Reactive precipitation of vaterite calcium carbonate microspheres in supercritical carbon dioxide-water dispersion by microfluidics

Vaterite, a polymorphic form of precipitated calcium carbonate, is an interesting material for various applications such as formulation of drug delivery systems due to its nanoporous structure. One of the carbonation processes to obtain nanostructured microspheres of vaterite consists in mixing an aqueous calcium phase with a supercritical CO2 phase, resulting in a heterogeneous dispersion. In this study, a continuous microfluidic method has been evaluated to produce monodisperse porous vaterite microparticles. A high-pressure microfluidic set-up has been developed, revealing that the dimensions and the dispersity of the CaCO3 particles are not affected by pressure but can be decreased by increasing the flow rate of the scCO(2) and aqueous phases or addition of polymers in the aqueous phase. These observations were shown not to be related to the degree of dispersion of each phase within the microfluidic channel but to the interaction of the polymer with the CaCO3 particles and to the depressurization step at the end of the channel.