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Estudo de reatores eletroqu?micos para remo??o de Cu2+ , Zn2+, Fenol e BTEX em ?gua produzidaRamalho, Adriana Margarida Zanbotto 01 August 2008 (has links)
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Previous issue date: 2008-08-01 / The production of water has become one of the most important wastes in the petroleum industry, specifically in the up stream segment. The treatment of this kind of effluents is complex and normally requires high costs. In this context, the electrochemical treatment emerges as an alternative methodology for treating the wastewaters. It employs electrochemical reactions to increase the capability and efficiency of the traditional chemical treatments for associated produced water. The use of electrochemical reactors can be effective with small changes in traditional treatments, generally not representing a significant additional surface area for new equipments (due to the high cost of square meter
on offshore platforms) and also it can use almost the same equipments, in continuous or batch flow, without others high costs investments. Electrochemical treatment causes low environmental impact, because the process uses electrons as reagent and generates small amount of wastes. In this work, it was studied two types of electrochemical reactors: eletroflocculation and eletroflotation, with the aim of removing of Cu2+, Zn2+, phenol and BTEX mixture of produced water. In eletroflocculation, an electrical potential was applied
to an aqueous solution containing NaCl. For this, it was used iron electrodes, which promote the dissolution of metal ions, generating Fe2+ and gases which, in appropriate pH, promote also clotting-flocculation reactions, removing Cu2+ and Zn2+. In eletroflotation, a
carbon steel cathode and a DSA type anode (Ti/TiO2-RuO2-SnO2) were used in a NaCl solution. It was applied an electrical current, producing strong oxidant agents as Cl2 and HOCl, increasing the degradation rate of BTEX and phenol. Under different flow rates, the
Zn2+ was removed by electrodeposition or by ZnOH formation, due the increasing of pH during the reaction. To better understand the electrochemical process, a statistical protocol factor (22) with central point was conducted to analyze the sensitivity of operating
parameters on removing Zn2+ by eletroflotation, confirming that the current density affected the process negatively and the flow rate positively. For economical viability of these two electrochemical treatments, the energy consumption was calculated, taking in account the kWh given by ANEEL. The treatment cost obtained were quite attractive in comparison with the current treatments used in Rio Grande do Norte state. In addition, it could still be reduced for the case of using other alternative energy source such as solar, wind or gas generated directly from the Petrochemical Plant or offshore platforms / A produ??o de ?gua tem sido a maior corrente de res?duos da ind?stria do petr?leo no segmento de Explora??o e Produ??o E&P. O tratamento deste efluente al?m de ser complexo, requer um alto custo. Neste contexto, surge o tratamento eletroqu?mico como uma metodologia alternativa que empregando rea??es de eletr?lise possibilita aumentar a capacidade e a efici?ncia do tratamento f?sico-qu?mico tradicional da ?gua produzida. A implanta??o de reatores eletroqu?micos pode ser efetivada com pequena modifica??o numa esta??o de tratamento tradicional, sem demandar ?rea significativa (tendo em vista o alto custo do metro quadrado nas plataformas em alto mar), aproveitando os equipamentos existentes, podendo realizar tratamento cont?nuo ou em bateladas, sem a necessidade de investimentos elevados. O tratamento eletrol?tico causa baixo impacto ambiental, pois o processo utiliza el?trons como reagente e gera poucos res?duos. Neste trabalho foram estudados dois tipos de reatores eletroqu?micos: um eletrofloculador e um eletroflotador, tendo como objetivo a remo??o de Cu2+, Zn2+ , fenol e BTEX presentes na ?gua produzida.
