Nanofiltration (NF)

Introduce

Nanofiltration membrane is a new type of separation membrane introduced in the late 1980s. Their molecular weight cut-off (MWCO) ranges between that of reverse osmosis membranes and ultrafiltration membranes, approximately 200-2000 Daltons. Based on this, it is speculated that nanofiltration membranes may possess a microporous structure with pore sizes around 1 nanometer, hence the name "nanofiltration". Most nanofiltration membranes are composite membranes, with their surface and separation layers composed of polyelectrolytes, thus exhibiting a certain retention rate for inorganic salts. Many commercially available nanofiltration membranes abroad are composed of an ultra-thin separation layer with nanoscale pore diameters, formed through interfacial polymerization and condensation on a microporous base membrane.

Material of Nanofiltration Membranes：Polyamide

Nanofiltration membranes are capable of retaining substances at the nanoscale (0.001 micrometers). Operating between ultrafiltration and reverse osmosis, nanofiltration membranes have a molecular weight cut-off for organic matter of approximately 200-800 MWCO, and a retention capacity for dissolved salts ranging from 20% to 98%. They have a lower removal rate for soluble monovalent ions compared to multivalent ions. Nanofiltration is commonly used to remove organics and pigments from surface water, reduce hardness and radium content in groundwater, and partially remove dissolved salts. It is also applied in the extraction and concentration of useful substances in food and pharmaceutical production. The operating pressure of nanofiltration membranes typically ranges from 3.5 to 30 bar.

Advantages：

1.The concentration and purification process is conducted at room temperature, without phase changes, chemical reactions, introduction of impurities, or decomposition and denaturation of the product. It is particularly suitable for heat-sensitive substances.

2.Nanofiltration can remove salt content, reduce ash content, improve product purity, and enhance product quality and yield. Compared to solvent desalination, it not only results in better product quality but also increases yield.

3.The process has high yield and minimal losses.

4.It allows recovery of acids, bases, alcohols, and other effective substances in the solution, facilitating resource recycling.

5.The equipment features a simple and compact structure, occupying a small footprint.

6.Operation is simple, and automation can be achieved, ensuring good stability and ease of maintenance.

The main products