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Spectrophotometry of Neptunium in Perchloric Acid Solutions

Description: Report discussing a study testing features of the absorption spectra of different oxidation states of neptunium and perchloric acid concentration's effects on the spectra. Data regarding a disproportionation reaction present in neptunium(V) solutions in concentrated acid is included.
Date: April 14, 1950
Creator: Sjoblom, R. K. & Hindman, J. C.
Partner: UNT Libraries Government Documents Department

The Development and Application of Capillary Absorption Cells

Description: Abstract: "Various types of capillary absorption cells have been constructed from a variety of materials. These cells, having volumes as low as 160 microliters, have been used to increase the sensitivity of several colorimetrics methods as much as 1000 fold without appreciable loss of accuracy. Small volumes of solution must be used in order to concentrate the colored material present."
Date: 1951
Creator: Rosenfels, R. S.; Kirk, P. L.; Kitson, R. E.; Patton, R. L. & Curtis, R. E.
Partner: UNT Libraries Government Documents Department

Complexation of Neptunium(V) with Fluoride at Elevated Temperatures

Description: Complexation of neptunium(V) with fluoride at elevated temperatures was studied by spectrophotometry and microcalorimetry. Two successive complexes, NpO{sub 2}F(aq) and NpO{sub 2}F{sub 2}{sup -}, were identified by spectrophotometry in the temperature range of 10-70 C. Thermodynamic parameters, including the equilibrium constants and enthalpy of complexation between Np(V) and fluoride at 10-70 C were determined. Results show that the complexation of Np(V) with fluoride is endothermic and that the complexation is enhanced by the increase in temperature - a two-fold increase in the stability constants of NpO{sub 2}F(aq) and more than five-fold increase in the stability constants of NpO{sub 2}F{sub 2}{sup -} as the temperature is increased from 10 to 70 C.
Date: June 16, 2008
Creator: Rao, Linfeng; Tian, Guoxin; Xia, Yuanxian & Friese, Judah I.
Partner: UNT Libraries Government Documents Department

Complexation of NpO2+ with N-methyl-iminodiacetic Acid: in Comparison with Iminodiacetic and Dipicolinic Acids

Description: Complexation of Np(V) with N-methyl-iminodiacetic acid (MIDA) in 1 M NaClO{sub 4} solution was studied with multiple techniques including potentiometry, spectrophotometry, and microcalorimetry. The 1:2 complex, NpO{sub 2}(MIDA){sub 2}{sup 3-} was identified for the first time in aqueous solution. The correlation between its optical absorption properties and symmetry was discussed, in comparison with Np(V) complexes with two structurally related nitrilo-dicarboxylic acids, iminodiacetic acid (IDA) and dipicolinic acid (DPA). The order of the binding strength (DPA > MIDA > IDA) is explained by the difference in the structural and electronic properties of the ligands. In general, the nitrilo-dicarboxylates form stronger complexes with Np(V) than oxy-dicarboxylates due to a much more favorable enthalpy of complexation.
Date: October 1, 2010
Creator: Tian, Guoxin & Rao, Linfeng
Partner: UNT Libraries Government Documents Department


Description: An investigation was conducted to compare the flame emission spectrum of Fe as recorded by the Beckman DU and the ORNL flame spectrophotometers. It was found that the ORNL instrument is best suited to the application. Optimum operating conditions are described as well as results of investigations to determine interferences. (J.R.D.)
Date: May 1, 1959
Creator: Menis, O
Partner: UNT Libraries Government Documents Department

The Spectrophotometric Determination of Uranium by Means of the Azide Ion

Description: Abstract: A method has been devised for the spectrophotometric determination of uranium by means of the azide ion. The method possesses several advantages over the various thiocyanate procedures. It has a slightly higher sensitivity, an aqueous medium is used, and the reaction product is more stable. Within the concentration limits tested, Beer's law is obeyed.
Date: August 1955
Creator: Feinstein, H. I.
Partner: UNT Libraries Government Documents Department

