WO2021203094A1

WO2021203094A1 - Antiviral filtration element and filtration devices containing same

Info

Publication number: WO2021203094A1
Application number: PCT/US2021/025769
Authority: WO
Inventors: Aruna Zhamu; Bor Z. Jang
Original assignee: Nanotek Instruments Group, Llc
Priority date: 2020-04-03
Filing date: 2021-04-05
Publication date: 2021-10-07
Also published as: CA3174421A1; JP2023521043A; CN116075337A

Abstract

Provided is an face mask comprising: (a) a mask body; and (b) a fastener; wherein the mask body includes (i) an air-permeable outer layer preferably comprising a hydrophobic material, (ii) an inner layer, and (iii) a graphene or graphene foam or graphite flake layer disposed in the mask body, wherein the graphene layer comprises a plurality of discrete single-layer or few-layer graphene sheets selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof. The graphene or foam or graphite layer may be disposed in the mask body between the outer layer and the inner layer or embedded (totally or partially) in the outer layer or the inner layer. The graphene or foam pore wall or graphite flake surfaces may be deposited with an antiviral or anti-bacteria compound.

Description

ANTIVIRAL FILTRATION ELEMENT AND FILTRATION DEVICES

CONTAINING SAME

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Patent Application No. 16/839,827 filed April 3, 2020, U.S. Patent Application No. 16/839,847 filed April 3, 2020, and U.S. Patent Application No. 16/844,062 filed April 9, 2020, the contents of each are hereby incorporated by reference for all purposes.

The present disclosure relates generally to the field of filters and, particularly, to an antiviral filtration element, filtering devices containing this element, and a process for producing and method of operating same. This disclosure is related to a filtration device that is capable of filtrating out bacteria, viruses, other air-bome particles, or liquid-borne contaminants. This device may be an oral and/or nasal air filter that can remove and neutralize harmful virus from inhaled air contaminated with such virus, and from contaminated air exhaled from patients infected with such virus. In particular, the disclosure relates to such a device in the form of a face mask. The disclosure also relates to filter materials or members suitable for use in such a face mask and other filtration devices.

BACKGROUND

The inhalation of air contaminated by harmful virus and/or other micro-organisms is a common route for infection of human beings, particularly health workers and others caused to work with infected humans or animals. It is also known that air exhaled by infected patients is a source of contamination. At the present time the risk of infection by the so called “COVID-19” coronavirus is of particular concern. Masks incorporating a suitable filter material would be ideal for use as a barrier to prevent infection by this virus.

Air filters that are believed to be capable of removing such virus and/or other micro organisms are known in the art. One type of such a filter comprises a fibrous or particulate substrate or layer and an antiviral or anti-bacteria compound deposited upon the surface and/or into the bulk of such a substrate or layer. This compound captures and/or neutralizes virus and/or other micro-organisms of concern. Examples of disclosures of such filters are summarized below:

For instance, U.S. Patent No. 4,856,509 provides a face mask wherein select portions of the mask contain a viral destroying agent such as citric acid. U.S. Patent No. 5,767,167 discloses aerogel foams suited for filtering media for capture of micro-organisms such as virus. U.S.

Patent No. 5,783,502 provides a fabric substrate with anti-viral molecules, particularly cationic groups such as quaternary ammonium cationic hydrocarbon groups bonded to the fabric. U.S. Patent No. 5,851,395 is directed at a virus filter comprising a filter material onto which is deposited a virus-capturing material based on sialic acid (9-carbon monosaccharides having a carboxylic acid substituent on the ring). U.S. Patent No. 6,182,659 discloses a virus-removing filter based on a Streptococcus agalactiae culture product. U.S. Patent No. 6,190,437 discloses an air filter for removing virus from the air comprising a carrier substrate impregnated with iodine resins. U.S. Patent No. 6,379,794 discloses filters based on glass and other high modulus fibers impregnated with an acrylic latex material. U.S. Patent No. 6,551,608 discloses a porous thermoplastic material substrate and an antiviral substance made by sintering at least one antiviral agent with the thermoplastic substance. U.S. Patent No. 7,029,516 discloses a filter system for removing particles from a fluid comprising a non- woven polypropylene base upon which is deposited an acidic polymer such as polyacrylic acid.

There is an ongoing and highly urgent need to improve such filters, particularly in view of concerns about the risks from “bird flu” and corona virus. The present inventors have identified filter materials or members which may be capable of increasing the level of removal of harmful virus and/or other micro-organisms from inhaled air and neutralization of these species, enabling the use of such materials in an improved nasal and/or mouth filter. The same filter materials may also be used as a filtration member in other filter devices, such as those for purification of water and air, separation of selected solvents, and recovery of spilled oil.

SUMMARY

The present disclosure provides a face mask comprising: (a) a mask body configured to cover at least wearer's mouth and nose; and (b) a fastener to hold the mask in place on the wearer's face (e.g. a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head); wherein the mask body includes (i) an air-permeable outer layer (e.g. a fiber sheet or piece of fabric, or a porous polymer membrane) preferably comprising a hydrophobic material (e.g. water-repelling fibers), (ii) an inner layer located on a wearer's side when the mask is worn, and (iii) a graphene or graphene foam layer disposed in the mask body. In one embodiment the graphene or graphene foam layer is disposed between the outer layer and the inner layer. In another embodiment the graphene or graphene foam layer is embedded in the outer layer. In another embodiment the graphene or graphene foam layer is embedded in the inner layer. The graphene or graphene foam layer may be totally or partially embedded in the outer layer or in the inner layer. The graphene layer may comprise a plurality of discrete single layer or few layer graphene sheets and the graphene foam layer may comprise a graphene material, where the graphene sheets and the graphene material are selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof.

In certain embodiments, the graphene sheets or foam layer is chemically bonded to a surface (e.g. the inner surface) of the outer layer or a surface (the surface facing the outer layer) of the inner layer, with or without using an adhesive or binder.

In the disclosed face mask, the graphene layer preferably has a density from 0.005 to 1.7 g/cm and a specific surface area from 10 to 3,200 m /g, but further preferably a specific surface area from 50 to 3,000 m 2 /g or a density from 0.1 to 1.2 g/cm 3 and the graphene foam layer preferably has a density from 0.005 to 1.0 g/cm 3 or a specific surface area from 40 to 2,600 m 2 /g, 2 but further preferably a specific surface area from 200 to 2,000 m /g or a density from 0.01 to 0.5 g/cm³.

The graphene or graphene foam layer-to-outer layer weight ratio or the graphene or graphene foam layer-to-inner layer weight ratio is preferably from 1/1000 to 1/0.1, more preferably from 1/100 to 1/1, and most preferably from 5/100 to 25/100.

In some embodiments, the graphene or graphene foam layer is a discrete layer that is embedded in at least one of the outer layer or the inner layer.

In the disclosed face mask, the outer layer or the inner layer may of the mask body comprise a woven or nonwoven structure of polymer or glass fibers. The outer layer or the inner layer may preferably comprise polymer fibers selected from the group of cotton, cellulose, wool, polyolefins (e.g. polyethylene and polypropylene), polyester (e.g. PET), polyamide (e.g. nylon), rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

The fastener may comprise a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head.

Preferably, the graphene sheets in the graphene layer or foam layer have an oxygen content from 5% to 50% by weight based on the total graphene sheet weight. The oxygen- containing functional groups on graphene surfaces appear to be capable of killing or de activating certain microbial agents.

In the disclosed face mask, the mask body may further comprise an anti-microbial compound. Preferably, the mask body further comprises an anti-microbial compound distributed on surfaces of the graphene sheets and the graphene sheets have a specific surface area from 50 to 2,630 m /g or on pore wall surfaces of the graphene foam. With such a high specific surface area, the mask body enables a dramatically higher surface of the anti-microbial compound that can directly attack the microbial pathogens (bacteria, virus, etc.)

The anti-microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid (e.g. 9-carbon monosaccharides having a carboxylic acid substituent on the ring), a cationic group (e.g. quaternary ammonium cationic hydrocarbon group bonded to the fabric or graphene sheets), a sulfonamide, a fluoroquinolone, or a combination thereof.

The present disclosure also provides a filtration material (or member) for use in the aforementioned face mask or other types of filtration devices. In certain embodiments, the filtration material comprises a layer of woven or nonwoven fabric having two primary surfaces and a graphene or graphene foam layer deposited on at least one of the two primary surfaces, or embedded in the layer of woven or nonwoven fabric.

In the filtration material, the graphene or graphene foam layer preferably comprises a plurality of discrete single-layer or few-layer graphene sheets or graphene material selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof. In some embodiments, the graphene sheets are chemically bonded to the at least one of the primary surfaces, with or without using an adhesive or binder. In the filtration material, the graphene layer preferably has a density from 0.005 to 1.7 g/cm , and a specific surface area from 10 to

3,200 m 2 /g and further preferably has a specific surface area from 50 to 3,000 m 2 /g or a density from 0.1 to 1.2 g/cm 3 or a density from 0.005 to 1.0 g/cm 3 , or a specific surface area from 10 to 2,600 m /g and further preferably has a specific surface area from 200 to 2,000 m /g or a density from 0.1 to 1.2 g/cm . The specific surface area is most desirably higher than 200 and the specific surface density of the foam is most desirably higher than 300 m /g.

In the filtration material, the graphene or graphene foam layer is preferably a discrete layer that is partially or totally embedded in the layer of woven or nonwoven fabric, or partially embedded into at least a primary surface thereof.

The disclosure further provides a filtration device comprising the disclosed filtration material as a filtration member. The filtration device may be a water-purifying device, an air- purifying device, an oil-recovering device, or a solvent-removing device.

Further provided in the instant disclosure is a process for producing the herein disclosed filtration material, the process comprising (a) preparing a layer of woven or nonwoven fabric having two primary surfaces; and (b) depositing a graphene layer on at least one of the two primary surfaces.

In certain embodiments, (b) comprises a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a gaseous medium to form a flowing fluid and impinging the flowing fluid upon at least one of the two primary surfaces, allowing said graphene sheets to adhere to said at least one primary surface.

In certain preferred embodiments, (b) comprises a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a liquid medium to form a slurry, depositing the slurry onto at least one of the two primary surfaces to form a wet graphene layer, and removing or drying the liquid medium from said wet graphene layer to form the graphene layer. Thermally curable or UV-curable adhesives are more desirable.

The procedure of depositing preferably comprises a procedure selected from casting, coating (e.g. slot-die coating, comma coating, reverse-roll coating, etc.), spraying (e.g. air- assisted spraying, static charge-assisted spraying, ultrasonic spraying, etc.), printing (e.g. inkjet printing, screen printing, etc.), brushing, painting, or a combination thereof.

The process is preferably a roll-to-roll or reel-to-reel process, wherein (a) comprises (i) preparing a roll of woven or nonwoven fabric, (ii) continuously feeding a continuous length of a sheet of the fabric from the roll (mounted on a roller or reel) into a deposition zone, (iii) depositing a graphene layer onto at least one of the two primary surfaces to form a graphene layer-coated fabric, and (iv) collecting the graphene layer-coated fabric on a winding roller.

The process may further comprise incorporating the filtration material into a mask body, which is fitted with fastener to form the face mask.

The present disclosure provides a filtration member for use in a filtration device, the filtration member comprising a layer of air-permeable membrane (e.g. a sheet of woven or nonwoven fabric, a porous polymeric membrane, a piece of open-cell foam, a sheet of air- breathable paper, etc.) having two primary surfaces and a layer of chemically functionalized graphite flakes deposited on at least one of the two primary surfaces or embedded in the layer of air-permeable membrane, wherein the graphite flakes comprise a chemical functional group containing l%-50% (preferably 5% to 35%) by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

In some embodiments, the layer of graphite flakes is chemically bonded to the at least one of the primary surfaces using an adhesive or binder.

Preferably, the layer of graphite flakes has a specific surface area from 10 to 500 m /g.

In the filtration member, the non- woven fabric preferably comprises polymer fibers selected from the group of cotton, cellulose, wool, polyolefins, polyester, polyamide, rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

In certain embodiments, the disclosed filtration member further comprises an anti microbial compound distributed on surfaces of graphite flakes. The anti-microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof

In some embodiments, the non-woven fabric in the filtration member comprises polymer fibers and an anti-microbial compound is distributed on surfaces of the polymer fibers. The anti microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof.

