Synthesis of graphene nanosheets from coffee ground waste and its incorporation to mixed-phase TiO₂ as photocatalyst in anthracene degradation

The increasing level of coffee consumption in Indonesia causes a significant amount of coffee ground waste as landfill, leading to serious environmental problems on account of phenol derivatives and acidic compounds as its constituents. Containing high carbon content, waste coffee ground is a favourable biomass candidate to be converted into carbon-based material, such as graphene nanosheet (GN). Having wide surface area, graphene derivatives can be used to modify surface of many materials, such as TiO₂. The aim of this study is to synthesize graphene-modified TiO₂ with a mixed anatase:rutile phase (9:1) and to analyse its photocatalytic activity towards the photodegradation of anthracene, in comparison with unmodified TiO₂. UV-DRS analysis showed a significant decrease in the band gap of TiO₂/GN-A (2.78 eV) compared with TiO₂ (3.00 eV), leading to an increase in photocatalytic activity (K_t TiO₂ = 7.26 × 10^-4 min⁻¹; K_t TiO₂/GN-A = 3.43 × 10^-3 min⁻¹). All in all, the synthesized photocatalyst materials presented promising potential to be applied as photocatalysts in photodegradation of organic compounds.