RU2394627C1 - Notwoven material including unltrafine or nano-size particles - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to nonwoven filtration materials. Proposed fibrous structure for fluids or gases represents a mix of aluminium oxide nano-fibers and second fibers arranged in matrix to produce asymmetric pores with mean size of 5 to 48 mcm wherein fine, superfine or nano-size particles, like powder activated coal, are bound without using binders. Said fibrous structure containing powder activated coal entraps impurities from fluid or gas flows. This invention covers also the method of producing and using said fibrous structure. ^ EFFECT: higher efficiency of entrapping ultrafine particles from fluid and gas phases. ^ 29 cl, 16 dwg, 21 tbl, 25 ex

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a partly ongoing application for US Patent No. 11/531107, entitled "Electrostatic Air Filter", filed September 12, 2006, which claims the priority of provisional application for US Patent No. 60/716218, entitled "Electrostatic Air Filter", filed 12 September 2005 This application also claims the priority of provisional patent application US No. 60/744043, entitled "Composition of impregnated alumina nanofiber metal", filed March 31, 2006

STATEMENT OF STATE RIGHTS

The invention was created as a result of a research project under the contract FA8650-0-0.5-Ms5822, concluded with the US Air Force. In this regard, the government has indisputable rights to this invention.

FIELD OF THE INVENTION

The present invention relates to nanoparticles, and in particular, to the use of nanopowders in non-woven filter material without the use of adhesives, to use in non-woven filter structures, for trapping contaminants from water, air and gas.

BACKGROUND

Currently, there is a rapid development of nanotechnology and the use of nanosized particles. In particular, nanopowders are being developed for use as abrasives (for example, tungsten carbides) and ultraviolet absorbers (for example, titanium and zinc oxides). In addition, there is great interest in creating nanostructures with biological effects, that is, in nanobiotechnology, and in investments in these developments. Small particles, and especially ultrafine and nanoparticles, have the advantage and unexpected sorption properties compared to large particles. This increased reactivity is the result of a significantly higher surface area and more active surface properties. The application of nanopowders to substrates, such as membranes, or to fibers is often associated with the need for their best use in the intended field. Therefore, for the production of nanocomposites using high-speed methods, it is desirable that the nanoparticles be fixed in a non-woven fibrous structural material.

Nanoparticles are too small for fixation in ordinary tissues, since nanoparticles are prone to the formation of agglomerates, which cause thickening of the liquid, prevent the passage of nanoparticles into the tissue used as a carrier, which leads to the loss of nanoparticles. This makes it impossible to produce nanoparticle-containing material using conventional high-speed, low-cost technology, such as paper technology. Despite the fact that binders can be used to attach nanoparticles to fibrous structures in the material, these binders easily envelop nanoparticles, resulting in partially or completely deactivating nanoparticles and significantly weakening their expected effect.

The prior art offers many types of materials that remove, filter or trap contaminants from gas streams. These filters, being quite effective when used in areas for which they have been specially developed, do not provide an appropriate level of efficiency when used in areas that place higher demands on filters. Currently, filtering material is required that would provide higher filtration efficiency, higher dirt holding capacity, lower pressure drop, lower cost, higher service life, increased resistance to chemical attack, and no particularization (i.e., the release of particles of filtering material into the stream filtrate) and mechanical strength withstanding pressure fluctuations. Smaller particles of the sorbent provide higher adsorption efficiency, but their use leads to an increase in the pressure drop across the filter.

Granular catalysts are used to purify liquids and gases. Their reactivity is strongly affected by the area of the external surface of the catalyst in contact with the flow of liquid or gas. Nanosized catalysts made of platinum and other noble metals are usually dispersed on an adsorbent material, which may include ceramic beads, honeycomb ceramic structures, and on larger granules such as activated carbon and activated alumina.

