Mercury-Bismuth co-modified Silica gel for gaseous radiodine capture

The silver-based materials are widely used in nuclear fuel reprocessing plant for iodine capture. They are powerful but expensive. In this paper, the mercury-bismuth co-modified silica gel (Hg-Bi-Silica gel) was studied and tried to displace the silver-based materials. Firstly, the Hg-Bi-Silica gel was prepared through activating, impregnating and drying. Mercury and bismuth existed as Hg(OH)NO 3 and [Bi 6 O 5 (OH) 3 ](NO 3 ) 5 ·2H 2 O in Hg-Bi-Silica gel, respectively. Secondly, the iodine adsorption performances of Hg-Bi-Silica gel were investigated. The static trapping capacity of I 2 and CH 3 I was 209.1 ± 1.7 mg/g and 151.0 ± 6.9 mg/g, respectively, which was better than that of the commercial silver-based materials (148.6 ± 3.5 mg/g and 132.7 ± 3.0 mg/g). The dynamic adsorption efficiency of CH 3 131/127 I was 99.996 %, which was closed to that of the commercial silver-based materials (99.990 %). Thirdly, the possible mechanism for iodine capture in the Hg-Bi-Silica gel system was proposed. I 2 was captured by Hg-Bi-Silica gel mainly in the form of HgI 2 and Hg(IO 3 ) 2 , however, CH 3 I was captured by Hg-Bi-Silica gel mainly in the form of HgI 2 . Furthermore, [Bi 6 O 5 (OH) 3 ](NO 3 ) 5 ·2H 2 O was cooperated with Hg(OH)NO 3 on capturing iodine. Finally, the stabilities of Hg-Bi-Silica gel were evaluated. The Hg-Bi-Silica gel showed excellent thermal stability, NO x -corrosion resistance and irradiation resistance. In summary, the more cost-effective Hg-Bi-Silica gel was a potential effective substitution of silver-based materials.