Decolorization and degradation of Ponceau S azo-dye in aqueous solutions by the electrochemical advanced Fenton oxidation

Oxidation (decolorization/degradation) of Ponceau S azo-dye in aqueous solutions by electro-generated Fenton's reagent (Fe2+/H2O2) was optimized. This was carried out in a reactor containing 0.05 M Na2SO4 solution of pH 2.5 and a catalytic quantity of 0.1 mM FeSO4 while a cathode potential of − 1.0 V (vs. SCE) was applied. The reactor was an undivided glass electrochemical cell with a reticulated vitreous carbon (RVC) cathode and a platinum gauze anode. Progress of oxidation of various concentrations of Ponceau S with time of electro-Fenton reaction was monitored by UV–visible absorption measurements. Mineralization of the dye solutions was examined by estimation of the chemical oxygen demand removal and HPLC analysis at various times of electro-Fenton oxidation. The complete color removal of 0.05, 0.1 and 0.3 mM Ponceau S was achieved by electro-Fenton oxidation for 30, 60 and 90 min, respectively. However, approximately 98% mineralization of 0.05, 0.1 and 0.3 mM Ponceau S was achieved due to electro-Fenton oxidation for 40, 60 and 120 min, respectively. HPLC analyses showed also that almost no aromatic compounds were remaining in the treated solutions indicating the efficiency of the electro-generated Fenton's reagent for complete decolorization and significant mineralization of the Ponceau S azo-dye in aqueous solutions.