Direct Oxidation of H2S by Air at Low Temperatures Using Catalysts Derived from Industrial Solid Waste

Abstract

When modifying solid waste materials (raw sludges) that were collected from the water supply plant with zinc nitrate by the impregnation method, followed by calcining at 400 °C, the obtained sample (denoted as ZnO/VT-400 catalyst) performed high activity toward H₂S oxidation, with the H₂S conversion ($$) of ∼91% after a reaction time of 270 min. For such a process, the following catalytic conditions were found to be optimal for the installed lab-scale model of H₂S treatment: reaction temperature of 150 °C; inlet H₂S concentration of 2000 ppm; total gas-air flowrate of 0.75 L/min; and catalyst mass of 1.0 g. Moreover, the catalyst showed its cycling stability, with $$ ≈ 89% after the 4^th cycle (after 32 h of use). The ZnO/VT-400 sample mainly consisted of Fe₂O₃, small amounts of SiO₂, and ZnO. These components existed in amorphous forms and were evenly distributed on the catalyst's surface. Two steps of the reaction process were proposed for the chemical mechanism of catalysis, including the chemisorption of H₂S on the active sites, followed by oxidation with the formation of sulfur elements. The work has demonstrated the positive use of industrial solid waste to develop low-cost and high-performance catalysts for H₂S removal from the air.