Effect of biological mediator, 3-hydroxyanthranilic acid, in dye decolorization by Fenton processes

• 3-Hydroxyanthranilic acid (3-HAA) exhibited prooxidant properties in the decolorization of dyes.
• Fenton reaction using Fe2+decolorized more dyes than Fe3+.
• 3-HAA increased dye decolorization without increasing the consumption of H2O2.

The fungal metabolite 3-hydroxyanthranilic acid (3-HAA), commonly produced by the white-rot fungus Picnoporus cinnabarinus, presents Fe3+-reducing activity and was used as redox mediator to increase the degradation of dyes by classical Fenton (Fe2+/H2O2) and Fenton-like reactions (Fe3+/H2O2) in solution. The experimental results were estimated in terms of decolorization to examine the treatment efficiency. 3-HAA displayed prooxidant properties in the decolorization of methylene blue, chromotrope 2R, methyl orange, phenol red, safranin T, and a mixture of dyes, and its use resulted in a more intense and continuous dye decolorization. For example, Fe2+/H2O2 decolorized 27% of safranin T, whereas Fe2+/H2O2/3-HAA decolorized 63% of the same dye after 60 min of reaction. The dyes were not decolorized in the presence of 1% (v/v) tert-butanol, which is an OH scavenger, confirming the involvement of this radical in the decolorization reactions. Assays concerning the influence of the concentration of 3-HAA showed that maximum decolorization of phenol red was reached at 30 μmol L−1 of this mediator. On the other hand, antioxidant property was observed at high concentration of this compound (above 90 μmol L−1). Generally, the consumption of H2O2 was increased in the reactions containing 3-HAA.