Effective diffusivity of neptunium and plutonium in granite from Inada, Ibaraki, Japan under anaerobic conditions

2002 ◽  
Vol 90 (12) ◽  
Author(s):  
Tetsuji Yamaguchi ◽  
S. Nakayama ◽  
H. Okamoto
Keyword(s):  
Effective Diffusivity ◽  
Diffusion Method ◽  
Anaerobic Conditions ◽  
Through Diffusion ◽  
Effective Diffusivities

SummaryThe effective diffusivities of neptunium and plutonium in Inada granite have been determined using the through–diffusion method. Experiments were performed under anaerobic conditions in the presence of carbonate. The actinides are expected to be present as carbonato or carbonatohydroxo complexes. Effective diffusivity (D

Mineralogical Changes of Cement and Bentonite Accompanied ith Their Interactions

2009 ◽  
Vol 1193 ◽  
Author(s):  
Seiichi Hoshino ◽  
Tetsuji Yamaguchi ◽  
Toshikatsu Maeda ◽  
Masayuki Mukai ◽  
Tadao Tanaka ◽  
...  
Keyword(s):  
Tritiated Water ◽  
Effective Diffusivity ◽  
Diffusion Method ◽  
Hardened Cement ◽  
Computational Studies ◽  
Secondary Phases ◽  
Hardened Cement Paste ◽  
Xrd Pattern ◽  
Through Diffusion ◽  
Primary Minerals

AbstractMineralogical changes of cement and bentonite accompanied with their interaction wereexperimentally studied by mixing granulated hardened cement paste and bentonite, and aging the mixture for91 days at 50° C. Mineralogical changes of cement and bentonite were identified by XRD. Hydratedcalcium-silicate phases (C-S-H), Ca(OH)2, ettringite and monosulfate were identified in the unalteredhardened cement. While Ca(OH)2 and monosulfate decreased with aging and disappeared after 91 days,calcite and katoite (Ca3Al2(SiO4)(OH)8) were formed concurrently. Montmorillonite, quartz (and/orchalcedony), clinoptilolite, plagioclase, calcite, analcime and pyrite were identified in the unaltered bentonite.The XRD pattern showed that diffraction intensities of these minerals decreased with aging. It seems thatthese primary minerals dissolved in the course of the alteration. C-S-H appeared in bentonite during the agingas secondary phases, indicating the participation of silicon dissolved from the bentonite and calcium from thecement formed the C-S-H. The formation of C-S-H that had been predicted by previous modeling studieswas confirmed by the present experiments.In addition, diffusivity of tritiated water in mixed specimen with granulated hardened cement andbentonite was determined by a through-diffusion method. The effective diffusivity of tritiated water decreasedwith aging. The result suggests that the mass diffusivity in the interface of cement-bentonite system willdecrease with their interactions. The results of the diffusion experiments are qualitatively consistent with thediffusivity change in cement-bentonite systems predicted by some computational studies.

Diffusion of Cs, Np, Am and Co in compacted sand-bentonite mixtures: evidence for surface diffusion of Cs cations

Clay Minerals ◽  
2013 ◽  
Vol 48 (2) ◽  
pp. 411-422 ◽  
Author(s):  
T. Sawaguchi ◽  
T. Yamaguchi ◽  
Y. Iida ◽  
T. Tanaka ◽  
I. Kitagawa
Keyword(s):  
Surface Diffusion ◽  
Pore Water ◽  
Concentration Gradient ◽  
Unit Volume ◽  
Effective Diffusivity ◽  
The Other ◽  
Diffusion Method ◽  
Diffusive Flux ◽  
Diffusive Transport ◽  
Through Diffusion

AbstractWe studied the diffusive transport of Cs, Np, Am and Co in compacted sandbentonite mixtures by using the through-diffusion method. The experiments for Cs were performed under various aqueous compositions. Effective diffusivity (De) values of 4.7×10–10 to 5.9×10–9 m2 s–1 were obtained with a somewhat large variation. Apparent diffusivity (Da) values, on the other hand, showed less variation, ranging from 2.0×10–12 to 6.2×10–12 m2 s–1. The results indicated that diffusive flux was proportional to the concentration gradient on the basis of the amount of Cs in the unit volume of the compacted sand-bentonite mixtures rather than the Cs concentration gradient in pore water. Because the former concentration gradient in the mixtures was nearly equal to that of adsorbed Cs, the diffusion of Cs in the mixtures was probably dominated by the concentration gradient of the Cs adsorbed on the mixtures. In addition, the effective/apparent diffusivity of 237Np(IV) and apparent diffusivity of 241Am(III) and 60Co(II) in the mixtures were determined in 0.3/0.03 mol l–1 (NH4)2CO3/Na2S2O4 solution.

