Effects of the Orientation of Clay Particles and Ionic Strength on Diffusion and Activation Enthalpies of I−and Cs+ Ions in Compacted Bentonite

2004 ◽  
Vol 824 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Ionic Strength ◽  
Free Water ◽  
Interlayer Distance ◽  
Perpendicular Direction ◽  
Dry Density ◽  
Clay Particles ◽  
Compacted Bentonite ◽  
Parallel Direction ◽  
Cs Ions ◽  
And Diffusion

AbstractApparent diffusivities (Da) for I− and Cs+ in compacted Na-smectite were studied as a function of smectite's dry density (0.9–1.4 Mg/m3, ionic strength (IS: [NaCl]=0.01, 0.51 M), temperature (22–60 °C) and diffusion directionto the orientated direction of smectite particles. The Da-values for both ions in parallel direction to the orientated direction showed a tendency to be higher than those in the perpendicular direction at lowIS. The Da-values for I− showed different trends depending on diffusion direction and dry density at high IS, but Da-values for Cs+ increased with increasing IS in both diffusion directions. The activation enthalpies (ΔEa) for I−, slightly higher than that of diffusivity in free water (Do) at low IS, similar level to that of Do at high IS, increased with increasing dry density. While, ΔEa-values for Cs+, clearly higher than that of Do for all conditions, increased with increasing dry density. Since it is known that interlayer distance depends on both dry density and IS, diffusive pathway is considered to differ depending on the charge of diffusion species.

Effects of the Orientation of Clay Particles and Ionic Strength on Diffusion and Activation Enthalpies of I− and Cs+ Ions in Compacted Bentonite (II)

2006 ◽  
Vol 932 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Free Water ◽  
Dry Density ◽  
Combined Effects ◽  
Clay Particles ◽  
Compacted Bentonite ◽  
Parallel Direction ◽  
Ionic Diffusivity ◽  
Cs Ions

ABSTRACTThe apparent diffusivities (Da) and activation enthalpies (ΔEa) for I− and Cs+ ions in compacted Na-smectite were obtained in the parallel and perpendicular directions to the orientation of smectite particles as a function of smectite's dry density (0.9-1.4 Mg/m3), salinity ([NaCl]=0.01, 0.51 M) and temperature (295-333 K). The Da-values for both ions tended to be higher in the parallel direction than in the perpendicular direction to the orientation of smectite particles. The Da-values of I− ions in the parallel direction decreased with increasing salinity only at low dry density, but those of Cs+ ions increased with increasing salinity for all conditions. Based on this, it is interpreted that I− ions predominantly diffuse in external pores and Cs+ ions diffuse in both interlayer and external pores. The ΔEa-values forI− ions are at similar levels as those for the ionic diffusivity in free water (D°) of I− ions at low dry density and increased with increasing dry density. The ΔEa-values for Cs+ ions are higher than those for the D° of Cs+ ions even at low dry density and increased with increasing dry density. Such high ΔEa-values for Cs+ ions are considered to be due to the combined effects of the ion exchange enthalpy between Cs+ and Na+ ions in smectite and the lowering in the activity of porewater.

Diffusion Behavior of Humic Acid in Compacted Bentonite: Effect of Ionic Strength, Dry Density and Molecular Weight of Humic Acid

2008 ◽  
Author(s):  
Kazuki Iijima ◽  
Seiichi Kurosawa ◽  
Minoru Tobita ◽  
Satoshi Kibe ◽  
Yuji Ohuchi
Keyword(s):  
Molecular Weight ◽  
Humic Acid ◽  
Ionic Strength ◽  
Dry Density ◽  
Diffusion Behavior ◽  
Compacted Bentonite

Thermodynamic Properties of Water in Compacted Bentonite Under External Pressure-free Conditions

1994 ◽  
Vol 353 ◽  
Author(s):  
Yuji Torikai ◽  
Seichi Sato ◽  
Hiroshi Ohashi
Keyword(s):  
Thermodynamic Properties ◽  
Water Content ◽  
Pure Water ◽  
Bound Water ◽  
Free Water ◽  
External Pressure ◽  
Dry Density ◽  
X Ray Diffraction ◽  
Molar Gibbs Free Energy ◽  
Compacted Bentonite

