Combination of microwave discharge electrodeless lamp and a TiO2/HZSM-5 composite for the photocatalytic degradation of dimethyl sulphide

Abstract

In this study, an integrated photocatalytic system consisting of a microwave discharge electrodeless lamp (MDEL) and TiO2/HZSM-5 was established to investigate the intensified degradation of dimethyl sulphide (DMS). The system targets optimisation of the reactive oxygen species (ROS) and photocatalytic degradation pathways without catalyst deactivation. TiO2/HZSM-5, containing highly dispersed TiO2 nanoparticles, was prepared through the sol-gel method. TiO2/HZSM-5 exhibits strong acidity and can adsorb DMS in multiple adsorption forms. Thus, the adsorption capacity of TiO2/HZSM-5 is 20 and 53 times higher than that of Aeroxide TiO2 (P25) in dry and highly humid air, respectively. UV–Vis analysis was performed to investigate the ROS in the gas phase. The results show that the concentrations of the ROS increased by 8% and 62.7% in dry and highly humid air, respectively. 1O2 and O (1D), as well as ·OH are the major ROS, accounting for 73.6% and 61.6% in dry and highly humid air, respectively. A total of 92.5% DMS was removed over 600 min in dry air. Microwaves have strong desorption effects on absorbed substances, promoting the degradation of DMS via ROS in the gas phase. Moreover, 1O2, O (1D), and ·OH can mineralise more DMS molecules into SO2 and SO3 through methanesulfonic acid. The highest mineralisation rate of 89.48% was obtained at 90% humidity over 600 min without catalyst deactivation. Therefore, this integrated system induced by microwave radiation can improve ROS production and prevent catalyst deactivation, providing an alternative to achieve higher photocatalytic performances in dry and highly humid air.