The assignee for this patent application is The Trustees of
Reporters obtained the following quote from the background information supplied by the inventors: "The presently disclosed subject matter relates to systems and methods for modification of substrate membranes, including microfiltration and ultrafiltration membranes by depositing nanoparticles layer by layer on the substrate membrane.
"Membranes can act as a unique solution for many separation requirements acting as an interphase, governed by different driving forces, and a selective barrier between two adjacent phases, regulating the transport of substances between the two compartments. One application for membranes is water purification. Physical water scarcity--characterized by severe environmental degradation, declining groundwater, and water allocations that favor some groups over others--is a growing problem around the world. In some regions, the stress on water resources is severe. Water withdrawals are high in arid and semi-arid lands, where they are needed for irrigation, and lower in tropical countries. Wastewater reuse and sea water desalination have emerged as foci of research to address these growing problems and several improvements through membrane technologies have been achieved. Examples include the membrane bioreactor (MBR) and the active integrated desalination membrane process system through hollow fiber micro/ultrafiltration and reverse osmosis (MF/RO).
"Water Nano-filtration, often referred to as 'low pressure RO membrane' nano-filtration, is a filtration process which can be applied to brackish water found, e.g., in surface and ground water streams. Water nano-filtration can soften brackish water and remove disinfection by-product (DBP) precursors and/or natural organic matter (NOM). The transmembrane pressure (TMP) required (which can be between about 50 psi and 150 psi) can be lower than those used for RO membranes (which can be between about 300 psi and 1200 psi). However, NF membranes can still be subject to scaling and fouling, and modifiers such as anti-scalants can be required for use.
"Reverse Osmosis technology has been used for water demineralization for decades. Although effective, RO can be expensive and difficult to control. Further, certain RO membranes, based on polyamides, can exhibit little or no resistance to typical process chemicals and low recovery.
"Accordingly, there remains a need for improved generation of membrane separation composites."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "In accordance with one aspect of the disclosed subject matter, a method for fabricating a thin film composite having a porous polymeric substrate membrane is provided. At least one polyelectrolyte layer can be deposited onto the surface of the substrate membrane, which can impart a charge to the surface. The substrate membrane can be immersed into a bath including a nanoparticle solution, thus depositing at least one nanoparticle-only layer on the substrate membrane to form a thin film composite.
"In one embodiment, the substrate membrane can be a microfiltration membrane or an ultrafiltration membrane. The substrate membrane can be, for example, polycarbonate track etched, polyethersulfone, sulfonated polyethersulfone membranes, or sulfonated poly etherethersulfone.
"The polyelectrolyte layer can be deposited by immersing the substrate membrane in a cationic PAH solution, rinsing the substrate membrane, and immersing the substrate membrane in an anionic PAA solution. This can be repeated to deposit 2.5 bi-layers of polyelectrolyte coating, one layer being a PAH layer.
"Deposition of the nanoparticle layer can be accomplished by immersing the substrate membrane in a first bath including anionic nanoparticles, rinsing the substrate membrane, immersing the substrate membrane in a second bath including cationic nanoparticles to form a bi-layer, and rinsing the substrate membrane again. This can be sequentially repeated to deposit a predetermined number of bi-layers. The anionic nanoparticles can be, for example, spherical anionic silica nanoparticles or elongated anionic silica nanoparticles. The cationic nanoparticles can be, for example, spherical cationic silica nanoparticles
"In accordance with another aspect of the disclosed subject matter, a system for fabricating a thin film composite having a porous polymeric substrate membrane is disclosed. At least one vessel containing a polyelectrolyte solution can be included for depositing at least one polyelectrolyte layer to the surface of the substrate membrane, thereby imparting a charge to the surface. At least one vessel containing a nanoparticle solution can be included for immersing the substrate into a bath comprising a nanoparticle solution, thereby depositing at least one nanoparticle-only layer on the substrate membrane to form a thin film composite.
"In one embodiment, the system can include at least a first vessel and a second vessel for containing polyelectrolyte solution, the first vessel containing cationic PAH solution and the second vessel containing anionic PAA solution. Additionally, the system can include at least a first vessel and a second vessel for containing nanoparticle solutions, the first vessel containing cationic nanoparticles and the second vessel containing anionic nanoparticles. A programmable robotic dipper having a dipping basket adapted to receive the substrate membrane can be configured to sequentially alternate immersing the dipping basket into the first and second vessels for containing polyelectrolyte solution, and configured to sequentially alternate immersing the dipping basket into the first and second vessels for containing nanoparticle solution.
BRIEF DESCRIPTION OF THE DRAWINGS
"It will be noted here that for a better understanding, like components are designated by like reference numerals throughout the various figures.
"FIG. 1 is a flow diagram of a method for fabricating a thin film composite according to an embodiment of the disclosed subject matter.
"FIG. 2 is a schematic diagram of a system for fabricating a thin film composite according to and embodiment of the disclosed subject matter.
"FIG. 3 is a schematic diagram illustrating layer by layer deposition of nanoparticles according to an embodiment of the disclosed subject matter.
"FIG. 4 is a schematic representation of glass slide disposition using binder clip clamps and wire according to an embodiment of the disclosed subject matter.
"FIG. 5 is a top view scanning electron microscope image of various substrate membranes for use in accordance with an embodiment of the disclosed subject matter.
"FIG. 6 is a cross-sectional scanning electron microscope image of various substrate membranes modified with layer by layer deposition of polyelectrolytes only.
"FIG. 7 shows scanning electron microscope images of thin film composites fabricated according to embodiments of the disclosed subject matter.
"FIG. 8 illustrates the relationship between the thickness profile of a nanoparticle only layer and the number of bi-layers fabricated according to an embodiment of the disclosed subject matter.
"FIG. 9 is a chart demonstrating the filtration spectra."
For more information, see this patent application: Durning, Christopher; Escobar-Ferrand, Luis. Nanoparticle-Only Layer by Layer Surface Modification of Substrate Membrane. Filed
Keywords for this news article include: Nanoparticle, Nanotechnology, Emerging Technologies, The Trustees of
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