Surface-functionalized spongy zinc ferrite as a robust visible-light driven nanocatalyst for wastewater remediation: characterization, kinetic, and mechanistic insight

Three different types of zinc ferrite nanoparticles (ZnFe2O4 NPs) were successfully synthesized through the co-precipitation route. The synthesized ZnFe2O4 NPs were structurally characterized by Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer Emmet Teller spectroscopic analyses. FT-IR analysis confirmed that the (3-APTES) is well grafted on the ZnFe2O4 NPs surface. XRD analysis shows the crystalline structure of calcined and modified ZnFe2O4 NPs, while the amorphous nature of bare ZnFe2O4 NPs was observed. SEM micrographs displayed a flat surface morphology with almost monodispersed grain size and irregular shape structure for all ZnFe2O4 NPs. The grain size of the synthesized ZnFe2O4 NPs was found to be 106.5, 23.3, and 13.9 nm for bare, calcined, and modified ZnFe2O4 NPs, respectively. Optical bandgap energy (LUMO–HOMO gap) was experimentally calculated in acidic and basic mediums (2.47 and 2.70 eV) using a taulc plot. The photocatalytic performance of the synthesized ZnFe2O4 NPs was investigated under visible irradiation in an aqueous medium against bromophenol blue dye. The influence of various parameters like irradiation time, photocatalyst dose, dye dose, pH effect, and H2O2 on the degradation efficiency was investigated. Results showed that all the three types of ZnFe2O4 NPs exhibited excellent photocatalytic properties, where the highest degradation (95.4%) was displayed by modified ZNFe2O4 NPs, followed by calcined (90.2%) and bare ZnFe2O4 84.6%). The synthesized ZnFe2O4 NPs were reused and recycled, retaining the excellent photocatalytic property for four consecutive cycles. Kinetic models demonstrate that the degradation rate was pseudo 1st order of kinetics. The turnover number reached up to 21.3 × 106, 22.5 × 106, and 23.8 × 106 for bare, annealed, and functionalized ZNFe2O4 nanoparticles, respectively. In short, the developed spongy zinc ferrite nanoparticles indicate a high potential of photo-driven catalytic remediation of tested bromophenol blue drained into the water systems.