Enhanced photo-degradation of gaseous toluene over MnOx/TiO2/activated carbon under a novel microwave discharge electrodeless lamps system

Abstract

Traditional photocatalytic oxidation of volatile organic compounds (VOCs) suffers low oxidation and mineralization capability, the short lifetime of the lamps, etc. The usage of microwave discharge electrodeless lamps (MDELs) is an energetic approach to eliminate pollutants with lamps having a long lifetime. Herein, a novel MDELs-photocatalytic system using MnOx/TiO2/activated carbon (AC) as the photocatalyst was explored to degrade toluene. The system displayed a superior toluene removal efficiency (94%) and mineralization rate (91%), and there was nearly no ozone emission. Owing to the formation of MnTiO3, the photocatalytic degradation activity over MnOx/TiO2/AC was remarkably increased by producing more reactive oxygen species, such as O(1D) and OH·. MnO and MnTiO3 in MnOx/TiO2/AC also promoted the decomposition of ozone to further degrade toluene via catalytic ozonation. Moreover, the excellent microwave absorbing property of MnOx/TiO2/AC increased the catalyst bed temperature to nearly 150 °C, accelerating the thermal decomposition of toluene due to the “hot spots” effect. The degradation mechanism was proposed tentatively. This work shed new light on the effective removal of VOCs using a novel MDELs photodegradation system over multi-functional catalysts.