Control Crystallization of Calcium Carbonate in Aqueous Solution with In-Situ Radical Polymerization of Sodium Acrylate as a Latent Inductor for Crystal Nucleation and Growth

Abstract

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).

Effect of Molecular Weights of Poly(acrylic acid) on Crystallization of Calcium Carbonate by the Delayed Addition Method

“…20,31 Furthermore, it was reported that the formation of vaterite was favored under the condition of high pH environment (pH ¼ 10) at room temperature. 32,48 In this work, we found that different CaCO 3 particlesformation mechanisms were formed. All the vaterite products in Table I obtained by the delayed addition of PAA-Na were observed exhibiting the characteristic radiating features, which indicate a spherulitic growth mechanism, as shown in the images of insect and as the arrow indicating in Figure 1.…”

“…15,32,44 It was found that the stabilizing ability of the vaterite products modified by the higher molecular weights of PAA-Na was stronger than that by PAA1.2k-Na. In the previous report, we proposed that the strong stabilizing effect was attributed to the strong binding strength between PAA-Na and the surfaces of the vaterite particles.…”

“…15,32,33 In our previous work, the sodium salt of poly(acrylic acid) (PAA-Na) (PAA5k, M w ¼ 5000) for selectively interacting with the crystallization of calcium carbonate at different stages was studied by a delayed addition method. 33 Although PAA5k-Na acted as an inhibitor for the crystallization in the initial presence of PAA5k-Na, stable vaterite particles were successfully obtained by delaying the addition of PAA5k-Na from 1 to 60 min.…”

Formation of Stable Vaterite with Poly(acrylic acid) by the Delayed Addition Method

“…acrylate and a water-soluble radical initiator were used for selective interaction with the mineral at different stages during the crystal-forming process. 26 While sodium acrylate does not affect the nucleation and growth of the crystals, poly(acrylate) affects crystal morphology by inhibiting the growth of particular crystal faces. Three different crystal polymorphs of CaCO 3 (aragonite, vaterite, and calcite) were selectively induced by changing the addition time of the radical initiator.…”

“…The precipitation of CaCO 3 was carried out by a double jet method to prevent heterogeneous nucleation on glass walls, 35 and the sodium salt of PAA was added by a delayed addition method. 26 The effects of different concentrations of calcium reagents were also examined. Although the initial presence of PAA acted as an inhibitor for crystal formation and no crystals were produced, 13,27,29,32 vaterite particles were obtained by the delayed addition of PAA.…”