Synergetic effect of secondary nucleation and growth on the lithium carbonate particle size in the gas–liquid reactive crystallization of LiCl–NH3·H2O–CO2

In this study, the gas‒liquid reactive crystallization of LiCl–NH3·H2O–CO2 was adopted to produce Li2CO3. The weakly alkaline nature of NH3·H2O in the absence of any recarbonation process resulted in a unimodal and easily controllable particle size distribution (PSD) of the obtained Li2CO3. The reaction temperature significantly influenced both the Li2CO3 particle size and PSD. By increasing the temperature from 25 to 60 °C, the volume weighted mean particle size increased from 50.5 to 100.5 μm, respectively. The Li2CO3 secondary nucleation rate and growth rate were obtained by focused beam reflectance measurements and a laser particle size analyzer, respectively. The secondary nucleation rate of Li2CO3 reduced as a function of temperature, whereas the growth rate increased. In addition to improving the surface energy of the crystals to enhance the growth process, higher temperatures also reduced the supersolubility of Li2CO3, which also plays a role to decrease the secondary nucleation rate. At a constant temperature, supersaturation affects the Li2CO3 particle size through the synergistic effect of secondary nucleation and growth. Hence, with improved supersaturation, the mean particle size of Li2CO3 decreased. The results provide a meaningful way to evaluate the crystallization process and to regulate the particle size.