The desalination rate is the percentage of soluble impurities removed from the inlet water of the equipment through a reverse osmosis membrane. Desalination rate=(1- salt content in produced water/salt content in influent) × 100%. The desalination rate of reverse osmosis membrane elements is determined during their manufacturing process, and the high or low desalination rate depends on the density of the ultra-thin desalination layer on the surface of the reverse osmosis membrane element. The denser the desalination layer, the higher its desalination rate and the lower its water production. The removal rate of different substances by reverse osmosis is mainly determined by the structure and molecular weight of the substances. Imported reverse osmosis membrane elements can achieve a removal rate of over 99% for high valence and complex monovalent ions, while the removal rate for monovalent ions such as sodium ions, potassium ions, and chloride ions is slightly lower but still exceeds 98%; The removal rate of organic compounds with a molecular weight greater than 100 can also reach 98%. The factors that affect the desalination rate of reverse osmosis include: ◆ The desalination rate of ion valence increases with the increase of ion valence, and the desalination rate of divalent and trivalent salts is also higher than that of monovalent salts
The desalination rate increases with the increase of molecular diameter due to the increase of molecular size
When the raw water temperature increases, the desalination rate increases due to the decrease in water viscosity
When the concentration of raw water increases, the desalination rate decreases
When work pressure increases, the desalination rate increases but not significantly
Although the membrane is not easily clogged under acidic pH conditions, the desalination rate will decrease slightly
Dissolved gases are easily permeable in their free state without removing CO2, SO2, O2, Cl2, H2S, etc;
Hydrogen bonding tends to occur in compounds containing strong hydrogen bonds, with low removal rates, such as water, phenol, and ammonia; It is precisely because of this that impurities and dissolved substances in water can be removed to achieve separation from other substances
Organic substances in water have a polluting effect on membranes, and the more organic substances there are, the more susceptible the membrane performance is to deterioration
The higher the hardness of water, the easier it is for the membrane to clog. For high hardness water, it should be softened first to reduce its hardness before entering reverse osmosis
Solid particles pose a great threat to reverse osmosis membranes and require pre-treatment
Microorganisms and bacteria in microbial water pose a threat to membranes and require pre-treatment.
Metal oxides cannot be removed by reverse osmosis on their own, and should be regularly removed by chemical agents.
