Dynamics of Surface Charges and Water Splitting in Microchannels Containing Nanoporous Ion-selective Membranes

We present a theoretical study of ion transport in microchannels containing nanoporous ion-selective membranes. The developed model includes the effect of water splitting as well as reactions between the liquid and the surface groups on the walls. By numerically solving the full PNP (Poisson–Nernst–Planck) problem coupled with the flow problem, results are obtained both in the simple non-advective regime and in the regimes were electroosmosis is important. The surface charge is determined dynamically via interactions with water ions, and the water ions are thus an important part of the system. To understand the behavior of these ions we supplement the numerical study with analytical models for the water ion transport valid in the case of fixed and vanishing surface charge density.