Removal of dye and heavy metal ion using a novel synthetic polyethersulfone nanofiltration membrane modified by magnetic graphene oxide/metformin hybrid

In this research, active groups of biguanide were grafted to the surface of graphene oxide sheets through covalent functionalization and combined with magnetic nanoparticles to produce a magnetic graphene-based composite (MMGO). Then, the fabricated MMGO hybrid was introduced into the polyethersulfone (PES) polymer through phase inversion induced by immersion precipitation method. The prepared MMGO embedded PES membranes were examined for pure water flux permeability, salt rejection, antifouling, copper removal, and dye retention capability. The effect of MMGO hybrid on the cross-sectional morphology, hydrophilicity, and roughness of the PES membrane was investigated as well. Embedding MMGO hybrid was eventuated in a significant increase in the pure water flux because of changes in surface roughness and hydrophilicity of the membranes. Besides, the copper and dye removal capability of the prepared membranes remarkably raised due to the presence of hydrophilic functional groups on the surface of MMGO hybrid. The fabricated nanofiltration membrane with 0.5 wt % MMGO hybrid had the highest affinity for copper ions removal (92%). Dye rejection of the MMGO embedded PES membranes at different concentrations of MMGO hybrid was almost the same (about 99%) while the value of the bare PES membrane was 91%. Flux reduction of the MMGO embedded PES membranes was lower than that of the bare PES membrane during repeated filtration.