The ability of pre-magnetized zero-valent iron for peroxymonosulfate activation to remove ofloxacin

Pre-magnetization can boost the activity of zero-valent iron (ZVI), facilitating the removal of contaminants by pre-magnetized ZVI (Pre-ZVI) activated peroxides. However, Pre-ZVI's persistence and stability in the activation of peroxides are little known. In this work, we investigated the ability of dry and wet Pre-ZVI activated per-oxymonosulfate (Pre-ZVI/PMS) to enhance the removal of ofloxacin (OFX), the influence of environmental pa-rameters as well as the evaluation of the long-term performance of Pre-ZVI/PMS. The results showed that the dry Pre-ZVI/PMS system had better removal performance in the wide pH range (4-9), with OFX removal efficiencies of over 90 % and high PMS utilization within 120 min. The presence of different environmental factors signif-icantly affected the degradation process. Remarkably, the ability of dry and wet Pre-ZVI to activate PMS decreased over time, with all systems experiencing a decrease of reaction rate constant (k) of approximately 20-47 % from day 1 to day 30. The catalytic efficacy could be considerably recovered by re-magnetization, but it dropped again with time. The vulnerable sites and degradation mechanism of OFX were determined by liquid chromatography-tandem mass spectrometry analysis and density functional theory calculation, and the toxicities of the transformation products in the system were predicted. This work is a guide for clarifying the long-term viability of the Pre-ZVI-activated peroxides used in environmental remediation.

Automated summary

In this study, the ability of dry and wet Pre-ZVI/PMS to enhance the removal of ofloxacin (OFX) was investigated, along with the influence of environmental parameters and the long-term performance of Pre-ZVI/PMS. The results showed that the dry Pre-ZVI/PMS system had better removal performance in a wide pH range, with high OFX removal efficiencies and PMS utilization. However, the ability of Pre-ZVI to activate PMS decreased over time, but could be recovered with re-magnetization.