Activation of peroxymonosulfate by magnetic Co-Fe/SiO2 layered catalyst derived from iron sludge for ciprofloxacin degradation

Drinking water treatment sludge provides the iron resource and a promising support to create bimetallic composites. In this work, a magnetic Co-Fe/SiO2 layered catalyst (LC) was synthesized by a facile hydrothermal method and used as an effective peroxymonosulfate (PMS) activator to degrade ciprofloxacin (CIP), a typical refractory antibiotic agent contaminant. Co-Fe/SiO2 LC exhibited superior catalytic performance with 98% CIP degradation efficiency in 10 min compared to other Co/Fe monometallic oxides and ions. The catalyst had great potential for practical application under various conditions. A synergistic effect between solid Co and Fe occurred on the surface of the catalyst due to the accelerated reduction of Co3+ by Fe2+. Both sulfate radicals (SO4•−) and hydroxyl radicals (•OH) were produced in the PMS activation process, and SO4•− contributed to much more CIP degradation. Based on kinetic models, the CIP degradation at different catalyst loadings could be well predicted. The catalyst showed excellent stability and reusability due to the strong Co/Fe-O and Co/Fe-Si interaction. This work provided a promising iron sludge reuse method to convert the “waste sludge” to a high-efficiency and low-cost bimetallic catalyst for the degradation of refractory organic contaminants in aquatic environments.