|Recovery||90% to 95%|
|Panel View||600 HMI|
Electrode ionization (EDI) is an electrically-driven water treatment technology that uses electricity, ion exchange and resin to remove ionized species from water. The combination of ion-exchange resins and ion-exchange membranes, which are used to move ionic impurities into a waste or concentrate water stream leaving purified product water.
As impurities leave via the concentrate water system, their build-up does not exhaust the resin and therefore prolongs resin lifespan. A single EDI unit may operate for many years before a replacement is required. Typically product water resistivity of 15 M.cm is consistently achieved using this process. This technology can be used as an alternative to single-use purification cartridges.
Its development and use in water purification overcame some of the limitations of ion exchange resin beds, particularly the release of ions as the beds exhaust.
How does it work?
Water enters the EDI module, where an applied current forces ions to move through the resins and across the membranes. These ions are collected into concentrate streams which can then be put to drain or be recycled. The deionizer product water can then be used directly or undergo further treatment for enhanced water purity.
When the ions are moved through the resins and between the caution or anion selective membranes, they are exchanged for H+and OH- ions. Ions that become bound to the ion exchange resins migrate to a separate chamber under the influence of an externally applied electric field. This also produces the H+ and OH-ions necessary to maintain the resins in their regenerated state. Ions in the separate chamber are flushed to waste.
The ion exchange beds in our EDI systems are regenerated continuously so that they do not exhaust in the same way as ion exchange beds that are operated in batch mode.
Process of Electrode ionization
The Electro pure EDI design combines two well-established water purification technologies—electro dialysis and ion-exchange resin deionization. Through this revolutionary technique, dissolved salts can be removed with low energy cost and without the need for chemical regeneration; the result is high-quality pure water of multi resistivity which can be produced continuously at substantial flow rates.
Electro pure EDI removes ions from water by forcing them out of the feed stream into adjacent streams via an electric potential. EDI is different from ED by using resins in the diluting chambers—the resins allow for more efficient migration of ions in very low conductivity water. The resins operate in steady state; they act not as an ion reservoir but as an ion conduit.
The electrode ionization process uses a combination of ion-selective membranes and ion-exchange resins sandwiched between two electrodes (anode (+) and cathode (-) under a DC voltage potential to remove ions from RO-pretreated water.
Ion-selective membranes operate using the same principle and materials as ion exchange resins, and they are used to transport specific ions away from their counter ions. Anion-selective membranes are permeable to anions but not to captions; caution-selective membranes are permeable to captions but not to anions. The membranes are not water-permeable.
By spacing alternating layers of anion- and caution-selective membranes within a plate and frame module, “stack” of parallel purifying and concentrating compartments are created.
The ion-selective membranes are fixed to an inert polymer frame, which is filled with mixed ion-exchange resins to form the purifying chambers.