(Invited) Scalability of an Ion Concentration Polarization-Based Water Purification Platform

This presentation will discuss the development of a portable water purification and desalting system to address water insecurity in regions with limited basic water infrastructure, water contamination, or frequent interruptions caused by climate change or natural disasters. Current membrane desalination technologies, such as reverse osmosis (RO) and electrodialysis (ED), are more suitable for urban areas than for resource-limited environments or places sensitive to natural disasters, e.g., flood or drought [2]. Most of the few commercially available portable RO systems require high-pressure pumping and water preconditioning before purification. RO systems are also prone to membrane fouling and require continuous maintenance, which limits deployment flexibility and adds to the total system cost. ED systems have higher energy loss than RO systems, especially for high salinity water purification [2-4]. Even with advancements in low-resistance membranes to improve power efficiency, ED systems still struggle to avoid ion diffusion from the concentrated brine and to remove microparticles (e.g., microplastics) [3]. Thus, alternative point-of-use water purification systems are urgently needed. We have developed a water desalting and purification method that employs a nonlinear electrokinetic phenomenon to divert charged species (salts, molecular ions, bacteria, microplastics) from flowing feedwater into a physically separated waste stream. This electrokinetic phenomenon, ion concentration polarization (ICP), occurs when a voltage bias is applied across ion-selective features such as electrodes or highly charged membranes. This process selectively transports ions, subsequently creating ion depletion and enrichment zones (IEZ & IDZ) at the opposing ends of the ion-selective feature. For water desalination, ICP captures or redirects charged particles at the boundary between the background electrolyte and the IDZ, effectively removing not only salts but also bacteria and oil-in-water emulsions with negative zeta potential. While planar membrane-based desalination using ICP has been demonstrated, its throughput is insufficient for practical use due to the instability of the electric field and electroconvective vortices generated. Figure 1