of the Diploma Thesis In this Diploma Thesis, the electrochemical behavior of 4-nitrophenol (4-NP) was studied at a newly prepared large-surface carbon film electrode (ls-CFE) using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) with the aim to develop sensitive analytical methods for its determination. Voltammetric behavior of 4-NP was investigated in the region of anodic potentials, in dependence on the pH of the medium used (realized using Britton-Robinson buffer). The optimum pH values for the determination of 4-NP were chosen as follows: pH 3.0 (for DCV) and pH 7.0 (for DPV). During anodic oxidation of 4-NP on the ls-CFE at the concentration of the analyte of 1·10-4 mol/l, the passivation of the electrode surface occurred. Thus, it was decided to record series of measurements always at a new carbon film. Using the sample of 4-NP (at the concentration of 1·10-4 mol/l), the repeatability of the application of individual carbon films was tested, with obtained RSD values of 3.7% and 3.6% for DCV and DPV, respectively. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 1·10-6 to 1·10-4 mol/l, with the limits of quantification (LQs) of 1.5·10-6 mol/l (for DCV at the ls-CFE) and 4.6·10-7 mol/l (for DPV at the...

Neste trabalho estudou-se o uso do ferro de valência zero em meio redutivo e oxidativo, a fim de desenvolver um processo que promova tanto a degradação quanto a mineralização de substâncias orgânicas com centros deficientes de elétrons, como, por exemplo, espécies que contêm o grupo nitro ligado ao anel aromático. O processo de degradação empregando-se ferro metálico, em ambos os meios estudados, apresentou grande eficiência no tratamento do p-nitrofenol, utilizado como poluente modelo. Para soluções contendo concentração inicial de p-nitrofenol igual a 100 mg L-1, tanto para o meio redutivo quanto para o oxidativo, em condições ótimas, as taxas de degradação obtidas foram superiores a 98% ao final de 15 minutos de tratamento. Para o meio com atmosfera oxidante, foi possível observar a geração de H2O2 in situ (cerca de 0,030 mmol L-1, em 45 minutos), proporcionando uma reação do tipo Fenton. Dessa forma, foi possível obter uma redução do teor de carbono orgânico dissolvido de cerca de 20%, em 60 minutos de reação. A fim de elevar a taxa de mineralização do p-nitrofenol, realizou-se a integração dos processos redutivo e oxidativo. O emprego deste sistema de tratamento proporcionou um aumento de 100% na redução do teor de carbono orgânico dissolvido, para o mesmo tempo de tratamento. Assim, pode-se inferir que a associação dos processos estudados levou à formação de substâncias mais susceptíveis ao ataque de agentes oxidantes. Por fim, avaliou-se o emprego de ferro de valência zero sintetizado via redução de íons Fe2+ por boridreto de sódio. Utilizando-se o sistema de tratamento integrado, este material proporcionou uma taxa de mineralização de cerca de 50%, demonstrando-se como uma boa alternativa para a obtenção do ferro de valência zero. Dessa forma, pode-se concluir que o sistema integrado apresenta-se como uma alternativa viável e eficiente, com grande potencial de aplicabilidade para o tratamento de substâncias recalcitrantes aos processos de tratamento convencionais, uma vez que apresentou bons resultados na degradação/mineralização da substância modelo. / In this work, we studied the use of zero-valent iron under reductive and oxidative medium, in order to develop a process that promotes the degradation and the mineralization of organic substances with deficient electron centers, such as nitroaromatic compounds. In both mediums, the degradation process promoted by the metallic iron showed good efficiency to degrade p-itrophenol, used as pollutant model. For solutions of p-nitrophenol with initial concentration of 100 mg L-1, degradation percentages were above 98% after 15 minutes of the treatment in reductive and oxidative mediums (optimal conditions). Under oxidant atmosphere, the in situ generation of H2O2 (about 0,030 mmol L-1, in 45 minutes) leaded to a Fenton-like reaction. So, it provided a reduction of total organic carbon levels up to 20% in 60 minutes. In order to raise the mineralization of p-nitrophenol, the reductive and oxidative processes were integrated. The used of this treatment system provided an increase of 100% in the reduction of the dissolved organic carbon, for the same treatment time. Thus, we can in infer that the association of the two processes led to the formation of more susceptible substances to the attack of oxidant agents. Finally, it was evaluated the use zero-valent iron synthesized through reduction of Fe2+ ions by NaBH4. The obtained material provided about 50% of p-nitrophenol mineralization, showing to be a good source of zero-valent iron. So, it can be concluded that the use of the integrated system is a viable and efficient alternative, with a great potential of applicability for the treatment of recalcitrants substances to the conventional treatment processes, because it presented good results in the degradation/mineralization of studied pollutant model.

