Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Electrochemical decolorization of Rhodamine B dye: Influence of anode material, chloride concentration and current density Ali Baddouh a,b , Guilherme Garcia Bessegato b , Mohamed M. Rguiti a , Brahim El Ibrahimi a, ⁎ , Lahcen Bazzi a , Mustapha Hilali a , Maria Valnice Boldrin Zanoni b a Applied Chemistry-Physic Team, Faculty of Sciences, IBN ZOHR University, B.P. 8106 Cité Dakhla, Agadir, Morocco b Universidade Estadual Paulista (Unesp), Instituto de Química, Araraquara. Av. Prof. Francisco Degni, 55, 14800-060, Araraquara, SP, Brazil ARTICLE INFO Keywords: Degradation Electrochemical oxidation Rhodamine B DSA SnO 2 electrode ABSTRACT Surface water contamination by dyes released from a variety of industries is an environmental problem of great concern. However, electrochemical oxidation is a promising alternative for water treatment. In this paper, we studied the electrochemical oxidation of Rhodamine B (RhB) dye on the Ti/RuO 2 –IrO 2 (DSA ® ) and SnO 2 anodes comparing their efficiencies. The effect of some parameters, such as current density, initial pH (pH 0 ), nature, concentration of electrolyte and temperature at the electrochemical oxidation was investigated evaluating the decolorization and the chemical oxygen demand (COD) removal at optimal conditions. Complete decolorization of RhB was achieved in the presence of chloride ions at different times using both electrodes. An optimum efficiency was obtained at pH 6.5, T = 25 °C. Also, the current density of 40 mA cm -2 using the DSA electrode in NaCl 0.05 mol L -1 + Na 2 SO 4 0.1 mol L -1 mixture solution as a supporting electrolyte, 100% color removal and 61.7% chemical oxygen demand removal after 90 min of electrolysis were achieved. DSA showed better per- formance than SnO 2 in wide operating conditions and was proved to be more cost-effective and more efficient. The effectiveness of the degradation is explained by indirect electrochemical oxidation, where in the presence of chlorides electrolyte leads to the electro-generation of strong oxidant species, such as Cl 2 and ClO - ions, im- proving the efficiency of treatment at both electrodes. 1. Introduction Surface water contamination by wastewater from paper and textile industries are greatly colored due to the existence of dyes and harmful compounds. Textile and printing industries are important causes of water pollution in developing countries, since its discharged waste- water could not only contain persistent organic dyes but also toxic byproducts. Residual dyestuffs are characterized by a strong color, high organic content and stable chemical structure due to the presence of azo functional groups. Therefore, they have affected serious menaces for environmental pollution [1,2]. Various methods are commonly used to dye removal from wastewater such as biological degradation method [3], adsorption [4,5], coagulation–flocculation [6], Fenton’s oxidation [7], membrane separation [8] and ozonation [9]. The literature also recommended the use of electrochemical processes as an advanced al- ternative for removing dyes from colored effluents [10–14]. The elec- trochemical treatment is commonly based on the elimination of pollu- tants directly on the anode surface, via production of OH% [15–17], or/ and other oxidants such as chlorine, persulfate, and others. It has been demonstrated that the anode material plays an essential part in the electro-degradation of organic pollutants. Various materials have been tested and assessed for dye removal from effluents. The dimensionally stable anode (DSA ® ) is made of a titanium base metal covered with a thin conducting ruthenium or iridium oxide. The DSA anode exhibits the high chemical and electrochemical stability even at high current densities, longer operating lifetime, commercially available and com- paratively low cost [18,19]. These anodes are mainly used in the pre- sence of Cl - to produce active chlorine oxidants (Cl 2 , HOCl and OCl - ) via the following equations: 2Cl - → Cl 2 + 2e - (1) Cl 2 +H 2 O → HClO + H + + Cl - (2) The concentration of the weak acid: HOCl and its conjugate base OCl - depends on the pH solution: HClO ⇆ OCl - +H + (3) The DSA has been classified as ‘active’ or ‘non-active’ depending on https://doi.org/10.1016/j.jece.2018.03.007 Received 8 November 2017; Received in revised form 18 February 2018; Accepted 5 March 2018 ⁎ Corresponding author. E-mail address: brahim.elibrahimi@edu.uiz.ac.ma (B. El Ibrahimi). Journal of Environmental Chemical Engineering 6 (2018) 2041–2047 Available online 06 March 2018 2213-3437/ © 2018 Elsevier Ltd. All rights reserved. T