阅读说明：本技术 用于气体脱水的选择性渗透的氧化石墨烯隔膜 (Selectively permeable graphene oxide membranes for gas dehydration ) 是由 郑世俊 林伟平 王鹏 北原勇 碧*·巴吉 约翰·埃里克森 于 2019-06-20 设计创作，主要内容包括：本文描述的是一种为除湿应用提供选择性气体和蒸气抗性的基于氧化石墨烯材料和聚合物的选择性渗透元件。所述氧化石墨烯与聚乙烯醇交联,所述聚合物包括铵盐聚合物,例如聚(二烯丙基二甲基氯化铵)。本文还描述了选择性渗透元件,其中石墨烯可以选自还原的氧化石墨烯、氧化石墨烯,并且还被官能化或交联。本文还描述了选择性渗透元件,其中在石墨烯和/或聚合物之间存在交联以提供具有水蒸气渗透性的增强的抗气体性。本文还描述了一种选择性渗透装置,该装置结合了该选择性渗透元件,并且还包括包围该选择性渗透元件的基材和保护涂层。本文还描述了用于制造上述选择性渗透元件和相关装置的方法。(Described herein is a selectively permeable element based on graphene oxide materials and polymers that provides selective gas and vapor resistance for dehumidification applications. The graphene oxide is crosslinked with polyvinyl alcohol, which includes ammonium salt polymers, such as poly (diallyldimethylammonium chloride). Also described herein are permselective elements, wherein the graphene may be selected from reduced graphene oxide, and further functionalized or crosslinked. Also described herein are selectively permeable elements in which there is crosslinking between the graphene and/or polymer to provide enhanced gas resistance with water vapor permeability. Also described herein is a selectively permeable device that incorporates the selectively permeable element and further includes a substrate and a protective coating surrounding the selectively permeable element. Methods for making the aforementioned selectively permeable elements and related devices are also described herein.)

1. A membrane for gas dehydration, comprising:

a porous support;

a composite material comprising a graphene oxide compound and an ammonium salt polymer;

wherein the composite is coated on the porous support; and is

Wherein the separator has high moisture permeability and low air permeability.

2. The septum of claim 1, wherein the septum has greater than 1x10^-5g/m²s.Pa and a moisture permeability of less than 1x10^-8L/m²Gas permeability of s.Pa.

3. A separator as claimed in claim 1 or 2 wherein the ammonium salt polymer is a poly (diallyldimethylammonium) salt.

4. A separator as claimed in claim 1, 2 or 3 wherein the ammonium salt polymer is poly (diallyldimethylammonium chloride).

5. The separator of claim 1, 2, 3 or 4, wherein the porous support comprises polypropylene, polyethylene terephthalate, polysulfone or polyethersulfone.

6. The separator of claim 1, 2, 3, 4, or 5, further comprising polyvinyl alcohol.

7. The separator of claim 6, wherein the graphene oxide compound and the polyvinyl alcohol are cross-linked.

8. The separator of claim 6 or 7, wherein the weight ratio of the graphene oxide compound to the polyvinyl alcohol is about 0.1:100 to about 9: 1.

9. The separator of claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the graphene oxide compound comprises graphene oxide, reduced graphene oxide, functionalized graphene oxide, or functionalized and reduced graphene oxide.

10. The separator of claim 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the graphene oxide compound has a platelet size of about 0.05 μ ι η to about 100 μ ι η.

11. The membrane of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, further comprising an alkaline earth metal.

12. A diaphragm according to claim 11, wherein the alkaline earth metal comprises calcium chloride.

13. The membrane of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, further comprising a surfactant.

14. The membrane of claim 13, wherein the surfactant is sodium lauryl sulfate.

15. The membrane of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the composite material is a layer having a thickness of about 1 μ ι η to about 200 μ ι η.

16. The membrane of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, further comprising a protective layer.

17. A method of dehydrating a gas, comprising:

introducing a first gas comprising water vapor into a first side of the membrane of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein,

the water vapor pressure on the first side of the membrane is higher than the water vapor pressure on the second side of the membrane, and water vapor from a first gas passes through the membrane from the first side to the second side;

wherein the retained gas remains on the first side of the membrane to produce a second gas;

wherein the second gas has a lower water vapor pressure than the first gas.

18. The method of claim 17, further comprising removing a purge gas of water vapor on the second side of the membrane.

19. A method of making a membrane for gas dehydration comprising:

annealing and drying the coating on the treated support;

wherein the carrier is corona treated;

wherein the coating is a mixture comprising: 1) graphene oxide; and 2) PVA, PDADMA, SLS, CaCl₂Or any combination thereof; and is

Optionally a protective layer is added.

Technical Field

Embodiments of the present application relate to polymeric membranes, including membranes comprising graphene materials, for applications such as water or water vapor removal from air or other gas streams and Energy Recovery Ventilation (ERV).

Background

The presence of high humidity levels in the air can be uncomfortable and can also cause serious health problems by promoting the growth of mold, fungus and dust mites. In manufacturing and storage facilities, high humidity environments can accelerate product degradation, powder agglomeration, seed germination, corrosion, and other undesirable effects, which are a concern in the chemical, pharmaceutical, food, and electronics industries. One of the conventional methods for dehydrating air includes passing wet air through a moisture absorbent such as ethylene glycol, silica gel, molecular sieves, calcium chloride, phosphorus pentoxide, and the like. This method has a number of disadvantages: for example, the desiccant must be entrained in a dry air stream; and the desiccant also needs to be replaced or regenerated over time, which makes the dehydration process expensive and time consuming. Another conventional air dehydration process is a cryogenic process involving compressing and cooling humid air to condense the moisture, however, this process is energy intensive.

Membrane-based gas dehumidification techniques have significant technical and economic advantages over the conventional dehydration or dehumidification techniques described above. Its advantages are less investment, simple operation, high energy efficiency, low cost and high treating power. This technique has been successfully applied to the dehydration of nitrogen, oxygen and compressed air. For Energy Recovery Ventilator (ERV) applications, such as building interiors, it is desirable to provide fresh air from the outside. Energy is required to cool and dehumidify fresh air, particularly in hot and humid climates where the outside air is hotter and has more moisture than the air inside the building. The energy required for heating and cooling may be reduced by the ERV system transferring heat and moisture between the exhaust air and the incoming fresh air. ERV systems include a membrane that physically separates the exhaust air from the intake air, but allows heat and moisture exchange. Key properties required for ERV membranes include: (1) low permeability to gases other than air and water vapor; (2) high permeability of water vapor for effectively transferring moisture between the incoming and outgoing gas streams while preventing the passage of other gases; and (3) high thermal conductivity for efficient heat transfer.

