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

Abstract

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 Co1−xS/Co3S4 (CoS) and Co1−xS/Co3S4 embedded porous carbon (CoS-PC), which can be ascribed to the difference in crystal structure between Co9S8 and Co1−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.