Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T11:26:33Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T11:26:33Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta uma nova metodologia, simples e de baixo custo, para quantificação direta de urânio em compostos do ciclo do combustível nuclear, baseada na espectroscopia no infravermelho com transformada de Fourier (FTIR), utilizando a técnica de pastilhamento em KBr. Diferentes matrizes foram utilizadas para o desenvolvimento e validação analítica: nitrato de uranilo complexado com TBP (UO2(NO3)2.2TBP) em fase orgânica e nitrato de uranilo (UO2(NO3)2) em fase aquosa. O método para matriz de urânio em fase orgânica (UO2(NO3)2.2TBP em hexano/incorporado em KBr) apresentou linearidade (r = 0,9980) dentro da faixa analítica de 0,20% 2,85% de urânio na pastilha de KBr, LD de 0,02% e LQ de 0,03%, exatidão com recuperações acima de 101,0%, robustez e precisão (DPR < 1,6%). O método para matriz de urânio em fase aquosa (UO2(NO3)2/incorporado em KBr) apresentou linearidade (r = 0,9900) dentro da faixa analítica de 0,14% 0,29% de urânio na pastilha de KBr, LD de 0,01% e LQ de 0,02%, exatidão com recuperações acima de 99,4%, robustez e precisão (DPR < 1,6 %). Amostras de processo do ciclo do combustível nuclear foram submetidas a avaliação intralaboratorial e os resultados foram comparados estatisticamente por outras técnicas: Espectrometria de Fluorescência de Raios-X (FRX) e gravimetria. Os testes estatísticos (t-Student e Fischer) indicaram que a técnica por FTIR e as de referência são equivalentes, demonstrando que a nova metodologia pode ser empregada com sucesso nas análises de rotina para o controle de qualidade dos compostos nucleares. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Um dos temas modernos em fotoquímica em soluções aquosas é a observação de prototropismo de estados eletrônicos excitados. Resumidamente, moléculas orgânicas contendo grupamentos ácido-base quando excitadas, e cujo tempo de vida do estado excitado seja longo o suficiente, reações competitivas de transferência de prótons com as do processo de relaxação poderão ocorrer. No caso de aumento de acidez os compostos são denominados fotoácidos e no contrário fotobases. Este fenômeno é atribuído a um estado isoeletrônico da molécula no estado fundamental tendo sido descritos variações de até sete unidades de pKa. Do ponto de vista da investigação Físico-Química o estudo da circunvizinhança, na qual as espécies excitadas percorrem uma superfície de potencial seja na direção da reassociação seja na da ionização com posterior solvatação das mesmas, fornece uma importante ferramenta de análise de propriedades de micro ambiente. Esta possibilidade advém das excelentes propriedades espectrais dos grupos cromofóricos desta classe de compostos o que facilita o monitoramento das espécies transientes adicionado ao estágio técnico atual de medidas ultra-rápidas. Neste estudo enfocamos o estudo de derivados de quinolina (fotobase), contendo grupos passíveis de reação de polimerização. Os derivados 3-alil-2-metilquinolin-4-ol (HIQ) e 3-alil-4-cloro-2-metilquinolina (CLQ) foram preparados e as propriedades fotoprototrópicas determinadas. O primeiro monômero comporta-se como fotobase ou fotoácido dependendo do pH do meio que este se encontra e o CLQ como fotobase. Na seqüência tentamos obter polímeros do HIQ e CLQ, porém não se obteve um resultado positivo devido a dificuldade da polimerização de grupos alil inclusive por via eletroquímica. Em seqüência prosseguimos à determinação das propriedades fotoquímicas e fotofísicas de derivados de di-naftalimidas, devido às inúmeras aplicações destes compostos em novos materiais. Propriedades destas ftalimidas são em geral devidas à conjugação dos elétrons do grupo imida aos do anel naftalênico. Esta conjugação confere uma alto grau de planaridade aos derivados, de forma que a solvatação é dificultada. Observa-se via de regra espectros tanto de absorção como de emissão de fluorescência com alta resolução vibrônica seja nas transições S0-S1 ou S0-S2. Os efeitos espectroscópicos esperados de solventes devem ser função das cadeias laterais nos grupos imidas. Neste contexto foram preparados vários derivados para uso como sondas. Foram estudados sete compostos: N,N\'-n-butil-1,4,5,8-di-naftalimida (BUNDI); N,N\'-(2-cloro-etileno)-1,4,5,8-di-naftalimida (CLNDI); N,N\'-(2-bromo-etileno)-1,4,5,8-di-naftalimida (BRNDI); N,N\'-2-hidroxietileno-1,4,5,8-di-naftalimida (OHNDI); N,N\'-(N,N\'-dimetiletilenodiamina)-1,4,5,8-di-naftalimida (DMNDI); N,N\'-amino-1,4,5,8-di-naftalimida(DANDI) e N,N\'-1,4,5,8-di-naftalimida (NDI). Os derivados aqui estudados responderam de forma excelente às expectativas levando seja à formação de dímeros e agregados seja a alterações nas intensidades e relações das bandas vibrônicas (excitação e emissão) das transições S0-S1. Demonstra-se aqui a excelente qualidade destes compostos como repórteres do próprio estado de suas moléculas como do meio circunvizinho. / Excited state proto transfer reactions