Precious Metal Recovery from Fuel Cell MEA's

Description: In 2003, Engelhard Corporation received a DOE award to develop a cost-effective, environmentally friendly approach to recover Pt from fuel cell membrane electrode assemblies (MEA’s). The most important precious metal used in fuel cells is platinum, but ruthenium is also added to the anode electrocatalyst if CO is present in the hydrogen stream. As part of the project, a large number of measurements of Pt and Ru need to be made. A low-cost approach to measuring Pt is using the industry standard spectrophotometric measurement of Pt complexed with stannous chloride. The interference of Ru can be eliminated by reading the Pt absorbance at 450 nm. Spectrophotometric methods for measuring Ru, while reported in the literature, are not as robust. This paper will discuss the options for measuring Pt and Ru using the method of UV-VIS spectrophotometry
Date: April 25, 2004
Creator: Shore, Lawrence
Partner: UNT Libraries Government Documents Department

Complexation of Lactate with Nd(III) and Eu(III) at Variable Temperatures: Studies by Potentiometry, Microcalorimetry, Optical Absorption and Luminescence Spectroscopy

Description: Complexation of neodymium(III) and europium(III) with lactate was studied at variable temperatures by potentiometry, absorption spectrophotometry, luminescence spectroscopy and microcalorimetry. Stability constants of three successive lactate complexes (ML{sup 2+}, ML{sup 2+} and ML{sub 3}(aq), where M stands for Nd and Eu, and L stands for lactate) at 10, 25, 40, 55 and 70 C were determined. The enthalpies of complexation at 25 C were determined by microcalorimetry. Thermodynamic data show that the complexation of trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) with lactate is exothermic, and the complexation becomes weaker at higher temperatures. Results from optical absorption and luminescence spectroscopy suggest that the complexes are inner-sphere chelate complexes in which the protonated {alpha}-hydroxyl group of lactate participates in the complexation.
Date: October 1, 2010
Creator: Tian, Guoxin; Martin, Leigh R. & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Interactions of Ionic Liquids with Uranium and its Bioreduction

Description: We investigated the influence of ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM]{sup +}[PF{sub 6}]{sup -}, N-ethylpyridinium trifluoroacetate [EtPy]{sup +}[CF{sub 3}COO]{sup -} and N-ethylpyridinium tetrafluoroborate [Et-Py]{sup +}[BF{sub 4}]{sup -} on uranium reduction by Clostridium sp. under anaerobic conditions. Potentiometric titration, UV-vis spectrophotometry, LC-MS and EXAFS analyses showed monodentate complexation between uranyl and BF{sub 4}{sup -} PF{sub 6}{sup -}; and bidentate complexation with CF{sub 3}COO{sup -}. Ionic liquids affected the growth of Clostridium sp. as evidenced by decrease in optical density, changes in pH, gas production, and the extent of U(VI) reduction and precipitation of U(IV) from solution. Reduction of U(VI) to U(IV) was observed in the presence of [EtPy][BF{sub 4}] and [BMIM][PF{sub 6}] but not with [EtPy][CF{sub 3}COO].
Date: September 18, 2012
Creator: Zhang, C. & Francis, A.
Partner: UNT Libraries Government Documents Department

Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes

Description: Complexation of neodymium(III) with nitrate was studied at variable temperatures (25, 40, 55 and 70 C) by spectrophotometry and microcalorimetry. The NdNO{sub 3}{sup 2+} complex is weak and becomes slightly stronger as the temperature is increased. The enthalpy of complexation at 25 C was determined by microcalorimetry to be small and positive, (1.5 {+-} 0.2) kJ {center_dot} mol{sup -1}, in good agreement with the trend of the stability constant at variable temperatures. Luminescence emission spectra and lifetime of Eu(III) in nitrate solutions suggest that inner-sphere and bidentate complexes form between trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) and nitrate in aqueous solutions. Specific Ion Interaction approach (SIT) was used to obtain the stability constants of NdNO{sub 3}{sup 2+} at infinite dilution and variable temperatures.
Date: December 10, 2008
Creator: Rao, Linfeng & Tian, Guoxin
Partner: UNT Libraries Government Documents Department

