What Is a Deionizers
A deionizer is a device used to remove ions dissolved in water and produce pure water.
Impurities such as calcium ions, sodium ions (cation), sulfate ions (anion), among others, are dissolved in water. A deionizer is a device that utilizes ion exchange resins, ion exchange membranes, direct current, and other methods to electrically remove ions from water.
Applications of Deionizers
Deionizers are used when the presence of ion species in water becomes problematic, and there is a need to remove these ion species.
Common impurities found in water include salts such as calcium, sodium, and silica, which are dissolved as ion species. The presence of ion species in water can lead to instability in the chemical properties and quality of products when used as raw materials. During evaporation of water used in cleaning, impurities may precipitate and adhere as scale. In boilers and pipelines, the occurrence of scale can lead to blockages, posing an issue that needs to be avoided.
In research and development, deionizers are primarily used in biology, chemistry, and other fields to enhance the reliability and reproducibility of experiments and instrument cleaning. In industrial applications, deionizers find use in various scenarios:
- Cleaning processes in the manufacturing of glass for semiconductor substrates, electronic circuit boards, and LCD panels.
- Beverage manufacturing processes
- Pharmaceutical manufacturing
- General industrial product manufacturing
- Water-based cleaning processes for equipment and products
- Boiler and piping water
- Electrolyte for lead-acid batteries
- Cleaning solution for contact lenses
Principles of Deionizers
Deionizers use the principles of ion separation and adsorption using ion exchange resins and ion exchange membranes. There are devices that employ mechanisms such as Electro Deionization (EDI) and Continuous Deionization (CDI®).
1. Ion Exchange Membrane and Ion Exchange Resin
Ion exchange resin is a synthetic resin with ion exchange groups. It captures cations and anions, impurities in water, releasing hydrogen ions and hydroxide ions originally bound to the resin.
An ion exchange membrane is an ion-permeable membrane with the property of selectively allowing or blocking ions based on the charge of the ions.
2. Electro Deionization (EDI)
Electro deionization (EDI) is a technology that separates and removes cations and anions in water by passing an electric current through water using ion exchange resins and ion exchange membranes. The device has a structure with desalting chambers and concentration chambers arranged alternately between an anode and a cathode. The desalting chamber and concentration chamber are separated by cation exchange membranes and anion exchange membranes. The desalting chamber is filled with ion exchange resin.
When a current flows from the electrode, anions such as chloride ions and sulfate ions move to the anode side, and cations such as sodium ions and calcium ions move to the cathode side. In the desalting chamber, which is filled with ion exchange resin, pure water is produced through the adsorption of impurity ions and the release of hydroxide ions and hydrogen ions. Simultaneously, by allowing impurity ions to pass through cation exchange membranes and anion exchange membranes, concentration of impurity ions occurs in the concentration chamber.
In EDI, the desalting chamber simultaneously performs desalting using ion exchange resin and continuous regeneration of ion exchange resin by direct current. In the usual ion exchange method, regeneration of ion exchange resin using chemicals is necessary, but in EDI, regeneration of ion exchange resin is continuously carried out by direct current, maintaining ion removal performance for an extended period.
Types of Deionizers
There are various types of deionizers for industrial and research purposes, varying in size to suit different applications. On the functional side, some devices use activated carbon to prevent scaling and improve resin regeneration efficiency.
One notable type of device is the CDI system. CDI, a mechanism licensed by IONPURE® in the United States, is also known as a Continuous Deionization system. In CDI devices, ion exchange resin is filled in both the desalting chamber and the concentration chamber, resulting in high ion movement efficiency. Regeneration of resin is achieved by continuously regenerating ion exchange resin with high-pressure electricity. This allows for the continuous production of pure water without the use of chemical agents for resin regeneration, contributing to reduced environmental impact, space savings, and a zero-discharge system.