Electrochemical oxidation of dyeing baths bearing disperse dyes

This paper presents the results of the electro-oxidation of pollutants in s ynthetic textile wastewater containing partially soluble disperse dyes. The experiments were performed in an electrochemical undivided cell reactor us ing seven different anode materials and 0.1 M NaCl as the supporting electr olyte. 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 resea rch 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 conditi ons of free pH evolution 39% removal of chemical oxygen demand was obtained after 40 min of electrolysis. The apparent pseudo-first-order rate constan t for the removal of color was equal to 2.54 x 10(-4) s(-1) and it increase d to 8.23 x 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 s tudies on the chemical oxidation of pollutants by hypochlorite far lower ef ficiency was obtained.