Degradation of ciprofloxacin using magnetite nanoparticle-activated periodate: Kinetic, mechanistic and toxicity evaluation

In this study, the activation mechanisms of periodate (IO4−) by magnetite (Fe3O4) were investigated for the degradation of ciprofloxacin (CIP). Compared to standalone IO4− (PI) and Fe3O4, the combined Fe3O4/IO4− system exhibited superior degradation efficiency, especially at elevated pH levels, such as 11. Scavenger experiments revealed IO3· and IO4· as critical radicals at pH 6.5, while ·OH was the key reactive species at pH 11. X-ray photoelectron spectroscopy (XPS) identified electron transfer between Fe(II)/Fe(III) species as the main mechanism resulting in the partial reduction of Fe3O4. The study confirmed the high thermal stability of periodate and found that N2 purging reduced the degradation efficiency of the Fe3O4/PI system. High degradation efficiency was maintained in real wastewater and tap water, with Fe3O4 showing minimal structural and performance changes during repeated oxidation processes. Its magnetic properties allow for easy collection and reuse, thus minimizing costs and environmental harm. Liquid chromatography high-resolution mass spectrometry (LC-QTOF-MS) identified CIP degradation products and degradation pathways at different pH values (i.e., 3, 6.5, and 11), with piperazine ring opening and decarboxylation as the main mechanisms. Ecological Structure Activity Relationships (ECOSAR) predicted low acute and chronic toxicity to fish, daphnids and green algae for most CIP degradation products. Overall, the Fe3O4/IO4− system offers an efficient alternative for treating effluents containing CIP across various water media.