En una primera parte de esta tesis fue desarrollado un nuevo electrodo a base de pasta de grafito-epoxi composite (GECE) conteniendo nitrato de bismuto [Bi(NO3)3] como precursor de bismuto incorporado [Bi(NO3)3-GECE)], como una posible alternativa para el análisis electroquímico por redisolución de metales pesados en cantidades traza. Los resultados claramente muestran las ventajas del Bi(NO3)3-GECE en combinación con la técnica de voltamperometría de redisolución anódica de onda cuadrada (SWASV) para la detección de metales pesados. Se llevaron a cabo medidas individuales y simultáneas de Pb y Cd y los resultados mostraron claramente las ventajas del Bi(NO3)3-GECE en combinación con la técnica SWASV para la detección de metales pesados. Con el uso del Bi(NO3)3-GECE construido se pueden realizar análisis rápidos y eficaces de iones de metal en cantidades traza como Pb y Cd entre otros en muestras ambientales de suelo, aguas naturales y aguas residuales. La ventaja inherente de la no necesidad de mercurio elimina muchas de las objeciones para el uso de métodos electroquímicos en la detección de tales especies en estos medios. Comparando el Bi(NO3)3-GECE con el electrodo de película de mercurio comúnmente usado y electrodo de película de bismuto desarrollado antes por nuestro grupo, el nuevo electrodo propuesto ofrece un notable funcionamiento en el análisis de metales pesados en cantidades traza, que puede ser de gran ventaja en electroquímica, contribuyendo a una aplicabilidad más amplia de técnicas electroquímicas por redisolución relacionadas con electrodos "sin mercurio". Además de aplicaciones ambientales el electrodo desarrollado basado en bismuto tendría interés especial para la aplicación en la detección de puntos cuánticos (QDs) basados en metales pesados. Tales aplicaciones están actualmente en proceso de estudio en nuestro grupo de investigación para la detección de ADN.Las otras partes de la tesis se dedican al desarrollo de nuevos sensores de ADN y proteínas basados en la misma técnica electroquímica de redisolución y el uso de nanopartículas de oro como marcas. Actualmente la detección electroquímica de secuencias de ADN específicas vía el evento de hibridación es una cuestión importante por lo cual diversas estrategias han sido propuestas.Genosensores electroquímicos de afinidad basados en el marcaje con nanopartículas de oro (AuNPs) y el uso de partículas paramagnéticas (MB) como plataforma para la inmovilización de la sonda de ADN de captura también han sido desarrollados en esta tesis a fin de demostrar la inducción magnética eficaz de un nuevo electrodo de grafito-epoxi composite-magnético (M-GECE) el cual fue construido también con pasta de grafito-epoxi composite con un pequeño imán de neodimio integrado.Todos los ensayos para la detección electroquímica de la hibridación del ADN desarrollados en esta tesis fueron basados en la detección directa de las marcas de AuNPs por medio de la técnica de voltametría de pulso diferencial (DPV) usando el M-GECE donde la intensidad de la corriente de la señal generada es directamente proporcional a la cantidad de ADN en la muestra. Como también ha sido demostrado, con el sensor de ADN asistido magnéticamente, el ADN analito condujo a una muy bien definida señal mientras que esencialmente ninguna señal fue observada para el ADN no complementario.Un nuevo inmunoensayo electroquímico sensible ha sido desarrollado, también basado en AuNPs como marca y MB como plataforma. El método fue evaluado para un inmunoensayo heterogéneo no competitivo de una IgG humana como proteína modelo. La detección electroquímica fue llevada a cabo en la misma forma que lo fue para ADN.La detección electroquímica de marcas de AuNPs en biosensores de afinidad usando métodos de redisolución permite el estudio detallado de la hibridación de ADN así como también inmuno-reacciones con interés en aplicaciones relacionadas con genosensores o inmunosensores. Los métodos electroquímicos usados para la detección de AuNPs como marca pueden ser muy prometedores tomando en cuenta su sensibilidad alta, límite de detección bajo, selectividad, simplicidad, bajo coste, y disponibilidad de instrumentos portátiles.Como conclusión final, las estrategias de análisis electroquímico de ADN y proteínas fueron demostradas con éxito y debido a los resultados prometedores su uso en muestras reales es viable. Tales biosensores de ADN e inmunosensores dan lugar a un enorme potencial de aplicación principalmente para diagnóstico clínico y monitoreo ambiental entre otros campos. / In the first part of this thesis a new graphite-epoxy composite electrode containing bismuth nitrate [Bi(NO3)3-GECE)], as built-in bismuth precursor as a possible alternative for electrochemical stripping analysis of trace heavy metals has been developed. Individual and simultaneous measurements of Pb and Cd were carried out and the results clearly showed the advantages of the Bi(NO3)3-GECE in combination with square wave anodic stripping voltammetry (SWASV) technique for heavy metals detection. Fast and effective analyses of trace metal ions such as Pb and Cd among others in environmental samples of soil, natural waters and effluents can be carried out by using the new Bi(NO3)3-GECE constructed. The inherent advantage of no necessity of mercury removes many of the objections for the use of the developed sensor. When comparing the Bi(NO3)3-GECE with the commonly used mercury film electrode and previously developed bismuth film electrode, the newly proposed electrode offers a remarkable performance in analysis of trace heavy metals, which can be advantageous in electrochemical, hence contributing to the wider applicability of electrochemical stripping techniques in connection with "mercury-free" electrodes. Beside environmental applications the developed bismuth based electrode would have special interest for application to heavy metal based quantum dots. Such applications are currently in the studying process at our research group for DNA detection.The other parts of the thesis are dedicated to the application of electrochemical stripping analysis in connection to gold nanoparticles for DNA and protein detection. Currently the electrochemical detection of specific DNA sequences via hybridization event is an important issue by which diverse strategies have been proposed. Affinity electrochemical genosensors based on labelling with gold nanoparticles (AuNPs) and the use of paramagnetic beads (MB) as platform for the immobilization of capture DNA probe have been also developed in this thesis in order to demonstrate the effective magnetic triggering of a new magnetic-graphite epoxy composite electrode (M-GECE) which was constructed with graphite-epoxy composite paste, with a small neodymium magnet integrated.All the assays for the DNA hybridization electrochemical detection developed in this thesis were based on the direct detection of AuNPs labels (anchored onto the M-GECE) by means of differential pulse voltammetry (DPV). The intensity of the generated current is directly proportional to the amount of DNA at the sample. As also has been demonstrated, with this magnetically assisted DNA sensor, target DNA leaded to very well defined signal whereas essentially no signal was observed for non-complementary DNA. By the other side a novel, sensitive electrochemical immunoassay has been also developed based in AuNPs as label and MB as platform. The method was studied and evaluated for a noncompetitive heterogeneous immunoassay of a human IgG as a model protein. The electrochemical detection was carried out in the same way that as for DNA.The electrochemical detection of AuNPs labels in affinity biosensors using stripping methods allows the detailed study of DNA hybridization as well as immunoreactions with interest in genosensor or immunosensor applications. The developed detection methodologies may be very promising taking into account their high sensitivity, low detection limit, selectivity, simplicity, low cost, and availability of portable instruments.As final conclusion, the DNA and protein electrochemical analysis strategies were successfully demonstrated and according to the promising results obtained its use for real samples is viable. Such DNA biosensors and immunosensors hold an enormous application potential principally for clinical diagnostic and environmental monitoring among other fields.

