Journal of Hazardous Materials B137 (2006) 113–120 Comparison of electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil Lisbeth M. Ottosen a,∗ , Katarina Lepkova b , Martin Kubal b a Department of Civil Engineering, Kemitorvet, Building 204, Technical University of Denmark, 2800 Lyngby, Denmark b Institute of Chemical Technology, Technicka 5, Praha 6, Czech Republic Received 28 April 2004; received in revised form 6 April 2005; accepted 6 April 2005 Available online 14 March 2006 Abstract Electrokinetic remediation methods for removal of heavy metals from polluted soils have been subjected for quite intense research during the past years since these methods are well suitable for fine-grained soils where other remediation methods fail. Electrodialytic remediation is an electrokinetic remediation method which is based on applying an electric dc field and the use of ion exchange membranes that ensures the main transport of heavy metals to be out of the pollutes soil. An experimental investigation was made with electrodialytic removal of Cu from spiked kaolinite, spiked soil and industrially polluted soil under the same operational conditions (constant current density 0.2 mA/cm 2 and duration 28 days). The results of the present paper show that caution must be taken when generalising results obtained in spiked kaolinite to remediation of industrially polluted soils, as it was shown that the removal rate was higher in kaolinite than in both spiked soil and industrial polluted soil. The duration of spiking was found to be an important factor too, when attempting to relate remediation of spiked soil or kaolinite to remediation of industrially polluted soils. Spiking for 2 days was too short. However, spiking for 30 days resulted in a pattern that was more similar to that of industrially polluted soils with similar compositions both regarding sequential extraction and electrodialytic remediation result, though the remediation still progressed slightly faster in the spiked soil. Generalisation of remediation results to a variety of soil types must on the other hand be done with caution since the remediation results of different industrially polluted soils were very different. In one soil a total of 76% Cu was removed and in another soil no Cu was removed only redistributed within the soil. The factor with the highest influence on removal success was soil pH, which must be low in order to mobilize Cu, and thus the buffering capacity against acidification was the key soil characteristics determining the Cu removal rate. © 2006 Elsevier B.V. All rights reserved. Keywords: Electrodialytic remediation; Copper; Ion exchange membranes; Soil and kaolinite; Spiking 1. Introduction Electrokinetic soil remediation methods have gained interest since these methods are well suited for fine-grained soils where other methods as, e.g. soil washing or pump and treat methods are impractical or impossible to use. The electrokinetic methods are based on application of an electric dc field to the soil, and because the electric conductivity is highest in the fine fraction of the soil where also most pollutants are adsorbed, the electric field is strongest exactly where the pollution is mainly found. Electrodialytic remediation is one of the electrokinetic meth- ods, which differs in the use of ion exchange membranes for separation of soil and processing solutions. ∗ Corresponding author. Fax: +45 45 88 59 35. E-mail address: lo@byg.dtu.dk (L.M. Ottosen). To mobilize most heavy metals from soils, acidification is very effective, and for electrokinetic remediation the develop- ment of an acidic front often results in a successful remediation. In order to remove heavy metals from the whole soil volume it is necessary to prevent development of an alkaline front in the opposite direction. For example, Suer et al. [1] showed, that heavy metals precipitate into forms that fall into the residual frac- tion of a sequential extraction (i.e. to the hardest bound fraction) in the alkaline zone. In electrodialytic remediation development of an alkaline front is prevented with a cation exchange mem- brane. Electrokinetic remediation of spiked kaolinite has been studied extensively in laboratory scale, e.g. Refs. [2,3]. Sev- eral models have been developed, too, e.g. a mathematical model for multicomponent species transport under coupled hydraulic, electric and chemical potential differences [4] and a two-dimensional model for electrokinetic remediation of Cu 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2005.04.044