Enhanced Electrokinetic Remediation of Agricultural Soil: Assessment of Chromium (VI) Removal and Soil Property Alterations

This study evaluated the efficiency of enhanced electrokinetics (EKR) in removing hexavalent chromium Cr (VI) from agricultural soil using three potent electrolyte solutions: citric acid (CA), EDTA, and Tween 80. Distilled water was used as a control experiment. Further, to understand the influence of the applied current across the soil column and the targeted areas, a length-wise as well as depth-wise distribution of Cr (VI) was analyzed. Additionally, the key properties of agricultural soil, such as organic matter, carbonate content and sulfate ions, were investigated to study both the effect of soil properties on the efficiency of EKR, and the alterations in soil properties due to the EKR treatment. The findings revealed that CA was the most effective enhancing agent in removing Cr (VI), with 37.5% removal, followed by EDTA (33.4%), distilled water (23.8%), and Tween 80 (22.8%). The chromate ions, Cr-EDTA complexes, and Cr-Cit complexes migrated toward the anode through electro-migration, resulting in higher Cr (VI) in analytes and S1 and S2 soil sections. The surfactant could not form a metal complex but caused the mobilization of organic matter and soil colloids, resulting in relatively lower removal rates. The depth-wise Cr (VI) distribution indicated higher Cr (VI) retention at the bottom and middle sections due to gravitational leaching and compact soil arrangement. EKR was effective in eliminating excess sulfate ions from the soil, while improving the availability of essential nutrients through organic matter mobilization. The application of CA-enhanced EKR over Cr (VI)-contaminated agricultural field can give promising remediation with minimum disturbance to the soil properties.