Thermodynamic Model for the Solubility of TcO2· xH2O(am) in the Aqueous Tc(IV) – Na+– Cl-– H+– OH-– H2O System

Hess, Nancy J.; Xia, Yuanxian; Rai, Dhanpat; Conradson, Steven D.

doi:10.1023/b:josl.0000030285.11512.1f

Cited by 63 publications

(38 citation statements)

References 13 publications

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“…An increase in the solubility of technetium was also reported by , although only at relatively low pH values. In general, the data of Hess et al (2004) are consistent with those of .…”

Section: 8supporting

confidence: 81%

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The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

Icenhower¹,

Qafoku²,

Martin³

et al. 2008

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“…An increase in the solubility of technetium was also reported by , although only at relatively low pH values. In general, the data of Hess et al (2004) are consistent with those of .…”

Section: 8supporting

confidence: 81%

“…Although did not find evidence for an increase in solubility because of the presence of chloride in solution, Hess et al (2004) concluded otherwise. These latter investigators showed that in chloride solutions of 1 × 10 -3 to 5 M NaCl, technetium likely forms TcCl 6 2-and TcCl 4°( aq) complexes.…”

Section: 8mentioning

confidence: 93%

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

Icenhower¹,

Qafoku²,

Martin³

et al. 2008

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“…This observation strongly suggests that equilibrium conditions have been attained in the system, as well as hinting towards the expected pre- − as solubility controlling solid phase and Tc(IV) hydrolysis species in equilibrium, respectively. Tc concentrations determined in the acidic pH range are also in very good agreement with the undersaturation solubility data reported by Hess and coworkers [12] (also shown in Figure 3b). This indicates that the same solid phase has been obtained from oversaturation (present work) and undersaturation [12] conditions.…”

Section: Xanes Measurementssupporting

confidence: 90%

“…Tc concentrations determined in the acidic pH range are also in very good agreement with the undersaturation solubility data reported by Hess and coworkers [12] (also shown in Figure 3b). This indicates that the same solid phase has been obtained from oversaturation (present work) and undersaturation [12] conditions. Our data also confirm the strong effect of ionic strength on Tc(IV) solubility under acidic conditions, where [Tc] in equilibrium with TcO 2 ⋅ 1. cur.…”

Section: Xanes Measurementssupporting

confidence: 90%

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Redox chemistry of Tc(VII)/Tc(IV) in dilute to concentrated NaCl and MgCl₂ solutions

Yalçıntaş

Gaona²,

Scheinost

et al. 2014

Radiochimica Acta

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Redox speciation of Tc in the aqueous phase was further confirmed by solvent extraction. A good agreement is obtained between the experimentally determined Tc redox distribution and thermodynamic calculations based on NEA-TDB (Nuclear Energy Agency, Thermochemical Database) and ionic strength corrections by SIT or Pitzer approaches. These observations indicate that experimental pH c and h values in buffered systems can be considered as reliable parameters to predict the redox behaviour of Tc in dilute to highly concentrated NaCl and MgCl 2 solutions. h of the system and aqueous concentration of Tc(IV) in equilibrium with TcO 2 ⋅ 1.6H 2 O(s) are strongly affected by elevated ionic strength, especially in the case of 4.5 M MgCl 2 solutions. In such concentrated brines and under alkaline conditions (pH c = pH max ∼ 9), kinetics play a relevant role and thermodynamic equilibrium for the system Tc(IV)(aq) ⇔ Tc(IV)(s) was not attained from oversaturation conditions within the timeframe of this study (395 days). Tc(VII) is reduced to Tc(IV) by magnetite, mackinawite and siderite suspensions at pH c = 8-9 in concentrated NaCl and MgCl 2 solutions. Sorption is very high in

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Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

et al. 2022

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Technetium-99 is a prevalent fission product from nuclear waste. The long half-life (211,000 yr) and environmental mobility of pertechnetate (TcO 4 À ) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO 2 . Approach 1 is a low temperature chemical synthesis of TiO 2 doped with Tc(IV) from TcO 4 À intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge-shared Tc(IV) pairs. Approach 2 utilizes TiO 2 to photocatalytically reduce TcO 4 À to Tc(IV) stabilized on the surface of or within the TiO 2 lattice. The %Tc removed from solution and adsorbed to TiO 2 is pH dependent, with the maximum Tc(IV) adsorbed at pH 3-4 as either TcO 2 or edge-sharing Tc(IV) octahedra. The Tc(IV)-TiO 2 composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).

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Thermodynamic Model for the Solubility of TcO₂· xH₂O(am) in the Aqueous Tc(IV) – Na⁺– Cl^-– H⁺– OH^-– H₂O System

Cited by 63 publications

References 13 publications

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

Redox chemistry of Tc(VII)/Tc(IV) in dilute to concentrated NaCl and MgCl₂ solutions

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

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Thermodynamic Model for the Solubility of TcO2· xH2O(am) in the Aqueous Tc(IV) – Na+– Cl-– H+– OH-– H2O System

Cited by 63 publications

References 13 publications

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

Redox chemistry of Tc(VII)/Tc(IV) in dilute to concentrated NaCl and MgCl2 solutions

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

Contact Info

Product

Resources

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Thermodynamic Model for the Solubility of TcO₂· xH₂O(am) in the Aqueous Tc(IV) – Na⁺– Cl^-– H⁺– OH^-– H₂O System

Redox chemistry of Tc(VII)/Tc(IV) in dilute to concentrated NaCl and MgCl₂ solutions