The Effect of Pore Structural Factors on Diffusion in Compacted Sodium Bentonite

2000 ◽  
Vol 663 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Grain Size ◽  
Tritiated Water ◽  
Silica Sand ◽  
Single Fracture ◽  
Distilled Water ◽  
Structural Factors ◽  
Sodium Bentonite ◽  
Size Dependency ◽  
Through Diffusion ◽  
Effective Diffusivities

ABSTRACTFour kinds of diffusion experiments; (1) through-diffusion (T-D) experiments for diffusion direction dependency to compacted direction, (2) in-diffusion (I-D) experiments for composition dependency of silica sand in bentonite, (3) I-D experiments for initial bentonite grain size dependency, and (4) I-D experiments for the effect of a single fracture developed in bentonite, were carried out using tritiated water (HTO) to evaluate the effect of pore structural factors on diffusion. For (1), effective diffusivities (De) in Na-bentonites, Kunigel-V1Ŵ and Kunipia-FŴ, were measured for densities of 1.0 and 1.5 Mg.m-3 in the axial and perpendicular directions to compacted one. Although De values in Kunigel-V1Ŵ for both directions were similar over the density, De values for perpendicular direction to compacted one in Kunipia-FŴ were higher than those for the same direction as compacted one. For (2), apparent diffusivities (Da) in Kunigel-V1Ŵ with silica sand were measured for densities of 0.8 to 1.8 Mg.m-3. No significant effect of the mixture of silica sand was found. For (3), Da values for densities of 0.8 to 1.8 Mg.m-3 were measured for a granulated Na-bentonite, OT-9607Ŵ. However, no effect of initial bentonite grain size was found. For (4), Da values in Kunigel-V1Ŵ, in which a single fracture was artificially reproduced and immersed in distilled water, were measured. No effect of the fracture on Da was found. Based on this, it may be said that the composition of smectite in bentonite affects the orientation property of clay particle and also affects diffusion. Furthermore, a penetrated fracture formed in bentonite is restored for a short while and does not affect diffusion.

Comparative study of coral sand and silica sand in creep under general stress states

2017 ◽  
Vol 54 (11) ◽  
pp. 1601-1611 ◽  
Author(s):  
Yaru Lv ◽  
Feng Li ◽  
Yawen Liu ◽  
Pengxian Fan ◽  
Mingyang Wang
Keyword(s):  
Grain Size ◽  
Creep Behavior ◽  
Confining Pressure ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Particle Rotation ◽  
General Stress ◽  
Coral Sand ◽  
Stress States

Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

Adsorption, Desorption, and Leaching of Nitrofen and Oxyfluorfen

Weed Science ◽  
1977 ◽  
Vol 25 (2) ◽  
pp. 97-100 ◽  
Author(s):  
Omosuyi Fadayomi ◽  
G. F. Warren
Keyword(s):  
Aqueous Solution ◽  
Calcium Ions ◽  
Fine Sand ◽  
Silica Sand ◽  
Distilled Water ◽  
Silt Loam ◽  
Sand Soil ◽  
Muck Soil ◽  
Loam Soil ◽  
Adsorption Desorption

The adsorption of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and oxyfluorfen [2-cholor-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] from aqueous solution by muck soil, and by kaolinite and bentonite saturated with hydrogen or calcium ions, was studied using14C-labeled herbicides. Both compounds were readily adsorbed from solution by muck soil and Ca- and H-Al-bentonite but only slightly by Ca- and H-Al-kaolinite. Very little of the adsorbed compounds was desorbed after four extractions with distilled water. A bioactivity study using sorghum seedlings (Sorghum bicolorL. ‘RS610′) was conducted with the herbicides in a silica sand medium amended with 1% (w/w) of the various adsorbents. The herbicides were strongly inactivated by muck soil but there was very little inactivation by the clays. There was essentially no movement of either herbicide through 5-cm columns of a silt loam soil and a fine sand soil.

