Calcite Growth Rates As a Function of Aqueous Calcium-to-Carbonate Ratio, Saturation Index, and Inhibitor Concentration: Insight into the Mechanism of Reaction and Poisoning by Strontium
Calcite Growth Rates As a Function of Aqueous Calcium-to-Carbonate Ratio, Saturation Index, and Inhibitor Concentration: Insight into the Mechanism of Reaction and Poisoning by Strontium
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DOI：
10.1021/cg300350k
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发表时间：
2012-07-01
影响因子：
3.8
通讯作者：
Stack, Andrew G.
中科院分区：
文献类型：
--
作者：
Bracco, Jacquelyn N.;Grantham, Meg C.;Stack, Andrew G.
利用原位原子力显微镜，在两个饱和指数下，测量了{10（1）over bar 4}方解石表面上的钝台阶和锐台阶取向的生长速率，作为水溶液中碳酸钙比和水溶液中锶浓度的函数。发现抑制生长所需的锶的量与含水钙浓度相关，但与碳酸盐不相关，表明锶抑制钙离子附着到方解石表面上的反应位点。锶/钙阳离子交换选择性系数，K-ex，估计为1.09 +/- 0.09和1.44 +/- 0.19的反应位点上的钝和急性步骤的方向，分别。这项工作的含义是，为了避免毒害方解石的生长，钙的浓度应高于锶浓度和K-ex的商，而不管饱和指数。以前的分析模型的成核扭结网站的步骤扩展到包括在多个饱和指数和锶的影响的增长率。钙附着的速率常数被发现是相似的两个步骤的取向，但碳酸盐的变化显着。这项工作将对天然或工程方解石生长产生影响，例如隔离地下锶污染。
Using in situ atomic force microscopy, the growth rates of the obtuse and acute step orientations on the {10 (1) over bar4} calcite surface were measured at two saturation indices as a function of the aqueous calcium-to-carbonate ratio and aqueous strontium concentration. The amount of strontium required to inhibit growth was found to correlate with the aqueous calcium concentration, but did not correlate with carbonate, suggesting that strontium inhibits attachment of calcium ions to reactive sites on the calcite surface. Strontium/calcium cation exchange selectivity coefficients, K-ex, are estimated at 1.09 +/- 0.09 and 1.44 +/- 0.19 for reactive sites on the obtuse and acute step orientations, respectively. The implication of this work is that, to avoid poisoning calcite growth, the concentration of calcium should be higher than the quotient of the strontium concentration and K-ex, regardless of the saturation index. Previous analytical models of nucleation of kink sites on steps are expanded to include growth rates at multiple saturation indices and the effect of strontium. The rate constants for calcium attachment are found to be similar for the two step orientations, but those of carbonate vary significantly. This work will have implications for natural or engineered calcite growth, such as to sequester subsurface strontium contamination.