ABSTRACT:Single-or double-layered porous films consisting of polysulfone (PSF) and cerium-activated yttrium silicate (CAYS) were prepared through the phase inversion of polymeric solutions. For a single-layered structure, a casting solution including n-methylpyrrolidone (NMP) as a solvent was cast on a glass substrate and solidified by immersing into a nonsolvent bath. In a double-layered structure, the bottom layer is a dense PSF film, prepared by vacuum coagulation of a methylene chloride/PSF solution. The top layer was formulated by coagulating the NMP solution, cast over the dense film, in a nonsolvent bath. The morphology and the radionuclide detection efficiency of the prepared films were significantly affected by the nonsolvent coagulants used. The water-coagulated, double-layered film showed a relatively clear-cut interface between the two layers, indicating the rapid coagulation of the second layer. On the contrary, the film coagulated by isopropanol retained well-developed sponge structures highly intertwined in the interface, associated with the delayed precipitation of the second layer. When spotted on the prepared films, radionuclides stayed mainly on the top surface of the isopropanolcoagulated film, but went deep into the substructure of the film coagulated with water. In comparison with the monolayered films, the double-layered ones improved the detection capacity of the spotted radionuclides, owing to the dense support layer.
− This study examined the effect of concentration polarization on permeate flux in forward osmosis (FO) membrane process for saline and sucrose solution. The reduction in permeate flux during the FO membrane process is largely due to the formation of concentration polarization on membrane surfaces. The flux reduction due to internal concentration polarization formed on the porous support layer was larger than that due to the external concentration polarization on the active membrane surface. Water permeate flux through the FO membrane increased nonlinearly with the increase in osmotic pressure. The water permeability coefficient was 1.8081×10 -7 m/s·atm for draw solution on active layer (DS-AL) mode and 1.0957×10 -7 m/s·atm for draw solution on support layer (DS-SL) mode in NaCl solution system.The corresponding membrane resistance was 5.5306×10 6 and 9.1266×10 6 s·atm/m, respectively. With respect to the sucrose solution, the permeate flux for DS-AL mode was 1.33~1.90 times higher than that for DS-SL mode. The corresponding variation in the permeation flux (J) due to osmotic pressure (π) would be expressed as J=-0.0177+0.4506π-0.0032π 2 for the forward and J=0.0948+0.3292π-0.0037π 2 for the latter.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.