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An innovative upward electrokinetic soil remedial (UESR) technology was proposed to simultaneously remove heavy metals and organic contaminants from contaminated soils. The proposed technology was demonstrated to be effective through a series of laboratory scale experiments on clayey soils. In the UESR systems, rode-shaped anode was inserted into the bottom of the soil and ring-shaped cathode was placed on the soil surface to establish the non-uniform vertical electric fields in the soil. Driven by the electric fields, the contaminants were transported to the surface of the tested soil and removed via cathode effluent. As (III), Cr (III), Ni (II), Cu (II), Pb (II), Zn (II), and Cd (II) were selected as heavy metal contaminants. P-xylene (one of the BTEX compounds) and phenanthrene (one of the PAH compounds) were chosen as the target organic contaminants. Two types of kaolin clays were loaded either with heavy metals only or with a mixture of heavy metals and organic contaminants. The contaminated kaolin soils were packed into reactor cells of different sizes and treated under either constant current densities or constant voltage gradients for durations ranged from 4 to 30 days. The effects of specimen size, treatment duration, cathode chamber influent, current density, contaminants compositions, as well as soil type were investigated in 19 experiments. As(II1) and Cr(II1) were found to be the least mobile metals while Ni(II) and Cd(II) were found to be the most mobile metals. In most cases, the mobility of heavy metals followed the order Ni(II) > Cd(II) > Zn(II) = Cu(II) > Pb(II) > As(III) > Cr(III). The removal efficiencies of p-xylene in all experiments were higher than those of phenanthrene probably because p-xylene has much higher solubility than phenanthrene in water. It was found that acid flushing of the cathode electrode had significant effect on the removal of contaminants and saving of energy consumption. The upward movement of soil pore water by electroosmosis seemed to be the main mechanism that transported the organic compounds. Nevertheless, it was evident that dielectrophoresis affected the migration of phenanthrene and pore water. vi ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library

Removing heavy metals and organic contaminants from solids using an Upward Electrokinetic Soil Remedial (UESR) technology