Organic Iodide Sorption from Dilute Gas Streams

Greaney, Allison T.; Bruffey, Stephanie H.; Soelberg, Nick; Welty, Amy K.

doi:10.2172/1831626

Cited by 3 publications

(8 citation statements)

References 13 publications

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“…The results for the thin-bed iodine loading experiments have been reported by Greaney et al 5 Specifically, the iodine loading curves and saturated iodine capacities for each organic iodide species are presented in Figure 1a and Table 1, respectively. At equilibrium, all samples displayed similar iodine capacities (100 ± 10 mg I/g Ag 0 Z) though the loading rates differed.…”

Section: Iodine Loading Experimentssupporting

confidence: 66%

“…Specifically, the Ag 0 Z pellets were packed one at a time as a thin bed (1-3 pellets in depth) onto a sample holding plate. 5 Before I2 loading, the Ag 0 Z samples were first dried for 24h at 150 o C in a stream of compressed dry air (dew point <−70 • C) to remove excess physisorbed water. After that, a dry air gas stream containing one of four prototypical iodine species present in reprocessing off gas, i.e., I2, CH3I, iodobutane (C4H9I), or iodododecane (C12H25I), at a concentration of ~50 ppmv and a temperature of 150 o C was introduced.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…After that, a dry air gas stream containing one of four prototypical iodine species present in reprocessing off gas, i.e., I2, CH3I, iodobutane (C4H9I), or iodododecane (C12H25I), at a concentration of ~50 ppmv and a temperature of 150 o C was introduced. The detailed experimental procedures and results have been reported by Greaney et al 5 The unreduced AgZ, Ag 0 Z, and iodine loaded Ag 0 Z pellets were stored in opaque bottles and sent to Georgia Tech for further characterization.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…In previous studies, a series of visual examinations were performed and a shrinking-core process in the iodine-loaded pellets was observed. 5 A comprehensive investigation on the physical and chemical properties has, nonetheless, not been conducted. Table 1.…”

Section: Iodine Loading Experimentsmentioning

confidence: 99%

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Models to Incorporate Reaction Mechanisms into DG-OSPREY: Fixed-Bed Simulations for Organic Iodides Capture Using Ag<sup>0</sup>Z

Shen

Wiechert

Ladshaw

et al. 2022

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As one of the most potent radioisotopes released during spent nuclear fuel reprocessing, 129 I is strictly regulated and must be removed before discharge. Organic iodides (primarily alkyl iodides with different chain lengths, i.e., CH3I, C4H9I, and C12H25I) comprise ~2% of the total iodine in the reprocessing off-gases and are primarily present in vessel off-gas (VOG). Reduced silver mordenite (Ag 0 Z) is predominantly considered for the removal of radioiodine; however, its capture performance and underlying interaction processes with long-chain organic iodides are not fully understood. Two major tasks were accomplished in this study. First, to improve upon the previous experimental studies where Ag 0 Z was used to capture CH3I, C4H9I, and C12H25I at different concentrations, we comprehensively investigated the corresponding capture mechanisms by characterizing fully loaded Ag 0 Z samples. Second, computational codes were implemented to perform fixed-bed simulations that account for transport and reaction mechanisms.Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), powder X-ray diffraction (PXRD), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and thermogravimetric analysis (TGA) were conducted on Ag 0 Z samples that are saturated with I2, CH3I, C4H9I, and C12H25I, respectively. Results indicate that AgI is the predominant adsorption product regardless of the adsorbed iodine species, yet alkyl iodides with different carbon chain lengths may have different compositions of αand γ-AgI. Synchrotron pair distribution function (PDF) measurements and TGA coupled with a Fourier transformed infrared detector (TGA-FTIR) have been performed, and experimental data are currently analyzed. Results are expected to provide further insights into the adsorption mechanisms.The fixed-bed capture performance for CH3I was successfully simulated by solving mathematical equations that describe the underlying transport processes and adsorption reactions. The computational framework, Catalytic After Treatment System (CATS), that was originated in our research group, was used to solve the governing equations. Kinetic parameters, including the pore diffusivity and reaction rate constant were obtained by optimization techniques using data from thin-bed experiments performed at Oak Ridge National Laboratory. The performance of a deep bed predicted using the optimized parameters showed promising agreement with the experimental data. Part 1: Investigating the Mechanisms of Long-chain Organic Iodides Adsorption on Ag 0 Z Key Personnel Ziheng Shen (Ph.D. Student), Alexander Wiechert (Postdoc), Austin Ladshaw (Former Ph.D. Student), Costas Tsouris (Co-PI), Sotira Yiacoumi (PI) ScopeIn a reprocessing facility, it is generally acknowledged that over 90% of the iodine is volatilized to the dissolver off-gas (DOG) stream during the dissolution step and is primarily present as I2. Around 2% of the total iodine inventory is, nevertheless, released in vessel off-gas (VOG) as complex organic iodides (primarily alkyl ...

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Section: Iodine Loading Experimentssupporting

confidence: 66%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Iodine Loading Experimentsmentioning

confidence: 99%

See 2 more Smart Citations

Models to Incorporate Reaction Mechanisms into DG-OSPREY: Fixed-Bed Simulations for Organic Iodides Capture Using Ag<sup>0</sup>Z

Shen

Wiechert

Ladshaw

et al. 2022

View full text Add to dashboard Cite

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“…Apparent mass gain measured with the TGA is confirmed with neutron activation analysis (NAA) at the High Flux Isotope Reactor at Oak Ridge National Laboratory. Detailed methods can be found in other works ( Greaney et al, 2020 ; Greaney et al, 2021 ).…”

Section: Iodine Abatement Experimentsmentioning

confidence: 99%

Abatement of radioiodine in aqueous reprocessing off-gas

et al. 2023

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The reprocessing used nuclear fuel (UNF) releases volatile fission and activation products, including 129I, into the off-gas of a processing plant. Mitigation of the release of vapor phase radionuclides is necessary for meeting regulatory requirements in the United States and other countries. In an aqueous reprocessing plant, volatile radioiodine could be present in several forms, depending on the chemistry of the process used. Inorganic iodine will be the predominate species in any shearing or voloxidation pretreatment off-gas and dissolver off-gas (DOG). Organic iodides such as CH3I, C4H9I, and C12H25I have been proposed to be generated during solvent extraction; thus, these species must be captured from the vessel off-gas (VOG). The abatement of inorganic and organic iodide species to meet United States regulatory requirements has been demonstrated in laboratory experiments using Ag-based solid sorbents. The data presented in this paper includes the effect of gas composition (e.g., the presence of water vapor and NOx), iodine speciation (I2, CH3I, C4H9I, C12H25I), and sorbent bed parameters (e.g., temperature, sorbent age) on complete iodine capture on Ag-mordenite in an aqueous reprocessing plant.

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