No eletrofloculador aplicou-se um potencial el?trico a uma solu??o aquosa contendo NaCl, atrav?s de eletrodos de ferro, que promovendo a dissolu??o deste metal com a gera??o de ?ons Fe2+ e gases que em pH apropriado formou rea??es de coagula??o-flocula??o removendo Cu2+ e Zn2+. No eletroflotador utilizou-se c?todo de a?o carbono e ?nodo do tipo DSA de Ti/TiO2-RuO2-SnO2, em solu??o contendo NaCl, que atrav?s de uma corrente
el?trica produziu agentes oxidantes fortes como Cl2 e HOCl que ajudaram a degradar o BTEX e fenol em diferentes vaz?es; o Zn2+ foi removido por eletrodeposi??o ou pela forma??o de ZnOH devido ao aumento de pH durante a rea??o. Para compreender o
processo eletroqu?mico foi realizado um planejamento fatorial 22 com ponto central para avaliar a sensibilidade dos par?metros operacionais que influenciaram no processo de remo??o de Zn2+ na eletroflota??o, de forma que a densidade de corrente influenciou positivamente e a vaz?o negativamente. Como indicador da viabilidade econ?mica do tratamento eletroqu?mico foram analisados os consumos energ?ticos dos reatores tomando como base o valor kWh cobrado pela ANEEL. Os custos dos tratamentos desta pesquisa foram mais atrativos quando comparados ao utilizado atualmente no Rio Grande do Norte, podendo ser reduzidos caso seja utilizada fontes de energia alternativas, como solar, e?lica
ou a g?s gerada no pr?prio P?lo Petroqu?mico ou plataformas
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Influência dos íons cloreto na cinética de redução eletroquímica dos íons de Bi+3 e CU2+ no eletrodo de mercúrio / Influence of chloride ions on the electrochemical reduction of Bi3+ and Cu2+ ions on mercury electrodeSilvia Maria Leite Agostinho 03 November 1975 (has links)
A influência de pequenas concentrações de íons cloreto na cinética de redução eletroquímica dos íons Bi3+ e Cu2+ foi estudada através de medidas independentes de adsorção específica e de cinética eletroquímica. A adsorção específica foi determinada por meio das curvas eletrocapilares obtidas com o método do tempo de gota, para soluções aquosas de misturas de ácido clorídrico xM e de ácido perclórico (1 - x)M. Obeservou-se que, em concentrações de cloreto muito baixas, iguais ou inferiores a 10-2 M, a adsorção específica desses íons segue a isoterma de adsorção de Henry. A cinética da redução eletroquímica dos íons de Bi3+ e Cu2+, na presença de pequenas concentrações de íons cloreto, em meio de ácido perclórico 1 M, foi estudada por polarografia com o eletrodo de mercúrio. Os valores das constantes de velocidade foram calculados, a partir da relação existente entre a corrente, medida em cada potencial, e a corrente de difusão, usando as equações relativas a processos de eletrodos irreversíveis. Estes valores mostraram que, para as concentrações mais baixas de cloreto estudadas, esses íons aceleram as reações Bi3+ + 3e → Bi(Hg) e Cu2+ + 2e → Cu(Hg). O mecanismo de redução, por outro lado, permanece o mesmo já observado por outros autores em soluções de ácido perclórico puro, ou seja, os íons Bi3+ e Cu2+ são reduzidos em etapas de um elétron com velocidades comparáveis. No caso do bismuto, para as concentrações mais altas de cloreto estudadas, o efeito da complexação dos íons Cl- e Bi3+ no meio da solução se torna apreciável e a influência dos íons cloreto na velocidade de redução se deve a uma ação combinada da sua adsorção específica sobre o eletrodo e da sua tendência em formar complexos. No caso do cobre apenas a adsorção específica dos íons cloreto é a responsável pelo seu efeito na cinética do processo, em virtude da não complexação dos íons Cl- e Cu2+ presentes na solução. Tanto no caso do bismuto como o do cobre se observou uma relação linear entre os logaritmos das constantes de velocidade de redução e a carga especificamente adsorvida de íons cloreto, a um potencial constante. Esses resultados estão em concordância com os modelos teóricos de PARSONS e de GUIDELLI e FORESTI, sobre a influência de íons não eletroativos especificamente adsorvidos na cinética de reações de eletrodo. presença de uma carga especificamente adsorvida, dependente do potencial do eletrodo, justifica a variação no coeficiente de transferência à medida que se varia a concentração do íon especificamente adsorvido; no caso do cobre, onde apenas a adsorção específica é a responsável pelo aumento da velocidade de redução eletroquímica, a correção no valor do coeficiente de transferência a partir dos dados de adsorção, coincide com os resultados experimentais obtidos a partir da variação do logaritmo da constante de velocidade com o