spent Fuel and Waste Science and Technology (SFWST) (formerly called Used Fuel Disposal) Campaign is on repository-induced interactions that may affect the key safety characteristics of EBS bentonite and an argillaceous rock. These include thermal-hydrologicalmechanical- chemical (THMC) process interactions that occur as a result of repository construction and waste emplacement. Some of the key questions addressed in this report include the development of fracturing in the excavation damaged zone (EDZ) and THMC effects on the near-field argillaceous rock and buffer materials and petrophysical characteristics, particularly the impacts of temperature rise caused by waste heat.more » This report documents the following research activities. Section 2 presents THM model developments and validation, including modeling of underground heater experiments at Mont Terri and Bure underground research laboratories (URLs). The heater experiments modeled are the Mont Terri FE (Full-scale Emplacement) Experiment, conducted as part of the Mont Terri Project, and the TED in heater test conducted in Callovo-Oxfordian claystone (COx) at the Meuse/Haute-Marne (MHM) underground research laboratory in France. The modeling of the TED heater test is one of the Tasks of the DEvelopment of COupled Models and their VAlidation against EXperiments (DECOVALEX)-2019 project. Section 3 presents the development and application of thermal-hydrological-mechanical-chemical (THMC) modeling to evaluate EBS bentonite and argillite rock responses under different temperatures (100 °C and 200 °C). Model results are presented to help to understand the impact of high temperatures on the properties and behavior of bentonite and argillite rock. Eventually the process model will support a robust GDSA model for repository performance assessments. Section 4 presents coupled THMC modeling for an in situ test conducted at Grimsel underground laboratory in Switzerland in the Full-Scale Engineered Barrier Experiment Dismantling Project (FEBEX-DP). The data collected in the test after almost two decades of heating and two dismantling events provide a unique opportunity of validating coupled THMC models and enhancing our understanding of coupled THMC process in EBS bentonite. Section 5 presents a planned large in-situ test, “HotBENT,” at Grimsel Test Site, Switzerland. In this test, bentonite backfilled EBS in granite will be heated up to 200 °C, where the most relevant features of future emplacement conditions can be adequately reproduced. Lawrence Berkeley National Laboratory (LBNL) has very actively participated in the project since the very beginning and have conducted scoping calculations in FY17 to facilitate the final design of the experiment. Section 6 presents present LBNL’s activities for modeling gas migration in clay related to Task A of the international DECOVALEX-2019 project. This is an international collaborative activity in which DOE and LBNL gain access to unique laboratory and field data of gas migration that are studied with numerical modeling to better understand the processes, to improve numerical models that could eventually be applied in the performance assessment for nuclear waste disposal in clay host rocks and bentonite backfill. Section 7 summarizes the main research accomplishments for FY17 and proposes future work activities.« less

Neon as a Buffer Gas for a Mercury-Ion Clock

NASA Technical Reports Server (NTRS)

Prestage, John; Chung, Sang

2008-01-01

A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump is used to maintain the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a buffer gas. Neon was determined to be the best choice for the buffer gas: The pressure-induced frequency pulling by neon was found to be only about two-fifths of that of helium. Furthermore, because neon diffuses through solids much more slowly than does helium, the operational lifetime of a tube backfilled with neon could be considerably longer than that of a tube backfilled with helium.

Activation of a Ca-bentonite as buffer material

NASA Astrophysics Data System (ADS)

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-shaped time-swell curves of typical bentonites. That is, a greater part of swelling strain develops after the completion of primary swelling strain. At an optimal amount of 1% Na2CO3 in weight, the maximum swelling strain was found to be 3 times as much as that of untreated Zhisin clay. Furthermore, the Na2CO3-activated Zhisin clay exhibited improved resistance to thermal environments and behaved similar to Na-type bentonites under various hydrothermal temperatures.

Uranium and Cesium sorption to bentonite colloids in high salinity and carbonate-rich environments: Implications for radionuclide transport

NASA Astrophysics Data System (ADS)

Tran, E. L.; Teutsch, N.; Klein-BenDavid, O.; Weisbrod, N.

2017-12-01

When radionuclides are leaked into the subsurface due to engineered waste disposal container failure, the ultimate barrier to migration of radionuclides into local aquifers is sorption to the surrounding rock matrix and sediments, which often includes a bentonite backfill. The extent of this sorption is dependent on pH, ionic strength, surface area availability, radionuclide concentration, surface mineral composition, and solution chemistry. Colloidal-sized bentonite particles eroded from the backfill have been shown to facilitate the transport of radionuclides sorbed to them away from their source. Thus, sorption of radionuclides such as uranium and cesium to bentonite surfaces can be both a mobilization or retardation factor. Though numerous studies have been conducted to-date on sorption of radionuclides under low ionic strength and carbonate-poor conditions, there has been little research conducted on the behavior of radionuclides in high salinities and carbonate rich conditions typical of aquifers in the vicinity of some potential nuclear repositories. This study attempts to characterize the sorption properties of U(VI) and Cs to bentonite colloids under these conditions using controlled batch experiments. Results indicated that U(VI) undergoes little to no sorption to bentonite colloids in a high-salinity (TDS= 9000 mg/L) artificial groundwater. This lack of sorption was attributed to the formation of CaUO2(CO3)22- and Ca2UO2(CO3)3 aqueous ions which stabilize the UO22+ ions in solution. In contrast, Cs exhibited greater sorption, the extent to which was influenced greatly by the matrix water's ionic strength and the colloid concentration used. Surprisingly, when both U and Cs were together, the presence of U(VI) in solution decreased Cs sorption, possibly due to the formation of stabilizing CaUO2(CO3)22- anions. The implications of this research are that rather than undergoing colloid-facilitated transport, U(VI) is expected to migrate similarly to a conservative dissolved species under these conditions, and little retardation through sorption onto the surrounding rock matrix is predicted. Cs is expected to undergo more sorption, though U(VI) presence may have a mobilizing effect.

Coupled THMC models for bentonite in clay repository for nuclear waste

NASA Astrophysics Data System (ADS)

Zheng, L.; Rutqvist, J.; Birkholzer, J. T.; Li, Y.; Anguiano, H. H.

2015-12-01

Illitization, the transformation of smectite to illite, could compromise some beneficiary features of an engineered barrier system (EBS) that is composed primarily of bentonite and clay host rock. It is a major determining factor to establish the maximum design temperature of the repositories because it is believed that illitization could be greatly enhanced at temperatures higher than 100 oC and thus significantly lower the sorption and swelling capacity of bentonite and clay rock. However, existing experimental and modeling studies on the occurrence of illitization and related performance impacts are not conclusive, in part because the relevant couplings between the thermal, hydrological, chemical, and mechanical (THMC) processes have not been fully represented in the models. Here we present fully coupled THMC simulations of a generic nuclear waste repository in a clay formation with bentonite-backfilled EBS. Two scenarios were simulated for comparison: a case in which the temperature in the bentonite near the waste canister can reach about 200 oC and a case in which the temperature in the bentonite near the waste canister peaks at about 100 oC. The model simulations demonstrate that illitization is in general more significant at higher temperatures. We also compared the chemical changes and the resulting swelling stress change for two types of bentonite: Kunigel-VI and FEBEX bentonite. Higher temperatures also lead to much higher stress in the near field, caused by thermal pressurization and vapor pressure buildup in the EBS bentonite and clay host rock. Chemical changes lead to a reduction in swelling stress, which is more pronounced for Kunigel-VI bentonite than for FEBEX bentonite.

Efficiency of a borehole seal by means of pre-compacted bentonite blocks

NASA Astrophysics Data System (ADS)

Van Geet, M.; Volckaert, G.; Bastiaens, W.; Maes, N.; Weetjens, E.; Sillen, X.; Vallejan, B.; Gens, A.

The backfilling and sealing of shafts and galleries is an essential part of the design of underground repositories for high-level radioactive waste. Part of the EC funded project RESEAL studied the feasibility of sealing off a borehole in plastic Boom Clay by means of pre-compacted bentonite blocks. Two bentonites, namely the FoCa and Serrata clay, have been used. Based on laboratory tests, the bentonite blocks had an initial dry density of about 1.8 g/cm 3 to obtain a swelling pressure of about 4.4 MPa, corresponding to the in situ lithostatic stress, at full saturation. The set-up was equipped with several sensors to follow-up the behaviour of the seal and the surrounding host rock during hydration. Full saturation was reached after five months and was mainly reached by natural hydration. Swelling pressure was lower than originally foreseen due to the slow reconsolidation of the host rock. Later on, the efficiency of the seal with respect to water, gas and radionuclide migration was tested. The in situ measured permeability of the seals was about 5 × 10 -13 m/s. A gas breakthrough experiment did not show any preferential gas migration through the seal. No evidences of a preferential pathway could be detected from 125I tracer test results.

Fundamental properties of monolithic bentonite buffer material formed by cold isostatic pressing for high-level radioactive waste repository

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakami, S.; Yamanaka, Y.; Kato, K.

1999-07-01

The methods of fabrication, handling, and emplacement of engineered barriers used in a deep geological repository for high level radioactive waste should be planned as simply as possible from the engineering and economic viewpoints. Therefore, a new concept of a monolithic buffer material around a waste package have been proposed instead of the conventional concept with the use of small blocks, which would decrease the cost for buffer material. The monolithic buffer material is composed of two parts of highly compacted bentonite, a cup type body and a cover. As the forming method of the monolithic buffer material, compaction bymore » the cold isostatic pressing process (CIP) has been employed. In this study, monolithic bentonite bodies with the diameter of about 333 mm and the height of about 455 mm (corresponding to the approx. 1/5 scale for the Japanese reference concept) were made by the CIP of bentonite powder. The dry densities: {rho}d of the bodies as a whole were measured and the small samples were cut from several locations to investigate the density distribution. The swelling pressure and hydraulic conductivity as function of the monolithic body density for CIP-formed specimens were also measured. High density ({rho}d: 1.4--2.0 Mg/m{sup 3}) and homogeneous monolithic bodies were formed by the CIP. The measured results of the swelling pressure (3--15 MPa) and hydraulic conductivity (0.5--1.4 x 10{sup {minus}13} m/s) of the specimens were almost the same as those for the uniaxial compacted bentonite in the literature. It is shown that the vacuum hoist system is an applicable handling method for emplacement of the monolithic bentonite.« less

Thermal - Hydraulic Behavior of Unsaturated Bentonite and Sand-Bentonite Material as Seal for Nuclear Waste Repository: Numerical Simulation of Column Experiments

NASA Astrophysics Data System (ADS)

Ballarini, E.; Graupner, B.; Bauer, S.

2015-12-01

For deep geological repositories of high-level radioactive waste (HLRW), bentonite and sand bentonite mixtures are investigated as buffer materials to form a a sealing layer. This sealing layer surrounds the canisters and experiences an initial drying due to the heat produced by HLRW and a successive re-saturation with fluid from the host rock. These complex thermal, hydraulic and mechanical processes interact and were investigated in laboratory column experiments using MX-80 clay pellets as well as a mixture of 35% sand and 65% bentonite. The aim of this study is to both understand the individual processes taking place in the buffer materials and to identify the key physical parameters that determine the material behavior under heating and hydrating conditions. For this end, detailed and process-oriented numerical modelling was applied to the experiments, simulating heat transport, multiphase flow and mechanical effects from swelling. For both columns, the same set of parameters was assigned to the experimental set-up (i.e. insulation, heater and hydration system), while the parameters of the buffer material were adapted during model calibration. A good fit between model results and data was achieved for temperature, relative humidity, water intake and swelling pressure, thus explaining the material behavior. The key variables identified by the model are the permeability and relative permeability, the water retention curve and the thermal conductivity of the buffer material. The different hydraulic and thermal behavior of the two buffer materials observed in the laboratory observations was well reproduced by the numerical model.

Geological Disposal of Nuclear Waste: Investigating the Thermo-Hygro-Mechanical-Chemical (THMC) Coupled Processes at the Waste Canister- Bentonite Barrier Interface

NASA Astrophysics Data System (ADS)

Davies, C. W.; Davie, D. C.; Charles, D. A.

2015-12-01

Geological disposal of nuclear waste is being increasingly considered to deal with the growing volume of waste resulting from the nuclear legacy of numerous nations. Within the UK there is 650,000 cubic meters of waste safely stored and managed in near-surface interim facilities but with no conclusive permanent disposal route. A Geological Disposal Facility with incorporated Engineered Barrier Systems are currently being considered as a permanent waste management solution (Fig.1). This research focuses on the EBS bentonite buffer/waste canister interface, and experimentally replicates key environmental phases that would occur after canister emplacement. This progresses understanding of the temporal evolution of the EBS and the associated impact on its engineering, mineralogical and physicochemical state and considers any consequences for the EBS safety functions of containment and isolation. Correlation of engineering properties to the physicochemical state is the focus of this research. Changes to geotechnical properties such as Atterberg limits, swelling pressure and swelling kinetics are measured after laboratory exposure to THMC variables from interface and batch experiments. Factors affecting the barrier, post closure, include corrosion product interaction, precipitation of silica, near-field chemical environment, groundwater salinity and temperature. Results show that increasing groundwater salinity has a direct impact on the buffer, reducing swelling capacity and plasticity index by up to 80%. Similarly, thermal loading reduces swelling capacity by 23% and plasticity index by 5%. Bentonite/steel interaction studies show corrosion precipitates diffusing into compacted bentonite up to 3mm from the interface over a 4 month exposure (increasing with temperature), with reduction in swelling capacity in the affected zone, probably due to the development of poorly crystalline iron oxides. These results indicate that groundwater conditions, temperature and corrosion may affect the engineering performance of the bentonite buffer such that any interfaces between bentonite blocks that may be present immediately following buffer emplacement may persist in the longer term.

Strength characteristics of lightly solidified dredged marine clay admixed with bentonite

NASA Astrophysics Data System (ADS)

Ariffin, Syazwana Tajul; Chan, Chee-Ming

2017-11-01

Strength characteristic is a significant parameter in measuring the effect of soil improvement and effective composition of solidification. In this study, the dredged marine sediment (DMS) collected from Kuala Perlis (Malaysia) was examined to determine its strength characteristics under light cement solidification with bentonite. Dredged marine clay generally has the low shear strength and high void ratio, and consists mainly of soil particles of the fine-grained type. As a discarded geo-waste, it can be potentially treated to for reuse as a backfill material instead of being disposed of, hence reducing the negative impact on the environment. Physico-chemical parameters of the dredged sample were first determined, then solidification was carried out to improve the engineering properties by admixing ordinary Portland cement (OPC) as the binder and bentonite as a volume enhancer to the soil. The DMS was treated with the addition of 3 % and 6 % cement and bentonite within the range of 0-30 %. The specimens were cured at room temperature for 3, 7 and 14 days. The strength gain was measured by unconfined compression test and vane shear test. The laboratory test results were analyzed to establish the relationship between strength properties and solidification specifications. In summary, the strength of specimens increased with the increase of the quantity of bentonite and cement to get the effective composition of the specimen.

Fractal Approach to Erosion Threshold of Bentonites

NASA Astrophysics Data System (ADS)

Xu, Y. F.; Li, X. Y.

Bentonite has been considered as a candidate buffer material for the disposal of high-level radioactive waste (HLW) because of its low permeability, high sorption capacity, self-sealing characteristics and durability in a natural environment. Bentonite erosion caused by groundwater flow may take place at the interface of the compacted bentonite and fractured granite. Surface erosion of bentonite flocs is represented typically as an erosion threshold. Predicting the erosion threshold of bentonite flocs requires taking into account cohesion, which results from interactions between clay particles. Beyond the usual dependence on grain size, a significant correlation between erosion threshold and porosity measurements is confirmed for bentonite flocs. A fractal model for erosion threshold of bentonite flocs is proposed. Cohesion forces, the long-range van der Waals interaction between two clay particles are taken as the resource of the erosion threshold. The model verification is conducted by the comparison with experiments published in the literature. The results show that the proposed model for erosion threshold is in good agreement with the experimental data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zavarin, Mavrik; Joseph, C.

This progress report (Level 4 Milestone Number M4FT-16LL080303052) summarizes research conducted at Lawrence Livermore National Laboratory (LLNL) within the Crystalline Disposal R&D Activity Number FT-16LL080303051 and Crystalline International Collaborations Activity Number FT-16LL080303061. The focus of this research is the interaction of radionuclides with Engineered Barrier System (EBS) and host rock materials at various physico-chemical conditions relevant to subsurface repository environments. They include both chemical and physical processes such as solubility, sorption, and diffusion. The colloid-facilitated transport effort focused on preparation of a draft manuscript summarizing the state of knowledge and parameterization of colloid-facilitated transport mechanisms in support of reactive transportmore » and performance assessment models for generic crystalline repositories. This draft manuscript is being submitted as a level 3 milestone with LANL as the primary author. LLNL’s contribution to that effort is summarized only briefly in the present report. A manuscript summarizing long-term U(VI) diffusion experiments through bentonite backfill material was recently accepted for publication; the contents of that manuscript are summarized in the present report. The Np(IV) diffusion experiments were started mid-year and are ongoing. The completion of these experiments is planned for early FY17. Our progress in quantifying Np(IV) diffusion in bentonite backfill is summarized in the present report. Our involvement with the NEA TDB project was summarized in a recent Argillite Disposal activity report. It is not included in this report.« less

Measuring microbial metabolism in atypical environments: Bentonite in used nuclear fuel storage.

PubMed

Stone, Wendy; Kroukamp, Otini; Moes, Ana; McKelvie, Jennifer; Korber, Darren R; Wolfaardt, Gideon M

2016-01-01

Genomics enjoys overwhelming popularity in the study of microbial ecology. However, extreme or atypical environments often limit the use of such well-established tools and consequently demand a novel approach. The bentonite clay matrix proposed for use in Deep Geological Repositories for the long-term storage of used nuclear fuel is one such challenging microbial habitat. Simple, accessible tools were developed for the study of microbial ecology and metabolic processes that occur within this habitat, since the understanding of the microbiota-niche interaction is fundamental to describing microbial impacts on engineered systems such as compacted bentonite barriers. Even when genomic tools are useful for the study of community composition, techniques to describe such microbial impacts and niche interactions should complement these. Tools optimised for assessing localised microbial activity within bentonite included: (a) the qualitative use of the resazurin-resorufin indicator system for redox localisation, (b) the use of a CaCl2 buffer for the localisation of pH, and (c) fluorometry for the localisation of precipitated sulphide. The use of the Carbon Dioxide Evolution Monitoring System was also validated for measuring microbial activity in desiccated and saturated bentonite. Finally, the buffering of highly-basic bentonite at neutral pH improved the success of isolation of microbial populations, but not DNA, from the bentonite matrix. Thus, accessible techniques were optimised for exploring microbial metabolism in the atypical environments of clay matrices and desiccated conditions. These tools have application to the applied field of used nuclear fuel management, as well as for examining the fundamental biogeochemical cycles active in sedimentary and deep geological environments. Copyright © 2015 Elsevier B.V. All rights reserved.

Reactive Transport Modeling and Changes in Porosity at Reactive Interfaces in a HLW repository in Clay

NASA Astrophysics Data System (ADS)

Samper, J.; Mon, A.; Montenegro, L.; Naves, A.; Fernández, J.

2016-12-01

High-level radioactive waste disposal in a deep geological repository is based on a multibarrier concept which combines natural barriers such as the geological formation and artificial barriers such as metallic containers, bentonite and concrete buffers and sealing materials. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyperalkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyperalkaline plume at the concrete-clay interface. Here we present a nonisothermal reactive transport model of the long-term interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. This problem involves large pH changes with a hyperalkaline high-pH plume, complex mineral dissolution/precipitation patterns, cation exchange reactions and proton surface complexation. These reactions lead to large changes in porosity which can even lead to pore clogging. Model results show that magnetite, the main corrosion product, precipitates and reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The zones affected by pore clogging at the canister-bentonite, bentonite-concrete and concrete-clay interfaces at 1 Ma are equal to 10, 25 and 25 mm thick, respectively. The results of our simulations share many of the features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Narrow alteration zones; and 2) Pore clogging at the canister-bentonite, bentonite-concrete and concrete-clay interfaces.

Nuclear Repository steel canister: experimental corrosion rates

NASA Astrophysics Data System (ADS)

Caporuscio, F.; Norskog, K.

2017-12-01

The U.S. Spent Fuel & Waste Science & Technology campaign evaluates various generic geological repositories for the disposal of spent nuclear fuel. This experimental work analyzed and characterized the canister corrosion and steel interface mineralogy of bentonite-based EBS 304 stainless steel (SS), 316 SS, and low-carbon steel coupons in brine at higher heat loads and pressures. Experiments contrasted EBS with and without an argillite wall rock. Unprocessed bentonite from Colony, Wyoming simulated the clay buffer and Opalinus Clay represented the wall rock. Redox conditions were buffered at the magnetite-iron oxygen fugacity univariant curve. A K-Na-Ca-Cl-based brine was chosen to replicate generic granitic groundwater compositions, while Opalinous Clay groundwater was used in the wall rock series of experiments. Most experiments were run at 150 bar and 300°C for 4 to 6 weeks and one was held at elevated conditions for 6 months. The two major experimental mixtures were 1) brine-bentonite clay- steel, and 2) brine-bentonite clay-Opalinus Clay-steel. Both systems were equilibrated at a high liquid/clay ratio. Mineralogy and aqueous geochemistry of each experiment were evaluated to monitor the reactions that took place. In total 4291 measurements were obtained: 2500 measured steel corrosion depths and 1791 were of phyllosilicate mineral reactions/growths at the interface. The low carbon steel corrosion mechanism was via pit corrosion, while 304 SS and 316 SS were by general corrosion. The low carbon steel corrosion rate (1.95 μm/day) was most rapid. The 304 SS corrosion rate (0.37 μm/day) was slightly accelerated versus the 316 SS corrosion rate (0.26 μm/day). Note that the six month 316 SS experiment shows inhibited corrosion rates (0.07 μm/day). This may be in part due to mantling by the Fe-saponite/chlorite authigenic minerals. All phyllosilicate growth rates at the interface exhibit similar growth rate patterns to the steels (i.e. LCS>304>316> 316 six month).

Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids.

PubMed

Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

2015-10-01

Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater-bentonite-fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L(-1)) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10(-10) M (241)Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k(f)) of 0.01-0.02 h(-1). Am recoveries in each column were 55-60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h(-1) in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. Our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because of the ability of the fracture materials to rapidly strip Am from the bentonite colloids and the apparent lack of a strong binding site that would keep a fraction of the Am strongly-associated with the colloids. Published by Elsevier Ltd.

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

PubMed

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.

An assessment of strontium sorption onto bentonite buffer material in waste repository.

PubMed

Pathak, Pankaj

2017-03-01

In the present study, changes occurring in sorption characteristics of a representative bentonite (WIn-BT) exposed to SrCl 2 (0.001-0.1 M) under the pH range of 1-13 were investigated. Such interaction revealed a significant variation in surface charge density and binding energy of ions with respect to bentonite, and alteration in their physicochemical properties viz., specific surface area, cation exchange capacity, thermal and mechanical behaviour were observed. The distribution coefficients (k d ) calculated for sorption onto virgin (UCBT) and contaminated bentonite (CBT) indicated a greater influence of mineralogical changes occurred with variance of pH and strontium concentration. Notably, the sorption mechanism clearly elucidates the effect of structural negative charge and existence of anionic metal species onto CBT, and depicted the reason behind significant k d values at highly acidic and alkaline pH. The maximum k d of UCBT and CBT (0.001M SrCl2) were 8.99 and 2.92 L/kg, respectively, at the soil pH 8.5; whereas it was 2.37 and 1.23 L/kg at pH 1 for the CBT (0.1M SrCl2) and CBT (0.01M SrCl2) , respectively. The findings of this study can be useful to identify the physicochemical parameters of candidate buffer material and sorption reversibility in waste repository.

Fe-SAPONITE and Chlorite Growth on Stainless Steel in Hydrothermal Engineered Barrier Experiments

NASA Astrophysics Data System (ADS)

Cheshire, M. C.; Caporuscio, F. A.; McCarney, M.

2012-12-01

The United States recently has initiated the Used Fuel Disposition campaign to evaluate various generic geological repositories for the disposal of high-level, spent nuclear fuel within environments ranging from hard-rock, salt/clay, to deep borehole settings. Previous work describing Engineered Barrier Systems (EBS) for repositories focused on low temperature and pressure conditions. The focus of this experimental work is to characterize the stability and alteration of a bentonite-based EBS with different waste container materials in brine at higher heat loads and pressures. All experiments were run at ~150 bar and 125 to 300 C for ~1 month. Unprocessed bentonite from Colony, Wyoming was used in the experiments as the clay buffer material. The redox conditions for each system were buffered along the magnetite-iron oxygen fugacity univariant curve using Fe3O4 and Feo filings. A K-Na-Ca-Cl-based salt solution was chosen to replicate deep groundwater compositions. The experimental mixtures were 1) salt solution-clay; 2) salt solution -clay-304 stainless steel; and 3) salt solution -clay-316 stainless steel with a water/bentonite ratio of ~9. Mineralogy and aqueous geochemistry of each experiment was evaluated to monitor the reactions that took place. No smectite illitization was observed in these reactions. However, it appears that K-smectite was produced, possibly providing a precursor to illitization. It is unclear whether reaction times were sufficient for bentonite illitization at 212 and 300 C or whether conditions conducive to illite formation were obtained. The more notable clay mineral reactions occurred at the stainless steel surfaces. Authigenic chlorite and Fe-saponite grew with their basal planes near perpendicular to the steel plate, forming a 10 - 40 μm thick 'corrosion' layer. Partial dissolution of the steel plates was the likely iron source for chlorite/saponite formation; however, dissolution of the Feo/Fe3O4 may also have acted as an iron source, with the steel plates acting as a substrate for chlorite/saponite growth. Trace amounts of pyrite in the bentonite appeared to have reacted to form H2S gas and pentlandite ((Ni,Fe)8S9). Mineral growth on the waste containers was influenced by the container, buffer, and fluid compositions, in addition to pressure and temperature conditions. No significant mineralogical changes were apparent away from the steel-smectite interface. Results of this research show that the waste container may act as a substrate for mineral growth in response to corrosion. However, it is presently unknown whether chlorite and Fe-saponite will act as passivating agents or whether their presence will facilitate further corrosion of the waste containers. The role of these Fe-rich minerals on the stability of steel canisters at elevated heat loads is currently under investigation. LA-UR-12-23845

Design, testing and emplacement of sand-bentonite for the construction of a gas-permeable seal test (gast)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teodori, Sven-Peter; Ruedi, Jorg; Reinhold, Matthias

2013-07-01

The main aim of a gas-permeable seal is to increase the gas transport capacity of the backfilled underground structures without compromising the radionuclide retention capacity of the engineered barrier system or the host rock. Such a seal, proposed by NAGRA as part of the 'Engineered Gas Transport System' in a L/ILW repository, considers specially designed backfill and sealing materials such as sand/bentonite (S/B) mixtures with a bentonite content of 20- 30%. NAGRA's RD and D plan foresees demonstrating the construction and performance of repository seals and improving the understanding and the database for reliably predicting water and gas transport throughmore » these systems. The fluid flow and gas transport properties of these backfills have been determined at the laboratory scale and through modelling the maximum gas pressures in the near field of a repository system and the gas flow rates have been evaluated. Within this context, the Gas-permeable Seal Test (GAST) was constructed at Grimsel Test Site (GTS) to validate the effective functioning of gas-permeable seals at realistic scale. The intrinsic permeability of such seals should be in the order of 10-18 m2. Because the construction of S/B seals is not common practice for construction companies, a stepwise approach was followed to evaluate different construction and quality assurance methods. As a first step, an investigation campaign with simple tests in the laboratory and in the field followed by 1:1 scale pre-tests at GTS was performed. Through this gradual increase of the degree of complexity, practical experience was gained and confidence in the methods and procedures to be used was built, which allowed reliably producing and working with S/B mixtures at a realistic scale. During the whole pre-testing phase, a quality assurance (QA) programme for S/B mixtures was developed and different methods were assessed. They helped to evaluate and choose appropriate emplacement techniques and methodologies to achieve the target S/B dry density of 1.70 g/cm{sup 3}, which results in the desired intrinsic permeability throughout the experiment. The final QA methodology was targeted at engineering measures to decide if the work can proceed, and at producing high resolution material properties database for future water and gas transport modelling activities. The different applied QA techniques included standard core cutter tests, the application of neutron-gamma (Troxler) probes and two mass balance methods (2D and 3D). The methods, looking at different representative scales, have provided only slightly different results and showed that the average density of the emplaced S/B plug was between 1.65 and 1.73 g/cm{sup 3}. Spatial variability of dry densities was observed at decimeter scale. Overall, the pre-testing and QA programme performed for the GAST project demonstrated how the given design criteria and requirements can be met by appropriately planning and designing the material emplacement. (authors)« less

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

NASA Astrophysics Data System (ADS)

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 saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository.

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

PubMed

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 saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository. Copyright © 2015. Published by Elsevier B.V.

Free Available Chlorine Disinfection Criteria for Fixed Army Installation Primary Drinking Water

DTIC Science & Technology

1981-12-01

Buffered Water with Fuivic Acid (5 C.U.) at pH 9 and 60C ............................................ 6. FAC Disinfection of f 2 Coliphage in Buffered Water ...with and without 250 mg/L -Ca+ at pH 5, 7, and 9 and 6°C ............... 31 10. FAC Disinfection of f 2 Coliphage in Water Containing 5 NTU Bentonite2...rngi L Ca+ 2 at pH- 5, 7, and q and 60C ...... ........................ 34 13. FAC Disinfection of f 2 Coliphage in Borate-Buffered Water with 250 mg

Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids

DOE PAGES

Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; ...

2015-07-13

Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater–bentonite–fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. Themore » colloidal suspension (100 mg L –1) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10 –10 M 241Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k f) of 0.01–0.02 h –1. Am recoveries in each column were 55–60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h –1 in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. As a result, our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because of the ability of the fracture materials to rapidly strip Am from the bentonite colloids and the apparent lack of a strong binding site that would keep a fraction of the Am strongly-associated with the colloids.« less

Attenuation of heavy metals by geosynthetics in the coal gangue-filled columns.

PubMed

Wang, Ping; Hu, Zhenqi; Wang, Peijun

2013-01-01

In the subsided areas backfilled with coal gangue, an issue of continuing environmental concern is the migration of hazardous metals to the subsurface soil and groundwater. As an effective isolation material, geosynthetics have been scarcely applied into mining areas reclamation of China. This paper describes research aimed at characterizing the behaviours of different geosynthetics in the leaching columns filled with coal gangues. Four types of geosynthetics were selected: fibres needle-punched nonwoven geotextiles, high-density polyethylene, needle-punched Na-bentonite geosynthetic clay liner (GCL-NP) and Na-bentonite geosynthetic-overbited film. Heavy metals were significantly attenuated and by monitoring aqueous solutions in the whole percolation period, negative correlation was found between pH value and concentration of heavy metals. Generally, GCL-NP showed comparatively better effects on attenuating the migration of heavy metals. According to the meta-analysis of heavy metals present in the leachates and retained in the columns, geosynthetics have good capabilities of sorption and retardation, which can delay the breakthrough time of heavy metals and retard the accumulation in the subsurface. Future research will use X-ray diffraction and micro-imaging (electron microprobe and scanning electron microscopy) to further explain retention mechanisms.

Limits to the use of highly compacted bentonite as a deterrent for microbiologically influenced corrosion in a nuclear fuel waste repository

NASA Astrophysics Data System (ADS)

Stroes-Gascoyne, Simcha; Hamon, Connie J.; Maak, Peter

Recent studies have suggested that microbial activity in highly compacted bentonite (⩾1600 kg/m 3) is severely suppressed. Therefore, it appears that the dry density of emplaced bentonite barriers in a geological repository for nuclear waste may be tailored such that a microbiologically unfavorable environment can be created adjacent to used fuel containers. This would ensure that microbiologically influenced corrosion is a negligible contributor to the overall corrosion process. However, this premise is valid only as long as the emplaced bentonite maintains a uniform high dry density (⩾1600 kg/m 3) because it has been shown that high dry density only suppresses microbial activity but not necessarily eliminates the viable microbial population in bentonite. In a repository, a reduction in the dry density of highly compacted bentonite may occur at a number of interface locations, such as placement gaps, contact regions with materials of different densities and contact points with water-carrying fractures in the rock. Experiments were carried out in our laboratory to examine the effects of a reduction in dry density (from 1600 kg/m 3 to about 1000 kg/m 3) on the recovery of microbial culturability in compacted bentonite. Results showed that upon expansion of compacted bentonite into a void, the resulting reduction in dry density stimulated or restored culturability of indigenous microbes. In a repository this would increase the possibility of in situ activity, which might be detrimental for the longevity of waste containers. Reductions in dry density, therefore, should be minimized or eliminated by adequate design and placement methods of compacted bentonite. Materials compliance models can be used to determine the required as-placed dry densities of bentonite buffer and gap fillings to achieve specific targets for long-term equilibrium dry densities for various container placement room designs. Locations where flowing fractures could be in contact with highly compacted bentonite should either be avoided or grouted adequately to limit contact between bentonite and flowing water. Even if localized enhanced microbial activity at interfaces remains of concern, despite adequate engineering and placement methods, the potential consequences can be assessed and quantified adequately by a combination of in situ activity measurements and modeling calculations.

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

NASA Astrophysics Data System (ADS)

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.

Americium, Cesium, and Plutonium Colloid-Facilitated Transport in a Groundwater/Bentonite/Fracture Fill Material System: Column Experiments and Model Results

NASA Astrophysics Data System (ADS)

Dittrich, T. M.; Boukhalfa, H.; Reimus, P. W.

2014-12-01

The objective of this study was to investigate and quantify the effects of desorption kinetics and colloid transport on radionuclides with different sorption affinities. We focused on quantifying transport mechanisms important for upscaling in time and distance. This will help determine the long-term fate and transport of radionuclides to aid in risk assessments. We selected a fractured/weathered granodiorite at the Grimsel Test Site (GTS) in Switzerland as a model crystalline rock repository system because the system has been thoroughly studied and field experiments involving radionuclides have already been conducted. Working on this system provides a unique opportunity to compare lab experiments with field-scale observations. Weathered fracture fill material (FFM) and bentonite used as backfill at the GTS were characterized (e.g., BET, SEM/EDS, QXRD), and batch and breakthrough column experiments were conducted. Solutions were prepared in synthetic groundwaters that matched the natural water chemistry. FFM samples were crushed, rinsed, sieved (150-355 μm), and equilibrated with synthetic groundwater. Bentonite was crushed, sodium-saturated, equilibrated with synthetic groundwater, and settled to yield a stable suspension. Suspensions were equilibrated with Am, Cs, or Pu. All experiments were conducted with Teflon®materials to limit sorption to system components. After radionuclide/colloid injections reached stability, radionuclide-free solutions were injected to observe the desorption and release behavior. Aliquots of effluent were measured for pH, colloid concentration, and total and dissolved radionuclides. Unanalyzed effluent from the first column was then injected through a second column of fresh material. The process was repeated for a third column and the results of all three breakthrough curves were modeled with a multi-site/multi-rate MATLAB code to elucidate the sorption rate coefficients and binding site densities of the bentonite colloids and fracture fill material. Nearly 50% of the sorbed Am was exchanged from the colloids to the fracture filling material in each of the three columns; whereas, less Cs and Pu was desorbed with each pass through a new column. Using a two-site kinetic model allowed for interrogation of desorption rates and dominant transport parameters.

Dynamics of metals in backfill of a phosphate mine of guiyang, China using a three-step sequential extraction technique.

PubMed

Shi, Ying; Gan, Lei; Li, Xibing; He, Suya; Sun, Cheng; Gao, Li

2018-02-01

Phosphate rock in Guiyang (Southwest of China) is used for the phosphate production, and hence generating a by-product phosphogypsum (PG). From 2007, part of the PG was used as main raw material for cemented backfill. The main objective of this paper is to investigate the geochemical evolution of metals before and after the PG inclusion into the backfill matrix. A sequential extraction procedure was selected to determine the chemical speciation of metals in phosphate rock, PG, binder and field backfill samples. Dynamics of metals going from phosphate rock and PG to backfill have been evaluated. The results showed that almost all the metals in the PG and binder had been effectively transferred to the backfill. Furthermore, compared to metals taken out along with phosphate rock exploitation, PG-based cemented backfill might bring some metals back but with only little metals in mobile fraction. Additionally, in order to determine the long-term behavior of metals in PG-based cemented backfill, the field samples which were backfilled from 2007 to 2016 were collected and analyzed. The results showed that total amounts of metals in backfill were all within similar range, indicating that the cemented PG backfill could be an effective method to solidify/stabilize metals in PG. Nevertheless, Due to the high water-soluble fractions detected, the concentrations of As, Mn and Zn should be continuously monitored. Copyright © 2017. Published by Elsevier Ltd.

Multi-dimensional transport modelling of corrosive agents through a bentonite buffer in a Canadian deep geological repository.

PubMed

Briggs, Scott; McKelvie, Jennifer; Sleep, Brent; Krol, Magdalena

2017-12-01

The use of a deep geological repository (DGR) for the long-term disposal of used nuclear fuel is an approach currently being investigated by several agencies worldwide, including Canada's Nuclear Waste Management Organization (NWMO). Within the DGR, used nuclear fuel will be placed in copper-coated steel containers and surrounded by a bentonite clay buffer. While copper is generally thermodynamically stable, corrosion can occur due to the presence of sulphide under anaerobic conditions. As such, understanding transport of sulphide through the engineered barrier system to the used fuel container is an important consideration in DGR design. In this study, a three-dimensional (3D) model of sulphide transport in a DGR was developed. The numerical model is implemented using COMSOL Multiphysics, a commercial finite element software package. Previous sulphide transport models of the NWMO repository used a simplified one-dimensional system. This work illustrates the importance of 3D modelling to capture non-uniform effects, as results showed locations of maximum sulphide flux are 1.7 times higher than the average flux to the used fuel container. Copyright © 2017. Published by Elsevier B.V.

New Rapid Evaluation for Long-Term Behavior in Deep Geological Repository by Geotechnical Centrifuge—Part 2: Numerical Simulation of Model Tests in Isothermal Condition

NASA Astrophysics Data System (ADS)

Sawada, Masataka; Nishimoto, Soshi; Okada, Tetsuji

2017-01-01

In high-level radioactive waste disposal repositories, there are long-term complex thermal, hydraulic, and mechanical (T-H-M) phenomena that involve the generation of heat from the waste, the infiltration of ground water, and swelling of the bentonite buffer. The ability to model such coupled phenomena is of particular importance to the repository design and assessments of its safety. We have developed a T-H-M-coupled analysis program that evaluates the long-term behavior around the repository (called "near-field"). We have also conducted centrifugal model tests that model the long-term T-H-M-coupled behavior in the near-field. In this study, we conduct H-M-coupled numerical simulations of the centrifugal near-field model tests. We compare numerical results with each other and with results obtained from the centrifugal model tests. From the comparison, we deduce that: (1) in the numerical simulation, water infiltration in the rock mass was in agreement with the experimental observation. (2) The constant-stress boundary condition in the centrifugal model tests may cause a larger expansion of the rock mass than in the in situ condition, but the mechanical boundary condition did not affect the buffer behavior in the deposition hole. (3) The numerical simulation broadly reproduced the measured bentonite pressure and the overpack displacement, but did not reproduce the decreasing trend of the bentonite pressure after 100 equivalent years. This indicates the effect of the time-dependent characteristics of the surrounding rock mass. Further investigations are needed to determine the effect of initial heterogeneity in the deposition hole and the time-dependent behavior of the surrounding rock mass.

Interaction of human adenoviruses and coliphages with kaolinite and bentonite.

PubMed

Bellou, Maria I; Syngouna, Vasiliki I; Tselepi, Maria A; Kokkinos, Petros A; Paparrodopoulos, Spyros C; Vantarakis, Apostolos; Chrysikopoulos, Constantinos V

2015-06-01

Human adenoviruses (hAdVs) are pathogenic viruses responsible for public health problems worldwide. They have also been used as viral indicators in environmental systems. Coliphages (e.g., MS2, ΦX174) have also been studied as indicators of viral pollution in fecally contaminated water. Our objective was to evaluate the distribution of three viral fecal indicators (hAdVs, MS2, and ΦΧ174), between two different phyllosilicate clays (kaolinite and bentonite) and the aqueous phase. A series of static and dynamic experiments were conducted under two different temperatures (4, 25°C) for a time period of seven days. HAdV adsorption was examined in DNase I reaction buffer (pH=7.6, and ionic strength (IS)=1.4mM), whereas coliphage adsorption in phosphate buffered saline solution (pH=7, IS=2mM). Moreover, the effect of IS on hAdV adsorption under static conditions was evaluated. The adsorption of hAdV was assessed by real-time PCR and its infectivity was tested by cultivation methods. The coliphages MS2 and ΦΧ174 were assayed by the double-layer overlay method. The experimental results have shown that coliphage adsorption onto both kaolinite and bentonite was higher for the dynamic than the static experiments; whereas hAdV adsorption was lower under dynamic conditions. The adsorption of hAdV increased with decreasing temperature, contrary to the results obtained for the coliphages. This study examines the combined effect of temperature, agitation, clay type, and IS on hAdV adsorption onto clays. The results provide useful new information on the effective removal of viral fecal indicators (MS2, ΦX174 and hAdV) from dilute aqueous solutions by adsorption onto kaolinite and bentonite. Factors enabling enteric viruses to penetrate soils, groundwater and travel long distances within aquifers are important public health issues. Because the observed adsorption behavior of surrogate coliphages MS2 and ΦΧ174 is substantially different to that of hAdV, neither MS2 nor ΦΧ174 is recommended as a suitable model for adenovirus. Copyright © 2015 Elsevier B.V. All rights reserved.

Preliminary Interpretation of a Radionuclide and Colloid Tracer Test in a Granodiorite Shear Zone at the Grimsel Test Site, Switzerland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reimus, Paul W.

2012-08-30

In February and March 2012, a tracer test involving the injection of a radionuclide-colloid cocktail was conducted in the MI shear zone at the Grimsel Test Site, Switzerland, as part of the Colloids Formation and Migration (CFM) project. The colloids were derived from FEBEX bentonite, which is mined in Spain and is being considered as a potential waste package backfill in a Spanish nuclear waste repository. The tracer test, designated test 12-02 (second test in 2012), involved the injection of the tracer cocktail into borehole CFM 06.002i2 and extraction from the Pinkel surface packer at the main access tunnel wallmore » approximately 6.1 m from the injection interval. The test configuration is depicted in Figure 1. This configuration has been used in several conservative tracer tests and two colloid-homologue tracer tests since 2007, and it is will be employed in an upcoming test involving the emplacement of a radionuclide-doped bentonite plug into CFM 06.002i2 to evaluate the swelling and erosion of the bentonite and the transport of bentonite colloids and radionuclides from the source to the extraction point at the tunnel wall. Interpretive analyses of several of the previous tracer tests, from 09-01 through 12-02 were provided in two previous Used Fuel Disposition Program milestone reports (Arnold et al., 2011; Kersting et al., 2012). However, only the data for the conservative tracer Amino-G Acid was previously analyzed from test 12-02 because the other tracer data from this test were not available at the time. This report documents the first attempt to quantitatively analyze the radionuclide and colloid breakthrough curves from CFM test 12-02. This report was originally intended to also include an experimental assessment of colloid-facilitated transport of uranium by bentonite colloids in the Grimsel system, but this assessment was not conducted because it was reported by German collaborators at the Karlsruhe Institute of Technology (KIT) that neither uranium nor neptunium adsorbed appreciably to FEBEX bentonite colloids in Grimsel groundwater (Huber et al., 2011). The Grimsel groundwater has a relatively high pH of {approx}9, so the lack of uranium and neptunium adsorption to clay is not surprising given the tendency for these actinides to form very stable negative or neutrally-charged uranyl- or calcium-uranyl-carbonate complexes at these pH, particularly in a water that is effectively saturated with respect to calcite. It was also observed in testing conducted at LANL earlier in 2012 that uranium did not adsorb measurably to Grimsel granodiorite in a synthetic Grimsel groundwater at pH {approx}8.5 (Kersting et al., 2012). Thus, the planned experimental work was not pursued because all the available information clearly pointed to an expected result that uranium transport would not be facilitated by clay colloids in the Grimsel system.« less

Evaluating the methodology and performance of jetting and flooding of granular backfill materials.

DOT National Transportation Integrated Search

2014-11-01

Compaction of backfill in confined spaces on highway projects is often performed with small vibratory plates, based : solely on the experience of the contractor, leading to inadequate compaction. As a result, the backfill is prone to : erosion and of...

UNDERGROUNG PLACEMENT OF COAL PROCESSING WASTE AND COAL COMBUSTION BY-PRODUCTS BASED PASTE BACKFILL FOR ENHANCED MINING ECONOMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Y.P. Chugh; D. Biswas; D. Deb

2002-06-01

This project has successfully demonstrated that the extraction ratio in a room-and-pillar panel at an Illinois mine can be increased from the current value of approximately 56% to about 64%, with backfilling done from the surface upon completion of all mining activities. This was achieved without significant ground control problems due to the increased extraction ratio. The mined-out areas were backfilled from the surface with gob, coal combustion by-products (CCBs), and fine coal processing waste (FCPW)-based paste backfill containing 65%-70% solids to minimize short-term and long-term surface deformations risk. This concept has the potential to increase mine productivity, reduce miningmore » costs, manage large volumes of CCBs beneficially, and improve the miner's health, safety, and environment. Two injection holes were drilled over the demonstration panel to inject the paste backfill. Backfilling was started on August 11, 1999 through the first borehole. About 9,293 tons of paste backfill were injected through this borehole with a maximum flow distance of 300-ft underground. On September 27, 2000, backfilling operation was resumed through the second borehole with a mixture of F ash and FBC ash. A high-speed auger mixer (new technology) was used to mix solids with water. About 6,000 tons of paste backfill were injected underground through this hole. Underground backfilling using the ''Groutnet'' flow model was simulated. Studies indicate that grout flow over 300-foot distance is possible. Approximately 13,000 tons of grout may be pumped through a single hole. The effect of backfilling on the stability of the mine workings was analyzed using SIUPANEL.3D computer program and further verified using finite element analysis techniques. Stiffness of the backfill mix is most critical for enhancing the stability of mine workings. Mine openings do not have to be completely backfilled to enhance their stability. Backfill height of about 50% of the seam height is adequate to minimize surface deformations. Freeman United Coal Company performed engineering economic evaluation studies for commercialization. They found that the costs for underground management at the Crown III mine would be slightly higher than surface management at this time. The developed technologies have commercial potential but each site must be analyzed on its merit. The Company maintains significant interest in commercializing the technology.« less

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

PubMed

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.

Roadway backfill method to prevent geohazards induced by room and pillar mining: a case study in Changxing coal mine, China

NASA Astrophysics Data System (ADS)

Zhou, Nan; Li, Meng; Zhang, Jixiong; Gao, Rui

2016-11-01

Coal mines in the western areas of China experience low mining rates and induce many geohazards when using the room and pillar mining method. In this research, we proposed a roadway backfill method during longwall mining to target these problems. We tested the mechanical properties of the backfill materials to determine a reasonable ratio of backfill materials for the driving roadway during longwall mining. We also introduced the roadway layout and the backfill mining technique required for this method. Based on the effects of the abutment stress from a single roadway driving task, we designed the distance between roadways and a driving and filling sequence for multiple-roadway driving. By doing so, we found the movement characteristics of the strata with quadratic stabilization for backfill mining during roadway driving. Based on this research, the driving and filling sequence of the 3101 working face in Changxing coal mine was optimized to avoid the superimposed influence of mining-induced stress. According to the analysis of the surface monitoring data, the accumulated maximum subsidence is 15 mm and the maximum horizontal deformation is 0.8 mm m-1, which indicated that the ground basically had no obvious deformation after the implementation of the roadway backfill method at 3101 working face.

Strength and Permeability Evolution of Compressed Bentonite in Response to Salinity and Temperature Changes

NASA Astrophysics Data System (ADS)

Winnard, B. R.; Mitchell, T. M.; Browning, J.; Cuss, R. J.; Norris, S.; Meredith, P. G.

2017-12-01

Deep geological repositories are the preferred solution to dispose of radioactive waste; design concepts for these disposal facilities include compacted, saturated bentonite as a buffer between waste canister and host rock. Bentonite is favoured for its high swelling capacity, low permeability, and radionuclide retention properties. However, its thermo-hydro-mechanical tolerances must be thoroughly tested to ensure adequate long term performance. Climate variations are likely to induce periods of permafrost, and consequently, changes in groundwater salinity at depth. We performed laboratory experiments investigating effects of temperature and salinity change on uniaxial compressive strength (UCS), and permeability of compacted MX-80 bentonite cylinders. These specimens (moisture content = 22.9±0.1%, dry density = 1.66±0.02 g.cm-3) were compacted with deionised water, and a range of wt% NaCl, CaCl2, or KCl, to compare the effects of compaction fluid. Samples of compressed bentonite were cooled to -20 °C, and heated to 90 ºC, a possible temperature forecast for a repository dependent on factors such as geographical location, waste type, and facility design. Tests were all performed at room temperature, however in situ temperature tests are planned. The UCS of samples that experienced freeze thaw, and 40 ºC treatment failed at 6.5 MPa, with 4% strain, maintaining the same values as untreated bentonite compacted with deionised water. Samples compacted with saline solutions also yielded similar strengths, of 7 MPa, and failed at 4%. However, the 90 ºC, regardless of compaction fluid, failed at 15-18 MPa, at just 2% strain. In all experiments, the spread of strain accommodated varied inconsistently, however, peak stress was uniform. Further experiments into heterogeneity are needed to understand the responsible mechanisms. To obtain permeability, we utilised the pore pressure oscillation (PPO) technique with argon as the pore fluid. We also tested water as the pore fluid to assess the contribution of montmorillonite swelling and compare argon and water permeability. There is potential for salinity to markedly affect permeability, as electrolytes can initiate cation-exchange reactions. Permeability and strength are both key parameters to assess the long term safety of a geological disposal facility.

Preparation and characterization of natural bentonite in to nanoparticles by co-precipitation method

NASA Astrophysics Data System (ADS)

Sirait, Makmur; Bukit, Nurdin; Siregar, Nurdin

2017-01-01

The nanoparticle based on natural bentonite from Pahae village had been prepared using co-precipitation method. Bentonite was dried in the oven at 100°C during a week. Bentonite is crushed using a mortal and milled by planetary ball mill to obtain the powder form. Further, the bentonite powder is activated with chemical reaction by dissolves the 50 g bentonite to 100 ml of HCl at 10 M. The magnetic stirrer was employed to mix the solution at 300 rpm and temperature 70°C. After that, the bentonite solution is washed using distilled water until the pH is neutral. The bentonite powder is calcined at temperature of 600°C for 1 hour with fix increment 150°C. Finally, the powder is given High Energy Milling (HEM) treatment for 30 minutes to obtain the particle size. The X-ray Difractometer (XRD) and Scanning Electron Microscope (SEM) were used to characterize. From the characterization results it is reported that the average of bentonite nanoparticle size is 35.26 nm and the chemical constituents of natural bentonite Pahae are Al, Si, Ca, Fe and Ti.

Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings

PubMed Central

Zhang, Qinli; Xiao, Chongchun; Chen, Xin

2017-01-01

To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72–74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection. PMID:28662072

Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings.

PubMed

Chen, Qiusong; Zhang, Qinli; Xiao, Chongchun; Chen, Xin

2017-01-01

To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72-74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection.

Deformation Monitoring of Waste-Rock-Backfilled Mining Gob for Ground Control

PubMed Central

Zhao, Tongbin; Zhang, Yubao; Zhang, Zhenyu; Li, Zhanhai; Ma, Shuqi

2017-01-01

Backfill mining is an effective option to mitigate ground subsidence, especially for mining under surface infrastructure, such as buildings, dams, rivers and railways. To evaluate its performance, continual long-term field monitoring of the deformation of backfilled gob is important to satisfy strict public scrutiny. Based on industrial Ethernet, a real-time monitoring system was established to monitor the deformation of waste-rock-backfilled gob at −700 m depth in the Tangshan coal mine, Hebei Province, China. The designed deformation sensors, based on a resistance transducer mechanism, were placed vertically between the roof and floor. Stress sensors were installed above square steel plates that were anchored to the floor strata. Meanwhile, data cables were protected by steel tubes in case of damage. The developed system continually harvested field data for three months. The results show that industrial Ethernet technology can be reliably used for long-term data transmission in complicated underground mining conditions. The monitoring reveals that the roof subsidence of the backfilled gob area can be categorized into four phases. The bearing load of the backfill developed gradually and simultaneously with the deformation of the roof strata, and started to be almost invariable when the mining face passed 97 m. PMID:28475168

Deformation Monitoring of Waste-Rock-Backfilled Mining Gob for Ground Control.

PubMed

Zhao, Tongbin; Zhang, Yubao; Zhang, Zhenyu; Li, Zhanhai; Ma, Shuqi

2017-05-05

Backfill mining is an effective option to mitigate ground subsidence, especially for mining under surface infrastructure, such as buildings, dams, rivers and railways. To evaluate its performance, continual long-term field monitoring of the deformation of backfilled gob is important to satisfy strict public scrutiny. Based on industrial Ethernet, a real-time monitoring system was established to monitor the deformation of waste-rock-backfilled gob at -700 m depth in the Tangshan coal mine, Hebei Province, China. The designed deformation sensors, based on a resistance transducer mechanism, were placed vertically between the roof and floor. Stress sensors were installed above square steel plates that were anchored to the floor strata. Meanwhile, data cables were protected by steel tubes in case of damage. The developed system continually harvested field data for three months. The results show that industrial Ethernet technology can be reliably used for long-term data transmission in complicated underground mining conditions. The monitoring reveals that the roof subsidence of the backfilled gob area can be categorized into four phases. The bearing load of the backfill developed gradually and simultaneously with the deformation of the roof strata, and started to be almost invariable when the mining face passed 97 m.

N/Fe-TiO2 doped nanoparticles loaded on bentonite for increased photocatalytic activity for the degradation of organic pollutants

NASA Astrophysics Data System (ADS)

Espenilla, Mel Bryan L.; Magyaya, Ryan Carl S.; Conato, Marlon T.

2018-05-01

Photocatalyst materials based on Philippine bentonite-titanium oxide composites and their ability to degrade organic pollutants is reported. Nanosized-titanium dioxide (TiO2) was synthesized by sol-gel method from titanium tetraisopropoxide. This was then incorporated in the Philippine bentonite via hydrothermal methods. In order to shift the absorbance of the TiO2 to the visible region doping was done using iron and nitrogen ions. The hydrodynamic radius of the synthesized TiO2 was analyzed using a zeta-sizer and was found to be around 70 nm. The photocatalytic efficiency of the TiO2/bentonite, N-TiO2/bentonite, Fe-TiO2/bentonite and N-Fe-TiO2/bentonite was evaluated using a photocatalytic reactor. It was found out that the N-Fe-TiO2/bentonite to be the most efficient with 22% degradation of the model pollutant after 80 minutes. FT-IR analysis was done to determine the bonding of the different components. Scanning electron microscopy and atomic force microscopy analysis was also performed to characterize the products.

Use of a Dual-Structure Constitutive Model for Predicting the Long-Term Behavior of an Expansive Clay Buffer in a Nuclear Waste Repository

DOE PAGES

Vilarrasa, Víctor; Rutqvist, Jonny; Blanco Martin, Laura; ...

2015-12-31

Expansive soils are suitable as backfill and buffer materials in engineered barrier systems to isolate heat-generating nuclear waste in deep geological formations. The canisters containing nuclear waste would be placed in tunnels excavated at a depth of several hundred meters. The expansive soil should provide enough swelling capacity to support the tunnel walls, thereby reducing the impact of the excavation-damaged zone on the long-term mechanical and flow-barrier performance. In addition to their swelling capacity, expansive soils are characterized by accumulating irreversible strain on suction cycles and by effects of microstructural swelling on water permeability that for backfill or buffer materialsmore » can significantly delay the time it takes to reach full saturation. In order to simulate these characteristics of expansive soils, a dual-structure constitutive model that includes two porosity levels is necessary. The authors present the formulation of a dual-structure model and describe its implementation into a coupled fluid flow and geomechanical numerical simulator. The authors use the Barcelona Basic Model (BBM), which is an elastoplastic constitutive model for unsaturated soils, to model the macrostructure, and it is assumed that the strains of the microstructure, which are volumetric and elastic, induce plastic strain to the macrostructure. The authors tested and demonstrated the capabilities of the implemented dual-structure model by modeling and reproducing observed behavior in two laboratory tests of expansive clay. As observed in the experiments, the simulations yielded nonreversible strain accumulation with suction cycles and a decreasing swelling capacity with increasing confining stress. Finally, the authors modeled, for the first time using a dual-structure model, the long-term (100,000 years) performance of a generic heat-generating nuclear waste repository with waste emplacement in horizontal tunnels backfilled with expansive clay and hosted in a clay rock formation. The thermo-hydro-mechanical results of the dual-structure model were compared with those of the standard single-structure BBM. The main difference between the simulation results from the two models is that the dual-structure model predicted a time to fully saturate the expansive clay barrier on the order of thousands of years, whereas the standard single-structure BBM yielded a time on the order of tens of years. These examples show that a dual-structure model, such as the one presented here, is necessary to properly model the thermo-hydro-mechanical behavior of expansive soils.« less

A novel silica alumina-based backfill material composed of coal refuse and fly ash.

PubMed

Yao, Yuan; Sun, Henghu

2012-04-30

In this paper, a systematic study was conducted to investigate a novel silica alumina-based backfill material composed of coal refuse and fly ash. The coal refuse and fly ash had different properties under various thermal activation temperatures (20 °C, 150 °C, 350 °C, 550 °C, 750 °C and 950 °C). It is known that a thermal activation temperature ranging from 20 °C to 950 °C significantly increases the flowability and pozzolanic properties of the coal refuse; however, the flowability of fly ash decreases when the activation temperature is higher than 550 °C because of a severe agglomeration phenomenon on its surface. An optimal design for this backfill material was determined to include an activated portion composed of 5% coal refuse at 750 °C and 15% fly ash at 20 °C. This combination yields the best performance with excellent flowability, a high compressive strength and a low bleeding rate. The microanalysis results corresponded well with the performance tests at different activation conditions. In the coal refuse, kaolinite peaks began to decrease because of their transformation into metakaolin at 550 °C. Chlorite peaks disappeared at 750 °C. Muscovite peaks decreased at 750 °C and disappeared at 950 °C. During this process, muscovite 2M(1) gradually dehydroxylated to muscovite HT. Furthermore, this paper examined the environmental acceptance and economic feasibility of this technology and found that this silica alumina-based backfill material composed of coal refuse and fly ash not only meets EPA requirements but also has several advantages in industry feasibility when compared with hydraulic backfill, rock backfill and paste backfill. Published by Elsevier B.V.

Dielectric characterization of Bentonite clay at various moisture contents and with mixtures of biomass in the microwave spectrum

USDA-ARS?s Scientific Manuscript database

This study assesses the potential for using bentonite as a microwave absorber for microwave-assisted biomass pyrolysis based on the dielectric properties. Dielectric properties of bentonite at different moisture contents were measured using a coaxial line dielectric probe and vector network analyzer...

The Use of Modified Bentonite for Removal of Aromatic Organics from Contaminated Soil.

PubMed

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.

Investigating the Potential Barrier Function of Nanostructured Materials Formed in Engineered Barrier Systems (EBS) Designed for Nuclear Waste Isolation.

PubMed

Cuevas, Jaime; Ruiz, Ana Isabel; Fernández, Raúl

2018-02-21

Clay and cement are known nano-colloids originating from natural processes or traditional materials technology. Currently, they are used together as part of the engineered barrier system (EBS) to isolate high-level nuclear waste (HLW) metallic containers in deep geological repositories (DGR). The EBS should prevent radionuclide (RN) migration into the biosphere until the canisters fail, which is not expected for approximately 10 3  years. The interactions of cementitious materials with bentonite swelling clay have been the scope of our research team at the Autonomous University of Madrid (UAM) with participation in several European Union (EU) projects from 1998 up to now. Here, we describe the mineral and chemical nature and microstructure of the alteration rim generated by the contact between concrete and bentonite. Its ability to buffer the surrounding chemical environment may have potential for further protection against RN migration. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of fracture resistance of simulated immature teeth with an open apex using Biodentine and composite resin: An in vitro study.

PubMed

Zhabuawala, Murtuza Saifuddin; Nadig, Roopa R; Pai, Veena S; Gowda, Yashwanth

2016-01-01

To evaluate the fracture resistance in simulated immature teeth that had been backfilled using composite resin and Biodentine after using Biodentine as an apical plug material immediately and after 3 months of aging. Sixty extracted human maxillary central incisors were simulated in an immature open apex. The roots of all the specimens were then standardized to a length of 10 mm and canals were instrumented to obtain the radicular dentin thickness around 1.5 mm. All the specimens were then randomly divided into three groups of twenty teeth each. Group I (control) - 4 mm apical plug of Biodentine backfilled with thermoplasticized gutta-percha. Group II - 4 mm apical plug of Biodentine and then backfilled with ParaCore. Group III - completely filled with Biodentine. Ten samples from each group were randomly divided into two subgroups. In subgroup A: Specimens were stored for 1 week. In subgroup B: Specimens were stored in phosphate-buffered saline solution for 3 months and were subjected to universal testing machine. Statistical analysis was done using one-way analysis. No significant difference in fracture resistance between the groups was observed when tested immediately. After 3 months of aging, only Biodentine group showed a significant reduction in fracture resistance without significant reduction with other two groups. Biodentine group has shown a drastic reduction in fracture resistance after 3 months of aging, and hence cannot be recommended as a reinforcement material in immature teeth with thin dentin walls.

Bentonite deposits of the northern Black Hills district, Wyoming, Montana, and South Dakota

USGS Publications Warehouse

Knechtel, Maxwell M.; Patterson, Sam H.

1962-01-01

The northern Black Hills bentonite mining district includes parts of Crook County, Wyo., Carter County, Mont., and Butte County, S. Dak. Within this district, many beds of bentonite occur interspersed with sedimentary strata of Cretaceous age that have an average total thickness of about 3,000 feet and consist chiefly of marine shale, marl, and argillaceous sandstone. The bentonite beds occur in formations ranging upward from the Newcastle sandstone to the lower part of the Mitten black shale member of the Pierre shale. Tertiary (?) and Quaternary deposits of gravel, sand, and silt are present on extensive terraces, and deposits of such materials also extend along stream courses in all parts of the district. The overall geologic structure of the district is that of a broad northwestward- plunging anticline, in which the strata dip gently toward the northeast, north, and northwest. The overall structure is interrupted, however, by several subordinate folds which bring the bentonite beds to the surface repeatedly, so that large resources of bentonite are present under light overburden. The northern Black Hills district is an important source of commercial gel-forming sodium-type bentonite. During the period 1941-56 more than 5 million tons of raw bentonite was mined, most of which came from the Clay Spur bed near the top of the Mowry shale; a few thousand tons was mined from bed A in the Newcastle sandstone. Calcium-type bentonite occurs in bed B in the Mowry shale and in bed I at the base of the Mitten black shale member. Seven other beds are sufficiently thick and continuous to warrant consideration as prospective sources of bentonite for industrial use. Most of the bentonite produced is sold for use (a) as an ingredient of drilling mud; (b) for preparing metallurgical molding sand of superior dry strength; and (c) for the bonding material used in pelletizing taconite iron ore of the Lake Superior region. The results of drilling-mud and foundry-sand bonding-clay tests of several hundred samples, as well as analyses of selected samples, chiefly by X-ray, differential thermal, base exchange and spectrographic methods, are included in this report.

Progress Toward a Compact, Highly Stable Ion Clock

NASA Technical Reports Server (NTRS)

Prestage, John; Chung, Sang

2009-01-01

There was an update on the subject of two previous NASA Tech Briefs articles: Compact, Highly Stable Ion Clock (NPO-43075), Vol. 32, No. 5 (May 2008), page 63; and Neon as a Buffer Gas for a Mercury-Ion Clock (NPO-42919), Vol. 32, No. 7 (July 2008), page 62. To recapitulate: A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump maintains the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a neon buffer gas. There was progress in the development of the clock, with emphasis on the design, fabrication, pump-down, and bake-out of the vacuum tube (based on established practice in the travelingwave- tube-amplifier industry) and the ability of the tube to retain a vacuum after a year of operation. Other developments include some aspects of the operation of mercury-vapor source (a small appendage oven containing HgO) so as to maintain the optimum low concentration of mercury vapor, and further efforts to miniaturize the vacuum and optical subsystems to fit within a volume of 2 L.

Dustiness behaviour of loose and compacted Bentonite and organoclay powders: What is the difference in exposure risk?

NASA Astrophysics Data System (ADS)

Jensen, Keld Alstrup; Koponen, Ismo Kalevi; Clausen, Per Axel; Schneider, Thomas

2009-01-01

Single-drop and rotating drum dustiness testing was used to investigate the dustiness of loose and compacted montmorillonite (Bentonite) and an organoclay (Nanofil®5), which had been modified from montmorillonite-rich Bentonite. The dustiness was analysed based on filter measurements as well as particle size distributions, the particle generation rate, and the total number of generated particles. Particle monitoring was completed using a TSI Fast Mobility Particle Sizer (FMPS) and a TSI Aerosol Particle Sizer (APS) at 1 s resolution. Low-pressure uniaxial powder compaction of the starting materials showed a logarithmic compaction curve and samples subjected to 3.5 kg/cm2 were used for dustiness testing to evaluate the role of powder compaction, which could occur in powders from large shipments or high-volume storage facilities. The dustiness tests showed intermediate dustiness indices (1,077-2,077 mg/kg powder) in tests of Nanofil®5, Bentonite, and compacted Bentonite, while a high-level dustiness index was found for compacted Nanofil®5 (3,487 mg/kg powder). All powders produced multimodal particle size-distributions in the dust cloud with one mode around 300 nm (Bentonite) or 400 nm (Nanofil®5) as well as one (Nanofil®5) or two modes (Bentonite) with peaks between 1 and 2.5 μm. The dust release was found to occur either as a burst (loose Bentonite and Nanofil®5), constant rate (compacted Nanofil®5), or slowly increasing rate (compacted Bentonite). In rotating drum experiments, the number of particles generated in the FMPS and APS size-ranges were in general agreement with the mass-based dustiness index, but the same order was not observed in the single-drop tests. Compaction of Bentonite reduced the number of generated particles with app. 70 and 40% during single-drop and rotating drum dustiness tests, respectively. Compaction of Nanofil®5 reduced the dustiness in the single-drop test, but it was more than doubled in the rotating drum test. Physically relevant low-pressure compaction may reduce the risk of particle exposure if powders are handled in operations with few agitations such as pouring or tapping. Repeated agitation, e.g., mixing, of these compacted powders, would result in reduced (app. 20% for Bentonite) or highly increased (app. 225% for Nanofil®5) dustiness and thereby alter the exposure risk significantly.

