• Title, Summary, Keyword: capacitive deionization

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Comparison of CDI and MCDI applied with sulfonated and aminated polysulfone polymers

  • Kim, Ji Sun;Rhim, Ji Won
    • Membrane Water Treatment
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    • v.7 no.1
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    • pp.39-53
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    • 2016
  • In this study, polysufone (PSf) was used as a base polymer to synthesize sulfonated polysulfone (SPSf) and aminated polysulfone (APSf) as cation and anion exchange polymers, respectively. Then the ion exchange polymers were coated onto the surface of commercial carbon electrodes. To compare the capacitive deionization (CDI) and membrane capacitive deionization (MCDI) processes, the pristine carbon electrodes and ionic polymer coated electrodes were tested under various operating conditions such as feed flow rate, adsorption time at fixed desorption time, and feed concentration, etc., in terms of effluent concentration and salt removal efficiency. The MCDI was confirmed to be superior to the CDI process. The performance of MCDI was 2-3 times higher than that of CDI. In particular, the reverse desorption potential was a lot better than zero potential. Typically, the salt removal efficiency 100% for 100 mg/L NaCl was obtained for MCDI at feed flow rate of 15 ml/min and adsorption/desorption time of 3 min/1 min and applied voltages 1.0 V for adsorption and -0.3 V for desorption process, and for 500 mg/L, the salt removal efficiency 91% was observed.

Application of Capacitive Deionization Packed Ion Exchange Resins in Two Flow Channels (두 가지 유로 형태에 따라 이온교환수지를 채운 축전식 탈염기술)

  • Lee, Dong-Ju;Park, Jin-Soo
    • Journal of the Korean Electrochemical Society
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    • v.18 no.1
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    • pp.24-30
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    • 2015
  • To desalinate the aqueous solutions with high salt concentration using the capacitive deionization technology, two resin/membrane capacitive deionization(RMCDI) cells were fabricated by filling mixed ion exchange resins in two different flow channels (spacer and spiral type). The salt removal efficiency of the spacer- and spiral-RMCDI was 77.21 and 99.94%, respectively. Many ions were significantly removed in a spiral RMCDI cell because the feed solution could be more evenly contacted with the ion exchange resins filled on the spiral type flow channel. As the result of the changes of pH and accumulative charges, it was observed that Faradaic reaction was diminished for a spiral RMCDI cell filled by the mixture of cation and anion exchange resins. Therefore, the desalination of the aqueous solutions with high salt concentration by the capacitive deionization technology was proven. In addition, further studies on the optimization of the mixing ratio with ion exchange resins and the introduction of the regeneration process generally occurred in the continuous electrodeionization (CEDI) technology are required to improve the RMCDI technology.

Performance Study of Membrane Capacitive Deionization Installed with Sulfonated Poly(ether ether ketone) and Poly(vinyl amine)/poly(vinyl alcohol) Membranes (Sulfonated Poly(ether ether ketone) 및 Poly(vinyl amine)/poly(vinyl alcohol) 혼합막이 장착된 막결합형 축전식 탈염공정의 성능 연구)

  • Kim, Ka young;Rhim, Ji Won
    • Membrane Journal
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    • v.26 no.1
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    • pp.62-69
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    • 2016
  • In this study, sulfonated poly(ether ether ketone) (SPEEK) as cation exchange membrane and blended and crosslinked poly(vinyl amine) (PVAm) with poly(vinyl alcohol) (PVA) membrane as anion exchange membrane were used and then the performance experiments of the membrane capacitive deionization (MCDI) installed with both membranes were carried out. The newly prepared anion exchange membrane were characterized through water content, ion exchange capacity and FT-IR. The crosslinking time of 3 h to 5 h indicated that the salt removal was reduced from 81.3, 65.7% to 53.8%. The effect of PVAm contents from 40, 60, to 80% on the salt removal was shown 81.3, 75.2 and 37.7%, respectively. As a result, it was concluded that the crosslinking time and the content of PVAm had an influence on the salt removal efficiency.

