Al/Fe active species in the pH-dependent degradation of efficient removal of norfloxacin from water and product toxicity evaluation

Ferrihydrite with different Al contents was prepared for norfloxacin degradation. • A total of 24 degradation products were identified and 3 pathways were proposed. • The ECOSAR prediction and inhibition zone tests were used for toxicity analysis. • Strategies for removing pollutants using Fe Al mineral catalysts are proposed. The high surface area and reactivity of ferrihydrite nanoparticles facilitate the transformation of contaminants. However, the interaction mechanisms between Al-substituted reconstituted ferrihydrite (Al-Fh) catalysts and contaminants are not well understood, which limits our ability to predict and optimize their environmental reactivity. In this study, we focused on the typical fluoroquinolone antibiotic, norfloxacin (NOR), and investigated its degradation characteristics and mechanisms in five Al-Fh catalytic systems under three pH conditions. It was confirmed that pH regulated the molecular configuration and charged distribution of NOR by density functional theory calculations. This affected the selection of the degradation pathway and the efficiency of electron transfer. The inhibition zone tests for Staphylococcus aureus and Escherichia coli showed that the diameters decreased by 20.44 mm and 18.39 mm, respectively. The predicted toxicity of NOR and its degradation products showed that over 80% of the degradation products were harmless substances, and the toxicity of the products was minimal at pH = 7.5, posing less potential risk to the ecological environment. The findings of this study contribute to a deeper understanding of the interaction mechanisms between Al-Fh catalysts and fluoroquinolone antibiotics, and provide critical insights to mitigate the environmental risks posed by these emerging contaminants. Download: Download high-res image (135KB) Download: Download full-size image