Gaseous 1,2-dichlorobenzene (1,2-DCBz) was photocatalytically decomposed on a powdered TiO2 layer using UV-light, or the latter combined with ozone addition. The effect of various experimental parameters was studied, including inlet concentrations of ozone, UV irradiation or not, carrier gas (dry air or nitrogen) and treatment time period. A temperature of 150 degrees C is selected, to replicate flue gas conditions after bag house filter. An optimum ozone addition of ca. 165 ppm was established, higher concentrations barely improving photocatalytic removal. Possible pathways and mechanisms are discussed on the basis of the intermediate products identified, the chloride ions distribution in the effluent and catalyst surface, and a carbon conversion balance. (c) 2012 Elsevier B.V. All rights reserved.