High-efficient adsorption and removal of elemental mercury from smelting flue gas by cobalt sulfide

Nonferrous metal smelting produces a large amount of Hg⁰ in flue gas, which has caused serious damage to the environment and human health. In this work, amorphous cobalt sulfide was synthesized by a liquid-phase precipitation method and was used for capturing gaseous Hg⁰ from simulated smelting flue gas at low temperatures (50~150 °C). In the adsorption process, Hg⁰ can be transformed into the stable mercury compound, which is confirmed to be HgS by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of Hg (Hg-TPD) analysis. Meanwhile, XPS results also demonstrate that S₂^2- species on the surface of cobalt sulfide play an important role in Hg⁰ transformation. At the temperature of 50 °C (inlet Hg⁰ concentration of 214 μg·m^-3), the Hg⁰ adsorption capacity of cobalt sulfide (penetration rate of 25%) is as high as 2.07 mg·g^-1, which is much higher than that of popular adsorbents such as activated carbons and metal oxides. In addition, it was found that the Hg⁰ removal efficiency by cobalt sulfide in the flue gas with high concentration of SO₂ (5%) remained more than 94%. The good adsorption and Hg⁰ removal performance guarantee cobalt sulfide the great superiority and application potential in the treatment of Hg⁰ in smelting flue gas with high concentration of SO₂.