Desenvolvimento de um fotocatalisador de nanotubos de TiO2 decorados com Ru para degradação fotoeletroquímica de agrotóxico

• Ano de defesa: 2015
• Autor(a) principal: Castelhano, Douglas Iafrate [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo
• Palavras-chave em Português: TiO2 nanotubes; Electrodeposition of Ru; Heterogeneous photocatalysis; Carbedazim; TiO2 decoration; Nanotubos de TiO2; Eletrodeposição de Ru; Fotocatálise heterogênea; Decoração TiO2
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=2625670; http://repositorio.unifesp.br/handle/11600/47967

Brazil is a world leader in the production and exportation of several agricultural products. This remarkable performance of the national agricultural production is directly related to the growth of the pesticide market in Brazil, making it one of the six largest consumers of pesticides in the world. Parallel to this dramatic scenario of agrochemical industries in the national economy as well as increasing the production of this in Brazil, there are many cases of environmental contamination resulting from the irresponsibility of pesticide manufacturers and due to the leaching process after use of same, due to the porosity of the soil, reaching groundwater, rivers and water bodies. Among the pesticides used in Brazilian crops, there is carbendazim, a fungicide with medium toxicity, classified as a possible carcinogen in humans. Given the growing demand of using pesticides and the need to develop capable technologies to eliminate these contaminants in human drinking water, this manuscript studied the degradation of carbendazim pesticide by photocatalytic and photoelectrocatalytic process using as semiconductor TiO2 nanostructured with and without modification with Ru by electrodeposition process. TiO2 nanostructures were obtained by anodizing process in aqueous solution containing 0.3% (v/v) HF under a potential difference of 20 V for 2 h with a ramp potential of 2 V min-1. Nanotubes were obtained with length and internal diameter of approximately 330 nm and 90 nm, respectively. Then, the nanostructures were heat treated at 450 °C to obtain the anatase phase. Voltammetric studies were conducted to elucidate the Ru reduction route on the TiO2 surface and select the potential range for electrodeposition. Although the Ru has been electrodeposited in a potential range of -0.025 to -0.188 V vs. Ag / AgCl, the deposition at 0.3 mC cm-2 at -0.100 V resulted in a value of photocurrent ten times greater compared to that obtained for the unmodified TiO2 nanotubes. By analysis of diffuse reflectance spectroscopy and adjustments using the Kubelka-Munk function it was possible to observe a substantial reduction in energy band gap from 3.11 eV for TiO2 without modification to 1.87 eV for nanotubes modified with Ru. This drastic reduction in band gap energy makes it an attractive photocatalyst electrode for environmental applications using of sunlight. The performance of these electrodes were tested in degradation of carbendazim and a greater reduction in the fungicidal concentration was observed employing the TiO2 electrode modified with Ru by photoelectrochemical process under UV light radiation of 80W, with a density of energy of 0,808 W cm-2 and potential difference of 1V, with reduction of total organic carbon around 56%.