Photocatalytic oxidation of 2,4,6-trinitrotoluene in the presence of ozone under irradiation with UV and visible light

The photooxidation of 2,4,6-trinitrotoluene (TNT), catalysed by nanosized photocatalysts: TiO2, WO3/TiO2, Au/TiO2 and Au/WO3/TiO2 was studied under irradiation with UV or visible light in the presence of O-2 or O-2-O-3 mixture. The photocatalysts were characterized by the BET, XPS, TEM methods and adsorption of the model pollutant. The effectiveness of the processes of under UV-A. UV-C and visible light irradiation destruction in the presence of O-3, photocatalysed by the WO3/TiO2,Au/TiO2 and Au/WO3/TiO2 samples is considerably higher than that registered in process, occurring with pure TiO2. Thus in the presence of O-3 the rate constants of 2,4,6-trinitrotoluene photooxidation under UV-A, UV-C and visible light irradiation catalysed by Au/WO3/TiO2 are respectively 2.1, 1.4 and 6.2 times higher than that registered with pure TiO2. On the other side the ozone rate constants of 2,4,6-trinitrotoluene photooxidation under UV or visible light irradiation are also much higher than those, registered in the presence of O-2 only. Thus under UV light irradiation the O-3 rate constants of 2,4,6-trinitrotoluene photooxidation, catalysed by Au/WO3/TiO2 are 6 times higher, while under visible light they are 11 times higher than those with oxygen only. Under irradiation with UV-A, UV-C and visible light in the presence of ozone a synergistic effect has been registered, expressed most strongly in the case of TNT destruction, photocatalysed by Au/WO3/TiO2. Doping of the semiconductor materials with gold nanoparticles increases 1.4-2.2 times the rate constants of 2,4,6-trinitrotoluene mineralization, compared to the undoped samples, which is due to more efficient separation of the electron-hole charges generated upon irradiation. (C) 2012 Elsevier B.V. All rights reserved.