Facile synthesis of Bi2Fe4O9 nanoplate and its application as a novel adsorbent for Cu(II) removal

Abstract

To our knowledge, there were hardly any reports on the application of Bi₂Fe₄O₉ for adsorptive removal of heavy metal ions. In this study, Bi₂Fe₄O₉ nanoplate was successfully fabricated through a facile hydrothermal method without addition of any template agents. The adsorption mechanism of Cu(II) and its behaviour on Bi₂Fe₄O₉ were investigated comprehensively. The adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and the N₂ adsorption-desorption isotherm, respectively. The investigation on adsorption kinetics and isotherm showed that the pseudo-second-order kinetic and Langmuir isotherm models could well fit the experimental adsorption data. The maximum adsorption capacity of Bi₂Fe₄O₉ for Cu(II) was found to be 42.7 mg g⁻¹ at short equilibrium time of 40 min and ambient temperature, which was higher than those of other adsorbents reported in literatures. Thermodynamic survey on Gibbs free energy (ΔG < 0), enthalpy (ΔH > 0) and entropy (ΔS > 0) demonstrated that the adsorption process was endothermic and spontaneous. Due to the adsorptive reaction of Cu²⁺ on the surface, the regular plates of product were corroded to fragments, which illustrated that OH, FeO, FeOFe, OFeO and BiO involved in the adsorption process by FTIR. After recycling five times, the decline of adsorption capacity of product for Cu(II) was 7.2%, which indicated that the adsorbent could be recycled in the removal of Cu(II). Therefore, Bi₂Fe₄O₉ nanoplate might be potentially applied in the removal of heavy metal ions from aqueous solution.