Degradation of gas-phase organic contaminants via nitrogen-embedded one-dimensional rod-shaped titania in a plug-flow reactor

Abstract

In this study, one-dimensional rod-shaped titania (RST) and nitrogen-doped RST (N-RST) with different ratios of N to Ti were prepared using a hydrothermal method and their applications for purification of indoor toxic organic contaminants in a plug-flow reactor were examined under visible or ultraviolet (UV) irradiation. The surface characteristics of as-prepared photocatalysts were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-visible spectroscopy. The TEM images revealed that both pure RSTs and N-RSTs displayed uniform and nanorod-shaped structures. XRD revealed that the photocatalysts had crystalline TiO2. The UV-visible spectra demonstrated that the N-RSTs could be activated in the visible region. In most cases, N-RSTs showed higher degradation efficiencies than pure RSTs under visible-light and UV irradiation. N-RSTs with a N-to-Ti ratio of 0.5 exhibited the highest degradation efficiencies of benzene, toluene, ethyl benzene, and o-xylene (BTEX), suggesting the presence of an optimal N-to-Ti ratio for preparation of N-RSTs. In addition, the average degradation efficiencies of BTEX determined for the N-RSTs with a N-to-Ti ratio of 0.5 under visible-light irradiation for the lowest initial concentration (IC, 0.1 ppm) were 19%, 53%, 85%, and 92%, respectively, while the degradation efficiencies for the highest IC (2.0 ppm) were 2%, 8%, 17%, and 33%. These values decreased as the stream flow rate increased. Overall, the as-prepared N-RSTs could be effectively applied for degradation of toxic gas-phase organic contaminants under visible-light as well as UV irradiation.

Preparation of TiO2 and Fe-TiO2 with an Impinging Stream-Rotating Packed Bed by the Precipitation Method for the Photodegradation of Gaseous Toluene

“…Toluene was taken as the target VOC mainly because it is one of the most common pollutants both indoors or outdoors [28,29]. Furthermore, there have been many studies on the photocatalytic degradation of toluene, and thus there is a sufficient theoretical basis and practical feasibility [30,31,32].…”

Enhanced Photocatalysis of Graphene and TiO2 Dual-Coupled Carbon Nanofibers Post-treated at Various Temperatures

“…3 Therefore, under high initial concentration conditions, fewer sites are available for adsorption of the target chemicals before the surface reactions occur, suggesting that the adsorption process is the ratedetermining step for photocatalysis of the target pollutants over GTCNs. Similarly, recent studies 31,32 have found that the photocatalytic activities determined using other types of catalysts or reactor systems, with respect to the degradation of selected gaseous and aqueous contaminants, were lower under high initial concentration conditions. Specifically, Jo et al 32 noted that the decomposition efficiencies for gaseous benzene, toluene, ethylbenzene, and o-xylene over visible-lightactivated rod-shaped TiO 2 in a plug-flow reactor decreased from 19% to 2%, 53% to 8%, 85% to 17%, and 92% to 33%, respectively, when the concentration of these chemicals was raised from 0.1 to 2.0 ppm.…”

“…Similarly, recent studies 31,32 have found that the photocatalytic activities determined using other types of catalysts or reactor systems, with respect to the degradation of selected gaseous and aqueous contaminants, were lower under high initial concentration conditions. Specifically, Jo et al 32 noted that the decomposition efficiencies for gaseous benzene, toluene, ethylbenzene, and o-xylene over visible-lightactivated rod-shaped TiO 2 in a plug-flow reactor decreased from 19% to 2%, 53% to 8%, 85% to 17%, and 92% to 33%, respectively, when the concentration of these chemicals was raised from 0.1 to 2.0 ppm. Romaõ et al 33 stated that the PDE of cortisone acetate, as determined using P25 TiO 2 suspended in a water-containing batch reactor under UV irradiation, decreased gradually as the initial concentration of this compound increased from 5 to 40 mg L −1 .…”