Effect of temperature on the complexation of Uranium(VI) with fluoride in aqueous solutions

Description: Complexation of U(VI) with fluoride at elevated temperatures in aqueous solutions was studied by spectrophotometry. Four successive complexes, UO{sub 2}F{sup +}, UO{sub 2}F{sub 2}(aq), UO{sub 2}F{sub 3}{sup -}, and UO{sub 2}F{sub 4}{sup 2-}, were identified, and the stability constants at 25, 40, 55, and 70 C were calculated. The stability of the complexes increased as the temperature was elevated. The enthalpies of complexation at 25 C were determined by microcalorimetry. Thermodynamic parameters indicate that the complexation of U(VI) with fluoride in aqueous solutions at 25 to 70 C is slightly endothermic and entropy-driven. The Specific Ion Interaction (SIT) approach was used to obtain the thermodynamic parameters of complexation at infinite dilution. Structural information on the U(VI)/fluoride complexes was obtained by extended X-ray absorption fine structure spectroscopy.
Date: May 18, 2009
Creator: Tian, Guoxin & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Thermodynamics of the Complexation of Uranium(VI) by oxalate in aqueous solution at 10-70oC

Description: The protonation reactions of oxalate (ox) and the complex formation of uranium(VI) with oxalate in 1.05 mol kg{sup -1} NaClO{sub 4} were studied at variable temperatures (10-70 C). Three U(VI)/ox complexes (UO{sub 2}ox{sub j}{sup (2-2j){sup +}} with j = 1, 2, 3) were identified in this temperature range. The formation constants and the molar enthalpies of complexation were determined by spectrophotometry and calorimetry. The complexation of uranium(VI) with oxalate ion is exothermic at lower temperatures (10-40 C) and becomes endothermic at higher temperatures (55-70 C). In spite of this, the free energy of complexation becomes more negative at higher temperatures due to increasingly more positive entropy of complexation that exceeds the increase of the enthalpy of complexation. The thermodynamic parameters at different temperatures, in conjunction with the literature data for other dicarboxylic acids, provide insight into the relative strength of U(VI) complexes with a series of dicarboxylic acids (oxalic, malonic and oxydiacetic) and rationalization for the highest stability of U(VI)/oxalate complexes in the series. The data reported in this study are of importance in predicting the migration of uranium(VI) in geological environments in the case of failure of the engineering barriers which protect waste repositories.
Date: March 31, 2009
Creator: Di Bernardo, Plinio; Zanonato, Pier Luigi; Tian, Guoxin; Tolazzi, Marilena & Rao, Linfeng
Partner: UNT Libraries Government Documents Department


Description: In the present study an existing spectrophotometry system was upgraded to provide high-resolution ultraviolet (UV), visible (Vis), and near infrared (NIR) analyses of test solutions to measure the relative solubilities of petroleum residua dissolved in eighteen test solvents. Test solutions were prepared by dissolving ten percent petroleum residue in a given test solvent, agitating the mixture, followed by filtration and/or centrifugation to remove insoluble materials. These solutions were finally diluted with a good solvent resulting in a supernatant solution that was analyzed by spectrophotometry to quantify the degree of dissolution of a particular residue in the suite of test solvents that were selected. Results obtained from this approach were compared with spot-test data (to be discussed) obtained from the cosponsor.
Date: March 1, 2006
Creator: Redelius, Per
Partner: UNT Libraries Government Documents Department

A comparative study of the complexation of Np(V) with N,N-dimethyl-3-oxa-glutaramic acid and related ligands: thermodynamics, optical properties and structural aspects

