Nucleation and growth phenomena in producing monodispersed lead sulfate particles by reactive crystallization

In this study, lead sulfate particles were produced in a batch crystallizer, by feeding lead nitrate and sodium sulfate solutions (concentration: 0.025-0.4 mol/1) continuously to the vicinity of an agitator rotating at 400 rpm from individual feed pipes. The batch crystallizer contained a solution of Pb 10^-2 mol/1, gelatin 5 wt% and acetic acid 3.48 mol/1. In the crystallization process, crystals were sampled over time to measure crystal size distribution based on number, and to observe the shape and surface condition of crystals. From the results of experiments, it was shown that the position, where the nucleation phenomenon was detected in the equipment, changed for a feed concentration 0.4-0.5 mol/1. This phenomenon was considered with respect to the supersaturation ratio in the equipment. Moreover, in the range of experimental conditions, where relatively monodispersed fine particles were produced, it was observed that crystals of unstable state were fromed in the beginning of the reaction, but after that they were transformed to a stable rhombic shape. The stable crystals were considered to grow while consuming all the reactant components in the equipment. Also, an experimental equation was presented showing that formation rate of nuclei to become product crystal was proportional to the fifth power of the feed supersaturation ratio.