Effects of cathode coating materials and operational time on the mercury removal performance of electrokinetic remediation system for marine sediment

• Published in: Journal of environmental management Vol. 288; p. 112443
• Main Authors: Bunditboondee, Chotikoon, Lohwacharin, Jenyuk, Khan, Eakalak, Kulyakoon, Saifon, Laohhasurayotin, Kritapas
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 15.06.2021
• Subjects: Cu foam; Electrodes; Electrokinetic remediation (EK); Environmental Restoration and Remediation; Geologic Sediments; Hg migration; Manganese Compounds; Manganese oxide (MnO2); Marine sediment; Mercury; Oxides; Soil Pollutants - analysis; Cu foam; Electrokinetic remediation (EK); Manganese oxide (MnO2); Hg migration; Marine sediment; Manganese oxide (MnO)
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.112443

Electrokinetic remediation (EK) is a promising in-situ technique for removing mercury (Hg) from contaminated sites; yet it demands long operational periods when conventional electrodes are used. Herein, we investigate the effectiveness of lab-prepared cathodes (Cu foam coated with reduced graphene oxide (rGO) or manganese oxide (MnO2)) to enhance Hg removal rates from sediment by EK. Although short term (2 h) Hg removal rates were insignificantly different (p-value > 0.05) when using the uncoated and coated Cu foam cathodes, long term (60 h) operations saw greater Hg removal by coated Cu foam cathodes over pure Cu foam, probably owing to the time required for Hg to migrate towards the electrodes from sediment. The highest Hg removal at the cathode was achieved when an αMnO2-coated Cu foam cathode was used with a strong-base anion exchange membrane (AEM) in the system. Using H3PO4, as a cathodic electrolyte resulted in a higher Hg removal efficiency than using NaCl and HCl electrolytes. Electromigration was found to be the dominant Hg-ions (e.g. HHgO2−, Hg2+) transport mechanism in the marine sediment during remediation. Overall, this research demonstrates that employing enhanced electrodes and AEMs can enhance Hg removal by EK processes in relatively shorter operating times than conventional EK processes. [Display omitted] •MnO2 and rGO were coated on Cu foam to enhance electron transfer and ion migration.•The highest Hg removal of ca. 70% at the cathode compartment was achieved.•H3PO4 as a cathode electrolyte offered a greater Hg removal than HCl and NaCl.•Installing strong-base anion exchange membrane increased Hg migration to cathode.•MnO2 and strong-base anion exchange membrane can decrease Hg remediation time.