potencial. / In the present work, the effect of chloride ions in small concentrations on the electrochemical reduction of Bi3+ and Cu2+ ions was studied by means of independent measurements of specific adsorption and electrode kinetics. Specific adsorption was calculated irom electrocapillary curve data, obtained by means of the drop time method for aqueous solutions of xM hydrochloric acid and (1 - x)M perchloric acid mixtures. It was observed that, for low chloride concentrations (less than or equal to 10-2M), specific adsorption of these ions on the mercury electrode obeys the Henrys adsorption isotherm. The kinetics of the electrochemical reduction of Bi3+ and Cu2+ ions, in the presence of emall concentrations of chloride ions in 1M HC104 was studied by dropping mercury electrode polarography. The rate constants was calculated from the ratio between the current, measured at each potential, and the diffusion current, using the equations for irreversible electrode processes. It is shown from these rate constansts, that for the smaller chloride concentrations, the velocity of the reaction Bi3+ + 3e → Bi(Hg) and Cu2+ + 2e Cu(Hg) is increased by the presence of chloride ions. The reduction mechanism remains the same as that observed by other investigators in pure HC104, i.e., the reduction occur in one electron steps and the rates of each step are compa¬rable. In the case of bismuth the effect of complexation of Bi3+ by Cl- ions is appreciable for the higher chloride concentrations; the influence of the chloride ions on the reduction velocity thus results from a combination of its specific adsorption on the electrode and its tendency for complex formation. In the case of copper, only the specific adsorption of chloride ions is responsible for their effect on the electrode process kinetics since there is no complexation of the Cu2+ ion by Cl- in solution. For the reductions of bath bismuth and copper ions, a linear relation between the logarithms of the rate constants and the specifically adsorbed charge of Cl- ions is observed at constant potencial. These results agree with the theoretical models of PARSONS and of GUIDELLI and FORESTI describing the effect of non-electroactive, specifically adsorbed ions on the kinetics of electrode processes. The presence of specifically adsorbed charge, that depends on the electrode potential, explains the observed variation of the transfer coefficient as the concentration of the specifically adsorbed ion is increased. For copper, in which only apecific adsorption is responsible for the increase of the velocity, transfer coefficients corrected using the specific adsorption data are in agreement with the experimental results obtained from the variation of the logarithm of the rate constant with the potential.
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Obtenção de nanocristais semicondutores de CdTe via síntese in situ em matrizes mesoporosas MCM-41 para aplicação em sensores eletroquímicos na detecção de íons Cu2+ / Obtaining semiconductors nanocrystals CdTe by synthesis in situ into mesoporous of MCM-41 matrix for application electrochemical sensors in the Cu2+ ions detectionSantos, José Carlos dos 05 April 2016 (has links)
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / CdTe semiconductor nanoparticles have unique optical properties, which can be tunable sizes, due to the quantum confinement effect. In the present work, stable CdTe nanocrystals were grown in the mesoporous environment of thiol-functionalized MCM-41 mesoporous silica from an approach employing 3-mercaptopropionic acid, an efficient capping agent. The obtained materials were characterized by infrared spectroscopy, N2 dessortion/adsorption, UV-Vis emission and absorption spectroscopy, transmission electron microscopy (TEM) and electrochemical characterization; X-ray diffraction (XRD) and thermogravimetric analyses were used to MCM-41 silica. The emission properties of CdTe were found to be dependent on the proportion of mesoporous matrix used in the synthesis, yielding CdTe nanocrystals emitting below the wavelength range usually obtained from aqueous colloidal synthesis. The detection of Cu2+ ions using modified carbon paste electrodes by anodic stripping voltammetry was possible only with samples of CdTe in situ, evidencing the role of the semiconductor as active phase. The most active sample obtained here was exactly that containing the lowest CdTe loading, showing it is possible to reduce the dosage of Cd-containing nanocrystals while improving their properties, which is crucial to concretize applications of CdTe