Bismuth-impregnated aluminum/copper oxide-pillared montmorillonite for efficient vapor iodine sorption

AlCu-oxides pillared Montmorillonite (MMN) was synthesized by the ion-exchange reaction and then impregnated by bismuth (Bi) to produce single-phase material (Bi@AlCu-PILC) aiming at vapor iodine (I₂) capture. The resulting Bi@AlCu-PILC mesoporous material demonstrated high capture capacity and thermal stability. The displayed capture capacity, 485 ± 54 mg-I/g-sorbent, was benefited from the strong affinity of Bi to iodine and the pores of the material. The gaseous I₂ was captured chemically by Bi@AlCu-PILC via Bi-O-I and BiI₃ formation in the inner surface of the AlCu-PILC and pillars, respectively. In addition to the chemisorption, molecular I₂ was captured physically in the pores of the material. The stability of the iodine-containing material was investigated by a leaching experiment before and after Bi₂O₃ treatment of the material. Without Bi₂O₃ treatment, Bi@AlCu-PILC-I showed 22.12 mass% iodine losses after exposure to hot aqueous media for 7 days. On the other hand, after the post-sorption treatment at 500 °C, the iodine loss was only 0.75 mass% under similar conditions, indicating the material is stabilized significantly after the treatment. Post-sorption treatment of Bi@AlCu-PILC-I by Bi₂O₃ at high temperature transformed BiI₃ into a more thermally durable form (Bi-O-I). These results indicate that Bi@AlCu-PILC is a promising material for vapor iodine capture and subsequent final disposal.