Ion exchange kinetics of fission products between molten salt and zeolite-A

Shaltry, Michael R.; Phongikaroon, Supathorn; Simpson, Michael F.

doi:10.1016/j.micromeso.2011.11.035

Cited by 18 publications

(4 citation statements)

References 16 publications

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“…Counter cations are generally involved not in the framework, but inside the nanocavities. Such counter cations inside the nanocavities can be easily substituted by various cations, even at low temperatures, leading to zeolites with distinct ion-exchange ability and cation-specific selectivity, which is advantageous for the efficient removal of fission products from high-level harmful nuclear waste123. Application to the management of radioactive waste leaks, such as 137 Cs, has especially attracted attention after the earthquake disaster in 20114.…”

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confidence: 99%

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Yoshida

Toyoura

Matsunaga

et al. 2013

Sci Rep

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Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations.

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confidence: 99%

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Yoshida

Toyoura

Matsunaga

et al. 2013

Sci Rep

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“…The slope and intercept of the linear plot give a calculated q e of 8.27 mg·g –1 and a k 2 of 0.00165. This model has benn shown to be reasonably valid for describing the kinetics of Sr 2+ adsorption by other materials such as metal oxides, − clays, , polymers, , and nanocomposites. , Nevertheless, it was rarely applied for chalcogenide Sr 2+ ion exchangers until some recent work …”

Section: Results and Discussionmentioning

confidence: 99%

Effective and Rapid Adsorption of Sr²⁺ Ions by a Hydrated Pentasodium Cluster Templated Zinc Thiostannate

et al. 2019

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Separation of 90Sr from radioactive wastewater not only is essential for human public health and environmental remediation but also bears importance for alternate medical and industrial applications. Here, we report the facile synthesis of an open framework zinc thiostannate, Na5Zn3.5Sn3.5S13·6H2O (ZnSnS-1), templated by hydrated pentasodium clusters. This compound exhibits an effective and rapid ion exchange property for Sr2+ ions. The exchange kinetics conforms to a pseudo-second-order model, implying that the chemical adsorption of Sr2+ may be the rate-determining step. According to the Langmuir–Freundlich isotherm, the maximum exchange capacity of ZnSnS-1 for Sr2+ is 124.2 mg/g and ranks ahead of those of all the reported metal sulfide Sr2+ adsorbents. High exchange performance is observed over the broad pH range 2.5–13, although it could be inhibited to some extent by coexisting ions, especially Na+ and Ca2+. ZnSnS-1 shows a higher affinity for Sr2+ compared to Cs+, and the performance is almost unaffected by the presence of coexisting Cs+ even in excess amounts. Importantly, the Sr2+ in the exchanged product can be conveniently eluted by a concentrated KCl solution, and the recycled exchanger can be further used for Sr2+ exchange. These advantages combined with the robust framework for recycling concerns make ZnSnS-1 a highly promising exchanger for removal of radioactive Sr from the liquid nuclear waste.

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“…Cesium and strontium ions would then be removed from the salt by the zeolite material in the columns and the exit salt would be returned to the electrorefiner. Fundamental studies on this process have been conducted at equilibrium [13][14][15][16][17], and transient conditions [18]. Results from these studies indicate that the ion exchange process could effectively reduce waste volume by a factor of two [19].…”

Section: Proposed Molten Salt Purification Techniquesmentioning

confidence: 99%

Zone Freezing Study for Pyrochemical Process Waste Minimization

Williams¹

2012

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Pyroprocessing technology is a non-aqueous separation process for treatment of used nuclear fuel. At the heart of pyroprocessing lies the electrorefiner, which electrochemically dissolves uranium from the used fuel at the anode and deposits it onto a cathode. During this operation, sodium, transuranics, and fission product chlorides accumulate in the electrolyte salt (LiCl-KCl). These contaminates change the characteristics of the salt overtime and as a result, large volumes of contaminated salt are being removed, reprocessed and stored as radioactive waste. To reduce the storage volumes and improve recycling process for cost minimization, a salt purification method called zone freezing has been proposed at Korea Atomic Energy Research Institute (KAERI).Zone freezing is melt crystallization process similar to the vertical Bridgeman method. In this process, the eutectic salt is slowly cooled axially from top to bottom. As solidification occurs, the fission products are rejected from the solid interface and forced into the liquid phase. The resulting product is a grown crystal with the bulk of the fission products near the bottom of the salt ingot, where they can be easily be sectioned and removed. Despite successful feasibility report from KAERI on this process, there were many unexplored parameters to help understanding and improving its operational routines. Thus, this becomes the main motivation of this proposed study. The majority of this work has been focused on the CsCl-LiCl-KCl ternary salt. CeCl 3 -LiCl-KCl was also investigated to check whether or not this process is feasible for the trivalent species-surrogate for rare-earths and transuranics. For the main part of the work, several parameters were varied, they are: (1) the retort advancement rate-1.8, 3.2, and 5.0 mm/hr, (2) the crucible lid configurations-lid versus no-lid, (3) the amount or size of mixture-50 and 400 g, (4) the composition of CsCl in the salt-1, 3, and 5 wt%, and (5) the temperature differences between the high and low furnace zones-200 and 300 qC.During each experiment, the temperatures at selected locations around the crucible were measured and recorded to provide temperature profiles. Following each experiment, samples were collected and elemental analysis was done to determine the composition of iv the salt. Several models-non-mixed, well-mixed, Favier, and hybrid-were explored to describe the zone freezing process.For CsCl-LiCl-KCl system, experimental results indicate that through this process up to 90% of the used salt can be recycled, effectively reducing waste volume by a factor of ten. The optimal configuration was found to be a 5.0 mm/hr rate with a lid configuration and a ΔT of 200°C. The larger 400 g mixtures had recycle percentages similar to the 50 g mixtures; however, the throughput per time was greater for the 400 g case. As a result, the 400 g case is recommended. For the CeCl 3 -LiCl-KCl system, the result implies that it is possible to use this process to separate the rare-earth and transuranics chlorides. ...

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Ion exchange kinetics of fission products between molten salt and zeolite-A

Cited by 18 publications

References 16 publications

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Effective and Rapid Adsorption of Sr²⁺ Ions by a Hydrated Pentasodium Cluster Templated Zinc Thiostannate

Zone Freezing Study for Pyrochemical Process Waste Minimization

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Ion exchange kinetics of fission products between molten salt and zeolite-A

Cited by 18 publications

References 16 publications

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Atomic sites and stability of Cs+ captured within zeolitic nanocavities

Effective and Rapid Adsorption of Sr2+ Ions by a Hydrated Pentasodium Cluster Templated Zinc Thiostannate

Zone Freezing Study for Pyrochemical Process Waste Minimization

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Effective and Rapid Adsorption of Sr²⁺ Ions by a Hydrated Pentasodium Cluster Templated Zinc Thiostannate