An increasingly arid world requires the innovation of sustainable technologies to produce potable water from impaired and saline water sources. Existing desalination technologies, like reverse osmosis (RO), remain an unsustainable option due to high energy costs and environmentally harmful brine discharges. Forward osmosis (FO) is an innovative and sustainable desalination alternative that promises to provide potable water from saline water sources at radically reduced cost, energy consumption, and brine discharge. Unlike RO, which requires a hydraulic driving force for separation, FO utilizes an osmotic driving force generated by a draw solution. The novelty of FO lies in the use of NH3-CO2 salts as a draw solute. These salts were identified by the PI and co-PI for their osmotic efficiency (capable of generating osmotic pressures up to 3,000 psi or 7,000 ft of head) and easy removal and reuse using only low grade waste heat (down to 40°C). The single obstacle to the successful commercialization of FO technologies is the poor productivity of existing salt-rejecting membranes due to a severe mass transfer limitation known as internal concentration polarization. The University of Connecticut (UConn) and Oasys WaterTM (Oasys) are combining their efforts to enable this transformational technology by considering revolutionary thin film composite (TFC) membrane designs that will mitigate the effects of this debilitating phenomenon. Key technical areas of innovation, identified by the PI and co-PI in previous efforts, are focused on making the membrane supporting structure thinner, more porous and less tortuous. This proposed work considers the implementation of electrospun nanofiber nonwovens as novel support structures in next generation TFC membranes tailored for NH3-CO2 forward osmosis. Electrospinning is a method that is commonly used to create highly porous and thin nanofibrous nonwoven materials. This project is the first effort to apply this unique structure with tunable properties in TFC membranes for FO applications. The nanofiber nonwoven will serve to anchor a crosslinked polyamide barrier layer deposited by in situ polymerization of m-phenylenediamine. The resulting TFC membranes will be characterized and evaluated for flux and selectivity performance. FO flux modeling techniques, developed by the PI, will be used to determine the severity of internal concentration polarization and provide input for future iterations of membrane design.
This effort will for the first time employ an electrospun nanofiber nonwoven as a support structure for a TFC membrane tailored for FO. This work will further enable FO, an emerging membrane technology, to deliver on promised results of lower water cost and higher recovery. Constructing these membranes in the laboratory will require a comprehensive approach that will consider all aspects of the electrospun support fabrication and polyamide selective layer formation, thus requiring a unique combination of expertise in polymer science, nanotechnology, and mass transport. This project will also result in fundamental understanding of how the support layer structure impacts the in situ polymerization process and the performance of the resulting film. The PI and co-PI, both considered world experts on FO, are uniquely suited to complete this proposed work. Both have access to facilities and expertise that are customized specifically for the tasks outlined in this proposal.
This emerging technology platform will serve as an excellent educational tool for students at UConn. Forward osmosis is a multistep process which relies on several unit operations. We will thus specifically integrate forward osmosis into the Chemical Engineering capstone Senior Design Course, giving multiple groups an opportunity to compete for the best design configuration which uses the least energy and has the lowest capital cost. This effort will be of interest to Oasys, which will sponsor an internship program for UConn engineering students that will facilitate the employment of engineers from UConn as well as foster a long term academic-industrial partnership. A safe and sustainable water supply in the 21st century is the most daunting task humanity faces with regards to public health. We must augment our existing water supplies through the treatment of compromised sources with sustainable and affordable technologies like FO. Nowhere are these issues more relevant than in the developing world. The PI will thus embark on a unique project in collaboration with the UConn chapter of Engineers without Borders (EWB) to install commercial FO systems in Ethiopia as remote water purifiers and teaching tools. This effort will be part of an existing US Agency for International Development/Higher Education (US-AID/HED) project conducted through UConn.