The disclosure also provides a filtration device comprising the above-described filtration member as a functional component. The filtration device may be a water-purifying device, an air-purifying device, a solvent-removing device, an oil-recovering device, or a face mask, particularly a medical face mask or respirator.

In certain embodiments, the disclosed face mask comprises (a) a mask body configured to cover at least wearer's mouth and nose; and (b) a fastener to hold the mask in place on the wearer's face; wherein the mask body comprises (i) an air-permeable outer layer, (ii) an inner layer located on a wearer's side when the mask is worn, and (iii) the aforementioned filtration member that is disposed between the outer layer and the inner layer or embedded in the outer layer or in the inner layer.

It may be noted that the layer of woven or nonwoven fabric supporting the layer of graphite flakes may be the outer layer or the inner layer. In other words, the layer of chemically functionalized graphite flakes may be deposited on the internal surface of the outer layer or on the outer surface (opposite of the wearer’s face) of the inner layer.

Thus, the present disclosure also provides a face mask comprising: (a) a mask body configured to cover at least wearer's mouth and nose; and (b) fastening device to hold the mask in place on the wearer's face (e.g. a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head); wherein the mask body includes (i) an air-permeable outer layer (e.g. a fiber sheet or piece of fabric, or a porous polymer membrane) preferably comprising a hydrophobic material (e.g. water-repelling fibers), (ii) an inner layer located on a wearer's side when the mask is worn, and (iii) a layer of chemically functionalized expanded graphite flakes disposed between the outer layer and the inner layer or totally or partially embedded in the outer layer or in the inner layer. The graphite flakes comprise chemical functional groups containing l%-50% (preferably 5% to 35%) by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

Generally speaking, the present disclosure also provides a face mask that comprises chemically functionalized graphite flakes as an antiviral agent, wherein the graphite flakes comprise a chemical functional group containing l%-50% by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof. Particularly useful are graphite flakes that carry chemical functional groups such as -COOH, -OH, >0, -F, -Cl, -Br, -I, and/or - NH₂.

In certain embodiments, the graphite flake layer is chemically bonded to a surface (e.g. the inner surface) of the outer layer or a surface (the surface facing the outer layer) of the inner layer using an adhesive or binder. In the disclosed face mask, the graphite flakes preferably have a specific surface area from 10 to 500 m²/g.

The graphite flake layer-to-outer layer weight ratio or the graphite flake layer-to-inner layer weight ratio is preferably from 1/1000 to 1/0.1, more preferably from 1/100 to 1/1, and most preferably from 5/100 to 25/100.

In some embodiments, the graphite flake layer is a discrete layer that is embedded in at least one of the outer layer or the inner layer.

In the disclosed face mask, the outer layer or the inner layer of the mask body may comprise a woven or nonwoven structure of polymer or glass fibers, a porous polymer membrane (e.g. porous PE-PP copolymer membrane, polytetrafluoroethylene or Teflon membrane), an air-breathable sheet of paper, or a combination thereof. The outer layer or the inner layer may preferably comprise polymer fibers selected from the group of cotton, cellulose, wool, polyolefins (e.g. polyethylene and polypropylene), polyester (e.g. PET), polyamide (e.g. nylon), rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

Preferably, the graphite flake layer has an oxygen or nitrogen content from 5% to 50% by weight or halogen content from 5% to 30% based on the total graphite flake weight. The oxygen- , nitrogen-, or halogen-containing functional groups on graphite flake surfaces appear to be capable of killing or de-activating certain microbial agents.

In the disclosed face mask, the mask body may further comprise an anti-microbial compound. Preferably, the mask body further comprises an anti-microbial compound distributed on surfaces of the graphite flakes. With such a high specific surface area, the mask body enables a dramatically higher effective amount of the anti-microbial compound that can directly attack the microbial pathogens (bacteria, virus, etc.). Substantially all of the anti-microbial compound can be utilized. The anti-microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid (e.g. 9-carbon monosaccharides having a carboxylic acid substituent on the ring), a cationic group (e.g. quaternary ammonium cationic hydrocarbon group bonded to the fabric or graphite flakes), a sulfonamide, a fluoroquinolone, hypericin, curcumin (including polymeric curcumin), or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A flow chart showing the most commonly used prior art process for producing graphene sheets.

FIG. 2 Schematic of a face mask according to an embodiment of the present disclosure.

FIG. 3(A) Schematic drawing illustrating the processes for producing intercalated and/or oxidized graphite, subsequently exfoliated graphite worms, and expanded graphite flakes; FIG. 3(B) An SEM image of exfoliated carbon (exfoliated carbon worms), containing interconnected graphite flakes; upon exposure to low-intensity air jet milling, these worms become isolated expanded graphite flakes.

FIG. 3(C) Another SEM image of graphite worms, containing interconnected graphite flakes; upon exposure to low-intensity air jet milling, these worms become isolated expanded graphite flakes.

FIG. 3(D) Schematic drawing illustrating the approaches of producing thermally expanded/exfoliated graphite structures containing interconnected graphite flakes; upon exposure to low-intensity air jet milling, these worms become isolated expanded graphite flakes.

FIG. 4(A) Schematic of a face mask structure according to an embodiment wherein the graphene, graphene foam, or graphite flake layer is a discrete layer that is embedded in the outer layer.

FIG. 4(B) Schematic of a face mask structure according to an embodiment wherein the graphene, graphene foam, or graphite flake layer is a discrete layer that is embedded in the inner layer.

DETAILED DESCRIPTION The present disclosure provides a filtration element (member) and a filtration device containing such a member. The filtration device may be selected from a water filter device, an air filter device, a solvent purification device, an oil-recovering device, or a face mask (e.g., a surgical face mask, a respirator, such as a N95 face mask).

The filtration member preferably comprises a layer of air-permeable membrane (e.g. a sheet of woven or nonwoven fabric, a porous polymeric membrane, a piece of open-cell foam, a sheet of air-breathable paper, etc.) having two primary surfaces and a layer of chemically functionalized graphite flakes deposited on at least one of the two primary surfaces or embedded in the layer of air-permeable membrane, wherein the graphite flakes comprise a chemical functional group containing l%-50% (preferably 5% to 35%) by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

In some embodiments, the layer of graphite flakes is chemically bonded to the at least one of the primary surfaces using an adhesive or binder. Preferably, the layer of graphite flakes has a specific surface area from 10 to 500 m2/g.

In certain embodiments, the disclosed filtration member further comprises an anti microbial compound distributed on surfaces of graphite flakes. The anti-microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof.

In certain embodiments, as schematically illustrated in FIG. 2, the disclosed face mask comprises: (a) a mask body configured to cover at least wearer's mouth and nose; and (b) a fastener to hold the mask in place on the wearer's face (e.g. a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head); wherein the mask body includes (i) an air-permeable outer layer (e.g. a fiber sheet or piece of fabric) comprising a hydrophobic material (e.g. water- repelling fibers), (ii) an inner layer located on a wearer's side when the mask is worn, and (iii) a layer of graphene material or foam or graphite flakes disposed between the outer layer and the inner layer or totally or partially embedded in the outer layer or in the inner layer.

The graphene or graphene foam layer preferably comprises a plurality of discrete single layer or few-layer graphene sheets or graphene material selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof. Face masks include surgical masks, respirators, and non-medical masks, etc.

The graphite flakes comprise a chemical functional group containing l%-50% (preferably 5% to 35%) by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof. The fastener has a portion or portions which engage the face mask body and a portion or portions of the fastener which engage with the wearer. In one embodiment a portion of the elastic straps are sewn to the face mask body, while the other portion of elastic straps wrap around the ears of the wearer. The outer layer or the inner layer may be each a multi-ply or multi-layer structure. In some embodiments, a graphene, graphene foam, or graphite flake layer may be embedded as one of the multiple layers in either of the outer layer (FIG. 4(A)) or the inner layer (FIG. 4(B)). The air-permeable structure may comprise an air permeable membrane, such as a fibrous substrate or fabric, which can either be a woven or non-woven fabric. Examples of woven materials include those natural and synthetic fibers such as cotton, cellulose, wool, polyolefins (e.g. PE and PP), polyester (e.g. PET and PBT), polyamide (e.g. nylon), rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls and any other synthetic polymers that can be processed into fibers. Examples of non-woven materials include polypropylene, polyethylene, polyester, nylon, PET and PLA. For the presently disclosed device, non-woven is preferred, which may be in the form of a non-woven sheet or pad.

Non-woven polyester is a preferred air-permeable structure because some of the desired anti-viral or anti-bacteria compounds, such as an acidic polymer, adhere better to polyester material. Also preferred is polypropylene non-woven fabric. The graphene sheets or foam or graphite flake layers/structures investigated herein appear to be compatible with all the polymeric fiber-based fabric structures. The grade of fibrous substrate or fabric which may be used to support graphene sheets or foam or graphite flakes may be determined by practice to achieve a suitable through-flow of air, and the density may be as known from the face-mask art to provide a mask of a comfortable weight.

Non-woven polypropylene of the type conventionally used for surgical masks and the like is widely available in sheet form. Suitable grades of non-woven polypropylene include the well-known grades commonly used for surgical face masks. Typical non-woven polypropylene materials found suitable for use in the face mask or other filtration devices have areal weights of 10-50 g/m (gsm). Other suitable material weights can be determined empirically, without any difficulty. Typical non-woven polyester suitable for use in the filtration devices has areal weights of 10-300 g/m . For face mask applications, polyester materials of weight 20-100 g/m are preferred. Such materials are commercially available. Other suitable materials may be determined empirically without difficulty. Alternatively, the porous layer substrate, other than non-woven or woven fabric, may be in other forms such as an open-cell foam, e.g. a polyurethane foam as is also used for air filters.

A graphene foam layer and a polymer foam layer are then bonded or laminated together to form a body of structural integrity. A graphite flake layer and a polymer foam layer are then bonded or laminated together to form a body of structural integrity. Alternatively, graphite flakes may be deposited onto a surface of a foam (or any other type of air-permeable membrane) using casting, coating, printing, spraying, painting, etc.

Again, face masks, including surgical masks and respirators, are commonly made with non-woven fabric, which has better bacteria filtration and air permeability while remaining less slippery than woven cloth. The material most commonly used to make them is polypropylene, but again can also be made of polystyrene, polycarbonate, polyethylene, or polyester, etc. The mask material of 20 g/m or gsm is typically made in a spun-bond process, which involves extruding the melted plastic onto a conveyor. The material is extruded in a web, in which strands bond with each other as they cool. The 25 gsm fabric is typically made through the melt-blown process, wherein plastic is extruded through a die with hundreds of small nozzles and blown by hot air to become ultra- small fibers, cooling and binding on a conveyor. These fibers are typically less than a micron in diameter. A graphene foam layer may be combined with the plastic fabric during or after the fabric production procedure. A graphite flake layer may be combined with the polymer fabric during or after the fabric production procedure.

Surgical masks are generally composed of a multi-layered structure, generally by covering a layer of textile with non-woven bonded fabric on both sides. Non-woven materials are less expensive to make and cleaner due to their disposable nature. The structure incorporated as part of a mask body may be made with three or four layers. These disposable masks are often made with two filter layers effective in filtering out particles, such as bacteria above 1 micron. The filtration level of a mask depends on the fiber, the manufacturing process, the web structure, and the cross-sectional shape of the fiber. In the disclosed mask, the graphene or graphene foam or graphite flake layer can be incorporated as one of the multi-layers, but preferably not directly exposed to the outside air (not the outermost layer) and not directly in contact with the face of the wearer (not the inner-most layer). Masks may be made on a machine line that assembles the nonwovens from bobbins, ultrasonically welds the layers together, and stamps the masks with nose strips, ear loops, and other pieces. These procedures are well-known in the art.

