Dynamics and transport in charged porous media

Charged porous media are filled at least by counterions and often water and occasionally coions. The dynamics of those counterions, water molecules and coions depends strongly on the water content of the medium. For very compact media the water content is low and water and ions are slowed down. For less compact media the dynamics of inserted water and counterions tends towards that in bulk solution. Different levels of theoretical description can be used for that dynamics, according to the water content of the system. Low water content requires an explicit molecular description by either molecular dynamics (MD) or Monte Carlo (MC), whereas large water content can be treated by continuous solvent models, either Poisson–Boltzmann, with point counterions, or the primitive model (PM), with finite size counterions. The comparison of the molecular model to the continuous solvent models gives the limit of validity of the continuous solvent models, for the low water content region. The results include the evaluation of the electroosmotic flows by a proper evaluation of the Kubo–Smoluchowski relations, adapted to those systems.