Fe3O4/ZnO/NiWO4 nanocomposites with p-n heterojunctions were synthesized through a facile refluxing method at 96 degrees C. The as-prepared samples were characterized using XRD, EDX, SEM, TEM, UV-vis DRS, PL, and VSM instruments. It was found that in the nanocomposites, Fe3O4, ZnO, and NiWO4 components were uniformly combined to each other. Photocatalytic activity of the nanocomposites was evaluated by degradation of rhodamine B under visible-light irradiation, revealing that the nanocomposites exhibit enhanced photocatalytic activity compared to the Fe3O4/ZnO and Fe3O4/NiWO4 samples. Photocatalytic activity of the Fe3O4/ZnO/NiWO4 (40%) nanocomposite was enhanced 36 and 6.3-times relative to the Fe3O4/ZnO and Fe3O4/NiWO4 samples, respectively. This enhancement was explained by the efficient separation of the photogenerated electron-hole pairs due to formation of p-n heterojunctions between NiWO4 and ZnO semiconductors. Additionally, it was found that h(+) and center dot O-2(-) species generated in the photocatalytic process played a key role in the degradation reaction. More importantly, the nanocomposite can be separated from the reaction media by applying an external magnetic field and it can be reused for five cycles without significant changes in the degradation efficiency. (C) 2017 Elsevier B.V. All rights reserved.