Fabrication of magnetic MnFe2O4@HL composites with an in situ Fenton-like reaction for enhancing tetracycline degradation

Abstract

Novel magnetic MnFe2O4@honey locust-derived carbon (MnFe2O4@HL) composites were synthesized via an in-situ hydrothermal precipitation method, and were characterized as an excellent Fenton-like catalyst for tetracycline (TC) degradation. Results showed that the vast majority of TC was mineralized in hydrogen peroxide (H2O2)/MnFe2O4@HL system after 120 min of reaction time with 92.3% of removal efficiency and the removal of 71.3% of total organic carbon (TOC). Systematic characterization approaches including scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM) were introduced to reveal the microstructure and properties of magnetic MnFe2O4@HL composites. Hydroxyl radicals (•OH) were identified as the major reactive oxygen species (ROS) via the quenching experiments and electron spin resonance (ESR) analysis, while superoxide radicals (·O2−) played a negligible role. The dual cycles of both Fe3+/Fe2+ and Mn3+/Mn2+ were significant enhanced through the bimetallic redox effect and the electron transfer effect of the carbon-based functional group, accelerating the generation of •OH. The removal of TC was still up to 79.3% after five reuses of magnetic composites, demonstrating the MnFe2O4@HL with excellent stability and reuse performance. The influence of various experimental control conditions involving initial pH, catalyst and H2O2 dosage, temperature, as well as common anions (Cl−, NO3−, and HCO3−) on the degradation of TC were finally evaluated. This study provides an efficient in-situ generation method of emerging magnetic materials, and systematically reveals its mechanism of homogeneous Fenton-like catalysis, which shows promising applications for the degradation of environmental contaminants.