Desempenho de dióxido de titânio dopado com ferro na fotodegradação de pesticidas ou corante em meio aquoso

• Autor(a) principal: Guerra, Wilson Nunes de Almeida
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/11885
• topic: Photocatalysis; photo-fenton; pesticides; dye; TiO2; Fotocatálise; foto-fenton; pesticidas; corante; TiO2; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA::TECNOLOGIA QUIMICA

In this work, the degradation of Indigo Carmine (IC) dye and commercial pesticides Tamaron (active ingredient methamidophos) and Lannate (active ingredient methomyl) were evaluated using Fe/TiO2 in a photocatalytic process under visible and/or solar radiation. Fe/TiO2 catalysts were prepared by impregnation of uncalcined (Ti), or calcined (Ti500), commercial TiO2 P25 using Fe(NO3)3.9H2O and FeCl3.6H2O salts. The materials were treated by drying at 100°C, some samples being subjected to calcination at 500°C, the latter being named by TiFe(X)500 or Ti500Fe(X)500, where X = N or Cl, depending on the precursor iron salt used. The IC dye was used preliminarily in different experimental conditions, aiming at the selection of the most promising catalysts. In addition to photocatalysis, other treatments, such as photolysis and adsorption, as well as H2O2/Vis, catalyst/H2O2 (in the dark) and photo-Fenton processes (catalyst/H2O2/Vis), were also tested with the IC dye. The toxicity of the dye solution was evaluated by the use of lettuce seeds (Lactuca sativa). The best results of discolouration of the IC dye by photocatalysis were obtained with the highest concentration of catalyst tested (0.1 g L-1) and for a total visible light irradiation time of 300 min, in the following order: TiFe(Cl) > Ti = TiFe(N) > TiFe(Cl)500 > TiFe(N)500. For the photo-Fenton process, and the same catalyst concentration, the most promising results were obtained with the TiFe(N) and TiFe(Cl) catalysts and with irradiation for less than 50 minutes. However, after photo-Fenton process, the solutions of the dye showed high toxicity even proceeding for up to 300 minutes, unlike the photocatalytic process that was shown to produce products with very low toxicity. For both pesticides, the optimum concentration of catalyst was 1 g L-1. After 300 min exposure to visible radiation, the methamidophos photodegradation efficiency follows the following order: Ti > TiFe(N) > TiFe(Cl) > TiFe(N)500 > TiFe(Cl)500. Superior results were achieved under sunlight after 180 min of reaction. Using the catalysts treated at 100°C, the degradation of methomyl was almost complete after 180 min of visible radiation exposure, and fairly effective (about 50% degradation) with rapid (60 minutes) results were achieved by using sunlight. The best catalysts were characterized using X-ray diffraction, adsorption/desorption of N2, atomic absorption spectroscopy, UV-Vis diffuse reflectance spectroscopy and zeta potential. The diffractograms of the iron-impregnated samples did not indicate significant structural changes in relation to Ti. Iron doping reduced the specific area values in relation to Ti. The DRS results showed that the energy band gap of the Fe doped samples were lower than Ti undoped. Therefore, impregnation with iron ions contributed to photocatalysts band gap change to the visible region. There was a correlation between the zeta potential and the degradability of the compounds tested. The results showed that Fe/TiO2 catalysts treated at low temperature (100°C) are efficient in the photodegradation of recalcitrant compounds, such as pesticides and dyes