For ERV applications, membranes with high water vapor permeability and low air permeability are required.

Disclosure of Invention

The present disclosure relates to gas separation membranes, wherein high moisture permeability and low gas permeability can be used to achieve dehydration of gases. Described herein are membrane elements comprising Graphene Oxide (GO) composites that can reduce water swelling, as well as increase the selectivity of water vapor/air permeation. Some embodiments also include an ammonium salt polymer, which can provide improved dehydration membranes relative to traditional polymer (e.g., PVA) membranes. Embodiments of the present invention include selectively permeable elements that may be used in applications where limited breathability is desired while allowing fluids or water vapor to pass therethrough. Methods of efficiently and economically manufacturing these GO membrane elements are also described. Water can be used as a solvent for making these elements, making the process more environmentally friendly and more cost effective.

Some embodiments include a dehydration membrane comprising a support and a composite comprising a graphene oxide compound and an ammonium salt polymer. In some embodiments, the ammonium salt polymer comprises poly (diallyldimethylammonium chloride). In some embodiments, the composite material may be coated on a support. In some embodiments, the separator may have high moisture permeability and low air permeability. In some embodiments, the membrane may be dehydrated. In some embodiments, the membrane may be selectively permeable to water vapor. In some embodiments, the membrane is relatively impermeable to a gas (e.g., air). In some embodiments, the carrier is porous. In some embodiments, the separator may further comprise polyvinyl alcohol (PVA). In some embodiments, the graphene oxide compound and the polyvinyl alcohol may be crosslinked. In some embodiments, the graphene oxide compound is selected from the group consisting of graphene oxide, reduced graphene oxide, functionalized graphene oxide, and functionalized reduced graphene oxide. In some embodiments, the composite material may further comprise lithium chloride. In some embodiments, the composite material may further comprise calcium chloride. In some embodiments, the composite material may further comprise a surfactant. In some embodiments, the surfactant may be sodium lauryl sulfate.

Some embodiments include methods for making a moisture and/or gas permeable barrier element. The method may include mixing a polymer solution, a graphene solution, and a crosslinker solution to produce an aqueous mixture; coating the mixture on a substrate to produce a film of about 1 μm to about 200 μm; drying the mixture at a temperature of from 20 ℃ to about 120 ℃ for from about 15 minutes to about 72 hours; the resulting coating is annealed at a temperature in the range of about 40 ℃ to about 200 ℃ for about 10 hours to about 72 hours. In some embodiments, the method may include mixing a polymer solution, a graphene solution, a crosslinker solution, and an alkali metal halide or alkaline earth metal halide to produce an aqueous mixture. In some examples, the element further comprises a protective coating.

Some embodiments include a method for dehydrating a gas comprising introducing a gas into a membrane described herein, wherein the water vapor permeates the membrane and the gas does not permeate the membrane.

These and other embodiments are described in more detail below.

Drawings

Fig. 1 is a possible embodiment of a nanocomposite membrane device that can be used in separation/dehydration applications.

Figure 2 is one possible embodiment of a method of making a separation/dehydration element and/or device.

Detailed Description

Selectively permeable membranes include membranes that are relatively permeable to one material and relatively impermeable to another material. For example, the membrane may be relatively permeable to water vapor and relatively impermeable to gases such as oxygen and/or nitrogen. The ratio of the permeabilities of the different materials can be used to describe their selective permeability.

The present disclosure relates to gas separation membranes, wherein high moisture permeability and low gas permeability can be used to achieve dehydration of gases. The membrane material may be suitable for dehumidification of air, oxygen, nitrogen, hydrogen, methane, propylene, carbon dioxide, natural gas, methanol, ethanol, and/or isopropanol. In some embodiments, a separator comprising a moisture permeable GO-ammonium salt polymer separator component can have a high H₂O/air selectivity. These embodiments may improve the energy efficiency of the dehydration membrane and/or the ERV system, as well as increase the separation efficiency.

Dehydration diaphragm

Described herein are membranes comprising highly selective hydrophilic GO-based composites with high water vapor permeability, low gas permeability, and high mechanical and chemical stability. These membranes can be used in applications requiring dry gas or gas with low water vapor content.

In some embodiments, the membrane may be a dehydration membrane. In some embodiments, the membrane may be an air dehydration membrane. In some embodiments, the membrane may be a gas separation membrane. In some embodiments, a moisture-permeable and/or gas-impermeable barrier element containing a graphene material (e.g., graphene oxide) can provide a desired selective gas, fluid, and/or vapor permeability resistance. In some embodiments, the selectively permeable element may comprise a plurality of layers, wherein at least one layer is a layer comprising a graphene material.

Typically, the dehydration membrane comprises a porous support and a composite material coated on the support. For example, as shown in FIG. 1, a selective permeation device 100 includes at least a porous support 120 and a composite material 110, the composite material 110 including a graphene compound and a polymer. Due to these layers, the permselective device can provide a durable dehydration system that is selectively permeable to water vapor and less permeable to one or more gases. Because of these layers, the permselective device can provide a durable dehydration system that can effectively dehydrate air or other desired gases or feed fluids. The composite, such as composite 110, may further comprise a cross-linked polymer, a cross-linking agent, and additives, including but not limited to dispersants, surfactants, binders, alkali metal salts, alkaline earth metal salts, and solvents.

In some embodiments, the gas permeability of the separator may be less than 1x10^-5L/m²s Pa. A suitable method for determining breathability may be ASTM D-727-58, TAPPI-T-536-88 standard method.

In some embodiments, the moisture permeability of the separator may be greater than 500g/m²Day or 1X10^-5g/m²s.Pa. In some embodiments, the moisture permeability may be a measure of the water vapor permeability/transfer rate at the levels described above. A suitable method for determining moisture (water vapor) permeability is ASTM E96, ASTM D-6701 Standard method.

