Comparison of electrocoagulation using iron and aluminium electrodes with chemical coagulation for the removal of a highly soluble acid dye

Abstract The decolorization of a synthetic textile wastewater was investigated using electrocoagulation (EC) in a batch electrochemical cell. Orange II, a typical mono-azo acid dye, was used. Aluminum and iron electrodes were compared. The respective effects of operational parameters (initial dye concentration, current density, electrolysis time) and wastewater properties (initial pH and conductivity) were analyzed by comparing the performance of color removal, energy input, electrode mass consumption and the amount of sludge produced. Operating costs were deduced. A comparison with chemical coagulation (CC) using the same amount of metal cations as in EC was also carried out. Experimental results showed that EC maximized decolorization (up to 98%) in comparison to CC (limited to 53%). For EC, iron electrodes exhibited the highest decolorization yield and minimized simultaneously energy requirements, the amount of floc and operation costs in comparison to aluminium. As voltage vs. current curves did not differ significantly between Al and Fe, higher current was required with Al electrodes to achieve a similar decolorization yield. This was partly explained by differences in the decolorization mechanism, as Al electrodes seemed to promote the electroreduction of the azo bond of Orange II, contrary to Fe electrodes.