Photocatalytic performance of graphene/TiO₂-Ag composites on amaranth dye degradation

Ternary nanocomposites containing TiO₂, silver and graphene with different reduction levels were prepared and used as photocatalysts for amaranth azo dye degradation, under UV and natural light exposure. The obtained materials were characterized by TEM, XRD, FTIR and UV-Vis spectroscopy, confirming the successful formation of the nanocomposites. HPLC analysis along with UV-Vis spectroscopy were employed to quantify the concentration of non-degraded dye in solution. The graphene/TiO₂-Ag nanocomposites proved to have remarkable photocatalytic activities for amaranth degradation under UV and solar irradiation (85.3–98% of dye has disappeared in the first 2 h). Also, significant removal efficiencies (between 40.5 and 71.8%) of photocatalysts, in day light conditions, were demonstrated. The best result for amaranth dye degradation was obtained with the reduced graphene/TiO₂-Ag catalyst (up to 99.9%). Based on the degradation products analysis, a photodegradation pathway of amaranth dye was also proposed. - Highlights: • Graphene/TiO₂-Ag composites were prepared by a combined chemical-thermal method. • The composites showed improved light-absorption characteristics. • A significant degradation performance of amaranth was obtained with these composites under UV and natural light exposure. • Graphene/TiO₂-Ag composites offer a high potential for various photocatalytic applications in pollutant removal processes.