Application of Modified Electrocoagulation for Efficient Color Removal from Synthetic Methylene Blue Wastewater

Treatment of synthetic wastewater containing methylene blue (MB) by electrocoagulation with periodic electrode reversal (PerevEC) was evaluated. The Response Surface Methodology (RSM) procedure was employed to obtain optimal conditions for decolorization, electrode consumption and sludge production which were found to be cell voltage of 3.1 V, current density of 347 mA. cm(-2), electrode reversal period of 2.5 s and inter-electrode gap of 2 cm. Under these conditions 97 +/- 2 % of the color was removed, the electrode consumption and sludge production were 0.25 +/- 0.02 kg(Al).kg(MBr)(-1) (where kg(MBr)(-1) is per kg MB removed) and 1.9 +/- 0.9 kg(sludge).kg(MBr)(-1), respectively. NMR, IR and SEM analyses of the precipitates, solutions and electrodes for PerevEC and traditional electrocoagulation without periodic reversal of the electrodes (TradiEC) show greater Al-13 Keggin ion polymer is formed in the electrolytic solution during PerevEC. Periodical reversal of the electrodes establishes improved conditions for precipitation and solution diffusion of Al3+ with decreased anodic passivation and cathodic polarization. For both PerevEC and TradiEC, the disappearance of characteristic IR peaks at 800-890, 1350, 1490 and 1604 cm(-1) indicates the complete destruction of the methylene blue molecule by breakage of the central and side aromatic rings as well as demethylation. These results indicate that the PerevEC process, as compared to TradiEC, for dye wastewater treatment may be applied more widely due to the greater decolorization and reduced anodic passivation and cathodic polarization, although there is greater electrode consumption and sludge production.