- Five impurities commonly contained in natural water
- Electrolytes, including charged particles, common cations include H+, Na+, K+, NH4+, Mg2+, Ca2+, Fe3+, Cu2+, Mn2+, Al3+, etc.; anions include F-, Cl-, NO3-, HCO3-, SO42-, PO43-, H2PO4-, HSiO3-, etc.
- Organic substances, such as: organic acids, pesticides, hydrocarbons, alcohols and esters, etc.
- Particulate matter
- Microorganisms
- Dissolved gases, including: N2, O2, Cl2, H2S, CO, CO2, CH4, etc.
- The so-called water purification is to remove these impurities. The more thoroughly the impurities are removed, the purer the water quality will be
- Distilled water: water that is distilled and condensed
- Deionized water: water is passed through a cation exchange resin (commonly used is a styrene-type strong acid cation exchange resin), then the cations in the water are absorbed by the resin, and the cations H+ on the resin are replaced into the water, and form corresponding inorganic acids with the cations in the water
- High-purity water: refers to water with extremely high chemical purity, which is mainly used in biology, chemistry, metallurgy, aerospace, electricity and other fields
III. Classification of purified water
- High-purity water refers to water with a conductivity of less than 0.1 μs/cm and a residual salt content of less than 0.3 mg/L at 25°C, and water with non-dielectric trace bacteria, microorganisms, particles and other impurities removed. Preparation methods include distillation, membrane separation, ion exchange and sterilization. It is mainly used in the electronics and microelectronics industries, and also in food, papermaking, medicine, electronics, nuclear industry and other industries.
- Ultrapure water resistivity 10MΩ*cm (25°C). When the working temperature is 25℃, the highest theoretical value of resistivity can reach 18.25MΩ/cm. The actual highest value of ultrapure water equipment online test is 18.2MΩ/cm.
- Pure water resistivity 0.1×10^6 Ω/cm (25℃, distilled water test data, pure water is theoretically non-conductive)
