Mechanistic Insights and Kinetic Modeling of Photocatalytic Degradation of Organic Dyes Using TiO₂–Graphene Nanocomposites

https://doi.org/10.5281/zenodo.17576892

Abstract

When water resources undergo contamination by persistent organic dyes from industrial effluents, complicated procedures for treatment are required. This study examines the enhanced photocatalytic degradation of methylene blue (MB) using a TiO₂–graphene nanocomposite that was created using a sol-gel assisted hydrothermal method. Complete characterization using XRD, SEM, BET, and DRS demonstrated the successful integration of graphene with TiO₂. This contributed to a narrower band gap, improved absorption of visible light, and a higher specific surface area. Superior photocatalytic performance has been demonstrated by the nanocomposite's degradation efficiency, which was significantly greater than that of pure TiO₂ when exposed to UV-visible light. Kinetic analysis revealed that the degradation process followed a pseudo-first-order model and that the nanocomposite had a substantially greater apparent rate constant. Mechanistic studies using radical scavenging experiments demonstrate that the primary reactive species that contribute to dye degradation are photogenerated holes (h⁺) and superoxide radicals (•O₂⁻). This illustrated how graphene may successfully accept particles and stop charge carrier recombination. Furthermore, the nanocomposite exhibited outstanding strength and reusability with minimal activity loss over a total of five consecutive cycles. With regard to these outcomes, the TiO₂–graphene nanocomposite is a highly effective and persistent photocatalyst for wastewater remediation, providing significant kinetic framework and mechanistic insights.