Highly Radioiodine Gas Capture by 2-Mercaptobenzimidazole-functionalized Bi/Mg Oxide and Effective Iodine Waste Immobilization by Etidronic-Bi2O3 Complex.

Abstract

The present work prepared a novel BiMgO-2MBD (X=0.42) material for iodine vapor capture in temperature conditions related to spent nuclear fuel reprocessing and nuclear accidents. BiMgO-2MBD (X=0.42) was synthesized by a solvothermal process and exhibited an exceptional ultrafast and high iodine uptake with a capacity of 4352.12mg/g and 5147.08mg/g after 5h at 75oC and 150oC, respectively. The TGA analysis shows that Bi/Mg oxide substrate highly contributed to improving the thermal stability of the functionalized BiMgO-2MB (X=0.42) as indicated by the weight losses of the material components of 3.77wt %, 29.32wt %, and 97.72wt %, respectively for Bi/Mg oxide, BiMgO-2MBD, and 2-MBD. The material characterization and DFT calculations indicate that 2-MBD played a significant role towards improving iodine capture capacity. For long-term and safe waste disposal, a chemically durable waste form was made from etidronic acid and Bi2O3, and successfully immobilized the iodine-loaded wastes (I2@BiMgO-2MBD) which exhibited a low normalized leaching rate of 1.098×10-6g.m2/day for 7 days under the PCT-A method. In addition, BiMgO-2MBD (X=0.42) showed an ability to be reused after several regeneration cycles. The comparison with previously reported materials shows that the current BiMgO-2MBD (X=0.42) is the first functionalized metal oxide comparable to metal-organic and covalent organic frameworks for iodine uptake. BiMgO-2MBD (X=0.42) shows promising results for practical applications in the gas phase capture of radioactive iodine. Environmental ImplicationDuring nuclear fuel reprocessing activities, volatile radioactive iodine is released into the environment, reaches humans via bioaccumulation, and poses serious health problems. Therefore, designing materials with fast and high iodine capture capacity is of great importance to counteract its toxicological effects. Since the long-lived 129I is highly mobile, it is important to prevent its release into water bodies after its capture. Bismuth oxide –based materials have been suggested as effective materials to immobilize volatile iodine through chemisorption. However, additional techniques are required for immobilization synergy. In this regard, this work also provides an effective material for post-sorption waste immobilization.