Colloidal behavior of aqueous montmorillonite suspensions in the presence of non-ionic polymer

NASA Astrophysics Data System (ADS)

Gareche, M.; Azri, N.; Allal, A.; Zeraibi, N.

2015-04-01

In this paper we characterized at first, the rheological behavior of the bentonite suspensions and the aqueous solutions of polyethylene oxide (PEO), then we were investigated the influence of this polymer in a water-based drilling fluid model (6% of bentonite suspension). The objective is to exhibit how the non ionic polymer with molecular weight 6×103 g/mol. of varying concentration mass (0.7%, 1%, 2% et 3%) significantly alter the rheological properties (yield stress, viscosity, loss and elastic modulus) of the bentonite suspensions. The rheological measurements made in simple shear and in dynamic on the mixture (water-bentonite-PEO), showed rheological properties of bentonite suspensions both in the presence and absence of non-ionic polymer. The PEO presents an affinity for the bentonite particles slowing down their kinetic aggregation. The analysis by X-rays diffraction also allowed understanding the structure of this mixture. It had revealed the intercalation between of the clay platelets on one hand, and the links bridges assured by the chains of polymer between bentonite particles beyond a critical concentration in PEO on the other hand. The Herschel- Bulkley rheological model is used for the correlation of our experimental results.

Preparation and characterization Al3+-bentonite Turen Malang for esterification fatty acid (palmitic acid, oleic acid and linoleic acid)

NASA Astrophysics Data System (ADS)

Abdulloh, Abdulloh; Aminah, Nanik Siti; Triyono, Mudasir, Trisunaryanti, Wega

2016-03-01

Catalyst preparation and characterization of Al3+-bentonite for esterification of palmitic acid, oleic acid and linoleic acid has been done. Al3+-bentonite catalyst was prepared from natural bentonite of Turen Malang through cation exchange reaction using AlCl3 solution. The catalysts obtained were characterized by XRD, XRF, pyridine-FTIR and surface area analyser using the BET method. Catalyst activity test of Al3+-bentonite for esterification reaction was done at 65°C using molar ratio of metanol-fatty acid of 30:1 and 0.25 g of Al3+-bentonite catalyst for the period of ½, 1, 2, 3, 4 and 5 hours. Based on the characterization results, the Al3+-bentonite Turen Malang catalyst has a d-spacing of 15.63 Ǻ, acid sites of Brönsted and Lewis respectively of 230.79 µmol/g and 99.39 µmol/g, surface area of 507.3 m2/g and the average of radius pore of 20.09 Å. GC-MS analysis results of the oil phase after esterification reaction showed the formation of biodiesel (FAME: Fatty acid methyl ester), namely methyl palmitate, methyl oleate and methyl linoleate. The number of conversions resulted in esterification reaction using Al3+-bentonite Turen Malang catalyst was 74.61%, 37.75%, and 20, 93% for the esterification of palmitic acid, oleic acid and linoleic acid respectively.

Modeling transient heat transfer in nuclear waste repositories.

PubMed

Yang, Shaw-Yang; Yeh, Hund-Der

2009-09-30

The heat of high-level nuclear waste may be generated and released from a canister at final disposal sites. The waste heat may affect the engineering properties of waste canisters, buffers, and backfill material in the emplacement tunnel and the host rock. This study addresses the problem of the heat generated from the waste canister and analyzes the heat distribution between the buffer and the host rock, which is considered as a radial two-layer heat flux problem. A conceptual model is first constructed for the heat conduction in a nuclear waste repository and then mathematical equations are formulated for modeling heat flow distribution at repository sites. The Laplace transforms are employed to develop a solution for the temperature distributions in the buffer and the host rock in the Laplace domain, which is numerically inverted to the time-domain solution using the modified Crump method. The transient temperature distributions for both the single- and multi-borehole cases are simulated in the hypothetical geological repositories of nuclear waste. The results show that the temperature distributions in the thermal field are significantly affected by the decay heat of the waste canister, the thermal properties of the buffer and the host rock, the disposal spacing, and the thickness of the host rock at a nuclear waste repository.

Excavation Induced Hydraulic Response of Opalinus Clay - Investigations of the FE-Experiment at the Mont Terri URL in Switzerland

NASA Astrophysics Data System (ADS)

Vogt, T.; Müller, H. R.; Garitte, B.; Sakaki, T.; Vietor, T.

2013-12-01

The Full-Scale Emplacement (FE) Experiment at the Mont Terri underground research laboratory in Switzerland is a full-scale heater test in a clay-rich formation (Opalinus Clay). Based on the Swiss disposal concept it simulates the construction, emplacement, backfilling, and post-closure thermo-hydro-mechanical (THM) evolution of a spent fuel / vitrified high-level waste (SF / HLW) repository tunnel in a realistic manner. The main aim of this experiment is to investigate SF / HLW repository-induced THM coupled effects mainly in the host rock but also in the engineered barrier system (EBS), which consists of bentonite pellets and blocks. A further aim is to gather experience with full-scale tunnel construction and associated hydro-mechanical (HM) processes in the host rock. The entire experiment implementation (in a 50 m long gallery with approx. 3 m diameter) as well as the post-closure THM evolution will be monitored using a network of several hundred sensors (state-of-the-art sensors and measurement systems as well as fiber-optic sensors). The sensors are distributed in the host rock's near- and far-field, the tunnel lining, the EBS, and on the heaters. The heater emplacement and backfilling has not started yet, therefore only the host rock instrumentation is installed at the moment and is currently generating data. We will present the instrumentation concept and rationale as well as the first monitoring results of the excavation and ventilation phase. In particular, we investigated the excavation induced hydraulic response of the host rock. Therefore, the spatiotemporal evolution of porewater-pressure time series was analyzed to get a better understanding of HM coupled processes during and after the excavation phase as well as the impact of anisotropic geomechanic and hydraulic properties of the clay-rich formation on its hydraulic behavior. Excavation related investigations were completed by means of inclinometer data to characterize the non-elastic and time-dependent deformations. In addition, we evaluated the effect of drainage and suction processes during the ventilation phase on the pressure distribution in the host rock. Based on our results the conceptual models of HM processes and hydraulic behavior of clay rich formations during excavation and ventilation phases could be improved.

Water Migration and Swelling in Bentonite Quantified using Neutron Radiography

NASA Astrophysics Data System (ADS)

Vial, A.; DiStefano, V. H.; Perfect, E.; Hale, R. E.; Anovitz, L. M.; McFarlane, J.

2016-12-01

Permanent disposal of radioactive waste remains a critical challenge for the nation's energy future. All disposal system concepts include interfaces between engineered systems and natural materials requiring extensive characterization. Bentonite is often used to buffer subsurface disposal systems from geologic media containing ground water. Bentonite characterization experiments were carried out using the CG-1D neutron imaging beam line at Oak Ridge National Laboratory. Dry bentonite was packed into vertically-oriented aluminum cylinders. Water was ponded on the top surface of each packed cylinder. Images were acquired at 2 min intervals using dynamic neutron radiography. The detector consisted of stacked neutron sensitive microchannel plates above a quad Timepix readout with a 28 x 28 mm2 field of view. The spatial resolution of the detector was 55 μm. Raw neutron radiographs were imported into ImageJ and normalized with respect to the initial completely dry state. The wetting process was 1-dimensional, and vertical intensity profiles were computed by averaging pixel rows. The vertical distance between the clay-water interface and the wetting front could then be determined as a function of time. Depth of water infiltration increased linearly with the square root of time, yielding a sorptivity value of 0.75 (± 0.070) mm/min0.5. Swelling occurred in the form of upward movement of clay particles into the ponded water over time. The resulting low density assemblage was discernable by normalizing the raw profiles with respect to the intensity profile immediately after ponding. The packed clay-water interface was clearly visible in the normalized profiles, and swelling was quantified as the height of the low density assemblage above the original interface. Swelling occurred as a linear function of time, at a rate of 0.054 (± 0.020) mm/min. Further experiments of this type are planned under variable temperature and pressure regimes applicable to subsurface repositories.

Experimental Study on the Coupling Mechanism of Early-strength Backfill and Rock

NASA Astrophysics Data System (ADS)

Wang, Mingxu

2017-11-01

In order to study the interaction mechanism between the ore rock and backfill at the early stage, paraffin is chosen as the cementing agent. Based on the damage mechanics and fractal theory, the interaction mechanism between the ore rock and backfill is characterized by the relevant tests on the complex of proportioned ore rock and backfill with resistance strain gauge, crack propagation, microscopic imaging and AE. The experimental results showed that: 1) Through the axial loading test, compared with the early strength of the cemented filling and paraffin mechanical deformation characteristics, the stress and strain curves of the two had a common linear deformation law, while in the early strength of the filling elastic capacity strong, with a certain degree of resilience. 2) The bearing capacity of the backfill was weak, but the deformation ability was strong. During the bearing process, the deformation of the upper load was mainly caused by the ore rock, which leaded to the damage of the rock. 3) The distribution of AE points during the co-carrying of the filling and the ore rock was monitored by the acoustic emission instrument. The damage occurred mainly in the contact zone between the backfill and the ore rock zone. The corresponding AE point distribution also validated the crack happening.

Rheological behavior of clay-nanoparticle hybrid-added bentonite suspensions: specific role of hybrid additives on the gelation of clay-based fluids.

PubMed

Jung, Youngsoo; Son, You-Hwan; Lee, Jung-Kun; Phuoc, Tran X; Soong, Yee; Chyu, Minking K

2011-09-01

Two different types of clay nanoparticle hybrid, iron oxide nanoparticle clay hybrid (ICH) and Al(2)O(3)-SiO(2) nanoparticle clay hybrid (ASCH), were synthesized and their effects on the rheological properties of aqueous bentonite fluids in steady state and dynamic state were explored. When ICH particles were added, bentonite particles in the fluid cross-link to form relatively well-oriented porous structure. This is attributed to the development of positively charged edge surfaces in ICH that leads to strengthening of the gel structure of the bentonite susensions. The role of ASCH particles on the interparticle association of the bentonite fluids is different from that of ICH and sensitive to pH. As pH of ASCH-added bentonite suspensions increased, the viscosity, yield stress, storage modulus, and flow stress decreased. In contrast, at low pH, the clay suspensions containing ASCH additives were coagulated and their rheological properties become close to those of ICH added bentonite fluids. A correlation between the net surface charge of the hybrid additives and the rheological properties of the fluids indicates that the embedded nanoparticles within the interlayer space control the variable charge of the edge surfaces of the platelets and determine the particles association behavior of the clay fluids.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vilarrasa, Víctor; Rutqvist, Jonny; Blanco Martin, Laura

Expansive soils are suitable as backfill and buffer materials in engineered barrier systems to isolate heat-generating nuclear waste in deep geological formations. The canisters containing nuclear waste would be placed in tunnels excavated at a depth of several hundred meters. The expansive soil should provide enough swelling capacity to support the tunnel walls, thereby reducing the impact of the excavation-damaged zone on the long-term mechanical and flow-barrier performance. In addition to their swelling capacity, expansive soils are characterized by accumulating irreversible strain on suction cycles and by effects of microstructural swelling on water permeability that for backfill or buffer materialsmore » can significantly delay the time it takes to reach full saturation. In order to simulate these characteristics of expansive soils, a dual-structure constitutive model that includes two porosity levels is necessary. The authors present the formulation of a dual-structure model and describe its implementation into a coupled fluid flow and geomechanical numerical simulator. The authors use the Barcelona Basic Model (BBM), which is an elastoplastic constitutive model for unsaturated soils, to model the macrostructure, and it is assumed that the strains of the microstructure, which are volumetric and elastic, induce plastic strain to the macrostructure. The authors tested and demonstrated the capabilities of the implemented dual-structure model by modeling and reproducing observed behavior in two laboratory tests of expansive clay. As observed in the experiments, the simulations yielded nonreversible strain accumulation with suction cycles and a decreasing swelling capacity with increasing confining stress. Finally, the authors modeled, for the first time using a dual-structure model, the long-term (100,000 years) performance of a generic heat-generating nuclear waste repository with waste emplacement in horizontal tunnels backfilled with expansive clay and hosted in a clay rock formation. The thermo-hydro-mechanical results of the dual-structure model were compared with those of the standard single-structure BBM. The main difference between the simulation results from the two models is that the dual-structure model predicted a time to fully saturate the expansive clay barrier on the order of thousands of years, whereas the standard single-structure BBM yielded a time on the order of tens of years. These examples show that a dual-structure model, such as the one presented here, is necessary to properly model the thermo-hydro-mechanical behavior of expansive soils.« less

Interaction of acid mine drainage with Ordinary Portland Cement blended solid residues generated from active treatment of acid mine drainage with coal fly ash.

PubMed

Gitari, Wilson M; Petrik, Leslie F; Key, David L; Okujeni, Charles

2011-01-01

Fly ash (FA) has been investigated as a possible treatment agent for Acid mine drainage (AMD) and established to be an alternative, cheap and economically viable agent compared to the conventional alkaline agents. However, this treatment option also leads to generation of solid residues (SR) that require disposal and one of the proposed disposal method is a backfill in coal mine voids. In this study, the interaction of the SR with AMD that is likely to be present in such backfill scenario was simulated by draining columns packed with SR and SR + 6% Ordinary Portland Cement (OPC) unsaturated with simulated AMD over a 6 month period. The evolving geochemistry of the liquid/solid (L/S) system was evaluated in-terms of the mineral phases likely or controlling contaminants attenuation at the different pH regimes generated. Stepwise acidification of the percolates was observed as the drainage progressed. Two pH buffer zones were observed (7.5-9 and 3-4) for SR and (11.2-11.3 and 3.5-4) for SR + 6% OPC. The solid residue cores (SR) appeared to have a significant buffering capacity, maintaining a neutral to slightly alkaline pH in the leachates for an extended period of time (97 days: L/S 4.3) while SR + 6% OPC reduced this neutralization capacity to 22 days (L/S 1.9). Interaction of AMD with SR or SR + 6% OPC generated alkaline conditions that favored precipitation of Fe, Al, Mn-(oxy) hydroxides, Fe and Ca-Al hydroxysulphates that greatly contributed to the contaminants removal. However, precipitation of these phases was restricted to the pH of the leachates remaining at neutral to circum-neutral levels. Backfill of mine voids with SR promises to be a feasible technology for the disposal of the SR but its success will greatly depend on the disposal scenario, AMD generated and the alkalinity generating potential of the SR. A disadvantage would be the possible re-dissolution of the precipitated phases at pH < 4 that would release the contaminants back to the water column. However extrapolation of this concept to a field scenario can greatly enhance beneficial application of fly ash (FA) and solid residues (SR) generated from treatment of AMD.

Backfilled, self-assembled monolayers and methods of making same

DOEpatents

Fryxell, Glen E [Kennewick, WA; Zemanian, Thomas S [Richland, WA; Addleman, R Shane [Benton City, WA; Aardahl, Christopher L [Sequim, WA; Zheng, Feng [Richland, WA; Busche, Brad [Raleigh, NC; Egorov, Oleg B [West Richland, WA

2009-06-30

Backfilled, self-assembled monolayers and methods of making the same are disclosed. The self-assembled monolayer comprises at least one functional organosilane species and a substantially random dispersion of at least one backfilling organosilane species among the functional organosilane species, wherein the functional and backfilling organosilane species have been sequentially deposited on a substrate. The method comprises depositing sequentially a first organosilane species followed by a backfilling organosilane species, and employing a relaxation agent before or during deposition of the backfilling organosilane species, wherein the first and backfilling organosilane species are substantially randomly dispersed on a substrate.

The Lower Silurian Osmundsberg K-bentonite. Part I: Stratigraphic position, distribution, and palaeogeographic significance

USGS Publications Warehouse

Bergstrom, Stig M.; Huff, W.D.; Kolata, Dennis R.

1998-01-01

A large number of Lower Silurian (Llandovery) K-bentonite beds have been recorded from northwestern Europe, particularly in Baltoscandia and the British Isles, but previous attempts to trace single beds regionally have yielded inconclusive results. The present study suggests that based on its unusual thickness, stratigraphic position and trace element geochemistry, one Telychian ash bed, the Osmundsberg K-bentonite, can be recognized at many localities in Estonia, Sweden and Norway and probably also in Scotland and Northern Ireland. This bed, which is up to 115 cm thick, is in the lower-middle turriculatus Zone. The stratigraphic position, thickness variation and geographic distribution of the Osmundsberg K-bentonite are illustrated by means of 12 selected Llandovery successions in Sweden, Estonia, Norway, Denmark, Scotland and Northern Ireland. In Baltoscandia, the Osmundsberg K-bentonite shows a trend of general thickness increase in a western direction suggesting that its source area was located in the northern Iapetus region between Baltica and Laurentia. Because large-magnitude ash falls like the one that produced the Osmundsberg K-bentonite last at most a few weeks, such an ash bed may be used as a unique time-plane for a variety of regional geological and palaeontological studies.

Correlation of Mohawkian (Ordovician) K-bentonites in post-Black River rocks of Ohio, Kentucky, and Michigan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schumacher, G.A.; Carlton, R.W.; Bergstroem, S.M.

1992-01-01

One to 10 K-bentonites are recognized in the Curdsville and Logana Members of the Lexington Limestone of Kentucky and southwestern Ohio and in coeval strata in west-central and northwestern Ohio and southeastern Michigan. These beds occur in the Phragmodus undatus and Amorphognathus tyaerensis conodont zones and the Orthograptus ruedemanni and Climacograptus spiniferus graptolite zones. Individual beds range in thickness from 1 mm to 30 cm and occur 16 cm to 19 m above the base of the Lexington Limestone and equivalents. Seventy-five percent of the observed K-bentonites occur in three narrow stratigraphic intervals. Some K-bentonites are traceable over parts ofmore » Ohio but insufficient data from northern Kentucky and west-central Ohio complicate regional lithostratigraphic correlation. Conodont biostratigraphy suggests that each k-bentonite complex is correlative regionally. Most conodont species range throughout all, or most, of the study interval but the ranges of Belodina compressa, Polyplacognathus ramosus, and Amorphognathus tyaerensis show only minor overlap. Preliminary correlation suggests that the oldest K- bentonite complex occurs in the interval characterized by B. compressa, the second complex in the P. Ramosus interval, and the third complex in the A. tyaerensis interval. This study provides the basis for potential correlation with coeval K-bentonites in areas outside of the study area. Also it provides an enhanced understanding of the lithostratigraphy and conodont biofacies of this complex stratigraphic interval. The K-bentonite succession also adds information on the timing of the initiation of the Sebree Trough.« less

Removal of phenols from water accompanied with synthesis of organobentonite in one-step process.

PubMed

Ma, Jianfeng; Zhu, Lizhong

2007-08-01

A novel technology of wastewater treatment was proposed based on simultaneously synthesis of organobentonite and removal of organic pollutants such as phenols from water in one-step, which resulted that both surfactants and organic pollutants were removed from water by bentonite. The effects of contact time, pH and inorganic salt on the removal of phenols were investigated. Kinetic results showed that phenols and cetyltrimethylammonium bromide (CTMAB) could be removed by bentonite in 25 min. The removal efficiencies were achieved at 69%, 92% and 99%, respectively, for phenol, p-nitrophenol and beta-naphthol at the initial amount of CTMAB at about 120% cation exchange capacity of bentonite. Better dispersion property and more rapid bentonite sedimentation were observed in the process. The results indicated that the one-step process is an efficient, simple and low cost technology for removal of organic pollutants and cationic surfactants from water. The proposed technology made it possible that bentonite was applied as sorbent for wastewater treatment in industrial scale.

Implementation of Paste Backfill Mining Technology in Chinese Coal Mines

PubMed Central

Chang, Qingliang; Zhou, Huaqiang; Bai, Jianbiao

2014-01-01

Implementation of clean mining technology at coal mines is crucial to protect the environment and maintain balance among energy resources, consumption, and ecology. After reviewing present coal clean mining technology, we introduce the technology principles and technological process of paste backfill mining in coal mines and discuss the components and features of backfill materials, the constitution of the backfill system, and the backfill process. Specific implementation of this technology and its application are analyzed for paste backfill mining in Daizhuang Coal Mine; a practical implementation shows that paste backfill mining can improve the safety and excavation rate of coal mining, which can effectively resolve surface subsidence problems caused by underground mining activities, by utilizing solid waste such as coal gangues as a resource. Therefore, paste backfill mining is an effective clean coal mining technology, which has widespread application. PMID:25258737

Implementation of paste backfill mining technology in Chinese coal mines.

PubMed

Chang, Qingliang; Chen, Jianhang; Zhou, Huaqiang; Bai, Jianbiao

2014-01-01

Implementation of clean mining technology at coal mines is crucial to protect the environment and maintain balance among energy resources, consumption, and ecology. After reviewing present coal clean mining technology, we introduce the technology principles and technological process of paste backfill mining in coal mines and discuss the components and features of backfill materials, the constitution of the backfill system, and the backfill process. Specific implementation of this technology and its application are analyzed for paste backfill mining in Daizhuang Coal Mine; a practical implementation shows that paste backfill mining can improve the safety and excavation rate of coal mining, which can effectively resolve surface subsidence problems caused by underground mining activities, by utilizing solid waste such as coal gangues as a resource. Therefore, paste backfill mining is an effective clean coal mining technology, which has widespread application.

Study on HDPE Mixed with Sand as Backfilled Material on Retaining Structure

NASA Astrophysics Data System (ADS)

Talib, Z. A.

2018-04-01

The failure of the retaining wall is closely related to backfill material. Granular soils such as sand and gravel are most suitable backfill material because of its drainage properties. However two basic materials are quite heavy and contribute high amount of lateral loads. This study was to determine the effectiveness High Density Polyethylene (HDPE) as a backfill material. HDPE has a lighter weight compare to the sand. It makes HDPE has potential to be used as backfill material. The objective of this study is to identify the most effective percentage of HDPE to replace sand as a backfill material. The percentage of HDPE used in this study was 20%, 30%, 50%, 75% and also 100%. Testing involved in this study were sieve analysis test, constant head permeability test, direct shear test and relative density test. The result shows that the HDPE can be used as backfilled material and save the cost of backfill material

NMR imaging and cryoporometry of swelling clays

NASA Astrophysics Data System (ADS)

Dvinskikh, Sergey V.; Szutkowski, Kosma; Petrov, Oleg V.; Furó, István.

2010-05-01

Compacted bentonite clay is currently attracting attention as a promising "self-sealing" buffer material to build in-ground barriers for the encapsulation of radioactive waste. It is expected to fill up the space between waste canister and surrounding ground by swelling and thus delay flow and migration from the host rock to the canister. In environmental sciences, evaluation and understanding of the swelling properties of pre-compacted clay are of uttermost importance for designing such buffers. Major goal of present study was to provide, in a non-invasive manner, a quantitative measure of bentonite distribution in extended samples during different physical processes in an aqueous environment such as swelling, dissolution, and sedimentation on the time scale from minutes to years. The propagation of the swelling front during clay expansion depending on the geometry of the confining space was also studied. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were adapted and used as main experimental techniques. With this approach, spatially resolved movement of the clay/water interface as well as clay particle distributions in gel phase can be monitored [1]. Bulk samples with swelling in a vertical tube and in a horizontal channel were investigated and clay content distribution profiles in the concentration range over five orders of magnitude and with sub-millimetre spatial resolution were obtained. Expansion rates for bulk swelling and swelling in narrow slits were compared. For sodium-exchanged montmorillonite in contact with de-ionised water, we observed a remarkable acceleration of expansion as compared to that obtained in the bulk. To characterize the porosity of the clay a cryoporometric study [2] has been performed. Our results have important implications to waste repository designs and for the assessment of its long-term performance. Further research exploring clay-water interaction over a wide variety of clay composition and water ionic strength as well as investigating the effect of the confining geometry and material surface properties seem to be worth to pursue. Acknowledgements: This work has been supported by the Swedish Nuclear Fuel and Waste Management Co (SKB) and the Swedish Research Council VR. References: [1] Dvinskikh S. V., Szutkowski K., Furó I. MRI profiles over a very wide concentration ranges: application to swelling of a bentonite clay. J. Magn. Reson. 198, 146 (2009). [2] Petrov O. V., Furó I. NMR cryoporometry: Principles, applications and potential. Prog. Nucl. Magn. Reson. Spec. 54, 97 (2009).

Reinforced cassava starch based edible film incorporated with essential oil and sodium bentonite nanoclay as food packaging material.

PubMed

Iamareerat, Butsadee; Singh, Manisha; Sadiq, Muhammad Bilal; Anal, Anil Kumar

2018-05-01

Biodegradable packaging in food materials is a green technology based novel approach to replace the synthetic and conventional packaging systems. This study is aimed to formulate the biodegradable cassava starch based films incorporated with cinnamon essential oil and sodium bentonite clay nanoparticles. The films were characterized for their application as a packaging material for meatballs. The cassava starch films incorporated with sodium bentonite and cinnamon oil showed significant antibacterial potential against all test bacteria; Escherichia coli , Salmonella typhimurium and Staphylococcus aureus. Antibacterial effect of films increased significantly when the concentration of cinnamon oil was increased. The cassava starch film incorporated with 0.75% (w/w) sodium bentonite, 2% (w/w) glycerol and 2.5% (w/w) cinnamon oil was selected based on physical, mechanical and antibacterial potential to evaluate shelf life of meatballs. The meatballs stored at ambient temperature in cassava starch film incorporated with cinnamon oil and nanoclay, significantly inhibited the microbial growth till 96 h below the FDA limits (10 6  CFU/g) in foods compared to control films that exceeded above the limit within 48 h. Hence cassava starch based film incorporated with essential oils and clay nanoparticles can be an alternate approach as a packaging material for food industries to prolong the shelf life of products.

Prediction of unsaturated flow and water backfill during infiltration in layered soils

NASA Astrophysics Data System (ADS)

Cui, Guotao; Zhu, Jianting

2018-02-01

We develop a new analytical infiltration model to determine water flow dynamics around layer interfaces during infiltration process in layered soils. The model mainly involves the analytical solutions to quadratic equations to determine the flux rates around the interfaces. Active water content profile behind the wetting front is developed based on the solution of steady state flow to dynamically update active parameters in sharp wetting front infiltration equations and to predict unsaturated flow in coarse layers before the front reaches an impeding fine layer. The effect of water backfill to saturate the coarse layers after the wetting front encounters the impeding fine layer is analytically expressed based on the active water content profiles. Comparison to the numerical solutions of the Richards equation shows that the new model can well capture water dynamics in relation to the arrangement of soil layers. The steady state active water content profile can be used to predict the saturation state of all layers when the wetting front first passes through these layers during the unsteady infiltration process. Water backfill effect may occur when the unsaturated wetting front encounters a fine layer underlying a coarse layer. Sensitivity analysis shows that saturated hydraulic conductivity is the parameter dictating the occurrence of unsaturated flow and water backfill and can be used to represent the coarseness of soil layers. Water backfill effect occurs in coarse layers between upper and lower fine layers when the lower layer is not significantly coarser than the upper layer.

Evaluation of the endotoxin binding efficiency of clay minerals using the Limulus Amebocyte lysate test: an in vitro study

PubMed Central

2014-01-01

Endotoxins are part of the cell wall of Gram-negative bacteria. They are potent immune stimulators and can lead to death if present in high concentrations. Feed additives, which bind endotoxins in the gastrointestinal tract of animals, could help to prevent their negative impact. The objective of our study was to determine the potential of a bentonite (Bentonite 1), a sodium bentonite (Bentonite 2), a chemically treated smectite (Organoclay 1) and a modified attapulgite (Organoclay 2) to bind endotoxins in vitro. Polymyxin B served as positive control. The kinetic chromogenic Limulus Amebocyte lysate test was adapted to measure endotoxin activity. Firstly, a single sorption experiment (10 endotoxin units/mL (EU/mL)) was performed. Polymyxin B and organoclays showed 100% binding efficiency. Secondly, the adsorption efficiency of sorbents in aqueous solution with increasing endotoxin concentrations (2,450 – 51,700 EU/mL) was investigated. Organoclay 1 (0.1%) showed a good binding efficiency in aqueous solution (average 81%), whereas Bentonite 1 (0.1%) obtained a lower binding efficiency (21-54%). The following absorbent capacities were calculated in highest endotoxin concentration: 5.59 mg/g (Organoclay 1) > 3.97 mg/g (Polymyxin B) > 2.58mg/g (Organoclay 2) > 1.55 mg/g (Bentonite 1) > 1.23 mg/g (Bentonite 2). Thirdly, a sorption experiment in artificial intestinal fluid was conducted. Especially for organoclays, which are known to be unspecific adsorbents, the endotoxin binding capacity was significantly reduced. In contrast, Bentonite 1 showed comparable results in artificial intestinal fluid and aqueous solution. Based on the results of this in vitro study, the effect of promising clay minerals will be investigated in in vivo trials. PMID:24383578

An upscaling method and a numerical analysis of swelling/shrinking processes in a compacted bentonite/sand mixture

NASA Astrophysics Data System (ADS)

Xie, M.; Agus, S. S.; Schanz, T.; Kolditz, O.

2004-12-01

This paper presents an upscaling concept of swelling/shrinking processes of a compacted bentonite/sand mixture, which also applies to swelling of porous media in general. A constitutive approach for highly compacted bentonite/sand mixture is developed accordingly. The concept is based on the diffuse double layer theory and connects microstructural properties of the bentonite as well as chemical properties of the pore fluid with swelling potential. Main factors influencing the swelling potential of bentonite, i.e. variation of water content, dry density, chemical composition of pore fluid, as well as the microstructures and the amount of swelling minerals are taken into account. According to the proposed model, porosity is divided into interparticle and interlayer porosity. Swelling is the potential of interlayer porosity increase, which reveals itself as volume change in the case of free expansion, or turns to be swelling pressure in the case of constrained swelling. The constitutive equations for swelling/shrinking are implemented in the software GeoSys/RockFlow as a new chemo-hydro-mechanical model, which is able to simulate isothermal multiphase flow in bentonite. Details of the mathematical and numerical multiphase flow formulations, as well as the code implementation are described. The proposed model is verified using experimental data of tests on a highly compacted bentonite/sand mixture. Comparison of the 1D modelling results with the experimental data evidences the capability of the proposed model to satisfactorily predict free swelling of the material under investigation. Copyright

Sodium Bentonite-Based Fire Retardant Coatings Containing Starch

USDA-ARS?s Scientific Manuscript database

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

Characteristics of Thermoplastic Potato Starch/Bentonite Nanocomposite Film

NASA Astrophysics Data System (ADS)

Zakaria, N. H.; Muhammad, N.; Abdullah, M. M. A. B.; Sandu, I. G.; Wan, C. L. Mei

2018-06-01

The aim of this study is to investigate the effect of bentonite towards thermoplastic potato starch nanocomposite films on the mechanical, microstructure and physical properties. The nanocomposite films were prepared using bentonite nano filler (0, 1, 5, 10, 15 and 20%) through solution casting technique. Obtained result indicate that, tensile strength increased significantly with increasing bentonite content and the highest tensile strength was recorded for nanocomposite film with 20% bentonite content. Meanwhile, elongation at break increased as the bentonite content increased from 0 to 15%, however significantly decreased at 20% bentonite content due to ductile structure and anti-plasticizing effect. Besides, good dispersion between bentonite nano filler and starch matrix with slightly remaining anglomerates was evident in scanning electron microscopy (SEM) image. Overall result shows that the addition of bentonite nano filler in potato starch film significantly influenced the properties of the films.

Phenol hydroxylation on Al-Fe modified-bentonite: Effect of Fe loading, temperature and reaction time

NASA Astrophysics Data System (ADS)

Widi, R. K.; Budhyantoro, A.; Christianto, A.

2017-11-01

The present work reflects the study of the phenol hydroxylation reactions to synthesize hydroquinone and catechol on Al-Fe modified-bentonite. This study started with synthesizes the catalyst material based on the modified bentonite. Natural bentonite from Pacitan, Indonesia was intercalated with Cetyl-TetramethylammoniumBromida (CTMA-Br) followed by pillarization using Alumina. The pillared bentonite was then impregnated with Fe solution (0.01 M, 0.05 M, and 0.1 M). The solid material obtained was calcined at 723 K for 4 hours. All the materials were characterized using BET N2 adsorption. Their catalytic activity and selectivity were studied for phenol hydroxylation using H2O2 (30%). The reaction conditions of this reaction were as follows: ratio of phenol/H2O2 = 1:1 (molar ratio), concentration of phenol = 1 M and ratio of catalyst/phenol was 1:10. Reaction temperatures were varied at 333, 343 and 353 K. The reaction time was also varied at 3, 4 and 5 hours. The result shows that the materials have potential catalyst activity.

Functions of an engineered barrier system for a nuclear waste repository in basalt

NASA Astrophysics Data System (ADS)

Coons, W. E.; Moore, E. L.; Smith, M. J.; Kaser, J. D.

1980-01-01

The functions of components selected for an engineered barrier system for a nuclear waste repository in basalt are defined providing a focal point for barrier material research and development by delineating the purpose and operative lifetime of each component of the engineered system. A five component system (comprised of waste form, canister, buffer, overpack, and tailored backfill) is discussed. Redundancy is provided by subsystems of physical and chemical barriers which act in concert with the geology to provide a formidable barrier to transport of hazardous materials to the biosphere. The barrier system is clarified by examples pertinent to storage in basalt, and a technical approach to barrier design and material selection is proposed.

Synthesis of H/Bentonite and Ni/Al2O3-bentonite and its application to produce biogasoline from nyamplung seed (Calophyllum inophillum Linn) oil by catalytic hydrocracking

NASA Astrophysics Data System (ADS)

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.

Silurian K-bentonites of the Dnestr Basin, Podolia, Ukraine

USGS Publications Warehouse

Huff, W.D.; Bergstrom, Stig M.; Kolata, Dennis R.

2000-01-01

The Dnestr Basin of Podolia, Ukraine, is an epicratonic basin consisting of neritic carbonate and calcareous mudstone facies including a nearly complete Silurian sequence ranging from late Llandovery to late Pridoli in age. The Silurian section has served as a standard for regional and interregional studies as a consequence of its well-documented macro- and microfaunal assemblages. Approximately 24 mid- to Late Silurian K-bentonites are present in this succession, and their lateral persistence has aided in establishing regional correlations. The K-bentonites range from 1 to 40 cm in thickness and occur in the Bagovitsa (late Wenlock), Malinovtsy (Ludlow) and Skala (Pridoli) Formations. Discrimination diagrams based on immobile trace elements together with rare earth element data suggest the K-bentonites had a volcanic origin in a collision margin setting related to subduction. Thickness and stratigraphic distribution considerations are consistent with a source area in the Rheic Ocean.

Tempe Waste Water Degradation Using TiO2-N/Bentonite alginate Granule Photocatalyst with Ultraviolet Light Irradiation

NASA Astrophysics Data System (ADS)

Khoirun Nisaa', Aldila; Wardhani, Sri; Purwonugroho, Danar; Darjito

2018-01-01

Tempe waste water stew has high ammonia concentration which causes odor due to polluting by anaerobic decay. Free ammonia in the waste has exceeded the limit, thus endangering the aquatic environment. This research aims to determine the activity of photocatalyst granule TiO2-N/bentonite-alginate as decomposers of compounds in the photodegradation process. Photodegradation is the decomposition process of compounds by semiconductors with light. Results expected includes the photocatalyst activity of TiO2-N/bentonite-alginate granule produced by ultraviolet rays is known based on the effect of dopant N concentration on the catalyst and the effect of photocatalytic ratio toward tempe waste water. Methods proposed in this research are activation of bentonite using H2SO4 0.8 M, TiO2-N synthesize by sonication method with urea as the source of N, then TiO2-N impregnation into bentonite. Photocatalyst in granule form synthesized with alginate was then dripped with syringe pump into 3% (w/v) CaCl2. The photocatalyst characterization will be performed using XRD. The optimum tempe waste water degradation at the concentration of TiO2-N 0.4 (g/g) bentonite is 53.66%. The ratio of photocatalyst and tempe waste water, optimum at 150 mg of photocatalyst with 25 mL of waste equal to 53.66%.

Sorption kinetics and isotherm modelling of imidacloprid on bentonite and organobentonites.

PubMed

Jain, Shailesh K; Shakil, Najam A; Dutta, Anirban; Kumar, Jitendra; Saini, Mukesh K

2017-05-04

Bentonite was modified by quaternary ammonium cations viz. cetytrimethylammonium (CTA), cetylpyridinium (CP), rioctylmethylammonium (TOM) and pcholine (PTC) at 100% cation exchange capacity of bentonite and was characterized by X-ray diffraction, CHNS elemental analyser and Fourier transform infrared spectroscopy. The sorption of imidacloprid on organobentonites/bentonite was studied by batch method. Normal bentonite could adsorb imidacloprid only upto 19.31-22.18% while all organobentonites except PTC bentonite (PTCB), enhanced its adsorption by three to four times. Highest adsorption was observed in case of TOM bentonite (TOMB) (76.94-83.16%). Adsorption kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. For normal bentonite data were best fitted to pseudo-first-order kinetic, while for organobentonites fitted to pseudo-second-order kinetics. Sorption data were analysed using Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherm models. Data were well fitted to Freundlich adsorption isotherm. Product of Freundlich adsorption constant and heterogeneity parameter (K f .1/n) was in following order: TOMB (301.87) > CTA bentonite (CTAB) (152.12) > CP bentonite (CPB) (92.58) > bentonite (27.25). Desorption study confirmed hysteresis and concentration dependence. The present study showed that the organobentonite could be a good sorbent for removal of imidacloprid from natural water sample also. Percentage adsorption and Distribution coefficient (mL g -1 ) value of different adsorbent was in following order: TOMB (74.85% and 297.54) > CTAB (55.78% and 126.15) > CPB (45.81% and 84.55) > bentonite (10.65% and 11.92).

Bentonite modification with pillarization method using metal stannum

NASA Astrophysics Data System (ADS)

Widjaya, Robert R.; Juwono, Ariadne L.; Rinaldi, Nino

2017-11-01

Clay minerals have received considerable attention in the last years because of their environmental compatibility, low cost, high selectivity, and operational simplicity. Although clays are very useful for many application in the field of catalysis, they have main disadvantage: their lack of pore volume and spesific surface area. Porosity and stability of these materials are improved by pillaring the clay layers with SnCl4, which leads to materials known as pillared clays (PILC). This research aims were to characterize the Bentonite and Sn-Bentonite as catalysts for cracking and oligomerization. The Sn-Bentonite was prepared by pillarization method with a variation in metal ratio of 5 mmol dan 10 mmol.gr-1 of bentonit. The catalyst characterized by X-ray Diffraction, X-ray Fluorescence, Fourier Transform Infra Red, Brunauer Emmett Teller, Thermogravimetric Analysis. The results showed that the Sn-Bentonite catalyst had large basal spacing and good porous structure, and the specific surface areas increased. XRF detected the Sn in the Bentonite and TGA results showed the ability Sn-Bentonite in receiving heat. FTIR test showed two type of acidity, broansted and lewis acid. The characterized results indicated that Sn-Bentonite with metal ratio 5 mmol.gr-1 better than Sn-Bentonite with metal ratio 10 mmol.gr-1, in which there was a significant increase the basal spacings, specific surface area, and pore volume. The TGA results for Sn-Bentonite appeared to be more thermally stable than Bentonite.

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

NASA Astrophysics Data System (ADS)

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 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.

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

PubMed

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.

Ordovidan K-bentonites in the Precordillera of San Juan and its tectomasmatic significance

USGS Publications Warehouse

Cingolani, C.A.; Huff, W.; Bergstrom, S.; Kolata, D.

1997-01-01

A succession of approximately 35 early Middle Ordovician K-bentonite beds are exposed in the Precordillera region near the town of Jachal, in San Juan Province (at Cerro Viejo and La Chilca sections). They occur in argillaceous limestone in the upper part of the San Juan Limestone and in the interbedded shales and mudstones at the base of the overlying Los Azules Formation. Total thickness of the K-bentonite-bearing interval is 23 m and individual beds range from 1 to 65 cm thick. An essentially Arenig-Llanvirn age for the K-bentonite succession is indicated by the presence of graptolites diagnostic of the Paraglossograptus tentaculatus Zone and conodonts indicating the Eoplacognathus suecicus Zone. The bentonites consist mainly of Rl ordered illite/smectite, characteristic of most of the lower Paleozoic K-bentonites, plus volcanogenic crystals. Similar to other K-bentonites, these probably represent the distal, glass-rich portion of fall-out ash beds derived from collision zone explosive volcanism. The geochemical data and preliminary plots on the magmatic discrimination diagram indicate the parental magma was of rhyolite to trachyandesite composition. Tectonic discrimination diagrams show the setting of Cerro Viejo ash layers as falling on the boundary between volcanic arc and within plate rocks, typical of collision margin felsic volcanic rocks. U-Pb isotope dating for two zircon fractions from one sample show a lower concordia intercept of 461, +7-10 Ma coincident with the biostratigraphic age. Thus, they have important implications for the origin and early history of the allochtonous Precordillera terrane and the Pacific margin of South America. Furthermore, they are potentially important in interpretations of the paleogeographic relations of Laurentia and Gondwana during Ordovician time. ?? 1997 Asociacio??n Geolo??gica Argentina.

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

NASA Astrophysics Data System (ADS)

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.

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

PubMed

Hassanien, Mohamed M; Abou-El-Sherbini, Khaled S; Al-Muaikel, Nayef S

2010-06-15

Methylene blue was immobilized onto bentonite (BNT). The modified clay (MB-BNT) was used to extract Hg(2+) at pH 6.0 yielding Hg-MB-BNT. BNT, MB-BNT and Hg-MB-BNT were characterized by X-ray diffractometry, infrared spectra, and elemental and thermogravimetric analyses. MB is suggested to be intercalated into the major phase of BNT; montmorillonite mineral (MMT), lying parallel to the aluminosilicate layers, with a capacity of 36 mequiv./100g. MB-BNT shows good stability in 0.1-1M hydrochloric or nitric acids, ammonium hydroxide, and concentrated Na(+), K(+) or NH(4)(+) chlorides or iodides. It shows good selectivity towards Hg(2+) with an extraction capacity of 37 mequiv./100g in the presence of I(-) giving rise to a ratio of MB/Hg(2+)/I(-) 1:1:3 in the clay phase. Extracted Hg(2+) could be quantitatively recovered by ammonia buffer at pH 8.5. MB-BNT was successfully applied to recover Hg(2+) from spiked natural water and cinnabar mineral samples using the optimum conditions; pH 6.0, time of stirring 10 min and 10 mL of 0.05 M NH(4)Cl/NH(4)OH at pH 8.5 as eluent. Copyright 2010 Elsevier B.V. All rights reserved.

In Situ Immobilization of Heavy-Metal Contaminated Soil

DTIC Science & Technology

1988-06-01

Scavenging DH 524 Molecules DH 565 DH 566 Natural Materials Clays Slurry BEN 125 Bentonite 325 Bentonite HPM 20 Microfine Bentonite Attasorb LVM Satintone...HPM 20 Microfine Bentonite are sodium- montmorillonite clays of different particle sizes and purities. Na- montmorillonite clay is a three-layered...a powder of 325 Mesh and has a purity of 90 percent. - -PM 20 Microfine Bentonite (Reference 24). This is a microfine clay having a purity of 99.75

Electrical resistivity measurement of mechanically stabilized Earth wall backfill : technical summary.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically : backfilled with coarse aggregate. Current backfill material testing procedures used : by the Kansas Department of Transportation (KDOT) utilize on-site observations for : ...

Jetting and flooding of granular backfill materials : [summary].

DOT National Transportation Integrated Search

2015-03-01

Granular backfill materials on highway projects are often compacted by mechanical methods. : This requires the contractor to place backfill material into loose lifts of varying thickness : and use compaction equipment to reduce air voids and increase...

Electrical resistivity measurement of mechanically stabilized Earth wall backfill : final report.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically backfilled with coarse aggregate. : Current backfill material testing procedures used by the Kansas Department of Transportation (KDOT) utilize on-site : observations for co...

Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 thenmore » 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.« less

Preparation of fly ash-granulated blast furnace slag-carbide slag binder and application in total tailings paste backfill

NASA Astrophysics Data System (ADS)

Li, Chao; Hao, Ya-fei; Zhao, Feng-qing

2018-03-01

Based on activation and synergistic effect among various materials, a low-cost mine backfill cementing material, FGC binder, was prepared by using fly ash, granulated blast-furnace slag (GBFS), carbide slag and composite activator. The proper proportioning of FGC binder is obtained by response surface experiment optimization method: fly ash 62 %, GBFS 20 %, carbide slag 8 % and compound activators 10 %. Adjusting the material ratio obtains different cementing material which could satisfy requirements of different mined-out areas. With the mass ratio of cementing material and tailings 1:4∼1:8, the concentration of total solid 70 %, the compressive strength values of total tailings filling body at 28 d reaches 1.64∼4.14 MPa, and the backfilling cost is 20 % lower than using OPC cement.

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis.

PubMed

Zheng, Liange; Samper, Javier; Montenegro, Luis

2011-09-25

The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collected after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO(2)(g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO(3)(-) and pH data cannot be explained solely by solute transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions. Published by Elsevier B.V.

Diffusion of Eu(III) in compacted bentonite-effect of pH, solution concentration and humic acid.

PubMed

Wang, Xiangke; Chen, Yixue; Wu, Yican

2004-06-01

The effect of pH, Eu(III) solution concentration and humic acid on the diffusion of Eu(III) in compacted bentonite (rho(b) = 1000 +/- 30 kg/m(3)) was studied with "in-diffusion" method at an ionic strength of 0.1M NaClO(4). The results (K(d) values from the first slice and theoretical calculation, apparent and effective diffusion coefficients) derived from the new capillary method are in good agreement with the literature data under similar conditions, and fit the Fick's second law very well. The results suggest that the diffusion of Eu(III) is dependent on pH values and independent on solution concentration in our experimental conditions. Humic acid forms precipitation/complexation with Eu(III) at the surface of compacted bentonite and thus deduces the diffusion/transport of Eu(III) in compacted bentonite. The K(d) values in compacted bentonite are in most cases lower than those in powdered bentonite obtained from batch experiments. The difference between the K(d) values from powdered and compacted bentonite is a strong function of the bulk density of the bentonite. The results suggest that the content of interlaminary space plays a very important role to the diffusion, sorption and migration of Eu(III) in compacted bentonite.

Spectral characteristics of the bentonite loaded with benzyldimethyloctadecylammonium chloride, hexadecyltrimethylammonium bromide and dimethyldioctadecylammonium bromide

NASA Astrophysics Data System (ADS)

Majdan, Marek; Maryuk, Oksana; Gładysz-Płaska, Agnieszka; Pikus, Stanisław; Kwiatkowski, Ryszard

2008-02-01

The spectral characterization, including the FTIR, DRIFT (diffusive reflectance), SWAXS (small and wide angle X-ray scattering) spectra comparison of the sodium bentonite modified by BDMODA-Cl (benzyldimethyloctadecylammonium chloride), HDTMA-Br (hexadecyltrimethylammonium bromide), DDA-Br (dimethyldioctadecylammonium bromide) is presented in the paper. The FTIR spectra show the shift of C-H stretching vibrations: νsym(CH2), νasym(CH2) of surfactants methylene chains toward lower frequencies (from 2855 to 2851 cm -1 for νsym(CH2) and from 2927 to 2918 cm -1 for νansym(CH2) with the surfactant concentration in bentonite phase. The bending vibrations δH-O-H in water molecules change their positions in the direction of higher frequencies (from 1634 to 1647 cm -1) with the surfactant concentration for bentonite-BDMODA and bentonite-DDA contrary to bentonite-HDTMA, where the constant position δH-O-H is explained as the consequence of the lower concentration of the hydrogen bonded water in bentonite-HDTMA phase when compared with the remaining forms of bentonite. The DRIFT spectra reveal dramatic shift of the νSi-O stretching vibration toward higher frequencies upon intercalation of the sodium bentonite with the surfactant cations. The SWAXS spectra and SEM images of the bentonite are the evidence of somewhat different sorption mechanism of DDA-Br when compared with the BDMODA-Cl and HDTMA-Br, including remarkable external surface sorption contribution in the overall sorption.

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

NASA Astrophysics Data System (ADS)

Dehn, Hanna; Haase, Hanna; Schanz, Tom

2015-04-01

Bentonites are often used as barrier materials in landfill technology to prevent infiltration of leachates to the natural environment. Since decades, geoenvironmental engineering aims at improving the hydro-mechanical performance of landfill liners. Various studies on the permeability performance of geosynthetic clay liners (GCLs) show effects of non-standard liquids on behaviour of Na+-bentonite regarding its sealing capacity. With increasing concentration of chemical aggressive solutions the sealing capacity decreases (Shackelford et al. 2000). An opportunity to improve the hydraulic permeability of the bentonites is the addition of polymers. The changes in hydraulic permeability performance of polymer treated and untreated bentonites while adding chemical aggressive solutions were studied by several authors. Results obtained by Scalia et al. (2014) illustrate that an increase in permeability can be prevented by adding polymer to Na+-bentonite. On the other hand, Ashmawy et al. (2002) presented results on the incapability of several commercial bentonite-polymer-products. The objective of this study is to characterize the influence of polymer addition on hydraulic performance of Na+-bentonite systematically. Therefore, the influence of 1% polymer addition of cationic and anionic polyacrylamide on the swelling pressure and hydraulic permeability of MX 80 bentonite was investigated. Preparation of bentonite-polymer composites was conducted (1) in dry conditions and (2) using solution-intercalation method. Experiments on hydraulic permeability were carried out using distilled water as well as CaCl2-solution. References Ashmawy, A. K., El-Hajji, D., Sotelo, N. & Muhammad, N. (2002), `Hydraulic Performance of Untreated and Polymer-treated Bentonite in Inorganic Landfill Leachates', Clays and Clay Minerals 50(5), 546-552. Scalia, J., Benson, C., Bohnhoff, G., Edil, T. & Shackelford, C. (2014), 'Long-Term Hydraulic Conductivity of a Bentonite-Polymer Composite Permeated with Aggressive Inorganic Solutions', Journal of Geotechnical and Geoenvironmental Engineering 140(3). Shackelford, C. D., Benson, C. H., Katsumi, T., Edil, T. B. & Lin, L. (2000), 'Evaluating the hydraulic conductivity of GCLs permeated with non-standard liquids', Geotextiles and Geomembranes 18, 133-161.

Incorporating Zataria multiflora Boiss. essential oil and sodium bentonite nano-clay open a new perspective to use zein films as bioactive packaging materials.

PubMed

Kashiri, Mahboobeh; Maghsoudlo, Yahya; Khomeiri, Morteza

2017-10-01

Active zein films with different levels of Zataria multiflora Boiss. essential oil were produced successfully. To enhance properties of this biopolymer for food packaging applications, sodium bentonite clay was used at two levels (2 and 4%). The results indicated that the addition of Z. multiflora Boiss. essential oil caused a reduction in tensile strength and Young's modulus and slight increase in the percent of elongation at break of the films. Maximum solubility in water and water vapor permeability was observed by incorporation of 10% Z. multiflora Boiss. essential oil in the zein matrix. Transmission electron microscopy micrographs of zein film were verified by the exfoliation of the layers of sodium bentonite clay in the zein matrix. Stronger films with lower water vapor permeability and water solubility were evident of good distribution of sodium bentonite clay in the zein matrix. According to the results, 2% sodium bentonite clay was selected for evaluation of nano active film properties. Water vapor permeability, UV light barrier, tensile strength, and Young's modulus values of active films were improved by incorporation of 2% sodium bentonite clay. The antibacterial activity of different contents of Z. multiflora Boiss. essential oil in vapor phase demonstrated that use of Z. multiflora Boiss. essential oil in the liquid phase was more effective than in vapor phase. The antibacterial zein-based films showed that active zein film with 5 and 10% Z. multiflora Boiss. essential oil had reductions of 1.68 log and 2.99 log, respectively, against Listeria monocytogenes and 1.39 and 3.07 log against Escherichia coli. Nano active zein film containing 10% Z. multiflora Boiss. essential oil and 2% sodium bentonite clay showed better antibacterial properties against L. monocytogenes (3.23 log) and E. coli (3.17 log).

DNA Electrochemistry with Tethered Methylene Blue

PubMed Central

Pheeney, Catrina G.

2012-01-01

Methylene blue (MB′), covalently attached to DNA through a flexible C12 alkyl linker, provides a sensitive redox reporter in DNA electrochemistry measurements. Tethered, intercalated MB′ is reduced through DNA-mediated charge transport; the incorporation of a single base mismatch at position 3, 10, or 14 of a 17-mer causes an attenuation of the signal to 62 ± 3% of the well-matched DNA, irrespective of position in the duplex. The redox signal intensity for MB′–DNA is found to be least 3-fold larger than that of Nile blue (NB)–DNA, indicating that MB′ is even more strongly coupled to the π-stack. The signal attenuation due to an intervening mismatch does, however, depend on DNA film density and the backfilling agent used to passivate the surface. These results highlight two mechanisms for reduction of MB′ on the DNA-modified electrode: reduction mediated by the DNA base pair stack and direct surface reduction of MB′ at the electrode. These two mechanisms are distinguished by their rates of electron transfer that differ by 20-fold. The extent of direct reduction at the surface can be controlled by assembly and buffer conditions. PMID:22512327

Use of a 10.22 m diameter EPB shield: a case study in Beijing subway construction.

PubMed

Li, Xinggao; Yuan, Dajun; Guo, Yuhai; Cai, Zhiyong

2016-01-01

Beijing subway line 14 includes four stations and approximately 2.8 km of tunnels between the Dongfengbeiqiao and Jingshunlu areas of the city. Due to the surface and underground space limitations of this section, a double-track running tunnel instead of two single-track running tunnels was adopted to connect the two stations. The double-track tunnels were excavated by a 10.22 m diameter earth pressure balance (EPB) shield. It was the first time that an EPB shield more than 10 m in diameter was used in Beijing subway construction. The shield, which passes underneath densely built-up areas of the city and is equipped with a spoke-type cutterhead, with balance between the ground pressure and the earth chamber pressure at the tunnel face, is of great importance. Referring to experiences gained in the EPB shield tunneling, attention was paid to the function of soil conditioning and simultaneous backfilling grouting of the shield, and some special designs were considered in manufacturing the machine. In addition to the agitating rods welded to the cutterhead, two independently driven agitators were added to fully mix everything in the earth chamber. Independent pipelines were arranged for injecting different conditioning agents. Indoor tests in combination with field tests were conducted to find suitable additives and injection ratios of the additives, and determine the mix ratio of the two-component grout for simultaneous backfilling grouting. A scheme was employed for simultaneously injecting the bentonite slurry at 8% concentration and the foam liquid at 5% concentration to condition the excavated soil. The cement-sodium silicate grout was adopted to fill the tail void and the injection volume per ring was 14.1-15.3 m 3 . The performance of the shield and evaluation of the corresponding tunneling technologies are introduced in terms of the shield tunneling induced ground surface settlements. The success of the project is of great significance to Beijing subway construction and underground space utilization. The findings serve as a useful reference for similar projects.

30 CFR 816.105 - Backfilling and grading: Thick overburden.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Backfilling and grading: Thick overburden. 816...-SURFACE MINING ACTIVITIES § 816.105 Backfilling and grading: Thick overburden. (a) Definition. Thick... surrounding terrain. (b) Performance standards. Where thick overburden occurs within the permit area, the...

Interaction processes at the concrete-bentonite interface after 13 years of FEBEX-Plug operation. Part II: Bentonite contact

NASA Astrophysics Data System (ADS)

Fernández, Raúl; Torres, Elena; Ruiz, Ana I.; Cuevas, Jaime; Alonso, María Cruz; García Calvo, José Luis; Rodríguez, Enrique; Turrero, María Jesús

2017-06-01

The in situ FEBEX experiment performed at the URL in Grimsel (Swizerland) was dismantled after 18 years of operation. Interface samples between bentonite and a shotcreted concrete plug that was constructed in a second operational phase have been studied after 13 years of interaction. Mineralogical and geochemical characterization of samples have been performed by XRD, SEM-EDX, TG and FTIR techniques in addition to determinations of major ions by chemical analysis of aqueous extracts, δ18O and δ13C stable isotopes both in concrete paste and bentonite, and exchangeable cations in bentonite. Low mineralogical alteration impact was observed in bentonite that is only affected by a few millimeters. A large accumulation of Mg was observed at the bentonite side of the interface precipitating as silicates in various forms. In addition, heterogeneous carbonation was observed at the interface, but mostly affecting the concrete side. Migration of aqueous species occurred, being the most relevant the diffusion of chloride and sulfate from bentonite to concrete, in agreement with Part I of this study. Chloride advanced more into the concrete, while sulfates reacted to form ettringite, which has an evident alteration impact at the very interface (<0.5 mm rim) within the concrete. The ionic mobility has also redistributed the exchangeable cations in bentonite, increasing the content in Ca2+ and Na+, compensated by a decrease in Mg2+. The results presented in this paper complement those presented in Part I, focusing on the alteration of concrete by the bentonite and the granite groundwater.

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

NASA Astrophysics Data System (ADS)

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.

Thermal treatment of bentonite reduces aflatoxin b1 adsorption and affects stem cell death.

PubMed

Nones, Janaína; Nones, Jader; Riella, Humberto Gracher; Poli, Anicleto; Trentin, Andrea Gonçalves; Kuhnen, Nivaldo Cabral

2015-10-01

Bentonites are clays that highly adsorb aflatoxin B1 (AFB1) and, therefore, protect human and animal cells from damage. We have recently demonstrated that bentonite protects the neural crest (NC) stem cells from the toxicity of AFB1. Its protective effects are due to the physico-chemical properties and chemical composition altered by heat treatment. The aim of this study is to prepare and characterize the natural and thermal treatments (125 to 1000 °C) of bentonite from Criciúma, Santa Catarina, Brazil and to investigate their effects in the AFB1 adsorption and in NC cell viability after challenging with AFB1. The displacement of water and mineralogical phases transformations were observed after the thermal treatments. Kaolinite disappeared at 500 °C and muscovite and montmorillonite at 1000 °C. Slight changes in morphology, chemical composition, and density of bentonite were observed. The adsorptive capacity of the bentonite particles progressively reduced with the increase in temperature. The observed alterations in the structure of bentonite suggest that the heat treatments influence its interlayer distance and also its adsorptive capacity. Therefore, bentonite, even after the thermal treatment (125 to 1000 °C), is able to increase the viability of NC stem cells previously treated with AFB1. Our results demonstrate the effectiveness of bentonite in preventing the toxic effects of AFB1. Copyright © 2015 Elsevier B.V. All rights reserved.

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, L.; Samper, J.; Montenegro, L.

The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collectedmore » after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO{sub 2}(g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO{sub 3}{sup -} and pH data cannot be explained solely by solute transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions.« less

Surface modification of a low cost bentonite for post-combustion CO2 capture

NASA Astrophysics Data System (ADS)

Chen, Chao; Park, Dong-Wha; Ahn, Wha-Seung

2013-10-01

A low cost bentonite was modified with PEI (polyethylenimine) through a physical impregnation method. Bentonite in its natural state and after amine modification were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, N2 adsorption-desorption isotherms, and investigated for CO2 capture using a thermogravimetric analysis unit connected to a flow panel. The effect of adsorption temperature, PEI loading and CO2 partial pressure on the CO2 capture performance of the PEI-modified bentonite was examined. A cyclic CO2 adsorption-desorption test was also carried out to assess the stability of PEI-modified bentonite as a CO2 adsorbent. Bentonite in its natural state showed negligible CO2 uptake. After amine modification, the CO2 uptake increased significantly due to CO2 capture by amine species introduced via chemisorption. The PEI-modified bentonites showed high CO2 capture selectivity over N2, and exhibited excellent stability in cyclic CO2 adsorption-desorption runs.

Bacterial Diversity in Bentonites, Engineered Barrier for Deep Geological Disposal of Radioactive Wastes.

PubMed

Lopez-Fernandez, Margarita; Cherkouk, Andrea; Vilchez-Vargas, Ramiro; Jauregui, Ruy; Pieper, Dietmar; Boon, Nico; Sanchez-Castro, Ivan; Merroun, Mohamed L

2015-11-01

The long-term disposal of radioactive wastes in a deep geological repository is the accepted international solution for the treatment and management of these special residues. The microbial community of the selected host rocks and engineered barriers for the deep geological repository may affect the performance and the safety of the radioactive waste disposal. In this work, the bacterial population of bentonite formations of Almeria (Spain), selected as a reference material for bentonite-engineered barriers in the disposal of radioactive wastes, was studied. 16S ribosomal RNA (rRNA) gene-based approaches were used to study the bacterial community of the bentonite samples by traditional clone libraries and Illumina sequencing. Using both techniques, the bacterial diversity analysis revealed similar results, with phylotypes belonging to 14 different bacterial phyla: Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Chloroflexi, Cyanobacteria, Deinococcus-Thermus, Firmicutes, Gemmatimonadetes, Planctomycetes, Proteobacteria, Nitrospirae, Verrucomicrobia and an unknown phylum. The dominant groups of the community were represented by Proteobacteria and Bacteroidetes. A high diversity was found in three of the studied samples. However, two samples were less diverse and dominated by Betaproteobacteria.

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Auger mining: Backfilling and grading. 819.19 Section 819.19 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE... MINING § 819.19 Auger mining: Backfilling and grading. (a) General. Auger mining shall be conducted in...

Repository Drift Backfilling Demonstrator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Londe, I.; Dubois, J.Ph.; Bauer, C.

2008-07-01

The 'Backfilling Demonstrator' is one of the technological demonstrators developed by ANDRA in the framework of the feasibility studies for a geological repository for high-level long-lived (HL-LL waste) within a clay formation. The demonstrator concerns the standard and supporting backfills as defined in Andra's 2005 design. The standard backfill is intended to fill up almost all drifts of the underground repository in order to limit any deformation of the rock after the degradation of the drift lining. The supporting backfill only concerns a small portion of the volume to be backfilled in order to counter the swelling pressure of themore » swelling clay contained in the sealing structures. The first objective of the demonstrator was to show the possibility of manufacturing a satisfactory backfill, in spite of the exiguity of the underground structures, and of reusing as much as possible the argillite muck. For the purpose of this experiment, the argillite muck was collected on Andra's work-site for the implementation of an underground research laboratory. Still ongoing, the second objective is to follow up the long-term evolution of the backfill. Approximately 200 m{sup 3} of compacted backfill material have been gathered in a large concrete tube simulating a repository drift. The standard backfill was manufactured exclusively with argillite. The supporting backfill was made by forming a mixture of argillite and sand. Operations were carried out mostly at Richwiller, close to Mulhouse, France. The objectives of the demonstrator were met: an application method was tested and proven satisfactory. The resulting dry densities are relatively high, although the moduli of deformation do not always reach the set goal. The selected objective for the demonstrator was a dry density corresponding to a relatively high compaction level (95% of the standard Proctor optimum [SPO]), for both pure argillite and the argillite-sand mixture. The plate-percussion compaction technique was used and proved satisfactory. The measured dry densities are higher than the 95%-SPO objective. The implementation rates remain very low due to the experimental conditions involved. The metal supply mode would need to be revised before any industrial application is contemplated. The Demonstrator Program started in August 2004 and is followed up today over the long term. With that objective in mind, sensors and a water-saturation system have been installed. (author)« less

The effect of iron on montmorillonite stability. (II) Experimental investigation

NASA Astrophysics Data System (ADS)

Wilson, James; Cressey, Gordon; Cressey, Barbara; Cuadros, Javier; Ragnarsdottir, K. Vala; Savage, David; Shibata, Masahiro

2006-01-01

Several designs proposed for high-level nuclear waste (HLW) repositories include steel waste canisters surrounded by montmorillonite clay. This work investigates montmorillonite stability in the presence of native Fe, magnetite and aqueous solutions under hydrothermal conditions. Two series of experiments were conducted. In the first, mixtures of Na-montmorillonite, magnetite, native Fe, calcite, and NaCl solutions were reacted at 250 °C, Psat for between 93 and 114 days. In the second series, the starting mixtures included Na-montmorillonite, native Fe and solutions of FeCl 2 which were reacted at temperatures of 80, 150, and 250 °C, Psat, for 90-92 days. Experiments were analysed using XRD, FT-IR, TEM, ICP-AES, and ICP-MS. In the first series of experiments, native Fe oxidised to produce magnetite and the starting montmorillonite material was transformed to Fe-rich smectite only when the Fe was added predominantly as Fe metal rather than Fe oxide (magnetite). The Fe-rich smectite was initially Fe(II)-rich, which oxidised to produce an Fe(III)-rich form on exposure to air. The expansion of this material on ethylene glycol solvation was much reduced compared to the montmorillonite starting material. TEM imaging shows that partial loss of tetrahedral sheets occurred during transformation of the montmorillonite, resulting in adjacent layers becoming H-bonded with a 7 Å repeat. The reduced swelling property of the Fe-smectite product may be due predominantly to the structural disruption of smectite layers and the formation of H-bonds. Solute activities corresponded to the approximate stability field calculated for hypothetical Fe(II)-saponite. In the second series of experiments, significant smectite alteration was only observed at 250 °C and the product contained a small proportion of a 7 Å repeat structure, observable by XRD. In these experiments, solute activities coincide with berthierine. The experiments indicate that although bentonite is still a desirable choice of backfill material for HLW repositories, some loss of expandability may result if montmorillonite is altered to Fe-rich smectite at the interface between steel canisters and bentonite.

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

NASA Astrophysics Data System (ADS)

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 forms a synchronous surface in this part of the Cretaceous section. This is significant due to it being a potential previously unknown bout of volcanism, which, if the source can be found, implies a new region that may have experienced thermal maturation of hydrocarbon source rocks at a shallower depth than would have been expected under the normal geothermal gradient.

Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay

NASA Astrophysics Data System (ADS)

Mon, Alba; Samper, Javier; Montenegro, Luis; Naves, Acacia; Fernández, Jesús

2017-02-01

Radioactive waste disposal in deep geological repositories envisages engineered barriers such as carbon-steel canisters, compacted bentonite and concrete liners. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyper-alkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyper-alkaline plume at the concrete-clay interface. Here we present a non-isothermal multicomponent reactive transport model of the long-term (1 Ma) interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. Model results show that magnetite is the main corrosion product. Its precipitation reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The reduction of the porosity becomes especially relevant at t = 104 years. The zones affected by pore clogging at the canister-bentonite and concrete-clay interfaces at 1 Ma are approximately equal to 1 and 3.3 cm thick, respectively. The hyper-alkaline front (pH > 8.5) spreads 2.5 cm into the clay formation after 1 Ma. Our simulation results share the key features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Pore clogging at the canister-bentonite and concrete-clay interfaces; 2) Narrow alteration zones; and 3) Limited smectite dissolution after 1 Ma.

Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay.

PubMed

Mon, Alba; Samper, Javier; Montenegro, Luis; Naves, Acacia; Fernández, Jesús

2017-02-01

Radioactive waste disposal in deep geological repositories envisages engineered barriers such as carbon-steel canisters, compacted bentonite and concrete liners. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyper-alkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyper-alkaline plume at the concrete-clay interface. Here we present a non-isothermal multicomponent reactive transport model of the long-term (1Ma) interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. Model results show that magnetite is the main corrosion product. Its precipitation reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The reduction of the porosity becomes especially relevant at t=10 4 years. The zones affected by pore clogging at the canister-bentonite and concrete-clay interfaces at 1Ma are approximately equal to 1 and 3.3cm thick, respectively. The hyper-alkaline front (pH>8.5) spreads 2.5cm into the clay formation after 1Ma. Our simulation results share the key features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Pore clogging at the canister-bentonite and concrete-clay interfaces; 2) Narrow alteration zones; and 3) Limited smectite dissolution after 1Ma. Copyright © 2016 Elsevier B.V. All rights reserved.

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2010 CFR

2010-07-01

... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger... nonacid-, nontoxic-forming material and the backfill graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability. (4) Any remnant...

Preparation of Fe3O4/Bentonite Nanocomposite from Natural Iron Sand by Co-precipitation Method for Adsorbents Materials

NASA Astrophysics Data System (ADS)

Sebayang, Perdamean; Kurniawan, Candra; Aryanto, Didik; Arief Setiadi, Eko; Tamba, Konni; Djuhana; Sudiro, Toto

2018-03-01

An adsorption method is one of the effective ways to filter the heavy metals wastes in aqueous system. In this paper, the Fe3O4/bentonite nanocomposites were successfully prepared from natural iron sand by co-precipitation method. The chemical process was carried out by dissolving and hot stirring the milled iron sand and bentonite in acid solution and precipitating it by NH4OH. The sediment was then washed using distilled water to neutralize pH and dried at 100 °C for 5 hours to produce Fe3O4/bentonite powders. The samples were characterized by XRD, FTIR, BET, TEM, VSM and AAS. All samples were composed by Fe3O4 single phase with a spinnel structure and lattice parameter of 8.373 Å. The transmittance peak of FTIR curve proved that the Fe3O4 particles and bentonite had a molecular bonding. The addition of bentonite to Fe3O4 nanoparticles generally reduced the magnetic properties of Fe3O4/bentonite nanocomposites. The optimum condition of 30 wt% bentonite resulted 105.9 m2/g in surface area, 14 nm in an average particle size and 3.2 nm in pore size. It can be used as Cu and Pb adsorbent materials.

Electrical resisitivity of mechancially stablized earth wall backfill

NASA Astrophysics Data System (ADS)

Snapp, Michael; Tucker-Kulesza, Stacey; Koehn, Weston

2017-06-01

Mechanically stabilized earth (MSE) retaining walls utilized in transportation projects are typically backfilled with coarse aggregate. One of the current testing procedures to select backfill material for construction of MSE walls is the American Association of State Highway and Transportation Officials standard T 288: ;Standard Method of Test for Determining Minimum Laboratory Soil Resistivity.; T 288 is designed to test a soil sample's electrical resistivity which correlates to its corrosive potential. The test is run on soil material passing the No. 10 sieve and believed to be inappropriate for coarse aggregate. Therefore, researchers have proposed new methods to measure the electrical resistivity of coarse aggregate samples in the laboratory. There is a need to verify that the proposed methods yield results representative of the in situ conditions; however, no in situ measurement of the electrical resistivity of MSE wall backfill is established. Electrical resistivity tomography (ERT) provides a two-dimensional (2D) profile of the bulk resistivity of backfill material in situ. The objective of this study was to characterize bulk resistivity of in-place MSE wall backfill aggregate using ERT. Five MSE walls were tested via ERT to determine the bulk resistivity of the backfill. Three of the walls were reinforced with polymeric geogrid, one wall was reinforced with metallic strips, and one wall was a gravity retaining wall with no reinforcement. Variability of the measured resistivity distribution within the backfill may be a result of non-uniform particle sizes, thoroughness of compaction, and the presence of water. A quantitative post processing algorithm was developed to calculate mean bulk resistivity of in-situ backfill. Recommendations of the study were that the ERT data be used to verify proposed testing methods for coarse aggregate that are designed to yield data representative of in situ conditions. A preliminary analysis suggests that ERT may be utilized as construction quality assurance for thoroughness of compaction in MSE construction; however more data are needed at this time.

Effect of Na+ on surface fractal dimension of compacted bentonite

NASA Astrophysics Data System (ADS)

Xiang, G. S.; Xu, Y. F.; Jiang, H.

2015-05-01

Compacted Tsukinuno bentonite was immersed into NaCl solutions of different concentrations in oedometers, and the surface fractal dimension of bentonite-saline association was measured by nitrogen adsorption isotherms. The application of the Frenkel-Halsey-Hill equation and the Neimark thermodynamic method to nitrogen adsorption isotherms indicated that the surface roughness was greater for the bentonite-saline association. The surface fractal dimension of bentonite increased in the NaCl solution with low Na+ concentration, but decreased at high Na+ concentration. This process was accompanied by the same tendency in specific surface area and microporosity with the presence of Na+ coating in the clay particles.

Organo-modified bentonites as new flame retardant fillers in epoxy resin nanocomposites

NASA Astrophysics Data System (ADS)

Benelli, Tiziana; D'Angelo, Emanuele; Mazzocchetti, Laura; Saraga, Federico; Sambri, Letizia; Franchini, Mauro Comes; Giorgini, Loris

2016-05-01

The present work deals with two organophilic bentonites, based on nitrogen-containing compounds: these organoclays were synthesized via an ion exchange process starting from pristine bentonite with 6-(4-butylphenyl)-1,3,5-triazine-2,4-diamine (BFTDA) and 11-amino-N-(pyridine-2yl)undecanamide (APUA) and then used for the production of epoxy-based flame retardant nanocomposites. The amount of organic modifier in the organoclays Bento-BFTDA and Bento-APUA was determined with a TGA analysis and is around 0.4mmol/g for both samples. The effect of the organoclays on a commercial epoxy resin nanocomposite's thermo-mechanical and flammability properties was investigated. Composites containing 3wt% and 5wt% of the nanofillers were prepared by solventless addition of each organoclay to the epoxy resin, followed by further addition of the hardener component. For the sake of comparison a similar nanocomposite with the plain unmodified bentonite was produced in similar condition. The nanocomposites's thermo-mechanical properties of all the produced samples were measured and they resulted slightly improved or practically unaffected. On the contrary, when the flame behaviour was assessed in the cone-calorimeter, an encouraging decrease of 17% in the peak heat released rate (pHRR) was obtained at 3wt% loading level with Bento-APUA. This is a promising result, assessing that the APUA modified organoclay might act as flame retardant.

Role of bentonite clays on cell growth.

PubMed

Cervini-Silva, Javiera; Ramírez-Apan, María Teresa; Kaufhold, Stephan; Ufer, Kristian; Palacios, Eduardo; Montoya, Ascención

2016-04-01

Bentonites, naturally occurring clays, are produced industrially because of their adsorbent capacity but little is known about their effects on human health. This manuscript reports on the effect of bentonites on cell growth behaviour. Bentonites collected from India (Bent-India), Hungary (Bent-Hungary), Argentina (Bent-Argentina), and Indonesia (Bent-Indonesia) were studied. All four bentonites were screened in-vitro against two human cancer cell lines [U251 (central nervous system, glioblastoma) and SKLU-1 (lung adenocarcinoma)] supplied by the National Cancer Institute (USA). Bentonites induced growth inhibition in the presence of U251 cells, and growth increment in the presence of SKLU-1 cells, showing that interactions between bentonite and cell surfaces were highly specific. The proliferation response for U251 cells was explained because clay surfaces controlled the levels of metabolic growth components, thereby inhibiting the development of high-grade gliomas, particularly primary glioblastomas. On the other hand, the proliferation response for SKLU-1 was explained by an exacerbated growth favoured by swelling, and concomitant accumulation of solutes, and their hydration and transformation via clay-surface mediated reactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of CEC value (Cation Exchange Capacity) of Bentonites from North Aceh and Bener Meriah, Aceh Province, Indonesia using three methods

NASA Astrophysics Data System (ADS)

Rihayat, T.; Salim, S.; Arlina, A.; Fona, Z.; Jalal, R.; Alam, P. N.; Zaimahwati; Sami, M.; Syarif, J.; Juhan, N.

2018-03-01

Research on determination of value CEC (Cation Exchange Capacity) Bentonite North Aceh and Bener Meriah with three methods has been studied. The purpose of this study was to determine the value of CEC bentonite North Aceh and Bener Meriah. The methods used in this research were pH equilibrium, BaCl2/MgSO4 and the adsorption of methylene blue. These three methods used to determine, compare, and calculation of the CEC value and determine the effect of particle size of bentonite on the value of the CEC. Bentonite North Aceh and Bener Meriah sieved with particle sizes of 80, 100, 150, 200, 250 mesh. The results showed that determination of the value of CEC bentonite North Aceh using BaCl2/MgSO4 with a particle size of 250 mesh is the value of the highest, reaching 79.09 meq/100 g.

Bentonite Clay Adsorption Procedure for Concentrating Enteroviruses from Water.

DTIC Science & Technology

1992-07-01

1 pm (nominal porosity) wool filter bags, and filter beds of sand, glass, or diatomaceous earth , did not retain clay- adsorbed virus as effectively as...number) L/ A method of adsorbing enteroviruses to bentonite clay was developed for use as a concentration technique designed to sample low levels of...bentonite within a 20 minute contact period. A minimum bentonite level of 50 mg/L was necessary to adsorb the virus and to still allow efficient

Comparison of additives amendment for mitigation of greenhouse gases and ammonia emission during sewage sludge co-composting based on correlation analysis.

PubMed

Wang, Meijing; Awasthi, Mukesh Kumar; Wang, Quan; Chen, Hongyu; Ren, Xiuna; Zhao, Junchao; Li, Ronghua; Zhang, Zengqiang

2017-11-01

In this study, the pilot scale co-composting of sewage sludge (SS)+wheat straw amended with 10% (dry weight ratio of basis) of three different additives (zeolite, Ca-bentonite and medical stone) was conducted for 56days to evaluate the greenhouse gases (GHGs) and nitrogen conservation efficacy and its correlation with analyzed physicochemical, gaseous and biological parameters. The results indicated that all of three additives could adequately buffer pH, considerably increase temperature, and enhance organic matter degradation as well as reduce ammonia and GHGs emission. Particularly, zeolite amended treatment showed the maximum reduction of CH 4 emission by 88.45% and less amount of nitrogen loss by 28.80%, meanwhile reduced the maturity period by 2weeks. In addition, the redundancy analysis was confirmed most significant relationship between biological, GHGs, bacterial community and nutrients concentration in 10% zeolite applied treatment than other treatments. The result suggested 10% zeolite could be a suitable additive to improve the quality of sewage sludge composting. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of weld metal microstructure in a Ni-30Cr alloy with additions of niobium and molybdenum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheeling, Rebecca A., E-mail: wheeling.8@osu.edu; Lippold, John C., E-mail: lippold.1@osu.edu

2016-05-15

Additions of niobium (Nb) and molybdenum (Mo) were made to an Alloy 690 base alloy in order to investigate the formation of a eutectic constituent at the end of solidification and to evaluate the effect of the eutectic liquid on backfilling (or healing) of solidification cracks. Solidification cracking was induced using the cast pin tear test (CPTT) and regions of backfilling were located and characterized via optical and electron microscopy. Computational predictions of fraction eutectic and composition of the eutectic constituent were compared to experimental findings and were found to correlate well in both cases. The extent of crack backfillingmore » increased significantly with increasing Nb content, but the addition of Mo did not seem to influence the amount of eutectic constituent or the degree of backfilling. SEM/EDS analysis confirmed that the eutectic composition is constant and that increasing Nb above 4 wt% has little effect on expanding the solidification temperature range, but has a beneficial effect on mitigating solidification cracking by a crack healing effect. - Highlights: • Increasing fraction eutectic as a function of Nb, as predicted by ThermoCalc™, is consistent with image analysis results. • Nb, unlike Mo, had a significant effect on the fraction eutectic formed. • Both influence the composition of the eutectic. • Thermocalc™ predictions regarding Nb content in eutectic are consistent with EDS results, but are high for the Mo content. • Increased levels of niobium resulted in a higher degree of crack backfilling and leads to a lower cracking susceptibility. • Mo may influence the eutectic liquid along solidification grain boundaries, improving backfill and thus cracking resistance.« less

Laboratory and Field Investigations of Small Crater Repair Technologies

DTIC Science & Technology

2007-09-01

caps over debris backfill or specially placed or compacted backfill, structural systems to bridge craters, foamed crater backfills, and structural ...Jeb S. Tingle, and Timothy J. McCaffrey Geotechnical and Structures Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry...Engineer Research and Development Center (ERDC), Geotechnical and Structures Laboratory (GSL), Vicksburg, MS. The findings and recommendations presented

Filling temporary underground structures and workings at high-head hydro developments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ilyushin, V.F.

1994-12-01

Examples of backfilling temporary underground structures and workings at hydroelectric stations in Russia are cited. Structures backfilled include temporary tunnels and auxiliary workings (shafts, chambers, etc.). Detail drawings illustrate many of the examples. Examples of backfilling at a number of hydropower plants are given; however, the main emphasis is on construction of Nurek Hydroelectric Station. 8 refs., 11 figs.

Research of Cemented Paste Backfill in Offshore Environments

NASA Astrophysics Data System (ADS)

Wang, Kun; Yang, Peng; Lyu, Wensheng; Lin, Zhixiang

2018-01-01

To promote comprehensive utilization of mine waste tailings and control ground pressure, filling mine stopes with cement paste backfill (CPB) is becoming the most widely used and applicable method in contemporary underground mining. However, many urgent new problems have arisen during the exploitation in offshore mines owing to the complex geohydrology conditions. A series of rheological, settling and mechanical tests were carried out to study the influences of bittern ions on CPB properties in offshore mining. The results showed that: (1) the bittern ion compositions and concentrations of backfill water sampled in mine filling station were similar to seawater. Backfill water mixed CPB slurry with its higher viscosity coefficient was adverse to pipeline gravity transporting; (2) Bleeding rate of backfill water mixed slurry was lower than that prepared with tap water at each cement-tailings ratio; (3) The UCS values of backfill water mixed samples were higher at early curing ages (3d, 7d) and then became lower after longer curing time at 14d and 28d. Therefore, for mine production practice, the offshore environments can have adverse effects on the pipeline gravity transporting and have positive effects on stope dewatering process and early-age strength growth.

Application of Paste Backfill in Underground Coal Fires

NASA Astrophysics Data System (ADS)

Masniyom, M.; Drebenstedt, C.

2009-04-01

Coal fires are known from different coalfields worldwide. China, India, USA, Australia, Indonesia and South Africa are the main countries affected by coal fires. The fires is thermally intensive and cause numerous sinkholes, large-scale subsidence, air pollution, global warming, loss of mining productivity and increasing safety risk. The Wuda Inner Mongolia coalfield has been selected as a possible test area for paste backfill. The traditional methods, executed by fire fighting teams, by covering the coalfire areas with soil, blasting burning coal outcrops and injecting water in the subsurface fire pockets are continuously improved and extended. Initiatives to introduce modern techniques, such as backfill placement at fracture and borehole, to cool down the burning coal and cut off the air supply. This study is to investigate backfill materials and techniques suited for underground coal fires. Laboratory tests were carried out on physical, chemical and mechanical properties of different backfill materials and mixtures thereof. Special attention was paid to materials generated as by-products and other cheaply available materials e.g. fly ash from power plants. There is a good chance that one of the different material mixtures investigated can be used as a technically and economically viable backfill for underground coal fires.

Field demonstration of two pneumatic backfilling technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyni, R.C.; Burnett, M.; Philbin, D.

1995-12-31

This US Bureau of Mines (USBM) report summarizes a field demonstration of pneumatic backfilling technologies conducted at the abandoned Hillside Coal and Iron Slope in Vandling, PA. Researchers demonstrated two pneumatic backfilling technologies recently developed under the USBM`s Abandoned Mine Reclamation Research Program, the Pneumatic Pipefeeder and the High-Efficiency Ejector. Both systems had previously been evaluated at the USBM`s subsidence abatement investigation laboratory near Fairchance, PA. The objective of the demonstration was to fill 100% of the abandoned tunnel with backfill stone to prevent further subsidence. The pneumatic Pipefeeder was used for 21 days, at a rate of 63 tomore » 124 t/d (69 to 136 st/d), to fill 88% of the tunnel. The High-Efficiency Ejector was used for 2 days, at a rate of 125 to 132 T/d (138 to 146 st/d) to fill the remaining 12% of the tunnel. The backfill placed by both systems was tightly compacted. The major problem encountered was wear on the polyethylene pipeline from the abrasion of the high-velocity backfill. The use of heavier steel pipe minimized the problem. A cost analysis for the entire project is given.« less

Effect on physical properties of laterite soil with difference percentage of sodium bentonite

NASA Astrophysics Data System (ADS)

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.

Stabilization of heavy metals in soil using two organo-bentonites.

PubMed

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.

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

PubMed

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.

Confined wetting of FoCa clay powder/pellet mixtures: Experimentation and numerical modeling

NASA Astrophysics Data System (ADS)

Maugis, Pascal; Imbert, Christophe

Potential geological nuclear waste disposals must be properly sealed to prevent contamination of the biosphere by radionuclides. In the framework of the RESEAL project, the performance of a bentonite shaft seal is currently studied at Mol (Belgium). This paper focuses on the hydro-mechanical physical behavior of centimetric, unsaturated samples of the backfilling material - a mixture of FoCa-clay powder and pellets - during oedometer tests. The hydro-mechanical response of the samples is observed experimentally, and then compared to numerical simulations performed by our Cast3M Finite Element code. The generalized Darcy’s law and the Barcelona Basic Model mechanical model formed the physical basis of the numerical model and the interpretation. They are widely used in engineered barriers modeling. Vertical swelling pressure and water intake were measured throughout the test. Although water income presents a monotonous increase, the swelling pressure evolution is marked by a peak, and then a local minimum before increasing again to an asymptotic value. This unexpected behavior is explained by yielding rather than by heterogeneity. It is satisfactorily reproduced by the model after parameter calibration. Several samples with different heights ranging from 5 to 12 cm show the same hydro-mechanical response, apart from a dilatation of the time scale. The interest of the characterization of centimetric samples to predicting the efficiency of a metric sealing is discussed.

30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas. 717.14 Section 717.14 Mineral Resources OFFICE OF SURFACE... MINING GENERAL PERFORMANCE STANDARDS § 717.14 Backfilling and grading of road cuts, mine entry area cuts...

Enhancement of the bentonite sorption properties.

PubMed

Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

2010-08-15

The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. Copyright 2010 Elsevier B.V. All rights reserved.

Removal of heavy metals using bentonite supported nano-zero valent iron particles

NASA Astrophysics Data System (ADS)

Zarime, Nur Aishah; Yaacob, Wan Zuhari Wan; Jamil, Habibah

2018-04-01

This study reports the composite nanoscale zero-valent iron (nZVI) which was successfully synthesized using low cost natural clay (bentonite). Bentonite composite nZVI (B-nZVI) was introduced to reduce the agglomeration of nZVI particles, thus will used for heavy metals treatment. The synthesized material was analyzed using physical, mineralogy and morphology analysis such as Brunnaer-Emmett-Teller (BET) surface area, Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The batch adsorption test of Bentonite and B-nZVI with heavy metals solutions (Pb, Cu, Cd, Co, Ni and Zn) was also conducted to determine their effectiveness in removing heavy metals. Through Batch test, B-nZVI shows the highest adsorption capacity (qe= 50.25 mg/g) compared to bentonite (qe= 27.75 mg/g). This occurred because B-nZVI can reduce aggregation of nZVI, dispersed well in bentonite layers thus it can provide more sites for adsorbing heavy metals.

Research on preventive technologies for bed-separation water hazard in China coal mines

NASA Astrophysics Data System (ADS)

Gui, Herong; Tong, Shijie; Qiu, Weizhong; Lin, Manli

2018-03-01

Bed-separation water is one of the major water hazards in coal mines. Targeted researches on the preventive technologies are of paramount importance to safe mining. This article studied the restrictive effect of geological and mining factors, such as lithological properties of roof strata, coal seam inclination, water source to bed separations, roof management method, dimensions of mining working face, and mining progress, on the formation of bed-separation water hazard. The key techniques to prevent bed-separation water-related accidents include interception, diversion, destructing the buffer layer, grouting and backfilling, etc. The operation and efficiency of each technique are corroborated in field engineering cases. The results of this study will offer reference to countries with similar mining conditions in the researches on bed-separation water burst and hazard control in coal mines.

Thermal analysis of underground power cable system

NASA Astrophysics Data System (ADS)

Rerak, Monika; Ocłoń, Paweł

2017-10-01

The paper presents the application of Finite Element Method in thermal analysis of underground power cable system. The computations were performed for power cables buried in-line in the ground at a depth of 2 meters. The developed mathematical model allows determining the two-dimensional temperature distribution in the soil, thermal backfill and power cables. The simulations studied the effect of soil and cable backfill thermal conductivity on the maximum temperature of the cable conductor. Also, the effect of cable diameter on the temperature of cable core was studied. Numerical analyses were performed based on a program written in MATLAB.

Oxygen and hydrogen isotope geochemistry of Cretaceous bentonites and shales from the Disturbed Belt, Montana

NASA Astrophysics Data System (ADS)

Eslinger, Eric V.; Yeh, Hsueh-Wen

1986-01-01

The mineralogy, δO 18, and δD of the <0.1 μm fraction of 22 Cretaceous bentonites and the mineralogy and δO 18 of the < 0.1 μm fraction of 14 adjacent shales collected from outcrops in the Sweetgrass Arch and Disturbed Belt, Montana, have been determined. Mixed-layer illite/smectite (I/S) is the dominant mineral in the bulk bentonite and usually the only mineral in the < 0.1 μm fraction. I/S is also the major clay mineral in the shales. The diagenetic grade in bentonite is qualitatively given by the percentage of illite layers in I/S, which varies from 2 to 25 (Sweetgrass Arch) to as high as 95 (Disturbed Belt). δO 18 of < 0.1 μm bentonite generally decreases from about +20%. to about +13%. with increasing diagenetic grade. On a plot of δD versus δO 18, data for the < 0.1 μm bentonite define a field that generally parallels, but falls on the meteoric water line side of the smectite-water line (Savin and Epstein, 1970). δO 18 of bulk bentonite is 1 to 3%. more negative than the δO 18 of the < 0.1 μm fraction, due to the presence of volcanic quartz and feldspar. δO 18 of several size fractions of clay-sized quartz separated from the bentonite varies from +11%. to +24%., and, in a given bentonite, generally increases with decreasing grain size. Among the different bentonites, the δO 18 range of the different grain sizes decreases as the percentage of illite layers in the coexisting I/S increases. The δO 18 of 0.1-0.5 μm shale quartz is generally 1 to 4%. more positive than clay-sized quartz from an adjacent bentonite, and the δO 18 of < 0.1 μm I/S concentrate of shales is generally < 1 to 4%. more negative than the < 0.1 μm I/S from an adjacent bentonite. Isotopic temperatures, interpreted to be maximum burial temperatures, range between about 160°C (shale), to about 250°C (bentonite). The isotopic data can be interpreted using the stages: 1) deposition of volcanic glassy ash containing some quartz and feldspar; 2) devitrification into mostly 100% expandable smectite with a δO 18 of about 20%. and δD of -60 to -80%.; 3) tectonic burial beneath thrust sheets in the Disturbed Belt region which induced elevated temperatures that allowed oxygen and hydrogen isotope reequilibration as the percentage of illite layers in I/S increased and diagenetic quartz formed; and 4) exhumation of the strata with preservation of O 18/O 16 and D/H attained during burial.

Testing of candidate waste-package backfill and canister materials for basalt

NASA Astrophysics Data System (ADS)

Wood, M. I.; Anderson, W. J.; Aden, G. D.

1982-09-01

The Basalt Waste Isolation Project (BWIP) is developing a multiple-barrier waste package to contain high-level nuclear waste as part of an overall system (e.g., waste package, repository sealing system, and host rock) designed to isolate the waste in a repository located in basalt beneath the Hanford Site, Richland, Washington. The three basic components of the waste package are the waste form, the canister, and the backfill. An extensive testing program is under way to determine the chemical, physical, and mechanical properties of potential canister and backfill materials. The data derived from this testing program will be used to recommend those materials that most adequately perform the functions assigned to the canister and backfill.

Bentonite toxicology and epidemiology - a review.

PubMed

Maxim, L Daniel; Niebo, Ron; McConnell, Ernest E

2016-11-01

Bentonite, a clay with numerous industrial and consumer applications, is mined and processed in many countries of the world. Its many beneficial uses also create the potential for widespread occupational and consumer exposure. The available studies on toxicity and epidemiology indicate that the principal exposure pathway of concern is inhalation of respirable dust by occupationally exposed cohorts. Bentonite itself is probably not more toxic than any other particulate not otherwise regulated and is not classified as a carcinogen by any regulatory or advisory body, but some bentonite may contain variable amounts of respirable crystalline silica, a recognized human carcinogen. Therefore, prudent management and adherence to occupational exposure limits is appropriate. This review summarizes the literature available on production, applications, exposure, toxicity, and epidemiology of bentonite and identifies data gaps and limitations.

γ-radiation induced corrosion of copper in bentonite-water systems under anaerobic conditions

NASA Astrophysics Data System (ADS)

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.

The effect of landfill leachate composition on organics and nitrogen removal in an activated sludge system with bentonite additive.

PubMed

Wiszniowski, J; Surmacz-Górska, J; Robert, D; Weber, J-V

2007-10-01

A pre-denitrification activated sludge system (AS) without internal recycle was used in lab-scale studies of landfill leachate treatment. A bentonite supplement at a ratio of 1:4 (mineral : biomass) was used to ensure high sludge settling levels and to serve as a micro-organisms carrier. The system was operated within different parameters such as hydraulic retention time (HRT), ammonia loading rate (ALR) or external recycle ratio, which was adapted to treat varying leachate concentrations of COD and ammonia, ranging from 1020 to 2680 mgO(2)l(-1) and 400-890 mgNH(4)-Nl(-1) respectively. The nitrification was complete and ammonia oxidation reached 99%; this was obtained while the ALR did not exceed 0.09 g NH(4)(+)-Ng(-1)MLVSS d(-1) and HRT was not lower than 1 day (in the aeration reactor). The performance of denitrification was successfully improved by controlling the external recycle rate, when the BOD(5)/N ratio in the raw leachate was 4.1. Consequently, N-removal of up to 80% was achieved. A 10-fold decrease in the denitrification rate was obtained at a BOD(5)/N ratio of 0.5. The efficiency of COD removal varied significantly from 36% to 84%. The positive effect of bentonite addition was determined and is discussed based on preliminary studies. The experiments were carried out in fill-and-draw activated sludge with bentonite; the biomass ratio was 1:2. The activated sludge with bentonite was fed with a synthetic high ammonia and organic-free medium.

A unique Middle Ordovician K-bentonite bed succession at Röstånga, S. Sweden

USGS Publications Warehouse

Bergstrom, Stig M.; Huff, Warren D.; Kolata, Dennis R.; Yost, Deborah A.; Hart, Charles P.

1997-01-01

An approximately 8.5 m thick sequence of upper Viruan (upper Middle Ordovician) shales, mudstones, and limestones in an outcrop at Kyrkbäcken near Röstånga in W‐central Skåne contains 19 K‐bentonite beds, several of which are as much as 40–67 cm thick. Thirteen of these beds are in the upper part of the Sularp Fm., four in the Skagen Fm., and two questionable beds in the Mossen Fm. Evidence from macrofossils, chitinozoans, and conodonts are used for biostratigraphic age assessment of the K‐bentonite succession. Regional comparison of the sequence with those at Kinnekulle (Kullatorp), Koängen, and Tommarp suggests that its total stratigraphie thickness is smaller than those at the two former sites but the thicknesses of several of the Kyrkbacken ash beds are greater than those in similar stratigraphic positions in the other successions. The K‐bentonites at Kyrkbacken have a similar clay mineralogy and major and trace element composition as other Ordovician K‐bentonites, and these data indicate that the parental magma was of felsic, probably rhyolitic composition. Based on amphibole geoba‐rometry, the magma chamber is interpreted to have been at a depth of 14–20 km. The relatively large number of unusually thick ash beds of Middle Ordovician age makes the easily accessible Kyrkbäcken outcrop unique not only in Baltoscandia but, as far as we are aware, also on the entire northern hemisphere, and only one comparable exposure is known in the southern hemisphere, namely in the Precordillera of northern Argentina.

Alginate-immobilized bentonite clay: adsorption efficacy and reusability for Cu(II) removal from aqueous solution.

PubMed

Tan, Wei Shang; Ting, Adeline Su Yien

2014-05-01

This study evaluated the use of alginate-immobilized bentonite to remove Cu(II) as an alternative to mitigate clogging problems. The adsorption efficacy (under the influence of time, pH and initial Cu(II) concentration) and reusability of immobilized-bentonite (1% w/v bentonite) was tested against plain alginate beads. Results revealed that immobilized bentonite demonstrated significantly higher sorption efficacy compared to plain alginate beads with 114.70 and 94.04 mg Cu(II) adsorbed g(-1) adsorbent, respectively. Both sorbents were comparable in other aspects where sorption equilibrium was achieved within 6 h, with optimum pH between pH 4 and 5 for adsorption, displayed maximum adsorption capacity at initial Cu(II) concentrations of 400 mg l(-1), and demonstrated excellent reusability potential with desorption greater than 90% throughout three consecutive adsorption-desorption cycles. Both sorbents also conformed to Langmuir isotherm and pseudo-second order kinetic model. Immobilized bentonite is therefore recommended for use in water treatments to remove Cu(II) without clogging the system. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of the natural bentonite to reduce COD in palm oil mill effluent by using a hybrid adsorption-flotation method

NASA Astrophysics Data System (ADS)

Dewi, Ratni; Sari, Ratna; Syafruddin

2017-06-01

Palm oil mill effluent is waste produced from palm oil processing activities. This waste are comingfrom condensate water, process water and hydrocyclone water. The high levels of contaminants in the palm oil mill effluent causes the waste becomes inappropriate to be discharged to water body before processing, one of the most major contaminants in wastewater is fats, oils and COD.This study investigated the effectiveness of chemically activated bentonite that serves as an alternative to reduce the COD in adsorption and floatation based palm oil effluent waste processing. Natural bentonite was activated by using nitrit acid and benzene. In the existing adsorption material to improve COD reduction capability whereas the flotation method was used to further remove residual effluent which is still remain after the adsorption process. An adsorption columns which operated in batch was used in the present study. By varying the circulation time and adsorbent treatment (activated and non-activated), it was shown that percentage of COD reduction reached 75% at the circulation time of 180 minutes for non activated adsorbent. On the other hand the percentof COD reduction in adsorption and flotation process using activated bentonite reached as high as 88% and 93% at the circulation time of 180 minutes.

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

NASA Astrophysics Data System (ADS)

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.

Improvement of Expansive Soils Using Chemical Stabilizers

NASA Astrophysics Data System (ADS)

Ikizler, S. B.; Senol, A.; Khosrowshahi, S. K.; Hatipoğlu, M.

2014-12-01

The aim of this study is to investigate the effect of two chemical stabilizers on the swelling potential of expansive soil. A high plasticity sodium bentonite was used as the expansive soil. The additive materials including fly ash (FA) and lime (L) were evaluated as potential stabilizers to decrease the swelling pressure of bentonite. Depending on the type of additive materials, they were blended with bentonite in different percentages to assess the optimum state and approch the maximum swell pressure reduction. According to the results of swell pressure test, both fly ash and lime reduce the swelling potential of bentonite but the maximum improvement occurs using bentonite-lime mixture while the swelling pressure reduction approaches to 49%. The results reveal a significant reduction of swelling potential of expansive soil using chemical stabilizers. Keywords: Expansive soil; swell pressure; chemical stabilization; fly ash; lime

Adsorption of Acid Blue 25 dye by bentonite and surfactant modified bentonite

NASA Astrophysics Data System (ADS)

Jeeva, Mark; Wan Zuhairi, W. Y.

2018-04-01

Adsorption of Acid Blue (AB 25) from water via batch adsorption experiments onto Na-Bentonite (NB) and CTAB-modified bentonite (CTAB-Ben) was investigated. Studies concerning the factors influencing the adsorption capacities of NB and CTAB-Ben, such as initial dye concentration, adsorbent dosage, pH, contact time and temperature were investigated and discussed. The results revealed that CTAB-modified bentonite demonstrated high adsorption capacities toward acid dyes, while NB exhibited sorption capacities lower than CTAB-Ben. The maximum adsorption efficiency was found to be 50% at an AB 25 concentration of 50 mg/L, adsorbent dosage of 1.8 g/L, reaction time of 90 min and equilibrium pH of 11. The results of isotherm study fit the Langmuir and Freundlich models (R2 > 0.93) and (R2 > 0.9) respectively.

Geochemical processes and the effects of natural organic solutes on the solubility of selenium in coal-mine backfill samples from the Powder River basin, Wyoming

USGS Publications Warehouse

See, R.B.; Reddy, K.J.; Vance, G.F.; Fadlelmawla, A.A.; Blaylock, M.J.

1995-01-01

Geochemical processes and the effects of natural organic solutes on the solubility of selenium in coal-mine backfill aquifers were investigated. Backfill and ground-water samples were collected at coal mines in the Powder River Basin, Wyoming. Backfill was generally dominated by aluminum (14,400 to 49,000 mg/kg (milligrams per kilogram)), iron (3,330 to 23,200 mg/kg), and potassium (7,950 to 18,000 mg/kg). Backfill saturated-paste selenium concentrations ranged from 1 to 156 mg/kg (microsiemens per kilogram). Ground-water total selenium concentrations ranged from 3 to 125 mg/L. Dissolved organic carbon in all ground-water samples was dominated by hydrophobic and hydrophilic acids (38 to 84 percent). Selenite sorption/desorption experiments were conducted using background solutions of distilled-deionized water, 0.1 molar calcium chloride, and isolated hydrophobic and hydrophilic acids. Selenite sorption was larger when 0.1 molar calcium chloride was used. The addition of hydrophilic acid decreased selenite sorption more than the addition of hydrophobic acids. Geochemical modelling was used to predict the solid phases controlling dissolved selenium concentrations and to evaluate the effects of dissolved organic carbon on selenium solubility. Results suggested that 55 to 90 percent of selenium in backfill precipitation/dissolution extracts was dominated by magnesium selenate ion pairs. Dissolved organic carbon had little effect on selenium speciation. A redox chamber was constructed to control Eh and pH in water and backfill-core sample suspensions. The response of selenite and selenate in water samples to redox conditions did not follow thermodynamic predictions. Reduction of selenate in water samples did not occur at any of the redox levels tested.

Electrospun PVA/Bentonite Nanocomposites Mats for Drug Delivery

PubMed Central

Ferrández-Rives, Mariola; Gómez Ribelles, José Luis

2017-01-01

Electrospun mats and films of polyvinyl alcohol (PVA) hydrogel are produced for drug delivery. To provide mechanical consistency to the gel a reinforcement by nanoclays is introduced in the polymer matrix. Four different suspensions of nanoparticles in the polymer solution are prepared in an adequate solvent. These suspensions are subjected to an electrospinning process to produce the nanofiber mat, while films are produced by casting. The influence of the process parameters over the nanofibers microstructure is analyzed by scanning electron microscopy (SEM). The effectiveness of nanoclay encapsulation in the nanocomposites is tested by a thermogravimetric analysis. A crosslinking reaction in solution is carried out to prevent the dissolution of the nanocomposites in aqueous media. A model protein (bovine serum albumin, BSA) is absorbed in the nanocomposites to characterize the release kinetics in phosphate-buffered saline (PBS). PMID:29261123

Backfilling with guarantees granted upon job submission.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leung, Vitus Joseph; Bunde, David P.; Lindsay, Alexander M.

2011-01-01

In this paper, we present scheduling algorithms that simultaneously support guaranteed starting times and favor jobs with system desired traits. To achieve the first of these goals, our algorithms keep a profile with potential starting times for every unfinished job and never move these starting times later, just as in Conservative Backfilling. To achieve the second, they exploit previously unrecognized flexibility in the handling of holes opened in this profile when jobs finish early. We find that, with one choice of job selection function, our algorithms can consistently yield a lower average waiting time than Conservative Backfilling while still providingmore » a guaranteed start time to each job as it arrives. In fact, in most cases, the algorithms give a lower average waiting time than the more aggressive EASY backfilling algorithm, which does not provide guaranteed start times. Alternately, with a different choice of job selection function, our algorithms can focus the benefit on the widest submitted jobs, the reason for the existence of parallel systems. In this case, these jobs experience significantly lower waiting time than Conservative Backfilling with minimal impact on other jobs.« less

Nanoscale Zero-Valent Iron Decorated on Bentonite/Graphene Oxide for Removal of Copper Ions from Aqueous Solution.

PubMed

Shao, Jicheng; Yu, Xiaoniu; Zhou, Min; Cai, Xiaoqing; Yu, Chuang

2018-06-04

The removal efficiency of Cu(II) in aqueous solution by bentonite, graphene oxide (GO), and nanoscale iron decorated on bentonite (B-nZVI) and nanoscale iron decorated on bentonite/graphene oxide (GO-B-nZVI) was investigated. The results indicated that GO-B-nZVI had the best removal efficiency in different experimental environments (with time, pH, concentration of copper ions, and temperature). For 16 hours, the removal efficiency of copper ions was 82% in GO-B-nZVI, however, it was 71% in B-nZVI, 26% in bentonite, and 18% in GO. Bentonite, GO, B-nZVI, and GO-B-nZVI showed an increased removal efficiency of copper ions with the increase of pH under a certain pH range. The removal efficiency of copper ions by GO-B-nZVI first increased and then fluctuated slightly with the increase of temperature, while B-nZVI and bentonite increased and GO decreased slightly with the increase of temperature. Lorentz-Transmission Electron Microscope (TEM) images showed the nZVI particles of GO-B-nZVI dispersed evenly with diameters ranging from 10 to 86.93 nm. Scanning electron microscope (SEM) images indicated that the nanoscale iron particles were dispersed evenly on bentonite and GO with no obvious agglomeration. The q e,cal (73.37 mg·g -1 and 83.89 mg·g -1 ) was closer to the experimental value q e,exp according to the pseudo-second-order kinetic model. The q m of B-nZVI and GO-B-nZVI were 130.7 mg·g -1 and 184.5 mg·g -1 according to the Langmuir model.

Organophilic treatments of bentonite increase the adsorption of aflatoxin B1 and protect stem cells against cellular damage.

PubMed

Nones, Janaína; Nones, Jader; Poli, Anicleto; Trentin, Andrea Gonçalves; Riella, Humberto Gracher; Kuhnen, Nivaldo Cabral

2016-09-01

Bentonite clays exhibit high adsorptive capacity for contaminants, including aflatoxin B1 (AFB1), a mycotoxin responsible for causing severe toxicity in several species including pigs, poultry and man. Organophilic treatments is known to increase the adsorption capacity of bentonites, and the primary aim of this study was to evaluate the ability of Brazilian bentonite and two organic salts - benzalkonium chloride (BAC) and cetyltrimethylammonium bromide (CTAB) to adsorb AFB1. For this end, 2(2) factorial designs were used in order to analyze if BAC or CTAB was able to increase AFB1 adsorption when submitted in different temperature and concentration. Both BAC and CTAB treatment (at 30°C and 2% of salt concentration) were found to increase the adsorption of AFB1 significantly compared with untreated bentonite. After organophilic bentonite treatments with BAC or CTAB, a vibration of CH stretch (2850 and 2920cm(-1)) were detected. A frequency of the SiO stretch (1020 and 1090cm(-1)) was changed by intercalation of organic cation. Furthermore, the interlayer spacing of bentonite increases to 1.23nm (d001 reflection at 2θ=7.16) and 1.22 (d001 reflection at 2θ=7.22) after the addition of BAC and CTAB, respectively. Another aim of the study was to observe the effects of these two bentonite salts in neural crest stem cell cultures. The two materials that were created by organophilic treatments were not found to be toxic to stem cells. Furthermore the results indicate that the two materials tested may protect the neural crest stem cells against damage caused by AFB1. Copyright © 2016 Elsevier B.V. All rights reserved.

Pyronin Y (basic xanthene dye)-bentonite composite: A spectroscopic study

NASA Astrophysics Data System (ADS)

Tabak, A.; Kaya, M.; Yilmaz, N.; Meral, K.; Onganer, Y.; Caglar, B.; Sungur, O.

2014-02-01

The expansion by 1.43 Angstrom of basal spacing and the shift to higher frequencies of in-plane ring vibrations of the Pyronin Y molecule at 1603 and 1527 cm-1 on the formation of Pyronin Y-bentonite composite exhibited that the dye cations might be oriented as a monolayer form in the interlamellar spacing with aromatic rings parallel to clay layers. Thermal analysis results of this composite compared to those of raw bentonite signified the different outer sphere water entities associated with the replacement of inorganic cations with organic dye cations and the gradual decomposition of the organic molecule in the interlamellar spacing. Thermo-Infrared spectra of Pyronin Y-bentonite sample up to high temperatures showed the thermal stability of the dye-clay composite as a result of the presence of π interactions. The pore structure characteristics of Pyronin Y-bentonite composite exhibited the increase in the number of mesopores during formation of the composite.

Microstructure of bentonite in iron ore green pellets.

PubMed

Bhuiyan, Iftekhar U; Mouzon, Johanne; Schröppel, Birgit; Kaech, Andres; Dobryden, Illia; Forsmo, Seija P E; Hedlund, Jonas

2014-02-01

Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

Use of rubber and bentonite added fly ash as a liner material.

PubMed

Cokca, Erdal; Yilmaz, Zeka

2004-01-01

In many countries regulations require all hazardous waste disposal facilities to be lined with suitable impermeable barriers to protect against contamination. In this study, a series of laboratory tests on rubber and bentonite added fly ash were conducted. The aim of the tests was to evaluate the feasibility of utilizing fly ash, rubber and bentonite as a low hydraulic conductivity liner material. Type C fly ash was obtained from Soma thermal power plant in Turkey; rubber in pulverized form was waste from the retreading industry. To investigate the properties of rubber and bentonite added fly ash, hydraulic conductivity, leachate analysis, unconfined compression, split tensile strength, one-dimensional consolidation, swell and freeze/thaw cycle tests were performed. The overall evaluation of results have revealed that rubber and bentonite added fly ash showed good promise and a candidate for construction of a liner.

Timing of the Blount and Martinsburg foreland basin development during the Taconic Orogeny based on the Deicke and Millbrig K-bentonite marker horizons

DOE Office of Scientific and Technical Information (OSTI.GOV)

McVey, D.E.; Huff, W.D.

1993-03-01

During the Taconic Orogeny (Middle and Late Ordovician), the eastern continental margin of North America developed several foreland basins as a result of the collision of one or more island arc/microplate complexes. These collisions occurred along a subduction zone characterized by a string of explosively eruptive volcanoes which produced widespread K-bentonite beds. Volcanism coincided with the filling of thick accumulations of sediment in two of the basins: the Blount (southern Appalachians) and the Martinsburg (central Appalachians). Two prominent K-bentonites, the Deicke and Millbrig, have been correlated across the two basins in this study. These two K-bentonites are stratigraphically significant becausemore » they are excellent time lines since they represent short-term events in geologic history. The foreland basins developed by the Taconic Orogeny become successively younger to the north due to a shift in the focus of collision (Read, 1980). The Blount basin was nearly filled with sediment by the time the Martinsburg basin began to form. This coincides with previous suggestions that the Taconic Orogeny was not one climactic event but a series of events where the collisions migrated northward like the closing of a zipper. The Deicke and Millbrig K-bentonites occur within the platform carbonates of the Eggleston and Liberty Hall formations and the red bed clastic facies of the Bays formation in the Blount basin, and they occur within the slope carbonates of the New Enterprise Member of the Salona formation and the black shale and turbidite facies of the Martinsburg formation in the Martinsburg basin. This correlation establishes a more precise time framework for the formation of the two foreland basins.« less

Hydration products and thermokinetic properties of cement-bentonite and cement-chalk mortars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klyusov, A.A.

1988-08-20

Bentonite and chalk are the most popular auxiliary additives to portland cement for borehole cementation. The authors studied by physicochemical analysis methods (x-ray phase, derivatographic, and scanning and electron microscopy in combination with microdiffraction) the newly formed solid-phase composition of cement-bentonite and cement-chalk mortars (binder-additive ratio 9:1) prepared from portland cement for cold boreholes and 8% calcium chloride solution at a water-mixing ratio of 0.9. The mechanism of the influence of Ca-bentonite and chalk additives on the portland cement hydration rate was ascertained from the heat evolution rate curves. It was found that the phase compositions of the hydration productsmore » are represented in the studied systems by newly formed substances typical for portland cement. It has been noted that Ca-bentonite interacts with the calcium hydroxide of hydrated cement with the formation of hexagonal and cubic calcium hydroaluminates. Unlike Ca-bentonite, chalk does not react with portland cement at normal and reduced temperatures, does not block hydrated cement particles, which, in turn, ensures all other conditions remaining equal, a higher initial rate of hydration of cement-chalk mortar.« less

Temperature dependence of soil water potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, A.M.O.; Yong, R.N.; Cheung, S.C.H.

1992-12-01

To understand the process of coupled heat and water transport, the relationship between temperature and soil water potential must be known. Two clays, Avonlea bentonite and Lake Agassiz clay, are being considered as the clay-based sealing materials for the Canadian nuclear fuel waste disposal vault. Avonlea bentonite is distinguished from Lake Agassiz clay by its high sealing potential in water. A series of experiments was performed in which the two clays were mixed with equal amounts of sand and were compacted to a dry density of 1.67 Mg/m[sup 3] under various moisture contents and temperatures. A psychrometer was placed withinmore » the compacted clay-sand to measure the soil water potential based on the electromotive force measured by the psychrometer. The results indicate that the soil water potential at a particular temperature is higher for both clay-sand mixtures than predicted by the change in the surface tension of water; this effect is much more prominent in the Avonlea bentonite and at low moisture contents. The paper presents empirical equations relating the soil water potential with the moisture content and temperature of the two clay-sand mixtures. 24 refs., 8 figs., 2 tabs.« less

Synthesis and characterization of polyurethane/bentonite nanoclay based nanocomposites using different diisocyanates: relation between mechanical and thermal properties

NASA Astrophysics Data System (ADS)

Bocchio, Javier; Wittemberg, Víctor; Quagliano, Javier

2017-05-01

Polyurethanes (PUs) and polyurethane nanocomposites (PUNC) with bentonite nanoclay were prepared by the reaction of toluene-2,4-diisocyanate (TDI), dimeryl diisocyanate (DDI) and isophorone diisocyanate (IPDI) with two different polymers: hydroxyl terminated polybutadiene (HTPB) and polytetramethylene ether glycol (PTMEG), and the chains were further extended with 1,4-butanediol (1,4-BDO) to get final PUs and PUNCs. PUNCs were prepared by dispersing within the polymers a commercial and a synthesized bentonite nanoclay by mechanical dispersion. Mechanical properties showed that the addition of a small amount of nanoclay resulted in a significant increase in tensile strength and reduction in elongation at break (maximum increase of 2.3 and 5-times reduction, respectively, for a HTPB-TDI-BDO PUNCs). Thermal analysis revealed that the addition of nanoclays improved the thermal stability and increased decomposition temperature of PUNCs. We concluded that there is a positive correlation between mechanical and thermal properties as a result of nanoclay addition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, M.A.; Khan, S.A.

Sorption studies of cesium, strontium, and cobalt (Cs, Sr, and Co) on bentonite under various experimental conditions, such as contact time, pH, sorbent and sorbate concentration, and temperature, have been performed. The sorption data for all these metals have been interpreted in terms of Freundlich, Langmuir, and Dubinin-Radushkevich equations. Thermodynamics parameters, such as heat of sorption {Delta}H{degrees}, free energy change {Delta}G{degrees}, and entropy change {Delta}S{degrees}, for the sorption of these metals on bentonite have been calculated. The value of {Delta}H{degrees} shows that the sorption of Cs was exothermic, while the sorption of Sr and Co on bentonite were endothermic inmore » nature. The value of {Delta}G{degrees} for their sorption was negative, showing the spontaneity of the process. The maximum loading capacity of Cs, Sr, and Co were 75.5, 22, and 27.5 meq, respectively, for 100 g of bentonite. The mean free energy E of Cs, Sr, and Co sorption on bentonite was 14.5, 9, and 7.7 kJ/mol, respectively. The value of E indicates that ion exchange may be the predominant mode of sorption for these radionuclides. The desorption studies with 0.01 M CaCl{sub 2} and groundwater at low-metal loading on bentonite showed that about 95% of Cs, 85-90% of Sr, and 97% of Co were irreversibly sorbed. Bentonite could be effectively used for the decontamination of wastewater effluent containing low concentrations of radioactive nuclides of Cs, Sr, and Co. 16 refs., 7 figs., 3 tabs.« less

Comparing the effects of Bentonite & Calendula on the improvement of infantile diaper dermatitis: A randomized controlled trial.

PubMed

Mahmoudi, Mansoreh; Adib-Hajbaghery, Mohsen; Mashaiekhi, Mahdi

2015-12-01

Infantile diaper dermatitis is a common, acute inflammatory reaction of the skin around diaper among infants. This study was undertaken to compare the effect of topical application of Bentonite and Calendula creams on the improvement of infantile diaper dermatitis. This double blind randomized controlled trial was undertaken on 100 patients of infantile diaper dermatitis. The 100 participants were randomly assigned into two groups of 50 each, and were prescribed the coded medicine. The mothers were trained to apply the cream and level of improvement was judged by observing the affected area on the first visit and then after three days of receiving treatment. The mean age of infants was 6.45±5.53 months in Calendula group and 7.35±6.28 months in Bentonite group. Overall, 88 per cent of lesions in the Bentonite group started improving in the first six hours while this rate was 54 per cent in Calendula group (P<0.001). The risk ratio for the improvement in the first six hours was 2.99 folds in the Bentonite group. Also, lesions in 86 per cent infants in the Bentonite group and 52 per cent in the Calendula group were completely improved in the first three days after treatment (P<0.001). Our results showed that in comparison with Calendula, Bentonite had faster healing effect and was more effective on the improvement of infantile diaper dermatitis (IRCT ID: IRCT 2012112811593N1).

Obtainment and partial characterization of biodegradable gelatin films with tannic acid, bentonite and glycerol.

PubMed

Ortiz-Zarama, Maria A; Jiménez-Aparicio, Antonio R; Solorza-Feria, Javier

2016-08-01

Research studies concerning the overall effect of the addition of plasticizers, cross-linking and strengthening agents in gelatin film-forming mixtures are very scarce. Also, there are no studies focused on the interactions among their individual components, or showing what sort of effects they might cause all together. A gelatin film obtained from a composite consisting of tannic acid, bentonite and glycerol was evaluated. Nine gelatin films were manufactured by the casting method, using these materials, following a 2(3) factorial design with five replicates on the central point. The interactions among gelatin, tannic acid and bentonite caused a decrease in hydrogen bonds, while the polar groups of the gelatin chains were less exposed to interactions with water molecules. There was an increase in temperature and enthalpy of gelatin denaturation, due to increasing tannic acid and bentonite concentration. Tactoids were found in the gelatin films, caused mainly by bentonite polydispersion. A synergistic effect among tannic acid, bentonite and glycerol, which overall improved the measured gelatin film properties, was found. The best film formulation was that with 40, 150 and 250 g kg(-1) gelatin of tannic acid, bentonite and glycerol respectively, displaying a tensile strength of 38 MPa, an elongation at break of 136%, water vapor permeability of 1.28 × 10(-12) g (Pa s m)(-1) and solubility of 23.4%. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Monitoring water content in Opalinus Clay within the FE-Experiment: Test application of dielectric water content sensors

NASA Astrophysics Data System (ADS)

Sakaki, T.; Vogt, T.; Komatsu, M.; Müller, H. R.

2013-12-01

The spatiotemporal variation of water content in the near field rock around repository tunnels for radioactive waste in clay formations is one of the essential quantities to be monitored for safety assessment in many waste disposal programs. Reliable measurements of water content are important not only for the understanding and prediction of coupled hydraulic-mechanic processes that occur during tunnel construction and ventilation phase, but also for the understanding of coupled thermal-hydraulic-mechanical (THM) processes that take place in the host rock during the post closure phase of a repository tunnel for spent fuel and high level radioactive waste (SF/HLW). The host rock of the Swiss disposal concept for SF/HLW is the Opalinus Clay formation (age of approx. 175 Million years). To better understand the THM effects in a full-scale heater-engineered barrier-rock system in Opalinus Clay, a full-scale heater test, namely the Full-Scale Emplacement (FE) experiment, was initiated in 2010 at the Mont Terri underground rock laboratory in north-western Switzerland. The experiment is designed to simulate the THM evolution of a SF/HLW repository tunnel based on the Swiss disposal concept in a realistic manner during the construction, emplacement, backfilling, and post-closure phases. The entire experiment implementation (in a 50 m long gallery with approx. 3 m diameter) as well as the post-closure THM evolution will be monitored using a network of several hundred sensors. The sensors will be distributed in the host rock, the tunnel lining, the engineered barrier, which consists of bentonite pellets and blocks, and on the heaters. The excavation is completed and the tunnel is currently being ventilated. Measuring water content in partially saturated clay-rich high-salinity rock with a deformable grain skeleton is challenging. Therefore, we use the ventilation phase (before backfilling and heating) to examine the applicability of commercial water content sensors and to design custom-made TDR sensors. The focus of this study is mainly on dielectric-based commercial water content sensors. Unlike soils for which the sensors were originally designed, it requires significantly more attention to properly install it onto rock (i.e., a good contact with the sensor and rock). The results will be used to select and design the instrumentation set-up for monitoring water content during the heating phase where sensors have to withstand harsh conditions (high salinity, high temperature, high pressures, high clay content and long term monitoring up to 10 years). The sensor tests are beneficial also in the sense that the water content data generated during these tests provide insights into drainage processes after tunnel construction and seasonal water content variations in the near field rock around the test gallery. We will present results from the tests and measurements performed during the first year.

An alternative method for the treatment of waste produced at a dye and a metal-plating industry using natural and/or waste materials.

PubMed

Fatta, Despo; Papadopoulos, Achilleas; Stefanakis, Nikos; Loizidou, Maria; Savvides, Chrysanthos

2004-08-01

The aim of this study was to develop cost-effective, appropriate solidification technologies for treating hazardous industrial wastes that are currently disposed of in ways that may threaten the quality of local groundwater. One major objective was to use materials other than cement, and preferably materials that are themselves wastes, as the solidification additives, namely using wastes to treat wastes or locally available natural material. This research examines the cement-based and lime-based stabilization/solidification (S/S) techniques applied for waste generated at a metal-plating industry and a dye industry. For the lime-based S/S process the following binder mixtures were used: cement kiln dust/ lime, bentonite/lime and gypsum/lime. For the cement-based S/S process three binder mixtures were used: cement kiln dust/cement, bentonite/cement and gypsum/cement. The leachability of the wastes was evaluated using the toxicity characteristic leaching procedure. The applicability and optimum weight ratio of the binder mixtures were estimated using the unconfined compressive strength test. The optimum ratio mixtures were mixed with waste samples in different ratios and cured for 28 days in order to find the S/S products with the highest strength and lowest leachability at the same time. The results of this work showed that the cement-and lime-based S/S process, using cement kiln dust and bentonite as additives can be effectively used in order to treat industrial waste.

Seismic passive earth resistance using modified pseudo-dynamic method

NASA Astrophysics Data System (ADS)

Pain, Anindya; Choudhury, Deepankar; Bhattacharyya, S. K.

2017-04-01

In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study.

Development of a Korean reference HLW disposal system under the Korean representative geologic conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Heui-Joo; Lee, Jong Youl; Choi, Jongwon

2007-07-01

The development of a Korean Reference disposal System for the spent fuels from PWR and CANDU reactors is outlined in this paper. Around 36,000 tU of spent fuels are being projected based on the lifetimes of 28 nuclear power reactors in Korea. Since the site for the geological disposal has not yet been decided, a hypothetical site with representative Korean geologic conditions is proposed for the conceptual design of the repository. The disposal rates of the spent fuels are determined according to the total operation time of 55 years. The canisters are optimized by considering natural Korean conditions, and themore » buffer is designed with domestic Ca-bentonite. The depth of the repository is determined to be 500 m below the ground's surface. The canister separation distances are determined through a thermal analysis. The main features of the repository are presented from the layout to the closure. A computer program has been developed to calculate and analyze the volume and the area of the disposal system to help in the cost analysis. The final output of the design is presented as a unit disposal cost, US $315 /kgU. (authors)« less

Native backfill materials for mechanically stabilized earth walls.

DOT National Transportation Integrated Search

2005-01-01

Mechanically stabilized earth walls are an attractive alternative to conventional reinforced concrete retaining walls. The economy of these walls for non-critical applications might be improved by using alternative backfills consisting of on-site soi...

A Coupled THMC model of FEBEX mock-up test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Liange; Samper, Javier

2008-09-15

FEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project for the engineered barrier system (EBS) of a radioactive waste repository in granite. It includes two full-scale heating and hydration tests: the in situ test performed at Grimsel (Switzerland) and a mock-up test operating at CIEMAT facilities in Madrid (Spain). The mock-up test provides valuable insight on thermal, hydrodynamic, mechanical and chemical (THMC) behavior of EBS because its hydration is controlled better than that of in situ test in which the buffer is saturated with water from the surrounding granitic rock. Here we present a coupled THMC model ofmore » the mock-up test which accounts for thermal and chemical osmosis and bentonite swelling with a state-surface approach. The THMC model reproduces measured temperature and cumulative water inflow data. It fits also relative humidity data at the outer part of the buffer, but underestimates relative humidities near the heater. Dilution due to hydration and evaporation near the heater are the main processes controlling the concentration of conservative species while surface complexation, mineral dissolution/precipitation and cation exchanges affect significantly reactive species as well. Results of sensitivity analyses to chemical processes show that pH is mostly controlled by surface complexation while dissolved cations concentrations are controlled by cation exchange reactions.« less

The Resource Usage Aware Backfilling

NASA Astrophysics Data System (ADS)

Guim, Francesc; Rodero, Ivan; Corbalan, Julita

Job scheduling policies for HPC centers have been extensively studied in the last few years, especially backfilling based policies. Almost all of these studies have been done using simulation tools. All the existent simulators use the runtime (either estimated or real) provided in the workload as a basis of their simulations. In our previous work we analyzed the impact on system performance of considering the resource sharing (memory bandwidth) of running jobs including a new resource model in the Alvio simulator. Based on this studies we proposed the LessConsume and LessConsume Threshold resource selection policies. Both are oriented to reduce the saturation of the shared resources thus increasing the performance of the system. The results showed how both resource allocation policies shown how the performance of the system can be improved by considering where the jobs are finally allocated.

Generic Argillite/Shale Disposal Reference Case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Liange; Colon, Carlos Jové; Bianchi, Marco

Radioactive waste disposal in a deep subsurface repository hosted in clay/shale/argillite is a subject of widespread interest given the desirable isolation properties, geochemically reduced conditions, and widespread geologic occurrence of this rock type (Hansen 2010; Bianchi et al. 2013). Bianchi et al. (2013) provides a description of diffusion in a clay-hosted repository based on single-phase flow and full saturation using parametric data from documented studies in Europe (e.g., ANDRA 2005). The predominance of diffusive transport and sorption phenomena in this clay media are key attributes to impede radionuclide mobility making clay rock formations target sites for disposal of high-level radioactivemore » waste. The reports by Hansen et al. (2010) and those from numerous studies in clay-hosted underground research laboratories (URLs) in Belgium, France and Switzerland outline the extensive scientific knowledge obtained to assess long-term clay/shale/argillite repository isolation performance of nuclear waste. In the past several years under the UFDC, various kinds of models have been developed for argillite repository to demonstrate the model capability, understand the spatial and temporal alteration of the repository, and evaluate different scenarios. These models include the coupled Thermal-Hydrological-Mechanical (THM) and Thermal-Hydrological-Mechanical-Chemical (THMC) models (e.g. Liu et al. 2013; Rutqvist et al. 2014a, Zheng et al. 2014a) that focus on THMC processes in the Engineered Barrier System (EBS) bentonite and argillite host hock, the large scale hydrogeologic model (Bianchi et al. 2014) that investigates the hydraulic connection between an emplacement drift and surrounding hydrogeological units, and Disposal Systems Evaluation Framework (DSEF) models (Greenberg et al. 2013) that evaluate thermal evolution in the host rock approximated as a thermal conduction process to facilitate the analysis of design options. However, the assumptions and the properties (parameters) used in these models are different, which not only make inter-model comparisons difficult, but also compromise the applicability of the lessons learned from one model to another model. The establishment of a reference case would therefore be helpful to set up a baseline for model development. A generic salt repository reference case was developed in Freeze et al. (2013) and the generic argillite repository reference case is presented in this report. The definition of a reference case requires the characterization of the waste inventory, waste form, waste package, repository layout, EBS backfill, host rock, and biosphere. This report mainly documents the processes in EBS bentonite and host rock that are potentially important for performance assessment and properties that are needed to describe these processes, with brief description other components such as waste inventory, waste form, waste package, repository layout, aquifer, and biosphere. A thorough description of the generic argillite repository reference case will be given in Jové Colon et al. (2014).« less

Preparation of immobilized glucose oxidase wafer enzyme on calcium-bentonite modified by surfactant

NASA Astrophysics Data System (ADS)

Widi, R. K.; Trisulo, D. C.; Budhyantoro, A.; Chrisnasari, R.

2017-07-01

Wafer glucose oxidase (GOx) enzymes was produced by addition of PAH (Poly-Allyamine Hydrochloride) polymer into immobilized GOx enzyme on modified-Tetramethylammonium Hydroxide (TMAH) 5%-calsium-bentonite. The use of surfactant molecul (TMAH) is to modify the surface properties and pore size distribution of the Ca-bentonite. These properties are very important to ensure GOx molecules can be bound on the Ca-bentonit surface to be immobilized. The addition of the polymer (PAH) is expected to lead the substrates to be adsorbed onto the enzyme. In this study, wafer enzymes were made in various concentration ratio (Ca-bentonite : PAH) which are 1:0, 1:1, 1:2 and 1:3. The effect of PAH (Poly-Allyamine Hydrochloride) polymer added with various ratios of concentrations can be shown from the capacitance value on LCR meter and enzyme activity using DNS method. The addition of the polymer (PAH) showed effect on the activity of GOx, it can be shown from the decreasing of capacitance value by increasing of PAH concentration.

Influence of nano-material on the expansive and shrinkage soil behavior

NASA Astrophysics Data System (ADS)

Taha, Mohd Raihan; Taha, Omer Muhie Eldeen

2012-10-01

This paper presents an experimental study performed on four types of soils mixed with three types of nano-material of different percentages. The expansion and shrinkage tests were conducted to investigate the effect of three type of nano-materials (nano-clay, nano-alumina, and nano-copper) additive on repressing strains in compacted residual soil mixed with different ratios of bentonite (S1 = 0 % bentonite, S2 = 5 % bentonite, S3 = 10 % bentonite, and S4 = 20 % bentonite). The soil specimens were compacted under the condition of maximum dry unit weight and optimum water content ( w opt) using standard compaction test. The physical and mechanical results of the treated samples were determined. The untreated soil values were used as control points for comparison purposes. It was found that with the addition of optimum percentage of nano-material, both the swell strain and shrinkage strain reduced. The results show that nano-material decreases the development of desiccation cracks on the surface of compacted samples without decrease in the hydraulic conductivity.

Impact of clay mineral on air oxidation of PAH-contaminated soils.

PubMed

Biache, Coralie; Kouadio, Olivier; Lorgeoux, Catherine; Faure, Pierre

2014-09-01

This work investigated the impact of a clay mineral (bentonite) on the air oxidation of the solvent extractable organic matters (EOMs) and the PAHs from contaminated soils. EOMs were isolated from two coking plant soils and mixed with silica sand or bentonite. These samples, as well as raw soils and bentonite/soil mixtures, were oxidized in air at 60 and 100 °C for 160 days. Mineralization was followed by measuring the CO2 produced over the experiments. EOM, polycyclic aromatic compound (PAC), including PAH, contents were also determined. Oxidation led to a decrease in EOM contents and PAH concentrations, these diminutions were enhanced by the presence of bentonite. Transfer of carbon from EOM to insoluble organic matter pointed out a condensation phenomenon leading to a stabilization of the contamination. Higher mineralization rates, observed during the oxidation of the soil/bentonite mixtures, seem to indicate that this clay mineral had a positive influence on the transformation of PAC into CO2.

Precise U/Pb zircons dates of bentonites in Upper Ordovician and Lower Silurian reference sections in North America and Britain.

NASA Astrophysics Data System (ADS)

Suarez, S. E.; Brookfield, M. E.; Catlos, E. J.; Stockli, D. F.; Batchelor, R. A.

