Heavy Metal Removal from Shooting Range Soil by Hybrid Electrokinetics with Bacteria and Enhancing Agents

Abstract

This study presents a method for heavy metal removal from a shooting range soil by a newly suggested hybrid technology. Active bioaugmentation was performed using Acidithiobacillus thiooxidans in the bioleaching step, and each test was sequentially combined with acid-enhanced and EDTA-enhanced electrokinetics. The results of the bioleaching processes indicated that S-oxidizing bacteria enhanced the mobility of heavy metals in the soil, based on their chemical forms. This process improved the final removal efficiencies of Cu and Zn in the hybrid electrokinetics. In the case of Pb, however, anglesite (PbSO4) has been easily formed in the bioleaching step from sulfate, a byproduct of S oxidation. Despite the potential negative effect on combining acid-enhanced electrokinetics, this problem was overcome by the application of an electrokinetic EDTA injection. Moreover, this method showed enhanced removal efficiency for Pb (92.7%) that was superior to that of an abiotic process. This hybrid method of EDTA-enhanced bioelectrokinetics demonstrated an adequate removal efficiency of heavy metals, especially Pb, with lower power consumption and eco-friendly soil conditions.