La détection et l'identification de bactéries pathogènes revêt une grande importance dans de nombreux domaines tels que la santé et l’industrie agroalimentaire. Dans ce contexte, les travaux de thèse s’intéressent à détection non invasive de Salmonella via la fraction volatile de son métabolome dont les métabolites volatils caractéristiques sont le sulfure d’hydrogène et la cadavérine. Ils illustrent également le concept de substrats osmogènes libérant des mCOV exogènes sous l’action d’enzyme spécifique d’Escherichia coli. Un premier capteur colorimétrique capable de distinguer le sulfure d’hydrogène du méthanethiol a été préparé. Il s’agit d’une matrice de silicate nanoporeuse dopée avec les réactifs N,N-diméthyl-p-phénylènediamine et ions Fe3+. Une bonne stabilité de l’intermédiaire réactionnel issu de ces réactifs, la quinonediimine (QD), est obtenue pour une forte concentration d’acide chlorhydrique. La réaction entre QD et 1000 ppm de sulfure d’hydrogène et de méthanethiol entraîne l’apparition respective d’une coloration verte et rouge-marron du capteur. Le capteur fluorimétrique de cadavérine, basé sur la formation d’un complexe fluorescent entre le Naphthol AS-BI déméthylé (ArOH) et la cadavérine, permet de détecter 250 ppb de cadavérine. La preuve de concept de substrats osmogènes a été illustrée avec la détection de p-nitrophénol (pNP) et de β-naphthylamine (β-NA) libérés en présence d’enzymes de E. coli, β-D-glucuronidase et L-alanine- β-naphthylamidase. Les capteurs nanoporeux produits, de taille de pores contrôlée, peuvent détecter 100 ppm de pNP, composé coloré (jaune) et 100 ppm de β-NA, composé fluorescent, ou encore 100 ppm de β-NA par dérivation chimique de ce dernier avec le diméthyl-p-aminocinnamaldéhyde (formation d’un produit rouge). En milieu biologique, l’eau est un interférent majeur. / Microbial contamination of food and biological samples is a big issue in the industry as much as in the medical field. In that context, the present thesis brings innovative solutions. A first explored way is the identification of Salmonella by detecting and measuring the specific metabolomics volatile organic compounds (mVOC) released, H2S and cadaverine. Another new concept is the use of osmogenic substrates able to release mVOC under the action of specific enzyme of Escherichia coli.A first colorimetric sensor able to discriminate H2S from CH3SH was produced, using a nanoporous silicate matrix doped with N,N-dimethyl-p-phenylenediamine and Fe3+ ions. A very acidic medium is needed to stabilize the “key” intermediate of the reaction, the quinonediimine species (QD), which gives with H2S and CH3SH a green and red-brown product, respectively. The fluorimetric sensor of cadaverine is based on the formation of a fluorescent complex between AS-BI demethylated Naphthol and cadaverine and can detect 250 ppb of cadaverine. A proof of concept of osmogenic substrates is given with the detection of p-nitrophenol (pNP) et de β-naphthylamine (β-NA) released under the action of Escherichia coli enzymes, β-D-glucuronidase et L-alanine- β-naphthylamidase. Various nanoporous sensors are produced with tailored pore size, which can detect 100 ppm of the yellow pNP, 100 ppm of the fluorescent β-NA and 100 ppm of the red product issued from the derivation of β-NA with dimethyl-p-aminocinnamaldehyde. In biological media, water remains the major interfering agent.

