Visible Light-Induced Reactive Yellow 145 Discoloration: Structural and Photocatalytic Studies of Graphene Quantum Dot-Incorporated TiO₂

Visible light-induced photocatalytic treatment of organic waste is considered a green and efficient route. This study explored the structural and photocatalytic performance of graphene quantum dot (GQD)-incorporated TiO₂ nanocomposites to treat reactive yellow 145 (RY145) dye. For the effective removal of the RY145, efforts were made to better understand the kinetics of the process and optimization of the treatment parameters. Different GQD-doped TiO₂ nanocomposites were synthesized employing the sol-gel method. Physicochemical characteristics of the synthesized nanocomposites were studied through FTIR, XRD, UV-visible spectroscopy, SEM, and EDX. Screening studies were conducted for synthesis and reaction optimization. The results indicated that GQD-TiO₂ significantly enhanced the photocatalytic discoloration for RY145 dye. Among the synthesized nanocomposites, 15GQD-TiO₂ calcined at 300 exhibited 99.3% RY145 discoloration in 30 min under visible light irradiation. Following the pseudo-first-order reaction, the photocatalytic reaction constant K_app progressively declined with an increase in the concentration of RY145. The heterogeneous reaction system conformed to the Langmuir-Hinshelwood isotherm, as indicated by the K_C (1.08 mg L^-1 min^-1) and the K_LH (0.18 L mg^-1) values. O₂^•- was found to be the major contributor in GQD-TiO₂-300 to decolorize RY154, while TiO₂ and GQDs played a vital role in generation of electrons and holes. Additionally, after recycling to the seventh cycle, only 9% decline in photocatalytic performance was observed for the synthesized nanocomposite.