Preparation and application of iron oxide/persimmon tannin/ graphene oxide nanocomposites for efficient adsorption of erbium from aqueous solution

Abstract Rare earth elements (REEs) are used for the development of new energy materials owing to their intrinsic physicochemical property. However, excess REEs in water threaten the safety of animals, plants and humans. An efficient way to separate REEs from the water is therefore needed. In this study, a biosorbent consisting of iron oxide (Fe3O4), persimmon tannin (PT), and graphene oxide (GO) as Fe3O4/PT/GO was prepared, and the adsorption of trivalent erbium (Er3+) ions from aqueous solution was investigated. The adsorption process for Er3+ ions conformed to pseudo-second order kinetic and the Langmuir isotherm model behavior. Thermodynamic studies indicated that the adsorption process was spontaneous and endothermic. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET) analysis, and vibrating sample magnetometer (VSM) were used to assess the adsorption mechanism of Er3+ ions onto the Fe3O4/PT/GO biosorbent. A combination of electrostatic interactions, redox reactivity and chelation are responsible for adsorption of Er3+ ions on the Fe3O4/PT/GO biosorbent. The magnetic Fe3O4/PT/GO biosorbent can be easily separated under the magnetic field for effective recycle of Er3+ ions from aqueous solution. Therefore, this new biomass composite holds great promise for wastewater treatment.