Promoted wet oxidation of the azo dye orange II under mild conditions

Wet oxidation (WO) reactions of the azo dye Orange II were carried out unde r moderate conditions (T = 130-190 degreesC, pH = 2, p(oxygen) = 1.0 MPa) w ith addition of a promoter and (FeSO4)-S-II. The promoted wet oxidation (PW O)leads to a faster decay of the dye compared with the unpromoted WO experi ments. The decomposition of the dye can be described by first-order kinetic s over the temperature range. The temperature dependency can be described b e an Arrhenius relationship; A reduction in TOC of 70% was achieved at 160 and 190 degreesC. The influence of the promoter was established at 160 degr eesC. The results indicate a strong dependency on the dye decomposition rat es and show a changing reaction order. Whereas the nonpromoted decay can be described with zero-order kinetics, the addition of the promoter changes t he decay to first-order kinetics. A combined rate law was adapted fdr the e xperimental results to describe the influence of the promoter on the dye de composition. The influence of the initial promoter concentration was found to be of first order. The combination of the pH, the ferrous ions, and the promoter allows for degradation rates of the azo dye comparable with those of heterogeneously catalyzed wet oxidation. The amount of added promoter is , therefore, an important parameter in the promoted wet oxidation.