In this research, manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, ethanol, and propanol were used as alternative solvents during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid manganese oxide modified by additions of carbon nanotubes was further prepared. The effects of different solutions and heat treatment temperatures on the morphology, physical characteristics, and electrochemical properties of the manganese oxide based materials were investigated. Particle size of pristine manganese oxide samples prepared from methanol, ethanol, and propanol were compared by SEM and TEM image analysis. Smallest particle size was observed for manganese oxide prepared from propanol, with diameters range from 16 nm to 50nm. XRD results showed that the as-prepared manganese oxide based samples treated at calcination temperature of 300ºC and above were composed of Mn2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance of manganese oxide prepared from methanol, ethanol, and propanol at scan rate of 10 mV/s measured using two electrode systems were 88.3, 66.0, and 104.8 F/g, respectively and that for the hybrid sample was 140.5 F/g. Results from electrochemical impedance spectroscopy (EIS) also showed superior electrochemical properties of the hybrid sample over pristine manganese oxide samples. It is evident that the addition of carbon nanotubes not only improved the specific capacitance but also the overall electrochemical properties of the manganese oxide supercapacitor.

Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being.

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Thesis (M.Tech-Chemical Engineering)--Cape Technikon, Cape Town, 2001 / The white-rot fungus (WRF), Phanerochaete chrysosporium, is a well known microorganism which produces ligninolytic enzymes. These enzymes can play a major role in the bioremediation of a diverse range of environmental aromatic pollutants present in industrial effluents. Bioremediation of aromatic pollutants using ligninolytic enzymes has been extensively researched by academic, industrial and government institutions, and has been shown to have considerable potential for industrial applications. Previously the production of these enzymes was done using batch cultures. However, this resulted in low yields of enzyme production and therefore an alternative method had to be developed. Little success on scale-up and industrialisation of conventional bioreactor systems has been attained due to problems associated with the continuous production of the pollutant degrading enzymes. It was proposed to construct an effective capillary membrane bioreactor, which would provide an ideal growing environment to continuously culture an immobilised biofilm of P; chrysosporium (Strain BKMF-1767) for the continuous production of the ligninolytic enzymes, Lignin(LiP) and Manganese(MnP) Peroridase. A novel membrane gradostat reactor (MGR) was shown to be superior to more conventional systems of laboratory scale enzyme production (Leukes et.al., 1996 and Leukes, 1999). This concept was based on simulating the native state ofthe WRF, which has evolved on a wood-air interface and involved irnmobilisng the fungus onto an externally skinless ultrafiltration membrane. The MGR however, was not subjected to optimisation on a laboratory scale. The gradostat reactor and concept was used in this work and was operated in the deadend filtration mode. The viability of the polysulphone membrane for cultivation of the fungus was investigated. The suitability of the membrane bioreactor for enzyme production was evaluated. The effect of microbial growth on membrane pressure and permeability was monitored. A possible procedure for scaling up from a single fibre membrane bioreactor to a multi-capillary system was evaluated. Results indicated that the polysulphone membrane was ideal for the cultivation of P chrysosporium, as the micro-organism was successfully immobi1ised in the macrovoids of the membrane resulting in uniform biofilm growth along the outside of the membrane. The production of Lignin and Manganese Peroxidase was demonstrated. The enzyme was secreted and then transported into the permeate without a rapid decline in activity. Growth within the relatively confined macrovoids of the membrane contributed to the loss of membrane permeability. A modified Bruining Model was successfully applied in the prediction of pressure and permeability along the membrane The study also evaluated the effect of potential1y important parameters on the production of the enzymes within the membrane bioreactor. These parameters include air flow (Ch concentration), temperature, nutrient flow, relative redox potential and nutrient concentrations A sensitivity analyses was performed on temperature and Ch concentration. The bioreactor was exposed to normal room temperature and a controlled temperature at 37°C. The reactors were then exposed to different O2 concentration between 21% and 99"10. It was found that the optimum temperature fur enzymes production is 3TJC. When oxygen was used instead of air, there was an increase in enzyme activity. From the results obtained, it was clear that unique culture conditions are required for the production of LiP and MnP from Phanerochaete chrysosporium. These culture conditions are essential fur the optimisation and stability of the bioreactor.

