Comparison of advanced oxidation processes for degrading Ponceau S dye. Application of photo-Fenton process.

Abstract

The major part of this work is devoted to the examination of the degradation of Ponceau S (PS) in aqueous medium by using the photo-Fenton process. The influence of pH of the medium, oxidant dose (H2O2), ferrous ion dose and the presence of inorganic ions such as bicarbonate, sulphate and nitrate on degradation kinetics was also analyzed. Before that, the efficiency of this process was compared to three other advanced oxidation processes (AOPs) such as H2O2/UV, Fenton (Fe2+/H2O2), and solar photo-Fenton. It was found that all dye degradation kinetics obeyed a pseudo-first order, and their apparent rate constants were represented by the ratios: kapp (H2O2/UV/Fe2+) =0.295 kapp (sunlight/Fe2+/H2O2) =0.141 kapp (Fe2+/H2O2) = 0.111 kapp (H2O2/UV) =0.031.Under reference conditions (0.06 mM of PS in ultrapure water), photo-Fenton oxidation using 0.06 mM of Fe2+, 1mM of H2O2 and the pH optimal value of 3 yielded more than 94.3% in only10 min of dye degradation with an apparent rate constant of 0.2951 min-1. Elsewhere, the addition of the salts in aqueous medium has, in general, an inhibition effect on the decolorization kinetics due to controlled ionic interactions of metals with inorganic ions. The most adverse effect on PS disappearance rate was observed when bicarbonate ions were present in the treated medium.