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Obten??o de ferrita de cobalto atrav?s de dois m?todos de s?ntese: m?todo de complexa??o combinando EDTA/Citrato e m?todo hidrot?rmico / Obtaining cobalt ferrite through two synthesis methods: Complexation Method Conbining EDTA/Citrate and Hydrothermal MethodMedeiros, Indira Aritana Fernandes de 17 December 2013 (has links)
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Previous issue date: 2013-12-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work it was synthesized and characterized the cobalt ferrite (CoFe2O4) by
two methods: complexation combining EDTA/Citrate and hydrothermal investigating the
influence of the synthesis conditions on phase formation and on the crystallite size. The
powders were mainly characterized by x-ray diffraction. In specific cases, it was also used
scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray
fluorescence (XRF) and isotherms of adsorption and desorption of nitrogen (BET method).
The study of the crystallite size was based on the interpretation of x-ray diffractograms
obtained and estimated by the method of Halder-Wagner-Scherrer and Langford. An
experimental design was made in order to assist in quantifying the influence of synthesis
conditions on the response variables. The synthesis parameters evaluated in this study were:
pH of the reaction medium (8, 9 and 10), the calcination temperature (combined complexation
method EDTA/Citrate 600?C, 800?C and 1000?C), synthesis temperature (hydrothermal
method 120?C, 140?C and 160?C), calcination time (combined complexation method
EDTA/Citrate - 2, 4 and 6 hours) and time of synthesis (hydrothermal method 6, 15 and 24
hours). By the hydrothermal method was possible to produce mesoporous powders with high
purity, with an average crystallite size up to 7 nm, with a surface area of 113.44 m?/g in the
form of pellets with irregular morphology. By using the method of combined complexation
EDTA/Citrate, mesoporous powders were produced with greater purity, crystallite size up to
22nm and 27.95 m?/g of surface area in the form of pellets with a regular morphology of
plaques. In the experimental design was found that the hydrothermal method to all the studied
parameters (pH, temperature and time) have significant effect on the crystallite size, while to
the combined complexation method EDTA/Citrate, only temperature and time were
significant / Neste trabalho foi sintetizada e caracterizada a ferrita de cobalto (CoFe2O4)
atrav?s dos m?todos complexa??o combinada EDTA/Citrato e hidrot?rmico, investigando a
influ?ncia das condi??es de s?ntese na forma??o da fase e no tamanho m?dio de cristalito. Os
p?s foram caracterizados principalmente por difra??o de raios-x. Em casos espec?ficos,
tamb?m foi utilizado microscopia eletr?nica de varredura (MEV), espectroscopia de energia
dispersiva (EDS), fluoresc?ncia de raios-x (FRX) e isotermas de adsor??o e dessor??o de
nitrog?nio (M?todo BET). O estudo do tamanho de cristalito foi baseado na interpreta??o dos
difratogramas de raios-x obtidos e estimado atrav?s do m?todo de Halder-Wagner-Langford
(HWL) e de Scherrer. Um planejamento experimental foi realizado com a finalidade de
auxiliar na quantifica??o da influ?ncia das condi??es de s?ntese nas vari?veis-resposta. Os
par?metros de s?ntese avaliados neste trabalho foram: pH do meio reacional (8, 9 e 10),
temperatura de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 600?C,
800?C e 1000?C), temperatura de s?ntese (m?todo hidrot?rmico 120?C, 140?C e 160?C),
tempo de calcina??o (m?todo de complexa??o combinando EDTA/Citrato 2, 4 e 6 hrs) e
tempo de s?ntese (m?todo hidrot?rmico 6, 15 e 24 hrs). Pelo m?todo hidrot?rmico foi
poss?vel produzir p?s mesoporosos com elevado grau de pureza, com tamanho m?dio de
cristalito de at? 7nm, com ?rea superficial de 113,44m?/g e na forma de aglomerados com
morfologia irregular. Ao se utilizar o m?todo de complexa??o combinando EDTA/Citrato
foram produzidos p?s mesoporosos com maior pureza, cristalitos com at? 22nm de tamanho,
27,95m?/g de ?rea superficial e na forma de aglomerados com morfologia regular de placas.
