Doping zinc oxide (ZnO) nanoparticles with molybdenum boosts photocatalytic degradation of Rhodamine b (RhB): Particle characterization, degradation kinetics and aquatic toxicity testing

Undoped and Mo-doped ZnO photocatalysts were synthesized by hydrothermal method and characterized by field emission scanning electron microscopy coupled to energy dispersive- X ray spectroscopy (FESEM- EDAX), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) and thermogravimetric analysis (TGA) analyses. The photocatalytic activity of the photocatalysts and the kinetic of the reaction was assessed by degrading Rhodamine B under UV and sun light irradiation under variable conditions. Eventually the acute toxicity of undoped and doped nanophotocatalysts, RhB and the consequences of photocatalytic treatment were assessed using zebrafish (Danio rerio). The analytical results showed that Mo doping increased catalysts specific surface area and thermal stability. The results of photocatalytic degradation demonstrated that Mo doping has increased the photocatalytic activity under both UV and sunlight irradiation with 95 % RhB degradation efficiency and 41 % TOC removal efficiency over 30 min. The reusability of photocatalysts showed constant degradation efficiency over multiple cycles. The 96 h LC₅₀ of undoped ZnO, Mo doped ZnO and RhB were 482.71 and 459.05 and 20.38 mg/L, respectively. Moreover, a lower toxicity was observed for the treated compared to untreated dye solution. This study indicates a promising potential of Mo-doped ZnO nanophotocatalysts for wastewater treatment and warrants further studies in this direction.