Reverse osmosis membranes are the core components for achieving reverse osmosis. They are artificial semi-permeable membranes with certain characteristics made by simulating biological semi-permeable membranes. It is generally made of polymer materials. Such as cellulose acetate membrane, aromatic polyacylhydrazine membrane, aromatic polyamide membrane. The diameter of the surface micropores is generally within0.5～10nmThe degree of permeability is related to the chemical structure of the membrane itself. Some polymer materials have good salt repulsion, but their water permeation rate is not good. Some polymer materials have a chemical structure with more hydrophilic groups, so the permeation rate of water is relatively fast. When choosing reverse osmosisROThe membrane needs to be considered3The factors are: desalination rate, water production, and recovery rate.

I.ROThe desalination rate and salt permeability of reverse osmosis membranes

ROThe desalination rate of reverse osmosis membrane elements is determined during their manufacturing and forming process, and the level of desalination rate depends on reverse osmosisROThe density of the ultra-thin desalination layer on the surface of the membrane element: the denser the desalination layer, the higher the desalination rate, but the lower the water production. The desalination rate of reverse osmosis membranes for different substances is mainly determined by the structure and molecular weight of the substances. The desalination rate for high-valent ions and complex monovalent ions can exceed99%The desalination rate for monovalent ions such as sodium ions, potassium ions and chloride ions is slightly lower, but it can still exceed98%The longer the reverse osmosis membrane is used and the more times it undergoes chemical cleaning, the lower the desalination rate of the reverse osmosis membrane will be. The molecular weight is greater than100The organic matter removal rate can also be exceeded98%However, the molecular weight is less than100The organic matter removal rate is relatively low. 　　

Calculation methods for desalination rate and salt permeation rate of reverse osmosis membranes: 　　

ROThe salt permeability of the membrane=ROMembrane water production concentration/Influent concentration×100% 　　

ROThe desalination rate of the membrane=(1-ROThe salt content of the water produced by the membrane/Influent salt content×100% 　　

ROThe salt permeability of the membrane=100%-Desalination rate.

Ii.ROThe water production capacity and permeation flow rate of reverse osmosis membranes 　　

ROThe water production capacity of a membrane refers to the water production capacity of a reverse osmosis system, that is, the water permeation per unit timeROThe water volume of the membrane is usually measured in tons/Hours or gallons/Tian Lai indicated. 　　

ROThe permeation flow rate of the membrane is an important indicator for representing the water production of reverse osmosis membrane elements. It refers to the flow rate of the permeate per unit membrane area, usually expressed in gallons per square foot per day.GFDIt indicates. An excessively high permeation flow rate will lead to perpendicularityROThe water flow rate on the membrane surface increases, intensifying membrane fouling.

Iii.ROThe recovery rate of reverse osmosis membranes

ROThe recovery rate of a membrane refers to the percentage of feed water converted into product water or permeate in a reverse osmosis membrane system. It is determined based on the influent water quality and water usage requirements of the pretreatment in the reverse osmosis system.ROThe recovery rate of the membrane system has been determined during the design stage.

RORecovery rate of the membrane=(ROThe water production flow rate of the membrane/Influent flow rate×100%

The calculation formulas for the recovery rate, salt permeability rate and desalination rate of reverse osmosis membrane modules are as follows: 　　

The recovery rate of reverse osmosis membrane modules= ROWater production capacity of membrane modules/Inflow volume×100% 　　

The salt permeability of reverse osmosis membrane modules=ROWater production concentration of membrane modules/Influent concentration×100%

The above is the selection of reverse osmosisROThe membrane should be considered when needed3One factor, if in reverse osmosisROIf you have any questions regarding membrane selection, please consult Yuanlai Water Treatment Equipment Co., LTD.15With years of focus on the water treatment industry, you can trust us!