Respirators also comprise multiple layers. The outer layer on both sides may be made of a protective nonwoven fabric between 20 and 100 g/m² density to create a barrier both against the outside environment and, on the inside, against the wearer’s own exhalations. A pre-filtration layer follows which can be as dense as 250 g/m². This is usually a needled nonwoven which is produced through hot calendaring, in which plastic fibers are thermally bonded by running them through high pressure heated rolls. A graphene or graphene foam or graphite flake layer may be used to partially or totally replace this layer. In the case of partial substitution, graphene foam or sheets or graphite flakes may be deposited or bonded onto a primary surface of this needled nonwoven layer. This makes the pre-filtration layer thicker and stiffer to form the desired shape as the mask is used. The last layer may be a high efficiency melt-blown electret nonwoven material, which determines the filtration efficiency. This melt-blown layer, instead of or in addition to the pre-filtration layer, may be deposited or bonded with a graphene or graphene foam or graphite flake layer.

The graphene sheet surfaces or pore wall graphene surfaces in graphene foam or graphite flakes may be deposited with an anti-viral or anti-bacterial compound. This deposition may be conducted before or after the graphene sheets or foam form into a graphene layer or the graphite flakes form into a layer. The anti-microbial compound may comprise an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver- organic idine antibacterial agent, an iodine resin, a sialic acid (e.g. 9-carbon monosaccharides having a carboxylic acid substituent on the ring), a cationic group (e.g. quaternary ammonium cationic hydrocarbon group bonded to the fabric or graphene sheets), a sulfonamide, a fluoroquinolone, hypericin, curcumin (including polymeric curcumin), or a combination thereof.

It has been found that acidic polymers are effective at capturing and neutralizing vims in air passing through such a filtration member (substrate) featuring an acidic polymer. Without being limited to a specific theory, it is believed that upon contact with the surface of the substrate the virus interact with the polymer, are entrapped and the localized low pH environment (e.g. pH value of 2.8 to 5) of the acidic polymer inactivates the virus. It is believed that the filter member and filtration device containing such a member herein disclosed may be effective in this manner against the vims that cause colds, influenza, SARS, RSV, bird flu, corona vims, and mutated serotypes of these.

Poly- (carboxylic acid) polymers, as examples of acidic polymers, are typically polymers which include — COOH groups in their structure, or derivative groups such as acid- anhydride groups, readily cleavable carboxylic acid ester groups which readily cleave to yield — COOH groups. A poly- (carboxylic acid) polymer may have its — COOH groups (or derivative groups) directly linked to its backbone, or the polymer may be a so-called grafted or dendritic polymers in which the — COOH (or derivative) groups are attached to side chains branching off from the backbone.

The functionalized expanded graphite flakes as disclosed herein can be readily made to contain -COOH groups on their surfaces or edges. These functionalized groups carried by the graphite flakes are also expected to be antiviral as well.

It is imperative that face masks and respirators produced are sterilized before being sent out of the factory.

The production of graphene and graphene foam is well-known in the art, but may be further described below for the convenience of the reader:

Carbon materials can assume an essentially amorphous structure (glassy carbon), a highly organized crystal (graphite), or a whole range of intermediate structures that are characterized in that various proportions and sizes of graphite crystallites and defects are dispersed in an amorphous matrix. Typically, a graphite crystallite is composed of a number of graphene sheets or basal planes that are bonded together through van der Waals forces in the c-axis direction, the direction perpendicular to the basal plane. These graphite crystallites are typically micron- or nanometer- sized. The graphite crystallites are dispersed in or connected by crystal defects or an amorphous phase in a graphite particle, which can be a graphite flake, carbon/graphite fiber segment, carbon/graphite whisker, or carbon/graphite nano-fiber. In other words, graphene planes (hexagonal lattice structure of carbon atoms) constitute a significant portion of a graphite particle.

A single-layer graphene sheet is composed of carbon atoms occupying a two-dimensional hexagonal lattice. Multi-layer graphene is a platelet composed of more than one graphene plane. Individual single-layer graphene sheets and multi-layer graphene platelets are herein collectively called nano graphene platelets (NGPs) or graphene materials. NGPs include pristine graphene (essentially 99% of carbon atoms), slightly oxidized graphene (< 5% by weight of oxygen), graphene oxide (> 5% by weight of oxygen), slightly fluorinated graphene (< 5% by weight of fluorine), graphene fluoride ((> 5% by weight of fluorine), other halogenated graphene, and chemically functionalized graphene.

Our research group was among the first to discover graphene [B. Z. Jang and W. C. Huang, “Nano-scaled Graphene Plates,” U.S. Patent Application No. 10/274,473, submitted on October 21, 2002; now US Pat. No. 7,071,258 (07/04/2006)]. The processes for producing NGPs and NGP nanocomposites were recently reviewed by us [Bor Z. Jang and A Zhamu, “Processing of Nano Graphene Platelets (NGPs) and NGP Nanocomposites: A Review,” J. Materials Sci. 43 (2008) 5092-5101]. The production of various types of graphene sheets is well-known in the art.

For instance, the chemical processes for producing graphene sheets or platelets typically involve immersing powder of graphite or other graphitic material in a mixture of concentrated sulfuric acid, nitric acid, and an oxidizer, such as potassium permanganate or sodium perchlorate, forming a reacting mass that requires typically 5-120 hours to complete the chemical intercalation/oxidation reaction. Once the reaction is completed, the slurry is subjected to repeated steps of rinsing and washing with water. The purified product is commonly referred to as graphite intercalation compound (GIC) or graphite oxide (GO). The suspension containing GIC or GO in water may be subjected to ultrasonication to produce isolated/separated graphene oxide sheets dispersed in water. The resulting products are typically highly oxidized graphene (i.e. graphene oxide with a high oxygen content), which must be chemically or thermal reduced to obtain reduced graphene oxide (RGO).

Alternatively, the GIC suspension may be subjected to drying treatments to remove water. The dried powder is then subjected to a thermal shock treatment. This can be accomplished by placing GIC in a furnace pre-set at a temperature of typically 800-1100°C (more typically 950-1050°C) to produce exfoliated graphite (or graphite worms), which may be subjected to a high shear or ultrasonication treatment to produce isolated graphene sheets.

Alternatively, graphite worms may be re-compressed into a film form to obtain a flexible graphite sheet. Flexible graphite sheets are commercially available from many sources worldwide.

The starting graphitic material may be selected from natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fiber, graphitic nano-fiber, graphite fluoride, chemically modified graphite, meso-carbon micro-bead, partially crystalline graphite, or a combination thereof.

Pristine graphene sheets may be produced by the well-known liquid phase exfoliation or metal-catalyzed chemical vapor deposition (CVD).

Graphene films, flexible graphite sheets, and artificial graphite films are commonly regarded as three fundamentally different and patently distinct classes of materials.

As schematically illustrated in the upper portion of FIG. 1, bulk natural graphite is a 3-D graphitic material with each graphite particle being composed of multiple grains (a grain being a graphite single crystal or crystallite) with grain boundaries (amorphous or defect zones) demarcating neighboring graphite single crystals. Each grain is composed of multiple graphene planes that are oriented parallel to one another. A graphene plane or hexagonal carbon atom plane in a graphite crystallite is composed of carbon atoms occupying a two-dimensional, hexagonal lattice. In a given grain or single crystal, the graphene planes are stacked and bonded via van der Waal forces in the crystallographic c-direction (perpendicular to the graphene plane or basal plane). The inter-graphene plane spacing in a natural graphite material is approximately 0.3354 nm. Artificial graphite materials also contain constituent graphene planes, but they have an inter-graphene planar spacing, doo2, typically from 0.32 nm to 0.36 nm (more typically from 0.3339 to 0.3465 nm), as measured by X-ray diffraction. Many carbon or quasi-graphite materials also contain graphite crystals (also referred to as graphite crystallites, domains, or crystal grains) that are each composed of stacked graphene planes. These include meso-carbon micro-beads (MCMBs), meso-phase carbon, soft carbon, hard carbon, coke (e.g. needle coke), carbon or graphite fibers (including vapor-grown carbon nano-fibers or graphite nano-fibers), and multi- walled carbon nanotubes (MW-CNT). The spacing between two graphene rings or walls in a MW-CNT is approximately 0.27 to 0.42 nm. The most common spacing values in MW-CNTs are in the range from 0.32-0.35 nm, which do not strongly depend on the synthesis method.

It may be noted that the “soft carbon” refers to a carbon material containing graphite domains wherein the orientation of the hexagonal carbon planes (or graphene planes) in one domain and the orientation in neighboring graphite domains are not too mis-matched from each other so that these domains can be readily merged together when heated to a temperature above 2,000°C (more typically above 2,500°C). Such a heat treatment is commonly referred to as graphitization. Thus, the soft carbon can be defined as a carbonaceous material that can be graphitized. In contrast, a “hard carbon” can be defined as a carbonaceous material that contain highly mis-oriented graphite domains that cannot be thermally merged together to obtain larger domains; i.e. the hard carbon cannot be graphitized.

The spacing between constituent graphene planes of a graphite crystallite in a natural graphite, artificial graphite, and other graphitic carbon materials in the above list can be expanded (i.e. the doo2 spacing being increased from the original range of 0.27- 0.42 nm to the range of 0.42-2.0 nm) using several expansion treatment approaches, including oxidation, fluorination, chlorination, bromination, iodization, nitrogenation, intercalation, combined oxidation-intercalation, combined fluorination-intercalation, combined chlorination-intercalation, combined bromination-intercalation, combined iodization-intercalation, or combined nitrogenation-intercalation of the graphite or carbon material. More specifically, due to the van der Waals forces holding the parallel graphene planes together being relatively weak, natural graphite can be treated so that the spacing between the graphene planes can be increased to provide a marked expansion in the c-axis direction. This results in a graphite material having an expanded spacing, but the laminar character of the hexagonal carbon layers is substantially retained. The inter-planar spacing (also referred to as inter-graphene spacing) of graphite crystallites can be increased (expanded) via several approaches, including oxidation, fluorination, and/or intercalation of graphite. This is schematically illustrated in FIG. 3(D). The presence of an intercalant, oxygen-containing group, or fluorine-containing group serves to increase the spacing between two graphene planes in a graphite crystallite.

The inter-planar spaces between certain graphene planes may be significantly increased (actually, exfoliated) if the graphite/carbon material having expanded d spacing is exposed to a thermal shock (e.g. by rapidly placing this carbon material in a furnace pre-set at a temperature of typically 800-2, 500°C) without constraint (i.e. being allowed to freely increase volume). Under these conditions, the thermally exfoliated graphite/carbon material appears like worms, wherein each graphite worm is composed of many graphite flakes remaining interconnected (please see FIG. 3(C)). However, these graphite flakes have inter-flake pores typically in the pore size range of 20 nm to 10 pm. These worms may be broken up (e.g., using an airjet mill) to produce isolated expanded graphite flakes.

Alternatively, the intercalated, oxidized, or fluorinated graphite/carbon material having expanded d spacing may be exposed to a moderate temperature (100-800°C) under a constant- volume condition for a sufficient length of time. The conditions may be adjusted to obtain a product of limited exfoliation, having inter-flake pores of 2-20 nm in average size. This is herein referred to as a constrained expansion/exfoliation treatment. We have surprisingly observed that an A1 cell having a cathode of graphite/carbon having inter-planar spaces 2-20 nm is capable of delivering a high energy density, high power density, and long cycle life.

In one process, graphite materials having an expanded inter-planar spacing are obtained by intercalating natural graphite particles with a strong acid and/or an oxidizing agent to obtain a graphite intercalation compound (GIC) or graphite oxide (GO), as illustrated in FIG. 3(A). The presence of chemical species or functional groups in the interstitial spaces between graphene planes serves to increase the inter-graphene spacing, docn, as determined by X-ray diffraction, thereby significantly reducing the van der Waals forces that otherwise hold graphene planes together along the c-axis direction. The GIC or GO is most often produced by immersing natural graphite powder (100 in FIG. 3(A)) in a mixture of sulfuric acid, nitric acid (an oxidizing agent), and another oxidizing agent (e.g. potassium permanganate or sodium perchlorate). The resulting GIC (102) is actually some type of graphite oxide (GO) particles if an oxidizing agent is present during the intercalation procedure. This GIC or GO is then repeatedly washed and rinsed in water to remove excess acids, resulting in a graphite oxide suspension or dispersion, which contains discrete and visually discernible graphite oxide particles dispersed in water.

