Principle and application of reverse osmosis process
Reverse osmosis technology is the most advanced and energy efficient separation technology available today. The principle is to separate the solute in the solution from the solvent by a selective retention of a semipermeable membrane that allows only water to pass through without allowing other materials to permeate under pressure above the osmotic pressure of the solution. By using the separation characteristics of the reverse osmosis membrane, impurities such as dissolved salts, colloids, organic matter, bacteria, and microorganisms in the water can be effectively removed. It has the advantages of low energy consumption, no pollution, advanced technology, and easy operation and maintenance.
Among various membrane separation technologies, reverse osmosis technology is the most successful, fastest-growing and most popular one in China in recent years. The largest application area of China’s reverse osmosis membrane industry is still large-scale boiler feed water, all kinds of industrial pure. The market for water and drinking water is second, and membrane applications in the electronics, semiconductor, pharmaceutical, medical, food, beverage, alcohol, chemical, environmental, metallurgical, textile and other industries have also formed a certain scale. Potential applications in the future include sewage treatment of cooling water from power plants, large-scale seawater desalination, brackish water desalination, and large municipal and industrial wastewater treatment.
2. The latest development and development trend of reverse osmosis membrane
2.1 ultra low pressure membrane
Due to the advantages of saving power consumption and lowering the pressure level of related mechanical components, the application of ultra-low pressure membranes has been increasing since 1996, which is most prominent in small devices using 4-inch membranes.
2.2 Low pollution film
Membrane fouling is the biggest hazard in reverse osmosis applications. It not only shortens membrane life, increases operating costs, but also directly affects the efficient and continuous operation of membrane systems. At present, there are several low-pollution membranes with strong anti-pollution performance, long service life, low cleaning frequency and easy cleaning.
2.3 Positively charged reverse osmosis membrane
The widely used low-pressure and ultra-low-pressure composite membranes are all made of aromatic polyamide, and the surface of the membrane is negatively charged. Now, membrane manufacturers have developed low-pressure composite membranes with positive charges on the surface. In the preparation of high resistivity high purity water system.
2.4 High temperature resistant, food grade, sanitary grade reverse osmosis membrane
The normal water treatment reverse osmosis membrane is used at a temperature of 0 to 45 ° C. However, in the special case where high temperature sterilization is required at 90 ° C, a high temperature resistant chemical resistant reverse osmosis membrane can be used. In addition, various food grade or sanitary grade reverse osmosis membranes with special membrane element structures have also begun to be used in China.
Reverse osmosis equipment application areas:
- Electronic industry water, integrated circuit, silicon wafer, display tube, electrode foil and other electronic components flushing water
- water for the pharmaceutical industry, large infusions, injections, tablets, biochemical products, equipment cleaning, etc.
- Process water for chemical industry Chemical circulating water, chemical product manufacturing, fertilizer, etc.
- power supply boiler boiler water supply power generation boiler, plant mine medium and low pressure boiler power system
- Water for food industry Application of pure water, beverages, beer, liquor, health products, etc.
- seawater, brackish water desalination islands, ships, offshore drilling platforms, brackish waters
- drinking pure water, real estate, community, enterprises, etc.
- Other process water Automotive, home appliance coating, coated glass, cosmetics, fine chemicals, printing and dyeing, etc.