Electrodialysis Equipment Information

What is Electrodialysis Equipment

Electrodialysis equipment is a separation device that uses charged membranes and electrical potential difference to separate ionic species from an aqueous solution and other uncharged components. It consists of an electrodialysis stack assembled on the filter press principle, with cationic and anionic membranes assembled in pairs between two electrodes. When an electrical potential difference is applied, cations and anions in the feed solution move toward the cathode and anode respectively, passing through the corresponding ion exchange membranes and being concentrated in alternate cells, thus achieving the separation, concentration, desalination, refining and purification of the solution.

History of Electrodialysis Equipment

Electrodialysis technology was first made successful by Ionics Corp in the 1950s and 1960s with the advent of ion-selective membranes. In the 1970s and 1980s, further research and development led to the emergence of new concepts and technologies, such as filled bed electrodialysis (EDI) proposed in 1983. Since then, electrodialysis equipment has continuously evolved and improved, with increasing applications in various fields.

Purpose of Electrodialysis Equipment

Electrodialysis equipment is mainly used for the physical and chemical processes of material concentration, purification and separation, such as:

• Desalination of brackish water and seawater to produce potable water or for salt production.
• Production of pure water and ultrapure water by electrodeionization (EDI).
• Treatment of wastewater and waste liquid and the recovery of precious metals, such as the recovery of nickel from electroplating waste liquid.
• Food processing, such as juice deacidification and purification, and refined dairy products.
• Chemical product production and pre-treatment of high-purity water in electronics, medicine and other industries.

Principle of Electrodialysis Equipment

Electrodialysis equipment utilizes the principle of ion exchange membrane selectivity under the action of a DC electric field. The cation exchange membrane allows positively charged cations to pass through, while the anion exchange membrane allows negatively charged anions to pass through. When an electrical potential difference is applied between the two electrodes, cations in the feed solution move toward the cathode and easily pass through the negatively charged cation exchange membranes, but are retained by the positively charged anion exchange membranes. Similarly, anions migrate towards the anode, pass through the anion exchange membrane and are retained by the cation exchange membrane. As a result, the migrating ions become concentrated in each alternate cell in the stack, and ions removed from the aqueous feed solution are concentrated into two separate streams.

Features of Electrodialysis Equipment

Electrodialysis equipment has the following features:

• High separation efficiency: It can effectively separate ions from the solution, achieving a high degree of desalination and purification.
• Low energy consumption: Compared with some traditional separation methods, it generally consumes less energy.
• Continuous operation: It can operate continuously, with stable performance and high production efficiency, suitable for large-scale industrial production.
• High selectivity: The ion exchange membrane has high selectivity for ions, which can selectively separate different types of ions according to needs.
• Simple operation and maintenance: The equipment is relatively simple in structure and easy to operate and maintain, reducing labor costs and maintenance time.

Types of Electrodialysis Equipment

There are several types of electrodialysis equipment, including:

• Conventional electrodialysis equipment: It is the most basic type, mainly used for general desalination, concentration and separation of aqueous solutions.
• Inverted electrodialysis equipment (EDR): The polarity of the electrodes is reversed at regular intervals to automatically clean the dirt on the ion exchange membrane and electrode surface, improving the stability and efficiency of the equipment, and is especially suitable for wastewater treatment.
• Filled bed electrodialysis equipment (EDI): It combines electrodialysis and ion exchange methods, and uses the water dissociation generated by H? and OH? to automatically regenerate the mixed bed ion exchange resin filled in the fresh water chamber, achieving continuous deep desalination and is widely used in the production of high-purity water.
• Bipolar membrane electrodialysis equipment: It uses bipolar membrane, and the water molecules passing through the membrane are immediately decomposed into H? and OH?, which can be used as the source of supply of H? and OH?. It has the advantages of simple process, high energy efficiency and low waste emission, and is mainly used in acid-base preparation and other fields.