This thesis was dedicated to the possibility of replacing glassy carbon electrode using cheaper composite carbon rod with carbon coating applied onto its surface and to the consequences of adding a modifier to the electrode material. To understand the effects of having pasting liquid contained in carbon paste electrode on substance accumulation, partitioning coefficient of mineral oil/water compound was experimentally determined for 2NP, 4NP, 24DNP and 24TNP. Adsorption coefficient was experimentally determined to find out sorption possibilities of 2NP and 4NP on MMT. Surface of the carbon coating was imaged using scanning electron microscope to find out distribution of MMT and polystyrene in said carbon coating. A method for accumulating 2-nitrophenol and 4-nitrophenol on montmorillonite-modified carbon coating was successfully developed

La industria textil es una de las industrias con mayor consumo de agua y las aguas residuales que se generan contienen un gran número de contaminantes de diferente naturaleza, tales como colorantes y compuestos orgánicos. Muchos colorantes son visibles en agua a concentraciones tan bajas como 1 mg L-1. Los efluentes textiles típicamente presentan un contenido de colorante en el intervalo 10-200 mg L-1 y son altamente coloreados. La liberación de estos colorantes supone un peligro eco-tóxico. Es así que la descarga de aguas residuales coloreadas es actualmente un grave problema de la gestión ambiental. Como una alternativa ventajosa a los tratamientos físicos, químicos y biológicos convencionales para eliminar el color de las aguas residuales, surgen los procesos de oxidación avanzada (POA), que pueden convertir los contaminantes orgánicos en compuestos menos tóxicos, inocuos o incluso mineralizarse completamente, degradándose a sus constituyentes minerales. El objetivo de esta Tesis fue estudiar la eliminación de tres colorantes azo: Anaranjado de Metilo, Naranja G y Rojo Congo, aplicando POA, que implican la formación de compuestos con alto poder oxidante, generalmente radicales, que remueven los contaminantes recalcitrantes y refractarios. Para ello, se prepararon catalizadores de diferente naturaleza, modificados con metales de transición (Cu, Co, Mn) para favorecer la activación de los oxidantes empleados (persulfato o peroximonosulfato). Asimismo, se estudió brevemente la reducción catalítica de 4-nitrofenol, un subproducto tóxico y recalcitrante de la industria textil. El compuesto final de la reducción, el 4-aminofenol, se utiliza en diversos campos industriales. En el Capítulo I se presenta una introducción general y se enuncian los objetivos generales y específicos del trabajo. En el Capítulo II se describe la síntesis de los materiales empleados, diferenciándolos en catalizadores compuestos por una única fase (goetita parcialmente sustituida y óxidos mixtos tipo espinela) y catalizadores basados en soportes silíceos mesoporosos (MCM-41, SBA-15 y SBA-16). Se brindan detalles de la modificación de los soportes, empleando dos técnicas diferentes para la carga metálica (funcionalización e impregnación). El Capítulo III reúne los resultados de caracterización de los catalizadores preparados, empleando diversas técnicas, tales como microscopía electrónica de barrido (MEB), microscopía de transmisión electrónica (MET), espectroscopía infrarroja por trasformada de Fourier (FTIR), difracción de rayos X de polvos (DRX), espectroscopia de absorción atómica (EAA), espectroscopia fotoelectrónica de rayos X (XPS) y medidas de isotermas de adsorción-desorción de N2 a 77 K. Se llevó a cabo un análisis estructural a partir del refinamiento de los datos de DRX empleando el método Rietveld, y los resultados se informan en los Anexos I y II. En el Capítulo IV se presentan y analizan los resultados de la evaluación catalítica de los catalizadores constituidos por una única fase en la degradación oxidativa de Anaranjado de Metilo. Se estudia además el reuso de los catalizadores y se plantea un posible mecanismo de reacción. En el Capítulo V se amplía el estudio desarrollado en el capítulo anterior, evaluando los catalizadores mesoporosos obtenidos por diferentes técnicas, en la degradación oxidativa de los tres colorantes elegidos. Los resultados complementarios relacionados con las condiciones experimentales elegidas se informan en el Anexo III. El Capítulo VI resume los resultados obtenidos de la reducción catalítica del 4-nitrofenol empleando materiales mesoporosos seleccionados. Finalmente, se informan las conclusiones generales de este trabajo de tesis. / The textile production is one of the industries with higher consumption of water, and the generated sewage contains pollutants of different nature, such as dyes and organic compounds. Many dyes are visible in water at concentrations as low as 1 mg L-1. The textile effluents are highly colored, and the dye content ranges between 10-200 mg L-1. The release of these compounds implies an eco-toxic danger. Thus, the discharge of colored wastewater is currently a serious problem of environmental management. As an advantageous alternative to conventional physical, chemical and biological treatments to remove color from sewage, advanced oxidation processes (AOP) arise, which can transform organic pollutants in less toxic and innocuous compounds, or even mineralize the organic matter into simple inorganic compounds. The objective of this thesis was to study the removal of three dyes azo: Methyl Orange, Orange G and Congo Red, applying AOP. The process involves the formation of compounds with high oxidizing power, generally radicals, that remove refractory and recalcitrant contaminants. For that, catalyst materials of different nature, modified with transition metals (Cu, Co, Mn) were synthesized in order to promote the activation of employed oxidants (persulfate or peroxymonosulfate anion). The catalytic reduction of 4-nitrophenol, a toxic and recalcitrant byproduct of the textile industry was also briefly studied. The final product of the reduction, 4-aminophenol, is used in various industrial fields. Chapter I presents a general introduction. The general and specific objectives of this work are given. Chapter II describes the synthesis of the studied materials. Distinction is made for single phase catalysts (partially substituted goethite and spinel mixed oxides) and mesoporous silica based catalysts (MCM-41, SBA-15 and SBA-16). Two different techniques for the supports modification are described (functionalization and impregnation). Chapter III refers to the characterization of the catalysts. The employed techniques were transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), atomic absorption spectroscopy (AAS), X-ray photoelectron spectroscopy (XPS). Textural properties of the catalysts were determined from N2 adsorption-desorption isotherms data at 77 K. A structural analysis from the refinement of data from XRD using the Rietveld method was carried out, and the results are reported in Annexes I and II. In Chapter IV, the catalytic evaluation of the single phase catalysts on the oxidative degradation of Methyl Orange is presented and analyzed. The reuse of the catalysts and the possible reaction mechanism is also explored. Chapter V extends the study carried out in the previous chapter, evaluating mesoporous catalysts obtained by different techniques on the oxidative degradation of the three selected azo dyes. Complementary results related to the selected experimental conditions are reported in Annex III. Chapter VI summarizes the results of the catalytic reduction of 4-nitrophenol using selected mesoporous materials. Finally, the general conclusions of this thesis work are informed.

