Active chlorine species electrogenerated on Ti/Ru 0.3 Ti 0.7 O 2 surface: Electrochemical behavior, concentration determination and their application Dayanne Chianca de Moura a , Cynthia Kérzia Costa de Araújo a , Carmem L.P.S. Zanta b , Ricardo Salazar c , Carlos Alberto Martínez-Huitle a,⇑ a Federal University of Rio Grande do Norte, Institute of Chemistry, Lagoa Nova CEP 59.072-970, RN, Brazil b Institute of Chemistry and Biotechnology, Federal University of Alagoas, CEP 57072-970, Maceió-Al, Brazil c Universidad de Santiago de Chile, Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Av. Libertador B. O’Higgins 3363, Santiago, Chile article info Article history: Received 17 June 2014 Received in revised form 5 August 2014 Accepted 6 August 2014 Available online 23 August 2014 Keywords: Active chlorine DSA anode Water treatment Oxidants determination Electrochemical behavior abstract In the present work, the evolution of chlorine-related species was investigated by cyclic voltammetric, polarization and electrolytic analyses in order to establish whether their formation and consumption related to either chemical or electrochemical reactions. This study was performed at Ti/Ru 0.3 Ti 0.7 O 2 anode by adding known concentrations of Cl  in solution by applying different current densities. The results demonstrated that dissolved Cl 2 , HClO, ClO  , chlorite, chlorine dioxide and chlorate can be electrochem- ically formed. The concentration trends of dissolved Cl 2 and chlorite indicated that the electrochemical route was responsible for their presence in the bulk solution, and these active species are responsible of the formation of the other chlorine species. By using Ti/Ru 0.3 Ti 0.7 O 2 as anode, the efficient treatment of real effluent was favored by applying 25, 50 and 75 mA cm 2 in presence of NaCl (1.25 g L 1 ), achieving higher elimination of organic matter, ranging from 80% to 86%. Results clearly have demonstrated that the oxygen evolution inhibition depends predominantly on the specific electrochemical species formed in association with pH, nature of electrode and applied current. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction As environmental regulations become stringent, new and novel processes for efficient treatment of various kinds of wastewater at relatively low operating cost are needed. The decontamination and disinfection of waters by means of direct or integrated electro- chemical processes are being considered as a very promising alter- native due to the significant improvement of the electrode materials and the coupling with low-cost renewable energy sources [1]. The application of electrochemical technologies to environmen- tal pollution abatement has been the topic of several books and authoritative reviews [2–9]. The main electrochemical procedures utilized for the remediation of wastewaters are electrocoagulation, electroreduction, electroflotation, electrochemical oxidation and indirect electro-oxidation with active oxidants, so-called mediated electrochemical oxidation. Recently, the treatment by emerging technologies such as electro-Fenton and photoassisted systems like photoelectro-Fenton and photoelectrocatalysis has also received great attention [3]. The electrochemical treatment by direct or indirect approaches, is based on the elimination of pollutants directly on the anode sur- face, via production of d OH [9–11] or/and other oxidants, such as chlorine, (per)bromate, persulfate, ozone, hydrogen peroxide, per- carbonate, and others, directly on-site using only water, salt, and energy. In the case of active chlorine, the interest in this oxidant is based on the ubiquitous presence of chloride ions in a certain number of effluents and natural waters, making possible the involvement of active chlorine during electrochemical treatment; and the chemistry and electrochemistry of higher oxidation states for chlorine close to neutral pH [6,7]. However, the addition of electrolyte is inevitable if the wastewater sample is not sufficiently conducting. In many cases, the electrolyte is deliberately added to enhance the degradation process and several studies have employed NaCl as the salt to increase the conductivity [6,7,9]. Several mixed metal oxide electrodes have been used in the electrochemical wastewater treatment by indirect electrochemical http://dx.doi.org/10.1016/j.jelechem.2014.08.008 1572-6657/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: carlosmh@quimica.ufrn.br (C.A. Martínez-Huitle). Journal of Electroanalytical Chemistry 731 (2014) 145–152 Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem