Treatment of synthetic wastewater containing methylene blue (MB) by electrocoagulation withperiodic electrode reversal (PerevEC) was evaluated. The Response Surface Methodology (RSM)procedure was employed to obtain optimal conditions for decolorization, electrode consumption andsludge 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 % ofthe color was removed, the electrode consumption and sludge production were 0.25 ± 0.02kg(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 andtraditional electrocoagulation without periodic reversal of the electrodes (TradiEC) show greater Al13Keggin ion polymer is formed in the electrolytic solution during PerevEC. Periodical reversal of theelectrodes establishes improved conditions for precipitation and solution diffusion of Al3+ withdecreased anodic passivation and cathodic polarization. For both PerevEC and TradiEC, thedisappearance of characteristic IR peaks at 800?890, 1350, 1490 and 1604 cm?1 indicates the completedestruction of the methylene blue molecule by breakage of the central and side aromatic rings as wellas demethylation. These results indicate that the PerevEC process, as compared to TradiEC, for dyewastewater treatment may be applied more widely due to the greater decolorization and reducedanodic passivation and cathodic polarization, although there is greater electrode consumption andsludge production.
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