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Impact of Citrate Ions on the Nucleation and Growth of Anhydrous CaCO3
Crystal Growth & Design ( IF 3.8 ) Pub Date : 2017-09-08 00:00:00 , DOI: 10.1021/acs.cgd.7b00796
G. Montanari 1 , J. D. Rodriguez-Blanco 1, 2 , N. Bovet 1 , S. L. S. Stipp 1 , D. J. Tobler 1
Affiliation  

Citrate has been shown to inhibit CaCO3 growth and it is also found in biogenic calcite, but full understanding about how citrate controls CaCO3 formation, and hence CaCO3 polymorph stability and crystal morphology, is still lacking. We investigated the effect of citrate (CIT) on CaCO3 crystallization by monitoring crystallization rates and crystal polymorph, size, and morphology as a function of increasing mol % CIT/Ca ([Ca2+] = [CO32–] = 4 mM). At CIT/Ca ≤ 50%, both vaterite and calcite formed, but nucleation and growth were retarded as CIT/Ca was increased, demonstrated by the increase in induction time and decrease in the reaction rate constant, fitted using the Johnson-Mehl-Avrami-Kolmogorov model. This is partly explained by increased CIT-Ca complexation with higher [CIT], thus reducing saturation state with respect to vaterite and calcite. Simultaneously, CIT sorption inhibited crystal growth, demonstrated by smaller vaterite spheres and more elongated calcite crystals as CIT/Ca increased. At CIT/Ca ≥ 75%, vaterite formation was completely inhibited, with only elongated calcite forming and growth rate decreased further as CIT/Ca was increased. Overall, citrate inhibited growth rates most at CIT/Ca ≤ 50%, while nucleation was less affected. In contrast, at CIT/Ca > 50%, citrate strongly inhibited nucleation but had less effect on the growth rate. The results illustrate the spectrum of impacts that complexing compounds can have on CaCO3 crystallization, by forming complexes in solution, affecting CaCO3 saturation state, and also by interacting with the crystal surfaces, thereby controlling nucleation and growth. The extent and the type of effect depend on concentration regimes.

中文翻译:

柠檬酸根离子对无水CaCO 3成核和生长的影响

柠檬酸盐已经显示出抑制CaCO 3的生长,并且在生物方解石中也发现了柠檬酸盐,但是仍然缺乏对柠檬酸盐如何控制CaCO 3形成以及因此CaCO 3多晶型物稳定性和晶体形态的充分了解。我们研究了柠檬酸盐(CIT)的效果上的CaCO 3结晶通过监测结晶速率和结晶多形体,大小和形态作为增加的函数摩尔%CIT /钙(内[Ca 2+ ] = [CO 3 2-] = 4 mM)。在CIT / Ca≤50%时,球v石和方解石均形成,但随着CIT / Ca的增加,成核和生长受到阻碍,这通过诱导时间的增加和反应速率常数的降低证明,使用Johnson-Mehl-Avrami拟合-Kolmogorov模型。部分原因是CIT-Ca络合度越高[CIT]越高,从而相对于球ate石和方解石降低了饱和状态。同时,随着CIT / Ca的增加,较小的球ate石球和更长的方解石晶体证明了CIT的吸附抑制了晶体的生长。当CIT / Ca≥75%时,球ate石的形成被完全抑制,仅长方解石形成,且随着CIT / Ca的增加,生长速率进一步降低。总体而言,在CIT / Ca≤50%时,柠檬酸盐对生长的抑制作用最大,而对成核的影响较小。相反,当CIT / Ca> 50%时,柠檬酸盐强烈抑制成核作用,但对生长速率的影响较小。结果说明了络合化合物对CaCO的影响范围3结晶,通过在溶液中形成配合物,从而影响的CaCO 3饱和状态,并且还通过与晶体表面相互作用,从而控制成核和生长。影响的程度和类型取决于集中制度。
更新日期:2017-09-08
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