nanocrystals. / Nanopartículas semicondutoras de CdTe possuem propriedades ópticas únicas ajustáveis, que são dependentes de seus tamanhos, devido ao efeito do confinamento quântico. No presente trabalho, nanopartículas estáveis de CdTe foram sintetizadas confinadas em um ambiente mesoporoso de uma sílica MCM-41 funcionalizada com grupos tióis, através do método de funcionalização com o uso do ácido 3-mercaptopropiônico. Os materiais obtidos foram caracterizados por espectroscopia vibracional na região do infravermelho, adsorção/dessorção de nitrogênio, espectroscopias eletrônicas de absorção UV-Vis e emissão, microscopia eletrônica de transmissão (MET) e caracterização eletroquímica; já as caracterizações por difração de raios X (DRX) e análise termogravimétrica foram usadas para sílica MCM-41. As propriedades de emissão do CdTe mostraram relação de dependência da proporção da matriz mesoporosa usada nas sínteses, resultando em emissão abaixo da faixa de comprimento de onda usualmente obtido para CdTe em meio coloidal aquoso. A detecção de íons Cu2+ através de eletrodos de pasta de carbono modificados foi realizada por voltametria de redissolução anódica, a qual apresentou sinal somente para as amostras de CdTe in situ, o que evidenciou o papel do semicondutor como fase ativa do eletrodo. A amostra mais ativa foi aquela que continha a menor proporção CdTe, evidenciando que é possível reduzir a dosagem de Cd2+ nos nanocristais enquanto se aperfeiçoam suas propriedades, o que é crucial do ponto de vista das aplicações de nanocristais de CdTe.
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2D struktury na bázi fosfonátů kovů; vztahy mezi uspořádáním a vlastnostmi studované metodami molekulárních simulací / 2D structures based on metal phosphonates; relationships between arrangement and properties studied by molecular simulations methodsŠkoda, Jakub January 2019 (has links)
This work deals with the structural analysis of layered zirconium sulfophenylphosphonates and their intercalates with the use of the classical molecular simulation methods. The inner composition of both fully and partially sulfonated layers was determined in agreement with available experimental data, especially chemical analysis, thermogravimetric measurements and X-ray diffraction. The calculations revealed the positions of the water molecules in the planes of sulfo groups which strongly affect the resultant diffraction pattern. Within the zirconium sulfophenylphosphonate layered structure, the arrangements of intercalated species based on optically active dipyridylamine molecules and cations of sodium, copper and iron were solved with the respect to the agreement with experimental results and values of potential energy. In case of the dipyridylamine molecules and its derivatives, the resultant disordered partially row arrangements of the organic molecules in the interlayer were showed to influence the dipole moment of the intercalate. From this point of view, nitro-derivative has been picked out as the most suitable for potential applications. Regarding the intercalated cations, sodium cations take up the space of water molecules next to the sulfo groups while copper and iron cations are distributed in a...
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Synthesis and Characterization of Transition Metal Ion-based Hydrogels with Auxiliary Carboxylate Spacer Ligands for Selective Carbon Dioxide Separation and Other Potential ApplicationsAl Dossary, Mona 11 1900 (has links)
Metallo-supramolecular hydrogels have interesting dynamic properties for many applications. We report a simple method for synthesizing copper-based polymer hydrogels made from nontoxic poly(methyl vinyl ether-alt-maleic anhydride) (PVM-alt-MA) in the absence or presence of added dicarboxylates, such as adipate and terephthalate. We utilize metal-polycarboxylate backbone and carboxylate spacer ligands between polymers strands engineered via non-covalent metal ion coordination. Rheological measurements revealed that the mechanical stability of the hydrogels was enhanced by the addition of supplementary dicarboxylate ligands. The optimal ratio of polymer to dicarboxylate to Cu2+ was 10:4:2.5. Our scanning electron microscope (SEM) and Cryo-SEM imaging and physical adsorption measurements revealed the formation of pores. The Brunauer–Emmett–Teller (BET) surface area of the dried hydrogels increased from 177.96 m2 g−1 in a dried hydrogel without added dicarboxylate to 646.90 and 536.44 m2 g−1 with the addition of adipate and terephthalate, respectively. The pore volume increased as well.
