Title : 『 A portable and high energy efficient seawater desalination device by ion concentration polarization 』

Speaker : Dr. Sung Jae Kim

(Dept. of Electrical Engg. and Computer Science, MIT)

Date : 19 SEP, 2011(Mon) 10:00~

Place : #1101, W1-3 Bldg.

Abstract :

The shortage of fresh water is the acute challenges and the energy efficient seawater desalination strategy can provide substantial answer for the water-crisis. Current desalination methods utilizing reverse-osmosis and electrodialysis mechanisms required high power consumptions/large-scale infrastructures which are not suitable for resource-limited settings. This work elucidates a novel micro/nanofluidic desalination process utilizing ion concentration polarization (ICP) leading a portable and low power consumed system.

The nanoporous membrane conducts only cations preferentially, which is not matching with the ion conductivities in bulk electrolytes. Once ICP is triggered, the concentrations of both cations and anions decrease on the anodic side of the membrane (ion depletion) and increase on the cathodic side (ion enrichment). With the strong ICP, both anions and cations are depleted near the nanojunctions. Combined with a pressure-driven flow, one could obtain a steady-state depletion zone using the device. In the experiments done with local real seawater, the depletion zone was formed to divert charged ions into the salted stream. It was also shown that the ICP layer acts as a virtual barrier for ANY charged particles, including most solid particles and biomolecules found in water. Therefore, both small salt ions and large microoranisms can be removed from the desalted stream, essentially eliminating the membrane fouling. In situ conductivity measurement of desalted stream showed that 99.4% salt removal with ~3.5Wh/L energy efficiency which is superior to any conventional desalination method. Thus, the system could be made into a small scale desalination system, with the possibility of battery/solar cell-powered operation. Current development regarding massive parallelization of the device promises a flow rate more than 1mL/min in 1/4 inch disk scale at the same power consumption. With the proper expansion of this parallelization, a meaningful flow rate (1L/min) would be achieved for remote- and resource limited settings. In addition, the science behind the ICP phenomenon will be also discussed.

※ For international students, attendance of this seminar will be considered as attendance of department seminar during regular semester.