Fouling decline and retention increase of polyethersulfone membrane by incorporating melamine-based dendrimer amine functionalized graphene oxide nanosheets (GO/MDA)

Graphene oxide (GO) nanosheets were prepared using modified Hummers method and then amino-functionalized with melamine-based dendrimer amines (MDA). The resulted nanofiller (GO/MDA) was incorporated into the polyethersulfone (PES) membrane matrix with the phase inversion technique. The effects of this incorporation on membrane properties were studied in different terms including hydrophilicity, porosity, surface and cross-sectional morphology, mean pore radius, permeability, fouling resistance and nanofiltration performance. The resulted membranes presented enhanced hydrophilicity, porosity and permeability due to the presence of super hydrophilic GO/MDA nanocomposite in the membrane matrix. The pure water flux of the PES membranes under the operating pressure of 0.3 MPa was increased from 19.9 kg/m2 h for the bare PES to 38.1 kg/m2 h and 53.9 kg/m2 h for the optimum contents of GO and GO/MDA, respectively. The flux recovery ratio (FRR) was enhanced from 50.4% for the bare PES to 78.5% for the membrane containing the optimum content of GO/MDA (0.25 wt%). This membrane also presented the minimum total and irreversible fouling ratios. Nanofiltration performance of the membranes was proved with near total rejection of anionic dye reactive red 198, alongside the remarkable retention of divalent ions (77.4% and 56.4% for Na2SO4 and MgSO4, respectively) and slight retention of monovalent ion NaCl (18.9%). Eventually, the results of the present study introduced MDAs as ideal dendrimer ligands for the preparation of highly hydrophilic and antifouling nanofillers.