The degradation of reactive red dye from wastewaters by advanced electrochemical oxidation

Abstract

In the present study, electrochemical degradation experiments were conducted to degrade a textile dye namely Reactive Red 147 (RR) from water. The process performance was assessed in terms of the electrochemical decolourisation and mineralization of aqueous RR solutions. Electrolyses were carried out under galvanostatic conditions using boron-doped diamond (BDD) electrodes in 0.1 M Na2SO4 supporting electrolyte using undivided electrolytic cell. Also, the effect of in-situ electrolytic generation of chlorine/hypochlorite at BDD electrode from a mixture of 0.05 M Na2SO4 and 0.05 M NaCl supporting electrolyte on the electrochemical degradation process of RR has been studied. Prior to electrolysis application, the electrochemical behaviour of RR dye on BDD electrode was characterized in both supporting electrolytes without/with chloride presence by cyclic voltammetry in order to establish the working potential-current conditions. The influence of operating variables on the electrochemical process efficiency was studied as a function of the supporting electrolyte type, current density, and the initial pH. Under all applied conditions, the complete decolourisation of dye synthetic solution was achieved after several minutes of electrolysis. Acidic medium and the chlorine/hypochlorite generation favored the decolorization and mineralization process of RR. The complete mineralization of dye synthetic solution was not achieved, and the maximum mineralization efficiency of 35% was reached under the working conditions of hypochlorite presence, which informs about the intermediates generation during the application of electrochemical process based on BDD electrodes.