Diffusion and Gas Flow Dynamics in Partially Saturated Smectites

Clays and clay rocks are considered good natural engineered barriers for deep geological disposal of nuclear waste worldwide. Metal corrosion organic degradation in underground repositories generate significant amounts gas that should be able to migrate through the multibarrier system avoid potential pressure buildup, which could compromising integrity host rocks. The is expected accumulate larger pores eventually form an interconnected network. Under such conditions, migration molecules takes place both pore water films gas-filled macropores. Therefore, mass fluxes depend on distribution between water-rich gas-rich phases their mobility compartments. Classical molecular dynamics (MD) simulations were employed investigate mobilities He, H2, CO2, Ar, CH4 a Na-montmorillonite mesopore as function degree saturation, well evaluate hydrodynamic behavior fluid partially saturated clays. diffusivity was determined by observing asymptotic mean square displacement phase at gas–water interface. partition coefficient Gibbs free energy analyzed transfer trajectories they cross vapor–liquid results revealed diffusion increased with increasing width converged asymptotically toward bulk state. It shown dissolved remained constant long interacting surface bulk-liquid-like phase. This changes very thin films. observed partitioning solid–liquid interface nearly same Partitioning strongly dependent temperature weights. In second part study, nonequilibrium (NEMD) performed gases pressure-driven decoupled gas-phase (DGPD) coupled (CGWPD) slit mesopore. dynamic viscosity calculated from NEMD indicated almost methods (DGPD CGWPD). average slip length also calculated, revealing slip-free boundary condition assumed continuum models generally invalid microfluidics exists microscale specific interactions. Finally, Bosanquet-type equation developed predict width, mean-free path, geometric factor, thickness adsorbed film.