Electrodialytic remediation of soils polluted with Cu, Cr, Hg, Pb and Zn

Abstract

Electrodialytic remediation of heavy metal polluted soil is a method which combines the technique of electrodialysis with the electromigration of ions in the polluted soil. Results from laboratory-scale remediation experiments of soil samples from three real contaminated sites with di †erent heavy metals are presented. In the three cases it was possible to mobilize and reduce the amount of the pollutants in the soil. The pollutants were (1) copper and chromium, (2) mercury and (3) copper, lead and zinc. For a loamy sand polluted with copper and chromium it was possible to decontaminate the soil to an extent lower than the recommended critical values for metal concentration in soil. Parameters that were identiÐed as important for the efficiency of the electrodialytic remediation method were pH in the soil, lime content and speciation of the heavy metal.

Electrokinetics and soil decontamination: concepts and overview (Review)

“…Korfiatis et al [91] used an experimental approach to assess the relative magnitudes of hydraulic and electro-osmotic permeability under application of hydraulic or electric gradients or both and to study the extent of pH changes during the electro-osmotic process. The practical and theoretical aspects of ion exchange resins and membranes have been investigated by Hansen [85,92]. Acar et al [30] estimated the electroosmotic permeability in kaolinite to be in the range of 0.80 × 10 -5 to 3.0 × 10 -5 cm 2 V -1 s -1 which is within the range reported in the literature.…”

“…Their study found that decontamination of soil was to an extent lower than the recommended critical values for metal concentration in soil. The elctrochemical analysis of ion-exchange membrane with respect to a possible use in electrodialytic decontamination of soil polluted with heavy metals was also studied by Hansen et al [85]. Their study revealed that cation-exchange membranes show the transport number of average 0.97 in NaCl and CaCl 2 solutions and anion-exchange membranes about 0.95 in NaCl, CaCl 2 and ZnCl 2 solutions.…”

“…A number of important apparatuses that have been used for soil remediation by electrokinetics are mentioned here. The apparatuses currently available for the purpose of electrokinetic remediation include those developed at Louisiana State University [31,79], Lehigh University [52,80,81], University of Texas at Austin [11,82], the University of California at Berkeley [3,83], Massachusetts Institute of Technology [38,47,59], Texas A & M University [6], The Technical University of Denmark [84,85], Vanderbilt University, Nashville, Tennessee [86], Royal Institute of Technology, Stockholm, Sweden [87][88][89], University of South Carolina [58] and many others. A comprehensive review of the apparatus used in the EKD experiments has been presented by Yeung et al [6].…”

“…Their study found that 55 % of lead removal across the soil precipitated within the last 2 cm close to the cathode, 15 % left in the soil before reaching this zone, 20 % precipitated on the fabric separating the soil from cathode and 10 % unaccounted. Hansen et al [84] investigated the removal of Cu, Cr, Hg, Pb and Zn from sandy loam by electrodialysis. Their study found that decontamination of soil was to an extent lower than the recommended critical values for metal concentration in soil.…”

A Review Article: Electrokinetic Bioremediation Current Knowledge and New Prospects

“…The conventional techniques include the use of an ion selective membrane such as cation-exchange membrane, which prevents the transport of the hydroxide ions from the cathode to the soil as shown in Figure 1 [57], continuous changing/removing of the solution in the electrode compartments [58], addition of chemical conditioning agents such as ethylenediaminetetraacetic (EDTA) [59] [60], acetic acid [55], and nitric acid [61]. Innovative techniques on the other hand include a stepwise moving anode [62] [63], polarity exchange [12] [64], circulation of an electrolyte (anolyte and catholyte) solution in the electrode compartments (see Figure 2) [35] [43] [65], and the two anodes technique (TAT) (see Figure 3) which has investigated the control of the advancement of the acid and the base fronts.…”