Fenton•Cu2+ system for phenol mineralization

• Cu(II) ions catalyze the mineralization of phenol by Fenton oxidation.
• The effect of Cu(II) is dependent on the initial concentration of Fe(II).
• 94% of phenol is mineralized by Fenton oxidation under dark conditions.
• The degradation of oxalic acid, a refractory intermediate, is observed.
• This method is effective for other organic pollutants such as Orange II.

In this study, Cu(II) ions along with Fenton reagent were used to enhance the mineralization of phenol in the water and a significant catalytic activity of Cu(II) ions on the mineralization of phenol was observed. At 0.1 and 1.0 mM initial concentrations of Fe(II) and Cu(II) ions, respectively, 94% phenol, on a carbon basis, was mineralized under dark conditions, whereas about 60% of total organic carbon remained in the water in the absence of Cu(II) ions. Oxalic acid was found to be degraded and mineralized in the presence of both Cu(II) ions and reducing intermediates. This is supported by experiments using hydroquinone, which is one of the reducing intermediates formed during the degradation of phenol by Fenton oxidation. The Fe(III) ions coordinated to oxalic acids are reduced to Fe(II) ions in the presence of both Cu(II) ions and hydroquinone. These results suggest that Cu(II) ions catalyze the reduction of Fe(III) ions by the reducing intermediates resulting in enhanced phenol mineralization by Fenton reagent. The addition of Cu(II) ions was also found to be effective for enhancing mineralization of 4-nitrophenol, Orange II, 2,4-dichlorophenoxyacetic acid, and bisphenol A.