wcm.03.2025.574.582

Heavy metals and organic dyes present in industrial wastewater pose significant risks to human health and the environment. Among available treatment methods, the advanced oxidation process (AOP) has gained attention for its ability to achieve complete degradation and removal of such contaminants. This study aims to synthesize a TiO2-reduced graphene oxide (rGO) composite and evaluate the role of each component in the combined adsorption-desorption and photocatalytic degradation mechanisms. The rGO was derived from agricultural waste—sugarcane bagasse and coconut shell—and combined with TiO2 via a hydrothermal method. The resulting composites, C-SB (from sugarcane bagasse) and C-CS (from coconut shell), demonstrated effective removal of Cu(II) and methylene blue (MB). C-SB achieved removal efficiencies of 87% for Cu(II) and 46% for MB, slightly outperforming C-CS with 76% and 44%, respectively. TiO2 exhibited a dominant photocatalytic effect in MB degradation, while rGO primarily facilitated Cu(II) removal through adsorption. The adsorption-desorption phase was found to significantly influence the photocatalytic efficiency. Kinetic analysis indicated that a pseudo-first-order model best described the MB adsorption-desorption process (R2 = 1), while a first-order kinetic model effectively represented the photocatalytic degradation, with R2 values of 98.68% for C-SB and 95.67% for C-CS. These findings highlight the potential of TiO2-rGO composites, especially those derived from sugarcane bagasse, in treating complex wastewater through a synergistic mechanism of adsorption and photocatalysis.