2016-12-01

The end of the Ordovician marks one of the greatest of the Earth's mass extinctions. One hypothesis explains this mass extinction as the result of a short-lived, major glaciation preceded by episodes of increased volcanism brought on by the Taconic orogeny. K-bentonites, weathered volcanic ash, provide evidence for increased volcanism. However, there is a lack of modern precise U-Pb dating of these ashes and some confusion in the biostratigraphy. The aim of this study is to obtain more precise U-Pb zircon ages from biostratigraphically constrained bentonites which will lead to better correlation of the Upper Ordovician and Lower Silurian relative time scales, as well as time the pulses of eruption. Zircon grains were extracted from the samples by heavy mineral separation and U-Pb dated using the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer at the University of Texas-Austin. We report here 3 precise U-Pb zircon ages from the Trenton Group, Ontario, Canada, and Dob's Linn, Scotland. The youngest age from the top of the Kirkfield Formation in Ontario is 448.0 +/- 18 Ma, which fits with existing late Ordovician stratigraphic ages. At Dob's Linn, Scotland, the site of the Ordovician/Silurian Global Boundary Stratigraphic Section and Point (GSSP), the youngest age for DL7, a bentonite 5 meters below the GSSP is 402.0 +/- 12.0 Ma, and for DL24L, a bentonite 8 meters above the GSSP is 358.2 +/- 7.9 Ma. These are Devonian ages in current timescales - the current age for the GSSP is 443.8 +/- 1.8 Ma, based on an U/Pb dates from a bentonite 1.6 meters above the GSSP at Dob's Linn. We are confident that our techniques rule out contamination and the most likely explanation is that the small zircons we analyzed either suffered Pb loss, or grew overgrowths during low grade hydrothermal metamorphism of the sediments during the intrusion of the Southern Upland Devonian granites during the Caledonian orogeny. These Devonian ages suggest that the 443.8 +/- 1.8 Ma age may also be suspect. The Dob's Linn site is therefore unsuitable for calibrating the biostratigraphic horizons. Work in progress will provide more U-Pb dating of bentonites from around the Ordovician-Silurian boundary in Canada, United States, Britain and Scandinavia with the aim of calibrating the local series and stages in order to help in International correlations.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Fat metaplasia and backfill are key intermediaries in the development of sacroiliac joint ankylosis in patients with ankylosing spondylitis.

PubMed

Maksymowych, Walter P; Wichuk, Stephanie; Chiowchanwisawakit, Praveena; Lambert, Robert G; Pedersen, Susanne J

2014-11-01

Fat metaplasia in bone marrow on T1-weighted magnetic resonance imaging (MRI) scans may develop after resolution of inflammation in patients with ankylosing spondylitis (AS) and may predict new bone formation in the spine. Similar tissue, termed backfill, may also fill areas of excavated bone in the sacroiliac (SI) joints and may reflect resolution of inflammation and tissue repair at sites of erosions. The purpose of this study was to test our hypothesis that SI joint ankylosis develops following repair of erosions and that tissue characterized by fat metaplasia is a key intermediary step in this pathway. We used the Spondyloarthritis Research Consortium of Canada (SPARCC) SI structural lesion score (SSS) method to assess fat metaplasia, erosions, backfill, and ankylosis on MRIs of the SI joints in 147 patients with AS monitored for 2 years. Univariate and multivariate regression analyses focused first on identifying significant MRI predictors of new backfill and fat metaplasia. We then assessed the role of backfill and fat metaplasia in the development of new ankylosis. All analyses were adjusted for demographic features, treatment, and baseline and 2-year change in SSS values for parameters of inflammation and MRI structural lesions. Resolution of inflammation and reduction of erosions were each independently associated with the development of new backfill and fat metaplasia at 2 years on multivariate analyses. Multivariate regression analysis that included demographic features, baseline and 2-year change in parameters of inflammation and MRI structural lesion showed that reduction in erosions (P = 0.0005) and increase in fat metaplasia (P = 0.002) at 2 years was each independently associated with the development of new ankylosis. Our data support a disease model whereby ankylosis develops following repair of erosions, and fat metaplasia and backfill are key intermediary steps in this pathway. Copyright © 2014 by the American College of Rheumatology.

Comparing the effects of Bentonite & Calendula on the improvement of infantile diaper dermatitis: A randomized controlled trial

PubMed Central

Mahmoudi, Mansoreh; Adib-Hajbaghery, Mohsen; Mashaiekhi, Mahdi

2015-01-01

Background & objectives: Infantile diaper dermatitis is a common, acute inflammatory reaction of the skin around diaper among infants. This study was undertaken to compare the effect of topical application of Bentonite and Calendula creams on the improvement of infantile diaper dermatitis. Methods: This double blind randomized controlled trial was undertaken on 100 patients of infantile diaper dermatitis. The 100 participants were randomly assigned into two groups of 50 each, and were prescribed the coded medicine. The mothers were trained to apply the cream and level of improvement was judged by observing the affected area on the first visit and then after three days of receiving treatment. Results: The mean age of infants was 6.45±5.53 months in Calendula group and 7.35±6.28 months in Bentonite group. Overall, 88 per cent of lesions in the Bentonite group started improving in the first six hours while this rate was 54 per cent in Calendula group (P<0.001). The risk ratio for the improvement in the first six hours was 2.99 folds in the Bentonite group. Also, lesions in 86 per cent infants in the Bentonite group and 52 per cent in the Calendula group were completely improved in the first three days after treatment (P<0.001). Interpretation & conclusions: Our results showed that in comparison with Calendula, Bentonite had faster healing effect and was more effective on the improvement of infantile diaper dermatitis (IRCT ID: IRCT 2012112811593N1). PMID:26831423

Prevention of poison ivy and poison oak allergic contact dermatitis by quaternium-18 bentonite.

PubMed

Marks, J G; Fowler, J F; Sheretz, E F; Rietschel, R L

1995-08-01

Poison ivy and poison oak are the most common causes of allergic contact dermatitis in North America. We investigated whether a new topical lotion containing 5% quaternium-18 bentonite prevents experimentally induced poison ivy and poison oak allergic contact dermatitis. A single-blind, paired comparison, randomized, multicenter investigation was used to evaluate the effectiveness and safety of quaternium-18 bentonite lotion in preventing experimentally induced poison ivy and poison oak allergic contact dermatitis in susceptible volunteers. One hour before both forearms were patch tested with urushiol, the allergenic resin from poison ivy and poison oak, 5% quaternium-18 bentonite lotion was applied on one forearm. The test patches were removed after 4 hours and the sites interpreted for reaction 2, 5, and 8 days later. The difference in reactions between treated and untreated patch test sites was statistically analyzed. Two hundred eleven subjects with a history of allergic contact dermatitis to poison ivy and poison oak were studied. One hundred forty-four subjects had positive reactions to urushiol. The test sites pretreated with quaternium-18 bentonite lotion had absent or significantly reduced reactions to the urushiol compared with untreated control sites (p < 0.0001) on all test days. When it occurred, the reaction consistently appeared later on treated than on control sites (p < 0.0001). One occurrence of mild, transient erythema at the application site was the only side effect from the quaternium-18 bentonite lotion. Quaternium-18 bentonite lotion was effective in preventing or diminishing experimentally produced poison ivy and poison oak allergic contact dermatitis.

Effect Of Coir Fibres On The Compaction And Unconfined Compressive Strength Of Bentonite-Lime-Gypsum Mixture

NASA Astrophysics Data System (ADS)

Tilak B., Vidya; Dutta, Rakesh Kumar; Mohanty, Bijayananda

2015-06-01

This paper presents the effect of coir fibres on the compaction and unconfined compressive strength of a bentonite-lime-gypsum mixture. The coir fiber content varied from 0.5 to 2 %. The results indicated that the dry unit weight and the optimum moisture content of a bentonite - lime mix increased with the addition of gypsum. The unconfined compressive strength of the bentonite increased with the increase in the lime content up to 8 %. Beyond 8 %, the unconfined compressive strength decreased. The dry unit weight of the reference mix decreased, and the optimum moisture content increased with the addition of coir fibre. The unconfined compressive strength of the bentonite + 8 % lime mix increased up to 4 % with the gypsum. Beyond 4 %, the unconfined compressive strength decreased. The unconfined compressive strength of the reference mix increased with the addition of coir fibre up to a fibre content of 1.5 %. The unconfined compressive strength of the reference mix-coir fibre composite was less in comparison to the reference mix. The unconfined compressive strength of the bentonite increased with the addition of lime and gypsum and with the increase in the curing period. The improvement in the post-peak region was better for the reference mix with reinforced coir fibres as compared to the unreinforced reference mix. The improved post-peak behaviour of the bentonite-lime-gypsum-coir fibre mixture could boost the construction of temporary roads on such problematic soils. Further, its use will also provide an environmental motivation for providing a means of consuming large quantities of coir fibres.

Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste

NASA Astrophysics Data System (ADS)

Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

2015-04-01

Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.

Dynamic passive pressure on abutments and pile caps.

DOT National Transportation Integrated Search

2010-08-01

This study investigated the lateral load response of a full-scale pile cap with nine different backfill conditions, more specifically being: 1) no backfill present (baseline response), 2) densely compacted clean sand, 3) loosely compacted clean sand,...

30 CFR 816.106 - Backfilling and grading: Previously mined areas.

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation shall be included within the permit area. (2) The backfill shall be graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability...

30 CFR 817.106 - Backfilling and grading: Previously mined areas.

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation shall be included within the permit area. (2) The backfill shall be graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability...

Glass corrosion in natural environments

NASA Technical Reports Server (NTRS)

Thorpe, Arthur N.; Barkatt, Aaron

1992-01-01

Experiments carried out during the progress period are summarized. Experiments carried out involving glass samples exposed to solutions of Tris have shown the appearance of 'spikes' upon monitoring glass dissolution as a function of time. The periodic 'spikes' observed in Tris-based media were interpreted in terms of cracking due to excessive stress in the surface region of the glass. Studies of the interactions of silicate glasses with metal ions in buffered media were extended to systems containing Al. Caps buffer was used to establish the pH. The procedures used are described and the results are given. Preliminary studies were initiated as to the feasibility of adding a slowly dissolving solid compound of the additive to the glass-water system to maintain a supply of dissolved additive. It appears that several magnesium compounds have a suitable combination of solubility and affinity towards silicate glass surfaces to have a pronounced retarding effect on the extraction of uranium from the glass. These preliminary findings raise the possibility that introducing a magnesium source into geologic repositories for nuclear waste glass in the form of a sparingly soluble Mg-based backfill material may cause a substantial reduction in the extent of long-term glass corrosion. The studies described also provide mechanistic understanding of the roles of various metal solutes in the leachant. Such understanding forms the basis for developing long-term predictions of nuclear waste glass durability under repository conditions. From what is known about natural highly reduced glasses such as tektites, it is clear that iron is dissolved as ferrous iron with little or no ferric iron. The reducing conditions were high enough to cause metallic iron to exsolve out of the glass in the form of submicroscopic spherules. As the nuclear waste glass is much less reduced, a study was initiated on other natural glasses in addition to the nuclear waste glass. Extensive measurements were carried out on these glasses in order to characterize their magnetic properties. Results of these studies are described.

Use of fly-ash slurry in backfill grouting in coal mines.

PubMed

Jiang, Ning; Zhao, Jinhai; Sun, Xizhen; Bai, Liyang; Wang, Changxiang

2017-11-01

Cave backfill grouting implies grouting of the caving rock mass prior to it being compacted. The filling materials strengthen the caving rock and support the overlying strata to achieve the purpose of slowing down the surface subsidence. The broken roof will fail and collapse during mining operations performed without appropriate supporting measures being taken. It is difficult to perform continuous backfill mining on the working face of such roofs using the existing mining technology. In order to solve the above problems, fly ash and mine water are considered as filling materials, and flow characteristics of fly-ash slurry are investigated through laboratory experiments and theoretical analyses. Laws governing the diffusion of fly-ash slurry in the void of caving rock masses and in the void between a caving rock mass and a basic roof are obtained and verified. Based on the results obtained from the above analyses and actual conditions at the Zhaoguan coal mine, Shandong Province, China, a cave backfill grouting system of the hauling pipeline is developed and successfully tested at the 1703 working face in the Zhaoguan coal mine. The results demonstrate that a filling rate of 43.46% is achieved, and the surface subsidence coefficient of the grouting process is found to be 0.475. Compared to the total caving method, the proposed system is found to achieve a reduction rate of 40.63%. This effectively helps in lowering the value of the surface subsidence coefficient. Fly ash and mine water, considered as primary materials in this study, also play a significant role in improving the air quality and water environment.

Evaluation of the predictive capability of coupled thermo-hydro-mechanical models for a heated bentonite/clay system (HE-E) in the Mont Terri Rock Laboratory

DOE PAGES

Garitte, B.; Shao, H.; Wang, X. R.; ...

2017-01-09

Process understanding and parameter identification using numerical methods based on experimental findings are a key aspect of the international cooperative project DECOVALEX. Comparing the predictions from numerical models against experimental results increases confidence in the site selection and site evaluation process for a radioactive waste repository in deep geological formations. In the present phase of the project, DECOVALEX-2015, eight research teams have developed and applied models for simulating an in-situ heater experiment HE-E in the Opalinus Clay in the Mont Terri Rock Laboratory in Switzerland. The modelling task was divided into two study stages, related to prediction and interpretation ofmore » the experiment. A blind prediction of the HE-E experiment was performed based on calibrated parameter values for both the Opalinus Clay, that were based on the modelling of another in-situ experiment (HE-D), and modelling of laboratory column experiments on MX80 granular bentonite and a sand/bentonite mixture .. After publication of the experimental data, additional coupling functions were analysed and considered in the different models. Moreover, parameter values were varied to interpret the measured temperature, relative humidity and pore pressure evolution. The analysis of the predictive and interpretative results reveals the current state of understanding and predictability of coupled THM behaviours associated with geologic nuclear waste disposal in clay formations.« less

Comparison of solvent extraction and extraction chromatography resin techniques for uranium isotopic characterization in high-level radioactive waste and barrier materials.

PubMed

Hurtado-Bermúdez, Santiago; Villa-Alfageme, María; Mas, José Luis; Alba, María Dolores

2018-07-01

The development of Deep Geological Repositories (DGP) to the storage of high-level radioactive waste (HLRW) is mainly focused in systems of multiple barriers based on the use of clays, and particularly bentonites, as natural and engineered barriers in nuclear waste isolation due to their remarkable properties. Due to the fact that uranium is the major component of HLRW, it is required to go in depth in the analysis of the chemistry of the reaction of this element within bentonites. The determination of uranium under the conditions of HLRW, including the analysis of silicate matrices before and after the uranium-bentonite reaction, was investigated. The performances of a state-of-the-art and widespread radiochemical method based on chromatographic UTEVA resins, and a well-known and traditional method based on solvent extraction with tri-n-butyl phosphate (TBP), for the analysis of uranium and thorium isotopes in solid matrices with high concentrations of uranium were analysed in detail. In the development of this comparison, both radiochemical approaches have an overall excellent performance in order to analyse uranium concentration in HLRW samples. However, due to the high uranium concentration in the samples, the chromatographic resin is not able to avoid completely the uranium contamination in the thorium fraction. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evaluation of the predictive capability of coupled thermo-hydro-mechanical models for a heated bentonite/clay system (HE-E) in the Mont Terri Rock Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garitte, B.; Shao, H.; Wang, X. R.

Process understanding and parameter identification using numerical methods based on experimental findings are a key aspect of the international cooperative project DECOVALEX. Comparing the predictions from numerical models against experimental results increases confidence in the site selection and site evaluation process for a radioactive waste repository in deep geological formations. In the present phase of the project, DECOVALEX-2015, eight research teams have developed and applied models for simulating an in-situ heater experiment HE-E in the Opalinus Clay in the Mont Terri Rock Laboratory in Switzerland. The modelling task was divided into two study stages, related to prediction and interpretation ofmore » the experiment. A blind prediction of the HE-E experiment was performed based on calibrated parameter values for both the Opalinus Clay, that were based on the modelling of another in-situ experiment (HE-D), and modelling of laboratory column experiments on MX80 granular bentonite and a sand/bentonite mixture .. After publication of the experimental data, additional coupling functions were analysed and considered in the different models. Moreover, parameter values were varied to interpret the measured temperature, relative humidity and pore pressure evolution. The analysis of the predictive and interpretative results reveals the current state of understanding and predictability of coupled THM behaviours associated with geologic nuclear waste disposal in clay formations.« less

Application of mine water leaching protocol on coal fly ash to assess leaching characteristics for suitability as a mine backfill material.

PubMed

Madzivire, Godfrey; Ramasenya, Koena; Tlowana, Supi; Coetzee, Henk; Vadapalli, Viswanath R K

2018-04-16

Over the years, coal mining in the Mpumalanga Province of South Africa has negatively affected the environment by causing pollution of water resources, land subsidence and spontaneous coal combustion. Previous studies show that in-situ treatment of acid mine drainage (AMD) using coal fly ash (CFA) from local power stations was possible and sludge recovered out of such treatment can be used to backfill mines. In this article, the authors have attempted to understand the leaching characteristics of CFA when placed underground as a backfill material using the mine water leaching protocol (MWLP). The results show that the migration of contaminants between the coal fly ash and the AMD in the mine voids depends on the pH and quality of the mine water. While backfilling mine voids with CFA can neutralize and scavenge between 50% and 95% of certain environmentally sensitive elements from AMD such as Fe, Al, Zn, Cu, Ni, Co and Mn. At this moment, it is also important to point out that certain scavenged/removed contaminants from the AMD during initial phases of backfilling can be remobilized by the influx of acidic water into the mine voids. It has therefore been concluded that, while CFA can be used to backfill mine voids, the influx of fresh acidic mine water should be avoided to minimize the remobilization of trapped contaminants such as Fe, Al, Mn and As. However, the pozzolanic material resulting from the CFA-AMD interaction could prevent such influx.

Curling and warping of concrete pavement: an investigation and proof of concept study : technical summary.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically : backfilled with coarse aggregate. Current backfill material testing procedures used : by the Kansas Department of Transportation (KDOT) utilize on-site observations for : ...

30 CFR 917.12 - State regulatory program and proposed program amendment provisions not approved.

Code of Federal Regulations, 2013 CFR

2013-07-01

... depression left by backfilling and grading, that is not a sedimentation pond or coal mine waste impoundment... completely incised or created by a depression left by backfilling and grading but not meeting MSHA...

30 CFR 917.12 - State regulatory program and proposed program amendment provisions not approved.

Code of Federal Regulations, 2014 CFR

2014-07-01

... depression left by backfilling and grading, that is not a sedimentation pond or coal mine waste impoundment... completely incised or created by a depression left by backfilling and grading but not meeting MSHA...

30 CFR 917.12 - State regulatory program and proposed program amendment provisions not approved.

Code of Federal Regulations, 2012 CFR

2012-07-01

... depression left by backfilling and grading, that is not a sedimentation pond or coal mine waste impoundment... completely incised or created by a depression left by backfilling and grading but not meeting MSHA...

The formation of unsaturated zones within cemented paste backfill mixtures-effects on the release of copper, nickel, and zinc.

PubMed

Hamberg, Roger; Maurice, Christian; Alakangas, Lena

2018-05-13

Flooding of cemented paste backfill (CPB) filled mine workings is, commonly, a slow process and could lead to the formation of unsaturated zones within the CPB fillings. This facilitates the oxidation of sulfide minerals and thereby increases the risk of trace metal leaching. Pyrrhotitic tailings from a gold mine (cyanidation tailing (CT)), containing elevated concentrations of nickel (Ni), copper (Cu), and zinc (Zn), were mixed with cement and/or fly ash (1-3 wt%) to form CT-CPB mixtures. Pyrrhotite oxidation progressed more extensively during unsaturated conditions, where acidity resulted in dissolution of the Ni, Cu, and Zn associated with amorphous Fe precipitates and/or cementitious phases. The establishment of acidic, unsaturated conditions in CT-CBP:s with low fractions (1 wt%) of binders increased the Cu release (to be higher than that from CT), owing to the dissolution of Cu-associated amorphous Fe precipitates. In CT-CPB:s with relatively high proportions of binder, acidity from pyrrhotite oxidation was buffered to a greater extent. At this stage, Zn leaching increased due the occurrence of fly ash-specific Zn species soluble in alkaline conditions. Irrespective of binder proportion and water saturation level, the Ni and Zn release were lower, compared to that in CT. Fractions of Ni, Zn, and Cu associated with acid-soluble phases or amorphous Fe precipitates, susceptible to remobilization under acidic conditions, increased in tandem with binder fractions. Pyrrhotite oxidation occurred irrespective of the water saturation level in the CPB mixtures. That, in turn, poses an environmental risk, whereas a substantial proportion of Ni, Cu, and Zn was associated with acid-soluble phases.

10 CFR 60.102 - Concepts.

Code of Federal Regulations, 2010 CFR

2010-01-01

... openings and backfill materials, but excluding shafts, boreholes, and their seals, is designated the... structure, including openings and backfill materials, but excluding, shafts, boreholes, and their seals. (2... includes sealing of shafts. Permanent closure represents the end of active human intervention with respect...

Numerical analysis of dense narrow backfills for increasing lateral passive resistance.

DOT National Transportation Integrated Search

2010-08-01

Previously, full-scale lateral load tests conducted on pile caps with different aspect ratios showed that placement : of a narrow, dense backfill zone against the cap could substantially increase the passive resistance. The objective : of this study ...

Curling and warping of concrete pavement: an investigation and proof of concept study : final report.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically backfilled with coarse aggregate. : Current backfill material testing procedures used by the Kansas Department of Transportation (KDOT) utilize on-site : observations for co...

The effect of various backfilling techniques on the fracture resistance of simulated immature teeth performed apical plug with Biodentine.

PubMed

Topçuoğlu, Hüseyin Sinan; Kesim, Bertan; Düzgün, Salih; Tuncay, Öznur; Demirbuga, Sezer; Topçuoğlu, Gamze

2015-07-01

To evaluate the fracture resistance of simulated immature teeth that had been backfilled using different materials after using Biodentine as the apical plug material. Seventy-five single-rooted teeth were divided into five groups (n = 15). The 15 teeth in group 1 served as a negative control group and received no treatment. The remaining 60 teeth were instrumented to a #6 Peeso reamer to obtain a standard internal diameter of 1.5 mm. The apical 4 mm of 60 teeth was filled with Biodentine. The backfilling was then performed on each group as follows: group 2--no backfilling (positive control), group 3--gutta-percha, group 4--fiber post, and group 5--Biodentine. Specimens were then subjected to fracture testing. The force required to fracture each specimen was recorded, and the data were statistically analyzed. The mean fracture values of groups 1 and 4 were significantly higher than groups 2, 3, and 5 (P < 0.05). The values of groups 3 and 5 were significantly higher than group 2 (P < 0.05). The backfilling with fiber post after an apical Biodentine plug provided the highest fracture resistance among all experimental groups. © 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Conodont and k-bentonite stratigraphy across the Blackriveran/Trentonian (Ordovician) boundary, north-central New York

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leslie, S.A.; Bergstroem, S.M.

1993-03-01

Integrated conodont and K-bentonite stratigraphy at City Brook and Watertown, New York reveals a pattern that is correlatable to coeval strata in the Midcontinent. The portion of the City Brook section examined consists of upper Lowville Limestone (upper Blackriveran) unconformably overlain by King Falls Limestone (lower Trentonian). The Lowville conodont fauna is a typical Blackriveran assemblage dominated by neurodontiform (hyaline) species of Curtognathus and Erismodus in association with Belodina compressa, Drepanoistodus suberectus, Panderodus and Plectodina aculeatus. The King Falls conodont fauna is dominated by Phragmodus undatus in association with Dapsilodus cf. D. mutatus, Oistodus cf. O. venustus, Panderodus, Periodon cf.more » P. grandis and Scandodus. Blackriveran faunal elements are also present in low abundance throughout the King Falls. The King Falls fauna is present and dominant in a packstone at the top of the upper Lowville below the unconformity. This occurrence supports the idea that these faunas are to some degree facies controlled. Four K-bentonite beds are present, 3 in the Lowville and 1 in the King Falls. A 6-cm thick K-bentonite in the King Falls has the approximate stratigraphic position of the Hounsfield K-bentonite. The Watertown section examined consists of upper Lowville Limestone overlain conformably or para conformable by the Watertown Limestone. The conodont fauna in both the Lowville and Watertown is identical to the Lowville fauna from City Brook, but lacks any Trentonian faunal elements. There is a 6-cm thick K-bentonite in the Lowville in virtually the same stratigraphic position as the lowest K-bentonite in the City Brook section. The stratigraphic positions and conodont faunal patterns observed in the City Brook and Watertown sections are similar to those in coeval sections in the Midcontinent.« less

Long term chemo-hydro-mechanical behavior of compacted soil bentonite polymer complex submitted to synthetic leachate.

PubMed

Razakamanantsoa, Andry Rico; Djeran-Maigre, Irini

2016-07-01

An experimental program is carried out to investigate the long term hydro-mechanical behavior correlated with chemical one of compacted soils with low concentration of Ca-bentonite and Ca-bentonite polymer mixture. The effect of prehydration on the hydraulic performance is compared to the polymer adding effect. All specimens are submitted to synthetic leachate (LS) under different permeation conditions. Several issues are studied: mechanical stability, hydraulic performance, chemical exchange of cations validated with microstructure observations. Scanning Electron Microscope (SEM) observations demonstrate two distinct behaviors: dispersive for Bentonite (B) and B with Polymer P1 (BP1) and flocculated for B with Polymer P2 (BP2). Direct shear tests show that bentonite adding increases the Soil (S) cohesion and decreases the friction angle. Polymer adding behaves similarly by maintaining the soil cohesion and increasing the friction angle. Hydraulic conductivity of prehydrated soil bentonite (SB) and direct permeation of polymer added soil bentonite are studied (SBP1 and SBP2). Hydraulic test duration are in range of 45days to 556days long. Prehydration allows to delay the aggressive effect of the LS in short term but seems to increase its negative effect on the hydraulic conductivity value in long term exposure. SB and SBP1 behave similarly and seem to act in the long term as a granular filler effect. SBP2 presents positive results comparing to the other mixtures: it maintains the hydraulic conductivity and the chemical resistance. Chemical analysis confirms that all specimens are subjected to Na(+) dissolution and Ca(2+) retention which are more pronounced for prehydrated specimen. The short term effect of prehydration and the positive effect of SBP2 are also confirmed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of heteroaggregation processes between intrinsic colloids and carrier colloids on cerium(III) mobility through fractured carbonate rocks.

PubMed

Tran, Emily; Klein Ben-David, Ofra; Teutch, Nadya; Weisbrod, Noam

2016-09-01

Colloid facilitated transport of radionuclides has been implicated as a major transport vector for leaked nuclear waste in the subsurface. Sorption of radionuclides onto mobile carrier colloids such as bentonite and humic acid often accelerates their transport through saturated rock fractures. Here, we employ column studies to investigate the impact of intrinsic, bentonite and humic acid colloids on the transport and recovery of Ce(III) through a fractured chalk core. Ce(III) recovery where either bentonite or humic colloids were added was 7.7-26.9% Ce for all experiments. Greater Ce(III) recovery was observed when both types of carrier colloids were present (25.4-37.4%). When only bentonite colloids were present, Ce(III) appeared to be fractionated between chemical sorption to the bentonite colloid surfaces and heteroaggregation of bentonite colloids with intrinsic carbonate colloids, precipitated naturally in solution. However, scanning electron microscope (SEM) images and colloid stability experiments reveal that in suspensions of humic acid colloids, colloid-facilitated Ce(III) migration results only from the latter attachment mechanism rather than from chemical sorption. This observed heteroaggregation of different colloid types may be an important factor to consider when predicting potential mobility of leaked radionuclides from geological repositories for spent fuel located in carbonate rocks. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ball clay and bentonite deposits of the central and western Gulf of Mexico Coastal Plain, United States

USGS Publications Warehouse

Hosterman, John W.

1984-01-01

The Gulf of Mexico Coastal Plain produces approximately 85 percent of the ball clay used in the United States. The best commercial-grade clay deposits are composed of poorly crystalline kaolinite and small amounts of Md illite and (or) smectite. Sand and silt and iron oxide minerals are virtually absent, but quartz is present in the clay-size fraction. The best grade ball clays are found as lenses limited to the Wilcox Group (Paleocene and lower Eocene) and Claiborne Group (middle Eocene). Reserves of ball clay are sufficient for the present, but because of the lenticular nature of the clay bodies, close-spaced drilling, detailed sampling, mineralogic analyses, and ceramic testing are needed to prove future reserves.Approximately 11 percent of the total bentonite produced in the United States comes from the Gulf Coast region. The commercial-grade bentonites are composed primarily of smectite with little or no Md illite and kaolinite. The nonclay impurities are quartz, feldspar, muscovite, biotite, calcite, dolomite, gypsum, and heulandite. Commercial bentonites occur in the Upper Cretaceous formations in Alabama and Mississippi, in Paleocene formations in Mississippi and Tennessee, and in Eocene and Miocene formations in Texas. The demand for low-swelling bentonite of the Gulf Coastal Plain has not increased along with the demand for swelling bentonite; therefore the reserves are adequate.

The effect of a new impregnated gauze containing bentonite and halloysite minerals on blood coagulation and wound healing.

PubMed

Alavi, Mehrosadat; Totonchi, Alireza; Okhovat, Mohammad Ali; Motazedian, Motahareh; Rezaei, Peyman; Atefi, Mohammad

2014-12-01

In recent years, a wide variety of research has been carried out in the field of novel technologies to stop severe bleeding. In several studies, coagulation properties of minerals such as zeolite, bentonite and halloysite have been proven. In this study, the effect of a new impregnated sterile gauze containing bentonite and halloysite minerals was studied on blood coagulation and wound healing rate in male Wistar rats. Initially, impregnated sterile gauze was prepared from the mixture of bentonite and halloysite minerals and petroleum jelly (Vaseline). Then, the effect of gauze was studied on the blood coagulation time and wound healing process in 40 Wistar rats. SPSS software was used for data analysis and P values less than 0.05 were considered significant. The coagulation time of 81.10 ± 2.532 s in the control group and 33.00 ± 1.214 s in the study group (bentonite-halloysite treated) were reported (P < 0.0005). Time for complete wound healing in the group, which is treated with impregnated sterile pads, was calculated approximately from 10 to 12 days. However, in the control group, there was no complete wound healing (P < 0.0005). According to the results of the present study, topical application of the bentonite-halloysite impregnated sterile gauze significantly decreases the clotting time and increase the wound healing rate.

The effects of Bentonite and Calendula on the improvement of infantile diaper dermatitis

PubMed Central

Adib-Hajbaghery, Mohsen; Mahmoudi, Mansoreh; Mashaiekhi, Mahdi

2014-01-01

Background: Diaper dermatitis is one of the most common skin disorders of infancy and childhood. The present study aimed to compare the effects of Bentonite and Calendula on the improvement of diaper dermatitis in infants. Materials and Methods: A double-blind randomized controlled trial, which was conducted on 60 out-patient infants referred to health care centers or pediatric clinics in Khomein city and diagnosed with diaper dermatitis. Data were collected by checklist and observation, and analyzed using t-test, Chi-square, and Fisher's exact test. Results: Mean (standard error) age of the total sample was 6.55 ± 0.69 months. Totally, 93.3% of lesions in the Bentonite group started its recovery in the first 6 h, while this rate was 40% in Calendula group (P < 0.001). Furthermore, 90% of infants in the Bentonite group and 36.7% in the Calendula group were improved completely in the first 3 days (P < 0.001). Conclusion: Bentonite was effective on the improvement of diaper dermatitis, and also had faster effects compared with Calendula. PMID:25097603

Time evolution of the general characteristics and Cu retention capacity in an acid soil amended with a bentonite winery waste.

PubMed

Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

2015-03-01

The effect of bentonite waste added to a "poor" soil on its general characteristic and copper adsorption capacity was assessed. The soil was amended with different bentonite waste concentrations (0, 10, 20, 40 and 80 Mg ha(-1)) in laboratory pots, and different times of incubation of samples were tested (one day and one, four and eight months). The addition of bentonite waste increased the pH, organic matter content and phosphorus and potassium concentrations in the soil, being stable for P and K, whereas the organic matter decreased with time. Additionally, the copper sorption capacity of the soil and the energy of the Cu bonds increased with bentonite waste additions. However, the use of this type of waste in soil presented important drawbacks for waste dosages higher than 20 Mg ha(-1), such as an excessive increase of the soil pH and an increase of copper in the soil solution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Controlled low strength materials (CLSM), reported by ACI Committee 229

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajendran, N.

1997-07-01

Controlled low-strength material (CLSM) is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. Many terms are currently used to describe this material including flowable fill, unshrinkable fill, controlled density fill, flowable mortar, flowable fly ash, fly ash slurry, plastic soil-cement, soil-cement slurry, K-Krete and other various names. This report contains information on applications, material properties, mix proportioning, construction and quality-control procedures. This report`s intent is to provide basic information on CLSM technology, with emphasis on CLSM material characteristics and advantages over conventional compacted fill. Applications include backfills, structural fills, insulating and isolation fills, pavementmore » bases, conduit bedding, erosion control, void filling, and radioactive waste management.« less

Pullout resistance of mechanically stabilized earth wall steel strip reinforcement in uniform aggregate.

DOT National Transportation Integrated Search

2015-11-01

A wide range of reinforcement-backfill combinations have been used in mechanically stabilized earth (MSE) walls. Steel : strips are one type of reinforcement used to stabilize aggregate backfill through anchorage. In the current MSE wall design, pull...

Recycled Asphalt Pavement and Crushed Concrete Backfill: State-of-the-Art Review and Material Characterization

DOT National Transportation Integrated Search

2001-10-01

This report describes research results from the first year of a three-year study focused on the use of recycled asphalt pavement (RAP) and crushed concrete (CC) as backfill for mechanically stabilized earth (MSE) walls.

Bentonite Clay as a Natural Remedy: A Brief Review

PubMed Central

2017-01-01

Background: From old times, the human kind has used clays, externally or internally, for maintaining body health or treating some diseases. Meanwhile there are few scientific articles reviewing the beneficial effects of clays on body function. Bentonite clay is one of the available clays in nature, used as traditional habits, and remedies in many cultures. Methods: These articles explored among 2500 scientific articles published in PubMed to sort the scientific works have been done on the effects of this clay on body function (it was about 100 articles). Results: Bentonite has a broad range of action on different parts of body. Conclusion: As traditional remedies seem to have a deep root in maintaining body health, it merits doing more research works on bentonite clay and its impacts on body function. PMID:29026782

Decreasing Ni, Cu, Cd, and Zn heavy metal magnetite-bentonite nanocomposites and adsorption isotherm study

NASA Astrophysics Data System (ADS)

Eskandari, M.; Zakeri Khatir, M.; Khodadadi Darban, A.; Meshkini, M.

2018-04-01

This present study was conducted to investigate the effect of magnetite-bentonite nanocomposite on heavy metal removal from an effluent. For this purpose, magnetite-bentonite nanocomposite was prepared through the chemical method and characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, followed by studying the effect of produced nanocomposite on the removal of Ni2+, Cu2+, Cd2+, and Zn2+ heavy metal ions. The results showed that adsorption capacity of magnetite-bentonite nanocomposites for the studied ions is in the order of Zn2+ > Cd2+ > Cu2+ > Ni2+. Adsorption isotherms were drawn for Ni2+, Cu2+, Cd2+, and Zn2+ cations and found that cations adsorption on nanocomposite fit into Langmuir model.

Rapid Assessment of Remedial Effectiveness and Rebound in Fractured Bedrock

DTIC Science & Technology

2017-10-01

Permanent 5-inch diameter steel casing was then installed to a depth of 58.3 ft-bgs, and pressure-grouted in place using cement /bentonite grout. Once the...collected from 64 feet to 78 feet bgs. A 2-inch stainless steel well, screened from 64 to 74 feet bgs, was installed within the borehole. A filter pack was...installed from 63.5 ft to 74.5 ft bgs, and the remainder of the borehole was sealed with a bentonite seal and cement /bentonite grout. Therefore

Pullout resistance of mechanically stabilized earth wall steel strip reinforcement in uniform aggregate : [technical summary].

DOT National Transportation Integrated Search

2015-11-01

A wide range of reinforcement-backfill combinations have been used in mechanically : stabilized earth (MSE) walls. Steel strips are one type of reinforcement used to stabilize : aggregate backfill through anchorage. In the current MSE wall design, pu...

Determination of adsorptive and catalytic properties of copper, silver and iron contain titanium-pillared bentonite for the removal bisphenol A from aqueous solution

NASA Astrophysics Data System (ADS)

Tomul, Fatma; Turgut Basoglu, Funda; Canbay, Hale

2016-01-01

Ti-pillared bentonite, Cu, Ag and Fe modified Ti-pillared bentonite and Cu/Ti- and Fe/Ti-mixed pillared bentonite were synthesized using different titanium sources by direct synthesis or by modification after synthesis. The effects of synthesis conditions on the surface characteristics, pore structure and acidity of the pillared bentonites were investigated by SEM⿿EDS, XPS, XRD, N2-adsorption/desorption and FTIR analyses before and after ammonia adsorption. The results of EDS, XPS and XRD analysis confirmed that titanium, copper, silver and iron were incorporated into the bentonite structure. In the XRD patterns, the formation of delaminated structure reflecting the non-parallel distribution of the bentonite layers by pillaring with Ti, Cu/Ti and Fe/Ti-pillars was observed. XPS spectra indicated the presence of TiO2, CuO, Ag and Ag2O and Fe2O3 species depending on the source of active metals in the synthesized samples. In the FTIR spectra, an increase in the Bronsted/Lewis peak intensity was observed with the loading of copper and iron, whereas a decrease in Lewis and Bronsted acidities was observed with incorporation of silver. Adsorption studies indicated that the adsorption capacity of the sample synthesized using titanium (IV) propoxide and incorporating iron to the structure by ion exchange (Fe-PTi-PILC) were higher than those in other samples. The adsorption of BPA (bisphenol A) by all tested samples was found to fit the Langmuir isotherm. In the catalytic wet peroxide oxidation (CWPO) over PTi-PILC (prepared by titanium (IV) propoxide), Fe-PTi-PILC and Cu-PTi-PILC (prepared by copper impregnated Ti-pillared bentonite) samples, BPA values close to complete conversion were achieved within 30 min at 25 °C, pH 4 and 5 g/L mcat. CWPO results showed that increasement of pH causes a decrease the rate of oxidation. On the other hand, by the time catalyst and BPA concentration is increased, the rate of oxidation is increased as well.

Alteration of bentonite when contacted with supercritical CO2

NASA Astrophysics Data System (ADS)

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 diffusion of ions into the interlayer.

Evaluation and analysis of current compaction methods for FDOT pipe trench backfills in areas of high water tables

DOT National Transportation Integrated Search

1999-01-01

This research project was undertaken to examine the practicality and adequacy of the FDOT specifications regarding compaction methods for pipe trench backfills under high water table. Given the difficulty to determine density and to attain desired de...

COMPATIBILITY OF BENTONITE AND DNAPLS

EPA Science Inventory

The compatibility of dense non-aqueous phase liquids (DNAPLs), trichloroethylene (TCE), methylene chloride (MC), and creosote with commercially available sodium bentonite pellets was evaluated using stainless steel, double-ring, falling-head permeameters. The Hydraulic conductiv...

Influence of pH, soil humic/fulvic acid, ionic strength, foreign ions and addition sequences on adsorption of Pb(II) onto GMZ bentonite.

PubMed

Wang, Suowei; Hu, Jun; Li, Jiaxing; Dong, Yunhui

2009-08-15

This work contributed to the adsorption of Pb(II) onto GMZ bentonite in the absence and presence of soil humic acid (HA)/fulvic acid (FA) using a batch technique. The influences of pH from 2 to 12, ionic strengths from 0.004M to 0.05M NaNO(3), soil HA/FA concentrations from 1.6 mg/L to 20mg/L, foreign cations (Li+, Na+, K+), anions (Cl(-), NO(3)(-)), and addition sequences on the adsorption of Pb(II) onto GMZ bentonite were tested. The adsorption isotherms of Pb(II) were determined at pH 3.6+/-0.1 and simulated with the Langmuir, Freundlich, and D-R adsorption models, respectively. The results demonstrated that the adsorption of Pb(II) onto GMZ bentonite increased with increasing pH from 2 to 6. HA was shown to enhance Pb(II) adsorption at low pH, but to reduce Pb(II) adsorption at high pH, whereas FA was shown to decrease Pb(II) adsorption at pH from 2 to 11. The results also demonstrated that the adsorption was strongly dependent on ionic strength and slightly dependent on the concentration of HA/FA. The adsorption of Pb(II) onto GMZ bentonite was dependent on foreign ions in solution. The addition sequences of bentonite/Pb(II)/HA had no effect on the adsorption of Pb(II).

Installation Restoration Program (IRP), Phase II, Stage 1 - Problem Confirmation Study, Norton Air Force Base, San Bernardino, California. Volume 1. Technical Report.

DTIC Science & Technology

1985-07-01

protein, and AFFF (Air Force Firefighting Foam). The frequency of training exercises has varied considerably over the years. During the early 1970’s...Surface ’ Cement/ Bentonite Grout Bentonite Seal Sand Pack 1. Ground Water Elevation r Mamaur July 4.5, 194 * . FIGURE 3-9 WELL CONSTRUCTION SUMMARY, ZONE...e zzzzzzzzz z I z z Z 0 -. N N E-3 3 0 3 3 w 3 w 0 o z ~ zzzzzzzz z z z z E- 0 0 E- 0z zzzzzzzz zz aua E- 0 4 10 zw 3 E- z 0 0 U)z V fC InZ OE- 3

Assessment of (222)Rn emanation from ore body and backfill tailings in low-grade underground uranium mine.

PubMed

Mishra, Devi Prasad; Sahu, Patitapaban; Panigrahi, Durga Charan; Jha, Vivekanand; Patnaik, R Lokeswara

2014-02-01

This paper presents a comparative study of (222)Rn emanation from the ore and backfill tailings in an underground uranium mine located at Jaduguda, India. The effects of surface area, porosity, (226)Ra and moisture contents on (222)Rn emanation rate were examined. The study revealed that the bulk porosity of backfill tailings is more than two orders of magnitude than that of the ore. The geometric mean radon emanation rates from the ore body and backfill tailings were found to be 10.01 × 10(-3) and 1.03 Bq m(-2) s(-1), respectively. Significant positive linear correlations between (222)Rn emanation rate and the (226)Ra content of ore and tailings were observed. For normalised (226)Ra content, the (222)Rn emanation rate from tailings was found to be 283 times higher than the ore due to higher bulk porosity and surface area. The relative radon emanation from the tailings with moisture fraction of 0.14 was found to be 2.4 times higher than the oven-dried tailings. The study suggested that the mill tailings used as a backfill material significantly contributes to radon emanation as compared to the ore body itself and the (226)Ra content and bulk porosity are the dominant factors for radon emanation into the mine atmosphere.

Application of mixed based membrane technology from component materials bintaro, zeolite and bentonite to reduction of songket waste liquid cloth

NASA Astrophysics Data System (ADS)

Dahlan, Muhammad Hatta; Saleh, Abdullah; Asip, Faisol; Makmun, Akbar; Defi

2017-11-01

Application of membrane technology based on clay mixture, Activated Carbon from Bintaro, Zeolite and Bentonit to process the waste water of Songket cloth is Palembang traditionally cloth. The applied research is into the superior field of industrial and household waste processing with membrane ceramic technology. The objective of this research is to design the liquid waste separation tool of jumputan cloth using better and simpler ceramic membrane so that it can help the artisans of Palembang songket or songket in processing the waste in accordance with the standard of environmental quality standard (BML) and Pergub Sumsel no. 16 in 2005. The specific target to be achieved can decrease the waste of cloth jumputan in accordance with applicable environmental quality standards the method used in achieving the objectives of this study using 2 processes namely the adsorption process using activated carbon and the separation process using a ceramic membrane based on the composition of the mixture. The activated carbon from bintaro seeds is expected to decrease the concentration of liquid waste of Songket cloth. Bintaro seeds are non-edible fruits where the composition contains organic ingredients that can absorb because contains dyes and filler metals. The process of membranization in the processing is expected to decrease the concentration of waste better and clear water that can be used as recycled water for household use. With the composition of a mixture of clay-based materials: zeolite, bentonit, activated carbon from bintaro seeds are expected Find the solution and get the novelty value in the form of patent in this research

Biochar, Bentonite and Zeolite Supplemented Feeding of Layer Chickens Alters Intestinal Microbiota and Reduces Campylobacter Load

PubMed Central

Prasai, Tanka P.; Walsh, Kerry B.; Bhattarai, Surya P.; Midmore, David J.; Van, Thi T. H.; Moore, Robert J.; Stanley, Dragana

2016-01-01

A range of feed supplements, including antibiotics, have been commonly used in poultry production to improve health and productivity. Alternative methods are needed to suppress pathogen loads and maintain productivity. As an alternative to antibiotics use, we investigated the ability of biochar, bentonite and zeolite as separate 4% feed additives, to selectively remove pathogens without reducing microbial richness and diversity in the gut. Neither biochar, bentonite nor zeolite made any significant alterations to the overall richness and diversity of intestinal bacterial community. However, reduction of some bacterial species, including some potential pathogens was detected. The microbiota of bentonite fed animals were lacking all members of the order Campylobacterales. Specifically, the following operational taxonomic units (OTUs) were absent: an OTU 100% identical to Campylobacter jejuni; an OTU 99% identical to Helicobacter pullorum; multiple Gallibacterium anatis (>97%) related OTUs; Bacteroides dorei (99%) and Clostridium aldenense (95%) related OTUs. Biochar and zeolite treatments had similar but milder effects compared to bentonite. Zeolite amended feed was also associated with significant reduction in the phylum Proteobacteria. All three additives showed potential for the control of major poultry zoonotic pathogens. PMID:27116607

30 CFR 816.101 - Backfilling and grading: Time and distance requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... provided in paragraph (b) of this section, rough backfilling and grading for surface mining activities... not more than four spoil ridges behind the pit being worked, the spoil from the active pit constituting the first ridge; or (3) Other surface mining methods. In accordance with the schedule established...

30 CFR 816.101 - Backfilling and grading: Time and distance requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... provided in paragraph (b) of this section, rough backfilling and grading for surface mining activities... not more than four spoil ridges behind the pit being worked, the spoil from the active pit constituting the first ridge; or (3) Other surface mining methods. In accordance with the schedule established...

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2014 CFR

2014-07-01

... health and safety or to the environment. ... of the highwall shall be stable and not pose a hazard to the public health and safety or to the... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger...

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2013 CFR

2013-07-01

... health and safety or to the environment. ... of the highwall shall be stable and not pose a hazard to the public health and safety or to the... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger...

Long-term diffusion of U(VI) in bentonite: Dependence on density

DOE PAGES

Joseph, Claudia; Mibus, Jens; Trepte, Paul; ...

2016-10-12

As a contribution to the safety assessment of nuclear waste repositories, U(VI) diffusion through the potential buffer material MX-80 bentonite was investigated at three clay dry densities over six years. Synthetic MX-80 model pore water was used as background electrolyte. Speciation calculations showed that Ca 2UO 2(CO 3) 3(aq) was the main U(VI) species. The in- and out-diffusion of U(VI) was investigated separately. U(VI) diffused about 3 mm, 1.5 mm, and 1 mm into the clay plug at ρ = 1.3, 1.6, and 1.9 g/cm 3, respectively. No through-diffusion of the U(VI) tracer was observed. However, leaching of natural uraniummore » contained in the clay occurred and uranium was detected in all receiving reservoirs. As expected, the effective and apparent diffusion coefficients, D e and D a, decreased with increasing dry density. The D a values for the out-diffusion of natural U(VI) were in good agreement with previously determined values. Surprisingly, D a values for the in-diffusion of U(VI) were about two orders of magnitude lower than values obtained in short-term in-diffusion experiments reported in the literature. Some potential reasons for this behavior that were evaluated are changes of the U(VI) speciation within the clay (precipitation, reduction) or changes of the clay porosity and pore connectivity with time. By applying Archie's law and the extended Archie's law, it was estimated that a significantly smaller effective porosity must be present for the long-term in-diffusion of U(VI). Finally, the results suggest that long-term studies of key transport phenomena may reveal additional processes that can directly impact long-term repository safety assessments.« less

Research to develop guidelines for cathodic protection of concentric neutral cables, volume 1

NASA Astrophysics Data System (ADS)

Hanck, J. A.; Nekoksa, G.

1981-08-01

Data associated with corrosion of concentric neutrals (CN) of direct buried cables from field tests conducted at 36 bellholes excavated in California, Oklahoma, and North Carolina are presented. The electrochemical, chemical, bacteriological, and sieve analyses of native soil and imported backfill samples are included. Up to 129 values were determined for each bellhole and stored on cards as a data bank. All values were statistically analyzed and correlated with corrosion found. The severity of corrosion correlated best with CN corrosion potentials, CN resistance measurements, coarseness of backfill, and soil resistivity. The guidelines for installation of cathodic protection on CN cables are to be based upon the evaluation of over 100 experimental cathodic protection systems and upon laboratory testing for protection criteria with and without ac effects.

Iron-montmorillonite clays as active sorbents for the decontamination of hazardous chemical warfare agents.

PubMed

Carniato, F; Bisio, C; Evangelisti, C; Psaro, R; Dal Santo, V; Costenaro, D; Marchese, L; Guidotti, M

2018-02-27

A class of heterogeneous catalysts based on commercial bentonite from natural origin, containing at least 80 wt% of montmorillonite clay, was designed to transform selectively and under mild conditions toxic organosulfur and organophosphorus chemical warfare agents into non-noxious products with a reduced impact on health and environment. The bentonite from the natural origin was modified by introducing iron species and acid sites in the interlayer space, aiming to obtain a sorbent with strong catalytic oxidising and hydrolytic properties. The catalytic performance of these materials was evaluated in the oxidative abatement of (2-chloroethyl)ethyl sulfide (CEES), a simulant of sulfur mustard, in the presence of aqueous hydrogen peroxide as an oxidant. A new decontamination formulation was, moreover, proposed and obtained by mixing sodium perborate, as a solid oxidant, to iron-bentonite catalysts. Solid-phase decontamination tests, performed on a cotton textile support contaminated with organosulfide and organophosphonate simulant agents revealed the good activity of the solid formulation, especially in the in situ detoxification of blistering agents. Tests carried out on the real blistering warfare agent, sulfur mustard (HD agent), showed that, thanks to the co-presence of the iron-based clay together with the solid oxidant component, a good decontamination of the test surface from the real warfare agent could be achieved (80% contaminant degradation, under ambient conditions, in 24 h).

Serological Studies of Types A, B, and E Botulinal Toxins by Passive Hemagglutination and Bentonite Flocculation

PubMed Central

Johnson, H. M.; Brenner, K.; Angelotti, R.; Hall, H. E.

1966-01-01

Johnson, H. M. (Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio), K. Brenner, R. Angelotti, and H. E. Hall. Serological studies of types A, B, and E botulinal toxins by passive hemagglutination and bentonite flocculation. J. Bacteriol. 91:967–974. 1966.—Formalinized sheep red blood cells (SRBC), sensitized with types A, B, and E botulinal toxoids and toxins by bis-diazotized benzidine (BDB), were tested against A, B, and E antitoxins prepared in horses and rabbits. Type B antitoxin cross-reacted with A toxoid SRBC, but the reciprocal cross-reaction was not observed. E toxin SRBC were specifically agglutinated by E antitoxin. Flocculation of antigen-sensitized bentonite particles was less sensitive in titration of antitoxin than hemagglutination. Also, reciprocal cross-reactions were observed between types A and B antitoxins. Cross-reactions in both serological tests were eliminated by titration of antitoxins in the presence of the heterologous antigens, with no inhibitory effect on the homologous antitoxins. Generally, equine antitoxins were less suitable for agglutinations, especially of antigen-sensitized bentonite particles. Types A, B, and E antitoxins were specifically inhibited by 43, 39, and 245 mouse ld50 of their respective homologous toxins in the hemagglutination-inhibition test. A, B, and E antitoxins were specifically inhibited by 500, 950, and 1,500 mouse ld50 of their respective homologous toxins in bentonite flocculation inhibitions. Formalinized SRBC sensitized with rabbit types A and B antitoxins by BDB were respectively clumped by as little as 0.75 to 1.3 mouse ld50 of A toxin and 2.3 ld50 of B toxin, whereas bentonite particles sensitized by the same antitoxins were specifically clumped by 150 ld50 of A toxin and 630 ld50 of B toxin. E antitoxin sensitization of SRBC or bentonite particles was not successful. Evidence is presented that indicates that the serological procedures are applicable to the detection of botulinal toxins in food. PMID:5326104

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santiago, Denise Ester O.; Department of Chemical Engineering, University of the Philippines, Los Baños, College, Laguna 4031 Philippines; Pajarito, Bryan B.

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 bentonitemore » 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.« less

Used Fuel Disposal in Crystalline Rocks. FY15 Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yifeng

2015-08-20

The objective of the Crystalline Disposal R&D Work Package is to advance our understanding of long-term disposal of used fuel in crystalline rocks and to develop necessary experimental and computational capabilities to evaluate various disposal concepts in such media. Chapter headings are as follows: Fuel matrix degradation model and its integration with performance assessments, Investigation of thermal effects on the chemical behavior of clays, Investigation of uranium diffusion and retardation in bentonite, Long-term diffusion of U(VI) in bentonite: dependence on density, Sorption and desorption of plutonium by bentonite, Dissolution of plutonium intrinsic colloids in the presence of clay and asmore » a function of temperature, Laboratory investigation of colloid-facilitated transport of cesium by bentonite colloids in a crystalline rock system, Development and demonstration of discrete fracture network model, Fracture continuum model and its comparison with discrete fracture network model.« less

Adsorption Processes of Lead Ions on the Mixture Surface of Bentonite and Bottom Sediments.

PubMed

Hegedűsová, Alžbeta; Hegedűs, Ondrej; Tóth, Tomáš; Vollmannová, Alena; Andrejiová, Alena; Šlosár, Miroslav; Mezeyová, Ivana; Pernyeszi, Tímea

2016-12-01

The adsorption of contaminants plays an important role in the process of their elimination from a polluted environment. This work describes the issue of loading environment with lead Pb(II) and the resulting negative impact it has on plants and living organisms. It also focuses on bentonite as a natural adsorbent and on the adsorption process of Pb(II) ions on the mixture of bentonite and bottom sediment from the water reservoir in Kolíňany (SR). The equilibrium and kinetic experimental data were evaluated using Langmuir isotherm kinetic pseudo-first and pseudo-second-order rate equations the intraparticle and surface diffusion models. Langmuir isotherm model was successfully used to characterize the lead ions adsorption equilibrium on the mixture of bentonite and bottom sediment. The pseudo second-order model, the intraparticle and surface (film) diffusion models could be simultaneously fitted the experimental kinetic data.

The stabilization of the rock mass of the wieliczka salt mine through the backfilling of the witos chamber with the use of injection methods / Stabilizacji górotworu kopalni soli "wieliczka" poprzez likwidację komór "witos" z zastosowaniem metod iniekcji

NASA Astrophysics Data System (ADS)

D'Obyrn, Kajetan

2012-10-01

The Wieliczka Salt Mine is the most famous and the most visited mining industry monument in the world and it requires modern methods to ensure rock mass stability and tourists' security. Both for conservation and tourism organization reasons, the group of Warszawa-Wisla-Budryk-Lebzeltern-Upper Witos Chambers (Photo. 1, 2. 3) located the Kazanów mid-level at a depth of 117 m underground is extremely important. Discontinuous deformation occurring in this Chamber complex was eliminated by comprehensive securing work with anchor housing, but their final securing and stability is conditioned by further backfilling and sealing the Witos Chambers situated directly beneath. In the 1940s and 1950s, the Witos Chamber was backfilled with slag from the mine boilerhouse. However, slags with 80% compressibility are not backfilling material which would ensure the stability of the rock mass. The chambers were exploited in the early nineteenth century in the Spizit salts of the central part of the layered deposit. The condition of the Upper Witos, Wisla, Warszawa, Budryk, and Lebzeltern Chambers is generally good. The western part if the Lebzeltern Chamber (Fig. 1), which was threatened with collapse, was backfilled with sand. In all the chambers of the Witos complex, local deformation of ceiling rock of varying intensity is observed as well as significant destruction of the side walls of pillars between chambers. No hydrogeological phenomena are observed in the chambers. It has been attempted to solve the problem of stability of the rock mass in this region of the mine by extracting the slag and backfilling with sand, erecting concrete supporting pillars, backfilling the voids with sand, anchoring the ceiling and the side walls, the use of the pillar housing. The methods have either not been applied or have been proved insufficient to properly protect the excavation situated above. In order to select the optimal securing method, a geomechanical analysis was conducted in order to determine the condition of the chambers with particular emphasis on the pillars between the chambers. The analysis demonstrated the need to backfilling the Witos Chambers in order to improve the strength parameters of the pillars and the cross-level ledge. The next step consisted of selecting the sealing mix and testing how the additional burden and improving the slag strength parameters shall affect the stability of the excavations of the Kazanów mid-level. In order to determine the optimal composition of the backfilling mixtures, formulas of sealing brine slurries have been developed. Laboratory tests were also conducted concerning the strain parameters specifications of slags extracted from the Witos Chamber. Taking into account the slurry tests, and in particular, the density, strength and strain parameters, the optimal composition of the sealing mix was selected. The analysis of the results of numerical recalculations demonstrate that even the use of highest-density mixtures, backfilling(sealing) of the Witos Chambers should not cause significant disturbance of the current tension in the surrounding rock mass. The longterm impact of sealing should lead to improvement of the strain levels on the ledges between Level III and Kazanów mid-level chambers. The positive results of applying in the Mine of injection slurries for sealing and stabilizing the rock mass and the construction of the injection node on the surface of the Kosciuszko shaft area have allowed resuming work in the Witos Chambers. The main injection over 1,000 m long pipeline was constructed from the injection node through the Kosciuszko Shaft and along Level III of the mine. The sealing of the Witos Chambers complex was divided into three areas (Fig. 2) separated by backfilling dams. Each region was connected to an injection and venting pipeline, and areas of possible injection material off-flow from backfilling locations were secured. Once that the Chambers are sealed with the use of the pipeline seven bore holes will be drilled from excavations situated above through which the sealing slurry will be administered. The operation will serve to eliminate any voids and re-seal the slag, and it will be conducted until pressures of approximately 0.5 MPa on the bore hole collar is achieved. As past experience indicates, injection slurry formula can be regularly adjusted adequately to the changing geomechanical parameters and the type of sealing work at the Wieliczka Mine. Once that the backfilling and sealing process in the Witos Chambers complex is completed, it shall be necessary to conduct monitoring activities in order to determine the processes occurring in the rock mass after the backfilling. The properties of sealing mixtures qualify those for use in the environment both of salt mines and other mineral ore mines to stabilize the rock mass in the mining-geomechanical context precluding the possibility of weakening the rock mass strength parameters and at the same time sealing the rock mass and the loose material deposited in the excavation.

Effects of feeding bentonite clay upon ochratoxin A-induced immunosuppression in broiler chicks.

PubMed

Khatoon, Aisha; Khan, Muhammad Zargham; Abidin, Zain Ul; Bhatti, Sheraz Ahmed

2018-03-01

A presence of mycotoxins in feed is one of the most alarming issues in the poultry feed industry. Ochratoxins, produced by several Aspergillus and Penicillium species, are important mycotoxin regarding the health status of poultry birds. Ochratoxins are further classified into to several subtypes (A, B, C, etc) depending on their chemical structures, but ochratoxin A (OTA) is considered the most important and toxic. Bentonite clay, belonging to phyllosilicates and formed from weathering of volcanic ashes, has adsorbent ability for several mycotoxins. The present study was designed to study the effects of bentonite clay upon OTA-induced immunosuppression in broiler chicks. For this, 480 day-old broiler chicks were procured from a local hatchery and then different combinations of OTA (0.15, 0.3, or 1.0 mg/kg) and bentonite clay (5, 10, and 20 g/kg) were incorporated into their feed. At 13, 30, and 42 days of age, parameters such as antibody responses to sheep red blood cells, in situ lymphoproliferative responses to mitogen (PHA-P), and in situ phagocytic activity (i.e., via carbon clearance) were determined respectively. The results indicated there was a significant reduction of total antibody and immunoglobulin titres, lymphoproliferative responses, and phagocytic potential in OTA-treated birds, suggesting clear immunosuppression by OTA in birds in a dose-dependent manner. These results were also significantly lower in all combination groups (OTA with bentonite clay), suggesting few to no effects of feeding bentonite clay upon OTA- induced alterations in different immune parameters.

Backfill composition for secondary barriers in nuclear waste repositories

DOEpatents

Beall, Gary W.; Allard, Bert M.

1982-01-01

A backfill composition for sorbing and retaining hazardous elements of nuclear wastes comprises 50-70% by weight of quartz, 10-30% by weight of montmorillonite, 1-10% by weight of phosphate mineral, 1-10% by weight of ferrous mineral, 1-10% by weight of sulfate mineral and 1-10% by weight of attapulgite.

Multicomponent Nanomaterials with Complex Networked Architectures from Orthogonal Degradation and Binary Metal Backfilling in ABC Triblock Terpolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowman, Christina D.; Padgett, Elliot; Tan, Kwan Wee

2015-05-13

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etchingmore » and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer–inorganic hybrid materials with two distinct metal networks. Multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures.« less

Multicomponent nanomaterials with complex networked architectures from orthogonal degradation and binary metal backfilling in ABC triblock terpolymers

DOE PAGES

Cowman, Christina D.; Padgett, Elliot; Tan, Kwan Wee; ...

2015-04-02

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etchingmore » and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer–inorganic hybrid materials with two distinct metal networks. Lastly, multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures.« less

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage.

PubMed

Li, Chuanchang; Fu, Liangjie; Ouyang, Jing; Yang, Huaming

2013-01-01

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated.

40 CFR 264.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., smectites, Fuller's earth, bentonite, calcium bentonite, montmorillonite, calcined montmorillonite.../hydroxides, alumina, lime, silica (sand), diatomaceous earth; perlite (volcanic glass); expanded volcanic... contain, hazardous waste; and (2) Placement in such owner or operator's landfill will not present a risk...

40 CFR 264.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., smectites, Fuller's earth, bentonite, calcium bentonite, montmorillonite, calcined montmorillonite.../hydroxides, alumina, lime, silica (sand), diatomaceous earth; perlite (volcanic glass); expanded volcanic... contain, hazardous waste; and (2) Placement in such owner or operator's landfill will not present a risk...

40 CFR 264.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., smectites, Fuller's earth, bentonite, calcium bentonite, montmorillonite, calcined montmorillonite.../hydroxides, alumina, lime, silica (sand), diatomaceous earth; perlite (volcanic glass); expanded volcanic... contain, hazardous waste; and (2) Placement in such owner or operator's landfill will not present a risk...

Removal of metal ions and humic acids through polyetherimide membrane with grafted bentonite clay.

PubMed

Hebbar, Raghavendra S; Isloor, Arun M; Prabhu, Balakrishna; Inamuddin; Asiri, Abdullah M; Ismail, A F

2018-03-16

Functional surfaces and polymers with branched structures have a major impact on physicochemical properties and performance of membrane materials. With the aim of greener approach for enhancement of permeation, fouling resistance and detrimental heavy metal ion rejection capacity of polyetherimide membrane, novel grafting of poly (4-styrenesulfonate) brushes on low cost, natural bentonite was carried out via distillation-precipitation polymerisation method and employed as a performance modifier. It has been demonstrated that, modified bentonite clay exhibited significant improvement in the hydrophilicity, porosity, and water uptake capacity with 3 wt. % of additive dosage. SEM and AFM analysis showed the increase in macrovoides and surface roughness with increased additive concentration. Moreover, the inclusion of modified bentonite displayed an increase in permeation rate and high anti-irreversible fouling properties with reversible fouling ratio of 75.6%. The humic acid rejection study revealed that, PEM-3 membrane having rejection efficiency up to 87.6% and foulants can be easily removed by simple hydraulic cleaning. Further, nanocomposite membranes can be significantly employed for the removal of hazardous heavy metal ions with a rejection rate of 80% and its tentative mechanism was discussed. Conspicuously, bentonite clay-bearing poly (4-styrenesulfonate) brushes are having a synergistic effect on physicochemical properties of nanocomposite membrane to enhance the performance in real field applications.

Effects of Radiation and Temperature on Iodide Sorption by Surfactant-Modified Bentonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choung, Sungwook; Kim, Min Kyung; Yang, Jungseok

2014-08-04

Bentonite, which is used as an engineered barrier in geological repositories, is ineffective for sorbing anionic radionuclides because of its negatively charged surface. This study modified raw bentonite using a cationic surfactant (i.e., hexadecyltrimethylammonium [HDTMA]-Br) to improve its sorption capability for radioactive iodide. The effects of temperature and radiation on the iodide sorption of surfactant-modified bentonite (SMB) were evaluated under alkaline pH condition similar to that found in repository environments. Different amounts of surfactant, equivalent to the 50, 100, and 200% cation-exchange capacity of the bentonite, were used to produce the HDTMA-SMB for iodide sorption. The sorption reaction of themore » SMB with iodide reached equilibrium rapidly within 10 min regardless of temperature and radiation conditions. The rate of iodide sorption increased as the amount of the added surfactant was increased and nonlinear sorption behavior was exhibited. However, high temperature and γ-irradiation (60Co) resulted in significantly (~2–10 times) lower iodide Kd values for the SMB. The results of Fourier transform infrared spectroscopy analysis suggested that the decrease in iodide sorption may be caused by weakened physical electrostatic force between the HDTMA and iodide, and by the surfactant becoming detached from the SMB during the heating and irradiation processes.« less

Simultaneous adsorption of Cu2+ and Acid fuchsin (AF) from aqueous solutions by CMC/bentonite composite.

