Photocatalytic abatement of indoor air pollutant toluene by graphene oxide/S/TiO2 composites under visible light

Abstract

With the life style change people spend almost 80% time in indoor environment Thus the indoor air quality has received much attention The indoor air pollutants are mainly volatile organic compounds (VOCs) Among them toluene is one of the most predominant VOCs It can be found from the paint furniture disinfectant and so on Moreover toluene has high toxicity carcinogenicity and long persistence in indoor environment Thus it is necessary to find a technique to remove toluene from indoor air There are some traditional methods to eliminate VOCs Adsorption applies adsorbent to capture VOCs Its drawbacks are the formation of secondary pollutant and desorption Biological technology can degrade VOCs by microorganism but it is hard to maintain On the contrary photocatalytic oxidation process is a promising and green technology for VOCs removal and it can degrade VOCs into CO2 and H2O TiO2 is a widely used photocatalyst because of its low-cost stability and chemical inertness with strong oxidation power However its band gap is rather high resulted in less photocatalytic activity in indoors where commonly use visible light As a result it is inevitable to modify TiO2 to facilitate visible light absorption In this study sulfur and graphene oxide were doped into TiO2 They were expected to enhance the utilization of visible light for TiO2 According to UV-visible spectrometry the doping of sulfur and graphene oxide into TiO2 can obviously increase the visible light adsorption Through XRD SEM and TEM analysis the crystallite phase of TiO2 is anatase after calcination at 400℃ under nitrogen flow; the crystallite sizes of graphene oxide/S/TiO2 are around 10 nm which are smaller than that of bare TiO2 The XPS spectra prove the presence of Ti4+ S6+ and O2- and forming Ti-O-S From the C1s XPS spectra it can be seen that the graphene oxide is reduced because of the decrease of oxygen-containing groups during the preparation of photocatalysts Besides the result of the activity test of photocatalysts shows that 5wt%GO-S0 05TiO2 has the best photocatalytic performance More graphene oxide addition could cause the shield of the light In the various parameters test the conversion of toluene deceases when the relative humidity increases It is due to competitive adsorption between adsorbed water and toluene The conversion of toluene increases with the increasing temperature It suggests that higher temperature results in an increasing collision frequency and the less quantity of adsorbed water The conversion of toluene decreases with an increase of inlet toluene concentration

Date of Award	2016 Aug 3
Original language	English
Supervisor	Hsin Chu (Supervisor)