Thermodynamic and Spectroscopic Studies of Levitated Microdroplets of Highly Supersaturated Solutions

摘要CTS-9625178艾伦·迈尔森该项目研究了在结晶前必须形成的过饱和溶液的行为。溶液结晶是一种重要的分离工艺，广泛应用于各行各业。本项目将利用电悬浮溶液微滴测量过饱和电解质水溶液(如氯化钾、硫酸铝钾和硫酸铵)和非电解质水溶液(如甘氨酸、己二酸和丁二酸)的溶剂活度。这项技术的使用去除了容器壁和溶液中的大部分灰尘和污垢，因此可以实现非常高的过饱和度。这将允许在接近旋节的大范围内确定过饱和溶液的热力学性质。此外，拉曼光谱还将用于研究亚临界分子团簇的形成和时间演化。对热力学和光谱数据进行了适当的理论处理，并用于计算形核诱导时间、团簇尺寸分布和亚稳极限边界。过饱和溶液的热力学性质和团簇演化的研究是相当困难的，因为这些溶液很难制备和保持稳定。悬浮微滴技术为制备高过饱和溶液提供了一种独特的方法，可以用拉曼光谱进行检测。高过饱和溶液的拉曼光谱可以提供成核前分子团簇在过饱和溶液中随时间演化的重要信息。此外，这将是对非水溶液过饱和溶液的热力学和光谱性质的首次研究。该项目将提供有关工业重要体系过饱和溶液热力学性质的更多数据，从而能够利用热力学过饱和度(基于活度而不是浓度的过饱和度)对这些体系的成核和晶体生长进行建模。对于过饱和度在10%以上的情况，根据浓度使用过饱和度的误差很大，并且随着过饱和度的增加而迅速增加。此外，这项工作将通过光谱测量提供关于成核前亚临界星团形成的基本数据。使用适当的理论，这些数据将允许计算对结晶的工业实践很重要的性质，并将有助于结晶工艺的设计和开发。***

ABSTRACT CTS-9625178 Allan Myerson The project examines the behavior of supersaturated solutions which must be formed prior to crystallization. Crystallization from solution is an important separation process which is used in a wide variety of industries. In this project, the solvent activity of supersaturated aqueous solutions of electrolytes (such as potassium chloride, potassium aluminum sulfate and ammonium sulfate) and aqueous and non aqueous solutions of non-electrolytes (such as glycine, adipic acid and succine acid) will be measured employing electrodynamically levitated solution microdroplets. The use of this technique removes the container walls and most dust and dirt from the solution so that very high supersaturation can be achieved. This will allow determination of the thermodynamic properties of supersaturated solutions over a wide range approaching the spinodal. In addition, Raman spectroscopy will be used to examine the formation and time evolution of subcritical molecular clusters. Appropriate theoretical treatments of the thermodynamic and spectroscopic date will be developed and used to calculate the nucleation induction time, size distribution of clusters and metastable limit boundaries. The study of the thermodynamics properties and cluster evolution in supersaturated solutions is quite difficult because these solutions are hard to prepare and keep stable. The technique of levitated microdroplets provides a unique method to prepare highly supersaturated solutions which can be examined employing Raman spectroscopy. Raman spectra of highly supersaturated solutions should yield important information on the time evolution of molecular clusters in supersaturated solutions prior to nucleation. In addition, these will be the first studies of thermodynamic and spectroscopic properties of supersaturated solutions of non-aqueous solutions. This project will supply additional data on the thermodynamic properties of supersaturated solutions of industrially important systems thus allowing modeling of the nucleation and crystal growth of these systems making use of the thermodynamic supersaturation (supersaturation based on activity instead of concentration). For cases in which the supersaturation is above 10%, it has been shown that the error in using supersaturated based on concentration is significant and increases rapidly with increasing supersaturation. In addition the work will supply fundamental data on the formation of subcritical clusters prior to nucleation through spectroscopic measurements. Using appropriate theory, this data will allow calculation of properties which are important to the industrial practice of crystallization and will aid in the design and development of crystallization processes. ***