Calorimetric Investigation of Kinetics of Solid Phase Dissolution: Calcium Carbonate Dissolution in Aqueous EDTA Solution

✍ Scribed by Nikola Kallay; Vlasta Tomašić; Suzana Žalac; Ljerka Brečević

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 143 KB
• Volume: 188
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.4729

✦ Synopsis

temperature 6) on the rate of dissolution has been The calorimetric method for examination of the kinetics of solid studied. Different methods and techniques (1-4, 7-9) have phase dissolution is presented. The thermograms are interpreted been applied, and a number of kinetic models for dissolution by considering the heat evolution due to the reaction as well as 6, and crystal growth 11, of calcium the heat transfer in the calorimeter. The kinetic interpretation is carbonates have been developed. The enthalpy changes for based on the change of particle surface area during the dissolution calcium carbonate monohydrate, calcite, and aragonite dissoprocess. The experimental results confirm the applicability of the lution (7-9), as well as for calcite, aragonite, and vaterite proposed method. The rate constant and the enthalpy of dissoluprecipitation (2) were reported.

tion of solid CaCO 3 in aqueous EDTA and NaOH solutions are

The dissolution process takes place in several steps foldetermined. The experiments show that the process is the first order with respect to the surface area, indicating that the detach-lowing one another. In the case of calcite dissolution, for ment of EDTA complex from the surface is the responsible mechaexample, these steps might be detachment of Ca 2/ and nism. ᭧ 1997 Academic Press CO 20 3 from the crystal lattice, protonation of these ions and Key Words: calorimetry; kinetics; solid phase dissolution; caltheir diffusion away from the crystal surface. The slowest cium carbonate.

of these consecutive reactions will be the rate-controlling step of the overall dissolution process. If a complexing agent is present in the system the so-called ''chemical dissolution'' Accordingly, the calculated enthalpy change corresponds to 1 To whom correspondence should be addressed.

the sum of the contributions of the above reactions. 68