In some embodiments, the selective permeability of the membrane may be reflected in a ratio of the permeability of water vapor to the permeability of at least one selected gas (e.g., oxygen and/or nitrogen). In some embodiments, the separator may exhibit a ratio of water vapor permeability to gas permeability of greater than 50, greater than 100, greater than 200, greater than 400, greater than 1000, greater than 5000, greater than 10000, greater than 15000, or greater than 20000. In some embodiments, the selective permeability may be water vapor at the levels described above: a measure of the gas permeability/transfer rate ratio. Suitable methods for determining the water vapour permeability and/or the gas permeability have been disclosed above.

In some embodiments, the selectively permeable element comprises a composite of a support and a coated support material. In some embodiments, the membrane has a relatively high water vapor permeability. In some embodiments, the membrane may have low gas permeability. In some embodiments, the support may be porous.

In some embodiments, a selectively permeable membrane may be disposed between or separate a first fluid reservoir and a second fluid reservoir in fluid communication. In some embodiments, the first reservoir may contain the feed fluid upstream and/or at the selectively permeable element. In some embodiments, the first reservoir may contain treated fluid downstream and/or at the selectively permeable element. In some embodiments, the selectively permeable element selectively passes unwanted water vapor therethrough while retaining or reducing the passage of another gas or fluid material therethrough. In some embodiments, the selectively permeable element may provide a filtration element to selectively remove water vapor from the feed fluid while being capable of retaining the treated fluid substantially free of unwanted water or water vapor as described herein. In some embodiments, the selectively permeable element has a desired flow rate. In some embodiments, the selectively permeable element may comprise an ultrafiltration material. In some embodiments, the selectively permeable element exhibits at least about 0.001 literA flow rate of from about 0.1 liter per minute; a flow rate of about 0.005 liters/minute to about 0.075 liters/minute; and/or a flow rate of about 0.01 liters/minute to about 0.05 liters/minute, such as at least about 0.005 liters/minute, at least about 0.01 liters/minute, at least about 0.02 liters/minute, at least about 0.05 liters/minute, at least about 0.1 liters/minute, at least about 0.5 liters/minute, and/or at least about 1.0 liters/minute. In some embodiments, the selectively permeable element exhibits a flow rate of any combination of the aforementioned flow rates. In some embodiments, the permselective element can comprise an ultrafiltration material. In some embodiments, the selective permeable element comprises a filter characterized by a molecular weight cut-off (MWCO) of at least 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99% of the material having a molecular weight of 5000-. In some embodiments, the ultrafiltration material or membrane comprising such material may have an average pore size of about 0.01 μm (10nm) to about 0.1 μm (100nm), and/or about 0.01 μm (10nm) to about 0.05 μm (50nm) or fluid channels having an average diameter of about 0.01 μm (10nm) to about 0.1 μm (100nm), and/or about 0.01 μm (10nm) to about 0.05 μm (50 nm). In some embodiments, the surface area of the separator is about 0.01m²、0.05m²、0.10m²、0.25m²、0.35m²To about 0.50m²、0.60m²、0.70m²、0.75m²、1.00m²，1.50m²To about 2.50m²Or any combination of said areas. In some embodiments, the surface area of the membrane is about at least 50m²。

Porous carrier

The porous support may be any suitable material, and may be in any suitable form, upon which a layer, such as a composite layer, may be deposited or disposed. In some embodiments, the porous support may comprise hollow fibers or a porous material. In some embodiments, the porous support may comprise a porous material, such as a polymer or a hollow fiber. Some porous supports may comprise a nonwoven fabric. In some embodiments, the polymer may be polyamide (nylon), Polyimide (PI), polyvinylidene fluoride (PVDF), Polyethylene (PE), stretched PE, polypropylene (including stretched polypropylene), polyethylene terephthalate (PET), Polysulfone (PSF), Polyethersulfone (PEs), cellulose acetate, polyacrylonitrile (e.g., PA200), or combinations thereof. In some embodiments, the polymer may comprise PET. In some embodiments, the polymer comprises polypropylene. In some embodiments, the polymer comprises a stretched polypropylene. In some embodiments, the polymer comprises polyethylene. In some embodiments, the polymer comprises a stretched polyethylene.

Composite material

In some embodiments, a composite material, such as composite material 110, may coat a support. In some embodiments, a composite material comprises a graphene material and one or more polymers. Some embodiments include additional polymers and/or additives. In some embodiments, the graphene material and the polymer are covalently linked to each other. In some embodiments, the graphene material may be dispersed in the polymer material. In some embodiments, the permselective membrane further comprises a crosslinker material.

In some embodiments, the graphene-containing composite further comprises an alkali metal halide or an alkaline earth metal halide. In some embodiments, the composite further comprises a surfactant, binder, or solvent.

The separator of the present disclosure comprises a support and a composite material containing a graphene oxide compound and an ammonium salt polymer. In some embodiments, the ammonium salt polymer may be poly (diallyldimethylammonium chloride) (polyDADMAC, polyDDA, PDADMA, and/or polyquaternium-6, see structures below).

Ammonium salt polymer PDADMA

In some embodiments, the graphene material may be arranged in the polymer material in a manner that produces an exfoliated nanocomposite, an intercalated nanocomposite, or a phase separated nanocomposite. The phase separated nanocomposite phase may be such that, upon mixing, the graphene material exists as a separate and distinct phase from the polymer. The intercalated nanocomposite may be such that when the polymer compound is initially doped in or between graphene platelets, the graphene material may not be distributed throughout the polymer.

Graphene oxide

In general, graphene-based materials have many attractive properties, such as two-dimensional sheet structures with very high mechanical strength and nanoscale thickness. Graphene Oxide (GO) is an exfoliated oxidation product of graphite, which can be produced on a large scale at low cost. Graphene oxide has high water permeability due to its high degree of oxidation, and also exhibits versatility through the functionalization of many functional groups (e.g., amines or alcohols) to form various membrane structures. Unlike conventional membranes, in which water is transported through the pores of the material, in graphene oxide membranes, the transport of water can occur between the interlayer spaces. The capillary effect of GO can lead to longer water slide lengths, providing fast water transport rates. In addition, the selectivity and water flux of the membrane can be controlled by adjusting the interlayer distance of the graphene sheets or by using different cross-linked segments.

