Nanofiltration (NF):

The process of nanofiltration is slightly different from the reverse osmosis process in the sense that the permeating species in this case is solvent as well as low molecular solutes or low valency solutes. This procedure also operates along with hydrostatic pressure difference across a semipermeable membrane having pore sizes that are slightly larger than which of reverse osmosis membranes. The pore sizes of NF membranes are within the range of 10 -30 Å. The hydrostatic pressure used in this process could vary from 1.5 Mpa to 2 MPa. This process is essentially used to fractionate solutes based on valency of either cation or anion and also to separate several organic solutes of low molecular weights.