Coordinatively Unsaturated Selenides over CuFeSe₂ toward Highly Efficient Mercury Immobilization

Abstract

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.

Sequential Capture of Gaseous Hg0 in Flue Gas and Aqueous Hg2+ in Desulfurization Solution by Cu–ZnS: Mechanisms, Kinetics, and Its Application in Hg Recovery as a Supplement of Selective Catalytic Reduction + Wet Flue Gas Desulfurization

“…According to eq , the rate of Cu–ZnS for aqueous Hg 0 capture (i.e., η) can be described as η = prefix− normald [ Hg ( g ) 0 ] normald t = prefix− normald [ Hg ( aq ) 0 ] normald t = prefix− normald [ Hg ( ad ) 0 ] normald t = k 4 [ Hg ( ad ) 0 ] false[ CuS false] α where k 4 , [Hg 0 (aq) ], [Hg 0 (ad) ], and α are the kinetic constant of eq , concentrations of aqueous Hg 0 and Hg 0 physically adsorbed on Cu–ZnS, and reaction order of eq with respect to [CuS], respectively. Due to the low solubility of gaseous Hg 0 in the desulfurization solution, aqueous Hg 0 rapidly reached saturation, resulting in a constant of [Hg 0 (aq) ]. As there was a linear relationship between [Hg 0 (ad) ] and [Hg 0 (aq) ], eq was re-written as η = k 4 λ [ Hg ( aq ) 0 ] false[ CuS false] α ...…”

“…According to eq 2, the rate of Cu−ZnS for aqueous Hg 0 capture (i.e., η) can be described as ) where k 4 [Hg 0 (aq) ], [Hg 0 (ad) ], and α are the kinetic constant of eq 2, concentrations of aqueous Hg 0 and Hg 0 physically adsorbed on Cu−ZnS, and reaction order of eq 2 with respect to [CuS], respectively. Due to the low solubility of gaseous Hg 0 in the desulfurization solution, 47 aqueous Hg 0 rapidly reached saturation, resulting in a constant of [Hg 0 (aq) ]. As there was a linear relationship between [Hg 0 (ad) ] and [Hg 0 (aq) ], eq 16 was re-written as ) where λ is partition coefficient of Hg 0 between aqueous solution and the sorbent.…”

Simultaneous Adsorption of Gaseous Hg0 and Hg(II) by Regenerable Monolithic FeMoSx/TiO2: Mechanism and its Application in the Centralized Control of Hg Pollution in Coal-Fired Flue Gas

“…The other path is to convert Hg 0 to Hg p by injecting sorbents (mainly activated carbon, ACI) upstream of the ESPs, which are then removed by ESPs with particulate matter. ,− Because the spent sorbents are difficult to recover from the mixture with fly ash for recycling, the cost of ACI+ESP to control Hg emissions is relatively high . Additionally, most of the Hg 0 in CFG is transformed into fly ash.…”

Structure-Directing Role of Support on Hg0 Oxidation over V2O5/TiO2 Catalyst Revealed for NOx and Hg0 Simultaneous Control in an SCR Reactor

“…Mercury (Hg) caused various kinds of harmful impacts on human health and biological systems due to its high toxicity and bioaccumulation. − In general, mercury exists in the flue gas in three forms of particle-bound mercury (Hg p ), oxidized mercury (Hg 2+ ), and elemental mercury (Hg 0 ) . Among these mercury-containing compounds, it is extremely difficult to remove Hg 0 by currently available air pollution control devices (APCDs), due to its high volatility and insolubility in water. , To date, several technologies have been successfully developed for Hg 0 control, such as adsorption, − catalytic oxidation, , and photochemical oxidation . Among these, catalytic oxidation of Hg 0 in selective catalytic reduction (SCR) system has proven to be the most economic technology, as which a low-cost option for control of mercury can be achieved by this co-benefit of SCR installation. − Notably, the use of suitable catalysts could effectively promote the Hg 0 oxidation …”

“…4 Among these mercury-containing compounds, it is extremely difficult to remove Hg 0 by currently available air pollution control devices (APCDs), due to its high volatility and insolubility in water. 5,6 To date, several technologies have been successfully developed for Hg 0 control, such as adsorption, 7−9 catalytic oxidation, 10,11 and photochemical oxidation. 12 Among these, catalytic oxidation of Hg 0 in selective catalytic reduction (SCR) system has proven to be the most economic technology, as which a low-cost option for control of mercury can be achieved by this co-benefit of SCR installation.…”