Microwave catalytic activities of MFe2O4@CMT (M = Ni, Co) supported catalysts for the degradation of dimethyl phthalate

Abstract

Meso–macroporous MFe₂O₄@CMT (M = Ni, Co) catalysts were synthesized by coating carbon microtubes (CMTs) employing a calcination method. The obtained materials NiFe₂O₄@CMT (PCNF) and CoFe₂O₄@CMT (PCCF) were characterized via X-ray powder diffraction (XRD), pore structure analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The electromagnetic (EM) wave absorption of catalysts was measured and it was found that the maximum reflection loss value of PCCF and PCNF was about −41.50 dB at a thickness of 1.85 mm and −24.70 dB at a thickness of 6.55 mm, respectively. The composite catalysts were prepared for the microwave (MW)-induced Fenton-like catalytic degradation of dimethyl phthalate (DMP). The microwave catalytic activity of PCNF was higher than that of PCCF, which was closely related to its higher concentration of active species, better microwave-absorbing ability and high interaction between NiFe₂O₄ and CMT. Moreover, the degradation kinetics could be well-fitted by the pseudo-first-order kinetic model. With an increase in the MW power, initial pH, catalyst dosage, and H₂O₂ concentration, the DMP degradation rate initially increased and then decreased, while it declined continuously with an increase in the initial DMP concentration. The introduction of metal oxides increased the mobility of the surface oxygen, playing a crucial role in the generation of surface oxygen species. The catalysts maintained high stability after five reaction cycles. The overall findings provide new insight into PCCF and PCNF under MW irradiation for the degradation of DMP and other relevant organic pollutants.