3D hierarchical iron-cobalt sulfide anchored on carbon fiber with abundant active short chain sulfur for high-efficiency capture of elemental mercury

[Display omitted] •A 3D structure FexCo(1-x)Sy@CF adsorbent consisting of cobalt-iron sulfide anchored on carbon fiber was purposefully synthesized.•The as-prepared Fe0.5Co0.5Sy@CF sorbent exhibits the best performance for Hg0 capture performance.•The spent FexCo(1-x)Sy@CF adsorbents display excellent recycling performance.•A reasonable proportion of Fe and Co benefits the formation of active short chain sulfur S22-. Developing a cost-effective and environmentally friendly strategy for elemental mercury (Hg0) entrapment from industrial flue gas becomes an urgent need to smoothly fulfil the Minamata Convention on Mercury. The conversion of gaseous Hg0 into stable mercury species using low-cost and recyclable materials has been a consensus. Herein, a novel 3D structure adsorbent, consisting of hierarchical cobalt-iron sulfide anchored on carbon fiber (FexCo(1-x)Sy@CF), was purposefully synthesized to provide a practicable support for efficient capture of Hg0. Benefiting from the hierarchical structure and synergistic effects between Fe and Co bimetal, the prepared Fe0.5Co0.5Sy@CF sorbent exhibits the best performance for Hg0 immobilization. Approximately 100% of Hg0 can be removed even under extreme conditions with SO2 concentration and gas hourly space velocity as high as 1.5% and 398000 h−1, respectively. The average Hg0 capture rate and adsorption capacity reached over 2.5 μg/g/min and 45.6 mg/g, respectively, which are much higher than previously reported metal sulfides and carbon material. The recycle experiment for Hg0 entrapment indicated that Fe0.5Co0.5Sy@CF could be efficiently regenerated and reused, adequately reflecting its potential application value. Bimetallic Fe/Co sulfide with a reasonable proportion benefits the formation of active short chain sulfur S22- which plays a crucial role in the immobilization of Hg0. Meanwhile, the final product is stable HgS that has negligible environmental toxicity. This work provides a practical and yet easy-to-adopt strategy for mercury pollution control, while opening a new avenue to realize the resource utilization toward toxic elements.