Sorption of nickel and cobalt ions onto cobalt and nickel ferrites.

The corrosion of the metal parts in the primary circuit of pressurized water reactors leads to the release of colloidal particles (NiFe(2)O(4), CoFe(2)O(4), NiO, Ni...

Characterization of acid-base properties of two gibbsite samples in the context of literature results.

Two different gibbsites, one commercial and one synthesized according to a frequently applied recipe, were studied in an interlaboratory attempt to gain insight into the origin of widely differing reports on gibbsite acid-base surface properties. In addition to a thorough characterization of the two solids, several methods relevant to the interfacial charging were applied to the two samples: potentiometric titrations to obtain the "apparent" proton related surface charge density, zeta-potential measurements characterizing the potential at the plane of shear, and Attenuated Total Reflection Infrared Spectroscopy (ATR-IR) to obtain information on the variation of counter-ion adsorption with pH (using nitrate as a probe). Values of the IEP at 9-10 and 11.

Influence of temperature and reducing conditions on the sorption of sulfate on magnetite.

The reactivity of aqueous sulfate toward magnetite was studied between 50 and 275 °C as a function of pH and the redox conditions. Under oxidizing conditions, we did not observe redox reactions and the sorption of aqueous sulfate is promoted under acidic conditions when the magnetite surface is positively charged. The effect of temperature on this retention is moderate but complex.

Determination of isoelectric points of metals and metallic alloys by adhesion of latex particles.

A set-up and a method were developed to determine the isoelectric point of metals and metallic alloys samples (stainless steels, inconel, zircaloy, aluminum and dural) by measuring the adhesion rate of negative latex particles. The concentration of polystyrene spheres with surface carboxylate groups (initially 0.5-1 mg L(-1)) in contact with metallic samples was measured as a function of pH and time by turbidimetry.

Deposition of hematite particles on polypropylene walls in dynamic conditions.

An experimental circulating water loop has been constructed to study the deposition of hematite particles of average diameter 320 nm on polypropylene pipe walls in the ranges pH 4-11, Re 3300-17,700 at 25 degrees C. Real-time turbidimetric measurements were used to measure the deposited concentrations. Results showed that the deposition rate increased when pH decreased and when the flow rate increased.

Sorption of sulfate ions onto magnetite.

In order to acquire data necessary to understand and predict the behavior of oxide particles in the secondary circuits of pressurized water reactors (PWR) and study the role of redox and interface reactions, the acid-base properties of magnetite and sorption of sulfate ions were studied at 25 degrees C. Redox reactions with magnetite predicted from thermodynamic data were not observed and sulfur species always remain as sulfate. From zetametric measurements, mass titrations and acid-base titrations an IEP at 6.

Effect of the adsorption of lithium and borate species on the zeta potential of particles of cobalt ferrite, nickel ferrite, and magnetite.

Zetametric measurements on suspensions of oxide particles (cobalt ferrite, nickel ferrite, and magnetite) representative of corrosion products from primary circuits of pressurized water reactors were performed at 25 and 70 degrees C in the presence of lithium and borate species. No effect of lithium ions was observed. Borate species cause a decrease of the isoelectric point (IEP), attributed to the sorption of borate as a negative complex MOB(OH)3(-).

Sorption of uranyl ions on titanium oxide studied by ATR-IR spectroscopy.

ATR-IR spectroscopy was used to study the sorption of uranyl ions (10(-4) M) onto titanium oxide (mixture of rutile and anatase). A circulation setup, filled with a solution in D(2)O, allowed recording of the evolution of the antisymmetric O=U=O stretching of uranyl species onto titanium oxide particles deposited on the ATR crystal. The band centered at 915 cm(-1) has been decomposed in two Gaussian peaks at 920 and 905 cm(-1).

Influence of kinetics on the determination of the surface reactivity of oxide suspensions by acid-base titration.

The effect of acid-base titration protocol and speed on pH measurement and surface charge calculation was studied on suspensions of gamma-alumina, hematite, goethite, and silica, whose size and porosity have been well characterized. The titration protocol has an important effect on surface charge calculation as well as on acid-base constants obtained by fitting of the titration curves. Variations of pH versus time after addition of acid or base to the suspension were interpreted as diffusion processes.

Sorption of selenite ions on hematite.

The sorption of selenite from aqueous solutions onto hematite was investigated as a function of pH (2-12), ionic strength (0.01-0.1 M), and concentration of selenium (10(-7)-10(-2) M).

An inverse gas chromatography study of the adsorption of organics on nickel- and copper-hexacyanoferrates at zero surface coverage.

The surface properties of Ni and Cu hexacyanoferrates were investigated by the inverse gas chromatography method. Retentions of 10 organic compounds were measured at zero surface coverage in the temperature range 80 to 95 degrees C. The gas/solid partition coefficients and the related thermodynamic data of adsorption (standard free energy change, standard state enthalpies, and entropy changes) also at zero surface coverage were determined.

Morphology and surface heterogeneities in synthetic goethites.

In the framework on a study of the acido-basic and sorption properties of iron oxides, a thorough characterization of two types of goethite powders was performed in several laboratories joined in a common project. Chemical analysis by ICPAES; high-resolution SEM, TEM, and AFM observations; XRD with line width analysis; and argon and nitrogen sorption isotherms were used for that purpose. The main crystallographic faces of goethite particles could be identified as {001}, {101}, and {121}, and their abundance correlated with the distribution of low-pressure argon adsorption local isotherms.

Study of uranyl sorption onto hematite by in situ attenuated total reflection-infrared spectroscopy.