La formation de patines noires riches en fer et/ou manganèse sur les édifices en grès est un phénomène observé pour une grande variété d’environnements mais qui n’est pas encore totalement compris. Le château de Lunéville, situé dans l’est de la France, est un cas d’étude intéressant puisqu'il présente des patines apparues pour différentes conditions : certaines semblent s’être formées naturellement alors que d’autres se sont développées sur des pierres ayant été exposées à un incendie. Ces dernières ont connu une élévation de leur température de surface, mais ont surtout été soumises à de grandes quantités d’eau lors de l’intervention des pompiers. Ce travail de thèse vise à mieux comprendre le phénomène de formation des patines en étudiant différents faciès de grès prélevés sur le château de Lunéville et en carrière. Afin d’appréhender l’influence des paramètres intrinsèques aux grès, des faciès patinés et non patinés ont été comparés d’un point de vue pétrophysique, chimique et minéralogique en s’appuyant sur des techniques d’analyse de laboratoire (microscopies optique et électronique avec sonde d’analyse dispersive en énergie, diffraction des rayons X, spectrométrie Raman, mesures de perméabilité, porosité et capillarité, ...), et sur de grands instruments (analyses par émission de rayons X induits par des particules (PIXE) sur l’accélérateur de proton AGLAE, analyses en micro-diffraction des rayons X et micro-spectrométrie d’absorption X (XANES) au synchrotron SOLEIL). En complément de cette caractérisation des blocs de pierre, les patines formées dans différents environnements ont également été comparées afin de dégager les paramètres extrinsèques dominants. Enfin, l’aspect dynamique de la libération du manganèse par les grès a été étudié, d’une part en menant des expériences de dissolution pour plusieurs pH, d’autre part en montrant qu’il était possible de recréer une patine de manganèse en laboratoire, par imbibition d’une éprouvette de grès. Les résultats obtenus permettent de proposer un modèle de formation des patines basé sur la dissolution des phases manganésifères initialement présentes dans les grès, puis la migration des ions libérés en solution dans le milieu poreux vers la surface des pierres / The formation of iron and/or manganese black patina on sandstone buildings is a phenomenon observed for various environments but which is not fully understood yet. The palace of Lunéville, in eastern France, is an interesting example because it has patinas that have developed in different conditions : some seem to have grown naturally while others have appeared on stones which were exposed to a fire. These stones experienced an increase of their surface temperature, but most of all, they were subjected to a substantial volume of water as part of attempts to extinguish the fire. The goal of this thesis is to understand the formation of the patinas by investigating different sandstone facies collected from the palace of Lunéville and from quarry. In order to understand the influence of the sandstones intrinsic parameters, the patinated and unpatinated facies were compared from petrophysical, chemical and mineralogical point of view, using laboratory techniques (optical and electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectrometry, permeability, porosity and capillarity measurements, ...) and large instruments (Particle Induced X-ray Emission (PIXE) on the AGLAE proton accelerator, X-ray micro-diffraction analysis and X-ray absorption micro spectroscopy (XANES) at the SOLEIL synchrotron). In addition to this characterization, patinas coming from different environments were also compared in order to extract the main extrinsic parameters. Finally, the dynamical aspect of the release of manganese from the sandstones was investigated by conducting dissolution experiments at various pH, and by demonstrating the possibility to recreate a Mn patina in laboratory, using sandstone imbibition techniques. The results allow to propose a model for the patina formation based on the dissolution of the Mn-phases initially present in the sandstones’ bulks, followed by the migration through the porous network towards the surface of the ions released in the solution

