TY - JOUR
T1 - Silver-functionalized silica aerogel for iodine capture
T2 - Adsorbent aging by NO2 in spent nuclear fuel reprocessing off-gas
AU - Shen, Ziheng
AU - Wiechert, Alexander I.
AU - Choi, Seungrag
AU - Ladshaw, Austin P.
AU - Tavlarides, Lawrence L.
AU - Tsouris, Costas
AU - Yiacoumi, Sotira
N1 - Publisher Copyright:
© 2022
PY - 2022/5
Y1 - 2022/5
N2 - Silver-functionalized silica aerogel (Ag0-Aerogel) is considered a promising porous adsorbent for the capture of iodine from nuclear fuel reprocessing off-gas. The Ag0-Aerogel, nevertheless, experiences a steady loss of capacity when exposed to NO2 in the off-gas. This phenomenon is known as aging and its governing processes remain unclear. We exposed Ag0-Aerogel samples to 2% NO2 in dry air at 150 °C for up to 1 month, followed by I2 loading. Samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Our results elucidated the precise Ag species in Ag0-Aerogel that adsorb I2: (i) Ag0 nanoparticles, (ii) Ag thiolates (Ag–S-r) covering the nanoparticles and the aerogel backbone, and (iii) Ag–S complexes including amorphous Ag2S. We unraveled the two predominant underlying processes of aging in NO2: (i) Ag–S-r is oxidized by NO2 forming silver sulfonate (Ag–SO3-r) which is oxidized further to silver sulfate (Ag2SO4) molecules, (ii) Ag2SO4 molecules then migrate from the pores to the aerogel surface and aggregate yielding Ag2SO4 particles that do not adsorb I2. Plausible reaction pathways and aggregation mechanisms are explored. These findings may be used to guide the discovery of more advanced materials for iodine capture and the development of accurate predictive models.
AB - Silver-functionalized silica aerogel (Ag0-Aerogel) is considered a promising porous adsorbent for the capture of iodine from nuclear fuel reprocessing off-gas. The Ag0-Aerogel, nevertheless, experiences a steady loss of capacity when exposed to NO2 in the off-gas. This phenomenon is known as aging and its governing processes remain unclear. We exposed Ag0-Aerogel samples to 2% NO2 in dry air at 150 °C for up to 1 month, followed by I2 loading. Samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Our results elucidated the precise Ag species in Ag0-Aerogel that adsorb I2: (i) Ag0 nanoparticles, (ii) Ag thiolates (Ag–S-r) covering the nanoparticles and the aerogel backbone, and (iii) Ag–S complexes including amorphous Ag2S. We unraveled the two predominant underlying processes of aging in NO2: (i) Ag–S-r is oxidized by NO2 forming silver sulfonate (Ag–SO3-r) which is oxidized further to silver sulfate (Ag2SO4) molecules, (ii) Ag2SO4 molecules then migrate from the pores to the aerogel surface and aggregate yielding Ag2SO4 particles that do not adsorb I2. Plausible reaction pathways and aggregation mechanisms are explored. These findings may be used to guide the discovery of more advanced materials for iodine capture and the development of accurate predictive models.
KW - Adsorbent aging
KW - Adsorption
KW - Nuclear fuel reprocessing
KW - Off-gas radioactive iodine
KW - Silver functionalized silica aerogel
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U2 - 10.1016/j.micromeso.2022.111898
DO - 10.1016/j.micromeso.2022.111898
M3 - Article
AN - SCOPUS:85128220228
SN - 1387-1811
VL - 336
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
M1 - 111898
ER -