Journal of Hazardous Materials 179 (2010) 1156–1160 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Short communication Electrokinetic remediation of PAH mixtures from kaolin M.T. Alcántara, J. Gómez, M. Pazos, M.A. Sanromán ∗ Department of Chemical Engineering, University of Vigo, E-36310 Vigo, Spain article info Article history: Received 2 December 2009 Received in revised form 2 February 2010 Accepted 3 March 2010 Available online 9 March 2010 Keywords: PAHs Surfactant Tween 80 Fluoranthene Pyrene Benzanthracene Electro-osmotic flow abstract Because of increased industrialisation and new manufacturing processes, elevated amounts of organic pollutants are released into the environment. Hydrophobic organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), are toxic and persistent contaminants that are not treatable by natu- ral attenuation. In this work, electroremediation is proposed for cleaning soil contaminated by organic compounds. Model samples of kaolin clay polluted with a mixture of PAHs (fluoranthene, pyrene, and benzanthracene) were treated. Electroremediation of kaolin contaminated with a mixture of these three PAHs was carried out using a solution of 1% Tween 80 and 0.1 M Na 2 SO 4 as the processing fluid. Under these conditions, low removal was obtained. However, by using the same processing fluid and controlling the pH at 7 in the anode chamber, high electro-osmotic flow was detected. After the treatment, removal of around 40% of the PAHs was achieved. The created environment inside the soil during the electroki- netic treatment greatly influenced the process. The results of this work reveal the high potential for the application of the electroremediation process on soil polluted with different PAHs. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Due to increased industrialisation and manufacturing processes, elevated amounts of organic pollutants are released into the envi- ronment. The permanence of organic compounds inside the soil depends on the type and characteristics of the pollutant as well as the properties of the solid matrix. Some organic pollutants can be degraded inside the soil by indigenous microorganisms [1]. However, hydrophobic organic contaminants (HOC) comprise a large group of toxic and persistent contaminants that are not suit- able to be treated by natural attenuation. The low solubility of these compounds hinders their accessibility to microorganisms for bio-degradation. A well-known group of these pollutants is polycyclic aromatic hydrocarbons (PAHs), a class of organic sub- stances consisting of two or more fused benzene rings made up of carbon and hydrogen atoms. These compounds are formed dur- ing the thermal decomposition and subsequent recombination of organic molecules. They exhibit recalcitrant and strong muta- genic/carcinogenic properties to living beings [2]. Because of these recalcitrant contaminants, new techniques must be developed to remove them from the soil. Recently, electrokinetic remediation of soil contaminated with organic com- pounds has shown encouraging results in soil restoration [3–9]. This technique, originally used for heavy metal extraction, utilises electric current to promote the movement of contaminants. During the electrokinetic treatment of soil, contaminants are transported ∗ Corresponding author. Tel.: +34 986 812383; fax: +34 986 812380. E-mail address: sanroman@uvigo.es (M.A. Sanromán). towards the electrodes by electromigration (migration of ions towards the oppositely charged electrode) and electro-osmosis (movement of liquids relative to the charged particles) [10]. How- ever, some modifications of this technique are needed to effectively remove PAHs. The low water solubility, hydrophobicity, and slow desorption rates of PAHs make their removal difficult from sub- surface environments using traditional electrokinetic remediation technology. Enhanced PAH desorption from the polluted soil and a favourable environment for transport towards the electrode cham- bers are needed. The use of surfactants as solubilising agents has been shown to be adequate for improving electrokinetic treatments [5,6,11–13]. However, most of the research on electrokinetics has been assayed in soil contaminated with a single PAH. Surfactants are chemical compounds that consist of a strongly hydrophilic group as the head of the molecule and a strongly hydrophobic group as the tail. The hydrophilic group allows for surfactants to exhibit high solubility in water, while the hydrophobic group associates preferentially with hydrophobic molecules, such as PAHs. In electrokinetic treatments, nonionic surfactants are generally chosen because of their higher solubilisation capacities and economic value when compared to cationic and anionic ones. In addition, nonionic surfactants are safer to use due to their higher biodegradability in natural environments [14,15]. During the electroremediation process, these agents can be added directly into the soil or to the electrode chamber solutions; then, they are introduced into the soil by electro-osmosis and/or electromigration. In this work, the electrokinetic technique was employed to clean soil contaminated by organic compounds using model samples of kaolin clay polluted with a mixture of PAHs. Three PAHs, fluo- 0304-3894/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.03.010