(272b) Rationale Design of Ion-Exchange Membranes for Low Energy Brackish Water Desalination Via Membrane Capacitive Deionization
MCDI, an electrochemical technology, offers the enticing prospect of low energy water desalination as it can recover energy (demonstrated up to 83%)2 when discharging the saturated electrodes as a supercapacitor. Most research today has focused on porous carbon electrodes to increase MCDI capacity. However, material innovation with regard to the ion-exchange membranes used in MCDI has been neglected. Todayâs MCDI currently uses electrodialysis (ED) membranes â not originally designed for MCDI. The ion-exchange membranes for ED tend to be thick as they serve as a separator in addition to an ion-conducting electrolyte in electrodialysis. In MCDI, the ion-exchange membranes do not serve as separator and they are employed to prevent co-ion adsorption to the porous carbon electrodes.
This talk will demonstrate how thinner ion-exchange membranes with higher ionic conductivity substantially reduces the energy footprint for MCDI - approximately 35 kT per ion removed with ED membranes to 15 kT per ion removed with new ion-exchange membranes. Additionally, the new ion-exchange membranes displayed a significantly higher Coulombic efficiency. The talk will showcase how ex-situ properties of ion-exchange membranes, such as ionic conductivity, thickness, and permselectivity, are instrumental for lowering the energy footprint of MCDI.
 D. Bauer, M. Philbrick, B. Vallario in The Water-Energy Nexus: Challenges and Opportunities, 2014.
 P. Dlugolecki, A. van der Wal Environmental Science & Technology. 2013, 47, 4904-4910.