Impact of Sodium Polyacrylate on the Amorphous Calcium Carbonate Formation from Supersaturated Solution

Abstract

A detailed in situ scattering study has been carried out on the formation of amorphous calcium carbonate (ACC) particles modulated by the presence of small amounts of sodium polyacrylate chains. The work is aiming at an insight into the modulation of ACC formation by means of two polyacrylate samples differing in their molecular weight by a factor of 50. The ACC formation process was initiated by an in situ generation of CO(3)(2-) ions via hydrolysis of 10 mM dimethylcarbonate in the presence of 10 mM CaCl(2). Analysis of the formation process by means of time-resolved small-angle X-ray and light scattering in the absence of any additives provided evidence for a monomer addition mechanism for the growth of ACC particles. ACC formation under these conditions sets in after a lag-period of some 350 s. In the presence of sodium polyacrylate chains, calcium polyacrylate aggregates are formed during the lag-period, succeeded by a modulated ACC growth in a second step. The presence of anionic polyacrylate chains changed the shape of the growing particles toward loose and less homogeneous entities. In the case of low amounts (1.5-7.5 mg/L) of the long chain additive with 97 kDa, the size of the aggregates is comparable to the size of the successively formed hybrid particles. No variation of the lag-period has been observed in this case. Use of the short chain additive with 2 kDa enabled increase of the additive concentration up to 100 mg/L and resulted in a significant increase of the lag-period. This fact, together with the finding that the resulting hybrid particles remained stable in the latter case, identified short chain sodium polyacrylates as more efficient modulators than long chain polyacrylates.

Formation of Nanoparticles and Nanostructures—An Industrial Perspective on CaCO3, Cement, and Polymers

“…4) Polymer-ion, polymer-ion pairs, or polymer-cluster complexes may act as nucleating centers. [89] All this indicates that the mode of action of polymers at the level of precursors and initial particles is still not well understood and that further research is needed to enable a fully rational design of these polymers. A promising step in this direction has recently been made by the development of a quantitative, titration-based crystallization assay that allows different stages during the pre-and early post-nucleation phase to be probed.…”

Conductometric study of calcium carbonate prenucleation stage: underlining the role of CaCO3o ion pairs

“…In recent years, few works were interested on the effect of chemical inhibitors on the formed species as an intermediate phase (precursor) during the nucleation process, especially on the stabilization of amorphous calcium carbonate (ACC) . Nevertheless, no study was performed on the effect of inhibitors on the pre‐nuclei formation.…”

Investigation of scale inhibitors effect on calcium carbonate nucleation process

“…Consequently, the distinction between the prenucleation and precipitation thresholds is easier. Liu et al [28] proved that the nucleation was delayed after the addition of sodium polyacrylate. They supposed that the ionic association of the inhibitor have not interfered with the formation of CaCO 3 clusters, but rather they protected them.…”