Ag3PO4/CoFe2O4 magnetic nanocomposite: synthesis, characterization and applications in catalytic reduction of nitrophenols and sunlight-assisted photocatalytic degradation of organic dye pollutants

Abstract

A novel magnetically recyclable Ag₃PO₄/CoFe₂O₄ nanocomposite (containing 30 wt%. CoFe₂O₄) was synthesized by a facile hydrothermal method. The composition and microstructure of the nanocomposite was fully characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-vis), field emission scanning electron microscopy (FESEM)-energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), and a vibrating sample magnetometer (VSM). Thereafter, the catalytic performance of the Ag₃PO₄/CoFe₂O₄ nanocomposite was investigated. The Ag₃PO₄/CoFe₂O₄ nanocomposite showed high efficiency for the degradation of methylene blue (MB) and Rhodamine B (RhB) dyes under direct sunlight irradiation. The photocatalytic activity of Ag₃PO₄/CoFe₂O₄ under sunlight irradiation was almost 1.5 and 4.7 times as high as those of the pure Ag₃PO₄ and CoFe₂O₄, respectively. The enhancement of sunlight photocatalytic activity in Ag₃PO₄/CoFe₂O₄ should be assigned to the effective separation and transfer of photogenerated charges originating from the well-matched overlapping band-structures. Trapping experiments indicated that superoxide anion (˙O₂⁻) radicals were the main reactive species for dye degradation in the present sonocatalytic system. A proposed mechanism for the enhanced photocatalytic activity is also discussed based on the experimental results. In addition, the catalytic activity of the nanocomposite in the reduction of nitrophenols by using NaBH₄ was evaluated. The results showed that Ag₃PO₄/CoFe₂O₄ exhibited the best performance in the reduction of 4-nitrophenol (4-NP) and 2-nitrophenol (2-NP) and revealed 100% conversion into the corresponding amino derivatives within 24–46 min with rate constant equal to 0.0714 min⁻¹ and 0.0329 min⁻¹, respectively. Moreover, due to the existence of the CoFe₂O₄, the Ag₃PO₄/CoFe₂O₄ nanocomposite could be magnetically separated from the reaction mixture and reused without any change in structure.