Collaborative Research: Dry-Wet Phase Inversion Pathway of Graphene Oxide (GO)-Based Mixed-Matrix Membranes for Mineral Ions Separation by Membrane Distillation

日益严重的污染和水资源短缺使得人们需要获取和回收非常规水源。其中一个来源是高矿化度的采出水，这些水在石油或天然气生产过程中从地下浮出水面。采出水的矿物质浓度过高，不符合饮用水可接受质量的监管标准。然而，通过去除这些不需要的成分，产出水可以重新用于农业应用，如灌溉、牲畜灌溉和水产养殖。因此，确定一种脱盐采出水的工艺具有重要的社会意义。反渗透是一种压力驱动的膜过程，用于淡化含有相对较低矿物质浓度的水，如地下水。采出水中的矿物质浓度非常高，因此反渗透法不适用于海水淡化。膜蒸馏由于其独特的热膜特性，是一种很有前途的高盐度水中矿物分离技术。氧化石墨烯基膜具有高效的防污性能，有望改善膜蒸馏过程。基于氧化石墨烯的膜是用一种称为相反转的最先进的方法制造的。相反转通过将氧化石墨烯直接集成到聚合物材料中来生产这些膜。该项目旨在对氧化石墨烯在新型干湿相转化合成中所起的作用进行详细的基础和机理理解，以生产用于膜蒸馏的膜。该项目还将结合研究和教育活动，培养膜技术多用途领域的新一代专家，特别是应用于水处理的专家。用于海水淡化和采出水处理的膜技术有可能从根本上改变社会对水再利用的看法。提高水处理能力将使农村、干旱和偏远地区获得有限的水，拥有便携式和可靠的膜系统来处理水。推进有前途的脱盐膜分离工艺，如膜蒸馏，需要获得功能材料和结构-性能关系的基本知识来设计有效的膜。膜蒸馏是多级闪蒸和多效蒸馏过程的一种节能替代方法，可以配置为浓缩盐水。然而，由于缺乏具有高渗透通量、水回收率和抗结垢性的合适膜，膜蒸馏在规模上的应用受到限制。本项目的目标是建立和理解干湿相反相膜的发展方法，以克服这些限制，用于采出水净化。氧化石墨烯是一种多功能的防污纳米材料，将用于合成混合基质膜，具有特定于膜蒸馏应用的特性。确定了三个研究目标，以提供对干湿相转化过程的基本见解。在第一个目标中，研究人员将确定氧化石墨烯片的pH值对孔隙形成和疏水性的影响，并确定氧化石墨烯的分散机制。第二个目标是研究在膜蒸馏过程中干湿相转化氧化石墨烯基膜上的离子保留。第三个目标是表征干湿相间的氧化石墨烯基膜的化学、热和机械稳定性。总之，这些知识将为推进膜蒸馏用于高盐度水净化奠定基础。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。

Increasing pollution and water scarcity have created the need to access and recover unconventional water sources. One such source is high-salinity produced water, which surfaces from underground during oil or gas production. Produced water has an excess concentration of minerals and does not meet the regulatory standards of acceptable quality for drinking water. However, by removing these undesirable constituents, the produced water can be reused for agricultural applications such as irrigation, livestock watering, and aquaculture. Therefore, identifying a process to desalinate produced water is of great societal importance. Reverse osmosis is a pressure-driven membrane process used to desalinate water containing relatively low mineral concentrations, such as groundwater. The mineral concentrations of produced water are sufficiently high that reverse osmosis is unsuitable for desalination. Membrane distillation is a promising alternative technology capable of separating minerals from high-salinity water due to its unique thermal-membrane characteristics. Graphene oxide-based membranes, with their efficient antifouling properties, are expected to enhance the membrane distillation process. Graphene oxide-based membranes are fabricated using a state-of-the-art method called phase inversion. Phase inversion produces these membranes by integrating graphene oxide directly into the polymeric materials. This project sets out to develop a detailed fundamental and mechanistic understanding of the role that graphene oxide plays in a novel dry-wet phase inversion synthesis to produce membranes for membrane distillation. This project will also combine research and education activities to train a new generation of experts in the versatile area of membrane technology, particularly as applied to water treatment.Membrane technology for water desalination and treatment of produced water has the potential to fundamentally alter the way society views water reuse. Augmenting water treatment capacity will allow rural, arid, and isolated regions with limited access to water, to have portable and reliable membrane systems for treating water. Advancing promising membrane separation processes for desalination, such as membrane distillation, requires access to fundamental knowledge of functional materials and structure-property relationship to engineer effective membranes. Membrane distillation is an energy-efficient alternative to multi-stage flash and multi-effect distillation processes and can be configured to concentrate brines. However, application of membrane distillation at scale is limited by the lack of suitable membranes exhibiting high permeate flux, water recovery, and resistance to scaling. The goal of this project is to establish and understand the dry-wet phase inversion membrane development approach to overcome these limitations in utility for produced water purification. Graphene oxide is a versatile anti-fouling nanomaterial that will be used in the synthesis of mixed-matrix membranes with properties specific to application in membrane distillation. Three research objectives are defined to provide fundamental insights into the dry-wet phase inversion process. In the first objective, the investigators will establish the role of graphene oxide sheet pH on pore formation and hydrophobic properties and determine the mechanism of dispersion of graphene oxide. The second objective examines ion retention on dry-wet phase inversion graphene oxide-based membranes during membrane distillation. And the third objective focuses on characterizing of the chemical, thermal, and mechanical stability of the dry-wet phase inversion graphene oxide-based membranes. Together, this knowledge will form a foundation for advancing membrane distillation for high-salinity water purification.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.