A simultaneous determination of nucleation and growth rates from batch spontaneous precipitation

A review of the literature shows that many methods for determining the nucl eation and growth rates from batch precipitation experiments are inaccurate . Therefore, a new method has been developed to derive these two rates base d on the simultaneous measurement of the supersaturation and the crystal si ze distribution during a batch spontaneous precipitation. All experimental data are used without any previous numerical treatment and the differential kinetic equations are replaced by integral ones Id avoid numeric derivatio n. The kinetic parameters of the two postulated laws of nucleation and crys tal growth rates in kinetic equations are separately determined by non-line ar optimization. This method was applied to barium sulphate precipitation. Experiments were performed in a 201 stirred reactor. Effects of reagent add ing order and stirring speed were noticed. The influence of initial supersa turation was determined. The nucleation rate was found to obey an exponenti al law with a primary heterogeneous dominating process. The linear rate of crystal growth follows a 2.1 power law and the process seems to be limited by a surface integration step. The kinetic results were compared to those p reviously reported. (C) 1999 Elsevier Science Ltd. All rights reserved.