Removal of tritiated water vapor by adsorption on molecular sieves - effect of co-existing H2O

Tanaka, Seiya; Ono, Futaba; Takahashi, Yoshinori; Kiyose, Ryohei

doi:10.1016/0020-708x(85)90141-3

Cited by 3 publications

(4 citation statements)

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“…The tritium released from this process further reacts with oxygen to form tritiated water . Water adsorption by solid adsorbents represents the state-of-the-art of tritiated water vapor capture from used fuel reprocessing off-gases. − Over the past four decades, various adsorbents have been developed and tested for the capture of tritiated water vapor, including silica gel, molecular sieves (3A, 4A, 5A, 13X), anhydrous calcium sulfate (e.g., Drierite) and activated alumina. Among these adsorbents, molecular sieves have been the most favorable choice for capture and immobilization of tritiated water…”

Section: Introductionmentioning

confidence: 99%

Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

Lin

Ladshaw

Nan

et al. 2015

Ind. Eng. Chem. Res.

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This work is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K + /Na + molar ratio of this particular type of molecular sieve 3A was ∼4:6. Our results showed that the GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. The second adsorption stage is significantly affected by the K + /Na + molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K + /Na + molar ratio increases.

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Section: Introductionmentioning

confidence: 99%

Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

Lin

Ladshaw

Nan

et al. 2015

Ind. Eng. Chem. Res.

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“…The tritium released during voloxidation further reacts with oxygen to form tritiated water, which is released to off-gas systems . The state of the art of tritiated water-vapor capture from spent fuel reprocessing off-gases is adsorption by solid sorbents. − Over the past four decades, various sorbents have been investigated for the capture of tritiated water vapor including silica gel, molecular sieves (3A, 4A, 5A, 13X), Drierite, and activated alumina. Among these sorbents, molecular sieves, such as molecular sieve 3A, have been the most favorable choice for the removal and temporary storage of tritiated water…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Water Vapor Adsorption on Single-Layer Molecular Sieve 3A: Experiments and Modeling

Lin

Liu

Nan

et al. 2014

Ind. Eng. Chem. Res.

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The objective of the current work was to shorten the gap for fundamental adsorption kinetic data required for the development of advanced adsorption unit-operation models to be incorporated into an overall plant-level model for spent nuclear fuel reprocessing. The kinetics of water-vapor adsorption on molecular sieve 3A was investigated at 25–80 °C and water dew points from −69 to 17 °C. Water uptake curves were fitted with three kinetic models including the linear-driving-force model, the shrinking-core model, and the Langmuir kinetic model. The results suggest that the water-vapor adsorption on molecular sieve 3A under the investigated experimental conditions was controlled by both external film resistance and internal macropore resistance. The contribution of the external film resistance varied from 25% to 50% of the total mass-transfer resistance depending on the adsorption temperature. It was also found that the Langmuir kinetic model fitted individual sets of kinetic data very well, but the Langmuir adsorption constant obtained from curve fitting decreased with increasing adsorption temperature and with increasing water vapor pressure. This result indicates a significant surface heterogeneity of molecular sieve 3A and also implicitly verifies that the Langmuir isotherm model is unable to represent isotherms of water adsorption on molecular sieve 3A.

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“…(4), which was derived from Eqs. (1)- (3). The balance of water amount, that of tritium amount and the water uptake were individually checked for the validity of the factor.…”

Section: Measurement Of Isotope Separation Factor By Staticmentioning

confidence: 99%

“…3) Ono and Nakazawa presented the equilibrium partition coefficient of tritiated water between water adsorbed on a commercial molecular sieve 5A and environmental water to be 1.1-1.4. 4) They indicated that the concentration dependence of the coefficient was not appreciable in the range from 370 to 3:7 Â 10 6 Bq/ml at 278-318 K. Kotoh and Nishikawa also presented the equilibrium partition coefficients of the commercial molecular sieves 3A, 4A, 5A, and 13X to be 1.1-1.3 in the range from 148 to 7400 Bq/ml at 278-293 K. 5) As for the water adsorption capacity, which is a key to determine the adsorption column size, Tsutaya et al indicated the NaX and NaY faujasite-type zeolites have larger capacities than silica gel, activated alumina, USY, and silicalite at 298 K. 6) Recent research has focused more on the content of zeolite and adsorption properties.…”

Section: Introductionmentioning

confidence: 99%

Influence of Framework Silica-to-Alumina Ratio on the Tritiated Water Adsorption and Desorption Characteristics of NaX and NaY Zeolites

Iwai

Yamanishi

2008

Journal of Nuclear Science and Technology

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The fixed-bed adsorption process has been studied as one of the promising processes for the recovery of tritiated water in the field of nuclear fusion. The influence of the framework SiO 2 /Al 2 O 3 ratio ranging from 2.0 to 10.0 on the tritiated water adsorption and desorption characteristics in the H 2 O-HTO binary systems was systematically examined using NaX and NaY zeolites. A large difference in isotherm was observed by changing the SiO 2 /Al 2 O 3 ratio from 7.0 to 10.0. The framework SiO 2 -to-Al 2 O 3 ratio has a slight effect on the isotope separation factor. The capacity of removable water from NaY10.0 around room temperature is approximately four times larger than that from NaA2.0 even though both zeolites have nearly the same capacity for absorbable H 2 O at nearly P=P 0 ¼ 1:0. The weaker interaction generates the isotope effect on desorption. The HTO dehydration ratio has a strong interrelation with the accumulative amount of purge gas. Dehydration is independent of the flow rate of the purge gas. On the design side of the water adsorption process with multi-absorber systems, the size of the water absorber such as a dryer or dehumidifier can be downscaled with NaY10.0 as the adsorbent since the consideration of the heating and cooling periods necessary for the temperature swing desorption process is not required in the NaY10.0 column.

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Removal of tritiated water vapor by adsorption on molecular sieves - effect of co-existing H2O

Cited by 3 publications

References 0 publications

Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

Kinetics of Water Vapor Adsorption on Single-Layer Molecular Sieve 3A: Experiments and Modeling

Influence of Framework Silica-to-Alumina Ratio on the Tritiated Water Adsorption and Desorption Characteristics of NaX and NaY Zeolites

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