Neste trabalho, buscou-se verificar a possibilidade de, com a utilização do processo eletrolítico, se obter dióxido de manganês a partir da reciclagem de pilhas e baterias exauridas, visto a grande demanda por produtos que utilizam esse mineral. Utilizou-se, para tanto, uma solução eletrolítica que continha os íons metálicos: Ca (270mg/L), Ni (3000 mg/L), Co (630 mg/L), Mn(115300 mg/L), Ti (400 mg/L) e Pb (20 mg/L) em meio de ácido sulfúrico, sintetizada, seguindo-se dados de pesquisa anterior. A produção do dióxido de manganês eletrolítico (DME) foi realizada galvanostaticamente, com a utilização de uma fonte estabilizada que monitorava o potencial do eletrodo de trabalho. Utilizaram-se, preliminarmente, um eletrodo de trabalho de chumbo e dois contra-eletrodos de grafite, à temperatura de 98 ºC (±2ºC) e densidade de corrente de 1,69 A.dm-2. Após a verificação preliminar da possibilidade de obtenção do DME, repetiu-se sistematicamente o processo, aplicando-se variações de densidade de corrente (0,61 A.dm-2 a 1,93 A.dm-2) e de pH (0,00 a 1,20). O material obtido com essas variações foi analisado através dos processos de espectrometria de fluorescência de raios-X, difração de raios-X, área superficial específica pelo método BET e microscopia eletrônica de varredura (MEV). Os melhores resultados quanto a eficiência de corrente, pureza e área superficial se obtiveram com densidade de corrente entre 1,02 A.dm-2 e 1,39 A.dm-2 e com pH 0,50. Em todos os experimentos, como comprova a análise de difração de raios-X, foi constatada a obtenção da variedade alotrópica -MnO2, uma das formas viáveis para utilização na fabricação de pilhas. Os resultados apontam para a viabilidade desse processo de reciclagem como alternativa diante da escassez de fontes naturais de MnO2 com características compatíveis com a aplicação em questão e como forma de diminuição da poluição ambiental causada pelo descarte de pilhas e baterias. / Considering the growing demand for products containing manganese in its composition, this work seeks to verify the possibility of using depleted batteries as a source of manganese applying the electrolytic process. It was used an electrolyte solution containing the metal ions: Ca (270mg / L), Ni (3000 mg / L), Co (630 mg / L), Mn (115300 mg / L), Ti (400 mg / L) and Pb (20 mg / L) in concentrated sulfuric acid, following data from previous research. The production of electrolytic manganese dioxide (EMD) was performed through galvanization using a stabilized source that monitored the potential of the working electrode. It was preliminary used an electrode of lead and two counter electrodes of graphite at a temperature of 98ºC (± 2ºC) and current density of 1.69A.dm-2. After preliminary verifying the possibility of obtaining electrolytic manganese dioxide (EMD), the process was systematically repeated, applying different current density (0.61A.dm-2 to 2.51A.dm-2) and pH (0.00 to 1.20). The material obtained at these variations was analyzed through the process of X-ray fluorescence spectrometry, X-ray diffraction, specific surface area (BET) and scanning electron microscopy (SEM). The best values referring to current efficiency, level of purity and specific surface area were obtained with the current density ranging between 1.02 A.dm-2 and 1.39 A.dm-2, and pH 0.50. In any of the tested electrolysis conditions the -MnO2 structure was obtained as evidenced by the diffraction of X-rays analysis. The results indicate the feasibility of this recycling process as an alternative before shortage of natural sources of MnO2 and as a means of reducing environmental pollution caused by the disposal of batteries.

