Degradação de estrogênio presente em águas de abastecimento empregando eletrodo de óxido nanoestruturado crescido sobre liga de TiW

• Ano de defesa: 2014
• Autor(a) principal: Oliveira, Marizilda Escudeiro de [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo
• Palavras-chave em Português: Sustainability; Nanotubulares oxides; Semiconductor; Estrogen; Heterogeneous photoelectrocatalysis; Sustentabilidade; Óxidos nanotubulares; Semicondutor; Estrogênio; Fotoeletrocatálise heterogênea
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=3358288; http://repositorio.unifesp.br/handle/11600/47893

The advanced oxidation process (AOP) has been a sustainable alternative for treatment of water supplies of urban centers, mainly for the degradation of endogenous hormones estrone (E1) and 17 α-ethinyl estradiol (EE2), called endocrine disrupting compounds (EDC). Among the AOP, the heterogeneous photocatalysis the most promising. It involves the formation hydroxyl radical (OH •) from the UV irradiation on a photocatalyst, usually a semiconductor-type TiO2. Aiming to increase the efficiency of photocatalytic processes this work studied the formation of nanotubulares structures on Ti-0.5W in function of concentration of HF in the electrolyte solution, varying from 0.1 to 0.2 mol L-1 HF in ethylene glycol; applied potential, from 80 to 130V, and anodization time, from 10 to 60 min. The use of nanostructured oxides grown on TiW alloy in photocatalytic processes is attractive because of the proximity of the valence bands and conduction of these metals which contributes to the reduction of recombination of photogenerated charges, increasing the efficiency of the process. The best condition for obtaining a well-defined, regular and homogeneous layer of nanostructured oxide on Ti-0.5W surface was: HF solution 0.2 mol L-1 at 120V during 30 minutes. In order to eliminate an irregular layer of oxide over the nanotubes, known as nanograss, it was made a treatment after the anodizing process using ethanol bath for 24h. Because of the amorphous characteristics of nanotubular oxides, different annealing temperatures were evaluated to obtain a highly ordered crystalline phase, mainly anatase. Photoactivity studies shown that the best temperature of heat treatment is 450 ° C, reaching current values around 1.8 mA cm-2 , about 50% higher than an nanotubular oxide layer grown on pure Ti using HF aqueous solution 0.3% (v/v) at 20V for 2 hours, followed by heat treatment at 450 °C. Then the performance of degradation of estrogens E1 and EE2 was evaluated via photolysis, photocatalysis and electroassisted photocatalysis employing as semiconductor oxide nanostructures grown on Ti alloy (Ti-0.5W) and pure Ti. CLAE analysis shown a decrease in initial concentration of E1 and EE2 in less than 2 minutes of treatment for all process investigated, regardless of the type of semiconductor used. While for E1 was observed 50% of degradation after 1 min in photoelectrocatalysis process using Ti0.5W. The subproducts generated from the degradation of these estrogens also shown a decrease in concentration until 120 minutes of treatment, due to subsequent degradations.