Kinetic study of decomposition of azo dyes and phenol in advanced oxidation processes reaction mechanisms, pathways and intermediates

Advanced Oxidation Processes (AOP) are an emerging technology for treatment of various hazardous organics in wastewater and groundwater. However, the kinetics and mechanisms for AOP have not been well understood. A mechanism including light intensity was studied for the decomposition of azo dyes and phenol in an AOP reactor with a 5,000 watt low pressure mercury lamp. UV light absorption is an important parameter. The effect of pH, hydrogen peroxide dosage, and dye concentration on the decomposition of azo dyes in an H2O2/UV reactor were also studied. Reaction pathways and intermediates of phenol oxidation by different processes were obtained using GC/MS analysis. Phenol oxidation by OH. produced some high molecular weight compounds (i.e. 2-phenoxy-phenol, 1,1\u27-bipheny1-2,2\u27-diol etc.) as well as organic acids. This phenomena has not been reported previously in other AOP studies. The results of computer modeling gave excellent agreement with experimental data for different initial conditions, and rate constants obtained from optimization method showed reasonable agreement with literature data of this type. In this study, light intensity in the reactor and absorbance of solution were considered to improve the accuracy of modeling. To use literature data for the fundamental reactions in stead of floating fitting make the modeling results more consistent with literature. The modeling results of the proposed mechanism can fit various initial conditions to prove its effectiveness