A group of researchers that includes chemistry’s Daniel Strongin has unlocked the structure of ferrihydrite, a nano-phased mineral that acts as a very effective absorbent in nature and could have possible applications in environmental clean-up.

The researchers published their findings, “The Structure of Ferrihydrite, a Nanaocrystalline Material,” in the June 22 issue of Science (www.sciencemag.org/content/vol316/
issue5832).

An intrinsically nano-phased mineral that is found in surface waters and soils, ferrihydrite has been used in industry as an absorbent for decades, but a detailed understanding of its structure had eluded scientists until now.

“A lot of people have been trying to determine the structure of this mineral for a long time,” said Strongin, who collaborated with researchers from Stony Brook University and the Argonne National Laboratory. “We think we have a pretty solid structural determination.”

Strongin’s collaborators at Stony Brook have expertise in using a pair distribution function (PDF) analysis of X-ray diffraction data as a way of determining structural details of nanomaterials. Strongin is an investigator in the NSF-funded Center for Environmental Molecular Science along with the Stony Brook researchers.

According to Strongin, ferrihydrite exists naturally in soils or can be made synthetically in a lab and acts to remove toxins in natural environments. Since it has a very high surface area that can be used to sorb species, synthetic as well as natural ferrihydrite has been studied as a material to remove such toxins as arsenic and chromium from industrial waste waters.

“We know that ferrihydrite is a mineral made out of iron, oxygen and hydrogen, but what we wanted to determine was atomic arrangement of those atoms in three dimensions,” he said. “Once you know that, you can then develop an understanding of what are the atoms on the surface of that material that interact with environmental species such as chromium and arsenic.”

Strongin has been working with ferrihydrite in his lab for the past three years trying to understand its reactivity.

“So it’s really important for our research to understand the structure and relate that to the reactivity of the material,” he said. “If you know the structure of the mineral, that really leads to an understanding of how the material works.

“People are starting to look at this naturally occurring mineral for use in environmental clean-up,” he added. “With the structure of the material now in hand, it is easier for us to get a microscopic view of what is happening on the material’s surface and where the environmental species can dock on that surface.”