Lee, Hyungsub Kim, Dongho Kang, Ji Yoon Bong, Ki Wan Lee, Soo Hyun Kwak, Rhokyun 2024-01-19T20:02:34Z 2024-01-19T20:02:34Z 2021-09-02 2019-05-15 0011-9164 https://pubs.kist.re.kr/handle/201004/119988 Capacitive deionization (CDI) is an emerging desalination technique by utilizing the electrosorption of porous electrodes. Thus far, only linear concentration profiles in bulk electrolyte between the electrodes have been observed, during ion charging (ion depletion) or ion discharging (ion enrichment). This so-called linear ion concentration polarization (ICP) can be predicted by the simple convective-diffusion model. In this study, we demonstrate that capacitive charging can induce nonlinear concentration profiles in the electrolyte. To visualize nonlinear ICP dynamics, a miniaturized CDI platform is developed to observe in situ ion concentration profiles. Determined by the ion flux mismatching of electrosorption and bulk ion transport, we discovered four ICP regimes in CDI steady, linear ICP, delayed-nonlinear ICP, and nonlinear ICP. We directly observed the signatures of nonlinear ICP: i) flat depletion zone with extremely low ion concentration, and ii) corresponding exponential current drop. Based on this observation, two scaling models are formulated to predict i) when the nonlinear ICP occurs, and ii) the propagation speed of the flat depletion zone. To the best of our knowledge, this is the first microscopic characterization of ICP in CDI systems, and it firmly establishes the existence of nonlinear ion transport dynamics in CDI's bulk electrolyte. English ELSEVIER SCIENCE BV ACTIVATED CARBON CLOTH WATER DESALINATION FARADAIC REACTIONS POROUS-ELECTRODES ENERGY MODEL CDI ELECTRODIALYSIS TECHNOLOGY TRANSPORT Nonlinear dynamics of ion concentration polarization in capacitive deionization Article 10.1016/j.desal.2019.01.032 1 DESALINATION, v.458, pp.14 - 24 DESALINATION 458 14 24 scie scopus 000462695500002 2-s2.0-85061427293 Engineering, Chemical Water Resources Engineering Water Resources Article ACTIVATED CARBON CLOTH WATER DESALINATION FARADAIC REACTIONS POROUS-ELECTRODES ENERGY MODEL CDI ELECTRODIALYSIS TECHNOLOGY TRANSPORT Capacitive deionization Desalination Ion concentration polarization