Wet scrubber coupled with UV/PMS process for efficient removal of gaseous VOCs: Roles of sulfate and hydroxyl radicals

In this study, wet scrubber coupled with UV/peroxymonosulfate (PMS) was used as a semi-batch process for removing gaseous VOCs. Both ethyl acetate and toluene could be removed efficiently using this coupled process due to the generation of SO4 center dot- and HO center dot. The mass-transfer coefficients in this coupled process were larger than in wet scrubbing only process. The roles of SO4 center dot- and HO center dot were investigated, in which SO4 center dot- acted as the predominant radical for toluene degradation while HO center dot was major for ethyl acetate. This could be further confirmed by simultaneous degradation of ethyl and toluene. Moreover, the reaction solution reused at least four times still showed excellent performance for VOCs removal via re-adding PMS. A possible mechanism on toluene degradation was proposed based on the evolutions of intermediates during the process. This study clarified the roles of non-selective radical (i.e. HO center dot) and selective radical (i.e. SO4 center dot- and Cl-center dot) in the removal of a continuous-flow gaseous VOCs by this coupled process.