Contents lists available at ScienceDirect Catalysis Today journal homepage: www.elsevier.com/locate/cattod Optimization of electro fenton process for effective degradation of organochlorine pesticide lindane Carmen M. Dominguez a,b, ⁎ , Nihal Oturan b , Arturo Romero a , Aurora Santos a , Mehmet A. Oturan b, ⁎ a Dpto Ingeniería Química, Facultad de Ciencias Químicas, Universidad Complutense Madrid, Ciudad Universitaria S/N. 28040, Madrid, Spain b Université Paris-Est, Laboratoire Géomatériaux et Environnement, EA 4508, UPEM, 5 Bd Descartes, 77454 Marne-la-Vallée Cedex 2, France ARTICLE INFO Keywords: Lindane Hexachlorocyclohexane Electro-Fenton BDD Carbon felt Hydroxyl radicals ABSTRACT Lindane is an organochlorine pesticide broadly used in the last decades. It is persistent and recalcitrant in aquatic environments and difficult to biodegrade. This study is focused on the complete degradation of lindane by an electrochemical advanced oxidation process, the electro-Fenton (EF) process, using a BDD anode and carbon felt (CF) cathode. The influence of the main operating parameters, i.e., applied current intensity (50–1000 mA), catalyst concentration (0.0–0.5 mM) and initial pollutant concentration (5.0–10.0 mg L -1 ) has been investigated and optimized. The applied current plays a determinant role both in oxidation of lindane and mineralization of its aqueous solution. Taking into account the mineralization current efficiency (MCE) and the specific energy consumption (EC), the applied current of 400 mA was found to be the most convenient value. Catalyst (Fe 2+ ) concentration as low as 0.05 mM, promotes efficiently H 2 O 2 decomposition into hydroxyl radicals improving the efficiency of the process and minimizing the involvement of parasitic reactions. The initial pollutant con- centration does not affect the performance of the process. At the optimum operating conditions, the complete degradation of 10 mg L -1 lindane solution and 80% of TOC removal were achieved at 15 min and 4 h, re- spectively. 1. Introduction The extensive use of synthetic organochlorine pesticides (OCPs) in the agricultural sector during the last decades has led to their occur- rence in aquatic, soil and air environment throughout the world. OCPs are toxic and bioaccumulative persistent organic pollutants and re- present a great environmental concern nowadays [1,2]. Among them, lindane (γ-hexachlorocyclohexane) has been widely used on fruit, grain and vegetable crops and in warehouses for insect-borne disease control [3] since the Second World War until the 1990s [4,5], making this compound one of the most frequently detected chlorinated con- taminants in the environment [6]. Lindane can be detected in water in a quite broad range depending on the use of this pesticide in a given area: from ng L -1 in natural water [7] to near its water solubility (10 mg L -1 ) when polluted water comes directly from the washing of the solid product (HCH residues were often stockpiled in open piles) or by the dissolution of dense non aqueous phase liquid of this compound. Due to its high toxicity lindane brings potential health risks to humans and animals (skin irritation, dizziness, headaches, diarrhea, nausea, vomiting, convulsions, possible changes in the levels of sex hormones in the blood and eventually, even death) [8]. Its low aqueous solubility, relative high stability, lipophilicity and chlorinated nature contribute to its environmental persistence and resistance to degradation. Lindane has been classified as a potential carcinogen to human’s beings by the International Agency for Research on Cancer (IARC) [9] and as neu- rotoxic, carcinogen and teratogen by the Environmental Protection Agency (EPA) and World Health Organization (WHO) [10] resulting in its final inclusion (along to α- and β-HCH) in the list of persistent or- ganic pollutants (POPs) in the Stockholm Convention in 2009 [11]. Therefore, the development of viable treatments for the removal of such a contaminant has become a priority for the scientific community. The main industrial process for lindane destruction involves thermal oxidation at 1000 °C, an expensive treatment that can lead to the for- mation of highly toxic by-products such as dioxins and furans [12,13]. This fact, coupled with the refractory nature of lindane, has driven the development of advanced technologies for its destruction. Due to the high chloride content of the lindane molecule, reduction over zero valent metals was employed as a promising alternative, zero valent iron (ZVI) being the most common metal used [14]. In the pre- sence of ZVI microparticles (ZVIm), lindane is completely dechlorinated obtaining benzene and chloride as final products [15]. ZVIm showed excellent stability and the presence of the most common salts in http://dx.doi.org/10.1016/j.cattod.2017.10.028 Received 14 August 2017; Received in revised form 11 October 2017; Accepted 24 October 2017 ⁎ Corresponding authors at: Dpto Ingeniería Química, Facultad de Ciencias Químicas, Universidad Complutense Madrid., Ciudad Universitaria S/N. 28040, Madrid, Spain. E-mail addresses: carmdomi@ucm.es, cm.domingueztorre@ucm.es (C.M. Dominguez), mehmet.oturan@univ-paris-est.fr (M.A. Oturan). Catalysis Today xxx (xxxx) xxx–xxx 0920-5861/ © 2017 Published by Elsevier B.V. Please cite this article as: Domínguez, C.M., Catalysis Today (2017), http://dx.doi.org/10.1016/j.cattod.2017.10.028