Preparation and characteristics of quaternized chitosan/poly(acrylonitrile) composite nanofiltration membrane from epichlorohydrin cross-linking

Quaternized chitosan was prepared by modifying chitosan with 2,3-epoxypropy trimethylammonium chloride. A novel positively charged composite NF membrane was prepared by coating aq. quaternized chitosan onto a PAN UF membrane, subsequently cross-linked with epichlorohydrin. The effects of membrane preparation conditions on membrane properties and membrane characteristics were studied. The molecular weight cut-off of the representative membrane was obtained at about 560 Da (in NF range), and the structure was characterized by Scanning Electron Microscope, suggesting the composite structure of this membrane. At 25 °C, the pure water permeability is 9.25 L/h m2 MPa, and the order of rejection to different model solutes was MgCl2 ≈ CaCl2 > NaCl ≈ KCl > MgSO4 > Na2SO4, revealing the characteristic of positively charged NF membranes. The rejections to 1000 g/L MgCl2 and CaCl2 solutes were more than 0.96, so this membrane developed can be expected to use in the hardness removal of waste-water.