Abstract: Micron-size food-grade vaterite CaCO3 were prepared by CO2 carbonization method. The effects of temperature, Ca2+ concentration and CO2 proportion in gas mixture on the morphology and polymorph of the CaCO3 crystals and influences of ammonia amount and carbonization time on the yield of CaCO3 were investigated. The microstructures and morphology of the prepared samples were systematically investigated by FT-IR, XRD and SEM. The crystal of prepared CaCO3 changed from vaterite to calcite with increasing carbonization temperature and decreasing the proportion of CO2 in gas mixture. The particle size of CaCO3 increased with increasing the concentration of Ca2+. The yield of the prepared CaCO3 increased and then decreased with prolonging the carbonization time. The average size of the prepared CaCO3 particles was 3. 79 μm with uniform particle distribution and the yield was higher than 99% at the carbonization temperature of 20 ℃, Ca2+ concentration of 0. 3 mol/L, CO2 proportion in gas mixture of 30%, [ammonia]/2[Ca2+] of 1. 1, the carbonization time of 24 min. Heavy metal content was lower than the limits of national standard "Food additive GB1898-2007 light calcium carbonate additive".

Key words: CO2 carbonization method;food-grade CaCO3;micron-size;vaterite