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Magnetic ZnFe2O4–C3N4 hybrids were successfully synthesized through a simple reflux treatment of ZnFe2O4 nanoparticles (NPs) (ca. 19.1 nm) with graphitic C3N4 sheets in methanol at 90 °C, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. Also, the catalytic activities of heterogeneous ZnFe2O4–C3N4 catalysts were evaluated in photo-Fenton discoloration toward Orange II using H2O2 as an oxidant under visible light (λ > 420 nm) irradiation. The reaction kinetics, degradation mechanism, and catalyst stability, as well as the roles of ZnFe2O4 and C3N4 in photoreaction, were comprehensively studied. It was found that the ZnFe2O4–C3N4 photocatalysts presented remarkable catalytic ability at neutral conditions, which is a great advantage over the traditional Fenton system (Fe2+/H2O2). The ZnFe2O4–C3N4 hybrid (mass ratio of ZnFe2O4/g-C3N4 = 2:3) exhibits the highest degradation rate of 0.012 min–1, which is nearly 2.4 times higher than that of the simple mixture of g-C3N4 and ZnFe2O4 NPs. g-C3N4 acted as not only a p-conjugated material for the heterojunction formation with ZnFe2O4, but also a catalyst for the decomposition of H2O2 to ·OH radicals. The heterogeneous ZnFe2O4–C3N4 hybrid exhibited stable performance without losing activity after five successive runs, showing a promising application for the photo-oxidative degradation of organic contaminants.

A magnetic ZnFe2O4-reduced graphene oxide (rGO) hybrid was successfully developed as a heterogeneous catalyst for photo-Fenton-like decolorization of various dyes using peroxymonosulfate (PMS) as an oxidant under visible light irradiation. Through an in situ chemical deposition and reduction, ZnFe2O4 nanoparticles (NPs) with an average size of 23.7 nm were anchored uniformly on rGO sheets to form a ZnFe2O4-rGO hybrid. The catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and strength, catalytic stability, degradation mechanism, as well as the roles of ZnFe2O4 and graphene were also studied. ZnFe2O4-rGO showed to be a promising photocatalyst with magnetism for the oxidative degradation of aqueous organic pollutants and simple separation. The combination of ZnFe2O4 NPs with graphene sheets leads to a much higher catalytic activity than pure ZnFe2O4. Graphene acted as not only a support and stabilizer for ZnFe2O4 to prevent them from aggregation, largely improving the charge separation in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time. The ZnFe2O4-rGO hybrid exhibited stable performance without losing activity after five successive runs.