Activation of ClO<sub>2</sub> by Nanoscale Zero-Valent Iron for Efficient Soil Polycyclic Aromatic Hydrocarbon Degradation: New Insight into the Relative Contribution of Fe(IV) and Hydroxyl Radicals
Recently, the activation of chlorine dioxide (ClO<sub>2</sub>) by metal(oxide) for soil remediation has gained notable attention. However, the related activation mechanisms are still not clear. Herein, the variation of iron species and ClO<sub>2</sub>, the generated reactive...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Toxics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2305-6304/13/1/36 |
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| Summary: | Recently, the activation of chlorine dioxide (ClO<sub>2</sub>) by metal(oxide) for soil remediation has gained notable attention. However, the related activation mechanisms are still not clear. Herein, the variation of iron species and ClO<sub>2</sub>, the generated reactive oxygen species, and the toxicity of the degradation intermediates were explored and evaluated with nanoscale zero-valent iron (nFe<sup>0</sup>) being employed to activate ClO<sub>2</sub> for soil polycyclic aromatic hydrocarbon (PAH) removal. With an optimized ClO<sub>2</sub>/nFe<sup>0</sup> molar ratio of 15:1 and a soil/water ratio of 3:1, the degradation efficiency of phenanthrene improved 12% in comparison with that of a ClO<sub>2</sub>-alone system. The presence of nFe<sup>0</sup> significantly promoted ClO<sub>2</sub> consumption (improved 85.4%) but restrained ClO<sub>2</sub><sup>−</sup> generation (reduced 22.5%). The surface Fe(II) and soluble Fe(II) in the ClO<sub>2</sub>/nFe<sup>0</sup> system was 2.0-fold and 2.8-fold that in the nFe<sup>0</sup> system after 2 min. Electron paramagnetic resonance analysis, along with quenching experiments, revealed that Fe(IV), HOCl, and •OH dominated phenanthrene degradation in a ClO<sub>2</sub>/nFe<sup>0</sup> system, with oxidation contributions, respectively, of 34.3%, 52.8% and 12.9%. The degradation intermediates of PAHs in the ClO<sub>2</sub>/nFe<sup>0</sup> system had lower estimated toxicity than those of the ClO<sub>2</sub> system. The lettuces grown in ClO<sub>2</sub>/nFe<sup>0</sup>-treated soil displayed better results in bioassay indexes than those grown in ClO<sub>2</sub>-treated soil. This study offers new perspectives for the remediation of organic-pollutant-contaminated soil by using metal-activated ClO<sub>2</sub> technology. |
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| ISSN: | 2305-6304 |