Modeling of Heavy Metals Transport in High Acid Buffering Soil during Electrokinetic Remediation

This paper addresses the soil-contaminant-water interactions in a high acid buffering soil during electrokinetic remediation. A one-dimensional transport model was developed to predict the transport and speciation of heavy metals (chromium, nickel, and cadmium) in high acid buffering glacial till soil during electrokinetics. The developed model assimilates geochemical reactions into electrokinetic transport modeling. The transport model incorporates: (1) presence of carbonates in soil; (2) adsorption of contaminants to soil surface; and (3) synergistic effects of multiple chemical species on contaminant transport during electrokinetic remediation. The model was validated with bench-scale electrokinetic experiments. The predicted pH profiles, electroosmotic flow, and contaminant distribution of chromium, nickel, and cadmium in glacial till soil during electrokinetic remediation were found to agree with the experimental results. The model also predicted the contaminant speciation and form (aqueous, adsorbed, and precipitated) in soil during electrokinetics. The model showed that chemical precipitation and adsorption are, respectively, the main fixation mechanisms for the cationic (nickel cadmium) and anioinic (hexavalent chromium) metals in glacial till during electrokinteic remediation. Overall, the model predictions allowed for an understanding of the transport and physico-chemical processes that control electrokinetic remediation of high acid buffering contaminated soil.