Experimental and Theoretical Aspects of Azo Dye Degradation by UV/H2O2 Process: Review and experimental comparison of some kinetic rate expressions

Abstract

Due to their unique properties, azo dyes are extensively used, especially in the textile industry. Due to their low biodegradability, these compounds cannot be treated in wastewater treatment plants and discharges of these effluents poses a serious threat to the receiving water bodies. In the literature, several advanced oxidation processes have been studied for decolorization and mineralization of these toxic compounds. Among these advanced oxidation processes, the UV/H 2 O 2 process has attracted great attention with its high efficiency in removing these compounds. The goal of this paper is to review the kinetic rate expressions developed to describe azo dye degradation by UV/H 2 O 2 process. A detailed review of pseudo-first-order reaction mechanism, as well as reactor design models, is provided. Finally, a set of experiments are conducted with Reactive Black 5 to compare the model estimations with the observed data. In addition, a regression model is developed using response surface methodology to optimize operating conditions. The experimental results indicate that the optimum pH value that gives the maximum reaction constant is 5.74. Moreover, initial dye concentration is found to be a more significant parameter for decay rate constant than pH value. The open questions and future research topics are also discussed.