Surface Studies of Minerals Reveal Insight into Cleaning Contaminated Environments

Finding solutions to large-scale environmental problems often requires researchers to start small— microscopically small. By studying the interactions of fluids with mineral surfaces at the molecular scale, Argonne scientists hope to learn more about larger-scale environmental processes. The interactions of mineral surfaces and fluids are crucial to the weathering of rocks, the formation of ore deposits and petroleum reservoirs, soil formation and plant nutrition, and the transport of contaminants through groundwater aquifers.

Ultimately, a better understanding of mineral-fluid interactions could lead to cost reductions in cleaning contaminated areas. For example, researchers could better predict how dissolved toxins will react with minerals. “If you can understand the fundamental mechanisms of these systems, then you can predict and manipulate them,” said physicist Paul Fenter.

SOLUTIONS
To study these mineral-fluid interactions, researchers are combining geology, chemistry, materials science and physics. They use the intense X-ray beams generated by Argonne’s Advanced Photon Source (APS) to make extremely high-resolution measurements of the atomic structures of the interfaces where fluids and minerals contact one another.

“We’re pioneering the use of X-ray scattering and standing-wave techniques in studying mineral surfaces as they react with synthetic ground water solutions,” said geochemist Neil Sturchio. The brilliance of the APS X-rays is critical because significantly fewer atoms are available at surfaces than in the interiors of solids. Also, fluids with dissolved metal ions can absorb X-ray beams.

Scientists have determined the structure of the calcite-water interface and will continue to study calcite-water interactions at the atomic level. Calcite, one of the most common minerals, is found in soils, rocks and ocean sediments, as well as in shells of many marine organisms. The researchers also study other common minerals, such as feldspar, mica and quartz, over a range of temperatures and chemical conditions.

“This research will help address some basic geological problems, such as how rocks erode and affect the composition of ocean water, and applied problems involving ground water and soil contamination” said Fenter. “Using the APS allows us to attack classical problems that are still unresolved.”

Sturchio believes environmental researchers still haven’t used the APS’s full potential. “We can push the technology farther by using microbeams and new detectors,” he said. “This work is at the frontiers of geochemistry and environmental science.

Argonne environmental scientists work with colleagues from universities and other national laboratories at the Basic Energy Sciences Synchrotron Radiation Center Collaborative Access Team (CAT), the Synchrotron Radiation Instrumentation CAT and the GeoSoilEnviro Consortium for Advanced Radiation Sources CAT at the APS. Their work is funded by the Department of Energy, Office of Basic Energy Sciences, Geosciences Research Program.

For more information please contact Dave Baurac at 630-252-5584

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