Deionization Shocks in Crossflow

Abstract

Shock electrodialysis is a recently developed electrochemical water treatment method which shows promise for water deionization and ionic separations. Although simple models and scaling laws have been proposed, a predictive theory has not yet emerged to fit experimental data and enable system design. Here, we extend and analyze existing "leaky membrane" models for the canonical case of a steady shock in cross flow, as in recent experimental prototypes. Two-dimensional numerical solutions are compared with analytical boundary-layer approximations and experimental data. The boundary-layer theory accurately reproduces the simulation results for desalination, and both models predict the data collapse of the desalination factor with dimensionless current, scaled to the incoming convective flux of cations. The numerical simulation also predicts the water recovery increase with current. Nevertheless, both approaches cannot quantitatively fit the transition from normal to over-limiting current, which suggests gaps in our understanding of extreme electrokinetic phenomena in porous media.

References in corpus (10)

• The Charge of Glass and Silica Surfaces
• Overlimiting current in a microchannel
• Current-induced membrane discharge
• Desalination shocks in microstructures
• Experimental Verification of Overlimiting Current by Surface Conduction and Electro-osmotic Flow in Microchannels
• Concentration polarization, surface currents, and bulk advection in a microchannel
• Asymptotics of Reaction-Diffusion Fronts with One Static and One Diffusing Reactant
• The asymptotic behaviour of the initially separated A + B(static) -> 0 reaction-diffusion systems
• Theory of shock electrodialysis I: Water dissociation and electrosmotic vortices
• Vortices of Electro-osmotic Flow in Heterogeneous Porous Media

Cited by in corpus (1)

• Theory of shock electrodialysis I: Water dissociation and electrosmotic vortices