Sequestration Enhancement of Metals in Soils by Addition of Iron Oxides Recovered from Coal Mine Drainage Sites

Abstract

Iron oxides recovered from abandoned coal mine drainage (AMD) sites (Lowber, Scrubgrass, and Horner) as a soil amendment were investigated in this laboratory study for their effectiveness in the stabilization of cadmium, copper, and zinc in two metal-contaminated soils. The adsorption experimental results demonstrated that all three AMD iron oxides possess significant capacity for adsorption of Cd(II), Cu(II), and Zn(II). Horner iron oxide exhibited the highest adsorption capacity. Both the adsorption and the extraction experimental results showed metal sequestration enhancement through addition of Horner iron oxide to soil (5% to 50% by weight). With soil pH of 4.5 to neutral range, AMD iron oxide addition worked best for strongly adsorbed metals such as Cu, not so well for more weakly adsorbed metals such as Cd and Zn. The more AMD iron oxide amendment added, the less the mobility of the cationic target metals. Addition of AMD iron oxide for metal sequestration was more effective for the contaminated soils with low organic content.

Keywords:

• Iron oxide
• AMD
• contaminated soil
• metals
• adsorption

Acknowledgments

This work was supported by the National Science Foundation through the GOALI program (grant BES-0402966). The authors wish to thank Dr. A.M. Jacobson for help with the BET specific surface area measurements, and The RETEC Group, Inc. (now part of AECOM Environment) for the estimates of costs for use of AMD iron oxide as a soil amendment.