No planejamento experimental foi constatado que no caso do m?todo hidrot?rmico todos os
par?metros estudados (pH, Temperatura e tempo) apresentam efeito significativo no tamanho
de cristalito, enquanto que, para o m?todo de complexa??o combinando EDTA/Citrato,
apenas a temperatura e o tempo foram significativos / 2020-01-01
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Thermodynamic and structural study of the interaction between Ru(bpy)2dppz 2+ and DNA / Interaction entre (Ru(bpy)2dppz(2+ et un brin court d'ADN : étude thermodynamique et structuraleJia, Fuchao 22 November 2013 (has links)
Dans une première partie, nous mesurons l'affinité de l'interaction entre [Ru(pby)2dppz]2+ et l'ADN en utilisant la luminescence induite lors de la complexation. Nous étudions l'évolution de l'affinité lorsque la force ionique de la solution augmente. Dans une deuxième partie, nous modifions les extrémités d'un double brin d'ADN en y greffant des fluorophores. De la mesure de transfert d'énergie non-radiative entre ces fluorophores, nous étudions l'évolution de la longueur du complexe. Nous effectuons un dosage d'un double brin de 15 paires de bases d'ADN par le complexe ruthéné. Nous nous servons de la luminescence induite par l'intercalation du groupement dppz. Cependant, l'incrément de luminescence par groupement intercalé n'est pas connu, et nous ne pouvons pas le mesurer en saturant le brin d'ADN. Nous utilisons alors une technique mise au point par Nishida [Method for Measuring the Binding of Small Molecules to Proteins from Binding-Induced Alterations of Physical-Chemical Properties], dans laquelle deux titrations de deux solutions d'ADN de deux concentrations différentes sont effectuées. En utilisant le fait que, lorsque deux solutions d'ADN complexé par le composé ruthéné, possèdent la même luminescence par paire de base , le taux de complexation de ces deux solutions doit être le même, nous pouvons alors déterminer, sans hypothèse supplémentaire, le taux de complexation de l'ADN. De l'évolution de ce taux en fonction avec la concentration de ligand, nous déduisons son affinité pour l'ADN. Nous étudions maintenant le changement de longueur d'un double brin d'ADN de 15 paires de bases, modifié à ses deux extrémités par deux fluorophores : Alexa488 et Alexa568. Lorsque Alexa 488 est porté dans un état excité, il peut se désexciter en transférant de l'énergie de manière non-radiative à Alexa568, qui se désexcite alors en émettant des photons de plus faibles énergie que ceux émis par Alexa488. L'efficacité de ce transfert d'énergie peut être quantifié à partir de la mesure des intensités émises à basse et haute énergie. Elle dépend a priori de l'efficacité couplage (et en conséquence de la distance) entre les deux fluorophores. Nous effectuons des mesures de temps de vie des états excités de chacun des fluorophores. Nous avons observé que l'addition de ligand a pour conséquence une forte inhibition quenching des fluorophores. De l'analyse de l'évolution du temps de vie du fluorophore donneur d'une part et de celui du fluorophore accepteur d'autre part, nous déduisons l'évolution de l'efficacité du transfert d'énergie en fonction de la concentration de ligand. Nous confrontons les résultats obtenus par chacune de ces analyses, et en déduisons finalement, en nous servant de l'analyse de l'équilibre effectuée dans la première partie, l'évolution de la longueur de la chaîne en fonction du taux de complexation / This Ph.D thesis is mainly divided in to 2 parts. The first part is luminescence study, we are interested in the affinity constant (Ka) change under different salinity environments when the complexation of [Ru(bpy)2dppz]2+-DNA arrive equilibrium. In the second part, we focus our attention on the kinetic study by fluorescence which comes from the fluorophore. The distance change between 2 fluorophores is explored when [Ru(bpy)2dppz]2+ intercalates into DNA, which lead to the variation of DNA conformation. Any changes in DNA conformation will be reflected by the efficiency change of fluorescence resonance energy transfer (FRET). Quantitative analysis on the Ru(bpy)2dppz]2+-DNA interaction will be built in the second part. In the first part, the