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

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 (Fe 3 O 4 ), persimmon tannin (PT), and graphene oxide (GO) as Fe 3 O 4 /PT/GO was prepared, and the adsorption of trivalent erbium (Er 3+ ) ions from aqueous solution was investigated. The adsorption process for Er 3+ ions conforms to pseudo-second order kinetic and the Langmuir isotherm model behavior. Thermodynamic studies indicate that the adsorption process is 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 Er 3+ ions onto the Fe 3 O 4 /PT/GO biosorbent. A combination of electrostatic interactions , redox reactivity and chelation are responsible for adsorption of Er 3+ ions on the Fe 3 O 4 /PT/GO biosorbent. The magnetic Fe 3 O 4 /PT/GO biosorbent can be easily separated under the magnetic field for effective recycle of Er 3+ ions from aqueous solution. Therefore, this new biomass composite holds great promise for wastewater treatment.