Collaborative Research: A Bioinspired Approach towards Sustainable Membranes for Resilient Brine Treatment

Many water treatment and industrial processes generate significant amounts of high-salinity brines including seawater desalination, inland brackish water desalination, and oil and gas production by fracking. The management of hazardous high-salinity brines from water desalination plants and oil/gas production wells has emerged as a global environmental challenge.

Membrane distillation (MD) is a promising technology for the treatment of high-salinity brines that could reduce the amounts of brine that need to be disposed of while generating a purified water permeate to support industrial and agricultural usages. During the last decade, significant progress has been made toward the development of more efficient MD membranes with high wetting and scaling resistance for high-salinity brine treatment.

However, these membranes are typically prepared by modifying their surfaces with long-chain per- and polyfluoroalkyl substances (PFAS), which have become priority pollutants due to increasing concerns about their persistence in the environment, stability, and toxicity to humans and living organisms. The overarching goal of this project is to explore the design and fabrication of wetting- and scaling-resistant MD membranes for brine treatment without the use of PFAS.

Inspired by the unique repellency of springtails towards low surface tension liquids, the Principal Investigators propose to test the hypothesis that efficient MD membranes, with both high wetting resistance and high scaling resistance, can be fabricated by covalent attachment of springtail-inspired supracolloidal structures onto the surface of a hydrophobic flat sheet membrane. The successful completion of this project will benefit society through the development of new fundamental knowledge to guide the design and fabrication of PFAS-free membrane materials for robust and efficient brine treatment.

Additional benefits to society will be achieved through outreach and educational activities including the mentoring of one graduate student at the University of Tennessee, Knoxville and one graduate student at Colorado State University.

The effectiveness of membrane distillation (MD) as a brine treatment technology is limited by both the intrusion of brines into membrane pores (membrane pore wetting) and the precipitation of minerals on the membrane surfaces (membrane scaling). The goal of this project is to design and fabricate a new family of biomimetic wetting- and scaling-resistant MD membranes without using PFAS building blocks.

To advance this goal, the Principal Investigators (PIs) proposal to explore new strategies to modify the surface of a commercially available hydrophobic flat sheet membrane by covalent attachment of supracolloidal structures that mimic the overhang texture of springtails and their unique capability to repel low surface tension liquids. These supracolloidal structures will be formed through controlled assembly of smaller colloids onto the surfaces of larger colloids that have overhang structures with negative curvature and non-fluorinated ligands.

The specific objectives of the research are to: 1) Elucidate the design criteria of supracolloidal structures for wetting resistant membranes, 2) Characterize and unravel the mechanisms of scaling resistance of the new biomimetic MD membranes, and 3) Evaluate the treatment effectiveness of the new MD membranes using model brine mixtures and a high salinity produced water from an oil and gas production field in Colorado. The successful completion of this project has the potential for transformative impact through the generation of new fundamental knowledge and functional materials to advance the development of PFAS-free MD membranes for efficient and cost-effective treatment of high salinity brines.

To implement the educational and training goals of this project, the Principal Investigators (PIs) plan to integrate the findings from this research into existing undergraduate and graduate courses at the University of Tennessee, Knoxville (UTK) and Colorado State University (CSU). In addition, the PIs propose to leverage existing programs at UTK and CSU to launch outreach activities to recruit and engage high and middle school students from underrepresented groups with a focus on the utilization of bioinspired materials to improve water sustainability.

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.