Superoxide mediated production of hydroxyl radicals by magnetite nanoparticles: Demonstration in the degradation of 2-chlorobiphenyl

• Published in: Journal of hazardous materials 2013-04, Vol.250-251, p.68-75
• Main Authors: Fang, Guo-Dong, Zhou, Dong-Mei, Dionysiou, Dionysios D.
• Format: Article
• Language: English
• Subjects: 2-CB; Advanced oxidation processes (AOPs); Anions; Applied sciences; Biphenyl Compounds - chemistry; Chemical engineering; Degradation; Environmental Pollutants - analysis; Environmental Pollutants - isolation & purification; Exact sciences and technology; Hydrogen Peroxide - chemistry; Hydrogen-Ion Concentration; Hydroxyl Radical; Hydroxyl radicals; Iron - chemistry; Magnetite nanoparticles; Magnetite Nanoparticles - chemistry; Models, Chemical; Oxygen - chemistry; Pollution; Reactive Oxygen Species; Reactors; Superoxides - chemistry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.01.054

[Display omitted] ► The role of the generation of ROS by MNPs for the degradation of 2-CB was elucidated. ► The mechanism of the generation of ROS by MNPs was investigated. ► EPR and quenching studies were used to identify the ROS in this process. Increasing attention has been paid to magnetite nanoparticles (MNPs) due to their highly reductive reactivity toward environmental contaminants. However, there is little information related to the generation of reactive oxygen species (ROS) by MNPs, which in fact plays a vital role for the transformation of contaminants. In this paper, the degradation of 2-chlorobiphenyl (2-CB) by MNPs was investigated. The role of ROS generated by MNPs in this process was elucidated. The results demonstrated that hydroxyl radicals (OH) generated by MNPs at low pH could efficiently degrade 2-CB. The mechanism of the formation of OH by MNPs was divided into two steps: (i) the superoxide radical anion (O2−) mediated production of hydrogen peroxide (H2O2), and (ii) the reaction of formed H2O2 with Fe(II) dissolved from MNPs to produce OH through Fenton reaction. Comparison of the degradation products of 2-CB by MNPs with MNPs/ethanol and Fenton reagents further supported the involvement of OH in the degradation of 2-CB. The degradation efficiency of 2-CB by MNPs under acidic conditions was higher than that in alkaline solution. These findings provide a new insight into the understanding of reactivity of MNPs for the transformation of 2-CB and possibly other relevant environmental contaminants.