Abstract
Synthetic dyes are extensively used in textile dyeing, paper printing, colour photography, pharmaceuticals, food, cosmetics and other industries. In spite of their diversity there are a certain number of properties common to many dye compounds, such as aromatic constitution, chromophore groups and others. Similarly to other dyes and due to the formation of colour intermediates, in the case of Rhodamine 6G colour capacity is maintained in the initial steps of dye degradation. For this reason in the degradation of a dye it is necessary to distinguish between two processes that take place simultaneously: dye removal and decolourization. This study was conducted by using a water solution of 50 mg/L of Rhodamine 6G (Rh-6G), as a model of a dye wastewater, in the hydrogen peroxide/UV system. The kinetic model proposed in this paper for the removing of Rh- 6G is a sequential first-order reaction. This model describes acceptably the changes in two kinds of compound for a wide interval of H2O2 dosages between 0 and 400 M H2O2/M Rh-6G. A study of the degradation of coloured compounds in water is also performed. The relationship of the changes over time in dye and colour is also determined. Financial evaluation factors of the UV/ H2O2 process for Rh-6G removal and Decolourization at various dosages of oxidant was also estimated. When the effect of H2O2 dosages on the two processes is analysed, it is observed that for doses of oxidant between 60 and 120 M H2O2/M Rh-6G, the tendency of all the apparent constants previously defined undergoes a major change. A brief mineralization study was also carried out through the Mineralization Degree parameter that relates mineralization to decolourization.
© 2016 by Walter de Gruyter Berlin/Boston