SBIR Phase II: Chemically Resistant Membranes for Water Purification

This SBIR Phase II project will develop breakthrough polymeric membranes to purify water by reverse osmosis. It will address the recognized global need for clean drinking water driven by increasing population and urbanization that affect billions of people living in water-stressed lands. The impurities in water from different geographical locations and different types of water (e.g., seawater, industrial wastewater, tap water reuse) differ, and separation membranes that can selectively remove different combinations of impurities will be critical to addressing this world challenge. The technology provides a means to greatly eliminate costly cleaning operations and minimize plant downtime in this ~$5 billion market. Industrial and Enhanced energy and operating efficiency will be achieved through reduced required pretreatment and enhanced fouling resistance, leading to extended use cycles and improved water flux over the lifetime of the membranes. This SBIR Phase II project will produce thin film composite reverse osmosis (RO) membranes comprised of precisely sulfonated polysulfone polymers in the ~100-nm thick range on a porous support. These novel membranes will provide a long sought after revolution in water purification membranes with their high resistance to chlorine for disinfection and ability to prevent biofouling. For the first time, they will also efficiently remove monovalent salts that contaminate seawater and brackish water from their mixed salt compositions. Sulfonated polysulfones have been considered previously for RO membranes due to their inherent chemical resistance, but they failed due to low salt rejection at high ionic strengths and their inferiority in salt rejections in mixed salt feedwater. Municipal water requirements are high and their process water is often contaminated with toxic products (boron and arsenic moieties, hydrocarbons, perfluorinated surfactants, biofilms), making reuse difficult to impossible technically and economically. This project advances material synthesis and material processing through precisely sulfonated polymers. Phase II will take advantage of these advances to optimize the membrane coating process, scale it to pilot quantities, and measure resistance to a range of impurities found in tap water reuse, industrial water purification, as well as in purification of brackish surface and groundwater and highly saline seawater. 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.