NOx Removal Process in Pulsed Corona Discharge Combined with TiO2 Photocatalyst

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Abstract
The NOx removal process was studied experimentally in the pulsed corona discharge combined with the TiO2 photocatalytic reaction. First, the adsorption and desorption properties of NOx on the photocatalyst were investigated using UV irradiation from a black light without gas discharge. We found that NO2 was easily adsorbed on the photocatalyst surface, whereas NO was hardly adsorbed. Addition of water vapor enhanced the NO2 adsorption. Next, the relationship between the plasma-enhanced chemical reaction and the photocatalytic reaction was investigated using pulsed corona discharge with wire-plate-type electrodes positioned between two photocatalysts. The TiO2 photocatalyst efficiently assisted the increase of the NOx removal rate. The main role of the plasma-chemical reaction in this system is the oxidation of NO into NO2. A considerable part of NO2 is adsorbed on the photocatalyst surface, and is transformed to HNO3 through photocatalytic reaction with OH. HNO3 on the photocatalyst is hardly desorbed from the catalyst surface.