• Title, Summary, Keyword: capacitive deionization

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Anatase TiO2-doped activated carbon fibers prepared by ultrasonication and their capacitive deionization characteristics

  • Kang, Da Hee;Jo, Hanjoo;Jung, Min-Jung;Kim, Kyoung Hoon;Lee, Young-Seak
    • Carbon letters
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    • v.27
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    • pp.64-71
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    • 2018
  • $TiO_2$-doped activated carbon fibers (ACFs) were successfully prepared as capacitive deionization (CDI) electrode materials by facile ultrasonication-assisted process. ACFs were treated with titanium isopropoxide (TTIP) and isopropyl alcohol solutions of different concentrations and then calcinated by ultrasonication without heat-treatment. The results show that a certain amount of anatase $TiO_2$ was present on the ACF surface. The specific capacitance of the $TiO_2$-doped ACF electrode was remarkably improved (by 93.8% at scan rate of $50mV\;s^{-1}$) over that of the untreated ACF electrode, despite decreases in the specific surface area and total pore volume upon $TiO_2$ doping. From the CDI experiments, the salt adsorption capacity and charge efficiency of the sample with TTIP percent concentration of 15% were found to considerably increase by 71.9 and 57.1%, respectively. These increases are attributed to the improved wettability of the electrode, which increases the number of surface active sites and facilitates salt ion diffusion in the ACF pores. Additionally, the Ti-OH groups of $TiO_2$ act as electrosorption sites, which increases the electrosorption capacity.

Development and Application of Cation-exchange Membranes Including Chelating Resin for Efficient Heavy-metal Ion Removal (효율적인 중금속 이온 제거를 위한 킬레이팅 수지를 포함한 양이온 교환막의 개발 및 응용)

  • Kim, Do-Hyeong;Choi, Young-Eun;Park, Jin-Soo;Kang, Moon-Sung
    • Membrane Journal
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    • v.27 no.2
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    • pp.129-137
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    • 2017
  • In this study, we have developed cation-exchange membranes (CEMs) which can efficiently separate heavy-metal ions among the cations contained in a water system. Sulfonated polyetheretherketone (SPEEK) was used as a base polymer and a powdered chelating resin with strong binding ability to heavy-metal ions was added into it. In order to optimize the performance of the CEM, the content of chelating resin powder and the ion exchange capacity of SPEEK have been controlled. As a result, it was confirmed that the removal efficiency of heavy metal ion was improved by more than 20% by applying the CEM to membrane capacitive deionization (MCDI).

The Study of Capacitive Deionization Technology by the Analysis of Patents and Papers (특허 및 논문 분석을 통한 축전식 탈염(CDI) 기술 연구)

  • Son, Won-Keun;Kim, Tae-Il;Han, Hye-Jung;Kang, Kyung-Seok
    • Korean Chemical Engineering Research
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    • v.49 no.6
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    • pp.697-703
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    • 2011
  • Capacitive deionization(CDI) is an ion removal technology that employs the basic electrochemical principle of absorbing ions in high surface area electrode. CDI technology reduce power consumption because it operates at lower electrode potential(about 1~2 V). Also, it is an environmentally friendly technology because no acid, base, or salts are required to generate the surface. In this study, we searched the patents and papers to investigate the trend of CDI technologies. Database was collected from WIPS and Scopus site and was investigated according to electrode, module and application technology of CDI. The technology trend of CDI was analyzed based on patent application year, countries, main applications and technologies.

Preparation and application of reduced graphene oxide as the conductive material for capacitive deionization

  • Nugrahenny, Ayu Tyas Utami;Kim, Jiyoung;Kim, Sang-Kyung;Peck, Dong-Hyun;Yoon, Seong-Ho;Jung, Doo-Hwan
    • Carbon letters
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    • v.15 no.1
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    • pp.38-44
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    • 2014
  • This paper reports the effect of adding reduced graphene oxide (RGO) as a conductive material to the composition of an electrode for capacitive deionization (CDI), a process to remove salt from water using ionic adsorption and desorption driven by external applied voltage. RGO can be synthesized in an inexpensive way by the reduction and exfoliation of GO, and removing the oxygen-containing groups and recovering a conjugated structure. GO powder can be obtained from the modification of Hummers method and reduced into RGO using a thermal method. The physical and electrochemical characteristics of RGO material were evaluated and its desalination performance was tested with a CDI unit cell with a potentiostat and conductivity meter, by varying the applied voltage and feed rate of the salt solution. The performance of RGO was compared to graphite as a conductive material in a CDI electrode. The result showed RGO can increase the capacitance, reduce the equivalent series resistance, and improve the electrosorption capacity of CDI electrode.

Analysis of newly designed CDI cells by CFD and its performance comparison

  • Kwon, Se Hwan;Rhim, Ji Won
    • Membrane Water Treatment
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    • v.7 no.2
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    • pp.115-126
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    • 2016
  • In this study, computational fluid dynamics (CFD) analysis was conducted to investigate the flow pattern and to find the occurrence of dead zones in an existing capacitive deionization (CDI) cell. Newly designed cells-specifically designed to avoid dead zones-were analyzed by CFD in accordance with the flow rates of 15, 25 and 35 ml/min. Next, the separation performances between the existing and newly designed cell were compared by conducting CDI experiments in terms of salt removal efficiency at the same flow rates. Then, the computational and experimental results were compared to each other. The salt removal efficiencies of the hexagon flow channel 1 (HFC1) and hexagon flow channel 2 (HFC2) were increased 88-124% at 15 ml/min and 49-50% at 25 ml/min, respectively. There was no difference between the existing cell and the foursquare flow cell (FFC) at 35 ml/min.

