title: Using electrocoagulation for metal and chelant separation from washing solution after EDTA leaching of Pb, Zn and Cd contaminated soil.
abstract: Electrocoagulation with an Al sacrificial anode was tested for the separation of chelant and heavy metals from a washing solution obtained after leaching Pb (3200 mg kg(-1)), Zn (1100 mg kg(-1)), and Cd (21 mg kg(-1)) contaminated soil with EDTA. In the electrochemical process, the sacrificial anode corroded to release Al(3+) which served as coagulant for precipitation of chelant and metals. A constant current density of 16-128 mAc m(-2) applied between the Al anode and the stainless-steel cathode removed up to 95% Pb, 68% Zn and 66% Cd from the soil washing solution. Approximately half of the initial EDTA remained in the washing solution after treatment, up to 16.3% of the EDTA was adsorbed on Al coagulant and precipitated, the rest of the EDTA was degraded by anodic oxidation. In a separate laboratory-scale remediation experiment, we leached a soil with 40 mmol EDTA per kg of soil and reused the washing solution (after electrocoagulation) in a closed loop. It removed 53% of Pb, 26% of Zn and 52% of Cd from the soil. The discharge solution was clear and colourless, with pH 7.52 and 170 mg L(-1) Pb, 50 mg L(-1) Zn, 1.5 mg L(-1) Cd and 11 mM EDTA.
authors.affiliation: Agronomy Department, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Pociecha
authors.forename: Domen
authors.initials: D
authors.lastname: Lestan
mesh_terms: D002104:Cadmium / Q000302:isolation & purification*; D002614:Chelating Agents / Q000302:isolation & purification*; D004492:Edetic Acid / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D007854:Lead / Q000302:isolation & purification*; D012989:Soil Pollutants / Q000302:isolation & purification*; D015032:Zinc / Q000302:isolation & purification*
chemical_list: D002614:Chelating Agents; D012989:Soil Pollutants; D002104:Cadmium; D007854:Lead; D004492:Edetic Acid; D015032:Zinc