Photodegradation of C.I. Reactive Red 2 in the Bi2WO6 system: the determination of surface characteristics and photocatalytic activities of Bi2WO6

Abstract

In this study, Bi2WO6 was synthesized by the one-step ethylene glycol (EG)-assisted solvothermal method. The effects of the amount of EG, heating time and temperature in the solvothermal method were elucidated. The surface characteristics of the prepared Bi2WO6 were identified by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, specific surface area analysis, UV–Vis spectrophotometry and X-ray photoelectron spectroscopy. C.I. Reactive Red 2 (RR2) was used for studying the photocatalytic activity of prepared Bi2WO6. The effects of the RR2 concentration, Bi2WO6 dose and pH on RR2 photodegradation were elucidated. The optimal experimental conditions for synthesizing Bi2WO6 via the solvothermal method were 100 % EG as the solvent with Bi and W precursors, heated at 433 K for 12 h; the obtained product was EG70-12 h-433 K. The crystal size, specific surface area and band gap of EG70-12 h-433 K were 8.0 nm, 100.3 m2/g and 3.1 eV. The rate of RR2 removal by the prepared Bi2WO6 followed a pseudo-first order kinetic model and the rate constant of EG70-12 h-433 K was 3.02 h−1. The RR2 photodegradation rate increased with the EG70-12 h-433 K dose; it fell as the RR2 concentration or pH increased. The results of adding a scavenger suggested that the photogenerated holes were the main oxidative species in RR2 photodegradation over EG70-12 h-433 K.