interaction of [Ru(bpy)2dppz]2+ with DNA is studied in a wide range of DNA / [Ru(bpy)2dppz]2+ ratios by using the luminescence signal which comes from complex. The affinity constant (Ka) is explored under different chloride sodium concentration (NaCl=[0, 100 mM]), when the complexation reaches equilibrium. Nishida method is employed to compute the value of Ka without any hypothesis. The value of affinity constant is at the level scale of 106 M-1 which is basically identical to the other researcher’s results. Ka decreased with increasing the concentration of NaCl as we expected. Quantitative analysis on the Ru(bpy)2dppz]2+-DNA interaction will be done in the second part. DNA was modified by different fluorophores at its extremities, 5’ end and 3’ end were labeled with alexa488 (seen as donor) and alexa568 (seen as acceptor), respectively. Our goal is to study the efficiency change of FRET and the change of distance between 2 fluorophores with fluorescence technique when one Ruthenium molecule intercalate in to DAN base pair. Two methods will be employed to achieve our idea. One is that the efficiency of FRET can be computed from the donor emission (alexa488), the other is the efficiency of FRET can be calculated from the acceptor emission (acceptor), the efficiency of FRET is highly dependent on the distance of 2 fluorophores (), any changes in distance will cause the efficiency change. The FRET efficiency decreased when the [Ru(bpy)2dppz]2+ intercalated into DNA structure, which also meant that the distance between 2 fluorohore increased.
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[en] STUDY OF EFFECT FOR APLICATION TO A HUMIC COMPOUND OF MINERAL SOURCE ON HEAVY METALS PRESENTS IN SEWAGE SLUDGE / [pt] ESTUDO DO EFEITO DA APLICAÇÃO DE UM COMPOSTO HÚMICO DE ORIGEM MINERAL SOBRE METAIS PESADOS PRESENTES EM LODO DE ESGOTOMARCUS PAULO FOURNIER LESSA 10 February 2005 (has links)
[pt] Com base no procedimento EPA-3050B, estudou-se o teor de
metais (Cd, Cr, Cu, Ni, Pb, e Zn) em lodos de esgoto da
CETESB. Foram analisadas duas amostras e os resultados
obtidos foram (Cd =3,4 ; Cr =367,5 ; Cu =263,0 ;
Ni=290,6 ; Pb =91,5 ; Zn =1324,9 mg/ kg) para primeira
amostra e (Cd =3,0 ; Cr =332,2 ; Cu =190,5 ; Ni=274,6 ; Pb
=82,5 ; Zn =1284,2 mg/ kg) para segunda amostra,
resultados estes inferiores aos descritos pela CETESB para
amostras de lodo da mesma estação de tratamento. Dada uma
potencial utilização deste material como adubo agrícola,
foi determinada a fração disponível destes metais. Com
exceção do níquel (25%), uma fração pequena dos metais
estudados encontra-se na forma assimilável pelas plantas
(< 20%), com base no procedimento descrito pela
EMBRAPASolos (extração com DTPA). Os efeitos de uma
eventual utilização de composto húmico mineral (CHM) como
aditivo ao lodo, visando uma redução na fração assimilável
de metais, foi estudada em função da quantidade de CHM
aplicado e do pH da solução final. Os resultados obtidos
demonstraram que o CHM possui um poder de complexação para
os metais semelhante ao do DTPA e que, sua aplicação ao
lodo de esgoto, teria, na realidade um efeito de
potencializar a fração disponível de certos metais como o
zinco. / [en] Based on the EPA-3050B procedure, the concentration of
metals (Cd, Cr, Cu, Ni, Pb and Zn) in sludge source at
CETESB studied. Two samples were analyzed and the results
obtained were (Cd =3,4 ; Cr =367,5 ; Cu =263,0 ;
Ni=290,6 ; Pb =91,5 ; Zn =1324,9 mg/ kg) and (Cd =3,0 ; Cr
=332,2 ; Cu =190,5 ; Ni=274,6 ; Pb =82,5 ; Zn =1284,2 mg/
kg). These concentrations were below those descried by
SABESP for sludge samples measured in the same treatment
station. Due to the potential utilization of these
materials as manure in agriculture, the disposal fraction
of these metals was determined. Except nickel (25%), a
little fraction of metals studied is assimilated by plants
(< 20%), base on the procedure already descried by EMBRAPA-
Solos (extraction with DTPA). The effect of an eventual
utilization to humic mineral compound (HMC), as additive
in sludge, aiming the reduction of the assimilated
fraction of metals, were studied in function of both, the
amount of HMC applied and the final pH of the solution.
