Journal
JOURNAL OF HAZARDOUS MATERIALS
Volume 387, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jhazmat.2019.121679
Keywords
Hg(II) sampling; SO2 influence; CaO-based trap; Flue gas; DFT
Categories
Funding
- National Key Research and Development Program [2016YFC0201105]
- Graduate Student Research and Innovation Program of Jiangsu Province [KYCX18_0085]
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Reliable gaseous Fig(II) measurement is crucial to mercury emissions control from coal-fired flue gas, but Hg(II) sampling under SO2 condition could probably increase the uncertainty of sorbent traps. CaO-AcS synthesized from calcium acetate and porous support were previously demonstrated to be effective for Hg(II) trapping under SO2-free condition. This work further evaluated SO2 influence on its Hg(II) retention ability via integrating experimental and DFT computational studies. Increased breakthrough rate of HgCl2 was found in a two-section CaO-AcS trap under SO2 conditions. Significant basicity and porosity loss of CaO-AcS were attributed to the formation of agglomerate CaSO3. Hg-0 release from CaO-AcS samples suggested potential reactions between Hg (II) and SO2. The detected HgO and Hg2SO4 species by Hg-TPD in CaO-AcS further confirmed this speculation. Moreover, both competition and reduction effects of SO2 on surface-bound Hg(II) species were substantiated by DFT calculations. SO2 showed a stronger interaction with CaO than HgCl2 because SO2 has a lower LUMO level and can accept electrons easier. Reaction pathways indicated Hg(II) was partially reduced to Hg2SO4 under SO2-deficient condition, or directly reduced to Hg under SO2-rich condition. This work fully proposed the SO2 influence mechanisms and improvement countermeasures for practical gaseous Hg(II) sampling.
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