This study elucidates the synergistic dual-process mechanism underlying the high efficiency of Ag-Fe-TiO₂ composite beads in degrading ciprofloxacin (CIP) under solar irradiation. The system integrates photocatalysis and photo-Fenton reactions within a fixed-bed configuration, enabling simultaneous generation of hydroxyl radicals (•OH) and other reactive oxygen species (ROS) through complementary pathways. The catalytic framework is built upon fly ash (FA) and foundry sand (FS), which serve as iron-rich supports to facilitate Fe³⁺ leaching and Fenton cycling, while silver-doped TiO₂ provides visible-light-responsive photocatalytic activity.
The degradation kinetics followed first-order Langmuir-Hinshelwood behavior, with a rate constant of 0.068 min⁻¹ under optimal conditions (pH 3.5, H₂O₂ 300 mg/L, 100% bead coverage, A/V ratio 0.712 cm²/mL). This rapid reaction rate stems from the synergistic interplay between two processes: (1) photocatalytic generation of •OH via electron-hole pair separation on Ag-TiO₂, and (2) photo-Fenton-driven •OH production through Fe²⁺/Fe³⁺ redox cycling initiated by solar light. The presence of Ag nanoparticles enhances charge transfer by acting as an electron sink, reducing recombination and promoting the reduction of Fe³⁺ to Fe²⁺, thereby accelerating the Fenton cycle.
Radical scavenging experiments confirmed that •OH is the dominant oxidant, contributing over 85% of the total degradation. The addition of tert-butanol, a known •OH scavenger, significantly suppressed CIP degradation, while no notable inhibition was observed with superoxide or singlet oxygen quenchers. ESR spectroscopy further validated the presence of •OH radicals during irradiation. Additionally, the formation of O₂•⁻ and H₂O₂ was detected, indicating secondary ROS generation pathways that support sustained oxidation.
The reaction pathway was reconstructed based on GC-MS analysis of intermediates, including desethylene-CIP, 7-amino-CIP, and various hydroxylated derivatives. These compounds undergo sequential deamination, defluorination, and ring cleavage, ultimately leading to complete mineralization into CO₂, H₂O, NO₃⁻, NO₂⁻, and F⁻.70-25-7 Molecular Weight The absence of toxic by-products after 60 minutes of treatment was confirmed through toxicity assays using E. coli DH-5a, where no zone of inhibition was observed—demonstrating effective detoxification.
System efficiency was maximized at a flow rate of 3.5 L/min, ensuring adequate dissolved oxygen for mineralization, and at a moderate H₂O₂ dose (300 mg/L), avoiding scavenging effects at higher concentrations.1402423-29-3 Synonym The integration of waste materials into the catalyst matrix not only reduces raw material costs but also transforms industrial by-products into valuable environmental assets.PMID:30725752 Overall, this work demonstrates that the Ag-Fe-TiO₂ dual-process system achieves superior performance through rational design of electron transfer dynamics, optimized radical generation, and efficient pollutant breakdown—all under natural sunlight. This approach offers a scalable, sustainable, and high-performance solution for emerging contaminants in water treatment.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com