Synthesis and Characterization of C/ZnO–NiO Nanoflower Composite as an Efficacious Photocatalyst for Degradation of Reactive Red 120 Dye Under Visible Light

The present study aimed at preparing an efficient nanocomposite composing activated carbon (C), ZnO and NiO as a highly reactive photocatalyst for degradation of reactive red 120 (RR120) wastewater under LED light irradiation. The combination of ZnO and NiO motivates charge recombination from one photocatalyst to the other, thus suppressing charge recombination which is a big target in photocatalytic process. On the other hand, the dispersion of photocatalyst particles over activated carbon matrix leads to the efficient light absorption and promoting photocatalytic activity. The photocatalysts were prepared hydrothermally and characterized by XRD, FTIR, SEM, EDS, BET and UV–vis DRS analyses. The C/ZnO–NiO photocatalyst demonstrated a flower-like morphology with mesoporous features. To obtain the best photocatalytic dye degradation, a step-by-step study was carried out to find out the optimum values of ZnO/NiO molar ratio, photocatalyst amount, carbon mesh size, solution pH, initial RR120 concentration, H₂O₂ and power of LED lamp. The maximum photocatalytic RR120 degradation of 94.88% was observed under the optimum conditions of ZnO/NiO molar ratio of 1:2, photocatalyst amount of 50 mg, carbon mesh size of 270, solution pH 3, initial RR120 concentration of 5 ppm, H₂O₂ quantity of 0.2 mL and of LED power of 50 W. Kinetic studies confirmed the applicability of the Langmuir–Hinshelwood theory by which the dye concentration is a first-order function of time. The reusability study of the C/ZnO–NiO photocatalyst showed good stability of the photocatalyst after recycling 7 times under the optimum conditions.