Potassium mercury nitrate loaded silica gel (K2Hg(NO3)4@SiO2) for high-efficiency capture of radioiodine from spent fuel reprocessing off-gas

Silver-based adsorbents have demonstrated exceptional performance in capturing gaseous radioactive iodine from nuclear fuel reprocessing plants. However, their widespread industrial applications have been hindered by high costs. In this paper, K 2 Hg(NO 3 ) 4 @SiO 2 was first studied to trap gaseous iodine, which was synthesized by hydrothermal reaction, impregnation treatment and drying processing. K 2 Hg(NO 3 ) 4 was used as the adsorption active sites and was uniformly dispersed in the silica gel. The static adsorption capacities of K 2 Hg(NO 3 ) 4 @SiO 2 for I 2 and CH 3 I were 253.5 ± 2.3 mg/g and 257.7 ± 5.4 mg/g, respectively. The dynamic adsorption capacities of K 2 Hg(NO 3 ) 4 @SiO 2 were 200.2 mg/g and 131.3 mg/g at the inlet concentrations of 20.0 ± 0.5 mg/L and 5.2 ± 0.2 mg/L of I 2 , respectively. Furthermore, the dynamic adsorption capacities of K 2 Hg(NO 3 ) 4 @SiO 2 were 198.2 mg/g and 127.7 mg/g at the inlet concentrations of 7.6 ± 0.3 mg/L and 2.8 ± 0.2 mg/L of CH 3 I, respectively. The adsorption mechanistic analyses revealed that the I 2 was primarily captured through the formation of HgI 2 and Hg(IO 3 ) 2 , while the CH 3 I was predominantly captured in the form of HgI 2 . Regarding stability, K 2 Hg(NO 3 ) 4 @SiO 2 exhibited excellent stability in environments with strong oxidizing, strong radiation and high temperatures. More importantly, the cost of K 2 Hg(NO 3 ) 4 @SiO 2 was less than one-third that of silver-based adsorbents. Generally, the K 2 Hg(NO 3 ) 4 @SiO 2 gained advantages in adsorption performance and application cost, which was a promising alternative to silver-based adsorbents.