Pyrolysis of nitrilotriacetic acid-Mn/Fe to produce MnFe2O4/C nanoparticles: Excellent performance of activating periodate to degrade organic pollutants

The abuse of tetracycline (TC) may lead to environmental risks and cause harm to human health. Advanced oxidation process (AOPs) can produce highly reactive free radicals, which can effectively degrade pollutants. Periodate (PI) has received more attention in AOPs due to its excellent oxidation property. To improve the degradation efficiency of pollutants, nitrilotriacetic acid (NTA) formed complexes with Fe and Mn, then MnFe2O4/C was successfully synthesized by pyrolysis to activate PI. The catalyst dosage, PI concentration, and pH values were investigated. Under optimal conditions (catalyst = 200 mg/L, PI = 500 mg/L, and pH = 4.0), the degradation efficiency of TC reached 94.0 % at 60 min. The excellent PI activation performance of MnFe2O4/C was attributed to the redox cycle of Mn3+/Mn2+ and Fe3+/Fe2+. Through quenching experiments, it has been demonstrated that iodine radical (IO3 center dot) was the main active species for TC degradation. Furthermore, the degradation efficiency of TC in this system was not seriously affected by SO42-, Cl-, CO32-, HCO3-, NO3-, and humic acid (HA). Finally, the degradation pathways of TC were proposed by high performance liquid chromatography mass (HPLC-MS) and density functional theory (DFT). The intermediates were not seriously toxic, and no toxic iodine species (I2, I3-, HOI) were produced. Overall, this study did not generate toxic substances in the process of degradation of pollutants, which is safe and environmentally friendly.