AHG. Trabajos de Grado y Tesis

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Evaluación de la residualidad de plaguicidas en papa (Solanum tuberosum) cultivada en Ventaquemada (Boyacá)
(Universidad Pedagógica y Tecnológica de Colombia, 2015) Lara Sandoval, Adriana Elizabeth; Chaparro Acuña, Sandra Patricia
Electrochemical methods for of glyphosate, paraquat, methomyl, carbofuran and mancozeb determination were validated for quantification in potato. The study was conducted using a voltammetric analyzer as supporting electrolyte Britton-Robinson buffer solution, the working electrode of glassy carbon, Ag / AgCl as reference electrode and platinum as counter electrode. Pesticides were extracted by solid-liquid partition method. Validation was carried out by two analysts who evaluated six batches consisting of two natural samples, two standard and two spiked or fortified samples. The methods showed no significant difference generating accurate and reliable results for the quantification of pesticides in samples of potato with a precision (%) and accuracy (%) of: 86.23 and 94.11 glyphosate, paraquat 86,04 and 96, 90, 85.93 and 83.016 methomyl, carbofuran 88.63 and 95.56 and 87.65 and 88.39 mancozeb, with a confidence level of 95%. The detection and quantification limits for the compounds were: 0.074 ppm and 0.19 ppm for glyphosate, 0.05 ppm and 0.55 ppm for paraquat, 0.12 ppm and 0.32 ppm for methomyl, 0.5 ppm and 1.98 ppm for carbofuran and 0.015 ppm and 0.076 ppm for mancozeb. Control charts were developed to evaluate the performance of validated methods and no value exceeded the warning limits. 100 samples collected in Ventaquemada village (Boyacá) were evaluated and the results state that none of the samples exceeded the maximum residue limit (MRL) of glyphosate (15 mg / kg) and mancozeb (0.2 mg / kg), 97 paraquat exceeded the MRL (0.05 mg / kg), 100 exceeded the MRL carbofuran (0.2 mg / kg) and methomyl not detected in any of the samples. In conclusion, paraquat herbicide and insecticide carbofuran are commonly used in this village to control weeds and insects, like the fungicide mancozeb, which is not used so indiscriminately as the previous two.
Propiedades estructurales, electrónicas y vibracionales del Diseleniuro de Diacetilo, CH3C(O)SeSeC(O)CH3 : un estudio combinado teórico−experimental
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Salamanca Rincón, Ana Rocio; Gómez Castaño, Jovanny Arlés
El presente trabajo abarca la preparación, el aislamiento y el estudio de las propiedades estructurales, electrónicas, vibracionales y fotoquímicas del diseleniuro de diacetilo, CH3C(O)SeSeC(O)CH3.
Síntesis y caracterización de óxidos nanoestructurados de cerio modificados con praseodimio para ser aplicados en pilas de combustible de óxido sólido
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Cruz Pacheco, Andrés Felipe; Gómez Cuaspud, Jairo Alberto; Parra Vargas, Carlos Arturo
The properties of cerium dioxide are due to the fluorite crystal structure, which guarantees the mobility of oxygen ions and electrons on the surface and inside the material. In addition, the modification of cerium cations by praseodymium increase oxygen vacancies due to the interconversion of their oxidation states, causing in the solids, high structural stability at high temperatures, accompanied by improvements in the properties of ionic and electronic conductivity make it of great interest to be used as component in solid oxide fuel cells (SOFC). In this way, the (Ce1-xPrxO2 (X = 0.0, 0.2, 0.4, 0.6, 0.8) and Pr6O11) system were obtained by the combustion method using citric acid as a chelating agent. In order to determine the best synthesis conditions in terms of the optimum temperature for the consolidation of the desired crystalline phases, thermogravimetric and differential thermal analyzes (TGA-DTA) were performed in a temperature range between 25 °C and 1000 °C. After the combustion and calcination processes, the obtained solids were characterized by infrared spectroscopy (FTIR), to determine the absorption bands associated with the citrate species formed and the subsequent removal of them after the heat treatment. The structural and morphological characteristics that resulted in the different modifications of cerium oxide after the calcination process at 800 °C were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), evidencing the obtaining of nanometric crystallites with homogeneous morphology. The magnetic behavior of the different synthesized systems was evaluated by the measurements of magnetization as a function of the temperature and the applied magnetic field, showing that all modifications of cerium oxide with praseodymium ions and pure praseodymium oxide have a paramagnetic behavior, in contrast with CeO2, which exhibits a diamagnetic behavior. In the same way, the magnetic susceptibility analyzes allowed to give an approximation of the oxidation states of the Ce and Pr ions in each of the synthesized oxides, by calculating the effective magnetic moments. X-ray photoelectron spectroscopy (XPS) analyzes corroborated the magnetic analyzes as to the identification of the valences and binding energies of the cerium and praseodymium cations. Surface area analysis using nitrogen adsorption isotherms by the BET method revealed that all the systems synthesized exhibit values between 70 and 135 m2 g-1, with pore volumes consistent with the classification of mesoporous materials. The oxygen storage capacity (OSC) measurements show that the proportional substitution of Ce ions by Pr increases the oxygen storage due to the generation of oxygen vacancies, caused by the presence of Pr3+ ions. In order to determine the structural stability of each oxide synthesized in reducing environments, programmed hydrogen reduction (TPR-H2) experiments were carried out, which allowed us to determine that the materials are partially stable up to 830 ° C. Finally, the electrical characterization by impedance spectroscopy (IE) allowed the determination of the electrical and ionic conduction processes by analyzing the equivalent circuits and the Nyquist diagrams of all the synthesized and calcined solids, identifying the most relevant material in terms conduction, structural stability, morphology and texture to be a possible anodic component in solid oxide fuel cells.