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.

Grouted Waste Leach Tests: Pursuit of Mechanisms and Data for Long-Term Performance Assessment

1989 ◽  
Vol 176 ◽  
Author(s):  
R. Jeff Serne
Keyword(s):  
Diffusion Processes ◽  
Scale Up ◽  
Liquid Waste ◽  
Effective Diffusivity ◽  
Cementitious Materials ◽  
Solidified Waste ◽  
Effective Diffusivities ◽  
Long Term Performance ◽  
Term Performance

ABSTRACTAt Hanford, low-level liquid nuclear waste is being mixed with cementitious materials (grout) to form leach-resistant solid waste. Prior to grouting each liquid waste, an assessment must be performed to evaluate the long-term environmental impact. These predictions rely upon a diffusioncontrolled release model and short-term laboratory leach data on small grout samples. This paper describes size scale-up and inventory scale-up experiments that evaluate whether diffusion does in fact control the release of contaminants. The results of the volume scale-up test suggest that tests on grout cylinders between the sizes 3 cm dia. by 3 cm length and 30 cm dia. by 29 cm length yield comparable results. These data and other available literature suggest that extrapolation of leach results to large blocks of solidified waste is defensible.The inventory scale-up tests for 125I and selenium show a constant effective diffusivity regardless of the original inventory. This suggests that diffusion processes do in fact control the release of iodide and selenium from grout. The 99Tc effective diffusivities may not remain constant with changes in inventory.

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.

scholarly journals Sorption and Diffusion Properties of H- and Modified Forms of ZSM-5 Zeolites

1996 ◽  
Vol 13 (6) ◽  
pp. 495-508 ◽  
Author(s):  
P. Hudek ◽  
D. Bobok ◽  
A. Smiešková ◽  
Z. Židek
Keyword(s):  
Physical Adsorption ◽  
Gravimetric Method ◽  
Equilibrium Concentration ◽  
Sorption Isotherms ◽  
Effective Diffusivity ◽  
Micropore Volume ◽  
Unit Cell ◽  
Adsorption Of Nitrogen ◽  
Effective Diffusivities ◽  
Modified Forms

The sorption properties of samples of H-ZSM-5 zeolite and their forms modified with P, B and Mg were determined by the physical adsorption of nitrogen and evaluated by BET isotherm and t-plot methods. The diffusivities of the samples were measured using a new flow gravimetric method involving the sorption of p- and o-xylenes. The BET specific surface area decreased from 358 m2/g to 35–90 m2/g mainly because of a decrease in micropore volume as determined by the t-plot method. The rate of sorption of p-xylene on all the samples investigated followed Fick's second law of diffusion, leading to an effective diffusivity of ca. 1.7 × 10−11 m2/s, irrespective of whether the H-form or the modified forms were investigated. The sorption isotherms for o-xylene showed some unusual steps. Values for the effective diffusivities decreased from 2.6 × 10−12 m2/s for the H-form to 2.0–2.3 × 10−12 m2/s for the modified forms. The equilibrium concentration of o-xylene at P/P0 = 0.1 was only 0.38–0.68 mol/unit cell, while that of p-xylene was 4.40–5.98 mol/unit cell.

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.

Matrix Diffusion Measurements – Through Diffusion versus Electrical Conductivity Measurements

2000 ◽  
Vol 663 ◽  
Author(s):  
Y. Ohlsson ◽  
I. Neretnieks
Keyword(s):  
Electrical Conductivity ◽  
Pure Water ◽  
Effective Diffusivity ◽  
Surface Conductivity ◽  
Bulk Liquid ◽  
Matrix Diffusion ◽  
Conductivity Measurements ◽  
Formation Factor ◽  
Conductivity Method ◽  
Through Diffusion

