ORIGINAL PAPER Integrated electrokinetic-soil flushing to remove mixed organic and metal contaminants Krishna R. Reddy • Claudio Cameselle • Prasanth Ala Received: 22 July 2009 / Accepted: 29 January 2010 / Published online: 18 February 2010 Ó Springer Science+Business Media B.V. 2010 Abstract The integrated use of hydraulic flushing and electrokinetic treatment was investigated for the remedia- tion of silty sand contaminated by both PAHs and heavy metals. The soil was collected from a polluted former manufactured gas plant (MGP). Four bench-scale experi- ments were conducted to analyze the ability of the com- bined hydraulic flushing and the electrokinetic treatment for the simultaneous removal of PAHs and heavy metals. Sequential flushing with ethylenediaminetetraacetic acid (EDTA) or Igepal CA-720 were tested with or without the simultaneous application of a low intensity direct electric field (1 VDC cm -1 ). The best results were obtained with 0.2 M EDTA flushing in two stages (without and with voltage gradient, 1 VDC cm -1 ), followed by 5% Igepal flushing in two stages (without and with 1 VDC cm -1 ). Heavy metals were removed mainly during the EDTA flushing, with removal efficiencies of about 60% for Zn, 80% for Pb, and 30% for Cu. During Igepal flushing, no heavy metals were removed, but PAHs were removed, including 40% phenanthrene, 30% pyrene, and 20% ben- zo[a]pyrene. Overall, this study showed that a carefully designed sequential hydraulic flushing scheme with selec- ted chelant and surfactant is needed for the removal of both heavy metals and PAHs from MGP silty sands. Combining electrokinetics with hydraulic flushing may not necessarily improve contaminant removal from such soils. Keywords Remediation Á Pollution Á Soil Á Heavy metals Á PAHs Á Flushing Á Electrokinetics 1 Introduction In 1940 and 1950s, many manufactured gas plants (MGPs) in the United States were closed [1]. An estimate by Larsen [2] indicated that there may be more than 5,000 former MGP sites across the US that are posing significant envi- ronmental threat and require immediate remediation action. A major factor complicating the cleanup of many of these sites is the co-occurrence of organics, such as polycyclic aromatic hydrocarbons (PAHs), and heavy metals, such as lead, zinc and nickel [3–5]. Treatment processes usually employed for contaminated soils include chemical oxida- tion, biodegradation, thermal desorption, and incineration [6–10], but these processes do not always yield satisfactory results, especially in the case of soils with low hydraulic permeability or those soils contaminated by mixed organic–inorganic wastes. Therefore, the development of processes and technologies for the simultaneous remedia- tion of soils contaminated by heavy metals and organics has emerged as an important area of current research in soil remediation research field. Electrokinetic remediation has been used for the reme- diation of many soils contaminated with heavy metals for the last 20 years with high efficiency [11–13]. The elec- trokinetic treatment has been recognized as an efficient in situ process for the remediation of contaminated soils containing organic contaminants [14–17]. Recently, sev- eral attempts were carried out to test the ability of K. R. Reddy Á P. Ala Department of Civil and Materials Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, IL 60607, USA e-mail: kreddy@uic.edu C. Cameselle (&) Department of Chemical Engineering, University of Vigo, University Campus, Fundicion Building, 36310 Vigo, Spain e-mail: claudio@uvigo.es 123 J Appl Electrochem (2010) 40:1269–1279 DOI 10.1007/s10800-010-0102-1