A Comprehensive Computational Fluid Dynamics Modeling of Lithium Sulphate Electrodialysis

Electrodialysis (ED) is employed to extract lithium hydroxide and sulfuric acid from the lithium sulphate solution derived from a recycling process of spent lithium-ion battery material. 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 occurring at the electrode surfaces are estimated. The distributions of all species' velocity, potential, and concentrations are determined. An excellent 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 transfer from dilute to concentrate channels reducing the concentration of concentrate compartments, the generated ionic convection flux through channels reversely affects this quantity. A parametric study is performed to investigate the effects of applied current, inlet concentration, inlet velocity, and membrane properties. It is found that 37% growth of outlet concentration of dilute channel is obtained when inlet velocity increases from 50 to 100 µm·s-1. The enhancement of the water volume fraction of IEMs also reduces the transmembrane water flow rate.