The present work describes the development of a highly sensitive and selective molecularly imprinted electrochemical sensor for 4-nitrophenol detection. A glassy carbon electrode was modified with vyniltrimethoxisylane (VTMS) and multiwall carbon nanotubes (MWCNT). The introduced nanocomposite increased surface area and active sites for electron transfer. When the sillane is used on the synthesis, it is named MIS (molecularly imprinted silane) and NIS (non-imprinted silane) when the analyte is not on the synthesis. For those silane films characterization, it was used the scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). This sensor showed its best performance in 0.1 mol L-1 phosphate buffer solution, at pH 7.0. After optimizing the operational conditions, this sensor provided a linear response range for 4-NP from 0.1 up to 100 μmol L-1 and good parameters as LOD, LOQ and sensibility, 0.03 μmol L-1, 0.1 μmol L-1 and 1.4×10-2 A mol L-1 respectively. Furthermore, the MIS/PNP sensor exhibited good stability with adequate reproducibility and accuracy. / No presente trabalho é descrito o desenvolvimento de um sensor eletroquímico altamente sensível e seletivo baseado na tecnolgia dos Polímeros Impresso Molecularmente para detecção de 4-nitrofenol. Um eletrodo de carbono vítreo foi modificado com viniltrimetoxisilano (VTMS) e nanotubos de carbono de pardes múltiplas (MWCNT). O nanocompósito de carbono introduzido aumentou a área superficial e os locais ativos para transferência de elétrons. No método sol-gel quando um sillano é usado na síntese, é denominado MIS (Molecular Imprinted Silane) e NIS (non-imprinted Silane) quando o analito não está na síntese. Para a caracterização dos filmes de silanos utilizou - se a microscopia eletrônica de varredura (MEV), a análise termogravimétrica (TGA) e a espectroscopia de infravermelho por transformação de Fourier (FTIR). Este sensor apresentou o seu melhor desempenho em solução tampão fosfato 0,1 mol L-1, a pH 7,0. Depois de otimizado as condições operacionais, este sensor proporcionou uma faixa de resposta linear para o 4-nitrofenol de 0,1 a 100 μmol L-1 e bons parâmetros como limite de detecção, quantificação e sensibilidade de 0,03 μmol L-1, 0,1 μmol L-1 e 1,4×10-2 A mol L-1 respectivamente. Além disso, o sensor MIS/4-nitrofenol apresentou boa estabilidade com reprodutibilidade e precisão adequadas.

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...