In this paper, we present results of ATR-IR spectroscopy of uranyl complexes adsorbed on hematite. This method allowed the in situ recording of infrared spectra of uranyl sorbed on hematite in presence of aqueous solution and to detect one peak at 906 cm(-1) attributed to the antisymmetric O=U=O stretching. The intensity of the peak increases with pH, but its shape does not evolve, indicating that the same surface species is responsible for the sorption in the pH range 5-8.

Effect of solubility on the determination of the protonable surface site density of oxyhydroxides.

The impact of the dissolved quantity of aluminum on the calculation of surface charge from titration experiments of hydrated gamma-alumina was investigated. Two methods were developed to correct this effect: direct determination of aluminum in solution in batch titration experiments and application of a dissolution rate model in continuous titration experiments. There is a large effect of dissolution on surface charge determination for pH>10 and pH < 4.

Sorption of selenium anionic species on apatites and iron oxides from aqueous solutions.

The sorption of selenite and selenate ions from aqueous solutions was investigated on hydroxyapatite, fluorapatite, goethite and hematite, in order to simulate the behavior of radioactive selenium in natural or artificial sorbing media. Correlation studies with acido-basic properties and solubility of the solids were also performed. The sorption is pH dependant, but these solids are very efficient for retaining selenite at pH values generally encountered in natural waters, with however higher K(d) values for oxides than apatites.

Morphology of RuO2-TiO2 coatings and TEM characterization of oxide sols used for their preparation.

Characterization of RuO(2) and TiO(2) sols of different aging times, obtained by forced hydrolysis of appropriate chloride salts, was performed by transmission electron microscopy (TEM). The aging time of TiO(2) sols was observed to affect the size of particles as well as the crystallinity of the solid phase of the sols. The surface morphology of RuO(2)-TiO(2) coatings on titanium, obtained by the sol-gel procedure using TiO(2) sols of different aging times and RuO(2) sol of fixed aging time, was investigated by scanning tunneling microscopy (STM) at three different scan sizes.

Sorption Mechanisms of Eu(3+) on CSH Phases of Hydrated Cements.

The sorption mechanisms of Eu(3+) on calcium silicate hydrate (CSH) phases of hydrated cement were investigated as a tool for the prediction of the behavior of trivalent radionuclides with aged/degraded cements in radioactive waste repositories. Four techniques were used: site-selective and time-resolved luminescence spectroscopy, XPS, high-resolution SEM coupled with EDX, and XRD. Results showed that europium is not precipitated in the solution despite its low solubility limit.

Sorption of Selenite (SeO(3)(2-)) on Hydroxyapatite: An Exchange Process.

The sorption of SeO(3)(2-) on hydroxyapatite surface was investigated in batch experiments over a range of pH and SeO(3)(2-) concentrations in the absence and presence of additional Ca and PO(4). The sorption is pH dependent with a maximum observed at pH values generally encountered in natural waters. While the presence of phosphate lowers SeO(3)(2-) sorption by direct competition, the presence of calcium enhances it.

A study of strontium binding to albumins, by a chromatographic method involving atomic emission spectrometric detection.

A chromatographic method involving ICP-AES (inductively coupled plasma atomic emission spectrometry) detection has been successfully applied for the study of strontium-protein complexes. The chromatographic step involves the use of gel filtration-a large-zone Hummel and Dreyer method-which allows to dissociate the bound metallic ions and the free ones. This step is followed by an ICP-AES analysis of fractions collected throughout the chromatographic experiment: the concentration of ionic metallic species in solution can therefore be calculated.

Characterization of the Sorption of Europium(III) on Calcite by Site-Selective and Time-Resolved Luminescence Spectroscopy.

Sorption of europium(III) on calcite from aqueous solution was investigated by kinetics and sorption isotherms at 323 K and by site-selective and time-resolved luminescence spectroscopy at 15 K. Three sorption sites (A, B, C) were characterized by this last technique. B constitutes a major family which appears in all samples with sorbed Eu and is characterized by an environment involving water or hydroxyl ions.

Chromatographic method involving inductively coupled plasma atomic emission spectrometric detection for the study of metal-protein complexes.

A chromatographic method has been used to study metal ion-protein complexes. It involves successively a gel filtration technique to separate and distinguish the complexed from the free metallic ions, and a spectrometric technique, inductively coupled plasma atomic emission spectrometry (ICP-AES), which allows us to calculate accurately the concentration of ionic metallic species in solution. In the chromatographic step, we applied a large-zone Hummel and Dreyer method.

Compositions and structures of copper hexacyanoferrates(II) and (III): experimental results.

The preparation, composition and structure of copper hexacyanoferrates have been investigated. Three methods were used: precipitation, local growth in an aqueous solution, and growth in a gel. Four compounds were obtained, either in powdered form or as single crystals: Cu(II)(2)Fe(II)(CN)(6) .

Copper hexacyanoferrates: Preparation, composition and structure.

A review on the chemistry of copper hexacyanoferrates during the period 1933-1993 with an emphasis on their compositions and structures in relation to the methods of preparation.

Preparation, composition and structure of some nickel and zinc ferrocyanides: Experimental results.

Several methods have been used for preparation of nickel and zinc ferrocyanides: precipitation, growth in a gel and a new method based on growth on a solid alkali-metal ferrocyanide. The granulometry, morphology, composition and structure of the compounds were studied. Only the last method of preparation gives products suitable for use as ion fixators in columns on a large scale.

Zinc and nickel ferrocyanides: preparation, composition and structure.

A review is given of work on nickel and zinc ferrocyanides during the period 1922-1983 with an emphasis on their compositions and structures in relation to the methods of preparation.