Photocatalytic removal of NOx using TiO2-coated zeolite.

Application of photocatalytic nanoparticles has been recently gaining an increased attention as air purifying material for sustainable urban development. The present work reports the photocatalytic removal of gaseous phase nitrogen oxides (NO_x) using TiO₂-coated zeolite to be applied as a filter media for the urban green infrastructure such as raingardens. The TiO₂-coated zeolite was synthesized by simple wet chemistry method and tested in a continuous-flow photo-reactor for its removal efficiency of NO_x under different conditions of the weight percentage of TiO₂ coated on the zeolite, and gas retention time. The removal efficiency of NO_x in general increased as the weight percentage of TiO₂ coated on the zeolite increased up to 15-20%. Greater than 90% of NO_x was removed at a retention time of one minute using the TiO₂-coated zeolite (TiO₂ weight percentage = 20%). Overall, TiO₂-coated zeolite showed greater efficiency of NO_x removal compared to TiO₂ powder probably by providing additional reaction sites from the porous structure of zeolite. It was presumed that the degradation of NO_x is attributed to both the physical adsorption and photocatalytic oxidation that could simultaneously occur at the catalyst surface. [ABSTRACT FROM AUTHOR]