ZnCo2O4/g-C3N4/Cu nanocomposite as a new efficient and recyclable heterogeneous photocatalyst with enhanced photocatalytic activity towards the metronidazole degradation under the solar light irradiation

In this study, ZnCo₂O₄/g-C₃N₄/Cu is synthesized as a new and highly effectual solar light-driven heterogeneous photocatalyst. The prepared photocatalyst is characterized using FT-IR, XRD, XPS, DRS, FESEM, TEM, EDS, and elemental mapping techniques. The performance of ZnCo₂O₄/g-C₃N₄/Cu is studied towards the metronidazole (MNZ) degradation under solar light irradiation. The kinetics of MNZ degradation and efficacy of the operational parameters comprising the initial MNZ amount (10–30 mg L⁻¹), photocatalyst dosage (0.005–0.05 g L⁻¹), pH (3–11), and contact time (5–30 min) on the MNZ degradation process are investigated. Surprisingly, the ZnCo₂O₄/g-C₃N₄/Cu nanocomposite presents a privileged photocatalytic performance towards the MNZ degradation under solar light irradiation. The enhanced photocatalytic activity of this photocatalyst can be ascribed to the synergistic optical effects of ZnCo₂O₄, g-C₃N₄, and Cu. The value of band gap energy for ZnCo₂O₄/g-C₃N₄/Cu is estimated to be 2.3 eV based on the Tauc plot of (αhν)² vs. hν. The radical quenching experiments confirm that the superoxide radicals and holes are the principal active species in the photocatalytic degradation of MNZ, whereas the hydroxyl radicals have no major role in such degradation. The as-prepared photocatalyst is simply isolated and recycled for at least eight runs without noticeable loss of the efficiency. Using the natural sunlight source, applying a very low amount of the photocatalyst, neutrality of the reaction medium, short reaction time, high efficiency of the degradation procedure, utilizing air as the oxidant, low operational costs, and easy to recover and reuse of the photocatalyst are the significant highlights of the present method. It is supposed that the current investigation can be a step forward in the representation of an efficacious photocatalytic system in the treatment of a wide range of contaminated aquatic environments.