Patent number 8617394 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "This invention relates to heterogenous pore polymer nanotube membranes useful in filtration, such as reverse osmosis desalination, nanofiltration, ultrafiltration and gas separation.
"Polymer membranes with pores in the polymer surface are often used in reverse osmosis purification of fluids, such as water. These membranes permit transport of water through a solution-diffusion mechanism. A disadvantage is that water must dissolve into the polymer material comprising the membrane and diffuse through. The result is a very low water flux compared to membrane materials that contain open channels through the membrane.
"To increase flux in conventional membrane materials, the constituent polymer structure can be made looser by judicious choice of polymerization parameters. However, the rejection performance of the membrane is reduced as a result. In some cases, materials have been added to the polymer to adjust permeability properties. For example, U.S. Pat. No. 4,277,344 (
"A different type of membrane involves directing water flux through carbon nanotubes attached to a silicon chip. US patent publication no. 2006/033180 (The Regents of the
"There remains a need for a scalable filtration membrane that provides adequate flux and selectivity for commercial use in desalination, nanofiltration, and ultrafiltration."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "One aspect of the invention is a membrane of selective permeability, which membrane comprises a porous polymer and terminating on one side in a skin, with nanotubes embedded in said membrane and protruding through said skin and said skin forming a substantially impermeable barrier around said nanotubes, said membrane having pores increasing in diameter with increasing distance from said skin.
"A second aspect of the invention is a membrane of selective permeability, which membrane comprises a porous polymer and terminating on one side in a skin and terminating on the opposite side from said skin in a porous non-woven substrate, with nanotubes embedded in said membrane and protruding through said skin and said skin forming a substantially impermeable barrier around said nanotubes, said membrane having pores increasing in diameter with increasing distance from said skin.
"A third aspect of the invention is a process for the fabrication of a membrane of selective permeability, said process comprises: (a) coating a substrate with a film of polymer solution comprising a polymer dissolved in a solvent; (b) forming over said film of polymer solution a nanotube dispersion layer comprising nanotubes dispersed in a liquid carrier that is partially miscible with, but forms a separate liquid phase from, said polymer solution; © evaporating said liquid carrier from said nanotube dispersion layer to leave a residual nanotube dispersion layer over said substrate, said residual nanotube dispersion layer comprising said nanotubes dispersed in said polymer solution and protruding from said nanotube dispersion layer; (d) contacting said residual nanotube dispersion layer with a liquid that is at least partially miscible with said solvent but in which said polymer is substantially insoluble, to cause precipitation of said polymer to form a porous membrane terminating on one side in a skin, with barrier around said nanotubes, said membrane having pores increasing in diameter with increasing distance from said skin; and (e) optionally separating said porous membrane from said substrate."
URL and more information on this patent, see: Ratto, Timothy V.;
Keywords for this news article include: Silicon, Nanotechnology,
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