Coordinatively Unsaturated Selenides over CuFeSe2 toward Highly Efficient Mercury Immobilization

Metal selenides have been demonstrated as promising Hg0 remediators, while their inadequate adsorption rate primarily impedes their application feasibility. Based on the critical role of coordinatively unsaturated selenide ligands in immobilizing Hg0, this work proposed a novel strategy to enhance the Hg0 adsorption rate of metal selenides by magnitudes by purposefully adjusting the selenide saturation. Copper iron diselenide (CuFeSe2), in which the surface reconstruction tended to occur at ambient temperature, was adopted as the concentrator of unsaturated selenides. The adsorption rate of CuFeSe2 reached as high as 900.71 μg·g-1·min-1, far exceeding those of the previously reported metal selenides by at least 1 magnitude. The excellent resistance of CuFeSe2 to flue gas interference and temperature fluctuation warrants its applicability in real-world conditions. The theoretical investigations and mechanistic interpretations based on density functional theory (DFT) calculation further confirmed the indispensable role of unsaturated selenides in Hg0 adsorption. This work aims not only to develop a Hg0 remediator with extensive applicability in coal combustion flue gas but also to take a step toward the rational design of selenide-based sorbents for diverse environmental remediation by the facile surface functionalization of coordinatively adjustable ligands.