Nucleation of calcium oxalate monohydrate: use of turbidity measurements and computer-assisted simulations in characterizing early events in crystal formation

Abstract

To examine the nucleation of calcium oxalate monohydrate (COM) crystallization, we have determined the time interval from initial formation of a supersaturated COM solution to the first appearance of turbidity or crystals. The turbidity measurements were conducted with the unaided eye, whereas crystal formation was analyzed using an inverted and an image analysis system. The lag time kinetics were compared with previous nucleation studies using computer simulations with the Gibbs-Thomson nucleation equation and the parabolic growth rate law. The nucleation behavior can be described as homogeneous or heterogeneous depending on the range of initial relative supersaturation. The calculated interfacial energies for homogeneous and heterogeneous nucleation agreed rather well with earlier investigations. Moreover, this investigation provided the opportunity to verify the utility of our particle size distribution program for simulating precipitating systems, and the experimentally determined surface energy was obtained from simulations of the nucleation kinetics.