Dye adsorptive thin-film composite membrane with magnetite decorated sulfonated graphene oxide for efficient dye/salt mixture separation

In this study, a thin-film composite (TFC) loose nanofiltration (NF) membrane comprising a poly(piperazine-amide) (PPA) active layer was successfully fabricated by the electrospray interfacial polymerization (EIP) method. Sulfonated graphene oxide (SGO) and magnetite-decorated SGO (MGO) were synthesized and individually embedded in the polymer matrix of the substrate via a phase inversion method. The hydrophilicity, surface roughness, porosity, and pure water permeance of the prepared substrates, in which the additive existed, were found to be improved in comparison with those of the pristine substrate. The MGO nanoparticle-incorporated TFC membrane (M-MGO) exhibited high permeation of salt (96.1% for NaCl) and water permeance (44.4 ± 4.0 LMH bar−1) owing to the loose structure of the active layer. The M-MGO also exhibited the highest dye rejection (Congo red, 99.0%) owing to the presence of MGO nanoparticles with an adsorption capacity. When permeating the dye and salt mixture, M-MGO achieved the highest dye/salt selectivity in comparison with those of the other membranes. Moreover, the M-MGO achieved better antifouling properties with a high flux recovery ratio (FRR) of 99.0%, whereas the pristine membrane exhibited a low FRR of 97.6% or less. This method presents a high potential for the fabrication of novel saline wastewater treatment membranes.