Calcite and other crystalline polymorphs of CaCO3 can form by pathways involving amorphous calcium carbonate (ACC). Apparent inconsistencies in the literature indicate the relationships between ACC composition, local conditions, and the subsequent crystalline polymorphs are not yet established. This experimental study quantifies the control of solution composition on the transformation of ACC into crystalline polymorphs in the presence of magnesium. Using a mixed flow reactor to control solution chemistry, ACC was synthesized with variable Mg contents by tuning input pH, Mg/Ca, and total carbonate concentration. ACC products were allowed to transform within the output suspension under stirred or quiescent conditions while characterizing the evolving solutions and solids. As the ACC transforms into a crystalline phase, the solutions record a polymorph-specific evolution of pH and Mg/Ca.
Revised: June 19, 2019 |
Published: January 1, 2017
Citation
Blue C.R., A.J. Giuffre, S. Mergelsberg, N. Han, J.J. De Yoreo, and P.M. Dove. 2017.Chemical and physical controls on the transformation of amorphous calcium carbonate into crystalline CaCO3 polymorphs.Geochimica et Cosmochimica Acta 196.PNNL-SA-129795.doi:10.1016/j.gca.2016.09.004