Static Dissolution of Uo2 in Interstitial Boom Clay Water

1999 ◽  
Vol 556 ◽  
Author(s):  
K. Lemmens ◽  
C. Cachoir ◽  
P. Van Iseghem
Keyword(s):  
Uranium Concentration ◽  
Solid Phase ◽  
Experimental Conditions ◽  
Boom Clay ◽  
Carbonate Concentration ◽  
Reducing Conditions ◽  
Ph Conditions ◽  
The Impact ◽  
Uranium Species ◽  
Sulfide Species

AbstractStatic dissolution experiments were performed with unirradiatcd UO2 in Boom Clay water. The objectives were (1) to measure the solubility of uranium species in Boom Clay water, with UO2 as the solid phase, and (2) to assess the impact of dissolved organic matter and carbonate concentration on this solubility. The tests were supported by calculations with geochemical codes to indicate possibly solubility controlling solid phases. The tests were performed in anoxic and reducing conditions, at 20 and 25°C. The following conclusions could be drawn: (1) Within 2 months in anoxic conditions, the uranium concentrations appear to approach saturation. (2) The “near-saturation” concentrations are between 2.4 and 7.8× 10−7 M. (3) The influence of the carbonate concentration and humic acids on the uranium concentration was apparently small, but the interpretation is hampered by pH and Eh variations. (4) The concentrations tend to be higher than the concentrations found in literature for similar Eh and/or pH conditions; this can probably be explained by small differences in experimental conditions. (5) The measured “near steadystate” uranium concentration in the real clay water agrees relatively well with the solubility calculated for uraninite. (6) Addition of sulfide species reduced the rcdox potential, but not the uranium concentrations, except in real Boom Clay water.

Dissolution of uranium dioxide in simulated Boom clay water

2002 ◽  
Vol 90 (2) ◽  
Author(s):  
S. Guilbert ◽  
M.J. Guittet ◽  
N. Barré ◽  
P. Trocellier ◽  
M. Gautier-Soyer ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Uranium Dioxide ◽  
Uranium Concentration ◽  
Boom Clay ◽  
Solubility Behavior ◽  
Fuel Pellets ◽  
Reducing Conditions ◽  
Comparable Period

SummaryThe solubility behavior of uranium dioxide was studied under oxidizing and reducing conditions in simulated Belgian Boom clay water at 25 °C, on unirradiated fuel pellets. For a comparable period (1 month), the uranium concentration and the dissolution rate (10

Dissolution of UO2 at Various Parametric Conditions: A Comparison Between Calculated and Experimental Results

1988 ◽  
Vol 127 ◽  
Author(s):  
Kaija Olliia
Keyword(s):  
Solid Phase ◽  
Reaction Pathway ◽  
Critical Factor ◽  
Limiting Factor ◽  
Carbonate Concentration ◽  
Reducing Conditions ◽  
Lower Solubility ◽  
Solubility Constant ◽  
Experimental Solubility ◽  
Bicarbonate Solutions

ABSTRACTThe solubilities of uranium measured in deionized water, in sodium bicarbonate solutions as a function of carbonate concentration and in two types of synthetic groundwaters have been compared with those predicted using the reaction pathway program, PHREEQE. All the measurements were carried out under both air-saturated, oxidizing and anoxic, reducing conditions.The experimental solubility values of uranium under oxidizing conditions are, in general, lower when compared to the corresponding theoretical ones calculated by PHREEQE. A critical factor is the choice of solubility constant for the solid phase. The reason for the lower solubility values may also be the mechanism of dissolution leading for example either to a situation where low dissolution rate is a limiting factor, or to formation of some solid phase of uranium with lower solubility. The experimental solubility values under reducing conditions appear to be in good agreement with the theoretical solubility values.

Mechanism of Unirradiated UO2 (S) Dissolution in Nacl and Mgcl2 Brines at 25°C

1994 ◽  
Vol 353 ◽  
Author(s):  
Joan de Pablo ◽  
J. Giménez ◽  
M. E. Torrero ◽  
I. Casas
Keyword(s):  
Computer Program ◽  
Phase Formation ◽  
Uranium Concentration ◽  
Solid Phase ◽  
Secondary Phase ◽  
Release Rates ◽  
Reducing Conditions ◽  
Secondary Phase Formation ◽  
Initial Release

AbstractThe dissolution of unirradiated UO2 (s) has been studied in NaCl and MgCl2 brines under both reducing and oxidizing conditions.The initial uranium release under reducing conditions has been attributed to the dissolution of an initial oxidized layer. The final uranium concentrations have been modeled by using the PHRQPITZ computer program giving the solubility of the solid phase UO2 (s).Under oxidizing conditions, the initial release is the sum of the oxidized layer dissolution and the oxidation/dissolution of the UO2. The release rates calculated are 1.4·10−5 mol d−1 m−2 in NaCl2-brine and 3.6·10−5 mol d−1 m−2 in MgCl2-brine. After the initial release, uranium concentration in the NaCI-brine reaches a constant value, which has been attributed to the formation of a secondary solid phase. In MgCl2-brine, the uranium concentration increases slowly indicating, in this case, no control by secondary phase formation.

