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

Abstract

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 peroxymonosulfate (Pre-ZVI/PMS) to enhance the removal of ofloxacin (OFX), the influence of environmental parameters 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 significantly 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.