Electrodialysis of Lithium Sulphate Solution: Model Development and Validation

A comprehensive mathematical model is proposed to study the transport phenomena in an Electrodialysis (ED) process employed to recover lithium hydroxide and sulfuric acid from the lithium sulphate solution derived from a recycling process of spent lithium-ion battery material. The model is developed based on the conservation equations of mass and ions, and considers electrolyte solutions consisting of mono- and multivalence ions. The concentration polarization at ion exchanged membranes (IEMs) and their adjacent diffusion boundary layers as a function of the applied current, inlet concentrations and flow rate are computed. Experimental data from a three-compartment ED cell are used for validation. A parametric study is performed to evaluate the impact of parameters on transmembrane fluxes of ion and water. It is revealed that increasing current leads to the enhancement of the transmembrane water and concentration polarization across IEMs. Feeding solutions consisting of smaller ions result in lower water transfer through IEMs. Raising the lithium concentration at the dilute channel increases the LiOH concentration due to reduced transmembrane water transfer. Using the uncertainty propagation method, it is found that current and counter-ion radius are the most influential parameters affecting the outlet concentration of concentrate channel and transmembrane water transfer.