Adsorption and photocatalysis of 2-ethyl-1-hexanol over graphene oxide-TiO2 hybrids post-treated under various thermal conditions

High temperature (>300 degrees C) post-treatment of two-dimensional graphene oxide-coupled titania (GO-TiO2) hybrids may enhance their photocatalytic performances. This concept has not yet been fully assessed. In the present study, we explored the applicability of GO-TiO2 hybrids synthesized using a chemical mixing method, followed by post-treatment under various thermal conditions (200-500 degrees C), for the degradation of low-concentration gas-phase 2-ethyl-1-hexanol (2E1H) in continuous-flow mode under visible-light illumination. The morphological and optical characteristics of the synthesized photocatalysts were investigated by field-emission transmission electron microscopy, thermal gravimetric analysis, X-ray diffraction technique, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and N-2 adsorption-desorption analysis. The GO-TiO2 hybrid post-treated at 400 degrees C exhibited longer breakthrough and saturation times and a higher capacity for 2E1H adsorption than did GO-TiO2 posttreated at 200 degrees C. The photocatalytic 2E1H degradation efficiencies of the post-treated GO-TiO2 hybrids were superior to those of the untreated GO-TiO2 hybrid and neat TiO2 Samples. Moreover, the photocatalytic activities of the GOkTiO(2) hybrids increased as the post-treatment temperature increased from 200 to 400 degrees C, and decreased as the temperature was further increased to 500 degrees C, indicating that the treatment temperature can be increased up to at least 400 degrees C without significant reduction of the photocatalytic performance. The photocatalytic activity of the GO-TiO2 hybrid post-treated at 400 degrees C depended strongly on three process parameters: relative humidity, initial contaminant concentration, and catalyst mass. There was no appreciable loss of photocatalytic efficiency for the GO-TiO2 hybrid post-treated at 400 degrees C after five cycles. The average 2E1H mineralization efficiency was 55.1%, while the average photocatalytic efficiency was 99.3%. Two gaseous organic compounds, i.e., 3-heptanone and 2-ethyl hexanal, and carbon monoxide were identified as the primary partially oxidized intermediates. The average carbon monoxide concentration (0.49 ppm) was well below the permissible 8-h exposure level (25 ppm). (C) 2015 Elsevier B.V. All rights reserved.