Surface Dissolution of Hydroxyapatite Prepared by Microwave Sintering

2007 ◽  
Vol 330-332 ◽  
pp. 227-230
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Kyu Hong Hwang ◽  
Jong Kook Lee
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Heating Rate ◽  
Microwave Sintering ◽  
Starting Material ◽  
Dissolution Behavior ◽  
Distilled Water ◽  
Sintering Process ◽  
Conventional Sintering ◽  
Boundary Dissolution

The aim of this study was to prepare dense hydroxyapatite (HA) by microwave sintering and to evaluate the dissolution behavior in distilled water. Commercially-obtained HA powders having Ca/P ratio of 1.67 were used as a starting material. The as-received powder of granular type consists of nano-sized particles. Microwave sintering was operated at 1200°C for 5 min with a heating rate of 50°C/min. Microwave sintering process reduced grain size of HA, compared with the case of conventional sintering. During the immersion in distilled water for 3-14 days, grain boundary dissolution occurred and the dissolution extended into the bulk following this path. As a result, particles were separated from the structure leaving micron-scale defects.

Matrix Diffusion of Some Alkali- and Alkaline Earth-Metals in Granitic Rock

1996 ◽  
Vol 465 ◽  
Author(s):  
H. Johansson ◽  
J. Byegård ◽  
G. Skarnemark ◽  
M. Skålberg
Keyword(s):  
Alkaline Earth ◽  
Tritiated Water ◽  
Size Fraction ◽  
Effective Diffusivity ◽  
Alkaline Earth Metals ◽  
Capacity Factor ◽  
Dimensional Solution ◽  
Crushed Material ◽  
Fine Grained ◽  
Effective Diffusivities

ABSTRACTStatic through-diffusion experiments were performed to study the diffusion of alkali- and alkaline earth-metals in fine-grained granite and medium-grained Äspö-diorite. Tritiated water was used as an inert reference tracer. Radionuclides of the alkali- and alkaline earth-metals (mono- and divalent elements which are not influenced by hydrolysis in the pH-range studied) were used as tracers, i.e. 22Na+, 45Ca2+ and Sr The effective diffusivity and the rock capacity factor were calculated by fitting the breakthrough curve to the one-dimensional solution of the diffusion equation. Sorption coefficients, Kd, that were derived from the rock capacity factor (diffusion experiments) were compared with Kd determined in batch experiments using crushed material of different size fractions.The results show that the tracers were retarded in the same order as was expected from the measured batch Kd. Furthermore, the largest size fraction was the most representative when comparing batch Kd with Kd evaluated from the diffusion experiments. The observed effective diffusivities tended to decrease with increasing cell lengths, indicating that the “transport” porosity decreases with increasing sample lengths used in the diffusion experiments.

Effect of Different Processing on Properties of Silica Sand

2010 ◽  
Vol 139-141 ◽  
pp. 528-531
Author(s):  
Qing Zhou Sun ◽  
Rong Fu Xu ◽  
Zhong Kui Zhao ◽  
Pu Qing Zhang ◽  
Wei Liu
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Downward Trend ◽  
Silica Sand ◽  
Test Results ◽  
Molding Sand ◽  
Physical Chemical ◽  
Chemical Attributes

This paper will cover some processing routes along with grading and physical/chemical attributes of silica sand. The silica sand in this experiment was divided into four lots, and each of them was processed by the methods of calcining, scrubbing, mulling or rubbing respectively. The test results show that the sand grains which processed by different processing methods are irregular, the acid demand value of sand is lower than that of the base sand, and the grain size distribution of sand is similar to that of the base sand. However, the SiO2 content of processed sand is increased, the impurities content has a downward trend. Compared with the base sand, it can be found that the tensile strength value of molding sand prepared using the processed sands is higher and the bench life is almost no change.

Effects of Processing Factors on Microstructure and Diffusivity of Diethylbenzene Dehydrogenation Catalyst

2010 ◽  
Vol 297-301 ◽  
pp. 233-238
Author(s):  
Mohammad Ebrahim Zeynali ◽  
I. Soltani
Keyword(s):  
Grain Size ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Bulk Diffusion ◽  
Effective Diffusivity ◽  
Catalyst Pellet ◽  
Different Types ◽  
Effective Diffusivities ◽  
Processing Factors

In this study, different mechanisms of diffusion such as Knudsen and bulk were investigated for diethylbenzene diffusion into a catalyst and it was concluded that the pore sizes should be in the range that permit transitional diffusion (both Knudsen and bulk diffusion). The catalyst grain size can be controlled and varied by different parameters such as speed and time of mixing, type of alkali, temperature and pH. Particle size distribution experiments were conducted for different types of alkali and speed of mixing to characterize the catalyst. The effects of grain size formed during coprecipitation on pore size distribution of the catalyst pellet which affect the effective diffusivity were discussed. Pore size distribution of the model catalyst was obtained and the effective diffusivities were calculated by numerical integration of Johanson-Stewart equation.

