New insights into the degradation of nitrobenzene by activated persulfate with sulfidated nanoscale zero-valent iron: Synergistic effects of reduction and reactive oxygen species oxidation

Abstract

In recent years, nitrobenzene (NB) leakage has emerged as one of the most pressing environmental issues related to groundwater contamination that requires immediate attention. This study aimed to combine S-nZVI reduction with persulfate (PDS) oxidation for NB degradation in aquatic environment. The strong synergistic effect of reduction and oxidative degradation of NB in the S-nZVI/PDS system was demonstrated for the first time. To throughly investigate the mechanism of PDS activation by S-nZVI, chemical quenching tests, detection of electron spin resonance (ESR), and monitoring of oxidant consumption were conducted. According to the results, the reactive oxygen species in the reaction system originated predominantly from the presence of ≡Fe2+ on the surface of S-nZVI and from the free state of Fe2+ in the co-activation of PDS in solution. The main role of S(-II) on the surface of S-nZVI is to enhance the electron transfer ability and act as an electron donor to facilitate the conversion between Fe2+ and Fe3+. In addition, density functional theory calculations was used to reveal the reactive sites of NB and clarify the possible degradation pathways of NB. The results of this study will deepen the understanding of the mechanism of S-nZVI driven persulfate activation and provide fundimental support for the future practical application of the S-nZVI/PDS system for the remediation of nitrobenzene contaminated groundwater.