Effective Capture and Immobilization of Hg⁰ from Flue Gas Using a Novel Selenium-Functionalized SrFeO_3-δ/HNTs Half-Metal Composite: Adsorption, Photocatalytic Oxidation, and Mechanism

Abstract

One novel/multifunctional selenium-doped SrFeO3‑δ/HNTs composite was fabricated and used for immobilization of gaseous mercury. The composite showed excellent performances for Hg0 removal via adsorption coupled with photocatalytic oxidation in visible-light conditions. The adsorption capacity of 4271.15 μg·g–1, rate of 5.0 μg·g–1·min–1, and removal efficiency of ∼100% were obtained under N2+O2, which was further confirmed by reaction kinetics. SrFeO3‑δ was selenized into iron diselenide and a Se–Fe bond with high affinity toward Hg0. In addition, the yielding of •O2 – and the separation of photoexcited electrons and holes (h+) promoted the photocatalytic oxidation of mercury. The composite with intrinsic magnetism could be easily recycled for reuse by magnetic separation. Moreover, the composite possessed favorable tolerance to the complicated flue gas. An online lab-built thermal decomposition system demonstrated that the immobilized Hg was primarily HgSe, which exhibited very high stability and low toxicity. Density functional theory (DFT) calculations proved that the composite was half metal with magnetism, indicating that Hg on Se-SrFeO3‑δ/HNTs formed the stable structure releasing 1.055 eV. The doping of selenium promoted the charge transfer between O (2p) and Hg (6s), which also favored Hg0 removal. Se-SrFeO3‑δ/HNTs with recyclability possess great potentials for Hg0 efficient removal and immobilization/detoxification from flue gas.

Microwave Enhanced Solidification of Gaseous Mercury from Flue Gas by a Novel Selenium Functional FeCo-LDH Based Halloysite Adsorbent

“…The new peak at 53.9 eV was generated after reaction under microwaves, which was attributed to the yielding of HgSe. 16 This phenomenon proved that the immobilization efficiency for Hg 0 under microwaves was more excellent than that without microwaves. The binding energy peak at 103.2 eV was ascribed to HgSe, confirming the generation of HgSe in Figure 10d.…”

“…Based on our previous report, Se favored the removal of mercury vapor because of the high binding capacity and affinity between Se and Hg. 16 The FT-IR profiles are displayed in Figure 7a. The vibration and stretching bands at 1021 and 3711 cm −1 were attributed to the OH groups from HNTs.…”

“…3 The total flow rate and sample dose are consistent with precious work. 16 The online detection system (Lumex RA-915M) was employed to detect the inlet and outlet Hg 0 concentration. Before being discharged into the environment, the residual gas was rolled into an absorption solution (2%H 2 SO 4 +0.1%KMnO 4 ).…”

“…15 Among these matrices, materials with nanotube structures (two-dimensional) have excellent performance due to their high electronic conductivity, high surface-volume ratio, and abundant potential anchor sites. 16 Based on the advantages of nanotubes, Liu et al made carbon nanotubes (CNTs) as carriers to prepare CuS 2 /MWCNTs, studying the removal of mercury vapor by experiment and theory calculations. 17 CuS 2 /MWCNTs realized a high mercury removal efficiency.…”

“…The different structure matrices, such as one-dimensional, two-dimensional, and three-dimensional structures, can break the surface energy, which can reduce and release the aggregation of materials, promote the full exposure of active substances, and improve atomic utilization efficiency . Among these matrices, materials with nanotube structures (two-dimensional) have excellent performance due to their high electronic conductivity, high surface-volume ratio, and abundant potential anchor sites . Based on the advantages of nanotubes, Liu et al made carbon nanotubes (CNTs) as carriers to prepare CuS 2 /MWCNTs, studying the removal of mercury vapor by experiment and theory calculations .…”