Estudio de sistemas bifuncionales para la obtención de 5-(Hidroximetil)-2-Furaldehído y Acido 5-(Hidroximetil)Furan-2-Carboxílico
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Aguilera Palacios, Edna Ximena; Rojas Sarmiento, Hugo Alfonso; Martínez Zambrano, José Jobanny
In this work the dehydration of fructose and glucose to 5-(hydroxymethyl)-2-furaldehyde (HMF) was studied on a bifunctional system based on LaOCl/Nb2O5 catalysts and hot compressed water. The catalysts were prepared by impregnation of LaCl3 over Nb2O5 with different loads. The solids were characterized by X-ray energy dispersion spectroscopy (EDX), thermogravimetry (TGA), N2 physisorption, pyridine and CO2 adsorption followed by Fourier transform infrared spectroscopy with diffuse reflectance (FT-IR); the acid and basic force was determined by NH3 and CO2 desorption at programmed temperature, respectively. The use of acid-base systems for the production of HMF mainly from glucose requires weak basic sites and conditions of moderate acidity which is reached with LaOCl/Nb2O5 as was confirmed by the acidity and basicity analyzes. The presence of Nb2O5 in the solids increased the yield to HMF (> 50%) and prevented the formation of undesirable products under compressed hot water conditions. With the same objective to produce HMF, a bifunctional system was developed; this is based on the design of solids with acid-basic characteristics to convert glucose to the HMF in which a step of isomerization of the glucose to the fructose supplied by the effect of the basic sites of oxides such as CeO2, La2O3 and SiO2 and a dehydration step in which the participation of acid sites derived from the functionalization of oxides with sulfonic groups -SO3H is required. The oxides were functionalized with 3-mercaptopropyltrimethoxysilane in relation to the density of hydroxyl groups chemically bound to the surface, for that purpose the amount of hydroxyl groups was determined by analysis of physisorption, thermogravimetric analysis and infrared spectroscopy by Fourier transform. The catalysts obtained were characterized by N2 physisorption, pyridine and CO2 adsorption by diffuse reflectance infrared spectroscopy with Fourier transform; desorption analysis at programmed temperature of NH3 and CO2. The results showed that the functionalization process with groups -SO3H decreases the volume of the pores and therefore their surface area due to the interaction of the oxides with organosilanes. Analyzes of the nature of the acidic sites of the solids by adsorption of pyridine showed that in all the solids there are both types of acidity; Lewis and Brönsted, the latter attributed to the acid sulfonic groups anchored to the oxides. As for its catalytic activity, the highest conversion of glucose was found when La2O3-SO3H was used as the catalyst, achieving an HMF yield of 58%. Given the importance of HMF as a platform molecule to obtain high added value compounds with pharmaceutical and polymer applications, a bifunctional system involving the use of Rh catalysts supported in reducible and non-reducible oxides and an aqueous alkaline medium to produce 5-(hydroxymethyl)furan-2-carboxylic acid (HMFCA). Synthesized catalysts were characterized by EDX, transmission electron microscopy (TEM), chemisorption and FT-IR pyridine. The results revealed that the reaction pathway did not follow the typical HMF oxidation path but followed the Cannizzaro reaction path so the main products were (furan-2,5-diyl) dimethanol (DHMF), salt of the HMFCA and some degradation products such as levulinic and formic acids as a consequence of the degradation of HMF by the effect of the alkaline medium. The oxide with the best activity was CeO2, based on these results the possible reaction mechanism was elucidated when Rh/CeO2 was used as catalyst in the presence of molecular oxygen. In addition it was shown that at lower particle sizes HMFCA yield increased.
Extracción de solasodina de la especie Solanum marginatun usando β-Glucosidasa inmovilizada sobre nanopartículas magnéticas de CoFe2O4
(Universidad Pedagógica y Tecnológica de Colombia, 2017) García Colmenares, José Mauricio; Reyes Cuellar, Julia Constanza
A nivel industrial, el uso de enzimas inmovilizadas simplifica el proceso y disminuye el costo económico de la producción. Se investigó el reusó de la enzima β-glucosidasa inmovilizada sobre nanopartículas magnéticas de ferrita de cobalto CoFe2O4 activadas con glutaraldehído, para aplicarla en la hidrólisis de extractos de solasonina, provenientes de frutos semimaduros de la especie Solanum marginatum. El trabajo se dividió en cinco capítulos. En el capítulo I, se aborda el soporte teórico del trabajo de investigación. En el capítulo II, se presenta la síntesis y caracterización de las nanopartículas magnéticas de ferrita de cobalto (CoFe2O4). Se sintetizaron tres relaciones molares de nanopartículas. Se evaluó el rendimiento de síntesis y la atracción magnética, obteniendo mejores resultados con la relación Co40Fe60. Con estas nanopartículas, en el capítulo II, se realizó el proceso de inmovilización usando como modelo la enzima bromelina. La inmovilización se efectuó covalentemente mediante puentes de glutaraldehído y nanopartículas recubiertas con quitosano. Los resultados de este capítulo se condensan en un artículo titulado: Cinética de bromelina inmovilizada sobre nanopartículas magnéticas de cobalto-hierro (CoFe2O4), enviado a la revista South African Journal of Science, el cual se encuentra en evaluación. En el capítulo III, se realizó la aplicación del sistema de inmovilización y caracterización de la enzima β-glucosidasa sobre nanopartículas magnéticas de CoFe2O4 activadas con glutaraldehído. Se evaluaron cuatro tipos de inmovilización. La β-glucosidasa tipo A presentó la mayor eficiencia de inmovilización con 84,6 ± 2,1%. La actividad catalítica de la enzima libre e inmovilizada fue determinada en 93 ±2,6 y 82 ± 2,8% respectivamente. La inmovilización tipo D presentó el porcentaje de inmovilización más bajos con 25 ±2,4%. El sistema fue optimizado bajo las siguientes condiciones: 200 mg de NPM, glutaraldehído 1M, β-glucosidasa 5,7E-5M, tiempo de inmovilización 16 horas a 60 °C. La β-glucosidasa inmovilizada puede ser reutilizada durante diez ciclos manteniendo el 52 ± 2,5% de su actividad. La caracterización de las nanopartículas CoFe2O4 (Co40Fe60) y de la β-glucosidasa se evaluó por: microscopía electrónica de transmisión (TEM-STEM), difracción de rayos X (DRX) espectroscopias FT-IR y UV-vis, voltametría cíclica (VC), voltametría de onda cuadrada (VOC) y magnetometría de muestra vibrante (VSM). En el capítulo IV, se presenta la aplicación de la β-glucosidasa inmovilizada, en la hidrólisis de solasonina para obtención de solasodina a partir de frutos semimaduros de Solanum marginatum, logrando obtener un rendimiento de 1,8-2,5% y pureza de 89,2-91,3 %. Siendo mayor cando se realiza la extracción vía hidrólisis ácida. Sin embargo, esta diferencia es superada por la β-glucosidasa inmovilizada al lograr ser reutilizada durante diez ciclos y es amigable con el entorno natural. Como aporte, se realizó la caracterización por técnicas voltamperométricas aún no reportadas en la literatura, de las NPM-CoFe2O4 y de la β-glucosidasa inmovilizada. Se modificó el proceso de extracción de solasonina, fundamentado en la formación de sales de acetato de solasodina, haciéndolo amigable con el medio ambiente.
