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(NO 3 ) 3 ·9H 2 O) catalyst was synthesized through simple carbonization of the mixture of glucose and iron salt Fe(NO 3 ) 3 ·9H 2 O 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 N 2 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(NO 3 ) 3 ·9H 2 O/NH 4 Cl of 5:2:16.8 exhibited the highest TC removal in the Fe/N-C-2/H 2 O 2 /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/H 2 O 2 /TC/US system was 1.83, 18.69, and 28.75 times of that in Fe/N-C-2/TC/H 2 O 2 , H 2 O 2 /TC/US, and TC/H 2 O 2 systems, showing a positive synergistic action between US and Fe/N-C-2. The effects of catalyst dosage, H 2 O 2 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.