Preparation of Carbon Electrodes Using Activated Carbon Fibers and Their Performance Characterization for Capacitive Deionization Process (활성탄소섬유를 이용한 탄소전극의 제조 및 축전식 탈염공정에서의 성능평가)

  • Park, Cheol Oh;Oh, Ju Seok;Rhim, Ji Won
    • Membrane Journal
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    • v.28 no.4
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    • pp.271-278
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    • 2018
  • In this study, the carbon electrodes using activated carbon fibers (ACFs) were prepared for the capacitive deionization process. The Polyvinylidene fluoride (PVDF) was used as the binder and the mixed ACFs with proper solvent was cast on the commercial graphite sheets to prepare the carbon electrodes. At this moment, the different particle sizes of ACFs were applied and the mixing ratio of solvent, PVDF and ACFs, 80 : 2 : 18 and 80 : 5 : 15, were used for the electrode preparation. Then their salt removal efficiencies were characterized under the various operating conditions, adsorption potential and time, desorption potential and time, concentration of feed NaCl solution and flow rate as well. Typically, the salt removal efficiency of 53.6% were obtained at the particle size below $32{\mu}m$, mixing ratio 80 : 2 : 18, adsorption 1.2 V and 3 min, desorption -0.1V and 1 min, and 15 mL/min flow rate of NaCl 100 mg/L.

Stable Desalination of Hardness Substances through Charge Control in a Capacitive Deionization System (축전식 탈염 시스템에서 전하량 제어를 통한 경도물질의 안정적인 탈염)

  • Kim, Yoon-Tae;Choi, Jae-Hwan
    • Applied Chemistry for Engineering
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    • v.30 no.4
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    • pp.472-478
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    • 2019
  • A stable desalination method of the hardness substance such as $Ca^{2+}$ by controlling the total charge (TC) supplied to the membrane capacitive deionization (MCDI) cell was studied. The adsorption (1.5 V) and desorption (0.0 V) were repeated 30 times while varying the TC in the adsorption process. The concentration and pH of effluent, adsorption and desorption amounts, current densities and cell potentials were analyzed in the desalination process. The maximum allowable charge (MAC) of the carbon electrode used in MCDI cell was measured to be 46 C/g. As a result of operation at TC (40 C/g) below the MAC value, electrode reactions did not occur, resulted in the stable desalination characteristics for a long-term operation. When operating at TCs (50, 60 C/g) above the MAC value, however, the concentration and pH of effluent varied greatly. Also, the scale was formed on the electrode surface due to electrode reactions, and the electric resistance of the cell gradually increased. It was thus concluded that it is possible to remove stably the hardness substance without any electrode reactions by controlling the charge supplied to MCDI cell during the adsorption process.

Crosslinking of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes (폴리페닐렌 옥사이드 음이온 교환막의 가교결합)

  • Lee, Seung-Gwan;Kim, Mi-Yang;So, Won-Wook;Kang, Kyung-Seok;Kim, Kwang-Je
    • Membrane Journal
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    • v.28 no.5
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    • pp.326-331
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    • 2018
  • Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes, which can be used for capacitive deionization (CDI), was investigated. PPO Anion exchange polymer was prepared through bromination and amination reaction steps and crosslinked with bisphenol A diglycidylether (BADGE), m-phenylenediamine (m-PDA), and hexamethylenediamine (HMDA). The gelation time by crosslinking was short in the order of HMDA > m-PDA > BADGE. The anion exchange membranes crosslinked at room temperature over a certain amount of crosslinking agent did not dissolve in an aprotic solvent such as 1-methylpyrrolidone (NMP) and the chemical durability of their membranes to organic solvent increased. The ion exchange capacity and water uptake of anion exchange membranes crosslinked with different crosslinker (BADGE) contents were measured and compared. The CDI performance of the crosslinked PPO anion exchange membrane immersed in the HMDA solution was almost the same as that of the non - crosslinked membrane except for the initial stage of the adsorption step.

Studies of Performance and Enlarged Capacity through Multi-stages Stacked Module in Membrane Capacitive Deionization Process (막 축전식 탈염 공정의 다단 적층 모듈을 통한 처리 용량 증대 및 이의 성능 연구)

  • Song, Yye jin;Yun, Won Seob;Rhim, Ji Won
    • Membrane Journal
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    • v.27 no.5
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    • pp.449-457
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    • 2017
  • In this study, the 10 stages stacked module was designed by increasing the number of unit cells in the membrane capacitive deionization(MCDI) process. The aminated polysulfone and sulfonated poly(ether ether ketone) were synthesized and coated on porous carbon electrode by casting method. The salt removal efficiency was measured for the 10 stage stacked module under the operation conditions of adsorption voltage and time, desorption voltage and time, flow rate and concentration of feed water, and di-valent solutions including $CaSO_4$, $MgCl_2$ and tap water. Typically, when 100 mg/L of NaCl as the feed was used, the salt removal efficiency was 98.3% at a flow rate of 100 mL/min, the adsorption condition of 1.2 V/3 min and desorption condition of -0.5 V/5 min.