Water colorless, odorless and tasteless may seem simple, but its interaction with minerals can be difficult to study. Ions (ranging from nutrients such as calcium, to contaminants such as lead) are present in natural waters, but their transport is often limited by adsorption to mineral surfaces. The more scientists can understand about the interaction of minerals with water and ions, the more effectively they can control water quality in our environment, and Argonne's research in this area is making a leading contribution to the field.
Contrary to generally held scientific assumptions, the simple textbook description of how ions adsorb to mineral-water interfaces has been shown to not be universally true. Argonne Physicist Paul Fenter stated "Ions are known to carry a hydration shell in water. Previously, it was thought that ions either adsorb to a mineral surface with this shell intact as an outer-sphere ion, or remove part of this shell to directly bind to the mineral as an inner-sphere ion. We now know that this is not just a black and white difference, but have discovered new shades of gray by showing that outer-sphere and inner-sphere species of the same ion can co-exist."
This revelation was the outcome of a new element-specific method developed to understand the behavior of ions at the interface between minerals and liquids, like water. According to Argonne Chemist Changyong Park, "Conventional methods provided no direct sensitivity to observing this behavior. Outer-sphere species were almost invisible and extremely difficult to identify. There was just no way to see the co-existence of both species previo
Contact: Eleanor Taylor
DOE/Argonne National Laboratory