Novel MWNTs–Bi2WO6 composites with enhanced simulated solar photoactivity toward adsorbed and free tetracycline in water

A novel three-dimensional (3D) mesoporous multiwalled carbon nanotubes-Bi2WO6 (MWNTs–Bi2WO6) microsphere photocatalyst with excellent photocatalytic performance was synthesized by a facile hydrothermal method and used to catalytically degrade tetracycline (TC) in water. Compared with pure Bi2WO6, the photocatalytic activity of the MWNTs–Bi2WO6 composites was enhanced significantly. The incorporated MWNTs facilitated the photogenerated electron transfer and enhanced the separation of photogenerated hole and electron pairs. In addition, the composite displayed stronger light absorption in the visible light region. Furthermore, the large surface as well as π–π electron coupling with the contaminants of MWNTs promoted the adsorption of TC on the photocatalyst surface. As a result, the incorporation of MWNTs with Bi2WO6 enhanced photocatalytic activity. The best photocatalytic performance was achieved with MWNTs proportion of 3%. Almost 100% of TC (20 mg/L) was removed by the solids of 3% MWNTs–Bi2WO6 (0.5 g/L) after irradiation with simulated solar light for 60 min and the degradation efficiency increased about 35% compared with the bare Bi2WO6. The degradation of the adsorbed TC on the catalyst was also investigated. The FT-IR and DTG analyses demonstrated that the adsorbed TC was slightly degraded in 1 h irradiation although the free TC in solution was completely degraded. As the irradiation extended for 3 h, the adsorbed TC was also degraded. The results indicated that the prepared MWNTs–Bi2WO6 composite has great potential for treatment of organic pollutants in water.