Photosensitization of Fe3O4/ZnO by AgBr and Ag3PO4 to fabricate novel magnetically recoverable nanocomposites with significantly enhanced photocatalytic activity under visible-light irradiation

In this paper, novel quaternary Fe3O4/ZnO/AgBr/Ag3PO4 nanocomposites with different weight percents of Ag3PO4 were successfully prepared through refluxing method at 96 °C. The as-prepared products were characterized with XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, PL, and VSM techniques to determine their phase structure, purity, morphology, spectroscopic, and magnetic properties. Photocatalytic degradation of rhodamine B under visible-light irradiation indicated that the nanocomposite with 20% of Ag3PO4 has the best activity. Photocatalytic activity of this nanocomposite is nearly 68, 5.0, and 3.4-folds greater than those of the Fe3O4/ZnO, Fe3O4/ZnO/AgBr, and Fe3O4/ZnO/Ag3PO4 samples in degradation of rhodamine B, whereas 17, 6.7, and 2.8-folds greater in degradation of methylene blue, respectively. The activity enhancement was mainly ascribed to the enhanced visible-light absorption ability and formation of tandem n-n heterojunctions between counterparts of the nanocomposites, which facilitate the generation and separation of charge carriers. An additional advantage of these photocatalysts is magnetic recoverability using external magnetic field. In addition, using different scavengers, superoxide ion radicals were identified as the main oxidative species in the degradation reaction of rhodamine B. Finally, photocatalytic stability of the nanocomposite was evaluated for six cycles.