Nonthermal plasma coupled with liquid-phase UV/Fe–C for chlorobenzene removal

Abstract

Catalyst poisoning problems limit the application of gas-solid non-thermal plasma (NTP) catalyzed decomposition of chlorinated volatile organic compounds (Cl–VOCs). To mitigate the catalyst deactivation, catalyst iron-loaded activated carbon (Fe–C) was added to the UV-activated liquid phase downstream of the NTP reactor (NTP + UV/Fe–C(L)) for the degradation of chlorobenzene (CB) in this study. The CB removal efficiency and mineralization efficiency (MR) of NTP + UV/Fe–C(L) were up to 94% and 68%, respectively, which were increased by 39% and 30% compared with the single NTP system. Compared with the conventional gas-solid NTP + UV/Fe–C(S) system, the stability of the NTP + UV/Fe–C(L) system was significantly improved due to the dissolved organic intermediates and low residuals on the catalyst surface. Reactive oxygen species ·OH and ·O2− dominated the decomposition of CB in the liquid phase, and with the help of UV, much more ·OH and ·O2− were produced by Fe–C catalytic O3. In addition, Fe–C improved the removal of CB by increasing its absorption mass transfer coefficient from 0.0016 to 0.0157 s−1. The degradation pathway of CB in the NTP + UV/Fe–C(L) system was proposed based on the detected organic intermediates. Overall, this study provides a new tactic to solve the catalyst poisoning problem in the NTP catalytic oxidation of Cl–VOCs.