[Sn2S6]4- Anion-Intercalated Layered Double Hydroxides for Highly Efficient Capture of Iodine

The development of low-cost and high-efficiency iodine sorbents is of great significance for the control of nuclear pollution. In this work, we intercalate the tin sulfide cluster of [Sn2S6](4-) to Mg/Al-type layered double hydroxides to obtain Sn2S6-LDH, which exhibits highly efficient capture performance of iodine vapor and iodine in solutions. The dispersion effect of the positively charged LDH layers contributes to the adequate exposure of [Sn2S6](4-) anions, providing plentiful adsorption sites. For iodine vapor, Sn2S6-LDH showed an extremely large iodine capture capacity of 2954 mg/g with a large contribution from physisorption. For iodine in solutions, a significantly large sorption capacity of 1308 mg/g was achieved. During iodine capture, I-2 molecules were reduced to I- ions (by S2- in [Sn2S6](4-)), which then reacted with Sn4+ to form SnI4, where the molar amount of captured iodine is 4-fold that of Sn. Besides, the as-reduced I- combined with I-2 again to generate [I-3](-), which then entered the LDH interlayers to maintain electric neutrality. While reducing iodine, S2- itself in [Sn2S6](4-) was oxidized to S-8, which further combined with SnI4 to form a novel compound of SnI4(S-8)(2). The excellent iodine capture capability endows Sn2S6-LDH with a promising application in trapping radioactive iodine.

Automated summary

The development of low-cost and high-efficiency iodine sorbents is essential for nuclear pollution control. In this study, we intercalated the tin sulfide cluster of [Sn2S6](4-) into Mg/Al-type layered double hydroxides to obtain Sn2S6-LDH, which exhibited highly efficient capture performance for iodine in both vapor and solution forms. The adsorption capacity of Sn2S6-LDH for iodine vapor reached 2954 mg/g, mainly through physisorption, while the sorption capacity for iodine in solutions achieved a significantly large value of 1308 mg/g. During iodine capture, the reduction of I-2 molecules to I- ions by S2- in [Sn2S6](4-) led to the formation of SnI4, where the amount of captured iodine was four times that of Sn. The excellent iodine capture capability of Sn2S6-LDH makes it a promising material for trapping radioactive iodine.