Evaluation of the Specific Energy Consumption of Sea Water Reverse Osmosis Integrated with Membrane Distillation and Pressure-Retarded Osmosis Processes with Theoretical Models.

In this study, theoretical models for specific energy consumption (SEC) were established for water recovery in different integrated processes, such as RO-PRO, RO-MD and RO-MD-PRO. Our models can evaluate SEC under different water recovery conditions and for various proportions of supplied waste heat. Simulation results showed that SEC in RO increases with the water recovery rate when the rate is greater than 30%. For the RO-PRO process, the SEC also increases with the water recovery rate when the rate is higher than 38%, but an opposite trend can be observed at lower water recovery rates. If sufficient waste heat is available as the heat source for MD, the integration of MD with the RO or RO-PRO process can significantly reduce SEC. If the total water recovery rate is 50% and MD accounts for 10% of the recovery when sufficient waste heat is available, the SEC values of RO, RO-PRO, RO-MD and RO-MD-PRO are found to be 2.28, 1.47, 1.75 and 0.67 kWh/m3, respectively. These critical analyses provide a road map for the future development of process integration for desalination.

Performance evaluation of ePTFE and PVDF flat-sheet module direct contact membrane distillation.

This paper reports experiments using a flat-sheet module with 0.18 approximately 0.45 microm ePTFE (expanded polytetrafluoroethylene) and PVDF (polyvinylidene fluoride) membranes to show the effects of membrane properties, salt concentration and fluid hydrodynamics on the permeate flux and salt rejection of DCMD (direct contact membrane distillation). A theoretical prediction of the permeate flux was carried out, and was in close agreement with the experimental results. In addition, the energy integration of the process was also analyzed in order to evaluate module design to increase energy efficiency. According to the simulated results of the energy integration design, a combination of simultaneous cooling of the permeate stream and an additional heat exchanger to lower the temperature of the permeate stream not only enhances the MD flux, but also reduces energy consumption.

Electrostatic immobilization of DNA polyplexes on small intestinal submucosa for tissue substrate-mediated transfection.

Naturally occurring extracellular matrices (ECMs) such as small intestinal submucosa (SIS) have received significant attention for their therapeutic applications in tissue repair and regeneration. However, there have been no reports exploring the electrostatic properties of naturally occurring ECMs as a means to control transgene delivery. In the present study, we electrostatically adsorbed DNA polyplexes onto SIS for transfection upon cellular adhesion. To associate polyplexes with SIS, we first used a streaming potential method to characterize the surface charge of SIS and obtained a negative zeta potential at neutral pH, which can be attributed to the abundant glycosaminoglycan (GAG) content in SIS. We next prepared cationic polyethylenimine (PEI)/DNA polyplexes to associate with the negatively charged SIS for conjugation. Using the Cy(TM)3 dye-labeled control DNA as the reporter, we visualized the adsorption of PEI/DNA polyplexes at the SIS surface. Using luciferase, green fluorescent protein and beta-galactosidase as reporter proteins, we showed that the adsorbed PEI/DNA polyplexes were active and capable of carrying out transfection upon cellular adhesion, indicating that the electrostatic binding of polyplexes with SIS was reversible. In addition, the SIS-mediated transfection was contact-dependent: separation of SIS from the target cells via a 0.5 mm porous polyester membrane significantly reduced the efficiency of transfection in comparison to a direct seeding of cells onto SIS. We conclude that electrostatic immobilization of PEI/DNA polyplexes on SIS is capable of initiating efficient transgene delivery, which can be a useful tool in developing localized gene transfer.