The emission of off-gas streams from used fuel recycling is a concern in nuclear energy usage as they contain radioactive compounds, such as, 3H, 14C, 85Kr, 131I, and 129I that can be harmful to human health and environment. Radioactive iodine, 129I, is particularly troublesome as it has a half-life of more than 15 million years and is prone to accumulate in human thyroid glands. Organic iodides are hazardous even at very low concentrations, and hence the capture of 129I is extremely important. Dynamic adsorption experiments were conducted to determine the efficiency of sodium mordenite, partially exchanged silver mordenite, and fully exchanged silver mordenite for the removal of methyl iodide present at parts per billion concentrations in a simulated off-gas stream. Kinetic analysis of the system was conducted incorporating the effects of diffusion and mass transfer. The possible reaction mechanism is postulated and the order of the reaction and the values of the rate constants were determined from the experimental data. Adsorbent characterization is performed to investigate the nature of the adsorbent before and after iodine loading. This paper will offer a comprehensive understanding of the methyl iodide behavior when in contact with the mordenites.

The Ag0-containing sorbents synthesized by Na, Al, and Si alkoxides have higher maximum iodine capture capacity and textural properties than zeolite-based Ag0-containing sorbents. However, these sorbents were prepared in the form of granules via a step for cutting cylindrical alcogels. Since asmade sorbents decreased packing density, they must be additionally crushed and then classified into an appropriate size for increasing packing density. The bead formation in the step of sol-gelation could bring about the simplification of sorbent preparation process and an improvement of packing density. In the Na, Al, and Si alkoxides as starting materials, sol solution was hydrophilic and lower density than vegetable oil, which transformed sol droplets to sol-gel beads. Thus, in these precursors, sol droplets, which must be sprayed by single nozzle placed at bottom side of oil column, can rise up through oil column. Acetic acid (HOAc) was used as the catalyst for the hydrolysis of Na alkoxide (TEOS) and gelation of the Na+AlSi-OH alcosol. For obtaining sol-gel beads, experiments were performed by the flowrate change of sol solution and HOAc at different nozzle sizes using soybean oil column of 1 m in length. At a sol/HOAc flowrate ratio of 3.85, some Na+AlSi-OH alcogel beads were obtained. After the Ag/Na ion-exchange, Ag content in Ag+AlSi-OH hydrogel was low due to reaction between Na+ and HOAc during sol-gelation and aging step. The Ag+AlSi-OH hydrogel with high Ag content could be prepared by Na addition. After the solvent exchange and drying at ambient pressure, the bead sorbents had higher Ag0 content and larger pore size than granular sorbents. However, further experiments are needed to increase yield rate in bead sorbent.

Hydrogen-bonded organic frameworks (HOFs) are a new type of porous crystalline material that are constructed by intermolecular hydrogen bonding of organic building blocks to form twodimensional (2D) and three-dimensional (3D) crystalline networks. High-quality HOF single crystals are easily grown for direct superstructure analysis using single crystal X-ray diffraction, which is essential for revealing the relationship between structure and properties. The unique advantages of HOF, such as high crystallinity, porosity and fast regeneration, have allowed it to be used in a variety of applications including catalysis and gas separation. Squaric acid (SQA) is a non-carboxylic, organic acid with proton donor and acceptor ability which is known to take on a variety of coordination modes with metal ions. Pyrazine is a six-membered aromatic heterocycle bearing two nitrogen atoms, which has sp2 hybridized C atoms with C-H hydrogen bonds. This work describes the synthesis and structural characteristics of HOF based on squaric acid and pyrazine. Based on single crystal X-ray diffraction data, this MOF crystallizes in the triclinic P-1 space group. Each asymmetric unit is composed of H2SQ and pyrazine. All squaric acid molecules share one H atom with the N atom of pyrazine molecules. The layer distance between nearby O atoms from squaric acid in different layers equals 5.29 Å. Also, our HOF showed high adsorption capacity the during experiments. The composition and comparative characteristics of HOF are given using SCXRD, PXRD, SEM and UV-vis.

The Na, Al, and Si akoxides-based sorbents for iodine capture have higher maximum iodine capture capacity and pore properties than zeolite-based sorbents. However, these sorbents were prepared in the form of granules via a step for cutting cylindrical alcogels. Since as-made sorbents decreased packing density, they must be additionally crushed and then classified into an appropriate size for increasing packing density. The bead formation in the step of sol-gelation could bring about the simplification of sorbent fabrication process and an improvement of packing density. For the formation of gel bead, characteristics such as hydrophilic or hydrophobic property and density of sol solution were investigated to design sol-gelation equipment. The sol-gel bead preparation equipment in the reflection of sol solution characteristics was fabricated through selection of oil for formation of sol bead, solvent for collection of gel bead, and nozzle for spray of sol droplet formation. The continuous or discontinuous formation of sol beads from NaAlSi-OH sol solution were observed according to flow rates of 6 to 8 mL·min−1 and nozzle diameters of 0.4 to 0.8 mm. In the sphericity of sol bead, the best sol beads were obtained from 0.5 mm nozzle without clogging by sol solution in the flow rate range of 6–8·min−1.

Efficient capture and storage of radioactive iodine (consisting of two isotopes: 129I and 131I), produced or released from nuclear activities, are of paramount importance for sustainable development of nuclear energy due to their volatility and long half-life. Therefore, it is very important to develop new adsorbents for efficient utilization of radioactive iodine from nuclear waste. Various methods and materials are used for I2 capturing and removing, including MOFs due to their high porosity and fast adsorption kinetics, which are rightfully considered effective sorbents for removing I2. Metal–organic frameworks (MOFs) are porous crystalline materials which have diverse pore geometry and unique physicochemical properties, have attracted enormous attention for use in gas storage, separation and catalysis. The ability of MOFs to adsorb volatile products at room temperature can significantly improve the cost-effectiveness of the utilization process. This work describes the synthesis and characterization of three new metal-organic frameworks based on pyrazine (pyz), 44’bipyridine (bpy), 1,2 -bis(4 - pyridyl) – ethane (bpe) and copper (II) hexafluorozironate, as potential adsorbents for I2 capture. All of these three MOFs exhibit a two - dimensional (2D) crystal structure consisting from infinity non-crossing linear chains. The crystal structure of [Cu(pyz)2(ZrF6)2(H2O)2], [Cu(bpy)4(H2O)2ZrF6] and [Cu(bpe)4(H2O)2ZrF6] were characterized using powder X-ray diffraction (PXRD), single crystal X-ray diffraction (SC-XRD). Comparative characteristics of synthesized MOFs, including Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were also performed. The I2 sorption experiments were examined by UV-vis spectroscopy.