Silver nanoparticles-anchored reduced graphene oxide obtained by orange peel extract-mediated synthesis for visible light photodegradation of organic dye

Orange peel extract, as green alternative to the traditional chemicals, was applied as reducing agent for the preparation of photoactive material (OPE-rGO@AgNPs) composed by silver nanoparticles and reduced graphene oxide, starting from silver nitrate and graphene oxide as precursors in alkaline aqueous solution. Different amounts of silver ions were used and the optimized photocatalysts were fully characterized by UV–Vis, FT-IR, Raman and SEM analysis confirming the effective reduction of graphene oxide and the incorporation of the AgNPs. The photocatalysts were supported on a regenerated cellulose filter and the photodegradation efficiency, under visible light, was measured monitoring the degradation of methylene blue (MB) dye, as a target pollutant. The photodegradation efficiency of MB, tested at 20 ppm, increased from a 40 % for the non-modified OPE-rGO material, up to 81 % of MB degradation for the OPE-rGO@AgNPs5 photocatalyst; this material showed a 95 % of MB photodegradation at 10 ppm. The photodegradation results correlated with the calculated band gap values of the different tested materials, showing a progressive decrease in band gap for the material modified with AgNPs, from 3.22 eV for OPE-rGO to 2.90 eV for the OPE-rGO@AgNPs5, that exhibited the best efficiency as photocatalyst for the MB photodegradation.