Efficient removal of methylene blue dye by a hybrid adsorption-photocatalysis process using reduced graphene oxide/titanate nanotube composites for water reuse

In this study, reduced graphene oxide/titanate nanotube (rGO/TNT) composites were fabricated by a one-step facile hydrothermal process. The structures and physicochemical properties of the prepared materials were comprehensively determined. The incorporation of a small amount of rGO into the composites led to the enhancement of the absorption intensity of visible light and the separation of photogenerated charged carriers. The rGO/TNT composite with the optimal amount of rGO of 3% by weight showed the highest photocatalytic activity for both methylene blue (MB) and methyl orange. Moreover, 3 wt.% rGO/TNT exhibited higher adsorption capability and photocatalytic activity for MB, a cationic dye, than TNTs and commercial TiO2 P25. The maximum amount of MB adsorbed on 3 wt.% rGO/TNT was 26.3 mg/g at 25 degrees C, and the adsorption rapidly reached equilibrium after 40 min of contact time. Approximately 100% decolorization and 77.4% mineralization over 3% rGO/TNT composite were achieved under 100 W UV irradiation for 1 h, whereas 95.0% decolorization and 78.8% mineralization were achieved under visible light irradiation for 3 h. The degradation pathways of MB over P25, TNTs, and 3 wt. % rGO/TNT composite were finally proposed and compared. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.