Preparation of thin film composite nanofiltration membrane with improved structural stability through the mediation of polydopamine

Thin film composite (TFC) nanofiltration membranes with good structural stability were prepared by interfacial polymerization under the mediation of polydopamine (PD). Polyethersulfone (PES) support layer was firstly modified by PD prior to the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) to form polyamide active layer. PD played the following two important roles: (1) rendering the PES support layer with the reactive groups to enhance the interfacial strength between the support layer and active layer; (2) rendering the PES support layer with higher hydrophilicity to facilitate interfacial polymerization. The TFC membrane prepared under optimal conditions exhibited a flux of 22.8 L/(m2 h) while the rejection of Na2SO4 reached 93.5% under 0.2 MPa. Particularly, the TFC membrane exhibited good structural stability (less than 5% decline in salt rejection) as tested by alcohol treatment due to the strong interactions between the active layer and the modified PES support layer.