Characterization of Th Carbonate Solutions Using XAS and Implications for Thermodynamic Modeling

1996 ◽  
Vol 465 ◽  
Author(s):  
N. J. Hess ◽  
A. R. Felmy ◽  
D. Rai ◽  
S. D. Conradson
Keyword(s):  
Chemical Speciation ◽  
Chelating Agents ◽  
Chemical Species ◽  
Oxidation States ◽  
Carbonate Solutions ◽  
Ph Conditions ◽  
High Concentrations ◽  
Aqueous Complexes ◽  
Aqueous Species

ABSTRACTThe chemical behavior of actinide elements in tank solutions, in soil, and in groundwater is dependent upon the chemical species that form when aqueous solutions come in contact with the actinide compounds. In particular the chemical speciation of the reduced actinide oxidation states (III and IV) are important, for example, to DOE waste tank processing and, more generally, to nuclear waste disposal issues. Predicting the solubility of the actinides in these solutions requires identification of the strong aqueous complexes, such as carbonates and organic chelating agents, that can form in aqueous solution.Previous speciation work has often relied on indirect techniques such as potentiometric titrations or solubility measurements. Recent XAS experiments determine directly the speciation of the Th carbonato species of seven solutions under a range of carbonate concentrations and pH conditions. The presence of the pentacarbonato complex is confirmed and the complex's stability at low carbonate concentrations is determined. These experimental results support a proposed thermodynamic model that describes the solubility of Th(IV) hydrous oxide in the aqueous Na+-HCO3--CO32--OH--ClO4--H2O system extending to high concentrations at 25°C. This model is relatively simple in that only two aqueous species are included Th(OH)3CO3- and Th(CO3)56-.

scholarly journals Treatment and remediation by the stabilization/solidification process based on hydraulic binders of soil contaminated by heavy metals

2019 ◽  
Vol 18 (2) ◽  
pp. 166-178
Author(s):  
Rachid Sahnoune ◽  
Karim Moussaceb
Keyword(s):  
Heavy Metals ◽  
Chemical Species ◽  
Solidification Process ◽  
Absorption Spectrometry ◽  
Xrd Analysis ◽  
Soil Samples ◽  
Metallic Elements ◽  
Depth Analysis ◽  
High Concentrations

Abstract Nature and the environment are affected by various human industrial and/or urban discharges. Remediation for this problem requires first and foremost an in-depth analysis and an overall characterization of the intrinsic properties of the pollution-receiving environments. Secondly it is necessary to predict in these environments the behavior of dangerous chemical species (here particularly heavy metals) in the long term. This study focuses mainly on a detailed characterization of 4 soil samples sampled in vicinity of wild dump-BOULIMAT located 15 km west of the city of Bejaia-Algeria. The samples were characterised by atomic absorption spectrometry, X-ray diffraction, Fluorescence X and Infrared spectroscopy. The data showed high concentrations of metallic elements especially Zn (2,651.8 mg.kg−1) and Ni (163.44 mg.kg−1) in the soil samples. For their remediation, the stabilization/solidification (S/S) process with hydraulic binders appeared promising in reducing the polluting power of metal. This approach has considerably reduced the content of pollutants; 98 % removal was obtained for Ni and 99 % for Zn. The XRD analysis technique revealed the occurrence or absence of metallic elements in the crystallized phases.

Chemical speciation terminology: chromium chemistry and cancer

2005 ◽  
Vol 69 (5) ◽  
pp. 557-562 ◽  
Author(s):  
J. H. Duffus
Keyword(s):  
Lung Cancer ◽  
Elemental Analysis ◽  
Chemical Speciation ◽  
Chemical Species ◽  
Oxidation States ◽  
Chemical Nomenclature ◽  
Environmental Media ◽  
Chromium Vi ◽  
Carbon Compounds ◽  
Route Of Exposure

