The nanofiltration process is selective because it has negative charged groups on the nanofiltration membrane or in the membrane. They interact with each other through static electricity, blocking the permeation of polyvalent ions.
The potential charge density of nanofiltration membrane is 0.5 ~ 2meq/g.
The separation principle of nanofiltration membrane.
Between RO and UF membrane, nanofiltration membrane for the removal rate is under 90% NaCL, reverse osmosis membrane for almost all the solute has a high removal rate, but the nanofiltration membrane only for a particular solute with high removal rate;
Nanofiltration membrane mainly eliminate diameter for a nanometer (nm) of solute particles, intercept molecular weight is 100 ~ 1000, in the field of drinking water is mainly used for removing trihalomethanes intermediates, bad breath, chromaticity, pesticide, synthetic detergent, soluble organic matter, Ca, Mg and composition of hardness and evaporation residue.