A Comprehensive Computational Fluid Dynamics Modeling of Lithium Sulphate Electrodialysis

As a part of the recycling process of spent lithium-ion batteries, electrodialysis (ED) is used to extract lithium hydroxide and sulfuric acid from the lithium sulphate solution. This study reports on a multicomponent, 2-dimensional ED model based on simultaneously solving the Nernst-Planck equation, Navier-Stokes equations, species conservation with electrochemical reactions, and electro-osmotic water flow equations using computational fluid dynamics technique. To satisfy the electroneutrality assumption in the ED device, the fluxes of H+ and OH- ions produced from electrochemical reactions are estimated. The distributions of velocity, potential, and species' concentrations are determined. A close agreement between the present model and experimental data shows the accuracy and validity of this work. The influence of transmembrane water flow is investigated. It is revealed that although the water molecules transferring from dilute to concentrate compartments reduce the concentration of concentrate channels, the generated ionic convection flux reversely affects this quantity. A parametric study is carried out to study the effects of operation conditions and membrane properties. It is found that 37% growth of dilute channel concentration is observed when inlet velocity increases from 50 to 100 & mu;m & BULL;s-1. The enhancement of the water volume fraction of membranes also reduces the transmembrane water flow rate.