The alternating and direct current effect on the elimination of cationic and anionic dye from aqueous solutions by electrocoagulation and coagulation flocculation

Abstract

In this study, we investigated the effect of alternating current (AC) and direct current (DC) on the elimination of methylene blue (MB) and indigo carmine (IC) by the electrocoagulation process using two Pb electrodes in comparison with the coagulation–flocculation process. Different parameters influencing the elimination of these dyes were studied, namely initial dye concentration, initial pH, voltage, temperature, coagulant and flocculant concentration and current density. The elimination of MB reached 98.8% with AC and 97.3% with DC at current density of 0.5 A/m3 and pH of 7.0. However, the energy consumed was lower in the case of AC (4.89 × 10−6 kWh/m3) than DC (7.6 × 10−6 kWh/m3). The elimination was also faster in the case of AC (0.47 mg L−1/min) than the DC (0.066 mg L−1/min). The same behavior was observed with the IC where the effectiveness of dye elimination was, respectively, 98.5 and 100% with an energy consumed (E c) of 4.35 × 10−5 and 2.03 × 10−6 kWh/m3, respectively, with DC and AC. The adsorption kinetic data were obtained using pseudo-first-order and pseudo-second-order models. The pseudo-second-order was more appropriate describing the adsorption kinetics of methylene blue and the pseudo-first-order was more appropriate describing the adsorption kinetics of indigo carmine. Langmuir, Freundlich and Sips models were used to optimize the elimination dye process. The Sips model displayed the best fit of the equilibrium data.