La présence de microorganismes peut être révélée par des métabolites volatils caractéristiques. Cette approche est particulièrement intéressante pour la détection non-invasive de pathogènes dans des échantillons complexes comme les matrices alimentaires, les échantillons sanguins, ou encore les plaies chroniques. Des capteurs nanoporeux à grande surface spécifique ont été préparés par voie sol-gel (xérogels) ; leur rôle est à la fois de capturer, concentrer et permettre une détection optique des Composés Organiques Volatils (COV) microbiens. Des capteurs dopés avec une molécule sonde, l'acide 5,5′ dithiobis 2 nitrobenzoïque, ont été développés pour mettre en évidence le sulfure d'hydrogène (H2S) produit par Salmonella, un pathogène d'intérêt dans le domaine de l'agroalimentaire. La capture d'H2S provoque un changement de couleur du capteur dès 5 ppm. Une partie du travail de recherche porte également sur la détection de métabolites dits « exogènes », libérés suite à l'hydrolyse d'un substrat enzymatique. C'est alors l'activité enzymatique qui est spécifique du micro-organisme ciblé. Deux COV exogènes sont envisagés : la β naphthylamine (β NA) et le 2 nitrophénol (2 NP). La première est issue d'activités enzymatiques peptidases, le second est issu d'activités glycosidases ou estérases. Pour ce dernier, une détection directe est possible dès 14 ppb grâce à son absorbance intrinsèque dans le visible. Après un travail sur la composition chimique des xérogels, une mise en forme originale par moulage des gels en forme de coin de cube permet une lecture de l'absorbance des xérogels en réflexion. Enfin, les capteurs obtenus ont été testés vis-à-vis de COV générés par 3 pathogènes: Salmonella, Escherichia coli et Staphylococcus aureus dans des matrices complexes (sang et échantillons alimentaires). / The presence of micro-organisms can be revealed by specific volatile metabolites. This approach is interesting for the non-invasive detection of pathogenic species in complex samples, such as food, blood or exudate. Nanoporous materials developing a high surface area have been prepared by sol-gel process (xerogels). They trap, concentrate and reveal the presence of microbial Volatile Organic Compounds (VOC) by means of an optical detection. Sensors have been doped with a probe molecule (5,5′ dithiobis 2 nitrobenzoic acid) in order to detect hydrogen sulfide emitted by foodborne pathogen Salmonella. The colour of sensor changes in the presence of 5 ppm of H2S. Another detection method is the use of enzymatic substrates which release exogenous VOCs. In this approach, the enzymatic activity is specific to the targeted pathogenic bacteria. Sensors have been developed for two exogenous VOCs: β naphthylamine (β NA) and 2 nitrophenol (2-NP). β NA is issued from peptidase activity, whereas 2 NP is produced by glycosidase or esterase activity. The latter can be detected above 14 ppb through absorbance in the visible region. The work focused both on the chemical composition of the xerogels and on their shape. After molding the xerogels into a trihedral prism (“corner reflector”), the absorbance can be easily monitored using the reflected light. VOCs produced by 3 pathogenic bacteria, Salmonella, Escherichia coli and Staphylococcus aureus, in complex media (blood and food samples) have been monitored with the obtained sensors.

The FT-Raman techniques were developed to quantify reactions that follow on mixing aqueous solutions of bis-(1,3-diaminopropane)diaquacobalt( III) ion ([Co(tn)2(0H)(H20)]2+) and p-nitrophenylphosphate (PNPP). For the development and validation of the kinetic modelling technique, the well-studied inversion of sucrose was utilized. Rate constants and concentrations could be estimated using calibration solutions and modelling methods. It was found that the results obtained are comparable to literature values. Hence this technique could be further used for the [Co(tn)2(0H)(H20)]2+ assisted hydrolysis of PNPP. It was found that rate constants where the pH is maintained at 7.30 give results which differ from those where the pH is started at 7.30 and allowed to change during the reaction. The average rate constant for 2:1 ([Co(tn)2(0H)(H20)]2+:PNPP reactions was found to be approximately 3 x 104 times the unassisted PNPP hydrolysis rate. / Chemistry / M. Sc. (Chemistry)

