A magnetically active nanocomposite based on reduced graphene oxide (rGO) was fabricated using the vanadium doped ZnO (V-ZnO) semiconductor. It was magnetized with Fe3O4 nanoparticles for sunlight photodegradation of Rhodamine B (RhB) and Methylene blue (MB) as two water pollutant dyes. The fabricated magnetic nanocomposite, rGO/Fe3O4/V-ZnO, was characterized using X-ray diffraction (XRD), transmission and scanning electron microscopies (TEM and SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), diffuse reflectance spectroscopy (DRS), Raman and photoluminescence (PL) spectroscopies, as well as Brunauere− Emmette− Teller (BET), total organic carbon (TOC) and chemical oxygen demand (COD) analyses. The fabricated rGO/Fe3O4/V-ZnO nanocomposite showed the saturation magnetization (Ms) of 17.50 emu/g and band gap energy (Eg) of 1.81 eV (based on Tauc’s equation) with the calculated V-ZnO conduction band and valence band energies of ECB = -0.16 eV and EVB = 3.17 eV. The photocatalytic activity and effciency of the rGO/Fe3O4/V-ZnO nanocomposite were investigated through photodegradation experiments under different conditions including dye to composite amounts ratio, adsorption and irradiation times, pH and composite component. Up to 96 % and 93 % of the photodegradation by the rGO/Fe3O4/V-ZnO photocatalyst, at the optimum pH of 6.5 obtained through the pH of zero point of charge (pHzpc), were revealed by 92 % and 89 % of TOC removal and 90 % and 87 % of decrement in the initial COD. The effciency of MB and RhB photodegradation by the fabricated composite also increased more than 23 % and 47 %, respectively, in comparison to neat ZnO. The photocatalysis kinetics and plausible mechanism were also evaluated through Langmuir–Hinshelwood model and hydroxyl radical experiments, respectively. The pseudo-frst order kinetic constants (kapp) for MB and RhB photodegradation being accurately compatible with pseudo frst-order photodegradation, were found to be 0.0137 and 0.0109 min− 1, respectively. The results confrmed strictly the formation of •OH and O2 •- radicals during the dye degradation process by the rGO/Fe3O4/V-ZnO composite.