AbstractIn an attempt to determine the thermodynamic properties of water in bentonite, the vapor pressure of water in compacted bentonite was measured as functions of water content and temperature, under external pressure-free conditions. The relative partial molar Gibbs free energy ΔGH2O, enthalpy ΔHH2Oand entropy ΔSH2O of tne waler in bentonite were determined at temperature of 298.15K. The interlayer distance of montmorillonite in bentonite was also measured by X-ray diffraction.It is probable that one fourth of the total water included in the bentonite at water content of 20.3wt% and dry density of 1.76 × 103kg/m3 is nearly free water; the water is not regarded as dilute electrolytic solution but the solution with higher ionic strength. Another one fourth of the water in the bentonite at the water content is bound water; the partial molar entropy of the bound water referred to pure water is from a half to whole of solidification entropy of pure water. The remainder is regarded as intermediately bound water.

Diffusion and Migration of Ions in Sedimentary Rock Matrix: Effects of Ionic Strength and Tracer Concentration on Diffusion of Cs+ ions in Sandstone

2003 ◽  
Vol 807 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Ionic Strength ◽  
Matrix Effects ◽  
Chemical Properties ◽  
Effective Diffusivity ◽  
Concentration Profiles ◽  
Tracer Concentration ◽  
And Migration ◽  
Physical And Chemical ◽  
Cs Ions ◽  
And Chemical Properties

ABSTRACTIn-diffusion experiments for Cs+ and I− in sandstone were performed as a function of ionic strength ([NaCl]=0.01, 0.51M) and tracer concentration ([CsI]=7.5E-5, 1.5E-2M) together with the measurements of the physical and chemical properties of sandstone, and apparent diffusivities (Da) for Cs+ were obtained. The obtained Da-values for Cs+ scarcely depended on [NaCl], but increased with increasing [Cs+]. This trend is consistent with that of rock capacity factors (α), indicating that distribution coefficient (Kd) onto sandstone and effective diffusivity scarcely depend on [NaCl]. The concentration profiles of I− were all in already breakthrough. Although this indicates that I− diffusion is faster than that of Cs+, the concentration profiles of I− may have been lower than those for blank samples, judging synthetically from the correlations between α-values and the concentration profiles of Cs+ and from the concentration profiles of I− in the blank samples. Finally, the effects of [Cs+] and[NaCl] on Kd/-values for Cs+ were discussed from the viewpoint of adsorption by ion exchange and electrostatic attraction. The kd-values were considered to be combined sorption by both reactions.

Influence of electric field intensity, ionic strength, and migration distance on the mobility and diffusion in DNA surface electrophoresis

2006 ◽  
Vol 27 (7) ◽  
pp. 1312-1321 ◽  
Author(s):  
Bingquan Li ◽  
Xiaohua Fang ◽  
Haobin Luo ◽  
Eric Petersen ◽  
Young-Soo Seo ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Migration Distance ◽  
And Migration ◽  
And Diffusion

Influence of Operational Conditions on Retardation Parameters Measured by Diffusion Experiment in Compacted Bentonite

2010 ◽  
Vol 1265 ◽  
Author(s):  
Ishii Yasuo ◽  
Yoshimi Seida ◽  
Yukio Tachi ◽  
Hideki Yoshikawa
Keyword(s):  
Mass Transfer ◽  
Ionic Strength ◽  
Test Solution ◽  
Test Method ◽  
Diffusion Experiment ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
Operational Conditions ◽  
Diffusion Data ◽  
Compacted Bentonite

AbstractInfluence of operation factors in diffusion test of compacted bentonite (such as agitation of test solution in the reservoir, feed rate of the test solution and mass transfer resistance in the filter) on the diffusion data was examined by reservoir depletion (RD) test method using Cs+. The influence of these factors on the diffusion data was also analyzed based on the mathematical sorption-diffusion model which considered the feed of test solution and mass transfer resistance in the filter as well. The reservoir depletion data showed some remarkable influences of these operational conditions, especially in the system with low ionic strength. Change in mass transfer resistance at filter-compacted bentonite due to the operational conditions was found to be potential factor which disturb the diffusion data. The influence was reduced in the system with high ionic strength of solution.