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Realizaram-se estudos potenciométricos, em combinação com medições espectrofotométricas, para caracterizar a espécie de íon manganês obtida a partir de oxidação coulométrica a corrente constante utilizando-se solução de Mn(II) (0,050 mol.L-1) em N3- (0,50 a 2,0 mol.L-1) e H+ (0,01 mol.L-1). Graficamente foi possível concluir que a espécie gerada é Mn(III) e obter os valores dos potenciais condicionais de redução, E0\'x, do par Mn(III)/Mn(II), em soluções tampão N3-/HN3, de concentração de N3- 0,50; 1,0; 1,5; 2,0 e 4,0 mol.L-1 e H+ 0,010 mol.L-1, sendo 0,468, 0,421, 0,396, 0,377 e 0,336 V (vs. ECS), respectivamente. Esses valores de E0\'x permitiram o cálculo das constantes de equilíbrio para os complexos no sistema Mn(III)/N3-, sendo: β1 = 1,23.105 M-1, β2 = 6,03.108 M-2, β3 = 2,37.1011 M-3, β4 = 1,54.1011 M-4 e β5 = 9,57.1011 M-5 (T = 25,0 ± 0,1 ºC, I = 2,0 mol.L-1 com NaClO4). Os valores calculados para as absortividades molares, em 430 nm, para as espécies [Mn(N3)3], [Mn(N3)4]- e [Mn(N3)5]2- foram 226, 3.680 e 6560 mol-1.L.cm-1, respectivamente. Para o estudo do cátion Co(II), foram efetuadas oxidações coulométricas da mesma forma e nas mesmas condições que para o cátion Mn(II). Os valores de E0\'x encontrados para o par Co(III)/Co(II) foram 0,400, 0,338, 0,302, 0,277 e 0,228 V (vs. ECS), para as concentrações de N3- 0,50; 1,0; 1,5; 2,0 e 4,0 mol.L-1 e H+ 0,010 mol.L-1. Com os valores de E0\'x obtidos para os pares Co(III)/Co(II) e Mn(III)/Mn(II), calcularam-se as constante de equilíbrio global, K, para a reação redox entre [Co(N3)n]3-n e [Mn(N3)n]2-n, encontrando-se os valores 7,1xl0-2, 4,0x10-2, 2,6x10-2, 2,0x10-2 e l,5x10-2, para os tampões acima descritos, respectivamente. Outros estudos revelaram a possível formação da espécies Mn(VI) quando KMnO4 e K2MnO4 são adicionados, separadamente, a uma solução tampão azoteto, por exemplo, N3- = 1,5 mol.L-1 e HN3 = 0,05 mol.L-1. / Spectrophotometric studies combined with coulometric generation of Mn(III), in presence of large excess of Mn(II), showed a maximum absorbance peak at 430 nm. The average molar absorptivity increases with azide concentration (0.44 to 3.9 mol.L-1) from 3,100 to 6,300 mol-1.L.cm-1, showing a stepwise complex formation. Potential measurements of the Mn(III)/Mn(II) system in several azide aqueous buffers solutions: 1.0x10-2 mol.L-1 HN3, (0.50 to 2.0 mol.L-1) N3- and 5.0x10-1 mol.L-1 Mn(II) and constant ionic strength 2.0 mol.L-1, kept with sodium perchlorate, leads to the conditional potential, E0\'x, in several azide concentrations at 25.0 ± 0.1 ºC (0.468, 0.421, 0.396, 0.377 e 0.336 V (vs. SCE) for the 0.50; 1.0; 1.5; 2.0 and 4.0 mol.L-1 N3- concentration, respectively). Considering the overall formation constants of Mn(II)/N3-, from former studies, and the potential, E0\'s = 1.063 V vs. SCE, for Mn(III)/Mn(II) system in non-complexing medium, it was possible to calculate the Fronaeus function, F0(L), and the following overall formation constants: β1 = 1.2x105 M-1, β2 = 6.0x108 M-2, β3 = (2.4±0.7)x1011 M-3, β4 = (1.5±0.5)x1011 M-4 and β5 = (9.6±.0.8)x1011 M-5 for the Mn(III)/N3- complexes. The molar absorptivity values, at 430 nm, found for the species [Mn(N3)3], [Mn(N3)4]- and [Mn(N3)5]2- were 226, 3,680 and 6,560 mol-1.L.cm-1, respectively. Similar studies with Co(II) in the same conditions, lead to the following conditional potentials, E0\'x, for the Co(III)/Co(II) system: 0.400, 0.338, 0.302, 0.277 e 0.228 V (vs. SCE). Using the E0\'x values obtained for both systems, Co(III)/Co(II) and Mn(III)/Mn(II), it was possible to calculate the equilibrium constant for the redox reaction between [Co(N3)n]3-n and [Mn(N3)n]2-n. The values found were 7.1xl0-2, 4.0x10-2, 2.6x10-2, 2.0x10-2 and 1.5x10-2, for 0.50; 1.0; 1.5; 2.0 and 4.0 mol.L-1 N3- concentration, respectively, in the same acidity (1.0x10-2 mol.L-1 HN3).