Síntesis de un biofloculante sustituto de mucilagos naturales en el proceso de producción de panela
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Rincón Fuentes, Liliana Marcela; Moreno, Lucia Marlen; Medina Vargas, Oscar Julio
Panela is produced in 30 countries; Colombia is the second producer of panela after India. In the panela production process, residual biomass is generated in the mill for the extraction of sugarcane juices, which generate problems for the producers who use it as fuel for the heating of the burners in the production process, generating gas toxic (CO2). The bagasse in its cell wall contains cellulose, one of the most abundant polymers in nature, offering alternatives in the food and environmental conservation industries. Another disadvantage for panela producers is in the process of clarification, vegetable mucilages from each region are used, such as balsa, guácimo and caldillo, which has been affected by its indiscriminate use, which has led to an increase in its cost and use alternative flocculants. A cationic flocculant is proposed from residual biomass of sugarcane bagasse, performing a cellulose extraction of the biomass and carrying out a selective chemical modification of the cationic dialdehyde cellulose (CDAC), and comparing the flocculation of the cationic flocculant with the balsa brought from the trapiche Buena Vista in the municipality of Santana Boyacá. Cellulose and CDAC were characterized by techniques such as infrared spectroscopy with Fourier transform (FT-IR), Raman, X-ray diffraction (XRD), a thermal properties study by thermogravimetry (TGA) and differential scanning calorimetry. (DSC) corroborating the successful extraction of cellulose with a yield of 50% and the modification to CDAC, the clarifying capacity of the cationic flocculant is efficient compared to the native balsa of the Boyacá region.
Floculación y fotocatálisis como procesos combinados en el tratamiento de aguas residuales derivadas de la producción industrial de lácteos
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Hernández Laverde, Mónica Sirley; Murcia Mesa, Julie Joseane; Rojas Sarmiento, Hugo Alfonso
Wastewater coming from dairy industry shedding currently represents a latent environmental problem in Colombia. The treatment applied to these effluents has been focused in the elimination of organic pollutants and microorganism, thus leading to achieve the potential recycle of these effluents and to compliance normativity expressed in the resolution 0631 of 2015 of Ministerio de Medio Ambiente y Desarrollo Sostenible for dumping wastewater. In the present research, flocculation and photocatalysis were employed in treatment of these effluents. Flocculation, as the primary treatment, had been focused in the reduction of suspended solids, thus this increasing the passage of light to the reaction system, which is fundamental during the photocatalytic process. Photocatalysis is based on the formation of hydroxyl radicals (•OH), which allow the oxidation of organic matter and also have bactericidal effect due to the decomposition of the bacteria cell wall by peroxidation of the phospholipids, due this is mainly to the action of the •OH radicals. This document presents the results of the initial analysis of wastewater coming from 6 dairy industries located in Boyacá, Colombia. This analysis allow to determine that an average of 40% of the parameters requested in the Article 12 of resolution 0631 was over the permised range, COD (chemical oxygen demand) had values higher than 4700 mg/L, this is the parameter with the greatest non-compliance, also it was found a high load of pathogenic microorganisms, thus demonstrating the need to treat wastewater coming from the dairy industry. In the present work different flocculating materials and photocatalysts have been synthesized and employed in the treatment of these effluents. Firstly, a biodegradable organic cationic flocculant was synthesized, which was compared with two commercial flocculants. The synthesized photocatalysts were based on titanium dioxide, and they were modified by fluorination and sulfation processes, in order to improve the photocatalytic properties of solid, commercial TiO2 was used as a reference. The synthesized materials were deeply characterized by different techniques. By Fourier Transform Infrared Spectroscopy (FTIR) it was possible to identify bands assigned to amine and confirm the presence of a polyacrylamide in the commercial materials. In the case of the photocatalysts, by FTIR it was found that S-TiO2 presented the highest degree of hydroxylation, also it was possible to find bands characteristic of sulfate groups. The characterization study also allowed us to observe that, the modifications applied to TiO2, lead to modify the physical chemical properties of this oxide leading to obtain highest surface area and to obtain only the crystalline phase Anatase, also the optical properties were slightly modified after fluorination or sulfation. The effectiveness of the flocculants and photocatalytic materials was evaluated in the treatment of wastewater coming dairy industries. Firstly, 7 commercial flocculants and the lab prepared flocculant were evaluated and it was determined optimum concentration for its application, the best effectiveness was achieved by using the commercial material called FL31N at 18ppm. This behavior can be explained taking into account the high cationic charge of this material, which that favors the neutralization of charges in the wastewater, leading to improve the formation of the floccule. After primary treatment, it were evaluated the effects of the light intensity in the photolysis reaction for the treatment of effluents coming from dairy industry, the bactericidal effect of light was evidenced in these tests which were carried out at 30 W/m2. In these tests it was possible the reduction of 80% of E. coli load, 85.6% of coliforms total and 58.0% of other enterobacteriaceae were also eliminated. A similar behavior was observed in the photocatalytic tests carried out at 