Effect of Lignin-Derived Methoxyphenols in Dye Decolorization by Fenton Systems

Abstract

Lignin-derived methoxyphenols (MPs) with Fe3+-reducing activity were used as potential mediators to increase the decolorization of dyes by classical Fenton (Fe2+/H2O2) and Fenton-like reactions (Fe3+/H2O2). In this study, several MPs such as vanillin, vanillic alcohol, syringaldehyde, ferulic, vanillic, and syringic acids were evaluated. The results showed that all MPs displayed similar prooxidant activities in the decolorization of methylene blue, chromotrope 2R, methyl orange, and phenol red. For example, the reaction performed with Fe3+/H2O2 decolorized 27 % of chromotrope 2R, whereas the treatments with Fe3+/H2O2/MP decolorized around 70 % of the same dye after 60 min. For Fe2+/H2O2 systems, two stages of decolorization were visibly observed. In the first stage, the MPs inhibited the treatments, and then they increased the decolorization rate in the second stage. Prooxidant and antioxidant properties were observed for decolorization of methylene blue performed in the presence of low and high concentrations of vanillin, respectively. Overall, the MPs increased dye decolorization without increasing the consumption of H2O2.