The invention belongs to the technical field of membrane separation, and provides a positively charged composite
nanofiltration membrane and a preparation method thereof. The composite
nanofiltration membrane has the positively charged performance, and comprises a separation functional layer and a support layer, wherein the support layer is positioned under the separation functional layer; the separation functional layer is an ultra-thin compact membrane formed by a soaking and
coating method; the thickness is within 200nm; the ultra-thin compact membrane is prepared from epoxypropyltrimethyl
ammonium chloride chitosan, additives, cross linking agents and solvents. The positively charged composite
nanofiltration membrane is a flat plate membrane or a
hollow fiber membrane. The commercial epoxypropyltrimethyl
ammonium chloride chitosan is used in the functional layer in the preparation process, so that the prepared
composite membrane has the positively charged characteristics, so that the high interception rate can be realized on the hypervalent
inorganic salts. Meanwhile, the membrane also has high anti-oxidization performance; the use range is expanded. The membrane can also be applied to the treatment of waste water containing heavy
metal ions and the treatment of other
wastewater containing high oxidability.