Chemical Thermodynamics for Industry
Written by leading experts in the field, this book presents the latest developments in applied thermodynamics and highlights the role of thermodynamics in the chemical industry.
TABLE OF CONTENTS Chemical Thermodynamics for Industry
Chapter 20: Thermodynamics of Crystallization
Amyn S. Teja, Ronald W. Rousseau
1 Introduction
Crystallization generally involves the separation of a solute from a solution (mother liquor) via the creation of a second (solid) phase. The solid phase may be a pure compound, a nonstoichiometric compound, a "mixed crystal" phase, or a solid solution. The solid may be thermodynamically stable, or metastable due to slow rates of change to more stable forms. Metastable solid phases are quite common, and can result from surface heterogeneities as well as slow kinetics. The driving force for crystallization is supersaturation, which is defined as the difference between the chemical potential of the solute in the solution under the prevailing conditions, and that in the solution at equilibrium. Although a state of equilibrium may not be achieved in solid liquid systems because of kinetic considerations, thermodynamics plays a key role in determining the driving force for the crystallization process via the determination of supersaturation. Phase diagrams provide information about the equilibrium characteristics of a particular system and are essential to an understanding of the crystallization process. The focus of what follows is therefore on phase diagrams of solid liquid systems, and the representation of the solid liquid equilibrium curves by means of thermodynamic relationships.
2 Pure Component Phase Behavior
Phase diagrams of mixtures terminate at pure-component freezing points where the pure solid crystallizes. A proper understanding of the solid liquid behavior of multi-component systems therefore requires a description of the freezing points of the pure components. A typical pressure temperature phase diagram for a single-component system...
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