in aqueous media is among current themes in photochemistry research. Shortly, organic molecules having acid or basic groups and presenting excited state lifetimes long enough, competitive prototropic reactions can occur. This phenomenon is attributed to an isoelectronic state of the ground state molecule and up to seven units of pKa changes have been described. From the Physical Chemistry investigation viewpoint the study of the neighborhood where the excited species have a potential surface to describe either for the re association reaction or for the ionization followed by solvation, presents an important tool for the analysis of the microenvironment. This feature arises from the optimal spectral properties of the chromophoric groups of this class of compounds, which facilitates monitoring transient species as well by the current technology standards. In this work focused a photobase derivative from quinoline having a suitable polymerizable group. The 3-allyl-2-methylquinolin-4-ol (HIQ) and the 3-allyl-4-chloro-2-methylquinoline (CLQ) were synthesized and their photoprotrtopic behavior determined. The first compound shows both photoacid and photobase character as a function of the solution pH whereas CLQ is a photobase. Following attempts to obtain polymers were unsuccessful either using electrochemical routes. Given the several applications of di-naphthalimides as new materials, photochemical and photophysical of some derivatives were determined. The properties of these phthalimides arise from the conjugation of the imide electrons with vicinal naphthalic ring. This conjugation confers a high planarity degree and hindering the chromophore solvation. Accordingly high vibronic resolution is observed in both excitation and emission spectra either in the S0-S1 or S0-S2 transitions. Expected solvent spectroscopic effects are thus due to the radical N-imide groups. In this subject several di-imides derivatives were prepared for the use as medium probes. Seven compounds were investigated: N,N\'-n-butyl-1,4,5,8-di-naphthalimide (BUNDI; N,N\'-(2-chloroethylene)-1,4,5,8-di-naphthalimide (CLNDI); N,N\'-(2-bromoethylene) )-1,4,5,8-di-naphthalimide (BRNDI), N,N\'-2-hydroxiethylene-1,4,5,8-di-naphthalimide (OHNDI); N,N\'-(N,N\'-dimethylethylenodiamine)-1,4,5,8-di-naphthtalimide (DMNDI); N,N\'-amine-1,4,5,8-di-naphthalimide (DANDI) and N,N\'-1,4,5,8-di-naphthalimide (NDI). The derivatives studied fully satisfied the expectations leading to either a dimer and aggregate formation or to changes in the intensities or in the vibronic bands intensities relationships (excitation and emission) of the S0-S1 transitions. Here it is shown the excellent quality of these molecules as self and microenvironment probes.

No description available.

In spite of their high abundance and importance, aqueous systems are enigmatic on the microscopic scale. In order to obtain information about their geometrical and electronic structure, simple aqueous solutions have been studied experimentally by photo- and Auger electron spectroscopy using the novel liquid micro-jet technique in conjunction with synchrotron radiation. The thesis is thematically divided into three parts. In the first part we utilize the surface sensitivity of photoelectron spectroscopy to probe the distributions of solutes near the water surface. In agreement with recent theoretical predictions we find that large polarizable anions, such as I- and ClO4-, display enhanced surface propensities compared to smaller rigid ions. Surface effects arising from ion-ion interactions at higher electrolyte concentrations and as function of pH are investigated. Studies of linear mono-carboxylic acids and benzoic acid show that the neutral molecular forms of such weak acids are better stabilized at the water surface than their respective conjugate base forms. The second part examines what type of information core-electron spectra can yield about the chemical state and hydration structure of small organic molecules in water. We demonstrate that the method is sensitive to the protonation state of titratable functional groups and that core-level lineshapes are dependent on local water hydration configurations. Using a combination of photoelectron and X-ray absorption spectroscopy we also show that the electronic re-arrangement upon hydrolysis of aldehydes yields characteristic fingerprints in core-level spectra. In the last part of this thesis we study ultrafast charge delocalization dynamics in aqueous solutions using resonant and off-resonant Auger spectroscopy. Intermolecular Coulombic decay (ICD) is found to occur in a number of core-excited solutions where excess energy is transferred between the solvent and the solute. The rate of ultrafast electron delocalization between hydrogen bonded water molecules upon oxygen 1s resonant core-excitation is found to decrease upon solvation of inorganic ions. The presented work is illustrative of how core-level photoelectron spectroscopy can be valuable in the study of fundamental phenomena in aqueous solutions.