Dissolution Behaviour of UO2 in Anoxic Conditions. Comparison of Ca-bentonite and Boom Clay

2006 ◽  
Vol 985 ◽  
Author(s):  
Thierry Mennecart ◽  
Christelle Cachoir ◽  
Karel Lemmens
Keyword(s):  
Uranium Concentration ◽  
General Concept ◽  
Spent Fuel ◽  
Retention Capacity ◽  
Anoxic Conditions ◽  
Boom Clay ◽  
Reducing Conditions ◽  
Dissolution Behaviour ◽  
Main Component ◽  
Colloidal Fraction

AbstractA general concept for the disposal of spent fuel in clay formations is based on the multibarrier principle. In such concept, the barriers for radionuclides released into the environment are the clay host rock, the backfill, the canister overpack and the fuel itself. The innermost barrier is the dissolution of UO2 matrix, which is the main component of spent fuel. However the dissolution of UO2 upon groundwater contact depends strongly on the (geo)chemical constraints prevailing in the repository. In order to determine in how far the clay properties influence the dissolution of spent fuel, two different kinds of clay were considered: Ca-bentonite which presents an initial oxidizing environment, and Boom Clay which is characterized by its strong reducing capacity. The experiments were carried out with depleted UO2 in presence of either compacted dry Ca-bentonite with Boom Clay groundwater or compacted dry Boom Clay with Boom Clay groundwater. The leach tests were performed at 25°C in anoxic atmosphere (glove box under 0.4%CO2/99.6%Ar) for 2 years. The U concentrations were sampled during these 2 years, once every 6 months and the amount of U was determined in the clay after 2 years in order to determine the dissolution rate. After 2 years, an unexpected uranium concentration was found 50 times higher in the system Boom Clay with Boom Clay water (2.10-7 mol/L) than in the system Ca-bentonite with Boom Clay water (4.10-9 mol/L), maybe resulting from a larger colloidal fraction in the system Boom Clay with Boom Clay water. Final results are expected to allow the comparison of the U retention capacity of Ca- bentonite and Boom Clay in anoxic conditions with the U retention of Boom Clay found in reducing conditions.

Development of Strategies for Glycopeptide Synthesis: An Overview on the Glycosidic Linkage

2020 ◽  
Vol 24 (21) ◽  
pp. 2475-2497
Author(s):  
Andrea Verónica Rodríguez-Mayor ◽  
German Jesid Peralta-Camacho ◽  
Karen Johanna Cárdenas-Martínez ◽  
Javier Eduardo García-Castañeda
Keyword(s):  
Chemical Synthesis ◽  
Solid Phase ◽  
Building Blocks ◽  
Heterogeneous Environments ◽  
Phase Synthesis ◽  
Low Concentrations ◽  
Biological Sources ◽  
Synthetic Routes ◽  
The Impact ◽  
Potential Use

Glycoproteins and glycopeptides are an interesting focus of research, because of their potential use as therapeutic agents, since they are related to carbohydrate-carbohydrate, carbohydrate-protein, and carbohydrate-lipid interactions, which are commonly involved in biological processes. It has been established that natural glycoconjugates could be an important source of templates for the design and development of molecules with therapeutic applications. However, isolating large quantities of glycoconjugates from biological sources with the required purity is extremely complex, because these molecules are found in heterogeneous environments and in very low concentrations. As an alternative to solving this problem, the chemical synthesis of glycoconjugates has been developed. In this context, several methods for the synthesis of glycopeptides in solution and/or solid-phase have been reported. In most of these methods, glycosylated amino acid derivatives are used as building blocks for both solution and solid-phase synthesis. The synthetic viability of glycoconjugates is a critical parameter for allowing their use as drugs to mitigate the impact of microbial resistance and/or cancer. However, the chemical synthesis of glycoconjugates is a challenge, because these molecules possess multiple reaction sites and have a very specific stereochemistry. Therefore, it is necessary to design and implement synthetic routes, which may involve various protection schemes but can be stereoselective, environmentally friendly, and high-yielding. This review focuses on glycopeptide synthesis by recapitulating the progress made over the last 15 years.

Introduction to geomicrobiology

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Fossil Fuels ◽  
Solid Phase ◽  
Direct Reduction ◽  
Iron Oxidation ◽  
Mineral Dissolution ◽  
Precipitation Process ◽  
Soluble Ions ◽  
Chemolithoautotrophic Bacteria ◽  
The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

scholarly journals Glucuronides Hydrolysis by Intestinal Microbial β-Glucuronidases (GUS) Is Affected by Sampling, Enzyme Preparation, Buffer pH, and Species

Pharmaceutics ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1043
Author(s):  
Christabel Ebuzoeme ◽  
Imoh Etim ◽  
Autumn Ikimi ◽  
Jamie Song ◽  
Ting Du ◽  
...  
Keyword(s):  
Enzyme Preparation ◽  
Reaction System ◽  
Reaction Rates ◽  
Experimental Conditions ◽  
Model Animal ◽  
Fresh Feces ◽  
Time Buffer ◽  
Exogenous Compounds ◽  
Activity Loss ◽  
The Impact

