Co-assembly of SbS₄^3– Anions with Layered Double Hydroxide Nanosheets for Highly Efficient Capture of Gaseous Iodine

The development of highly efficient sorbents to trap iodine from nuclear waste holds immense significance. Dispersion of the NO3– type MgAl layered double hydroxide (LDH) into formamide leads to a swollen phase with LDH nanoscale sheets, thereby providing an opportunity for bulky anions of SbS43– going into the interlayers. The SbS4-LDH nanocomposite assembled via swelling/restoration exhibits excellent sorption performance for iodine vapor. Due to the charge-area matching effect, the positively charged LDH nanosheets may well disperse the negatively charged SbS43– anions, thereby offering abundant capture sites. Based on hard and soft acids and bases (HSAB) theorty, the SbS43– as a soft Lewis base has strong affinity to I2 with a soft Lewis acidic nature. Besides, oxidation–reduction reaction (REDOX) plays an essential role in the fixation of iodine. The S2– ions of SbS43– reduce I2 to I– ions, which then bind with Sb5+, forming SbI5 with an I:Sb molar ratio of 5. The as-reduced I– ions may further combine with I2 to produce a polyiodide ion of I3–, which can be immobilized within the LDH interlayers. Profiting from the collective effect of HSAB, REDOX, and metal iodide formation (MIF), the SbS4-LDH nanostructure demonstrates an extremely large iodine sorption capacity (qm) of 2398 mg/g. This study offers an important reference to tailor highly efficient iodine sorbents for controlling nuclear pollution.