Cotti Martina, Stahlbuhk Amelie, Fischer Hartmut R, Steiger Michael, Adan Olaf C G, Huinink Henk P
Eindhoven Institute of Renewable Energy Systems, Eindhoven University of Technology, PO Box 513, Eindhoven 5600 MB, The Netherlands.
Transport in Permeable Media group, Department of Applied Physics, Eindhoven University of Technology, PO Box 513, Eindhoven 5600 MB, The Netherlands.
Cryst Growth Des. 2024 Dec 9;24(24):10082-10093. doi: 10.1021/acs.cgd.4c00589. eCollection 2024 Dec 18.
The hydration of salt hydrates is often described as a solution mediated nucleation and growth mechanism, occurring between a reagent and a product in thermodynamic equilibrium with each other. If a system possesses more than one hydrate phase, the kinetic pathway may involve additional mechanisms due to the formation of intermediate hydrate species. We elected CuSO as our model system and analyzed the pathway leading from CuSO·HO (C1H) to CuSO·5HO (C5H), while CuSO·3HO (C3H) being a possible intermediate. We found that C1H hydration is mediated by the formation of C3H and that C5H does not nucleate directly from C1H, at the studied conditions. The hydration pathway therefore is characterized by the same mechanism occurring twice, nucleation and growth of C3H and nucleation and growth of C5H. Analysis of the hydration kinetics of C1H revealed that C5H nucleates rapidly from C3H, as if the metastability of C3H was reduced when starting from C1H. Therefore, we concluded that the hydration kinetics of C1H are probably controlled by the growth process of C5H. Despite being controlled by a single reaction process, we show that a single front 1D diffusion model is insufficient to describe the reaction kinetics at the tablet level. Understanding of these complex transformations is necessary to evaluate the suitability of these reactions for application, in particular with respect to the achieved power output.
盐水合物的水合作用通常被描述为一种溶液介导的成核和生长机制，发生在彼此处于热力学平衡的试剂和产物之间。如果一个系统具有不止一种水合物相，由于中间水合物物种的形成，动力学途径可能涉及其他机制。我们选择硫酸铜作为我们的模型系统，分析了从硫酸铜·一水合物（C1H）到硫酸铜·五水合物（C5H）的途径，而硫酸铜·三水合物（C3H）是一种可能的中间体。我们发现，在研究条件下，C1H的水合作用是由C3H的形成介导的，并且C5H不是直接从C1H中形成晶核的。因此，水合途径的特征是相同的机制发生两次，即C3H的成核和生长以及C5H的成核和生长。对C1H水合动力学的分析表明，C5H从C3H中快速形成晶核，就好像从C1H开始时C3H的亚稳性降低了一样。因此，我们得出结论，C1H的水合动力学可能由C5H的生长过程控制。尽管由单一反应过程控制，但我们表明，单一前沿一维扩散模型不足以描述片剂水平的反应动力学。了解这些复杂的转变对于评估这些反应在应用中的适用性是必要的，特别是在实现的功率输出方面。
