Recent studies show that osmotically driven membrane processes may be a viable technology for desalination, water and wastewater treatment, and power generation. However, the absence of a membrane designed for such processes is a significant obstacle hindering further advancements of this technology. This work presents the development of a high performance thin-film composite membrane for forward osmosis applications. The membrane consists of a selective polyamide active layer formed by interfacial polymerization on top of a polysulfone support layer fabricated by phase separation onto a thin (40 mum) polyester nonwoven fabric. By careful selection of the polysulfone casting solution (i.e., polymer concentration and solvent composition) and tailoring the casting process, we produced a support layer with a mix of finger-like and sponge-like morphologies that give significantly enhanced membrane performance. The structure and performance of the new thin-film composite forward osmosis membrane are compared with those of commercial membranes. Using a 1.5 M NaCl draw solution and a pure water feed, the fabricated membranes produced water fluxes exceeding 18 L m(2-)h(-1), while consistently maintaining observed salt rejection greater than 97%. The high water flux of the fabricated thin-film composite forward osmosis membranes was directly related to the thickness, porosity, tortuosity, and pore structure of the polysulfone support layer. Furthermore, membrane performance did not degrade after prolonged exposure to an ammonium bicarbonate draw solution.

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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).

Osmotically-driven membrane processes have the potential to treat impaired water sources, desalinate sea/brackish waters, and sustainably produce energy. The development of a membrane tailored for these processes is essential to advancing the technology to the point that it is commercially viable. Here, a systematic investigation of the influence of thin-film composite membrane support layer structure on forward osmosis performance is conducted. The membranes consist of a selective polyamide active layer formed by interfacial polymerization on top of a polysulfone support layer fabricated by phase separation. By systematically varying the conditions used during the casting of the polysulfone layer, an array of support layers with differing structures were produced. The role that solvent quality, dope polymer concentration, fabric layer wetting, and casting blade gate height play in the support layer structure formation was investigated. Using a 1 M NaCl draw solution and a deionized water feed, water fluxes ranging from 4 to around 25 L m -2 h -1 with consistently high salt rejection (>95.5%) were produced. The relationship between membrane structure and performance was analyzed. This study confirms the hypothesis that the optimal forward osmosis membrane consists of a mixedstructure support layer, where a thin sponge-like layer sits on top of highly porous macrovoids.Both the active layer transport properties and the support layer structural characteristics need to be optimized in order to fabricate a high performance forward osmosis membrane.

Current strategies to treat chronic wounds offer limited relief to the 7.75 million patients who suffer from burns or chronic skin ulcers. Thus, as long as chronic wounds remain a global healthcare problem, the development of alternate treatments remain desperately needed. This review explores the recent strategies employed to tailor electrospun nanofiber mats towards accelerating the wound healing process. Porous nanofiber mats readily produced by the electrospinning process offer a promising solution to the management of wounds. The matrix chemistry, surface functionality, and mat degradation rate all can be fine-tuned to govern the interactions that occur at the materials-biology interface. In this review, first we briefly discuss the wound healing process and then highlight recent advances in drug release, biologics encapsulation, and antibacterial activity that have been demonstrated via electrospinning. While this versatile biomaterial has shown much progress, commercializing nanofiber mats that fully address the needs of an individual patient remains an ambitious challenge.