DI water has had all ions removed, such as cations from sodium, calcium, magnesium and potassium, and anions such as chloride, nitrates and sulphates. It is typically required for applications where it is critical that impurities are removed from water, such as in scientific research.

One of the latest water purification methods, known as Continuous Electro-Deionisation or CEDi, is able to produce DI water without the use of cation and anion resins regenerated with acid and caustic solutions. The new method of producing DI water is significantly safer and more environmentally friendly than the traditional use of chemicals, while also offering a cost-effective solution.

Each CEDi cell is made from alternating layers of cation and anion permeable membranes, which do not allow the passage of water only ions. On the outer sides of the stack are placed the cathode and anode electrodes. Feedwater enters the stack and is then split accordingly: 90% into the feed/dilution chamber, 5-10% into the concentration chamber and <5% into the electrolyte compartment. Next, the unwanted ions in the feedwater are exchanged onto the ion exchange resin and the applied DC potential draws the ions towards the relevant electrodes. As the cations move towards the cathode they pass through the cation permeable membrane and into one of the concentration compartments. Additional movement towards the cathode is halted by anion permeable membranes, and the cations are neutralised by anions rejected from the other corresponding chambers. The rejected ions are finally flushed from the system in a concentrate stream.

For more information on the latest water purification technology that produces DI water, click here.

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