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 SO42-. Overall, the catalyst and the product can be effectively separated.