Kinetics of Electrode Processes in Fused Salts and Organic Media Containing Thorium, Uranium or Neptunium Ions: Application to Concentrated Solutions

Martinot, L.; Lopes, L.

doi:10.1524/ract.1996.75.2.105

Cited by 3 publications

(4 citation statements)

References 9 publications

(25 reference statements)

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“…Two platinum foils (10 cm 2 each) were used as counter-electrodes. It has been shown previously that the solvent and the electrolyte are not electroactive in the range of potential used in these electropolymerization experiments 18a. Also, the Pt pseudo-reference electrode is stable in the potential range considered here, 18b,18c which means that the voltammograms are not affected by distortion from potential drift.…”

Section: Methodsmentioning

confidence: 54%

“…On one hand, ellipsometric studies show that the reduction of the oxide initially present at the surface appears to be a prerequisite for PAN film deposition . On the other hand, highly uniform and adherent thin films of PAN or PMAN can be deposited in a cathodic process on a series of metals (Ni, Cu, Fe, Pt); on others (Al, Zn), however, the polymer film appears to easily peel off. ,,,18a …”

Section: Introductionmentioning

confidence: 99%

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Controlling the Electrografting of Polymers onto Transition Metal Surfaces through Solvent vs Monomer Adsorption

et al. 1998

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Electropolymerization of methacrylic monomers opens the possibility of chemically grafting a wide range of polymers onto transition metal surfaces. In this work, the electropolymerization of polyacrylonitrile and polyethyl acrylate is studied in different solvents; we experimentally confirm that the choice of solvent is a critical parameter for obtaining electrografted polymers. A density-functional theory−based study modeling the interaction of solvent (acetonitrile, dimethylformamide, and pyridine) or monomer (acrylonitrile and ethyl acrylate) molecules with the Ni(100) metal surface provides the means to classify the organic molecules with respect to their ability to interact with the surface. The surface binding-energy difference between monomer and solvent is introduced in a Frumkin-type isotherm. This allows us to rationalize the experimental observations in terms of a competitive adsorption at the metal surface between the monomer and the solvent. The first step in the electrografting mechanism thus appears to be the chemisorption of the monomer at the electrode surface before cathodic polarization is applied; the chemisorbed monomer is therefore the first species reduced, giving rise to an adsorbed reactive intermediate, which is thus able to start the polymerization of a grafted chain.

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Section: Methodsmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Controlling the Electrografting of Polymers onto Transition Metal Surfaces through Solvent vs Monomer Adsorption

et al. 1998

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“…[6][7][8][9][10][11] T h(I V ) + 4e − ↔ T h [3] In fluoride systems, Clayton et al, 12 Experimental set-up.-Electrochemical experiments were performed in the cell (glassy-carbon crucible) which was placed in an electrolyzer made of INCONEL 625 (Fig. 1).…”

mentioning

confidence: 99%

“…The one-step reduction of Th(IV) ions in chloride media according to Equation 3 was described in papers. [6][7][8][9][10][11] T h(I V ) + 4e − ↔ T h [3] In fluoride systems, Clayton et al, 12 Baes 13 and Chamelot et al 4,14 observed the one-step reduction (Eq. 3) with four exchanged electrons.…”

mentioning

confidence: 99%

Electrochemical and Microscopic Study of Thorium in a Molten Fluoride System

Straka

Szatmáry

Šubrt

2015

J. Electrochem. Soc.

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The electrochemistry of thorium in molten LiF-CaF 2 was examined on inert (Mo) and reactive (Ni) electrodes at 1173 K using cyclic voltammetry and chronopotentiometry. A single-step reduction mechanism was observed on the Mo electrode. Voltammetric results show signs of irreversibility. The diffusion coefficient of Th(IV) ions was calculated from the chronopotentiometric data. Deposition of metallic thorium was verified from the electrolytic experiment and subsequent XRD and SEM analyses. The formation of Th-Ni alloys was confirmed on the Ni electrode using cyclic voltammetry, open-circuit chronopotentiometry and SEM + EDS analysis of the deposit after a short electrolysis.Molten salts (fluorides or chlorides) were initially considered for nuclear energy production because of their advantageous physical and chemical properties: good heat transfer capacity, radiation insensitivity, high boiling point, and wide range solubility for actinides. In addition, it was realized that molten salts could be used in numerous situations: high-temperature heat transfer, core coolants with solid fuels, liquid fuel in a molten-salt reactor, solvents for spent nuclear solid fuel in the case of pyro-reprocessing and coolant, among others. 1 Among other applications, the electrochemical separation of actinides from lanthanides, 2 and molten salt/liquid metal extractions 3 are considered to be suitable methods for the reprocessing of spent nuclear fuel in the fuel cycles of future types of nuclear reactors. 2,4 Pyrochemical processes based on molten-salt systems (chlorides or fluorides) have significant advantages over aqueous processes (higher radiation stability, wide temperature range of usability, low process volume, etc.). The knowledge of actinide and lanthanide electrochemistry is necessary to develop pyrochemical separation methods. This paper aims to describe the basic electrochemical behavior of thorium in a molten-fluoride system (LiF-CaF 2 ), characterize the solidified melts with SEM + EDS and evaluate possibilities of electrolytic deposition of Thorium based on the obtained results. Inert (Mo) and reactive (Ni) electrodes were used.Untill now, several papers were published on the electrochemistry of Th in both molten chlorides and fluorides. Two different mechanisms were proposed based on the obtained results in molten chlorides. Smirnov et al. 5 observed a two-step mechanism according to the reactions:The one-step reduction of Th(IV) ions in chloride media according to Equation 3 was described in papers. 6-11In fluoride systems, Clayton et al., 12 Baes 13 and Chamelot et al. 4,14 observed the one-step reduction (Eq. 3) with four exchanged electrons. In, 4 it is stated that the electrolysis of Th on an inert electrode is a suitable method to separate thorium from lanthanides. ExperimentalChemicals and materials.-LiF and CaF 2 of commercial origin (purity 99.50% and 99.96% respectively) were dried in a vacuum dryer at 250 • C. The ThF 4 purity was verified with XRD analysis. The impurities were under the detection level ...

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Serrano

Taxil

1999

Journal of Applied Electrochemistry

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Kinetics of Electrode Processes in Fused Salts and Organic Media Containing Thorium, Uranium or Neptunium Ions: Application to Concentrated Solutions

Cited by 3 publications

References 9 publications

Controlling the Electrografting of Polymers onto Transition Metal Surfaces through Solvent vs Monomer Adsorption

Controlling the Electrografting of Polymers onto Transition Metal Surfaces through Solvent vs Monomer Adsorption

Electrochemical and Microscopic Study of Thorium in a Molten Fluoride System

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