Ultrasound-Assisted Removal of Tetracycline by a Fe/N–C Hybrids/H₂O₂ Fenton-like System

In this work, the degradation of tetracycline (TC) in water by the integrated ultrasound (US)-Fenton process was investigated. For this, a new composite Fe/N–C-x (x is the molar ratio of iron salt Fe­(NO3)3·9H2O) catalyst was synthesized through simple carbonization of the mixture of glucose and iron salt Fe­(NO3)3·9H2O in the presence of ammonium chloride as the nitrogen source. The resultant catalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometer, and N2 adsorption–desorption, showing a typical graphite porous structure and good magnetic properties. The results indicated that the optimized Fe/N–C-2 catalyst prepared with a mole ratio of glucose/Fe­(NO3)3·9H2O/NH4Cl of 5:2:16.8 exhibited the highest TC removal in the Fe/N–C-2/H2O2/US system at a wide pH range from 3.0 to 11.0. At an initial pH of 7.0, TC removal in the Fe/N–C-2/H2O2/TC/US system was 1.83, 18.69, and 28.75 times of that in Fe/N–C-2/TC/H2O2, H2O2/TC/US, and TC/H2O2 systems, showing a positive synergistic action between US and Fe/N–C-2. The effects of catalyst dosage, H2O2 concentration, ultrasonic power, humic acid, and coexisting anions on TC removal were investigated. The preliminary analysis suggested that the Fe–N species and the graphite N dispersed in the carbon matrix are responsible for the efficient catalytic activity. By a simple magnetic separation, the Fe/N–C-2 catalyst was easily recovered and used for the next degradation experiment. Above 88% catalytic ability of Fe/N–C-2 was retained even after six successive runs, suggesting its good reusability. The simple preparation strategy, good magnetic property, and good catalytic ability of the Fe/N–C-2 materials make them promising alternative Fenton-like catalysts for the antibiotics abatement in water