Microbubble-assisted pressure carbonation for preparation of high purity lithium carbonate

Abstract

The direct carbonation of industrial grade Li2CO3 using pure CO2 induces the formation of impurity-free water-soluble LiHCO3. In this study, microbubble-assisted pressure carbonation using CO2 is performed on industrial grade Li2CO3 to facilitate LiHCO3 formation. The conversion rate is increased by 20–30% compared to that of conventional carbonation methods. The optimum conditions for CO2 carbonation are determined as follows: reaction temperature of 25 °C, pulp density of 60 g L−1, CO2 flow rate of 1.0 L min−1, CO2 partial pressure of 0.4 MPa, reaction time of 120 min, and stirring speed of 400 rpm. The carbonation kinetics of the material is shown to be controlled by surface chemical reactions, with an activation energy of −8.705 kJ mol−1 obtained at 25–55 °C. The mechanism of the surface chemical reactions is further corroborated by XRD patterns and SEM images of the material and the generated residues. Reprecipitation of 83.14% Li in the LiHCO3 solution with 99.99% pure Li2CO3 is achieved via purification and decomposition. This proves the process is possible and practical.

Keywords

• Lithium carbonate
• Lithium bicarbonate
• Pressure carbonation
• Microbubble
• Kinetics