Antisolvent Crystallization Salting-Out

In this type of batch crystallization, a solute is crystallized from a primary solvent by the addition of a second solvent (antisolvent) in which the solute is relatively insoluble. The antisolvent is miscible with the primary solvent and brings about a solubility decrease of the solute in the resulting binary solvent mixture. 

The major advantage of the anti-solvent crystallization is that the process can be carried out at the ambient temperature, which—aside from the convenience and economical aspects—is of a paramount importance for heat-sensitive substances. The disadvantage of this process is that the binary solvent mixture must be subsequently separated in order to recover and recycle one or both solvents. Frequently, however, the added cost of the separation operation is fully absorbed by the valuable and expensive products, such as pharmaceuticals. 

Using an analogy with the programmed cooling crystallization, Karpinski and Nyvlt (1983) suggested that the quality of the 

Batch crystallization has several desirable features and advantages in laboratory and industrial applications. Industrial batch crystallizers are commonly used to manufacture a wide variety of crystalline materials with desirable product features and quality. Laboratory batch crystallizers are often used to characterize crystallization kinetics and CSDs and to determine the effects of process conditions on these kinetics and CSDs. 

The analysis of batch crystallizers normally requires the consideration of the time-dependent, batch conservation equations (e.g., population, mass, and energy balances), together with appropriate nucleation and growth kinetic equations. The solution of these nonlinear partial differential equations is relatively difficult. Under certain conditions, these batch conservation equations can be solved numerically by a moment technique. Several simple and useful techniques to study crystallization kinetics and CSDs are discussed. These include the thermal response technique, the desupersaturation curve technique, the cumulative CSD method, and the characterization of CSD maximum. 

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