Microwave-assisted synthesis of graphene–ZnO (Gr–ZnO) nanorods for efficient solar photocatalytic removal of methylene blue as a model pollutant dye

Abstract

The widespread use of methylene blue (MB) dye in the textile industry contributes to environmental pollution, as it is hard to degrade and can pollute water and soil, negatively affecting aquatic life and ecosystems. This study presents the development of a graphene–ZnO nanorod-based (Gr–ZnO) photocatalyst through a combination of soaking and microwave-assisted synthesis suitable for efficient MB removal from water. It was found that the prepared Gr–ZnO photocatalyst consists of radially grown ZnO nanorods with a mean length of ∼237 nm and a width of ∼40 nm, growing from a common Gr sheet center. The synthesized Gr–ZnO photocatalyst exhibited remarkable photocatalytic performance, successfully degrading ∼97.5% of an MB solution (V = 30 mL and C_o = 3 × 10⁻⁵ M) in just 40 minutes under solar irradiation by using only 3 mg of the photocatalyst. The effects of catalyst dosage, pH, and the presence of HCO₃⁻, CO₃²⁻, NO₃⁻, and Cl⁻ anions were also evaluated to confirm the potential of the photocatalyst for real wastewater treatment. The potential mechanism of MB removal was examined and proposed with the help of radical scavengers. In conclusion, the synthesized Gr–ZnO photocatalyst was shown to be more effective as compared to other similar structures, underscoring its potential for wastewater treatment applications.