PubMed

Gong, Ning; Liu, Yanping; Huang, Ruihua

2018-04-21

Carboxymethyl-chitosan (CMC)/bentonite composite was prepared by the method of membrane-forming, and characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques. The simultaneous adsorption of Cu 2+ and Acid fuchsin (AF) applying CMC/bentonite composite as an adsorbent in single or binary systems was investigated. The adsorption study was conducted systematically by varying the ratio of CMC to bentonite, adsorbent dosage, initial pH value, initial Cu 2+ (or AF) concentration, contact time and the interaction of two components in binary solutions. The results showed that the presence of Cu 2+ hindered the adsorption of AF, while the presence of AF almost had no influence on the adsorption of Cu 2+ in binary systems. The adsorption data of Cu 2+ and AF were both suitable for Langmuir isotherm model, and the maximum adsorption capacities of CMC/bentonite composite, according to the Langmuir isotherm model were 81.4 mg/g for Cu 2+ and 253.2 mg/g for AF at 298 K. The pseudo-second-order model could better describe the adsorption process of Cu 2+ and AF. Thermodynamic constant values illustrated that the adsorption of Cu 2+ was endothermic, while the adsorption process of AF was exothermic. Copyright © 2018. Published by Elsevier B.V.

Magnesium incorporated bentonite clay for defluoridation of drinking water.

PubMed

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.

Sorption equilibrium, thermodynamics and pH-indicator properties of cresyl violet dye/bentonite composite system.

PubMed

Georgieva, Nedyalka; Yaneva, Zvezdelina; Dermendzhieva, Diyana

2017-09-01

The aim of the present study was to develop cresyl violet (CV)/bentonite composite system, to investigate the equilibrium sorption of the fluorescent dye on bentonite, to determine the characteristic equilibrium and thermodynamic parameters of the system by appropriate empirical isotherm models and to assess its pH-indicator properties. The absorption characteristics of CV solutions were investigated by UV/VIS spectrophotometer. Equilibrium experiments were conducted and the experimental data were modelled by six mathematical isotherm models. The analyses of the experimental data showed that bentonite exhibited significantly high capacity - 169.92 mg/g, towards CV. The encapsulation efficiency was 85%. The Langmuir, Flory-Huggins and El-Awady models best represented the experimental results. The free Gibbs energy of adsorption (ΔG o ) was calculated on the basis of the values of the equilibrium coefficients determined by the proposed models. The values of ΔG determined by the Langmuir, Temkin and Flory-Huggins models are within the range -20 to -40 kJ/mol, which indicates that the adsorption process is spontaneous and chemisorption takes place due to charge sharing or transfer from the dye molecules to the sorbent surface as a coordinate type of bond. The investigations of the obtained CV/bentonite hybrid systems for application as pH-markers showed satisfactory results.

Investigation of melamine derived quaternary as ammonium salt potential shale inhibitor

NASA Astrophysics Data System (ADS)

Yu, Hongjiang; Hu, Weimin; Guo, Gang; Huang, Lei; Li, Lili; Gu, Xuefan; Zhang, Zhifang; Zhang, Jie; Chen, Gang

2017-06-01

Melamine, sodium chloroacetate and sodium hydroxide were used as raw materials to synthesize a kind of neutral quaternary ammonium salt (NQAS) as potential clay swelling inhibitor and water-based drilling fluid additive, and the reaction conditions were screened based on the linear expansion rate of bentonite. The inhibitive properties of NQASs were investigated by various methods, including montmorillonite (MMT) linear expansion test, mud ball immersing test, particle distribution measurement, thermogravimetric analysis and scanning electron microscopy etc. The results indicate that NQAS can inhibit expansion and dispersion of clay in water effectively. At the same condition, the bentonite linear expansion rate in NQAS-6 solution is much lower than those of others, and the hydration expansion degree of the mud ball in 0.5% NQAS-6 solution is appreciably weaker than the control test. The compatibility test indicates NQAS-6 could be compatible with the conventional additives in water-based drilling fluids, and the temperature resistance of modified starch was improved effectively. Meanwhile, the inhibitive mechanism was discussed through the particle distribution measurement.

Long-Term Modeling of Coupled Processes in a Generic Salt Repository for Heat-Generating Nuclear Waste: Analysis of the Impacts of Halite Solubility Constraints

NASA Astrophysics Data System (ADS)

Blanco Martin, L.; Rutqvist, J.; Battistelli, A.; Birkholzer, J. T.

2015-12-01

Rock salt is a potential medium for the underground disposal of nuclear waste because it has several assets, such as its ability to creep and heal fractures and its water and gas tightness in the undisturbed state. In this research, we focus on disposal of heat-generating nuclear waste and we consider a generic salt repository with in-drift emplacement of waste packages and crushed salt backfill. As the natural salt creeps, the crushed salt backfill gets progressively compacted and an engineered barrier system is subsequently created [1]. The safety requirements for such a repository impose that long time scales be considered, during which the integrity of the natural and engineered barriers have to be demonstrated. In order to evaluate this long-term integrity, we perform numerical modeling based on state-of-the-art knowledge. Here, we analyze the impacts of halite dissolution and precipitation within the backfill and the host rock. For this purpose, we use an enhanced equation-of-state module of TOUGH2 that properly includes temperature-dependent solubility constraints [2]. We perform coupled thermal-hydraulic-mechanical modeling and we investigate the influence of the mentioned impacts. The TOUGH-FLAC simulator, adapted for large strains and creep, is used [3]. In order to quantify the importance of salt dissolution and precipitation on the effective porosity, permeability, pore pressure, temperature and stress field, we compare numerical results that include or disregard fluids of variable salinity. The sensitivity of the results to some parameters, such as the initial saturation within the backfill, is also addressed. References: [1] Bechthold, W. et al. Backfilling and Sealing of Underground Repositories for Radioactive Waste in Salt (BAMBUS II Project). Report EUR20621 EN: European Atomic Energy Community, 2004. [2] Battistelli A. Improving the treatment of saline brines in EWASG for the simulation of hydrothermal systems. Proceedings, TOUGH Symposium 2012, Lawrence Berkeley National Laboratory, Berkeley, California, Sept. 17-19, 2012. [3] Blanco-Martín L, Rutqvist J, Birkholzer JT. Long-term modelling of the thermal-hydraulic-mechanical response of a generic salt repository for heat generating nuclear waste. Eng Geol 2015;193:198-211. doi:10.1016/j.enggeo.2015.04.014.

TrigDB back-filling method in EEW for the regional earthquake for reducing false location of the deep focus earthquake event by considering neighborhood triggers and forced association.

NASA Astrophysics Data System (ADS)

Park, J. H.; Chi, H. C.; Lim, I. S.; Seong, Y. J.; Pak, J.

2017-12-01

During the first phase of EEW(Earthquake Early Warning) service to the public by KMA (Korea Meteorological Administration) from 2015 in Korea, KIGAM(Korea Institute of Geoscience and Mineral Resources) has adopted ElarmS2 of UC Berkeley BSL and modified local magnitude relation, travel time curves and association procedures so called TrigDB back-filling method. The TrigDB back-filling method uses a database of sorted lists of stations based on epicentral distances of the pre-defined events located on the grids for 1,401 × 1,601 = 2,243,001 events around the Korean Peninsula at a grid spacing of 0.05 degrees. When the version of an event is updated, the TrigDB back-filling method is invoked. First, the grid closest to the epicenter of an event is chosen from the database and candidate stations, which are stations corresponding to the chosen grid and also adjacent to the already-associated stations, are selected. Second, the directions from the chosen grid to the associated stations are averaged to represent the direction of wave propagation, which is used as a reference for computing apparent travel times. The apparent travel times for the associated stations are computed using a P wave velocity of 5.5 km/s from the grid to the projected points in the reference direction. The travel times for the triggered candidate stations are also computed and used to obtain the difference between the apparent travel times of the associated stations and the triggered candidates. Finally, if the difference in the apparent travel times is less than that of the arrival times, the method forces the triggered candidate station to be associated with the event and updates the event location. This method is useful to reduce false locations of events which could be generated from the deep (> 500 km) and regional distance earthquakes happening on the subduction pacific plate boundaries. In comparison of the case study between TrigDB back-filling applied system and the others, we could get the more reliable results in the early stagy of the version updating by forced association of the neighbored stations.

Operational forest stream crossings effects on water quality in the Virginia Piedmont

Treesearch

Wallace M. Aust; Matthew B. Carroll; M. Chad Bolding; Andy Dolloff

2011-01-01

Water quality indices were examined for paired upstream and downstream samples for 23 operational stream crossings and approaches during four periods. Stream crossings were (1) portable bridges (BRIDGE), (2) culverts backfilled with poles (POLE), (3) culverts with earth backfill (CULVERT), and (4) reinforced fords (FORD). The four operational periods were (1) prior to...

30 CFR 917.12 - State regulatory program and proposed program amendment provisions not approved.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., effective June 20, 2001. (c) The amendment submitted by letter dated April 12, 2002, proposing a new section... depression left by backfilling and grading, that is not a sedimentation pond or coal mine waste impoundment... completely incised or created by a depression left by backfilling and grading but not meeting MSHA...

30 CFR 917.12 - State regulatory program and proposed program amendment provisions not approved.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., effective June 20, 2001. (c) The amendment submitted by letter dated April 12, 2002, proposing a new section... depression left by backfilling and grading, that is not a sedimentation pond or coal mine waste impoundment... completely incised or created by a depression left by backfilling and grading but not meeting MSHA...

40 CFR 265.314 - Special requirements for bulk and containerized liquids.

Code of Federal Regulations, 2011 CFR

2011-07-01

... carbon (e.g., aluminosilicates, clays, smectites, Fuller's earth, bentonite, calcium bentonite... charcoal/activated carbon); or (ii) High molecular weight synthetic polymers (e.g., polyethylene, high..., polyisobutylene, ground synthetic rubber, cross-linked allylstyrene and tertiary butyl copolymers). This does not...

Ordovician K-bentonites in the Argentine Precordillera: relations to Gondwana margin evolution

USGS Publications Warehouse

Huff, W.D.; Bergstrom, Stig M.; Kolata, Dennis R.; Cingolani, C.A.; Astini, R.A.

1998-01-01

This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. Ordovician K-bentonites have now been recorded from >20 localities in the vicinity of the Argentine Precordillera. Most occur in the eastern thrust belts, in the San Juan Limestone and the overlying the Gualcamayo Formation, but a few ash beds are known also from the central thrust belts. The oldest occur in the middle Arenig I, victoriae lunatus graptolite (Oe. evae conodont) Zone, and the youngest in the middle Llanvirn P. elegans (P. suecicus) Zone. Mineralogical characteristics, typical of other Ordovician K-bentonites, include a matrix of illite/smectite mixed-layer clay and a typical felsic volcanic phenocryst assemblage: biotite, beta-form quartz, alkali and plagioclase feldspar, apatite, and zircon, with lesser amounts of hornblende, clinopyroxene, titanite and Fe-Ti oxides. The proportions of the mineral phases and variations in their crystal chemistry are commonly unique to individual (or small groups of) K-bentonite beds. Glass melt inclusions preserved in quartz are rhyolitic in composition. The sequence is unique in its abundance of K-bentonite beds, but a close association between the Precordillera and other Ordovician sedimentary basins cannot be established. The ash distribution is most consistent with palaeogeographical reconstructions in which early Ordovician drifting of the Precordillera occurred in proximity to one or more volcanic arcs, and with eventual collision along the Andean margin of Gondwana during the mid-Ordovician Ocloyic event of the Famatinian orogeny. The Puna-Famatina terrane northeast of the Precordillera might have served as the source of the K-bentonite ashes, possibly in concert with active arc magmatism on the Gondwana plate itself.

Intrinsic and Carrier Colloid-facilitated transport of lanthanides through discrete fractures in chalk

NASA Astrophysics Data System (ADS)

Weisbrod, N.; Tran, E. L.; Klein-BenDavid, O.; Teutsch, N.

2015-12-01

Geological disposal of high-level radioactive waste is the long term solution for the disposal of long lived radionuclides and spent fuel. However, some radionuclides might be released from these repositories into the subsurface as a result of leakage, which ultimately make their way into groundwater. Engineered bentonite barriers around nuclear waste repositories are generally considered sufficient to impede the transport of radionuclides from their source to the groundwater. However, colloidal-sized mobile bentonite particles ("carrier" colloids) originating from these barriers have come under investigation as a potential transport vector for radionuclides sorbed to them. As lanthanides are generally accepted to have the same chemical behaviors as their more toxic actinide counterparts, lanthanides are considered an acceptable substitute for research on radionuclide transportation. This study aims to evaluate the transport behaviors of lanthanides in colloid-facilitated transport through a fractured chalk matrix and under geochemical conditions representative the Negev desert, Israel. The migration of Ce both with and without colloidal particles was explored and compared to the migration of a conservative tracer (bromide) using a flow system constructed around a naturally fractured chalk core. Results suggest that mobility of Ce as a solute is negligible. In experiments conducted without bentonite colloids, the 1% of the Ce that was recovered migrated as "intrinsic" colloids in the form of carbonate precipitates. However, the total recovery of the Ce increased to 9% when it was injected into the core in the presence of bentonite colloids and 13% when both bentonite and precipitate colloids were injected. This indicates that lanthanides are essentially immobile in chalk as a solute but may be mobile as carbonate precipitates. Bentonite colloids, however, markedly increase the mobility of lanthanides through fractured chalk matrices.

Influence of clay particles on the transport and retention of titanium dioxide nanoparticles in quartz sand.

PubMed

Cai, Li; Tong, Meiping; Wang, Xueting; Kim, Hyunjung

2014-07-01

This study investigated the influence of two representative suspended clay particles, bentonite and kaolinite, on the transport of titanium dioxide nanoparticles (nTiO2) in saturated quartz sand in both NaCl (1 and 10 mM ionic strength) and CaCl2 solutions (0.1 and 1 mM ionic strength) at pH 7. The breakthrough curves of nTiO2 with bentonite or kaolinite were higher than those without the presence of clay particles in NaCl solutions, indicating that both types of clay particles increased nTiO2 transport in NaCl solutions. Moreover, the enhancement of nTiO2 transport was more significant when bentonite was present in nTiO2 suspensions relative to kaolinite. Similar to NaCl solutions, in CaCl2 solutions, the breakthrough curves of nTiO2 with bentonite were also higher than those without clay particles, while the breakthrough curves of nTiO2 with kaolinite were lower than those without clay particles. Clearly, in CaCl2 solutions, the presence of bentonite in suspensions increased nTiO2 transport, whereas, kaolinite decreased nTiO2 transport in quartz sand. The attachment of nTiO2 onto clay particles (both bentonite and kaolinite) were observed under all experimental conditions. The increased transport of nTiO2 in most experimental conditions (except for kaolinite in CaCl2 solutions) was attributed mainly to the clay-facilitated nTiO2 transport. The straining of larger nTiO2-kaolinite clusters yet contributed to the decreased transport (enhanced retention) of nTiO2 in divalent CaCl2 solutions when kaolinite particles were copresent in suspensions.

Remediation of AMD using natural and waste material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basir, Nur Athirah Mohamad; Yaacob, Wan Zuhairi Wan

2014-09-03

Acid Mine Drainage (AMD) is highly acidic, sulphate rich and frequently carries a high transition metal and heavy metal burden. These AMD's eventually migrate into streams and rivers and impact negatively on the quality of these water bodies. So it is dire necessary to treat this AMD. Various materials such as ladle furnace slag (LFS), bentonite, zeolite, active carbon and kaolinite are currently available to remove heavy metals from contaminated water. All these materials are capable to rise up the pH value and adsorb heavy metals. The process is divided into two stages; screening test and tank experiment. Screening testmore » is conduct by using Batch Equilibrium Test (BET), X-Ray Fluorescene (XRF) identification also Scanning Electron Microscopic (SEM) characteristic. The results showed that all the concentration of heavy metal are decreasing extremely and pH value rise up except for kaolinite. From screening test only ladle furnace slag, bentonite, zeolite and active carbon are chosen for the tank experiment. Tank experiment design with 18cm (H) X 15cm (L) X 15cm (H) was made by silica glass. All these treatment materials were stirred in the tank for 30 days. Initial pH for all tanks is 2.4 and after 30 days is changing into 6.11, 3.91, 2.98 and 2.71 for LFS, bentonite, active carbon as well as zeolite respectively. LFS is the best material for absorption of Zn, Mn and Cu in the synthetic solution. Meanwhile, bentonite is the best absorbent for Ni, Fe and Cd. The conclusion shows that LFS might have big potentials to control AMD pollution base on neutralize pH resulting in a great improvement in the quality of the water.« less

Remediation of AMD using natural and waste material

NASA Astrophysics Data System (ADS)

Basir, Nur Athirah Mohamad; Yaacob, Wan Zuhairi Wan

2014-09-01

Acid Mine Drainage (AMD) is highly acidic, sulphate rich and frequently carries a high transition metal and heavy metal burden. These AMD's eventually migrate into streams and rivers and impact negatively on the quality of these water bodies. So it is dire necessary to treat this AMD. Various materials such as ladle furnace slag (LFS), bentonite, zeolite, active carbon and kaolinite are currently available to remove heavy metals from contaminated water. All these materials are capable to rise up the pH value and adsorb heavy metals. The process is divided into two stages; screening test and tank experiment. Screening test is conduct by using Batch Equilibrium Test (BET), X-Ray Fluorescene (XRF) identification also Scanning Electron Microscopic (SEM) characteristic. The results showed that all the concentration of heavy metal are decreasing extremely and pH value rise up except for kaolinite. From screening test only ladle furnace slag, bentonite, zeolite and active carbon are chosen for the tank experiment. Tank experiment design with 18cm (H) X 15cm (L) X 15cm (H) was made by silica glass. All these treatment materials were stirred in the tank for 30 days. Initial pH for all tanks is 2.4 and after 30 days is changing into 6.11, 3.91, 2.98 and 2.71 for LFS, bentonite, active carbon as well as zeolite respectively. LFS is the best material for absorption of Zn, Mn and Cu in the synthetic solution. Meanwhile, bentonite is the best absorbent for Ni, Fe and Cd. The conclusion shows that LFS might have big potentials to control AMD pollution base on neutralize pH resulting in a great improvement in the quality of the water.

Effects of combined lime and fly ash stabilization on the elastic moduli of montmorillonitic soils : final report.

DOT National Transportation Integrated Search

1988-04-01

A laboratory study using bentonite to simulate the montmorillonite component of soils common to Louisiana was undertaken to evaluate the effects of combined lime and fly ash additions on stabilization reactions. Samples containing bentonite (75 weigh...

Physicochemical of pillared clays prepared by several metal oxides

NASA Astrophysics Data System (ADS)

Rinaldi, Nino; Kristiani, Anis

2017-03-01

Natural clays could be modified by the pillarization method, called as Pillared Clays (PILCs). PILCs have been known as porous materials that can be used for many applications, one of the fields is catalysis. PILCs as two dimensional materials are interesting because their structures and textural properties can be controlled by using a metal oxide as the pillar. Different metal oxide used as the pillar causes different properties results of pillared clays. Usually, natural smectite clays/bentonites are used as a raw material. Therefore, a series of bentonite pillared by metal oxides was prepared through pillarization method. Variation of metals pillared into bentonite are aluminium, chromium, zirconium, and ferro. The physicochemical properties of catalysts were characterized by using X-ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halenda (BJH) analysis, and Fourier transform infrared spectroscopy (FTIR) measurement. Noteworthy characterization results showed that different metals pillared into bentonite affected physical and chemical properties, i.e. basal spacing, surface area, pore size distribution, thermal stability and acidity.

Corrosion of copper and authigenic sulfide mineral growth in hydrothermal bentonite experiments

NASA Astrophysics Data System (ADS)

Caporuscio, F. A.; Palaich, S. E. M.; Cheshire, M. C.; Jové Colón, C. F.

2017-03-01

The focus of this experimental work is to characterize interaction of bentonite with possible used-fuel waste container materials. Experiments were performed up to 300 °C at 150-160 bars for five to six weeks. Bentonite was saturated with a 1900 ppm K-Ca-Na-Cl-bearing water with Cu-foils. Copper rapidly degrades into chalcocite (CuS2) and minor covellite (CuS) in the presence of H2S. Chalcocite growth and corrosion pit depths were measured for four different experimental runs yielding corrosion rates between 8.8 and 116 μm/yr depending on duration of experiment, brine composition, and clay type (bentonite vs. Opalinus Clay). Results of this research show that although pit-corrosion is demonstrated on Cu substrates, experiments show that the reactions that ensue, and the formation of minerals that develop, are extraordinarily slow. This supports the use of Cu in nuclide-containment systems as a possible engineered barrier system material.

Nonlinear isotherm and kinetics of adsorption of copper from aqueous solutions on bentonite

NASA Astrophysics Data System (ADS)

Sadeghalvad, Bahareh; Khosravi, Sara; Azadmehr, Amir Reza

2016-11-01

Bentonite is one of the most significant of clay minerals that has been studied extensively due to its potential applications in removal of various environmental pollutants. This ability is related to its high ionic exchange capacity and high specific surface area. Copper is one of the important elements of non-ferrous metals found in industrial waste waters. In the present work, the removal of copper from aqueous solutions with Iranian bentonite (from Birjand area, southeastern Iran) used without any chemical pretreatment, was studied. The experimental results were fitted by adsorption isotherms equations with two or three parameters, which include Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Redlich-Peterson, Khan, and Toth models. The best correlation coefficient ( r 2) is 0.9879 observed for Langmuir model, maximum adsorption capacity of bentonite was 55.71 mg/g. The first-order and pseudo-second-order kinetic equations were used to describe the kinetics of adsorption. The experimental data were well fitted by the pseudo-second-order kinetics.

Corrosion of copper and authigenic sulfide mineral growth in hydrothermal bentonite experiments

DOE PAGES

Caporuscio, F. A.; Palaich, Sarah E. M.; Cheshire, M. C.; ...

2016-12-29

The focus of this experimental paper is to characterize interaction of bentonite with possible used-fuel waste container materials. Experiments were performed up to 300 °C at 150–160 bars for five to six weeks. Bentonite was saturated with a 1900 ppm K-Ca-Na-Cl-bearing water with Cu-foils. Copper rapidly degrades into chalcocite (CuS 2) and minor covellite (CuS) in the presence of H 2S. Chalcocite growth and corrosion pit depths were measured for four different experimental runs yielding corrosion rates between 8.8 and 116 μm/yr depending on duration of experiment, brine composition, and clay type (bentonite vs. Opalinus Clay). Results of this researchmore » show that although pit-corrosion is demonstrated on Cu substrates, experiments show that the reactions that ensue, and the formation of minerals that develop, are extraordinarily slow. Finally, this supports the use of Cu in nuclide-containment systems as a possible engineered barrier system material.« less

Backfill composition for secondary barriers in nuclear waste repositories

DOEpatents

Beall, G.W.; Allard, B.M.

1980-05-30

A backfill composition for sorbing and retaining hazardous elements of nuclear wastes comprises 50 to 70% by weight of quartz, 10 to 30% by weight of montmorillonite, 1 to 10% by weight of phosphate mineral, 1 to 10% by weight of ferrous mineral, 1 to 10% by weight of sulfate mineral and 1 to 10% by weight of attapulgite.

The role of vegetation on gully erosion stabilization at a severely degraded landscape: A case study from Calhoun Experimental Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Bastola, S.; Dialynas, Y. G.; Bras, R. L.; Noto, L. V.; Istanbulluoglu, E.

2018-05-01

Gully erosion was evidence of land degradation in the southern Piedmont, site of the Calhoun Critical Zone Observatory (CCZO), during the cotton farming era. Understanding of the underlying gully erosion processes is essential to develop gully erosion models that could be useful in assessing the effectiveness of remedial and soil erosion control measures such as gully backfilling, revegetation, and terracing. Development and validation of process-based gully erosion models is difficult because observations of the formation and progression of gullies are limited. In this study, analytic formulations of the two dominant gullying processes, namely, plunge pool erosion and slab failure, are utilized to simulate the gullying processes in the 4-km2 Holcombe's Branch watershed. In order to calibrate parameters of the gully erosion model, gully features (e.g., depth and area) extracted from a high-resolution LiDAR map are used. After the calibration, the gully model is able to delineate the spatial extent of gullies whose statistics are in close agreement with the gullies extracted from the LiDAR DEM. Several simulations with the calibrated model are explored to evaluate the effectiveness of various gully remedial measures, such as backfilling and revegetation. The results show that in the short-term, the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies (e.g., backfilling decreased the spatial extent of gullies by 21-46% and decreased the average depth of gullies by up to 9%). Revegetation, however, is a more effective approach to stabilizing gullies that would otherwise expand if no gully remedial measures are implemented. Analyses of our simulations show that the gully stabilization effect of revegetation varies over a wide range, i.e., leading to 23-69% reduction of the spatial extent of gullies and up to 45% reduction in the depth of gullies, depending on the selection of plant species and management practices.

21 CFR 184.1155 - Bentonite.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Bentonite. 184.1155 Section 184.1155 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific...

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

PubMed

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

2003-03-01

The possible mechanisms of colloid generation at the near field/far field interface of a radioactive repository have been investigated by means of novel column experiments simulating the granite/bentonite boundary, both in dynamic and in quasi-static water flow conditions. It has been shown that solid particles and colloids can be detached from the bulk and mobilised by the water flow. The higher the flow rate, the higher the concentration of particles found in the water, according to an erosion process. However, the gel formation and the intrinsic tactoid structure of the clay play an important role in the submicron particle generation even in the compacted clay and in a confined system. In fact, once a bentonite gel is formed, in the regions where the clay is contacted with water, clay colloids can be formed even in quasi-static flow conditions. The potential relevance of these colloids in radionuclide transport has been studied by evaluating their stability in different chemical environments. The coagulation kinetics of natural bentonite colloids was experimentally studied as a function of the ionic strength and pH, by means of time-resolved light scattering techniques. It has been shown that these colloids are very stable in low saline (approximately 1 x 10(-3) M) and alkaline (pH > or = 8) waters. Copyright 2002 Elsevier Science B.V.

Insertion of bentonite with Organometallic [Fe3O(OOC6H5)6(H2O)3(NO3).nH2O] as Adsorbent of Congo Red

NASA Astrophysics Data System (ADS)

Said, Muhammad; Paluta Utami, Hasja; Hayati, Ferlina

2018-01-01

The adsorption of Congo red using bentonite inserted organometallic has been investigated. The insertion bentonite was characterized using FT-IR Spectrophotometer, XRD and XRF analysis. The FT-IR characterization showed the higher intensity of peak wavenumber at 470.6 cm-1 for Fe3O on the ratio 1:3. While the XRD characterization showed the shift of diffraction angle of 2θ was 5.2° and has a basal spacing of 16.8 Å. In the XRF characterization, the insertion process of organometallic occurred optimally with the percentage of metal oxide reached 71.75 %. The adsorption process of bentonite inserted organometallic compound [Fe3O(OOC6H5)6(H2O)3(NO3)·nH2O] showed the adsorption rate (k) is 0.050 min-1, the largest adsorption capacity (b) at 70°C is 4.48 mol/g, the largest adsorption energy at temperature 30°C which is 6.4 kJ/mol Organometallic compounds. The value of the enthalpy (ΔH) and entropy (ΔS) decreased with increasing concentrations of the Congo red. Effect of pH on the adsorption on at pH 3 shows the biggest of number Congo red absorbed is 19.52 mg/L for insertion of bentonite.

Optimization of permeability for quality improvement by using factorial design

NASA Astrophysics Data System (ADS)

Said, Rahaini Mohd; Miswan, Nor Hamizah; Juan, Ng Shu; Hussin, Nor Hafizah; Ahmad, Aminah; Kamal, Mohamad Ridzuan Mohamad

2017-05-01

Sand castings are used worldwide by the manufacturing process in Metal Casting Industry, whereby the green sand are the commonly used sand mould type in the industry of sand casting. The defects on the surface of casting product is one of the problems in the industry of sand casting. The problems that relates to the defect composition of green sand are such as blowholes, pinholes shrinkage and porosity. Our objective is to optimize the best composition of green sand in order to minimize the occurrence of defects. Sand specimen of difference parameters (Bentonite, Green Sand, Cold dust and water) were design and prepared to undergo permeability test. The 24 factorial design experiment with four factors at difference composition were runs, and the total of 16 runs experiment were conducted. The developed models based on the experimental design necessary models were obtained. The model with a high coefficient of determination (R2=0.9841) and model for predicted and actual fitted well with the experimental data. Using the Analysis of Design Expert software, we identified that bentonite and water are the main interaction effect in the experiments. The optimal settings for green sand composition are 100g silica sand, 21g bentonite, 6.5 g water and 6g coal dust. This composition gives an effect of permeability number 598.3GP.

Numerical modelling of effective thermal conductivity for modified geomaterial using lattice element method

NASA Astrophysics Data System (ADS)

Rizvi, Zarghaam Haider; Shrestha, Dinesh; Sattari, Amir S.; Wuttke, Frank

2018-02-01

Macroscopic parameters such as effective thermal conductivity (ETC) is an important parameter which is affected by micro and meso level behaviour of particulate materials, and has been extensively examined in the past decades. In this paper, a new lattice based numerical model is developed to predict the ETC of sand and modified high thermal backfill material for energy transportation used for underground power cables. 2D and 3D simulations are performed to analyse and detect differences resulting from model simplification. The thermal conductivity of the granular mixture is determined numerically considering the volume and the shape of the each constituting portion. The new numerical method is validated with transient needle measurements and the existing theoretical and semi empirical models for thermal conductivity prediction sand and the modified backfill material for dry condition. The numerical prediction and the measured values are in agreement to a large extent.

Structure of selenium incorporated in pyrite and mackinawite as determined by XAFS analyses

NASA Astrophysics Data System (ADS)

Diener, A.; Neumann, T.; Kramar, U.; Schild, D.

2012-05-01

Selenium has a toxic potential leading to diseases by ingestion and a radiotoxic potential as 79Se radionuclide if discharged from a high-level nuclear waste repository in deep geological formations into the biosphere. Selenium is often associated with sulfides, such as pyrite, the most important near-surface iron sulfide and constituent of host rocks and bentonite backfills considered for radioactive waste disposal. This study was aimed at investigating the incorporation of Se2- and Se4+ into pyrite and mackinawite to determine the relevance of iron sulfides to Se retention and the type of structural bonding. The syntheses of pyrite and mackinawite occurred via direct precipitation in batches and also produced coatings on natural pyrite in mixed-flow reactor experiments (MFR) under anoxic conditions at Se concentrations in the solutions of up to 10- 3 mol/L. Mineralogical analyses by SEM and XRD reveal the formation of pyrite and mackinawite phases. The average Se2- uptake in pyrite in batch experiments amounts to 98.6%. In MFR syntheses, it reaches 99.5%, both suggesting a high potential for retention. XAFS results indicate a substitution of sulfur by selenide during instantaneous precipitation in highly supersaturated solutions only. In selenide-doted mackinawite S2- was substituted by Se2-, resulting in a mackinawite-type compound. S- is substituted by Se- in selenide-doted pyrite, yielding a FeSSe compound as a slightly distorted pyrite structure. Under slighter supersaturated conditions, XAFS results indicate an incorporation of Se2- and Se4+ predominantly as Se0. This study shows that a substitution of S by Se in iron sulfides is probable only for highly supersaturated solutions under acidic and anoxic conditions. Under closer equilibrium conditions, Se0 is expected to be the most stable species.

Production of bio-oil and biochar from soapstock via microwave-assisted co-catalytic fast pyrolysis.

PubMed

Dai, Leilei; Fan, Liangliang; Liu, Yuhuan; Ruan, Roger; Wang, Yunpu; Zhou, Yue; Zhao, Yunfeng; Yu, Zhenting

2017-02-01

In this study, production of bio-oil and biochar from soapstock via microwave-assisted co-catalytic fast pyrolysis combining the advantages of in-situ and ex-situ catalysis was performed. The effects of catalyst and pyrolysis temperature on product fractional yields and bio-oil chemical compositions were investigated. From the perspective of bio-oil yield, the optimal pyrolysis temperature was 550°C. The use of catalysts reduced the water content, and the addition of bentonite increased the bio-oil yield. Up to 84.16wt.% selectivity of hydrocarbons in the bio-oil was obtained in the co-catalytic process. In addition, the co-catalytic process can reduce the proportion of oxygenates in the bio-oil to 15.84wt.% and eliminate the N-containing compounds completely. The addition of bentonite enhanced the BET surface area of bio-char. In addition, the bio-char removal efficiency of Cd 2+ from soapstock pyrolysis in presence of bentonite was 27.4wt.% higher than without bentonite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quality characteristics of Bali sardinella (Sardinella lemuru) oil purified with bentonite as an adsorbent

NASA Astrophysics Data System (ADS)

Nadhiro, U.; Subekti, S.; Tjahjaningsih, W.; Patmawati

2018-04-01

Crude fish oil extracted from fish canning industry a low quality, therefore refining process is required to obtain feasible fish oil for food purposes. Purification of fish oil can through steps of degumming, neutralization, and bleaching by using bentonite as the adsorbent. This study aims to analyze the results of the purification process of crude fish oil by-product of canning industry of lemuru fish by using bentonite adsorbent with different concentrations. The method used was an experimental method by descriptive data analysis. The results showed that the highest yield (33.418 %) obtained from oil purification of lemuru with bentonite concentration of 6 % are classified as follows: free fatty acid content of 0.265 %, peroxide value of 6.343 mEq / kg, produce clarity 60.275 % T, 88.075 % T, 87.5 % T, 87.425 % T, 87.975 % T at a wavelength (λ) of 450 nm, 550 nm, 620 nm, 665 nm, 700 nm, para-anisidine value of 3.725 mEq / kg; and value of oxidation total of 16.41 meq / kg.

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage

PubMed Central

Li, Chuanchang; Fu, Liangjie; Ouyang, Jing; Yang, Huaming

2013-01-01

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated. PMID:23712069

Multi-metals column adsorption of lead(II), cadmium(II) and manganese(II) onto natural bentonite clay.

PubMed

Alexander, Jock Asanja; Surajudeen, Abdulsalam; Aliyu, El-Nafaty Usman; Omeiza, Aroke Umar; Zaini, Muhammad Abbas Ahmad

2017-10-01

The present work was aimed at evaluating the multi-metals column adsorption of lead(II), cadmium(II) and manganese(II) ions onto natural bentonite. The bentonite clay adsorbent was characterized for physical and chemical properties using X-ray diffraction, X-ray fluorescence, Brunauer-Emmett-Teller surface area and cation exchange capacity. The column performance was evaluated using adsorbent bed height of 5.0 cm, with varying influent concentrations (10 mg/L and 50 mg/L) and flow rates (1.4 mL/min and 2.4 mL/min). The result shows that the breakthrough time for all metal ions ranged from 50 to 480 minutes. The maximum adsorption capacity was obtained at initial concentration of 10 mg/L and flow rate of 1.4 mL/min, with 2.22 mg/g of lead(II), 1.71 mg/g of cadmium(II) and 0.37 mg/g of manganese(II). The order of metal ions removal by natural bentonite is lead(II) > cadmium(II) > manganese(II). The sorption performance and the dynamic behaviour of the column were predicted using Adams-Bohart, Thomas, and Yoon-Nelson models. The linear regression analysis demonstrated that the Thomas and Yoon-Nelson models fitted well with the column adsorption data for all metal ions. The natural bentonite was effective for the treatment of wastewater laden with multi-metals, and the process parameters obtained from this work can be used at the industrial scale.

Tests for the evaluation of ammonium attenuation in MSW landfill leachate by adsorption into bentonite in a landfill liner.

PubMed

Pivato, A; Raga, R

2006-01-01

Uncontrolled leachate emissions are one of the key factors in the environmental impact of municipal solid waste (MSW) landfills. The concentration of ammonium, given the anaerobic conditions in traditional landfills, can remain significantly high for a very long period of time, as degradation does not take place and volatilisation is not significant (the pH is not high enough to considerably shift the equilibrium towards un-ionised ammonia). Recent years have witnessed a continuous enhancement of landfill technology in order to minimize uncontrolled emissions into the environment; bottom lining systems have been improved and more attention has been devoted to the study of the attenuation of the different chemicals in leachate in case of migration through the mineral barrier. Different natural materials have been considered for use as components of landfill liners in the last years and tested in order to evaluate the performance of the different alternatives. Among those materials, bentonite is often used, coupled with other materials in two different ways: in addition to in situ soil or in geocomposite clay liner (GCL). A lab-scale test was carried out in order to further investigate the influence of bentonite on the attenuation of ammonium in leachate passing through a landfill liner. Two different tests were conducted: a standardized batch test with pulverized bentonite and a batch test with compacted bentonite. The latter was proposed in order to better simulate the real conditions in a landfill liner. The two tests produced values for the partition coefficient K(d) higher than the average measured for other natural materials usually utilized as components of landfill liners. Moreover, the two tests showed similar results, thus providing a further validation of the suitability of the standard batch test with pulverized bentonite. A thorough knowledge of attenuation processes of ammonium in landfill liners is the basis for the application of risk analysis models for the evaluation of the failure of bottom liners or their components.

Colloid facilitated transport of lanthanides through discrete fractures in chalk

NASA Astrophysics Data System (ADS)

Tran, Emily; Klein Ben-David, Ofra; Teutsch, Nadya; Weisbrod, Noam

2015-04-01

Geological disposal of high-level radioactive waste is the internationally agreed-upon, long term solution for the disposal of long lived radionuclides and spent fuel. Eventually, corrosion of the waste canisters may lead to leakage of their hazardous contents, and the radionuclides can ultimately make their way into groundwater and pose a threat to the biosphere. Engineered bentonite barriers placed around nuclear waste repositories are generally considered sufficient to impede the transport of radionuclides from their storage location to the groundwater. However, colloidal-sized mobile bentonite particles eroding from these barriers have come under investigation as a potential transport vector for radionuclides sorbed to them. In addition, the presence of organic matter in groundwater has been shown to additionally facilitate the uptake of radionuclides by the clay colloids. This study aims to evaluate the transport behaviors of radionuclides in colloid-facilitated transport through a fractured chalk matrix and under geochemical conditions representative of the Negev desert, Israel. Lanthanides are considered an acceptable substitute to actinides for research on radionuclide transportation due to their similar chemical behavior. In this study, the migration of Ce both with and without colloidal particles was explored and compared to the migration of a conservative tracer (bromide). Tracer solutions containing known concentrations of Ce, bentonite colloids, humic acid and bromide were prepared in a matrix solution containing salt concentrations representative of that of the average rain water found in the Negev. These solutions were then injected into a flow system constructed around a naturally fractured chalk core. Samples were analyzed for Ce and Br using ICP-MS, and colloid concentrations were determined using spectrophotographic analysis. Breakthrough curves comparing the rates of transportation of each tracer were obtained, allowing for comparison of transport rates and calculation of overall tracer recovery. Preliminary results suggest that mobility of Ce as a solute is negligible, and in experiments conducted without bentonite colloids, the 2% of the Ce that was recovered during the experiments travelled as "intrinsic" colloids in the form of Ce2(CO3)3-6H2O precipitate. However, the total recovery of the Ce increased to 9% when it was injected into the core in the presence of bentonite colloids and 13% when both bentonite and the carbonate precipitate colloids were injected. In addition, the maximum relative concentration (C/C0) of the Ce in the samples from the experiments conducted without bentonite colloids is about 0.002, whereas that of the experiments conducted in the presence of bentonite colloids reaches almost 0.2. This indicates that colloid presence does indeed markedly increase the mobility of radionuclides through fractured chalk matrices and should therefore be considered in models representing transport of radionuclide waste originating from nuclear repositories.

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

PubMed

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

2016-06-15

Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads: 1.4-6.7 tonnes ha(-1)) in concentrations of surface water total phosphorus (TP; data available from 15 lakes), soluble reactive phosphorus (SRP; 14 lakes), and chlorophyll a (15 lakes), and in Secchi disk depths (15 lakes), aquatic macrophyte species numbers (6 lakes) and aquatic macrophyte maximum colonisation depths (4 lakes) across the treated lakes. Data availability varied across the lakes and variables, and in general monitoring was more frequent closer to the application dates. Median annual TP concentrations decreased significantly across the lakes, following the La-bentonite applications (from 0.08 mg L(-1) in the 24 months pre-application to 0.03 mg L(-1) in the 24 months post-application), particularly in autumn (0.08 mg L(-1) to 0.03 mg L(-1)) and winter (0.08 mg L(-1) to 0.02 mg L(-1)). Significant decreases in SRP concentrations over annual (0.019 mg L(-1) to 0.005 mg L(-1)), summer (0.018 mg L(-1) to 0.004 mg L(-1)), autumn (0.019 mg L(-1) to 0.005 mg L(-1)) and winter (0.033 mg L(-1) to 0.005 mg L(-1)) periods were also reported. P concentrations following La-bentonite application varied across the lakes and were correlated positively with dissolved organic carbon concentrations. Relatively weak, but significant responses were reported for summer chlorophyll a concentrations and Secchi disk depths following La-bentonite applications, the 75th percentile values decreasing from 119 μg L(-1) to 74 μg L(-1) and increasing from 398 cm to 506 cm, respectively. Aquatic macrophyte species numbers and maximum colonisation depths increased following La-bentonite application from a median of 5.5 species to 7.0 species and a median of 1.8 m to 2.5 m, respectively. The aquatic macrophyte responses varied significantly between lakes. La-bentonite application resulted in a general improvement in water quality leading to an improvement in the aquatic macrophyte community within 24 months. However, because, the responses were highly site-specific, we stress the need for comprehensive pre- and post-application assessments of processes driving ecological structure and function in candidate lakes to inform future use of this and similar products. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Environmental Assessment of Selected Cone Penetrometer Grouts and a Tracer

DTIC Science & Technology

1993-08-01

Bentonite Clay ............ ...................... A2 Attapulgite Clay ................................... A22 Microfine Portland Cement...and the tracer are a. Bentonite clay. b. Attapulgite clay. c. Microfine portland cement. d. Joosten grout (calcium silicate grout). e. Urethane grout. f...Inc., on an attapulgite clay product (trade name: Zeogel). " Microfine portland cement. Information was obtained for two micro- fine portland cements

A facile method to modify bentonite nanoclay with silane

NASA Astrophysics Data System (ADS)

Abeywardena, Sujani B. Y.; Perera, Srimala; Nalin de Silva, K. M.; Tissera, Nadeeka P.

2017-07-01

Immobilization of smectite clay onto a desirable surface has received much attention, since its nanospace can be utilized for many applications in material science. Here, we present an efficient method to functionalize surface of bentonite nanoclay (BNC) through the grafting of 3-aminotriethoxysilane (APTES). Infrared spectroscopy and elemental analysis confirmed the presence of organic chains and amine groups in modified nanoclay. XRD analysis confirmed grafting of APTES on the surface of bentonite nanoclay without intercalation. The accomplishment of the surface modification was quantitatively proved by TGA analysis. Modified BNC can covalently couple with different material surfaces, allowing its nanospace to be utilized for intercalation of cations, bio-molecules, and polymeric materials, to be used in advanced military aerospace, pharmaceuticals, and many other commercial applications.

Backfilling-Free Strategy for Biopatterning on Intrinsically Dual-Functionalized Poly[2-Aminoethyl Methacrylate-co-Oligo(Ethylene Glycol) Methacrylate] Films.

PubMed

Lee, Bong Soo; Lee, Juno; Han, Gyeongyeop; Ha, EunRae; Choi, Insung S; Lee, Jungkyu K

2016-07-20

We demonstrated protein and cellular patterning with a soft lithography technique using poly[2-aminoethyl methacrylate-co-oligo(ethylene glycol) methacrylate] films on gold surfaces without employing a backfilling process. The backfilling process plays an important role in successfully generating biopatterns; however, it has potential disadvantages in several interesting research and technical applications. To overcome the issue, a copolymer system having highly reactive functional groups and bioinert properties was introduced through a surface-initiated controlled radical polymerization with 2-aminoethyl methacrylate hydrochloride (AMA) and oligo(ethylene glycol) methacrylate (OEGMA). The prepared poly(AMA-co-OEGMA) film was fully characterized, and among the films having different thicknesses, the 35 nm-thick biotinylated, poly(AMA-co-OEGMA) film exhibited an optimum performance, such as the lowest nonspecific adsorption and the highest specific binding capability toward proteins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous adsorption and degradation of Zn(2+) and Cu (2+) from wastewaters using nanoscale zero-valent iron impregnated with clays.

PubMed

Shi, Li-Na; Zhou, Yan; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

2013-06-01

Clays such as kaolin, bentonite and zeolite were evaluated as support material for nanoscale zero-valent iron (nZVI) to simultaneously remove Cu(2+) and Zn(2+) from aqueous solution. Of the three supported nZVIs, bentonite-supported nZVI (B-nZVI) was most effective in the simultaneous removal of Cu(2+) and Zn(2+) from a aqueous solution containing a 100 mg/l of Cu(2+) and Zn(2+), where 92.9 % Cu(2+) and 58.3 % Zn(2+) were removed. Scanning electronic microscope (SEM) revealed that the aggregation of nZVI decreased as the proportion of bentonite increased due to the good dispersion of nZVI, while energy dispersive spectroscopy (EDS) demonstrated the deposition of copper and zinc on B-nZVI after B-nZVI reacted with Cu(2+) and Zn(2+). A kinetics study indicated that removing Cu(2+) and Zn(2+) with B-nZVI accorded with the pseudo first-order model. These suggest that simultaneous adsorption of Cu(2+)and Zn(2+) on bentonite and the degradation of Cu(2+)and Zn(2+) by nZVI on the bentonite. However, Cu(2+) removal by B-nZVI was reduced rather than adsorption, while Zn(2+) removal was main adsorption. Finally, Cu(2+), Zn(2+), Ni(2+), Pb(2+) and total Cr from various wastewaters were removed by B-nZVI, and reusability of B-nZVI with different treatment was tested, which demonstrates that B-nZVI is a potential material for the removal of heavy metals from wastewaters.

Organic contaminant removal efficiency of sodium bentonite/clay (BC) mixtures in high permeability regions utilizing reclaimed wastewater: A meso-scale study

NASA Astrophysics Data System (ADS)

Xiao, Yang; Li, Yunkai; Ning, Zigong; Li, Pengxiang; Yang, Peiling; Liu, Chengcheng; Liu, Zhongwei; Xu, Feipeng; Hynds, Paul Dylan

2018-03-01

Wastewater reclamation now represents an effective measure for sustainable water resource management in arid regions, however wastewater components (organic micropollutants) may potentially impact local ecological and/or human health. Previous studies have shown that sodium bentonite/natural clay (BC) mixes may be used to effectively reduce riverbed infiltration in regions characterized by excessively high hydraulic conductivity. Accordingly, the current study sought to investigate the contaminant removal efficiency (Re) of several BC mass ratios in simulated dry riverbeds. Results indicate that the measured Re of NH4+-N, CODcr and BOD5 increased in concurrence with an increasing sodium bentonite ratio, up to a maximum Re of 97.4% (NH4+-N), 55.2% (CODcr), and 51.5% (BOD5). The primary contaminant removal site was shown to be the infiltration-reducing (BC) layer, accounting for approximately 40%, 60%, and 70% of NH4+-N, CODcr and BOD5 removal, respectively. Conversely, the removal efficiency of NO3-N was found to be low (<15%), while total phosphorous (TP) was found to actively leach from the infiltration-reduction layer, resulting in measured TP discharges 2.4-4.8 times those of initial infiltration values. The current study provides a technical baseline for the efficacy of sodium bentonite as an effective bi-functional material in areas utilizing reclaimed water i.e. concurrent reduction of infiltration rates (Function 1) and decontamination of reclaimed wastewater infiltration/recharge (Function 2). Findings indicate that sodium bentonite-clay mixes may represent a feasible alternative for managing recharge of non-potable aquifers with reclaimed wastewater.

The biological costs of not reclaiming bentonite mine spoils

Treesearch

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...

Mechanism of smectic arrangement of montmorillonite and bentonite clay platelets incorporated in gels of poly(acrylamide) induced by the interaction with cationic surfactants.

PubMed

Starodoubtsev, S G; Lavrentyeva, E K; Khokhlov, A R; Allegra, G; Famulari, A; Meille, S V

2006-01-03

Structure transitions, induced by the interaction with the cationic surfactant cetylpyridinium chloride in nanocomposite gels of poly(acrylamide) with incorporated suspensions of the two closely related layered clays bentonite and montmorillonite, were studied. Unexpectedly, different behaviors were revealed. X-ray diffraction measurements confirm that, due to the interaction with the surfactant, initially disordered bentonite platelets arrange into highly ordered structures incorporating alternating clay platelets and surfactant bilayers. The formation of these smectic structures also in the cross-linked polymer gels, upon addition of the surfactant, is explained by the existence of preformed, poorly ordered aggregates of the clay platelets in the suspensions before the gel formation. In the case of montmorillonite, smectic ordering of the disordered platelets in the presence of the surfactant is observed only after drying the suspensions and the clay-gel composites. Rheology studies of aqueous suspensions of the two clays, in the absence of both surfactant and gel, evidence a much higher viscosity for bentonite than for montmorillonite, suggesting smaller clay-aggregate size in the latter case. Qualitatively consistent results are obtained from optical micrographs.

Immobilization of dextranase from Chaetomium erraticum.

PubMed

Erhardt, Frank Alwin; Jördening, Hans-Joachim

2007-09-30

In order to facilitate the Co-Immobilization of dextransucrase and dextranase, various techniques for the immobilization of industrial endo-dextranase from Chaetomium erraticum (Novozymes A/S) were researched. Adsorption isotherms at various pH-values have been determined for bentonite (Montmorillonite), hydroxyapatite and Streamline DEAE. Using bentonite and hydroxyapatite, highest activity loads (12,000 Ug(-1); 2900 Ug(-1), respectively) can be achieved without a significant change of the apparent Michaelis-Menten constant K(M). For successful adsorption, enzyme to bentonite ratios greater than 0.4 (w/w) have to be used as lower ratios lead to 90% enzyme inactivation due to bentonite contact. In addition, covalent linkage using the activated oxiran carriers Eupergit C and Eupergit C250L as well as linkage with aminopropyl silica via metaperiodate activation of glycosyl moiety of dextranase are discussed. This is also the first report probing the structure of a matrix containing dextranase by use of substrate species with different molecular weights. From this we can observe a relationship between the porosity of Eupergit and dextran dependent activity. For the reactor concept using Co-Immobilisates, hydroxyapatite will be preferred to Eupergit because of its higher specific activity and dispersity.

Activated carbons as potentially useful non-nutritive additives to prevent the effect of fumonisin B1 on sodium bentonite activity against chronic aflatoxicosis.

PubMed

Monge, María Del Pilar; Magnoli, Alejandra Paola; Bergesio, Maria Virginia; Tancredi, Nestor; Magnoli, Carina E; Chiacchiera, Stella Maris

2016-06-01

Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are mycotoxins that often co-occur in feedstuffs. The ingestion of AFB1 causes aflatoxicosis in humans and animals. Sodium bentonite (NaB), a cheap non-nutritive unselective sequestering agent incorporated in animal diets, can effectively prevent aflatoxicosis. Fumonisins are responsible for equine leukoencephalomalacia and porcine pulmonary oedema, and often have subclinical toxic effects in poultries. Fumonisin B1 and aflatoxin B1 are both strongly adsorbed in vitro on sodium bentonite. Co-adsorption studies, carried out with a weight ratio of FB1 to AFB1 that mimics the natural occurrence (200:1), showed that FB1 greatly decreases the in vitro ability of NaB to adsorb AFB1. The ability of two activated carbons to adsorb FB1 was also investigated. Both carbons showed high affinity for FB1. A complex behaviour of the FB1 adsorption isotherms with pH was observed. In vitro results suggest that under natural contamination levels of AFB1 and FB1, a mixture of activated carbon and sodium bentonite might be potentially useful for prevention of sub-acute aflatoxicosis.

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

NASA Astrophysics Data System (ADS)

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 experiments with NO3- will support the understanding of sorption behavior of the anions. All hydrophilic samples have a higher retardation capacity, indicated by diffusion coefficients of 2.44 x 10-11 m/s2 for original bentonite and ˜2.1 x 10-11m/s2 for hydrophilic organo-clays. For hydrophobic organo-clays the H2O diffusion can be higher and is increased at high bulk density (1-1.5 g/m3) up to 2.76 x 10-10m2/s. Experiments with NO3- at bulk density of 1.5 g/m3 reveal that the apparent diffusion coefficients of nitrate are with results up to 5.61 x 1012 m2/s distinctively lower than free diffusion of nitrate in pure water (6.46 x 1010 m2/s at experimental conditions) and nitrate diffusion in natural bentonite (2.63 x 1011 m2/s). The measurements allow the interpretation of the different sorption mechanisms, retardation capacity and diffusion behavior of the analyzed clays at different anion concentrations. Ongoing molecular dynamic simulations will contribute understanding of diffusion processes in organo-clays including the conditions at the interface of the clay minerals and in solution. References: [1] Shackelford, C.D., Moore S.M. (2013) Fickian diffusion of radionuclides for engineered containment barriers: Diffusion coefficients, porosities, and complicating issues. Engineering Geology, 152, 133-147. [2] Rytwo, G., Nir, S., Shuali, U. (2012) Clay and water treatment. Applied Clay Science, 67-68, 117-118. [3] Lorenzetti, R.L., Bartelt-Hunt, S.L., Burns, S.E., Smith, J.A. (2005) Hydraulic conductivities and effective diffusion coefficients of geosynthetic clay liners with organobentonite amendments. Geotextiles and Geomembranes, 23, 385-400. [4] Schampera, B., Dultz, S. (2011) H2O self-diffusion in compacted clays as influenced by surface charge and wettability - obstruction effects of bound H2O layers. Clay and Clay Minerals,59, 42-57.

Government Draw Bentonite Beds: a newly identified stratigraphic marker in the Virgin Creek Member of the Pierre Shale, central South Dakota ( USA).

USGS Publications Warehouse

Nichols, T.C.; Chleborad, A.F.; Collins, D.S.

1987-01-01

A grouping of four bentonite beds, herein named the Government Draw Bentonite Beds, is identified as a stratigraphic marker within the Virgin Creek Member of the Pierre Shale. The beds are found west of Pierre, South Dakota, over an area of at least 130 mi2 (210 km2) where no other markers within the Virgin Creek Member have been identified. In this area, the Government Draw is a potential tool needed to determine the stratigraphic and structural relationships within the upper part of the Pierre Shale, heretofore little known. A better understanding of structural elements found in the Pierre Shale is needed to unravel the Late Cretaceous and younger geologic history of the area. -Authors

Experimental Study on Application of Boron Mud Secondary Resource to Oxidized Pellets Production

NASA Astrophysics Data System (ADS)

Fu, Xiao-Jiao; Chu, Man-Sheng; Zhao, Jia-Qi; Chen, Shuang-Yin; Liu, Zheng-Gen; Wang, Si-Yuan

2017-07-01

In order to realize comprehensive and massive treatment of boron mud secondary resource, fundamental study on boron mud applied to oxidized pellets production as additive was carried out in the paper under laboratory conditions. The effects of boron mud on the performance of oxidized pellets were investigated systemically, and boron mud was combined with other boron-rich material innovatively. The results showed that, within certain limits, boron mud can improve properties of oxidized pellets. The bentonite content decreased to 0.3 % when adding 1.0 % boron mud additive and the pellets met blast furnace requirements. With the combination additive content 0.8 %, bentonite content can be further decreased to 0.2 %, and the pellets properties were better than base pellet. Therefore, it was an effective way to reduce environmental pollution and optimize blast furnace operation by developing boron mud secondary resource as pellets additive.

Environmental behavior of cement-based stabilized foundry sludge products incorporating additives.

PubMed

Ruiz, M C; Irabien, A

2004-06-18

A series of experiments were conducted to stabilize the inorganic and organic pollutants in a foundry sludge from a cast iron activity using Portland cement as binder and three different types of additives, organophilic bentonite, lime and coal fly ash. Ecotoxicological and chemical behavior of stabilized mixes of foundry sludge were analyzed to assess the feasibility to immobilize both types of contaminants, all determined on the basis of compliance leaching tests. The incorporation of lime reduces the ecotoxicity of stabilized mixes and enhances stabilization of organic pollutants obtaining better results when a 50% of cement is replaced by lime. However, the alkalinity of lime increases slightly the leached zinc up to concentrations above the limit set under neutral conditions by the European regulations. The addition of organophilic bentonite and coal fly ash can immobilize the phenolic compounds but are inefficient to reduce the ecotoxicity and mobility of zinc of final products.

International collaboration on used fuel disposition crystalline rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yifeng; Gardner, Payton; Kim, Geon-Young

Active participation in international R&D is crucial for achieving the UFD long-term goals of conducting “experiments to fill data needs and confirm advanced modeling approaches” (by 2015) and of having a “robust modeling and experimental basis for evaluation of multiple disposal system options” (by 2020). DOE’s Office of Nuclear Energy (NE) and its Office of Used Fuel Disposition Research and Development (UFD) have developed a strategic plan to advance cooperation with international partners. The international collaboration on the evaluation of crystalline disposal media at Sandia National Laboratories (SNL) in FY16 focused on the following four activities: (1) thermal-hydrologic-mechanical-chemical modeling singlemore » fracture evolution; (2) simulations of flow and transport in Bedrichov Tunnel, Czech Republic, (3) completion of streaming potential testing at Korean Atomic Energy Research Institute (KAERI), and (4) technical data exchange with KAERI on thermal-hydrologic-mechanical (THM) properties and specifications of bentonite buffer materials. The first two activities are part of the Development of Coupled Models and their Validation against Experiments (DECOVALEX-2015) project.« less

Wormhole Formation in RSRM Nozzle Joint Backfill

NASA Technical Reports Server (NTRS)

Stevens, J.

2000-01-01

The RSRM nozzle uses a barrier of RTV rubber upstream of the nozzle O-ring seals. Post flight inspection of the RSRM nozzle continues to reveal occurrence of "wormholes" into the RTV backfill. The term "wormholes", sometimes called "gas paths", indicates a gas flow path not caused by pre-existing voids, but by a little-understood internal failure mode of the material during motor operation. Fundamental understanding of the mechanics of the RSRM nozzle joints during motor operation, nonlinear viscoelastic characterization of the RTV backfill material, identification of the conditions that predispose the RTV to form wormholes, and screening of candidate replacement materials is being pursued by a joint effort between Thiokol Propulsion, NASA, and the Army Propulsion & Structures Directorate at Redstone Arsenal. The performance of the RTV backfill in the joint is controlled by the joint environment. Joint movement, which applies a tension and shear load on the material, coupled with the introduction of high pressure gas in combination create an environment that exceeds the capability of the material to withstand the wormhole effect. Little data exists to evaluate why the material fails under the modeled joint conditions, so an effort to characterize and evaluate the material under these conditions was undertaken. Viscoelastic property data from characterization testing will anchor structural analysis models. Data over a range of temperatures, environmental pressures, and strain rates was used to develop a nonlinear viscoelastic model to predict material performance, develop criteria for replacement materials, and quantify material properties influencing wormhole growth. Three joint simulation analogs were developed to analyze and validate joint thermal barrier (backfill) material performance. Two exploratory tests focus on detection of wormhole failure under specific motor operating conditions. A "validation" test system provides data to "validate" computer models and predictions. Finally, two candidate replacement materials are being screened and "validated" using the developed test systems.

Graded porous inorganic materials derived from self-assembled block copolymer templates.

PubMed

Gu, Yibei; Werner, Jörg G; Dorin, Rachel M; Robbins, Spencer W; Wiesner, Ulrich

2015-03-19

Graded porous inorganic materials directed by macromolecular self-assembly are expected to offer unique structural platforms relative to conventional porous inorganic materials. Their preparation to date remains a challenge, however, based on the sparsity of viable synthetic self-assembly pathways to control structural asymmetry. Here we demonstrate the fabrication of graded porous carbon, metal, and metal oxide film structures from self-assembled block copolymer templates by using various backfilling techniques in combination with thermal treatments for template removal and chemical transformations. The asymmetric inorganic structures display mesopores in the film top layers and a gradual pore size increase along the film normal in the macroporous sponge-like support structure. Substructure walls between macropores are themselves mesoporous, constituting a structural hierarchy in addition to the pore gradation. Final graded structures can be tailored by tuning casting conditions of self-assembled templates as well as the backfilling processes. We expect that these graded porous inorganic materials may find use in applications including separation, catalysis, biomedical implants, and energy conversion and storage.

Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications

NASA Astrophysics Data System (ADS)

Fan, Haifeng; Wen, Hanjie; Hu, Ruizhong; Zhao, Hui

2011-12-01

To understand the impact of Selenium (Se) into the biogeochemical cycle and implications for palaeo-redox environment, a sequential extraction method was utilized for samples including black shales, cherts, a Ni-Mo-Se sulfide layer, K-bentonite and phosphorite from Lower Cambrian Se-enriched strata in southern China. Seven species (water-soluble, phosphate exchangeable, base-soluble, acetic acid-soluble, sulfide/selenide associated, residual Se) and different oxidation states (selenate Se(VI), selenite Se(IV), organic Se, Se (0) and mineral Se(-II)) were determinated in this study. We found that the Ni-Mo-Se sulfide layer contained a significantly greater amount of Se(-II) associated with sulfides/selenides than those in host black shales and cherts. Furthermore, a positive correlation between the degree of sulfidation of iron (DOS) and the percentage of the sulfide/selenide-associated Se(-II) was observed for samples, which suggests the proportion of sulfide/selenide-associated Se(-II) could serve as a proxy for palaeo-redox conditions. In addition, the higher percentage of Se(IV) in K-bentonite and phosphorite was found and possibly attributed to the adsorption of Se by clay minerals, iron hydroxide surfaces and organic particles. Based on the negative correlations between the percentage of Se(IV) and that of Se(-II) in samples, we propose that the K-bentonite has been altered under the acid oxic conditions, and the most of black shale (and cherts) and the Ni-Mo-Se sulfide layer formed under the anoxic and euxinic environments, respectively. Concerning Se accumulation in the Ni-Mo-Se sulfide layer, the major mechanism can be described by (1) biotic and abiotic adsorption and further dissimilatory reduction from oxidized Se(VI) and Se(IV) to Se(-II), through elemental Se, (2) contribution of hydrothermal fluid with mineral Se(-II).

The Mohawkian Chronostratigraphic Problem: building a reliable timescale by combining biostratigraphy, chemostratigraphy, and tephrochronology

NASA Astrophysics Data System (ADS)

Sell, B. K.; Sadler, P.; Leslie, S.; Mitchell, C.; Samson, S. D.

2011-12-01

The abundant exposures of Mohawkian (late Sandbian to early Katian) sedimentary rocks in eastern North America have been well-studied for insights into the Taconic orogeny and potential petroleum sources. Considerable information has been published toward establishing the sequence stratigraphic architecture, biozones for conodonts, graptolites and chitinozoans, chemostratigraphic correlations and a tephrochronologic framework. And yet, correlation remains difficult. Problems arise from complex sedimentary facies changes across the Laurentian margin and associated provincalism of the faunas. The difficulties are exacerbated by some imprecise usage of bentonite names, the short time spans of key stratigraphic sections, and a paucity of sections with muliple kinds of information. Also, linking so many taxon range end, ash-fall, and stable isotope excursion events into a coherent stratigraphic sequence is a daunting numerical problem. It falls into the notorious "NP-Complete" category because the number of possible solutions grows so fast as the number of events increases. "Simulated annealing" is one of the algorithms developed for such problems. We adopt it to solve the stratigraphic sequencing problem as a constrained optimization (CONOP). Nevertheless, to realize the full potential, more bentonite charactization and dating is needed in sections with detailed range charts for fossil species. CONOP works best with the individual taxon ranges, not the derived biozone boundaries. We examine the potential resolving power of CONOP in the context of a re-evaluation of bentonite correlations and newly acquired CA-TIMS U-Pb zircon dates from sections with rich biostratigraphic data. In particular we use 206Pb/238U zircon dates from two bentonites in the Womble Shale at the Katian Global Stratotype Section and Point (452.8 ± 0.2 and 453.5 ± 0.3 Ma, weighted mean with 2σ internal error) to compare various correlations with other dated bentonites in eastern North America. Preliminary dates for five long-range (>1000 km) bentonite correlations made on the basis of single-crystal apatite trace-element analyses (Mg, Cl, Mn, Fe, Ce, Y) help resolve previous conflicts among various biostratgraphic data, but raise new questions about the interpretation of stratigraphic sequences and chemostratigraphic data.

Adsorptive removal of Lead from water by the effective and reusable magnetic cellulose nanocomposite beads entrapping activated bentonite.

PubMed

Luo, Xiaogang; Lei, Xiaojuan; Xie, Xiuping; Yu, Bo; Cai, Ning; Yu, Faquan

2016-10-20

Many efforts have been driven to decontaminate the drinking water, and the development of efficient adsorbents with the advantages of cost-effectiveness and operating convenience for the removal of Pb(2+) from water is a major challenge. This work was aimed to explore the possibility of using cellulose-based adsorbents for efficient adsorption of Pb(2+). The millimeter-scale magnetic cellulose-based nanocomposite beads were fabricated via an optimal extrusion dropping technology by blending cellulose with the carboxyl-functionalized magnetite nanoparticles and acid-activated bentonite in NaOH/urea aqueous solution, and then they had been tested to evaluate the effectiveness in the removal of Pb(2+) from water. The effects of contact time, initial heavy metal ion concentrations, adsorption isotherms and solution pH on the sorption behavior were studied. The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption processes were feasible, spontaneous, endothermic and mainly controlled by chemical mechanisms. The reusability of the adsorbent was also studied. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clay-based matrices incorporating radioactive silts: A case study of sediments from spent fuel pool

NASA Astrophysics Data System (ADS)

Antonenko, Mikhail; Myshkin, Vyacheslav; Grigoriev, Alexander; Chubreev, Dmitry

2018-03-01

Radioactive silt sediments from uranium reactors may be effectively and safely included by ceramic compounds. The purpose of the paper is to determine the influence of composition and preparation conditions on physicochemical and mechanical properties of clay-based matrices containing radioactive silt. Clay matrices were prepared from four minerals, took from Siberian regions, as kaolin, loan, bentonite and red clay, and they included radioactive silt sediments collected from Spent Fuel Pool of a Uranium-graphite Reactor. The rate of 137Cs leaching from the matrices of different compositions was studied. The results of the studies allowed determining the optimal compositions and the preparation conditions of the matrices. It has been shown that red clay from "Zykovskaya" career (Krasnoyarsk region, Russia) is preferable for use as a matrix for incorporating the silt sediments compared to kaolin, loam and bentonite due to the maximum values tensile strength and minimal change in ultimate strength for compression after irradiation, freezing and water exposure. Nevertheless, 137Cs leaching rate of all studied composites did not exceed 10-3 g/cm2.day.

