Flow-electrode capacitive deionization with highly enhanced salt removal performance utilizing high-aspect ratio functionalized carbon nanotubes

Cho, Younghyun; Yoo, Chung‐Yul; Lee, Seung Woo; Yoon, Ho Kyoung; Lee, Ki Sook; Yang, SeungCheol; Kim, Dong Kook

doi:10.1016/j.watres.2018.11.080

Cited by 132 publications

(62 citation statements)

References 47 publications

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“…It further decreased to 15.3 Ω and 13.5 Ω for 10% and 20% ZIF-67@CNT, respectively. The addition of CNT improved the electrical conductivity of AC by forming electrical contacts between AC particles, as reported in a previous study [11], and the addition of ZIF-67@CNT increased the surface area of the electrode by about 87% in comparison with the 10% CNT electrode (See Figure 6c). Therefore, R1 was found to decrease in the order of AC > 10% CNT > 10% ZIF-67@CNT > 20% and ZIF-67@CNT, while R2 decreased from 5.99 Ω (pristine AC) to 3.73 Ω and 1.81 Ω for 10% CNT and 10% ZIF-67@CNT, respectively.…”

Section: Resultssupporting

confidence: 82%

“…Various approaches for realizing enhanced desalination performance have been reported so far. The addition of CNT could improve the desalination performance by formation of a conducting bridge [11]. There have also been efforts to improve desalination capacitance by involving redox active materials including metal oxide, conducting polymer, and hybrid materials [12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…However, the conductivity of most untreated MOFs is relatively low, which limits their applications for electrochemical devices. Nanostructured carbon materials, including carbon nanotubes (CNTs) and graphene, have been widely investigated as highly conductive agents, which can significantly enhance the electrical interconnectivity between individual electrode particles, including AC [11,[33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Desalination Performance of Capacitive Deionization Using Nanoporous Carbon Derived from ZIF-67 Metal Organic Frameworks and CNTs

et al. 2020

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Capacitive deionization (CDI) based on ion electrosorption has recently emerged as a promising desalination technology due to its low energy consumption and environmental friendliness compared to conventional purification technologies. Carbon-based materials, including activated carbon (AC), carbon aerogel, carbon cloth, and carbon fiber, have been mostly used in CDI electrodes due their high surface area, electrochemical stability, and abundance. However, the low electrical conductivity and non-regular pore shape and size distribution of carbon-based electrodes limits the maximization of the salt removal performance of a CDI desalination system using such electrodes. Metal-organic frameworks (MOFs) are novel porous materials with periodic three-dimensional structures consisting of metal center and organic ligands. MOFs have received substantial attention due to their high surface area, adjustable pore size, periodical unsaturated pores of metal center, and high thermal and chemical stabilities. In this study, we have synthesized ZIF-67 using CNTs as a substrate to fully utilize the unique advantages of both MOF and nanocarbon materials. Such synthesis of ZIF-67 carbon nanostructures was confirmed by TEM, SEM, and XRD. The results showed that the 3D-connected ZIF-67 nanostructures bridging by CNTs were successfully prepared. We applied this nanostructured ZIF-67@CNT to CDI electrodes for desalination. We found that the salt removal performance was significantly enhanced by 88% for 30% ZIF-67@CNTs-included electrodes as compared with pristine AC electrodes. This increase in salt removal behavior was analyzed by electrochemical analysis such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, and the results indicate reduced electrical impedance and enhanced electrode capacitance in the presence of ZIF-67@CNTs.

