Airborne Benzene Oxidized in Water-Sprinkled Pulsed Corona Discharge Followed by Catalytic Removal of Residual Ozone

Air at a flow rate of 100 L min−1 containing 251 μg L−1 of benzene was treated using a pulsed corona discharge (PCD) reactor equipped with a water-sprinkling system. Sprinkled water improved the benzene degradation efficiency by 20% compared with that observed under dry-air conditions, resulting in more than 57% benzene removal at the maximum PCD power of 100 W. Benzene was oxidized mostly in the gas phase; oxidation of aqueous benzene was minor. An additional beneficial effect of water sprinkling was the absorption of benzene degradation products that would otherwise be released from the reactor with the treated air stream. Aqueous degradation intermediates included phenolic and nitro compounds. Water sprinkling was found to suppress ozone formation, a common secondary pollutant generated during plasma-induced air treatment. At a pulsed power of 100 W, ozone concentration decreased from 1200 to 490 μg L−1. The residual ozone was subsequently catalytically decomposed by passing the exhaust gas through a layer of pyrolusite ore containing MnO2. Pyrolusite demonstrated an ability to decompose ozone, maintaining its concentration below the detection limit for the first 10 and 30 min under humid- and dry-air conditions, respectively. Air humidity thus exerted a pronounced deactivating effect on the catalyst. However, subsequent thermal treatment of MnO2 resulted in a recovery of catalytic performance, with the material exhibiting behavior comparable to that in its pristine state.