It is believed that a large number (-30%) of epoxy groups may be present on GO, which can readily react with hydroxyl groups at elevated temperatures. GO flakes are also considered to have very high aspect ratios. Such high aspect ratios can increase the available gas diffusion surface if dispersed in a polymer membrane (e.g., an ammonium salt polymer membrane). Thus, the ammonium salt polymer crosslinked by GO can not only reduce water swelling of the membrane, but can also improve membrane gas separation efficiency.

In some embodiments, the graphene oxide compound may be selected from the group consisting of graphene oxide, reduced graphene oxide, functionalized graphene oxide, and functionalized reduced graphene oxide. In some embodiments, the graphene may have the following platelet sizes: about 0.001 μm, 0.05 μm, 0.10 μm, 0.5 μm or 1.0 μm, and up to: about 50 μm, about 100 μm, about 200 μm, and/or about 250 μm, about 0.001-10 μm, about 10-20 μm, about 20-30 μm, about 30-40 μm, about 40-50 μm, about 50-60 μm, about 60-70 μm, about 70-80 μm, about 80-90 μm, about 90-100 μm, about 100-110 μm, about 110-120 μm, about 120-130 μm, about 130-140 μm, about 140-150 μm, about 150-160 μm, about 160-170 μm, about 170-180 μm, about 180-190 μm, about 190-200 μm, about 200-210 μm, about 210-220 μm, about 220-230 μm, about 240 μm, about 180-250 μm, about 240.001-50 μm, about 50-100 μm, about 100-150 μm, about 150-200 μm, about 200-250 μm, about 0.001-100 μm, about 100-200 μm, about 100-250 μm, and/or any combination thereof.

The individual graphene platelets may be distributed within the polymer or throughout the polymer. The exfoliated nanocomposite phase can be achieved by chemically exfoliating graphene materials by the modified Hummer's method, which is a method well known to those of ordinary skill. The exfoliated nanocomposite phase can be achieved by chemically exfoliating the graphene material by a modified hermeres process, which is described in the examples below. It is believed that this method can be used to provide graphene oxide sheets of appropriate size for use in the presently described applications. In some embodiments, the graphene oxide material may be well dispersed with the polymer as the majority or greater than majority material phase with each other.

In some embodiments, the graphene material may be in the form of a sheet, plane, or flake. In some embodiments, the graphene material may be in the form of platelets. In some embodiments, the graphene may have a platelet size of about 0.05 μm to about 300 μm. In some embodiments, the graphene may have a platelet size of about 75 μm to about 175 μm. In some embodiments, the graphene material may have about 1m²/gm to about 5000m²/g、1-100m²/g、100-200m²/g、200-300m²/g、300-400m²/g、400-500m²/g、500-600m²/g、600-700m²/g、700-800m²/g、800-900m²/g、900-1000m²/g、1000-2000m²/g、2000-3000m²/g、3000-4000m²(g or 4000-) 5000m²Surface area in g. In some embodiments, the graphene material may have about 150m²G to about 4000m²Surface area in g. In some embodiments, the graphene material may have about 200m²G to about 1000m²Surface area per g, e.g. about 400m²G to about 500m²(ii) in terms of/g. It is believed that the graphene material component of the membrane provides the membrane with a desired level of second gas impermeability, e.g., the membrane may have less than 0.1L/m²s Pa, less than 0.5L/m²s Pa, or less than 1.0X10^-5L/m²s Pa of second gas permeability.

In some embodiments, the graphene material may not be modified and may include a non-functionalized graphene substrate. In some embodiments, the graphene material may comprise modified graphene. In some embodiments, the modified graphene may comprise functionalized graphene. In some embodiments, at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, or at least about 90% of the graphene may be functionalized. In other embodiments, most of the graphene materials may be functionalized. In other embodiments, substantially all of the graphene material may be functionalized. In some embodiments, the functionalized graphene may comprise a graphene substrate and a functional compound. When one or more types of functional compounds other than hydroxides are present at the carboxylic acid groups or one or more hydroxyl groups of the graphene substrate, the graphene may be "functionalized" to become functionalized graphene. In some embodiments, the graphene substrate may be selected from graphene oxide, reduced graphene oxide, functionalized graphene oxide, and/or functionalized and reduced graphene oxide.

The composite material can contain any suitable amount of the graphene oxide compound, for example, from about 0.01% to about 20%, such as from about 0.01% to about 0.1%, from about 0.1% to about 0.2%, from about 0.2% to about 0.3%, from about 0.3% to about 0.4%, from about 0.4% to about 0.5%, from about 0.5% to about 0.6%, from about 0.6% to about 0.7%, from about 0.7% to about 0.8%, from about 0.9% to about 1%, from about 1.1% to about 1.1%, from about 1.2% to about 1.3%, from about 1.3% to about 1.4%, from about 1.4% to about 1.5%, from about 1.5% to about 1.6%, from about 1.6% to about 1.7%, from about 1.7% to about 1.8%, from about 1.9% to about 2%, from about 0% to about 1%, from about 1% to about 2%, from about 2% to about 3%, from about 3% to about 4%, from about 5% to about 6%, from about 7% to about 6% to about 7%, about 8-9%, about 9-10%, about 10-11%, about 11-12%, about 12-13%, about 13-14%, about 14% -15%, about 15-16%, about 16-17%, about 17-18%, about 18-19%, about 19-20%, about 0.01-3%, about 0.01-5%, about 5-10%, about 10-15%, about 15-20%.

Crosslinking agent

In some embodiments, the composite material comprises a graphene oxide compound and a polymer. In some cases, the polymer is a crosslinked polymer. One possible crosslinked polymer is polyvinyl alcohol. In some embodiments, the weight ratio of graphene oxide to polyvinyl alcohol may be about 0.1:100 to about 1: 10. In some embodiments, additional crosslinking elements may be provided. In some embodiments, the additional crosslinking elements may be potassium tetraborate (KBO) and sodium Lignin Sulfate (LSU). In some embodiments, the composite material may further comprise lithium chloride. In some embodiments, the composite material may further comprise calcium chloride. In some embodiments, the composite material may further comprise a surfactant. In some embodiments, the surfactant may be sodium lauryl sulfate.