Separation of CO2 from post-combustion flue gases is important for environmental and economic sustainability. The PVM-alt-Na-MA:adipate:Cu2+ hydrogels are promising material for post-combustion CO2 separation. At normal conditions (298 K and 1 bar), the PVM-alt-Na-MA:adipate:Cu2+ hydrogel samples with 10:4:2.5 ratio, showed notable CO2/N2 selectivity of 78.46 and a high CO2/CH4 selectivity
reaching 26.09 at 1 bar. Additionally, we investigated in detail the effect of transition metal ion on the rigidity and structure of hydrogels using Al3+, Fe3+, Cu2+, Ni2+, Zn2+, and Co2+. We also studied the effect of using tricarboxylate spacer ligands such as nitrilotriacetic (NTA) and trisodium citrate or tetracarboxylate such as ethylenediaminetetraacetic acid (EDTA).
It is important to mention that one of the main advantages of our facile synthesis method is being simple and can be scaled up for commercial applications. For scaling up the synthesis of hydrogels, we utilized a filling machine that is able to increase the amount of hydrogel aliquots with variable volume. Silver-based hydrogels showed significant antibacterial activity, due to the presence of silver nanoparticles. We utilized a filling machine for application of amorphous wound dressing. The optimization of the conditions of the filling enabled us to scale up the synthesis and the filling process.
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Spectral Selective Photothermal Materials and Energy ApplicationsLin, Jou January 2022 (has links)
No description available.
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Síntese e arranjos supramoleculares de complexos Bis(triazenido) macrocíclicos e triazenido 1-óxido com os cátions Cu2+, Ni2+, Cu+, K+ / Synthesis and supramolecular arrangements of bis(triazenide) macrocyclic and triazenide 1-oxide complexes with Cu2+, Ni2+, Cu+, K+ cationsSantos, Aline Joana Rolina Wohlmuth Alves dos 09 June 2010 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work elaborates on the determination of crystal and molecular structures of four pro-ligands, emphasizing bis(triazenes), triazene 1-oxide and a new class of bis(triazenes) macrocyclic, and eight complexes involving Cu+, Cu2 +, Ni2 + and K+. Pro-ligands triazenes 1-oxide are relatively small and simple molecules. When they are deprotonated they presen a high ability to form supramolecular assemblies, either because they are planar and facilitate the metal-metal approach and the formation of π···π interactions _ as in the case of complex (2) _, or because they have substituents with capacity of act as agent of secondary complexation forming polycationic structures _ as in the case of complex (3). Pro-ligand bis(triazenes) are double agents of complexation. The bis(triazene) (4) complexed Copper(I) forming a binuclear complex (5). The same ligand also led to binuclear complexes of Copper(II) through the chelate and macrocyclic effect, forming two types of crystal structures, one non-centrosymmetric (6), the other
centrosymmetric (7). The pro-ligand bis(triazene) macrocyclic (8) has a cavity with ideal size for the complexation of transition metals, resulting, for example, in complex (9) with the cation Nickel(II). The ligand in this complex has substituents in para position. These substituents, two pyridine molecules (in the coordination sphere of the metal) and two pyridine molecules (as solvate of crystallization) form weak electrostatic interactions in the supramolecular arrangement.
The bis(triazene) macrocyclic (10) has a central cavity larger than the bis(triazene) macrocyclic (8),
allowing the complexation of larger molecules or ions.
The analysis by X-ray diffraction on single crystal for the compound (10) revealed the presence of disordered water molecules inside the cavity, forming a chain of water molecules perpendicular to the stacked molecules of (10). When the compound (10) is deprotonated with a weak base such as pyridine, the deprotonation occurs
partially, leading to a binuclear complex with Copper(II)-bridged μ2-OH (11). Two molecules of the ligand
coordinate the two Copper(II) cations, and the coordination sphere is completed by two axial pyridine molecules. When the compound (10) is deprotonated with a strong base such as sodium or potassium ethanolate,
the deprotonation occurs totally, leading to a binuclear conmplex with Copper(II)-bridged μ2-OCH2CH3 (12).
