EAGER: Water Continuity on the Performance of Osmotically Driven Membrane Processes

EAGER：水连续性对渗透驱动膜工艺性能的影响

• 批准号: 2219936
• 负责人: Lianfa Song
• 金额: $ 24.88万
• 依托单位: Texas Tech University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219936&HistoricalAwards=false
• 关键词: EAGER; Water; Continuity; Performance; Osmotically

Osmotically-driven membrane processes (ODMPs) leverage the difference in chemical potentials between two solutions that are separated by a semipermeable membrane (i.e., osmotic pressure) to move water from the low solute concentration side (feed water) to the high solute concentration side (draw solution). This ability to transport water through a membrane via osmotic pressure, without applying an external hydraulic pressure driving force, can be used to supply clean water and produce renewable energy directly from saline waters. However, low water flux across the membrane limits the performance of ODMPs and their potential to meet global water and energy needs. A phenomenon called internal concentration polarization (ICP) has received much of the blame for the low water flux under an osmotic pressure-driving force alone. The prevailing theory is that a strong ICP develops in the membrane’s porous support layer and diminishes the effective osmotic pressure driving water across the active (skin) layer relative to the total osmotic pressure of the membrane draw solution. Yet, membranes designed to minimize or eliminate ICP and, thus, improve water flux have yielded few technological breakthroughs. This project will consider the controversial idea that the collapse of water continuity across the membrane, instead of ICP, is mainly responsible for the low water flux under osmotic pressure. Successfully demonstrating that water continuity within the membrane is a key factor in ODMP performance has the potential to transform the field of membrane-based water treatment and purification. The project will also provide opportunities for graduate student training and STEM outreach through the Texas Tech University Chapter of the Society for the Advancement of Chicanos and Native Americans in Science. The goal of this project is to demonstrate that the loss of water continuity inside the membrane of an ODMP is a principal factor contributing to low water flux. A custom membrane system will be constructed such that hydraulic pressure can be independently manipulated on both the feed water and draw solution sides and that the pressure in the feed chamber can be measured when it is sealed and detached from the feed water tank. The membrane system will be used to observe the buildup of negative pressure in the sealed feed chamber under osmotic pressure. Under typical ODMP operating conditions, the system is expected to exhibit a process of negative pressure buildup and abrupt dissipation, wherein the negative pressure is relieved by the collapse of water continuity (i.e., cavitation). In addition to demonstrating the breakup of water continuity, the study will systematically examine the relationship between water flux in ODMPs and the status of water continuity as a function of operating conditions and membrane material. The independence of the hydraulic pressures applied to the feed water and draw solution sides will also be evaluated. The research is expected to generate new insights into osmotic pressure-driven water transport mechanisms across membranes.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.

渗透驱动的膜过程（ODMP）利用了两种溶液之间的化学电位差异，这些溶液通过半透明的膜分离（即渗透压）将水从低溶解度浓度（进给水）移至高溶解度浓度侧（DARD溶液）。这种能够通过渗透压力通过渗透压力运输水的能力，而无需施加外部水压驱动力，可用于供应清洁的水并直接从盐水中产生可再生能源。但是，整个膜的水通量低限制了ODMP的性能及其满足全球水和能源需求的潜力。一种称为内部浓度极化的现象（ICP）仅在渗透压力驾驶力下就获得了低水通量的大部分模糊。流行的理论是，强大的ICP在膜的多孔支撑层中发展，并减少相对于膜绘制溶液的总渗透压，有效的渗透压驱动水（皮肤）层。然而，旨在最大程度地减少或消除ICP的膜，因此改善水通量几乎没有技术突破。该项目将考虑一个有争议的观念，即整个膜的水连续性而不是ICP的崩溃主要负责渗透压力下的低水通量。成功地证明膜内的水连续性是ODMP性能的关键因素，具有改变基于膜的水处理和纯化领域的潜力。该项目还将通过德克萨斯理工大学促进学会和美国原住民科学学院的德克萨斯理工大学分会为研究生培训和STEM推广提供机会。该项目的目的是证明ODMP膜内水连续性的损失是导致低水通量的主要因素。将构建一个定制的膜系统，以便可以在进料水和绘制溶液侧独立操纵水压压力，并在将其密封并从进料水箱中脱离时测量进料室中的压力。膜系统将用于观察在渗透压下密封进料室中负压积累。在典型的ODMP操作条件下，该系统有望耗尽负压积聚和突然耗散的过程，其中水连续性崩溃（即空化）可以缓解负压。除了证明水连续性的破裂外，该研究还将系统地检查ODMP中的水通量与水连续性状态与工作条件和膜材料的函数之间的关系。还将评估施加到进料水和绘制溶液侧的水解压力的独立性。这项研究有望产生对跨膜渗透压驱动的水运输机制的新见解。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响评估标准，被视为通过评估来获得珍贵的支持。