120 W/m2. Different studies reported in the literature have indicated that fluorination and sulfation allow to optimize the photocatalytic properties, however, it is well known that the effectiveness of the treatment depends on the substrate to be degraded. In the present research it was evaluated a highly complex sample matrix for that reason it is possible that the effectiveness of fluorinated and sulfated materials in the treatment of these samples decrease. The highest effectiveness was achieved by using P25 as photocatalysts, it can be explained by the low grain size and the best homogeneity with the sample to be degraded. Finally, the combination of Flocculation-Photocatalysis treatments was evaluated at intensities of 30 and 120 W/m2. In these analyzes were obtained the best results compared whit the use of the individual treatments. It was found that the average effectiveness was increased in 5.2% compared to photocatalysis. In this work also analyze the effect of increasing the photocatalyst concentration and the reaction time up to 10 hours. From these tests it was evidenced the formation of new species of organic compounds which have demonstrated to be more resistant to the treatment, also in the recycle of the photocatalyst was observed loss of activity in each use. The reduction of BOD5, fats and oils, total suspended solids and sediments solids, calcium hardness and total hardness, sulfates, turbidity and color was achieved using the commercial material FL31N at 18ppm as flocculant, 5 hours of photocatalytic treatment by using 30 and 120 W/m2 of light intensity and 1 g/L of P25 as photocatalyst, the samples thus treated are under the maximum limits indicated in the resolution 0631 of 2015 of Ministerio de Medio Ambiente y Desarrollo Sostenible.On the other hand, the COD was also reduced, however, it was not possible to obtain suitable results according with the Colombian normative. Total elimination of E. coli and reduction of 99.99% of total coliforms and other enterobacteriaceae were achieved. This demonstrates the contribution of this research in the treatment of effluents coming from dairy industries and its potential reuse. This document explains in detail the results obtained throughout the research.
Modificación del almidón, nanoalmidón y su aplicación en lodos de perforación
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Rodríguez Pineda, Lina María; Muñoz Prieto, Efren de Jesús; Palacios Alquisira, Joaquín
Starch is a naturally occurring polymer with unique physicochemical properties and yet some key structural properties of starch that can be modified to meet specific requirements. The transition from starch to nano-starch and subsequent chemical modification provides a variety of benefits such as greater thermal stability and lower biodegradability. The preparation of potato starch nanoparticles (NPA) were prepared with combined methods of acid hydrolysis and sonication, after the NPA was made two modifications, a copolymer of potato starch nanoparticles grafted with polyacrylamide by free radicals, using persulfate of potassium (PSP), as initiator and carboxymethyl nano-starch of potato using potassium hydroxide as the activating agent and monochloroacetic acid as the esterifying agent, the two preparations were carried out by microwave irradiation. The true size of the nanoparticles could not be determined by SEM, because it presented agglomerations, the NPA obtained were amorphous, which indicated that the ultrasound affected the crystalline zones of the starch. The confirmation of the modification of the potato starch nanoparticles was observed by the presence of new bands in the infrared spectrum (FTIR), for the copolymer in 3191 and 1649 cm-1, the presence of the NH group and C = O respectively, and for the carboxymethyl nano-starch the presence of the carbonyl group at 1595 and 1406 cm-1. Finally, the grafted copolymer NPA-i-PAM (MCI-2) and carboxymethyl nano-starch potato (CMNPA), prepared above, were added and added to a water-based bentonite mud (8%), where an increase in viscosity was observed and decreased filtrate loss by 45 and 32% respectively, which indicated that these products could be used as additives in drilling muds as viscosifying and filtering reducing agents.
Estudio teórico-experimental de la síntesis y propiedades físico-químicas de derivados de N-bencil-1-(2-furanil) Metanamina
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Corredor Montaña, Jeisson David; Gómez Castaño, Jovanny Arlés
Theoretical and experimental study of the reaction system and DA cycloaddition products of N-benzyl-1-(furan-2-yl)methanamine (1a), and N-benzyl-N-(furan-2-ylmethyl)acetamide (1b) was developed using maleic anhydride (AnM) as dienophile. Organic synthesis was carried out by adjusting the experimental methodologies within the framework of green chemistry. Spectroscopic characterization of all the molecules was completed through one and two-dimensional NMR, FTIR, FTRaman, Mass Spectrometry and computational vibrational calculations at the B3LYP/6-31G+(d) level. Cycloaddition adduct of amine 1a was obtained as a racemic mixture of exo isomer with monoclinic crystalline structure. The molecules are arranged forming central-symmetric dimers linked by hydrogen bonds. Preliminary computational study at the level B3LYP/6-31G+(d) of transition structures proposed for this system, allowed to identify some factors that can determine the mechanism of reaction. The two evaluated routes present factors can lead exo selectivity of the adduct. Experimental evidence of NMR and FTIR require complementary analyzes to give clarity regarding the intermediary detected. Amide 1b obtained by acetylation of amine 1a, was obtained as a mixture of E-Z isomers and conformers that presents differentiation of shields in NMR. Its cycloaddition produced the Z-exo isomer of the adduct, which presents cycloreversibility in solution at room temperature, regenerating the E-Z isomeric mixture. Also, the synthesis of the organic salts maleate and acetate of amine 1a was reported.
