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    Home > Coatings News > Paints and Coatings Market > Principle of reverse osmosis

    Principle of reverse osmosis

    • Last Update: 2020-02-25
    • Source: Internet
    • Author: User
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    Water, the first element of life, is abundant and covers 71% of the earth's surface However, water in its natural state cannot be directly used as drinking water or industrial water For example, in various types of industrial applications, such as electroplating, brewing, food processing, chemical and pharmaceutical, metal processing and electronic industry, high-purity water is required, that is, water that separates salt, organic matter and bacterial components At present, there are four methods to make pure water: distillation, electrodialysis, ion exchange and reverse osmosis (RO) A Distillation is the process of vaporizing water by heating and then condensing it into liquid; B ion exchange is the principle of chemical replacement; C electrodialysis is the process of manufacturing pure water according to the principle of physical chemistry (the process and equipment of the above three water production methods are complex and energy consumption is high.) D Reverse osmosis technology is the most advanced, energy-saving and efficient separation technology The principle is to separate the solute and solvent in the solution under the pressure higher than the osmotic pressure of the solution, with the help of the selective interception of the reverse osmosis membrane which only allows water molecules to pass through, so as to achieve the purpose of purified water The reverse osmosis membrane is composed of polymer cellulose with highly ordered matrix structure It has a pore size of 0.1nm-1nm, which is one tenth of a meter (equivalent to one thousandth of the size of E.coli and one percent of the virus) Reverse osmosis technology: reverse osmosis is the original reverse osmosis It is the result of years of research by NASA, with the support of the government, and spending billions of dollars It was originally used to recycle the living water of astronauts and make it drinkable again, so that the spacecraft does not have to carry a large amount of drinking water, so it is called space technology The water it produces is also called "space water" The working principle of reverse osmosis: 1 Osmosis and osmotic pressure osmosis are common in nature For example, if a cucumber is put into salt water, it will become smaller due to water loss The process of cucumber water molecules entering into saline solution is the infiltration process As shown in the figure below, if a water pool is separated into two parts by a membrane that only water molecules can penetrate, pure water and salt water are injected into both sides of the membrane to the same height After a period of time, it can be found that the level of pure water has decreased, while the level of salt water has increased The phenomenon that we transfer water molecules through this membrane into brine is called osmosis Salt water level rise is not endless, to a certain height will reach a balance point At this time, the pressure represented by the liquid level difference at both ends of the diaphragm is called osmotic pressure The osmotic pressure is directly related to the concentration of brine 2 Reverse osmosis phenomenon and reverse osmosis water purification technology If a certain pressure is applied on the surface of the brine end after the above device reaches equilibrium, the water molecules will migrate from the brine end to the pure water end The process of migration of liquid agent molecules from dilute solution to concentrated solution under pressure is called reverse osmosis If salt water is added to one end of the above facilities and pressure is applied at that end beyond the osmotic pressure of the salt water, we can get pure water at the other end This is the principle of RO water purification There are two keys to produce pure water in reverse osmosis facilities One is a selective membrane, which we call semi permeable membrane, and the other is a certain pressure In short, there are many pores on the reverse osmosis membrane The size of these pores is the same as that of water molecules Because bacteria, viruses, most organic pollutants and hydrated ions are much larger than water molecules, they cannot be separated from water through the reverse osmosis membrane Soluble salts are the most difficult to be removed from many impurities in water Therefore, the water purification effect of reverse osmosis is often determined by the desalting rate The desalting rate of reverse osmosis mainly depends on the selectivity of reverse osmosis semi permeable membrane At present, the desalination rate of high selective reverse osmosis membrane element can be as high as 99.7% At present, the reverse osmosis membrane of our company is imported from America Its form is roll type element According to the principle of reverse osmosis, the semi permeable membrane, diversion layer and partition net are bound and rolled on the central pipe with drain holes The raw water enters into the partition layer from one end of the element When passing through the partition layer, under the pressure, part of the water penetrates into the diversion pipe through the semi permeable membrane, and can flow into the central pipe through the water channel of the diversion layer, The remaining part is discharged from the other end of the screen layer According to the water yield, the water utilization rate and the different composition of the inlet and outlet water quality can be designed as a high-pressure shell and a membrane element group, or as a high-pressure shell and multiple membrane elements According to different requirements of users, different water quality standards and different water solutions and solutes separated, the reverse osmosis device can be designed in the form of multi-level series parallel multi-level components, parallel and series combination Reverse osmosis device has one-stage one-stage, one-stage multi-stage and multi-stage All membranes are imported from abroad It can remove impurities, various ions, molecules, organics, colloids, bacteria, viruses and heat sources in water with a removal rate of 95-99% The desalination rate of RO membrane is more than 96% The process flow chart of RO treatment can be divided into three parts according to the sequence of treatment: pretreatment, membrane separation and post-treatment The pretreatment adjusts the water quality and quantity of raw water to meet the requirements of membrane separation treatment so as to ensure the final treatment effect The basic parameters of water inlet required by general polyaromatic amide composite membrane module are: pollution index (FI) < 3-5, free residual chlorine < 0.1mg/l, water inlet temperature: 1-45 ℃, pH value range: 4- The post-treatment mainly aims at the treatment measures that some indexes of reverse osmosis treatment water can not meet the final requirements, such as degassing, ultraviolet irradiation, ultrafiltration and other separate or combined processes Standard configuration: the pretreatment is raw water pump and fiberglass drum (i.e sand, carbon, softening) The carbon filter of sand filter is a manual valve, the softener is a Fulai automatic control valve, the reverse osmosis membrane is a vontron of American fluid production line, the reverse osmosis membrane shell is a stainless steel shell raw water pump and a high-pressure pump is a special stainless steel pump in the south, the frame is carbon steel spray plastic, and the connecting pipe valve is UPVC
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