Neste trabalho estudou-se o uso do ferro de valência zero em meio redutivo e oxidativo, a fim de desenvolver um processo que promova tanto a degradação quanto a mineralização de substâncias orgânicas com centros deficientes de elétrons, como, por exemplo, espécies que contêm o grupo nitro ligado ao anel aromático. O processo de degradação empregando-se ferro metálico, em ambos os meios estudados, apresentou grande eficiência no tratamento do p-nitrofenol, utilizado como poluente modelo. Para soluções contendo concentração inicial de p-nitrofenol igual a 100 mg L-1, tanto para o meio redutivo quanto para o oxidativo, em condições ótimas, as taxas de degradação obtidas foram superiores a 98% ao final de 15 minutos de tratamento. Para o meio com atmosfera oxidante, foi possível observar a geração de H2O2 in situ (cerca de 0,030 mmol L-1, em 45 minutos), proporcionando uma reação do tipo Fenton. Dessa forma, foi possível obter uma redução do teor de carbono orgânico dissolvido de cerca de 20%, em 60 minutos de reação. A fim de elevar a taxa de mineralização do p-nitrofenol, realizou-se a integração dos processos redutivo e oxidativo. O emprego deste sistema de tratamento proporcionou um aumento de 100% na redução do teor de carbono orgânico dissolvido, para o mesmo tempo de tratamento. Assim, pode-se inferir que a associação dos processos estudados levou à formação de substâncias mais susceptíveis ao ataque de agentes oxidantes. Por fim, avaliou-se o emprego de ferro de valência zero sintetizado via redução de íons Fe2+ por boridreto de sódio. Utilizando-se o sistema de tratamento integrado, este material proporcionou uma taxa de mineralização de cerca de 50%, demonstrando-se como uma boa alternativa para a obtenção do ferro de valência zero. Dessa forma, pode-se concluir que o sistema integrado apresenta-se como uma alternativa viável e eficiente, com grande potencial de aplicabilidade para o tratamento de substâncias recalcitrantes aos processos de tratamento convencionais, uma vez que apresentou bons resultados na degradação/mineralização da substância modelo. / In this work, we studied the use of zero-valent iron under reductive and oxidative medium, in order to develop a process that promotes the degradation and the mineralization of organic substances with deficient electron centers, such as nitroaromatic compounds. In both mediums, the degradation process promoted by the metallic iron showed good efficiency to degrade p-itrophenol, used as pollutant model. For solutions of p-nitrophenol with initial concentration of 100 mg L-1, degradation percentages were above 98% after 15 minutes of the treatment in reductive and oxidative mediums (optimal conditions). Under oxidant atmosphere, the in situ generation of H2O2 (about 0,030 mmol L-1, in 45 minutes) leaded to a Fenton-like reaction. So, it provided a reduction of total organic carbon levels up to 20% in 60 minutes. In order to raise the mineralization of p-nitrophenol, the reductive and oxidative processes were integrated. The used of this treatment system provided an increase of 100% in the reduction of the dissolved organic carbon, for the same treatment time. Thus, we can in infer that the association of the two processes led to the formation of more susceptible substances to the attack of oxidant agents. Finally, it was evaluated the use zero-valent iron synthesized through reduction of Fe2+ ions by NaBH4. The obtained material provided about 50% of p-nitrophenol mineralization, showing to be a good source of zero-valent iron. So, it can be concluded that the use of the integrated system is a viable and efficient alternative, with a great potential of applicability for the treatment of recalcitrants substances to the conventional treatment processes, because it presented good results in the degradation/mineralization of studied pollutant model.

