Abstract
Electrodeionization (EDI) technology is limited by low regeneration efficiency of ion exchange resins, requirements of high-quality influent water, fouling of the ion exchange membrane and electrode, etc. In this work, a novel bed type called a compound bed in which cation and anion exchange resins were near the cation and anion exchange membrane and placed in layers, was proposed to implement high-efficiency regeneration of ion exchange resins. The influence of different operating conditions on the regeneration efficiency of ion exchange resins was elucidated as well. The regeneration efficiency of ion exchange resins could reach 73.1%, when the device was operated for 5 h under current density of 9 mA/cm2, with a cation and anion exchange resins ratio of 2: 3, influent water conductivity of 1,360 μS/cm and hardness of 400 mg/L. Therefore, the proposed compound bed structure not only widened the inlet water conditions, but also achieved the high-efficiency regeneration of ion exchange resins and anti-fouling of membranes and electrodes.
Highlights
IntroductionElectrodeionization (EDI) combines the ion exchange resins (IER) and ion exchange membrane (IEM) to produce hydrogen ions (Hþ) and hydroxide ions (OHÀ) in the water2550 X
Electrodeionization (EDI) combines the ion exchange resins (IER) and ion exchange membrane (IEM) to produce hydrogen ions (Hþ) and hydroxide ions (OHÀ) in the waterDownloaded from http://iwaponline.com/wst/article-pdf/83/10/2549/892141/wst083102549.pdf by guest2550 X
According to the definition of the limit current density (Strathmann ), with current gradually increasing, the ions in the diluted chamber were continuously transferred to the concentrated chamber, which caused the ions existing at the membrane/solution interface to be insufficient to carry an appropriate current flow
Summary
Electrodeionization (EDI) combines the ion exchange resins (IER) and ion exchange membrane (IEM) to produce hydrogen ions (Hþ) and hydroxide ions (OHÀ) in the water2550 X. Many efforts have been concentrated on regenerating IER efficiently (Jordan et al ), in which reducing the overall stack resistance and enhancing water dissociation reaction are the main purpose (Hakim et al ). The water dissociation reaction in the separated-bed configuration can be enhanced by inserting a bipolar membrane between the two beds (Strathmann ; Lakehal & Bouhidel ). These methods have successfully enhanced the regeneration of IER, it is considered to be a more economical and effective method to enhance the regeneration of IER by changing the bed type (Jin et al ). Consistent with the traditional bipolar membrane process, this method enhances water dissociation reaction, improving the regeneration efficiency of IER. Different from the traditional bipolar membrane process, this method is favorable for formation of a great many channels, rapid migration of ions and enhancement of ion conduction efficiency and current efficiency, because the same type of IER relatively concentrates
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