Coordinative sulfur site over flower-structured MoS2 for efficient elemental mercury uptake from coal-fired flue gas

Metal sulfides have recently been considered as promising options for mercury removal owing to their large number of active sulfur sites, environmental friendliness, morphological diversity, resistance to high concentrations of sulfur dioxide, high activity and low cost. Herein, due to the strong affinity between Hg and S, MoS2 was selected to adsorb Hg0 from coal-fired flue gas in power plants. The mercury removal experiments indicate that compared with ZnS, CuS and SnS, MoS2 has the strongest ability to remove elemental mercury. The effects of different adsorption temperatures and different gas components (O2, NO, SO2) and other reaction conditions on the removal performance of Hg0 were further discussed. It was found that the presence of O2, NO or SO2 had no significant effect on the removal of Hg0 by MoS2. Thanks to the abundant edge unsaturated sulfur sites, the flower-like MoS2 not only exhibits good sulfur resistance, but also has excellent long-term stable properties. The equilibrium adsorption capacity of MoS2 is 54.308 mg g−1, and the initial adsorption rate is 66.79 μg g−1 min−1. It is better than most metal sulfide adsorbents, in which the equilibrium adsorption capacity is 24 times that of sulfur modified activated carbon (S-AC), and the initial adsorption rate is 133 times that of S-AC. Moreover, density functional theory (DFT) calculations proved that elemental mercury was chemically adsorbed on surface of MoS2 nanosheets, forming stable HgS. This work can promote the proper design and innovation of adsorbent materials and achieve fruitful treatment of environmental pollutants.