Kinetics of mass crystallization of calcium carbonate at 25, 30 and 37 °C

Calcium carbonate crystal growth kinetics was studied by simple mass crystallization, recording pH as function of time. The phase crystallizing was vaterite at 25 degrees C, calcite at 30 degrees C and aragonite at 37 degrees C. Growth kinetics at the initial stage followed that of the polynuclear surface nucleation mechanism, and from the slopes of linearized graphs edge free energies of the three phases could be determined. The values were: calcite 35.4 pJ/m at 30 degrees C, aragonite 32.3 pJ/m at 37 degrees C and vaterite 24.2 pJ/m at 25 degrees C. These values agree reasonably well with literature values determined by other methods, and they are useful in testing the validity of the relation between step distance of a growth spiral and size of a critical surface nucleus as assumed in the Burton-Cabrera-Frank theory. (c) 2010 Elsevier B.V. All rights reserved.