Energy-efficient three-dimensional electrokinetic remediation of Cr-contaminated sites using particle electrodes with synergistic effects of oxidation and adsorption

The sustainable remediation of chromium (Cr) contaminated sites is of concern. Although electrokinetic remediation is a promising remediation technology, Cr(III) removal has been hindered by its low mobility. Conventional enhancement techniques are costly and environmentally risky. Therefore, this work attempts to establish a sustainable three-dimensional electrokinetic remediation (3D-EKR) system for the effective removal of Cr in a low-voltage electric field (0.2 V/cm). The Mn/NH₂-functionalized particle electrodes (Mn/NH₂-GAC) with the synergistic effects of adsorption and oxidation were prepared. Two groups of treatments were conducted, one using commercial activated carbon (3D-EKR) and the other using Mn/NH₂-GAC (Mn/NH₂-3D-EKR). The total Cr removal efficiency was up to 91.50 %, and the Cr(III) leaching toxicity decreased by 78.57 %. The Cr(III) removal of Mn/NH₂-3D-EKR was almost twofold that of 3D-EKR, while the cost and greenhouse gas emissions per unit mass of Cr(III) removal were only half of those of 3D-EKR. The environmental impacts were determined through a life cycle assessment (LCA), which revealed that the remediation process can be considered environmentally friendly. Batch experiments and characterization analyses reveal that the Cr removal was the result of a synergistic effect of electromigration, adsorption, and redox processes. The final in-situ removal of Cr was achieved by separating the Mn/NH₂-GAC from the soil. The synergistic remediation of Cr-contaminated sites by oxidation and adsorption provides a sustainable option for the reduction of Cr toxicity.