Navegando por Autor "Teixeira, Antonio Carlos Silva Costa"
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Artigo Degradation of 2,4,6-trichlorophenol in aqueous systems through the association of zero-valent-copper-mediated reduction and UVC/H2O2: effect of water matrix and toxicity assessment(Springer Nature, 2021-01-09) Chiavone Filho, Osvaldo; Souza, Larissa Pinheiro de; Graça, Cátia Alexandra Leça; Teixeira, Antonio Carlos Silva CostaThe presence of toxic chlorinated compounds in drinking water, generated during the disinfection step in water treatment plants, is of great concern for public health. In the present study, the performance of the UVC/H2O2 process, preceded by zero-valent-copper reduction, was evaluated for degrading 2,4,6-trichlorophenol (TCP). With this aim, the oxidation performed alone or in combination with the pre-reductive step was evaluated regarding TCP concentration over time, removal rate, mineralization, and toxicity to Vibrio fischeri, as well as oxidant dosage and the effect of water matrix. The UV/H2O2 process achieved fast (kobs = 1.4 min-1) and complete TCP degradation, as well as important mineralization (40.4%), with best results obtained for initial H2O2 concentration of 0.056 mmol L–1. Coupling of reductive and oxidative processes intensified contaminant mineralization, due to the synergistic effect of copper ions leached in the reductive process, particularly Cu(I), providing an additional route of H2O2 activation for generating HO• radicals (photo-Fenton-like process). High toxicity removals and increased mineralization could be successfully accomplished by the combined processes even in tap water, which is a clear advantage for practical applicationArtigo Estudo da caracterização da borra de petróleo e processo de extração do óleo(Associação Brasileira de Engenharia Sanitária e Ambiental - ABES, 2016) Chiavone Filho, Osvaldo; Guimarães, Adriana Karla Virgolino; Nascimento, Claudio Augusto Oller do; Teixeira, Antonio Carlos Silva Costa; Melo, Henio Normando de SouzaNesse trabalho, objetivou-se recuperar o óleo presente na borra oleosa por processo de extração, a fim de reutilizá-lo como combustível. Foram aplicados dois planejamentos experimentais: fatorial fracionado e Doehlert. Através da caracterização da borra oleosa (análises físico-químicos, elementar CHN e S, orgânicas e inorgânicas), constatou-se que a borra oleosa utilizada é constituída de 36,2% de óleo, 16,8% de cinzas, 40% de água e 7% de compostos voláteis. A eficiência média do processo de extração foi 70%. Entretanto, a análise estatística mostrou que o modelo quadrático não se ajustou bem ao processo, devido à complexidade do material estudado. Por outro lado, aplicando-se a modelagem de RNA, o coeficiente de determinação foi de 87,5%, mostrando-se bastante satisfatórioArtigo Insights into the reactivity of zero-valent-copper-containing materials as reducing agents of 2,4,6-trichlorophenol in a recirculating packed-column system: Degradation mechanism and toxicity evaluation(Elsevier, 2019-07) Chiavone Filho, Osvaldo; Souza, Larissa Pinheiro; Graça, Cátia Alexandra Leça; Taqueda, Maria Elena Santos; Teixeira, Antonio Carlos Silva CostaThe presence of toxic chlorinated compounds in drinking water, generated during the disinfection step in water treatment plants is of great concern for public health. Therefore, special attention has been given to the development of effective organochlorine-removal techniques. The reductive degradation via zero-valent-metals is recognized as a promising alternative. In this study, the capacity of zero-valent-copper (ZVC) containing materials to degrade 2,4,6-thichlorophenol (TCP) was investigated, using a bench-scale recirculating packed column system. The results indicate that this metal is effective for TCP degradation and dechlorination, even when derived from scrap. The kinetic model that better suits the degradation profiles is a second-order model, with an average normalized surface area rate constant (kSA’) of (2.44 ± 1.27) × 10−3 L2 min−1 m−2 for ZVC-containing materials. The ZVC scrap-derived material was found attractive for field applications due to its reusability and low leachability, despite its performance being affected in the presence of water natural constituents. The degradation by-products elucidated confirm that dechlorination is the main degradation pathway, leading to the formation of totally dechlorinated by-products such as phenol-like compounds and cyclohexanone. However, these may still pose a threat to aquatic organisms as revealed by toxicity assays and activity-structure relationship model (ECOSAR USEPA) predictions. Further investigation is therefore required aiming at following by-products formation with degradation time in order to find the best residence time that generates innocuous and/or adequate effluents for environmental disposalArtigo Non-traditional atrazine degradation induced by zero-valent-copper: process optimization by the Doehlert experimental design, intermediates detection and toxicity assessment(Journal of Chemical Technology and Biotechnology, 2018-11-01) Chiavone Filho, Osvaldo; Hollanda, Luana Rabelo; Graça, Cátia A. L.; Andrade, Lidiane M.; Mendes, Maria A.; Teixeira, Antonio Carlos Silva CostaBACKGROUND Over recent years, several studies exploring new technologies capable of degrading persistent organochlorine compounds have been published. Special attention has been dedicated to atrazine (ATZ), due to its ecotoxicological relevance together with its frequent detection in the environment. Degradation of organochlorines via zero-valent metals has gained great importance given its practicality and versatility, zero-valent-iron (ZVI) being the most applied metal for this purpose. Alternatively, zero-valent-copper (ZVCu) was proved to exhibit higher reactivity against chlorinated aromatics, therefore deserving further investigation. RESULTS The optimum degradation conditions for ATZ removal with ZVCu were explored through a Doehlert experimental design. The same conditions were tested for the traditional ZVI, which confirmed that ZVCu was more reactive. The analysis of the degradation products suggests that both reductive and oxidative pathways coexist in the studied process. CONCLUSIONS ZVCu was effective in ATZ degradation, both by reductive and oxidation pathways, within a wide range of pH values, although faster in acidic media. The resulting solution from the experiment that promoted the fastest degradation is less toxic than ATZ against microalgae Chlorella vulgaris, which is a positive output regarding the application of this process as a pre-treatment step of ATZ-contaminated water matrices. © 2018 Society of Chemical Industry