Diffusion of Chloride and Uranium in Compacted Sodium Bentonite

1988 ◽  
Vol 127 ◽  
Author(s):  
Arto Muurinen ◽  
Pirkkd Pemtilä-Hiltunen ◽  
Kari Uusheimo
Keyword(s):  
Salt Concentration ◽  
Sodium Bentonite ◽  
Ion Exclusion ◽  
Diffusion Mechanisms ◽  
And Diffusion

ABSTRACTSorption and diffusion of chloride (Cl-36) and uranium in conpacted sodium bentonite MX-80 were measured. No sorption was observed in the Sorption tests, however, in the diffusion tests slight sorption of uranium was noticed. The diffusivities of Cl-36 were found to be strongly dependent on the compaction of bentonite and on the salt concentration of the solution. Ion-exclusion can propably explain these phenomena.The diffusivities of uranium were also strongly dependent on the compaction of bentonite. Uranium shews features of both ion-exclusion and sorption. Farther studies are, however, needed to explain the diffusion mechanisms of uranium.

Diffusion Mechanisms of Strontium, Cesium and Cobalt in Compacted Sodium Bentonite

1985 ◽  
Vol 50 ◽  
Author(s):  
Arto Muurinen ◽  
Juha Rantanen ◽  
Pirkko Penttilä-Hiltunen
Keyword(s):  
Surface Diffusion ◽  
Pore Water ◽  
Diffusion Mechanism ◽  
Solid Material ◽  
Sodium Bentonite ◽  
Sodium Chloride Solutions ◽  
Steady State Method ◽  
Diffusion Mechanisms ◽  
Water Saturated ◽  
And Diffusion

AbstractFor a porous water-saturated material where diffusion in the pore water, sorption on the solid material and diffusion of the sorbed ions (surface diffusion) occur, a diffusion equation can be derived where the apparent diffusivity includes two terms. One represents diffusion in the pore-water, the other surface diffusion.In this research diffusion mechanisms were studied. The apparent diffusivities of strontium, cesium and cobalt in compacted sodium bentonite were measured by a non-steady state method. The sorption factors were adjusted using different sodium chloride solutions, groundwater and addition of EDTA for saturation of the bentonite samples. The corresponding sorption factors were measured by a batch method.The results suggest that cations diffuse also while being sorbed. A combined pore diffusion-surface diffusion model has been used to explain the transport and the corresponding diffusivities have been evaluated. The surface diffusivities (Ds) of Sr and Cs were 8-9·10-12 m2/s and 4-7·10-13 m2 /s respectively. The pore diffusivity eD of Cs was 3.5.10-11 m2 /s which has been used also for Sr.The sorption mechanism of Co seems to be different from that of Sr or Cs and the results allow no specific conclusions of the diffusion mechanism of Co. The apparent diffusivity of Co ranged from 2·10-14 to 7·10-14 m2/s.The anionic Co-EDTA seems to follow some other diffusion mechanism than the cations.

Li+ionic conductivities and diffusion mechanisms in Li-based imides and lithium amide

2012 ◽  
Vol 14 (5) ◽  
pp. 1596-1606 ◽  
Author(s):  
Wen Li ◽  
Guotao Wu ◽  
Zhitao Xiong ◽  
Yuan Ping Feng ◽  
Ping Chen
Keyword(s):  
Ionic Conductivities ◽  
Lithium Amide ◽  
Diffusion Mechanisms ◽  
And Diffusion

THE STABILITY OF LOW INDEX METAL SURFACES TO TOPOLOGICAL DEFECTS

1991 ◽  
Vol 05 (03) ◽  
pp. 427-459 ◽  
Author(s):  
EDWARD H. CONRAD
Keyword(s):  
Metal Surfaces ◽  
Surface Defects ◽  
Defect Formation ◽  
Fundamental Problem ◽  
Topological Defects ◽  
Surface Roughening ◽  
Thermal Generation ◽  
Diffusion Mechanisms ◽  
The Stability ◽  
And Diffusion

The study of defect formation at metal surfaces is a fundamental problem in surface physics. An understanding of defect formation is pertinent to growth and diffusion mechanisms. In addition, surface roughening, faceting, and surface melting are all defect mediated phase transitions involving the formation of different topological defects. While the importance of defects at surfaces is well recognized, the study of surface defects has been hampered by the lack of sufficiently accurate experimental techniques. In fact, it is only in the past 6 years that experiments on the thermal generation of defects on metal surfaces have been performed. This review attempts to outline both the theoretical and experimental work on surface defect formation on metal systems.

New Tight-Binding Method for Simulation of Defect Configurations, Creation and Diffusion Mechanisms in Solids: Application to Silicon

1998 ◽  
Vol 527 ◽  
Author(s):  
Zokirkhon M. Khakimov
Keyword(s):  
Tight Binding ◽  
The Self ◽  
Atomic Diffusion ◽  
Self Consistent ◽  
Tight Binding Method ◽  
Comparable Accuracy ◽  
Diffusion Mechanisms ◽  
New Generation ◽  
And Diffusion ◽  
Metastable Defect

ABSTRACTThis paper presents the self-consistent tight-binding method of new generation which, unlike other tight-binding methods, allows one to calculate structural energies of multiatomic systems (molecules, clusters, defects in solids) and their spectroscopic energies in the framework of the same computational scheme and with comparable accuracy. Reliability of the method is illustrated considering defect state problems in crystalline and amorphous silicon (electron-enhanced-atomic diffusion, metastable defect creation, defects with effective-negative correlation energies, etc.) and comparing obtained results with ab initio calculations and experimental data.

New Tight-Binding Method for Simulation of Defect Configurations, Creation and Diffusion Mechanisms in Solids: Application to Silicon

1998 ◽  
Vol 532 ◽  
Author(s):  
Zokirkhon M. Khakimov
Keyword(s):  
Tight Binding ◽  
The Self ◽  
Atomic Diffusion ◽  
Self Consistent ◽  
Tight Binding Method ◽  
Comparable Accuracy ◽  
Diffusion Mechanisms ◽  
New Generation ◽  
And Diffusion ◽  
Metastable Defect

ABSTRACTThis paper presents the self-consistent tight-binding method of new generation which, unlike other tight-binding methods, allows one to calculate structural energies of multiatomic systems (molecules, clusters, defects in solids) and their spectroscopic energies in the framework of the same computational scheme and with comparable accuracy. Reliability of the method is illustrated considering defect state problems in crystalline and amorphous silicon (electronenhanced- atomic diffusion, metastable defect creation, defects with effective-negative correlation energies, etc.) and comparing obtained results with ab initio calculations and experimental data.

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