Tutorial review of reverse osmosis and electrodialysis

Reverse osmosis (RO) and electrodialysis (ED) are the two most important membrane technologies for water desalination treatment. Their transport mechanisms very different, but on a closer look also have many similarities. In this tutorial review, we describe state-of-the-art theory both processes, focusing simple examples that helpful non-specialist classroom teaching. We relevant ion coupling with chemical mechanical equilibrium membrane/solution interfaces. For RO of neutral solutes, explain solution-friction (SF) model which is closely related to classical sieving or pore flow model. The SF includes advection, diffusion, solute partitioning, leads relationships coupled fluxes solutes (and thus retention as well), when diffusion boundary (or concentration polarization) layer included in Subsequently extended symmetric salt solutions charged membranes. solutions, ED present two-dimensional module-scale calculations lead characteristic curve determines optimum operational conditions based cost calculation offsets energy material costs. discuss two-fluid (TFM) comprehensively describes ED, how accurately experiments where ions transported opposite directions through membrane. Finally, results optimization studies combination multiple modules evaluate relevance polarization by using 3D cross-current an module.