The results obtained showed that HMC has a complexation
potential for metals similar to DTPA and that, its
application in sludge, has in fact, a potential effect on
the disposal fraction of metals such as zinc.
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Synthesis and studies of new optimised chelating agents for targeting chemokine receptor CXCR4 / Synthèse et étude de nouveaux agents chélatants optimisés ciblant le récepteur de chimiokine CXCR4Désogère, Pauline 22 November 2012 (has links)
L’objectif de ce travail de thèse était de développer des outils pour détecter et traiter le cancer àun stade précoce. Nous avons donc entrepris la synthèse de nouveaux radiopharmaceutiques ciblantspécifiquement le récepteur CXCR4, en utilisant le savoir-faire et l'expertise de notre groupe dans lasynthèse et la fonctionnalisation des polyazacycloalcanes. Nous avons travaillé simultanément surdeux aspects : l’agent chélatant et la molécule vectrice.Dans un premier temps, les travaux ont concerné la conception, la synthèse et la caractérisationde nouveaux macrocycles à fort potentiel pour la chélation du cuivre et du gallium. Nous avons toutd’abord développé une nouvelle voie de synthèse permettant d’accéder à des dérivés homocyclènesC-functionnalisés. Nous nous sommes ensuite intéressés aux dérivés du 1,4,7-triazacyclononane(TACN). En optimisant une voie de synthèse déjà développée au laboratoire, nous avons facilitél’accès à des dérivés TACN N- et C-fonctionnalisés. Nous avons ainsi préparé une série denouveaux agents chélatants bifonctionnels adaptés pour la complexation du cuivre ou du gallium, envariant la nature de la fonction de greffage et des bras coordinants. Nous avons également réalisé lasynthèse de nouveaux cryptands en série cyclène et nous avons étudié leur propriété decomplexation vis à vis du cuivre.Dans un second temps, nous avons développé une nouvelle famille d’agents imageants duCXCR4 en modifiant la structure des AMD3100 et AMD3465. Ce travail a tout d’abord nécessité lamise au point de nouvelles méthodes de fonctionnalisation de ces structures. Nous avons ainsi pupréparer de nouveaux synthons porteur d’une fonction de greffage dans les deux séries. Nous avonsensuite introduit différentes sondes imageantes, telles que des chélates adaptés pour la complexationdu cuivre, gallium et indium ainsi que des sondes fluorescentes de type bodipy / The objective of this thesis work was to develop CXCR4-targeted tools to localize and treat cancer at an early stage. In this line, we investigated the synthesis of new target-specific radiopharmaceuticals. The work focused on two main axes, i.e. the chelating agent and the carrier, by using the know-how and the expertise of our group in polyazacycloalkanes synthesis and functionalization. In the first part, we were interested in developing new macrocyclic scaffolds of high potential for copper and gallium chelation. We first focused on the development of a new powerful route towards selectively functionalized constrained homocyclens. The second part was based on C-functionalized 1,4,7-triazacyclononane (TACN) and its derivatives. From a synthetic route previously developed in our group, we were able to facilitate and optimize the synthesis of selectively N- and C-functionalized TACN. By varying the grafting functions and the pendant coordinating arms, we prepared several really promising bifunctional chelating agents for copper and gallium chelation. We also investigated the synthesis of new cryptands based on cyclen and we studied their properties towards copper complexation. In the second part of this thesis work, we were interested in generating a new family of imaging agents based on well-known CXCR4 antagonists, i.e. AMD3100 and AMD3465. The access towards these agents first required the preparation of original building blocks by modification of the AMD3100 and AMD3465 cores. The conjugation of such platforms onto the appropriate probe enabled the synthesis of various systems for optical and nuclear imaging. Thus, we were able to introduce a bodipy dye and several chelators adapted for gallium, copper and indium chelation
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Study of the photodegradation and photostability of anti-cancer drugs in different media towards the development of both new actinometers and liquid formulationsLee, Lok Yan January 2016 (has links)
