Highly efficient capture of iodine vapor by [MoS] intercalated layered double hydroxides.

From the swollen LDH, bulky [MoS] anions are facilely introduced into the LDH interlayers to assemble the MoS-LDH composite, which exhibits excellent iodine capture performance and good irradiation resistance. The positive-charged LDH layers may disperse the [MoS] 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 I 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 S/S in [MoS] can reduce the I to [I] ions, which are facilely fixed within the LDH gallery in virtue of electrostatic attraction. Meanwhile, the S/S themselves are oxidized to S and SO, while Mo is oxidized (by O in air) to Mo, which combines with SO forming amorphous Mo(SO). With the collective interactions of chemical and physical adsorption, the MoS-LDH demonstrates an extremely large iodine adsorption capacity of 1580 mg/g. Under γ radiation, the structure of MoS-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.