One molecule ligand coordinates two Copper(II) cations and the coordination sphere is also supplemented by
two axial pyridine molecules. The synthesis of a new class of macrocyclic triazenes has been successfully performed as well as the synthesis of their metallic complexes. The characterization of their structures and supramolecular assemblies was performed using the analysis by X-ray diffraction on single crystal and other secondary methods. / Este trabalho apresenta as determinações das estruturas cristalinas/moleculares de quatro pró-ligantes, enfatizando bis(triazenos), triazeno 1-óxido e a nova classe de bis(triazenos) macrocíclicos, e oito complexos envolvendo os cátions Cu+, Cu2+, Ni2+ e K+. Pró-ligantes triazenos 1-óxido são moléculas relativamente pequenas e simples, que quando desprotonadas apresentam elevada capacidade de formação de arranjos supramoleculares, sejam pelo fato de serem planares e facilitarem a aproximação metal-metal e a formação de interações π···π, como no caso do complexo (2), ou pelo fato de apresentarem substituintes capazes de atuarem como complexantes secundários, formando estruturas policatiônicas complexas, como no caso do complexo (3). Pró-ligantes bis(triazenos) são agentes duplos de complexação. O bis(triazeno) (4) mostrou-se capaz de complexar o íon cobre(I) formando um complexo binuclear (5). O mesmo ligante, ainda, originou complexos binucleares de cobre(II), através do efeito quelato e macrocíclico, formando dois tipos de estruturas cristalinas, uma não-centrossimétrica (6) e outra centrossimétrica (7). O pró-ligante bis(triazeno) macrocíclico (8) apresenta uma cavidade com tamanho ideal para a
complexação de metais de transição, originando, por exemplo, o complexo (9) com o cátion níquel(II). O ligante neste complexo apresenta substituintes em posição para e estes subtituintes, adicionados às moléculas de piridina que completam a esfera de coordenação do metal e às moléculas de piridina como solvato de cristalização, formam o arranjo supramolecular, através de interações eletrostáticas fracas.
O pró-ligante bis(triazeno) macrocíclico (10) apresenta uma cavidade central maior que o pró-ligante bis(triazeno) macrocíclico (8), possibilitando a complexação de moléculas ou cátions maiores. A difração de raios-x em monocristal de (10) revelou a presença de moléculas de água desordenadas no interior da cavidade, formando uma cadeia perpendicular às moléculas empacotadas do pró-ligante macrocíclico.
Quando o composto (10) é desprotonado com base fraca, como piridina, a desprotonação ocorre de maneira parcial, originando um complexo binuclear de cobre(II) unido por pontes μ2-OH (11), onde duas moléculas de ligante coordenam os dois íons cobre(II) e a esfera de coordenação quadrática é completada por duas moléculas de piridina axiais. Quando o composto (10) é desprotonado com base forte, como etóxido de sódio ou potássio, a desprotonação ocorre de maneira total, originando um complexo binuclear de cobre(II) unido por pontes μ2-OCH2CH3 (12), onde uma molécula de ligante coordena os dois íons cobre(II) e a esfera de
coordenação quadrática também é completada por duas moléculas de piridina axiais. A síntese de mais representantes da nova classe de triazenos macrocíclicos foi realizada com sucesso neste trabalho, bem como a síntese de complexos, envolvendo triazenidos macrocíclicos. A caracterização de
suas estruturas e arranjos supramoleculares foi realizada através de difração de raios-x em monocristal e outros
métodos secundários.
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Charakterizace vybraných bakteriálních kmenů získaných během evolučních experimentů / Characterization of bacterial strains obtained in evolutionary engineeringHrabalová, Vendula January 2020 (has links)
This diploma thesis deals with application of evolutionary engineering on PHA producing bacterial strains. Two bacterial strains, Cupriavidus necator H16 and Halomonas halophila, were chosen for the evolutionary experiments. Copper cations (Cu2+) and sodium chloride (NaCl) were chosen as the selective pressure for C. necator H16; acetic acid (AA) and levulinic acid (LA) for Halomonas halophila. The adapted strains were during long-time evolutionary experiments characterized by GC-FID and SEC-MALS. The growth of the adapted strains was studied by the mean of optical density measurement. The amount of viable cells was determined by spectral FC after their expositon to selected stress factors. Specific enzyme activities of enzymes involved in citrate and glyoxalate cycle, enzymes generating NADPH, LA metabolism enzyme and PHA biosynthesis enzymes were determined. The adapted strains were compared with the wild-type of strains. The successfull adaptation of C. necator H16 adapted to Cu2+ was detected. Biomass and PHA production of both wild and adapted H. halophila strains cultivated in lignocellulosis waste were determined. It was found out that H. halophila adapted to the LA is capable of producing more PHA than the wild strain of this bacteria.
