In the laboratory, water is a very common and particularly important substance. Whether it is cultivating bacterial cells, doing electrophoresis experiments, or analyzing and testing work for mass spectrometry, trace metal detection, and so on, water is indispensable. Moreover, the purity of water varies greatly from experiment to experiment and analysis to analysis.
Generally speaking, there are several grades of laboratory water, like pure water, deionized water, distilled water and ultrapure water. With different levels of purity, they have different uses and can fulfill different experimental needs. The purer the water, the better it can be used for experiments that require a high degree of precision and accuracy.
Understanding the classification and use of laboratory water, as well as mastering the correct storage and use methods, is essential to ensure the smooth progress of experiments and the accuracy and reliability of the results. Today, I would like to tell you in detail about the related knowledge of laboratory water, and hope to give friends who work and study in the laboratory some help and reference!
What is Deionized Water
Deionization of water is the removal of ions, such as minerals and salts, from water through the process of ion exchange. Ions are electrically charged atoms or molecules that have a net negative or net positive charge. Positively charged ions are called cations and negatively charged ions are called anions.
In the deionization process, water flows through a layer of positively or negatively charged resin beads. The positively charged resin attracts and traps negative ions, while the negatively charged resin attracts and traps positive cations. The resin then releases hydrogen ions (H+) in exchange for cations and hydroxide ions (OH-) in exchange for anions. Finally, the hydrogen and hydroxide ions combine to form water (H+ + OH- = HOH or H2O). Only water molecules remain, which is why deionized water is known as one of the purest forms of water.
Natural water usually contains five kinds of impurities:
1. Electrolytes: electrolytes cover soluble inorganic and organic matter in water, as well as charged colloidal particles. Including charged particles, common cations are H+, Na+, K+, NH4+,, Mg2+, Ca2+, Fe3+, Cu2+, Mn2+, Al3+, etc.; anions are F-, Cl-, NO3-, HCO3-, SO42-, PO43-, H2PO4-, HSiO3- and so on. In chemical analysis, too much electrolyte will interfere with the results of the experiment, in which the impact of anions and cations is particularly significant.
2. Organic substances: organic matter in water mainly contains organic acids and organometallic compounds. Such as: organic acids, pesticides, hydrocarbons, alcohols and esters. In order to measure the content of organic matter in water, generally indirectly through the determination of chemical oxygen consumption to reflect, thereby assessing the ability of organic matter in water to consume oxidants.
3. Particulate matter: particulate matter includes sediment, dust, organic matter and microorganisms. Detection of such impurities, with the help of specialized particle sizer, accurate determination of its content and particle size distribution.
4. Microorganisms: microorganisms are mainly composed of bacteria, plankton and algae. They not only affect the water quality, some microorganisms may also be harmful to human health, need to use specific microbial detection technology to analyze the type and quantity.
5. Dissolved gases, including: N2, O2, Cl2, H2S, CO, CO2, CH4 and so on. The so-called water purification is to remove these impurities. The more thoroughly the impurities are removed, the purer the water will be.
The main process of deionized water equipment:
The process of deionized water can be roughly divided into four kinds:
The first kind: deionized water obtained by using cation-anion exchange resin. Generally after passing, the conductivity of the water can be reduced to below 10us/cm, and then after the mixed bed can reach below 1us/cm. But this method of water cost is extremely high, and too many particles of impurities, can not meet the ideal requirements.
The second: pretreatment (i.e., sand carbon filter + precision filter) + reverse osmosis + mixed bed process;
This method is currently the most used. Because of the low investment cost of reverse osmosis, can remove more than 90% of the ions in the water, which can make the water conductivity: 5-10us/cm or so. This is currently the most popular method.
The third: the use of two-stage reverse osmosis:
The process is as follows: tap water → multi-media filter → activated carbon filter → water softener → intermediate tank → low-pressure pump → precision filter → a reverse osmosis → PH adjustment → mixer → two reverse osmosis (reverse osmosis membrane surface with a positive charge) → purified water tank → pure water pump → microporous filters → point of use;
The fourth: the mixed-bed using EDI continuous desalination membrane block instead of. This does not use acid and alkali to regenerate the resin, but with electric regeneration. The whole process is pollution-free, and the treated water quality can reach: more than 15M.
Laboratory water: distilled, deionized, purified, and ultrapure
Deionized water, ultrapure water, and distilled water are among the indispensable solvents in the laboratory, but what are the differences in composition among the three, besides the different manufacturing methods? Which one is more pure?
Distilled water: distilled water refers to the distillation, condensation operation of water, steam the second called redistilled water, three times called triple distilled water. Low oxygen consumption of water, add potassium permanganate and acid industrial distilled water is obtained by distillation method.
Deionized water: Deionized water refers to the removal of impurities in the form of ions after the pure water, mainly by RO reverse osmosis method. The application of ion exchange resins removes anions and cations from the water, but soluble organic matter still exists in the water, and it is easy to cause bacterial reproduction after storage.
Pure water: Purified water (deionized water or deeply desalinated water) refers to water that has a resistivity greater than 0.1x10^6 Ω*cm at temperatures greater than 25°C.
Ultra-pure water: Ultra-pure water, also known as UP water, is water with a resistivity of 18 MΩ*cm (25°C). There are few impurities in ultrapure water except for water molecules, not to mention bacteria, viruses, chlorinated dioxins and other organic matter.
According to the order of purity level is: ultrapure water, deionized water, pure water (RO water), distilled water.
Distilled water and deionized water application difference
Distilled water is mostly used in life, pharmaceutical industry and laboratory; and deionized water is mostly used in laboratories, laboratories, general laboratory routine tests, configuration of standing solutions, cleaning glassware, etc., electronic industrial production and petrochemical industry.
Deionized water in modern industry has a very wide range of use, because the number of ions in the deionized water can be artificially controlled, so that its resistivity, solubility, corrosivity, viruses, bacteria and other indicators to get good control. Deionized water is generally used for routine tests, configuration of standing solutions, cleaning glassware and so on.
Water purifier, ultrapure and deionized water machine recommendations
Water purifier
Ultrapure water machine
Deionized water machine
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