Ce travail, sur la dépollution de l’eau par OVHC sur charbon actif (CA), étudie l'interaction oxydation - adsorption : comment l'oxydation sur charbon de produits aromatiques modifie ses propriétés et en particulier sa capacité d'adsorption et d'oxydation (désactivation). Divers charbons commerciaux, mais aussi issus de boues activées, ont été caractérisés avant et après oxydation : propriétés texturales, composition élémentaire (CHNSO), fonctions de surface, pH au point de charge nulle et allure des courbes ATG. Seule leur teneur en cendres semble différer notablement. Les charbons actifs de boues ont une surface spécifique bien moindre (de 90 à 265 m².g-1) et un taux de cendres supérieur à 50% qui en font de moins bons adsorbants. Cependant la présence de métal, notamment le fer, a un effet positif sur l'oxydation catalytique. L'étude comparative en oxydation catalytique de 4 CA commerciaux en grains montre une désactivation intense (qui augmente avec la concentration de polluant) sur les 3-4 premières utilisations, puis une stabilisation. Le charbon résultant est nettement moins adsorbant. Les CA S23 et F22 ainsi stabilisés ont ensuite été utilisés pour déterminer la cinétique d'oxydation catalytique apparente et intrinsèque du phénol, grâce à un modèle incluant la diffusion. La comparaison de l'OVHC de 4 polluants aromatiques seuls et en divers mélanges synthétiques met en évidence des effets de mélange significatifs: les polluants les plus réfractaires en oxydation catalytique se dégradent beaucoup plus vite en mélange (ex 4NP) et inversement, les polluants les plus oxydés, lorsqu'ils sont seuls en solution, voient leur cinétique diminuer lorsqu'ils sont mélangés aux autres polluants (ex phénol, 4chlorophénol). Le mélange tend donc à uniformiser les comportements particuliers. Enfin, les essais de faisabilité du procédé de régénération oxydante AD-OX ont été effectués sur des effluents industriels. La régénération du charbon actif comme adsorbant est moins limitée qu'avec des mélanges de phénols substitués. / This work, on water treatment by catalytic Wet Air Oxidation (CWAO) using activated carbon (AC), aimed to study the interaction between oxidation-adsorption phenomena: how the oxidation of aromatic compounds on AC can modify its properties and specially its adsorption and oxidation characteristics (deactivation). Various commercials AC, and AC produced from activated sludge, have been characterized before and after oxidation by according methods such as textural characterization, elemental analysis (CHNSO), functional groups on carbon surfaces analysis, pH of the point of zero charge (pHpzc) analysis and thermogravimetric analysis (TGA); however, only their ash level was significantly different. In addition, the sludge based AC (SBAC) have a specific surface range of 90 to 265 m².g-1, which is lower than commercial AC, and with an ash level over 50%. Consequently they are less good adsorbents. However, the presence of metal, e.g. iron, has a positive affect on catalytic oxidation. The comparative study of catalytic oxidation with 4 commercial AC, show a severe deactivation (which increase with the pollutant concentration) on the first 3-4 utilizations before stabilization. The residual AC is clearly poor adsorbent. After stabilization, 2 commercials AC, only S23 and F22 CA, were studied on catalytic oxidation of phenol in term of apparent and intrinsic kinetics with including the diffusion effect in the model. The CWAO of 4 pure aromatic pollutants, and their various synthetic mixtures, showed mixing effects significantly: the most oxidation catalytic refractory pollutants were degraded rapidly when they mixed (e.g. 4-nitrophenol) but the kinetic was slow down for the pure pollutant whereas, the most oxidised pollutants, for pure solution, have an oxidation kinetic slower than when they mixed with others pollutants (e.g. Phenol, 4-chlorophenol). Therefore, the mixture tends to standardize from the individual behaviour. In conclude, the feasibility study of the oxidative regeneration process (AD-OX) was performed on industrial waste water. The regeneration AC as adsorbent is less limited than with mixtures of substituted phenols.

El creciente número de controles analíticos requeridos en áreas como la sanitaria, el medio ambiente o la alimentación conlleva la necesaria automatización de los procesos analíticos.De acuerdo con ello, en esta tesis se han desarrollado, implementado y puesto a punto nuevos métodos automáticos de análisis robustos y económicos para la determinación de analitos de interés medioambiental, clínico e industrial. La automatización de las metodologías, empleando las técnicas de flujo MSFIA y MPFS, simplifican de forma considerable el procesamiento analítico con un importante ahorro de reactivos y tiempo, y permiten una mayor frecuencia de análisis, con la consecuente reducción del coste por análisis y en la generación de residuos. Los métodos propuestos son selectivos, reproducibles, precisos, robustos y en casi su totalidad son ejecutados sin la intervención del analista. / O crescente número de controlos analíticos requeridos em diversas áreas como o médio ambiente, a indústria sanitária ou a alimentar, conduziu à necessidade de automatização dos processos analíticos.Indo de encontro a estes requisitos, nesta tese desenvolveu-se, implementou-se e colocou-se em prática novos métodos de análise automáticos robustos e económicos para a determinação de analitos com interesse ambiental, clínico e industrial. A automatização das metodologias aplicando as técnicas de fluxo MSFIA e MPFS, simplificam de forma considerável o procedimento analítico com um decréscimo importante de reagentes gastos e tempo de análise, permitindo uma maior frequência de análise, com consequente redução do custo de análise e de geração de resíduos. Os métodos propostos são selectivos, reprodutíveis, precisos e robustos.