Silver Sulfide and Silver Sulfate as Aging Byproducts and Adsorbents for Gaseous Iodine Capture in Spent Nuclear Fuel Reprocessing

While it is considered a promising adsorbent for radioiodine capture in spent nuclear fuel reprocessing off-gas, silver functionalized silica aerogel (Ag⁰-aerogel) experiences a capacity loss when exposed to other off-gas components (O₂, H₂O, NO, and NO₂) through a process known as aging. Ag₂S and Ag₂SO₄ were identified as major byproducts of aging, but their impact on iodine adsorption remains unclear. Thus, to further investigate aging, we loaded Ag₂S and Ag₂SO₄ powders with molecular iodine (I₂) at 150 °C and characterized their properties. The I₂ adsorption capacity of Ag₂SO₄ was 0.12 wt % after 72 h, suggesting its formation directly reduces the capacity of the Ag⁰-aerogel. Conversely, Ag₂S had an iodine capacity of 86.8 wt % and near total Ag utilization after 240 h. Given its high capacity and availability, we evaluated the feasibility of Ag₂S as an I₂ adsorbent in future applications. Finally, several drawbacks need to be overcome, including the relatively slow uptake rate, potential emission of another hazardous byproduct (SO₂), and potential aging effects (e.g., Ag₂S conversion to Ag₂SO₄) before Ag₂S can be applied for the radioiodine capture process.