Reverse electrodialysis through nanochannels with inhomogeneously charged surfaces and overlapped electric double layers

Modeling of electro-chemo-mechanical transport phenomena in simple (nanochannel) or complex (nanoporous media) geometries with inhomogeneous surface charge and overlapped electric double layers remains challenging. This bottleneck originates from lack of a comprehensive model to predict the local surface charge density based on the variable local solution properties. This work aims to propose a model, so-called representative bulk layer (RBL), which makes the chemically non-isolated solid liquid interfaces (due to the electric double layers interaction) as isolated interfaces by introducing a local effective bulk ion concentration. Using RBL together with the electrical triple layer model to provide boundary conditions for the multi-physio-chemical transport equations (PNP + NS), we investigate the reverse electrodialysis (RED) in nanochannels. Our modeling results indicate that the length of an ion selective membrane not only influences the ionic current but also the logarithm of the slope of current-voltage curve increases linearly with the ratio of nanochannel length to height. This interesting finding inspires us to propose a dimensionless relation for the current-voltage curve that is independent of the nanochannel dimensions. The present contribution numerical framework could shed light on the electro-chemo-mechanical transport mechanism through nanofluidic devices and membranes. (C) 2018 Elsevier Inc. All rights reserved.