Single and multi-antibiotics removal via peroxymonosulfate activation using molybdenum disulfide (MoS): Central composite design and degradation pathway.

The efficacy of molybdenum disulfide (MoS) for the degradation of metronidazole (MET), tetracycline (TET), and ciprofloxacin (CIP) in single and multicomponent systems through peroxymonosulfate (PMS) activation was investigated. Several characterization techniques, such as SEM, XRD, XPS, and EPR were performed to understand the removal mechanism of the three antibiotics in PMS/MoS system. In single component system with an initial antibiotic concentration of 10 mg L, >95% removal of MET, TET, and CIP were observed within 60 min (PMS = 100 mg L; MoS = 0.5 g L). It was observed that sulfate radical (SO) and reactive ≡Mo- OOSO complex played a major role in the removal of antibiotics. Adsorption on MoS and direct oxidation by PMS contributed to the removal of TET and CIP in MoS/PMS system. A Central composite design (CCD) with response surface methodology (RSM) was used to model the removal of MET, TET, and CIP in a multi-antibiotic system. The presence of multiple antibiotics affected the performance of MoS/PMS system as antibiotics competed for the adsorption sites on MoS and the generated reactive species. CIP predominantly deterred the removal of both MET and TET. On the other hand, MET removal was decreased up to 25-40% in the presence of both TET and CIP. Similarly, TET removal decreased up to 15-20% in the presence of MET and CIP. CIP removal decreased up to 15-25% in the presence of MET and TET. In the presence of multiple antibiotics, the deterring effect of one pollutant over another can be overcome by increasing the MoS concentration above 1200 mg L and PMS above 200 mg L to obtain 100% removal of all three pollutants. Overall, MoS could be an ideal catalyst for the removal of antibiotics through PMS activation.