Development of Eco-friendly CQDs/TiO₂ Nanocomposite for Enhanced Photocatalytic Degradation of Methyl Orange Dye

Abstract This research explores the photocatalytic degradation of methyl orange (MO) dye using a novel TiO₂/biowaste-derived carbon quantum dots (CQDs) composite under visible light. The TiO2, biowaste-derived CQDs, and TiO2/CQDs composite were synthesized via a hydrothermal method and characterized using UV-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). TEM analysis revealed a uniform distribution of CQDs within the TiO2 matrix, confirming the successful integration of CQDs into the nanocomposite structure. The incorporation of CQDs significantly reduced the band gap of the composite, enhancing its photocatalytic activity under visible light. Photocatalytic experiments, conducted with a 300 W Xe lamp as the light source, utilized a 20 mg catalyst dosage for a 15 ppm MO solution. The TiO2/CQDs composite demonstrated an outstanding degradation efficiency of 85% within 130 minutes, following a pseudo-first-order kinetic model with a rate constant of K = 0.01353 min-1. In comparison, pure TiO₂ and CQDs achieved degradation efficiencies of 61% and 19%, respectively, under the same conditions. These findings underline the potential of TiO2/biowaste-derived CQDs composites as a sustainable, eco-friendly approach for wastewater treatment and environmental remediation through visible-light-driven photocatalysis.