NSF-BSF: Ion transport and selectivity in salt-rejecting membranes operating at elevated salinities and pressures

从咸水和海水淡化以及石油和天然气生产产生的废物中，会产生大量极咸的水。净化这些废水是一个重要的优先事项，因为它(1)通过增加供水来促进人类的福祉和繁荣，(2)通过减少潜在有害废水的排放来保护公众健康。尽管净化非常咸的水很重要，但目前的净化过程需要大量的热能或热量。这项研究项目将研究如何使用聚合物膜来处理极咸的水源。与传统的加热系统相比，这种膜处理可以使用不到十分之一的能量。新的实验和分子模拟将被用来更好地了解聚合物膜在高盐和高压条件下的性能，这是净化这类废水所需的。通过这些实验获得的知识将使开发专门用于高盐废水的聚合物膜成为可能。学生和研究人员将直接与国际合作伙伴合作，包括前往以色列促进文化和科学交流。将通过创建一个创新的“解决水资源短缺的工程解决方案”模块来改进本科教育，由合作者担任客座讲师。该项目的跨学科性质将通过CU Boulder BOLD中心激发人们对化学工程、环境工程和分离科学的兴趣，加强对未被充分代表的第一代大学本科生的指导。将通过开发和实施课堂课程、实践活动和将公开提供的关于全球缺水挑战和工程解决方案的短片，实现对高中生的推广。该研究项目将阐明高盐度盐水处理过程中膜中离子传输的机制，并通过调整化学和结构来创建设计具有更高水盐选择性的膜的框架。中心假设是，盐度和压力的升高通过聚合物脱胀、静电电荷屏蔽、膜压实和离子水化性质的根本改变，导致固有离子传输性质的显著变化。将使用先进的传输表征技术全面调查极端盐度和压力条件对这些现象的影响。特别是，过渡态理论将被应用于膜的渗透性，以阐明在离子传输过程中发生的与分子水平的焓和熵相关的效应，这些效应源于极端的盐度和压力条件。这种分子水平的效应将通过对离子通过膜的传输的分子模拟来进一步探索。基于所获得的洞察力，将探索在盐度和压力升高的情况下使用定制的电荷、疏水性和交联度来提高膜的水盐选择性。最终，该项目的结果将揭示高盐度和高压力对反渗透和纳滤膜孔极端限制下的分子传输的影响，提高对聚合物中离子传输的基本了解，并创建有助于开发基于膜的高盐度盐水处理过程的设计建议。该奖项反映了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。

Extremely salty water is produced in enormous quantities as waste from brackish water and seawater desalination, and oil and gas production. Purifying these wastewaters is a significant priority because it (1) advances human welfare and prosperity by increasing water supplies and (2) protects public health by reducing the discharge of potentially harmful wastewaters. Despite the importance of purifying very salty waters, current purification processes require substantial amounts of thermal energy or heat. This research project will investigate how to use polymer membranes to treat extremely salty water sources. Such membrane treatments can use less than one-tenth of the energy compared to conventional thermal systems. Novel experiments and molecular simulations will be used to better understand how polymer membranes perform under the high salt and high-pressure conditions needed for purifying this type of wastewater. The knowledge gained by these experiments will make it possible to develop polymer membranes specifically for high-salt wastewaters. Students researchers will collaborate directly with international partners, including travelling to Israel to improve cultural and scientific exchange. Undergraduate education will be improved through the creation of an innovative “Engineered Solutions to Water Scarcity” module where collaborators serve as guest lecturers. The interdisciplinary nature of this project will enhance mentorship of underrepresented and first-generation university undergraduate students through the CU Boulder BOLD Center by motivating interest in chemical engineering, environmental engineering, and separations science. Outreach to high-school students will be accomplished by developing and implementing classroom lessons, hands-on activities, and a short video that will be made publicly available on global water scarcity challenges and engineered solutions. The research project will elucidate mechanisms governing ion transport in membranes during high-salinity brine treatment and create a framework for designing membranes with improved water-salt selectivity by tuning chemistry and structure. The central hypothesis is that elevated salinity and pressure cause significant variations in the intrinsic ion transport properties through polymer deswelling, electrostatic charge shielding, membrane compaction, and fundamental changes in ionic hydration properties. The impact of extreme salinity and pressure conditions on these phenomena will be comprehensively investigated using advanced transport characterization techniques. In particular, transition state theory will be applied to membrane permeability to elucidate molecular-level enthalpy- and entropy-related effects that occur during ion transport and stem from extreme salinity and pressure conditions. Such molecular-level effects will be further explored using molecular simulations of ion transport through the membrane. Based on the insights gained, increasing water-salt selectivity of membranes at elevated salinity and pressure using tailored charge, hydrophobicity, and crosslinking density will be explored. Ultimately, the results of this project will reveal the effect of high salinity and pressure on molecular transport under the extreme confinement of reverse osmosis and nanofiltration membrane pores, improve the fundamental understanding of ion transport in polymers, and create design recommendations that will aid in the development of membrane-based processes for high-salinity brine treatment.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.