The polyvinyl alcohol may be present in any suitable amount, such as from about 1% to about 80%, from about 0.01% to about 1%, from about 1% to about 2%, from about 2% to about 3%, from about 3% to about 4%, from about 4% to about 5%, from about 5% to about 6%, from about 6% to about 7%, from about 7% to about 8%, from about 8% to about 9%, from about 9% to about 10%, from about 10% to about 11%, from about 11% to about 12%, from about 12% to about 13%, from about 13% to about 14%, from about 14% to about 15%, from about 15% to about 16%, from about 16% to about 17%, from about 17% to about 18%, from about 18% to about 19%, from about 19% to about 20%, from about 30% to about 32%, from about 34% to about 36%, from about 36% to about 38%, from about 38% to about, about 46-48%, about 48-50%, about 50-52%, about 52-54%, about 54-56%, about 56-58%, about 58-60%, about 60-62%, about 62-64%, about 64-66%, about 66-68%, about 68-70%, about 70-72%, about 72-74%, about 74-76%, about 76-78%, about 78-80%, about 0.1-10%, about 10-20%, about 20-30%, about 30-40%, about 40-50%, about 50-60%, about 60-70%, or about 70-80%.

In some embodiments, the polymeric material may be a crosslinked polymeric material, wherein the polymers may be crosslinked within the same polymer and/or with different polymers through crosslinker materials/bridges. In some embodiments, the polymeric material may include a crystalline polymeric material and/or an amorphous polymeric material. It is believed that the polymer crystals and chains that may be interposed between sheets of graphene material may provide separation of the sheets and/or provide a mechanical and chemical barrier to invading fluids and/or gases to significantly increase the permeation distance, resulting in increased gas separation performance. In some embodiments, the polymeric material may further comprise polyvinyl alcohol. It is believed that the polymer component of the separator provides the desired level of water vapor permeability.

In some embodiments, the ammonium salt polymer can be

(ammonium salt polymer, wherein n ═ 100 to 5,000)

The ammonium salt polymer (e.g., PDADMA) can be present in any suitable amount, such as from about 10 to 95%, from about 20 to 22%, from about 22 to 24%, from about 24 to 26%, from about 26 to 28%, from about 28 to 30%, from about 30 to 32%, from about 32 to 34%, from about 34 to 36%, from about 36 to 38%, from about 38 to 40%, from about 40 to 42%, from about 42 to 44%, from about 44 to 46%, from about 46 to 48%, from about 48 to 50%, from about 50 to 52%, from about 52 to 54%, from about 54 to 56%, from about 56 to 58%, from about 58 to 60%, from about 60 to 62%, from about 62 to 64%, from about 64 to 66%, from about 66 to 68%, from about 68 to 70%, from about 70 to 72%, from about 72 to 74%, about 74-76%, about 76-78%, about 78-80%, about 80-82%, about 82-84%, about 84-86%, about 86-88%, about 88-90%, about 90-92%, about 92-94%, about 10-20%, about 20-30%, about 30-40%, about 40-50%, about 50-60%, about 60-70%, about 70-80%, about 80-90%, or about 90-95%.

In preparation for crosslinking, the graphene compound may be mixed with a polymer solution (e.g., PVA and ammonium salt polymer) to form an aqueous mixture. In some embodiments, the graphene is in the form of an aqueous solution. In some embodiments, the polymer comprises a polymer in an aqueous solution. In some embodiments, the two solutions are mixed in a ratio of about 0.1:100, about 1:10, about 1:4, about 1:2, about 1:1, about 2:1, about 4:1, about 9:1 and about 10:1 parts graphene compound solution to polymer solution. Some embodiments preferably use a mixing ratio of about 1: 30. Some embodiments preferably use a mixing ratio of about 1: 50. Some embodiments preferably use a mixing ratio of about 1: 90.

In some embodiments, a crosslinker solution is added in addition to the two solutions (of graphene compound and polymer solution). In some embodiments, the mixing ratio may be about 0.1:100, about 1:10, about 1:4, about 1:2, about 1:1, about 2:1, about 4:1, about 9:1, and about 10:1 parts graphene compound solution to crosslinker solution. Some embodiments preferably use a mixing ratio of about 1: 10. Some embodiments preferably use a mixing ratio of about 1: 50. Some embodiments preferably use a mixing ratio of about 1: 70.

In some embodiments, the graphene compound and the polymer solution are mixed such that a major phase of the mixture comprises the exfoliated nanocomposite. The reason for the need for an exfoliated nanocomposite phase is that the graphene platelets are aligned in this phase, so that permeability in the finished membrane is reduced by lengthening the possible molecular paths through the membrane. In some embodiments, the graphene compound may comprise any combination of the following: graphene, graphene oxide and/or functionalized graphene oxide. In some embodiments, the graphene composition is suspended in an aqueous solution of about 0.1 wt% to about 5 wt%, about 0.1-0.5 wt%, about 0.5-1 wt%, about 1-2 wt%, about 2-3 wt%, about 3-4 wt%, about 4-5 wt%, about 0.9 wt%, or about 0.8 wt% graphene oxide.

In some embodiments, the polymeric material comprises an aqueous solution of about 1-5 wt%, about 5-10 wt%, about 10-15 wt%, about 15-20 wt%, about 20-25 wt%, about 25-30 wt%, about 30-35 wt%, about 35-40 wt%, about 40-45 wt%, about 45-50 wt%, about 50-55 wt%, about 55-60 wt%, about 60-65 wt%, about 65-70 wt%, about 70-75 wt%, about 75-80 wt%, about 80-85 wt%, about 85-90 wt%, about 90-95 wt%, or about 95-99 wt% of the polymer.

In some embodiments, the graphene material and the polymeric material may be crosslinked using a crosslinker material. In some embodiments, the graphene material and the polymeric material may be crosslinked by thermal reaction and/or UV radiation. In some embodiments, the graphene material and the polymeric material may be crosslinked without additional crosslinker materials by heating the materials to a sufficient temperature to thermally crosslink the materials. In some embodiments, for example, when the polymeric material may be polyvinyl alcohol, the graphene material and the polymeric material may be crosslinked by holding between about 50 ℃ to about 125 ℃ for a time period of 5 minutes to 4 hours, for example, about 30 minutes at 90 ℃. In some embodiments, the graphene material and the polymeric material may be crosslinked by sufficient exposure to ultraviolet radiation without additional crosslinker material.

In some embodiments, the same type of crosslinker material is used to crosslink the graphene material, the polymeric material, or both the graphene and the polymeric material, e.g., the same type of crosslinker material may covalently link the graphene material and the polymeric material; and/or the polymeric material is covalently linked to itself or to other polymeric materials. In some embodiments, the same crosslinker material is used to crosslink the graphene material as well as the polymer material.

