Ciencias Exactas y Ciencias de la Salud
Permanent URI for this collectionhttps://hdl.handle.net/11285/551039
Pertenecen a esta colección Tesis y Trabajos de grado de las Maestrías correspondientes a las Escuelas de Ingeniería y Ciencias así como a Medicina y Ciencias de la Salud.
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- Fabrication of low-Cost SnO2 anodes on silicon for the electrochemical degradation of organic pollutants in water(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2025-06-10) Díaz Gallegos, Juan José; García Farrera, Brenda; emipsanchez; Karthik Tangirala, Venkata Krishna; Reyna González, Juan Manuel; Barrios Pérez, José Antonio; School of Engineering and Sciences; Campus Estado de México; Cano Quiroz, AnaidIndirect anodic oxidation is a promising electrochemical advanced oxidation process (EAOP) that has demonstrated high efficiency in oxidating organic pollutants in water. The effectiveness of this process depends critically on anode’s ability to generate hydroxyl radicals while minimizing radical adsorption and resisting corrosion under high oxidative stress. Therefore, scaling up this technology demands electrode fabrication methods that are not only effective but also scalable, reproducible, and cost-effective. As an alternative to extrinsic dopants, depositing SnO2 films onto silicon substrates creates a p-n heterojunction that induces sufficient electronic conductivity and thus anodic activity without intentional doping. This work investigates two scalable manufacturing routes, reactive magnetron sputtering and ultrasonic spray pyrolysis to deposit SnO2 thin films on silicon, as well as the optimization of their performance as anodic oxidation electrodes. Comprehensive electrochemical characterizations including linear sweep voltammetry, cyclic voltammetry, and dye-removal assays are used to link each film’s electrochemical performance with its morphology and composition. Physicochemical analyses such as scanning electron microscopy (SEM) for surface morphology, atomic force microscopy (AFM) for topography and roughness, energy-dispersive X- ray spectroscopy (EDS) for elemental mapping, and X-ray diffraction (XRD) for phase identification are used to provide deeper insights into the impact of fabrication parameters on film structural properties and long-term stability. Magnetron sputtered films suffered from incomplete oxidation, revealing metallic Sn peaks, poor adhesion, and low corrosion resistance, highlighting reactor design limitations and indicating that, with the current reactor configuration, full SnO2 stoichiometry via PVD cannot be achieved without substrate pre-heating, cyclic voltammograms showed that these films had SnO2 like behavior but their reproducibility was compromised by its low mechanical stability during the electrochemical characterization. In contrast, films fabricated via ultrasonic spray pyrolysis formed rutile phase SnO2. The Si/SnO2 film exhibited an oxygen evolution potential of 1.93 V vs. Ag/AgCl, which increased to 2.21 V after annealing, and a significant decrease in their charge-transfer resistance. Both samples, with and without annealing, exhibited excellent methylene blue color removal (>95%), with the annealed samples demonstrating superior mechanical stability and corrosion resistance under electrooxidation stress. Finally, this thesis reviews the testing protocols implemented to refine both physicochemical and electrochemical characterizations, elucidating how each fabrication parameter impacts film properties and their subsequent performance in electrochemical evaluations, thus providing guidance for further optimization toward cost-effective, scalable manufacturing of SnO2 anodes for advanced water treatment applications.
- Electrochemical Advanced Oxidation Process for the Degradation of Acetaminophen, Naproxen and their Transformation Products in Surface Water(Instituto Tecnológico y de Estudios Superiores de Monterrey) Anglés-Vega, Diego; 886158; López-Zavala, Miguel Ángel; Videa-Vargas, Marcelo; García-Orozco, Jorge Humberto; Campus MonterreyThe use of electrochemical advanced oxidation processes has been studied in the last decades to develop an effective and affordable method for the degradation of pharmaceuticals and their transformation products. In this research, acetaminophen, naproxen and their transformation products were totally degraded in surface water by electrochemical oxidation using stainless-steel electrodes. Evaluation of pH and current density effects were assessed, anodic oxidation and oxidation with active chlorine species mechanisms described, and degradation kinetics explained. Analysis of generated iron hydroxides due the use of stainless-steel electrodes was don; mineralization percentages based on total organic carbon and chemical oxygen demand removals were also obtained. Total degradation of acetaminophen and naproxen was achieved at 2.5 minutes reaction time at pH 3 and 20.3 mA/cm2. Higher current densities and lower pH values promoted faster degradations. Acetaminophen transformation products were totally degraded at 7.5 minutes reaction time at pH 5 and 16.3 mA/cm2; naproxen transformation products required 10 minutes reaction time at pH 3 and 20.3 mA/cm2 for total degradation. Oxidation with active chlorine species achieved shorter reaction times compared to anodic oxidation. This might be because the degradation mechanism with “active” anodes of SST was enhanced by Cl- and HClO alone or in combination with hydroxyl radicals instead of only oxidizing the pharmaceuticals by AO or with “active oxygen” species. Degradation of pharmaceuticals followed first order kinetics with rate constants (k) were highly correlated to pH and the applied current density. Higher rate constants were achieved at lower pH values and higher current densities. Electrochemical oxidation with active chlorine species created a higher amount of transformation products for both pharmaceuticals than anodic oxidation. In case of acetaminophen seven transformation products were detected when oxidation with active chlorine species took place compared to three when anodic oxidation governed the degradation process. For naproxen, eighteen transformation products were detected compared to five respectively. Nevertheless, shorter reaction times for total degradation of the transformation products with active chlorine species were needed. Identification of these compounds was out of the scope of this research. It was found that iron hydroxides generated during the electrochemical oxidation process, trapped some transformation products of acetaminophen and naproxen and consequently required longer reaction times for their complete degradation. However, at the end such transformation products were totally oxidized. Thus, iron hydroxides formation delays the oxidation of transformation products. Energy consumption per milligram of APAP, NAP and their transformation products for total degradation was obtained. Optimal operational conditions were used; energy consumptions of 0.68 kWh/mg and 1.22 kWh/mg were required for APAP and NAP respectively.