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Mécanismes d'adsorption des métaux lourds par les exopolysaccharides bactériens : Le système Xanthane-Cuivre comme modèle d'étudeCausse, Benjamin 11 December 2009 (has links) (PDF)
Les ExoPolySaccharides (EPS) bactériens constituent une fraction réactive du sol vis-à-vis des Eléments Traces Métalliques (ETM). Le système xanthane-cuivre est étudié comme modèle de complexation des ETM par les EPS. L'étude à l'échelle macroscopique, par titrages acido-basiques, détermine les valeurs des pKa du xanthane (pKmoyenI=0.1M=2.5) et propose un modèle électrostatique à condensateur cylindrique pour expliquer les variations de pKa en fonction de la force ionique. Les titrages en présence de cuivre et isothermes d'adsorption montrent un résultat inédit : le xanthane adsorbe plus de cuivre à pH3.5 qu'à pH5.5. Les valeurs des constantes apparentes de complexation valent LogKCu-XanpH3.5=3 et LogKCu-XanpH5.5=2.6. Les résultats de dichroïsme circulaire suggèrent un changement conformationnel du xanthane pH-dépendant. Un modèle thermodynamique à deux états (xanthane désordonné à pH<5 vs ordonné à pH>5), couplé aux données pKa et LogKCu, permet de reconstruire dèlement les données expérimentales. L'étude à l'échelle moléculaire par modélisation moléculaire (MM) montre que la structure désordonnée de l'EPS à pH3 favorise la formation de complexes chelatants très stabilisants entre deux chaînes latérales du xanthane et Cu2+. A contrario, à pH5.5 en (structure hélices ordonnées) ce sont les sites complexants simples, moins stabilisants pour le cuivre, qui prédominent. Les résultats d'EXAFS et leur modélisation MM conrment la plus forte anité du cuivre pour le xanthane à pH3 qu'à pH5.5. Cette étude montre l'importance de la conformation des EPS dans leur capacité à xer les ETM, et l'intérêt de l'outil MM pour la compréhension de ces phénomènes à l'échelle moléculaire.
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Μελέτη αλληλεπιδράσεων ιόντων Cu2+ με συμπολυμερή του ακρυλικού οξέος σε υδατικό διάλυμα / Study of the interactions between Cu2 + ion with acrylic acid copolymers in aqueous mediaΤσοπελάκης, Φίλιππος 02 April 2014 (has links)
Στην εργασία αυτή προχωρήσαμε στη μελέτη της αλληλεπίδρασης των ιόντων δισθενούς χαλκού, Cu2+ με στατιστικά συμπολυμερή P(ANa-co-SSNa) του ακρυλικού οξέος, (ANa) με το στυρενοσουλφονικό οξύ (SSNa). Συντέθηκαν τα συμπολυμερή P(ANa50-co-SSNa) και P(AΝa80-co-SSNa) που περιέχουν 50 mol% και 80 mol% ακρυλικού οξέος αντίστοιχα. Τα συμπολυμερή αυτά χαρακτηρίστηκαν με φασματοσκοπία πυρηνικού μαγνητικού συντονισμού 1H NMR.
