Regulated adsorption sites using atomically single cluster over biochar for efficient elemental mercury uptake

Highlights

•	A facile chelated coupled pyrolysis strategy was reported to prepare Mn single-cluster Hg0 adsorbent.
•	The nitrogen-containing group in biomass determined the size of atomically dispersed manganese.
•	The presence of oxygen and small size Mn clusters in biochar promoted Hg0 adsorption.

Abstract

Carbon-based materials have been widely used in gaseous pollutant removal because of their sufficient surface functional groups; however, its removal efficiency for elemental mercury (Hg⁰) is low. In this study, we fabricated biomass using a chelated coupled pyrolysis strategy and further constructed the regulated adsorption sites for gaseous Hg⁰ uptake. A series of Mn_δ-N₂O₂/BC with different manganese cluster sizes demonstrated that manganese clusters anchored on biochar acted as highly active and durable adsorbents for Hg⁰ immobilization, which increased the adsorption efficiency of Hg⁰ by up to 50%. Shrimp- and crab-based biochar adsorbents exhibited excellent Hg⁰ removal because of their chitosan-like structure. In particular, small Mn clusters and oxygen species around the defect led to a boost in the Hg⁰ adsorption by carbon. The results of density functional theory calculation revealed that the presence of oxygen in the carbon skeleton can tune the electrons of small-sized Mn clusters, thereby promoting the affinity of mercury atoms. The newly developed Mn_δ-N₂O₂/BC_shrimp had an adsorption capacity of 7.98–11.52 mg g⁻¹ over a broad temperature range (50–200 °C) and showed a high tolerance to different industrial flue gases (H₂O, NO, HCl, and SO₂). These results provide novel green and low-carbon disposal methods for biomass resource utilization and industrial Hg⁰ emission control.

Funding

National Natural Science Foundation of China(52070129)