Favorably adjusting the pore characteristics of copper sulfide by template regulation for vapor-phase elemental mercury immobilization

Abstract

Use of copper sulfide (CuS) is an effective solution to address the ecosystem concerns about mercury under the restriction of the Minamata Convention on Mercury, and to mitigate the intensive elemental mercury (Hg⁰) pollution worldwide. However, the method to further enhance the Hg⁰ capture performance of CuS remains to be developed due to its inherently dense structure that is unfavorable for the mass transfer of Hg⁰. To effectively overcome this critical challenge, a novel template regulation method is proposed in this paper to synthesize CuS under mild conditions, in which the abundance of active ligand and the integrity of pore structure are rationally and optimally traded off. The as synthesized CuS-based sorbent was mainly composed of homogenous hexagonal CuS nanocrystals that form hierarchical channels and promote the mass transfer of Hg⁰. Thus, it exhibited the Hg⁰ adsorption capacity and uptake rate reaching as high as 208.5 mg g⁻¹ and 97.3 μg g⁻¹ min⁻¹, respectively, both of which ranked first compared to all the metal sulfides (MSs) reported in previous studies. The polysulfide (S_x²⁻) with a rich abundance and high accessibility was found to be the ligand which could primarily account for the conversion and immobilization of Hg⁰ over the surface of template-regulated CuS. The goal of this work was not only to extend the performance enhancement of the MSs, but also to inspire further exploration for the cost-effective application of structurally-favorable MSs for Hg⁰ capture from anthropogenic sources.