Overview of hardness in ultrapure water equipment and maintenance of ion exchange resin

     

 

Water hardness is an important monitoring indicator of water quality. It can be found through monitoring whether it can be used in industrial production and daily life. For example, water with high hardness can precipitate soap and greatly reduce the utility of detergent. The textile is rough and difficult to dye; the boiler is easy to block the pipeline, causing boiler explosion accident; high hardness water, difficult to drink, bitter and astringent taste, even affecting gastrointestinal function after drinking; feeding livestock can cause abortion of pregnant animals. Therefore, the study of the determination method of water hardness can not be ignored. At present, there are many analytical methods and methods, which can be mainly divided into chemical analysis methods and instrumental analysis methods .

The hardness of water is divided into carbonate hardness and non-carbonate hardness .

Ultrapure water equipment industry ---- mainly carbonate hardness hardness, the hardness of a small amount of calcium carbonate, magnesium bicarbonate [Ca (HCO3) 2, Mg (HCO3) 2] is formed. The hardness of the bicarbonate is decomposed into a precipitate after heating and is removed from the water, so it is also called temporary hardness.
　　
　　 Ultrapure water equipment industry ---- mainly non-carbonate hardness hardness of sulfate, chloride salts such as calcium and magnesium salts, and xiao being formed. Such hardness cannot be removed by thermal decomposition, so it is also called permanent hardness, such as CaSO4 , MgSO4 , CaCL2 , MgCL2 , Ca(NO3)2 , Mg(NO3)2, and the like.

In ultrapure water equipment , ion exchange resin is very important, and its performance is directly related to water resistivity, electrical conductivity, and the number of anions and cations in water. Therefore, the maintenance of the ion exchange resin is important.

First, the storage of ion exchange resins in ultrapure water equipment. The ion exchange resin contains a certain amount of water. When stored, it should not be stored in the open air. It should be kept moist during storage and transportation to avoid air drying and dehydration, so that the resin is broken. If the resin is dehydrated during storage, it should be soaked in concentrated brine ( 10% ). Then gradually dilute, not directly into the water, so as to prevent the resin from expanding and breaking , which affects the performance of the resin. At the same time, the storage temperature is kept at 5-40 °C , avoiding too cold or overheating, affecting the quality . If there is no heat preservation equipment in winter, the resin can be stored in the brine. The salt water concentration can be determined according to the temperature.

Secondly, the cleaning of the ion exchange resin in the ultrapure water equipment . In the production or use of the resin, inorganic impurities such as iron, lead, copper, etc. (mainly rust) may be absorbed. When the resin is exposed to water, acids, alkalis or other solutions (such as alcohol, hydrogen peroxide, etc.) it will dissolve in it. In addition, the reacted resin can be reacted with a corresponding acid or base or a salt solution to restore the ion exchange activity of the resin, wherein the different types of resins use slightly different solutions.

Finally, the ion exchange resin in the ultrapure water equipment is organic, so oil, organic molecules, microorganisms, etc. have a detrimental effect on it, so before the ion exchange resin treats the water, the water is pretreated to remove oil and the like in the water. In general, the acid resin is metal-proof and can be soaked with 4-5% dilute hydrochloric acid ; the alkaline resin is protected against organic matter, and can be soaked or rinsed to neutral with a 10% NaC1 + 2-5% NaOH mixed solution , if necessary. 1% aqueous solution of hydrogen peroxide can be used for several minutes. Others can also be treated by acid-base alternate treatment, bleaching treatment, alcohol treatment and various sterilization methods.

In addition, in the process of using ultrapure water equipment or ultrapure water machine , pay attention to detecting the resistivity and conductivity of water. If the conditions are sufficient, it is possible to detect whether the content of ions in water is within the normal range.