One-step hydrothermal synthesis of surface fluorinated TiO2/reduced graphene oxide nanocomposites for photocatalytic degradation of estrogens

The surface fluorinated TiO2/reduced graphene oxide (RGO) nanocomposites (denoted as FTG) were synthesized by a facile one-step hydrothermal method. The prepared photocatalysts were characterized by Transmission electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The results showed that, the anatase TiO2 nanoparticles were well dispersed on RGO sheets, and there was a C-Ti bond in FTG. Moreover, the F- was adsorbed on the surface of TiO2, and generated the stable F-Ti bonds. The adsorption ability and photocatalytic activity of the nanocomposites was evaluated by degradation of 17 beta-estradiol (E2) and 17 alpha-ethynyl-estradiol (EE2) under UV light illumination. The removal ratio was strongly affected by the mass ratio of RGO in FTG, and the optimal mass ratio of RGO for both E2 and EE2 was 4.0 wt% (FTG-4). Further more, the presence of F- enhanced the photocatalytic activity effectively. Under the optimal degradation conditions, the total removal ratios of E2 over FTG-4, TiO2/4 wt% RGO (denoted as TG, without adding hydrofluoric acid) and P25 (Commercial TiO2) were 99.8%, 833% and 74.4%, respectively. And the total removal ratios of EE2 over the same catalysts were 99.7%, 82.6% and 75.6%, respectively. The results indicated that FTG exhibited much higher efficient removal ability for estrogens compared to TG and P25. The introduction of GO in the TiO2 can enhance the adsorption ability for estrogens, meanwhile, GO and the F- can both improve the photocatalytic activity of TiO2 for degradation of estrogens greatly. Further more, the prepared catalyst was found to be reusable. (C) 2015 Elsevier Ltd. All rights reserved.