AbstractIn classical toxicology, speciation of carbon is taken for granted and the carbon compounds responsible for toxicity are always described with the appropriate chemical nomenclature. By contrast, speciation of other elements is largely ignored and elements other than carbon are often condemned as toxic because of evidence relating toxicity to only a few of the chemical species in which they occur. In some cases, such as chromium, the distinction between oxidation states (chromium III and chromium VI) may be recognized as important. The fact that chromium VI may only be a toxicological problem in certain well defined forms, such as specific chromate salts that may cause nasal and lung cancer, and then only by the respiratory route of exposure, is largely ignored. Failure to consider properly chemical speciation of elements other than carbon can lead to poor use of our resources. Laws and regulations based on simple elemental analysis may wrongly condemn environmental media or products as toxic and prevent the use of important resources.

Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

2019 ◽  
Author(s):  
Oriol Planas ◽  
Feng Wang ◽  
Markus Leutzsch ◽  
Josep Cornella
Keyword(s):  
Transition Metal ◽  
Main Group ◽  
Group Element ◽  
Oxidation States ◽  
Boron Compounds ◽  
Main Text ◽  
Main Group Element ◽  
Rational Ligand Design ◽  
Supplementary Material

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts.<br>A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.<br>

scholarly journals Adsorption Studies on Magnetic Nanoparticles Functionalized with Silver to Remove Nitrates from Waters

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1757
Author(s):  
Yesica Vicente-Martínez ◽  
Manuel Caravaca ◽  
Antonio Soto-Meca ◽  
Miguel Ángel Martín-Pereira ◽  
María del Carmen García-Onsurbe
Keyword(s):  
Magnetic Nanoparticles ◽  
Nitrate Content ◽  
Adsorption Efficiency ◽  
Experimental Conditions ◽  
Dependent Behavior ◽  
Before And After ◽  
Naoh Solution ◽  
High Concentrations ◽  
Interference Studies

This paper presents a novel procedure for the treatment of contaminated water with high concentrations of nitrates, which are considered as one of the main causes of the eutrophication phenomena. For this purpose, magnetic nanoparticles functionalized with silver (Fe3O4@AgNPs) were synthesized and used as an adsorbent of nitrates. Experimental conditions, including the pH, adsorbent and adsorbate dose, temperature and contact time, were analyzed to obtain the highest adsorption efficiency for different concentration of nitrates in water. A maximum removal efficiency of 100% was reached for 2, 5, 10 and 50 mg/L of nitrate at pH = 5, room temperature, and 50, 100, 250 and 500 µL of Fe3O4@AgNPs, respectively. The characterization of the adsorbent, before and after adsorption, was performed by energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Nitrates can be desorbed, and the adsorbent can be reused using 500 µL of NaOH solution 0.01 M, remaining unchanged for the first three cycles, and exhibiting 90% adsorption efficiency after three regenerations. A deep study on equilibrium isotherms reveals a pH-dependent behavior, characterized by Langmuir and Freundlich models at pH = 5 and pH = 1, respectively. Thermodynamic studies were consistent with physicochemical adsorption for all experiments but showed a change from endothermic to exothermic behavior as the temperature increases. Interference studies of other ions commonly present in water were carried out, enabling this procedure as very selective for nitrate ions. In addition, the method was applied to real samples of seawater, showing its ability to eliminate the total nitrate content in eutrophized waters.

scholarly journals Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhifang Chai ◽  
Amares Chatt ◽  
Peter Bode ◽  
Jan Kučera ◽  
Robert Greenberg ◽  
...  
Keyword(s):  
Nuclear Reactions ◽  
Hyperfine Interactions ◽  
Chemical Species ◽  
Radiation Detectors ◽  
Nuclear Analysis ◽  
Characterization Of Materials ◽  
Nuclear Effects ◽  
Nuclear Processes ◽  
Radioanalytical Methods

