1. Introduction to reverse osmosis equipment

Reverse osmosis equipment is a type of membrane water treatment equipment. Introduction to reverse osmosis technology Reverse osmosis technology is currently a widely used equipment for the preparation of pure water and high purity water. Among the membrane equipment, reverse osmosis membrane can remove ionic impurities, so that the effluent reaches the standard of pure water and high purity water. The membrane pore size of the reverse osmosis membrane is very small (only about 10A), so it can effectively remove dissolved salts, colloids, microorganisms, and organic matter in the water (removal rate as high as 97-98%). The system has the advantages of good water quality, low energy consumption, simple process and easy operation.

2. Principle of reverse osmosis

Reverse osmosis is a concept corresponding to osmosis, that is, a pressure higher than the natural osmotic pressure is applied to one side of the dope, so that the solvent (water) in the dope is pressed into the dilute solution on the other side of the semipermeable membrane. The process is opposite to the normal infiltration process in nature. Therefore, it can intercept the impurities in the water on one side of the membrane, and let the water to the other side of the membrane, thereby preparing pure water and high purity water.

There are two keys to the production of pure water in reverse osmosis facilities. One is a selective membrane, which we call a semi-permeable membrane, and the other is a certain pressure. Simply put, the reverse osmosis semipermeable membrane has many pores, the size of these pores is equivalent to the size of water molecules. Since viruses, most organic pollutants and hydrated ions are much larger than water molecules, they cannot penetrate the reverse osmosis membrane. The semi-permeable membrane is permeated and separated from the water passing through the reverse osmosis membrane.

3. Desalting characteristics of reverse osmosis

Among the many impurities in water, soluble salts are difficult to eliminate. Therefore, the water purification effect of reverse osmosis is often determined according to the level of salt removal rate. The level of reverse osmosis salt removal rate is mainly determined by the reverse osmosis semipermeable membrane. Selective. At present, the salt removal rate of highly selective reverse osmosis membrane elements can be as high as 99.7%. The desalination and separation characteristics of reverse osmosis membranes are as follows:

Organic matter is easier to separate than inorganic matter;

Electrolytes are easier to separate than non-electrolytes. For electrolytes, the separation of high charge is good. The order of removal rate of several common ions is: Al3+>Mg2+>Ca2+>Na+; PO43->SO42->CL-;

The removal rate of inorganic ions is affected by the number of hydrated ions and the radius of hydrated ions. The larger the hydrated ion radius (generally, the smaller the ion radius, the larger the hydrated ion radius), the easier it will be removed. The order of removal rate of some cations is: Mg2+, Ca2+>Li+>Na+>K+, and the order of anions is: F->Cl->Br->NO3-. Nitrate, permanganate, cyanide and hydrosulfide are not as easy to remove as chloride ions. The removal rate of ammonium salt is lower than that of sodium ion;

For non-electrolytes, the larger the molecule, the easier it is to remove;

Gas easily penetrates the membrane. The removal rate of ammonia, chlorine, carbon dioxide, hydrogen sulfide, oxygen and other gases is very low. It can be converted into ions for removal;

The removal rate of weak acids is low, such as boric acid and organic acids. In organic compounds, the order of removal rate is: citric acid>tartaric acid>acetic acid, acetaldehyde>ethanol>amine>acid.

4. Scope of application

In the past 30 years, reverse osmosis, electrodialysis, ultrafiltration and membrane filtration have entered industrial applications and have developed rapidly. As a kind of membrane filtration method, reverse osmosis is generally used in all industries that need to prepare pure water and high-purity water, mainly including:

Purification and preparation of pure water and ultrapure water in electronics, medicine, food and other industries; purification and preparation of water for textiles and chemical industry; purification and preparation of water for food and beverage and brewing process water; useful substances and concentration and concentration of aqueous solutions in industrial production Pre-desalination treatment of high-pressure boiler feed water for recycling power plants and other enterprises; Desalination and desalination of brackish water and seawater; As a primary desalination equipment for high-purity water production