Visible light mediated photocatalytic degradation of gaseous trichloroethylene and dimethyl sulfide on modified titanium dioxide

This paper reports the potential of four modified TiO2 photocatalysts to degrade gaseous volatile organic compounds under visible light irradiation. Two modified photocatalysts were prepared by sensitizing TiO2 Degussa P25 with CdS and eosin Y, respectively. Two other photocatalysts were S-doped TiO2. One was prepared through a recently described sot-gel method (S-doped TiO2-SG), whereas a new type was synthesized by a physical mixture method (S-doped TiO2-PM)All modified photocatalysts showed a shift in UV-vis absorbance towards higher wavelengths, up to 620 nm. Photocatalytic activity under near-UV and visible light irradiation was systematically investigated through the degradation of gaseous trichloroethylene (TCE) and dimethyl sulfide (DMS) in a batch reactor. Although TiO2 Degussa P25 showed 1.3-6.6 times higher TCE degradation rates than modified photocatalysts under near-UV irradiation, no significant activity was observed at X > 400 nm. In contrast, modified catalysts showed photocatalytic activity under both blue (400-540 nm) and yellow light (480-720 nm) irradiation, with S-doped TiO2-PM and S-doped TiO2-SG giving the highest TCE degradation rates, respectively. Under daylight irradiation (400-720 nm), S-doped TiO2-PM yielded the highest activity towards both TCE and DMS degradation, exemplified by removal efficiencies higher than 99% within 110 min of irradiation at concentrations up to 537 ppmv. (c) 2005 Elsevier B.V. All rights reserved.