Obtención de nanofibras Core/Shell de Acido Poliláctico/Carboximetil celulosa para su aplicación en liberación controlada de fármacos
(Universidad Pedagógica y Tecnológica de Colombia, 2018) León Pérez, Jadileyg Gabriela; Muñoz Prieto, Efren de Jesús; Olayo González, Roberto
Las nanofibras Core/Shell son un desarrollo revolucionario en el campo de la ciencia y la tecnología. La obtención de estas fibras a nanoescala mediante la técnica de electrohilado coaxial presenta potenciales aplicaciones médicas, entre ellas, la capacidad de incorporar y liberar fármacos de manera controlada. La carga de fármacos en nanofibras utilizando la técnica de electrohilado convencional produce tasas de liberación muy altas al inicio, las cuales disminuyen con el tiempo, al contrario de la configuración core/shell en la que se pueden obtener porcentajes de liberación de la droga más controlados debido la presencia de una envoltura y/o capa que protege el fármaco de la exposición directa con el medio de liberación. Dada la necesidad de reducir las dosis de medicamento ingeridas por un paciente y prolongar su efecto; se plantea un sistema de liberación de fármacos in vitro que permita mantener una liberación sostenida de la droga durante largos periodos. El presente proyecto de investigación se enfocó en la obtención de fibras core/shell por medio de la técnica de electrohilado coaxial, utilizando polímeros biodegradables como Carboximetil Celulosa (CMC) y Ácido Poliláctico (PLA), además, se evaluó el comportamiento de las nanofibras como potenciales vehículos de liberación de Curcumina (Cur), fitoquímico que ha sido objeto de ensayos clínicos debido a su gran actividad biológica, entre las que se destacan sus propiedades antiinflamatorias, antioxidantes, antitumorales y quimiopreventivas. Posteriormente, se caracterizó la estructura química de las nanofibras de CMC/PLA-Cur mediante técnicas instrumentales tales como Microscopia Electrónica de Barrido (SEM), Espectroscopia Infrarroja con Transformada de Fourier (FTIR), Espectroscopia Raman, Análisis Termogravimétrico (TGA) y Calorimetría Diferencial de Barrido (DSC). Se determinaron las tasas de dosificación in vitro de las nanofibras mediante Espectroscopia UV-VIS y los perfiles de liberación de Cur se ajustaron al modelo matemático de Korsmeyer-Peppas, obteniéndose como resultado, un mecanismo basado en la difusión/erosión de la matriz polimérica.
Evaluación de fotocatalizadores nanoestructurados basados en TiO2 y su efectividad en el tratamiento de bacterias patógenas y contaminantes orgánicos
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Avila Martínez, Elsa Giovanna; Murcia Mesa, Julie Joseane; Rojas Sarmiento, Hugo Alfonso; Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación “Francisco José Caldas-Colciencias”; Universidad Pedagógica y Tecnológica de Colombia. Vicerrectoría de Investigaciones
El trabajo de grado presentado en este documento, se encuentra organizado en cuatro capítulos que contienen información relevante para comprender la importancia de la investigación desarrollada, así como los datos necesarios para dar alcance a los objetivos propuestos. Inicialmente, en el capítulo 1 se incluye una descripción detallada del referente teórico y el estado del arte en el área de Fotocatálisis Heterogénea, de igual manera se realiza la descripción de los mecanismos de tratamiento, así como un recuento de los trabajos dedicados al estudio de los contaminantes analizados en la presente investigación, por último, se presentan los objetivos de la tesis de maestría. En el segundo capítulo del documento se describe detalladamente la metodología empleada para la síntesis de los fotocatalizadores y las técnicas de análisis instrumental utilizadas para la caracterización físico-química de los de los mismos. Adicionalmente, se indican los métodos y equipos empleados para el seguimiento de las reacciones fotocatalíticas y la configuración de los sistemas de reacción usados para determinar la actividad de los fotocatalizadores sintetizados. En el tercer capítulo se describen y analizan los resultados de la caracterización físico-química de los materiales fotocatalíticos sintetizados. Por último, en el cuarto capítulo se incluyen los resultados de la evaluación de desempeño fotocatalítico de las series de materiales preparados, en reacciones fotocatalíticas de interés ambiental e industrial. El presente trabajo de investigación se llevó a cabo en el laboratorio del Grupo de Catálisis de la Universidad Pedagógica y Tecnológica de Colombia en colaboración con instituciones de investigación de México y España. La investigación involucra el estudio de diferentes series de materiales fotocatalíticos basados en Dióxido de Titanio (TiO2) modificados por procesos de fluorización, sulfatación, fotodeposisción de metales nobles y sensibilización con colorantes. Estos materiales se evaluaron en reacciones fotocatalíticas de gran interés en el campo de la remediación ambiental y en la síntesis de compuestos de alto valor agregado. En la investigación se empleó como material de referencia TiO2 sintetizado en el laboratorio por el método Sol-gel y posteriormente sometido a diferentes tratamientos para la obtención de materiales con características optimizadas. Así, la serie 1 de fotocatalizadores se obtuvo mediante la modificación del TiO2 por procesos de fluorización, sulfatación y fotodeposición de diferentes contenidos de oro (Au) y platino (Pt). La segunda serie de fotocatalizadores corresponde a TiO2 en forma de polvo y de nanotubos modificados a través de sensibilización con los colorantes Protoporfirina de Zinc y Quinizarina. Los fotocatalizadores sintetizados fueron ampliamente caracterizados para determinar sus propiedades físico-químicas. Para ello, se emplearon diferentes técnicas como: Difracción de Rayos-X, Fisisorción de N2, Espectrometría de Fluorescencia de Rayos-X, Espectrofotometría UV-Vis de Reflectancia Difusa, Microscopía Electrónica de Transmisión y Espectroscopia Fotoelectrónica de rayos-X. Adicionalmente, se evaluó la actividad de los materiales en tres reacciones fotocatalíticas de interés ambiental que incluyeron el tratamiento de bacterias patógenas presentes en aguas residuales, la fotodegradación de Fenol y Naranja de Metilo (MO) y la foto-oxidación de Glicerol orientada a la obtención de compuestos de alto valor agregado, los ensayos de esta última reacción se llevaron a cabo en el Centro Conjunto de Investigación en Química Sustentable de la Universidad Autónoma del estado de México y la Universidad Nacional Autónoma de México, en el marco de una estancia de investigación a través del proyecto SGI 1709. En general, se encontró que la modificación superficial del TiO2 mediante procesos de fluorización, sulfatación y fotodeposición de metales nobles (Au y Pt) permite la obtención de materiales con propiedades fotocatalíticas optimizadas debido a la formación de la fase cristalina Anatasa del TiO2 que es considerada la forma más activa en fotocatálisis, además, los tratamientos indujeron una mayor absorción del TiO2 en la región visible del espectro electromagnético, en el rango comprendido entre 400 y 800 nm, disminuyeron el valor de Band gap y aumentaron la superficie específica del TiO2. Por su parte, la fotosensibilización con los colorantes Protoporfirina de Zinc y Quinizarina fue un tratamiento efectivo que permió obtener materiales de TiO2 (en forma de polvo y nanotubos) con actividad fotocatalítica bajo radiación visible, debido al aumento de la absorción en esta región y a la reducción de la energía de Band gap. En cuanto a la actividad fotocatalítica, se encontró que los fotocatalizadores nanoestructurados basados en TiO2 modificado por tratamientos de fluorización, sulfatación y fotodeposición Au y Pt son materiales altamente efectivos en el tratamiento de bacterias patógenas presentes en muestras de aguas residuales urbanas. Por su parte, la sensibilización con colorantes es un método efectivo para obtener fotocatalizadores de TiO2 activos y efectivos en la fotodegradación de Fenol y MO. De igual manera, la modificación superficial del TiO2 por adición de flúor y 2 wt.% de Pt, conduce a la obtención de materiales efectivos en la foto-oxidación de Glicerol orientada a la obtención de Gliceraldehído (GCA). De acuerdo con los resultados obtenidos, se considera que el tratamiento fotocatalítico basado en TiO2 representa una alternativa eficiente y prometedora para el tratamiento de diferentes contaminantes presentes en efluentes domésticos e industriales y para la obtención compuestos de alto valor agregado.
