Simultaneous Removal of Heavy Metals and Organic Matter by Ferrous Hydroxyl Complex Coupled with Ozone: A Case Study of Cu(Ⅱ)-EDTA Removal
Journal Title: Energy Environmental Protection - Year 2025, Vol 39, Issue 1
Abstract
Heavy metal-organic complexes in industrial wastewater pose significant challenges due to their resistance to biological treatment. This study proposes the use of ferrous hydroxyl complex (FHC) to break down copper ethylenediaminetetraacetate (Cu(Ⅱ)-EDTA) and remove copper, leveraging its strong reduction and complexation capabilities. The process involves in situ generation of CuFe2O4 and Cu2O from the reduction of Cu(Ⅱ)-EDTA by FHC. These active metal species catalyze the production of hydroxyl radicals (·OH) from ozone (O3), promoting the further mineralization of organic ligands and achieving synchronous removal of heavy metals and organic ligands. Under optimized conditions, the [Fe2+]∶[OH−] ratio of FHC is 1∶3, with a dosage of 2 mmol/L for FHC and 10 mg/min for O3. This allows the complete removal of 0.2 mmol/L Cu(Ⅱ)-EDTA within 60 minutes, with no residual dissolved iron. A ratio of [FHC (1∶3)]∶[Cu(Ⅱ)-EDTA] exceeding 5∶1 ensures complete decomplexation and removal of copper. The economic efficiency of Cu(Ⅱ)-EDTA decomplexation and removal can be enhanced by increasing the proportion of [OH−] in FHC rather than increasing the dosage of FHC. The process exhibits strong resistance to common anions such as chloride (Cl−), nitrate (\begin{document}$\mathrm{NO}_3^{-} $\end{document}), and sulfate (\begin{document}$\mathrm{SO}_4^{2-} $\end{document}), indicating its practical applicability in diverse wastewater. The in situ generated CuFe2O4, Cu2O, and Fe3O4 after ozonation are magnetic, offering potential for magnetic separation and further enhancing cost-effectiveness. To validate the mechanism, electron paramagnetic resonance (EPR) analysis was conducted. The results confirmed that the in situ generated products can effectively catalyze the production of hydroxyl radicals (·OH), singlet oxygen (1O2), and superoxide radicals (\begin{document}$\cdot \mathrm{O}_2^{-} $\end{document}) from O3. Quenching experiments were performed to investigate the role of reactive oxidative species (ROS) in the degradation of EDTA. The results showed that the removal rate of EDTA decreased from 100.0% to 57.7% upon the addition of tert-butanol (TBA), indirectly proving the involvement of ·OH in the degradation of EDTA. Liquid chromatography-mass spectrometry (LC-MS) analysis provided insights into the reaction pathways. The decomplexation of Cu(Ⅱ)-EDTA by FHC forms iron ethylenediaminetetraacetate (Fe-EDTA), and subsequent ozonation leads to the disruption of the N—C bonds in Fe-EDTA by ·OH and O3, generating intermediate products such as iron ethylenediaminetriacetate (Fe-ED3A), iron ethylenediaminediacetate (Fe-ED2A), glycine, Fe-nitrilotriacetate (Fe-NTA), and nitrilotriacetic acid (NTA). Further reactions may involve the substitution of acetyl groups to form Fe-iminodiacetate (Fe-IMDA) and iminodiacetic acid (IMDA), ultimately mineralizing to CO2 and H2O. In conclusion, this innovative technique provides a promising prospect for the treatment of heavy metal-organic complex wastewater, crucial for environmental protection and industrial sustainability.
Authors and Affiliations
Wei TAI, Guojie YE, Qunbiao HE, Deli WU
Keywords
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- EP ID EP762204
- DOI 10.20078/j.eep.20240910
- Views 8
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