Oxidative degradation of nitrobenzene by a Fenton-like reaction with Fe-Cu bimetallic catalysts

[Display omitted] •High-efficiency nitrobenzene degradation was achieved over a 5Fe2.5Cu-Al2O3 catalyst.•Cu atoms enhanced the generation of OH by accelerating the redox rate of Fe(II)↔Fe(III).•A degradation pathway of electrophilic addition and –NO2 reduction was proposed. De-nitrogen of organic contaminants in industrial wastewater is a great challenge for environmental remediation. In this work, alumina-supported bimetallic Fe-Cu catalysts were synthesized using a sol-gel method and exhibited high performance in catalytic degradation of nitrobenzene (NB). The bimetallic 5Fe2.5Cu-Al2O3 catalyst showed a 100% NB (100 ppm) removal within 1 h, which was superior to the NB degradation efficiency over monometallic Fe and Cu catalysts. With combination of the catalytic performance and the characterization results of X-ray photoelectron spectroscopy and H2-temperature-programmed reduction, we proposed that the synergistic effect between Fe and Cu species played a vital role in promoting the reduction of Fe3+ to Fe2+, thus enhancing the generation of hydroxyl radicals (OH) and the degradation efficiency of NB. To elucidate the degradation pathway, gas chromatography-mass spectrometry and dynamic ultraviolet-visible spectroscopy were used to detect the intermediates during the degradation process. The results indicated that the degradation predominantly occurred via electrophilic addition of aromatic ring by OH, followed by the ring opening reaction and mineralization reaction. Moreover, NB can be efficiently decomposed into less stable aniline, which is apt to degrade. This work has not only made significant progress on the development of high-performance catalysts for the degradation of NB, but also provided a deep understanding of the mechanism for NB degradation.