Altered brainstem anatomy in migraine

Cephalalgia ◽  
2017 ◽  
Vol 38 (3) ◽  
pp. 476-486 ◽  
Author(s):  
Kasia K Marciszewski ◽  
Noemi Meylakh ◽  
Flavia Di Pietro ◽  
Vaughan G Macefield ◽  
Paul M Macey ◽  
...  
Keyword(s):  
Grey Matter ◽  
Diffusion Tensor ◽  
Free Water ◽  
Trigeminal System ◽  
Grey Matter Volume ◽  
Matter Volume ◽  
Diffusion Weighted Images ◽  
Diffusion Tensor Images ◽  
And Diffusion ◽  
Brainstem Anatomy

Background The exact mechanisms responsible for migraine remain unknown, although it has been proposed that changes in brainstem anatomy and function, even between attacks, may contribute to the initiation and maintenance of headache during migraine attacks. The aim of this investigation is to use brainstem-specific analyses of anatomical and diffusion weighted images to determine if the trigeminal system displays altered structure in individuals with migraine. Methods Voxel-based morphometry of T1-weighted anatomical images (57 controls, 24 migraineurs) and diffusion tensor images (22 controls, 24 migraineurs) were used to assess brainstem anatomy in individuals with migraine compared with controls. Results We found grey matter volume decreases in migraineurs in the spinal trigeminal nucleus and dorsomedial pons. In addition, reduced grey matter volume and increased free water diffusivity occurred in areas of the descending pain modulatory system, including midbrain periaqueductal gray matter, dorsolateral pons, and medullary raphe. These changes were not correlated to migraine frequency, duration, intensity or time to next migraine. Conclusion Brainstem anatomy changes may underlie changes in activity that result in activation of the ascending trigeminal pathway and the perception of head pain during a migraine attack.

Size distribution analysis of colloid generated from compacted bentonite in low ionic strength aqueous solutions

2014 ◽  
Vol 95 ◽  
pp. 284-293 ◽  
Author(s):  
Nairoby Albarran ◽  
Claude Degueldre ◽  
Tiziana Missana ◽  
Ursula Alonso ◽  
Miguel García-Gutiérrez ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Size Distribution ◽  
Distribution Analysis ◽  
Compacted Bentonite ◽  
Low Ionic Strength

Influence of alkalinity on the hydraulic conductivity of bentonite-sand liners

1998 ◽  
Vol 38 (2) ◽  
pp. 151-157 ◽  
Author(s):  
David G. Wareham ◽  
Arman Farajollahi ◽  
Mark W. Milke
Keyword(s):  
Hydraulic Conductivity ◽  
Charge Density ◽  
Liquid Limit ◽  
Permeability Test ◽  
Clay Particles ◽  
Sand Mixture ◽  
Compacted Bentonite ◽  
Limit Test ◽  
The Impact

The aim of this research is to record the impact of specific changes in the molding water alkalinity on the hydraulic conductivity of a compacted bentonite-sand mixture. Adding alkalinity to the molding water influences the charge density existing on the clay particles. This can increase the amount of separation of the bentonite particles which causes a decrease in the hydraulic conductivity of the compacted mixture. At the optimum alkalinity the mixture possesses the smallest hydraulic conductivity. In this research an optimum alkalinity (pH=10.1) for a compacted bentonite-sand mixture (7.5% bentonite) was derived from the liquid limit test and the falling-head permeability test.

Study of Sorption and Diffusion of137Cs in Compacted Bentonite Saturated with Saline Water at 60°C

2007 ◽  
Vol 44 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Satoru SUZUKI ◽  
Masashi HAGINUMA ◽  
Kazunori SUZUKI
Keyword(s):  
Saline Water ◽  
Compacted Bentonite ◽  
And Diffusion
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