Influence of synthesis conditions on the calcium carbonate microparticle properties obtained by homogeneous and heterogeneous precipitation

Abstract

CaCO3 microparticles were obtained by chemical precipitation from CaCl2 solution using Na2CO3 or (NH4)2CO3 solutions (heterogeneous precipitation) or carbamide (homogeneous precipitation) as precipitation agents. The effects of various experimental conditions, such as the temperature, duration and reagent ratio on the properties of precipitated CaCO3 were experimentally investigated. It was found that the shape of particles and CaCO3 polymorphs depended on the precipitation agent and process temperature; the size of particles—on the reagent ratio, the precipitation agent and the deposition time. Biphasic calcite-vaterite spherical microparticles with the highest polydispersity coefficient (K = 0.98 with an average particle size ln ≈ 3 μm) were obtained using Na2CO3 solution as a precipitation agent under low temperature (20 °C). Calcite rhombohedral crystals (ln ≈ 3 μm) were obtained using carbamide at high temperature (100 °C). Increasing the temperature of Na2CO3 and (NH4)2CO3 solutions (70–100 °C) led to formation of the biphasic aragonite–calcite druses of needle crystals (druses size ≈ 10–30 μm). Increasing the aging time for sediments in the mother liquor up to 1 h did not affect the shape of CaCO3 particles.