Graphene oxide polypiperazine-amide nanofiltration membrane for improving flux and anti-fouling in water purification

In this study, a facile polypiperazine-amide (PPA) composite nanofiltration (NF) membrane with nanomaterial graphene oxide (GO) incorporated into a polyamide (PA) layer for high water flux and anti-fouling was fabricated by interfacial polymerization (IP). The chemical composition, structure and surface properties of the fabricated PPA/GO and PPA composite NF membranes were characterized by FTIR, XPS, FE-SEM, AFM, zeta-potential and contact angle measurements. The separation properties and anti-fouling ability of the PPA/GO NF membrane were investigated and discussed. The experimental results indicated that the water flux of the PPA/GO (300 mg L^-1 GO) membrane increased from 66 (L m^-2 h^-1) to 87.6 (L m^-2 h^-1) under the operating pressure of 0.6 MPa, almost 1.4 times that of the PPA (without GO) membrane. However, the high salt rejection was still retained in the order of Na₂SO₄ (98.2%) > MgSO₄ (96.5%) > NaCl (56.8%) > MgCl₂ (50.5%). An anti-fouling test revealed that the PPA/GO membrane had excellent anti-fouling properties due to the enhanced hydrophilicity and decreased roughness induced by the GO nanosheets. Thus, the PPA/GO membrane can be efficiently and endurably applied in water purification.