Water may be removed from the suspension to obtain “expandable graphite,” which is essentially a mass of dried GIC or dried graphite oxide particles. The inter-graphene spacing, dim, in the dried GIC or graphite oxide particles is typically in the range from 0.42-2.0 nm, more typically in the range from 0.5- 1.2 nm. It may be noted than the “expandable graphite” is not “expanded graphite” (to be further explained later).

Upon exposure of expandable graphite to a temperature in the range from typically 800 - 2,500°C (more typically 900-l,050°C) for approximately 30 seconds to 2 minutes, the GIC undergoes a rapid volume expansion by a factor of 30-300 to form “exfoliated graphite” or “graphite worms” (104). Graphite worms are each a collection of exfoliated, but largely un separated graphite flakes that remain interconnected (FIG. 3(B) and FIG. 3(C)). In exfoliated graphite, individual graphite flakes (each containing 1 to several hundred of graphene planes stacked together) are highly spaced from one another, having a spacing of typically 2.0 nm - 10 pm. However, they remain physically interconnected, forming an accordion or worm-like structure.

In graphite industry, graphite worms can be re-compressed to obtain flexible graphite sheets or foils (106) that typically have a thickness in the range from 0.1 mm (100 pm) - 0.5 mm (500 pm). Such flexible graphite sheets may be used as a type of graphitic heat spreader element. Alternatively, in graphite industry, one may choose to use a low-intensity air mill or shearing machine to simply break up the graphite worms for the purpose of producing the so- called “expanded graphite” flakes (108) which contain mostly graphite flakes or platelets thicker than 100 nm (hence, not a nano material by definition). It is clear that the “expanded graphite” is not “expandable graphite” and is not “exfoliated graphite worm” either. Rather, the “expandable graphite” can be thermally exfoliated to obtain “graphite worms,” which, in turn, can be subjected to mechanical shearing to break up the otherwise interconnected graphite flakes to obtain “expanded graphite” flakes. Expanded graphite flakes typically have the same or similar inter-planar spacing (typically 0.335 - 0.36 nm) of their original graphite. Multiple expanded graphite flakes may be roll-pressed together to form graphitic films, which are a variation of flexible graphite sheets. Or, multiple expanded graphite flakes, preferably after chemical functionalization, may be sprayed over or coated onto a surface of a non-woven fabric layer to produce a filtration member.

Alternatively, the exfoliated graphite or graphite worms may be subjected to high- intensity mechanical shearing (e.g. using an ultrasonicator, high-shear mixer, high-intensity air jet mill, or high-energy ball mill) to form separated single-layer and multi-layer graphene sheets (collectively called NGPs, 112), as disclosed in our US Application No. 10/858,814 (U.S. Pat. Pub. No. 2005/0271574) (now abandoned). Single-layer graphene can be as thin as 0.34 nm, while multi-layer graphene can have a thickness up to 100 nm, but more typically less than 3 nm (commonly referred to as few-layer graphene). Multiple graphene sheets or platelets may be made into a sheet of NGP paper (114) using a paper-making process.

In GIC or graphite oxide, the inter-graphene plane separation has been increased from 0.3354 nm in natural graphite to 0.5- 1.2 nm in highly oxidized graphite oxide, significantly weakening the van der Waals forces that hold neighboring planes together. Graphite oxide can have an oxygen content of 2%-50% by weight, more typically 20%-40% by weight. GIC or graphite oxide may be subjected to a special treatment herein referred to as “constrained thermal expansion”. If GIC or graphite oxide is exposed to a thermal shock in a furnace (e.g. at 800 - 1,050°C) and allowed to freely expand, the final product is exfoliated graphite worms. However, if the mass of GIC or graphite oxide is subjected to a constrained condition (e.g. being confined in an autoclave under a constant volume condition or under a uniaxial compression in a mold) while being slowly heated from 150°C to 800°C (more typically up to 600°) for a sufficient length of time (typically 2 minutes to 15 minutes), the extent of expansion can be constrained and controlled, and the product can have inter-flake spaces from 2.0 nm to 20 nm, or more desirably from 2 nm to 10 nm.

It may be noted that the “expandable graphite” or graphite with expanded inter-planar spacing may also be obtained by forming graphite fluoride (GF), instead of GO. Interaction of F2 with graphite in a fluorine gas at high temperature leads to covalent graphite fluorides, from (CF)„ to (C₂F)„, while at low temperatures graphite intercalation compounds (GIC) C_VF (2 <x < 24) form. In (CF)„ carbon atoms are sp3 -hybridized and thus the fluorocarbon layers are corrugated consisting of trans-linked cyclohexane chairs. In (C₂F)„ only half of the C atoms are fluorinated and every pair of the adjacent carbon sheets are linked together by covalent C-C bonds. Systematic studies on the fluorination reaction showed that the resulting F/C ratio is largely dependent on the fluorination temperature, the partial pressure of the fluorine in the fluorinating gas, and physical characteristics of the graphite precursor, including the degree of graphitization, particle size, and specific surface area. In addition to fluorine (F₂), other fluorinating agents (e.g. mixtures of F₂ with Br₂, Cl₂, or I₂) may be used, although most of the available literature involves fluorination with F₂ gas, sometimes in presence of fluorides.

It may be noted that expanded graphite flakes (with or without oxygen-containing species attached thereto) may be exposed to gas molecules of F₂, Br₂, Cl₂, or I₂, to produce expanded graphite flakes having F-, Br-, C1-, or I-containing functional groups.

We have observed that lightly fluorinated graphite, C_AF (2 < x < 24), obtained from electrochemical fluorination, typically has an inter-graphene spacing (doo₂) less than 0.37 nm, more typically < 0.35 nm. Only when x in C_AF is less than 2 (i.e. 0.5 <x < 2) can one observe a doo2 spacing greater than 0.5 nm (in fluorinated graphite produced by a gaseous phase fluorination or chemical fluorination procedure). When x in C_AF is less than 1.33 (i.e. 0.5 < JC < 1.33) one can observe a doo2 spacing greater than 0.6 nm. This heavily fluorinated graphite is obtained by fluorination at a high temperature (» 200°C) for a sufficiently long time, preferably under a pressure > 1 atm, and more preferably > 3 atm. For reasons remaining unclear, electrochemical fluorination of graphite leads to a product having a d spacing less than 0.4 nm even though the product C_VF has an x value from 1 to 2. It is possible that F atoms electrochemically introduced into graphite tend to reside in defects, such as grain boundaries, instead of between graphene planes and, consequently, do not act to expand the inter-graphene planar spacing.

The nitrogenation of graphite can be conducted by exposing a graphite oxide material or expanded graphite flakes to ammonia at high temperatures (200-400°C). Nitrogenation may also be conducted at lower temperatures by a hydrothermal method; e.g. by sealing GO and ammonia in an autoclave and then increased the temperature to 150-250°C.

In addition to N, O, F, Br, Cl, or H, the presence of other chemical species (e.g. Na, Li,

K, Ce, Ca, Fe, NH₄, etc.) between graphene planes can also serve to expand the inter-planar spacing, creating room to accommodate electrochemically active materials therein. The expanded interstitial spaces between graphene planes (hexagonal carbon planes or basal planes) are found by us in this study to be surprisingly capable of accommodating Al⁺³ ions and other anions (derived from electrolyte ingredients) as well, particularly when the spaces are from 2.0 nm to 20 nm. It may be noted that graphite can electrochemically intercalated with such chemical species as Na, Li, K, Ce, Ca, NFL, or their combinations, which can then be chemically or electrochemically ion-exchanged with metal elements (Bi, Fe, Co, Mn, Ni, Cu, etc.). All these chemical species can serve to expand the inter-planar spacing. The spacing may be dramatically expanded (exfoliated) to have inter-flake pores that are 20 nm - 10 pm in size (e.g., by exposing the Na- or Li-intercalated graphite to water or a mixture of water and alcohol).

Once the graphene sheets are produced, they can be made into a mask body according to several embodiments of the instant disclosure. One process for producing the herein disclosed filtration material or member comprises (a) preparing a layer of woven or nonwoven fabric having two primary surfaces; and (b) depositing a graphene layer on at least one of the two primary surfaces.

Subprocess (b) may comprise a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a gaseous medium to form a flowing fluid and impinging the flowing fluid upon at least one of the two primary surfaces, allowing said graphene sheets to adhere to said at least one primary surface.

Alternatively, Subprocess (b) can comprise a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a liquid medium to form a slurry, depositing the slurry onto at least one of the two primary surfaces to form a wet graphene layer, and removing or drying the liquid medium from said wet graphene layer to form the graphene layer. Thermally curable or UV-curable adhesives are more desirable.

The process is preferably a roll-to-roll or reel-to-reel process, wherein subprocess (a) comprises (i) preparing a roll of woven or nonwoven fabric, (ii) continuously feeding a continuous length of a sheet of the fabric from the roll (mounted on a roller or reel) into a deposition zone, (iii) depositing a graphene layer onto at least one of the two primary surfaces to form a graphene layer-coated fabric, and (iv) collecting the graphene layer-coated fabric on a winding roller.

Generally speaking, a foam or foamed material is composed of pores (or cells) and pore walls (a solid material). The pores can be interconnected to form an open-cell foam, which is preferred to a closed-cell foam in practicing instant disclosure. A graphene foam is composed of pores and pore walls that contain a graphene material. There are four major methods of producing graphene foams:

The first method is the hydrothermal reduction of graphene oxide hydrogel that typically involves sealing graphene oxide (GO) aqueous suspension in a high-pressure autoclave and heating the GO suspension under a high pressure (tens or hundreds of atm) at a temperature typically in the range from 180-300°C for an extended period of time (typically 12-36 hours). A useful reference for this method is given here: Y. Xu, et al. “Self-Assembled Graphene Hydrogel via a One-Step Hydrothermal Process,” ACS Nano 2010, 4, 4324-4330. The second method is based on a template-assisted catalytic CVD process, which involves CVD deposition of graphene on a sacrificial template (e.g. Ni foam). The graphene material conforms to the shape and dimensions of the Ni foam structure. The Ni foam is then etched away using an etching agent, leaving behind a monolith of graphene skeleton that is essentially an open-cell foam. A useful reference for this method is given here: Zongping Chen, et al., “Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapour deposition,” Nature Materials, 10 (June 2011) 424-428.

The third method of producing graphene foam also makes use of a sacrificial material (e.g. colloidal polystyrene particles, PS) that is coated with graphene oxide sheets using a self- assembly approach. For instance, Choi, et al. prepared chemically modified graphene (CMG) paper in two steps: fabrication of free-standing PS/CMG films by vacuum filtration of a mixed aqueous colloidal suspension of CMG and PS (2.0 pm PS spheres), followed by removal of PS beads to generate 3D macro-pores. [B. G. Choi, et al., “3D Macroporous Graphene Frameworks for Supercapacitors with High Energy and Power Densities,” ACS Nano, 6 (2012) 4020-4028.] Choi, et al. fabricated well-ordered free-standing PS/CMG paper by filtration, which began with separately preparing a negatively charged CMG colloidal and a positively charged PS suspension. A mixture of CMG colloidal and PS suspension was dispersed in solution under controlled pH (=2), where the two compounds had the same surface charges (zeta potential values of +13 + 2.4 mV for CMG and + 68 + 5.6 mV for PS). When the pH was raised to 6, CMGs (zeta potential = -29 + 3.7 mV) and PS spheres (zeta potential = +51 + 2.5 mV) were assembled due to the electrostatic interactions and hydrophobic characteristics between them, and these were subsequently integrated into PS/CMG composite paper through a filtering process.

