Adobes-Vidal Maria, Pearce Harriet, Unwin Patrick R
Electrochemistry and Interfaces Group, Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
Molecular Analytical Science Centre for Doctoral Training, Senate House, University of Warwick, Coventry, CV4 7AL, UK.
Phys Chem Chem Phys. 2017 Jul 21;19(27):17827-17833. doi: 10.1039/c7cp02252b. Epub 2017 Jun 28.
Although the dissolution kinetics of calcite in acid waters has been studied for more than a century, the process is not fully understood, and for particles and microcrystals the process is often assumed to be diffusion-controlled. Herein, the dissolution kinetics of calcite single microcrystals in aqueous solution (pH ca. 3) has been investigated for the first time by a combination of real-time optical microscopy coupled with numerical simulations. The small size and well-defined geometry of rhombohedral calcite single crystals enables the measurement of the dissolution rates of the individual crystal faces exposed to the solvent and an assessment of the relative importance of corners and edges compared to the {104} faces. Data are used to parameterise finite element method (FEM) models for the quantitative analysis of dissolution kinetics. The simulations provide an accurate determination of the near-interface concentration of solution species during dissolution, as well as concentration gradients. The intrinsic first-order dissolution rate constant for the attack of protons on the exposed {104} faces, k = (6.4 ± 2.8) × 10 m s, is in good agreement with previous microscopic and macroscopic measurements, corroborating the method. This study is a further demonstration of the power of simple in situ optical microscopy for quantitative interfacial (dissolution/growth) kinetic measurements, using a configuration of practical relevance for processes as diverse as the remediation of acid water and scale removal.
尽管方解石在酸性水中的溶解动力学已经研究了一个多世纪，但该过程仍未被完全理解，对于颗粒和微晶，通常认为该过程受扩散控制。在此，首次通过实时光学显微镜与数值模拟相结合的方法，研究了方解石单晶在水溶液（pH约为3）中的溶解动力学。菱面体方解石单晶的小尺寸和明确的几何形状，使得能够测量暴露于溶剂中的各个晶面的溶解速率，并评估角和边相对于{104}面的相对重要性。数据用于对方程溶解动力学定量分析的有限元方法（FEM）模型进行参数化。模拟能够精确确定溶解过程中溶液物种的近界面浓度以及浓度梯度。质子攻击暴露的{104}面的本征一级溶解速率常数k = (6.4 ± 2.8) × 10 m s，与先前的微观和宏观测量结果高度一致，证实了该方法。这项研究进一步证明了简单的原位光学显微镜在定量界面（溶解/生长）动力学测量方面的强大功能，其使用的配置与酸性水修复和水垢去除等多种过程具有实际相关性。
