Effective removal of heavy metal complexes from contaminated water remains a challenging task. In this work, a limestone/PMS system was constructed for the efficient degradation of Cu-EDTA. Under the conditions of 3.0 g/L limestone and 1.0 mM PMS, the degradation efficiency of 10.0 mg/L Cu-EDTA reached 99.0 % in 60 min, and the removal efficiency of Cu ions approached 50.0 %. The main active specie revealed by quenching and EPR experiments was the singlet oxygen ( 1 O 2 ). Interestingly, Trace amounts of Cu(II) in limestone react with PMS enhancing the degradation of Cu-EDTA. The results of the HPLC-MS analysis showed that the reactive species attacked the Cu–O and Cu–N bonds, as well as triggered a decarboxylation process, resulting in the decomposition of Cu-EDTA into six intermediates. Meanwhile, SEM and XPS analyses revealed that Cu ions released during the degradation of Cu-EDTA are deposited on the limestone surface as Cu(OH) 2 and Cu 2 (OH) 2 CO 3 . In addition, the initial pH and co-existing ions have a weak effect on the system. Finally, a one-month continuous flow experiment showed that the degradation efficiency of Cu-EDTA was about 95.0 % and the removal efficiency of Cu ions was 40.0 %. In conclusion, this study provides a new approach for the destruction of metal complexes and the removal of heavy metals.
Jiang Yu,Liu Xinyu,Huang Shikai,Wu Huifang,Liu Haiyan,Liu Shenzhe,Xu Jiale,Wang Kun
In this study, magnetic biochar (Fe-BC) was synthesized from phoenix tree leaves and FeSO 4 ·7H 2 O by impregnation-pyrolysis method, and was used to activate H 2 O 2 to degrade Cu-EDTA. The effects of preparation parameters on the degradation of Cu-EDTA by Fe-BC/H 2 O 2 system were investigated by degradation experiments and characterization methods (SEM, BET, FTIR, XRD and XPS). The results showed that the magnetic biochar prepared under the pyrolysis temperature of 400 °C, pyrolysis time of 3 h and iron content of 3 wt% had the best catalytic activity. Within 120 min, the breaking efficiency of Cu-EDTA binding, precipitation efficiency of Cu 2+ and removal efficiency of TOC could reach 78.48, 71.65 and 46.54% at the conditions of adding 1.0 g/L magnetic biochar and 25 mM H 2 O 2 and the iron dissolution was only 0.32 mg/L. The characterization results and comparison experiments demonstrated that the catalytic effect of magnetic biochar not only depends on the transfer of electrons to H 2 O 2 by the loaded iron oxides, but also the active oxygen functional groups (OFGs) and persistent free radicals (PFRs) contained on the surface can transfer electrons to H 2 O 2 or even dissolved oxygen to produce an amount of hydroxyl radicals ( · OH) and superoxide anion radicals ( ). The use of phoenix tree leaves as the precursor of magnetic biochar provides a new method for the disposal of garden waste, which is in accord with the concept of green and sustainable development. In the degradation system, the magnetic biochar catalyst relies on the OFGs and PFRs of biochar and the metal components loaded to activate H 2 O 2 to generate reactive oxygen species to degrade organic pollutants.
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