La adsorció sobre carbó actiu és un tractament habitual para a l'eliminació de metalls contaminants d'afluents aquosos. Amb la finalitat de reduir el cost dels tractament actuals s'està estudiant la utilització d'adsorbents de baix cost com a substituts dels sorbents convencionals que s'utilitzen usualment en els tractaments d'aigües. En aquesta tesi s'ha avaluat la possibilitat d'aprofitar diversos residus vegetals procedents de processos agrícoles o residus industrials, com a sorbents per a l'eliminació de metalls de solucions aquoses. En concret, el treball s'ha centrat en assolir dos grans objectius, primer de tot, conèixer la possibilitat d'utilitzar el pinyol d'oliva com a adsorbent de metalls divalents de solucions aquoses, com són el Cd(II), Cu(II), Ni(II) i Pb(II), i en segon lloc, avaluar la utilització de quatre residus vegetals (escorça de yohimbe, rapa de raïm, suro i pinyol d'oliva) per a l'extracció de Cr(VI) de solucions aquoses i utilitzar el residu vegetal més apropiat com a base per tal d'obtenir un nou sorbent, amb més bona morfologia per ser utilitzat en sistemes d'eliminació de Cr(VI) en continu. Les dades cinètiques d'adsorció es van tractar amb el model cinètic de pseudo-segon ordre, amb el que es van determinar la velocitat inicial d'adsorció dels metalls. Els models d'isotermes d'equilibri de Langmuir i Freundlich es van utilitzar per descriure els equilibris d'adsorció i calcular els paràmetres de les isotermes. En els assajos amb mescles binàries de metalls, els resultats es van tractar amb el model ampliat de Langmuir.En aquest treball s'ha determinat, primerament, que el pinyol d'oliva és un bon sorbent dels metalls divalents estudiats. S'ha determinat que l'adsorció dels metalls varia amb el pH de la solució i que la presència de sals en la solució provoca una davallada en l'adsorció. També es va determinar la competència en l'adsorció entre els metalls al realitzar assajos en mescles binàries.Amb els estudis d'extracció de Cr(VI) amb els quatre materials s'ha determinat que aquests vegetals poden adsorbir el Cr(VI) en solució, tot i que la rapa i la yohimbe són els materials que presenten unes capacitats d'adsorció més elevades. Les anàlisis amb espectroscòpia electrònica de Raig-X realitzats en la rapa de raïm i la yohimbe en contacte amb Cr(VI) varen demostrar la presència del metall en els dos estats d'oxidació, Cr(VI) i Cr(III), evidenciant la participació del mecanisme de reducció de Cr(VI) en l'adsorció del metall sobre els materials.Amb l'encapsulació de la rapa de raïm es va incrementar significativament la capacitat d'adsorció del metall respecta a la seva utilització en la forma original. Les dades experimentals es van tractar amb un model de difusió i es va determinar el coeficient de difusió en l'adsorció en el sorbent amb diferent percentatge de rapa en l'interior.Finalment s'han realitzat estudis preliminars d'adsorció de crom hexavalent en continu utilitzant columnes de petites dimensions farcides amb el sorbent format per boles de rapa encapsulada en alginat càlcic. En aquests assajos s'ha determinat l'efecte en l'adsorció de metall de diversos paràmetres d'operació, com la concentració inicial de metall, el cabal i l'alçada de llit. El model de transferència de matèria i difusió en columna emprat pel tractament de les dades experimentals va mostrar l'efecte de la concentració inicial i del cabal en els coeficients de difusió i transferència de matèria. El model BDST no va predir correctament el temps de servei en els diferents paràmetres d'operació experimentats a causa de la complexitat del procés d'adsorció. Amb aquests assajos preliminars s'han establert les bases de l'adsorció de Cr(VI) amb el nou sorbent en sistemes en continu amb la finalitat de realitzar estudis posteriors d'eliminació del metall en columnes de majors dimensions. / Adsorption with activated carbon is a usual treatment to remove metals from wastewater. In order to reduce the cost of the treatment, several studies have been carried out to evaluate the use of low cost sorbents as an alternative to conventional sorbents used in wastewater treatment. In this work, the use of different vegetable wastes from agricultural or industrial processes has been evaluated as sorbents for metal removal from aqueous solutions. The aim of this work was to study first, the usefulness of olive stones as a sorbent for divalent metals such as Cd(II), Cu(II), Ni(II) and Pb(II) from aqueous solutions and then the use of four vegetable wastes (yohimbe bark, grape stalks, cork and olive stones) for the removal of Cr(VI) from aqueous solutions. The vegetable waste powder was encapsulated in calcium alginate to obtain spherical gel beads that were used in continuous flow process for Cr(VI) removal.In all sorption