Superparamagnetic recoverable flowerlike Fe3O4@Bi2O3 core–shell with g-C3N4 sheet nanocomposite: synthesis, characterization, mechanism and kinetic study of photo-catalytic activity

In the present research study, a simple method was developed for the synthesis of three-dimensional flowerlike Fe3O4@Bi2O3 core–shell with g-C3N4 sheet nanocomposites. The X-ray diffraction, Fourier transform infrared spectroscopy, scanning electronic microscopy, transmission electron microscope, vibrating sample magnetometer, dynamic laser scattering analyzer and UV–Vis diffuse reflection spectroscopy were employed for the characterization of structure, purity and morphology of the resultant samples. The degradation of indigo carmine as a model of organic dye pollutant is applied for photo-catalytic activity. The parameters which are affecting the efficiency of various parameters, such as; pH (5–9), photo-catalyst dose (30–120 mg), initial concentration of dye (1.0 × 10−5–7.5 × 10−5 M) were studied. The results show that the high photo-degradation was obtained at pH 5, with 70 mg of photo-catalyst, for initial concentration of 1.0 × 10−5 M the indigo carmine. In the kinetic part of this study is found that the photo-degradation of the dye follows pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. The radical scavenger measurement illustrates that the electron generated from Bi2O3 was carried to the surface of Fe3O4 and this electron was shifted to the surface positive hole of g-C3N4. The electron on g-C3N4 surface reacted with O2 and produced ·O2. The h+ of Bi2O3 reacted with OH¯ to produce ·OH. The ·O2−, ·OH and h+ were the main active species in the photo-catalytic process.