Amino Acid Interaction with and Adsorption on Clays: FT-IR and Mössbauer Spectroscopy and X-ray Diffractometry Investigations

NASA Astrophysics Data System (ADS)

Benetoli, Luís O. B.; de Souza, Cláudio M. D.; da Silva, Klébson L.; de Souza, Ivan G.; de Santana, Henrique; Paesano, Andrea; da Costa, Antonio C. S.; Zaia, Cássia Thaïs B. V.; Zaia, Dimas A. M.

2007-12-01

In the present paper, the adsorption of amino acids (Ala, Met, Gln, Cys, Asp, Lys, His) on clays (bentonite, kaolinite) was studied at different pH (3.00, 6.00, 8.00). The amino acids were dissolved in seawater, which contains the major elements. There were two main findings in this study. First, amino acids with a charged R group (Asp, Lys, His) and Cys were adsorbed on clays more than Ala, Met and Gln (uncharged R groups). However, 74% of the amino acids in the proteins of modern organisms have uncharged R groups. These results raise some questions about the role of minerals in providing a prebiotic concentration mechanism for amino acids. Several mechanisms are also discussed that could produce peptide with a greater proportion of amino acids with uncharged R groups. Second, Cys could play an important role in prebiotic chemistry besides participating in the structure of peptides/proteins. The FT-IR spectra showed that the adsorption of amino acids on the clays occurs through the amine group. However, the Cys/clay interaction occurs through the sulfhydryl and amine groups. X-ray diffractometry showed that pH affects the bentonite interlayer, and at pH 3.00 the expansion of Cys/bentonite was greater than that of the samples of ethylene glycol/bentonite saturated with Mg. The Mössbauer spectrum for the sample with absorbed Cys showed a large increase (˜20%) in ferrous ions. This means that Cys was able to partially reduce iron present in bentonite. This result is similar to that which occurs with aconitase where the ferric ions are reduced to Fe 2.5.

Bentonite chemical features as proxy of late Cretaceous provenance changes: A case study from the Western Interior Basin of Canada

NASA Astrophysics Data System (ADS)

Fanti, Federico

2009-05-01

Bentonite beds are fairly common in both marine and terrestrial Upper Cretaceous (Campanian-Maastrichtian) deposits of the Western Interior Basin of western Canada and northwestern United States. A detailed stratigraphic, sedimentologic, geochemical (X-ray fluorescence), and mineralogical (X-ray diffraction) study of twenty-one bentonites from the Puskwaskau and Wapiti formations in the Grande Prairie area (west-central Alberta, Canada) is here presented. Major and trace-element concentrations from altered volcanic ashes document the presence in the study area of predominantly trachyandesitic and rhyolitic volcanogenic products, resulted from intense volcanic arc to within-plate pyroclastic activity. Concentration values of high field strength elements (HFSE) and selected large ion lithophile elements (LILE) (e.g. Nb, Zr, Th, and Y) obtained by X-ray fluorescence spectroscopy strongly support the presence of multiple volcanic sources. Integrated paleoenvironmental and geochemical criteria for provenance determination indicate a bimodal occurrence of basic and acid volcanic products interpreted as reflection of source areas characterized by different tectonic setting and magmatic composition. A comparative analysis of geochemical compositions between Grande Prairie bentonites and 30 known volcanic beds from central and southern Alberta, Manitoba and Montana 1. documents a trend toward more acidic and alkali-depleted volcanic products during the late Campanian-early Maastrichtian interval, and 2. suggests a well constrained stratigraphic and geographic subdivision of the non-marine successions of the foreland basin on the basis of geochemical characteristic of volcanic ash beds. Furthermore, geochemical "fingerprints" of several decimeter to meter thick bentonite beds have been coupled with volcanic ash subsurface signature in order to investigate their role as marker beds. This multiple-approach provides a reliable tool for basin-scale identification and correlation of non-marine sedimentary successions.

Synthese et Caracterisation de Nanocomposites d'Argile et de Graphene Formes a Partir de Precurseurs Organiques =

NASA Astrophysics Data System (ADS)

Boussaboun, Zakariae

Les mineraux d'argile sont des catalyseurs possibles pour la formation du graphene a partir de precurseurs organiques, comme le saccharose. Les argiles sont abondantes, securitaires et economiques pour la formation du graphene. L'objectif principal de ce memoire est de demontrer qu'il est possible de synthetiser un materiau hybride contenant de l'argile et du graphene. La preparation de ces materiaux carbones a base de l'argile (bentonite et cloisite) et le saccharose a ete realisee selon deux methodes. La premiere methode est faite en trois etapes : 1) periode de contact entre l'argile et la source de carbone dans un environnement humide, 2) infiltration de la matiere carbonee et transformation au four a micro-onde, 3) chauffage a 750°C sous azote pour obtenir des materiaux carbones. Par contre la deuxieme methode est faite en deux etapes, sans micro-onde, et avec une augmentation de la quantite de source de carbone (saccharose et alginate). La caracterisation du materiau a permis de suivre les reactions de transformation de la source de carbone vers le graphene. Cette caracterisation a ete faite par la spectroscopie IRTF et Raman, l'analyse thermogravimetrique (TGA), la surface specifique (methode BET) et le microscope electronique a balayage (MEB). La conductivite electrique a ete mesuree par un spectrometre dielectrique et en fonction de la pression appliquee avec un multimetre. Le materiau realise etait incorpore dans une matrice avec un polyethylene a basse densite pour avoir un polymere avec des caracteristiques specifiques. La conductivite thermique a ete ensuite mesuree suivant la norme ASTM E1530. L'echantillon realise avec la deuxieme methode avec une proportion de bentonite pour 5 proportions de saccharose (M2 B1 : S5) signale la possibilite de produire des materiaux de graphene a partir de ressources naturelles. La surface specifique a considerablement augmente de (75,88 m2/g) pour bentonite non traiter a (139,76 m2/g) pour l'echantillon (M2 B1 : S5). Une augmentation significative de la conductivite par pression (95,3 S/m sous une pression de 6,5 MPa par rapport a 1,45*10 -3 S/m pour la bentonite) et la conductivite thermique dans le polyethylene basse densite a une concentration de 10% d'additif (0,332 W/m.K a 0,279 W/m.K) ont ete observes pour le meme echantillon M2 B1 : S5 comparativement a la bentonite non traitee. Les applications possibles sont par exemple les senseurs et les actuateurs par pression.

Investigation of Flash Fill{reg_sign} as a thermal backfill material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayers, P.H.; Charlton, C.B.; Frishette, C.W.

1995-09-01

Flash Fill{reg_sign} was created as a fast-setting, flowable backfill material made entirely from coal combustion by-products and water. Its quick-setting, self-leveling, self-compacting characteristics makes trench road repairs faster, easier, and more economical. Other uses include building foundations, fill around pipes, gas lines, and manholes, and replacement of weak subgrade beneath rooters. Flash Fill can be hand-excavated without the use of power assisted tools or machinery. To enhance thermal resistivity, the original Flash Fill mix was modified to include concrete sand. This resulted in a new Flash Fill, designated FSAND, with all of the aforementioned desirable characteristics of Flash Fill andmore » a thermal resistivity of approximately 50{degree} C-cm/watt. Thermal resistivity tests using conventional laboratory thermal probes, high-current thermal tests, and moisture migration tests have been performed to determine the properties of FSAND. As a result of these tests, FSAND has been approved for use as power cable thermal backfill on all AEP System distribution projects.« less

Salt Content Determination for Bentonite Mine Spoil: Saturation Extracts Versus 1:5 Extracts

Treesearch

Marguerite E. Voorhees; Daniel W. Uresk

2004-01-01

The reliability of estimating salt content in saturated extracts from 1:5 (1spoil:5water) extract levels for bentonite mine spoil was examined by regression analyses. Nine chemical variables were examined that included pH, EC, Ca++, Mg++, Na+, K+, HCO3-, SO4-, and Cl-. Ion concentrations from 1:5 extracts were estimated with high predictability for Ca++, Mg++, Na+, SO4...

Rational Selection of Tailored Amendment Mixtures and Composites for In Situ Remediation of Contaminated Sediments

DTIC Science & Technology

2008-12-01

Certification Program GAC granular activated carbon HGR sulfur impregnated activated carbon MCA Menzie Cura and Associates MRM Minimum Required...determination of iodine number was followed. The materials tested were granular activated carbon (GAC), alumina powder, ATS, apatite, bentonite, barite...materials tested were granular activated carbon (GAC), alumina powder, ATS, apatite, bentonite, barite, ConSep 20 and 42%, and ATC. The Iodine Number

Influence of the simultaneous addition of bentonite and cellulose fibers on the mechanical and barrier properties of starch composite-films.

PubMed

de Moraes, J Oliveira; Müller, C M O; Laurindo, J B

2012-02-01

The addition of nanoclay or cellulose fibers has been presented in the literature as a suitable alternative for reinforcing starch films. The aim of the present work was to evaluate the effect of the simultaneous incorporation of nanoclay (bentonite) and cellulose fibers on the mechanical and water barrier properties of the resultant composite-films. Films were prepared by casting with 3% in weight of cassava starch, using glycerol as plasticizer (0.30 g per g of starch), cellulose fibers at a concentration of 0.30 g of fibers per g of starch and nanoclay (0.05 g clay per g starch and 0.10 g clay per g starch). The addition of cellulose fibers and nanoclay increased the tensile strength of the films 8.5 times and the Young modulus 24 times but reduced the elongation capacity 14 times. The water barrier properties of the composite-films to which bentonite and cellulose fibers were added were approximately 60% inferior to those of starch films. Diffractograms showed that the nanoclay was intercalated in the polymeric matrix. These results indicate that the simultaneous addition of bentonite and cellulose fibers is a suitable alternative to increase the tensile strength of the films and decrease their water vapor permeabilities.

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose hydrogels reinforced with graphene oxide and bentonite for enhanced adsorption of methylene blue.

PubMed

Dai, Hongjie; Huang, Yue; Huang, Huihua

2018-04-01

Eco-friendly polyvinyl alcohol/carboxymethyl cellulose (isolated from pineapple peel) hydrogels reinforced with graphene oxide and bentonite were prepared as efficient adsorbents for methylene blue (MB). The structure and morphology of the prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and differential scanning calorimetry (DSC). Introducing graphene oxide and bentonite into the hydrogels evidently enhanced the thermal stability, swelling ability and MB adsorption capacity. The effects of initial concentration of MB, pH, contact time and temperature on MB adsorption capacity of the prepared hydrogels were investigated. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Langmuir isotherm model well, respectively. After introducing graphene oxide and bentonite into the hydrogels, the maximum adsorption capacity calculated from the Langmuir isotherm model reached 172.14 mg/g at 30 °C, obviously higher than the hydrogels prepared without these additions (83.33 mg/g). Furthermore, all the prepared hydrogels also displayed good reusability for the efficient removal of MB. Consequently, the prepared hydrogels could be served as eco-friendly, stable, efficient and reusable adsorbents for anionic dyes in wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surface tailored organobentonite enhances bacterial proliferation and phenanthrene biodegradation under cadmium co-contamination.

PubMed

Mandal, Asit; Biswas, Bhabananda; Sarkar, Binoy; Patra, Ashok K; Naidu, Ravi

2016-04-15

Co-contamination of soil and water with polycyclic aromatic hydrocarbon (PAH) and heavy metals makes biodegradation of the former extremely challenging. Modified clay-modulated microbial degradation provides a novel insight in addressing this issue. This study was conducted to evaluate the growth and phenanthrene degradation performance of Mycobacterium gilvum VF1 in the presence of a palmitic acid (PA)-grafted Arquad® 2HT-75-based organobentonite in cadmium (Cd)-phenanthrene co-contaminated water. The PA-grafted organobentonite (ABP) adsorbed a slightly greater quantity of Cd than bentonite at up to 30mgL(-1) metal concentration, but its highly negative surface charge imparted by carboxylic groups indicated the potential of being a significantly superior adsorbent of Cd at higher metal concentrations. In systems co-contained with Cd (5 and 10mgL(-1)), the Arquad® 2HT-75-modified bentonite (AB) and PA-grafted organobentonite (ABP) resulted in a significantly higher (72-78%) degradation of phenanthrene than bentonite (62%) by the bacterium. The growth and proliferation of bacteria were supported by ABP which not only eliminated Cd toxicity through adsorption but also created a congenial microenvironment for bacterial survival. The macromolecules produced during ABP-bacteria interaction could form a stable clay-bacterial cluster by overcoming the electrostatic repulsion among individual components. Findings of this study provide new insights for designing clay modulated PAH bioremediation technologies in mixed-contaminated water and soil. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessment of hydration process and mechanical properties of cemented paste backfill by electrical resistivity measurement

NASA Astrophysics Data System (ADS)

Xu, Wenbin; Tian, Xichun; Cao, Peiwang

2018-04-01

Cemented paste backfill (CPB) is an emerging mine backfill technique that allows environmentally hazardous tailings to return to the underground openings or stopes, thereby maximising the safety, efficiency and productivity of operation. Uniaxial compressive strength (UCS) is one of the most commonly used parameters for evaluating the mechanical performance of CPB; the prediction of the UCS of CPB structures from early to advanced ages is of great practical importance. This study aims to investigate the predictability of the UCS of CPB during the hydration process based on electrical resistivity (ER) measurement. For this purpose, the samples prepared at different cement-to-tailing ratios and solid contents were subjected to the ER test during the whole hydration process and UCS tests at 3, 7, 28 days of curing periods. The effect of cement-to-tailing ratio and solid content on the ER and UCS of CPB samples was obtained; the UCS values were correlated with the corresponding ER data. Microstructural analysis was also performed on CPB samples to understand the effect of microstructure on the ER data. The result shows that the ER of CPB decreases first and then increases with the speed which is faster in the previous part than the latter. The ER and UCS of CPB samples increased with increasing cement-to-tailing ratio and solid content and curing periods. A logarithmic relationship is established for each mixture in order to predict the UCS of CPB based on ER. Scanning electron microscope analyses have revealed that the microstructure of the CPB changes with the age from the initial floc to honeycomb, and eventually to the compact clumps. The ER properties of CPB samples were highly associated with their respective microstructural properties. The major output of this study is that ER test is effectively capable for a preliminary prediction of the UCS of CPB.

Utilization of cross-linked chitosan/bentonite composite in the removal of methyl orange from aqueous solution.

PubMed

Huang, Ruihua; Liu, Qian; Zhang, Lujie; Yang, Bingchao

2015-01-01

A kind of biocomposite was prepared by the intercalation of chitosan in bentonite and the cross-linking reaction of chitosan with glutaraldehyde, which was referred to as cross-linked chitosan/bentonite (CCS/BT) composite. Adsorptive removal of methyl orange (MO) from aqueous solutions was investigated by batch method. The adsorption of MO onto CCS/BT composite was affected by the ratio of chitosan to BT and contact time. pH value had only a minor impact on MO adsorption in a wide pH range. Adsorption kinetics was mainly controlled by the pseudo-second-order kinetic model. The adsorption of MO onto CCS/BT composite followed the Langmuir isotherm model, and the maximum adsorption capacity of CCS/BT composite calculated by the Langmuir model was 224.8 mg/g. Experimental results indicated that this adsorbent had a potential for the removal of MO from aqueous solutions.

Thermal properties of Bentonite Modified with 3-aminopropyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Pramono, E.; Pratiwi, W.; Wahyuningrum, D.; Radiman, C. L.

2018-03-01

Chemical modifications of Bentonite (BNT) clay have been carried out by using 3-aminoprophyltrimethoxysilane (APS) in various solvent media. The degradation properties of products (BNTAPS) were characterized by thermogravimetric analysis (TGA). Samples were heated at 30 to 700°C with a heating rate 10 deg/min, and the total silane-grafted amount was determined by calculating the weight loss at 200 – 600°C. The thermogram of TGA showed that there were three main decomposition regions which are attributed to the elimination of physically adsorbed water, decomposition of silane and dehydroxylation of Bentonite. High weight loss attributed to the thermal decomposition of silane was observed between 200 to 550°C. Quantitative analysis of grafted silane results high silane loaded using a solvent with high surface energy, which indicates the type of solvent affected interaction and adsorption of APS in BNT platelets.

The effects of apple pomace, bentonite and calcium superphosphate on swine manure aerobic composting.

PubMed

Jiang, Jishao; Huang, Yimei; Liu, Xueling; Huang, Hua

2014-09-01

The effects of additives such as apple pomace, bentonite and calcium superphosphate on swine manure composting were investigated in a self-built aerated static box (90 L) by assessing their influences on the transformation of nitrogen, carbon, phosphorous and compost maturity. The results showed that additives all prolonged the thermophilic stage in composting compared to control. Nitrogen losses amounted to 34-58% of the initial nitrogen, in which ammonia volatilization accounted for 0.3-4.6%. Calcium superphosphate was helpful in facilitating composting process as it significantly reduced the ammonia volatilization during thermophilic stage and increased the contents of total nitrogen and phosphorous in compost, but bentonite increased the ammonia volatilization and reduced the total nitrogen concentration. It suggested that calcium superphosphate is an effective additive for keeping nitrogen during swine manure composting. Copyright © 2014 Elsevier Ltd. All rights reserved.

HMSPP nanocomposite and Brazilian bentonite properties after gamma radiation exposure

NASA Astrophysics Data System (ADS)

Fermino, D. M.; Parra, D. F.; Oliani, W. L.; Lugao, A. B.; Díaz, F. R. V.

2013-03-01

This work concerns the study of the mechanical and thermal behavior of the nanocomposite high melt strength polypropylene (HMSPP) (obtained at a dose of 12.5 kGy) and a bentonite clay Brazilian Paraiba (PB), which is known as "chocolate" and is used in concentrations of 5% and 10% by weight, in comparison to the American Cloisite 20A clay nanocomposites. An agent compatibilizer polypropylene-graft (PP-g-AM) was added at a 3% concentration, and the clay was dispersed using the melt intercalation technique using a twin-screw extruder. The specimens were prepared by the injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the techniques of differential scanning calorimetry (DSC) and thermogravimetry (TGA). The morphology of the nanocomposites was studied with scanning electron microscopy (SEM), while the organophilic bentonite and nanocomposites were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).

DECOVALEX Project: from 1992 to 2007

NASA Astrophysics Data System (ADS)

Tsang, Chin-Fu; Stephansson, Ove; Jing, Lanru; Kautsky, Fritz

2009-05-01

The DECOVALEX project is a unique international research collaboration, initiated in 1992, for advancing the understanding and mathematical modelling of coupled thermo-hydro-mechanical (THM) and thermo-hydro-mechanical-chemical (THMC) processes in geological systems—subjects of importance for performance assessment of radioactive waste repositories in geological formations. From 1992 up to 2007, the project has made important progress and played a key role in the development of numerical modelling of coupled processes in fractured rocks and buffer/backfill materials. The project has been conducted by research teams supported by a large number of radioactive-waste-management organizations and regulatory authorities, including those of Canada, China, Finland, France, Japan, Germany, Spain, Sweden, UK, and the USA. Through this project, in-depth knowledge has been gained of coupled THM and THMC processes associated with nuclear waste repositories, as well as numerical simulation models for their quantitative analysis. The knowledge accumulated from this project, in the form of a large number of research reports and international journal and conference papers in the open literature, has been applied effectively in the implementation and review of national radioactive-waste-management programmes in the participating countries. This paper presents an overview of the project.

Evacuate and backfill apparatus and method

DOEpatents

Oakley, David J.; Groves, Oliver J.

1985-01-01

An apparatus and method for treatment of hollow articles by evacuating existing gas or gases therefrom and purging or backfilling the articles with a second gas such as helium. The apparatus includes a sealed enclosure having an article storage drum mounted therein. A multiplicity of such articles are fed singly into the enclosure and loaded into radial slots formed in the drum. The enclosure is successively evacuated and purged with helium to replace the existing gas in the articles with helium. The purged articles are then discharged singly from the drum and transported out of the enclosure.

The Study on Development of Light-Weight Foamed Mortar for Tunnel Backfill

NASA Astrophysics Data System (ADS)

Ma, Sang-Joon; Kang, Eun-Gu; Kim, Dong-Min

This study was intended to develop the Light-Weight Foamed Mortar which is used for NATM Composite lining backfill. In the wake of the study, the mixing method which satisfies the requirements for compressive strength, permeability coefficient, fluidity, specific gravity and settlement was developed and moreover field applicability was verified through the model test. Thus the mixing of Light-Weight Foamed Mortar developed in this study is expected to be applicable to NATM Composite lining, thereby making commitment to improving the stability and drainage performance of lining.

Large-magnitude Middle Ordovician volcanic ash falls in North America and Europe: Dimensions, emplacement and post-emplacement characteristics

USGS Publications Warehouse

Huff, W.D.; Kolata, Dennis R.; Bergstrom, Stig M.; Zhang, Y.-S.

1996-01-01

Middle Ordovician K-bentonites represent some of the largest known fallout ash deposits in the Phanerozoic Era. They cover minimally 2.2 ?? 106 km2 in eastern North America and 6.9 ?? 105 km2 in northwestern Europe, and represents the coeval accumulation of plinian and co-ignimbrite ash on both Laurentia and Baltica during the closure of the Iapetus Ocean. The three most widespread beds are the Deicke and Millbrig K-bentonites in North America and the Kinnekulle K-bentonite in northwestern Europe. The vents were located near the Laurentian margin of Iapetus on an arc or microplate undergoing collision with Laurentia. The volume of ash preserved in the stratigraphic record converted to dense rock equivalent (DRE) of silicic magma is minimally estimated to be 943 km3 for the Deicke, 1509 km3 for the Millbrig and 972 km3 for the Kinnekulle. The Millbrig and Kinnekulle beds are coeval and possibly equivalent, yielding a combined DRE volume of nearly 2500 km3. Some unknown but probably large amount of additional ash fell into oceanic regions of the Iapetus, but these areas became subducted and the ash is not preserved in the geologic record. The symmetry of the thickness contours is suggestive that one or more ash clouds interacting with equatorial stratospheric and tropospheric wind patterns dispersed pyroclastic material to both the northwest and southeast in terms of Ordovician paleogeography. Based on grain size measurements and thickness/area1/2 plots we conclude the three beds were each formed from co-ignimbrite or possibly phreatoplinian eruption columns. Analyses of melt inclusions in primary quartz crystals indicate the parental magma contained approximately 4% dissolved water at the time of the eruption. This water provided the explosive energy during the initial gas thrust phase. The implied fragmentation pressure on the magma would have reduced much of the ejecta to small particles, forming a deposit composed largely of single crystals and glassy dust. Conversion of the ash to K-bentonite resulted in a mass loss of approximately 35%, mostly in the form of Si with lesser amounts of Na and K.

Non-equilibrium Green's function calculation for GaN-based terahertz-quantum cascade laser structures

NASA Astrophysics Data System (ADS)

Yasuda, H.; Kubis, T.; Hosako, I.; Hirakawa, K.

2012-04-01

We theoretically investigated GaN-based resonant phonon terahertz-quantum cascade laser (QCL) structures for possible high-temperature operation by using the non-equilibrium Green's function method. It was found that the GaN-based THz-QCL structures do not necessarily have a gain sufficient for lasing, even though the thermal backfilling and the thermally activated phonon scattering are effectively suppressed. The main reason for this is the broadening of the subband levels caused by a very strong interaction between electrons and longitudinal optical (LO) phonons in GaN.

PNA-PEG modified silicon platforms as functional bio-interfaces for applications in DNA microarrays and biosensors.

PubMed

Cattani-Scholz, Anna; Pedone, Daniel; Blobner, Florian; Abstreiter, Gerhard; Schwartz, Jeffrey; Tornow, Marc; Andruzzi, Luisa

2009-03-09

The synthesis and characterization of two types of silicon-based biofunctional interfaces are reported; each interface bonds a dense layer of poly(ethylene glycol) (PEG(n)) and peptide nucleic acid (PNA) probes. Phosphonate self-assembled monolayers were derivatized with PNA using a maleimido-terminated PEG(45). Similarly, siloxane monolayers were functionalized with PNA using a maleimido-terminated PEG(45) spacer and were subsequently modified with a shorter methoxy-terminated PEG(12) ("back-filling"). The long PEG(45) spacer was used to distance the PNA probe from the surface and to minimize undesirable nonspecific adsorption of DNA analyte. The short PEG(12) "back-filler" was used to provide additional passivation of the surface against nonspecific DNA adsorption. X-ray photoelectron spectroscopic (XPS) analysis near the C 1s and N 1s ionization edges was done to characterize chemical groups formed in the near-surface region, which confirmed binding of PEG and PNA to the phosphonate and silane films. XPS also indicated that additional PEG chains were tethered to the surface during the back-filling process. Fluorescence hybridization experiments were carried out with complementary and noncDNA strands; both phosphonate and siloxane biofunctional surfaces were effective for hybridization of cDNA strands and significantly reduced nonspecific adsorption of the analyte. Spatial patterns were prepared by polydimethylsiloxane (PDMS) micromolding on the PNA-functionalized surfaces; selective hybridization of fluorescently labeled DNA was shown at the PNA functionalized regions, and physisorption at the probe-less PEG-functionalized regions was dramatically reduced. These results show that PNA-PEG derivatized phosphonate monolayers hold promise for the smooth integration of device surface chemistry with semiconductor technology for the fabrication of DNA biosensors. In addition, our results confirm that PNA-PEG derivatized self-assembled carboxyalkylsiloxane films are promising substrates for DNA microarray applications.

Specific adsorption of cadmium on surface-engineered biocompatible organoclay under metal-phenanthrene mixed-contamination.

PubMed

Biswas, Bhabananda; Sarkar, Binoy; Mandal, Asit; Naidu, Ravi

2016-11-01

Bioremediation of polycyclic aromatic hydrocarbons (PAHs) is extremely challenging when they coexist with heavy metals. This constrain has led to adsorption-based techniques that help immobilize the metals and reduce toxicity. However, the adsorbents can also non-selectively bind the organic compounds, which reduces their bioavailability. In this study we developed a surface-engineered organoclay (Arquad ® 2HT-75-bentonite-palmitic acid) which enhanced bacterial proliferation and adsorbed cadmium, but elevated phenanthrene bioavailability. Adsorption models of single and binary solutes revealed that the raw bentonite adsorbed cadmium and phenanthrene non-selectively at the same binding sites and sequestrated phenanthrene. In contrast, cadmium selectively bound to the deprotonated state of carboxyl groups in the organoclay and phenanthrene on the outer surface of the adsorbent led to a microbially congenial microenvironment with a higher phenanthrene bioavailability. This study provided valuable information which would be highly important for developing a novel clay-modulated bioremediation technology for cleaning up PAHs under mixed-contaminated situations. Copyright © 2016 Elsevier Ltd. All rights reserved.

A new code for modelling the near field diffusion releases from the final disposal of nuclear waste

NASA Astrophysics Data System (ADS)

Vopálka, D.; Vokál, A.

2003-01-01

The canisters with spent nuclear fuel produced during the operation of WWER reactors at the Czech power plants are planned, like in other countries, to be disposed of in an underground repository. Canisters will be surrounded by compacted bentonite that will retard the migration of safety-relevant radionuclides into the host rock. A new code that enables the modelling of the critical radionuclides transport from the canister through the bentonite layer in the cylindrical geometry was developed. The code enables to solve the diffusion equation for various types of initial and boundary conditions by means of the finite difference method and to take into account the non-linear shape of the sorption isotherm. A comparison of the code reported here with code PAGODA, which is based on analytical solution of the transport equation, was made for the actinide chain 4N+3 that includes 239Pu. A simple parametric study of the releases of 239Pu, 129I, and 14C into geosphere is discussed.

Preparation, Characterization, and In Vitro Testing of Nanoclay Antimicrobial Activities and Elicitor Capacity.

PubMed

Merino, Danila; Mansilla, Andrea Y; Casalongué, Claudia A; Alvarez, Vera A

2018-03-28

Clay-based nanocomposites (nanoclays) are interesting systems to hold a wide type of active substances with a wide field of industrial applications. Bentonite-chitosan nanoclay was obtained via cationic exchange of natural bentonite (Bent) with an aqueous solution of chitosan (CS). Their physicochemical and morphological properties were discussed under the light of Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. Bent-CS characterization indicated that CS was intercalated in 10% (w/w). This polycationic polymer was oriented mostly in a monolayer arrangement, interacting by electrostatic forces between Bent sheets. The antimicrobial action of Bent-CS nanoclay was assayed onto phytopathogens, the bacterium model Pseudomonas syringe pv. tomato DC3000 ( Psy) and the necrotrophic fungus Fusarium solani f. sp. eumartii ( F. eumartii). In addition to demonstrating cell death on both microorganisms, Bent-CS exerted elicitor property on tomato plantlets. The biological actions of this natural nanomaterial might make it proper to be used in crops.

Microbial effects on colloidal agglomeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hersman, L.

1995-11-01

Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared tomore » sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs.« less

Real-time gamma imaging of technetium transport through natural and engineered porous materials for radioactive waste disposal.

PubMed

Corkhill, Claire L; Bridge, Jonathan W; Chen, Xiaohui C; Hillel, Phil; Thornton, Steve F; Romero-Gonzalez, Maria E; Banwart, Steven A; Hyatt, Neil C

2013-12-03

We present a novel methodology for determining the transport of technetium-99m, a γ-emitting metastable isomer of (99)Tc, through quartz sand and porous media relevant to the disposal of nuclear waste in a geological disposal facility (GDF). Quartz sand is utilized as a model medium, and the applicability of the methodology to determine radionuclide transport in engineered backfill cement is explored using the UK GDF candidate backfill cement, Nirex Reference Vault Backfill (NRVB), in a model system. Two-dimensional distributions in (99m)Tc activity were collected at millimeter-resolution using decay-corrected gamma camera images. Pulse-inputs of ~20 MBq (99m)Tc were introduced into short (<10 cm) water-saturated columns at a constant flow of 0.33 mL min(-1). Changes in calibrated mass distribution of (99m)Tc at 30 s intervals, over a period of several hours, were quantified by spatial moments analysis. Transport parameters were fitted to the experimental data using a one-dimensional convection-dispersion equation, yielding transport properties for this radionuclide in a model GDF environment. These data demonstrate that (99)Tc in the pertechnetate form (Tc(VII)O4(-)) does not sorb to cement backfill during transport under model conditions, resulting in closely conservative transport behavior. This methodology represents a quantitative development of radiotracer imaging and offers the opportunity to conveniently and rapidly characterize transport of gamma-emitting isotopes in opaque media, relevant to the geological disposal of nuclear waste and potentially to a wide variety of other subsurface environments.

Real-Time Gamma Imaging of Technetium Transport through Natural and Engineered Porous Materials for Radioactive Waste Disposal

PubMed Central

2013-01-01

We present a novel methodology for determining the transport of technetium-99m, a γ-emitting metastable isomer of 99Tc, through quartz sand and porous media relevant to the disposal of nuclear waste in a geological disposal facility (GDF). Quartz sand is utilized as a model medium, and the applicability of the methodology to determine radionuclide transport in engineered backfill cement is explored using the UK GDF candidate backfill cement, Nirex Reference Vault Backfill (NRVB), in a model system. Two-dimensional distributions in 99mTc activity were collected at millimeter-resolution using decay-corrected gamma camera images. Pulse-inputs of ∼20 MBq 99mTc were introduced into short (<10 cm) water-saturated columns at a constant flow of 0.33 mL min–1. Changes in calibrated mass distribution of 99mTc at 30 s intervals, over a period of several hours, were quantified by spatial moments analysis. Transport parameters were fitted to the experimental data using a one-dimensional convection–dispersion equation, yielding transport properties for this radionuclide in a model GDF environment. These data demonstrate that 99Tc in the pertechnetate form (Tc(VII)O4–) does not sorb to cement backfill during transport under model conditions, resulting in closely conservative transport behavior. This methodology represents a quantitative development of radiotracer imaging and offers the opportunity to conveniently and rapidly characterize transport of gamma-emitting isotopes in opaque media, relevant to the geological disposal of nuclear waste and potentially to a wide variety of other subsurface environments. PMID:24147650

Measurement of earth pressures on concrete box culverts under highway embankments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, M.Z.; Drumm, E.C.; Bennett, R.M.

1999-07-01

To obtain a better understanding of the stresses acting on cast-in-place concrete box culverts, and to investigate the conditions which resulted in a culvert failure under about 12 meters of backfill, two sections of a new culvert were instrumented. The measured earth pressure distribution was found to depend upon the height of the embankment over the culvert. For low embankment heights (less than one-half the culvert width), the average measured vertical earth pressures, weighted by tributary length, were about 30% greater than the recommended AASHTO pressures. The measured lateral pressures were slightly greater than the AASHTO pressures. As the embankmentmore » height increased, the measured weighted average vertical stress exceeded the AASHTO pressures by about 20%. Lateral pressures which exceeded the vertical pressures were recorded at the bottom of the culvert walls, and small lateral pressures were recorded on the upper locations of the wall. The high lateral pressures at the base of the wall are consistent with the results from finite element analyses with high density (modulus) backfill material placed around the culvert.« less

Introducing a new aspect in marble quarry rehabilitation in Greece

NASA Astrophysics Data System (ADS)

Kaliampakos, D. C.; Mavrikos, A. A.

2006-06-01

For many years the marble extraction sector of the Greek mining industry has been in conflict with the public, especially in terms of rehabilitation of marble quarry sites. One of the main reasons for that is that the marble extraction sector has been unable to adjust to the existing legislative guidelines for the rehabilitation, such as extensive backfilling and re-vegetation. In the majority of cases these methods fail due to erosion of the backfill soil and adverse climatic conditions. As a result the number of abandoned marble quarry sites is continuously increasing. The present paper suggests a different approach regarding the rehabilitation of marble quarries. More specifically, the paper questions the applicability, the effectiveness, and the social usefulness of the above-mentioned guidelines and suggests the establishment of new land-uses, which are based on an in-depth analysis of the area’s special features, by taking full advantage of its potentials. What is more, the rehabilitation scheme proposes that the new land-uses and the quarrying activity may co-exist and operate simultaneously for a long period of time.

MODIFIED REVERSE OSMOSIS SYSTEM FOR TREATMENT OF PRODUCED WATERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert L. Lee; Junghan Dong

2004-06-03

This final report of ''Modified Reverse Osmosis System for Treatment of Produced Water,'' DOE project No. DE-FC26-00BC15326 describes work performed in the third year of the project. Several good results were obtained, which are documented in this report. The compacted bentonite membranes were replaced by supported bentonite membranes, which exhibited the same salt rejection capability. Unfortunately, it also inherited the clay expansion problem due to water invasion into the interlayer spaces of the compacted bentonite membranes. We noted that the supported bentonite membrane developed in the project was the first of its kind reported in the literature. An {alpha}-alumina-supported MFI-typemore » zeolite membrane synthesized by in-situ crystallization was fabricated and tested. Unlike the bentonite clay membranes, the zeolite membranes maintained stability and high salt rejection rate even for a highly saline solution. Actual produced brines from gas and oil fields were then tested. For gas fields producing brine, the 18,300 ppm TDS (total dissolved solids) in the produced brine was reduced to 3060 ppm, an 83.3% rejection rate of 15,240 ppm salt rejection. For oilfield brine, while the TDS was reduced from 181,600 ppm to 148,900 ppm, an 18% rejection rate of 32,700 ppm reduction, the zeolite membrane was stable. Preliminary results show the dissolved organics, mainly hydrocarbons, did not affect the salt rejection. However, the rejection of organics was inconclusive at this point. Finally, the by-product of this project, the {alpha}-alumina-supported Pt-Co/Na Y catalytic zeolite membrane was developed and demonstrated for overcoming the two-step limitation of nonoxidation methane (CH{sub 4}) conversion to higher hydrocarbons (C{sub 2+}) and hydrogen (H{sub 2}). Detailed experiments to obtain quantitative results of H{sub 2} generation for various conditions are now being conducted. Technology transfer efforts included five manuscripts submitted to peer-reviewed journals and five conference presentations.« less

Cellulose nanoparticles as modifiers for rheology and fluid loss in bentonite water-based fluids.

PubMed

Li, Mei-Chun; Wu, Qinglin; Song, Kunlin; Qing, Yan; Wu, Yiqiang

2015-03-04

Rheological and filtration characteristics of drilling fluids are considered as two critical aspects to ensure the success of a drilling operation. This research demonstrates the effectiveness of cellulose nanoparticles (CNPs), including microfibrillated cellulose (MFC) and cellulose nanocrystals (CNCs) in enhancing the rheological and filtration performances of bentonite (BT) water-based drilling fluids (WDFs). CNCs were isolated from MFC through sulfuric acid hydrolysis. In comparison with MFC, the resultant CNCs had much smaller dimensions, more negative surface charge, higher stability in aqueous solutions, lower viscosity, and less evident shear thinning behavior. These differences resulted in the distinctive microstructures between MFC/BT- and CNC/BT-WDFs. A typical "core-shell" structure was created in CNC/BT-WDFs due to the strong surface interactions among BT layers, CNCs, and immobilized water molecules. However, a similar structure was not formed in MFC/BT-WDFs. As a result, CNC/BT-WDFs had superior rheological properties, higher temperature stability, less fluid loss volume, and thinner filter cakes than BT and MFC/BT-WDFs. Moreover, the presence of polyanionic cellulose (PAC) further improved the rheological and filtration performances of CNC/BT-WDFs, suggesting a synergistic effect between PAC and CNCs.

Controlled release of isoproturon, imidacloprid, and cyromazine from alginate-bentonite-activated carbon formulations.

PubMed

Garrido-Herrera, F J; Gonzalez-Pradas, E; Fernandez-Pérez, M

2006-12-27

Different alginate-based systems of isoproturon, imidacloprid, and cyromazine have been investigated in order to obtain controlled release (CR) properties. The basic formulation [sodium alginate (1.50%), pesticide (0.30%), and water] was modified using different amounts of bentonite and activated carbon. The higher values of encapsulation efficiency corresponded to those formulations prepared with higher percentages of activated carbon, showing higher encapsulation efficiency values for isoproturon and imidacloprid than for cyromazine, which has a higher water solubility. The kinetic experiments of imidacloprid/isoproturon release in water have shown us that the release rate is higher in imidacloprid systems than in those prepared with isoproturon. Moreover, it can be deduced that the use of bentonite and/or activated carbon sorbents reduces the release rate of the isoproturon and imidacloprid in comparison with the technical product and with alginate formulation without modifying agents. The highest decrease in release rate corresponds to the formulations prepared with the highest percentage of activated carbon. The water uptake, permeability, and time taken for 50% of the active ingredient to be released into water, T50, were calculated to compare the formulations. On the basis of a parameter of an empirical equation used to fit the pesticide release data, the release of isoproturon and imidacloprid from the various formulations into water is controlled by a diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations were the most important factors modulating pesticide release. Finally, a linear correlation of the T50 values and the content of activated carbon in formulations were obtained.

Characteristics of the Roof Behaviors and Mine Pressure Manifestations During the Mining of Steep Coal Seam

NASA Astrophysics Data System (ADS)

Hong-Sheng, Tu; Shi-Hao, Tu; Cun, Zhang; Lei, Zhang; Xiao-Gang, Zhang

2017-12-01

A steep seam similar simulation system was developed based on the geological conditions of a steep coal seam in the Xintie Coal Mine. Basing on similar simulation, together with theoretical analysis and field measurement, an in-depth study was conducted to characterize the fracture and stability of the roof of steep working face and calculate the width of the region backfilled with gangue in the goaf. The results showed that, as mining progressed, the immediate roof of the steep face fell upon the goaf and backfilled its lower part due to gravity. As a result, the roof in the lower part had higher stability than the roof in the upper part of the working face. The deformation and fracture of main roof mainly occurred in the upper part of the working face; the fractured main roof then formed a "voussoir beam" structure in the strata's dip direction, which was subjected to the slip- and deformation-induced instability. The stability analysis indicated that, when the dip angle increased, the rock masses had greater capacity to withstand slip-induced instability but smaller capacity to withstand deformation-induced instability. Finally, the field measurement of the forces exerted on the hydraulic supports proved the characteristics of the roof's behaviors during the mining of a steep seam.

A VSA-based strategy for placing conservation buffers in agricultural watersheds.

PubMed

Qiu, Zeyuan

2003-09-01

Conservation buffers have the potential to reduce agricultural nonpoint source pollution and improve terrestrial wildlife habitat, landscape biodiversity, flood control, recreation, and aesthetics. Conservation buffers, streamside areas and riparian wetlands are being used or have been proposed to control agricultural nonpoint source pollution. This paper proposes an innovative strategy for placing conservation buffers based on the able source area (VSA) hydrology. VSAs are small, variable but predictable portion of a watershed that regularly contributes to runoff generation. The VSA-based strategy involves the following three steps: first, identifying VSAs in landscapes based on natural characteristics such as hydrology, land use/cover, topography and soils; second, targeting areas within VSAs for conservation buffers; third, refining the size and location of conservation buffers based on other factors such as weather, environmental objectives, available funding and other best management practices. Building conservation buffers in VSAs allows agricultural runoff to more uniformly enter buffers and stay there longer, which increases the buffer's capacity to remove sediments and nutrients. A field-scale example is presented to demonstrate the effectiveness and cost-effectiveness of the within-VSA conservation buffer scenario relative to a typical edge-of-field buffer scenario. The results enhance the understanding of hydrological processes and interactions between agricultural lands and conservation buffers in agricultural landscapes, and provide practical guidance for land resource managers and conservationists who use conservation buffers to improve water quality and amenity values of agricultural landscape.

Evacuate and backfill apparatus and method

DOEpatents

Oakley, D.J.; Groves, O.J.

1984-06-27

An apparatus and method as described for treatment of hollow articles by evacuating existing gas or gases therefrom and purging or backfilling the articles with a second gas such as helium. The apparatus includes a sealed enclosure having an article storage drum mounted therein. A multiplicity of such articles are fed singly into the enclosure and loaded into radial slots formed in the drum. The enclosure is successively evacuated and purged with helium to replace the existing gas in the articles with helium. The purged articles are then discharged singly from the drum and transported out of the enclosure.

Reactive composite compositions and mat barriers

DOEpatents

Langton, Christine A.; Narasimhan, Rajendran; Karraker, David G.

2001-01-01

A hazardous material storage area has a reactive multi-layer composite mat which lines an opening into which a reactive backfill and hazardous material are placed. A water-inhibiting cap may cover the hazardous material storage area. The reactive multi-layer composite mat has a backing onto which is placed an active layer which will neutralize or stabilize hazardous waste and a fronting layer so that the active layer is between the fronting and backing layers. The reactive backfill has a reactive agent which can stabilize or neutralize hazardous material and inhibit the movement of the hazardous material through the hazardous material storage area.

The effect of sodium chloride on the dissolution of calcium silicate hydrate gels.

PubMed

Hill, J; Harris, A W; Manning, M; Chambers, A; Swanton, S W

2006-01-01

The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium.

Ca/Na selectivity coefficients from the Poisson-Boltzmann theory

NASA Astrophysics Data System (ADS)

Hedström, Magnus; Karnland, Ola

As a model for ion equilibrium in montmorillonite, the Poisson-Boltzmann (PB) equation was solved for two parallel charged surfaces in contact with an external NaCl/CaCl 2 mixed solution. The ion concentration profiles in the montmorillonite interlayer were obtained from the PB equation and integration of those gave the occupancy of Na + and Ca 2+ in the clay. That information together with the composition of the external electrolyte were then used for the calculation of the Gaines-Thomas selectivity coefficient K GT. The predictions from the model were compared to experimental data from batch as well as compacted conditions, and the agreement was generally good. With a surface layer-charge density of one unit charge per 145 Å 2, which is close to the value for Wyoming-type montmorillonite, the calculated selectivity coefficients were found to vary from about 4 in batch to 8 in compacted montmorillonite with dry density ∼1700 kg/m 3. From the point of view of assessing the evolution, with regard to sodium-calcium ion exchange, of the bentonite buffer in a repository for spent nuclear fuel, these results justify the use of data obtained in batch experiments.

Sub-lethal effects of water-based drilling muds on the deep-water sponge Geodia barretti.

PubMed

Edge, Katelyn J; Johnston, Emma L; Dafforn, Katherine A; Simpson, Stuart L; Kutti, Tina; Bannister, Raymond J

2016-05-01

Offshore oil and gas activities can result in the discharge of large amounts of drilling muds. While these materials have generally been regarded as non-toxic to marine organisms, recent studies have demonstrated negative impacts to suspension feeding organisms. We exposed the arctic-boreal sponge Geodia barretti to the primary particulate components of two water-based drilling muds; barite and bentonite. Sponges were exposed to barite, bentonite and a natural reference sediment at a range of total suspended solid concentrations (TSS = 0, 10, 50 or 100 mg/L) for 12 h after which we measured a suite of biomarker responses (lysosomal membrane stability, lipid peroxidation and glutathione). In addition, we compared biomarker responses, organic energy content and metal accumulation in sponges, which had been continuously or intermittently exposed to suspended barite and natural sediment for 14 d at relevant concentrations (10 and 30 mg TSS/L). Lysosomal membrane stability was reduced in the sponges exposed to barite at 50 and 100 mg TSS/L after just 12 h and at 30 mg TSS/L for both continuous and intermittent exposures over 14 d. Evidence of compromised cellular viability was accompanied by barite analysis revealing concentrations of Cu and Pb well above reference sediments and Norwegian sediment quality guidelines. Metal bioaccumulation in sponge tissues was low and the total organic energy content (determined by the elemental composition of organic tissue) was not affected. Intermittent exposures to barite resulted in less toxicity than continuous exposure to barite. Short term exposures to bentonite did not alter any biomarker responses. This is the first time that these biomarkers have been used to indicate contaminant exposure in an arctic-boreal sponge. Our results illustrate the potential toxicity of barite and the importance of assessments that reflect the ways in which these contaminants are delivered under environmentally realistic conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite.

PubMed

Zheng, Hong; Liu, Donghong; Zheng, Yan; Liang, Shuping; Liu, Zhe

2009-08-15

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 degrees C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 degrees C. Dubinin-Redushkevich (D-R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

Potential removal of organic loads from petroleum wastewater and its effect on the corrosion behavior of municipal networks.

PubMed

El-Shamy, A M; Abdelfattah, Ibrahim; Elshafey, Ola I; Shehata, M F

2018-05-09

A potential and cost-effective treatment method utilizing thermally activated bentonite was evaluated for the treatment of highly loaded real petroleum processing wastewater (COD = 4500 mg/L) in order to reduce its COD and improve the corrosion properties. A save discharging COD limit of the treated effluent (800 mg/L) is achieved by using 6 g/L of calcinated bentonite after reaching the steady state (1 h of shaking) at pH 5. The durability of bentonite is proved. The corrosion behavior of the treated wastewater was investigated for mild steel by using electrochemical and weight loss measurements. The results proved that the corrosion rate of the wastewater was slightly reduced after the treatment process. More improvement of the corrosion resistance was achieved by adding sodium hexa-meta-phosphate (SHMP) corrosion inhibitor to the treated water. Tri-methyl ammonium bromide (CTAB) biocide was also added before discharging into municipal networks. Copyright © 2018. Published by Elsevier Ltd.

Evaluation of White Bentonite Modified by Acid Attack

NASA Astrophysics Data System (ADS)

Andrade, C. G. Bastos; Fermino, D. M.; Fernandes, M. G.; Valenzuela-Diaz, F. R.

For industrial use, the smectite clays must be cleared of impurities, usually obtained by acid modification, using a high concentration solution of inorganic acid at temperatures under boiling point. In the present paper, a sample of white bentonite from Paraiba, Brazil, was modified by hydrochloric acid under moderate conditions (90°C, reaction times of 1, 6, 12, 18 and 24hours in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5 M, acid solution/clay ratio of 1g/10mL). The purpose of these attacks is to reduce the concentration of impurities with minimal change in the clay minerals structure. The modified samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Cation Exchange Capacity (CEC), Stereomicroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Detector (EDS). Thus, this modified bentonite tends to be a good economic and environmental alternative in manufacturing of products with high added value such as cosmetics and polymer/clay nanocomposites.

Constraining the alteration history of a Late Cretaceous Patagonian volcaniclastic bentonite-ash-mudstone sequence using K-Ar and 40Ar/39Ar isotopes

NASA Astrophysics Data System (ADS)

Warr, L. N.; Hofmann, H.; van der Pluijm, B. A.

2017-01-01

Smectite is typically considered unsuitable for radiometric dating, as argon (40Ar) produced from decay of exchangeable potassium (40K) located in the interlayer sites can be lost during fluid-rock interaction and/or during wet sample preparation in the laboratory. However, age analysis of Late Cretaceous Argentinian bentonites and associated volcaniclastic rocks from Lago Pellegrini, Northern Patagonia, indicates that, in the case of these very low-permeability rocks, the radioactive 40Ar was retained and thus can provide information on smectite age and the timing of rock alteration. This study presents isotopic results that indicate the ash-to-bentonite conversion and alteration of the overlying tuffaceous mudstones in Northern Patagonia was complete 13-17 my after middle Campanian sedimentation when the system isotopically closed. The general absence of illite in these smectite-rich lithologies reflects the low activity of K and the low temperature (<60 °C) of the formation waters that altered the parent ash.

Adsorption of Heavy Metal Ions from Aqueous Solutions by Bentonite Nanocomposites.

PubMed

Ma, Jing; Su, Guojun; Zhang, Xueping; Huang, Wen

2016-08-01

A series of bentonite nanocomposites have been synthesized by modifying bentonite with hexadecyltrimethylammonium bromide (CTMAB) and the common complexing agents, complexone (ethylene diamine tetraacetic acid, EDTA) or mercaptocomplexant (2-Mercaptobenzothiazole, MBT). These adsorbents are used to remove heavy metal ions (Cu(2+), Zn(2+), Mn(2+),Co(2+)). The Bent-CTMAB-MBT adsorbed metal ions are higher than Bent-CTMAB-EDTA under the same ion concentration in AAS. Compared with the single ion system, the adsorption of the mixed ion system of Cu(2+), Zn(2+), Mn(2+), Co(2+) had decreased differently. In the mixed system, the adsorption of Mn(2+) is significantly lower, but the adsorption of Cu(2+) was highest. The adsorption sequence of these four metal ions was Cu(2+) > Zn(2+) > Co(2+) > Mn(2+), and the selective adsorption was closely related to the hydration energy of heavy metal ions. We could remove more metal ions in different stages with the adsorption sequence.

Influence of γ-radiation on the reactivity of montmorillonite towards H 2O 2

NASA Astrophysics Data System (ADS)

Holmboe, Michael; Jonsson, Mats; Wold, Susanna

2012-02-01

Compacted and water saturated bentonite will be used as an engineered barrier in deep geological repositories for radioactive waste in many countries. Due to the high dose rate of ionizing radiation outside the canisters holding the nuclear waste, radiolysis of the interlayer and pore water in the compacted bentonite is unavoidable. Upon reaction with the oxidizing and reducing species formed by water radiolysis (OH •, e -(aq), H •, H 2O 2, H 2, HO 2•, H 3O +), the overall redox properties in the bentonite barrier may change. In this study the influence of γ-radiation on the structural Fe(II)/Fe Tot ratio in montmorillonite and its reactivity towards hydrogen peroxide (H 2O 2) was investigated in parallel experiments. The results show that under anoxic conditions the structural Fe(II)/Fe Tot ratio of dispersed Montmorillonite increased from ≤3 to 25-30% after γ-doses comparable to repository conditions. Furthermore, a strong correlation between the structural Fe(II)/Fe Tot ratio and the H 2O 2 decomposition rate in montmorillonite dispersions was found. This correlation was further verified in experiments with consecutive H 2O 2 additions, since the structural Fe(II)/Fe Tot ratio was seen to decrease concordantly. This work shows that the structural iron in montmorillonite could be a sink for one of the major oxidants formed upon water radiolysis in the bentonite barrier, H 2O 2.

Microwave-assisted pyrolysis of textile dyeing sludge, and migration and distribution of heavy metals.

PubMed

Zhang, Hedong; Gao, Zuopeng; Liu, Yang; Ran, Chunmei; Mao, Xiao; Kang, Qinhao; Ao, Wenya; Fu, Jie; Li, Jing; Liu, Guangqing; Dai, Jianjun

2018-05-01

This study investigated the pyrolysis characteristic of textile dyeing sludge (DS) using an auger pyrolyser under microwave irradiation at different pyrolysis temperature. The migration and distribution characteristic of heavy metals and their potential ecological risks were investigated using inductively coupled plasma mass spectrometry (ICP-MS) techniques. Temperature and additives (e.g. Ca-bentonite, kaolin and CaO) significantly affected product distribution and yields. Heavy metals showed different enrichment characteristics during pyrolysis and a great percentage of the heavy metals was retained in the sludge char (SC), depending on different temperatures and additives. CaO had a strong ability for retention of S, Pb and Ni. Ca-bentonite, kaolin and CaO had considerable ability to retain Cr at 650 ℃. Ca-bentonite and CaO had positive effects on Ni retention at 450 °C and 650 °C. As was enriched at 450 °C with addition of Ca-bentonite. Cu and Zn were enriched at 450 °C and 850 °C without additives and the corresponding residue ratios (RRs) were 88.68-100%, which indicated good stability of these heavy metals during microwave pyrolysis of DS. The heavy metal contents in SC were lower than those in the national standards (CJ/T 362-2011, China) and these heavy metals showed slight potential ecological risk to the environment. Copyright © 2018 Elsevier B.V. All rights reserved.

Dissolved organic matter effects on the performance of a barrier to polycyclic aromatic hydrocarbon transport by groundwater

NASA Astrophysics Data System (ADS)

Moon, Jung-Won; Goltz, Mark N.; Ahn, Kyu-Hong; Park, Jae-Woo

2003-02-01

In order to contain the movement of organic contaminants in groundwater, a subsurface sorption barrier consisting of sand or clay minerals coated with a cationic surfactant has been proposed. The effectiveness of such a sorption barrier might be affected by the presence of dissolved organic matter (DOM) in the groundwater. To study the impact of DOM on barrier performance, a series of batch experiments were performed by measuring naphthalene and phenanthrene sorption onto sand coated with cetylpyridinium chloride (CPC) and bentonite coated with hexadecyltrimethylammonium bromide (HDTMA) in the presence of various concentrations of DOM. The overall soil-water distribution coefficient ( K*) of naphthalene and phenanthrene onto CPC-coated sand decreased with increasing DOM concentration, whereas the K* of the compounds onto HDTMA-coated bentonite slightly increased with increasing DOM concentration. To describe the overall distribution of polycyclic aromatic hydrocarbons (PAHs) in the systems, a competitive multiphase sorption (CMS) model was developed and compared with an overall mechanistic sorption (OMS) model. The modeling studies showed that while the OMS model did not explain the CPC-coated sand experimental results, a model that included competitive sorption between DOM and PAH did. The experimental results and the modeling study indicated that there was no apparent competition between DOM and PAH in the HDTMA-coated bentonite system, and indicated that in groundwater systems with high DOM, a barrier using HDTMA-coated bentonite might be more effective.

Clay/Polyaniline Hybrid through Diazonium Chemistry: Conductive Nanofiller with Unusual Effects on Interfacial Properties of Epoxy Nanocomposites.

PubMed

Jlassi, Khouloud; Chandran, Sarath; Poothanari, Mohammed A; Benna-Zayani, Mémia; Thomas, Sabu; Chehimi, Mohamed M

2016-04-12

The concept of conductive network structure in thermoset matrix without sacrificing the inherent mechanical properties of thermoset polymer (e.g., epoxy) is investigated here using "hairy" bentonite fillers. The latter were prepared through the in situ polymerization of aniline in the presence of 4-diphenylamine diazonium (DPA)-modified bentonite (B-DPA) resulting in a highly exfoliated bentonite-DPA/polyaniline (B-DPA/PANI). The nanocomposite filler was mixed with diglycidyl ether of bisphenol A (DGEBA), and the curing agent (4,4'-diaminodiphenylsulfone) (DDS) at high temperature in order to obtain nanocomposites through the conventional melt mixing technique. The role of B-DPA in the modification of the interface between epoxy and B-DPA/polyaniline (B-DPA/PANI) is investigated and compared with the filler B/PANI prepared without any diazonium modification of the bentonite. Synergistic improvement in dielectric properties and mechanical properties points to the fact that the DPA aryl groups from the diazonium precursor significantly modify the interface by acting as an efficient stress transfer medium. In DPA-containing nanocomposites, unique fibril formation was observed on the fracture surface. Moreover, dramatic improvement (210-220%) in fracture toughness of epoxy composite was obtained with B-DPA/PANI filler as compared to the weak improvement of 20-30% noted in the case of the B/PANI filler. This work shows that the DPA diazonium salt has an important effect on the improvement of the interfacial properties and adhesion of DGEBA and clay/PANI nanofillers.

Sintered bentonite ceramics for the immobilization of cesium- and strontium-bearing radioactive waste

NASA Astrophysics Data System (ADS)

Ortega, Luis Humberto

The Advanced Fuel Cycle Initiative (AFCI) is a Department of Energy (DOE) program, that has been investigating technologies to improve fuel cycle sustainability and proliferation resistance. One of the program's goals is to reduce the amount of radioactive waste requiring repository disposal. Cesium and strontium are two primary heat sources during the first 300 years of spent nuclear fuel's decay, specifically isotopes Cs-137 and Sr-90. Removal of these isotopes from spent nuclear fuel will reduce the activity of the bulk spent fuel, reducing the heat given off by the waste. Once the cesium and strontium are separated from the bulk of the spent nuclear fuel, the isotopes must be immobilized. This study is focused on a method to immobilize a cesium- and strontium-bearing radioactive liquid waste stream. While there are various schemes to remove these isotopes from spent fuel, this study has focused on a nitric acid based liquid waste. The waste liquid was mixed with the bentonite, dried then sintered. To be effective sintering temperatures from 1100 to 1200°C were required, and waste concentrations must be at least 25 wt%. The product is a leach resistant ceramic solid with the waste elements embedded within alumino-silicates and a silicon rich phase. The cesium is primarily incorporated into pollucite and the strontium into a monoclinic feldspar. The simulated waste was prepared from nitrate salts of stable ions. These ions were limited to cesium, strontium, barium and rubidium. Barium and rubidium will be co-extracted during separation due to similar chemical properties to cesium and strontium. The waste liquid was added to the bentonite clay incrementally with drying steps between each addition. The dry powder was pressed and then sintered at various temperatures. The maximum loading tested is 32 wt. percent waste, which refers to 13.9 wt. percent cesium, 12.2 wt. percent barium, 4.1 wt. percent strontium, and 2.0 wt. percent rubidium. Lower loadings of waste were also tested. The final solid product was a hard dense ceramic with a density that varied from 2.12 g/cm3 for a 19% waste loading with a 1200°C sintering temperature to 3.03 g/cm 3 with a 29% waste loading and sintered at 1100°C. Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA) of the loaded bentonite displayed mass loss steps which were consistent with water losses in pure bentonite. Water losses were complete after dehydroxylation at ˜650°C. No mass losses were evident beyond the dehydroxylation. The ceramic melts at temperatures greater than 1300°C. Light flash analysis found heat capacities of the ceramic to be comparable to those of strontium and barium feldspars as well as pollucite. Thermal conductivity improved with higher sintering temperatures, attributed to lower porosity. Porosity was minimized in 1200°C sinterings. Ceramics with waste loadings less than 25 wt% displayed slump, the lowest waste loading, 15 wt% bloated at a 1200°C sintering. Waste loading above 25 wt% produced smooth uniform ceramics when sintered >1100°C. Sintered bentonite may provide a simple alternative to vitrification and other engineered radioactive waste-forms.

Radon emanation from backfilled mill tailings in underground uranium mine.

PubMed

Sahu, Patitapaban; Mishra, Devi Prasad; Panigrahi, Durga Charan; Jha, Vivekananda; Patnaik, R Lokeswara; Sethy, Narendra Kumar

2014-04-01

Coarser mill tailings used as backfill to stabilize the stoped out areas in underground uranium mines is a potential source of radon contamination. This paper presents the quantitative assessment of radon emanation from the backfilled tailings in Jaduguda mine, India using a cylindrical accumulator. Some of the important parameters such as (226)Ra activity concentration, bulk density, bulk porosity, moisture content and radon emanation factor of the tailings affecting radon emanation were determined in the laboratory. The study revealed that the radon emanation rate of the tailings varied in the range of 0.12-7.03 Bq m(-2) s(-1) with geometric mean of 1.01 Bq m(-2) s(-1) and geometric standard deviation of 3.39. An increase in radon emanation rate was noticed up to a moisture saturation of 0.09 in the tailings, after which the emanation rate gradually started declining with saturation due to low diffusion coefficient of radon in the saturated tailings. Radon emanation factor of the tailings varied in the range of 0.08-0.23 with the mean value of 0.21. The emanation factor of the tailings with moisture saturation level over 0.09 was found to be about three times higher than that of the absolutely dry tailings. The empirical relationship obtained between (222)Rn emanation rate and (226)Ra activity concentration of the tailings indicated a significant positive linear correlation (r = 0.95, p < 0.001). This relationship may be useful for quick prediction of radon emanation rate from the backfill material of similar nature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Neuroanatomy of pars intercerebralis neurons with special reference to their connections with neurons immunoreactive for pigment-dispersing factor in the blow fly Protophormia terraenovae.

PubMed

Yasuyama, Kouji; Hase, Hiroaki; Shiga, Sakiko

2015-10-01

Input regions of pars intercerebralis (PI) neurons are examined by confocal and electron microscopies with special reference to their connections with neurons immunoreactive for pigment-dispersing factor (PDF) in the blow fly, Protophormia terraenovae. PI neurons are a prerequisite for ovarian development under long-day conditions. Backfills from the cardiac recurrent nerve after severance of the posterior lateral tracts labeled thin fibers derived from the PI neurons in the superior medial protocerebrum. These PI fibers were mainly synapsin-negative and postsynaptic to unknown varicose profiles containing dense-core vesicles. Backfilled fibers in the periesophageal neuropils, derived from the PI neurons or neurons with somata in the subesophageal zone, were varicose and some were synapsin-positive. Electron microscopy revealed the presence of both presynaptic and postsynaptic sites in backfilled fibers in the periesophageal neuropils. Many PDF-immunoreactive varicosities were found in the superior medial and lateral protocerebrum and double-labeling showed that 60-88 % of PDF-immunoreactive varicosities were also synapsin-immunoreactive. Double-labeling with the backfills and PDF immunocytochemistry showed that the PI fibers and PDF-immunoreactive varicosities were located close to each other in the superior medial protocerebrum. Results of triple-labeling of PI neurons, PDF-immunoreactive neurons and synapsin-immunoreactive terminals demonstrated that the synapsin-positive PDF-immunoreactive varicosities contacted the PI fibers. These data suggest that PI neurons receive synaptic contacts from PDF-immunoreactive fibers, which are derived from circadian clock neurons, of small ventral lateral neurons (previously called OL2) or posterior dorsal (PD) neurons with somata in the pars lateralis.

Controlled formation of closed-edge nanopores in graphene

NASA Astrophysics Data System (ADS)

He, Kuang; Robertson, Alex W.; Gong, Chuncheng; Allen, Christopher S.; Xu, Qiang; Zandbergen, Henny; Grossman, Jeffrey C.; Kirkland, Angus I.; Warner, Jamie H.

2015-07-01

Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport.Dangling bonds at the edge of a nanopore in monolayer graphene make it susceptible to back-filling at low temperatures from atmospheric hydrocarbons, leading to potential instability for nanopore applications, such as DNA sequencing. We show that closed edge nanopores in bilayer graphene are robust to back-filling under atmospheric conditions for days. A controlled method for closed edge nanopore formation starting from monolayer graphene is reported using an in situ heating holder and electron beam irradiation within an aberration-corrected transmission electron microscopy. Tailoring of closed-edge nanopore sizes is demonstrated from 1.4-7.4 nm. These results should provide mechanisms for improving the stability of nanopores in graphene for a wide range of applications involving mass transport. Electronic supplementary information (ESI) available: Low magnification images, image processing techniques employed, modelling and simulation of closed edge nanoribbon, comprehensive AC-TEM dataset, and supporting analysis. See DOI: 10.1039/c5nr02277k

Aerospace Expeditionary Force Implementation and the Effect on Team Cohesion

DTIC Science & Technology

2002-03-01

quickly load UTCs during real world conflicts, deployments, or exercises. The TPFDD is the Joint Operation Planning and Execution System data base... system in mission capable status in an efficeint manner. Time is saved by not having to establish work/personal relationships and new work peocesses...there wasn’t enough time for the system to process backfills for shortfalls that were, in reality, not shortfalls at all but a rainbow package. While

Using soil surveys to target riparian buffers in the Chesapeake Bay watershed

Treesearch

Michael G. Dosskey

2008-01-01

The efficacy of vegetative buffers for improving water quality could be enhanced by distinguishing differences in buffer capability across watersheds and accounting for them in buffer planning. A soil survey-based method was applied to riparian areas in the Chesapeake Bay watershed. The method is based on soil attributes that are important in determining buffer...

Sprayable low density ablator and application process

NASA Technical Reports Server (NTRS)

Sharpe, M. H.; Hill, W. E.; Simpson, W. G.; Carter, J. M.; Brown, E. L.; King, H. M.; Schuerer, P. H.; Webb, D. D. (Inventor)

1978-01-01

A sprayable, low density ablative composition is described consisting esentially of: (1) 100 parts by weight of a mixture of 25-65% by weight of phenolic microballoons, 0-20% by weight of glass microballoons, 4-10% by weight of glass fibers, 25-45% by weight of an epoxy-modified polyurethane resin, 2-4% by weight of a bentonite dispersing aid, and 1-2% by weight of an alcohol activator for the bentonite; (2) 1-10 parts by weight of an aromatic amine curing agent; and (3) 200-400 parts by weight of a solvent.

Compaction of Confining Materials in Pillar Blast Tests

NASA Astrophysics Data System (ADS)

Petropoulos, N.; Wimmer, M.; Johansson, D.; Nordlund, E.

