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 CO32-. 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.