Electrochemical Oxidation of Dyeing Baths Bearing Disperse Dyes

Abstract

This paper presents the results of the electro-oxidation of pollutants in synthetic textile wastewater containing partially soluble disperse dyes. The experiments were performed in an electrochemical undivided cell reactor using seven different anode materials and 0.1 M NaCl as the supporting electrolyte. With the Ti/Pt−Ir anode, which showed the best performance among all the tested materials, additional experiments were also carried out using 0.05 M Na2SO4 as the supporting electrolyte. Experimental results obtained in the electrochemical reactor, supported by the data obtained during cyclic voltammetry studies, showed that under the conditions of the present research the removal of pollutants was mediated by active chlorine generated by electro-oxidation of chloride ions or by other mediators generated in situ and not by a direct discharge of pollutants at the anode. Under the conditions of free pH evolution 39% removal of chemical oxygen demand was obtained after 40 min of electrolysis. The apparent pseudo-first-order rate constant for the removal of color was equal to 2.54 × 10-4 s-1 and it increased to 8.23 × 10-4 s-1 under pH control at the value of 4.5, resulting in 90% removal of color after the passage of 1.9 A h dm-3. In comparative studies on the chemical oxidation of pollutants by hypochlorite far lower efficiency was obtained.