experiments, kinetic data were modeled by the pseudo-second order kinetic equation and determine the constants sorption rates. Langmuir and Freundlich model isotherms were use to describe sorption equilibrium data and to obtain the isotherm parameters. In binary mixtures, the extended Langmuir isotherm model was used. The results showed that olive stones are a good sorbent for studied divalent metal. Metal uptake was pH dependent and the presence of salts in solution provokes a decrease in metal uptake. A clear competence between metals to be adsorbed on the waste was observed in metal binary mixtures. Although results obtained in Cr(VI) removal studies show that the four studied wastes can adsorb Cr(VI), grape stalks and yohimbe bark wastes showed the best chromium sorption capacity. X-Ray Photoelectron Spectroscopy analysis on grape stalks and yohimbe chromium loaded samples put into evidence that both Cr(VI) and Cr(III) were sorbed on wastes surface indicating that Cr(VI) sorption process involves a redox reaction. The gel beads obtained when encapsulating grape stalks in calcium alginate showed a significant increase in Cr(VI) sorption capacity compared to the original grape stalks waste. A diffusion model was used to analyze the experimental data and to determine the diffusion coefficient for Cr(VI) sorption by beads containing different percentage of grape stalks encapsulated in calcium alginate. Finally, preliminary studies of Cr(VI) removal in continuous flow using the beads containing grape stalks powder gel in laboratory columns have been carried out. The effect of operating parameters such as feed metal concentration, flow rate and bed depth was studied. The mass transfer and diffusion model used to describe column data showed the effect of feed metal concentration and flow rate in both, diffusion and mass transfer coefficients, respectively. The bed depth service time model (BDST) failed in predicting the service time when changing operating parameters due to the complexity of the sorption process. With these preliminary column experiments we established the basis for Cr(VI) sorption by the proposed sorbent in continuous flow process for further development of the process to be used in higher scale columns.

Monte-Carlo calculations are used to simulate the stochastic effects of fast neutron-induced chemical changes in the radiolysis of the ferrous sulfate (Fricke) dosimeter. To study the dependence of the yield of ferric ions, G(Fe[superscript 3+]), on fast neutron energy, we have simulated, at 25 [degree centigrade], the oxidation of ferrous ions in aerated aqueous 0.4 M H[subscript 2]SO[subscript 4] (pH 0.46) solutions when subjected to ~0.5-10 MeV incident neutrons, as a function of time up to ~50 s. The radiation effects due to fast neutrons are estimated on the basis of track segment (or"escape") yields calculated for the first four recoil protons with appropriate weighting according to the energy deposited by each of these protons. For example, a 0.8-MeV neutron generates recoil protons of 0.505, 0.186, 0.069, and 0.025 MeV, with linear energy transfer (LET) values of ~41, 69, 82, and 62 keV/[micro]m, respectively. In doing so, we consider that further recoils make only a negligible contribution to radiation processes. Our results show that the radiolysis of dilute aqueous solutions by fast neutrons produces smaller radical yields and larger molecular yields (relative to the corresponding yields for the radiolysis of water by [superscript 60]Co [gamma]-rays or fast electrons) due to the high LET associated to fast neutrons. The effect of recoil ions of oxygen, which is also taken into account in the calculations, is shown to decrease G(Fe[superscript 3+]) by about 10%. Our calculated values of G(Fe[superscript 3+]) are found to increase slightly with increasing neutron energy over the energy range covered in this study, in good agreement with available experimental data. We have also simulated the effect of temperature on the G(Fe[superscript 3+]) values in the fast neutron radiolysis of the Fricke dosimeter from 25 to 300 [degree centigrade]. Our results show an increase of G(Fe[superscript 3+]) with increasing temperature, which is readily explained by an increase in the yields of free radicals and a decrease in those of molecular products. For 0.8-MeV incident neutrons (the only case for which experimental data are available in the literature), there is a ~23% increase in G(Fe[superscript 3+]) on going from 25 to 300 [degree centigrade]. Although these results are in reasonable agreement with experiment, more experimental data, in particular for different incident neutron energies, would be needed to test more rigorously our Fe[superscript 3+] ion yield results at elevated temperatures.