Toward green nano adsorbents and catalysts: Highly active Fe/Mn nanoparticles for enhanced oxidation of oxytetracycline and levofloxacin

The widespread use of antibiotics, such as oxytetracycline (OTC) and levofloxacin (LEV), has led to dangerous levels of environmental contamination. In this study, functionalized iron/manganese nanoparticles (Fe/Mn NPs), which act as both adsorbent and Fenton catalyst, were green-synthesized using a reducing agent derived from a tea extract. The resulting pre-sorption/Fenton-like oxidation system effectively removed both OTC and LEV from the aqueous solution with adsorption capacities of Fe/Mn NPs for OTC and LEV of 58.8 and 192.3 mg·g−1, respectively. In addition, Fe/Mn NPs also showed high catalytic activity, oxidizing more than 99.9 % of both OTC and LEV, while sodium persulfate (PDS) removed only 26.6 and 29.0 % of OTC and LEV, respectively. Mechanisms of PDS activation typically involve either catalyst-initiated or mediated electron transfer reactions. Fe/Mn NPs through heterogeneous catalytic and metal leaching-induced homogeneous Fenton reactions, which generated various reactive oxygen species (ROS) including 1O2, ·OH, SO4-· and ·O2–. Characterization of Fe/Mn NPs before and after reaction, and the identification of specific OTC and LEV degradation products by LC-MS, helped to elucidate a potential degradation pathway, as well as the removal mechanism. Finally, the practicality of using this system for wastewater treatment was demonstrated using real wastewater samples indicating that the system has great potential for simultaneously degrading both OTC and LEV in contaminated wastewater.