In electro-deionization (EDI), what is generated for continuous regeneration?

In electro-deionization (EDI), the process relies on the generation of ions that facilitate the removal of dissolved salts from water. As an electric current is applied to the cell, it causes the electrolysis of water, which results in the continuous generation of hydrogen ions at the anode and hydroxyl ions at the cathode.

This generation of hydrogen and hydroxyl ions is crucial because these ions react with the feed water to form hydrogen ions (H⁺), which can displace cations from the resin, and hydroxyl ions (OH⁻), which can displace anions. As a result, both cation and anion exchange resins in the system are continuously regenerated without the need to add external chemicals. This dynamic ensures that the EDI system can maintain its efficiency for extended periods, making it an effective method for producing high-purity water.

The continuous regeneration of the ion exchange materials allows the system to function efficiently without the requirement for chemical reagents, heat, or pressure, as indicated by the other options. Thus, hydrogen and hydroxyl ions play a central role in the functioning and effectiveness of the electro-deionization process.