Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 49, Issue 20, Pages 12551-12559Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.5b01317
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Funding
- National Science Foundation [CBET 1232619, DGE-1122492]
- Advanced Research Projects Agency-Energy (ARPA-e), U.S. Department of Energy [DE-AR0000306]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1232619] Funding Source: National Science Foundation
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Pressure-retarded osmosis (PRO) is a promising source of renewable energy when hypersaline brines and other high concentration solutions are used. However, membrane performance under conditions suitable for these solutions is poorly understood. In this work, we use a new method to characterize membranes under a variety of pressures and concentrations, including hydraulic pressures up to 48.3 bar and concentrations of up to 3 M NaCl. We find membrane selectivity decreases as the draw solution concentration is increased, with the salt permeability coefficient increasing by a factor of 2 when the draw concentration is changed from 0.6 to 3 M NaCl, even when the applied hydraulic pressure is maintained constant. Additionally, we find that significant pumping energy is required to overcome frictional pressure losses in the spacer-filled feed channel and achieve suitable mass transfer on the feed side of the membrane, especially at high operating pressures. For a meter-long module operating at 41 bar, we estimate feedwater will have to be pumped in at a pressure of at least 3 bar. Both the reduced selectivity and increased pumping energy requirements we observe in PRO will significantly diminish the obtainable net energy, highlighting important new challenges for development of systems utilizing hypersaline draw solutions.
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