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Washington and Lee University

Washington and Lee University
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Maria Reimi '12 studies dirty, dirty calcite

Calcite synthesized in water with 50ppm Manganese. Cross polarized light. 40x. This picture shows distorted calcite crystals as well as crystocrystaline calcite masses.

Maria presented a poster at the 2011 AGU Fall Meeting based on research for this project. "Synthesis of sub-millimeter calcite from aqueous solution," by Maria Reimi '12, Washington and Lee University, and Jessica M. Morrison and Peter C. Burns, both of University of Notre Dame, reports on how a novel aqueous synthesis that leads to the formation of calcite (CaCO3) crystals, up to 500μm in diameter, will be used to facilitate the study of contaminant transport in aqueous environmental systems. Existing processes tend to be complicated and often yield nanometer-sized or amorphous CaCO3. The synthesis method presented here, which involves slow mixing of concentrated solutions of CaCl2 ¬and (NH4)2CO3, produces single crystals of rhombohedral calcite in 2 to 4 days. Variations on the experimental method, including changes in pH and solution
concentration, were explored to optimize the synthesis. Scanning Electron Microscope images show the differences in size and purity observed when the crystals are grown at pH values ranging from 2 to 6. The crystals grown from solutions of pH 2 were large (up to 500 micrometers in diameter) with minimal polycrystalline calcium carbonate, while crystals grown from solutions with pH values beyond 4 were smaller (up to 100 micrometers in diameter) with significant polycrystalline calcium carbonate.
The synthesis method, materials characterization, and use in future actinide contaminant studies will be discussed.