What Is Electrodeionization?


Electrodeionization is a water treatment technology that has gained popular acceptance because the process does not use chemical treatments.

In such a system, there are no moving parts. Water is passed between a positive electrode and a negative electrode. Semipermeable ion-exchange membranes separate the positive and negative ions, creating deionized water.

The commercial technology was first introduced about two decades ago and has continually improved.

Nduka Okafor, writing in Environmental Microbiology of Aquatic and Waste System,explains how the process works:

Electrodeionization (EDI) is a water treatment process that removes ionizable species from liquids using electrically active media and an electrical potential to effect ion transport. It differs from other water purification technologies such as conventional ion exchange in that it does not require the use of chemicals such as acid and caustic soda. In traditional ion exchange units, after the contaminants are trapped onto the resin sites, the resin continues to exhaust and lost capacity. In ED, the contaminants are continuously removed as they are attracted to one of the two electrical charges, and they migrate through the resin bed, through ion exchange membranes and into the concentrate stream where they are removed from the device. […] EDI is a polishing technology and requires reverse osmosis (RO) as pretreatment. The combination of RO-EDI provides the customer with a continuous, chemical-free system.

The process, which combines electrodialysis and ion exchange technology, has been widely adopted for producing ultrapure water because it is energy-efficient. As Felice DiMascio explains in The Electrochemical Society’s Interface (PDF), the process can either be completed in batches, as in capacitive deionization, or in a continuous process, referred to as continuous electrodeionization (CEDI).

Electrodeionization systems typically have a life cycle of more than five years. The lifecycle of the system can be prolonged based on the pretreated water quality.

Electrodeionization was initially developed as an extension of deionization. The seminal work took place at Argonne National Laboratory in the 1950s as a method for removing trace radioactive materials from water. Researchers applied batch electrodeionization to concentrate radioactive aqueous wastes, according to an IDS-Water white paper surveying the history of electrodeionization.

The first patents for the technology were applied for in 1953. These were specific to acetone purification, but soon other related technology patents were filed. The first commercially available EDI modules and systems were introduced in 1987 by Ionpure.

“Because of the competitive nature of the business, better manufacturing and improved designs, the price of EDI has dropped over 60 percent in the years since its inception, making it a competitive option,” according to Chris Gallagher, writing in Water Conditioning & Purification Magazine.

The technology is now used in a wide variety of industries, according to CEDI University, including water purification, steam generation, and semiconductor and chemical manufacturing, as well as in food and beverage manufacturing.

Sourced by ekomeri.com

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