Reverse osmosis, also known as reverse osmosis, is a membrane separation operation that uses the pressure difference as a driving force to separate the solvent from the solution. Because it is opposite to the direction of natural osmosis, it is called reverse osmosis. According to the different osmotic pressure of various materials, reverse osmosis pressure greater than the osmotic pressure can be used, that is, reverse osmosis method, to achieve the purpose of separation, extraction, purification and concentration.
Process principle of reverse osmosis
1. Semi-permeable membrane: The membrane that can only allow the passage of solvent molecules and not allow the passage of solute molecules is called ideal semi-permeable.
2. Penetration: under the same external pressure, when the solution and the pure solvent is separated from the semi-permeable film, the pure solvent will pass through the semi-permeable film is the phenomenon of solution thinning called penetration.
3. Osmotic balance: in the process of osmosis, the number of solvent molecules passing through the semi-permeable membrane from two opposite directions per unit time is equal to each other, that is, osmotic balance is reached.
4. Osmotic pressure: When a semi-permeable membrane separates the solution from the pure solvent, the extra pressure applied to the original solution to prevent the pure solvent from entering the solution is called osmotic pressure. Usually the thicker the solution, the higher the osmotic pressure of the solution.
5. Reverse osmosis: if the pressure on the solution exceeds the osmotic pressure, the solvent in the solution will instead flow to the direction of the pure solvent, this process is called reverse osmosis.
Reverse osmosis is the use of reverse osmosis membrane can only selectively through the solvent (usually water) and the properties of ionic material interception, with the static pressure difference on both sides of the membrane as the driving force to overcome the osmotic pressure of the solvent, so that the solvent through the reverse osmosis membrane to achieve the separation of liquid mixture membrane process.
Its operating pressure difference is generally 1.5 ~ 10.5MPa, and the size of the interception component is 1 ~ 10197. Small molecule solute. In addition, all other suspensions, solubles, and colloids can be removed from the liquid mixture.
Technical characteristics of reverse osmosis process
1. Solute and water can be separated under the condition of no phase change at room temperature, which is suitable for the separation and concentration of heat-sensitive substances. Compared with the separation method with phase change, the energy consumption is lower.
2. A wide range of impurities removal, not only can remove dissolved inorganic salts, but also can remove all kinds of organic ladle impurities.
3. High rate of salt removal and water reuse, can intercept the particle size of a few nanometers above the solute.
4. Because the pressure is only used as the driving force of membrane separation, the separation device is simple, easy to operate, control and maintain.
5. reverse osmosis device requires water to reach a certain index in order to operate normally, the doctor this raw water before entering the reverse osmosis device to use certain pretreatment measures. In order to extend the service life of the film, it is necessary to clean the film regularly to remove dirt.
Routine use
Reverse osmosis technology is usually used for seawater, brackish fresh water; Softening treatment of water; Wastewater treatment and food, pharmaceutical industry, chemical industry purification, concentration, separation and other aspects.
In addition, reverse osmosis technology applied to pre-salt treatment has also achieved good results, which can reduce the load of ion exchange resin by more than 90%, and the amount of resin regenerant can also be reduced by 90%.
Therefore, it not only saves money, but also helps the environment. Reverse osmosis technology can also be used in addition to the particles in water, organic substances, colloids, to reduce the pollution of ion exchange resin, prolong the service life has a good role.
