Interaction between pH and conductivity in the indirect electro-oxidation of azo dyes

The indirect electro-oxidation of dyes results in a rapid break of the dye molecules. The influence of the dye chromophore in this process has already been demonstrated. In this work, an electrochemical treatment in a batch cell with Ti/Pt anode is applied to degrade two reactive dyes (Color Index Reactive Oranges 4 and 13) in the presence of chloride ions, usually used as dyeing electrolyte. For the two dyes, kinetic constants were modeled. A clear influence of the reactive group in the response surfaces was found despite the unique difference between both dyes being only one substituent (OH or NH2). Models are strongly dependent on pH and conductivity. Also, an important interaction of both factors was evidenced, which can be attributed to different mechanisms of oxidizing species generation