Additive agent

In some cases, the additive or additive mixture may improve the performance of the composite. Some crosslinked GO-based composites may also include additive mixtures. In some embodiments, the selectively permeable element may comprise a dispersant. In some embodiments, the dispersant may be an ammonium salt, such as NH₄Cl; flowten; fish oil; a long chain polymer; stearic acid; oxidized menhaden oil (MFO); dicarboxylic acids such as, but not limited to, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and terephthalic acid; sorbitan monooleate; and itAnd (3) mixing. Some embodiments prefer to use oxidized MFO as the dispersant.

In some embodiments, the selectively permeable element may comprise a surfactant. In some embodiments, the surfactant may be sodium Lignin Sulfate (LSU). In some embodiments, the surfactant may be Sodium Lauryl Sulfate (SLS). In some embodiments, the LSU may be present in the selectively permeable member in an amount of about 1-5 wt%, about 1-2 wt%, about 2-3 wt%, about 3-4 wt%, about 4-5 wt%, or about 2 wt%. In some embodiments, the SLS may be present in the selectively permeable member in an amount of about 1-5 wt%, about 1-2 wt%, about 2-3 wt%, about 3-4 wt%, about 4-5 wt%, or about 2 wt%.

In some embodiments, the selectively permeable element may further comprise a binder. In some embodiments, the binder may be a lignin analog. In some embodiments, the lignin analog can comprise sodium lignin sulfate. In some embodiments, the binder may be an analog. In some embodiments, the binder may be, for example, potassium tetraborate (K)₂B₄O₇) And the like.

In some embodiments, the composite material of the selectively permeable element may further comprise an alkali metal halide. In some embodiments, the alkali metal can be lithium. In some embodiments, the halide may be chloride. In some embodiments, the alkali metal halide salt can be LiCl. In some embodiments, the alkali metal halide may be present in the selectively permeable member in an amount of about 1-5 wt%, about 5-10 wt%, about 10-15 wt%, about 15-20 wt%, about 20-25 wt%, about 25-30 wt%, about 30-35 wt%, about 35-40 wt%, about 40-45 wt%, about 45-50 wt%, about 30 wt%, or about 20 wt%.

In some embodiments, the composite material of the selectively permeable element may further comprise an alkaline earth metal halide. In some embodiments, the alkaline earth metal can be calcium. In some embodiments, the halide may be chloride. In some embodiments, the alkaline earth metal halide salt may be CaCl₂. In some embodiments, alkaline earth metal halidesThe compound may be present in the selectively permeable member in an amount of about 1-5 wt%, about 5-10 wt%, about 10-15 wt%, about 15-20 wt%, about 20-25 wt%, about 25-30 wt%, about 30-35 wt%, about 35-40 wt%, about 40-45 wt%, about 45-50 wt%, about 30 wt%, or about 20 wt%.

In some embodiments, a solvent may also be present in the selectively permeable element. Solvents used to make the material layer include, but are not limited to, water, lower alkanols (such as, but not limited to, ethanol, methanol, isopropanol), xylene, cyclohexanone, acetone, toluene, and methyl ethyl ketone, and mixtures thereof.

Protective coating

Some separators may further comprise a protective coating. For example, a protective coating may be provided on top of the membrane to protect it from the environment. The protective coating may have any composition suitable for protecting the membrane from the environment. Many polymers are suitable for the protective coating, for example one or a mixture of hydrophilic polymers, such as polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyethylene oxide (PEO), Polyethylene Oxide (POE), polyacrylic acid (PAA), polymethacrylic acid (PMMA) and Polyacrylamide (PAM), Polyethyleneimine (PEI), poly (2-oxazoline), Polyethersulfone (PES), Methylcellulose (MC), chitosan, poly (allylamine hydrochloride) (PAH), poly (sodium 4-styrenesulfonate) (PSS) and any combination thereof. In some embodiments, the protective coating may comprise PVA. In some embodiments, the protective coating is a polymer comprised of trimesoyl chloride and m-phenylenediamine.

Method for producing dehydration membranes

In some embodiments, methods for producing the selectively permeable elements described above are provided. Some embodiments include a method of making a dehydration membrane comprising: (a) mixing a graphene oxide material, a polymer such as PDADMA, and an additive in an aqueous mixture to produce a composite coating mixture; (b) applying the coating mixture to a porous support to form a coated support; (c) repeating step (b) as necessary to obtain a desired coating thickness; (d) the coating is cured at a temperature of about 60-120 ℃ for about 30 seconds to about 3 hours to promote crosslinking within the coated mixture. In some embodiments, the method comprises pretreating the porous support. In some embodiments, the method further comprises coating the component with a protective layer. An example of a possible method embodiment of manufacturing the above-described membrane is shown in figure 2.

In some embodiments, the porous support may be pretreated to aid in the adhesion of the composite layer to the porous support. In some embodiments, the porous support may be modified to become more hydrophilic. For example, the modification may include corona treatment with a power of 70W, which has 2-4 counts at a speed of 0.5 m/min.

In some embodiments, the mixture may be drawn down on a permeable or impermeable support to produce a film of about 1 μm to about 30 μm, for example, which may then be cast on the support to form part of the element. In some embodiments, the mixture can be deposited on the substrate by spray coating, dip coating, spin coating, and/or other methods known to those skilled in the art for depositing the mixture on a substrate. In some embodiments, casting may be accomplished by coextrusion, film deposition, knife coating, or any other method known to those skilled in the art for depositing a film on a substrate. In some embodiments, the mixture is cast onto a substrate by knife coating (or tape casting) using a doctor blade and dried to form a partial element. The thickness of the resulting cast strip can be adjusted by varying the gap between the doctor blade and the moving substrate. In some embodiments, the gap between the blade and the moving substrate is in the range of about 0.002mm to about 1.0 mm. In some embodiments, the gap between the blade and the moving substrate is preferably between about 0.20mm to about 0.50 mm. Meanwhile, the speed of the moving substrate may have a rate of about 30cm/min to about 600 cm/min. By adjusting the moving substrate speed and the gap between the blade and the moving substrate, the thickness of the resulting graphene polymer layer can be expected to be between about 1 μm and about 200 μm. In some embodiments, the layer may be about 10 μm thick, thereby maintaining transparency. In some embodiments, the coating is performed to produce a composite layer of a desired thickness. In some embodiments, the number of layers may be 1 to 250, about 1 to 100, 1 to 50, 1 to 20, 1 to 15, 1 to 10, or 1 to 5. This process results in a fully coated substrate, or coated support, which is a selectively permeable element. In some embodiments, the total thickness of the separator described herein can be from about 1 μm to about 200 μm. It is believed that the overall thickness of the membrane may contribute to high thermal conductivity to achieve efficient heat transfer.

