Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem An effective electroanalytical approach for the monitoring of electroactive dyes and intermediate products formed in electro-Fenton treatment Bakhta Bouzayani a,c , Elvira Bocos a , Sourour Chaâbane Elaoud c , Marta Pazos a , Maria Ángeles Sanromán a , Elisa González-Romero b,⁎ a Department of Chemical Engineering, University of Vigo, Campus As Lagoas-Marcosende, 36310 Vigo, Spain b Department of Analytical and Food Chemistry, University of Vigo, 36310 Vigo, Spain c Laboratory of Physical Chemistry of the Solid State, Department of Chemical, University of Sfax, 3000 Sfax, Tunisia ARTICLE INFO Keywords: Reactive Black 5 H-Acid Electro-Fenton Linear Sweep Voltammetry Screen-printed carbon electrodes Dye degradation monitoring ABSTRACT Reactive Black 5 (RB5) is an electroactive diazo dye compound derivate of H-acid (coupling reaction), which cannot be effectively degraded by conventional or biological processes. In this work, the feasibility of electro- Fenton (EF) process to treat a simulated effluent polluted by RB5 dye and the effectiveness of electroanalysis by Linear Sweep Voltammetry (LSV) to monitor RB5, intermediates and by-products during the EF treatment have been demonstrated. Several variables on the electrochemical behaviour of RB5 have been determined under EF experimental conditions. The key factors are scan rate and dye concentration (in the presence and the absence of iron) and their effect on shape, position and height of RB5 peaks have been determined to obtain the best sensitivity and selectivity in the voltammetric analysis. Moreover, the iron appears as a strong electrocatalyst that promotes the electron transfer for the oxidation reaction of RB5 on screen-printed carbon electrode, in part, due to a very stable coordinate complex formed with RB5. Besides that, the degradation profiles have revealed the main stages along the EF process and the voltammetric kinetic data has given selective information about the RB5 degradation and the evolution of the electroactive products generated. The formation of aromatic/cyclic organic intermediates, and evolution of carboxylic acids, as well as the inorganic ions released during the treatment were validated by other techniques and a plausible pathway is proposed based on the obtained results. 1. Introduction Around 80,000 tons of synthetic dyes are annually used by a large variety of industries such as textile, leather tanning, hair colouring, food products, etc. [1]. However, 1–10% of employed dyes are lost during their consumption and production, generating 87 million litres of wastewater per day [2]. The important volumes of consumed water and wastewater generated provide aquatic environments with colour and odour, causing an irreparable damage on these ecosystems. Such enormous scale production and the later discharge of these substances into the water streams cause not only non-aesthetic conditions but also eutrophication, entailing a potential risk for living beings health [3]. Within this context, concerns among population and scientific com- munity have force the environmental authorities to create more severe laws in matter of pollution and concentration limits of some chemical. As an example, attempts in this direction in Europe have included the redaction of the Directive 2002/61/EC, created to establish restrictions on the dyeing market and concentration limits of 70 ppm in the use of certain azocolourants [4]. Dyes use to be classified according to their chromophore group, being the azo class (eN]Ne) the most used ones at industrial scale. Reactive Black 5 (RB5) is an electroactive diazo dye derivate from H- acid, which is considered having irritating and toxic properties for living beings. Moreover, apart from azo groups RB5 present sulfonic acid groups to increase water solubility that also increase the re- calcitrant character of this compound [5]. Severe damages on the ecosystems and aquatic organisms due to their extremely high persis- tence and low biodegradability [6]. Lamentably, conventional wastewater treatment plants (WWTP) cannot achieve the complete elimination of these azo dyes. Consequently, numerous efforts have been addressed on research of alternative water technologies able to degrade these pollutants [7–10]. As an example, Electrochemical Advanced Oxidation Processes (EAOPs) are currently considered promising candidates able to achieve a com- plete and quick mineralization of nonbiodegradable organic matter [11]. These processes comprise the generation of hydroxyl radicals (% http://dx.doi.org/10.1016/j.jelechem.2017.06.035 Received 31 March 2017; Received in revised form 20 May 2017; Accepted 19 June 2017 ⁎ Corresponding author. E-mail addresses: ebocos@uvigo.es (E. Bocos), sourour.chaabane@fss.rnu.tn (S.C. Elaoud), mcurras@uvigo.es (M. Pazos), sanroman@uvigo.es (M.Á. Sanromán), eromero@uvigo.es (E. González-Romero). Journal of Electroanalytical Chemistry xxx (xxxx) xxx–xxx 1572-6657/ © 2017 Elsevier B.V. All rights reserved. Please cite this article as: Bouzayani, B., Journal of Electroanalytical Chemistry (2017), http://dx.doi.org/10.1016/j.jelechem.2017.06.035