CAREER: Influence of Pressure on Surfactant Thermodynamics and Transport

出于许多原因，水是一种理想而重要的溶剂。水的毒性低、蒸气压低，对许多化合物都有很高的溶解度。然而，作为一种资源，水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200多万加仑的水，这需要昂贵的水处理来去除污染物。这相当于4万个浴缸，这个水量在美国干旱的州引起了严重的关注。由于这些环境问题，超临界CO2压裂液的使用是一个重要的研究领域。超临界二氧化碳系统在减少用水量和极大地减少当前和下一代工业过程对环境的影响方面具有非凡的潜力。在许多这样的过程中，被称为表面活性剂的分子对它们的使用也是至关重要的。表面活性剂降低两种液体之间或一种液体和一种固体之间的表面张力。在这些涉及油、水、气体和固体的复杂环境中，表面活性剂会影响流体的传输。然而，人们对它们在高压下的影响知之甚少。这种认识的缺乏正在减缓在分离、化学反应、医疗器械制造和碳氢化合物压裂液中使用二氧化碳作为“绿色”替代溶剂方面的重大进展。首席研究人员最近开发并演示了一种仪器，可以准确测量高压界面和表面的表面活性剂的性质，并了解化学结构如何影响性能。该奖项将致力于通过最新开发的高压微张力计和分析技术，开发描述高压界面上表面活性剂界面活性的热力学和传输模型。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，将导致模型的参数化。这项工作将通过考虑界面曲率、表面活性剂浓度和主体流体流动的影响的时间尺度分析来极大地促进这项工作，这允许区分动力学和扩散传输机制。预计会有几种化学/性能关联。例如，各相分配系数的量化将决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了解泡沫和乳状液稳定性与化学结构和界面活性的关系。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的分子结构的设计。通过这项工作产生的模型参数将允许(1)更深入地了解加压下表面活性剂的热力学，(2)传输参数与表面活性剂结构之间的直接关联，并最终(3)在工业应用中分子结构与性能之间的关联。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制定一项STEM职业道路建设计划，涉及五所不同的小学/中学。我们将与路易斯·斯托克斯少数群体参与联盟合作，介绍代表不足的少数群体，并为他们在德雷克塞尔任期内的研究培训做好准备。最后，PI将举办一年一度的工业研讨会，邀请当地行业分享最近的发现和实验结果，以努力建立合作并增加基础知识和理解的传播。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.