Highly efficient capture of iodine vapor by [Mo₃S₁₃]^2- intercalated layered double hydroxides

From the swollen LDH, bulky [Mo₃S₁₃]^2- anions are facilely introduced into the LDH interlayers to assemble the Mo₃S₁₃-LDH composite, which exhibits excellent iodine capture performance and good irradiation resistance. The positive-charged LDH layers may disperse the [Mo₃S₁₃]^2- uniformly within the interlayers, providing abundant adsorption sites for effectively trapping iodine. The Mo-S bond serving as a soft Lewis base has strong affinity to I₂ with soft Lewis acidic characteristic, which is conducive to improvement of iodine capture via physical sorption. Besides, chemisorption has a significant contribution to the iodine adsorption. The S₂^2-/S^2- in [Mo₃S₁₃]^2- can reduce the I₂ to [I₃]^- ions, which are facilely fixed within the LDH gallery in virtue of electrostatic attraction. Meanwhile, the S₂^2-/S^2- themselves are oxidized to S₈ and SO₄^2-, while Mo⁴⁺ is oxidized (by O₂ in air) to Mo⁶⁺, which combines with SO₄^2- forming amorphous Mo(SO₄)₃. With the collective interactions of chemical and physical adsorption, the Mo₃S₁₃-LDH demonstrates an extremely large iodine adsorption capacity of 1580 mg/g. Under γ radiation, the structure of Mo₃S₁₃-LDH well maintains and iodine adsorption capability does not deteriorate, indicating the good irradiation resistance. This work provides an important reference to tailor cost-effective sorbents for trapping iodine from radioactive nuclear wastes.