Working Principle Of Reverse Osmosis Membrane

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The film that has selectivity for the substances that pass through is called semi permeable membrane. Generally, the film that can only pass through solvent but not solute is called ideal semi permeable membrane. When the same volume of dilute solution (such as fresh water) and concentrated solution (such as brine) are placed on both sides of the semi permeable membrane respectively, the solvent in the dilute solution will naturally pass through the semi permeable membrane and spontaneously flow to the side of the concentrated solution. This phenomenon is called infiltration. When the permeation reaches equilibrium, the liquid level on the concentrated solution side will be a certain height higher than that of the dilute solution, that is, a differential pressure will be formed, which is the osmotic pressure. The osmotic pressure depends on the inherent properties of the solution, that is, it is related to the type, concentration and temperature of the concentrated solution, but not to the properties of the semi permeable membrane. If a pressure greater than the osmotic pressure is applied on one side of the concentrated solution, the flow direction of the solvent will be opposite to the original infiltration direction and start to flow from the concentrated solution to the dilute solution side. This process is called reverse osmosis. Reverse osmosis is a reverse migration movement of osmosis. It is a separation method that separates solute and solvent in solution by means of selective interception of semi permeable membrane driven by pressure. It has been widely used in the purification and concentration of various liquids. The most common application example is the removal of inorganic ions, bacteria, viruses, organics, colloids and other impurities in raw water by reverse osmosis technology in water treatment process, To obtain high-quality purified water.