Obtención de ácido 5-Hidroximetil-2-Furancarboxílico (HMFCA) a partir de 5-Hidroximetilfurfural (5-HMF) con microorganismos aislados de bagazo de caña
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Muñoz Castiblanco, Deysi Tatiana; Martínez Zambrano, José Jobanny; Rojas Sarmiento, Hugo Alfonso; COLCIENCIAS
5-Hydroxymethyl-2-furancarboxylic acid (HMFCA) is important as a monomer in the synthesis of various polyesters and has possible antitumor activity. It is obtained by the selective oxidation of the formyl group from 5-hydroxymethylfurfural (5-HMF). However, obtaining HMFCA by conventional chemical methods has several disadvantages, such as the large amount of sodium hydroxide used and high temperatures, which, at an industrial level, represents a significant amount of pollutants and high production costs. In addition, the use of solid catalysts with high value metals makes the HMFCA synthesis process expensive. In response to this problem, biotechnological methods of synthesis that are less polluting and economically sustainable have been used, such as fermentations, with which it is possible to obtain products with high added value, such as HMFCA, when the conditions for the growth of microorganisms are optimized. In the present investigation, starting from cane bagasse residues, a bacterial strain capable of degrading 5-HMF and selectively converting it into HMFCA was isolated. According to the sequencing of the 16S ribosomal gene, the bacterial strain belongs to the species Serratia marcescens. The oxidation of 5-HMF to HMFCA was carried out in fermentations with whole cells. The follow-up of the 5-HMF transformation reaction was performed by high-resolution liquid chromatography (HPLC) and bacterial growth was determined by UV-Vis spectrophotometry. Two sources of 5-HMF were used, one corresponding to pure 5-HMF (5-HMFp) and the other more economical, obtained from fructose hydrolysates (5-HMFf)., using Nb2O5 as a catalyst. The tolerance level of Serratia marcescens was determined at different concentrations of 5-HMFp and 5-HMFf. It was demonstrated that the bacteria was able to metabolize a concentration of 5-HMFf of 10 mM, at 30 ° C and pH 8, obtaining a yield towards HMFCA of 78% in 12 hours of reaction. Subsequently, the reaction conditions were evaluated: temperature, pH and substrate concentration, in the yield to HMFCA from 5-HMFf with the use of the Box-Behnken design. The results showed yields above 60 % for HMFCA at 30 °C, pH 8, and a concentration of 5-HMF equal to 3 mM. Through the polymerase chain reaction (PCR), the presence of the family pyridine nucleotide disulfide oxidoreductases in S. marcescens was confirmed as a possible gene responsible for the transformation of 5-HMF to HMFCA. Also, the Fed-batch strategy with control of 5-HMFf concentration was used to obtain a higher concentration of the compound of interest in the culture medium, reaching a final HMFCA concentration of 790 mg L-1, using the most economical source of 5-HMF, without genetically modified microorganisms, and in 20 hours of reaction.
Modificaciones catiónicas de nanocristales de celulosa aplicadas como floculantes al tratamiento de aguas
(Universidad Pedagógica y Tecnológica de Colombia, 2017) Morantes Luis, Dana Zuliet; Muñoz Prieto, Efren de Jesús
Cellulose is the most abundant biopolymer on earth. The different cellulosic materials have been replaced by polymers derived from petroleum, offering a natural and sustainable alternative. Among them, the cellulose nanocrystals (CNC), which allow to explore a wide spectrum of applications such as water treatment. In this work, CNC was modified with the reagent of Girard's T (2-hydrazinyl-2-oxoethyltrimethylammonium chloride) and CHPTAC (3-chloro-2-hydroxypropyltrimethylammonium chloride) as cationic grafts. The synthesized materials were characterized chemically and structurally with Z potential, degree of substitution with elemental analysis, infrared spectroscopy with Fourier transform (FTIR), X-ray diffraction (XRD), hydrodynamic size with dynamic light scattering (DLS) and microscopy of atomic force (AFM). Additionally, thermal properties were studied with thermogravimetry (TGA) and differential scanning calorimetry (DSC). The flocculant capacity of CNC-EPTMAC on suspensions of silica (SiO2) at 0.25% w / w was evaluated and the optimum dose was determined. This work tests the flocculation capacity of CNC-EPTMAC in water in terms of elimination of turbidity and decrease of physicochemical parameters in surface water.