This dissertation seeks to reduce the energy consumption of steam stripping to regenerate aqueous amine used for CO₂ capture from coal-fired power plants. Rigorous rate-based models in Aspen Plus® were developed, and rate-based simulations were used for packed vapor/liquid separation units. Five main configurations with varying levels of complexity were evaluated with the two solvents. 8 m piperazine (PZ) always performed better than 9 m monoethanolamine (MEA). More complex flowsheets stripped CO₂ with higher efficiency due to the more reversible separation. Multi-stage flash configurations were competitive at their optimal lean loadings, but they had poor efficiency at low lean loading. The most efficient configuration was an interheated column, with more effective and distributed heat exchange. It had a secondary benefit of a cooler overhead temperature, so less water vapor exited with the CO₂. Using a rich loading of 0.40 mol CO₂/mol alkalinity in 8 m PZ, the optimal lean loading was 0.28 and the energy requirement was 30.9 kJ/mol CO₂. Case studies were also performed on cold rich bypass and the use of geothermal heat. When cold rich bypass is used with the 2-stage flash and 8 m PZ, it reduces equivalent work by 11% to 30.7 kJ/mol CO₂. PZ benefited the most from cold rich bypass because it had a higher water concentration in the overhead vapor than with MEA. In an advanced 2-stage flash with 8 m PZ, geothermal heat available from 150 down to 100 °C requires 35.5 kJ work/mol CO₂. The heat duty and equivalent work was higher than other optimized configurations, but it would be a valid option if separating the heat source from the steam cycle of a coal-fired power plant was highly valued. Pilot plant campaigns were simulated with the available thermodynamic models. Two campaigns with 8 m PZ were simulated within small deviation from the measured values. The average absolute errors in these campaigns were 2.5 and 2.7%. A campaign with 9 m MEA in a simple stripper demonstrated that the MEA model did not predict the solvent properties well enough to appropriately represent the pilot plant operation. / text