Effect of surface modification of carbon felts on capacitive deionization for desalination

  • Lee, Jong-Ho;Ahn, Hong-Joo;Cho, Donghwan;Youn, Jeong-Il;Kim, Young-Jig;Oh, Han-Jun
    • Carbon letters
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    • v.16 no.2
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    • pp.93-100
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    • 2015
  • Surface modified carbon felts were utilized as an electrode for the removal of inorganic ions from seawater. The surfaces of the carbon felts were chemically modified by alkaline and acidic solutions, respectively. The potassium hydroxide (KOH) modified carbon felt exhibited high Brunauer-Emmett-Teller (BET) surface areas and large pore volume, and oxygen-containing functional groups were increased during KOH chemical modification. However, the BET surface area significantly decreased by nitric acid ($HNO_3$) chemical modification due to severe chemical dissolution of the pore structure. The capability of electrosorption by an electrical double-layer and the efficiency of capacitive deionization (CDI) thus showed the greatest enhancement by chemical KOH modification due to the appropriate increase of carboxyl and hydroxyl functional groups and the enlargement of the specific surface area.

Effect of Ion Exchange Capacity on Salt Removal Rate in Membrane Capacitive Deionization Process (이온교환용량이 막 결합형 축전식 탈염공정에서 염 제거율에 미치는 영향)

  • Yun, Won Seob;Cheong, Seong Ihl;Rhim, Ji Won
    • Membrane Journal
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    • v.28 no.5
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    • pp.332-339
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    • 2018
  • In order to investigate the effect of ion exchange capacity of ion exchange membranes on the salt removal efficiency in the membrane capacitive deionization process, sulfosuccinic acid (SSA) as the cross linking agent was added to poly(vinyl alcohol)(PVA) and sulfonic acid-co-maleic acid (PSSA_MA) was put into PVA at different concentrations of 10, 50 and 90 wt% relative to PVA. As the content of PSSA_MA increased, the water content and ion exchange capacity increased and the salt removal efficiency was also increased in the membrane capacitive deionization process. The highest salt removal efficiency was 65.5% at 100 mg/L NaCl feed at a flow rate, 15 mL/min and adsorption, 1.4 V/5 min for PSSA_MA 90 wt%.

Desalination Effects of Capacitive Deionization Process Using Activated Carbon Composite Electrodes (활성 탄소 복합 전극을 이용한 Capacitive Deionization 공정의 제염 효과)

  • Lee, Jeong-Won;Kim, Hong-Il;Kim, Han-Joo;Shin, Hyun-Soo;Kim, Jeong-Sik;Jeong, Boong-Ik;Park, Soo-Gil
    • Journal of the Korean Electrochemical Society
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    • v.12 no.3
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    • pp.287-294
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    • 2009
  • Desalination effects of Capacitive deionization(CDI) process using activated carbon $TiO_2$ composite electrode. In this study, we made the activated carbon electrod and activated carbon $TiO_2$ composite electrode, which analysed at cyclic voltammetry and charge-discharge. The results measured for discharge capacitance in cyclic voltammetry were 125 F/g in activated carbon electrode and capacitance of activatd carbon composite electrode was increased about two time, 243 F/g. The $TiO_2$ content of activated carbon composite electrode was 10 wt.%. When it was added wtih TiO2, electric double layer adsorption content was increased, so it was increased 25% in ion removal ratio of activated carbon electrode.

Comparison of Selective Removal of Nitrate Ion in Constant Voltage and Constant Current Operation in Capacitive Deionization (축전식 탈염에서 정전압과 정전류 운전에 따른 질산 이온의 선택적 제거율 비교)

  • Choi, Jae-Hwan;Kim, Hyun-Ki
    • Korean Chemical Engineering Research
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    • v.53 no.3
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    • pp.269-275
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    • 2015
  • The adsorption characteristics of ions were evaluated for the nitrate-selective carbon electrode (NSCE) in accordance with power supply methods. The NSCE was fabricated by coating the surface of a carbon electrode with anion-exchange resin powders with high selectivity for the nitrate ion. Capacitive deionization (CDI) experiments were performed on a mixed solution of nitrate and chloride ion in constant voltage (CV) and constant current (CC) modes. The number of total adsorbed ions in CV mode was 15% greater than that in CC mode. The mole fraction of adsorbed nitrate ion showed the maximum 58%, though the mole fraction was 26% in the mixed solution. This indicates that the fabricated NSCE is highly effective for the selective adsorption of nitrate ions. The mole fraction of adsorbed nitrate was nearly constant value of 55-58% during the adsorption period in CC mode. In the case of CV mode, however, the values increased from the initial 30% to 58% at the end of adsorption. We confirmed that the current supplied to cell is important factor to determine the selective removal of nitrate.

