title: Thin-film composite pressure retarded osmosis membranes for sustainable power generation from salinity gradients.
abstract: Pressure retarded osmosis has the potential to produce renewable energy from natural salinity gradients. This work presents the fabrication of thin-film composite membranes customized for high performance in pressure retarded osmosis. We also present the development of a theoretical model to predict the water flux in pressure retarded osmosis, from which we can predict the power density that can be achieved by a membrane. The model is the first to incorporate external concentration polarization, a performance limiting phenomenon that becomes significant for high-performance membranes. The fabricated membranes consist of a selective polyamide layer formed by interfacial polymerization on top of a polysulfone support layer made by phase separation. The highly porous support layer (structural parameter S = 349 μm), which minimizes internal concentration polarization, allows the transport properties of the active layer to be customized to enhance PRO performance. It is shown that a hand-cast membrane that balances permeability and selectivity (A = 5.81 L m(-2) h(-1) bar(-1), B = 0.88 L m(-2) h(-1)) is projected to achieve the highest potential peak power density of 10.0 W/m(2) for a river water feed solution and seawater draw solution. The outstanding performance of this membrane is attributed to the high water permeability of the active layer, coupled with a moderate salt permeability and the ability of the support layer to suppress the undesirable accumulation of leaked salt in the porous support. Membranes with greater selectivity (i.e., lower salt permeability, B = 0.16 L m(-2) h(-1)) suffered from a lower water permeability (A = 1.74 L m(-2) h(-1) bar(-1)) and would yield a lower peak power density of 6.1 W/m(2), while membranes with a higher permeability and lower selectivity (A = 7.55 L m(-2) h(-1) bar(-1), B = 5.45 L m(-2) h(-1)) performed poorly due to severe reverse salt permeation, resulting in a similar projected peak power density of 6.1 W/m(2).
authors.affiliation: Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520-8286, USA.
authors.forename: Ngai Yin
authors.initials: NY
authors.lastname: Yip
authors.forename: Alberto
authors.initials: A
authors.lastname: Tiraferri
authors.forename: William A
authors.initials: WA
authors.lastname: Phillip
authors.forename: Jessica D
authors.initials: JD
authors.lastname: Schiffman
authors.forename: Laura A
authors.initials: LA
authors.lastname: Hoover
authors.forename: Yu Chang
authors.initials: YC
authors.lastname: Kim
authors.forename: Menachem
authors.initials: M
authors.lastname: Elimelech
mesh_terms: D003246:Conservation of Energy Resources / Q000379:methods; D005618:Fresh Water / Q000737:chemistry; D008567:Membranes, Artificial; D009995:Osmosis; D010539:Permeability; D011210:Power Plants / Q000295:instrumentation*; D011312:Pressure; D054712:Salinity; D012623:Seawater / Q000737:chemistry
chemical_list: D008567:Membranes, Artificial