2018-06-01

Two confined pillar tests were conducted at the Kiirunavaara mine to investigate the degree of compaction of three materials, i.e., 0-32-mm backfilled material, a blend of ore and waste material and caved material. Two blastholes were drilled parallel to each pillar wall, and several measurement holes were drilled in between the blastholes through each pillar. Both the measurement holes and backfilled materials, except the caved material, were instrumented. Two types of measurements were taken: dynamic measurements with accelerometers, and static measurements which considered the location of the instrumentation pre- and post-blast. Dynamic measurements involved the burden movement and the confining material behavior, and static measurements contained the final location of sensors inside and the angle of repose of the confining material. The results showed that the size distribution of the confining material affects its behavior under dynamic loading. The backfilled materials showed an apparent cohesion forming an agglomeration on the surface of the blasted burden. The burden moved as one slab due to simultaneous detonation. A gap was formed between the blasted burden and the new face. This gap was partially filled with burden erosion material which was finer fragmented than the blasted burden material.

The acid-base buffer capacity of podzolic soils and its changes under the impact of treatment with the Mehra-Jackson and Tamm reagents

NASA Astrophysics Data System (ADS)

Maksimova, Yu. G.; Maryakhina, N. N.; Tolpeshta, I. I.; Sokolova, T. A.

2010-10-01

The acid-base buffer capacity before and after the treatment with the Mehra-Jackson and Tamm reagents was assessed by continuous potentiometric titration for the main genetic horizons of two profiles of podzolic soils in the Central Forest State Reserve. The total buffer capacity was calculated in the pH range from the initial titration point (ITP) to 3 for the acid titration and from the ITP to 10 for the base titration, as well as the buffer capacities in the pH intervals of 0.25. It was found that both treatments abruptly decreased the base buffer capacity, which reached 70-90% in the E horizons. The high direct linear correlation of the difference between the total base buffer capacities before and after each treatment with the content of Fe in the Tamm extract was revealed. From the results obtained, a conclusion was drawn that finely dispersed Fe hydroxides were the main solid-phase constituents ensuring the base buffer capacity, and the deprotonation of hydroxyl groups on the surface of Fe hydroxides was the essential buffer reaction during the base titration.

Influence of layer charge and charge distribution of smectites on the flow behaviour and swelling of bentonites

USGS Publications Warehouse

Christidis, G.E.; Blum, A.E.; Eberl, D.D.

2006-01-01

The influence of layer charge and charge distribution of dioctahedral smectites on the rheological and swelling properties of bentonites is examined. Layer charge and charge distribution were determined by XRD using the LayerCharge program [Christidis, G.E., Eberl, D.D., 2003. Determination of layer charge characteristics of smectites. Clays Clay Miner. 51, 644-655.]. The rheological properties were determined, after sodium exchange using the optimum amount of Na2CO3, from free swelling tests. Rheological properties were determined using 6.42% suspensions according to industrial practice. In smectites with layer charges of - 0.425 to - 0.470 per half formula unit (phfu), layer charge is inversely correlated with free swelling, viscosity, gel strength, yield strength and thixotropic behaviour. In these smectites, the rheological properties are directly associated with the proportion of low charge layers. By contrast, in low charge and high charge smectites there is no systematic relation between layer charge or the proportion of low charge layers and rheological properties. However, low charge smectites yield more viscous suspensions and swell more than high charge smectites. The rheological properties of bentonites also are affected by the proportion of tetrahedral charge (i.e. beidellitic charge), by the existence of fine-grained minerals having clay size, such as opal-CT and to a lesser degree by the ionic strength and the pH of the suspension. A new method for classification of smectites according to the layer charge based on the XRD characteristics of smecites is proposed, that also is consistent with variations in rheological properties. In this classification scheme the term smectites with intermediate layer charge is proposed. ?? 2006 Elsevier B.V. All rights reserved.

Isotherm modeling of organic activated bentonite and humic acid polymer used as mycotoxin adsorbents.

PubMed

Santos, R R; Vermeulen, S; Haritova, A; Fink-Gremmels, J

2011-11-01

The aim of the current study was to evaluate and compare two representative samples of different classes of adsorbents intended for use as feed additives in the prevention or reduction of the adverse effects exerted by mycotoxins, specifically ochratoxin A (OTA) and zearalenone (ZEN). The adsorbents, an organically activated bentonite (OAB) and a humic acid polymer (HAP), were tested in a common in vitro model with a pH course comparing the maximum pH changes that can be expected in the digestive system of a monogastric animal, i.e. pH 7.4 for the oral cavity, pH 3.0 for the stomach, and pH 8.4 for the intestines. In the first experiment, the concentration-dependent adsorbent capacity of OAB and HAB were tested using a fixed concentration of either mycotoxin. Thereafter, adsorption was evaluated applying different isotherms models, such as Freundlich, Langmuir, Brunauer-Emmett-Teller (BET) and Redlich-Peterson, to characterize the adsorption process as being either homo- or heterogeneous and representing either mono- or multilayer binding. At the recommended statutory level for the mycotoxins of 0.1 mg kg(-1) OTA and 0.5 mg kg(-1) ZEN, OAB showed an adsorbed capacity of >96% towards both mycotoxins, regardless of the pH. The HAP product was also able to absorb >96% of both mycotoxins at pH 3.0, but extensive desorption occurred at pH 8.4. Based on χ-square (χ(2)) values, Langmuir and Redlich-Peterson equations proved to be the best models to predict monolayer equilibrium sorption of OTA and ZEN onto the organically activated bentonite and the humic acid polymer. The applied methodology has a sufficient robustness to facilitate further comparative studies with different mycotoxin-adsorbing agents.

Effects of Pulp and Na-Bentonite Amendments on the Mobility of Trace Elements, Soil Enzymes Activity and Microbial Parameters under Ex Situ Aided Phytostabilization

PubMed Central

Wasilkowski, Daniel; Mrozik, Agnieszka

2017-01-01

The objective of this study was to explore the potential use of pulp (by-product) from coffee processing and Na-bentonite (commercial product) for minimizing the environmental risk of Zn, Pb and Cd in soil collected from a former mine and zinc-lead smelter. The effects of soil amendments on the physicochemical properties of soil, the structural and functional diversity of the soil microbiome as well as soil enzymes were investigated. Moreover, biomass of Festuca arundinacea Schreb. (cultivar Asterix) and the uptake of trace elements in plant tissues were studied. The outdoor pot set contained the following soils: control soil (initial), untreated soil (without additives) with grass cultivation and soils treated (with additives) with and without plant development. All of the selected parameters were measured at the beginning of the experiment (t0), after 2 months of chemical stabilization (t2) and at the end of the aided phytostabilization process (t14). The obtained results indicated that both amendments efficiently immobilized the bioavailable fractions of Zn (87–91%) and Cd (70–83%) at t14; however, they were characterized by a lower ability to bind Pb (33–50%). Pulp and Na-bentonite drastically increased the activity of dehydrogenase (70- and 12-fold, respectively) at t14, while the activities of urease, acid and alkaline phosphatases differed significantly depending on the type of material that was added into the soil. Generally, the activities of these enzymes increased; however, the increase was greater for pulp (3.5-6-fold) than for the Na-bentonite treatment (1.3–2.2-fold) as compared to the control. Soil additives significantly influenced the composition and dynamics of the soil microbial biomass over the experiment. At the end, the contribution of microbial groups could be ordered as follows: gram negative bacteria, fungi, gram positive bacteria, actinomycetes regardless of the type of soil enrichment. Conversely, the shift in the functional diversity of the microorganisms in the treated soils mainly resulted from plant cultivation. Meanwhile, the highest biomass of plants at t14 was collected from the soil with Na-bentonite (6.7 g dw-1), while it was much lower in a case of pulp treatment (1.43–1.57 g dw-1). Moreover, the measurements of the heavy metal concentrations in the plant roots and shoots clearly indicated that the plants mainly accumulated metals in the roots but that the accumulation of individual metals depended on the soil additives. The efficiency of the accumulation of Pb, Cd and Zn by the roots was determined to be 124, 100 and 26% higher in the soil that was enriched with Na-bentonite in comparison with the soil that was amended with pulp, respectively. The values of the soil indices (soil fertility, soil quality and soil alteration) confirmed the better improvement of soil functioning after its enrichment with the pulp than in the presence of Na-bentonite. PMID:28068396

Double positive effect of adding hexaethyelene glycol when optimizing the hybridization efficiency of a microring DNA detection assay

NASA Astrophysics Data System (ADS)

Van Eeghem, Anabelle; Werquin, Sam; Hoste, Jan-Willem; Goes, Arne; Vanderleyden, Els; Bienstman, Peter; Dubruel, Peter

2017-05-01

In this paper, a method for detection of DNA molecules using silicon-on-insulator (SOI) microring resonators is described. The influence of temperature and the use of formamide on the hybridization efficiency were studied. It was shown that 50 v/v% of formamide in the hybridization buffer can ensure hybridization when working close to physiological temperature. Furthermore, the use of hexaethylene glycol (HEG) as backfilling agent was studied in order to resolve issues of non-specific adsorption to the surface. The results indicated that not only non-specific binding was reduced significantly but also that HEG improves the orientation of the DNA probes on the surface. This led to a 4-fold increase in hybridization efficiency and thus in an equal decrease in the detection limit, compared to hybridization without the use of HEG. An improvement in robustness of the assay was also observed. This DNA reorientation hypothesis was confirmed by studying the thickness and density of the layers by using dual polarization microring sensing. Finally, the different steps in the sensing experiment were characterized in more detail by static contact angle (SCA) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed quantitatively that the surface modifications were successful.

Performance Characteristics of the Electronic Snow Water Equivalent (SWE) Sensor in Arctic, Marine, and Humid Continental Climates

NASA Astrophysics Data System (ADS)

Johnson, J.; Gelvin, A. B.; Duvoy, P.; Schaefer, G. L.; Poole, G.; Horton, G. D.

2011-12-01

The USA ERDC CRREL and the USDA NRCS developed a 3-m square electronic SWE sensor (e-SWE sensor) consisting of nine perforated panels (a center panel to measure SWE and eight outer panels to buffer edge stress concentrations). Seven e-SWE sensors were installed in five different climate zones including north central and north coastal Alaska, Oregon, Newfoundland, and New York State. With the exception of New York State, the e-SWE sensors accurately measured SWE. The e-SWE sensor at Hogg Pass, OR, accurately measured SWE during five years of observations even when edge stress concentrations occurred. In windy conditions of northern Alaska, the sensor measured losses and gains in SWE with more reliability and higher accuracy than other standard methods. The sensor also detected snowdrift migration (comparing video and sensor measurements). In the thin, icy snow of New York the electronic SWE sensors over-measured SWE during midwinter. Over-measurement errors were caused by edge stress concentrations associated with strong icy layers, a shallow snow cover and possibly using a backfill material with different thermal properties and a large freeboard compared to the surrounding soil . Measurement accuracy improved in spring due to increased snow creep, associated with warming snow temperatures, which reduced edge stress concentrations.

International Approaches for Nuclear Waste Disposal in Geological Formations: Geological Challenges in Radioactive Waste Isolation—Fifth Worldwide Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faybishenko, Boris; Birkholzer, Jens; Sassani, David

The overall objective of the Fifth Worldwide Review (WWR-5) is to document the current state-of-the-art of major developments in a number of nations throughout the World pursuing geological disposal programs, and to summarize challenging problems and experience that have been obtained in siting, preparing and reviewing cases for the operational and long-term safety of proposed and operating nuclear waste repositories. The scope of the Review is to address current specific technical issues and challenges in safety case development along with the interplay of technical feasibility, siting, engineering design issues, and operational and post-closure safety. In particular, the chapters included inmore » the report present the following types of information: the current status of the deep geological repository programs for high level nuclear waste and low- and intermediate level nuclear waste in each country, concepts of siting and radioactive waste and spent nuclear fuel management in different countries (with the emphasis of nuclear waste disposal under different climatic conditions and different geological formations), progress in repository site selection and site characterization, technology development, buffer/backfill materials studies and testing, support activities, programs, and projects, international cooperation, and future plans, as well as regulatory issues and transboundary problems.« less

The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels.

PubMed

Ivanov, Peter; Griffiths, Tamara; Bryan, Nick D; Bozhikov, Gospodin; Dmitriev, Serguei

2012-11-01

The effect of humic acid (HA) on U(VI) sorption on bentonite was studied in batch experiments at room temperature and ambient atmosphere at a (237)U(VI) concentration of 8.4 × 10(-11) M and HA concentration of 100 mg L(-1). The distribution of U(VI) between the liquid and solid phases was studied as a function of pH and ionic strength both in the absence and presence of HA. It was shown that the uranyl sorption on bentonite is strongly dependent on pH and the presence of humics, and the effect of the addition order was negligible. In the absence of HA an enhancement in the uptake with increasing pH was observed and a sharp sorption edge was found to take place between pH 3.2 and 4.2. The presence of HA slightly increases uranium(VI) sorption at low pH and curtails it at moderate pH, compared to the absence of HA. In the basic pH range for both the presence and absence of HA the sorption of uranium is significantly reduced, which could be attributed to the formation of soluble uranyl carbonate complexes. The influence of ionic strength on U(VI) and HA uptake by bentonite were investigated in the range of 0.01-1.0 M, and while there was an enhancement in the sorption of humic acid with increasing ionic strength, no significant effect of the ionic strength on the U(VI) sorption was observed in both the absence and presence of HA.

A batch adsorption study on bentonite clay Pertinence to transport modeling?

NASA Astrophysics Data System (ADS)

BOURG, I.; BOURG, A. C.; SPOSITO, G.

2001-12-01

Bentonite clay is often used as a component of engineered barriers for the isolation of high-level toxic wastes. This swelling clay is used for its physical (impermeability, self-healing) but also for its chemical properties, mostly a high cation exchange capacity (CEC). The adsorbed cations being temporarily immobilized, this should slow down the release of cations from the waste to the surrounding environment. In order to assess the performance of the engineered barrier, the partitioning of solutes between the liquid and solid phases needs to be quantified for use in transport models. The usual method for characterizing the adsorption is through batch adsorption experiments on dispersed suspensions of the solid, yielding an adsorption isotherm (adsorbed concentration vs. dissolved concentration). This isotherm however should be a function of various environmental variables (e.g., pH, ionic strength, concentrations of various ligands and competing adsorbents), so that extrapolation of lab data to performance assessment in the field is problematic. We present results from a study of the adsorption of cesium, strontium, cadmium and lead on dispersed suspensions of the standard BX-80 bentonite. Through a wide range of experimental parameters (pH, ionic strength, reaction time, reactor open or closed to the atmosphere, study of a range of cations of differing properties), we seek a mechanistic interpretation of the results instead of an empirical determination of adsorption parameters. Depending on the mechanisms that control the adsorption in different experimental ranges, we discuss the degree to which the partitioning coefficient (Kd) obtained in the lab can be extrapolated to a transport model through compacted bentonite in a natural environment.

Steeply dipping heaving bedrock, Colorado: Part 2 - Mineralogical and engineering properties

USGS Publications Warehouse

Noe, D.C.; Higgins, J.D.; Olsen, H.W.

2007-01-01

This paper describes the mineralogical and engineering properties of steeply dipping, differentially heaving bedrock, which has caused severe damage near the Denver area. Several field sites in heave-prone areas have been characterized using high sample densities, numerous testing methodologies, and thousands of sample tests. Hydrometer testing shows that the strata range from siltstone to claystone (33 to 66 percent clay) with occasional bentonite seams (53 to 98 percent clay mixed with calcite). From X-ray diffraction analyses, the claystone contains varying proportions of illite-smectite and discrete (pure) smectite, and the bentonite contains discrete smectite. Accessory minerals include pyrite, gypsum, calcite, and oxidized iron compounds. The dominant exchangeable cation is Ca2+, except where gypsum is prevalent, and Mg2+ and Na1+ are elevated. Scanning electron microscope analyses show that the clay fabric is deformed and porous and that pyrite is absent within the weathered zone. Unified Soil Classification for the claystone varies from CL to CH, and the bentonite is CH to MH. Average moisture content values are 17 percent for claystone and 32 percent for bentonite, and these are typically 0 to 5 percent lower than the plastic limit. Swell-consolidation and suction testing shows a full range of swelling potentials from low to very high. These findings confirm that type I (bed-parallel, symmetrical to asymmetrical) heave features are strongly associated with changes in bedrock composition and mineralogy. Composition changes are not necessarily a factor for type II (bed-parallel to bed-oblique, strongly asymmetrical) heave features, which are associated with movements along subsurface shear zones.

Hydraulic Conductivity of Geosynthetic Clay Liners to Low-Level Radioactive Waste Leachate

DOE PAGES

Tian, Kuo; Benson, Craig H.; Likos, William J.

2016-04-25

Hydraulic conductivity was evaluated for eight commercially available geosynthetic clay liners (GCLs) permeated with leachate characteristic of low-level radioactive waste (LLW) disposal facilities operated by the U.S. Department of Energy (DOE). Two of the GCLs (CS and GS) contained conventional sodium bentonite (Na-B). The others contained a bentonite–polymer mixture (CPL, CPH, GPL1, GPL2, and GPH) or bentonite–polymer composite (BPC). All GCLs (except GPL2 and GPH) were permeated directly with two synthetic LLW leachates that are essentially identical, except one has no radionuclides (nonradioactive synthetic leachate, or NSL) and the other has radionuclides (radioactive synthetic leachate, or RSL). Hydraulic conductivities tomore » RSL and NSL were identical. For the CS and GS GCLs, the hydraulic conductivity gradually increased by a factor of 5–25 because divalent cations in the leachate replaced native sodium cations bound to the bentonite. The CPL, GPL1, and GPL2 GCLs with low polymer loading (1.2–3.3%) had hydraulic conductivities similar to the conventional GCLs. In contrast, hydraulic conductivity of the CPH, GPH, and BPC GCLs with high polymer loading (≥5%) to RSL or NSL was comparable to, or lower than, the hydraulic conductivity to deionized water. Permeation with leachate reduced the swell index of the bentonite in all of the GCLs. A conceptual model featuring pore blocking by polymer hydrogel is proposed to explain why the hydraulic conductivity of bentonite–polymer GCLs to LLW leachates remains low even though the leachate inhibits bentonite swelling.« less

Evaluation of soils for use as liner materials: a soil chemistry approach.

PubMed

DeSutter, Tom M; Pierzynski, Gary M

2005-01-01

Movement of NH(4)(+) below animal waste lagoons is generally a function of the whole-lagoon seepage rate, soil mineralogy, cations in the lagoon liquor, and selectivity for NH(4)(+) on the soil-exchange sites. Binary exchange reactions (Ca(2+)-K(+), Ca(2+)-NH(4)(+), and K(+)-NH(4)(+)) were conducted on two soils from the Great Plains and with combinations of these soils with bentonite or zeolite added. Binary exchanges were used to predict ternary exchanges Ca(2+)-K(+)-NH(4)(+) following the Rothmund-Kornfeld approach and Gaines-Thomas convention. Potassium and NH(4)(+) were preferred over Ca(2+), and K(+) was preferred over NH(4)(+) in all soils and soils with amendments. Generally, the addition of bentonite did not change cation selectivity over the native soils, whereas the addition of zeolite did. The Rothmund-Kornfeld approach worked well for predicting equivalent fractions of cations on the exchanger phase when only ternary-solution phase compositions were known. Actual swine- and cattle-lagoon solution compositions and the Rothmund-Kornfeld approach were used to project that native soils are predicted to retain 53 and 23%, respectively, of the downward-moving NH(4)(+) on their exchange sites. Additions of bentonite or zeolite to soils under swine lagoons may only slightly improve the equivalent fraction of NH(4)(+) on the exchange sites. Although additions of bentonite or zeolite may not help increase the NH(4)(+) selectivity of a liner material, increases in the overall cation exchange capacity (CEC) of a soil will ultimately decrease the amount of soil needed to adsorb downward-moving NH(4)(+).

Hydraulic Conductivity of Geosynthetic Clay Liners to Low-Level Radioactive Waste Leachate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Kuo; Benson, Craig H.; Likos, William J.

Hydraulic conductivity was evaluated for eight commercially available geosynthetic clay liners (GCLs) permeated with leachate characteristic of low-level radioactive waste (LLW) disposal facilities operated by the U.S. Department of Energy (DOE). Two of the GCLs (CS and GS) contained conventional sodium bentonite (Na-B). The others contained a bentonite–polymer mixture (CPL, CPH, GPL1, GPL2, and GPH) or bentonite–polymer composite (BPC). All GCLs (except GPL2 and GPH) were permeated directly with two synthetic LLW leachates that are essentially identical, except one has no radionuclides (nonradioactive synthetic leachate, or NSL) and the other has radionuclides (radioactive synthetic leachate, or RSL). Hydraulic conductivities tomore » RSL and NSL were identical. For the CS and GS GCLs, the hydraulic conductivity gradually increased by a factor of 5–25 because divalent cations in the leachate replaced native sodium cations bound to the bentonite. The CPL, GPL1, and GPL2 GCLs with low polymer loading (1.2–3.3%) had hydraulic conductivities similar to the conventional GCLs. In contrast, hydraulic conductivity of the CPH, GPH, and BPC GCLs with high polymer loading (≥5%) to RSL or NSL was comparable to, or lower than, the hydraulic conductivity to deionized water. Permeation with leachate reduced the swell index of the bentonite in all of the GCLs. A conceptual model featuring pore blocking by polymer hydrogel is proposed to explain why the hydraulic conductivity of bentonite–polymer GCLs to LLW leachates remains low even though the leachate inhibits bentonite swelling.« less

Soil properties affecting wheat yields following drilling-fluid application.

PubMed

Bauder, T A; Barbarick, K A; Ippolito, J A; Shanahan, J F; Ayers, P D

2005-01-01

Oil and gas drilling operations use drilling fluids (mud) to lubricate the drill bit and stem, transport formation cuttings to the surface, and seal off porous geologic formations. Following completion of the well, waste drilling fluid is often applied to cropland. We studied potential changes in soil compaction as indicated by cone penetration resistance, pH, electrical conductivity (EC(e)), sodium adsorption ratio (SAR), extractable soil and total straw and grain trace metal and nutrient concentrations, and winter wheat (Triticum aestivum L. 'TAM 107') grain yield following water-based, bentonitic drilling-fluid application (0-94 Mg ha(-1)) to field test plots. Three methods of application (normal, splash-plate, and spreader-bar) were used to study compaction effects. We measured increasing SAR, EC(e), and pH with drilling-fluid rates, but not to levels detrimental to crop production. Field measurements revealed significantly higher compaction within areas affected by truck travel, but also not enough to affect crop yield. In three of four site years, neither drilling-fluid rate nor application method affected grain yield. Extractions representing plant availability and plant analyses results indicated that drilling fluid did not significantly increase most trace elements or nutrient concentrations. These results support land application of water-based bentonitic drilling fluids as an acceptable practice on well-drained soils using controlled rates.

Deformation Behaviors of Geosynthetic Reinforced Soil Walls on Shallow Weak Ground

NASA Astrophysics Data System (ADS)

Kim, You-Seong; Won, Myoung-Soo

In this study, the fifteen-month behavior of two geosynthetic reinforced soil walls, which was constructed on the shallow weak ground, was measured and analyzed. The walls were backfilled with clayey soil obtained from the construction site nearby, and the safety factors obtained from general limit equilibrium analysis were less than 1.3 in both wall. To compare with the measured data from the real GRS walls and unreinforced soil mass, a series of finite element method (FEM) analyses on two field GRS walls and unreinforced soil mass were conducted. The FEM analysis results showed that failure plane of unreinforced soil mass was consistent with the Rankine active state, but failure plane did not occur in GRS walls. In addition, maximum horizontal displacements and shear strains in GRS walls were 50% smaller than those found in unreinforced soil mass. Modeling results such as the maximum horizontal displacements, horizontal pressure, and geosynthetic tensile strengths in GRS wall have a god agreement with the measured data. Based on this study, it could be concluded that geosynthetic reinforcement are effective to reduce the displacement of the wall face and/or the deformation of the backfill soil even if the mobilized tensile stress after construction is very small.

Synthesis, characterization, and potential application of Mn2+-intercalated bentonite in fluoride removal: adsorption modeling and mechanism evaluation

NASA Astrophysics Data System (ADS)

Mudzielwana, Rabelani; Gitari, Wilson M.; Akinyemi, Segun A.; Msagati, Titus A. M.

2017-12-01

The study synthesizes a low-cost adsorbent made from Mn2+-modified bentonite clay for groundwater defluoridation. The clays were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and Fourier transform infrared techniques. The fluoride adsorption capacity of the modified clay was evaluated using batch experiments. The adsorption kinetics results showed that the optimum fluoride (F-) uptake was achieved within the 30 min' contact time. The data fitted well to pseudo-second-order of reaction kinetics indicating that adsorption of F- occurred via chemisorption. In addition, the adsorption isotherm data fitted well to Langmuir isotherm model indicating that adsorption occurred on a mono-layered surface. Maximum F- removal of 57% was achieved from groundwater with an initial F- concentration of 5.4 mg L-1 and natural pH of 8.6 using adsorbent dosage of 1 g/100 mL. Fluoride adsorption occurred through ligands and ion exchange mechanisms. The synthesized adsorbent was successfully regenerated for up to five times. The study shows that Mn2+-intercalated bentonite clay has potential for application in defluoridation of groundwater.

Preparation of alpha-alumina-supported mesoporous bentonite membranes for reverse osmosis desalination of aqueous solutions.

PubMed

Li, Liangxiong; Dong, Junhang; Lee, Robert

2004-05-15

In this study, mesoporous bentonite clay membranes approximately 2 microm thick were prepared on porous alpha-alumina substrates by a sol-gel method. Nanosized clay particles were obtained from commercial Na-bentonite powders (Wyoming) by a process of sedimentation, washing, and freeze-drying. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption were employed for membrane characterization. It was found that the content of solids, concentration of polymer binder, and pH value of the clay colloidal suspension had critical influences on membrane formation during the dip-coating process. The membranes were tested for reverse osmosis separation of a 0.1 M NaCl solution. Both water permeability and Na(+) rejection rate of the supported membranes were comparable to those of the compacted thick membranes reported in the literature. However, due to the drastically reduced membrane thickness, water permeance and flux of the supported membranes were significantly higher than those of the compacted thick membranes. It was also observed that the calcination temperature played a critical role in determining structural stability in water and desalination performance of the clay membrane.

Removal of Chromium from Soils Cultivated with Maize (Zea Mays) After the Addition of Natural Minerals as Soil Amendments.

PubMed

Μolla, A; Ioannou, Z; Mollas, S; Skoufogianni, E; Dimirkou, A

2017-03-01

The efficiency of natural minerals, i.e. zeolite, bentonite and goethite, regarding the retention of chromium, from maize was examined. Specifically, 1.0 kg of soil, 1.0 g of soil amendment and either 50 mg L -1 Cr(III) or 1 mg L -1 Cr(VI) were added in plant pots. Then, seeds of maize were cultivated. Each treatment was repeated three times. The statistical results of the experiments were analyzed by LSD test. Cr(III) addition in soil has shown that zeolite was the only amendment that increased the dry weight. Zeolite and bentonite reduced significantly the total chromium in plants after the addition of 50 mg L -1 Cr(III). The addition of Cr(VI) in soil has shown that bentonite was the only amendment that increased the dry weight of biomass and the plants' height. All soil amendments reduced to zero the total chromium concentration measured to plants after the addition of 1 mg L -1 Cr(VI).

Removal of cyanobacteria and cyanotoxins from lake water by composites of bentonite with micelles of the cation octadecyltrimethyl ammonium (ODTMA).

PubMed

Sukenik, Assaf; Viner-Mozzini, Yehudit; Tavassi, Mordechay; Nir, Shlomo

2017-09-01

Cyanobacteria and their toxins present potential hazard to consumers of water from lakes, reservoirs and rivers, thus their removal via water treatment is essential. The capacity of nano-composites of Octadecyltrimethyl-ammonium (ODTMA) complexed with clay to remove cyanobacterial and their toxins from laboratory cultures and from lake water, was evaluated. Column filters packed with micelles of ODTMA complexed with bentonite and granulated were shown to significantly reduce the number of cyanobacteria cells or filaments and their corresponding toxins from laboratory cultures. Fluorescence measurements demonstrated that cyanobacteria cells lost their metabolic activity (photosynthesis) upon exposure to the micelle (ODTMA)-bentonite complex, or ODTMA monomers. The complex efficiently removed cyanobacteria toxins with an exceptional high removal rate of microcystins. The effectiveness of the complex in elimination of cyanobacteria was further demonstrated with lake water containing cyanobacteria and other phytoplankton species. These results and model calculations suggest that filters packed with granulated composites can secure the safety of drinking water in case of a temporary bloom event of toxic cyanobacteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

Retention-oxidation-adsorption process for emergent treatment of organic liquid spills.

PubMed

Liu, Xianjun; Li, Yu; Zhang, Xingwang; Lei, Lecheng

2011-11-15

The feasibility and effectiveness of retention-oxidation-adsorption process (ROA) for the elimination of organic contaminants induced by chemical accidents were investigated in this study. Organobentonites (DTMA-, TTA-, CTMA- and OTMA-bentonite), potassium ferrate (Fe(VI)), ozone and granular activated carbon (GAC) were used as rapid and efficient materials in the treatment and recovery of organic liquid spills. Results indicated that the retention capacities of organobentonites (especially CTMA-bentonite) were much higher than that of natural bentonite towards the chosen organic compounds. Additionally, pH, oxidant dosage, initial concentration of contaminant and chemical structure had significant influences on the effectiveness of the oxidation process. In a pilot-scale experiment, the ferrate/GAC (F/G) and ozone/GAC (O/G) processes made a comparatively good performance in the treatment of wastewater containing aniline or nitrobenzene, with the removal efficiencies of the contaminants greater than 80%. Overall, the ROA process showed a high efficiency and steady operation in the removal of hazardous organic liquids and subsequent clean up of the contaminated site. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

The role of vegetation on gully stabilization at a severely degraded landscape: a case study from Calhoun experimental critical zone observatory

NASA Astrophysics Data System (ADS)

Dialynas, Y. G.; Bastola, S.; Bras, R. L.; Noto, L. V.; Istanbulluoglu, E.

2016-12-01

Gully erosion was the primary driver of land degradation in Southern Piedmont, site of the Calhoun Critical Zone Observatory (CCZO), during the cotton farming era. Understanding of underlying erosion processes is essential to develop a model useful in assessing the effectiveness of gully stabilization and soil erosion control. Development of process-based gully erosion models is difficult because observations of the formation and progression of gullies are limited. In this study, analytic formulations of the two dominant gullying processes, namely, plunge pool erosion and slab failure, are utilized to simulate the gullying processes in the 4 km2 Holcombe's Branch watershed. Gully features (e.g., depth and area) automatically extracted from high-resolution LiDAR DEM are used to calibrate parameters of the gully model. The statistics of the spatial extent of simulated gullies are in close agreement with the gullies obtained from the LiDAR map. Simulations initialized with contemporary topography suggest that few gully complexes have the potential to progress further. Several simulations are used to evaluate the effectiveness of various gully treatment measures, such as backfilling of gullies and revegetation, by initializing the model with the historical topographical surface. Simulation results show that in the short-term, the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies (e.g., backfilling decreased the spatial extent of gullies by 20-38% and decreased the average depth by 0.005-8%). Revegetation, however, is a more effective approach to stabilizing gullies which would, otherwise, expand if left barren. Moreover simulations suggest that the gully stabilization effect of revegetation can lead to a 23-70% reduction of gully area and 1.3-45% reduction in the depth of gullies, depending on forest type and management practices.

A comparative analysis of selected wastewater pretreatment processes in food industry

NASA Astrophysics Data System (ADS)

Jaszczyszyn, Katarzyna; Góra, Wojciech; Dymaczewski, Zbysław; Borowiak, Robert

2018-02-01

The article presents a comparative analysis of the classical coagulation with the iron sulphate and adsorption on bentonite for the pretreatment of wastewater in the food industry. As a result of the studies, chemical oxygen demand (COD) and total nitrogen (TN) reduction were found to be comparable in both technologies, and a 29% higher total phosphorus removal efficiency by the coagulation was observed. After the coagulation and adsorption processes, a significant difference between mineral and organic fraction in the sludge was found (49% and 51% for bentonite and 28% and 72% for iron sulphate, respectively).

On the importance of coupled THM processes to predict the long-term response of a generic salt repository for high-level nuclear waste

NASA Astrophysics Data System (ADS)

Blanco Martin, L.; Rutqvist, J.; Birkholzer, J. T.

2013-12-01

Salt is a potential medium for the underground disposal of nuclear waste because it has several assets, in particular its ability to creep and heal fractures generated by excavation and its water and gas tightness in the undisturbed state. In this research, we focus on disposal of heat-generating nuclear waste (such as spent fuel) and we consider a generic salt repository with in-drift emplacement of waste packages and subsequent backfill of the drifts with run-of-mine crushed salt. As the natural salt creeps, the crushed salt backfill gets progressively compacted and an engineered barrier system is subsequently created. In order to evaluate the integrity of the natural and engineered barriers over the long-term, it is important to consider the coupled effects of the thermal, hydraulic and mechanical processes that take place. In particular, the results obtained so far show how the porosity reduction of the crushed salt affects the saturation and pore pressure evolution throughout the repository, both in time and space. Such compaction is induced by the stress and temperature regime within the natural salt. Also, transport properties of the host rock are modified not only by thermo-mechanically and hydraulically-induced damaged processes, but also by healing/sealing of existing fractures. In addition, the THM properties of the backfill evolve towards those of the natural salt during the compaction process. All these changes are based on dedicated laboratory experiments and on theoretical considerations [1-3]. Different scenarios are modeled and compared to evaluate the relevance of different processes from the perspective of effective nuclear waste repositories. The sensitivity of the results to some parameters, such as capillarity, is also addressed. The simulations are conducted using an updated version of the TOUGH2-FLAC3D simulator, which is based on a sequential explicit method to couple flow and geomechanics [4]. A new capability for large strains and creep has been introduced and validated. The time-dependent geomechanical response of salt is determined using the Lux/Wolters constitutive model, developed at Clausthal University of Technology (Germany). References: [1] R. Wolters, and K.-H. Lux. Evaluation of Rock Salt Barriers with Respect to Tightness: Influence of Thermomechanical Damage, Fluid Infiltration and Sealing/Healing. Proceedings of the 7th International Conference on the Mechanical Behavior of Salt (SaltMech7). Paris: Balkema, Rotterdam (2012). [2] W. Bechthold et al., Backfilling and Sealing of Underground Repositories for Radioactive Waste in Salt (BAMBUS Project), European Atomic Energy Community, Report EUR19124 EN (1999). [3] J. Kim, E.L Sonnenthal and J. Rutqvist, 'Formulation and sequential numerical algorithms of coupled fluid/heat flow and geomechanics for multiple porosity materials', Int. J. Numer. Meth. Engng., 92, 425 (2012). [4] J. Rutqvist. Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations. Computational Geosciences, 37, 739-750 (2011).

Granite disposal of U.S. high-level radioactive waste.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freeze, Geoffrey A.; Mariner, Paul E.; Lee, Joon H.

This report evaluates the feasibility of disposing U.S. high-level radioactive waste in granite several hundred meters below the surface of the earth. The U.S. has many granite formations with positive attributes for permanent disposal. Similar crystalline formations have been extensively studied by international programs, two of which, in Sweden and Finland, are the host rocks of submitted or imminent repository license applications. This report is enabled by the advanced work of the international community to establish functional and operational requirements for disposal of a range of waste forms in granite media. In this report we develop scoping performance analyses, basedmore » on the applicable features, events, and processes (FEPs) identified by international investigators, to support generic conclusions regarding post-closure safety. Unlike the safety analyses for disposal in salt, shale/clay, or deep boreholes, the safety analysis for a mined granite repository depends largely on waste package preservation. In crystalline rock, waste packages are preserved by the high mechanical stability of the excavations, the diffusive barrier of the buffer, and favorable chemical conditions. The buffer is preserved by low groundwater fluxes, favorable chemical conditions, backfill, and the rigid confines of the host rock. An added advantage of a mined granite repository is that waste packages would be fairly easy to retrieve, should retrievability be an important objective. The results of the safety analyses performed in this study are consistent with the results of comprehensive safety assessments performed for sites in Sweden, Finland, and Canada. They indicate that a granite repository would satisfy established safety criteria and suggest that a small number of FEPs would largely control the release and transport of radionuclides. In the event the U.S. decides to pursue a potential repository in granite, a detailed evaluation of these FEPs would be needed to inform site selection and safety assessment.« less

The effect of extracellular weak acids and bases on the intracellular buffering power of snail neurones.

PubMed Central

Szatkowski, M S

1989-01-01

1. Intracellular pH (pHi) was measured in snail neurones using pH-sensitive glass microelectrodes. The influence of externally applied weak acids and bases on the total intracellular buffering power (beta T) was investigated by monitoring the pHi changes caused by the intracellular ionophoretic injection of HCl. 2. In the absence of weak acids or bases a reduction in the extracellular HEPES concentration had no effect on pHi or on beta T. It did, however, reduce slightly the rate of pHi recovery following HCl injection. 3. The presence of CO2 greatly increased beta T. However, as predicted for an open buffer system, the contributions to intracellular buffering by CO2 (beta CO2) decreased as pHi decreased. 4. When added to the superfusate, procaine, 4-aminopyridine, trimethylamine and NH4Cl (1-10 mM) all increased steady-state pHi. Procaine was fastest at increasing pHi and 4-aminopyridine the slowest. All four of these weak bases increased beta T. 5. The intracellular buffering action by these weak bases varied. HCl injection in the presence of procaine usually resulted in steady-state pHi changes with no pHi transients. In the presence of the other three weak bases HCl injections resulted in intracellular acidifications which were followed by pHi recovery-like transients. However, these were not blocked by SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid) or by CaCl2 and I thus conclude that these transients were as a result of slow or incomplete intracellular buffering by the weak bases. 6. In many cells there was a good correlation between the measured contributions to intracellular buffering by the weak bases (beta base) and those predicted assuming a simple two-compartment open system. In all cases, as predicted, beta base increased as pHi decreased. 7. I found a clear relationship between the concentration of external buffer (HEPES) and the rate at which weak bases, applied to the superfusate, were able to increase pHi. The greater the extracellular buffer concentration the greater was the speed of intracellular alkalinization. 8. Lowering the extracellular buffer concentration reduced the efficiency of intracellular buffering by weak bases in response to an intracellular acid load. HCl injection in the presence of weak base caused a larger initial intracellular acidification if the extracellular HEPES concentration was reduced. 9. In conclusion, both weak acids and weak bases can make very large, pHi-dependent contributions to intracellular buffering by way of open buffer systems.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2555474

Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal.

PubMed

Felipe-Sotelo, M; Hinchliff, J; Field, L P; Milodowski, A E; Preedy, O; Read, D

2017-07-01

The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH) 2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO 2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40 μm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of Computational Method of High Reynolds Number Slurry Flow for Caverns Backfilling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bettin, Giorgia

2015-05-01

The abandonment of salt caverns used for brining or product storage poses a significant environmental and economic risk. Risk mitigation can in part be address ed by the process of backfilling which can improve the cavern geomechanical stability and reduce the risk o f fluid loss to the environment. This study evaluate s a currently available computational tool , Barracuda, to simulate such process es as slurry flow at high Reynolds number with high particle loading . Using Barracuda software, a parametric sequence of simu lations evaluated slurry flow at Re ynolds number up to 15000 and loading up tomore » 25%. Li mitations come into the long time required to run these simulation s due in particular to the mesh size requirement at the jet nozzle. This study has found that slurry - jet width and centerline velocities are functions of Re ynold s number and volume fractio n The solid phase was found to spread less than the water - phase with a spreading rate smaller than 1 , dependent on the volume fraction. Particle size distribution does seem to have a large influence on the jet flow development. This study constitutes a first step to understand the behavior of highly loaded slurries and their ultimate application to cavern backfilling.« less

More and more power plant flyash is being recycled

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golden, D.; Sauber, R.

A number of viable options have been demonstrated for recycling flyash, one of America's fastest-growing waste products. Application opportunities range from structural fills to pavement bases, concrete, stabilizing backfills, and a metal-castings alloy. But two stumbling blocks still face utilities and marketers of flyash. They are: (1) Convincing potential end users that flyash is a beneficial raw material and not an inferior waste product. (2) Persuading regulatory agencies to draft legislation, that promote, if not mandate, its use.

Corrosion inhibition by inorganic cationic inhibitors on the high strength alumunium alloy, 2024-T3

NASA Astrophysics Data System (ADS)

Chilukuri, Anusha

The toxicity and carcinogenic nature of chromates has led to the investigation of environmentally friendly compounds that offer good corrosion resistance to AA 2024-T3. Among the candidate inhibitors are rare earth metal cationic (REM) and zinc compounds, which have received much of attention over the past two decades. A comparative study on the corrosion inhibition caused by rare earth metal cations, Ce3+, Pr3+, La3+ and Zn2+ cations on the alloy was done. Cathodic polarization showed that these inhibitor ions suppress the oxygen reduction reaction (ORR) to varying extents with Zn2+ providing the best inhibition. Pr3+ exhibited windows of concentration (100-300 ppm) in which the corrosion rate is minimum; similar to the Ce3+ cation. Scanning Electron Microscopy (SEM) studies showed that the mechanism of inhibition of the Pr3+ ion is also similar to that of the Ce3+ ion. Potentiodynamic polarization experiments after 30 min immersion time showed greatest suppression of oxygen reduction reaction in neutral chloride solutions (pH 7), which reached a maximum at a Zn2+ ion concentration of 5 mM. Anodic polarization experiments after 30 min immersion time, showed no anodic inhibition by the inhibitor in any concentration (0.1 mM - 10 mM) and at any pH. However, anodic polarization of samples immersed after longer immersion times (upto 4 days) in mildly acidic Zn2+ (pH 4) solutions showed significant reduction in anodic kinetics indicating that zinc also acts as a “slow anodic inhibitor”. In contrast to the polarization experiments, coupons exposed to inhibited acidic solutions at pH 4 showed complete suppression of dissolution of Al2CuMg particles compared to zinc-free solutions in the SEM studies. Samples exposed in pH 4 Zn2+-bearing solution exhibited highest polarization resistance which was also observed to increase with time. In deaerated solutions, the inhibition by Zn2+ at pH 4 is not observed as strongly. The ability to make the interfacial electrolyte alkaline is retarded in the absence of oxygen. As a result precipitation of Zn oxides and hydroxides was suppressed. Impedance in decarbonated chloride solutions showed that the absence of CO 2 reduces inhibition by Zn2+ at pH 4. The carbonate protective layer formed in aerated solutions is essential for providing better protection of the substrate at pH 4. Inhibitor cations were exchanged into insoluble ion-exchanging sodium bentonites and incorporated as pigments in organic coatings applied to AA 2024-T3 substrates. XRD of the pigments ensured ion exchange and UV-visible spectroscopy was used to characterize inhibitor ion release from the bentonites. Salt spray exposure tests on scribed panels were preformed and results were compared to those from SrCrO4 pigmented coatings. Zn-exchanged bentonite pigmented coatings showed better performance compared to the other exchanged bentonites when incorporated into epoxy coatings with total impedance magnitude in the same order as SrCrO4. PVB (Polyvinyl Butyral) coatings containing Zn bentonite, however, did not show superior behaviour in the impedance response due to less or no water uptake. Salt spray exposures for a period of 336 h, showed that Zn bentonite incorporated into PVB suppressed blistering compared to the neat PVB and other pigmented bentonites.

Neighborhood-based PA and its environmental correlates: a GIS- and GPS based cross-sectional study in the Netherlands.

PubMed

Jansen, Marijke; Kamphuis, Carlijn B M; Pierik, Frank H; Ettema, Dick F; Dijst, Martin J

2018-02-09

To improve our understanding of the neighborhood environment - physical activity (PA) relationship, it is of importance to assess associations between neighborhood environmental characteristics and neighborhood-based PA. Participants' (N = 308; 45-65 years) light PA (LPA) and moderate-vigorous PA (MVPA) within a 400, 800, and 1600 m buffer around adults' homes was measured using accelerometers and GPS-devices. Land use data in ArcGIS provided neighborhood characteristics for the same buffers. Multilevel linear regression models, adjusted for socio-demographic variables and attitude towards PA, were used to assess associations of objective neighborhood characteristics with neighborhood-based LPA and MVPA. LPA was positively associated with the proportions of roads (within a 400 m buffer), and negatively associated with the proportions of recreational areas (within an 800 m buffer), and the proportion of green space (within the 800 m and 1600 m buffers). Multiple characteristics of 400 m buffers were positively associated with MVPA, i.e. proportions of green space, blue space, residences, shops and foodservice industry, sports terrain, and public social-cultural facilities. Also, characteristics of larger buffers were positively associated with MVPA, i.e. the proportions of shops and foodservice industry, sports terrain, and blue space (within an 800 m buffer), and the proportion of public social-cultural facilities (within the 800 m and 1600 m buffers). Objective neighborhood characteristics of smaller as well as larger sized buffers were associated with neighborhood-based LPA and MVPA. Green and blue spaces seem to be of particular importance for PA in the smallest buffer, i.e. in the direct surrounding of adults' homes.

Characterization of homoionic Fe 2+-type montmorillonite: Potential chemical species of iron contaminant

NASA Astrophysics Data System (ADS)

Kozai, Naofumi; Inada, Koichi; Adachi, Yoshifusa; Kawamura, Sachi; Kashimoto, Yusuke; Kozaki, Tamotsu; Sato, Seichi; Ohnuki, Toshihiko; Sakai, Takuro; Sato, Takahiro; Oikawa, Masakazu; Esaka, Fumitaka; Mitamura, Hisayoshi

2007-08-01

Fe 2+-montmorillonite with Fe 2+ ions occupying cation exchange sites is an ideal transformation product in bentonite buffer material. In our previous study on preparation and characterization of Fe 2+-montmorillonite, the montmorillonite sample that adsorbed Fe 2+ ions on almost all of the cation exchange sites was prepared using a FeCl 2 solution under an inert gas condition [N. Kozai, Y. Adachi, S. Kawamura, K. Inada, T. Kozaki, S. Sato, H. Ohashi, T. Ohnuki, T. Banba, J. Nucl. Sci. Technol. 38 (2001) 1141]. In view of the unstable nature of iron(II) chemical species, this study attempted to determine the potential contaminant iron chemical species in the sample. Nondestructive elemental analysis revealed that a small amount of chloride ions remained dispersed throughout the clay particles. The chloride ion retention may be due to the adsorption of FeCl + ion pairs in the initial FeCl 2 solution and the subsequent containment of the Cl - ions that are dissociated from the FeCl + ion pairs during excess salt removal treatment. Two explanations are advanced for the second process: the slow release of the remaining Cl - ions from the collapsed interlayer of the montmorillonite, and the transformation of a minor fraction of the remaining FeCl + ion pairs to iron(III) hydroxide chloride complexes having low solubility.

Metabolic component of intestinal PCO(2) during dysoxia.

PubMed

Raza, O; Schlichtig, R

2000-12-01

The adequacy of intestinal perfusion during shock and resuscitation might be estimated from intestinal tissue acid-base balance. We examined this idea from the perspective of conventional blood acid-base physicochemistry. As the O(2) supply diminishes with failing blood flow, tissue acid-base changes are first "respiratory, " with CO(2) coming from combustion of fuel and stagnating in the decreasing blood flow. When the O(2) supply decreases to critical, the changes become "metabolic" due to lactic acid. In blood, the respiratory vs. metabolic distinction is conventionally made using the buffer base principle, in which buffer base is the sum of HCO(3)(-) and noncarbonate buffer anion (A(-)). During purely respiratory acidosis, buffer base stays constant because HCO(3)(-) cannot buffer its own progenitor, carbonic acid, so that the rise of HCO(3)(-) equals the fall of A(-). During anaerobic "metabolism," however, lactate's H(+) is buffered by both A(-) and HCO(3)(-), causing buffer base to decrease. We quantified the partitioning of lactate's H(+) between HCO(3)(-) and A(-) buffer in anoxic intestine by compressing intestinal segments of anesthetized swine into a steel pipe and measuring PCO(2) and lactate at 5- to 10-min intervals. Their rises followed first-order kinetics, yielding k = 0. 031 min(-1) and half time = approximately 22 min. PCO(2) vs. lactate relations were linear. Over 3 h, lactate increased by 31 +/- 3 mmol/l tissue fluid (mM) and PCO(2) by approximately 17 mM, meaning that one-half of lactate's H(+) was buffered by tissue HCO(3)(-) and one-half by A(-). The data were consistent with a lumped pK(a) value near 6.1 and total A(-) concentration of approximately 30 mmol/kg. We conclude that the respiratory vs. metabolic distinction could be made in tissue by estimating tissue buffer base from measured pH and PCO(2).

In Vivo Predictive Dissolution: Comparing the Effect of Bicarbonate and Phosphate Buffer on the Dissolution of Weak Acids and Weak Bases.

PubMed

Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

2015-09-01

Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa . © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Dynamic Resource Management for Parallel Tasks in an Oversubscribed Energy-Constrained Heterogeneous Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imam, Neena; Koenig, Gregory A; Machovec, Dylan

2016-01-01

Abstract: The worth of completing parallel tasks is modeled using utility functions, which monotonically-decrease with time and represent the importance and urgency of a task. These functions define the utility earned by a task at the time of its completion. The performance of such a system is measured as the total utility earned by all completed tasks over some interval of time (e.g., 24 hours). To maximize system performance when scheduling dynamically arriving parallel tasks onto a high performance computing (HPC) system that is oversubscribed and energy-constrained, we have designed, analyzed, and compared different heuristic techniques. Four utility-aware heuristics (i.e.,more » Max Utility, Max Utility-per-Time, Max Utility-per-Resource, and Max Utility-per-Energy), three FCFS-based heuristics (Conservative Backfilling, EASY Backfilling, and FCFS with Multiple Queues), and a Random heuristic were examined in this study. A technique that is often used with the FCFS-based heuristics is the concept of a permanent reservation. We compare the performance of permanent reservations with temporary place-holders to demonstrate the advantages that place-holders can provide. We also present a novel energy filtering technique that constrains the maximum energy-per-resource used by each task. We conducted a simulation study to evaluate the performance of these heuristics and techniques in an energy-constrained oversubscribed HPC environment. With place-holders, energy filtering, and dropping tasks with low potential utility, our utility-aware heuristics are able to significantly outperform the existing FCFS-based techniques.« less

Signature-based store checking buffer

DOEpatents

Sridharan, Vilas; Gurumurthi, Sudhanva

2015-06-02

A system and method for optimizing redundant output verification, are provided. A hardware-based store fingerprint buffer receives multiple instances of output from multiple instances of computation. The store fingerprint buffer generates a signature from the content included in the multiple instances of output. When a barrier is reached, the store fingerprint buffer uses the signature to verify the content is error-free.

Integrated ground-based hyperspectral imaging and geochemical study of the Eagle Ford Group in West Texas

NASA Astrophysics Data System (ADS)

Sun, Lei; Khan, Shuhab; Godet, Alexis

2018-01-01

This study used ground-based hyperspectral imaging to map an outcrop of the Eagle Ford Group in west Texas. The Eagle Ford Group consists of alternating layers of mudstone - wackestone, grainstone - packstone facies and volcanic ash deposits with high total organic content deposited during the Cenomanian - Turonian time period. It is one of the few unconventional source rock and reservoirs that have surface representations. Ground-based hyperspectral imaging scanned an outcrop and hand samples at close ranges with very fine spatial resolution (centimeter to sub-millimeter). Spectral absorption modeling of clay minerals and calcite with the modified Gaussian model (MGM) allowed quantification of variations of mineral abundances. Petrographic analysis confirmed mineral identifications and shed light on sedimentary textures, and major element geochemistry supported the mineral quantification. Mineral quantification resulted in mapping of mudstone - wackestone, grainstone - packstone facies and bentonites (volcanic ash beds). The lack of spatial associations between the grainstones and bentonites on the outcrop calls into question the hypothesis that the primary productivity is controlled by iron availability from volcanic ash beds. Enrichment of molybdenum (Mo) and uranium (U) indicated "unrestricted marine" paleo-hydrogeology and anoxic to euxinic paleo-redox bottom water conditions. Hyperspectral remote sensing data also helped in creating a virtual outcrop model with detailed mineralogical compositions, and provided reservoir analog to extract compositional and geo-mechanical characteristics and variations. The utilization of these new techniques in geo-statistical analysis provides a workflow for employing remote sensing in resource exploration and exploitation.

Buffer$--An Economic Analysis Tool

Treesearch

Gary Bentrup

2007-01-01

Buffer$ is an economic spreadsheet tool for analyzing the cost-benefits of conservation buffers by resource professionals. Conservation buffers are linear strips of vegetation managed for multiple landowner and societal objectives. The Microsoft Excel based spreadsheet can calculate potential income derived from a buffer, including income from cost-share/incentive...

Utilization of SRS pond ash in controlled low strength material. Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langton, C.A.; Rajendran, N.

1995-12-01

Design mixes for Controlled Low Strength Material (CLSM) were developed which incorporate pond ashes (fly ashes) from the A-Area Ash Pile, the old F-Area Ash Basin and the D-Area Ash Basin. CLSM is a pumpable, flowable, excavatable backfill used in a variety of construction applications at SRS. Results indicate that CLSM which meets all of the SRS design specifications for backfill, can be made with the A-, D-, and F-Area pond ashes. Formulations for the design mixes are provided in this report. Use of the pond ashes may result in a cost savings for CLSM used at SRS and willmore » utilize a by-product waste material, thereby decreasing the amount of material requiring disposal.« less

The investigation of the effect of thermal treatment on bentonites from Turkey with Fourier transform infrared and solid state nuclear magnetic resonance spectroscopic methods.

PubMed

Erdoğan Alver, Burcu; Alver, Ozgür

2012-08-01

There is a great deal of interest in the building industry in burned clays for production of building materials. Therefore, the effect of heat treatment on natural bentonite from Turkey was investigated by Fourier transform infrared (FT-IR) between the region of 4000-400cm(-1) and (29)Si, (27)Al magic angle spinning nuclear magnetic resonance (MAS NMR) measurement techniques at various temperatures between 200 and 700°C for 2h. The structural changes were also investigated upon heat treatment. Copyright © 2012 Elsevier B.V. All rights reserved.

Heavy metal-immobilizing organoclay facilitates polycyclic aromatic hydrocarbon biodegradation in mixed-contaminated soil.

PubMed

Biswas, Bhabananda; Sarkar, Binoy; Mandal, Asit; Naidu, Ravi

2015-11-15

Soils contaminated with a mixture of heavy metals and polycyclic aromatic hydrocarbons (PAHs) pose toxic metal stress to native PAH-degrading microorganisms. Adsorbents such as clay and modified clay minerals can bind the metal and reduce its toxicity to microorganisms. However, in a mixed-contaminated soil, an adsorption process more specific to the metals without affecting the bioavailability of PAHs is desired for effective degradation. Furthermore, the adsorbent should enhance the viability of PAH-degrading microorganisms. A metal-immobilizing organoclay (Arquad(®) 2HT-75-bentonite treated with palmitic acid) (MIOC) able to reduce metal (cadmium (Cd)) toxicity and enhance PAH (phenanthrene) biodegradation was developed and characterized in this study. The MIOC differed considerably from the parent clay in terms of its ability to reduce metal toxicity (MIOC>unmodified bentonite>Arquad-bentonite). The MIOC variably increased the microbial count (10-43%) as well as activities (respiration 3-44%; enzymatic activities up to 68%), and simultaneously maintained phenanthrene in bioavailable form in a Cd-phenanthrene mixed-contaminated soil over a 21-day incubation period. This study may lead to a new MIOC-assisted bioremediation technique for PAHs in mixed-contaminated soils. Copyright © 2015 Elsevier B.V. All rights reserved.

Bentonite-Clay Waste Form for the Immobilization of Cesium and Strontium from Fuel Processing Waste Streams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaminski, Michael D.; Mertz, Carol J.

2016-01-01

The physical properties of a surrogate waste form containing cesium, strontium, rubidium, and barium sintered into bentonite clay were evaluated for several simulant feed streams: chlorinated cobalt dicarbollide/polyethylene glycol (CCD-PEG) strip solution, nitrate salt, and chloride salt feeds. We sintered bentonite clay samples with a loading of 30 mass% of cesium, strontium, rubidium, and barium to a density of approximately 3 g/cm 3. Sintering temperatures of up to 1000°C did not result in volatility of cesium. Instead, there was an increase in crystallinity of the waste form upon sintering to 1000ºC for chloride- and nitrate-salt loaded clays. The nitrate saltmore » feed produced various cesium pollucite phases, while the chloride salt feed did not produce these familiar phases. In fact, many of the x-ray diffraction peaks could not be matched to known phases. Assemblages of silicates were formed that incorporated the Sr, Rb, and Ba ions. Gas evolution during sintering to 1000°C was significant (35% weight loss for the CCD-PEG waste-loaded clay), with significant water being evolved at approximately 600°C.« less

Organically modified low-grade kaolin as a secondary containment material for underground storage tanks.

PubMed

Moon, Chul-Hwan; Lee, Jai-Young; Oh, Byung-Taek; Choi, Sang-Il

2007-08-01

Batch scale reactions were conducted to evaluate the efficacy of modified low-grade kaolin for the treatment of petroleum contaminants. Low-grade kaolin, which has been unvalued as material in the mining process because of its low quality for commercial products, was modified with HDTMA (hexadecyl-trimethylammonium), and its efficiency was compared with that of HDTMA-modified bentonite, which is used as a secondary containment barrier for underground storage tanks. The sorption capacity and hydraulic conductivity of both the HDTMA-modified bentonite and low-grade kaolin were investigated and showed distribution coefficients in the sorption of benzene, toluene, ethylbenzene and xylene ranging between 45.7 and 583.7 and 57.0 and 525.1, respectively. The hydraulic conductivities were 2.53 x 10(-8) and 5.62 x 10(-8) cm/s for the HDTMA-modified bentonite and low-grade kaolin, respectively. These results suggest that HDTMA-modified low-grade kaolin could be used as a hydraulic barrier against advection migration of petroleum contaminants. Simulation of the one-dimensional transport of benzene through a liner made of either one of the compounds was also performed. These results also showed that HDTMA-modified kaolin more effectively retards the transport of benzene.

Evaluation on expansive performance of the expansive soil using electrical responses

NASA Astrophysics Data System (ADS)

Chu, Ya; Liu, Songyu; Bate, Bate; Xu, Lei

2018-01-01

Light structures, such as highways and railroads, built on expansive soils are prone to damages from the swelling of their underlain soil layers. Considerable amount of research has been conducted to characterize the swelling properties of expansive soils. Current swell characterization models, however, are limited by lack of standardized tests. Electrical methods are non-destructive, and are faster and less expensive than the traditional geotechnical methods. Therefore, geo-electrical methods are attractive for defining soil characteristics, including the swelling behavior. In this study, comprehensive laboratory experiments were undertaken to measure the free swelling and electrical resistivity of the mixtures of commercial kaolinite and bentonite. The electrical conductivity of kaolinite-bentonite mixtures was measured by a self-developed four-electrode soil resistivity box. Increasing the free swelling rate of the kaolinite-bentonite mixtures (0.72 to 1 of porosity of soils samples) led to a reduction in the electrical resistivity and an increase in conductivity. A unique relationship between free swelling rate and normalized surface conductivity was constructed for expensive soils by eliminating influences of porosity and m exponent. Therefore, electrical response measurement can be used to characterize the free swelling rate of expensive soils.

The Effects of Mineral Matrices and Extraction Method on Quantification of Bacterial Phospholipid Fatty Acids.

NASA Astrophysics Data System (ADS)

Ford, S. E.; McKelvie, J. R. M.; Sherwood Lollar, B.; Slater, G. F.

2017-12-01

Understanding the distribution, abundances and metabolic activities of microbial life in the subsurface is fundamental to our understanding of biogeochemical cycling on Earth. Given that the most likely environments for life to still exist, or be preserved, on other planets and moons in the solar system are in the subsurface, a better understanding of subsurface life on Earth is also a key factor in our ability to search for life beyond the Earth. While we have made progress in investigating life in the continental subsurface in recent years, significant challenges remain. In particular, the low biomass abundance, heterogeneous distribution of biomass, and the potential for matrix effects during sampling and analysis mean that further development and optimization of methods to study subsurface life are needed. Phospholipid fatty acids (PLFA) are a useful biosignature of extant, viable microbial communities that are applied in a wide range of environments. Here we test the sensitivity of two methods of PLFA analysis (modified Bligh and Dyer, Microwave Assisted Extraction) to detect known numbers of cells doped into two distinct matrices (bentonite, crushed granite). Samples were prepared by adding known cellular concentrations of Basciullus subtilis subtilis (ATCC 6051) to crushed bentonite, or to granite, respectively, to create dilution series. Samples were extracted for PLFA using a dichloromethane-methanol modified Bligh & Dyer (mBD) or Microwave Assisted Extraction (MAE) and then quantified using GC - MS and GC - FID. Pure culture extractions yielded a linearly decreasing trend to the level of the process blank. The ratio of cells to PLFA for this trend was 2.4x104 +/- 1.9x104 cells/pmol at the lower end of the generic range of 2 to 6 x105 cells/pmol. For bentonite the PLFA results were lower than for the pure culture. PLFA results for bentonite followed a linear trend at higher concentrations, but departed from this at low concentrations indicating the potential for interference for low biomass samples. The ratio of cells to PLFA for the bentonite was to 6.2x104 +/- 4.5x104 cells/pmol, at the upper end of generic range. Ongoing comparison of the efficiency of microwave extraction and the effect of different matrices (e.g. granite) aims to optimize detection of PLFA for low biomass samples relevant to subsurface systems.

Reducing Error Bars through the Intercalibration of Radioisotopic and Astrochronologic Time Scales for the Cenomanian/Turonian Boundary Interval, Western Interior Basin, USA

NASA Astrophysics Data System (ADS)

Meyers, S. R.; Siewert, S. E.; Singer, B. S.; Sageman, B. B.; Condon, D. J.; Obradovich, J. D.; Jicha, B.; Sawyer, D. A.

2010-12-01

We develop a new intercalibrated astrochronologic and radioisotopic time scale for the Cenomanian/Turonian (C/T) boundary interval near the GSSP in Colorado, where orbitally-influenced rhythmic strata host bentonites that contain sanidine and zircon suitable for 40Ar/39Ar and U-Pb dating. This provides a rare opportunity to directly intercalibrate two independent radioisotopic chronometers against an astrochronologic age model. We present paired 40Ar/39Ar and U-Pb ages from four bentonites spanning the Vascoceras diartianum to Pseudaspidoceras flexuosum biozones, utilizing both newly collected material and legacy sanidine samples of Obradovich (1993). Full 2σ uncertainties (decay constant, standard age, analytical sources) for the 40Ar/39Ar ages, using a weighted mean of 33-103 concordant age determinations and an age of 28.201 Ma for Fish Canyon sanidine (FCs), range from ±0.15 to 0.19 Ma, with ages from 93.67 to 94.43 Ma. The traditional FCs age of 28.02 Ma yields ages from 93.04 to 93.78 Ma with full uncertainties of ±1.58 Ma. Using the ET535 tracer, single zircon CA-TIMS 206Pb/238U ages determined from each bentonite record a range of ages (up to 2.1 Ma), however, in three of the four bentonites the youngest single crystal ages are statistically indistinguishable from the 40Ar/39Ar ages calculated relative to 28.201 Ma FCs, supporting this calibration. Using the new radioisotopic data and published astrochronology (Sageman et al., 2006) we develop an integrated C/T boundary time scale using a Bayesian statistical approach that builds upon the strength of each geochronologic method. Whereas the radioisotopic data provide an age with a well-defined uncertainty for each bentonite, the orbital time scale yields a more highly resolved estimate of the duration between stratigraphic horizons, including the radioisotopically dated beds. The Bayesian algorithm yields a C/T time scale that is statistically compatible with the astrochronologic and radioisotopic data, but with smaller uncertainty than either method could achieve alone. The results firmly anchor the floating orbital time scale and yield astronomically-recalibrated radioisotopic ages with full uncertainties that approach the EARTHTIME goal of permil resolution.

Clarification of Muscat musts using wheat proteins and the flotation technique.

PubMed

Marchal, Richard; Lallement, Armelle; Jeandet, Philippe; Establet, Gérard

2003-03-26

The bovine spongiform encephalopathy (BSE, mad cow) crisis has led some wine-makers to question gelatin as a fining agent and to reject the use of these animal proteins. The search for a substitute for gelatin was begun by comparing vegetable proteins (particularly gluten) with gelatin fining treatments. Clairette de Die (French-controlled appellation) is a sparkling sweet wine. The alcoholic fermentation begins in a tank, continues in a crown-cap bottle, and stops before the complete consumption of sugar. All particles present in the bottle have to be removed before corking, and it is important to have a must as clear as possible. This study concerned the clarifying of a Muscat must, treated with pectinases, using a very efficient flotation technique. The must is fined with bentonite/silica/protein (fish gelatin, wheat gluten, or lupin isolate) to induce flocculation and then pressurized (6 bar). After depressurization, microbubbles cling to flocculates and climb to the top of the flotation tank (this flotation foam is clarified using a rotary filter). At laboratory scale, gluten (20 g/hL) and gelatin (10 g/hL) (each combined with bentonite and silica gel) gave turbidities of 50 and 35 NTU, respectively (6.5 and 4.1% of that of the nontreated must). The Muscat must was also clarified by static settling. The turbidity decreased by 86% for the gluten/bentonite fining and by 60% for the gelatin/bentonite fining. Visually, gluten flocculation takes longer to occur and flocculates sedimentation is longer than with gelati, but the removal of insoluble particles is more complete and leads to lower turbidities. At an industrial scale, gluten (20 g/hL) and gelatin (10 g/hL) (each combined with bentonite and silica gel) gave turbidities of 60 and 48 NTU, respectively. Turbidities measured in the tanks 14 h after the flotation showed a better efficiency for the wheat gluten (24 NTU) compared to gelatin (28 NTU). This is explained by the static settling that completed the clarifying effect of the flotation. The last experiment showed comparable efficiencies for wheat gluten and lupin proteins. BSE caused a situation of crisis (in Europe particularly) leading the public and wine-makers to lose their confidence in the use of gelatin as fining agent and to reject animal proteins in general. It is proposed here that vegetable proteins could efficiently replace gelatin.

