Crystallization kinetics of Li2CO3 from LiHCO3 solutions

The crystallization kinetics of Li2CO3 from LiHCO3 solutions was studied by a non-evaporation volume-constant batch reactor. The factors influencing the crystallization process such as initial concentration, temperature and stirring speed were investigated and discussed. In the experiment, CO2 was stripped from a slightly acidic solution of LiHCO3 by stirring resulting in critical supersaturation and precipitation of Li2CO3. The reduction of the Li+ concentration was recorded as a function of time by determination with flame atomic absorption spectrometry (FAAS), and the pH values were also measured.The results showed that the crystallization rate increased and the induction period shortened with increase in the initial concentration and temperature. In addition, high stirring speed could significantly promote this process.Thermodynamic parameters at critical conditions such as the surface free energy and critical radius of nucleus were estimated based on the crystallization theory and experimental results. The results showed that the crystallization kinetics of this process coincided with the second-order reaction rate equation, and the apparent activation energy of the process was obtained. The analysis of the crystal growth mechanism showed that the growth of Li2CO3 from LiHCO3 solutions was mainly controlled by diffusion.