RO (reverse osmosis), also known as reverse osmosis, is a membrane separation operation that uses pressure differences as a driving force to separate solvents from solutions. Because it is opposite to the direction of natural infiltration, it is called reverse osmosis. According to the different osmotic pressure of various materials, reverse osmosis pressure greater than osmotic pressure can be used, that is, reverse osmosis method, to achieve the purpose of separation, extraction, purification and concentration.

RO reverse osmosis membrane is the core component of reverse osmosis. It is a kind of artificial semi-permeable membrane made by simulating biological semi-permeable membrane with certain characteristics. Generally made of polymer materials. Such as cellulose acetate membrane, aromatic polyamide membrane.

The diameter of the surface micropores is generally between 0.5 nm and 10nm, and the transmittance is related to the chemical structure of the membrane itself. Some polymer materials have good repellency to salt, but water permeation speed is not good.

The working principle is to apply pressure to the material liquid on one side of the membrane. When the pressure exceeds its osmotic pressure, the solvent will reverse permeate against the direction of natural permeation. Thus, the permeating solvent is obtained on the low pressure side of the membrane, namely the permeating solution. The concentrated solution at the high pressure side is the concentrated solution.