Discussion on Electrodialysis Technology

Author：

Huanke

Electrodialysis is an efficient water treatment technology that utilizes the selective permeability of ion exchange membranes. Under the action of an external direct current electric field, anions and cations selectively penetrate the membrane, achieving the formation of concentrated water and fresh water in a water chamber separated by ion exchange membranes, achieving the purpose of brine separation. This technology can not only be used to desalinate high salinity water such as seawater and brackish water, but also to remove salt and harmful substances from industrial wastewater.
Electrodialysis is a membrane separation process that utilizes the anti ion migration principle of charged ion membranes to separate charged ions from aqueous solutions under the action of a direct current electric field. Inside the electrodialyzer, there are multiple sets of anion and cation exchange membranes arranged alternately. Under the action of an external direct current electric field, cations move towards the negative electrode through the positive membrane, while anions move towards the positive electrode through the negative membrane, forming a fresh water chamber for removing ions from water and a concentrated water chamber for concentrating ions. After draining the concentrated water, the fresh water obtained is desalinated water.
Electrodialysis technology is suitable for various types of water sources, such as natural water, tap water, industrial wastewater, etc. Its advantages lie in high desalination rate, low energy consumption, simple equipment, and convenient operation, which are widely used in water softening and desalination treatment. In addition, electrodialysis technology can also be applied to processes such as material concentration, purification, and separation. Generally speaking, electrodialysis technology is often applied to water treatment with high salinity, high hardness, or high alkalinity. For example, for desalination treatment of high salinity seawater and brackish water, electrodialysis technology can be selected after technical and economic comparison with other water treatment technologies such as reverse osmosis and distillation.

In electrodialysis devices, ion exchange membranes are crucial components for achieving ion directed migration, and the physical and chemical properties of the membranes also affect their separation efficiency. The commonly used ion exchange membranes include cation exchange membranes and anion exchange membranes, which only allow cations and anions to pass through, respectively. The electrodialysis device mainly consists of ion exchange membrane, power supply, and auxiliary materials (such as gaskets, electrodes, and sealing gaskets). Electrode materials are usually made of carbon materials such as titanium, aluminum oxide, and graphite, while ion exchange membranes are composed of active ion exchange groups, fixed functional groups, and hydrophobic substrates.
In the process of electrodialysis, in order to achieve the best separation effect, it is necessary to control some parameters, including current density, temperature, pressure, electrolyte concentration, and pH value. Usually, the electrodialysis process is carried out at lower current density and higher pressure, while maintaining a certain pH value and electrolyte concentration.
Overall, electrodialysis technology is a mature water treatment technology, particularly suitable for water treatment with high salt content, and has advantages such as energy conservation, efficiency, and environmental protection. However, it should be noted that the initial investment of the electrodialysis device is relatively high, and regular maintenance and cleaning are required to ensure its long-term stable operation.