Ion transport in fibrous electrodes for desalination cells: a three-dimensional Boltzmann simulation

Abstract

In this study, we investigated the effects of the electrode structure and operating conditions on the desalination process in a dual-electrolyte desalination system (DEDI) with fibrous electrodes. A 3-dimensional (3D) model was used to capture a realistic geometry of the fibrous electrodes and accurately simulate the internal electrochemical reactions. Various 3D fibrous electrodes with different porosities and fiber diameters were generated using a random reconstruction technique. Then, we applied the lattice Boltzmann method (LBM) to model the fluid flow and ion transport in the system. Our results show that increasing the inlet flow rate enhances the electrolyte velocity in the main channels and electrode pores, particularly the larger pores. Increasing the current density creates larger concentration differences between near and far regions of the pores, which enables the desalination process to more rapidly reach a steady state. In addition, increasing the porosity reduces the concentration gradient in the pores, which results in less variation in the ion adsorption on the fiber surface. However, this behavior reduces the number of active sites and overall desalination capacity. Finally, decreasing the fiber diameter improves the desalination rate, efficiency, and difference in sodium ion concentration between near and far regions of the electrode pores.