Effects of electric current type and electrode configuration on the removal of Indigo Carmine from aqueous solutions by electrocoagulation in a batch reactor

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Abstract
The aim of this study is to investigate several electrode configurations and establish the effects of alternating current (AC), alternating pulse current (APC), and direct current (DC) on an electrocoagulation (EC) process conducted in a batch reactor. Indigo Carmine (IC) was considered as pollutant model. The investigated electrode configurations consisted in aluminum/aluminum, mild steel/mild steel, and aluminum/mild steel pairs. The effects of electrode configurations and current regimes on the removal efficiency, energy consumption, electrical operating costs, and electrode dissolution rate are discussed. The most powerful electrode configuration for IC removal from aqueous solutions by EC consisted in an anode of mild steel and a cathode of aluminum. EC operated in AC mode resulted in low efficiencies in any electrode configuration of those considered. Contrariwise, APC provided higher performance to the EC process in comparison with DC. Also, it led to higher dissolution rates in case of aluminum electrodes and to a more stable removal of dye when mild steel anode was employed. Energy-Dispersive X-Ray spectroscopy, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) analytical methods were used to characterize the sludge separated by sedimentation and flotation in case of EC in APC mode using Al–Fe configuration. Thus, it was shown that IC dye was adsorbed on aluminum and iron hydroxides.

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