Activated carbon is a well-known sorbent particle. It has a micropore diameter of about 0.2 to 20 nm. Activated carbon is used as a sorbent particle due to the fact that its small pore sizes provide a corresponding large surface area per unit mass with a corresponding large number of active sorption centers on the particle. At the same time, pore sizes significantly affect the diffusion rate of liquid substances through the granule. Typically, the diffusion rates of liquid substances in a sorbent material are determined by the mean free path of the liquid molecules that is absorbed by such a sorbent material. The smaller the pores in such a sorbent, the more extended is the mean free path, and the slower are the diffusion rates. Therefore, small pores in activated carbon negatively affect the penetration of liquid substances into highly tortuous channels of small porosity. The reduction in particle size significantly reduces the path length, which reduces the time required for any adsorbed substance to reach the adsorption centers within the structure. This leads to greater filtration efficiency when removing contaminant from the stream.

It is known to use granular activated carbon (GAU) for water treatment, including drinking water, and in many industries, including the pharmaceutical industry and the beverage industry. In the case of drinking water, GAU is used to absorb soluble organic substances (many of which are toxic or carcinogenic) and chlorine. In the case of air purification, GAU is used to control odors and the content of gaseous and vaporous pollutants in hospitals, laboratories, restaurants, animal welfare facilities, libraries, airports, business buildings and respiratory equipment. GAUs are often included in a material to remove volatile organic compounds from air currents. The disadvantage of this approach is that to ensure a very low pressure drop, these filters have large voids between the particles. As a result, it is well known that these filters are ineffective in trapping small particles as well as volatile pollutants. If the pore size of these filters is significantly reduced in order to capture a large fraction (calculated) of particles in the air when passing it through the filter, then the filter would have a too high pressure drop (i.e., would have too high a flow resistance) in order to be used in forced air heating system. In addition, filters having very small pore sizes are easily and quickly clogged due to accumulation of debris on surfaces from the inlet side of the stream, which leads to a rapid decrease in the filter's ability to pass air without the need for an excessively high pressure gradient across the filter. GAU is often used as bulk granules in the filter layer. However, carbon layers are inconvenient to use in filter designs, since bulk particles can move, causing the formation of through ducts in the layer and clogging of the layer.

As filters, fibrous structural material is widely used. Compared with a layer of granules, such as GAU, the fibrous structure allows to minimize the formation of through ducts, allows you to significantly diversify the design of the filter, and it can be obtained using inexpensive technologies, such as those used in the manufacture of paper.

It is well known that powdered activated carbon (PAH) is characterized by a significantly higher adsorption rate compared to GAU, while having a higher external surface area and approximately equivalent iodine numbers. However, it is known from the prior art that the introduction of PAHs into the matrix of nonwoven material is difficult, since adhesives are required to attach it to the fibrous matrix, which leads to the fact that at least part of the particles becomes ineffective for filtration, since part of the surface particles contaminated with adhesive. In order to minimize this contamination, coarser particles are often used to minimize the contact point between the adhesive and the PAH particles. For example, it is known to use PAHs with a particle size of greater than about 100 microns for gas purification. Most often, the use of PAHs is limited to use for bleaching liquids. It is known in the art to impregnate activated carbon with various compounds, including catalysts and chemisorbents, which remove or modify pollutants poorly sorbed by carbon due to physical sorption. For example, ASC Whetlerite consists of activated carbon impregnated with salts of copper, chromium and silver, which absorb and destroy chemical warfare agents such as chlorocyanines, hydrocyanic acid and arsine. Copper and chromium (in the form of complexes with triethylenediamine (TEDA)) act as chemisorbents for chlorocyanines and hydrocyanic acid, while silver catalyzes the conversion of arsine to oxide. In other examples, to enhance the ability of activated carbon to adsorb ammonia, it is impregnated with citric acid, or it is impregnated with hydroxides such as sodium hydroxide or other alkalis to remove hydrogen sulfide. In the nuclear industry, it is known to impregnate filters comprising several layers of activated carbon with potassium iodide (KI) to exchange radioactive iodine with isotopes in case of emergency discharge into the air.

