Échange ionique

As the name suggests, ion exchange is the exchange of ions between ionized species in water with ion exchangers such as H+ and OH- ions. The process is reversible and the column can be regenerated by washing, through excess ions.

How does it work?

Water is circulated through beds of ion exchange resins where ions in solution migrate into the beads. Here, depending on their relative exchange densities (charge per hydrated volume), they compete for exchange sites. The resins themselves are porous beads less than 1 mm in size made of highly cross-linked insoluble polymers, with many highly ionic exchange sites.

Deionization beads are either cationic or anionic and exchange H+ ions for cations (e.g. Na+, Ca2+ and Al3+) or OH- ions for anions (e.g. Cl-, NO3- and SO42-). The hydrogen ion from the cation exchanger combines with the hydroxyl ion from the anion exchanger to form pure water.

Ion exchange resin beds are available in cartridges or cylinders, and are typically used for a period of time before being replaced. This occurs when the cations and anions have replaced most of the H+ and OH- active sites in the resin. Once depleted, the kits can be regenerated by washing with an excess of desirable ions, using strong acids and bases. This reverses the entire process and removes the unwanted cations and anions. However, this requires the use of harsh chemicals.

Why is ELGA the best solution?

In all deionization processes, weakly ionized impurities can elute from the resins and enter your application as they approach depletion. This is because after a period of use, the ion exchange capacity of a purification kit begins to be depleted and these compounds are released first, even before the resistivity has dropped below 18.2 MΩ.cm. ELGA’s patented PureSure ® technology prevents this process.

PureSure® is a dual purification pack and monitoring system that ensures accurate results and uninterrupted workflow. The secondary purification kit traps any organics and silica that may be released from the primary purification kit as it nears depletion, giving you time to change consumables without impacting your results. Not only does this help ensure the purity of your water, but it also provides added safety and advance warning of the useful life of the purification kits.