Deionization

Deionization (DI), also known as demineralization, is a water purification process that involves removing ions (charged particles) from water.  The goal of deionization is to produce water with a very low conductivity by eliminating both positively charged ions (cations) and negatively charged ions (anions).   This process is commonly used in laboratories, industries, and other applications where highly pure water is required.

The deionization process typically involves the use of ion exchange resins, which are substances that can selectively remove ions from water.  These resins consist of positively or negatively charged functional groups that attract and exchange ions in the water.

The deionization process often consists of two main steps

• Cation Exchange  -  In the first resin bed, cation exchange resins are used to replace positively charged ions (cations) in the water with hydrogen ions (H⁺) or other positively charged ions.  Common cations include calcium, magnesium, sodium, and others.
• Anion Exchange  -  In the second resin bed, anion exchange resins replace negatively charged ions (anions) with hydroxide ions or other negatively charged ions.  Common anions include chloride, sulfate, bicarbonate, and others.

The result is deionized water with significantly reduced ion concentration.  However, deionization is not always sufficient to remove all types of contaminants, such as certain organic or non-ionic substances.  Therefore, deionized water is often used in conjunction with other water purification processes, such as reverse osmosis or distillation, to achieve higher purity levels.

Deionized water finds applications in various fields, including laboratory experiments, electronics manufacturing, pharmaceutical production, and power generation, where the presence of ions could interfere with processes or damage equipment.