Inhibition characteristics of the electrokinetic removal of inorganic contaminants from soil due to evolution of the acidic and alkaline fronts

This study comprehensively investigates the inhibition characteristics of the electrokinetic removal (EKR) of inorganic pollutants from soil due to evolution of the acidic and alkaline fronts (EAAF). The effects of EAAF on the ion strength of the soil pore fluid, potential distribution, soil colloids, clay minerals, and soil microstructure are systematically examined, in addition to the control effects of non-target charged species on the removal of target pollutants. The results show that the transport of target species near the anode region is mainly inhibited by potential flattening, soil colloid aggregation, and the closure of soil pores. Migration near the cathode region is mainly inhibited by the immobile chemical states of metals, potential flattening, soil dehydration, and a high soil adsorption ability owing to the relatively developed pores. This results also show that H+, OH-, and soluble Al have a significantly control effect on the macroscopic dynamics of EKR of the target contaminants. The injection of acidic solution near the cathode alleviates the potential jump and prevents the formation of metal hydroxides to some extent. The average removal rates of nitrate, Pb, and Cd after EKR improved from 85.5%, 11.1%, and 21.8–98.5%, 35.8% and 47.7%, respectively.