Προχωρήσαμε στην φυσικοχημική μελέτη της αλληλεπίδρασης ιόντων δισθενούς χαλκού, Cu2+, με τα συμπολυμερή P(ANa50-co-SSNa) και P(AΝa80-co-SSNa) χρησιμοποιώντας διάφορες τεχνικές όπως η θολομετρία, η ιξωδομετρία και η φασματοσκοπία UV-vis. Τα πειράματα πραγματοποιήθηκαν σε υδατικά διαλύματα, στα οποία χρησιμοποιήθηκε ως διαλύτης τρισαπιονισμένο νερό, H2O-3D. Για λόγους σύγκρισης μελετήθηκαν επίσης τα αντίστοιχα ομοπολυμερή των μονομερών που αποτελούν τα συμπολυμερή P(ANa-co-SSNa). Έτσι, πραγματοποιήθηκε φυσικοχημική μελέτη της αλληλεπίδρασης των ιόντων Cu2+ με το πολυ(ακρυλικό νάτριο), PANa, και το πολυ(στυρενοσουλφονικό νάτριο), PSSNa, αντίστοιχα.
Από την ιξωδομετρική μελέτη προέκυψε πως η εισαγωγή ιόντων χαλκού Cu2+ σε υδατικό διάλυμα πολυμερούς οδηγεί στην μείωση του ανηγμένου ιξώδους. Μάλιστα η μείωση αυτή είναι πιο δραστική καθώς αυξανεται η συγκέντρωση ιόντων Cu2+ στο διάλυμα. Αυτή η συμπεριφορά αποτελεί ένδειξη της συμπλοκοποίησης των ιόντων χαλκού, Cu2+, με τις ομάδες καρβοξυλίων του ακρυλικού οξέος (ΑΑ). Διαπιστώθηκε πως στα συμπολυμερή P(ANa-co-SSNa) τα Cu2+ συμπλοκοποιούνται με τα καρβοξύλια του ακρυλικού οξέος σε αναλογία ιόντων χαλκού προς ομάδες καρβοξυλίων ίση με 1:2.
Όσον αφορά στην μελέτη με UV-vis, ενώ στην περίπτωση του ομοπολυμερούς PSSNa δεν υπάρχει κάποια ιδιαίτερη αλληλεπίδραση τύπου συμπλόκου ένταξης μεταξύ του πολυμερούς και των ιόντων του Cu2+, στην περίπτωση του συμπολυμερούς Ρ(ΑNa50-co-SSNa), παρατηρήθηκε μετατόπιση του σήματος των ιόντων Cu2+ (από τα 800 στα 745 nm) παρουσία του συμπολυμερούς. Αυτό είναι χαρακτηριστικό του σχηματισμού συμπλόκου ένταξης μεταξύ των ιόντων του Cu2+ και των ομάδων COO- του συμπολυμερούς. / In the present work we studied the interaction of bivalent copper ions Cu2+ with random copolymers P(ANa-co-SSNa) of acrylic acid (ANa) and styrenesulfonic acid (SSNa). Two copolymers, P(ANa50-co-SSNa) and P(AΝa80-co-SSNa) with 50 mol% and 80 mol% in acrylic acid, respectively, were synthesized and characterized by neutron magnetic resonance spectroscopy, 1H NMR.
We proceeded in the physicochemical study of the interaction
of bivalent copper ions, Cu2+, with P(ANa50-co-SSNa) and P(AΝa80-co-SSNa) copolymers using techniques like turbidimetry, viscometry and UV-vis spectroscopy. The experiments were performed in aqueous media using 3D water, H2O-3D. For reasons of comparison the respective homopolymers of sodium polyacrylate, PANa, and poly(styrene sulfonate), PSSNa, were also studied.
From viscometry it was found that the introduction of copper ions in the polymer aqueous solutions leads to the decrease of the reduced viscosity. Moreover, this decrease is more pronounced as the concentration of Cu2+ increases in the solution. This behavior is indicative of the complexation between Cu2+ with the carboxylate groups of acrylic acid (ΑΑ). In the P(ANa-co-SSNa)/Cu2+ system, it was found that complexation occurs when the ratio of copper ions to carboxylates is equal to 1:2.
UV-vis spectroscopy showed that, while in the case of PSSNa homopolymer there is not strong interaction with Cu2+, in the case of the Ρ(ΑNa50-co-SSNa) copolymer, the introduction of the polymer lead to a shift of the maximum absorbance of Cu2+ (from 800 to 745 nm). This was due to the complexation of Cu2+ with the COO- groups of the copolymer.
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