Abstract
Removal of hexavalent chromium [Cr(VI)] from soils and water has been widely studied for its high toxicity. Although leaching method is viewed as an effective approach to eliminate Cr(VI) and some studies attempted to enhance leaching performance via the external electric field, there is little knowledge about the influential factor in electro-leaching system on Cr(VI) removal performance. In this study, an electro-leaching technology was developed for removing Cr(VI) from groundwater aquifer to comprehensively discuss the correlation between the operational parameters and Cr(VI) removal efficiency. When the applied voltage was 20 V and the initial Cr(VI) concentration was 40 mg/kg, Cr(VI) removal efficiency achieved 99.9% in 120 min in the electro-leaching system, 15% higher than the system without the electric field. Cr(VI) removal efficiencies increased with the voltage demonstrating the significant enhancement of the electro-leaching method in removing Cr(VI). When Cr(VI) concentration climbed to 120 mg/kg, Cr(VI) removal efficiency remained above 85%. The effects of different voltages, Cr(VI) concentrations, pollutant distribution and salt content of leaching solution on the leaching effect were also investigated. Meanwhile, the relationship between the current intensity change and the amount of removed Cr(VI) during the electro-leaching process was first investigated, and the relevant model was fitted. There is a quadratic linear correlation between the amount of current change and the amount of removed Cr(VI). This novel electro-enhanced leaching method can effectively remove Cr(VI) from contaminated groundwater aquifer by enhancing the migration of charged contaminant ions during the leaching process, and it is worthy of further study of heavy metal remediation.
Highlights
Removal of hexavalent chromium [Cr(VI)] from soils and water has been widely studied for its high toxicity
The applied electric field strengthen the transportation of metal ions in groundwater and soil, and this electro-migration phenomenon could be useful for the heavy metal remediation in the environment
Without the external electric field, Cr(VI) removal efficiency was of 80% in the first 10 min and gradually achieved 85% after 30 min
Summary
Removal of hexavalent chromium [Cr(VI)] from soils and water has been widely studied for its high toxicity. There is a quadratic linear correlation between the amount of current change and the amount of removed Cr(VI) This novel electro-enhanced leaching method can effectively remove Cr(VI) from contaminated groundwater aquifer by enhancing the migration of charged contaminant ions during the leaching process, and it is worthy of further study of heavy metal remediation. Most applied reagents in the processing fluid are organic acids and ethylenediaminetetraacetic acid (EDTA)[8], which mobilize heavy metals by altering soil acidity, solution ionic strength, redox potential, and complexation[9] They are expensive and it is not affordable to use those agents in removing metals in huge amount of soils or groundwater aquifer. We innovated an electro-leaching system in a sand column with groundwater as the leaching solution and an external electric field applied This method could significantly enhance the electro-migration capacity of metal ions. Our results provided direct evidence that both migration capacity and removal efficiency of Cr(VI) were significant enhanced via electro-leaching under optimal conditions, offering both theoretical and technical support for its future practices in groundwater remediation engineering
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