Evaluation of a novel carbon-based micro-nano zero-valent iron composite for immobilization of heavy metals in soil

The novel carbonaceous material built-in micro-nano zero-valent iron (ZVI\NCM) was prepared by thermal reduction using the oily sludge (OS) and iron ore concentrate (IOC) and then applied for amendment of As, Cd, Cu, Pb and Zn in soil around the smelter. The results showed that the prepared material consists mainly of Fe0 and carbon (C), and Fe0 was embedded in a porous carbon skeleton with strong stability. Compared with the control, 3 % ZVI\NCM-900 application for 60 days increased the immobilization rates of As, Cd, Cu, Pb, and Zn to 74.10 %, 72.17 %, 95.67 %, 66.95 %, and 65.83 %, respectively in the simulated field remediation experiment. XRD and XPS characterization of magnetically separated ZVI\NCM-900 from incubated soil demonstrated that As was immobilized mainly by complexation and adsorption, and cations by chemical precipitation, ion exchange, and reduction. Moreover, European Community Bureau of Reference (BCR) and Wenzel sequential extraction procedures also confirmed that remarkably promote the conversion of heavy metals (HMs) from unstable to stable components in soil. This study indicated that the preparation of ZVI\NCM with OS reductant for soil HMs remediation was feasible and also provided a way for high value-added utilization of OS.

Automated summary

The novel carbonaceous material (ZVI\NCM) containing micro-nano zero-valent iron was prepared using oily sludge (OS) and iron ore concentrate (IOC) and successfully applied for the remediation of As, Cd, Cu, Pb, and Zn in soil near a smelter. The results showed that the prepared material had high stability and effectively immobilized the heavy metals in the soil. Characterization studies indicated that As was primarily immobilized through complexation and adsorption, while cations were immobilized through chemical precipitation, ion exchange, and reduction. Sequential extraction procedures confirmed the conversion of unstable heavy metal components in the soil to stable ones. This study demonstrates the feasibility of ZVI\NCM prepared using OS for the remediation of soil contaminated with heavy metals.