Reactive Crystallization of Lithium Carbonate Nanoparticles by Microwave Irradiation of Aqueous Solution Containing CO₂ Microbubbles

Abstract

In this study, we used minute gas–liquid interfaces around CO₂ microbubbles activated by microwave irradiation as new reaction fields and developed a crystallization technique to produce lithium carbonate (Li₂CO₃) nanoparticles. At the minute gas–liquid interfaces, nucleation occurs predominantly because of the formation of numerous local supersaturation regions at higher temperatures; hence, fine-sized Li₂CO₃ particles with a narrow size distribution are crystallized, as the Li₂CO₃ solubility decreases sharply with an increase in temperature. Microwaves (2.45 GHz) were used to irradiate an aqueous solution containing lithium ions and CO₂ microbubbles in a waveguide-type microwave apparatus. The heating method, rate of temperature increase (r_T) and average bubble size (d_bbl) were considered as the operation parameters and varied; the combined effects of CO₂ microbubble formation and microwave irradiation on the reactive crystallization of Li₂CO₃ nanoparticles were examined. Consequently, during microwave irradiation of the solution containing CO₂ microbubbles, the crystallization of Li₂CO₃ nanoparticles was significantly accelerated with an increase in r_T and a decrease in d_bbl.