Separation and Purification Technology 76 (2010) 146–150 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Oxidant availability in soil and its effect on HCB removal during electrokinetic Fenton process Anshy Oonnittan a,∗ , Pirjo Isosaari a,b , Mika Sillanpää a,c a Laboratory of Applied Environmental Chemistry, University of Eastern Finland, Patteristonkatu 1, FI-50100 Mikkeli, Finland b Department of Civil and Environmental Engineering, Aalto University School of Science and Technology, P.O. Box 16200, FI-00076 Aalto, Finland c Faculty of Technology, Lappeenranta University of Technology, Patteristonkatu 1, FI-50100 Mikkeli, Finland article info Article history: Received 16 August 2010 Received in revised form 29 September 2010 Accepted 29 September 2010 Keywords: Electrokinetics Fenton’s reagent Soil–oxidant interaction Hexachlorobenzene HCB Soil remediation abstract Electrokinetic technology in its various forms has already shown its potential as a promising technology for the remediation of organic compounds in soil. Efforts to improve and optimise the process have even- tually led to the coupling of electrokinetics with other remediation techniques like chemical oxidation. This paper reports the results of a series of electrokinetic Fenton experiments carried out to investigate the effect of oxidant delivery and availability on contaminant removal and its subsequent impact on the treatment duration. In doing so, we have tried to show that the treatment duration can be consid- erably reduced by the proper introduction of the oxidants to the soil for a better oxidant availability throughout the soil section. Experiments were conducted at laboratory scale using kaolin spiked with hexachlorobenzene (HCB). Though each experiment resulted in different removal rates, under specific experimental conditions, a maximum of 57% contaminant removal was obtained. However, the oxidation reactions in these experiments did not show any pH dependence in the range 2.9–5. A more uniform and better HCB degradation was possible in a shorter duration by the proper introduction of oxidant into the soil. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Coupled technologies are now increasingly being researched due to their potential for achieving better remediation goals and operational performances. Various research groups have estab- lished the success of electrokinetic technology for the remediation of low permeable soil contaminated with heavy metals and organic compounds at laboratory level [1–3]. Though, laboratory scale stud- ies have been in progress since nineties, published reports suggest that only few case studies and field performances have been done so far [4]. The growing awareness of the risks, both ecological and to human health, posed by persistent organic pollutants (POPs) in soil has put the research community in a constant search for effective and efficient ways to address the limitations of existing technologies for the remediation of soil. One such approach has led to the integration of electrokinetics with Fenton oxidation for the remediation of POPs in soil [5–7]. Fenton oxidation has proved to be effective for the remediation of soil contaminated with organic ∗ Corresponding author at: Laboratory of Applied Environmental Chemistry, Patteristonkatu 1 FIN-50100, Mikkeli, Finland. Tel.: +358 445567480; fax: +358 153556513. E-mail addresses: anshy.plamthottathil@uef.fi, anshy o@yahoo.com (A. Oonnittan). compounds [8–11]. The attractiveness of this coupled technology is that it addresses one of the major shortcomings of electroki- netic remediation by removing as well as destroying/degrading the contaminants, thus avoiding a further treatment or disposal of the waste stream. Also, Fentons oxidation is capable of oxidising the most recalcitrant organic compounds [12–15]. Electrokinetic Fenton process can be regarded as a relatively clean technology, since it employs a mixture of hydrogen peroxide and ferrous salts to achieve the remediation. Hydrogen peroxide which is environ- mentally benign is easily available, cheap and used commonly in various applications in environmental engineering [15,16]. The conventional Fenton’s reagent comprises of low concentra- tion hydrogen peroxide (H 2 O 2 ) and ferrous salts. In the presence of an oxidising substance the Fenton’s reagent generates hydroxyl radicals at the specified reaction conditions [17]. These hydroxyl radicals are active in aqueous form and hence are unable to attack sorbed contaminants [18]. However, the use of high concentra- tion hydrogen peroxide to oxidise sorbed contaminants is well documented [9,12]. This is because the use of high concentra- tions of H 2 O 2 that favours the generation of highly reactive species other than hydroxyl radical like hydroperoxide radicals (HO* 2 ), superoxide anions (O 2 * - ) and hydroperoxide anions (HO 2 * - ). The generation of these non hydroxyl radicals in the presence of high concentration hydrogen peroxide leads to aggressive reaction con- ditions which ultimately destroy the sorbed contaminants [19,20]. 1383-5866/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2010.09.034