Synthesis and Characterization of Rectorite/ZnO/TiO₂ Composites and Their Properties of Adsorption and Photocatalysis for the Removal of Methylene Blue Dye

Abstract

As efficient water treatment agents, a novel series of rectorite-based ZnO and TiO₂ hybrid composites (REC/ZnO/TiO₂) were synthesized and characterized in this study. Effects of experimental parameters including TiO₂ mass ratio, solution pH and catalyst dosage on the removal of methyl blue (MB) were also conducted. The presence of a little mass ratio (2%-6%) of TiO₂ highly promoted the photoactivity of REC/ZnO/TiO₂ in removal of MB dye from aqueous solution, in which ZnO and REC played a role of photocatalyst and adsorbent. The promotion effects of TiO₂ may result from the accelerated separation of electron-hole on ZnO. The observed kinetic constant for the degradation of MB over REC/ZnO and REC/ZnO/TiO₂ were 0.015 and 0.038 min^-1, respectively. The degradation kinetics of MB dye, which followed the Langmuir–Hinshelwood model, had a reaction constant of 0.17 mg/(L·min). The decrease of removal ratio of MB after five repetitive experiments was small, indicating REC/ZnO/TiO₂ has great potential as an effective and stable catalyst.

Keywords

TiO₂ / ZnO / methylene blue / photocatalysis / rectorite