EDTA-ENHANCED ELECTROREMEDIATION OF METAL-CONTAMINATED SOILS

Precipitation and sorption of heavy metals reduce their mobility and l imit the effectiveness of in-situ remediation technologies. In electro remediation, metal mobility can be further impeded by the development of regions of elevated pH near the collecting electrodes, This paper i nvestigates the feasibility of mobilizing precipitated heavy metals by delivering complexing agents into soils by ionic migration. Two metal s, lead and zinc, were selected as contaminants, and EDTA, a widely av ailable non-toxic chelating agent, was selected as the complexing agen t. It was found that EDTA added to the catholyte can be readily delive red into a sandy soil where it solubilizes the precipitated metals. Th e resulting complexes are then transported to the anode with metal rem oval efficiencies, for the spiked laboratory samples, approaching 100% . The poor ligand utilization obtained in the tests is attributed to t he low dissolution rate of the metals. Modifying the operating conditi ons to increase the concentration and the residence time of the ligand in the soil is expected to improve the utilization efficiency of the complexing agent. (C) 1997 Elsevier Science B.V.