The U.S. Department of Energy is looking into alternative sorbents for the removal of radioiodine from off-gas streams in a used nuclear fuel reprocessing plant. One class of sorbents considered are bismuth-functionalized silica aerogels which offer an efficient capture of iodine from off-gas streams and are environmentally friendly and lower cost when compared to silver-functionalized sorbents.
Two types of bismuth-functionalized silica aerogels were successfully manufactured using a hierarchical synthesis approach:1) The Bi3+-aerogel with bismuth oxide nitrate hydroxide hydrate particles and 2) Bi-aerogel with bismuth metal and bismuth sulfide nanoparticles. Both sorbents exhibited high sorption capacity for iodine. However, presence of particles of different composition, size, and distribution on aerogel support resulted in different iodine loadings. The Bi3+-aerogel exhibited sorption capacity of 289 mg/g. In contrast, Bi-aerogel exhibited more that 20% higher sorption capacity. The heat-treatment of Bi3+-aerogel at 225? under hydrogen atmosphere increased iodine loading capacity to 351 mg/g.