Sulfur Dioxide Promoted Mercury Fast Deposition over a Selenite-Chloride-Induced Surface from Wet Flue Gas.

Abstract

Gaseous elemental mercury (Hg0) extraction from industrial flue gases is undergoing intense research due to its unique properties. Selective adsorption that renders Hg0 to HgO or HgS over metal oxide- or sulfide-based sorbents is a promising method, yet the sorbents are easily poisoned by sulfur dioxide (SO2) and H2O vapor. The Se-Cl intermediate derived from SeO2 and HCl driven by SO2 has been demonstrated to stabilize Hg0. Thus, a surface-induced method was put forward when using γ-Al2O3 supported selenite-chloride (xSeO32--yCl-, named xSe-yCl) for mercury deposition. Results confirmed that under 3000 ppm SO2 and 4% H2O, Se-2Cl exhibited the highest induced adsorption performance at 160 °C and higher humidity can accelerate the induction process. Driven by SO2 under the wet interface, the in situ generated active Se0 has high affinity toward Hg0, and the introduction of Cl- enabled the fast-trapping and stabilization of Hg0 due to its intercalation in the HgSe product. Additionally, the long-time scale-up experiment showed a gradient color change of the Se-2Cl-induced surface, which maintained almost 100% Hg0 removal efficiency over 180 h with a normalized adsorption capacity of 157.26 mg/g. This surface-induced method has the potential for practical application and offers a guideline for reversing the negative effect of SO2 on gaseous pollutant removal.