Mechanism and kinetic study for the degradation of lindane by photo-Fenton process Ines Nitoi a , Tatiana Oncescu b , Petruta Oancea b, * a National Research & Development Institute for Industrial Ecology – ECOIND, Sos. Panduri 90-92, Bucharest 050663, Romania b Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Elisabeta 4-12, Bucharest 030016, Romania 1. Introduction g-HCH, also called lindane, the active component of HCH technical insecticide, had been widely used in agriculture throughout the world since the 1940s. The production and agricultural use of lindane are the primary causes of environmental contamination [1]. The production of lindane generates large amounts of waste hexachlorocyclohexane isomers, and it is estimated that every ton of lindane manufactured produces about 9 tons of toxic waste [2]. The traditional treatment technologies applied for the removal of pesticide from contaminated ground/wastewater, such as coagulation, flocculation, membrane separation or adsorption on activated carbon, only do a phase transfer of the pollutant. A modern oxidation technology like the photo-Fenton process has been applied for the degradation of several classes of pesticides and refractory compounds [3–5]. Generally, Fenton process involves application of iron salts and hydrogen peroxide to produce hydroxyl radicals. This reaction is spontaneous and can occur without the influence of light [4]. Fe 2þ þ H 2 O 2 ! Fe 3þ þ HO  þ OH  (1) This reagent is an attractive oxidative system for wastewater treatment due to the fact that iron is very abundant and non-toxic element and hydrogen peroxide is easy to handle and environ- mentally safe. The rate of pollutants degradation can be consider- ably increased via photochemical reaction in the UV/Fenton processes [6–8]. In this case the regeneration of Fe 2+ , with production of new  OH radicals, follows a photoreduction process: Fe 3þ þ H 2 O ! FeðHOÞ 2þ þ H þ (2) FeðOHÞ 2þ þ hn ! Fe 2þ þ HO  (3) In photo-Fenton process, in addition to the above reactions, the formation of hydroxyl radicals occurs also by the following reactions: Fe 3þ þ H 2 O þ hn ! HO  þ Fe 2þ þ H þ (4) H 2 O 2 þ hn ! 2HO  (5) Prior studies have shown that g-HCH undergoes dehydrochlo- rination in heterogeneous catalytic reduction system with Pd/C, Pt/ C and Roney-Ni [9] and with Pd/Al 2 O 3 [10] to yield benzene as the major final product. In addition, the photochemical transformation of lindane in the presence of humate-coated a-Fe 2 O 3 has been reported also [11]. Other studies revealed that lindane is very resistant to degradation by ozonation [12]. Only a few studies like Nienow et al. [13] focused on the application of advanced oxidation processes for lindane degradation in UV/H 2 O 2 system, limited data being available for photo-Fenton degradation of g-HCH (lindane). Journal of Industrial and Engineering Chemistry 19 (2013) 305–309 A R T I C L E I N F O Article history: Received 13 June 2012 Accepted 19 August 2012 Available online 24 August 2012 Keywords: Lindane Photo-Fenton Kinetic model Advanced oxidation processes A B S T R A C T Because application of classical treatment methods cannot allow an easily Lindane (gamma 1a,2a,3b,4a,5a,6b-hexachlorocyclohexane) degradation, development of more powerful water treatment techniques, like advanced oxidation processes (AOPs), was necessary. The degradation of lindane (g-HCH) has been studied using the photo-Fenton reaction. The degradation kinetics under irradiation was optimized in respect to H 2 O 2 concentration and Fe 2+ concentration at a constant lindane concentration. The degradation rate follows pseudo-first order kinetics with respect to lindane and organic clorine mineralization. Application of photo-Fenton system also assures total organic carbon removal with 95% efficiency at 2 h irradiation. The possible pathways of lindane photodegradation is also proposed. ß 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: petrutaoancea73@yahoo.com (P. Oancea). Contents lists available at SciVerse ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec 1226-086X/$ – see front matter ß 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jiec.2012.08.016