Visible-Light-Induced Degradation of Rhodamine B by Nanosized Bi2WO6

Abstract

Visible-light-induced photodegradation of rhodamine B over nanosized Bi₂WO₆ has been observed. Bi₂WO₆ exhibited a high photoactivity to photodegrade rhodamine B in the central pH solution under visible irradiation (λ > 420 nm). After five recycles for the photodegradation of rhodamine B, the catalyst did not exhibit any significant loss of activity, confirming the photocatalyst is essentially stable. The total organic carbon measurement displayed that a high degree of mineralization was achieved in the present photochemical system. The results of density functional theory calculation illuminated that the visible-light absorption band in the Bi₂WO₆ catalyst is attributed to the band transition from the hybrid orbitals of Bi6s and O2p to the W5d orbitals. The Bi₂WO₆-assisted photocatalytic degradation of rhodamine occurs via two competitive processes: a photocatalytic process and a photosensitized process. The transformation of rhodamine is mainly via the photocatalytic process. Kinetic studies by using electron spin resonance and the radical scavenger technologies suggest that •OH is not the dominant photooxidant. Direct hole transfers and O₂^•- could take part in Bi₂WO₆ photocatalysis. This study provided a possible treatment approach for organic pollutants by using visible light in aqueous ecosystems.