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

Abstract

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 2-10 nm. This work provides useful insights into designing highly efficient iron-based adsorbents for the desulfurization of blast furnace gas.