The fourth method for producing a solid graphene foam composed of multiple pores and pore walls was invented by us earlier [Aruna Zhamu and Bor Z. Jang, “Highly Conductive Graphene Foams and Process for Producing Same,” US Patent Application No. 14/120,959 (07/17/2014)]. The process comprises:

(a) preparing a graphene dispersion having a graphene material dispersed in a liquid medium, wherein the graphene material is selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or a combination thereof and wherein the dispersion contains an optional blowing agent;

(b) dispensing and depositing the graphene dispersion onto a surface of a supporting substrate (e.g. plastic film, rubber sheet, metal foil, glass sheet, paper sheet, etc.) to form a wet layer of graphene material, wherein the dispensing and depositing procedure includes subjecting the graphene dispersion to an orientation-inducing stress;

(c) partially or completely removing the liquid medium from the wet layer of graphene material to form a dried layer of graphene material having a content of non-carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.) no less than 5% by weight; and

(d) heat treating the dried layer of graphene material at a first heat treatment temperature from 100°C to 3,200°C at a desired heating rate sufficient to induce volatile gas molecules from the non-carbon elements or to activate said blowing agent for producing the solid graphene foam having a density from 0.01 to 1.7 g/cm (more typically from 0.1 to 1.5 g/cm , and even more typically from 0.1 to 1.0 g/cm , and most typically from 0.2 to 0.75 g/cm ), or a specific surface area from 50 to 3,000 m /g (more typically from 200 to 2,000 m /g, and most typically from 500 to 1,500 m²/g).

This optional blowing agent is not required if the graphene material has a content of non carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.) no less than 5% by weight (preferably no less than 10%, further preferably no less than 20%, even more preferably no less than 30% or 40%, and most preferably up to 50%). The subsequent high temperature treatment serves to remove a majority of these non-carbon elements from the graphene material, generating volatile gas species that produce pores or cells in the solid graphene material structure. In other words, quite surprisingly, these non-carbon elements play the role of a blowing agent. Hence, an externally added blowing agent is optional (not required). However, the use of a blowing agent can provide added flexibility in regulating or adjusting the porosity level and pore sizes for a desired application. The blowing agent is typically required if the non-carbon element content is less than 5%, such as pristine graphene that is essentially all-carbon. The graphene foam produced by the fourth method has the highest thermal conductivity among all graphene foam materials, and also exhibit a highly reversible and durable elastic deformation under tension or compression, enabling good, long-term contact between fabric layers of a filtration member or filtration device.

The process and the process of making face masks may comprise incorporating the graphene or graphene foam or graphite flake-enhanced filtration material (member) into a mask body, which is fitted with a fastener (e.g., elastic straps) to form the face mask.

The graphene layer-coated fabric or foam or graphite flake layer can be made to contain microscopic pores (< 2 nm), meso-scaled pores having a pore size from 2 nm to 50 nm, or larger pores (preferably 50 nm to 1 pm). Based on well-controlled pore size alone, the instant graphene layer-coated or foam or graphite flake layer supported by a fabric can be an exceptional filter material for air or water filtration.

Further, the graphene or graphene pore wall or graphite flake surface chemistry can be independently controlled to impart different amounts and/or types of functional groups to graphene sheets or graphite flakes (e.g., as reflected by the percentage of O, F, N, H, etc. in the sheets or by the percentage of O, F, Cl, Br, I, N, H, etc. in the flakes). In other words, the concurrent or independent control of both pore sizes and chemical functional groups at different sites of the internal structure or porous graphite flake layer provide unprecedented flexibility or highest degree of freedom in designing and making graphene-coated or graphite flake-coated fabric that exhibits many unexpected properties, synergistic effects, and some unique combination of properties that are normally considered mutually exclusive (e.g. some part of the structure is hydrophobic and other part hydrophilic; or the filtration structure is both hydrophobic and oleophilic). A surface or a material is said to be hydrophobic if water is repelled from this material or surface and that a droplet of water placed on a hydrophobic surface or material will form a large contact angle. A surface or a material is said to be oleophilic if it has a strong affinity for oils and not for water. The present method allows for precise control over hydrophobicity, hydrophilicity, and oleophilicity. The present disclosure also provides an oil-removing, oil- separating, or oil-recovering device, which contains the presently invented graphene or graphene foam layer-coated or bonded fabric as an oil-absorbing or oil-separating element. Also provided is a solvent-removing or solvent- separating device containing the graphene or graphene foam layer-coated or bonded fabric as a solvent-absorbing element.

A major advantage of using the instant graphene-coated or graphene foam-bonded fabric or graphite-flake-bonded fabric structure as an oil-absorbing element is its structural integrity. Due to the notion that graphene sheets or foam or graphite flakes can be of high structural integrity and the foam structure may be chemically bonded by an adhesive to a fabric layer, the resulting structure would not get disintegrated upon repeated oil absorption operations.

Another major advantage of the instant technology is the flexibility in designing and making oil-absorbing elements that are capable of absorbing oil up to a large amount yet still maintaining its structural shape (without significant expansion). This amount depends upon the specific pore volume of the filtration structure.

The disclosure also provides a method to separate/recover oil from an oil-water mixture (e.g. oil-spilled water or waste water from oil sand). The method comprises the (a) providing an oil-absorbing element comprising a graphene or graphene foam layer-coated or bonded fabric or chemically functionalized graphite flake layer-bonded fabric; (b) contacting an oil- water mixture with the element, which absorbs the oil from the mixture; and (c) retreating the oil-absorbing element from the mixture and extracting the oil from the element. Preferably, the method comprises (d) reusing the element.

Additionally, the disclosure provides a method to separate an organic solvent from a solvent-water mixture or from a multiple-solvent mixture. The method comprises (a) providing an organic solvent-absorbing element comprising an integral graphene or graphene foam layer- coated or bonded fabric structure or graphite flake layer-bonded fabric; (b) bringing the element in contact with an organic solvent-water mixture or a multiple-solvent mixture containing a first solvent and at least a second solvent; (c) allowing this element to absorb the organic solvent from the mixture or absorb the first solvent from the at least second solvent; and (d) retreating the element from the mixture and extracting the organic solvent or first solvent from the element. Preferably, the method contains (e) reusing the solvent-absorbing element.

The following examples are used to illustrate some specific details about the best modes of practicing the instant disclosure and should not be construed as limiting the scope of the disclosure.

Example 1: Preparation of single-layer graphene sheets and the graphene layer from meso- carbon micro-beads (MCMBs)

Meso-carbon microbeads (MCMBs) were supplied from China Steel Chemical Co.,

Kaohsiung, Taiwan. This material has a density of about 2.24 g/cm with a median particle size of about 16 pm. MCMB (10 grams) were intercalated with an acid solution (sulfuric acid, nitric acid, and potassium permanganate at a ratio of 4:1:0.05) for 48-96 hours. Upon completion of the reaction, the mixture was poured into deionized water and filtered. The intercalated MCMBs were repeatedly washed in a 5% solution of HC1 to remove most of the sulfate ions. The sample was then washed repeatedly with deionized water until the pH of the filtrate was no less than 4.5. The slurry was then subjected ultrasonication for 10-100 minutes to produce GO suspensions. TEM and atomic force microscopic studies indicate that most of the GO sheets were single-layer graphene when the oxidation treatment exceeded 72 hours, and 2- or 3-layer graphene when the oxidation time was from 48 to 72 hours.

The GO sheets contain oxygen proportion of approximately 35%-47% by weight for oxidation treatment times of 48-96 hours. GO sheets were suspended in water. The GO suspension was cast into thin graphene oxide films on a glass surface and, separately, was also slot die-coated onto a PET film substrate, dried, and peeled off from the PET substrate to form GO films. The GO films were separately heated from room temperature to 1,500°C and then slightly roll-pressed to obtain reduced graphene oxide (RGO) films (free-standing layers) for use as a porous graphene layer in a filtration device.

Separately, an ultrasonic spraying procedure was conducted to spray the GO-water solution onto a primary surface of a sheet of PP-based non-woven fabric. Upon drying, we obtained graphene layer-coated fabric structure. We observed that some of the GO sheets partially penetrated into the bulk of the PP non-woven structure. These GO sheets were held in place by the PP fibers even without using any adhesive resin.

Example 2: Preparation of pristine graphene sheets (0% oxygen) and graphene layer

Pristine graphene sheets were produced by using the direct ultrasonic ation or liquid-phase production process. In a typical procedure, five grams of graphite flakes, ground to approximately 20 pm or less in sizes, were dispersed in 1,000 mL of deionized water (containing 0.1% by weight of a dispersing agent, Zonyl® FSO from DuPont) to obtain a suspension. An ultrasonic energy level of 85 W (Branson S450 Ultrasonicator) was used for exfoliation, separation, and size reduction of graphene sheets for a period of 15 minutes to 2 hours. The resulting graphene sheets are pristine graphene that have never been oxidized and are oxygen- free and relatively defect-free. There are no other non-carbon elements.

The pristine graphene sheets were immersed into a 10 mM acetone solution of benzoyl peroxide (BPO) for 30 min and were then taken out drying naturally in air. The heat-initiated chemical reaction to functionalize graphene sheets was conducted at 80°C in a high-pressure stainless steel container filled with pure nitrogen. Subsequently, the samples were rinsed thoroughly in acetone to remove BPO residues for subsequent Raman characterization. As the reaction time increased, the characteristic disorder-induced D band around 1330 cm^-1 emerged and gradually became the most prominent feature of the Raman spectra. The D-band is originated from the Ai_g mode breathing vibrations of six-membered sp carbon rings, and becomes Raman active after neighboring sp carbon atoms are converted to sp hybridization. In addition, the double resonance 2D band around 2670 cm^-1 became significantly weakened, while the G band around 1580 cm^-1 was broadened due to the presence of a defect-induced D’ shoulder peak at -1620 cm^-1. These observations suggest that covalent C-C bonds were

2 formed and thus a degree of structural disorder was generated by the transformation from sp to sp configuration due to reaction with BPO.

The functionalized graphene sheets were re-dispersed in water to produce a graphene dispersion. The dispersion was then deposited onto a layer of PP nonwoven to form a functionalized graphene layer coated on fabric using comma coating. On a separate basis, non- functionalized pristine graphene sheets were also coated on PP non- woven layers to obtain pristine graphene-coated fabric structures.

Example 3: Preparation of graphene fluoride sheets and graphene layers

Several processes have been used by us to produce GF, but only one process is herein described as an example. In a typical procedure, highly exfoliated graphite (HEG) was prepared from intercalated compound CLF-ACIF,. HEG was further fluorinated by vapors of chlorine trifluoride to yield fluorinated highly exfoliated graphite (FHEG). Pre-cooled Teflon reactor was filled with 20-30 mL of liquid pre-cooled CIF3, the reactor was closed and cooled to liquid nitrogen temperature. Then, no more than 1 g of HEG was put in a container with holes for CIF3 gas to access and situated inside the reactor. In 7-10 days a gray-beige product with approximate formula C2F was formed.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixed with 20-30 mL of an organic solvent (methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, /_{<? /}7-butanol, isoamyl alcohol) and subjected to an ultrasound treatment (280 W) for 30 min, leading to the formation of homogeneous yellowish dispersions. Five minutes of sonication was enough to obtain a relatively homogenous dispersion, but a longer sonication time ensured better stability. Upon extrusion to form wet films on a PET fabric surface with the solvent removed, the dispersion became brownish films formed on the PET fabric surface. The dried films, upon drying and roll-pressing, became a good filtration member.

Example 4: Preparation of nitrogenated graphene sheets and graphene layers

Graphene oxide (GO), synthesized in Example 1, was finely ground with different proportions of urea and the pelletized mixture heated in a microwave reactor (900 W) for 30 s. The product was washed several times with deionized water and vacuum dried. In this method graphene oxide gets simultaneously reduced and doped with nitrogen. The products obtained with graphene/urea mass ratios of 1/0.5, 1/1 and 1/2 have the nitrogen contents of 14.7, 18.2 and 17.5 wt. %, respectively, as found by elemental analysis. These nitrogenated graphene sheets, without prior chemical functionalization, remain dispersible in water. The resulting suspensions were made into wet films on PET non- woven fabric layers using spray painting and then dried to form filtration members. Example 5: Various blowing agents and pore-forming (bubble-producing) processes

In the field of plastic processing, chemical blowing agents are mixed into the plastic pellets in the form of powder or pellets and dissolved at higher temperatures. Above a certain temperature specific for blowing agent dissolution, a gaseous reaction product (usually nitrogen or CO2) is generated, which acts as a blowing agent. However, a chemical blowing agent cannot be dissolved in a graphene material, which is a solid, not liquid. This presents a challenge to make use of a chemical blowing agent to generate pores or cells in a graphene material.

