Remediation of aqueous systems contaminated with heavy metals is receiving increased attention as their toxic effects to humans and the environment is better understood.

Marvin Warner and co-workers, Pacific Northwest National Laboratory, USA, have used superparamagnetic iron oxide nanoparticles as sorbents for heavy metals in contaminated water systems.

The nanoparticles were functionalized by a facile ligand exchange process which bound affinity ligands, such as thiol and EDTA, onto the nanoparticle surface. These were then applied to river samples spiked with 0.5 ppm of (each) Co, Cu, Ag, Cd, Hg, Tl, and Pb. The researchers found that their functionalized materials generally had higher K_d values, to indicate the more effective capturing and holding of the target species than the comparable commercial counterparts and unfunctionalized iron oxide nanoparticles.

• High-Performance, Superparamagnetic, Nanoparticle-Based Heavy Metal Sorbents for Removal of Contaminants from Natural Waters
  C. L. Warner, R. S. Addleman, A. D. Cinson, T. C. Droubay, M. H. Engelhard, M. A. Nash, W. Yantasee, M. G. Warner
  ChemSusChem, 2010, 3 (6), 749-757.
  DOI: 10.1002/cssc.201000027