Natural water typically contains five types of impurities:

1. Electrolytes, including charged particles, common cations include H+, Na+, K+, NH4+, Mg2+, Ca2+, Fe3+, Cu2+, Mn2+, Al3+, etc; Anion has F ˉ、 Cl ˉ、 NO3 ˉ、 HCO3 ˉ、 SO42 ˉ、 PO43 ˉ、 H2PO4 ˉ、 HSiO3 ˉ Etc.

2. Organic substances, such as organic acids, pesticides, hydrocarbons, alcohols, and esters.

3. Particulate matter.

4. Microorganisms.

5. Dissolved gases, including N2, O2, Cl2, H2S, CO, CO2, CH4, etc.

In daily life, what we call water purification is to remove these impurities. The more thoroughly impurities are removed, the purer the water quality becomes.

1. Deionized water: By passing water through a cation exchange resin (commonly used as a styrene type strong acidic cation exchange resin), the cations in the water are absorbed by the resin, and the cation H+on the resin is replaced into the water, forming a corresponding inorganic acid with the cations in the water; The water containing this inorganic acid is then replaced with OH - through anion exchange resins (commonly known as styrene type strong alkaline anions) and combined with H+in the water to form water, which is called deionized water. Deionized water has a very wide range of uses in modern industry. The use of deionized water is one of the important means for many industries in China to improve product quality and catch up with the world's advanced level. Due to the fact that the number of ions in deionized water can be artificially controlled, its electrical resistivity, solubility, corrosiveness, viruses, bacteria, and other physical, chemical, and pathological indicators can be well controlled. In industrial production and laboratory experiments, if deionized water is used in processes involving the use of water, many parameters will be closer to the design or ideal data, and product quality will become easier to control.

   
   

2. Distilled water: Water that is distilled and condensed. The water that is distilled twice is called re distilled water, and the water that is distilled three times is called triple distilled water. Sometimes, for special purposes, appropriate reagents are added before steaming, such as adding acid to the water for ammonia free purposes; Low oxygen consumption water, added with potassium permanganate and acid. Industrial distilled water is pure water obtained by the method of distilled water. Generally, the purity of water obtained by ordinary distillation is not high. After multi-stage distillation of water, the effluent can be very pure, and the cost is relatively high.

   
   

3. Pure water: refers to water with extremely high chemical purity, which is mainly used in fields such as biology, chemical engineering, metallurgy, aerospace, and power. However, it has high requirements for water quality purity, so the most common application is in the electronic industry. For example, pure water used in power systems requires a low impurity content of "micrograms per liter". In the production of pure water, the various indicators specified in the water quality standards should be determined based on the production process of electronic (microelectronic) components (or materials) (such as the size of particulate matter that is generally believed to cause circuit performance damage being 1/5-1/10 of its line width). However, due to the complexity of microelectronics technology and various factors affecting product quality, there is currently no complete water quality standard applicable to a certain circuit production obtained from process experiments. However, in recent years, electronic grade water standards have also been continuously revised, and many breakthroughs and developments in the field of high-purity water analysis, as well as the continuous application of new instruments and analytical methods, have created conditions for the development of water production processes. The national standards for high-purity water are GB1146.1-89 to GB1146.11-89 [168]. Currently, China's standard for high-purity water divides electronic grade moisture into five levels: Grade I, Grade II, Grade III, Grade IV, and Grade V. This standard is formulated based on ASTM electronic grade standards.

   
   

4. Ultra pure water can be considered to be a degree that is difficult to achieve by general processes. If the resistivity of water is greater than 18M Ω * cm (without clear boundaries), it is called ultra pure water. The key is to determine the purity and various characteristic indicators of your water, such as conductivity or resistivity, pH value, sodium, heavy metals, silica, dissolved organic matter, particulate matter, and microbial indicators.

(Source | New Horizon of Water Treatment)