After extensive experimenting, we have discovered that practically any chemical blowing agent (e.g. in a powder or pellet form) can be used to create pores or bubbles in a dried layer of graphene when the first heat treatment temperature is sufficient to activate the blowing reaction. The chemical blowing agent (powder or pellets) may be dispersed in the liquid medium to become a second dispersed phase (sheets of graphene material being the first dispersed phase) in the suspension, which can be deposited onto the solid supporting substrate to form a wet layer. This wet layer of graphene material may then be dried and heat treated to activate the chemical blowing agent. After a chemical blowing agent is activated and bubbles are generated, the resulting foamed graphene structure is largely maintained even when subsequently a higher heat treatment temperature is applied to the structure. This is quite unexpected, indeed.

Chemical foaming agents (CFAs) can be organic or inorganic compounds that release gasses upon thermal decomposition. CFAs are typically used to obtain medium- to high-density foams, and are often used in conjunction with physical blowing agents to obtain low-density foams. CFAs can be categorized as either endothermic or exothermic, which refers to the type of decomposition they undergo. Endothermic types absorb energy and typically release carbon dioxide and moisture upon decomposition, while the exothermic types release energy and usually generate nitrogen when decomposed. The overall gas yield and pressure of gas released by exothermic foaming agents is often higher than that of endothermic types. Endothermic CFAs are generally known to decompose in the range from 130 to 230°C (266-446°F), while some of the more common exothermic foaming agents decompose around 200°C (392°F). However, the decomposition range of most exothermic CFAs can be reduced by addition of certain compounds. The activation (decomposition) temperatures of CFAs fall into the range of our heat treatment temperatures. Examples of suitable chemical blowing agents include sodium bi carbonate (baking soda), hydrazine, hydrazide, azodicarbonamide (exothermic chemical blowing agents), nitroso compounds (e.g. N, N-Dinitroso pentamethylene tetramine), hydrazine derivatives (e.g. 4. 4’-Oxybis (benzenesulfonyl hydrazide) and Hydrazo dicarbonamide), and hydrogen carbonate (e.g. Sodium hydrogen carbonate). These are all commercially available in plastics industry.

In the production of foamed plastics, physical blowing agents are metered into the plastic melt during foam extrusion or injection molded foaming, or supplied to one of the precursor materials during polyurethane foaming. It has not been previously known that a physical blowing agent can be used to create pores in a graphene material, which is in a solid state (not melt). We have surprisingly observed that a physical blowing agent (e.g. CO2 or N2) can be injected into the stream of graphene suspension prior to being coated or cast onto the supporting substrate. This would result in a foamed structure even when the liquid medium (e.g. water and/or alcohol) is removed. The dried layer of graphene material is capable of maintaining a controlled amount of pores or bubbles during liquid removal and subsequent heat treatments.

Technically feasible blowing agents include Carbon dioxide (CO2), Nitrogen (N2), Isobutane (C₄H₁₀), Cyclopentane (C₅H₁₀), Isopentane (C₅H₁₂), CFC-11 (CFCI₃), HCFC-22 (CHF2CI), HCFC-142b (CF2CICH3), and HCFC-134a (CH₂FCF₃). However, in selecting a blowing agent, environmental safety is a major factor to consider. The Montreal Protocol and its influence on consequential agreements pose a great challenge for the producers of foam. Despite the effective properties and easy handling of the formerly applied chlorofluorocarbons, there was a worldwide agreement to ban these because of their ozone depletion potential (ODP). Partially halogenated chlorofluorocarbons are also not environmentally safe and therefore already forbidden in many countries. The alternatives are hydrocarbons, such as isobutane and pentane, and the gases such as CO2 and nitrogen.

Except for those regulated substances, all the blowing agents recited above have been tested in our experiments. For both physical blowing agents and chemical blowing agents, the blowing agent amount introduced into the suspension is defined as a blowing agent-to-graphene material weight ratio, which is typically from 0/1.0 to 1.0/1.0. Example 6: Preparation of discrete graphene oxide (GO) sheets and GO foam

Chopped graphite fibers with an average diameter of 12 pm and natural graphite particles were separately used as a starting material, which was immersed in a mixture of concentrated sulfuric acid, nitric acid, and potassium permanganate (as the chemical intercalate and oxidizer) to prepare graphite intercalation compounds (GICs). The starting material was first dried in a vacuum oven for 24 h at 80°C. Then, a mixture of concentrated sulfuric acid, fuming nitric acid, and potassium permanganate (at a weight ratio of 4:1:0.05) was slowly added, under appropriate cooling and stirring, to a three-neck flask containing fiber segments. After 5-16 hours of reaction, the acid-treated graphite fibers or natural graphite particles were filtered and washed thoroughly with deionized water until the pH level of the solution reached 6. After being dried at 100°C overnight, the resulting graphite intercalation compound (GIC) or graphite oxide fiber was re-dispersed in water and/or alcohol to form a slurry.

In one sample, five grams of the graphite oxide fibers were mixed with 2,000 ml alcohol solution consisting of alcohol and distilled water with a ratio of 15:85 to obtain a slurry mass. Then, the mixture slurry was subjected to ultrasonic irradiation with a power of 200 W for various lengths of time. After 20 minutes of sonication, GO fibers were effectively exfoliated and separated into thin graphene oxide sheets with oxygen content of approximately 23%-31% by weight. The resulting suspension contains GO sheets being suspended in water. A chemical blowing agent (hydrazo dicarbonamide) was added to the suspension just prior to casting.

The resulting suspension was then cast onto a glass surface using a doctor’s blade to exert shear stresses, inducing GO sheet orientations. The resulting GO coating films, after removal of liquid, have a thickness that can be varied from approximately 5 to 500 pm (preferably and typically from 10 pm to 50 pm).

For making a graphene foam specimen, the GO coating film was then subjected to heat treatments that typically involve an initial thermal reduction temperature of 80-350°C for 0.5-2 hours, followed by heat-treating at a second temperature of 500-l,500°C for 0.5 to 2 hours to produce GO foam sheets (typically 1-500 pm, but could be thinner or thicker, depending upon GO coating thickness). Example 7: Preparation of single-layer graphene sheets from meso-carbon micro-beads (MCMBs) and graphene foam

Meso-carbon microbeads (MCMBs) were supplied from China Steel Chemical Co.,

The GO sheets contain oxygen proportion of approximately 35%-47% by weight for oxidation treatment times of 48-96 hours. GO sheets were suspended in water. Baking soda (5- 20% by weight), as a chemical blowing agent, was added to the suspension just prior to casting. The suspension was then cast onto a glass surface using a doctor’s blade to exert shear stresses, inducing GO sheet orientations. Several samples were cast, some containing a blowing agent and some not. The resulting GO films, after removal of liquid, have a thickness that can be varied from approximately 10 to 500 pm.

The several sheets of the GO film, with or without a blowing agent, were then subjected to heat treatments that involve an initial (first) thermal reduction temperature of 80-500°C for 1-2 hours. This first heat treatment generated a graphene foam. However, the graphene domains in the foam wall can be further perfected (re-graphitized to become more ordered or having a higher degree of crystallinity and larger lateral dimensions of graphene planes, longer than the original graphene sheet dimensions due to chemical merging) if the foam is followed by heat- treating at a second temperature of 1, 500-2, 850°C.

Example 8: Preparation of pristine graphene foam (0% oxygen)

Recognizing the possibility of the high defect population in GO sheets acting to reduce the conductivity of individual graphene plane, we decided to study if the use of pristine graphene sheets (non-oxidized and oxygen-free, non-halo genated and halogen-free, etc.) can lead to a graphene foam having a higher thermal conductivity. Pristine graphene sheets were produced by using the direct ultrasonication or liquid-phase production process.

In a typical procedure, five grams of graphite flakes, ground to approximately 20 pm or less in sizes, were dispersed in 1,000 mL of deionized water (containing 0.1% by weight of a dispersing agent, Zonyl® FSO from DuPont) to obtain a suspension. An ultrasonic energy level of 85 W (Branson S450 Ultrasonicator) was used for exfoliation, separation, and size reduction of graphene sheets for a period of 15 minutes to 2 hours. The resulting graphene sheets are pristine graphene that have never been oxidized and are oxygen-free and relatively defect-free. There are no other non-carbon elements.

Various amounts (l%-30% by weight relative to graphene material) of chemical bowing agents (N, N-Dinitroso pentamethylene tetramine or 4. 4’-Oxybis (benzenesulfonyl hydrazide) were added to a suspension containing pristine graphene sheets and a surfactant. The suspension was then cast onto a glass surface using a doctor’s blade to exert shear stresses, inducing graphene sheet orientations. Several samples were cast, including one that was made using CO2 as a physical blowing agent introduced into the suspension just prior to casting). The resulting graphene films, after removal of liquid, have a thickness that can be varied from approximately 10 to 100 pm.

The graphene films were then subjected to heat treatments that involve an initial (first) thermal reduction temperature of 80-l,500°C for 1-5 hours. This first heat treatment generated a graphene foam. Some of the pristine foam samples were then subjected to a second temperature of 1, 500-2, 850°C to determine if the graphene domains in the foam wall could be further perfected (re-graphitized to become more ordered or having a higher degree of crystallinity).

Example 9: CVD graphene foams on Ni foam templates

The procedure was adapted from that disclosed in open literature: Chen, Z. et al. “Three- dimensional flexible and conductive interconnected graphene networks grown by chemical vapor deposition,” Nat. Mater. 10, 424-428 (2011). Nickel foam, a porous structure with an interconnected 3D scaffold of nickel was chosen as a template for the growth of graphene foam. Briefly, carbon was introduced into a nickel foam by decomposing CH4 at 1,000°C under ambient pressure, and graphene films were then deposited on the surface of the nickel foam. Due to the difference in the thermal expansion coefficients between nickel and graphene, ripples and wrinkles were formed on the graphene films. In order to recover (separate) graphene foam, Ni frame must be etched away. Before etching away the nickel skeleton by a hot HC1 (or FcCl·,) solution, a thin layer of poly(methyl methacrylate) (PMMA) was deposited on the surface of the graphene films as a support to prevent the graphene network from collapsing during nickel etching. After the PMMA layer was carefully removed by hot acetone, a fragile graphene foam sample was obtained. The use of the PMMA support layer is critical to preparing a free-standing film of graphene foam; only a severely distorted and deformed graphene foam sample was obtained without the PMMA support layer.

Example 10: Preparation of graphene oxide (GO) suspension from natural graphite and of subsequent GO foams

Graphite oxide was prepared by oxidation of graphite flakes with an oxidizer liquid consisting of sulfuric acid, sodium nitrate, and potassium permanganate at a ratio of 4:1:0.05 at 30°C. When natural graphite flakes (particle sizes of 14 pm) were immersed and dispersed in the oxidizer mixture liquid for 48 hours, the suspension or slurry appears and remains optically opaque and dark. After 48 hours, the reacting mass was rinsed with water 3 times to adjust the pH value to at least 3.0. A final amount of water was then added to prepare a series of GO-water suspensions. We observed that GO sheets form a liquid crystal phase when GO sheets occupy a weight fraction > 3% and typically from 5% to 15%.

By dispensing and coating the GO suspension on a polyethylene terephthalate (PET) film in a slurry coater and removing the liquid medium from the coated film we obtained a thin film of dried graphene oxide. Several GO film samples were then subjected to different heat treatments, which typically include a thermal reduction treatment at a first temperature of 100°C to 500°C for 1-10 hours, and at a second temperature of 1,500°C-2,850°C for 0.5-5 hours. With these heat treatments, also under a compressive stress, the GO films were transformed into graphene foam.

