Enhanced photocatalytic degradation of wastewater over RGO-TiO2/BiVO4 photocatalyst under solar light irradiation

Abstract

Treating wastewater via photocatalyst is a promising alternative technology to current conventional wastewater treatment technologies. Herein, visible light active RGO-TiO2/BiVO4 heterostructure photocatalysts were successfully synthesized via wet-impregnation method. The photocatalytic degradation performance of as-prepared RGO-TiO2/BiVO4 heterostructure photocatalysts via removal of synthetic wastewater, namely methylene blue were evaluated by varying the amount of total RGO loading (0, 0.4, 0.8, 1.0 and 1.2 wt%) on the surface of RGO-TiO2/BiVO4 heterostructure photocatalysts. The 1.0% RGO-TiO2/BiVO4 heterostructure photocatalysts exhibited fastest and complete methylene blue removal within 120 min. Moreover, the efficiency of 1.0% RGO-TiO2/BiVO4 heterostructure photocatalysts was further evaluated via treating the real petroleum wastewater. The result shows a significant reduction of turbidity, COD and TOC values with respect to initial concentration in which 100, 80.9 and 75.0% removal efficiency were achieved within 6 h, respectively. The superior photocatalytic degradation performance of 1.0% RGO-TiO2/BiVO4 heterostructure photocatalysts in treating the synthetic and real wastewater was attributed to the better crystallinity structure obtained as shown in XRD analysis. Furthermore, the intimate contact between the RGO, TiO2 and BiVO4 in the heterostructure sample as shown in FESEM micrograph images does help in allowing a smooth electron-hole pair separation and migration, resulting in more available OH and O2− radicals for photocatalytic degradation activities. Likewise, the incorporation of RGO in the heterostructure system can provide a low electron resistance pathway which can expedite the electron-hole pair separation and migration from the conduction band of BiVO4 to the adjacent TiO2. These results suggest that the as-prepared RGO-TiO2/BiVO4 heterostructure photocatalyst is an efficient photocatalyst that can be used in the real practical application of wastewater treatment.