Modeling of batch electrodialysis for hydrochloric acid recovery

Electrodialysis (ED) is a feasible method for acid recovery because it has the capability of separating ionic chemicals from non-ionic chemicals in process or waste streams to achieve product purity or eliminate wastes. At the same time, it can also enrich the separated chemicals. In this work, a model based on first principle was developed in order to understand the behavior of electrodialysis process. The Nernst–Planck derived relationship was used to build the ED process model which contains a set of ordinary differential equations (ODE). A degree of freedom analysis was carried out and a unique solution with 38 unknown parameters were identified. The parameters were determined from the literature and various equations. The developed model was then simulated and the results were compared to that from previous experimental work. The accuracy of the developed model was high with 99% degree of confidence. The sensitivity analysis of various ED parameters towards its performances was also analyzed. It was found that process time and energy consumption increased when higher initial HCl concentration in the dilute and concentrate tanks, higher current density and lower Vconc/Vdil ratio were applied. However, the effect of flowrate on process time and energy consumption was found to be insignificant.