REACTION-REACTOR MODELING AND KINETICS OF ANTHRAQUINONE DYE OXIDATION USING OZONE AND UV RADIATION

C. MARTÍN Y OTROS; LOVATO, MARIA EUGENIA; FIASCONARO, MARÍA LAURA; ANDINI, JUAN CARLOS

Ozone and Advanced Oxidation. Leading-edge science and technologies

The International Ozone Association

Lugar: París; Año: 2015; p. 501 - 511

Anthraquinone reactive dyes are one of the major groups among reactive dyes other than azo compounds, based on the classification of molecular structures. They are more resistant to biodegradation due to their fused aromatic structures compared to azo-based ones. In addition, they may cause acute toxicity or even mutagenic effects on exposed aquatic organisms. Therefore, anthraquinone reactive dyes have gradually attracted critical attention from the toxicological and environmental points of view, particularly in light of the current increase in their applications. Reactive Blue 19 (RB-19) is a commercially representative anthraquinone reactive dye. Up to the present, several studies have successfully identified the ozonated products of azo reactive dyes. On the contrary, little related ozonation research on anthraquinone reactive dyes is available.Ozone based methods may involve two different major oxidative species: ozone and ?OH radicals. Ozone can also react through the hydroxyl radical generated during its decomposition in water. ?OH generation is usually promoted at high pH, with the addition of hydrogen peroxide or UV irradiation. Thus, during ozonation in water, both molecular ozone and hydroxyl radical coexist, having different reactivity and selectivity. Ozonation involves complex gas?liquid processes where both mass transfer and chemical reactions can control the overall kinetics. In this aspect, a mechanistically sound kinetic model that incorporates mass transfer and reaction rates is desirable as the model can not only reveal important insights into the underlying mass transfer and reaction pathways, but also facilitate process design and optimization. In an O3/UV system, UV photons can react with dyestuffs and intermediates such as hydrogen peroxide to produce ?OH. There has been little information available on modeling the overall O3/UV kinetics considering the overall mechanisms such as gas?liquid mass transfer, and chemical reactions with both ozone and ?OH. Reactor modeling involving the evaluation of the radiation field is essential to obtain intrinsic kinetic expressions that can be used for the design and optimization of irradiated devices. In the present work, a kinetic model was developed, which represents the reaction of decomposition of RB19 taking into account all the O3 parallel paths of attack among which, the direct photolysis and its spontaneous decomposition in water cannot be excluded. This kinetic model must base on the mechanisms of ozone decomposition and dye degradation, and characteristic of gas?liquid mass transfer of reactor. Then, the overall rate constants and the kinetic regime of the reaction can be deducted by interpreting the experimental data with the model.