This study aims at tackling some of the problems often encountered in photostability testing and liquid formulation development. Three anti-cancer drugs will be employed as models; Dacarbazine (DBZ) has well established photostability issues, Axitinib (AXI) and Sunitinib (SUT) are two new drugs only commercially available in solid dosage forms. In ethanol, the photokinetics of these drugs were well described by the newly proposed Φ-order kinetic mathematical model. This has confirmed the photoreversible character of AXI and SUT’s and unimolecular photoreaction of DBZ’s photodegradations. Also, the Φ-order kinetics is proven to describe them better than the usually used classic thermal reaction orders. In aqueous solution, the drugs were found to undergo thermal and photochemical complex degradations, involving at least 3 photoproducts. A new photokinetic approach has been proposed in this work to solving and unravelling the attributes of such complex mechanisms. For the first time, the quantum yields (QY) of the three drugs were determined and found to increase with irradiation wavelength. SUT’s QY were comparable in ethanol and water (QY460 = 0.02), DBZ was found to be more photoefficient in water (QY330 = 0.04 and 0.1, respectively) and AXI in water (QY330 = 0.06 and 0.03). Φ-order kinetics’ potential for the development of reliable actinometers of the three drugs, without prior knowledge of unknown reaction parameters, has also been established. A general equation to describe the isotherm of a (Gn:Hm) guest-host multicomponent complex was proposed in this work to palliate the lack of a strategy for characterising nanosponge-drug complexes. It provides information on both stiochiometry and association constant of the complex. The results indicate that hydrophobic AXI forms a 1:0.8 complex, indicating the possibility of multiple association sites and/or different types of binding. The newly developed AXI/nanosponge liquid formulation has significantly increased solubility (5000-fold) and thermal stability. Furthermore, the photostability of DBZ and SUT were considerably improved by using a strategy based on light-absorption competitors. Their initial velocities reduced from 10 and 3 s-1 (respectively) to 1 and 0.13 s-1. The successful application of these methods to the model anti-cancer drugs has set out new approaches that might be found useful for future treatments of photodegradation data, development of drug-actinometers and liquid formulations of drugs.
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Coarse-grained modeling with constant pH of the protein complexation phenomena / Modelagem de granularidade grossa com pH constante para o fenômeno da complexação de proteínasSergio Alejandro Poveda Cuevas 10 April 2017 (has links)
Theoretical studies of the molecular mechanisms responsible for the formation and stability of protein complexes have gained importance due to their practical applications in the understanding of the molecular basis of several diseases, in protein engineering and biotechnology. The objective of this project is to critically analyze and refine a coarse-grained force field for protein-protein interactions based on experimental thermodynamic properties and to apply it to cancer-related S100A4 protein system. Our ultimate goal is to generate knowledge for a better understanding of the physical mechanisms responsible for the association of particular proteins in different environments. We studied the role of short and long-range interactions on the complexation of homo-associations. Furthermore, we analyzed the influence of the pH and its correlation with the charge regulation mechanism. We analyzed and refined the adjustable Lennard-Jones parameter for a mesoscopic model based on experimental second virial data for lysozyme, chymotrypsinogen, and ribonuclease A via Monte Carlo simulations. From of that, the S100A3 protein was used to test the new calibrated parameters. Finally, we evaluated the dimerization process of S100A4 proteins, observing the role of physical-chemistry variables involved in the thermodynamical stability of different oligomers. / Estudos teóricos dos mecanismos moleculares responsáveis pela formação e estabilidade dos complexos de proteínas vêm ganhando importância devido às suas aplicações práticas no entendimento da base molecular de várias doenças, em engenharia de proteínas e biotecnologia. O objetivo deste projeto é analisar criticamente e aperfeiçoar um campo de força de granulidade grossa para interação proteína-proteína com base em propriedades termodinâmicas experimentais e aplicá-lo ao sistema proteico S100A4 relacionado com o câncer. Nosso objetivo final é gerar conhecimento para uma melhor compreensão dos mecanismos físicos responsáveis pelas associações de proteínas particulares em diferentes ambientes. Estudamos o papel das interações de curto e longo alcance na complexação de homo-associações. Além disso, analisamos a influência do pH e sua correlação com o mecanismo de regulação de cargas. Por meio de simulações Monte Carlo, analisamos e refinamos o parametro ajustável de Lennard-Jones para um modelo mesoscópico, usando dados experimentais do segundo virial para a lisozima, o quimotripsinogênio e a ribonuclease A. A partir disso, a proteína S100A3 foi usada para testar os novos parâmetros calibrados. Finalmente, foi avaliado o processo de dimerização das proteínas S100A4, observando o papel de algumas variáveis físico-químicas envolvidas na estabilidade termondinâmica de diferentes oligómeros.