The City of Winnipeg, MB currently hauls by truck the leachate from the landfill, to be co-treated with the municipal wastewater at a wastewater treatment plant. Pre-treating the leachate with physico-chemical methods would allow for direct discharge to the sewer system, avoiding transportation. The goal of this research is to evaluate the effectiveness of different pre-treatment options as well as their impact on a biological nutrient removal system. In Phase I, the four pre-treatment options evaluated were air stripping, chemical coagulation, electro-coagulation and advanced oxidation with sodium ferrate. Chemical coagulation and air stripping reported the best COD and ammonia removal rates, respectively. Phase II evaluated the effectiveness of the selected pre-treatment methods in the response of a biological treatment system. The pre-treatment was successful in allowing complete nitrification by lowering the influent ammonia concentration. However, if the ratio of leachate to wastewater is low enough; pre-treatment may not be needed as the dilution lowers the impact of the leachate’s higher concentrations.

>Magister Scientiae - MSc / Platinum Group Metals (PGMs), particularly palladium (Pd), platinum (Pt) and rhodium (Rh) have been identified as pollutants in the environment due to their increased use in catalytic converters and mining in South Africa (as well as worldwide). Joining the continuous efforts to alleviate this dilemma, a new electrochemical sensor based on a nanoparticle film transducer has been developed to assess the level of these metals in the environment. The main goal of this study was to exploit the capabilities of nanostructured material for the development and application of an adsorptive stripping voltammetric method for reliable quantification of PGMs in environmental samples. In the study reported in this thesis, glassy carbon electrode (GCE) and screen-printed carbon electrode (SPCE) surfaces were modified with conducting films of nanostructured reduced graphene oxide-antimony nanoparticles (rGO-SbNPs) for application as electrochemical sensors. The rGO-SbNPs nanocomposite was prepared by Hummer`s synthesis of antimony nanoparticles in reaction medium containing reduced graphene oxide. Sensors were constructed by drop coating of the surfaces of the carbon electrodes with rGO-SbNPs films followed by air-drying. The nanocomposite material was characterised by: scanning and transmission electron miscroscopies; FTIR, UV-Vis and Ramanspectrosocopies; dc voltammetry; and electrochemical impedance spectroscopy. The real surface area of both electrodes were studied and estimated to be 1.66 × 10⁶ mol cm⁻² and 4.09 × 10³ mol cm⁻² for SPCE/rGO-SbNPs and GCE/rGO-SbNPs, respectively. The film thickness was also evaluated and estimated to be 0.36 cm and 1.69 × 10⁻⁶ cm for SPCE/rGO-SbNPs and GCE/rGO-SbNPs, respectively. Referring to these results, the SPCE/rGO-SbNPs sensor had a better sensitivity than the GCE/rGO-SbNPs sensor. The electroanalytical properties of the PGMs were first studied by cyclic voltammetry followed by indepth stripping voltammetric analysis. The development of the stripping voltammetry methodology involved the optimisation of experimental conditions such as selection of adequate supporting electrolyte, choice of pH and /or concentration of supporting electrolytes, deposition potential, deposition time, stirring conditions. The detection of Pd(II), Pt(II) and Rh(III) in environmental samples were performed SPCE/rGO-SbNPs and GCE/rGO-SbNPs at the optimised experimental conditions For the GCE/rGO-SbNPs sensor, the detection limit was found to be 0.45, 0.49 and 0.49 pg L⁻¹ (S/N = 3) for Pd(II), Pt(II) and Rh(III), respectively. For the SPCE/rGO-SbNPs sensor, the detection limit was found to be 0.42, 0.26 and 0.34 pg L⁻¹ (S/N = 3) for Pd(II), Pt(II) and Rh(III), respectively. The proposed adsorptive differential pulse cathodic stripping voltammetric (AdDPCSV) method was found to be sensitive, accurate, precise, fast and robust for the determination of PGMs in soil and dust samples. The simultaneous determination of PGMs was also investigated with promising results obtained. The AdDPCSV sensor performance was compared with that of inductive coupled plasma mass spectroscopy (ICP-MS) for the determination of PGM ions in soil and dust samples. It was found that though the metals could be determined by ICP-MS technique, it was limited from the standpoints of sensitivity, ease of operation and versatility compared to the AdDPCSV sensor. This study has show cased the successful construction and application of novel SPCE/rGO-SbNPs and GCE/rGO-SbNPs AdDPCSV sensors forthe determination of PGMs in environmental samples (specifically roadside dust and soil samples). The study provides a promising analytical tool for monitoring PGMs pollutants that are produced by automobiles and transported in the environment.

