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Physcial Sciences Division
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January 2008

Article on New Sorbent Method for Toxic Materials Attracts Attention

A paper about a highly dispersible sorbent that binds to mercury and other toxic metals and can then be separated from the solution using a magnet attracted significant attention, becoming one of the most accessed articles in Environmental Science and Technology in late 2007. This 6-page article was written by Pacific Northwest National Laboratory's Marvin Warner, Charles Timchalk, Wassana Yantasee, Cynthia Warner, R. Shane Addleman, Robert Wiacek, and Glen Fryxell; Chulalongkorn University's Thanapon Sangvanich; and University of Oregon's Timothy Carter.

Entitled "Removal of Heavy Metals from Aqueous Systems with Thiol Functionalized Superparamagentic Nanoparticles," the article discussed combining superparamagnetic iron oxide nanoparticles with a sulfur-containing acid, known as dimercaptosuccinic acid. These rust-colored particles, which look like the finest ground black pepper, possess a large surface area (114 m2/g) that results in more binding sites for the metals.

Toxic metals in water graphic
Thanks to magnets, thiol-functionalized superparamagnetic nanoparticles could provide quick and easy way to remove toxic metals from water.

"We took a material developed for bio-applications and moved it into environmental remediation applications," said Marvin Warner, a co-principal investigator on the research.

On the surface of the particles, mercury, silver, lead, cadmium, and thallium bind to the free sulfur on the DMSA strands. Arsenic binds to the iron oxide lattices. Loaded with toxic metals, the particles can be separated from the solution in about a minute using a 1.2-T magnet.

The chemical affinity, capacity, kinetics, and stability of these nanoparticles were compared to other sorbents using  river water, groundwater, seawater, and human blood and plasma loaded with toxic soft metals. The DMSA-modified particles removed 30-fold more mercury than conventional resin-based sorbents. Further, the particles removed 99 wt% of 1 mg/L lead in a minute, while other sorbents took up to 2 hours to remove nearly as much.

Not to rest on their laurels, the researchers are completing another paper that highlights their research on using these particles to detect low levels of contaminants in complex samples.

This work was funded by two National Institute of Health grants and a PNNL Directed Research and Development grant through the Lab's Homeland Security Initiative. The work was done in the U.S. Department of Energy's Environmental Molecular Sciences Laboratory, a national scientific user facility, at PNNL.

Citation: Yantasee W, CL Warner, T Sangvanich, RS Addleman, TG Carter, RJ Wiacek, GE Fryxell, C Timchalk, and MG Warner. 2007. "Removal of Heavy Metals from Aqueous Systems with Thiol Functionalized Superparamagnetic Nanoparticles." Environmental Science & Technology 41(14):5114-5119.  doi:10.1021/es0705238

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