Cathodic Fenton degradation of 4,6-dinitro-o-cresol with nano-magnetite

The successful removal of 4,6-dinitro-o-cresol (DNOC) is reported using nano-magnetite (Fe3O4) as the iron source and cathodic Fenton generation of hydrogen peroxide. Operating conditions were optimized by varying the electrolyte concentration, electric current, and O2 flow. The effects of different DNOC initial concentrations, pH values and nano-magnetite quantities on the degradation rate of DNOC were also examined. The results showed that a lower DNOC initial concentration and a lower pH led to faster degradation of DNOC. It was also observed that the amount of nano-magnetite affected the degradation rate at lower pH while having no influence at neutral pH. Both homogeneous and heterogeneous reactions in the system were investigated. The homogeneous reaction dominated at a lower pH; direct electrolysis appears to take place at neutral pH; and a contribution from a heterogeneous reaction was not obvious under the experimental conditions studied. A model was developed to describe the degradation mechanism at low pH conditions, and the model matched experimental data very well. The combination of nano-magnetite and cathodic Fenton provides a fast way to degrade organic contaminants with readily available materials. Furthermore, magnetite is more stable, reusable and easy to separate compared to ferrous salt and other iron rich minerals.

DNOC degradation was performed at different pH values (pH = 2.8 and 5.9). Direct electrolysis appears to take place at neutral pH and is fitted by zero-order reaction model. The homogeneous reaction dominates at low pH and is fitted by the new model developed in this study.Figure optionsDownload high-quality image (90 K)Download as PowerPoint slideHighlights
► We successfully removed DNOC using nano-magnetite and cathodic Fenton.
► We optimized the electrolyte concentration, electric current, and O2 flow.
► Homogeneous reaction dominates at low pH and direct electrolysis occurs at neutral.
► Heterogeneous reaction was not obvious under the experimental conditions.
► We developed a model to describe the degradation mechanism at low pH.