A novel ternary magnetic composite consisting of reduced graphene oxide (rGO), polypyrrole (Ppy) and Fe3O4 nanoparticles (Ppy–Fe3O4/rGO) were fabricated by a facile two-step reaction route. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential and specific surface area were used to characterize the Ppy–Fe3O4/rGO. Morphology, chemical structure and element analysis showed that the Fe3O4/rGO was successfully decorated with chain-like polypyrrole. The specific surface area of the ternary composite was calculated as 80.53 m2 g−1 by Brunauer–Emmett–Teller (BET) method. It was encouraging to find that the ternary Ppy–Fe3O4/rGO nanohybrid exhibited excellent performance for chromium (VI) removal from aqueous solution. The maximum adsorption capacity for Cr(VI) onto Ppy–Fe3O4/rGO was 293.3 mg g−1, which was much higher than that of Fe3O4/rGO. The removal process was pH dependence, exothermic and spontaneous. The adsorption of Cr(VI) species was facilitated through both electrostatic attraction and ion exchange process. Meanwhile, XPS analysis revealed that the Cr(VI) was reduced to the low-toxicity Cr(III) by the nitrogen species of Ppy. The Ppy–Fe3O4/rGO composite could be a promising material for the removal of Cr(VI) from wastewater.

Facile synthesis of polypyrrole decorated reduced graphene oxide–Fe3O4 magnetic composites and its application for the Cr(VI) removal