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced Desalination Performance of Capacitive Deionization Using Nanoporous Carbon Derived from ZIF-67 Metal Organic Frameworks and CNTs

et al. 2020

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“…Therefore, it has been investigated intensively for the last two decades for removal of sodium chloride ions from brackish water. Many researchers have developed CDI desalination systems in terms of theories, electrode materials, and various cell configurations [17][18][19][20][21][22][23][24][25][26][27][28]. Furthermore, in principle, not only sodium chloride but also various kinds of charged ions can be extracted [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

“…Due to such limitations of conventional CDI desalination, the salt removal performance has to be sacrificed, making its main target desalination of brackish water with a salt concentration of only few grams per liter. In order to solve such inherent disadvantages of the CDI system, desalination using CDI based on flow electrodes (FCDI) has been investigated [21,26,[32][33][34]. When a flow anode and cathode circulate the FCDI cell, ions are adsorbed onto the electric double layer of -porous electrode carbons and flow out together.…”

Section: Introductionmentioning

confidence: 99%

Continuous Lithium Extraction from Aqueous Solution Using Flow-Electrode Capacitive Deionization

Jung

Lim

et al. 2019

Energies

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Flow-electrode-based capacitive deionization (FCDI) is a desalination process that uses electrostatic adsorption and desorption of ions onto electrode materials. It provides a continuous desalination flow with high salt removal performance and low energy consumption. Since lithium has been regarded as an essential element for the last few decades, the efficient production of lithium from the natural environment has been intensively investigated. In this study, we have extracted lithium ions from aqueous solution by using FCDI desalination. We confirmed that lithium and chloride ions could be continuously collected and that the salt removal rate depends on various parameters, including feed-flow rate and a feed saline concentration. We found that the salt removal rate increases as the feed-flow rate decreases and the feed salt concentration increases. Furthermore, the salt removal rate depends on the circulation mode of the feed solution (continuous feed stream vs. batch feed stream), which allows control of the desalination performance (higher capacity vs. higher efficiency) depending on the purpose of the application. The salt removal rate was highest, at 215.06 µmol/m −2 s −1 , at the feed rate of 3 mL/min and the feed concentration of 100 mg/L. We believe that such efficient and continuous extraction of lithium chloride using FCDI desalination can open a new door for the current lithium-production industry, which typically uses natural water evaporation.

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PEDOT:PSS‐CNT Composite Particles Overcome Contact Resistances in Slurry Electrodes for Flow‐Electrode Capacitive Deionization

Rauer

Wang

Köller

et al. 2023

Adv Funct Materials

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Activated carbon (AC) particles constitute the current material of choice concerning the preparation of flow electrodes for flow‐electrode capacitive deionization (FCDI). They are inexpensive, mass‐producible, highly conductive, and exhibit a large specific surface area for ion adsorption. However, despite recent advances concerning the modification of AC slurries, their density, and hydrophobicity still constitute major challenges regarding particle aggregation, sedimentation, and pumpability, restricting their particle load to approximately 25 wt.%. Since the particle volume fraction directly correlates to the chance of particle contact, which dictates the charge transfer and hence the degree of flow electrode utilization, the development of AC‐based slurries seems to stagnate. This study addresses these challenges by investigating poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)‐based suspensions as an alternative to conventional carbon‐based flow electrodes. The corresponding conductive hydrogel particles feature softness, internal porosity, low density, hydrophilicity, and a mass‐specific salt adsorption capacity that exceeds AC by up to ten times. FCDI experiments can reveal that, contrary to AC, the inherent properties of PEDOT:PSS‐based particles simplify the slurry preparation process and enable flow electrode circulation at significantly higher particle volume fractions. These results suggest that PEDOT:PSS‐based hydrogel particles are a promising candidate to overcome the percolation and contact‐related challenges of state‐of‐the‐art AC slurries.

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Flow-electrode capacitive deionization with highly enhanced salt removal performance utilizing high-aspect ratio functionalized carbon nanotubes

Cited by 132 publications

References 47 publications

Enhanced Desalination Performance of Capacitive Deionization Using Nanoporous Carbon Derived from ZIF-67 Metal Organic Frameworks and CNTs

Enhanced Desalination Performance of Capacitive Deionization Using Nanoporous Carbon Derived from ZIF-67 Metal Organic Frameworks and CNTs

Continuous Lithium Extraction from Aqueous Solution Using Flow-Electrode Capacitive Deionization

PEDOT:PSS‐CNT Composite Particles Overcome Contact Resistances in Slurry Electrodes for Flow‐Electrode Capacitive Deionization

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