Immobilized TiO2-reduced graphene oxide nanocomposites on optical fibers as high performance photocatalysts for degradation of pharmaceuticals

A series of TiO2-reduced graphene oxide (rGO) coated side-glowing optical fibers (SOFs) were synthesized by polymer assisted hydrothermal deposition method (PAHD), and characterized by crystallographic and spectroscopic methods. Fourier transform infrared spectroscopy showed that the mixed graphene dioxide (GO) was reduced during PAHD coating of TiO2-GO nanocomposites. X-ray diffraction patterns revealed TiO2 presented as a mixture phase of anatase, rutile and brookite in the TiO2-rGO nanocomposites. UV- vis absorption spectra of TiO2-rGO nanocomposites indicated that mixing rGO into TiO2 particles could reduce band gap energy, thereby enhancing utilization efficiency of visible light. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO2-rGO nanocomposites exhibited significantly higher photocatalytic activities as compared to pure TiO2, and were strongly affected by the amount of rGO in the catalysts. While photocatalysis with 2.7% rGO achieved 54% degradation of carbamazepine, 81% of ibuprofen, and 92% of sulfamethoxazole after 180 min UV irradiation, the mineralization rates of the pharmaceuticals were similar between 52% and 59%. The photocatalytic oxidation of pharmaceuticals by the prepared nanocomposites followed the Langmuir-Hinshelwood kinetic model. There was an obvious positive correlation between degradation rate constant and quantum flux for both UV and visible light, with correlation coefficient of 0.991. In addition, long-term photoactivity testing of TiO2-rGO coated SOFs demonstrated the durability of the immobilized TiO2-rGO nanocomposites on optical fibers for water treatment. (C) 2016 Elsevier B.V. All rights reserved.