Microwave-assisted preparation of sepiolite-supported magnetite nanoparticles and their ability to remove low concentrations of Cr(vi)

Abstract

Sepiolite-supported magnetite nanoparticles (SSMNPs) were successfully prepared by a facile, robust and time-saving microwave-assisted method. The SSMNPs were characterized by a wide range of techniques including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectra (XPS), and Brunauer–Emmett–Teller (BET) gas sorptometry. It was found that the sepiolite-supported magnetite nanoparticles show better dispersion and less aggregation than their counterparts obtained by common heat method. Moreover, the removal ability of SSMNPs to Cr(VI) was investigated systematically. The SSMNPs exhibit excellent removal ability to low concentrations of Cr(VI), and their removal capacity is 33.4 mg g⁻¹ (per unit mass of magnetite) at pH 3.0 and adsorbent concentration 1.0 g L⁻¹, higher than that of the unsupported magnetite nanoparticles (22 mg g⁻¹). The adsorption data fit well with the Redlich–Peterson isotherm model. Due to the simplicity of the synthetic procedure, the high removal efficiency for Cr(VI) and reduced Fe³⁺ remaining in the treated solution, as well as the easy separation of the adsorbent from water, the sepiolite-supported magnetite nanoparticles have real potential for applications in water treatment.