Fe3O4/ZnO/CoWO4 nanocomposites: Novel magnetically separable visible-light-driven photocatalysts with enhanced activity in degradation of different dye pollutants

A series of novel magnetically separable Fe3O4/ZnO/CoWO4 nanocomposites with different contents of CoWO4 were fabricated using a facile refluxing method at 96 °C followed by a calcination step. The structure, purity, morphology, spectroscopic, and magnetic properties of the prepared samples were characterized by XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, PL, and VSM techniques. Photocatalytic activity of the nanocomposites was investigated by degradation of rhodamine B, methylene blue, methyl orange, and fuchsine under visible-light irradiation. The results showed remarkably enhanced activity for the Fe3O4/ZnO/CoWO4 (30%) nanocomposite relative to the Fe3O4/ZnO and Fe3O4/CoWO4 samples. The degradation rate constant of RhB over the optimal nanocomposite is nearly 24 and 5 times higher than those of the Fe3O4/ZnO and Fe3O4/CoWO4 samples, respectively. The intensive absorption of visible light and separation efficiency of the photogenerated electron-hole pairs in the ternary nanocomposites were confirmed by UV-vis DRS and PL techniques, respectively. In addition, a plausible mechanism for separation of the electron-hole pairs based on p-n heterojunction was proposed.