Nitrate mediated biotic zero valent iron corrosion for enhanced Cd(II) removal

Abstract

In this study, nitrate mediated biotic zero-valent iron (Fe0) corrosion was employed to enhance cadmium (Cd) removal from groundwater. In comparison with a 17.5% Cd(II) removal treated with abiotic Fe0, a 3.9 times higher Cd(II) removal of 86.2% was recorded in the nitrate-mediated biotic Fe0 system. Solids phase characterization confirmed that biogenic minerals such as green rust and iron sulfide could be formed in the nitrate-amended biotic Fe0 system, offering large amount of adsorption sites for Cd(II) removal. The decrease of nitrate concentration and the competition with cathodic hydrogen for biological nitrate reduction by extra organic substance such as sodium acetate both showed significant inhibition on Cd(II) removal, further proving that hydrogenotrophic denitrification was the main mechanism for enhanced Cd(II) removal. Besides, a relatively high Cd(II) removal efficiency was observed over a pH range of 5–8, and it increased with declining pH values. These results demonstrated that the bio-amended iron corrosion technology coupled Fe0-assisted H2 production with hydrogenotrophic denitrification exhibited excellent Cd(II) removal capacity, which enabled this technology a promising potential for Cd(II)-contaminated groundwater treatment and an alternative strategy for Cd(II) and nitrate co-contaminated groundwater remediation.