AbstractThese recommendations are a vocabulary of basic radioanalytical terms which are relevant to radioanalysis, nuclear analysis and related techniques. Radioanalytical methods consider all nuclear-related techniques for the characterization of materials where ‘characterization’ refers to compositional (in terms of the identity and quantity of specified elements, nuclides, and their chemical species) and structural (in terms of location, dislocation, etc. of specified elements, nuclides, and their species) analyses, involving nuclear processes (nuclear reactions, nuclear radiations, etc.), nuclear techniques (reactors, accelerators, radiation detectors, etc.), and nuclear effects (hyperfine interactions, etc.). In the present compilation, basic radioanalytical terms are included which are relevant to radioanalysis, nuclear analysis and related techniques.

scholarly journals Halogenated Volatile Organic Compounds in Water Samples and Inorganic Elements Levels in Ores for Characterizing a High Anthropogenic Polluted Area in the Northern Latium Region (Italy)

2021 ◽  
Vol 18 (4) ◽  
pp. 1628
Author(s):  
Mario Vincenzo Russo ◽  
Ivan Notardonato ◽  
Alberto Rosada ◽  
Giuseppe Ianiri ◽  
Pasquale Avino
Keyword(s):  
Organic Compounds ◽  
Mean Value ◽  
Greenhouse Crops ◽  
River Waters ◽  
Liquid Liquid Extraction ◽  
Volatile Organic ◽  
High Concentrations ◽  
Very High ◽  
Inorganic Fraction

This paper shows a characterization of the organic and inorganic fraction of river waters (Tiber and Marta) and ores/soil samples collected in the Northern Latium region of Italy for evaluating the anthropogenic/natural source contribution to the environmental pollution of this area. For organic compounds, organochloride volatile compounds in Tiber and Marta rivers were analyzed by two different clean-up methods (i.e., liquid–liquid extraction and static headspace) followed by gas chromatography–electron capture detector (GC-ECD) analysis. The results show very high concentrations of bromoform (up to 1.82 and 3.2 µg L−1 in Tiber and Marta rivers, respectively), due to the presence of greenhouse crops, and of chloroform and tetrachloroethene, due to the presence of handicrafts installations. For the qualitative and quantitative assessment of the inorganic fraction, it is highlighted the use of a nuclear analytical method, instrumental neutron activation analysis, which allows having more information as possible from the sample without performing any chemical-physical pretreatment. The results have evidenced high levels of mercury (mean value 88.6 µg g−1), antimony (77.7 µg g−1), strontium (12,039 µg g−1) and zinc (103 µg g−1), whereas rare earth elements show levels similar to the literature data. Particular consideration is drawn for arsenic (414 µg g−1): the levels found in this paper (ranging between 1 and 5100 µg g−1) explain the high content of such element (as arsenates) in the aquifer, a big issue in this area.

scholarly journals Characterization of the Adaptive Response to Trichloroethylene-Mediated Stresses in Ralstonia pickettii PKO1

2002 ◽  
Vol 68 (11) ◽  
pp. 5231-5240 ◽  
Author(s):  
Joonhong Park ◽  
Jerome J. Kukor ◽  
Linda M. Abriola
Keyword(s):  
Adaptive Response ◽  
Combined Effects ◽  
Similar Extent ◽  
Protective Response ◽  
Ralstonia Pickettii ◽  
Pathway Expression ◽  
High Concentrations ◽  
Tce Degradation ◽  
Solvent Stress

ABSTRACT In Ralstonia pickettii PKO1, a denitrifying toluene oxidizer that carries a toluene-3-monooxygenase (T3MO) pathway, the biodegradation of toluene and trichloroethylene (TCE) by the organism is induced by TCE at high concentrations. In this study, the effect of TCE preexposure was studied in the context of bacterial protective response to TCE-mediated toxicity in this organism. The results of TCE degradation experiments showed that cells induced by TCE at 110 mg/liter were more tolerant to TCE-mediated stress than were those induced by TCE at lower concentrations, indicating an ability of PKO1 to adapt to TCE-mediated stress. To characterize the bacterial protective response to TCE-mediated stress, the effect of TCE itself (solvent stress) was isolated from TCE degradation-dependent stress (toxic intermediate stress) in the subsequent chlorinated ethylene toxicity assays with both nondegradable tetrachloroethylene and degradable TCE. The results of the toxicity assays showed that TCE preexposure led to an increase in tolerance to TCE degradation-dependent stress rather than to solvent stress. The possibility that such tolerance was selected by TCE degradation-dependent stress during TCE preexposure was ruled out because a similar extent of tolerance was observed in cells that were induced by toluene, whose metabolism does not produce any toxic products. These findings suggest that the adaptation of TCE-induced cells to TCE degradation-dependent stress was caused by the combined effects of solvent stress response and T3MO pathway expression.

