ABSTRACT
Antibiotics may induce super-resistant bacteria if they are available in the environment. Therefore, the removal of aqueous nitrofurantoin (NFT), and more importantly, the removal of the remaining antimicrobial activity after treatment, by the photo-Fenton process, was herein studied. Degradation experiments were performed according to an experimental design (0.5% error; factors: concentrations of NFT, Fe3+, and H2O2). Degradation conditions were: 20 mg NFT L−1, 10 mg Fe3+ L−1, and 170 mg H2O2 L−1. Fixed parameters were: 100 mL of the NFT solution, pH 2.5, 15-min stirring, and 25.0 ± 0.5°C. The initial rate constant (k0) and the maximum oxidation capacity (MOC) of the system were 0.61 min−1 and 100%, respectively (R2 = 0.986). 97% of the NFT and 93% of the organic carbon initially present were removed. Five degradation products (DPs) were detected by HPLC-MS and their endpoints estimated by the ECOSAR (ECOlogical Structure–Activity Relationships) 2.0 software. NFT and its DPs presented no toxicity towards Lactuca sativa. The antimicrobial activity (Escherichia coli) of NFT and/or DPs was completely removed in 15 min. Structures were proposed for the detected DPs. In short, the tested advanced oxidation technology (AOP), besides being capable of removing and mineralizing aqueous NFT in a short time, 15 min, also rendered the treated water biologically inactive (no ecotoxicity, no antimicrobial activity).
Acknowledgements
The authors also thank Professor Quezia Bezerra Cass and Dr Bianca Rebelo Lopes for making the mass spectrometry analyses possible.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The data that support the findings of this study are available upon reasonable request from the corresponding author.