Hadjittofis Eftychios, Vargas Silvia M, Litster James D, Sedransk Campbell Kyra L
Department of Chemical and Biological Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, UK.
UCB Pharma SA, Chemin du Foriest, B-1420 Braine-l'Alleud, Belgium.
Proc Math Phys Eng Sci. 2021 Aug;477(2252):20210200. doi: 10.1098/rspa.2021.0200. Epub 2021 Aug 25.
The interplay between polymorphism and facet-specific surface energy on the dissolution of crystals is examined in this work. It is shown that, using cationic additives, it is possible to produce star-shaped calcite crystals at very high supersaturations. In crystallization processes following the Ostwald rule of stages these star-shaped crystals appear to have higher solubility than both their rhombohedral counterparts and needle-shaped aragonite crystals. The vapour pressures of vaterite, aragonite, star-shaped calcite and rhombohedral calcite crystals are measured using thermogravimetric analysis and the corresponding enthalpies of melting are obtained. Using inverse gas chromatography, the surface energy of the aforementioned crystals is measured as well and the surface energy of the main crystal facets is calculated. Combining the effect of facet-specific surface energies and the enthalpies of melting on a modified version of the classical solubility equation for regular solutions, it is proved that the star-shaped calcite crystals can indeed have higher apparent solubility than aragonitecrystals.
本工作研究了多晶型与晶面特定表面能对晶体溶解的相互作用。结果表明，使用阳离子添加剂，在非常高的过饱和度下有可能生成星形方解石晶体。在遵循奥斯特瓦尔德阶段规则的结晶过程中，这些星形晶体的溶解度似乎高于其菱面体对应物和针状文石晶体。使用热重分析测量球霰石、文石、星形方解石和菱面体方解石晶体的蒸气压，并获得相应的熔化焓。使用反相气相色谱法，还测量了上述晶体的表面能，并计算了主要晶面的表面能。将晶面特定表面能和熔化焓的影响结合到正则溶液经典溶解度方程的修正版本中，证明星形方解石晶体的表观溶解度确实可以高于文石晶体。
