Electro-enhanced leaching method for the mobilization of Cr(VI) in contaminated groundwater aquifer

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.

Bacterial Metal Accumulation as a Strategy for Waste Recycling Management

“…Traditional leaching technology often requires large quantities of leaching solution (EDTA, hydrochloric acid, and organic acids) which are expensive and unsuitable to remove hazardous heavy metals such as hexavalent chromium from sensitive environments [6,7]. Measures to improve traditional leaching via application of electric fields [8] or using more gentle chemicals [9] for metal solubilization are diverse. Recently, we have proposed to harness extreme metallophilic microorganisms such as Acidianus manzaensis to mobilize metals from waste products derived from steel production [10] and potentially feed them into a 2 of 13 circular process via selective adsorption processes, providing a gentle and cost-effective alternative to traditional technologies.…”