科研之友
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摘要
Diclofenac sodium (DCF) is frequently detected as a non-steroidal pharmaceutical in the aquatic environment. In this study, the degradation of DCF in two heterogeneous systems, pre-magnetization Fe-0/H2O2 (Pre-Fe-0/H2O2) and Fe-0/H2O2 system, was comparably studied. Our findings proved that Pre-Fe-0 could significantly improve the degradation and dechlorination of DCF due to the change of Fe-0 characteristics after pre-magnetization. Compared with Fe-0/H2O2 process, Pre-Fe-0/H2O2 process has 2.1-7.0 times higher rate constant for DCF degradation at different H2O2 dosages (0.25-2.0 mM), initial pH (3.0-6.0) and Fe-0 dosages (0.25-1.5 mM). The characterizations by X-ray Photoelectron Spectroscopy and Electron Paramagnetic Resonance confirmed that the enhancement attributed to the increase of Fe-0 corrosion and fast generation of (OH)-O-center dot. In addition, preliminary degradation mechanism was elucidated by major products identification using UPLC-MS, through which the degradation intermediates, such as 4-hydroxy-diclofenac or 5-hydroxydiclofenac, 2,6-dichloroaniline, phenylacetic acid, 1,3-dichlorobenzene and 2-aminophenylacetic acid were identified. Hydroxylation, decarboxylation, C-N bond cleavage and ring-opening involving the attack of (OH)-O-center dot or other substances, were the main degradation mechanism. Therefore, Pre-Fe-0/H2O2 process, which does not need extra energy and costly reagents, is an efficient and environmental-friendly process to degrade DCF.
