The fungal metabolite 3-hydroxyanthranilic acid (3-HAA) was used as a redox mediatorwith the aim of increasing dye degradation by Fenton oxidative processes (Fe2+/H2O2, Fe3+/H2O2). ItsFe3+-reducing activity can enhance the generation of reactive oxygen species as HO● radicals.Initially, the influence of 3-HAA on decolorization kinetics of five dyes (methylene blue,chromotrope 2R, methyl orange, phenol red, and safranin T) was investigated using decolorizationdata from a previous work conducted by the present research group. Fe3+-containing reaction datawere well fitted with first-order and mainly second-order kinetic models, whereas the BMG(Behnajady, Modirshahla and Ghanbary) model obtained optimal fit to Fe2+. Improvements inkinetic parameters (i.e., apparent rate constants and maximum oxidation capacity) were observedwith the addition of 3-HAA. In another set of experiments, a decrease in apparent activation energywas observed due to introducing 3-HAA into reactions containing either Fe2+ or Fe3+ in order todecolorize phenol red at different temperatures. This indicates that the redox mediator decreasesthe energy barrier so as to allow reactions to occur. Thus, based on recent experiments and thereaction kinetics models evaluated herein, pro-oxidant properties have been observed for 3-HAAin Fenton processes.
Keywords: 3-Hydroxyanthranilic; Dye decolorization; Fenton reaction; Kinetics; Pro-oxidant properties; iron.