Visible-Light-Driven Photocatalytic Degradation of Ciprofloxacin Using Plasmonic Ag-Cu@SiO₂ Nanocomposites: Synergistic Effects and Mechanistic Insights

Abstract

The persistent release of antibiotic residues to water bodies has escalated antimicrobial resistance thus necessitating effective and viable cleanup technologies. This paper presents the synthesis and systematic assessment of a visible-light-responsive bimetallic Ag-Cu@SiO₂ photocatalyst in degrading ciprofloxacin (CIP) in water. Mesoporous silica support facilitated a uniform dispersion of the Ag-Cu nanoparticles, contributing to surface stability, light absorbing properties and reusability. Photocatalytic experiments showed the rapid and efficient CIP degradation in the presence of visible light and the degradation kinetics could be well explained by a pseudo-first-order model in the temperature range of 303 to 333 K with a low activation energy (8.67 kJ mol^-1) and a positive enthalpy which means the degradation process is energetically efficient. Radical scavenging experiments have verified that the major reactive species were superoxide radicals (O^2-) and photogenerated holes, and that the minor role was played by hydroxyl radicals. It was found that the increased photocatalytic activity was due to the synergistic interaction of Ag-induced surface plasmon resonance and Cu-mediated charge separation that was efficient in preventing the electron-hole recombination. The reusability and stability of this catalyst were excellent since it retained its activity (more than 90 percent) in 5 consecutive cycles. All in all, Ag-Cu@SiO₂ photocatalyst has a high potential to be utilized practically in the treatment of antibiotic-contaminated wastewater under environmentally friendly conditions.