Consistency of the strontium transport parameters in Boom Clay obtained from different types of experiments: accounting for the filter plates

2012 ◽  
Vol 1475 ◽  
Author(s):  
Marc Aertsens ◽  
Joan Govaerts ◽  
Norbert Maes ◽  
Liesbeth Van Laer
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Tritiated Water ◽  
Capacity Factor ◽  
Retardation Factor ◽  
Transport Parameters ◽  
Boom Clay ◽  
Different Types ◽  
Apparent Diffusion ◽  
Through Diffusion

ABSTRACTIn a previous MRS paper, the consistency of migration parameters for strontium (Sr) in Boom Clay, obtained by different types of experiments, was examined. No consistent value could be obtained for the product ηR of the diffusion accessible porosity η and the retardation factor R. Furthermore the nearly flat concentration profile measured in one of the through diffusion experiments could not be explained by the traditional through diffusion model. A reason is that the filter plates confining the clay sample have not been taken into account.Therefore, for Sr and tritiated water (HTO), the apparent diffusion coefficient and the product ηR in the filters are measured in through diffusion experiments on filter plates.Taking into account the filter plates, the outlet fluxes and the Sr profiles in the clay of both Sr through diffusion experiments, are described well with (i) the previously estimated Sr apparent diffusion coefficient in the clay of 7 × 10-12 m2/s, (ii) an apparent filter diffusion coefficient in the range 2 × 10-12 m2/s to 5 × 10-11 m2/s (vs. 1 × 10-11 m2/s measured in the filter through diffusion experiments), (iii) a clay capacity factor ηR in the range between 5000 and 22000, and (iv) a filter capacity factor between 0.3 and 0.6 (in agreement with the filter through diffusion measurements). However, using the above parameters, the evolution at the inlet could not be described. So although inconsistency diminished, some inconsistency remains.

scholarly journals Comparison between in situ and laboratory diffusion studies of HTO and halides in Opalinus Clay from the Mont Terri

2004 ◽  
Vol 92 (9-11) ◽  
Author(s):  
Etienne Tevissen ◽  
J. M. Soler ◽  
P. Montarnal ◽  
A. Gautschi ◽  
Luc R. Van Loon
Keyword(s):  
Tritiated Water ◽  
Opalinus Clay ◽  
Diffusion Experiment ◽  
Diffusion Technique ◽  
Diffusion Studies ◽  
Through Diffusion ◽  
Mont Terri

SummaryA long-term single-borehole diffusion experiment (DI) using tritiated water (HTO) and stable iodide (All HTO results obtained with a through diffusion technique are within the same range as those obtained in the

scholarly journals Compaction Behaviour and Grain Size Alteration of Sand -Clay Mix

2019 ◽  
Vol 9 (1) ◽  
pp. 4106-4110
Keyword(s):  
Grain Size ◽  
Void Ratio ◽  
Research Output ◽  
Dry Density ◽  
Distribution Analysis ◽  
Sodium Bentonite ◽  
Liner Material ◽  
Uniformity Coefficient ◽  
Result Show ◽  
Coefficient Of Uniformity

Sand-bentonite mix is commonly used as liner material or backfill material in landfill sites. Bentonite belonging to group of montmorillionite clay provides higher density and less void ratio to lessen permeability of liner layer mixed with sand. This mix is inevitable and economical where soil nearby landfill site have sandy soil .Many literatures provided geotechnical aspects of using this mix.In this present study, the grain size distribution analysis and compaction of sand–bentonite mixture for 10%,20% and 30% bentonite mix is studied to propose economic and less permeable liner material with lower shrinkage. Locally available sand from different river , Odisha (India) was mixed with different proportions of commercial sodium bentonite. The following research output presented here elaborately show the effect of clay particle on compaction, Relative Density, Coefficient of uniformity,Coefficient of curvature, permeability by gradually adding commercial Sodium Bentonite 10% by weight upto 30%. The result show that there is a significant improvement in MDD and OMC of Sand-Bentonite mix along with decrease in void ratio. The grain size alteration eventually helped to increase the dry density and reduced void ratio will enhance the scope of this mix to be used as liner layer in landfill system.

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