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

摘要

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 (k(SA)') of (2.44 +/- 1.27) x 10(-3) L-2 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. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.