rGO-MoO3 Nanocomposite for superior methylene blue removal by adsorption and photocatalysis

•Facile method for effective adsorption of MB dye by rGO-MoO3 nanosorbents proposed.•Enhanced degradation is observed by adding minimal amount of catalyst.•Detailed analysis of adsorption is explained by adsorption isotherm and kinetics.•Degradation is also observed by combined action of adsorption and photocatalysis.•Scavenger studies were performed to analyze the mechanism of photocatalysis. Efficient MoO3 and rGO (0.5,1,2 wt.%)-MoO3 nanosorbent was prepared by facile hydrothermal method. X-ray diffraction (XRD) and Raman spectroscopy techniques confirms the orthorhombic phase. Remarkably in 10 ppm MB dye, complete removal was observed for 1:3, 1:5, 1:3.3, 1:3 (mass of catalyst: volume of dye solution) ratio for pure, 0.5 wt.%, 1 wt.%, 2 wt.% rGO-MoO3 nanocomposite, by merely stirring for one hour without any light exposure. The adsorption mechanism was examined in detail using different models including Langmuir isotherm and Pseudo second-order kinetic model. The composite sample, rGO (0.5 wt.%)-MoO3 is the most efficient nanosorbent whereas rGO (2 wt.%)-MoO3 showed the least adsorption. rGO (2 wt.%)-MoO3 was further used for time dependent study in the presence of UV and in the dark. The presence of UV enhances removal due to the combined effect of adsorption and photocatalysis. Scavenger studies were performed to analyze the mechanism of photocatalysis. [Display omitted]