A novel double-modified strategy to enhance the performance of thin-film nanocomposite nanofiltration membranes: Incorporating functionalized graphenes into supporting and selective layers

Abstract

A novel double-modified strategy by introducing sulfonated graphene (SG) and maleic anhydride modified graphene oxide (MAH-GO) nanofillers into the supporting layer and selective layer, respectively, was adopted to develop high-performance thin-film nanocomposite (TFN) nanofiltration (NF) membrane. First, the supporting layer was successively modified by investigating the impacts of sulfonated PSU and SG on the morphologies, properties and performance of the supporting membranes and the resultant thin-film composite (TFC) NF membranes. The results indicated that the structures and properties of supporting layers had significant influences on the resultant polypiperazine-amide (PPA) TFC NF membranes. The pristine PSU support exhibited a large surface pore size, medium porosity and strong hydrophobicity, which generated a low-flux PPA-TFC NF membrane. After modification with SPSU and SG, the optimal PSU-SPSU-SG blend support showed a small surface pore size, high porosity and improved hydrophilicity, which resulted in favor of the formation of a defect-free TFC NF membrane with a relatively high flux. Using the optimal PSU-SPSU-SG blend support, the further incorporation of MAH-GO nanofillers into the selective layer led to a thinner, smoother and more strongly hydrophilic TFN NF membrane with enhanced negative charge. The double-modified TFN NF membrane showed the superior permeaselectivity, anti-fouling ability and chlorine resistance over the conventional PPA-TFC NF membrane. Notably, without sacrificing the high salt rejection, the maximum water flux significantly reached 85.8 L m−2 h−1 equal to 264.8% of PPA-TFC membrane. This novel double-modified strategy shows a great potential in developing high-performance TFN NF membranes.