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Nanofiltration (NF) unit
Nanofiltration (NF)
I. Overview of Nanofiltration Membranes Nanofiltration membranes (Nanofiltration Membranes) are a novel type of separation membrane that emerged in the late 1980s. Their molecular weight cut-off (MWCO) ranges between that of reverse osmosis membranes and ultrafiltration membranes, approximately 200 - 2000. This suggests that nanofiltration membranes likely possess a microporous structure with a pore size of around 1 nm, hence the term "nanofiltration." Most nanofiltration membranes are composite membranes, with their surface separating layer composed of polyelectrolytes, endowing them with a certain rejection rate for inorganic salts. Most commercially available nanofiltration membranes abroad are formed by interfacial polycondensation and condensation methods, which composite an ultra-thin separating layer with nanoscale pore sizes onto a microporous base membrane. II. Material and Characteristics of Nanofiltration Membranes Material of Nanofiltration Membranes: Polyamide. Nanofiltration membranes can retain substances at the nanoscale (0.001 μm). The operating range of nanofiltration membranes lies between ultrafiltration and reverse osmosis. They have an MWCO for organic matter of approximately 200 - 800 MW, a rejection capacity for dissolved salts of 20% - 98%, and a lower removal rate for soluble monovalent ions compared to multivalent ions. Nanofiltration is commonly used to remove organic matter and pigments from surface water, hardness and radium from groundwater, and partially remove dissolved salts. It is also employed in the extraction and concentration of valuable substances in food and pharmaceutical production. The operating pressure of nanofiltration membranes typically ranges from 3.5 to 30 bar. |
