IMPACT OF SYSTEM CHEMISTRY ON ELECTROOSMOSIS IN CONTAMINATED SOIL

Electroosmosis in a copper-contaminated kaolinite was highly sensitive to chemical treatment schemes designed to remove the contamination. Nonuniform profiles of electric field intensity and pH as well as negative pore-water pressure develop during sustained electrokinetic treatment of clays. These nonlinearities and nonuniform pore-water pressures cannot be adequately described by classical analysis. Classical analysis is based on assumptions of a uniform and constant electroosmotic permeability coefficient, for instance. An extended capillary model which includes nonuniform contributions to electroosmosis and pore pressures that vary with space and time, is developed and compared with experimental findings. Subtle changes in initial and boundary conditions of the system chemistry have a very large effect on electroosmosis in soils. For instance, acid addition at the cathode reservoir may cause reversal of the direction of electroosmotic flow. Other species, such as the citrate, may form stable complexes with copper ions, thus reducing the impact of copper on the zeta potential of the clay. The model is used to simulate these effects.