Removal of nickel and lead from natural clay soil through the introduction of EDTA and coupling ion exchange processes with electrokinetic methodology

摘要

In clay soils having low initial pH values, electrokinetic transport of heavy metals has proven to be effective. The transport of these metals is predicated on maintaining a low pH throughout the cell, which in turn keeps the metals in the pore water phase, where they are accessible to EK transport. Development of high pH gradients in the cathode region due to the formation of OH$sp{-}$, from the dissociation of water, produces unfavorable conditions for the transport of heavy metals, namely precipitation. Standard electrokinetic methods have not been employed to a great extent in natural clayey soil. These soils tend to magnify the problems mentioned above and pose several unique problems related to remediation that currently used techniques cannot overcome. Most natural clayey soils have inherently high pH values. The use of EDTA, EK methodology and ion exchange textiles is a new hybrid technique for the enhanced solubilization, transport and localization of Pb and Ni respectively in natural clayey soils. A four-point examination of many of the important system properties related to this hybrid technique, and the effect of the textiles on these properties forms the subject of this thesis. Electrical parameters, system chemistry, enhanced solubilization and transport of EDTA and EK methods only, and the overall localization and removal efficiency of EDTA-EK-Textile experimentation. EDTA-EK methods, without textiles, produced enhanced solubility and transport of lead and nickel. Using all three techniques, solubility was enhanced and the localization and removal achieved was in the range of 90-95% of lead and nickel ions localized within 10% of the cell. This represents a significant improvement over standard EK methods (which typically have been applied only to low pH soil) and represents a viable remediation technique in natural clayey soil.