Removal mechanism of Sb(III) by a hybrid rGO-Fe/Ni composite prepared by green synthesis via a one-step method.

The annual influx of antimony (Sb) into the environment due to the widespread use of Sb compounds in industry and agriculture has become of global concern. Herein, a functional nanomaterial composite based on loading bimetallic iron/nickel nanoparticles on reduced graphene oxide (rGO-Fe/Ni) was initially prepared in a one-step phytogenic synthesis using a green tea extract. Subsequently, when applied for Sb(III) removal, the removal efficiency of rGO-Fe/Ni reached 69.7% within 3 h at an initial Sb concentration of 1.0 mg·L. Advanced materials characterization via scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that Sb(III) was initially adsorbed onto the surface of rGO and then oxidized to Sb(V). This result was also supported by adsorption isotherm, kinetics, and thermodynamic analysis. These studies revealed that the adsorption was spontaneous and endothermic, following a Langmuir adsorption model with pseudo-second-order kinetics and allowed a Sb(III) removal mechanism based on adsorption and catalytic oxidation to be proposed. Furthermore, when rGO-Fe/Ni was practically used to remove Sb(III) in groundwater a 95.7% removal efficiency was obtained at 1 mg·L Sb(III), thus successfully demonstrating that rGO-Fe/Ni has significant potential for the practical remediation of Sb contaminated groundwater.