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 under moderate conditions (T = 130−190 °C, pH = 2, poxygen = 1.0 MPa) with addition of a promoter and FeIISO4. The promoted wet oxidation (PWO) leads to a faster decay of the dye compared with the unpromoted WO experiments. The decomposition of the dye can be described by first-order kinetics over the temperature range. The temperature dependency can be described by an Arrhenius relationship. A reduction in TOC of 70% was achieved at 160 and 190 °C. The influence of the promoter was established at 160 °C. The results indicate a strong dependency on the dye decomposition rates and show a changing reaction order. Whereas the nonpromoted decay can be described with zero-order kinetics, the addition of the promoter changes the decay to first-order kinetics. A combined rate law was adapted for the experimental results to describe the influence of the promoter on the dye decomposition. The influence of the initial promoter concentration was ...