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

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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.