X-ray absorption spectroscopy and actinide electrochemistry: a setup dedicated to radioactive samples applied to neptunium chemistry.

A spectroelectrochemical setup has been developed to investigate radioactive elements in small volumes (0.7 to 2 ml) under oxidation-reduction (redox) controlled conditions by X-ray absorption spectroscopy (XAS). The cell design is presented together with in situ XAS measurements performed during neptunium redox reactions.

Electrochemical and Spectroscopic Study of Eu and Eu Coordination in the 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid.

Separation processes based on room temperature ionic liquids (RTIL) and electrochemical refining are promising strategies for the recovery of lanthanides from primary ores and electronic waste. However, they require the speciation of dissolved elements to be known with accuracy. In the present study, Eu coordination and Eu /Eu electrochemical behavior as a function of water content in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][NTf ]) was investigated using UV-visible spectrophotometry, time-resolved laser fluorescence spectroscopy, electrochemistry, and X-ray absorption spectroscopy.

Trivalent Actinide Uptake by Iron (Hydr)oxides.

The retention of Am(III) by coprecipitation with or adsorption onto preformed magnetite was investigated by X-ray diffraction (XRD), solution chemistry, and X-ray absorption spectroscopy (XAS). In the coprecipitation experiment, XAS data indicated the presence of seven O atoms at 2.44(1) Å, and can be explained by an Am incorporation at Fe structural sites at the magnetite surface.

Impact of iron-reducing bacteria on the corrosion rate of carbon steel under simulated geological disposal conditions.

The current projects for the disposal of high-level radioactive waste rely on underground burial and confinement by metallic envelopes that are susceptible to corrosion processes. The impact of microbial activity must be fully clarified in order to provide biological parameters for predictive reactive transport models. This study investigates the impact of hydrogenotrophic iron-reducing bacteria (Shewanella oneidensis strain MR-1) on the corrosion rate of carbon steel under simulated geological disposal conditions by using a geochemical approach.

Combined geochemical and electrochemical methodology to quantify corrosion of carbon steel by bacterial activity.

The availability of respiratory substrates, such as H2 and Fe(II,III) solid corrosion products within nuclear waste repository, will sustain the activities of hydrogen-oxidizing bacteria (HOB) and iron-reducing bacteria (IRB). This may have a direct effect on the rate of carbon steel corrosion. This study investigates the effects of Shewanella oneidensis (an HOB and IRB model organism) on the corrosion rate by looking at carbon steel dissolution in the presence of H2 as the sole electron donor.

Anodic activation of iron corrosion in clay media under water-saturated conditions at 90 degrees C: characterization of the corrosion interface.

To understand the process governing iron corrosion in clay over centuries, the chemical and mineralogical properties of solids formed by free or anodically activated corrosion of iron in water-saturated clay at 90 degrees C over 4 months were probed using microscopic and spectroscopic techniques. Free corrosion led to the formation of an internal discontinuous thin (<3 microm thick) magnetite layer, an external layer of Fe-rich phyllosilicate, and a clay transformation layer containing Ca-doped siderite (Ca(0.2)Fe(0.

Uranium uptake by hectorite and montmorillonite: a solution chemistry and polarized EXAFS study.

The mechanism of U(VI) retention on montmorillonite and hectorite at high ionic strength (0.5 M NaCl) was investigated by solution chemistry and, at near-neutral pH, polarized EXAFS spectroscopy. Uranium(VI) sorption increases from pH 3 to 7 on the two clays, but with a steeper edge for hectorite.

Sites of Lu(III) sorbed to and coprecipitated with hectorite.

The Lu(III) binding mechanisms by trioctahedral smectite hectorite in aqueous systems were investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. Coprecipitated hectorite (Lu755Hec), its precursor phase (Lu/Brucite), and the surface sorbed hectorite (Lu/SHCa1) were prepared as oriented samples to collect polarized EXAFS (P-EXAFS) data. EXAFS analysis indicated that Lu(III) is 6-fold coordinated by oxygen in Lu/Brucite and in Lu755Hec, and surrounded by Mg/Si shells.

Oxidation of FeS by oxygen-bearing acidic solutions.

Oxidation of FeS in oxygen-bearing acidic solutions was investigated at different temperatures (25 to 45 degrees C) and pH (2.75 to 3.45).

Zn incorporation in hydroxy-Al- and keggin Al13-intercalated montmorillonite: a powder and polarized EXAFS study.

The sorption mechanism of Zn on gibbsite and mont-morillonite exchanged with Al3+ (Al-mont) or Keggin Al13 polymer (Al13-mont) was probed by powder and polarized EXAFS spectroscopy as a function of pH (5.85-7), reaction time (1-65 days), and sorbate to sorbent ratio (50-Zn is octahedrally coordinated to oxygens at approximately 2.08(2) A, and surrounded in-plane by six Al atoms at 3.

Mechanism of europium retention by calcium silicate hydrates: an EXAFS study.

The uptake of Eu by calcium silicate hydrate (C-S-H) phases as a function of Eu/sorbate ratio (from 37 to 450 micromol g(-1) C-S-H), C-S-H Ca/Si mole ratio (1.3, 1.0, and 0.