The life of the catalyst is limited by poisons that are deposited on the surface of the granules or powder. A powdery catalyst is less prone to poisoning due to the fact that it has a higher surface area to volume ratio than a pelletized catalyst. In addition, the non-woven material used as a carrier for the powder catalyst provides a higher reactivity, a lower layer depth and an elastic structure giving freedom of action in the design. Therefore, there is a need to bind the powdered catalyst to a fibrous structure without the use of binders and with a strength sufficient to minimize the loss of catalysts with the flow of liquid or gas.

The filtration efficiency decreases as a result of compaction and the formation of through ducts in the sorbent layer, which occurs when the sorbent granules are abraded against each other. A nonwoven filter in which the sorbent is dispersed and enclosed within the structure without the use of binders could have an increased filtering ability. Based on the foregoing, customers and consumers in industry have a need for such a non-woven fibrous structure that holds ultrafine particles and nanoscale particles. It is desirable that the material, including the non-woven filtering structure, be highly efficient in capturing small particles of pollutants dissolved in water and volatile pollutants in the air.

SUMMARY OF THE INVENTION

The present invention addresses these needs. In one embodiment, the present invention is a new particulate filter or filter medium for a gaseous medium that meets the need for a high performance, high capacity particulate filter that captures pathogens and other solid particles from air or gas streams, including liquid aerosols solid particles, and also characterized by a low pressure drop.

In another embodiment, the present invention satisfies the need for a nonwoven fibrous material in which ultrafine or nanoparticles are held without the need for binders or adhesives.

Accordingly, it is an object of the present invention to provide filtration efficiency that is at least as high as that of HEPA filters and which is resistant to liquid aerosol clogging.

Another objective in an example embodiment of the invention is to develop a material that traps aerosolized bacteria and viruses.

Another objective in an example embodiment of the present invention is the development of an air filter that has a high porosity and therefore is more resistant to adsorption of water mists than traditional filter material.

Another objective in an example embodiment of the invention is to develop a material that has at least the same high filtering efficiency as conventional ULPA or Super ULPA filters.

Another objective in an example embodiment of the invention is the development of a filter material that is characterized by a lower pressure drop than that which occurs on traditional filters.

Another goal in the example of an embodiment of the invention is to develop a filter material that has a larger pore size and higher porosity than in HEPA filters, thereby providing a higher capacity for drops of water until flooding.

Another objective in an example embodiment of the invention is to develop a filter material that is energy efficient.

Another objective in an example embodiment of the present invention is to provide a filter material that has a longer filter life compared to conventional filters.

Another objective in an example embodiment of the present invention is the development of a filter material that is characterized by low maintenance.

Another objective in an example embodiment of the present invention is the development of a filter material that retains hazardous waste and requires minimal associated costs.

Another objective in an example embodiment of the present invention is the development of a filter material that is sufficiently strong when bent.

Another objective in an example embodiment of the present invention is the development of a method for producing a filter or filter material for cleaning a gaseous medium, the filtration efficiency of which is at least as high as that of traditional HEPA filters, and which is resistant to clogging with liquid aerosol.

Another objective in an example embodiment of the present invention is to develop a method of using a filter or filter material to remove particles and aerosols from a gaseous medium.

Another objective in an embodiment of the present invention is to provide a nonwoven fibrous matrix in which nanostructures are formed at low manufacturing costs.

In addition, an object in an embodiment of the present invention is to provide a nonwoven material that allows the removal of soluble and volatile organic compounds and halogens from liquid and gas streams with high efficiency, high capacity and low pressure drop.

Another objective in an embodiment of the present invention is the development of a chemisorption material that also traps solid particles, including microbial pathogens, from a liquid medium.

In addition, an object of an embodiment of the present invention is to introduce powdered, nanoscale catalysts, including photocatalysts, oxidation catalysts, or powdered activated carbon impregnated with catalysts, into a nonwoven material by attaching catalysts or powdered activated carbon to a nonwoven base.

Another objective in an embodiment of the present invention is the development of a nonwoven material containing ultrafine or nanosized powder, which is kept on the material to minimize dust formation.

Another objective in the embodiment of the present invention is the introduction of non-woven material finely ground or nanoscale ion-exchange resins and macroporous polymers.

Another objective in the embodiment of the present invention is the introduction of non-woven material biologically active components, such as DNA or RNA.

