Degradation of diclofenac by H2O2 activated with pre-magnetization Fe0: Influencing factors and degradation pathways

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 /H 2 O 2 (Pre-Fe 0 /H 2 O 2 ) and Fe 0 /H 2 O 2 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 /H 2 O 2 process, Pre-Fe 0 /H 2 O 2 process has 2.1–7.0 times higher rate constant for DCF degradation at different H 2 O 2 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 . 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 or other substances, were the main degradation mechanism. Therefore, Pre-Fe 0 /H 2 O 2 process, which does not need extra energy and costly reagents, is an efficient and environmental-friendly process to degrade DCF.