Made available in DSpace on 2014-06-12T17:35:19Z (GMT). No. of bitstreams: 2 arquivo2209_1.pdf: 2733214 bytes, checksum: f4972d9caa3286ed8c86630df56c5ed3 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O potencial poluidor do lixiviado está ligado às altas concentrações de contaminantes orgânicos e de substâncias tóxicas, como o nitrogênio amoniacal. O descarte inadequado deste efluente pode causar sérios problemas ambientais, principalmente para os corpos hídricos. O desenvolvimento de métodos de tratamento mais eficientes e de baixo custo para o lixiviado de aterros sanitários é um grande desafio, visto que esse tratamento apresenta inúmeras dificuldades devido à dinâmica das características qualitativas e quantitativas desse tipo de efluente. O presente trabalho consiste na avaliação do método de precipitação química associado ao stripping de amônia no tratamento de lixiviados gerados no Aterro da Muribeca-PE. No primeiro momento foi determinada a melhor dosagem de hidróxido de cálcio para remoção, principalmente, de cor do lixiviado e posteriormente, foi examinada essencialmente a remoção de nitrogênio amoniacal por injeção de ar. Paralelamente, a remoção de outros contaminantes orgânicos e inorgânicos foram analisadas nestas duas formas de tratamento. Os resultados mostram que o tratamento com precipitação química, utilizando concentrações de 15 e 35g/L de hidróxido de cálcio, proporcionou um grande potencial para remoção de turbidez e cor, resultando em remoções superiores a 50 e 60%, respectivamente. Dentre os parâmetros físico-químicos analisados, é dado destaque à baixa remoção de matéria orgânica (28,6% de DQO e 35,7% de DBO5) verificada após o processo. Na etapa posterior à precipitação química e estando o lixiviado previamente alcalinizado, o efluente foi submetido ao stripping com e sem aeração. Os melhores resultados foram obtidos com uma vazão de ar de 5 L/min por litro de lixiviado, pH 12 a uma temperatura constante de 26 oC e um tempo de aeração de 12 horas, alcançando uma eficiência de remoção superior a 90% de nitrogênio amoniacal. Adicionalmente, foram verificadas significativas remoções de DQO e alcalinidade nas mesmas condições. A associação dos dois métodos físico-químicos promoveu uma remoção significativa de cor, DQO, amônia e alcalinidade, melhorando a tratabilidade biológica dos lixiviados estudados. O resultado final foi um efluente com melhor biodegradabilidade e baixa toxicidade

No description available.

This study investigated effects of pilot-hole diameter, screw penetration depth depth, embedded screw orientation, magnitude of pushing-down force and turning speed on screw driving torques in particleboard (PB) and predicted screw driving torques for two PB clamped together. In addition, effects of material mechanical properties such as shear and tensile strength on screw direct withdrawal loads in PB were investigated and a model to predict screw direct withdrawal load capacity was developed. Furthermore, effects of screw driving torques on clamping pressure between two particleboards were investigated. It was concluded in general that stripping torques (STT) per thread for driving screws into tested PB materials had significantly higher means than seating torque (SET) per thread. The SET and STT per thread for screws driven into PB materials with 0.75-inch penetration depth was higher than 0.50-inch depth when no pilot-hole or pilot-holes with diameter of 1/8 in were drilled. Statistical analyses on screw driving torques for two PB materials clamped together, illustrated that the SET and STT tended to increase when the pilot-hole diameter decreased from 11/64 to 1/16 in. The prediction of the SET and STT values of driving screws through a face into an edge of PB materials can be predicted by the connection of two separate PB materials between a single face specimen with countersink in the surface and a single edge specimen. In addition, a face into a face PB connection, the prediction of both SET and STT can be predicted by connection of two separate face specimens. Results on shear and internal bond (IB) strength demonstrated that there was a clear trend that the shear and IB strengths were higher in the surface of the particleboards than the other levels. In the case of screw direct withdrawal (SDW), the results illustrated that the SDW values of particleboard types did not differ from each other when the pilot-hole diameters of 1/8 and 9/64 in used to drive the screw into the material.

No description available.

Moisture susceptibility of hot mix asphalt (HMA) pavements continues to be a major pavement distress. Past research has primarily focused on HMA stripping prevention through material component evaluation/testing and addition of preventative additives. Stripping is caused by traffic, water, and high in-place service temperatures. Today, agencies use various methods to evaluate HMA moisture susceptibility with varying degrees of success. The study objective was to evaluate a prototype stripping simulator?s ability to predict HMA moisture susceptibility. The simulator evaluates moisture susceptibility by measuring conditioning water turbidity. Boil test and indirect tensile strength testing were also conducted for comparison purposes. Stripping simulator results indicate further refinement is required before it can be used for moisture susceptibility prediction.

No description available.