Why is it necessary to add antiscalants during the operation of reverse osmosis equipment?

Reverse osmosis systems use fine filters, granular activated carbon filters, and compressed activated carbon filters to pre-treat the raw water. The water is then pressurized by a pump and passed through a reverse osmosis membrane with a pore size of 1/10000μ m This process converts high-concentration water into low-concentration water, simultaneously isolating industrial pollutants, heavy metals, bacteria, viruses, and other impurities from the water. This ensures the water meets the required physicochemical and hygiene standards for drinking, producing exceptionally pure water.

The reverse osmosis membrane is the key component of the reverse osmosis system. During prolonged continuous operation, ions such as calcium and magnesium in the water precipitate and adhere to the surface of the reverse osmosis membrane, forming scale that blocks the membrane pores. This reduces the water output efficiency of the reverse osmosis system and damages the membrane. Because reverse osmosis membranes are expensive, a chemical dosing system is added to the system to introduce a reverse osmosis antiscalant into the water, delaying the precipitation of calcium and magnesium ions and membrane scaling.

The basic function of a reverse osmosis antiscalant is its solubilizing effect. When dissolved in water, the reverse osmosis antiscalant ionizes , generating negatively charged molecular chains , These chains react with Ca2+ to form water-soluble complexes or chelates , increasing the solubility of inorganic salts , thus achieving the antiscaling effect.

① Inhibition of precipitation: In a system with an antiscalant, the ionic product at which the precipitation of easily scaling cations and anions begins is much larger than the critical precipitation ionic product in a system without an antiscalant.

② Dispersion function: In the presence of an antiscalant, the precipitated particles are smaller and less likely to aggregate, making them more difficult to settle than in the absence of an antiscalant.

③ Lattice distortion effect: In a system with an antiscalant, the precipitated crystals are amorphous, such as spherical, polyhedral, or snowflake-like. It is generally believed that amorphous crystals are formed when the antiscalant adsorbs onto the crystal growth points during crystal growth, causing a sharp decrease in the growth rate of the surface and the growth of crystals with different shapes.

④ Threshold effect: Even when the amount of antiscalant added is much lower than the scaling components in the water, it can still show an antiscaling effect.

      Antiscalants prevent the precipitation of impurities and scale formation in reverse osmosis equipment, significantly improving the filtration system, increasing water quality and yield, and making a significant contribution to water resource conservation.