Removal of gaseous As2O3 in flue gas by manganese minerals: Experimental and theoretical calculation

Atmospheric arsenic pollution, primarily caused by non-ferrous metal smelting and coal combustion, poses a significant environmental challenge. The removal of gaseous As₂O₃ from flue gas has become an urgent priority. Compared to synthetic adsorbents, natural manganese minerals (NMMs) possess advantages such as abundant reserves, low cost, and strong arsenic affinity, making them a promising candidate for large-scale gaseous As₂O₃ removal applications. This study investigates the As₂O₃ capture behavior of various NMMs through a combination of experiments and density functional theory (DFT) calculations. Pyrolusite (PY, 14.67 mg/g) and Hausmannite (HA, 20.69 mg/g) demonstrate superior adsorption performance compared to conventional adsorbents such as CaO (6.28 mg/g), Al₂O₃ (10.91 mg/g), and Fe₂O₃ (11.45 mg/g). DFT calculations and characterization results confirm that the adsorption of gaseous As₂O₃ by NMMs is primarily governed by chemisorption, with lattice oxygen serving as the key factor influencing the adsorption process. Surface oxygen sites on HA and PY serve as the primary active sites for As₂O₃ adsorption, where As₂O₃ forms stable covalent bonds with HA and PY. During the adsorption of gaseous As₂O₃, lattice oxygen is gradually consumed, while Mn facilitates the oxidation of arsenic. The findings of this study suggest that certain NMMs can efficiently capture gaseous As₂O₃ from high-temperature industrial flue gas, laying the foundation for the large-scale industrial application of adsorption-based As₂O₃ removal methods.