Sähködiaglyysi

Sähködiaglyysi, also known as electrodialysis, is an electrochemical separation process used to purify or concentrate ionic solutions. It utilizes a semipermeable membrane and an electric field to selectively transport ions across the membrane. In a typical electrodialysis stack, alternating cation-exchange and anion-exchange membranes are arranged between two electrodes. When a direct electric current is applied, positively charged ions (cations) migrate towards the cathode and negatively charged ions (anions) migrate towards the anode. The ion-exchange membranes act as selective barriers, allowing only ions of a specific charge to pass through. This creates alternating compartments where ions are either enriched or depleted, leading to separation of the ionic species from the bulk solution.

The primary application of electrodialysis is in water treatment, including desalination of brackish water and seawater, removal of specific ions like nitrates or heavy metals, and softening of water. It is also employed in the food industry for demineralization of whey, concentration of fruit juices, and production of edible salts. In the chemical industry, electrodialysis can be used for the recovery of valuable ions, the purification of process streams, and the production of chemicals. The efficiency of the process depends on factors such as membrane properties, current density, flow rate, and the concentration of the ions to be separated. Electrodialysis is considered an energy-efficient separation technique, particularly for solutions with moderate ionic concentrations.