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

Abstract

Gaseous elemental mercury (Hg 0 ) extraction from industrial flue gases is undergoing intense research due to its unique properties. Selective adsorption that renders Hg 0 to HgO or HgS over metal oxide-or sulfide-based sorbents is a promising method, yet the sorbents are easily poisoned by sulfur dioxide (SO 2 ) and H 2 O vapor. The Se-Cl intermediate derived from SeO 2 and HCl driven by SO 2 has been demonstrated to stabilize Hg 0 . Thus, a surface-induced method was put forward when using γ-Al 2 O 3 supported selenite-chloride (xSeO 3 2− -yCl − , named xSe-yCl) for mercury deposition. Results confirmed that under 3000 ppm SO 2 and 4% H 2 O, Se-2Cl exhibited the highest induced adsorption performance at 160 °C and higher humidity can accelerate the induction process. Driven by SO 2 under the wet interface, the in situ generated active Se 0 has high affinity toward Hg 0 , and the introduction of Cl − enabled the fast-trapping and stabilization of Hg 0 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% Hg 0 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 SO 2 on gaseous pollutant removal. KEYWORDS: high concentrations of SO 2 and H 2 O, fast-trapping of Hg 0 , selenite-chloride surface, induced adsorption, stability