Fused Salt Solutions Research Articles

In-Situ Spectroelectrochemistry of Lanthanides in Molten Chloride Salts

Molten Salt Reactors (MSRs) are a potential game-changing technology for next-generation nuclear power. Although the MSR concept was demonstrated at Oak Ridge National Laboratory (ORNL) in the 1960’s, it had not gathered attention from commercial vendors until recently. A fundamental knowledge of salt chemistry, including the speciation and solubility of corrosion and fission products is central to the safe and reliable operation of MSRs. The structural properties of fused salt solutions, especially the coordination geometry around the metal ions in the melt, are intricately dependent on the melt composition and temperature. In this work, a combination of in-situ electrochemistry and optical absorption spectroscopy techniques are utilized to understand the speciation and structure of lanthanides in molten chloride salts as a function of temperature, concentration and melt composition. The spectroelectrochemistry of metal species in molten salt media can be used as a potential process monitoring technique enabling the quantitative measurement of lanthanide and actinide metals within molten salt reactors or nuclear fuel pyro-processing applications.This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy (US-DOE), Office of Science, Basic Energy Sciences, at BNL, INL and ORNL under contracts DE-SC0012704, DE-AC07-05ID14517 and DE-FC02-04ER15533, respectively.

Measurement and Thermodynamic Interpretation to Identify Ionic Solutes in Simple and Complex Fused Salt Solutions

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Some generalities in the analyses of equilibria in lonic solutions

Despite great differences in the physical and chemical properties of various ionic media, common methods for analyzing internal equilibrium provide useful and simple means for interpreting and predicting their behavior. The formalism of M. Pourbaix for analyzing the activities and solubilities of solutes in aqueous solutions has provided a foundation for interpreting corrosion, solubilities, and electrochemical phenomena for such solutions. Although perhaps not so obvious, the formalism of Kroger-Vink (K-V) in plotting the point defect concentrations for ionic solids derives from the same mathematical method. Likewise, the activities and solubilities for solutes in fused salts, e.g., fused sodium sulfate, can be treated by exactly the same sort of simultaneous resolution of equilibria for reactions in an ionic medium. Suggestions for extension of this analysis to cryolite-base fused salt solutions important to aluminum extraction are discussed.

Thermodynamic treatment of multicomponent fused salt solutions: common anion reactive systems approximation

From a modified F.F.G. (1) thermodynamic cycle, equations have been developed from which the molar and partial molar excess thermodynamic properties of j-component molten salt solutions may be predicted from binary data.The theory is applicable to reactive molten salt systems and particularly to charge asymmetric fused salt solutions with common anions.It is shown that for a system having j + 1 components, such as [Formula: see text], any molar or partial molar property of mixing for MXq, may be calculated from available data on corresponding j-binary systems, such as MXq–AX, MXq–BX, and [Formula: see text].The equations are of the general form,[Formula: see text]The latter is applicable only when the multicomponent and the binary solutions have the same MXq content and same temperature.The theoretical expressions have been found to predict quite well available data on ternary and quarternary systems. New composition parameters for expressing the compositions in quarternary and quinary systems have been established. Key words: molten salt solutions, multicomponent systems, ternary systems, quarternary systems, quinary systems.

Thermodynamic Treatment of Multicomponent Fused Salt Solutions: Common Anion Reactive Systems Approximation

From a modified F.F.G. (1) thermodynamic cycle, equations have been developed from which the molar and partial molar excess thermodynamic properties of j-component molten salt solutions may be predicted from binary data.The theory is applicable to reactive molten salt systems and particularly to charge asymmetric fused salt solutions with common anions.It is shown that for a system having j + 1 components, such as , any molar or partial molar property of mixing for MXq, may be calculated from available data on corresponding j-binary systems, such as MXq–AX, MXq–BX, and .The equations are of the general form,The latter is applicable only when the multicomponent and the binary solutions have the same MXq content and same temperature.The theoretical expressions have been found to predict quite well available data on ternary and quarternary systems. New composition parameters for expressing the compositions in quarternary and quinary systems have been established. Key words: molten salt solutions, multicompon...

