Nanofiltration membranes are mostly composite membranes, with their surface separation layer consisting of polyelectrolytes, giving them a certain retention rate for inorganic salts. Most commercially available nanofiltration membranes overseas are composite with a ultra-thin separation layer with nanoscale pores, which is formed by interfacial polymerization and condensation on a microporous base membrane.
Nanofiltration membranes can remove organic substances, CMR substances, disinfection byproducts, volatile organic compounds, and are used for pipe direct drinking water applications.
Removal of organic substances in water: Nanofiltration membranes are used in drinking water treatment for decolorization, removal of natural and synthetic organic substances (such as pesticides), trihalomethanes, disinfection byproducts (trihalomethanes and haloacetic acids) and their precursors, as well as volatile organic compounds, to ensure the biological stability of drinking water.
Removal of trihalomethanes: Research has shown that nanofiltration membranes can remove most of the toxic and harmful organic substances and Ames mutagens in water, reducing the ratio of TA98 and TA100 strains to mutagenic ratio (MR) below 2 at each test dose, and the Ames test results are negative. Further research will investigate the retention characteristics of endocrine disruptors in drinking water by nanofiltration technology, providing a basis for safe and high-quality drinking water.
Disinfection byproducts removal: Disinfection byproducts mainly include trihalomethanes, haloacetic acids, and possible chlorinated acetaldehyde hydroxides. Overseas scientific and technical workers have conducted extensive research in this area, and nanofiltration membranes have an average retention rate of 97%, 94%, and 86% for these three disinfection byproduct precursors, respectively. With the appropriate nanofiltration membrane selection, the water quality of drinking water can meet higher safety and quality water standards. In addition, nanofiltration effluent is less corrosive, which has a positive effect on extending the service life of the drinking water distribution system and reducing the release of metal ions from pipeline materials. Experiments have shown that adopting nanofiltration membrane systems with necessary post-treatment can reduce the dissolution of lead in the network by 50%, while ensuring that the concentration of other dissolved metal ions meets drinking water quality standards.
Removal of volatile organic compounds: Has a high removal rate for trace amounts of volatile organic compounds in drinking water.
Application of pipe direct drinking water: Nanofiltration membranes can retain ions of divalent or higher valency and other particles, allowing only water molecules and some monovalent ions (such as sodium, potassium, and chloride ions) to pass through. Nanofiltration membranes can be used for producing direct drinking water, while retaining a certain amount of ions in the effluent, and reducing treatment costs.