Degradation of sulfapyridine antibiotics by chlorination in a pilot-scale water distribution system: kinetics, THMs, and DFT studies
Résumé
Sulfonamides have been proved to damage organisms if the contact time last over the long term. We studied the degradation kinetic of sulfapyridine in the chlorination stage of a pilot-scale water distribution system. Results show that the degradation of sulfapyridine simultaneously followed the first-order and pseudo second-order kinetics. In the beakers tests or water distribution system, the reaction rate reaches maximum values when the pH is about 7. The degradation rate of sulfapyridine would be higher with the increase of water velocity in the water distribution system. Degradation experiments in different pipe materials show that degradation efficiency is in the following order: stainless-steel pipe > ductile iron pipe > polyethylene pipe. We observed a significant increase in the content of trihalomethanes when chlorination of tap water-containing sulfapyridine were performed in both the water distribution system and beakers. The mechanism of this process was analyzed in combination with the intermediate products. In addition, density functional theory calculations were performed to assist in the identification of 6 intermediates and possible degradation pathways.
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