Unraveling the role of carbon coating on CoSe2 to enhance elemental mercury removal from smelting flue gas

Metal selenides have been demonstrated as promising Hg0 adsorbents, while their poor high temperature activity impedes their application feasibility in non-ferrous smelting flue gas. Herein, highly well-dispersed CoSe2 nanoparticles were immobilized on the inner of carbon layer via an in-situ carbon coating strategy, consequently demonstrating improved Hg0 removal performance. Compared to CoSe2, CoSe2/NC exhibited remarkably higher mercury removal activity, which may be attributed to more active sites (Co3+, Se2-2 ) exposed between carbon interfaces and CoSe2. More significantly, CoSe2/NC with a moderate carbonization temperature of 500 degrees C could maintain its stable Hg0 removal activity at a wide operating temperature range (60-240 degrees C). The saturation adsorption capacity of CoSe2/NC-500 could achieve 510.48 mg center dot g-1 at 180 degrees C. The outstanding adsorption activity at elevated temperature is mainly attributed to the thermostability of active Se species immobilized in the carbon layer by both space constraint and chemical interaction, leading to the enhanced mercury diffusion migration energy barrier from 0.41 to 0.79 eV on CoSe2. The present study aims to take an important step toward the rational design of selenium-based adsorbents for mercury removal from nonferrous smelting flue gas through the excellent protective properties of carbon coating.