Principle of preparation of pure water by ion exchange resin

If you want to make ultra-pure water, you must use ion exchange resin to make it, and improve the purity of water quality through ion replacement. However, many people do not understand the exchange principle, and today I will take you to understand the exchange principle of ion exchange resin.
The basic principle of preparing pure water by ion exchange resin
Yang and Yin resins are dissociated in water. When raw water passes through Yang resin, the cation in water is adsorbed by the resin, and the cation H+ on the resin is replaced into water, and the corresponding inorganic acid is formed with the anion in water. When the water containing inorganic acid passes through the negative resin, the anion in the water is adsorbed by the resin, and the anion OH- on the resin is replaced into the water, and combines with H+ in the water to form water. In this way, the raw water is constantly exchanged through the Yang and Yin resins to obtain deionized water.
New ultra pure water resin treatment and transformation
New resins are often mixed with soluble oligomers and other impurities, which affect the exchange reaction of the resin and the quality of the effluent, so the new resin must be treated and transformed before use. Most of the commercially available Yang resins are sodium types, and most of the Yin resins are chlorine types, so they must be converted into active hydrogen and hydrogen oxygen types.
The new Yang resin is soaked in normal water 1-2 angels to fully absorb water and expand, rinse repeatedly with normal water, remove the soluble matter in the water until the washing water is clear, and remove the remaining water as far as possible. Add the same amount of 7% hydrochloric acid solution to soak for about 1 hour and stir at any time, remove the acid, and then wash with normal water until the rinse water pH3.0-4.0, and dump the remaining water. Then add the same amount of 8% sodium hydroxide solution to soak for 1 hour, and stir at any time, remove the lye, wash with water exchanged by positive resin or deion until the rinsed solution pH9.0, and pour the remaining water. Finally, add 3 times the volume of 7% hydrochloric acid solution to soak for 2 hours and stir to make the Yang resin into hydrogen type, pour off the acid, and wash with deionized water until pH3.0-4.0.
The new Yin resin is soaked in regular water, and then washed repeatedly with water to remove the strong odor, such as odor washing is not enough, it can be soaked in 95% ethanol to remove the odor, pour the ethanol, and then washed with regular water to clear and odorless. Add the same amount of 8% sodium hydroxide solution to soak for 1 hour and stir, remove the lye, and then wash with water through Yang resin or deionized water to the rinsing solution pH9.0 (it is not suitable to wash with regular water, because Ca2+ and Mg2+ in regular water generate insoluble hydroxide precipitation in the lye), and pour the remaining water. Add the same amount of 7% hydrochloric acid solution to soak for 1 hour, remove the acid, and then wash with normal water until the rinsed solution pH3.0, pour the remaining water. Finally, add 3 times the amount of 8% sodium hydroxide solution to soak for 2 hours and stir, so that the Yin resin into hydrogen and oxygen type, pour the lye, wash with deionized water to pH8.0-9.0 can be used.
Combination of ultra pure water resin column
There are generally four forms: (1) single bed; (2) composite bed; (3) Combined bed; (4) Mixed bed. In various combinations (except for the mixing bed), the positive resin bed needs to be in the first place and cannot be reversed. Because the water contains alkaline earth metal ions (Ca2+, Mg2+), if it does not first pass through the positive resin bed and enter the negative resin, the negative resin is exchanged with the anion in the water, and the exchanged OH is precipitated with the alkaline earth metal ions outside the negative resin, which affects the exchange capacity.
In fact, the preparation of pure water by ion exchange resin is mainly through the exchange of ions in the resin particle with ions in the water, and the removal of other ions in the water except hydrogen and oxygen ions. And in the resin replacement process will be saturated, at this time it is necessary to regenerate the ultra-pure water ion exchange resin.