Decolorization and degradation of 2,4-dinitrophenol by Fenton's reagent

The Fenton's reagent was applied to decolor and degrade 2,4-dinitrophenol (DNP). Different concentrations of ferrous ion (Fe2+) and hydrogen peroxide (H2O2) were dosed to investigate their influences on the removal of DNP. The ADMI color value was adopted as an index to indicate the decoloring performance of the reaction. Low molecular weight of organic acids was monitored, and the role of dissolved oxygen during the DNP degradation was discussed. Results show that due to productions of colored intermediates and the oxalic acid, DNP was quickly removed, followed by the ADMI color value and DOC, respectively. Both initial removal rates of DNP and ADMI color value increased linearly at low dosages of Fe2+ and H2O2. A high dosage of Fe2+ (> 1mM) led to an insignificant response of the initial removal rate of DNP, whereas the initial removal rate of ADMI color value was not affected and kept increasing constantly. Because of the non-selective feature of the hydroxyl radical, leveling off in the initial removal rates of DNP and ADMI color value was observed when dosing with a high concentration of H2O2. The variation in dissolved oxygen associated with a change in color led to a proposed pathway to depict the oxidation of DNP in a Fenton's reaction.