elektrodialys

Elektrodialys, also known as electrodialysis, is a membrane-based separation process that uses an electric field to drive ions through selective ion-exchange membranes, thereby separating minerals from liquids. The system typically employs alternating cation-exchange membranes and anion-exchange membranes arranged in a stack between two electrodes.

In a standard electrodialysis setup, the stack creates multiple diluate and concentrate compartments. When direct current is applied, cations migrate through the cation-exchange membranes toward the cathode and anions migrate through the anion-exchange membranes toward the anode. This coordinated ion movement demineralizes the diluate streams while concentrating ions in the adjacent concentrate streams. The process is controlled by current and voltage, with performance described by parameters such as current efficiency and water recovery.

Common applications include desalination of brackish water and groundwater, treatment of saline wastewater, and demineralization of liquids in the food and beverage industry (for example dairy, sugar, and juice purification). Electrodialysis is also used in pharmaceutical manufacturing and process-water conditioning where selective ion removal is desired.

Advantages of electrodialysis include good energy efficiency at low to moderate salinities, modular and scalable equipment, and relatively low chemical requirements. Limitations involve reduced effectiveness at high salinity (such as seawater), membrane fouling and scaling, pretreatment needs to remove particulates, chlorine sensitivity of membranes, and the need for a continuous DC power supply. A related variant, electrodialysis reversal (EDR), periodically reverses polarity to mitigate fouling and scaling.