Coupling Electrokinetics and Phytoremediation to Remove Uranium from Contaminated Soil: A Laboratory Pilot-Scale Study

Abstract

Uranium is a naturally occurring trace element and radionuclide. Uranium is introduced to the environment anthropogenically as a result of industrial, military, and nuclear energy activities. The approach of coupled electrokinetic phytoremediation has been used to remove other heavy metals from contaminated soil. The objectives of this study are to investigate the distribution and solubility of uranium in soils with UO 2 , UO 3 , and uranyl and to examine the processes of coupled electrokinetic phytoremediation in removing U from soils with perennial ryegrass at a laboratory pilot scale. A low-intensity direct electric current field (typically 2 V•cm −1 ) was applied to the contaminated soil for 7 d at 8 h•d −1 after ryegrass was grown for 2 weeks, and then, polarity reversal was employed for another 7 d at 8 h•d −1 . The uranium redistribution took place among various solid-phase components due to changes in the pH and the chemistry of the electrolyte solution. The electrokinetic field (EKF) increased the U bioavailability in soils as water-soluble U and exchangeable U in contaminated soils with all U species. Thus, the EKF significantly increased the U uptake and bioaccumulation by ryegrass. The current laboratory pilot-scale test confirmed our previous observation from the pot greenhouse studythat the coupled electrokinetic phytoremediation may have potential for application in remediating U-contaminated sites.