Electrooxidation and electroflocculation effects on discoloration on solutions containing textile or food dyes

Abstract

Water pollution has been a much debated subject in every sector of society, since it is na essential resource for practically all human activities. The water contamination by synthetic dyes has been a point of concern, not only because of the difficulty of removing the resistent substances using conventional methods of treatment, but also for posing a risk to health and to the environment. Therefore, this work aimed to sudy two types of electrochemical treatments, electroflocculation and electrooxidation, on the decolorization efficiency of textile and food dye solutions. Four samples of dyes, two textile in moss green and red, and two food dyes in green and red, with mass concentration of approximately 50 mg.L^-1, were selected for the experiments. As supporting electrolyte, a solution of Na₂SO₄ at a concentration of 8,8 mmol.L^-1 was used. To monitor the decay of the concentration of dyes in solution with time passing, the UV-vis spectrophotometric method was applied. The experiments were performed potentiostatically by applying a cell potential of 25 V for 1 hour in the experiments carried out by electroflocculation using aluminum electrodes as working electrode and counter electrode, while in the electrooxidation experiments a cell potential of 5 V for 2 h, using a DSA type electrode as a working electrode and an aluminum electrode as a counter electrode. In the electrooxidation, aliquots were taken every 30 minutes to determine the color decay with the experiment time. As for the experiments carried out by electroflocculation, the concentrations were determined before the beginning of the experiment and after the end of the experiment. The experimental results showed efficiencies higher than 65% in color removal using both methods, although better efficiencies were found when the experiments were carried out by electrooxidation.