Efficient degradation of Reactive Blue 4 in carbon bed electrochemical reactor

A fixed bed electrochemical reactor comprising stainless steel cathode/granular activated carbon (GAC) bed//Carbon anode//GAC bed//stainless steel cathode configuration was fabricated and tested for degradation of Reactive Blue 4 aqueous solutions (RB4). On the basis of measured concentrations of residual RB4 dye and total organic carbon (TOC), approximately 80-90% of RB4 dye was found to be degraded at 0.30-0.90A and 13.4 +/- 0.1 V in 6 h under recirculation batch mode of operation (flow rate, 1.8 Lh(-1)). The dye removal due to adsorption on carbon was similar to 9-10% under the same experimental conditions but excluding applied current. The apparent Faradic efficiency and electrical energy consumption were estimated to be 2.8% and 16.0 kWh kg(-1) RB4 at the optimum current and voltage (0.6 A. 13.3 V). Further, the adsorption of the dye on GAC bed, cyclic voltammetric response of RB4. SEM and FT-IR characterization of original and spent carbon and ion chromatographic analysis of inorganic intermediates were carried out to elucidate the mechanism of dye degradation. It appears that the dye degradation takes place by ready scission of -SO3H groups, and oxidation of mainframe chromophore (anthraquinone group). The chlorotriazine group resists to the electrooxidation and remains as the final reaction product. (C) 2012 Elsevier B.V. All rights reserved.