Interactions of low molecular weight aromatic acids and amino acids with goethite, kaolinite and bentonite with or without organic matter coating

NASA Astrophysics Data System (ADS)

Gao, Jiajia; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

2015-04-01

Interaction of organic matter molecules with the soil's solid phase is a key factor influencing the stabilization of carbon in soils and thus forms a crucial aspect of the global carbon cycle. While subject of much research attention so far, we still have much to learn about such interactions at the molecular level; in particular in the light of competition between different classes of organic molecules and in the presence of previously adsorbed soil organic matter. We studied the interaction of a group of low molecular weight (LMW) aromatic acids (salicylic, syringic, vanillic and ferulic acid) and amino acids (lysine, glutamic, leucine and phenylalanine) on goethite, kaolinite and bentonite with and without previously adsorbed dissolved organic matter (DOM). For this we used batch experiments at pH = 6.0 where some of the organic compounds were positively charged (i.e. lysine) or negatively charged (i.e. glutamic and salicylic acid) while the minerals also displayed positively (i.e. goethite) or negatively charged surfaces (i.e. bentonite). We found much higher sorption of salicylic acid and lysine than other compounds. On the bare minerals we found a great variety of sorption strength, with salicylic acid strongly adsorbed, while syringic, vanillic and ferulic acid showed little or no adsorption. For the amino acids, protonated lysine showed a stronger affinity to negatively charged kaolinite and bentonite than other amino acids. While deprotonated glutamic acid showed the strongest adsorption on goethite. Leucine and phenylalanine showed hardly any adsorption on any of the minerals. When present concurrently, amino acids decreased the sorption of salicylic acid on the three types of mineral, while the presence of LMW aromatic acids increased the sorption of lysine on kaolinite and bentonite and the sorption of glutamic acid on goethite. The presence of previously adsorbed DOM reduced the sorption of salicylic acid and lysine. The results confirm that interactions of different classes of organic molecules with solid soil phases cannot be understood in isolation, but must be interpreted in the context of the presence of other classes of molecules. It seems that the presence of methoxy groups decreases the adsorption of aromatic acids to minerals. We did not find evidence for protein conditioning of any mineral surface, i.e. increased adsorption of aromatic acids after adsorption of amino acids.

Processing-structure-properties relationships in PLA nanocomposite films

NASA Astrophysics Data System (ADS)

Di Maio, L.; Scarfato, P.; Garofalo, E.; Galdi, M. R.; D'Arienzo, L.; Incarnato, L.

2014-05-01

This work deals on the possibility to improve performances of PLA-based nanocomposite films, for packaging applications, through conveniently tuning materials and processing conditions in melt compounding technology. In particular, two types of polylactic acid and different types of filler selected from montmorillonites and bentonites families were used to prepare the hybrid systems by using a twin-screw extruder. The effect of biaxial drawing on morphology and properties of the nanocomposites, produced by film blowing, was investigated.

Omaha Soil Mixing Study: Redistribution of Lead in ...

EPA Pesticide Factsheets

Urban soils within the Omaha Lead Superfund Site have been contaminated with lead (Pb) from atmospheric deposition of particulate materials from lead smelting and recycling activities. In May of 2009 the Final Record of Decision stated that any residential soil exceeding the preliminary remediation goal (PRG; 400 mgPb kg-1soil) would be excavated, backfilled and re-vegetated. The remedial action entailed excavating contaminated soil in the top 12 inches and excavation could stop when the concentration of soil Pb was less than 400 mg kg-1 in the top 12 inches, or less than 1200 mg kg-1 at depths greater than 1 ft. After removal of the contaminated soil, clean backfill was applied and a grass lawn was replanted. A depth of 12 inches was based on the assumption that Pb-contaminated soil at depth greater than 1 ft would not represent a future risk (ASTDR Health Consult, 2004). This assumption was based on the principal that mixing and other factors encountered during normal excavation practices would not result in Pb surface concentrations greater than the PRG. The goal of the current study was to investigate the redistribution of Pb in remediated residential surface soils after typical homeowner earth-disturbing activities in the OLS Site. Of specific interest to the region for protection of human health is determining whether soil mixing associated with normal homeowner excavation practices results in surface Pb concentrations greater than the preliminary r

Soy Protein Isolate As Fluid Loss Additive in Bentonite-Water-Based Drilling Fluids.

PubMed

Li, Mei-Chun; Wu, Qinglin; Song, Kunlin; Lee, Sunyoung; Jin, Chunde; Ren, Suxia; Lei, Tingzhou

2015-11-11

Wellbore instability and formation collapse caused by lost circulation are vital issues during well excavation in the oil industry. This study reports the novel utilization of soy protein isolate (SPI) as fluid loss additive in bentonite-water based drilling fluids (BT-WDFs) and describes how its particle size and concentration influence on the filtration property of SPI/BT-WDFs. It was found that high pressure homogenization (HPH)-treated SPI had superior filtration property over that of native SPI due to the improved ability for the plugging pore throat. HPH treatment also caused a significant change in the surface characteristic of SPI, leading to a considerable surface interaction with BT in aqueous solution. The concentration of SPI had a significant impact on the dispersion state of SPI/BT mixtures in aquesous solution. At low SPI concentrations, strong aggregations were created, resulting in the formation of thick, loose, high-porosity and high-permeability filter cakes and high fluid loss. At high SPI concentrations, intercatlated/exfoliated structures were generated, resulting in the formation of thin, compact, low-porosity and low-permeability filter cakes and low fluid loss. The SPI/BT-WDFs exhibited superior filtration property than pure BT-WDFs at the same solid concentraion, demonstrating the potential utilization of SPI as an effective, renewable, and biodegradable fluid loss reducer in well excavation applications.

Effects of additives on solidification of API separator sludge.

PubMed

Faschan, A; Tittlebaum, M; Cartledge, F; Eaton, H

1991-08-01

API separator sludge was solidified with various combinations of binders and absorbent soil additives. The binders utilized were Type I Portland Cement, Type C Flyash, and a 1:1 combination of the two. The soil additives used were bentonite, diatomite, Fuller's earth, and two brands of chemically altered bentonites, or organoclays. The effectiveness of the solidification materials was based on their effect on the physical and leaching characteristics of the sludge.It was determined the Portland cement and combination binders provided the sludge with adequate physical and strength characteristics. It was also determined the affinity of each additive for water had an important influence on the physical characteristics of the solidified sludge. The results of the leaching procedure indicated the binders alone reduced the leachability of organic constituents from the sludge by 1/5 to 1/10. It appeared the use of the additives with the binders may have further reduced the leachability of constituents from sludge, with the incorporation of the organoclay additives further reducing leachability by up to 1/2. Also, it appeared the absorbing capacity of the additives was directly related to their ability to reduce the leachability of organic constituents from the sludge.

High effective cytosolic H+ buffering in mouse cortical astrocytes attributable to fast bicarbonate transport.

PubMed

Theparambil, Shefeeq M; Deitmer, Joachim W

2015-09-01

Cytosolic H(+) buffering plays a major role for shaping intracellular H(+) shifts and hence for the availability of H(+) for biochemical reactions and acid/base-coupled transport processes. H(+) buffering is one of the prime means to protect the cell from large acid/base shifts. We have used the H(+) indicator dye BCECF and confocal microscopy to monitor the cytosolic H(+) concentration, [H(+)]i, in cultured cortical astrocytes of wild-type mice and of mice deficient in sodium/bicarbonate cotransporter NBCe1 (NBCe1-KO) or in carbonic anhydrase isoform II (CAII-KO). The steady-state buffer strength was calculated from the amplitude of [H(+)]i transients as evoked by CO2/HCO3(-) and by butyric acid in the presence and absence of CO2/HCO3(-). We tested the hypotheses if, in addition to instantaneous physicochemical H(+) buffering, rapid acid/base transport across the cell membrane contributes to the total, "effective" cytosolic H(+) buffering. In the presence of 5% CO2/26 mM HCO3(-), H(+) buffer strength in astrocytes was increased 4-6 fold, as compared with that in non-bicarbonate, HEPES-buffered solution, which was largely attributable to fast HCO3 (-) transport into the cells via NBCe1, supported by CAII activity. Our results show that within the time frame of determining physiological H(+) buffering in cells, fast transport and equilibration of CO2/H(+)/HCO3(-) can make a major contribution to the total "effective" H(+) buffer strength. Thus, "effective" cellular H(+) buffering is, to a large extent, attributable to membrane transport of base equivalents rather than a purely passive physicochemical process, and can be much larger than reported so far. Not only physicochemical H(+) buffering, but also rapid import of HCO3(-) via the electrogenic sodium-bicarbonate cotransporter NBCe1, supported by carbonic anhydrase II (CA II), was identified to enhance cytosolic H(+) buffer strength substantially. © 2015 Wiley Periodicals, Inc.

Effects of simulated clay gouges on the sliding behavior of Tennessee sandston

NASA Astrophysics Data System (ADS)

Shimamoto, Toshihiko; Logan, John M.

1981-06-01

The effects of simulated fault gouge on the sliding behavior of Tennessee sandstone are studied experimentally with special reference to the stabilizing effect of clay minerals mixed into the gouge. About 30 specimens with gouge composed of pure clays, of homogeneously mixed clay and anhydrite, or of layered clay and anhydrite, along a 35° precut are deformed dry in a triaxial apparatus at a confining pressure of 100 MPa, with a shortening rate of about 5 · 10 -4/sec, and at room temperature. Pure clay gouges exhibit only stable sliding, and the ultimate frictional strength is very low for bentonite (mont-morillonite), intermediate for chlorite and illite, and considerably higher for kaolinite. Anhydrite gouge shows violent stick-slip at 100 MPa confining pressure. When this mineral is mixed homogeneously with clays, the frictional coefficient of the mixed gouge, determined at its ultimate frictional strength, decreases monotonically with an increase in the clay content. The sliding mode changes from stick-slip to stable sliding when the frictional coefficient of the mixed clay-anhydrite gouge is lowered down below 90-95% of the coefficient of anhydrite gouge. The stabilizing effect of clay in mixed gouge is closely related to the ultimate frictional strength of pure clays; that is, the effect is conspicuous only for a mineral with low frictional strength. Only 15-20% of bentonite suppresses the violent stick-slip of anhydrite gouge. In contrast, violent stick-slip occurs even if the gouge contains as much as 75% of kaolinite. The behavior of illite and chlorite is intermediate between that of kaolinite and bentonite. Bentonite—anhydrite two-layer gouge exhibits stable sliding even when the bentonite content is only 5%. Thus, the presence of a thin, clay-rich layer in a fault zone stabilizes the behavior much more effectively than do the clay minerals mixed homogeneously with the gouge. This result brings out the mechanical significance of internal structures of a fault zone in understanding the effects of intrafault materials on the fault motion. Based on the present experimental results incorporated with some other experimental data, it is argued that although the stabilizing effect of montmorillonite and vermiculite is indeed remarkable at room temperature, the effect should be much less pronounced at elevated temperatures, due perhaps to the dewatering of the clays. In most geological environments where shallow earthquakes occur, the stabilizing effect of clays is probably not so conspicuous as to completely suppress the unstable motion of a fault.

Using temporarily coherent point interferometric synthetic aperture radar for land subsidence monitoring in a mining region of western China

NASA Astrophysics Data System (ADS)

Fan, Hongdong; Xu, Qiang; Hu, Zhongbo; Du, Sen

2017-04-01

Yuyang mine is located in the semiarid western region of China where, due to serious land subsidence caused by underground coal exploitation, the local ecological environment has become more fragile. An advanced interferometric synthetic aperture radar (InSAR) technique, temporarily coherent point InSAR, is applied to measure surface movements caused by different mining conditions. Fifteen high-resolution TerraSAR-X images acquired between October 2, 2012, and March 27, 2013, were processed to generate time-series data for ground deformation. The results show that the maximum accumulated values of subsidence and velocity were 86 mm and 162 mm/year, respectively; these measurements were taken above the fully mechanized longwall caving faces. Based on the dynamic land subsidence caused by the exploitation of one working face, the land subsidence range was deduced to have increased 38 m in the mining direction with 11 days' coal extraction. Although some mining faces were ceased in 2009, they could also have contributed to a small residual deformation of overlying strata. Surface subsidence of the backfill mining region was quite small, the maximum only 21 mm, so backfill exploitation is an effective method for reducing the land subsidence while coal is mined.

Sponge-Templated Macroporous Graphene Network for Piezoelectric ZnO Nanogenerator.

PubMed

Li, Xinda; Chen, Yi; Kumar, Amit; Mahmoud, Ahmed; Nychka, John A; Chung, Hyun-Joong

2015-09-23

We report a simple approach to fabricate zinc oxide (ZnO) nanowire based electricity generators on three-dimensional (3D) graphene networks by utilizing a commercial polyurethane (PU) sponge as a structural template. Here, a 3D network of graphene oxide is deposited from solution on the template and then is chemically reduced. Following steps of ZnO nanowire growth, polydimethylsiloxane (PDMS) backfilling and electrode lamination completes the fabrication processes. When compared to conventional generators with 2D planar geometry, the sponge template provides a 3D structure that has a potential to increase power density per unit area. The modified one-pot ZnO synthesis method allows the whole process to be inexpensive and environmentally benign. The nanogenerator yields an open circuit voltage of ∼0.5 V and short circuit current density of ∼2 μA/cm(2), while the output was found to be consistent after ∼3000 cycles. Finite element analysis of stress distribution showed that external stress is concentrated to deform ZnO nanowires by orders of magnitude compared to surrounding PU and PDMS, in agreement with our experiment. It is shown that the backfilled PDMS plays a crucial role for the stress concentration, which leads to an efficient electricity generation.

Development of composting plant rock surrounding pollution. Case study - Točna in Příbor, The Czech Republic

NASA Astrophysics Data System (ADS)

Ondrasikova, I.; Stancl, L.

2017-10-01

Composting plant Točna utilize and modifies biologically biodegradable waste by aerobic fermentation method. After emergency leakage of leachate water in 2010 the quality of rock surrounding is being regularly monitored in the range of indicators: pH, conductivity, COD (chemical oxygen demand, Cr), HCO3 -, Cl-, N-NH4 +, N-NO3 -, N-NO2 - and humic substances. Technical adjustments of the interest area has been also made to prevent leakage of contaminated water. Locality monitoring system is ensured separately for shallow backfill aquifer and deeper quaternary aquifer. Protective hydraulic barrier is running at the same time to prevent effluent of shallow water to groundwater. Nitrogenous substances (above all ammonium ions) and humic substances belongs among main groundwater contaminants of the interest area. Peak concentration level of this substances is connected with shallow backfill aquifer, near south-east and east edge of the locality, not in general quaternary water direction. From long-term monitoring results follows that concentration of monitored substances is gradually decreasing, especially in water connected with backfill layer. Drier weather of last year helps to this development. Quality of quaternary aquifer is not influenced significantly, only locally in spots, in the places of both aquifers connection where increase of ammonium ions occurs as result of humic substance decomposition. In effect, monitored substances are not disseminated in quaternary aquifer.

Digital-transport model study of Diisopropylmethylphosphonate (DIMP) ground-water contamination at the Rocky Mountain Arsenal, Colorado

USGS Publications Warehouse

Warner, James W.

1979-01-01

Diisopropylmethylphosphonate (DIMP) is an organic compound produced as a by-product of the manufacture and detoxification of GB nerve gas. Ground-water contamination by DIMP from the disposal of wastes into unlined surface ponds at the Rocky Mountain Arsenal occurred from 1952 to 1956. A digital-transport model was used to determine the effects on ground-water movement and on DIMP concentrations in the ground water of a bentonite barrier in the aquifer near the northern boundary of the arsenal. The transport model is based on an iterative-alternating-direction-implicit mathematical solution of the ground-water-flow equation coupled with a method-of-characteristics solution of the solute-transport equation. The model assumes conservative (nonreactive) transient transport of DIMP and steady-state ground-water flow. In the model simulations, a bentonite barrier was assumed that was impermeable and penetrated the entire saturated thickness of the aquifer. Ground water intercepted by the barrier was assumed to be pumped by wells located south (upgradient) of the barrier, to be treated to remove DIMP, and to be recharged by pits or wells to the aquifer north (downgradient) of the barrier. The amount of DIMP transported across the northern boundary of the arsenal was substantially reduced by a ground-water-barrier system of this type. For a 1,500-foot-long bentonite barrier located along the northern boundary of the arsenal near D Street, about 50 percent of the DIMP that would otherwise cross the boundary would be intercepted by the barrier. This barrier configuration and location were proposed by the U.S. Army. Of the ground water with DIMP concentrations greater than 500 micrograms per liter, the safe DIMP-concentration level determined by the U.S. Army, about 72 percent would be intercepted by the barrier system. The amount of DIMP underflow intercepted may be increased to 65 percent by doubling the pumpage, or to 73 percent by doubling the length of the barrier. (Kosco-USGS)

Improving the large scale purification of the HIV microbicide, griffithsin.

PubMed

Fuqua, Joshua L; Wanga, Valentine; Palmer, Kenneth E

2015-02-22

Griffithsin is a broad spectrum antiviral lectin that inhibits viral entry and maturation processes through binding clusters of oligomannose glycans on viral envelope glycoproteins. An efficient, scaleable manufacturing process for griffithsin active pharmaceutical ingredient (API) is essential for particularly cost-sensitive products such as griffithsin -based topical microbicides for HIV-1 prevention in resource poor settings. Our previously published purification method used ceramic filtration followed by two chromatography steps, resulting in a protein recovery of 30%. Our objective was to develop a scalable purification method for griffithsin expressed in Nicotiana benthamiana plants that would increase yield, reduce production costs, and simplify manufacturing techniques. Considering the future need to transfer griffithsin manufacturing technology to resource poor areas, we chose to focus modifying the purification process, paying particular attention to introducing simple, low-cost, and scalable procedures such as use of temperature, pH, ion concentration, and filtration to enhance product recovery. We achieved >99% pure griffithsin API by generating the initial green juice extract in pH 4 buffer, heating the extract to 55°C, incubating overnight with a bentonite MgCl2 mixture, and final purification with Capto™ multimodal chromatography. Griffithsin extracted with this protocol maintains activity comparable to griffithsin purified by the previously published method and we are able to recover a substantially higher yield: 88 ± 5% of griffithsin from the initial extract. The method was scaled to produce gram quantities of griffithsin with high yields, low endotoxin levels, and low purification costs maintained. The methodology developed to purify griffithsin introduces and develops multiple tools for purification of recombinant proteins from plants at an industrial scale. These tools allow for robust cost-effective production and purification of griffithsin. The methodology can be readily scaled to the bench top or industry and process components can be used for purification of additional proteins based on biophysical characteristics.

Dynamic Buffer Capacity in Acid-Base Systems.

PubMed

Michałowska-Kaczmarczyk, Anna M; Michałowski, Tadeusz

The generalized concept of 'dynamic' buffer capacity β V is related to electrolytic systems of different complexity where acid-base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton-Robinson buffers, taken as examples.

Assessing critical source areas in watersheds for conservation buffer planning and riparian restoration.

PubMed

Qiu, Zeyuan

2009-11-01

A science-based geographic information system (GIS) approach is presented to target critical source areas in watersheds for conservation buffer placement. Critical source areas are the intersection of hydrologically sensitive areas and pollutant source areas in watersheds. Hydrologically sensitive areas are areas that actively generate runoff in the watershed and are derived using a modified topographic index approach based on variable source area hydrology. Pollutant source areas are the areas in watersheds that are actively and intensively used for such activities as agricultural production. The method is applied to the Neshanic River watershed in Hunterdon County, New Jersey. The capacity of the topographic index in predicting the spatial pattern of runoff generation and the runoff contribution to stream flow in the watershed is evaluated. A simple cost-effectiveness assessment is conducted to compare the conservation buffer placement scenario based on this GIS method to conventional riparian buffer scenarios for placing conservation buffers in agricultural lands in the watershed. The results show that the topographic index reasonably predicts the runoff generation in the watershed. The GIS-based conservation buffer scenario appears to be more cost-effective than the conventional riparian buffer scenarios.

Installation Restoration Program: Rickenbacker Air National Guard Base, Columbus, Ohio. Additional Site Inspection Sampling. Addendum Number 1 to SI/RI/FS/RD Work Plan

DTIC Science & Technology

1989-10-01

Coord: Elev.PROTECTIVE CSG He~qht I Material /Type El e~. ________Diameter Elie.hI____ Depth BGS ___________Weep Hole (YIN) HSe.ht __ GUARD POSTS (YIN...Tremied I Y/14) SCR EE N Type Dimeter - --Slot Size Ck Type SUMP (YIN) Interval OGS Lcngth - 90tt0m Cop (YIN) BACKFILL PLUG Material ...for transport to the laboratory. The remaining liners will then be extruded and the material used for lithologic description and other analyses. The

Biodegradation of diesel by mixed bacteria immobilized onto a hybrid support of peat moss and additives: a batch experiment.

PubMed

Lee, Young-Chul; Shin, Hyun-Jae; Ahn, Yeonghee; Shin, Min-Chul; Lee, Myungjin; Yang, Ji-Won

2010-11-15

We report microbial cell immobilization onto a hybrid support of peat moss for diesel biodegradation. Three strains isolated from a site contaminated with diesel oil were used in this study: Acinetobacter sp., Gordonia sp., and Rhodococcus sp. To increase not only diesel adsorption but also diesel biodegradation, additives such as zeolite, bentonite, chitosan, and alginate were tested. In this study, a peat moss, bentonite, and alginate (2/2.9/0.1 g, w/w/w) hybrid support (PBA) was the best support matrix, considering both diesel physical adsorption capacity and mixed microbial immobilization. Copyright © 2010 Elsevier B.V. All rights reserved.

Contributions of separate reactions to the acid-base buffering of soils in brook floodplains (Central Forest State Reserve)

NASA Astrophysics Data System (ADS)

Sokolova, T. A.; Tolpeshta, I. I.; Rusakova, E. S.

2016-04-01

The acid-base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2-15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1-2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2-3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9-43%), the deprotonation of OH groups on the surface of illite crystals (3-19%), and the dissolution of unidentified aluminosilicates (9-14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1-5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.

49 CFR 192.614 - Damage prevention program.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., blasting, boring, tunneling, backfilling, the removal of aboveground structures by either explosive or...) Include the identity, on a current basis, of persons who normally engage in excavation activities in the...

49 CFR 192.614 - Damage prevention program.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., blasting, boring, tunneling, backfilling, the removal of aboveground structures by either explosive or...) Include the identity, on a current basis, of persons who normally engage in excavation activities in the...

49 CFR 192.614 - Damage prevention program.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., blasting, boring, tunneling, backfilling, the removal of aboveground structures by either explosive or...) Include the identity, on a current basis, of persons who normally engage in excavation activities in the...

49 CFR 192.614 - Damage prevention program.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., blasting, boring, tunneling, backfilling, the removal of aboveground structures by either explosive or...) Include the identity, on a current basis, of persons who normally engage in excavation activities in the...

49 CFR 192.614 - Damage prevention program.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., blasting, boring, tunneling, backfilling, the removal of aboveground structures by either explosive or...) Include the identity, on a current basis, of persons who normally engage in excavation activities in the...

Improved indexes for targeting placement of buffers of Hortonian runoff

Treesearch

M.G. Dosskey; Z. Qiu; M.J. Helmers; D.E. Eisenhauer

2011-01-01

Targeting specific locations within agricultural watersheds for installing vegetative buffers has been advocated as a way to enhance the impact of buffers and buffer programs on stream water quality. Existing models for targeting buffers of Hortonian, or infiltration-excess, runoff are not well developed. The objective was to improve on an existing soil survey–based...

Solar photodegradation of a textile azo dye using synthesized ZnO/Bentonite.

PubMed

Boutra, B; Trari, M

2017-03-01

The present work is devoted to the synthesis of a new photocatalyst ZnO (7.5%)/Bentonite prepared by impregnation method and its successful application for the degradation of Solophenyl Red 3BL (SR 3BL) under solar light (∼660 W/m 2 ). The X-ray diffraction (XRD) indicates mixed phases of the nanocomposite catalyst (ZnO/Bentonite), characterized by scanning electron microscopy, X-ray fluorescence and attenuated total reflection. The optical properties confirm the presence of the Wurtzite ZnO phase with an optical gap of 3.27 eV. The catalyst dose (0.25-1 gL -1 ), pH solution (2.5-11) and initial dye concentration (5-75 mg/L) are optimized. The optimal pH (∼6.7) is close to the natural environment. The photodegradation yield increases with decreasing the SR 3BL concentration. The equilibrium is reached within 160 min and the data are well fitted by the Langmuir-Hinshelwood model; the SR 3BL disappearance obeys to a first-order kinetic with an apparent rate constant of 10 - 2 mn - 1 . The best yield of SR 3BL photodegradation (92%) is achieved for a concentration of 5 mg/L and a catalyst dose of 0.75 gL -1 at free pH.

The combination of activated natural zeolite-bentonite to reduce Fe and Cu in refined bleached palm oil (RBPO) by using atomic absorption spectrophotometer method

NASA Astrophysics Data System (ADS)

Zakwan; Raja, PM; Giyanto

2018-02-01

Indonesia is one of the crude palm oil (CPO) production country in the world. As many products are derivated from the CPO, the quality must be increased continuously. One of the things that influence the quality of palm oil is the Fe and Cu content. The objective of this research was to reduce Fe and Cu content in Refined Bleached Palm Oil (RBPO). In processing CPO or Refined Bleachead Palm Oil (RBPO) may be contaminated by Fe and Cu from metal tank and pipe in the factory. The zeolite and bentonite was activated by maceration method using hydrochloric acid (0,1 N). Four batch reactions consisting of refined palm oil (RPO), activated natural zeolite-bentonite (ANZB) was bleached by heating and stirring them at about 105°C and 1200 rpm for 30 minutes. The results showed that all combinations of ANZB can reduce the Fe content. Thereafter, the optimal combination of ANZB was obtained in K1, K2 and K4 with Cu content 0.02 ppm. In the future, it is needed to study on the reduction of the Fe and Cu content in palm oil with the other adsorbent.

Design of optimal buffer layers for CuInGaSe2 thin-film solar cells(Conference Presentation)

NASA Astrophysics Data System (ADS)

Lordi, Vincenzo; Varley, Joel B.; He, Xiaoqing; Rockett, Angus A.; Bailey, Jeff; Zapalac, Geordie H.; Mackie, Neil; Poplavskyy, Dmitry; Bayman, Atiye

2016-09-01

Optimizing the buffer layer in manufactured thin-film PV is essential to maximize device efficiency. Here, we describe a combined synthesis, characterization, and theory effort to design optimal buffers based on the (Cd,Zn)(O,S) alloy system for CIGS devices. Optimization of buffer composition and absorber/buffer interface properties in light of several competing requirements for maximum device efficiency were performed, along with process variations to control the film and interface quality. The most relevant buffer properties controlling performance include band gap, conduction band offset with absorber, dopability, interface quality, and film crystallinity. Control of an all-PVD deposition process enabled variation of buffer composition, crystallinity, doping, and quality of the absorber/buffer interface. Analytical electron microscopy was used to characterize the film composition and morphology, while hybrid density functional theory was used to predict optimal compositions and growth parameters based on computed material properties. Process variations were developed to produce layers with controlled crystallinity, varying from amorphous to fully epitaxial, depending primarily on oxygen content. Elemental intermixing between buffer and absorber, particularly involving Cd and Cu, also is controlled and significantly affects device performance. Secondary phase formation at the interface is observed for some conditions and may be detrimental depending on the morphology. Theoretical calculations suggest optimal composition ranges for the buffer based on a suite of computed properties and drive process optimizations connected with observed film properties. Prepared by LLNL under Contract DE-AC52-07NA27344.

Progress in the understanding of the long-term corrosion behaviour of copper canisters

NASA Astrophysics Data System (ADS)

King, Fraser; Lilja, Christina; Vähänen, Marjut

2013-07-01

Copper has been proposed as a canister material for the disposal of spent nuclear fuel in a deep geologic repository in a number of countries worldwide. Since it was first proposed for this purpose in 1978, a significant number of studies have been performed to assess the corrosion performance of copper under repository conditions. These studies are critically reviewed and the suitability of copper as a canister material for nuclear waste is re-assessed. Over the past 30-35 years there has been considerable progress in our understanding of the expected corrosion behaviour of copper canisters. Crucial to this progress has been the improvement in the understanding of the nature of the repository environment and how it will evolve over time. With this improved understanding, it has been possible to predict the evolution of the corrosion behaviour from the initial period of warm, aerobic conditions in the repository to the long-term phase of cool, anoxic conditions dominated by the presence of sulphide. An historical review of the treatment of the corrosion behaviour of copper canisters is presented, from the initial corrosion assessment in 1978, through a major review of the corrosion behaviour in 2001, through to the current level of understanding based on the results of on-going studies. Compared with the initial corrosion assessment, there has been considerable progress in the treatment of localised corrosion, stress corrosion cracking, and microbiologically influenced corrosion of the canisters. Progress in the mechanistic modelling of the evolution of the corrosion behaviour of the canister is also reviewed, as is the continuing debate about the thermodynamic stability of copper in pure water. The overall conclusion of this critical review is that copper is a suitable material for the disposal of spent nuclear fuel and offers the prospect of containment of the waste for an extended period of time. The corrosion behaviour is influenced by the presence of the highly compacted bentonite buffer which (i) inhibits the transport of reactants to, and of corrosion products away from, the canister surface, (ii) limits the amount of atmospheric O2 initially trapped in the repository, and (iii) suppresses microbial activity close to the canister surface [5,6,9]. The environment will evolve with time as the initially trapped atmospheric O2 is consumed and as the canister cools. This evolution can be described as a transition from an early period of warm, oxidising conditions to an indefinite period of cool, anoxic conditions. In turn, this environmental evolution will impact the corrosion behaviour of the canister. Localised corrosion and stress corrosion cracking (SCC) will only be possible for a limited period of time initially when there is sufficient oxidant available to support these forms of corrosion. This aerobic phase is only expected to last a few tens or hundreds of years [10,11]. For the vast majority of the service life of the canister, the redox conditions will be determined by the absence of O2 and the presence of sulphide. Although obvious, it is important to remember that the corrosion behaviour is determined by the environmental conditions at the canister surface. Because of the presence of the compacted bentonite, the environment at the canister surface will be quite different from that in the ground water in the rock. In particular, the interfacial concentration of HS- will be small as the rate of corrosion in the presence of sulphide is transport limited [1,2,12]. The low interfacial [HS-] has important implications for various sulphur-related corrosion mechanisms. The relatively high salinity of the ground water (and, hence, of the bentonite pore water) promotes the general dissolution of copper and inhibits localised corrosion and SCC [5,6].

Toxic metal immobilization in contaminated sediment using bentonite- and kaolinite-supported nano zero-valent iron

NASA Astrophysics Data System (ADS)

Tomašević, D. D.; Kozma, G.; Kerkez, Dj. V.; Dalmacija, B. D.; Dalmacija, M. B.; Bečelić-Tomin, M. R.; Kukovecz, Á.; Kónya, Z.; Rončević, S.

2014-08-01

The objective of this study was to investigate the possibility of using supported nanoscale zero-valent iron with bentonite and kaolinite for immobilization of As, Pb and Zn in contaminated sediment from the Nadela river basin (Serbia). Assessment of the sediment quality based on the pseudo-total metal content (As, Pb and Zn) according to the corresponding Serbian standards shows its severe contamination, such that it requires disposal in special reservoirs and, if possible, remediation. A microwave-assisted sequential extraction procedure was employed to assess potential metal mobility and risk to the aquatic environment. According to these results, As showed lower risk to the environment than Pb and Zn, which both represent higher risk to the environment. The contaminated sediment, irrespective of the different speciation of the treated metals, was subjected to the same treatment. Semi-dynamic leaching test, based on leachability index and effective diffusion coefficients, was conducted for As-, Pb- and Zn-contaminated sediments in order to assess the long-term leaching behaviour. In order to simulate "worst case" leaching conditions, the test was modified using acetic and humic acid solution as leachants instead of deionized water. A diffusion-based model was used to elucidate the controlling leaching mechanisms; in the majority of samples, the controlling leaching mechanism appeared to be diffusion. Three different single-step leaching tests were applied to evaluate the extraction potential of examined metals. Generally, the test results indicated that the treated sediment is safe for disposal and could even be considered for "controlled utilization".

Acid-base buffering of soils in transitional and transitional-accumulative positions of undisturbed southern-taiga landscapes

NASA Astrophysics Data System (ADS)

Rusakova, E. S.; Ishkova, I. V.; Tolpeshta, I. I.; Sokolova, T. A.

2012-05-01

The method of continuous potentiometric titration (CPT) of soil water suspensions was used to evaluate the acid-base buffering of samples from the major genetic horizons of podzolic soils on a slope and soddy gley soils on the adjacent floodplain of a rivulet. In the soils of the slope, the buffering to acid upon titration from the pH of the initial titration point (ITP) to pH 3 in all the horizons was 1.5-2.0 times lower than that in the podzolic soils of the leveled interfluve, which could be due to the active leaching of exchangeable bases and oxalate-soluble aluminum and iron compounds with the later soil flows. In the soddy gley soils, the buffering to acid in the mineral horizons was 2-10 times higher than that in the podzolic soils. A direct dependence of the soil buffering to acid on the total content of exchangeable bases and on the content of oxalate-soluble aluminum compounds was found. A direct dependence of the buffering to basic upon titration from the ITP to pH 10 on the contents of the oxalate-soluble aluminum and organic matter was observed in the mineral horizons of all the studied soils. The soil treatment with Tamm's reagent resulted in the decrease of the buffering to acid in the soddy gley soils of the floodplain, as well as in the decrease of the buffering to basic in the soils on the slopes and in the soddy gley soils. It was also found that the redistribution of the mobile aluminum compounds between the eluvial, transitional, and transitional-accumulative positions in the undisturbed southern taiga landscapes leads to significant spatial differentiation of the acid-base buffering of the mineral soil horizons with a considerable increase in the buffer capacity of the soils within the transitional-accumulative terrain positions.

A newly discovered K-bentonite zone in the Lower Devonian of the Appalachian Basin; Basal Esopus and Needmore Formations (Late Pragian-Emsian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ver Straeten, C.A.

1992-01-01

The K-bentonite-rich interval of the Esopus Formation (eastern New York and northeastern Pennsylvania) overlies the coeval Oriskany/Glenerie/Ridgely Formations and ranges from 1 to 6.3 m in thickness. Six to seventeen soapy-feeling, yellow, tan, green, or gray clay to claystone beds (0.001 to 0.5 m-thick) interbedded with thin siltstone and chert beds (0.02--1 m-thick) characterize outcrops in eastern New York. Heavy mineral separates from these layers yield abundant uncorraded euhedral zircons and apatites, indicating that these are K-bentonites. In eastern Pennsylvania, the westernmost outcrop of the Esopus Formation displays a 2.3 m-thick massive, soapy-feeling clay to claystone-dominated interval. The presence ofmore » both coarse, highly abraded and small, fragile, pristine-appearing zircons and apatites from a 20 cm sampled interval may indicate a complex amalgamation/reworking history to the relatively thick, clay-dominated strata. Similar clay/claystone-rich strata have been found in the lower 0.15 to 1 m of the Beaverdam Member (Needmore Formation) in central Pennsylvania. Interbedded clays and claystones with or without minor siltstone beds characterize some outcrops. Other localities are clay-dominated, with minor amounts of quartz sand present in strata immediately overlying the Ridgely Sandstone. These newly discovered K-bentonite-rich strata mark a transition from shelfal orthoquartzites and carbonates to basinal black/dark gray shales similar to the overlying Middle Devonian Tioga ash interval. Deposition of ash-rich strata, associated with increased volcanic activity, coincided with subsidence of the foreland basin/relative sea level rise. These events were concurrent with a flush of siliciclastic sediments into the basin and are indicative of the onset of an early tectophase of the Devonian Acadian Orogeny.« less

High-throughput and multiplexed regeneration buffer scouting for affinity-based interactions.

PubMed

Geuijen, Karin P M; Schasfoort, Richard B; Wijffels, Rene H; Eppink, Michel H M

2014-06-01

Affinity-based analyses on biosensors depend partly on regeneration between measurements. Regeneration is performed with a buffer that efficiently breaks all interactions between ligand and analyte while maintaining the active binding site of the ligand. We demonstrated a regeneration buffer scouting using the combination of a continuous flow microspotter with a surface plasmon resonance imaging platform to simultaneously test 48 different regeneration buffers on a single biosensor. Optimal regeneration conditions are found within hours and consume little amounts of buffers, analyte, and ligand. This workflow can be applied to any ligand that is coupled through amine, thiol, or streptavidin immobilization. Copyright © 2014 Elsevier Inc. All rights reserved.

Modelling Iron-Bentonite Interactions

NASA Astrophysics Data System (ADS)

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

2009-04-01

The presence of both iron canisters and bentonitic clay in some engineered barrier system (EBS) designs for the geological disposal of high-level radioactive wastes creates the potential for chemical interactions which may impact upon the long-term performance of the clay as a barrier to radionuclide migration. Flooding of potential radionuclide sorption sites on the clay by ferrous ions and conversion of clay to non-swelling sheet silicates (e.g. berthierine) are two possible outcomes deleterious to long-term performance. Laboratory experimental studies of the corrosion of iron in clay show that corrosion product layers are generally thin (< 1 µm) with magnetite, siderite, or ‘green rust' occurring depending upon temperature and ambient partial pressure of carbon dioxide. In theory, incorporation of iron into clay alteration products could act as a ‘pump' to accelerate corrosion. However, the results of laboratory experiments to characterise the products of iron-bentonite interaction are less than unequivocal. The type and amounts of solid products appear to be strong functions of time, temperature, water/clay ratio, and clay and pore fluid compositions. For example, the products of high temperature experiments (> 250 °C) are dominated by chlorite, whereas lower temperatures produce berthierine, odinite, cronstedtite, or Fe-rich smectite. Unfortunately, the inevitable short-term nature of laboratory experimental studies introduces issues of metastability and kinetics. The sequential formation in time of minerals in natural systems often produces the formation of phases not predicted by equilibrium thermodynamics. Evidence from analogous natural systems suggests that the sequence of alteration of clay by Fe-rich fluids will proceed via an Ostwald step sequence. The computer code, QPAC, has been modified to incorporate processes of nucleation, growth, precursor cannibalisation, and Ostwald ripening to address the issues of the slow growth of bentonite alteration products. This, together with inclusion of processes of iron corrosion and diffusion, has enabled investigation of a representative model of the alteration of bentonite in a typical EBS environment. Simulations with fixed mineral surface areas show that berthierine dominates the solid product assemblage, with siderite replacing it at simulation times greater than 10 000 years. Simulations with time-dependent mineral surface areas show a sequence of solid alteration products, described by: magnetite -> cronstedtite -> berthierine -> chlorite. Using plausible estimates of mineral-fluid interfacial free energies, chlorite growth is not achieved until 5 000 years of simulation time. The results of this modelling work suggest that greater emphasis should be placed upon methods to up-scale the results of laboratory experiments to timescales of relevance to performance assessment.

32 CFR 240.6 - Retention program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... National Defense University (NDU) at Fort McNair in Washington, DC; and the Naval Postgraduate School (NPS... costs and required fees and books. All travel costs and necessary position back-fill for individuals...

32 CFR 240.6 - Retention program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... National Defense University (NDU) at Fort McNair in Washington, DC; and the Naval Postgraduate School (NPS... costs and required fees and books. All travel costs and necessary position back-fill for individuals...

Alternative methods to trench backfill.

DOT National Transportation Integrated Search

2005-04-30

Conduit structures dealing with hydraulic drainage needs in the Louisiana highway system include pipe culverts, pipe arch culverts, storm drains, sewers, etc. Although the Louisiana Department of Transportation and Development (LADOTD) has standard s...

The effect of respiration buffer composition on mitochondrial metabolism and function.

PubMed

Wollenman, Lucas C; Vander Ploeg, Matthew R; Miller, Mackinzie L; Zhang, Yizhu; Bazil, Jason N

2017-01-01

Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers.

The effect of respiration buffer composition on mitochondrial metabolism and function

PubMed Central

Wollenman, Lucas C.; Vander Ploeg, Matthew R.; Miller, Mackinzie L.; Zhang, Yizhu

2017-01-01

Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers. PMID:29091971

Interaction between clay-based sealing components and crystalline host rock

NASA Astrophysics Data System (ADS)

Priyanto, D. G.; Dixon, D. A.; Man, A. G.

The results of hydraulic-mechanical (H-M) numerical simulation of a shaft seal installed at a fracture zone (FZ) in a crystalline host rock using the finite element method are presented. The primary function of a shaft seal is to limit short-circuiting of the groundwater flow regime via the shaft in a deep geological repository. Two different stages of system evolution were considered in this numerical modelling. Stage 1 simulates the groundwater flow into an open shaft, prior to seal installation. Stage 2 simulates the groundwater flow into the shaft seal after seal installation. Four different cases were completed to: (i) evaluate H-M response due to the interaction between clay-based sealing material and crystalline host rock in the shaft seal structure; (ii) quantify the effect of the different times between the completion of the shaft excavation and the completion of shaft seal installation on the H-M response; and (iii) define the potential effects of different sealing material configurations. Shaft sealing materials include the bentonite-sand mixture (BSM), dense backfill (DBF), and concrete plug (CP). The BSM has greater swelling capacity and lower hydraulic conductivity ( K) than the DBF. The results of these analyses show that the decrease of the pore water pressure is concentrated along the fracture zone (FZ), which has the greatest K. As the time increases, the greatest decrease in pore water pressure is found around the FZ. Following FZ isolation and the subsequent filling of the shaft with water as it floods, the pore water pressure profile tends to recover back to the initial conditions prior to shaft excavation. The majority of the fluids that ultimately saturate the centre of the shaft seal flow radially inwards from the FZ. The time between the completion of the shaft excavation and the completion of shaft seal installation has a significant effect on the saturation time. A shorter time can reduce the saturation time. Since most of the inflow comes from the FZ, application of the BSM for extended distances above and below the FZ does not significantly affect the saturation time of the volume adjacent to the FZ. The application of BSM near the FZ rather than a low swelling capacity, more permeable filling material is very significant. This study assumed a perfect contact between seal materials and host rock. Limited to the assumptions used in this study, use of BSM near the FZ was found to increase the time before the centre of the shaft seal became fully saturated from between 4 and 30 years (when the DBF is used) to between 90 and 100 years (when the BSM is used).

High Temperature Thermosetting Polyimide Nanocomposites Prepared with Reduced Charge Organoclay

NASA Technical Reports Server (NTRS)

Campbell, Sandi; Liang, Margaret I.

2005-01-01

The naturally occurring sodium and calcium cations found in bentonite clay galleries were exchanged with lithium cations. Following the cation exchange, a series of reduced charge clays were prepared by heat treatment of the lithium bentonite at 130 C, 150 C, or 170 C. Inductively coupled plasma (ICP) analysis showed that heating the lithium clay at elevated temperatures reduced its cation exchange capacity. Ion exchange of heat-treated clays with either a protonated alkyl amine or a protonated aromatic diamine resulted in decreasing amounts of the organic modifier incorporated into the lithium clay. The level of silicate dispersion in a thermosetting polyimide matrix was dependent upon the temperature of Li-clay heat treatment as well as the organic modification. In general, clays treated at 150 C or 170 C, and exchanged with protonated octadcylamine or protonated 2,2'-dimethlybenzidine (DMBZ) showed a higher degree of dispersion than clays treated at 130 C, or exchanged with protonated dodecylamine. Dynamic mechanical analysis showed little change in the storage modulus or T(sub g) of the nanocomposites compared to the base resin. However, long term isothermal aging of the samples showed a significant decrease in the resin oxidative weight loss. Nanocomposite samples aged in air for 1000 hours at 288 C showed of to a decrease in weight loss compared to that of the base resin. This again was dependent on the temperature at which the Li-clay was heated and the choice of organic modification.

A preliminary evaluation of the nonfuel mineral potential of Somalia

USGS Publications Warehouse

Greenwood, W.R.

1982-01-01

Additional exploration in Somalia is warranted for a wide variety of metallic and nonmetallic deposits. In Precambrian rocks, deposit types favorable for exploration include: a banded iron formation; platinum-bearing mafic-ultramafic complexes; tin-bearing quartz veins; phosphorite; stratabound base-metal deposits; uranium associated with Precambrian(?) syenite; apatite, molybdenum, and alumina in alkalic rocks; Jurassic and Cretaceous black shales; possible bedded-barite and massive base- and precious-metal sulfide deposits; vein barite in Tertiary rocks in fault zones; sepiolite and bentonite for drilling muds and other industrial uses; celestite; possible Tertiary zeolite; and uranium deposits. Several of these deposit types could be Jointly developed and integrated into domestic industries; for example, phosphate and gypsum, or bentonite for pelletized iron from the banded iron deposits. Other deposits such as barite and sepiolite are of value because of their proximity to major drilling operations in the Arabian Gulf. Still other deposits, such as alumina and banded iron, might be marketable because of proximity to aluminum and iron-refining industries now being constructed in Saudi Arabia. Some deposits, such as celestite, can be developed with little capital investment; others, such as the iron deposits, would require large capital commitments. Exploration and evaluation for many of these deposits can be accomplished by Somali geologists with a few advisors. Most of the deposits require feasibility studies conducted by teams of economic geologists, extractive metallurgists, and economists. Some marginal deposits could be exploited if cooperative development schemes could be negotiated with governments in nearby countries.

Fabrication and characterization of fine ceramic based on alumina, bentonite, and glass bead

NASA Astrophysics Data System (ADS)

Sebayang, P.; Nurdina; Simbolon, S.; Kurniawan, C.; Yunus, M.; Setiadi, E. A.; Sitorus, Z.

2018-03-01

Fabrication of fine ceramics based on alumina, bentonite and glass bead has been carried out by powder metallurgy. The preparation of powder has been performed using High Energy Milling (HEM) with wet milling process and using toluene as medium for 2 hours. The powder milling result was dried in oven at 100 °C for 24 hours. After that, the powder was compacted into pellet by using hydraulic press with 80 kgf/cm2 pressure at room temperature. Then, the pellet was sintered at 900 °C for 4 hours. Materials characterization such as physical properties (true density, bulk density, porosity, and water absorption), average particle diameter, hardness, microstructure and phase were measured by Archimedes method, Particle Size Analyzer (PSA), Hardness Vickers (HV), Scanning Electron Microscope (SEM-EDX) and X-Ray Diffraction (XRD). From the result, the optimum condition is sample D (with addition of 30 wt.% γ-Al2O3) with sintering temperature of 900 °C for 4 hours. At this condition, these properties were measured: average particle diameter of 4.27 μm, true density of 2.32 g/cm3, porosity of 5.57%, water absorption of 2.46%, bulk density of 2.39 g/cm3, and hardness of 632 HV. The fine ceramic has four phases with albite (Al2NaO8Si3) and quartz (SiO2) as dominant phases and corundum (Al2O3) and nepheline (AlNaO4Si) as minor phases.

Assessment and preliminary design of an energy buffer for regenerative braking in electric vehicles

NASA Technical Reports Server (NTRS)

Buchholz, R.; Mathur, A. K.

1979-01-01

Energy buffer systems, capable of storing the vehicle energy during braking and reusing this stored energy during acceleration, were examined. Some of these buffer systems when incorporated in an electric vehicle would result in an improvement in the performance and range under stop and go driving conditions. Buffer systems considered included flywheels, hydropneumatic, pneumatic, spring, and regenerative braking. Buffer ranking and rating criteria were established. Buffer systems were rated based on predicted range improvements, consumer acceptance, driveability, safety, reliability and durability, and initial and life cycle costs. A hydropneumatic buffer system was selected.

30 CFR 715.14 - Backfilling and grading.

Code of Federal Regulations, 2011 CFR

2011-07-01

... configuration and the outslopes of the plateau shall not exceed 1v:2h, except where engineering data... land use or may result in additional erosion and sedimentation. (j) Covering coal and acid-forming...

Evaluation of hydraulic plate compactor.

DOT National Transportation Integrated Search

2014-12-01

This report presents the results of two parallel field investigations consisting of utility trench backfill compaction tests. The field : investigation at State College, Pa. was conducted to establish baseline measurements using a walk-behind vibrato...

Public Notice: KYV0070

EPA Pesticide Factsheets

The U.S. Environmental Protection Agency, Region 4 intends to issue one Class 5 UIC permit to the Warrior Coal, LLC. This permit would cover six (6) mine-backfill injection wells located in Hopkins County, Kentucky.

30 CFR 817.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... terrain if the following requirements are met: (1) All vegetative and organic material shall be removed... to conserve soil moisture, ensure stability, and control erosion on final-graded slopes, if the...

30 CFR 817.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... terrain if the following requirements are met: (1) All vegetative and organic material shall be removed... to conserve soil moisture, ensure stability, and control erosion on final-graded slopes, if the...

30 CFR 817.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... terrain if the following requirements are met: (1) All vegetative and organic material shall be removed... to conserve soil moisture, ensure stability, and control erosion on final-graded slopes, if the...

30 CFR 817.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... terrain if the following requirements are met: (1) All vegetative and organic material shall be removed... to conserve soil moisture, ensure stability, and control erosion on final-graded slopes, if the...

30 CFR 817.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... terrain if the following requirements are met: (1) All vegetative and organic material shall be removed... to conserve soil moisture, ensure stability, and control erosion on final-graded slopes, if the...

Investigation of the line arrangement of 2D resistivity surveys for 3D inversion*

NASA Astrophysics Data System (ADS)

Inoue, Keisuke; Nakazato, Hiroomi; Takeuchi, Mutsuo; Sugimoto, Yoshihiro; Kim, Hee Joon; Yoshisako, Hiroshi; Konno, Michiaki; Shoda, Daisuke

2018-03-01

We have conducted numerical and field experiments to investigate the applicability of electrode configurations and line layouts commonly used for two-dimensional (2D) resistivity surveys to 3D inversion. We examined three kinds of electrode configurations and two types of line arrangements, for 16 resistivity models of a conductive body in a homogeneous half-space. The results of the numerical experiment revealed that the parallel-line arrangement was effective in identifying the approximate location of the conductive body. The orthogonal-line arrangement was optimal for identifying a target body near the line intersection. As a result, we propose that parallel lines are useful to highlight areas of particular interest where further detailed work with an intersecting line could be carried out. In the field experiment, 2D resistivity data were measured on a loam layer with a backfilled pit. The reconstructed resistivity image derived from parallel-line data showed a low-resistivity portion near the backfilled pit. When an orthogonal line was added to the parallel lines, the newly estimated location of the backfilled pit coincided well with the actual location. In a further field application, we collected several 2D resistivity datasets in the Nojima Fault area in Awaji Island. The 3D inversion of these datasets provided a resistivity distribution corresponding to the geological structure. In particular, the Nojima Fault was imaged as the western boundary of a low-resistivity belt, from only two orthogonal lines.

RF driven sulfur lamp having driving electrodes arranged to cool the lamp

DOEpatents

Gabor, George; Orr, Thomas Robert; Greene, Charles Maurice; Crawford, Douglas Gordon; Berman, Samuel Maurice

1998-01-01

A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance.

RF driven sulfur lamp having driving electrodes arranged to cool the lamp

DOEpatents

Gabor, G.; Orr, T.R.; Greene, C.M.; Crawford, D.G.; Berman, S.M.

1998-10-20

A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance. 17 figs.

RF driven sulfur lamp having driving electrodes which face each other

DOEpatents

Gabor, G.; Orr, T.R.; Greene, C.M.; Crawford, D.G.; Berman, S.M.

1999-06-22

A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance. 17 figs.

RF driven sulfur lamp having driving electrodes which face each other

DOEpatents

Gabor, George; Orr, Thomas Robert; Greene, Charles Maurice; Crawford, Douglas Gordon; Berman, Samuel Maurice

1999-01-01

A high intensity discharge lamp without mercury is disclosed radiating a selected spectrum of which can be almost entirely in the visible range from an envelope that contains a sulfur containing substance. The lamp utilizes a signal source that generates an excitation signal that is externally coupled to the exterior surface of the envelope to excite the enclosed sulfur containing substance. Various embodiments of the lamp use electrodes adjacent the envelope to couple the excitation signal thereto with the face of the electrodes shaped to complement the shape of the exterior surface of the envelope. Two shapes discussed are spherical and cylindrical. To minimize filamentary discharges each envelope may include an elongated stem affixed to the exterior thereof whereby a rotational subsystem spins the envelope. In yet another embodiment the envelope has a Dewar configuration with two electrodes, one positioned near the external curved side surface of the body, and a second to the inner surface of the hole through the envelope. Further, the envelope may contain a backfill of a selected inert gas to assist in the excitation of lamp with that backfill at a pressure of less than 1 atmosphere, wherein the backfill pressure is directly related to the increase or decrease of peak output and inversely related to the increase and decrease of the emitted spectrum from the envelope. The emitting fill can be less than 6 mg/cc, or at least 2 mg/cc of the envelope of a sulfur containing substance.

Recent Ground Hold and Rapid Depressurization Testing of Multilayer Systems

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.

2014-01-01

In the development of flight insulation systems for large cryogenic orbital storage (spray on foam and multilayer insulation), testing need include all environments that are experienced during flight. While large efforts have been expended on studying, bounding, and modeling the orbital performance of the insulation systems, little effort has been expended on the ground hold and ascent phases of a mission. Historical cryogenic in-space systems that have flown have been able to ignore these phases of flight due to the insulation system being within a vacuum jacket. In the development phase of the Nuclear Mars Vehicle and the Shuttle Nuclear Vehicle, several insulation systems were evaluated for the full mission cycle. Since that time there had been minimal work on these phases of flight until the Constellation program began investigating cryogenic service modules and long duration upper stages. With the inception of the Cryogenic Propellant Storage and Transfer Technology Demonstration Mission, a specific need was seen for the data and as such, several tests were added to the Cryogenic Boil-off Reduction System liquid hydrogen test matrix to provide more data on a insulation system. Testing was attempted with both gaseous nitrogen (GN2) and gaseous helium (GHe) backfills. The initial tests with nitrogen backfill were not successfully completed due to nitrogen liquefaction and solidification preventing the rapid pumpdown of the vacuum chamber. Subsequent helium backfill tests were successful and showed minimal degradation. The results are compared to the historical data.

Thermally conductive cementitious grout for geothermal heat pump systems

DOEpatents

Allan, Marita

2001-01-01

A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

Finite Element Stress Analysis of Spent Nuclear Fuel Disposal Canister in a Deep Geological Repository

NASA Astrophysics Data System (ADS)

Kwon, Young Joo; Choi, Jong Won

This paper presents the finite element stress analysis of a spent nuclear fuel disposal canister to provide basic information for dimensioning the canister and configuration of canister components and consequently to suggest the structural analysis methodology for the disposal canister in a deep geological repository which is nowadays very important in the environmental waste treatment technology. Because of big differences in the pressurized water reactor (PWR) and the Canadian deuterium and uranium reactor (CANDU) fuel properties, two types of canisters are conceived. For manufacturing, operational reasons and standardization, however, both canisters have the same outer diameter and length. The construction type of canisters introduced here is a solid structure with a cast insert and a corrosion resistant overpack. The structural stress analysis is carried out using a finite element analysis code, NISA, and focused on the structural strength of the canister against the expected external pressures due to the swelling of the bentonite buffer and the hydrostatic head. The canister must withstand these large pressure loads. Consequently, canisters presented here contain 4 PWR fuel assemblies and 33×9 CANDU fuel bundles. The outside diameter of the canister for both fuels is 122cm and the cast insert diameter is 112cm. The total length of the canister is 483cm with the lid/bottom and the outer shell of 5cm.

Effect of dewatering on seismic performance of multi-anchor wall due to high ground water level

NASA Astrophysics Data System (ADS)

Kobayashi, Makoto; Miura, Kinya; Konami, Takeharu; Hayashi, Taketo; Sato, Hiroki

2017-10-01

Previous research reported that the ground water in the backfill of reinforced soil wall made it deteriorate. According to the damage investigation of Great East Earthquake 2011, the reinforced soil structure due to high ground water level by seismic wave were deformed remarkably. Some of them classified ultimate limit state or restorability limit state. However, more than 90% of reinforced soil structure, which suffered from this earthquake, were classified into no damage condition. Therefore, it is necessary that the seismic behaviors of multi-anchor wall due to seepage flow should be clarified in order to adopt the performance-based design in such reinforced soil structure. In this study, a series of centrifugal shaking table tests were conducted to investigate the seismic behavior of multi-anchor wall due to high ground water level. The reinforced drainage pipes were installed into the backfill in order to verify the dewatering effect and additional reinforcement. Furthermore, to check only the dewatering effect, the model tests was carried out with several ground water table that was modeled the case reinforced drainage pipes installed. The test results show unique behavior of reinforced region that moved integrally. This implies that the reinforced region has been behaved as if it became one mass, and this behavior make this structure increase seismic performance. Thus, the effectiveness of dewatering was observed remarkably because of decreasing the inertial force during earthquake.

Buffer-regulated biocorrosion of pure magnesium.

PubMed

Kirkland, Nicholas T; Waterman, Jay; Birbilis, Nick; Dias, George; Woodfield, Tim B F; Hartshorn, Richard M; Staiger, Mark P

2012-02-01

Magnesium (Mg) alloys are being actively investigated as potential load-bearing orthopaedic implant materials due to their biodegradability in vivo. With Mg biomaterials at an early stage in their development, the screening of alloy compositions for their biodegradation rate, and hence biocompatibility, is reliant on cost-effective in vitro methods. The use of a buffer to control pH during in vitro biodegradation is recognised as critically important as this seeks to mimic pH control as it occurs naturally in vivo. The two different types of in vitro buffer system available are based on either (i) zwitterionic organic compounds or (ii) carbonate buffers within a partial-CO(2) atmosphere. This study investigated the influence of the buffering system itself on the in vitro corrosion of Mg. It was found that the less realistic zwitterion-based buffer did not form the same corrosion layers as the carbonate buffer, and was potentially affecting the behaviour of the hydrated oxide layer that forms on Mg in all aqueous environments. Consequently it was recommended that Mg in vitro experiments use the more biorealistic carbonate buffering system when possible.

Accelerating Science with the NERSC Burst Buffer Early User Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhimji, Wahid; Bard, Debbie; Romanus, Melissa

NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burstmore » Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.« less

Effect of Different Gums on Rheological Properties of Slurry

NASA Astrophysics Data System (ADS)

Weikey, Yogita; Sinha, S. L.; Dewangan, S. K.

2018-02-01

This paper presents the effect of different natural gums on water-bentonite slurry, which is used as based fluid in water based drilling fluid. The gums used are Babul gum (Acacia nilotica), Dhawda gum (Anogeissus latifolia), Katira gum (Cochlospermum religiosum) and Semal gum (Bombax ceiba). For present investigation, samples have been prepared by varying concentration of gums. The variation of shear stress and shear rate has been plotted and on the basis of this behaviour of fluids has been explained. The value of k and n are calculated by using Power law. R 2 values are also calculated to support the choice of gum selection.

30 CFR 717.15 - Disposal of excess rock and earth materials on surface areas.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR INITIAL PROGRAM REGULATIONS UNDERGROUND MINING GENERAL PERFORMANCE... materials produced from an underground mine and not disposed in underground workings or used in backfilling...

78 FR 65376 - Notice of Inventory Completion: University of Michigan, Ann Arbor, MI

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-31

... operator found the remains in displaced dirt during construction activities associated with a housing... excavation. A backhoe had removed some of the remains. These were collected from the backfill dirt...

30 CFR 816.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... organic material shall be removed from the area. (2) The topsoil on the area shall be removed, segregated... may be allowed by the regulatory authority where— (1) Needed to conserve soil moisture, ensure...

30 CFR 816.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... organic material shall be removed from the area. (2) The topsoil on the area shall be removed, segregated... may be allowed by the regulatory authority where— (1) Needed to conserve soil moisture, ensure...

30 CFR 816.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... organic material shall be removed from the area. (2) The topsoil on the area shall be removed, segregated... may be allowed by the regulatory authority where— (1) Needed to conserve soil moisture, ensure...

30 CFR 816.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... organic material shall be removed from the area. (2) The topsoil on the area shall be removed, segregated... may be allowed by the regulatory authority where— (1) Needed to conserve soil moisture, ensure...

30 CFR 816.102 - Backfilling and grading: General requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... organic material shall be removed from the area. (2) The topsoil on the area shall be removed, segregated... may be allowed by the regulatory authority where— (1) Needed to conserve soil moisture, ensure...

Pervious Pavement System Evaluation

EPA Science Inventory

Porous pavement is a low impact development stormwater control. The Urban Watershed Management Branch is evaluating interlocking concrete pavers as a popular implementation. The pavers themselves are impermeable, but the spaces between the pavers are backfilled with washed, grade...

Photonic integrated circuit optical buffer for packet-switched networks.

PubMed

Burmeister, Emily F; Mack, John P; Poulsen, Henrik N; Masanović, Milan L; Stamenić, Biljana; Blumenthal, Daniel J; Bowers, John E

2009-04-13

A chip-scale optical buffer performs autonomous contention resolution for 40-byte packets with 99% packet recovery. The buffer consists of a fast, InP-based 2 x 2 optical switch and a silica-on-silicon low loss delay loop. The buffer is demonstrated in recirculating operation, but may be reconfigured in feed-forward operation for longer packet lengths. The recirculating buffer provides packet storage in integer multiples of the delay length of 12.86 ns up to 64.3 ns with 98% packet recovery. The buffer is used to resolve contention between two 40 Gb/s packet streams using multiple photonic chip optical buffers.

Magnetic resonance imaging of clays: swelling, sedimentation, dissolution

NASA Astrophysics Data System (ADS)

Dvinskikh, Sergey; Furo, Istvan

2010-05-01

While most magnetic resonance imaging (MRI) applications concern medical research, there is a rapidly increasing number of MRI studies in the field of environmental science and technology. In this presentation, MRI will be introduced from the latter perspective. While many processes in these areas are similar to those addressed in medical applications of MRI, parameters and experimental implementations are often quite different and, in many respects, far more demanding. This hinders direct transfer of existing methods developed for biomedical research, especially when facing the challenging task of obtaining spatially resolved quantitative information. In MRI investigation of soils, clays, and rocks, mainly water signal is detected, similarly to MRI of biological and medical samples. However, a strong variation of water mobility and a wide spread of water spin relaxation properties in these materials make it difficult to use standard MRI approaches. Other significant limitations can be identified as following: T2 relaxation and probe dead time effects; molecular diffusion artifacts; varying dielectric losses and induced currents in conductive samples; limited dynamic range; blurring artifacts accompanying drive for increasing sensitivity and/or imaging speed. Despite these limitations, by combining MRI techniques developed for solid and liquid states and using independent information on relaxation properties of water, interacting with the material of interest, true images of distributions of both water, material and molecular properties in a wide range of concentrations can be obtained. Examples of MRI application will be given in the areas of soil and mineral research where understanding water transport and erosion processes is one of the key challenges. Efforts in developing and adapting MRI approaches to study these kinds of systems will be outlined as well. Extensive studies of clay/water interaction have been carried out in order to provide a quantitative measure of clay distribution in extended samples during different physical processes such as swelling, dissolution, and sedimentation on the time scale from minutes to years [1-3]. To characterize the state of colloids that form after/during clay swelling the water self-diffusion coefficient was measured on a spatially resolved manner. Both natural clays and purified and ion-exchanged montmorillonite clays were investigated. The primary variables were clay composition and water ionic strength. These results have a significant impact for engineering barriers for storage of spent nuclear fuel where clay erosion by low salinity water must be addressed. Presented methods were developed under the motivation of using bentonite clays as a buffer medium to build in-ground barriers for the encapsulation of radioactive waste. Nevertheless, the same approaches can be found suitable in other applications in soil and environmental science to study other types of materials as they swell, dissolve, erode, or sediment. Acknowledgements: This work has been supported by the Swedish Nuclear Fuel and Waste Management Co (SKB) and the Swedish Research Council VR. [1] N. Nestle, T. Baumann, R. Niessner, Magnetic resonance imaging in environmental science. Environ. Sci. Techn. 36 154A (2002). [2] S. V. Dvinskikh, K. Szutkowski, I. Furó. MRI profiles over a very wide concentration ranges: application to swelling of a bentonite clay. J. Magn. Reson. 198 146 (2009). [3] S. V. Dvinskikh, I. Furó. Magnetic resonance imaging and nuclear magnetic resonance investigations of bentonite systems. Technical Report, TR-09-27, SKB (2009), www.skb.se.

Near single-crystalline, high-carrier-mobility silicon thin film on a polycrystalline/amorphous substrate

DOEpatents

Findikoglu, Alp T [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM; Arendt, Paul N [Los Alamos, NM; Matias, Vladimir [Santa Fe, NM; Choi, Woong [Los Alamos, NM

2009-10-27

A template article including a base substrate including: (i) a base material selected from the group consisting of polycrystalline substrates and amorphous substrates, and (ii) at least one layer of a differing material upon the surface of the base material; and, a buffer material layer upon the base substrate, the buffer material layer characterized by: (a) low chemical reactivity with the base substrate, (b) stability at temperatures up to at least about 800.degree. C. under low vacuum conditions, and (c) a lattice crystal structure adapted for subsequent deposition of a semiconductor material; is provided, together with a semiconductor article including a base substrate including: (i) a base material selected from the group consisting of polycrystalline substrates and amorphous substrates, and (ii) at least one layer of a differing material upon the surface of the base material; and, a buffer material layer upon the base substrate, the buffer material layer characterized by: (a) low chemical reactivity with the base substrate, (b) stability at temperatures up to at least about 800.degree. C. under low vacuum conditions, and (c) a lattice crystal structure adapted for subsequent deposition of a semiconductor material, and, a top-layer of semiconductor material upon the buffer material layer.

Riparian buffer design guidelines for water quality and wildlife habitat functions on agricultural landscapes in the Intermountain West

Treesearch

Craig W. Johnson; Susan Buffler

2008-01-01

Intermountain West planners, designers, and resource managers are looking for science-based procedures for determining buffer widths and management techniques that will optimize the benefits riparian ecosystems provide. This study reviewed the riparian buffer literature, including protocols used to determine optimum buffer widths for water quality and wildlife habitat...

8. Credit JPL. Photographic copy of photograph, view west down ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. Credit JPL. Photographic copy of photograph, view west down from Test Stand 'A' tower across newly installed tunnel tube to corner of Building 4201/E-2, Test Stand 'A' Workshop (demolished in 1985). Note the wooden retaining structure erected in the foreground to retain earth once the tunnel trench is backfilled (this retaining wall remained in 1994). Note also the propellant control piping on the Test Stand 'A' platform in the immediate foreground. (JPL negative no. 384-1547-C, 6 February 1957) - Jet Propulsion Laboratory Edwards Facility, Test Stand A, Edwards Air Force Base, Boron, Kern County, CA