BACKGROUNDThe relatively low solubility of reduced sulfur compounds can limit their removal in trickling filters treating large volumes of air at low residence times. This could be overcome by addition of an oxidizing agent. In this study, the oxidative absorption of reduced sulfur compounds-hydrogen sulfide (H2S), methanethiol (CH3SH) and dimethyl sulfide (CH3S2CH3)-in a high-porosity trickling filter with added iron chelated by ethylenediaminetetraacetic acid (EDTA) was examined. The process was observed online by proton transfer reaction mass spectrometry (PTR-MS). RESULTSRemoval efficiencies of H2S remained in the range 80-99% for all combinations of operating parameters tested. The removal efficiency of CH3SH was found to be limited compared to this, with removal efficiencies ranging from 10% to 74% and a strong dependence on gas flow rate and residence time was observed; CH3S2CH3 was found to be inactive. The FeEDTA solutions were prepared from ferrous chloride (FeCl2) as solutions of this compound were more stable than solutions prepared from ferric salts. Oxygen present in the gas stream allowed oxidation of Fe(2+)EDTA to Fe(3+)EDTA in situ, making regeneration prior to experimental runs unnecessary. To maintain high removal efficiencies during start-up, pH should be kept above 7. CONCLUSIONChelated iron catalysts could be effectively applied for H2S removal in a one-step trickling filter process treating low-concentration (<3.5ppm) and diluted waste gas streams, which are characteristic for environmental waste treatment facilities and livestock houses. However, removal of other reduced sulfur compounds important for deodorization was found to be limited. (c) 2019 Society of Chemical Industry