SusChEM: Development of Next-Generation, Ultra-Selective Aquaporin-Based Membranes for Sustainable Water Purification

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1437630ElimelechSusChEM: Development of Next-Generation, Ultra-selective Aquaporin-based Membranes for Sustainable Water PurificationThe production of drinking water from non-traditional sources, such as brackish water, seawater, and wastewater, is critical to augmenting global water supply. Reverse osmosis (RO) is the dominant technology for desalination and wastewater reuse, and its worldwide usage is expected to significantly increase in the future. In addition, an emerging membrane technology, forward osmosis (FO), has the potential to play an important role in desalination, wastewater reuse, and treatment of high salinity brines. Thin film composite polyamide membranes are currently the state-of-the-art technology for these processes. However, despite the relatively high salt rejection of these membranes (99 %), they have less-than-ideal selectivity to a wide range of solutes, which leads to higher energy consumption and increased capital and operation costs. Increasing solute selectivity can only be achieved at the expense of significant decrease in water permeability due to the intrinsic trade-off between permeability and selectivity of current generation polymeric membranes. A radically different approach for membrane design is critically needed in order to break the inherent permeability-selectivity tradeoff of current membrane technologies. This project will also promote diversity and to enhance the involvement of under-represented groups in science and engineering by: 1) establishing a biomolecular engineering workshop at a minority serving institution, 2) developing a tele-tutoring program to facilitate scholarship in STEM at a minority serving institution, 3) actively participate in conferences and workshops that promote diversity in science and engineering, 4) training and inspiring undergraduate students, focusing on under-represented groups in science and engineering, and, 5) participation in science outreach and science mentoring of inner city, low-income minority students. The overall goal of the proposed research is to develop a novel, ultra-selective aquaporin-based membrane for water purification. The proposed new approach utilizes the uniquely selective nature of aquaporin, an integral cell membrane protein that is permeable only to water, to overcome the intrinsic permeability-selectivity trade-off of current membranes. Specific objectives include: studying aquaporin incorporation and functionality in vesicles comprising polymerizable lipids or block co-polymers; developing a fundamental understanding of the effects of rupture technique, surface chemistry, lipid or block co-polymer chemistry, and aquaporin concentration on the formation of tethered supported bilayers through vesicle rupture; fabricating a stable and ultra-selective aquaporin-based layer on top of a chemically-modified membrane support; and characterizing the fabricated membrane to assess membrane water flux and selectivity for a variety of solutes. To complete the project the PIs propose the following tasks: 1) expression and purification of aquaporin; 2) end-functionalization of lipid or triblock co-polymer to allow for bilayer tethering and polymerization; 3) analysis of aquaporin permeability in polymerized lipid or polymer vesicles using stopped flow light scattering; 4) assessment of vesicle rupture techniques and bilayer formation kinetics on model surfaces; 5) fabrication of aquaporin-containing membranes using surface-modified commercial and hand-cast nanofiltration membranes as a bilayer support; 6) evaluation of the performance (water flux and solute rejection) of fabricated membranes in reverse osmosis and forward osmosis; and, 7) testing the membrane mechanical and chemical robustness. They will accomplish this they will: (i) study aquaporin functionality in polymerizable lipids, (ii) utilize a readily-occurring chemical reaction to covalently rupture aquaporin-containing vesicles, (iii) study the deposition and rupture kinetics of covalent-assisted aquaporin-containing vesicle rupture, (iv) chemically tether an aquaporin-containing bilayer onto a nanofiltration membrane support, and, (v) assess planar aquaporin-based membrane permeability of neutral solutes, such as ammonia, urea, and boron. The focus on solute ultra-selectivity also differs from previous membrane development efforts, which largely focused on maximizing water permeability.