Electrodeionization

Electrodeionization is an electrochemical process for removing ions broadest and ionizable substances from water. Is a combination of ion exchange and electrodialysis. The central module of a water treatment plant of this method is the so-called EDI module in which runs the Electrodeionisation.

These plants are used as final preparation stage for the production of ultrapure water, for example, for the pharmaceutical and semiconductor industries. Achieving operated in accordance with voraufbereitetem water treatment plants as a result of an electrical conductivity less than 6 × 10-6 S / m.

Mode of action and structure of the EDI module

The pre-treated water (prior art: Conductivity less than 2 mS / m) flows continuously into the module. Where ( diluate ) is produced by the removal of the remaining ingredients, salt-free water. The substances formerly included are released in dissolved form as waste water (concentrate ).

Within the EDI module, the water flows at right angles to the adjacent module the electric field through the chambers, each of an anion exchange membrane (AAT) as well as a cation exchange membrane (KAT ) is limited with a mixed bed ion exchanger (MB, a combination of anion and cation exchange resin ) is filled are.

By the electric field, there is a migration of the ion charge to the respective electrode. Exchange membranes which permit the passage of, for example Anions, while cations are prevented from penetration. Thus, a concentration of the ions is achieved in the concentrate compartment (KR ). Under the influence of the electric field at the same time there will be a dissociation of a portion of the water molecules. This causes a self-regeneration of Mischbettaustauscherharzes and permits a continuous and chemical- free operation.

Swell

• Klaus Ohlrogge, Katrin Ebert: Membranes: Principles, procedures and Industrial Applications 2006 Wiley -VCH ISBN 3527309799

• Separation processes
• Water treatment
• Membrane Technology