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 0.30–0.90 A 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 ∼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.

Reactive Blue 4 (RB4) degrades remarkably due to electrooxidation in a recirculation batch carbon bed electrochemical reactor (10 L of 53 mg L−1 RB4 solution, 1.8 L h−1) with 2.8% anode current efficiency and 16.0 kWh electrical energy consumption per kilogram RB4 at optimum applied potential (E = 13.3 V) current (I = 0.6 A) in 6 h.Figure optionsDownload as PowerPoint slideHighlights
► A 3D carbon bed electrochemical reactor (TDR) is fabricated and tested.
► Efficient (90 ± 3%) degradation of RB4 occurs in TDR.
► The anode efficiency and electrical energy consumption are worked out.
► Adsorption, CV, SEM and FT-IR & IC characterization done.
► The mechanism of dye degradation discussed.
► Method for carbon bed regeneration in TDR to treat fresh dye solution given
► The TDR can emerge as a potential environmental technology.