In some embodiments, the porous support is coated at a coating speed of 0.5 to 15 meters per minute, about 0.5 to 5 meters per minute, about 5 to 10 meters per minute, or about 10 to 15 meters per minute. These coating speeds are particularly suitable for forming coatings having a thickness of about 1-3 μm, about 1-2 μm, or about 2-3 μm. In some embodiments, the composite material has a thickness of about 0.01-1 μm, about 1-2 μm, about 2-3 μm, about 3-4 μm, about 4-5 μm, about 5-6 μm, about 6-7 μm, about 7-8 μm, about 8-9 μm, or about 9-10 μm.

In some embodiments, after the graphene layer is deposited on the substrate, the selectively permeable member may then be dried to remove the underlying solution from the graphene layer. In some embodiments, the drying temperature may be about room temperature, or 20 ℃ to about 120 ℃. In some embodiments, the drying time may be from about 15 minutes to about 72 hours, depending on the temperature. The purpose is to remove any water and precipitate the cast. Some embodiments prefer drying to be carried out at a temperature of about 90 ℃ for about 30 minutes.

In some embodiments, the method comprises drying the mixture at a temperature in the range of about 20 ℃ to about 120 ℃ for about 15 minutes to about 72 hours. In some embodiments, the dried selectively permeable element may be isothermally crystallized, and/or annealed. In some embodiments, the annealing may be performed at an annealing temperature of about 40 ℃ to about 200 ℃ for about 10 hours to about 72 hours. Some embodiments prefer annealing to be completed at a temperature of about 100 c for about 18 hours. Other embodiments preferably anneal at 100 ℃ for 16 hours.

In some embodiments, the selectively permeable element may further comprise a protective coating such that the graphene layer is sandwiched between the substrate and the protective layer. The method of adding the layers may be by coextrusion, film deposition, knife coating, or any other method known to those skilled in the art. In some embodiments, additional layers may be added to enhance the properties of the selectively permeable element. In some embodiments, the protective layer is affixed to the graphene by an adhesive layer to form a selectively permeable element to create a selectively permeable device. In other embodiments, the selectively permeable element is bonded directly to the substrate to create a selectively permeable device.

Method for reducing the water vapor content of a gas mixture

A permselective membrane, such as the dehydration membrane described herein, can be used in a process for removing water vapor or reducing the water vapor content from an untreated gas mixture (e.g., air) containing water vapor for applications where dry gas or low water vapor content is desired. The method includes passing a first gas mixture (untreated gas mixture, e.g., air) containing water vapor through a membrane, thereby allowing water vapor to pass through and be removed, while other gases in the gas mixture, e.g., air, remain to produce a second gas mixture (dehydrated gas mixture) having a reduced water vapor content. Embodiments disclosed herein may be provided as part of a module into which water vapor (saturated or near saturated) and compressed air are introduced. The module produces a dried pressurized product stream and a low pressure permeate stream. The permeate stream may contain a mixture of air and most of the water vapor introduced into the module.

In some embodiments, the water vapor permeability of the membrane is at least 0.5x10^-5g/m²s.Pa, at least 1.0x10^-5g/m²s.Pa, at least 1.5x10^-5g/m²s.Pa, at least 2.0x10^-5g/m²s.Pa, at least 2.5x10^{- 5}g/m²s.Pa, at least 3.0x10^-5g/m²s.Pa, at least 3.5x10^-5g/m²s.Pa, at least 4.0x10^-5g/m²s.Pa, at least 4.5x10^-5g/m²s.Pa, at least 5.0x10^-5g/m²s.Pa, at least 5.5x10^-5g/m²s.Pa, or at least 6.0x10^-5g/m²s.Pa. In some embodiments, applying the membrane comprises selectively passing water vapor therethrough. In some embodiments, the membrane is impermeable or relatively impermeable to the gas component.

In some embodiments, the gas permeability of the membrane is less than 1x10^-5L/m²s.Pa, less than 5x10^-6L/m²s.Pa, less than 1x10^-6L/m²s.Pa, less than 5x10^-7L/m²s.Pa, less than 1x10^-7L/m²s.Pa, less than 5x10^-8L/m²s.Pa, less than 1x10^-8L/m²s.Pa, less than 5x10^-9L/m²s.Pa, less than 1x10^-9L/m²s.Pa, less than 5x10^-10L/m²s.Pa, or less than 1x10^-10L/m²s.Pa. In some embodiments, the gas component may comprise air, hydrogen, carbon dioxide, and/or short chain hydrocarbons. In some embodiments, the short chain hydrocarbon may be methane, ethane, or propane.

The permeated air or secondary dry purge stream may be used to optimize the dehydration process. If the membrane is fully effective in water separation, all of the water or water vapor in the feed stream will be removed and nothing will be purged from the system. As the process proceeds, the partial pressure of water at the feed port or hole side becomes lower and lower, and the pressure at the shell side becomes higher. This pressure differential tends to prevent additional water from draining from the module. Since the purpose is to dry the orifice side, the pressure differential can interfere with the desired operation of the device. Thus, a purge stream may be used to remove water or water vapor from the shell side, partially by absorbing some of the water, and partially by physically pushing the water out.

If a purge stream is used, it may comprise an external dry source or a partially recycled module product stream. Generally, the degree of dehumidification will depend on the partial pressure ratio of the water vapor passing through the membrane and the product recovery (ratio of product flow to feed flow). A better membrane has high product recovery at low levels of product moisture and/or higher volumetric product flow rates.

A dehydration membrane may be used to remove water for Energy Recovery Ventilation (ERV). ERVs are energy recovery processes used to exchange energy contained in normally discharged building or space air and use it to treat (pre-treat) incoming outdoor ventilation air in residential and commercial HVAC systems. During warm seasons, ERV systems are pre-cooled and dehumidified, while during cooler seasons humidification and preheating are performed.