Electrode Potentials of Metal Chlorides in Binary and Ternary Fused Salt Solutions with Alkali Chlorides

The standard formal electrode potentials of several metals have been determined from 700–900 °C in NaCl, KCl, CsCl or the equimolar mixtures of these salts using galvanic or redox cells with a silver-silver chloride reference electrode. The activity coefficients and other partial molar properties of these solutions were calculated as a function of temperature from the emf measurements.

PHOSPHORESCENCE IN MOLTEN TETRABUTYLAMMONIUM TRIBROMOMANGANATE

Abstract The absorption and phosphorescence spectra and the phosphorescence lifetimes were measured for a series of fused salt solutions whose composition ranged between those of tetrabutylammonium tri-bromomanganate and bis-tetrabutylammonium tetrabromomanganate. The set of absorption spectra displayed an isosbestic point but the set of emission spectra was more complex. In mixed systems only a single lifetime was observed for the two different phosphorescence spectra indicating interconversion of the excited state species which were identified as four- and three-coordinate respectively. The graph of lifetime versus composition displays a pronounced curvature which is attributed to “structural quenching”. A comprehensive kinetic scheme is proposed to represent the system.

Electrodeposition of CdTe in fused salt solutions

Films of CdTe were deposited cathodically onto copper electrodes from a fused eutectic mixture of LiCl and KCl containing CdCl 2 and TeO 2 in various molar ratios. It was found that CdTe can also be obtained by electroless deposition at elevated temperatures or at higher concentrations of CdCl 2. In the reverse case Cu 2Te is obtained. The cubic modification (zinc blende) is usually obtained, the hexagonal modification (wurtzite) being observed in isolated cases.

Clusius-Dickel Separation: A New Look at an Old Technique

Abstract The Clusius-Dickel (CD) technique couples thermal diffusion to a counter-current, natural convective flow to effect separation of molecules of different molecular weights or shapes in liquid or gaseous solutions. Materials separable by the technique include: aqueous biological solutions, isotopes in both gas and liquid states, aqueous solutions of both ionized and un-ionized materials, organic solutions, liquid metallic solutions, fused salt solutions, and gas mixtures including ortho and para-hydrogen. The technique was discovered in the late 1930s by K. Clusius and G. Dickel but fell into relative obscurity for commerical applications about 20 years after its discovery. The reasons for its decline included a number of deleterious apparatus and operating features among which were large power requirements, costly equipment construction, and small processing volumes. The present study, however, after critically reexamining the Clusius-Dickel separation (CDS) technique, concludes that the objection...

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Nature of sulfur species in fused salt solutions

Nature of sulfur species in fused salt solutions

Selection of standard states in molecular interpretation of activity coefficients in fused salt solutions

The temperature dependence of emf of the cells ▪ (where Me = Sn or Bi) was determined.A change of the emf temperature coefficient has been found in the melting point of the complex compound formed by MeCln with (CH3)2NH2+Cl−. The entropies of “quasi-melting” phenomena in solution are calculated, and their concentration dependence is discussed and compared with those for pure complex compounds. A selection criterion for standard states is postulated for similar systems.

Note on the Heats of Mixing in Charge-Unsymmetrical Fused Salt Solutions

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The coordination chemistry of 3d transition metal ions in fused salt solutions

A review is presented of the spectroscopic studies of 3d transition metal ions and their complexes in chloride melts. An interpretation of the spectra on the basis of crystal field theory is given with criteria for selection of suitable host crystal lattices. A correlation of the results with electrostatic energies and crystal field stabilization energies is given. (D.L.C.)

Thermodynamic Properties of Fused Salt Solutions. VIII. Lead Chloride in Silver Chloride

Thermodynamic Properties of Fused Salt Solutions. VIII. Lead Chloride in Silver Chloride