Efficient removal of antimony from aqueous solution using Al-doped Fe3O4 nanoparticles: adsorption behavior and kinetics study

Fe3O4 magnetic nanoparticles have been employed as a cost-effective adsorbent for removing Sb from aqueous solutions. However, the widespread application is limited by its finite adsorption capacity and aggregation nature. In this study, Al-doped Fe3O4 nanoparticles were prepared via a facile solvothermal method to break through the current obstacle. Al-doped Fe3O4 nanoparticles were fully characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron microscopy (SEM), and infrared spectroscopy (FTIR). The results confirmed that Al atoms had been successfully doped into Fe3O4 crystal unit cells, resulting in smaller particle size, larger surface area, and higher isoelectric point. These changes led to the formation of more hydroxyl groups on the surface of Al-doped Fe3O4 nanoparticles. Compared to pristine Fe3O4, the maximum adsorption capacity toward Sb(III) and Sb(V) increased from 111.695 to 197.034 mg/g and from 34.479 to 187.459 mg/g at neutral pH, respectively. The doping of Al also had some negative impact on the original magnetic strength but still maintained a sufficient magnetic separation potential. These results indicated that Al-doped Fe3O4 nanoparticles could be employed as a promising adsorbent for removing Sb(III) and Sb(V) from wastewater.