Nano-flower spherical NiFe LDH adsorbent for efficient removal of H₂S in blast furnace gas

Removal of sulfur species from blast furnace gas is urgently needed due to the strict emission limits imposed on iron-steel industrial flue gas. Improving the sulfur capacity of H₂S is a crucial challenge to reduce the operation cost. NiFe layered double hydroxide (LDH) adsorbents were synthesized using the hydrothermal method to strengthen the adsorption of H₂S, achieving a high sulfur capacity of 133.6 mg/g at 50 °C. Characterization studies have revealed that the reaction pathway of H₂S on the NiFe LDH surface involves adsorption, dissociation and oxidation. It has been clarified that the high sulfur capacity can be attributed to the abundant H₂S dissociation sites and the excellent O₂ activation sites. The dissociation sites of H₂S encompass metal sites, -OH and CO₃^2-. The interaction between O₂ and the bridge site of asymmetric metal atoms significantly enhances the dissociation of O₂. Strengthening the dissociation of H₂S and O₂ improves the sulfur capacity. The deactivation of adsorbents comes from the continuous consumption of oxygen species mainly composed of -OH and the deposition of sulfur species in the smaller mesopores ranging from 2 to 10 nm. This work provides useful insights into designing highly efficient iron-based adsorbents for the desulfurization of blast furnace gas.