Synthesis and characterization of reduced graphene oxide-Fe3O4@polydopamine and application for adsorption of lead ions: Isotherm and kinetic studies

The functionalization of graphene causes many of its features to be altered, which can be used to better adsorption metal ions in aqueous solution. In this work, catecholamine, with a stable polymeric structure and as a safe material, was coated on graphene oxide by the self-polymerization and creates strong and toughness composite that exhibits high resistance to destruction due to stirring or sonication. Graphene oxide (GO) was reduced in the polymerization process and many functional groups including amine and hydroxyl groups are formed on the composite structure, which causes more interaction with Pb2+ ions. The surface area of the magnetic GO was increased after covering with polydopamine. The sorbent was characterized by Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Vibrating-sample magnetometer and Energy-dispersive X-ray spectroscopy. To achieve the highest adsorption efficiency, various parameters including pH, sorbent amount, breakthrough volume, adsorption time, desorption time and volume and concentration of eluent solution were optimized. The sorbent capacity was achieved as about 35.2 mg g(-1). The isotherm data fitted well with the Langmuir isotherm model. The experimental results proved that rGO/Fe3O4@PDA had higher stability than GO@Fe3O4 and can be reused many times after washing with eluent.