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Microscale electrodeionization: In situ concentration profiling and flow visualization

Title
Microscale electrodeionization: In situ concentration profiling and flow visualization
Author
곽노균
Keywords
Desalination; Electroconvection; Electrodeionization; Water splitting; Overlimiting current; Ion concentration polarization
Issue Date
2020-03
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Citation
WATER RESEARCH, v. 170, article no. 115310
Abstract
Electrodeionization (EDI) is membrane-based desalination utilizing ion exchange membranes and ion exchange resins. By combining Electrodialysis and Ion exchanger, EDI can produce ultrapure water in a continuous-flow manner. Although its theoretical mechanisms are well documented, there is no experimental platform that can provide microscopic details inside of the system. In this paper, we present microscale EDI that can visualize in situ ion concentration, pH, and fluid flows. The platform was fabricated by filling ion exchange resins as a monolayer in a transparent polydimethylsiloxane channel between cation and anion exchange membranes. According to operating voltages (0-15V), distinct behaviors of ion concentration profile, pH shift, and fluid flows were observed in Ohmic, limiting, and overlimiting regimes. It is noteworthy that overlimiting regimes can be sub-categorized as water-splitting and electroconvection regimes. In the early stage (4-8V), water-splitting is dominant with pH change near the membranes and resins; under a higher voltage (8-15V), electroconvection starts to occur even water-splitting tries to suppress the development of the extended space charge layer and corresponding electroconvective instability. Accelerated ionic migration by electroconvection can improve current efficiency up to 80%. This is a clear departure from overlimiting dynamics in electrodialysis (with electroconvection only), ion exchanger (with no distinct regime), and even from that in previous EDI experiments (with water splitting only). (C) 2019 Elsevier Ltd. All rights reserved.
URI
https://www.sciencedirect.com/science/article/pii/S004313541931084X?via%3Dihubhttps://repository.hanyang.ac.kr/handle/20.500.11754/165151
ISSN
0043-1354
DOI
10.1016/j.watres.2019.115310
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > MECHANICAL ENGINEERING(기계공학부) > Articles
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