Low-Resistant Ion-Exchange Membranes for Energy Efficient Membrane Capacitive Deionization

Abstract

Membrane capacitive deionization (MCDI) has emerged as an effective and energy efficient desalination technology for treating brackish water streams used in numerous industrial processes. Most material research studies on MCDI focus on improving the porous electrodes or using flowing electrode architectures, and little emphasis is given to the rationale design of ion-exchange membranes (IEMs) for MCDI. In this work, the ionic conductivity, permselectivity, and thickness for three different IEM chemistries (polyaliphatic, poly(arylene ether), and perfluorinated) were correlated to MCDI performance attributes: energy expended per ion removed, salt removal efficiency, and Coulombic efficiency. A 5-to 10-fold reduction in area specific resistance, which accounts for thickness and ionic conductivity, with unconventional perfluorinated and poly(arylene ether) IEMs reduced the energy expended per ion removed in MCDI by a factor of 2 when compared to conventional electrodialysis IEMs. In situ electrochemical impedance spectroscopy substantiated that thinner membranes with higher ionic conductivity helped in the reduction of energy expended per ion removed (more than 50%). Finally, the lower than 100% Coulombic efficiency is ascribed to carbon corrosion of the porous electrodes highlighting that further improvements in MCDI do not just necessitate more appropriate membranes but corrosion resilient electrodes.

Asymmetric Membrane Capacitive Deionization Using Anion-Exchange Membranes Based on Quaternized Polymer Blends

“…Low area resistance is preferential to improve ion transfer across the electrode/membrane interface, hence increasing the energy efficiency of the MCDI process. 49 All blended membranes showed reduced area resistance compared to Q0 membrane (8.76 Ω cm 2 ). Q10 (1.99 Ω cm 2 ) and Q20 (1.46 Ω cm 2 ) membranes exhibited significant reduction in area resistance, owing to their enhanced hydrophilic properties and IEC.…”

Advancing electrodeionization with conductive ionomer binders that immobilize ion-exchange resin particles into porous wafer substrates

“…Poly(arylene ether) ionomer synthesis procedures SPEEK ionomer binder: PEEK was sulfonated based on our previous work. 1 In short, PEEK was dissolved in concentrated sulfuric acid (H 2 SO 4 ) at room temperature. The degree of sulfonation (DS) in PEEK was monitored by assaying the reactor periodically throughout the reaction.…”

“…Electrochemical separations, which primarily consist of electrodialysis (ED), electrodeionization (EDI), and membrane capacitive deionization (MCDI/CDI), 1 are a subset of technologies primarily used for deionization and other water treatment processes. These technologies offer distinct advantages for desalination over osmotic based technologies (e.g., reverse osmosis) in certain scenarios such as selective ionic sorption [2][3][4][5] and deionization of liquid streams with relatively low dissolved ionic species concentrations (e.g., brackish water with less than 5000 mg L −1 6 ).…”

Exploring the Function of Ion-Exchange Membrane in Membrane Capacitive Deionization via a Fully Coupled Two-Dimensional Process Model

“…Ionic transfer resistance is captured by the NP equations in this model. Palakkal et al [77] discovered that thin IEMs with high ion conductivity possessed low resistance and reduced energy consumption. This model can be extended by modifying the transport and adsorption terms to incorporate the effects of temperature, electronic resistances, Faradaic reactions, and special affinity towards specific ions with a surface-modified electrode and IEM.…”