• Membrane Journal
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• v.30 no.5
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• pp.350-358
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• 2020

A membrane capacitive deionization (MCDI) cell is constructed by applying thin layer of a cation exchange membrane (Nafion) on cathode and an anion exchange membrane (aminated polyphenylene oxide, APPO) on anode. Compared to CDI cell without CEM and AEM coating, MCDI exhibits enhanced salt removal efficiency. When Nafion and APPO are used as CEM and AEM, optimized salt removal performance as high as 82.1% is observed when 1.2 V is applied for 3 min during absorption process and -1.0 V is applied for 1 min during desorption.

• Membrane and 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.

• 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.

• 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.

• 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.

• 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.

• Membrane Journal
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• v.30 no.5
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• pp.342-349
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• 2020

In this study, we suggest conditions to reduce fouling in capacitive deionization (CDI) caused by alginic acid sodium salt, one of the most common fouling-causing substances in natural water and wastewater management. First, NaCl is used as feed material, which is selected as the control of the experiment. As expected, fouling phenomena is not observed from NaCl. On the other hand, when alginic acid sodium salt is added to the inlet, the fouling phenomena can be observed. In order to minimize the fouling phenomena, the feed concentration of alginic acid sodium salt, applied potential during desorption process, and duration of applied potential to our CDI cell are controlled. With 7 mg/L of feed stream concentration, CDI performed using 1.2 V for 1 min during adsorption followed by desorption with -2 V for 1 min exhibited the highest alginic acid salt removal efficiency reaching 50.07%.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.552-559
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• 2020

Activated carbon-nickel (II) oxide (AC-NiO) electrodes were studied as materials for the capacitive deionization (CDI) of aqueous sodium chloride solution. AC-NiO electrodes were fabricated through physical mixing and low-temperature heating of precursor materials. The amount of NiO in the electrodes was varied and its effect on the deionization performance was investigated using a single-pass mode CDI setup. The pure activated carbon electrode showed the highest specific surface area among the electrodes. However, the AC-NiO electrode with approximately 10 and 20% of NiO displayed better deionization performance. The addition of a dielectric material like NiO to the carbon material resulted in the enhancement of the electric field, which eventually led to an improved deionization performance. Among all as-prepared electrodes, the AC-NiO electrode with approximately 10% of NiO gave the highest salt adsorption capacity and charge efficiency, which are equal to 7.46 mg/g and 90.1%, respectively. This finding can be attributed to the optimum enhancement of the physical and chemical characteristics of the electrode brought by the addition of the appropriate amount of NiO.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.77-81
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• 2005

Porous-composite electrodes have been developed using silica gel, which reduce carbon aerogel usage with high cost. Silica gel powder was added to the carbon aerogel to simplify the manufacturing procedure and to increase the wet-ability, the mechanical strength and the CDI efficiency. Porous composite electrodes composed of carbon aerogel and silica gel powder were prepared by paste rolling method. Carbon aerosol composite electrodes with $10\times10cm^2$ are placed face to face between spacers, and assembled the four-stage series cells for CDI process. Each stage is composed of 45 cells. Four-stage series cells (flow through cells) for CDI process are put in continuous-system reactor containing 1,000ml-NaCl solution bath of 1,000 ppm. The four-stage series cells with carbon aerogel electrodes are charged at 1.2V and are discharged at 0.001V, and then read the current. Conclusively, removal efficiencies of ions using the four-stage series cells composed of carbon aerogel composite electrodes show good removal efficiency of $99\%$ respectively.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.87-92
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• 2010

Desalination experiments were carried out with two types of cell configuration; a CDI cell constructed with carbon electrodes only and a membrane capacitive deionization (MCDI) cell having a cation-exchange membrane on the cathode surface. The salt removal rate and desalination efficiencies increased linearly with increasing the cell potential. Although the same carbon electrodes were used in the desalination experiments, the MCDI cell showed higher salt removal efficiency than that of the CDI cell. The amount of salt removal for the MCDI cell was enhanced by 33.1~135% compared to the CDI cell, depending on the applied cell potential in the range of 0.8~1.2 V. In addition, the current efficiency for the MCDI cell was about 80%, whereas the efficiency was under 40% for the CDI cell. The higher salt removal efficiency in the MCDI cell was attributed to the fact that ions were selectively transported between the electric double layer and the bulk solution in the MCDI cell configuration.