Synthesis and sonocatalytic performance of a ternary magnetic MIL-101(Cr)/RGO/ZnFe₂O₄ nanocomposite for degradation of dye pollutants

In this study, new ternary magnetic MIL-101(Cr)/RGO/ZnFe₂O₄ catalyst (with 30% wt of ZnFe₂O₄) was synthesized via a hydrothermal route for sonodegradation of organic dyes. The structural, optical and magnetic properties of the nanocomposite were detected by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–visible), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, vibrating sample magnetometer (VSM), atomic force microscopy (AFM), Raman spectroscopy and BET surface area analysis. To evaluate the sonocatalytic activity of the as-prepared MIL-101(Cr)/RGO/ZnFe₂O₄ nanocomposite, the H₂O₂-assisted degradation of organic dyes such as congo red (CR), methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) in aqueous solution was studied under ultrasound irradiation. The obtained results indicated that the ternary MIL-101(Cr)/RGO/ZnFe₂O₄ nanocomposite had better performance for sonodegradation of these dyes than MIL-101(Cr)/RGO, pure MIL-101(Cr) or ZnFe₂O₄. The enhanced sonocatalytic performance of the as-prepared ternary nanocomposite could be attributed to the fast generation and separation of charge carriers (electrons and holes) in ZnFe₂O₄ and MIL-101(Cr) and their transfer to the surface of graphene sheets. Moreover, the relatively high specific surface area of the MIL-101(Cr)/rGO and magnetic property of ZnFe₂O₄ improve the degradation efficiency of the dyes. The recovery of the ternary magnetic sonocatalyst from treated water could be easily achieved using an external magnetic field. The main influence factors on the sonocatalytic activity such as catalyst dosage and dye initial concentration were also investigated. The trapping experiments indicated that ^[rad]OH radicals are the prominent active species in dye degradation. In addition, the reusability test, was also carried out to ensure the stability of the employed sonocatalyst.