Description: Complexation of Np(V) with N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) was studied in comparison with its diamide analog, N,N,N{prime},N{prime}-tetramethyl-3-oxa-glutaramide (TMOGA), and dicarboxylate analog, oxydiacetic acid (ODA). Thermodynamic parameters, including the stability constant and the enthalpy of complexation, were determined by spectrophotometry and calorimetry. Single-crystal structure of NpO{sub 2}(H{sub 2}O)(DMOGA){center_dot}H{sub 2}O(c) was identified by X-ray diffractometry using synchrotron radiation. Like ODA and TMOGA, DMOGA forms a tridentate Np(V) complex, with three oxygen atoms coordinating to the linear NpO{sub 2}{sup +} moiety via the equatorial plane. The stability constants, enthalpy and entropy of complexation generally decrease in the order ODA > DMOGA > TMOGA, suggesting that the complexation is entropy driven and the substitution of a carboxylate group with an amide group reduces the strength of complexation with Np(V) due to the decrease in the entropy of complexation.
Date: March 29, 2010
Creator: Rao, Linfeng; Tian, Guoxin & Teat, Simon J.
Partner: UNT Libraries Government Documents Department

Regulation of Coal Polymer Degradation by Fungi

Description: During this reporting period we have further studied the oxidation of soluble coal macromolecules by lignin peroxidase from Phanerochaete chrysosporium . Previous studies by others have suggested that a soluble fraction (coal macromolecule B-111) from a nitric acid solubilized North Dakota Lignite is depolymerized by this enzyme. Our investigations indicate that fraction B-111 is a substrate for lignin peroxidase as this material is decolorized in the presence of lignin peroxidase H8 and hydrogen peroxide. Of interest, however, is the observation that little, if any, depolymerization of this material occurs. Instead, it appears that lignin peroxidase and coal macromolecule B-111 form a precipitate. These results are similar to those observed in our investigations of lignin peroxidase mediated oxidation of oxalate solubilize coal macromolecule. Previous studies in our laboratory using a spectrophotometric assay suggested that, in addition to oxalate, several other fungal metabolites are able to solubilize leonardite. We have reinvestigated this phenomenon using a more reliable gravimetric procedure for assessing solubilization. Our results confirm our earlier findings that malate, oxaloacetate and citrate are effective solubilizing agents whereas succinate, fumarate and x-ketoglutarate solubilize relatively small amounts of leonardite. Finally, we have studied the composition of the insoluble material remaining following extensive solubilization by sodium oxalate. The ratio of hydrogen to carbon is increased in the insoluble material relative to the parent leonardite. However, the ratio of oxygen to carbon is also increased in the insoluble material. Thus, the insoluble material does not appear to be more highly reduced that the parent leonardite and is not likely to be a better fuel that the parent material.
Date: September 1998
Partner: UNT Libraries Government Documents Department

Composition for detecting uranyl

Description: The present invention relates to an indicator composition for use in spectrophotometric detection of a substance in a solution, and a method for making the composition. Useful indicators are sensitive to the particular substance being measured, but are unaffected by the fluid and other chemical species that may be present in the fluid. Optical indicators are used to measure the uranium concentration of process solutions in facilities for extracting uranium from ores, production of nuclear fuels, and reprocessing of irradiated fuels. The composition comprises an organohalide covalently bonded to an indicator for the substance, in such a manner that the product is itself an indicator that provides increased spectral resolution for detecting the substance. The indicator is preferably arsenazo III and the organohalide is preferably cyanuric chloride. These form a composition that is ideally suited for detecting uranyl.
Date: January 1, 1994
Creator: Baylor, L.C. & Stephens, S.M.
Partner: UNT Libraries Government Documents Department

Procedure for plutonium determination using Pu(VI) spectra

Description: This document describes a simple spectrophotometric method for determining total plutonium in nitric acid solutions based on the spectrum of Pu(VI). Plutonium samples in nitric acid are oxidized to Pu(VI) with Ce(IV) and the net absorbance at the 830 nm peak is measured.
Date: September 1, 1996
Creator: Walker, L.F.; Temer, D.J. & Jackson, D.D.
Partner: UNT Libraries Government Documents Department