ABSTRACTMatrix diffusion laboratory experiments in dense porous rock are generally very time consuming and one is limited to rather short diffusion lengths, as well as to a small amount of samples. The large heterogeneity of rock, on the other hand, demands a large quantity of samples that are large enough to exclude effects from e.g. increases in interconnected porosity compared to that of the pristine rock.Electrical conductivity measurements are very fast and larger samples can be used than is practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied.In this study traditional through diffusion experiments as well as electrical conductivity measurements are carried out on the same rock samples. The formation factor is determined by both methods, and the methods are compared and discussed.The surface conductivity is studied by exchanging the surface sites with Na+, Sr2+ and Cs+. After leaching out the free pore ions the surface conductivity is measured.With the electrical conductivity method the formation factor is determined directly, whereas it has to be calculated using the bulk liquid diffusion coefficient in the diffusion experiments. This causes some uncertainties in the comparison between the experiments. In estimating the bulk liquid diffusivity, the value for infinitely diluted solutions and in pure water environment is commonly used. The calculated formation factor may therefore be somewhat underestimated.

scholarly journals Screening and Production of Antibacterial from Lactobacillus plantarum NS(9) Isolated from Nile Tilapia Bekasam

2016 ◽  
Vol 19 (2) ◽  
pp. 132
Author(s):  
Desniar Desniar ◽  
Iriani Setyaningsih ◽  
Yoga Indra Purnama
Keyword(s):  
Antibacterial Activity ◽  
Lactobacillus Plantarum ◽  
Ph Value ◽  
Diffusion Method ◽  
Exponential Growth Phase ◽  
Anaerobic Conditions ◽  
Inhibitory Zone ◽  
Antibacterial Compounds ◽  
E Coli ◽  
Growth Of Bacteria

<p>Lactic acid bacteria has been used as biopreservatif becouse produce a number of antibacterial<br />substances are safety and has inhibitory activity against enteropatogenic bacteria. The aims of this study<br />were to screen of antibacterial compounds produced by Lactobacillus plantarum NS (9) and to produce<br />their antibacterial compounds. The research was devided into two stages. In the first stage was L. plantarum<br />NS (9) inoculated at 37°C, for 24 hours in semi-anaerobic conditions. The cell-free supertnatant was given<br />three treatment, ie not neutralized (A), neutralized (pH 7) (N), and precipitated with ammonium sulfate<br />50% (P). This three supernatant was assayed their antibacterial activity against E. coli, S. typhimurium<br />ATCC 14028, S. aureus, B. cereus and L. monocytogenes using the agar well diffusion method. In the second<br />stage, production of antibacterial compound was L. plantarum NS (9) inoculated at 37°C, for 24 hours<br />in semi-anaerobic conditions. The Dencity Optical, value pH, acid total and antibacterial activity were<br />measured every three hours during growth of bacteria. The results of the antibacterial screening showed<br />that L. plantarum NS (9) produced inhibitory zone againts the five indicator bacteria from a supernatant,<br />whereas N and P supernatant were not produced inhibitory zone. This result indicated that inhibition.</p><p>produced at 6 hours of incubation and were increased to simultaneously with increasing of bacteria growth.<br />The highest antibacterial activity against E. coli, B. cereus and L.monocytogenes were produced at the end<br />of the exponential growth phase (12 -15 hours incubation) while against S. aureus and S. typhimurium<br />ATCC 14028 at 21 and 24 hour of incubation, respectively. The antibacterial activity also was increased to<br />simultaniously with increasing of acid total (1.350 to 4.050%) and decreasing of pH value (6-4) during<br />growth of bacteria.<br /><br /></p>

New Mathematical Models for Effective Drug Diffusivity Estimation in 2D

2007 ◽  
Vol 561-565 ◽  
pp. 1557-1560 ◽  
Author(s):  
Song Wang ◽  
Xia Lou
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Mathematical Models ◽  
Analytical Solutions ◽  
Least Squares Method ◽  
Effective Diffusivity ◽  
Data Set ◽  
Initial Burst ◽  
Effective Boundary ◽  
Effective Diffusivities

In this paper we propose several new mathematical models for estimating effective diffusivities of a drug released from a cylinder device to an external finite volume. These models can handle problems with ‘initial burst’ and boundary layers. Analytical solutions to the models are derived. To determine the unknown effective diffusivity, time of a initial burst and width of the effective boundary layer, a least-squares method can be used for a given experimental data set. The models were tested using experimental data and the numerical results show the usefulness and accuracy of these models.

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