Adsorption and mobility of water and organic molecules in carbonaceous adsorbents. 4. Self-diffusion coefficients of water molecules and organic substances in active carbon having relatively large micropores

1989 ◽  
Vol 38 (9) ◽  
pp. 1789-1791
Author(s):  
R. Sh. Vartapetyan ◽  
A. M. Voloshchuk ◽  
J. Kaerger ◽  
H. Pfeifer ◽  
W. Heink
Keyword(s):  
Active Carbon ◽  
Diffusion Coefficients ◽  
Organic Molecules ◽  
Water Molecules ◽  
Organic Substances ◽  
Self Diffusion ◽  
Carbonaceous Adsorbents

c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions

1994 ◽  
Vol 49 (3-4) ◽  
pp. 258-264 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann ◽  
C. Buttersack ◽  
K. Buchholz
Keyword(s):  
Field Gradient ◽  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
The Self ◽  
Water Molecules ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Sucrose Solutions ◽  
Wide Range

The self diffusion coefficients D of the water molecules and of sucrose have been determined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w suc.). All temperature dependencies can be fitted to a Vogel- Tammann-Fulcher equation. The isothermic concentration dependence of D for the sucrose is given by a simple exponential concentration dependence

Molecular Dynamics Study of a KCl Aqueous Solution: Dynamical Results

1987 ◽  
Vol 42 (3) ◽  
pp. 227-230 ◽  
Author(s):  
M. Migliore ◽  
S. L. Fornili ◽  
E. Spohr ◽  
K. Heinzinger
Keyword(s):  
Diffusion Coefficients ◽  
Md Simulation ◽  
Bulk Water ◽  
Water Molecules ◽  
Hydration Water ◽  
Self Diffusion ◽  
Average Temperature ◽  
Velocity Autocorrelation ◽  
Dynamical Properties ◽  
Velocity Autocorrelation Functions

In this paper we report on dynamical properties of a 2.2 molal aqueous KCl solution as obtained from an 8.7 ps MD simulation at an average temperature of 289 K. Velocity autocorrelation functions, self-diffusion coefficients and spectral densities of the hindered translational and librational motions of the ions and the water molecules assigned to three subsystems - hydration water of the cations, hydration water of the anions and bulk water - are discussed.

Investigation of Atomistic Scale Transport Phenomena of the Proton Exchange Membrane Fuel Cell

2006 ◽  
Vol 4 (4) ◽  
pp. 474-480 ◽  
Author(s):  
Chin-Hsien Cheng ◽  
Che-Wun Hong
Keyword(s):  
Fuel Cells ◽  
Diffusion Coefficients ◽  
Atomistic Simulation ◽  
Proton Exchange Membrane ◽  
Transport Phenomena ◽  
Proton Exchange ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Self Diffusion ◽  
Exchange Membrane

This paper studies the transport phenomena inside the electrolyte of proton exchange membrane fuel cells (PEMFCs) using atomistic simulation techniques. The investigated material of the electrolyte is Nafion®, which is the most widely adapted polymer membrane in low-temperature fuel cells. The molecular dynamics simulation system includes part of the Nafion structure, numerous water molecules, and the transporting cations. The cations are assumed to be hydroxoniums (H3O+), which are a hydrogen proton combined with a water molecule. Simulation results indicated that the electrostatic energy dominated the other potential energies in the total internal energy analysis. Clusters of water molecules tend to move toward the sulfonic acid group in the Nafion fragment, where the hydrophilic/hydrophobic characteristics can be observed. The transport phenomena of hydroxoniums are classified into two categories—continuous migration and noncontinuous hopping. The self-diffusion coefficients of the hydroxoniums and the water molecules in the membrane were evaluated to be 3.476×10−5cm2∕s and 4.993×10−5cm2∕s respectively, based on the Einstein relation. The calculated self-diffusion coefficients are of the same order of magnitude as the experimental results, which indicates this atomistic simulation is reaching more and more practical in engineering analysis.

Distinctive Diffusion Regimes of Organic Molecules in Clays: (De)coupled Motion with Water

2018 ◽  
Author(s):  
Eduardo Duque-Redondo ◽  
Iñigo López-Arbeloa ◽  
Hegoi Manzano
Keyword(s):  
Diffusion Coefficients ◽  
Sharp Increase ◽  
Guest Molecule ◽  
Organic Molecules ◽  
Water Molecules ◽  
Coupled Motion ◽  
Dynamics Simulations ◽  
New Generation ◽  
Inorganic Components ◽  
Water Contents

<div>The combination of organic and inorganic components enables the development of new generation of materials with innovative applications in many fields. Clays are commonly used to confine different ions and molecules since they act as an engineering barrier, avoiding the release of the entrapped species. In this work, we have employed molecular dynamics simulations to study the diffusivity of a variety of organic molecules enclosed in the interlaminar space of clays. We have found that the diffusivity of the organic molecules follows a universal trend, exhibiting low diffusion coefficients at low water contents, which are radically increased at a certain water content. This onset of diffusion is due to the rearrangement of the water molecules from monolayer to bilayer. At that point, the motion of the water/guest molecule cluster is decoupled, leading to the sharp increase of the diffusion coefficients.</div>

Distinctive Diffusion Regimes of Organic Molecules in Clays: (De)coupled Motion with Water

2018 ◽  
Author(s):  
Eduardo Duque-Redondo ◽  
Iñigo López-Arbeloa ◽  
Hegoi Manzano
Keyword(s):  
Diffusion Coefficients ◽  
Sharp Increase ◽  
Guest Molecule ◽  
Organic Molecules ◽  
Water Molecules ◽  
Coupled Motion ◽  
Dynamics Simulations ◽  
New Generation ◽  
Inorganic Components ◽  
Water Contents

<div>The combination of organic and inorganic components enables the development of new generation of materials with innovative applications in many fields. Clays are commonly used to confine different ions and molecules since they act as an engineering barrier, avoiding the release of the entrapped species. In this work, we have employed molecular dynamics simulations to study the diffusivity of a variety of organic molecules enclosed in the interlaminar space of clays. We have found that the diffusivity of the organic molecules follows a universal trend, exhibiting low diffusion coefficients at low water contents, which are radically increased at a certain water content. This onset of diffusion is due to the rearrangement of the water molecules from monolayer to bilayer. At that point, the motion of the water/guest molecule cluster is decoupled, leading to the sharp increase of the diffusion coefficients.</div>

scholarly journals Theoretical Modelling of Ion Exchange Processes in Glass: Advances and Challenges

2021 ◽  
Vol 11 (11) ◽  
pp. 5070
Author(s):  
Xesús Prieto-Blanco ◽  
Carlos Montero-Orille
Keyword(s):  
Ion Exchange ◽  
Diffusion Coefficients ◽  
Molten Salts ◽  
Theoretical Modelling ◽  
Copper Films ◽  
Theoretical Frameworks ◽  
Self Diffusion ◽  
Exchange Processes ◽  
The One ◽  
Made In

In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review.

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