Insight into lithium carbonate crystallization in the mild reaction system LiCl-NH3•H2O-CO2 by stabilizing the solution with NH3•H2O

In this work, a novel method was utilized for the gas-liquid reactive crystallization of Li2CO3 in a LiCl-NH3 center dot H2O-CO2 system and the time-dependences of crystallization parameters were investigated carefully. The results indicated that [NH4+] had great influence on the Li2CO3 precipitation process, and that it could inhibit the recarbonation of the Li2CO3 crystals, thus simplifying the carbonation process. Increasing the concentration of NH3 center dot H2O can improve the CO2 absorption efficiency and stabilize the metastable solution with enlarged metastable zone width (MSZW), and the existence of NH3 center dot H2O made the absorption of CO2 more sensitive to temperature. The crystallization rate was improved by increasing the temperature, while the supersaturation (S) restricted the increase of the crystallization rate at temperatures below 60 degrees C. The kinetics was estimated to provide insight into the mechanism controlling the crystallization, and the apparent activation energy was found to be 23.55 kJ/mol, which indicated that the crystallization of Li2CO3 from the LiCl-NH3 center dot H2O-CO2 system was controlled by a combination of surface reaction and diffusion.