CAREER: Influence of Pressure on Surfactant Thermodynamics and Transport

由于许多原因，水是一种理想而重要的溶剂。水对许多化合物具有低毒、低蒸气压和高溶解度的特点。然而，水作为一种资源正变得越来越有限和昂贵。例如，我们目前每口水力压裂井使用超过200万加仑的水，这需要昂贵的水处理来去除污染物。这相当于40,000个浴池的水量，这在干旱的美国各州引起了严重关注。由于这些环境问题，使用超临界CO2压裂液是一个重要的研究领域。超临界二氧化碳系统具有非凡的潜力，可以减少水的使用，大大减少当前和下一代工业过程对环境的影响。在许多这些过程中，被称为表面活性剂的分子对它们的使用也至关重要。表面活性剂降低两种液体之间或液体与固体之间的表面张力。在这些复杂的环境中，包括油、水、气体和固体，表面活性剂会影响流体的输送。然而，人们对它们在高压下的作用知之甚少。在分离、化学反应、医疗设备制造和碳氢化合物压裂液中，二氧化碳作为一种“绿色”替代溶剂的使用进展缓慢。首席研究员最近开发并演示了一种仪器，可以精确测量高压界面和表面表面活性剂的性质，并了解化学结构如何影响性能。该合同将侧重于通过新开发的高压微张力计和分析技术，开发描述高压界面下表面活性剂界面活性的热力学和输运模型。模型参数化将通过分析各种表面活性剂在不同界面上的静态和动态界面张力数据作为压力和温度的函数来实现。考虑到界面曲率、表面活性剂浓度和整体流体流动的影响，考虑到动力学和扩散输运机制之间的区别，时间尺度分析将极大地促进这项工作。预计会有一些化学/性能相关性。例如，各相分配系数的量化将确定不同化学结构的优先溶解度及其在高压过程中的适用性。界面流变学研究将有助于更好地理解泡沫和乳液的稳定性作为化学结构和界面活性的函数。结合动力学理论和热力学状态方程模型的理论框架将指导改进分子结构的设计。这项工作产生的模型参数将允许(1)更深入地了解表面活性剂在高压下的热力学(2)传输参数与表面活性剂结构之间的直接关联，以及最终(3)工业应用中分子结构与性能之间的相关性。在教育方面，这项与林迪学者计划和上达比学区合作的资助工作将开发一个涉及五所不同小学/中学的STEM职业道路建设计划。我们将与路易斯·斯托克斯-少数民族参与联盟合作，介绍和准备代表性不足的少数民族在德雷克塞尔大学任职期间接受研究培训。最后，PI将举办年度工业研讨会，邀请当地工业界分享最近的发现和实验结果，以建立合作并增加基本知识和理解的传播。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Water is a desirable and important solvent for many reasons. Water has low toxicity, low vapor pressure, and high solubility for many compounds. However, water is becoming increasingly limited and expensive as a resource. For example, we currently use more than 2 million gallons of water for each hydraulically fracked well, which requires costly water treatment to remove contaminants. This is equivalent to 40,000 baths, an amount of water that is raising serious concern in arid American states. Due to these environmental concerns, the use of supercritical CO2 fracking fluids is an important research area. Supercritical CO2 systems have extraordinary potential to reduce water use and greatly reduce the environmental impact of current and next-generation industrial processes. In many of these processes, molecules called surfactants are also vital to their use. Surfactants lower the surface tension between two liquids or between a liquid and a solid. Surfactants affect the transport of fluids in these complex environments involving oil, water, gases, and solids. However, very little is known regarding their effect at high pressure. This lack of understanding is slowing major strides in the use of CO2 as a "green" alternative solvent in separations, in chemical reactions, medical device fabrication, and hydrocarbon fracking fluids. The principal investigator has recently developed and demonstrated an instrument to accurately measure properties of surfactants at high pressure interfaces and surfaces and understand how chemical structure influences performance. This award will focus on developing thermodynamic and transport models describing surfactant interfacial activity at high pressure interfaces via a newly developed high pressure microtensiometer and analysis technique. Model parameterization will result from analyzing static and dynamic interfacial tension data of various surfactants at various interfaces as a function of pressure and temperature. This work will be highly facilitated by a time scale analysis taking into account the effect of interfacial curvature, surfactant concentration, and bulk fluid flow, which allows for the distinction between kinetic and diffusion transport mechanisms. Several chemistry/performance correlations are expected. For example, quantification of partition coefficients in various phases will determine the preferential solubility of different chemical structures and their applicability in high pressure processes. Interfacial rheology studies will allow for better understanding of foam and emulsion stability as a function of chemical structure and interfacial activity. A theoretical framework that combines kinetic theories and thermodynamic equations of state models will guide design of improved molecular architectures. The model parameters generated by this work will allow for (1) a deeper understanding of surfactant thermodynamics at elevated pressures (2) a direct correlation between transport parameters and surfactant structure and ultimately (3) correlation between molecular structure and performance in industrial applications. Educationally, this funded work in partnership with the Lindy Scholars Program and the Upper Darby School District, will develop a STEM CAREER path building program involving five diverse elementary/middle schools. In collaboration with the Louis Stokes-Alliance for Minority Participation, we will introduce and prepare under-represented minorities for research training during their Drexel tenure. Lastly, the PI will hold annual industrial workshops, inviting local industries, to share in recent discoveries and experimental findings in an effort to build collaboration and increase the dissemination of fundamental knowledge and understanding.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.