Fenton oxidation of Orange II by pre-reduction using nanoscale zero-valent iron

The reductive degradation of the azo dye, Orange II, was investigated using nanoscale zero-valent iron (nZVI) that was synthesized in the laboratory. The effects of pH and iron dosage on Orange II degradation were studied. Although nZVI reduction successfully decolorized the azo dye, its ability to mineralize organic compound residues was severely limited. Thus, an integrated nZVI reduction process coupled with an oxidation process, nZVI-H2O2, was employed in an attempt to achieve both complete decolorization and mineralization of the Orange II solution. In the integrated techniques, application of nZVI and the oxidation process was carried out simultaneously and sequentially. The TOC removal efficiencies of the simultaneous and sequential nZVI/H2O2 processes were 39% and 53% for a reaction time of 60 min, respectively. Based on a comparison of the TOC removal efficiencies, the sequential nZVI reduction and oxidation process was more efficient than the simultaneous process.

Research Highlights
► nZVI synthesized in the laboratory is applied for the degradation of the azo dye.
► Simultaneous and sequential nZVI/H2O2 processes are conducted.
► Integrated nZVI/H2O2 sequential process enhances TOC removal efficiency.