Deionized water (deionized water) refers to the removal of impurities in the form of ions after the pure water. International Organization for Standardization ISO/TC 147 "deionization" is defined as: "deionized water completely or incompletely remove ionic substances, mainly refers to the use of ion exchange resin treatment method." Today's process is mainly produced by RO reverse osmosis. The application of ion exchange resins removes anions and cations from the water, but soluble organic matter is still present in the water, which can contaminate the ion exchange columns and thus reduce their efficacy, and the deionized water is also susceptible to bacterial reproduction after storage. In the semiconductor industry, deionized water is referred to as "ultrapure water" or "18 megohm water".
I. Deionized water treatment integrated deionized water equipment
From the tap water to deionized water generally go through several steps of processing:
1, the first through the quartz sand filtration of coarse particles of impurities
2, and then high-pressure through the reverse osmosis membrane
3, the last generally have to go through a step of ultraviolet sterilization in order to remove microorganisms in the water
4, if the resistivity has not reached the required level, then the water will not be used as the water. If the resistivity has not reached the requirements, you can carry out another ion exchange process can reach a maximum resistivity of 18 trillion.
Relatively speaking, distilled water is only the first gasification and then condensation, its purity, such as conductivity is generally not as pure as deionized water, the semiconductor industry uses most of the high-purity deionized water
II. The difference between deionized water and other water
1. Distilled water: that is, the water distillation, condensation of water, steam the second called re-distilled water, three times called triple-distilled water. Sometimes for special purposes, before steaming will be added to the appropriate reagents, such as in order to no ammonia, will be added to the water with acid; low oxygen consumption of water, add potassium permanganate and acid. Industrial distilled water is the use of distilled water obtained by the method of pure water, generally ordinary distillation of the water obtained by the purity of the water is not high, after a multi-stage distillation of water, the water can reach a very pure, the cost is relatively high.
2. Deionized water is the water through the cation exchange resin (commonly used for styrene-type strong acidic cation exchange resin), the cations in the water are absorbed by the resin, the cation on the resin H + is displaced into the water, and the cations in the water to form the corresponding inorganic acid; water containing such inorganic acid and then through the anion exchange resin (commonly used for styrene-type strong alkaline anion) OH OH-is displaced into the water and combined with H+ in the water to form water, which is deionized water. Deionized water has a very wide range of uses in modern industry, the use of deionized water, many of China's industries to improve product quality, one of the important means of catching up with the world's advanced level. As the number of ions in deionized water can be artificially controlled, thus, making its resistivity, solubility, corrosivity, viruses and bacteria, such as physical, chemical and pathological indicators are under good control. In industrial production and laboratory experiments, if the process involves the use of water are used deionized water, then, many parameters will be closer to the design or ideal data, product quality will become easy to control.
3. High-purity water, refers to the chemical purity of water, which is mainly used in biology, chemical engineering, metallurgy, aerospace, power and other fields, but its water purity requirements are quite high, so the most common general application or the electronics industry. For example, the pure water used in the power system, the requirements of the impurity content of low to "micrograms / liter" level. In the production of pure water, water quality standards for the indicators should be based on electronic (microelectronics) components (or materials) of the production process (such as the general view that the size of the particulate matter caused by the destruction of the circuit performance of the line width of 1/5-1/10), but due to the complexity of microelectronics technology and product quality of the factors affecting the product quality, so far there is no one by the process of experimentation applicable to a certain circuit Production of a complete water quality standards. However, in recent years, electronic grade water standards have been revised, and many breakthroughs and developments in the field of high-purity water analysis, new instruments and new analytical methods continue to apply for the development of water production process to create the conditions. The national standard for high-purity water: GB1146.1-89 to GB1146.11-89 [168], China's current standard for high-purity water will be electronically graded water into five levels: Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅴ, the standard is developed with reference to the ASTM standard for electronic grade.
4., and ultrapure water, it can be considered a general process is difficult to achieve the degree, such as the resistivity of water greater than 18MΩ * cm (no obvious boundaries), it is called ultrapure water. The key is to look at the purity of your water and the signs of the indicators, such as conductivity or resistivity, PH, sodium, heavy metals, silica, dissolved organic matter, microparticles, and microbiological indicators.