Selection of Reverse Osmosis Reagents and Precautions for Use

Scale inhibitors for reverse osmosis and nanofiltration systems are a series of chemicals used to prevent precipitation and scaling of crystalline mineral salts. Most scale inhibitors are specially synthesized organic polymers (such as polyacrylic acid, carboxylic acid, polymaleic acid, organometallic phosphate, polyphosphate, phosphonate, anionic polymer, etc.) with molecular weight between 2000 and 10000 daltons. The scale inhibitor technology of reverse osmosis system is developed from the water chemistry of cooling circulating water and boiler water. For a large number of various scale inhibitors, the effect and efficiency of organic compounds in different applications are quite different.

Special care shall be taken when using polyacrylic acid scale inhibitors. When the iron content is high, it may cause membrane pollution, which will increase the operating pressure of the membrane. Pickling is required to effectively remove such pollution.

If cationic coagulant or filter aid is used in pretreatment, special attention shall be paid to the use of anionic scale inhibitor. It will produce a viscous pollutant, which will increase the operating pressure, and it is very difficult to clean this pollutant.

Sodium hexametaphosphate (SHMP) is a common scale inhibitor used in reverse osmosis at the early stage, but with the emergence of special scale inhibitor, the dosage has been greatly reduced. SHMP has some limitations. The solution should be prepared every 2-3 days, because it will hydrolyze when exposed to air. After hydrolysis, not only the scale inhibition effect will be reduced, but also the possibility of calcium phosphate scaling will be caused. SHMP can reduce calcium carbonate scaling, and LSI can reach+1.0. Scale inhibitors hinder the growth of salt crystals in RO influent and concentrated water, thus allowing insoluble salts to exceed saturation solubility in concentrated water. The scale inhibitor can be used instead of or in combination with acid addition. There are many factors that affect the formation of mineral scaling. The decrease of temperature will reduce the solubility of scaling minerals (except calcium carbonate, which, contrary to most substances, decreases with the increase of temperature), and the increase of TDS will increase the solubility of insoluble salts (because high ionic strength interferes with the formation of crystal seeds).

About the introduction of reverse osmosis agents, Tonglida has introduced it here today. I believe you have a certain understanding.