2004 Volume 77 Issue 4 Pages 827-833
Crystallization of CaCO3 with in-situ radical polymerization of sodium acrylate in aqueous solution was carried out by a double jet method to prevent heterogeneous nucleation at glass walls. The concentration of sodium acrylate was 1.71 mM and the feed ratio of sodium acrylate to calcium ions was 0.62. After addition of the calcium reactants into the aqueous solution of sodium acrylate was completed, an aqueous solution of potassium peroxodisulfate as a water-soluble radical initiator was added to the reaction mixture after incubation at 30 °C for several minutes (1, 3, or 20 min). Three different crystal polymorphs of CaCO3 (aragonite, vaterite, and calcite) were selectively induced by changing the time for adding the radical initiator to a calcium carbonate solution with sodium acrylate. Formation of crystalline CaCO3 in the presence of sodium acrylate with the radical initiator at different feed ratio of sodium acrylate to calcium ions was also studied. The higher concentration of sodium acrylate increased sizes of vaterite spherical particles. The present results indicate that the final crystalline phases are highly sensitive to the presence of the active additives at the very initial nucleation stage (within several minutes).
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