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

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg), 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 (HO) 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 Hg/HO. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved HO resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (S) that stabilized Hg via a bridging bond and repelled HO, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg over HO. The MSs exhibited 100% HO resistance even in the presence of 20% HO, which is much higher than the HO concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of HO 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 Hg removal from industrial flue gas in the future.