Obtención de materiales catódicos basados en los sistemas LiCoO2 y LiMn2O4 con aplicación en baterías secundarias
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Neira Guío, Ariatna Yizel; Gómez Cuaspud, Jairo Alberto
The magnitude of the environmental impact has been significant in recent years due to natural and anthropogenic effects, for the reason that other energy alternatives have been created to mitigate the effect of the use of hydrocarbons in these means of transport, allowing advancement in the design of electric cars that work by means of electrochemical accumulators. This project was limited to the synthesis and characterization of olycline and spinel polycationic oxides in LiCoO2 and LiMn2O4 systems, through the polymerizationcombustion method with citric acid, to obtain solids with conductive properties as cathode components in advanced systems (cellular, computers, cameras) and sustainable energy generation. To achieve this objective, is to implement a series of characterization techniques, which enable the evaluation of the chemical aspects specified in infrared spectroscopy (FTIR), visible ultraviolet (UV-Vis), thermogravimetric analysis (TGA-DTA), reduction analysis programmed temperature (TPR-H2) and adsorption isotherms (BET-N2). In a similar way, the most relevant aspects have been evaluated from the point of view of the chemical technique, X-ray analysis (XRD), X-ray photoelectronic spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) were performed. The best characterized materials were tested by means solid state impedances (IS), to establish the efficiency of the synthesis process and identify key aspects related to the potential applications of these oxides in the manufacture of lithium-ion batteries, during the development of the project, was relevant the participation of the Universitat Jaume I (UJI) from Spain, which contributes with the characterization for some samples of current research. The project looked to provide new technical knowledge to the process of synthesis of new ceramic materials, alternative systems at high levels of reliability, as an alternative system for the production of clean energy based on the use of new technologies that use electrochemical accumulators. Finally, the proposal was framed within the possibilities for the identification of new instruments that allow a future in the construction of electrochemical systems of autonomous and sustainable functioning, seeking the final implementation and the transfer of the technology derived from the present investigation.
Estudio del efecto de los parámetros de síntesis sobre las propiedades físicoquímicas y fotocatalíticas de sistemas Pt-F-TiO2
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Cely Macias, Angela Carolina; Murcia Mesa, Julie Joseane; Rojas Sarmiento, Hugo Alfonso
Currently, Titanium dioxide (TiO2) is one of the most used materials in different fields, such as: materials engineering, environment and electronics. This material has attracted the attention of hundreds of chemists, physicists, and engineers who have explored the properties of this oxide as a semiconductor and catalyst, it has been applied in pigments, as support in catalysis, photoconductors, dielectric materials, paints, and personal care products, among others. Titanium dioxide is the most commonly used semiconductor in photocatalytic processes and different strategies have been employed to improve the physicochemical properties and photo efficiency of this oxide; within these strategies are different methods of synthesis and surface modification treatments; from these treatments it is possible to modify the crystal size, particle size, surface area, amount of hydroxyl groups and band-gap. From these properties it is possible to obtain TiO2 with high efficiency in the degradation of toxic organic compounds and in the elimination of microbial species present in different contaminated environments. The main objective of this research was focused on the study of the effect of the synthesis parameters on the physicochemical properties of the obtained materials. Initially, the obtention of TiO2 was evaluated by two methods: Hydrothermal and Sol-gel, commercial TiO2 was also used as a reference material. In addition, and in order to improve their photocatalytic properties, these oxides were modified by fluorization treatment and subsequent addition of platinum nanoparticles. In order to obtain information about the physical and chemical properties, a complete characterization of the materials obtained was carried out; different techniques were employed to achieve this objetive: X-ray diffraction (XRD), N2 adsorption-desorption (SBET), X-ray fluorescence spectrometry (XRF), Spectrophotometry UV-Vis diffuse reflectance (UV-Vis DRS), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FT-IR). The thesis of Master in Chemistry was developed in the Grupo de Catálisis de la Universidad Pedagógica y Tecnológica de Colombia and to advance some of the physicochemical analysis involved in the experimental work, it was supported by different institutions such as the Instituto para la Investigación e Innovación en Ciencia y Tecnología de los Materiales (INCITEMA), Universidad Industrial de Santender (UIS), Instituto de Ciencia de Materiales de Sevilla (ICMS). All of the above derive in the obtaining of a very complete research work and of great contribution in the subject of Heterogeneous Photocatalysis applied in the treatment of industrial wastewater. This work was financed by the Universidad Pedagógica y Tecnológica de Colombia and Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación, Fondo Francisco José de Caldas (COLCIENCIAS), this institution funded the author's studies of the Master's Degree of the present work. The thesis document is divided into 4 main sections, the first of which corresponds to the conceptual and theoretical component within which the work was framed, a second section includes the description of the experimental development, the results and analyzes obtained from the characterization of photocatalytic materials and finally the results of the effectiveness of these materials in the treatment of commercial anilines and industrial effluents derived from the handicraft industry in the town of Nobsa, department of Boyacá. In general, the characterization made it possible to observe that the modifications made to titanium dioxide alter its physicochemical properties and give new properties to this oxide, which allows it to be more active in environmental decontamination processes. Regarding the effectiveness of the photocatalytic materials synthesized, it was observed that the fluorinated catalysts favor the formation of the Anatase crystalline phase, allowing a greater degradation of the commercial anilines and a high rate of elimination of pathogenic microorganisms present in the wastewater analyzed. It was also observed that the addition of Pt in the photocatalytic materials represents for many authors a positive strategy in the improvement of the effectiveness; in the present investigation it was possible to determine that the homogeneous dispersion of the particles is related to the surface area and the Anatase phase; Regarding the effectiveness of the photocatalytic materials synthesized, it was generally observed that in the fluorinated photocatalysts the formation of the Anatase crystalline phase is favored, allowing a greater degradation of the commercial anilines and a high rate of elimination of pathogenic microorganisms present in the wastewater analyzed. This represents an important contribution in the search for solutions to the environmental problems currently facing the department and will be an interesting alternative that encourages applied research and encourages the University - Government - Company - Community. Resulting in active materials in the visible region. These results will be discussed in detail throughout this document.
