Cost-Effective Manganese Ore Sorbent for Elemental Mercury Removal from Flue Gas

Mercury capture from flue gas remains a challenge for environmental protection due to the lack of cost-effective sorbents. Natural manganese ore (NMO) was developed as a cost-effective sorbent for elemental mercury removal from flue gas. NMO sorbent showed excellent Hg⁰ removal efficiency (>90%) in a wide temperature window (100-250 °C) under the conditions of simulated flue gas. O₂, NO, and HCl promoted Hg⁰ removal due to the surface reactions of Hg⁰ with these species. SO₂ and H₂O slightly inhibited Hg⁰ removal under the conditions of simulated flue gas. O₂ addition could also weaken the inhibitory effect of SO₂. NMO sorbent exhibited superior regeneration performance for Hg⁰ removal during ten-cycle experiments. Quantum chemistry calculations were used to identify the active components of NMO sorbent and to understand the atomic-level interaction between Hg⁰ and sorbent surface. Theoretical results indicated that Mn₃O₄ is the most active component of NMO sorbent for Hg⁰ removal. The atomic orbital hybridization and electrons sharing led to the stronger interaction between Hg⁰ and Mn₃O₄ surface. Finally, a chemical looping process based on NMO sorbent was proposed for the green recovery of Hg⁰ from flue gas. The low cost, excellent performance, superior regenerable properties suggest that the natural manganese ore is a promising sorbent for mercury removal from flue gas.