Engineered osmosis systems have the potential to sustainably produce fresh water from seawater or wastewater by forward osmosis or to generate power from salinity gradients by pressure retarded osmosis. These membrane-based processes utilize the osmotic gradient that develops between solutions of differing concentrations, which are separated by a semi-permeable membrane, to effect a more efficient separation or to sustainably generate power. However, despite the potential of these technologies to address the global water and energy challenges, osmotically-driven membrane processes have yet to progress significantly beyond conceptualization. The major impediment to advancing these technologies is the lack of an adequate membrane, because the performance of current membranes is significantly hampered by the phenomenon of internal concentration polarization. Similar diffusion-controlled phenomena in other processes have been improved by introducing a convective component of mass transfer. Therefore, this work will take inspiration from the field of microfluidics, where mixing fluids on the micrometer length is of utmost importance, and fabricate membranes for osmotically-driven membrane processes with static mixer-like features to minimize the deleterious effects of internal concentration polarization. To achieve this goal, a phase separation micromolding technique will be used to fabricate high-performance membranes for osmotically-driven membrane processes. The research will also develop a fundamental understanding of how the mixer geometry impacts the overall mass transfer and membrane performance in order to optimize the membrane structure.
The research addresses two of the major global challenges of our time: water scarcity and clean energy. Accomplishing this research will provide the scientific base and methodology to fabricate robust membranes that can find application in a variety of processes, including seawater and brackish water desalination, wastewater reclamation and reuse, and renewable power generation by pressure retarded osmosis. This work is also the first to directly incorporate static mixer-like features into the structure of asymmetric salt-rejecting membranes, with potential applications in a broad range of separation processes.
