Abstract
Hexavalent chromium from industrial residues is highly mobile in soil and can lead to the contamination of groundwater through runoff and leaching after rainfall. This paper focuses on the three-dimensional (3D) electrokinetic remediation (EKR) of chromium-contaminated soil from an industrial site. Activated carbon particles coupled with Fe ions (AC-Fe) were used as the third electrode. The optimum dose ratio of the electrode particles and remediation time were selected on the basis of single-factor experiments. X-ray photoelectron spectroscopy (XPS) analysis was carried out to explore the reduction of Cr(VI) on the surface of the electrode particles (AC-Fe). The results showed that AC-Fe had a positive effect on Cr(VI) reduction with a removal rate of 80.2%, which was achieved after 10 d by using a 5% dose of electrode particles. Finally, it was concluded that the removal mechanism combined the processes of electromigration, electrosorption/adsorption and reduction of Cr(VI) in the 3D EKR system.
Highlights
Chromium is widely used in a variety of industrial process
In the conventional 2D electrokinetic remediation (EKR) experiments, the maximum Cr(VI) removal rate of 59.4% was obtained in region S5, and the minimum removal ratio of 39.0% was obtained in S1, which indicated that Cr(VI) accumulated in S1 near the anode; this phenomenon was similar to the results reported previously[13,14]
The results indicated that the chromium present in the treated soil and adsorbed on the electrode particles predominantly existed in the trivalent form
Summary
Chromium is widely used in a variety of industrial process. As a result, a large amount of chromium-contaminated waste is produced, which pollute the soil, water and atmosphere[1,2,3,4]. Electrokinetic remediation (EKR) has become a promising technique for removing chromium from contaminated soils. This technique is based on an electrolytic cell, in which both electrodes are supplied with a low-voltage direct current or a low potential gradient to treat contaminated soil[9,10,11,12]. 3D EKR experiments were carried out to remediate chromium-contaminated soil from an abandoned industrial site by using iron-loaded activated carbon (AC-Fe) as the third electrode. Two single-factor experiments were conducted to explore the effects of the particle electrode dose and treatment time on the Cr(VI) and total Cr removal efficiencies. X-ray photoelectron spectroscopy (XPS) was performed on the particle-based electrode and the soil to explore the Cr removal mechanism
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