Removal of acid dye from aqueous solutions by electrocoagulation/GAC adsorption coupling: Kinetics and electrical operating costs Marius Sebastian Secula a , Benoı ˆt Cagnon b, *, Tatianne Ferreira de Oliveira c , Olivier Chedeville b , Henri Fauduet c a Department of Chemical Engineering, Faculty of Chemical Engineering and Environmental Protection, TUIASI – ‘‘Gheorghe Asachi’’ Technical University of Iasi, 73 Prof. Dr. Doc. D. Mangeron, 700050 Iasi, Romania b CRMD – Centre de Recherche sur la Matie `re Divise ´e, CNRS, Universite ´ d’Orle ´ans, 1B rue de la Fe ´rollerie, 45071 Orle ´ans Cedex 2, France c ICOA – Institut de Chimie Organique et Analytique CNRS-UMR 6005, Institut Universitaire Technologique, Universite ´ d’Orle ´ans, Rue d’Issoudun, BP 16729, 45067 Orle ´ans Cedex 02, France 1. Introduction In the last few years, numerous studies of wastewater treatment have been reported based on the electrocoagulation (EC) technique, which ensures relatively good quality effluent before its discharge into the aquatic environment. In fact, EC has regained the interest of scientists due both to a more thorough understanding of the underlying mechanisms of electrocoagula- tion processes, and to its ‘‘green technology’’ characteristics. Because of the inherent simplicity of its design and operation, together with the growing need for small-scale cost-effective water treatment systems, interest in the use of EC for industrial applications has been revived [1]. EC is a simple and efficient method for the treatment of many types of wastewater containing various pollutants that can be flocculated. In the literature, the separation by electrocoagulation of pollutants such as hydrocarbons [2,3], dyes [4–7], heavy metal ions [8,9], leachate [10], and various other ions such as boron [11] and fluorine [12] has been reported. According to the present theory of the EC mechanism, coagulants are generated in situ via anodic dissolution of a metal ion, such as iron, while water electrolysis takes place at the cathode. These ions move through the processed wastewater by electric field where chemical reactions occur. Further, the pollutants are transformed into amorphous precipitates of adsorbed forms on hydroxides such as FeOH 2+ , Fe(OH) 2 + , Fe(OH) 3 , Fe(OH) 4 and FeO(OH) at the anode [13]. Flocculated particles can then be separated by precipitation or/and flotation. In a previous study, Secula et al. [14] presented an experimental study on the removal of indigo carmine by the EC technique, and evaluated the efficiency of simple EC in relation to decolorization efficiency and energy consumption. Taking into account the relatively well known advantages of electrochemical technologies based on insoluble electrodes applied for the regeneration of spent Journal of the Taiwan Institute of Chemical Engineers xxx (2012) xxx–xxx * Corresponding author. Tel.: +33 2 38 49 44 31; fax: +33 2 38 49 44 25. E-mail address: benoit.cagnon@univ-orleans.fr (B. Cagnon). A R T I C L E I N F O Article history: Received 10 November 2011 Received in revised form 24 February 2012 Accepted 4 March 2012 Available online xxx Keywords: Granular activated carbon Adsorption Electrocoagulation Kinetics Acid dye Electrical operating cost A B S T R A C T The present work studies the removal of indigo carmine from aqueous solutions by an electrocoagulation (EC)/granular activated carbon (GAC) adsorption coupling process. The kinetics of this coupling process was studied using several GACs and different amounts of adsorbent material in order to identify the most appropriate adsorbent and dosage, respectively, for enhancing wastewater treatment. The influence of current density on the removal efficiency and electrical operating costs of the EC/GAC coupling process was also determined. Four GAC materials, Pica F22, L27, X17 and S21, were characterized and used in the study of the EC/GAC coupling process. The textural characteristics of adsorbent materials were established based on nitrogen adsorption and their surface chemical properties were investigated by FTIR spectroscopy. The coupling between electrocoagulation and GAC showed that the addition of an appropriate GAC resulted in the enhancement of the removal rate of indigo carmine especially at lower current densities, and in a considerable reduction in the contact time compared to the conventional simple EC process and simple adsorption process. Though the F22 exhibited outstanding adsorption properties related to indigo carmine dye, Pica L27/EC coupling provided the best rate constants. Based on the significant decrease in electrical operating costs, the EC/GAC coupling method could be recommended instead of the conventional simple EC. ß 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. G Model JTICE-443; No. of Pages 9 Please cite this article in press as: Secula, M.S., et al., Removal of acid dye from aqueous solutions by electrocoagulation/GAC adsorption coupling: Kinetics and electrical operating costs. J. Taiwan Inst. Chem. Eng. (2012), doi:10.1016/j.jtice.2012.03.003 Contents lists available at SciVerse ScienceDirect Journal of the Taiwan Institute of Chemical Engineers jou r nal h o mep age: w ww.els evier .co m/lo c ate/jtic e 1876-1070/$ – see front matter ß 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jtice.2012.03.003