Improved reductive transformation of iopromide by magnetite containing reduced graphene oxide nanosacks as electron shuttles

[Display omitted] •First successful application of magnetite containing reduced graphene oxide nanosacks as electron shuttles.•Magnetic nanosacks have properties to promote redox conversion processes.•Magnetic nanosacks enhanced up to 2.5-fold the reductive degradation of iopromide.•Dehalogenation, decarboxylation, demethylation, dehydration and N-dealkylation occurred.•Redox catalyst suitable for promoting degradation of emerging pollutants. The novel application of magnetite containing reduced graphene oxide nanosacks (MrGO-N) as electron shuttles to improve the reductive degradation of the pharmaceutical pollutant, iopromide (IOP), was evaluated. MrGO-N were synthesized by ultrasonicated nebulization process, and their physicochemical characterization was performed by potentiometric titrations, zeta potential, high resolution transmission electron microscopy (HR-TEM), X-ray diffraction, as well as by Raman and Fourier transform infrared spectroscopies. Results demonstrated the thermal reduction of precursor graphene oxide sheets, the removal of different oxygenated groups, and the successful assembly of magnetite nanoparticles (MNP) in the graphene sacks. Also, reduction experiments revealed 72% of IOP removal efficiency and up to 2.5-fold faster degradation of this pollutant performed with MrGO-N as redox catalysts in batch assays and with sulfide as electron donor. Chemical transformation pathway of IOP provides evidence of complete dehalogenation and further transformation of aromatic ring substituents. Greater redox-mediating ability of MrGO-N was observed, which was reflected in the catalytic activity of these nanomaterials during the reductive degradation of IOP. Transformation byproducts with simpler chemical structure were identified, which could lead to complete degradation by conventional methodologies in a complementary treatment process. Redox-mediating activity of MrGO-N could potentially be applied in wastewater treatment systems in order to facilitate the biodegradation of priority contaminants.