Effect of Chemically Treated / Untreated Carbon Cloth: Potential Use as Electrode Materials in the Capacitive Deionization Process of Desalination of Aqueous Salt Solution

  • Thamilselvan, Annadurai;Nesaraj, A Samson;Noel, Michael;James, E.J.
    • Journal of Electrochemical Science and Technology
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    • v.6 no.4
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    • pp.139-145
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    • 2015
  • Capacitive deionization (CDI) process is a novel approach for desalination of an aqueous salt solution. In the present study, an activated carbon cloth (ACC) is proposed as effective electrode material. Initially the carbon cloth was activated in 1 M and 8 M HNO3 for 9 hours at room temperature. The untreated and chemically activated carbon cloth (ACC) electrode materials were subjected to BET surface area measurements in order to get information about their specific surface area, average pore size, total pore volume and micropore area. The above materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) also. The electrochemical studies for the electrodes were done using cyclic voltammetry (CV) in 0.1 M Na2SO4 medium. From the studies, it was found that resistivity of the activated carbon cloth electrodes (treated in 1 M and 8 M HNO3) was decreased significantly by the chemical oxidation in nitric acid at room temperature and its capacitance was found to be 90 F/g (1 M HNO3) and 154 F/g (8 M HNO3) respectively in 0.1 M Na2SO4 solution. The capacitive deionization behavior of a single cell CDI with activated carbon cloth electrodes was also studied and reported in this work.

Improvement of Capacitive Deionization Performance by Coating Quaternized Poly(phenylene oxide) (4급화 폴리페닐렌 옥시드 코팅을 통한 축전식 탈이온 성능 향상)

  • Kim, Do-Hyeong;Kang, Moon-Sung
    • Membrane Journal
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    • v.24 no.4
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    • pp.332-339
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    • 2014
  • In this study, an anion-exchange ionomer solution was developed by employing poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as the base material for the improvement of the capacitive deionization (CDI) performances. It was found that prepared quaternized PPO (QPPO) exhibited excellent ion conductivity superior to that of a commercial anion-exchange membrane (AMX, Astom Corp., Japan) and also the electrochemical properties were shown to be comparable with each other. The CDI tests were conducted by employing the porous carbon electrode coated with the ionomer solution and the result showed the high salt removal efficiency of about 94.9%. By comparing the desalination efficiencies in conventional CDI, membrane CDI (MCDI) with a commercial anion-exchange membrane, and coated CDI (CCDI) employing the porous carbon electrode coated with QPPO, it was confirmed that CCDI shows the high salt removal performance improved by 52.1% and 18.3% compared with those of conventional CDI and MCDI, respectively.

Separation Characteristics of Barium Ion in Water Using Capacitive Deionization (CDI) Process (축전식탈염(CDI) 공정을 이용한 수용액 중 바륨 이온 분리 특성 연구)

  • Nam, Dong Hyun;Rhim, Ji Won
    • Membrane Journal
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    • v.29 no.6
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    • pp.355-361
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    • 2019
  • We studied the removal of barium ions that may be contained in industrial wastewater using the existing capacitive deionization (CDI). The 30 mg/L BaCl2 (barium chloride dihydrate) solution was used as the feed solution, and the flow rate was set to 10 mL/min. The adsorption conditions were varied from 1.2 V to 3, 5 and 7 min, and the desorption conditions were -1, -1.5, -2 V and 1, 2 and 3 min, respectively, to select the most efficient conditions. As a result, barium ion removal efficiency of 64.4% was obtained under the adsorption conditions of adsorption of 1.2 V/7 min and the desorption -1 V/1 min. For the desorption voltages and time, under the same experimental conditions, the removal efficiency of CDI for 30 mg/L NaCl aqueous solution with the same concentration as barium showed 69.9% removal efficiency under the adsorption conditions of and the desorption conditions of 1.2 V/7 min desorption -1 V/1 min, respectively.