Removal of Gaseous Hydrogen Sulfide by a FeOCl/H₂O₂ Wet Oxidation System

The removal of gaseous hydrogen sulfide using FeOCl/H₂O₂ was studied. The effects of the FeOCl dosage, the H₂O₂ concentration, the reaction temperature, and the gas flow rate on the removal of H₂S were investigated. The reaction products were analyzed, and the characterization of FeOCl was carried out by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. Furthermore, radical quenching experiments were carried out using butylated hydroxytoluene, isopropanol, and benzoquinone. It was found that the H₂S removal rate for a H₂S gas concentration of 160 ppm reached 85.6% when bubbling through 100 mL of an aqueous solution containing FeOCl (1 g/L) and H₂O₂ (0.33 mol/L) at 293 K with a flow rate of 135 mL/min. Although the dissolution of chlorine in FeOCl was found to result in reduced catalytic performance, the activity was restored after soaking the catalyst in concentrated hydrochloric acid (37%) and subsequent calcination. The mechanism of H₂S removal was also discussed, and it was found that this process was controlled by H₂S diffusion. FeOCl was found to activate H₂O₂ and produce radicals, such as ^•OH and ^•O₂ ^-, resulting in the formation of a water film rich in radicals on the FeOCl surface. Following the diffusion of H₂S into the water film, it underwent oxidation by radicals to produce SO₄ ^2-. Overall, the catalyst and the product can be effectively separated.