Example 11: Graphene foams from hydrothermally reduced graphene oxide For comparison, a self-assembled graphene hydrogel (SGH) sample was prepared by a one-step hydrothermal method. In a typical procedure, the SGH can be easily prepared by heating 2 mg/mL of homogeneous graphene oxide (GO) aqueous dispersion sealed in a Teflon- lined autoclave at 180°C for 12 h. The SGH containing about 2.6% (by weight) graphene sheets and 97.4% water has an electrical conductivity of approximately 5 x 10 S/cm. Upon drying and heat treating at 1,500°C, the resulting graphene foam exhibits an electrical conductivity of approximately 1.5 x 10¹ S/cm, which is 2 times lower than those of the presently invented graphene foams produced by heat treating at the same temperature.

Example 12: Plastic bead template-assisted formation of reduced graphene oxide foams

A hard template-directed ordered assembly for a macro-porous bubbled graphene film (MGF) was prepared. Mono-disperse poly methyl methacrylate (PMMA) latex spheres were used as the hard templates. The GO liquid crystal prepared in Example 9 was mixed with a PMMA spheres suspension. Subsequent vacuum filtration was then conducted to prepare the assembly of PMMA spheres and GO sheets, with GO sheets wrapped around the PMMA beads. A composite film was peeled off from the filter, air dried and calcinated at 800°C to remove the PMMA template and thermally reduce GO into RGO simultaneously. The grey free-standing PMMA/GO film turned black after calcination, while the graphene film remained porous. The resulting foam typically has a physical density in the range from approximately 0.05- 0.6 g/cm . The pore sizes can be varied between meso-scaled (2-50 nm) up to macro-scaled (several pm) depending upon the contents of non-carbon elements and the amount/type of blowing agent used. This level of flexibility and versatility in designing various types of graphene foams is unprecedented and un-matched by any prior art process.

Example 13: Preparation of graphene foams from graphene fluoride

Several processes have been used by us to produce GF, but only one process is herein described as an example. In a typical procedure, highly exfoliated graphite (HEG) was prepared from intercalated compound C_IF-ACIF-,. HEG was further fluorinated by vapors of chlorine trifluoride to yield fluorinated highly exfoliated graphite (FHEG). Pre-cooled Teflon reactor was filled with 20-30 mL of liquid pre-cooled CIF3, the reactor was closed and cooled to liquid nitrogen temperature. Then, no more than 1 g of HEG was put in a container with holes for CIF3 gas to access and situated inside the reactor. In 7-10 days a gray-beige product with approximate formula C2F was formed.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixed with 20-30 ruL of an organic solvent (methanol, ethanol, 1 -propanol, 2-propanol, 1 -butanol, /_{<? /7}-butanol, isoamyl alcohol) and subjected to an ultrasound treatment (280 W) for 30 min, leading to the formation of homogeneous yellowish dispersions. Five minutes of sonication was enough to obtain a relatively homogenous dispersion, but longer sonication times ensured better stability. Upon casting on a glass surface with the solvent removed, the dispersion became a brownish film formed on the glass surface. When GF films were heat-treated, fluorine was released as gases that helped to generate pores in the film. In some samples, a physical blowing agent (N2 gas) was injected into the wet GF film while being cast. These samples exhibit much higher pore volumes or lower foam densities. Without using a blowing agent, the resulting graphene fluoride foams exhibit physical densities from 0.35 to 1.38 g/cm . When a blowing agent was used (blowing agent/GF weight ratio from 0.5/1 to 0.05/1), a density from 0.02 to 0.35 g/cm was obtained. Typical fluorine contents are from 0.001% (HTT = 2,500°C) to 4.7% (HTT = 350°C), depending upon the final heat treatment temperature involved.

Example 14: Preparation of graphene foams from nitrogenated graphene

Graphene oxide (GO), synthesized in Example 6, was finely ground with different proportions of urea and the pelletized mixture heated in a microwave reactor (900 W) for 30 s. The product was washed several times with deionized water and vacuum dried. In this method graphene oxide gets simultaneously reduced and doped with nitrogen. The products obtained with graphene : urea mass ratios of 1 : 0.5, 1 : 1 and 1 : 2 are designated as NGO-1, NGO-2 and NGO-3 respectively and the nitrogen contents of these samples were 14.7, 18.2 and 17.5 wt% respectively as found by elemental analysis. These nitrogenated graphene sheets remain dispersible in water. The resulting suspensions were then cast, dried, and heat-treated initially at 200-350°C as a first heat treatment temperature and subsequently treated at a second temperature of 1,500°C. The resulting nitrogenated graphene foams exhibit physical densities from 0.45 to 1.28 g/cm³. Typical nitrogen contents of the foams are from 0.01% (HTT = 1,500°C) to 5.3% (HTT = 350°C), depending upon the final heat treatment temperature involved. Example 15: Production of graphite flakes through oxidation of graphite, thermal expansion/exfoliation of oxidized graphite, and air jet milling

Natural flake graphite, nominally sized at 45 pm, provided by Asbury Carbons (405 Old Main St., Asbury, N J. 08802, USA) was milled to reduce the size to approximately 14 pm (Sample la). The chemicals used in the present study, including fuming nitric acid (>90%), sulfuric acid (95-98%), potassium chlorate (98%), and hydrochloric acid (37%), were purchased from Sigma- Aldrich and used as received. Graphite oxide (GO) samples were prepared according to the following procedure:

A reaction flask containing a magnetic stir bar was charged with sulfuric acid (176 mL) and nitric acid (90 mL) and cooled by immersion in an ice bath. The acid mixture was stirred and allowed to cool for 15 min, and graphite (10 g) was added under vigorous stirring to avoid agglomeration. After the graphite powder was well dispersed, potassium chlorate (110 g) was added slowly over 15 min to avoid sudden increases in temperature. The reaction flask was loosely capped to allow evolution of gas from the reaction mixture, which was stirred for 24 hours at room temperature. On completion of the reaction, the mixture was poured into 8 L of deionized water and filtered. The GO was re-dispersed and washed in a 5% solution of HC1 to remove sulfate ions. The filtrate was tested intermittently with barium chloride to determine if sulfate ions are present. The HC1 washing step was repeated until this test was negative. The GO was then washed repeatedly with deionized water until the pH of the filtrate was neutral. The GO slurry was spray-dried and stored in a vacuum oven at 60°C and then subjected to free thermal exfoliation (1,050°C for 2 minutes) to obtain thermally exfoliated graphite worms. The graphite worms were then exposed to light-intensity air milling to produce isolated expanded graphite flakes (having thickness typically from 15 nm to 150 nm). Expanded graphite flakes are found to carry some amounts of chemical functional groups, such as -COOH, -OH, and >0.

Expanded graphite flakes were then immersed in a water solution of H2O2 (30% by weight) to impart additional oxygen-containing functional groups, particularly -COOH, to these graphite flakes. Certain graphite flakes were also exposed to ammonia, chlorine, fluorine, and bromine gases, separately, to produce different functional groups, containing -NH2, -Cl, -F, and -Br, respectively.

Example 16: Preparation of graphite oxide (GO) using a modified Hummers’ method

Graphite oxide was prepared by oxidation of natural graphite flakes with sulfuric acid, sodium nitrate, and potassium permanganate according to the method of Hummers [U.S. Pat. No. 2,798,878, Jul. 9, 1957]. In this example, for every 1 gram of graphite, we used a mixture of 22 ml of concentrated sulfuric acid, 2.8 grams of potassium permanganate, and 0.5 grams of sodium nitrate. The graphite flakes were immersed in the mixture solution and the reaction time was approximately one hour at 35. degree. C. It is important to caution that potassium permanganate should be gradually added to sulfuric acid in a well-controlled manner to avoid overheat and other safety issues. Upon completion of the reaction, the mixture was poured into deionized water and filtered. The sample was then washed repeatedly with deionized water until the pH of the filtrate was approximately 5. The slurry was spray-dried and stored in a vacuum oven at 60°C for 24 hours. Some of the powder was subsequently exfoliated in a furnace, pre-set at 950°C, for 1 minute to obtain thermally exfoliated graphite worms.

Some of the graphite worms were poured into a household food processor and sheared for 10 minutes to obtain expanded graphite flakes. Expanded graphite flakes, having 6% to 20% oxygen content, were dispersed in water to form a suspension, which was spray-coated onto a surface of a PP non- woven cloth to form a filtration member.

Example 17: Oxidation and exfoliation of meso-carbon micro-beads (MCMBs)

Graphite oxide was prepared by oxidation of meso-carbon micro-beads (MCMBs) according to the same procedure used in Example 1. MCMB microbeads were supplied by China

Steel Chemical Co. (Taiwan). This material has a density of about 2.14 g/cm ; a particle size of 25 microns; and an inter-planar distance of about 0.336 nm. After deep oxidation treatment, the inter-planar spacing in the resulting graphite oxide micro-beads is approximately 0.76 nm. Upon exfoliation for 2 minutes at 350°C, the exfoliated carbon worms have flakes having a thickness from 3 nm -15 nm. Some of the exfoliated carbon worms were then dispersed in an acidic solution (containing citric acid dissolved in water) to form a slurry. The slurry was then painted over a PP non-woven fabric sheet and, upon removal of water, an antiviral filtration member was obtained. The member contained citric acid dispersed on graphite flake surfaces and some dispersed on PP fiber surfaces.

Example 18: Fluorination of graphite to produce exfoliated and expanded graphite fluoride flakes

Natural graphite flakes, a sieve size of 200 to 250 mesh, were heated in vacuum (under _2 less than 10 mmHg) for about 2 hours to remove the residual moisture contained in the graphite. Fluorine gas was introduced into a reactor and the reaction was allowed to proceed at 375°C for 120 hours while maintaining the fluorine pressure at 200 mmHg. This was based on the procedure suggested by Watanabe, et al. disclosed in U.S. Pat. No. 4,139,474. The powder product obtained was black in color. The fluorine content of the product was measured as follows: The product was burnt according to the oxygen flask combustion method and the fluorine was absorbed into water as hydrogen fluoride. The amount of fluorine was determined by employing a fluorine ion electrode. From the result, we obtained a GF (Sample 5 A) having an empirical formula (CFo_.75)_n- X-ray diffraction indicated a major (002) peak at 2Q =13.5 degrees, corresponding to an inter-planar spacing of 6.25 A. Some of the graphite fluoride powder was thermally exfoliated to form graphite worms, which were air jet-milled to obtain expanded graphite fluoride flakes. These graphitic flakes were then dispersed in a water solution of Polyacrylic acid (2%) to form a suspension, which was sprayed over a non-woven fabric sheet to form an antiviral filtration member after water was dried.

Example 19: Halogenation of expanded graphite fluoride flakes

A sample of expanded graphite fluoride (CFo_.ex) obtained in EXAMPLE 4 was exposed at 250°C and 1 atmosphere to vapors of l,4-dibromo-2-butene (Br¾C — CH=.CH— CH BI ) for 3 hours. It was found that two-thirds of the fluorine was lost from the graphite fluoride sample. It is speculated that l,4-dibromo-2-butene actively reacts with graphite fluoride, removing fluorine from the graphite fluoride and forming bonds to carbon atoms in the graphite lattice. The resulting product is mixed halogenated graphite, likely a combination of graphite fluoride and graphite bromide. These halogenated graphite flakes were then painted on a sheet of melt-blown PP fabric, which was then laminated between an outer layer and an inner layer of fabric to form a face mask.

Claims

We claim:

1. A face mask for use by a wearer having a face, mouth, and nose, the face mask comprising: a) a mask body configured to cover at least the wearer's mouth and nose, the mask body having an inner side facing towards the wearer; and b) a fastener to hold the mask in place on the wearer's face, the fastener including a portion that engages with the mask body and a portion that engages with the wearer; wherein the mask body comprises (i) an air-permeable outer layer, (ii) an inner layer located on an inner side of the mask body, and (iii) a graphene layer that is disposed in the mask body, wherein said graphene layer comprises a plurality of discrete single-layer or few-layer graphene sheets selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof, wherein said fastener connects the mask body to the wearer.

2. The face mask of claim 1, wherein said graphene layer is disposed between the outer layer and the inner layer.

3. The face mask of claim 1 , wherein said graphene layer is embedded in the outer layer.

4. The face mask of claim 1 , wherein said graphene layer is embedded in the inner layer.

5. The face mask of claim 1, wherein said graphene sheets are chemically bonded to a surface of the mask body.

6. The face mask of claim 1, wherein said graphene sheets are chemically bonded to a surface of the mask body using an adhesive or binder.

