Calcite Precipitation with Palmitic and Stearic Acids

The objective of this project was to document the early stages of growth of carbonate minerals in the presence of two different organic compounds commonly associated with cell walls or found in biofilms. Organic molecules are believed to influence an environment to be more favorable for carbonate mineral precipitation or serve as a substrate for the initiation of crystal growth. Palmitic and stearic acids are common fatty acids that bind to cell walls and are the most common organic molecules in marine environments. Scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive X-ray spectroscopy (X-EDS) analyses were used to image the interface between the organic molecules and calcite minerals. The SEM and TEM images were used to further understand the interactions between organic compounds and calcite minerals. The palmitic and stearic acid showed a curious formation of spheroidal structures in a spatial relationship with calcite crystal growth. This research is significant because it shows that a spatial relationship exists between organic matter and the mineral calcite. More importantly, the organic material may be acting as a nucleation surface. These experiments represent patterns similar to those observed in nature.