Efficient photocatalytic degradation of ciprofloxacin under UVA-LED, using S,N-doped MgO nanoparticles: Synthesis, parametrization and mechanistic interpretation

Abstract

In this study, the degradation efficiency of ciprofloxacin (CIP) in aqueous solution was evaluated in the photocatalytic process using S,N-doped MgO (S,N-MgO) as an innovative photocatalyst. The photocatalytic activity of S,N-MgO was estimated under UVA-light emitting diodes (UVA-LED) irradiation at 365 nm. Based on differential reflectance spectroscopy (DRS) results, N and S atoms as a dopant modify the MgO lattice structure due to the bandgap energy reduction to 1.5 eV and change the valence band edge compared to pure MgO. The synthesized catalyst was confirmed by the transmission electron microscopy (TEM) analysis to be nano-sized (20–30 nm). The effect of operational factors including initial pH, catalyst concentration, water anions, and reaction time were studied on the S,N-MgO/LED photocatalytic process in the degradation and mineralization of ciprofloxacin (CIP). Furthermore, the intermediate products and reaction mechanisms were studied. The results showed the highest degradation efficiency, about 99%, could be obtained at pH 9, 0.1 g/L catalyst, and 50 mg/L CIP within 30 min. The reaction mechanism evaluation indicated that OH and holes (h+) played the main role in the enhanced photocatalytic activity of S,N-MgO nanoparticles for CIP oxidation. The reusability of the catalyst was tested four times without a considerable reduction in the activity. Therefore, S,N-MgO is an active and reusable catalyst than can be efficiently activated with UVA-LEDs to degrade and mineralize the pharmaceutical compounds.