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Biocatalytic Production, Preparation and Characterization of Large-ring CyclodextrinsMokhtar, Mohd Noriznan 26 January 2009 (has links)
Cyclodextrins (CD) are cyclic oligosaccharides composed of six to more than sixty
glucose units. Large-ring cyclodextrins (LR-CD) are novel CD comprised of more than eight
glucose units with cavity structures and sizes different from that of commercially available
CD<sub>6</sub> – CD<sub>8</sub>. LR-CD may offer unique molecular recognition properties and can be produced
biocatalytically from starch using cyclodextrin glucanotransferase (CGTase, E.C. 2.4.1.19) in
a short reaction time. LR-CD were isolated from glucose, CD<sub>6</sub> – CD<sub>8</sub> and other compounds by
complexation of CD<sub>6</sub> – CD<sub>8</sub> as well as precipitation techniques. The yield of LR-CD (degree
of polymerization from 9 to 21) was optimized using central composite design. Addition of
polar organic solvents to the synthesis resulted in higher yields of LR-CD. LR-CD composed
of 9 to 21 glucose units were successfully separated using reversed-phase of ODS-AQ
chromatography and normal-phase of polyamine II chromatography. Maintaining optimized
reaction conditions aided in a high yield of CD<sub>9</sub>; it could be separated with reasonable yield
using a single step of polyamine II chromatography. A co-grinding method helped to obtain
higher solubilization levels of glibenclamide, vitamin A acetate and vitamin D<sub>3</sub> in CD<sub>13</sub>, CD<sub>10</sub>
and CD<sub>11</sub>, respectively when compared to other CD. Vitamin K<sub>1</sub> was solubilized in distilled
water with CD<sub>6</sub> – CD<sub>13</sub> using a co-precipitation method. When compared with other CD, CD<sub>9</sub>
was seen to be the best solubilizer. The analysis of complexes using ESI MS showed
spironolactone and glibenclamide complexed with CD<sub>9</sub> and CD<sub>13</sub>, respectively.
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Efficient iron-mediated approach to pyrano[3,2-a]carbazole alkaloids - first total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine, first asymmetric synthesis and assignment of the absolute configuration of (−)-trans-dihydroxygirinimbineGruner, Konstanze K., Hopfmann, Thomas, Matsumoto, Kazuhiro, Jäger, Anne, Katsuki, Tsutomu, Knölker, Hans-Joachim January 2011 (has links)
Iron-mediated oxidative cyclisation provides an efficient approach to pyrano[3,2-a]carbazole alkaloids. Thus, improved routes to girinimbine and murrayacine as well as the first total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine are reported. Asymmetric epoxidation of girinimbine led to (−)-trans-dihydroxygirinimbine and the assignment of its absolute configuration. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Moderne Fraktioniermethoden zur Charakterisierung von verzweigten PolymerenBoye, Susanne 09 January 2013 (has links)
Die Charakterisierung von verzweigten Polymeren stellt eine große Herausforderung dar. In dieser Arbeit wurden zum einen die Asymmetrische Fluss-Feldflussfraktionierung (AF4) als Alternative zur Größenausschlusschromatographie angewandt, um dendritische Polymere zu charakterisieren. Dabei wurden erstmals auch Komplexierungs-und Aggregationsstudien von dendritischen Glykopolymeren durchgeführt. Weiterhin ist es mittels Adaption der Phasenverteilungschromatographie gelungen, in Abhängigkeit des Verzweigungscharakters aufzutrennen. Hierbei konnten lineare und sternförmige Polystyrenproben separiert werden.
