Sustainable Eco-Synthesis of CuO–TiO₂ Nanocomposites Using Hibiscus for Water Remediation

The widespread release of the methylene blue (MB) dye from textile industries poses serious environmental and health concerns. This study reports the green synthesis of CuO–TiO₂ nanocomposites using Hibiscus sabdariffa (HS) flower extract, which serves as a natural source of phytochemicals functioning as reducing and stabilizing agents. The nanocomposites were synthesized by combining CuO and TiO₂ nanoparticles in a 1:1 mass ratio via a plant-mediated co-precipitation method and applied for the photocatalytic degradation of MB under UV-light irradiation. The photocatalytic mechanism is driven by the generation of reactive oxygen species (ROS) under UV activation, facilitating dye degradation. Characterization was performed using synchrotron-based X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), photoluminescence (PL) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, thermogravimetric/differential thermal analysis (TGA/DTA), and gas chromatography–mass spectrometry (GC–MS). The nanocomposites exhibited a spherical morphology, enhanced crystallinity, good thermal stability, and a BET surface area of 59.52 m²/g. Photocatalytic performance was assessed using UV–Vis spectroscopy, achieving 81% degradation efficiency of MB within 160 minutes. These results demonstrate the potential of HS-mediated CuO–TiO₂ nanocomposites as efficient, sustainable photocatalysts for wastewater remediation.