Overview of Electrodeionization Technology

• The electro deionization module is constructed using multiple layers of ion exchange membranes, with the space between each membrane filled with ion exchange resin. Ionic exchange membranes are composed of alternating layers stacked between membranes that only pass through anions (anion exchange membranes) and membranes that only pass through cations (cation exchange membranes). These layers are placed between two electrodes, and the module is connected to a power source to generate continuous deionized electric driving force.

• When the feedwater enters the dilution channel module, the remaining salts and ionizable water impurities (such as carbon dioxide, silica, ammonia, and boron) first adhere to the ion exchange resin. The direct current electric field between the electrodes causes negative ions to move towards the anode through the negative ion exchange membrane and enter the next layer of ion exchange resin, where they are captured by the alternating use of cation exchange membranes in the concentration channel. On the contrary, the direct current electric field causes cations to move in the opposite direction towards the cathode through the cation exchange membrane, and are trapped again in the resin filled concentration channel by alternately using the anion exchange membrane. When water passes through the module in the dilution channel, impurities continue to be removed for the production of ultrapure or high-purity water.
• Although the EDI stack contains ion exchange resin, the current passing through the module will decompose water molecules into hydrogen ions and hydroxide ions, continuously regenerating the ion exchange resin inside the module to ensure consistent and stable ultrapure or high-purity water quality.

The benefits of E-Cell EDI over ion exchange

Electrodeionization is a key component in the evolution of demineralization systems from several continuous ion exchange containers to membrane based systems. In this process with reverse osmosis, the EDI system can replace the mixed bed ion exchange system and provide reliable production of ultrapure water or high-purity water. In addition:

• EDI does not require recycled chemicals, thereby reducing environmental, health, and safety issues and lowering chemical costs
• EDI operates continuously, minimizing the risk of resin depletion and eliminating the need to take the system offline for regeneration, simplifying operations
• EDI has a smaller footprint and lower height requirements than ion exchange, thereby reducing the requirements for facilities, especially supporting equipment such as chemical metering systems
• EDI has no harmful wastewater discharge and can easily recycle waste without the neutralization system required for ion exchange

For many customers, in addition to the benefits mentioned above, choosing to use E-Cell EDI technology can provide lower capital and operating costs compared to mixed bed ion exchange.

Winflows is one of the most advanced reverse osmosis (RO) and EDI computing tools on the market. It can model RO and EDI as independent operating systems, but its uniqueness lies in its ability to model RO+EDI systems as combined processes within a single tool. This improves the convenience of use, as most EDI systems have upstream RO to ensure that the EDI system has sufficient water quality. Using a tool to make EDI calculations easier than ever before.

Winflows includes all the features of the E-Cell stack and can be used for calculations of any size. The Winflows software can be downloaded here.