Self-Constructing 100% Water-Resistant Metal Sulfides through In Situ Acid Etching for Effective Elemental Mercury (Hg 0 ) Capture.

Metal sulfides (MSs) can efficiently entrap thiophilic components, such as elemental mercury (Hg 0 ), 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 (H 2 O) 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 0 /H 2 O. The introduction of abundant, undercoordinated sulfur onto the sorbent surface was the primary reason accounting for the significantly improved H 2 O resistance. The high surface coverage of undercoordinated sulfur induced the formation of polysulfur chains (S x 2- ) that stabilized Hg 0 via a bridging bond and repelled H 2 O, attributed to the favorable electron configurations. These properties made the surface of MSs highly hydrophobic and increased the adsorption selectivity toward Hg 0 over H 2 O. The MSs exhibited 100% H 2 O resistance even in the presence of 20% H 2 O, which is much higher than the H 2 O concentration under most practical scenarios. From these perspectives, this work for the first time overcame the detrimental effects of H 2 O 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 0 removal from industrial flue gas in the future.