Self-Constructing 100% Water-Resistant Metal Sulfides through In Situ Acid Etching for Effective Elemental Mercury...

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg⁰), and realize environmental remediation. However, there is still a critical problem challenging the extensive application of MSs in related areas, i.e., how to self-regulate their water (H₂O) resistance without complexing the sorbent preparation procedure. This work for the first time developed an in situ acid-etching method that self-engineered the water affinity of MSs through changing the interfacial interaction between MSs and Hg⁰/H₂O. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved H₂O resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (S^2-) that stabilized Hg⁰ via a bridging bond and repelled H₂O, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg⁰ over H₂O. The MSs exhibited 100% H₂O resistance even in the presence of 20% H₂O, which is much higher than the H₂O concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of H₂O on MSs through a self-regulating way that is scalable and negligibly complexes the sorbent preparation pathway. The highly water-resistant and cost-effective MSs as prepared can serve as efficient Hg⁰ removal from industrial flue gas in the future.