Reduced graphene oxide impregnated in TiO2 for photodegradation of dyes monitored in UV-LED mini-reactor

Abstract

The photocatalysts of rGO supported on TiO2 were obtained in situ by a sequence of an improved Hummers' method and an eco-friendly hydrothermal procedure. The XRD diffractograms did not present the signals corresponding with the rGO. However, they were detected in micro-Raman because of the characterized signals of D and G bands observed. From TEM, the rGO sheets were visualized covering the surface of TiO2. The photocatalytic experiments were conducted in a real-time monitoring UV-LED mini-reactor (3.0 mL, 5 W and λmax of 365 nm) with small aliquots of sample and catalysts. The catalysts were employed to photodegrade the organic dyes: methylene blue (MB) and tartrazine (TAR), as models or recalcitrant pollutants. The photocatalytic kinetic curves were described by first order kinetic model. Both dyes were completely degraded by all photocatalysts with up to 250 min of irradiation. All supported rGOTiO2 catalysts presented faster kinetics than the TiO2. For MB degradation, 1rGOTiO2 was 6× faster and for TAR degradation 1rGOTiO2 was 3× faster than TiO2. The main action of 1rGOTiO2 was attributed to the better charge transfer by the higher sp2 carbon domains. This result indicates that rGOTiO2 are promising photocatalysts for the degradation of recalcitrant organic pollutants.