Enhancement of electrokinetic decontamination with EDTA

Abstract

The effect of ethylenediaminetetraacetic acid (EDTA) during electrokinetic decontamination (EKD) was investigated in this research. EDTA is a ligand that can form soluble complexes with precipitated heavy metals inside soil pores. Millpond sludge, primarily contaminated with lead (Pb) and zinc (Zn), was subjected to EKD with and without the presence of EDTA. Dilute EDTA solutions with strengths of 0.05 M and 0.125 M were injected into the millpond sludge by electroosmosis. Several beneficial effects of using EDTA were observed in this research. One was that the presence of EDTA substantially increased the electroosmotic (EO) flow in the millpond sludge indicating that it could significantly reduce the duration of EKD. Another advantage was that a significantly higher percentage of Pb and Zn removal was achieved from the solid phase due to the complexation of EDTA with these heavy metals. Also, EDTA was able to prevent the precipitation of metals at the cathode electrode, typically observed in EKD process.

Remediation of Toxic Metal-Contaminated Soil Using EDTA Soil Washing

“…However, divalent and trivalent metals can be EDTA extracted from soil because the reported ordering of EDTA complex stability constantsNa < Mg < Ca < Fe < Al < Zn < Cd < Pb < Ni < Cu < Hg (Martell and Smith 2003)-favours the removal of metal contaminants over natural hardness ions (Almaroai et al 2013). Mobilisation of metals in soil by the formation of watersoluble toxic EDTA chelate (Karim and Khan 2012) poses a threat to the environment due to leaching into the subsurface (i.e. groundwater), and soil must be thoroughly rinsed to remove all mobilised toxic metal species and prevent emissions before remediated soil is returned to the site.…”

Heavy Metal Contamination of Soils

“…However, divalent and trivalent metals can be EDTA extracted from soil because the reported ordering of EDTA complex stability constants-Na < Mg < Ca < Fe < Al < Zn < Cd < Pb < Ni < Cu < Hg (Martell and Smith 2003)-favours the removal of metal contaminants over natural hardness ions (Almaroai et al 2013). Mobilisation of metals in soil by the formation of watersoluble toxic EDTA chelate (Karim and Khan 2012) poses a threat to the environment due to leaching into the subsurface (i.e. groundwater), and soil must be thoroughly rinsed to remove all mobilised toxic metal species and prevent emissions before remediated soil is returned to the site.…”

Simultaneous Removal of Pb, Cd, and Zn from Heavily Contaminated Mine Tailing Soil Using Enhanced Electrochemical Process

“…Externally triggered electrochemical processes using an applied direct current (DC) electric field to contaminated soils and sediments have been shown to aid in transformation of some metal ion species and organic molecules to their benign forms (Pamukcu et al, 2004;Alshawabkeh and Sarahney, 2005;Brosky and Pamukcu, 2013). Electrochemical remediation of contaminated soils can be enhanced further by introducing the substrate complexing agents, such as ethylenediamine tetraacetic acid (EDTA), citric acid, and S,S-ethylene-diaminedisuccinic acid (EDDS), to solubilize and make available the target substance in the soil pore space for effective transport (Yeung et al, 1996;Hosseini et al, 2011;Karim and Khan, 2012;Suzuki et al, 2014).…”