Influence of solubilizing agents (cyclodextrin or surfactant) on phenanthrene degradation by electro-Fenton process e Study of soil washing recycling possibilities and environmental impact Emmanuel Mousset a , Nihal Oturan a , Eric D. van Hullebusch a , Gilles Guibaud b , Giovanni Esposito c , Mehmet A. Oturan a, * a Universite ´ Paris-Est, Laboratoire Ge ´omate ´riaux et Environnement (EA 4508), UPEMLV, 77454 Marne-la-Valle ´e, France b Universite ´ de Limoges, Groupement de Recherche Eau Sol Environnement (EA 4330), Faculte ´ des Sciences et Techniques, 123 Avenue A. Thomas, 87060 Limoges Cedex, France c University of Cassino and the Southern Lazio, Department of Civil and Mechanical Engineering, Via Di Biasio, 43, 03043 Cassino, FR, Italy article info Article history: Received 14 June 2013 Received in revised form 14 September 2013 Accepted 20 September 2013 Available online 7 October 2013 Keywords: PAHs HPCD Tween 80 Advanced oxidation processes Recycling Bioassays abstract One of the aims in soil washing treatment is to reuse the extracting agent and to remove the pollutant in the meantime. Thus, electro-Fenton (EF) degradation of synthetic soil washing solutions heavily loaded with phenanthrene was suggested for the first time. Two solubilising agents hydroxypropyl-beta-cyclodextrin (HPCD) and Tween 80 Ò (TW 80) were chosen as cyclodextrin (CD) and surfactant representatives, respectively. In order to reuse HPCD and to degrade the pollutant simultaneously, the following optimal parameters were determined: [Fe 2þ ] ¼ 0.05 mM (catalyst), I ¼ 2000 mA, and natural solution pH (around 6), without any adjustment. Only 50% of TW 80 (still higher than the critical micelle con- centration (CMC)) can be reused against 90% in the case of HPCD while phenanthrene is completely degraded in the meantime, after only 180 min of treatment. This can be explained by the ternary complex formation (Fe 2þ -HPCD-organic pollutant) (equilibrium constant K ¼ 56 mM 1 ) that allows  OH to directly degrade the contaminant. This confirms that Fe 2þ plays an important role as a catalyst since it can promote formation of hydroxyl radicals near the pollutant and minimize HPCD degradation. After 2 h of treatment, HPCD/ phenanthrene solution got better biodegradability (BOD 5 /COD ¼ 0.1) and lower toxicity (80% inhibition of luminescence of Vibrio fischeri bacteria) than TW 80/phenanthrene (BOD 5 / COD ¼ 0.08; 99% inhibition of V. fischeri bacteria). According to these data, HPCD employed in this integrated (soil washing þ EF degradation) approach gave promising results in order to be reused whereas the pollutant is degraded in the meanwhile. ª 2013 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: þ33 149 32 90 65. E-mail addresses: Mehmet.oturan@univ-paris-est.fr, oturan@univ-mlv.fr (M.A. Oturan). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 48 (2014) 306 e316 0043-1354/$ e see front matter ª 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.watres.2013.09.044