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Joint project: Retention of radionuclides relevant for final disposal in natural clay rock and saline systemsSchmeide, Katja, Fritsch, Katharina, Lippold, Holger, Poetsch, Maria, Kulenkampff, Johannes, Lippmann-Pipke, Johanna, Jordan, Norbert, Joseph, Claudia, Moll, Henry, Cherkouk, Andrea, Bader, Miriam 15 March 2016 (has links) (PDF)
The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclide – organics – clay – aquifer. For this purpose, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol/kg) and the background electrolyte.
The U(VI) complexation by propionate was studied in dependence on ionic strength (up to 4 mol/kg NaClO4) by TRLFS, ATR FT-IR spectroscopy, and DFT calculations. An influence of ionic strength on stability constants was detected, depending on the charge of the respective complexes. The conditional stability constants, determined for 1:1, 1:2, and 1:3 complexes at specific ionic strengths, were extrapolated to zero ionic strength.
The interaction of the bacteria Sporomusa sp. MT-2.99 and Paenibacillus sp. MT-2.2 cells, isolated from Opalinus Clay, with Pu was studied. The experiments can be divided into such without an electron donor where biosorption is favored and such with addition of Na-pyruvate as an electron donor stimulating also bioreduction processes. Moreover, experiments were performed to study the interactions of the halophilic archaeon Halobacterium noricense DSM-15987 with U(VI), Eu(III), and Cm(III) in 3 M NaCl solutions.
Research for improving process understanding with respect to the mobility of multivalent metals in systems containing humic matter was focused on the reversibility of elementary processes and on their interaction. Kinetic stabilization processes in the dynamics of humate complexation equilibria were quantified in isotope exchange studies. The influence of high salinity on the mobilizing potential of humic-like clay organics was systematically investigated and was described by modeling.
The sorption of Tc(VII)/Tc(IV) onto the iron(II)-containing minerals magnetite and siderite was studied by means of batch sorption experiments, ATR FT-IR and X-ray absorption spectroscopy. The strong Tc retention at these minerals could be attributed to surface-mediated reduction of Tc(VII) to Tc(IV). An influence of ionic strength was not observed.
The influence of ionic strength (up to 3 mol/kg) and background electrolyte (NaCl, CaCl2, MgCl2) on U(VI) sorption onto montmorillonite was studied. The U(VI) sorption is influenced by the background electrolyte, the influence of ionic strength is small. Surface complexation modeling was performed applying the 2SPNE SC/CE model. Surface complexation constants were determined for the NaCl and CaCl2 system and were extrapolated to zero ionic strength. Surface complexation in mixed electrolytes can be modeled applying surface complexation constants derived for pure electrolytes.
The influence of citrate on U(VI) diffusion in Opalinus Clay was studied using Opalinus Clay pore water as background electrolyte. The diffusion parameter values obtained for the HTO through-diffusion and the U(VI) in-diffusion in the absence of citric acid were in agreement with literature data. In the presence of citric acid, U(VI) diffusion was significantly retarded, which was attributed to a change in speciation, probably U(VI) was reduced to U(IV).
Larger-scale heterogeneous material effects on diffusive transport were investigated with PET. Diffusion parameters were derived by optimum fit of a FEM-model to the measurement. These parameters are in accordance with the results from 1D-through-diffusion experiments. Deviations from the simple transversal-isotropic behavior, which are identified as residuals from the model, are indications for heterogeneous transport on the mm-scale.
PET measurements were also conducted in order to display the improvement of the EDZ with waterglass injections. These experiments enable to draw conclusions on the complex reactive transport process and thus an estimation of the achieved improvement of the barrier function. The image reconstruction procedure was largely improved, mainly with the aid of Monte-Carlo simulations, and now allows quantitative analysis and error estimation.
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