Improvement of desalination efficiency in capacitive deionization using a carbon electrode coated with an ion-exchange polymer

This study was conducted to evaluate the feasibility of using electrosorption to remove cesium (Cs+) ions from aqueous solutions using the membrane capacitive deionization (MCDI) process. The electrochemical properties were analyzed using cyclic voltammetry (CV) and impedance spectroscopy (EIS). The activated carbon electrode coated by a polymer layer showed higher specific adsorption capacity (SAC) and removal efficiency of Cs+ than the AC electrode. The effects of potential, flow rate, initial Cs+ concentration, and pH values were investigated to optimize the electrosorption performance. The electrosorption capacity increased with an increase in the applied potential and the concentration of Cs+ in the influent water. The pH value is an important parameter on electrosorption performance. The removal of Cs+ ions was affected by the pH of the influent water because H+ ions acted as competing ions during the electrosorption process. Cs+ was preferentially adsorbed to the electrode in the early stages of adsorption but was later replaced by H+. A higher presence of H+ ions could reduce the adsorption capacity of Cs+ ions. The ion-exchange layer coated AC electrode was shown to be favorable for the removal of Cs+, despite the limited electrosorption ability in a highly acidic solution.

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Analysis of Boron Removal for Reverse Osmosis, Ion Exchange, and Capacitive Deionization

Journal of Korean Society of Environmental Engineers ◽

10.4491/ksee.2021.43.10.654 ◽

2021 ◽

Vol 43 (10) ◽

pp. 654-663

Author(s):

Yu Chang Kim ◽

Sungil Lim ◽

Bangwoo Han ◽

Sang Bok Kim ◽

Inyong Park ◽

...

Keyword(s):

Energy Consumption ◽

Ion Exchange ◽

Reverse Osmosis ◽

Ion Selectivity ◽

Specific Energy Consumption ◽

Operating Conditions ◽

Feed Water ◽

Carbon Electrode ◽

Capacitive Deionization ◽

Boron Removal

Objectives : This article provides a comparative analysis of boron removal for brackish water reverse osmosis (BWRO), boron selective ion exchange (IX), or capacitive deionization (CDI) processes. Permeate of 1st-Pass RO process has to be post-treated for additional boron removal. Hence, we experimentally analyzed the performance of boron removal and specific energy consumption (SEC) of three aforementioned processes and investigated whether the processes are suitable for 2nd pass process of RO desalination.Methods : Raw feed water was prepared using NaCl and B(OH)3. Semi-pilot scale RO and IX systems (over 1 m3/hr capacity) and bench scale CDI system (over 2.5 L/min) were tested for performance comparison. Boron concentration was measured using Azomethine-H method for feed and product water. Energy consumption was monitored by using power quality analyzer.Results and Discussion : Each process has its own operating conditions. The RO process required high pH of feed water for high boron removal rate, the IX process was operated below breakthrough point considering adsorption capacity of boron selective resin, and the CDI process didn’t remove boron because chloride ion has higher ion selectivity for carbon electrode than boron. In terms of SEC, the pressure-driven RO process showed the highest SEC among three processes. The CDI process based on electrical adsorption of carbon electrode showed a considerable energy consumption as well. On the other hand, the IX process was operated at low energy consumption because its removal is just based on adsorption-desorption mechanism.Conclusions : The RO and CDI processes have received a lot of attention as leading and emerging technology while the IX process was regarded as a stubborn process because of regeneration of resin and its several segmentalized steps. However, we found that the IX process has a better performance for boron removal and energy consumption.

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High Performance Hybrid Capacitive Deionization with Ag-coated Activated Carbon Electrode

Environmental Science Water Research & Technology ◽

10.1039/d1ew00209k ◽

2021 ◽

Author(s):

Hongsik Yoon ◽

Jiho Lee ◽

Taijin Min ◽

Gunhee Lee ◽

Minsub Oh

Keyword(s):

Activated Carbon ◽

Water Treatment ◽

Industrial Application ◽

High Performance ◽

Treatment System ◽

Carbon Electrode ◽

Capacitive Deionization ◽

Water Treatment System

Capacitive deionization (CDI) has been highlighted as a promising electrochemical water treatment system. However, the low deionization capacity of CDI electrodes has been a major limitation for its industrial application,...

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