Centro de Tecnologia

URI Permanente desta comunidadehttps://repositorio.ufrn.br/handle/1/123

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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 Costa
The 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 application
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 Costa
The 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 disposal

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