Title : A research on process parameters of heavy metal immobilization using nano zero-valent iron (nZVI) in contaminated soils
Heavy metal contamination brought about by industrialization severely affects soils and groundwater sources. Elevated heavy metal concentrations in soils can cause toxic effects on living organisms by direct exposure or by entering into the food chain. Immobilization is a soil remediation method that aims to decrease the mobility and bioavailability of heavy metal contaminants to reduce the environmental impact of these contaminants. However conventional immobilization methods have destructive effects on soil structure and functionality. One of the innovative immobilization methods is nano-sized zero-valent iron (nZVI) technology. nZVI is a unique material that is highly reactive, environmentally friendly, and easy to use. Its small size makes it applicable to soil and groundwater contamination problems. On the other hand, the effective use of nZVI in soil media requires a thorough understanding of process parameters. Besides the efficiency of the process in complex contamination scenarios needs to be investigated. In this lab-scale study, nZVI was applied to Pb, Ni, Cr, and Cd contaminated soils for immobilization, and the process parameters (nZVI concentration, temperature, nZVI suspension pH, and contaminant concentration) were investigated using a factorial design approach. The immobilization performance of the process was measured by analyzing the most mobile soil heavy metal fractions (exchangeable and carbonate-bound fractions). The results showed that Pb, Ni, Cr, and Cd were immobilized 52.4, 43.8, 43.4, and 28.1%, respectively. The investigated process parameters had significant effects on the process efficiency and these effects varied for every heavy metal. A modified version of the process incorporating activated sludge addition was also tested on soil contaminated with Pb and diesel fuel. Besides Pb immobilization, biological degradation of diesel was detected. These results indicated the potential of nZVI application together with other remediation approaches for co-contaminated site reclamation.
- Nano zero-valent iron (nZVI) application is an effective immobilization tool for heavy metal-contaminated soils.
- There are different process parameters affecting the immobilization via nZVI application such as nZVI and contaminant concentrations, temperature, and pH.
- The effects of process parameters are not the same for every heavy metal.
- Combined use of the nZVI process and other remediation methods can be a solution for complex contamination scenarios.
- Findings of this research can be beneficial for remediation practitioners who deal with contaminated sites on industrial scale as well as academic researchers studying nanomaterials for contaminant clean-up.