Titanium dioxide/activated carbon composite photocatalysts were prepared through hydrothermal treatment of titanium dioxide and activated carbon.In a recirculating photocatalytic reactor,the degradation of low concentration butyraldehyde, a gaseous pollutant,over the catalyst was performed.Based on the Langmuir-Hindshelwood equation and some hypotheses,a transient model for the degradation of the butyraldehyde in the recirculating reaction system was proposed.The results obtained from the kinetic model were...