7. The face mask of claim 1, wherein the graphene layer has a density from 0.005 to 1.7 g/cm , and a specific surface area from 10 to 3,200 m /g.

8. The face mask of claim 1, wherein the graphene layer has a specific surface area from 50 to 3,000 m²/g or a density from 0.1 to 1.2 g/cm³.

9. The face mask of claim 1, wherein the graphene layer is a discrete layer.

10. The face mask of claim 1, wherein at least one of the outer layer or the inner layer comprises a woven or nonwoven structure of polymer fibers or glass fibers.

11. The face mask of claim 1, wherein the fastener comprises a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around one or more ears of the wearer.

12. The face mask of claim 1, wherein the fastener comprisesan elastic strap that is hooked around a head of the wearer.

13. The face mask of claim 1, wherein at least one of the outer layer or the inner layer comprises polymer fibers selected from the group of cotton, cellulose, wool, polyolefins, polyester, polyamide, rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

14. The face mask of claim 1, wherein said graphene sheets have an oxygen content from 5% to 50% by weight based on the total graphene sheet weight.

15. The face mask of claim 1, wherein the mask body further comprises an anti-microbial compound.

16. The face mask of claim 1, wherein the mask body further comprises an anti-microbial compound distributed on surfaces of the graphene sheets and the graphene sheets have a specific surface area from 50 to 2,630 m /g.

17. The face mask of claim 16, wherein the anti-microbial compound comprises an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, or a combination thereof.

18. A filtration material for use in the face mask of claim 1, said filtration material comprises a layer of woven or nonwoven fabric having two primary surfaces and a graphene layer deposited on at least one of the two primary surfaces or embedded in the layer of woven or nonwoven fabric.

19. The filtration material of claim 18, wherein said graphene layer comprises a plurality of discrete single-layer or few-layer graphene sheets selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof.

20. The filtration material of claim 19, wherein said graphene sheets are chemically bonded to said at least one of the primary surfaces, with or without using an adhesive or binder.

21. The filtration material of claim 19, wherein the graphene layer has a density from 0.005 to 1.7 g/cm , and a specific surface area from 10 to 3,200 m /g.

22. The filtration material of claim 19, wherein the graphene layer has a specific surface area from 50 to 3,000 m /g or a density from 0.1 to 1.2 g/cm .

23. A filtration device comprising the filtration material of claim 18 as a filtration member.

24. The filtration device of claim 23, which is a water-purifying device, an air-purifying device, a solvent-removing device, or an oil-recovering device.

25. A process for producing the filtration material of claim 18, the process comprising (a) preparing a layer of woven or nonwoven fabric having two primary surfaces; and (b) depositing a graphene layer on at least one of the two primary surfaces.

26. The process of claim 25, wherein (b) comprises a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a gaseous medium to form a flowing fluid and impinging the flowing fluid upon at least one of the two primary surfaces, allowing said graphene sheets to adhere to said at least one primary surface.

27. The process of claim 25, wherein (b) comprises a procedure of dispersing discrete graphene sheets, with or without an adhesive, in a liquid medium to form a slurry, depositing the slurry onto at least one of the two primary surfaces to form a wet graphene layer, and removing or drying the liquid medium from said wet graphene layer to form the graphene layer.

28. The process of claim 27, wherein said depositing comprises a procedure selected from casting, coating, spraying, printing, brushing, painting, or a combination thereof.

29. The process of claim 25, which is a roll-to-roll process wherein (a) comprises (i) preparing a roll of woven or nonwoven fabric, (ii) continuously feeding a continuous length of a sheet of said fabric from said roll (mounted on a roller or reel) into a deposition zone, (iii) depositing a graphene layer onto at least one of the two primary surfaces to form a graphene layer- coated fabric, and (iv) collecting the graphene layer-coated fabric on a winding roller.

30. The process of claim 25, further comprising incorporating the filtration material into a mask body, which is fitted with a fastener to form the face mask.

31. A face mask for use by a wearer having a face, mouth, and nose, the face mask comprising: c) a mask body configured to cover at least wearer's mouth and nose; and d) a fastener to hold the mask in place on the wearer's face, the fastener including a portion that engages with the mask body and a portion that engages with the wearer; wherein the mask body comprises (i) an air-permeable outer layer, (ii) an inner layer located on an inner side of the mask body, and (iii) a layer of graphene foam that is disposed in the mask body, wherein said fastener connects the mask body to the wearer.

32. The face mask of claim 31, wherein said graphene foam layer is disposed between the outer layer and the inner layer.

33. The face mask of claim 31, wherein said graphene foam layer is embedded in the outer layer.

34. The face mask of claim 31, wherein said graphene foam layer is embedded in the inner layer.

35. The face mask of claim 31, wherein said layer of graphene foam comprises a graphene material selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof.

36. The face mask of claim 31, wherein said graphene foam layer is chemically bonded to a surface of the mask body using an adhesive or binder.

37. The face mask of claim 31, wherein the graphene foam layer has a density from 0.005 to 1.0 g/cm 3 or a specific surface area from 40 to 2,600 m 2 /g.

38. The face mask of claim 31, wherein the graphene foam layer has a specific surface area from 200 to 2,000 m²/g or a density from 0.01 to 0.5 g/cm³.

39. The face mask of claim 31, wherein the graphene foam layer is a discrete layer.

40. The face mask of claim 31, wherein at least one of the outer layer or the inner layer comprises a woven or nonwoven structure of polymer fibers or glass fibers.

41. The face mask of claim 31, wherein the fastener comprises a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head.

42. The face mask of claim 31, wherein the outer layer or the inner layer comprises polymer fibers selected from the group of cotton, cellulose, wool, polyolefins, polyester, polyamide, rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

43. The face mask of claim 31, wherein said graphene foam layer has an oxygen content from 5% to 50% by weight based on the total graphene sheet weight.

44. The face mask of claim 31, wherein the mask body further comprises an anti-microbial compound.

45. The face mask of claim 31, wherein the mask body further comprises an anti-microbial compound distributed on pore wall surfaces of the graphene foam layer.

46. The face mask of claim 45, wherein the anti-microbial compound comprises an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, or a combination thereof.

47. A filtration member for use in the face mask of claim 31, said filtration member comprising a layer of woven or nonwoven fabric having two primary surfaces and a layer of graphene foam deposited on at least one of the two primary surfaces or embedded in the layer of woven or nonwoven fabric.

48. The filtration member of claim 47, wherein said graphene foam layer is chemically bonded to said at least one of the primary surfaces using an adhesive or binder.

49. The filtration member of claim 47, wherein the graphene foam layer has a density from 0.005 to 1.0 g/cm or a specific surface area from 40 to 2,600 m /g.

50. The filtration member of claim 47, wherein the graphene foam layer has a specific surface area from 200 to 2,000 m²/g or a density from 0.01 to 0.5 g/cm³.

51. A filtration device comprising the filtration member of claim 37 as a filtration member.

52. The filtration device of claim 51, which is a water-purifying device, an air-purifying device, a solvent-removing device, or an oil-recovering device.

53. A filtration member for use in a filtration device, said filtration member comprising a layer of air-permeable membrane, having two primary surfaces and a layer of chemically functionalized graphite flakes deposited on at least one of the two primary surfaces or embedded in the layer of air-permeable membrane, wherein said graphite flakes comprise a chemical functional group containing from 1% to 50% by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

54. The filtration member of claim 53, wherein the air-permeable membrane is selected from a sheet of woven or nonwoven fabric, a porous polymeric membrane, a piece of open-cell foam, a sheet of air-breathable paper, or a combination thereof.

55. The filtration member of claim 53, wherein said layer of graphite flakes is chemically bonded to said at least one of the primary surfaces using an adhesive or binder.

56. The filtration member of claim 53, wherein the layer of graphite flakes has a specific surface area from 10 to 500 m /g.

57. The filtration member of claim 54, wherein said non-woven fabric comprises polymer fibers selected from the group of cotton, cellulose, wool, polyolefins, polyester, polyamide, rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

58. The filtration member of claim 53, further comprising an anti-microbial compound distributed on surfaces of graphite flakes.

59. The filtration member of claim 54, wherein said non-woven fabric comprises polymer fibers and an anti-microbial compound distributed on surfaces of the polymer fibers.

60. The filtration member of claim 58, wherein the anti-microbial compound comprises an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof.

61. The filtration member of claim 59, wherein the anti-microbial compound comprises an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof.

62. A filtration device comprising the filtration member of claim 53.

63. The filtration device of claim 62, which is a water-purifying device, an air-purifying device, a solvent-removing device, or an oil-recovering device.

64. The filtration device of claim 62, which is a face mask.

65. A face mask for use by a wearer having a face, mouth, and nose the facemask comprising: e) a mask body configured to cover at least wearer's mouth and nose; and f) a fastener to hold the mask in place on the wearer's face, the fastener including a portion that engages with the mask body and a portion that engages with the wearer; wherein the mask body comprises (i) an air-permeable outer layer, (ii) an inner layer located on an inner side of the mask body, and (iii) the filtration member of claim 1 that is disposed in the mask body.

66. The face mask of claim 65, wherein said filtration member is disposed between the outer layer and the inner layer.

67. The face mask of claim 65, wherein said filtration member is embedded in the outer layer.

68. The face mask of claim 65, wherein said filtration member is embedded in the inner layer.

69. The face mask of claim 65, wherein the fastener comprises a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head.

70. A face mask for use by a wearer having a face, mouth, and nose the facemask comprising:

A) a mask body configured to cover at least wearer's mouth and nose; and

B) a fastener to hold the mask in place on the wearer's face, the fastener including a portion that engages with the mask body and a portion that engages with the wearer;; wherein the mask body comprises (i) an air-permeable outer layer, (ii) an inner layer located on an inner side of the mask body, and (iii) a layer of chemically functionalized graphite flakes disposed in the mask body, wherein the graphite flakes comprise a chemical functional group containing l%-50% by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

71. The face mask of claim 70, wherein said filtration member is disposed between the outer layer and the inner layer.

72. The face mask of claim 70, wherein said filtration member is embedded in the outer layer.

73. The face mask of claim 70, wherein said filtration member is embedded in the inner layer.

74. A face mask comprising chemically functionalized graphite flakes as an antiviral agent, wherein the graphite flakes comprise a chemical functional group containing l%-50% by weight of a non-carbon element selected from O, N, H, F, Cl, Br, I, or a combination thereof.

75. The face mask of claim 70, wherein said layer of chemically functionalized graphite flakes is chemically bonded to a surface of the outer layer or a surface of the inner layer using an adhesive or binder.

76. The face mask of claim 70, wherein the layer of chemically functionalized graphite flakes has a specific surface area from 10 to 500 m /g.

77. The face mask of claim 70, wherein the outer layer or the inner layer comprises a woven or nonwoven structure of polymer fibers or glass fibers, a porous polymer membrane, an air- breathable sheet of paper, or a combination thereof.

78. The face mask of claim 70, wherein the fastener comprises a pair of ear straps that extend from both sides of the mask body and are configured to be hooked around wearer's ears, or an elastic strap that is hooked around wearer’s head.

79. The face mask of claim 70, wherein the outer layer or the inner layer comprises polymer fibers selected from the group of cotton, cellulose, wool, polyolefins, polyester, polyamide, rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls, poly (carboxylic acid), a biodegradable polymer, a water-soluble polymer, copolymers thereof, and combinations thereof.

80. The face mask of claim 70, wherein the mask body further comprises an anti-microbial compound.

81. The face mask of claim 70, wherein the mask body further comprises an anti-microbial compound distributed on surfaces of the graphite flakes.

82. The face mask of claim 70, wherein the anti-microbial compound comprises an antiviral or anti-bacteria compound selected from acrylic acid, methacrylic acid, citric acid, an acidic polymer, a silver-organic idine antibacterial agent, an iodine resin, a sialic acid, a cationic group, a sulfonamide, a fluoroquinolone, hypericin, curcumin, or a combination thereof.