Arsenic removal from contaminated drinking water by electrocoagulation using hybrid Fe–Al electrodes: response surface methodology and mechanism study

Abstract

This study investigated the optimization and mechanism of arsenic (As) removal by electrocoagulation (EC) using hybrid Fe–Al electrodes. Response surface methodology (RSM) was employed to evaluate the effects of different operating conditions on As removal and voltage. Central composite design was established for the optimization of the EC process and to evaluate the effects and interactions of process variables: current density, pH, aeration intensity, and operating time. Analysis of variance showed a high coefficient of determination value (R2 = 0.9269), ensuring a satisfactory adjustment of the second-order regression model with the experimental data. Under the optimum conditions of current density 0.47 A/dm2, pH 7.0, aeration intensity 0.32 L/min, and operating time 20 min, 99.94% As were removed and the minimum energy consumption was obtained. Results confirmed the validity of the optimization and the adequacy of the model. Besides, scanning electron miscroscopy/energy dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared analysis demonstrated that adsorption onto iron and aluminum hydroxides/oxyhydroxides was the predominant mechanism of As removal by EC using hybrid Fe–Al electrodes.