No abstract

CaCO 3 microparticles were obtained by chemical precipitation from CaCl 2 solution using Na 2 CO 3 or (NH 4) 2 CO 3 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 CaCO 3 were experimentally investigated. It was found that the shape of particles and CaCO 3 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 l n ≈ 3 μm) were obtained using Na 2 CO 3 solution as a precipitation agent under low temperature (20 °C). Calcite rhombohedral crystals (l n ≈ 3 μm) were obtained using carbamide at high temperature (100 °C). Increasing the temperature of Na 2 CO 3 and (NH 4) 2 CO 3 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 CaCO 3 particles.