Removal of Gaseous Pollutants Using Photochemical Aerosol Formation — Removal of Nitrogen Oxides and Benzene, Toluene or Xylene —

Abstract

We have been researching air cleaning technology using gas-to-particle conversion of atmospheric gaseous pollutants by UV light irradiation. We measured removal efficiency of NO_x and typical aromatic hydrocarbons ; benzene, toluene and o-xylene(BTX) , by the irradiation with a high power UV (with 184.9 nm wavelength) lamp. The removal efficiencies of NO_x and BTX increased with increasing water vapor concentration. And 78-91 % NO_x removal efficiencies were achieved in 50 % RH. The removal efficiencies of benzene, toluene and o-xylene in 50 % RH were 64 %, 82 % and 90 %, respectively, which could be related to their chemical reaction rate with OH radicals. Larger particles were formed in NO-BTX-air systems than in a NO-air system. The decrease in the removal efficiency of NO_x by the addition of BTX could be ascribed to the competitive reaction of OH radicals with NO_x and BTX. The obtained experimental results suggest that hybrid air cleaning systems to remove both paniculate and gaseous pollutants from the air could be built in conjunction with catalyst and air filters.