Experimental and Numerical studies on remediation of mixed metal-contaminated sediments by electrokinetics focusing on fractionation changes

Electrokinetic remediation technique is widely applied for the removal of heavy metal from contaminated soil, but the soil buffering capacity and fractionation of heavy metals mainly affect the cost and duration of the treatment. This study aims to treat heavy metal-contaminated sediments by electrokinetic remediation (EKR) technique by using various enhancing agents such as EDTA, HNO3, HCI, H2SO4, acetic acid and citric acid for optimizing the cost and treatment duration. The optimum molar concentration of enhancing agent for treatment was estimated by batch experiments to maximize the dissolution of target heavy metals and reduce the dissolution of earth metals (Fe, Al and Ca) to maintain soil health. The EKR experiments were performed up to 15 days with the above enhancing agents to reduce the risk associated with heavy metals and the selection of enhancing agents based on removal efficiency was found to be in an order of EDTA > citric acid > acetic acid > HNO3 > HCl >= H2SO4. Also, a numerical model has been developed by incorporating main electrokinetic transport phenomena (electromigration and electroosmosis) and geochemical processes for the prediction of treatment duration and to scale up the EKR process. The model predicts well with experimental heavy metal removal with a MAPD of approximate to 2-18 %. The parametric study on electrode distance for full-scale EKR treatment was found in this study as approximate to 0.5 m.

Automated summary

This study aimed to treat heavy metal-contaminated sediments using various enhancing agents through the electrokinetic remediation technique to optimize cost and treatment duration. A numerical model was developed incorporating electrokinetic transport phenomena and geochemical processes to predict treatment duration and scale up the EKR process. The study found the optimal order of enhancing agents for heavy metal removal and identified a parametric study on electrode distance for full-scale EKR treatment.