Nanoscale zero-valent iron as a catalyst for heterogeneous Fenton oxidation of amoxicillin.

Nanoscale zero-valent iron (nZVI) was used as the catalyst to remove amoxicillin (AMX) using a heterogeneous Fenton-like system, where 86.5% of AMX was oxidized using nZVI/H2O2, while only 25.2% of AMX was removed when nZVI was used. The surface change in nZVI before and after reaction was characterized by various techniques. Scanning electron microscopy (SEM) showed that aggregation and corrosion of nZVI had occurred. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) confirmed the existence of Fe0 and the presence of iron oxide and iron oxohydroxide Fe(II), Fe(III), as well as UV-visible demonstrated that the absorption peak of AMX had disappeared after the reaction. To understand the degradation mechanism, LC-MS analysis of the degraded products shows that the LC-MS spectra found a new peak at m/z 301 (C8H14O9NS), and the mechanism for Fenton oxidation of AMX was proposed. Removal efficiency depended on the nZVI dosage, initial pH, initial H2O2 concentration and the temperature, where 86.5% of AMX was degraded and 71.2% of COD was removed after 25 min at conditions of H2O2 6.6 mM, nZVI 500 mg/L, AMX 50 mg/L, pH 3.0 and temperature 30 °C. Kinetics for the oxidation of AMX fitted well to the pseudo first-order model and the rate constant kobs increased as temperature increased with an apparent activation energy of 30.1 kJ/mol. Finally, nZVI demonstrated its capacity as a catalyst for heterogeneous Fenton oxidation of AMX from wastewater, and the removal percentage was 80.5%. [ABSTRACT FROM AUTHOR]