Effective degradation of amoxicillin using peroxymonosulfate activated with MWCNTs-CuNiFe2O4 as a new catalyst: optimization, degradation pathway, and toxicity assessment

In this study, copper-nickel ferrite (CuNiFe2O4) nanoparticles were fabricated on multi-walled carbon nanotubes (MWCNTs) by co-precipitation method and used to activate peroxymonosulfate (PMS) for amoxicillin (AMX) degradation in aqueous solution. Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses were performed for the surface morphology and physicochemical properties of the catalyst. High catalytic activity for AMX degradation by MWCNTs-CuNiFe2O4/PMS system (100%) was achieved at a reaction time of 120 min compared to other heterogeneous systems such as Fe3O4/PMS (67.85%), CuFe2O4/PMS (83.2%), and NiFe2O4/PMS (76.56%). The AMX degradation efficiency increased with increasing dosage of PMS and catalyst, while it decreased with the presence of high AMX concentration and different anions. For four consecutive reaction cycles, the degradation efficiency of AMX did not decrease significantly, indicating the good reusability of MWCNTs-CuNiFe2O4 in long-term treatment of AMX solution. Quenching tests showed that sulfate (SO4 center dot-) and hydroxyl (HO center dot) radicals are the main reactive species in AMX degradation. The high BOD5/COD ratio emphasizes that the present catalytic process can oxidize AMX to the compounds with low molecular weight. The presence of NH4+, NO3-, and SO42- ions in the treated effluent indicates that AMX is well mineralized. Toxicity tests performed by culture of Escherichia coli and Staphylococcus aureus explained that the MWCNTs-CuNiFe2O4/PMS system could reduce the toxicity of the major contaminant and its byproducts. The AMX degradation pathway was proposed through the identification of intermediates by gas chromatography-mass spectrometry (GC-MS).