Co9S8 nanoparticles-embedded porous carbon: A highly efficient sorbent for mercury capture from nonferrous smelting flue gas

Highlights: • Co₉S₈ anchored porous carbon is developed for Hg⁰ recovery from smelting flue gas. • Co₉S₈-PC shows better Hg⁰ capture ability than Co_1−xS/Co₃S₄ embedded porous carbon. • Hg⁰ adsorption mechanism is revealed by experimental analysis and kinetic study. In this study, a novel Co₉S₈ nanoparticles-embedded porous carbon (Co₉S₈-PC) was designed as an effective reusable sorbent for Hg⁰ capture from smelting flue gas. Some flue gas components can create more active sites on Co₉S₈-PC for Hg⁰ adsorption, but compete with Hg⁰ for the same sulfur sites over nano Co_1−xS/Co₃S₄ (CoS) and Co_1−xS/Co₃S₄ embedded porous carbon (CoS-PC), which can be ascribed to the difference in crystal structure between Co₉S₈ and Co_1−xS/Co₃S₄. Therefore, Co₉S₈-PC shows much better Hg⁰ capture ability than CoS and CoS-PC under smelting flue gas. O₂, SO₂ and HCl improve Hg⁰ adsorption on Co₉S₈-PC mainly through creating Co³⁺ site, but H₂O has neglectable effect on Hg⁰ capture. Co₉S₈-PC shows a remarkably large Hg⁰ adsorption capacity of 43.18 mg/g, which is greatly higher than the representative metal sulfides for Hg⁰ removal from smelting flue gas. During Hg⁰ adsorption, Co³⁺ is the primary site to directly interact with Hg⁰, and the adsorbed mercury exists as HgS. Co₉S₈-PC exhibits an excellent recyclability for capturing Hg⁰, which is mainly assigned to the replenishment of consumed Co³⁺ site by O₂, SO₂ and HCl. Therefore, Co₉S₈ nanoparticles-embedded porous carbon is an efficient, sustainable and highly recyclable sorbent for Hg⁰ recovery from smelting flue gas.