Funcionalización del silicato laminar de alta carga (Na-2-Mica) para la liberación controlada de los herbicidas MCPA y Paraquat
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Ruiz Bravo, Lisette Dyanna; Pazos Zarama, Mery Carolina
In this work, a high charge synthetic mica (Na-2-Mica) has been modified through of intercalated and pillaring process with the Keggin´s polycation and the functionalization with thiol and silanol groups were successfully obtained. Their potential application in controlled release of 2-methyl-4-chlorophenoxyacetic acid (MCPA) and N,N′-dimethyl-4,4′-bipyridinium dichloride (PARAQUAT) was investigated. The characterization techniques (XRD, FTIR, Elemental Analysis, XRF, TG - DTA and N2 isotherms) allowed to determine that the pillared materials had an expanded basal spacing (2.05 nm) even after the thermal treatment at 400 ° C for 2 hours, indicating effective incorporation of Al2O3 pillars covalently bonded to the sheets of the structure building pore networks with 40-fold higher specific surface than that of the starting material (79.246 Vs. 2.562 m2/g). Intercalated mica was treated with tetraethyl orthosilicate (TEOS) followed by calcination at 550 ° C for 6 hours generated mixed pillars Al2O3 - SiO2 and increasing the amount of silanol groups (SiOH) promoted to the hydrophobic character of this material; the characterization by XRD, FTIR and isotherms of N2 allowed to corroborate that the structure of the mica Al - Si pillared exhibited a basal spacing of 2.03 nm with a significant increase in the specific surface area 100-fold higher than that Na-2-Mica of the order of 274.125 m2/g . Functionalization of mica Al/Si pillared carried out via grafting using 3-Mercaptopropyltrimethoxysilane (MPTMS) allowed the obtaining of a material with molecules of organosilane covalently bonded to the Al - Si pillar improving its hydrophobic properties in comparison with the intercalated mica functionalized with TEOS. The set of synthesized materials were studied for their application in the design of controlled release formulations of MCPA and Paraquat herbicides through adsorption isotherms from aqueous solutions measured over a range of solute concentrations of 0.075 – 1.000 mM and leaching in soil columns. Adsorption equilibrium Isotherm of MCPA onto the Al-pillared mica and the functionalized with thiol groups - mica showed greater affinity than the functionalized with silanol groups – mica. While the last showed greater affinity adsorption by the herbicide Paraquat. The leaching study in soil columns showed that the formulations obtained through material - herbicide complexes allowed the reduction of the leaching of MCPA and Paraquat herbicides on the soil profile; in such a way that complexes of pillared mica - MCPA and functionalized with groups thiol mica - MCPA allowed the reduction of leaching in 54.6 and 19.0 % respectively compared to a commercial formulation of MCPA and the complex functionalized with silanols mica - Paraquat allowed the reduction of 21.8 % compared to the commercial formulation of Paraquat.
Estudio de decaniobatos modificados y su aplicación en la síntesis de derivados de 4H-Piranos y en la oxidación de 5-(Hidroximetil)-2-Furaldehído (5-HMF)
(Universidad Pedagógica y Tecnológica de Colombia, 2018) Gutiérrez Arias, Luisa Fernanda; Martínez Zambrano, José Jobanny; Cubillos Lobo, Jairo Antonio
En catálisis, la química de especies decaniobato ([Nb10O28]-6) ha tenido un interés considerable debido a su posible aplicación como catalizador básico, sin embargo, los estudios realizados en este campo aún son escasos. Por otra parte, aunque la síntesis de este tipo de compuestos se lleva a cabo mediante un procedimiento hidrotérmico convencional relativamente sencillo, el empleo de condiciones altamente alcalinas es indispensable, las cuales podrían generar la formación de una fase hexaniobato como impureza durante la síntesis. Dicho esto, la presente investigación plantea la síntesis de este tipo de polioxometalatos emplenado el método convencional, así, como la realización de una modificación con ácido fluorhídrico a la niobia precursora del decaniobato, con el fin de evitar la formación de la fase hexaniobato, obteniendo al final dos sólidos: HPNb y HPNb-HF. Adicionalmente, estos sólidos fueron evaluados como catalizadores básicos en la síntesis de derivados de 4H-piranos y en la oxidación de 5-hidroximetilfurfural (5-HMF), enriqueciendo así, los estudios en el campo de aplicación de este tipo de sólidos. Los resultados indican que, mediante la síntesis convencional reportada anteriormente en la literatura, es posible obtener decaniobato, sin embargo, al realizar la modificación con HF la estructura se desestabilizada generando una disociación rápida hacia ácido niobico. Además, la obtención de derivados de 4H-piranos fue posible con rendimientos de hasta un 90% inclusive en condiciones de baja basicidad (HPNb-HF). Al emplear calentamiento por radiación microondas, se encontró que los aldehídos que tienen grupos aceptores de electrones favorecen la reacción en tiempos de reacción más cortos, en comparación con los aldehídos que tienen grupos donadores de electrones. La oxidación de 5-HMF se llevó a cabo empleando H2O2 como agente oxidante en presencia de diferentes sistemas catalíticos, encontrando que la selectividad de la reacción puede ser modificada dependiendo de la naturaleza del catalizador y tipo de solvente usado. No obstante, se comprobó que la ruta de oxidación estudiada puede describirse mediante un mecanismo tipo Baeyer-Villiger (BMVO), en el cual, en ausencia de catalizador y empleando solventes de baja polaridad (diclorometano) se favorece la obtención de protoanemonina, resultado que es repetitivo en sistemas catalíticos ácidos. Los catalizadores básicos tipo decaniobato, muestran un desempeño catalítico menor, sin embargo, la producción HMFCA se favoreció en menor proporción al emplear este tipo de sólidos.

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