Magnetodielectric Ni ferrite ceramics with Bi2O3 additive for potential antenna miniaturizations

2009 ◽  
Vol 24 (2) ◽  
pp. 324-332 ◽  
Author(s):  
X.T. Liew ◽  
K.C. Chan ◽  
L.B. Kong
Keyword(s):  
Magnetic Properties ◽  
Dielectric Loss ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Magnetic Loss ◽  
Liquid Phase Sintering ◽  
X Ray Diffraction ◽  
Low Dielectric ◽  
High Concentrations

This paper reports on the preparation and characterization of nickel ferrite (NiFe1.98O4) ceramics doped with Bi2O3 as sintering aid. Focus has been on the effects of concentration of Bi2O3 and sintering temperature on the densification, grain growth, dielectric, and magnetic properties of the NiFe1.98O4 ceramics, with an aim at developing magnetodielectric properties, with almost equal real permeability and permittivity, as well as sufficiently low magnetic and dielectric loss tangents, over 3 to 30 MHz (high frequency or HF band). X-ray diffraction results indicated that there is no obvious reaction between NiFe1.98O4 and Bi2O3, at Bi2O3 levels of up to 7 wt% and temperatures up to 1150 °C. The addition of Bi2O3 facilitated a liquid phase sintering mechanism for the densification of NiFe1.98O4 ceramics. The addition of Bi2O3 not only improved the densification but also promoted the grain growth of NiFe1.98O4 ceramics. To achieve sufficiently low dielectric loss tangent, the concentration of Bi2O3 should not be less than 5 wt%. The low dielectric loss tangents of the samples doped with high concentrations of Bi2O3 can be attributed to the full densification of the ceramics. Magnetic properties of the NiFe1.98O4 ceramics, as a function of sintering temperature and Bi2O3 concentration, can be qualitatively explained by the Globus model. Promising magnetodielectric properties have been obtained in the sample doped with 5% Bi2O3 and sintered at 1050 °C for 2 h. The sample has almost equal values of permeability and permittivity of ∼12, together with low dielectric and magnetic loss tangents, over 3 to 30 MHz. This material might be useful for the miniaturization of HF (3 to 30 MHz) antennas.

Deposition of TRISO Particles With Superhard SiC Coatings and the Characterization of Anisotropy by Raman Spectroscopy

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
E. López-Honorato ◽  
P. J. Meadows ◽  
J. Tan ◽  
Y. Xiang ◽  
P. Xiao
Keyword(s):  
Solid Solution ◽  
Raman Spectroscopy ◽  
Pyrolytic Carbon ◽  
X Ray Diffraction ◽  
X Ray ◽  
Flat Substrate ◽  
High Concentrations ◽  
Triso Particles ◽  
Sic Coatings

In this work we have deposited silicon carbide (SiC) at 1300°C with the addition of small amounts of propylene. The use of propylene and high concentrations of methyltrichlorosilane (9 vol %) allowed the deposition of superhard SiC coatings (42 GPa). The superhard SiC could result from the presence of a SiC–C solid solution, undetectable by X-ray diffraction but visible by Raman spectroscopy. Another sample obtained by the use of 50 vol % Argon, also showed the formation of SiC with good properties. The use of a flat substrate together with the particles showed the importance of carrying out the analysis on actual particles rather than in flat substrates. We show that it is possible to characterize the anisotropy of pyrolytic carbon by Raman spectroscopy.

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