Impact of ionizing radiation on iodine capture by functionalized mesoporous silica

Abstract

The efficient capture of radioactive iodine is an important challenge for the nuclear industry, in order to prevent risks for the environment and for the health. The use of solid sorbent materials, able to capture significant amounts of iodine and to resist to harsh operating conditions, such as radiation, is then of paramount interest. Here, we have grafted a high surface area mesoporous silica, SBA-15, with the N-[3-(trimethoxysilyl)propyl]ethylenediamine “diamino” ligand. The resulting material is able to capture significant amounts of iodine (around 0.23 g per gram of material) due to a strong interaction between iodine and the lone pairs of the nitrogen atoms. We have also investigated the behavior of this grafted material towards ionizing radiation in order to assess its stability when placed in a radioactive environment. Upon irradiation, radiolysis of the ligand led to H2 production due to preferential cleavage of the N–H bonds, rather than cleavage of C–H bonds, hence forming imine functional groups as evidenced by infrared spectroscopy. After irradiation at the dose of 1 MGy, the thus-modified materials were still able to capture iodine, but in a lower proportion (around 0.11 g per gram of material). This was attributed to the loss of amine groups upon irradiation. Our work shows that these materials are potential candidates for the radioactive iodine capture, as they can be efficient up to doses of the order of 1 MGy.