Glucuronides hydrolysis by intestinal microbial β-Glucuronidases (GUS) is an important procedure for many endogenous and exogenous compounds. The purpose of this study is to determine the impact of experimental conditions on glucuronide hydrolysis by intestinal microbial GUS. Standard probe 4-Nitrophenyl β-D-glucopyranoside (pNPG) and a natural glucuronide wogonoside were used as the model compounds. Feces collection time, buffer conditions, interindividual, and species variations were evaluated by incubating the substrates with enzymes. The relative reaction activity of pNPG, reaction rates, and reaction kinetics for wogonoside were calculated. Fresh feces showed the highest hydrolysis activities. Sonication increased total protein yield during enzyme preparation. The pH of the reaction system increased the activity in 0.69–1.32-fold, 2.9–12.9-fold, and 0.28–1.56-fold for mouse, rat, and human at three different concentrations of wogonoside, respectively. The Vmax for wogonoside hydrolysis was 2.37 ± 0.06, 4.48 ± 0.11, and 5.17 ± 0.16 μmol/min/mg and Km was 6.51 ± 0.71, 3.04 ± 0.34, and 0.34 ± 0.047 μM for mouse, rat, and human, respectively. The inter-individual difference was significant (4–6-fold) using inbred rats as the model animal. Fresh feces should be used to avoid activity loss and sonication should be utilized in enzyme preparation to increase hydrolysis activity. The buffer pH should be appropriate according to the species. Inter-individual and species variations were significant.

A solid-phase extraction method that eliminates matrix effects of complex pulp mill effluents for the analysis of lipophilic wood extractives

2020 ◽  
Vol 35 (4) ◽  
pp. 577-588
Author(s):  
Sebastian España Orozco ◽  
Philipp Zeitlinger ◽  
Karin Fackler ◽  
Robert H. Bischof ◽  
Antje Potthast
Keyword(s):  
Solid Phase Extraction ◽  
Matrix Effects ◽  
Solid Phase ◽  
Internal Standard ◽  
Pulp Mill ◽  
Phase Extraction ◽  
Wood Extractives ◽  
Wood Extractive ◽  
Pulp Mill Effluents ◽  
The Impact

AbstractThe extraction of lipophilic wood extractives from pulp and paper process waters proves to be a challenging task, due to harsh and alternating process and sample conditions. This study has determined the potential use of polymeric sorbents for solid-phase extraction (SPE) and compared to classical silica-based reversed-phase packed columns, with polymeric hydrophilic-lipophilic balanced (HLB) cartridges being the sorbent with the most potential. Recovery functions were obtained with an internal standard mixture representative for the main lipophilic wood extractive groups, which are fatty acids and alcohols, sterols, sterol esters and triglycerides. The impact of pH, sample volume and sample matrix, expressed as TOC and cations, on the retention behavior of lipophilic extractives during SPE of industrial samples were determined with polymeric HLB sorbent. High variations in the composition of pulp mill matrices led to different optimal extraction conditions. Thus, a new SPE protocol was developed, which bypasses matrix interferences and omits the loss of analytes due to sample preparation. The method is applicable to different pulp mill effluents with large discrepancies in pH and sample matrices, resulting in recoveries >90 % with RSD <5 % for all lipophilic wood extractives.

scholarly journals Solid-Phase Extraction Embedded Dialysis (SPEED), an Innovative Procedure for the Investigation of Microbial Specialized Metabolites

Marine Drugs ◽  
2021 ◽  
Vol 19 (7) ◽  
pp. 371
Author(s):  
Phuong-Y Mai ◽  
Géraldine Le Goff ◽  
Erwan Poupon ◽  
Philippe Lopes ◽  
Xavier Moppert ◽  
...  
Keyword(s):  
Solid Phase Extraction ◽  
Solid Phase ◽  
Chemical Space ◽  
Molecular Profile ◽  
Phase Extraction ◽  
Specialized Metabolites ◽  
Streptomyces Albidoflavus ◽  
Cultivation Process ◽  
The Impact

Solid-phase extraction embedded dialysis (SPEED technology) is an innovative procedure developed to physically separate in-situ, during the cultivation, the mycelium of filament forming microorganisms, such as actinomycetes and fungi, and the XAD-16 resin used to trap the secreted specialized metabolites. SPEED consists of an external nylon cloth and an internal dialysis tube containing the XAD resin. The dialysis barrier selects the molecular weight of the trapped compounds, and prevents the aggregation of biomass or macromolecules on the XAD beads. The external nylon promotes the formation of a microbial biofilm, making SPEED a biofilm supported cultivation process. SPEED technology was applied to the marine Streptomyces albidoflavus 19-S21, isolated from a core of a submerged Kopara sampled at 20 m from the border of a saltwater pond. The chemical space of this strain was investigated effectively using a dereplication strategy based on molecular networking and in-depth chemical analysis. The results highlight the impact of culture support on the molecular profile of Streptomyces albidoflavus 19-S21 secondary metabolites.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

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