Degradation of aqueous disperse orange 25 by supercritical water oxidation

Oxidation of aqueous solutions of CI Disperse Orange 25 was studied in a continuous flow reactor that was operated between 400 and 600°C at a fixed pressure of 25 MPa. The dye total organic carbon (TOC) concentrations were in the range of 35.0 and 174.8 mmolL^-1 in the feed stock solution. Hydrogen peroxide (H₂O₂) was used as an oxygen source and the oxidant concentrations were between 147 and 735 mmolL^-1 in the feed stock solution. The results demonstrated that the supercritical water oxidation process decreases the TOC up to 99.96% in very short reaction times (at residence times of 4-12 s). According to the wastewater and oxidant concentrations, the global rate expression was regressed from the complete set of data. As a result of regression analysis, the pseudo first-order global rate expression according to the wastewater concentration was determined with an activation energy of 40.181 (±1.1) kJmol^-1 and a pre-exponential factor of 218.7 (±2.1) s^-1 to a 95% confidence level.