Factors affecting the salt rejection rate

Factors affecting the salt rejection rate of reverse osmosis are as follows:
◆ Ion valence
The salt rejection rate increases with the increase of ion valence. The salt rejection rates of divalent and trivalent salts are also higher than those of monovalent salts.
◆ Molecular size
The salt rejection rate increases with the increase of molecular diameter.
◆ Raw water temperature
When the raw water temperature rises, the salt rejection rate increases due to the decrease in water viscosity.
◆ Raw water concentration
When the raw water concentration increases, the salt rejection rate decreases.
◆ Operating pressure
When the operating pressure increases, the salt rejection rate increases slightly but not significantly.
◆ pH value
Under acidic conditions, although the membrane is not easy to be blocked, the salt rejection rate will decrease.
◆ Dissolved gases
Dissolved gases in a free state are easy to penetrate and are not removed, such as CO2, SO2, O2, Cl2, H2S, etc.
◆ Hydrogen - bonding tendency
For compounds with strong hydrogen - bonding tendencies, the rejection rate is very low, such as water, phenol, and ammonia, etc. (Precisely because of this, it is possible to remove impurities and dissolved substances in water to achieve separation from other substances.)
◆ Organic substances
Organic substances in water contaminate the membrane. The more organic substances there are, the easier it is for the membrane performance to deteriorate.
◆ Water hardness
The higher the water hardness, the easier it is for the membrane to be blocked. For water with high hardness, it should be softened first to reduce the hardness before entering the reverse osmosis system.
◆ Solid particles
Solid particles are extremely harmful to the reverse osmosis membrane and must be pretreated.
◆ Microorganisms
Microorganisms and bacteria in water are harmful to the membrane and must be pretreated.
◆ Oxides
Metal oxides entering the reverse osmosis system cannot be removed by themselves and should be removed regularly with chemical agents.