Publication: SÍNTESIS DE TiO2 DOPADO CON METALES DE TRANSICIÓN POR MÉTODO SOL-GEL: CARACTERIZACIÓN Y ESTUDIO FOTOCATALÍTICO ENFOCADO A DEGRADAR COMPUESTOS FENÓLICOS.
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Date
2017-08
Authors
PUGA MARTÍNEZ, FELIPE RUBÉN
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Abstract
Se preparó una familia de nuevos fotocatalizadores dopando TiO2 con diferentes metales
de transición mediante el método sol-gel. La determinación de la energía de banda
prohibida (Eg) de estos nuevos materiales permitió seleccionar dos compuestos con mayor
potencial para procesos fotocatáliticos: TiO2 (sin dopar) y 0,1%Cu-TiO2. Estos dos
compuestos fueron caracterizados mediante microscopia electrónica de barrido,
espectroscopía UV-Vis en reflectancia difusa, espectroscopía IR, difracción de rayos X,
fluorescencia de rayos X y determinación de área superficial por el método B.E.T. Mediante
estas técnicas se logró observar que estos compuestos poseen características físicas muy
similares, siendo ambos sólidos del tipo mesoporosos, sólo presentes en la fase anatasa,
con absorción en el rango de la luz visible y, con un área y tamaño promedio de 141,4
[m2/g] y 9,54 [nm] respectivamente.
La actividad fotocatalítica de estas nanoparticulas se evaluó estudiando la degradación de
dos compuestos fenólicos desde soluciones acuosas: catecol (CC) y ácido cafeico (AC), con
irradiación de luz UV (365 [nm]) o con irradiación de luz visible, estudiando el efecto que el
peróxido de hidrógeno tiene en la fotocatálisis. Ambos compuestos presentan un cierto
grado de adsorción en los sólidos, el cual disminuye al adicionar H2O2. Las mejores
condiciones para degradar el CC son: TiO2 como fotocatalizador, irradiación de luz UV,
adición de H2O2. Las mejores condiciones para degradar el AC son: 0,1%Cu-TiO2 como
fotocatalizador, irradiación de luz visible, sin adición de H2O2.
Se realizaron experimentos de fotodegradación complementarios usando 3,0 [L] de
solución (50 [ppm] de catecol, 25 [ppm] de ácido cafeico) en las condiciones favorables
previamente determinadas para cada compuesto, usando reactores diseñados para cada
caso. El diseño y fabricación de estos reactores se realizó en el Departamento de Química
de la UTFSM. La fotodegradación completa de ambos compuestos fenólicos se logró en
tiempos razonables. La cinética de estos procesos es de seudo-primer orden. Análisis de
carbono orgánico total (COT) y demanda química de oxigeno (DQO) en muestras iniciales,
intermedias y finales, permitieron determinar que la degradación completa de los
compuestos orgánicos no es acompañada de una mineralización total, debido a los
intermediarios generados en el proceso.
New TiO2 doped photocatalysts with different transition metals using the sol-gel method were prepared. By determining the band gap energy (Eg) of these new materials, allowed highlight the two compounds with the greatest potential for photocatalytic processes: TiO2 (undoped) and 0.1% Cu-TiO2. These two compounds were characterized by scanning electron microscopy, diffuse reflectance UV-Vis spectroscopy, IR spectroscopy, X-ray diffraction, X-ray fluorescence and surface area determination by B.E.T. Through these techniques it was possible to observe that both compounds have very similar physical characteristics, such as: they are mesoporous type, present in anatase phase, their range in absorption is in the visible and their area and average size are 141.4 [m2/g] and 9.54 [nm] respectively. The photocatalytic activity of these nanoparticles was evaluated by studying the degradation of aqueous solutions of two phenolic compounds, catechol (CC) and caffeic acid (CA) in the presence of UV light (365 [nm]) or visible, studying the effect of hydrogen peroxide in the process. Both compounds have a certain degree of adsorption on the solids, which is decreased by adding H2O2. The best conditions for degradation of CC is by using TiO2, UV light and addition of H2O2. The best conditions for AC degradation is by using 0.1% Cu-TiO2, visible light and without addition of H2O2. Photodegradation complementary experiments were performed using 3.0 [L] solution (50 [ppm] catechol, 25 [ppm] caffeic acid) under the favorable conditions previously determined for each compound, using reactors designed for each case. The design and manufacture of these reactors was performed in the Department of Chemistry UTFSM. The complete photodegradation of both phenolic compounds was achieved in reasonable time. The kinetics of these processes is pseudo-first order. The analysis of total organic carbon (TOC) and chemical oxygen demand (COD) in initial, intermediate and final samples revealed that, to complete degradation of the organic compound, they have not been fully mineralized, due to the intermediaries generated in the process.
New TiO2 doped photocatalysts with different transition metals using the sol-gel method were prepared. By determining the band gap energy (Eg) of these new materials, allowed highlight the two compounds with the greatest potential for photocatalytic processes: TiO2 (undoped) and 0.1% Cu-TiO2. These two compounds were characterized by scanning electron microscopy, diffuse reflectance UV-Vis spectroscopy, IR spectroscopy, X-ray diffraction, X-ray fluorescence and surface area determination by B.E.T. Through these techniques it was possible to observe that both compounds have very similar physical characteristics, such as: they are mesoporous type, present in anatase phase, their range in absorption is in the visible and their area and average size are 141.4 [m2/g] and 9.54 [nm] respectively. The photocatalytic activity of these nanoparticles was evaluated by studying the degradation of aqueous solutions of two phenolic compounds, catechol (CC) and caffeic acid (CA) in the presence of UV light (365 [nm]) or visible, studying the effect of hydrogen peroxide in the process. Both compounds have a certain degree of adsorption on the solids, which is decreased by adding H2O2. The best conditions for degradation of CC is by using TiO2, UV light and addition of H2O2. The best conditions for AC degradation is by using 0.1% Cu-TiO2, visible light and without addition of H2O2. Photodegradation complementary experiments were performed using 3.0 [L] solution (50 [ppm] catechol, 25 [ppm] caffeic acid) under the favorable conditions previously determined for each compound, using reactors designed for each case. The design and manufacture of these reactors was performed in the Department of Chemistry UTFSM. The complete photodegradation of both phenolic compounds was achieved in reasonable time. The kinetics of these processes is pseudo-first order. The analysis of total organic carbon (TOC) and chemical oxygen demand (COD) in initial, intermediate and final samples revealed that, to complete degradation of the organic compound, they have not been fully mineralized, due to the intermediaries generated in the process.
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Keywords
PROCESOS FOTOCATALÍTICOS