Models and experiments on electrokinetic removal of Pb(II) from kaolinite clay

Numerical and experimental studies were conducted to understand the Pb(II) transport through the fine-grained soil of low-hydraulic permeability under electrical fields. The numerical model involved multi-component species transport under coupled chemical and electrical potential gradients and incorporated several chemical reactions occurring within the kaolinite clay during the processing, such as aqueous phase reaction, adsorption, and precipitation. The model also emphasized physicochemical factors such as soil pH and zeta potential, which vary with location and processing time and directly affect the transport of species. The model predicted the soil pH distribution as well as the transport and fate of Pb(II). The validity of the model was confirmed by comparing the model prediction with experimental results. The model simulation and experimental results, using unenhanced and enhanced tests, clearly demonstrated that the change in pH within the soil specimen is a crucial factor affecting the solubilities of Pb(II) and its adsorption to the soil, resulting in governing the removal of Pb(II) by electrical fields. This study confirms that enhancement methods should be considered to control soil pH, in order to improve electrokinetic removal of heavy metal contaminants.