Demineralized water treatment equipment: introduction to ion exchange method

Two common ion exchange methods are hard water softening and deionization. Hard water softening is mainly used as a pre-treatment procedure to reduce water hardness before reverse osmosis (RO) treatment. The spherical resin in the softener softens the water by exchanging two sodium ions for one calcium ion or magnesium ion.

The ion exchange method is to filter the raw water with spherical resin (ion exchange resin), and the ions in the water will be exchanged with the ions fixed on the resin.

Ion exchange resins use hydrogen ions to exchange cations and hydroxide ions to exchange anions; cation exchange resins made from sulfonate-containing styrene and divinylbenzene exchange hydrogen ions for various cations encountered (such as Na+, Ca2+, Al3+). Likewise, anion exchange resins made from styrene containing quaternary ammonium salts will exchange hydroxide ions for various anions encountered (eg, Cl-). The hydrogen ions released from the cation exchange resin combine with the hydroxide ions released from the anion exchange resin to form pure water.

Anion and cation exchange resins can be packaged separately in different ion exchange beds, divided into so-called anion exchange beds and cation exchange beds. The cation exchange resin and the anion exchange resin can also be mixed together and placed in the same ion exchange bed. Either way, when the resin has exchanged the hydrogen and/or hydroxide ions on the resin with charged impurities in the water, it must be “regenerated”. The regeneration procedure is just the opposite of the purification procedure, using hydrogen ions and hydroxide ions for regeneration to exchange impurities attached to the ion exchange resin.

If the ion exchange method is used in combination with other water purification methods (such as reverse osmosis, filtration and activated carbon adsorption), the ion exchange method will play a very important part in the entire purification system. The ion exchange method can effectively remove ions, but it cannot effectively remove most of the organic matter or microorganisms. The microorganisms can attach to the resin and use the resin as a medium, so that the microorganisms can grow rapidly and generate heat. Therefore, it needs to be designed and used in conjunction with other purification methods.

Xi’an CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in various water processing devices. Aside from these individual products, which cover a number of types and series, we can also help with related comprehensive engineering projects. Thanks to our hard work and dedication upon our founding, we are now one of the fastest-developing water treatment equipment manufacturers in Western China.

Further reading:

C100E 05

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