Bimetallic sulfides ZnIn₂S₄ modified g-C₃N₄ adsorbent with wide temperature range for rapid elemental mercury uptake from coal-fired flue gas

The mercury pollution from coal-fired power plants posed huge threatens to the human health and the ecological environment. Here, a new type of bimetallic sulfide ZnIn2S4 modified g-C3N4 adsorbent have been prepared for capturing Hg-0 under wide temperature ranges (80-400 degrees C). When the weight percentage of ZnIn2S4 was 40 wt%, the as-synthesized 40ZIS/CN composite exhibited excellent Hg-0 adsorption performance. Although the efficiency decreased after 8 h of adsorption, it could still remain at the efficiency of about 81.0%, revealing a stable cycle life. The influences of flue gas components were studied, and it is found that the presence of NO, SO2 and H2O has little effects on the mercury removal performance. The adsorption capacity of the prepared 40ZIS/CN adsorbent is as high as 13.04 mg.g(-1). Density functional theory (DFT) was used to investigate the interactions between Hg-0 and the ZnIn2S4 (1 1 0) surface. The results show that chemical adsorption was the main reason for the adsorption of Hg-0 on ZnIn2S4 (1 1 0) surface. The formation of Hg-S bonds was demonstrated by depicting the projected densities of states profiles. XPS and Hg-TPD analysis further proved that adsorbed Hg-0 is converted into stable HgS through active sulfur sites on the surface. Therefore, this work not only proved that 40ZI5/CN is a promising material for Hg-0 removal from coal-fired flue gas, but also can guide the future development of multi-component sulfide modified materials for mercury pollution remediation from various industrial flue gases.