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Abstract: For the first time, a specially designed pressure retarded osmosis (PRO) hollow fiber membrane has been successfully developed and applied in the PRO process to demonstrate its potential for power generation. The membrane fabrication method is similar to that used for making thin-film composite (TFC) forward osmosis hollow fiber membranes, but further optimization and improvement have led to a new type of TFC hollow fiber membranes with much greater mechanical strength in addition to its excellent separation property and high water flux. The TFC PRO hollow fiber membranes have a water permeability (A) of 9.22×10−12 m/(sPa), salt permeability (B) of 3.86×10−8 m/s and structural parameter (S) of 4.6×10−4 m. It can withstand hydrostatic pressure as high as 9bar with its relatively large dimension of 0.98mm lumen diameter. This PRO hollow fiber membrane is superior to all other PRO membranes reported in the open literature in terms of power density. A power density as high as 10.6W/m2 can be achieved using seawater brine (1.0M NaCl) and wastewater brine (40mM NaCl), which suggests that the newly developed PRO hollow fiber membrane has great potential to be applied in PRO processes to harvest salinity gradient energy. A higher pressure is preferred as it allows generation of higher power density (pressures of 12bar may be optimal for seawater as the high salinity stream), and this can be realized by reduced fiber dimension. Further optimization of the membrane structure will be performed. [Copyright &y& Elsevier]

Abstract: There has been a resurgence of interest in forward osmosis (FO) as a potential means of desalination, dewatering and in pressure retarded osmosis, which Sidney Loeb was advocating over 3decades ago. This paper describes the characteristics and potential applications of a newly developed FO hollow fiber membrane, which was fabricated by interfacial polymerization on the inner surface of a polyethersulfone (PES) hollow fiber. This FO membrane presents excellent intrinsic separation properties, with a water flux of 42.6L/m2 h using 0.5M NaCl as the draw solution and DI water as the feed with the active layer facing the draw solution orientation at 23°C. The corresponding ratio of salt flux to water flux was only 0.094g/L, which is superior to all other FO membranes reported in the open literature. To evaluate different application scenarios, various NaCl solutions (500ppm (8.6mM), 1wt.% (0.17M) and 3.5wt.% (0.59M)) were used as the feed water to test the performance of the FO membrane. The membrane can achieve a water flux of 12.4L/m2 h with 3.5wt.% NaCl solution as the feed and 2M NaCl as the draw solution, suggesting it has good potential for seawater desalination. [ABSTRACT FROM AUTHOR]