(454h) Removal of Orange II Dye from Wastewater by Catalytic Wet Air Oxidation-Catalyst Selection and Reaction Kinetics

The aim of this study is to find an efficient catalyst for the CWAO of Orange II and determine a rate expression for the reaction. The experimental phase of this study focuses on the treatment of synthetically prepared Orange II containing waters by catalytic wet air oxidation. Initially, preliminary experiments were run to determine the experimental range for parameters and assess the treatment efficiency of different types of catalysts for further analysis. During these experiments, 130 and 180ºC were chosen as the low and high experimental temperatures, respectively, for a catalyst loading of 5 grams at 400 psi. Experiments were run for 120 minutes. It was confirmed experimentally that thermal degradation of the dye was not taking place during reactor heat-up. All collected samples were analyzed for Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD), and were also scanned with a UV-VIS spectrophotometer for absorbance. Color of the samples was measured at 311 nm, one of the characteristic maximum absorbance wavelengths for Orange II up to 100 mg/L. It was observed that at the lower reaction temperature, more removal of TOC and COD took place. This is probably due to the different kinds of intermediates formed and different reaction paths followed at different temperatures. It is possible that Orange II breaks down into smaller compounds that are easier to oxidize at lower temperatures, and polymerizes into more bulky compounds at higher temperatures. After the preliminary screening, screening experiments were conducted with 7 chosen catalysts that exhibited better removal capacities, according to a factorial design at 2-levels with a catalyst loading of 2-4 g, temperature of 80-120ºC and pressure of 300-400 psi. The reaction time was held constant at 120 minutes. The results of these experiments and the kinetic model will be presented.