The separator of the present disclosure is easily manufactured at low cost, and may be superior to existing commercial separators in terms of volumetric productivity or product recovery.

The following embodiments are contemplated.

Embodiment 1. a dehydration membrane, comprising:

a carrier;

a composite material comprising a graphene oxide compound and an ammonium salt polymer;

wherein the composite material coats the support; and is

Wherein the separator has high moisture permeability and low air permeability.

Embodiment 2 the separator of embodiment 1, wherein the ammonium salt polymer is a poly (diallyldimethylammonium) salt.

Embodiment 3 the membrane of embodiment 1, wherein the support is porous.

Embodiment 4 the separator of embodiment 1, wherein the support comprises polypropylene, polyethylene terephthalate, polysulfone, or polyethersulfone.

Embodiment 5 the separator of embodiment 1, further comprising polyvinyl alcohol.

Embodiment 6 the membrane of embodiment 5, wherein the graphene oxide and the polyvinyl alcohol are crosslinked.

Embodiment 7 the separator of embodiment 5, wherein the weight ratio of the graphene oxide to the polyvinyl alcohol is about 0.1:100 to about 9: 1.

Embodiment 8 the separator of embodiment 1, wherein the graphene oxide compound is selected from the group consisting of graphene oxide, reduced graphene oxide, functionalized graphene oxide, and functionalized reduced graphene oxide.

Embodiment 9 the membrane of embodiment 1, wherein the graphene has a platelet size of about 0.05 μ ι η to about 100 μ ι η.

Embodiment 10 the membrane of embodiment 1, wherein the membrane comprises hollow fibers.

Embodiment 11 the separator of embodiment 1, wherein the composite further comprises calcium chloride.

Embodiment 12 the separator of embodiment 1, wherein the composite further comprises a surfactant.

Embodiment 13 the membrane of embodiment 12, wherein the surfactant is sodium lauryl sulfate.

Embodiment 14 a method of treating a gas, comprising:

providing the separator of embodiments 1-13;

a membrane is applied to a complex mixture having a first gas component containing water vapor, the water vapor being removed from the first gas to produce a second gas component.

Examples

It has been found that embodiments of the selectively permeable elements described herein have improved permeability to oxygen and vapor, and have acceptable material properties, as compared to other selectively permeable elements. These benefits are further illustrated by the following examples, which are intended to be illustrative of embodiments of the present disclosure, but are not intended to limit the scope or underlying principles in any way.

Ammonium salt Polymer (Poly (diallyldimethylammonium chloride))

Poly (diallyldimethylammonium chloride) was purchased from Sigma-Aldrich (st. louis, MO, USA) and used without additional purification. A5 wt% solution was prepared with deionized water (DI).

Separator coating procedure

Preparation of coating solution:

improvements in useFrom graphite. Graphite flakes (4.0g, Aldrich, 100 mesh) were placed in NaNO₃(4.0g)、KMnO₄(24g) And concentrated 98% H₂SO₄(192mL) at 50 ℃ for 15 hours; the resulting pasty mixture was then poured into ice (800g) and 30% hydrogen peroxide (40mL) was added. The resulting suspension was stirred for 2 hours to reduce manganese dioxide and then filtered through filter paper, and the solids were washed with 500mL of 0.16M aqueous HCl and then twice with deionized water. The solid was collected and dispersed in DI water (2L) by stirring for two days, then sonicated with a 10W probe sonicator for 2 hours with ice water bath cooling. The resulting dispersion was centrifuged at 3000rpm for 40 minutes to remove large, non-exfoliated graphite oxide. Sufficient DI water was added to make a 0.1 wt% aqueous GO dispersion.

1mL GO (0.1%) was mixed with 4.4mL water and sonicated for about 3 minutes. After the GO was completely dispersed in water, 1mL poly (diallyldimethylammonium chloride) (PDADMA, 5.0 wt% aqueous solution) and 2mL PVA (2.5% aqueous solution) were added to the solution. The solution was then sonicated for about 8 minutes. After complete dissolution of PDADMA and PVA in the aqueous solution was observed, 0.4mL CaCl was added₂(5%) (Sigma Aldrich, St. Louis, MO, USA) and the solution was sonicated for about 6 minutes to completely dissolve CaCl in the solution₂。

As shown in Table 1 below, EX-1 through Ex-3 were prepared in a manner similar to Ex-4, except, for example, (a) different weight ratios of PVA and PDADMA were used, and (b) optional materials, e.g., SLS, CaCl₂In the amounts/ratios indicated.

Treating a base material: a porous polypropylene substrate (Celgard 2500) was modified by corona treatment using a power of 70W, 3 counts, and a speed of 0.5 m/min.

Coating and curing:

the coating solution was applied to the freshly treated substrate using a200 μm wet gap. The resulting film was dried and then cured at 110 ℃ for 5 minutes. During curing, GO and PVA crosslink.

Measurement of permselective elements

Ex-1, Ex-2, Ex-3 and Ex-4 prepared as described above were tested for nitrogen permeability at 23 ℃ and 0% Relative Humidity (RH) as described in ASTM 6701. The results are shown in Table 1.

Ex-1, Ex-2, Ex-3 and Ex-4 prepared as described above were tested for Water Vapor Transmission Rate (WVTR) at 20 ℃ and 100% Relative Humidity (RH) as described in ASTM E96 standard method. The results are shown in Table 1.

TABLE 1 Water vapor Permeability and H for GO-PVA-PDADMA membranes₂O/N₂Selectivity is

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties (e.g., molecular weights), reaction conditions, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless otherwise indicated, each numerical parameter set forth in the specification and claims is an divisor that can vary depending on the desired property sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The use of the terms "a," "an," "the" and similar articles or non-use articles in the context of the description of the disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referenced and embodied individually or in any combination with other members of the group or other elements found herein. It is contemplated that one or more members of a group may be included in or deleted from the group for convenience and/or patentability reasons.

Certain embodiments are described herein, including the best mode known to the inventors for carrying out the embodiments. Of course, variations on those described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the disclosure to be practiced otherwise than as specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

Finally, it should be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, and not limitation, alternative embodiments may be used in accordance with the teachings herein. Thus, the claims are not limited to the embodiments precisely as shown and described.