Removal of a Persistent Dye in Aqueous Solutions by Electrocoagulation Process: Modeling and Optimization Through Response Surface Methodology

This study is related to a laboratory study on the performance of electrocoagulation process using Fe and Al electrodes to treat bio-recalcitrant synthetic dye in a batch mode operation. The performance of the electrolytic cell resulted from its capability of generating in situ coagulants to remove methylene blue from aqueous solution. A factorial experimental design was firstly used to determine the effects of each parameter on methylene blue (MB) removal. The MB concentration, current intensity, electrolysis time, and electrode type were the main influent parameters on the response studied. The respective contributions of the main factors on the percentage of MB removal were 38.37, 18.41, 28.49, and 9.35%. Result analyses show that MB concentration had a negative effect, whereas current intensity and electrolysis time had positive effect on the efficiency. Using a 24 factorial matrix, the best performance for MB (89% of MB removed) was obtained by selecting Fe anode operated at a current intensity of 3.0 A during 40 min of treatment time in the presence of 20 mg/L of MB. A central composite design (CCD) methodology was subsequently used for optimization of EC process in treating MB. Under the optimal conditions determined by this method, EC can economically be applied to remove MB (89% of MB removal for a total cost of 0.32 US$/ m3) while using Fe anode operated at a current intensity of 1.44 A during 34 min of treatment time in the presence of 11.2 mg/L of MB.