Degradation of commercial azo dyes in water using ozonation and UV enhanced ozonation process

The chemical oxidation of eight non-biodegradable azo dyes by ozonation and photooxidation process was studied in a pilot scale photochemical (UV/ozone) reactor. In experiments with ozone bubbling, the degradation of eight azo dyes was found to occur in the absence of UV light. The degradation rate of azo dyes was observed to be first order with respected to both azo dye and ozone concentrations. The pH of the solution decreased while the azo dyes degraded. UV light did not significantly enhance the degradation ability of the ozonation reaction under various conditions. No degradation was observed when the azo dye solution was irradiated by UV light alone. Effects of ozone dosage, and initial concentrations of azo dyes are discussed. Time for removal of 50 % of azo dye and rate constants can be used to determine the decomposition rate of each azo dye by different oxidation processes as a function of various conditions.