Fabrication of hollow-fiber nanofiltration membrane with negative-positive dual-charged separation layer to remove low concentration CuSO4

•The LNF membrane with negative-positive dual-charged layer was prepared.•The relationship between microstructure of dual-charged layer and rejection was revealed.•The loose separation layer resulted in a high permeability (29.6 L m−2 h−1 bar−1).•The membrane exhibited excellent acid resistance and regeneration performance.