Photodecolorization of Rhodamine B on tungsten-doped TiO2/activated carbon under visible-light irradiation

Abstract

Tungsten-doped TiO2/activated carbon catalysts have been prepared by a supercritical-pretreatment-assisted sol–gel process. The structural features of the photocatalysts have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV/Vis diffuse-reflectance spectroscopy (DRS), electron dispersive X-ray (EDX), photoluminescence spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The results revealed that a W–TiO2 layer was coated on the AC surface, and had higher surface area and smaller crystallite size than TiO2/AC obtained by a similar route. The W dopant was responsible for narrowing the band gap of TiO2 and shifting its optical response from the ultraviolet (UV) to the visible-light region. The photocatalytic performances of the supported catalysts have been evaluated for the degradation of Rhodamine B (RhB) solution under visible-light irradiation. Compared with bulk W–TiO2, the photoactivity was obviously enhanced when it was coated onto AC. In addition, it was found that the reactivity showed a significant relationship with the amount of W dopant, and the photoactivity order of the catalysts from weak to strong showed good agreement with their PL intensities. The effects of TiO2 content, tungsten ion content, catalyst amount, pH, and initial RhB concentration have been examined as operational parameters. The photocatalytic reactions followed pseudo-first-order kinetics and are discussed in terms of the Langmuir–Hinshelwood model.