Resource recovery from iodine-containing silver-loaded silica gel: Recycling of silver and immobilization of iodine

Silver-loaded silica gel is widely used in spent fuel reprocessing plant due to its high adsorption efficiency of iodine and low influence of humidity and NO_x. This study proposed a novel method for the disposal of iodine-loaded silver-silica gel. The elution of iodine using Na₂S solution, the leaching of silver through HNO₃ solution. Subsequently, Zero-valent silver was synthesized via reduction of Ag⁺ with NaBH₄ to recover silver. Additionally, the eluted iodide ions were transformed into iodosodalite and then combined with borosilicate glass powder for secondary immobilization. The results demonstrated that the elution efficiency of Na₂S was 99.03 %, the leaching efficiency of HNO₃ was 99.20 %, and the recovery efficiency of Ag reached 86.93 %. The iodine static saturated adsorption capacity of the silver-loaded silica gel prepared using recycled silver was 129.95 ± 3.46 mg/g, higher than original silver-loaded silica gel. In addition, the secondary immobilization body had a dense structure. The iodine leaching rate was 1.2 × 10⁻⁴ g$\cdot$m⁻²$\cdot$d⁻¹, which showed a good chemical stability. This work successfully realized the recycling of silver in iodine-containing silver-loaded silica gel and the safe disposal of iodine, which can provide new ideas for the disposal of iodine waste in spent fuel reprocessing plant.