Oil-Water Transport in Clay-Hosted Nanopores: Effects of Long-Range
Electrostatic Forces
Abstract
Charged clay surfaces can impact storage and mobility of hydrocarbon and
water mixtures. Here, we use equilibrium molecular dynamics (MD) and
nonequilibrium MD simulations to investigate hydrocarbon-water mixtures
and their transport in slit-shaped illite nanopores. We construct two
illite pore models with different surface chemistries:
potassium-hydroxyl (P-H) and hydroxyl-hydroxyl (H-H) structures. In H-H
nanopore, we observe water adsorption on the clay surfaces. In P-H
nanopores, however, we observe the formation of water bridges or columns
between the top and bottom pore surfaces. This is because of the
existence of a local, long-range electric field within the P-H pore
causing water molecules to align in a specific direction promoting the
formation of a water bridge. Our NEMD simulations demonstrate that the
velocity profiles across the pore depends strongly on the presence or
absence of the water bridge. This study provides a theoretical basis for
understanding of nanofluidics with charged surfaces.