Synthesis of tungsten oxide/ amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO/N-CQDs) composites for methylene blue removal.

In this present study, the tungsten oxide/amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO/N-CQDs) composite has successfully been prepared through a simple mixing process. The WO was synthesized through a precipitation method, and CQDs were amino-functionalized using ethylenedinitrilotetraacetic acid (EDTA) and ethylenediamine (EDA) through one-pot hydrothermal method. It is revealed that N-CQDs incorporation into WO alters the bandgap energy, crystallinity, surface area, and photoluminescence (PL) properties. The produced composites exhibit higher monoclinic WO crystallinity, larger surface area, lower bandgap energy and quenched photoluminescence intensity. The as-prepared WO/N-CQDs composites exhibit better adsorption and photocatalytic degradation performance of methylene blue (MB) than the pristine WO. It shows that the combination of N-CQDs and WO enhanced visible light absorption, by lowering the bandgap energy of WO from 2.175 to 1.495 eV. The best performance composite is WO/N-CQDs EDA 2.5% with an efficiency of 96.86%, removal rate constant of 0.02017/min, and chemical oxidation demand (COD) removal efficiency achieved 84.61%. Moreover, the WO/N-CQDs EDA 2.5% shows a significant photocatalytic activity even at higher MB initial concentration with 92.93% removal for 50 ppm MB. Subsequently, the composite also has good stability after a sequential 3-times cycle of degradation with 86.85% removal. The increasing photocatalytic performance is affected by the quenching effect of PL and lower bandgap energy. The lower intensity of the PL indicates the reduced charge carrier recombination resulting in increased photocatalytic activity. The combination of N-CQDs and WO resulted in improved photodegradation, which shows its significant potential to be utilized for wastewater treatment.