Correlation equation for evaluating energy consumption and process performance of brackish water desalination by electrodialysis

Electrodialysis (ED) is an electro-driven desalination technology that relies on the selective transport of ions through ion exchange membranes. Though several approaches have been developed to model and evaluate the performance of ED, mechanistic ion-transport models, which rigorously solve the fundamental Nernst-Planck equation, remain some of the most reliable and utilized. However, complexity of the involved transport phenomena prevents analytical solutions of such models, and numerical solutions can be prohibitively intensive. Here, we use an equivalent circuit analogue to derive a simple correlation equation that predicts the energetic performance of ED for brackish water desalination. Specifically, our correlation equation predicts the specific energy consumption of ED for a given productivity, set of desalination parameters (i.e., feed salinity, salt removal, water recovery), and system properties. The correlation equation demonstrates robustness in predicting the specific energy consumption across a wide range of operational parameters, showing excellent agreement with a Nernst-Planck ion-transport model and literature-reported experimental data. Furthermore, we use the developed correlation equation to show the dependence of the specific energy consumption on the productivity, highlighting the tradeoff between the thermodynamic energy efficiency and desalination rate of the ED process. Overall, our developed correlation equation provides a convenient alternative to computationally intensive mechanistic models for performance analysis of the ED process. • Derived correlation equation for predicting energy consumption of electrodialysis • Demonstrated robustness of correlation equation as compared to ion transport model • Correlation equation reliably predicted literature reported energy consumption data • Utilized correlation equation as a simple yet powerful performance analysis tool