Synergistic Effect of Zero-valent Iron and Biological Sulfate Reduction on Iron Corrosion and Cadmium Stabilization in Sediment

In this study, simulated Cd(II)-contaminated sediment was incubated under anaerobic conditions for 7 d to evaluate the effect of sulfate-assisted biotic zero-valent iron (Fe 0 ) on Cd(II) immobilization. Microbes such as sulfate-reducing bacteria were employed to potentially facilitate iron corrosion and subsequent mineral formation by consuming cathodic hydrogen generated from anoxic iron corrosion with sulfate serving as an electron acceptor, ultimately enhancing the stabilization of Cd(II) in sediment treated with Fe 0 . Solid-phase analysis demonstrated that sulfate reduction and biological mineralization could promote Fe 0 corrosion, cadmium sulfide production, and secondary mineral generation, thereby enhancing the adsorption and precipitation of Cd(II). After 7 d remediation, the biotic Fe 0 system obtained an efficiency of 82.7% in aqueous Cd(II) removal. It was much higher than that of 15.9% in the abiotic Fe 0 system. Besides, an elevation in sulfate concentration and an increase in Fe 0 dosage both contributed to Cd(II) immobilization, further highlighting the essential role of Fe 0 -assisted sulfate reduction in promoting iron corrosion and Cd(II) stabilization. Results from sequential extraction and leaching test revealed a significant decline in Cd(II) leachability by 81.4%, concomitant with a substantial increase in residual Cd(II) fraction by 151.2% as compared to the untreated sediment. This study provided a scientific foundation for a deep insight into the environmental behavior of sulfate in stabilizing Cd(II) through biotic Fe 0 in sediments and for the development of efficient heavy metal detoxification technologies.