COUPLED ELECTROKINETICS-ADSORPTION TECHNIQUE FOR SIMULTANEOUS REMOVAL OF HEAVY METALS AND ORGANICS FROM SALINE-SODIC SOIL

In situ remediation technologies for contaminated soils are faced with significant technical challenges when the contaminated soil has low permeability. Popular traditional technologies are rendered ineffective due to the difficulty encountered in accessing the contaminants as well as when employed in settings where the soil contains mixed contaminants such as petroleum hydrocarbons, heavy metals and polar organics. This mixed contaminants scenario could produce synergistic or antagonistic effects on removal of the respective contaminants. Though electrokinetic methods have proven to be more effective than most traditional techniques used in remediating low permeability soils contaminated with mixed contaminants, there are still challenges - the application of optimal voltage gradient and the effective remediation of sodic soil (high acid buffering and alkaline). In this study, an integrated in situ remediation technique which couples electrokinetics with adsorption, using locally produced granular activated carbon from date palm pits in the treatment zones that are installed directly to bracket the contaminated soils at bench-scale is investigated. Natural sodic clay soil sampled from a coastal area, spiked with contaminant mixture (kerosene, phenol, Cr, Cd, Cu, Zn, Pb and Hg) was used in this study to investigate the efficiency of contaminant removal. The heavy metals digested from the samples were analyzed using flame atomic absorption spectrometry, whereas the organics were extracted using accelerated solvent extractor and injected into gas chromatography mass spectrometry for analytical quantification. From the results obtained, the overall adsorption selectivity sequences for the single and multi-component scenarios are Cr > Pb > Cu > Cd > Zn and Cr > Cu > Pb > Cd > Zn respectively. For the 21-day period of continuous electrokineticsadsorption experimental run, efficiency for the removal of Zn, Pb, Cu, Cd, Cr, Hg, phenol and kerosene were found to reach 26.8, 55.8, 41.0, 34.4, 75.9, 87.1, 100.0 and 49.8 % respectively. The results obtained suggest that integrating adsorption into electrokinetic technology is a promising solution for removal of contaminant mixture from sodic soils.