Deionisaatioon

Deionisaatioon, often written deionization or demineralization, is a water purification process that removes dissolved ions from water. The process exchanges ions in the water with ions fixed to solid resin beads or ion-exchange membranes, yielding water with extremely low conductivity. Deionized water is widely used where ionic impurities must be minimized, such as laboratories, electronics manufacturing, pharmaceuticals, and analytical instrumentation.

Most common implementation uses ion-exchange resins in a two-stage arrangement: cation exchange resins replace positive ions (such as calcium, magnesium, sodium) with hydrogen ions, while anion exchange resins replace negative ions (such as chloride, sulfate) with hydroxide ions. When combined, hydrogen and hydroxide form water, producing deionized water. Mixed-bed configurations provide higher purity; water passes through resin beds in a single pass or recirculates for higher purity. Resins are periodically regenerated with acid (for cations) and caustic soda (for anions).

Limitations and considerations: deionization removes inorganic ions but does not remove all organic contaminants; pretreatment (filtration, carbon adsorption) is often required. Regenerated waste streams contain concentrated salts and chemicals and must be managed. The quality of DI water is monitored by resistivity or conductivity; high-purity water is critical in semiconductor fabrication, pharmaceutical manufacturing, and laboratory analysis. Alternatives or complements include reverse osmosis and electrodialysis.