Another objective in an embodiment of the present invention is the development of a method for introducing nanoscale pigments, colored reactive chemicals and finely divided abrasives into a nonwoven material.

In general, the present invention is a filter or fibrous structure for fluids that includes alumina nanofibers, fluid absorbent particles, and a plurality of second fibers arranged in an alumina nanofiber matrix to create asymmetric pores. In one example, the second fibers are fibers whose minimum size is larger than the minimum size of alumina nanofibers by about one order of magnitude. The second fibers are introduced together with alumina nanofibers in order to provide a basis for creating pores or providing large interfiber spaces within or on them for dispersing alumina nanofibers. In the examples, the asymmetric pore size is approximately greater than 5 mm. In one embodiment, to improve the removal of contaminants from the liquid medium, a plurality of fine, ultrafine or nanosized particles are applied to the alumina nanofibres.

Preferably, said particles are selected from the group consisting of sorbent, ion exchange resin, catalyst, metal oxide.

Preferably, said sorbent particles are selected from the group consisting of powdered activated carbon, a noble metal, a macromolecular organic substance, a biological compound, and an antimicrobial agent.

Preferably, said metal oxide particles are selected from the group consisting of colloidal silicon dioxide, colloidal alumina, zinc nanooxide and titanium nanooxide.

Preferably, said catalyst is an oxidation catalyst.

Preferably, said metal oxide has a submicron size.

Larger fibers provide or form larger pores into which, or onto which, aluminum oxide nanofibers are dispersed. However, large fibers have a smaller surface area per unit volume or mass, and therefore, the amount of nano alumina dispersed on them, or into the pores, is significantly reduced. Therefore, in another embodiment, the second fibers are a combination of large and small fibers. The introduction of fine fibers provides additional surface area, as a result of which more alumina nanofibers can be loaded into the material, or onto the material.

Without delving into theory, however, it can be argued that ultrafine and nanosized particles with diameters smaller than the average pore size of the filter material are retained on alumina nanofibers due to electro-adhesive forces. Particles larger than the pore size of the material are retained mainly due to mechanical trapping. No binders are used in the fibrous structure to envelop or reduce the sensitivity of particles deposited on alumina nanofibres.

In another embodiment, the invention relates to methods for producing a filter material or fibrous structure.

In another embodiment, the invention relates to methods of using a filter material of nano alumina or a fibrous structure to remove toxic contaminants and other solid particles from liquid streams.

These and other details, objects, and advantages of the present invention will become more apparent or apparent from the following descriptions, examples, and figures illustrating embodiments thereof.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a graphical dependence of the air flow through the inventive filters of nano alumina and the HEPA filter from the pressure drop across the filters.

Figure 2 shows a graphical dependence of the turbidity on the missed volume during the filtration of latex spheres of 0.2 μm in size suspended in water through the inventive filters of aluminum nanooxide and a HEPA filter.

Figure 3 shows a graphical dependence of the permeability of the inventive filters of aluminum nanooxide and the HEPA filter during continuous filtration through them of NaCl aerosols with a particle size of 0.3 μm.

Figure 4 shows a graphical dependence of the air resistance for the inventive filters of nano alumina and the HEPA filter during continuous filtration through them of NaCl aerosols with a particle size of 0.3 μm.

Figure 5 shows a graphical dependence of the air flow rate through the inventive filters of aluminum nanooxide, pre-treated with latex spheres of 0.5 and 1 μm in size, on the pressure drop.

Figure 6 shows a graphical dependence of the permeability of the inventive filters of aluminum nanooxide pretreated with latex balls, in comparison with the filter of aluminum nanooxide not subjected to pretreatment, and the HEPA filter when filtering NaCl aerosols with a particle size of 0.3 μm through them.

Figure 7 shows a graphical dependence of air resistance for the inventive filters of aluminum nanooxide pretreated with latex balls, in comparison with a filter of nano alumina not subjected to pretreatment, and the HEPA filter.

On Fig shows a graphical dependence of the permeability of the inventive filters of nano alumina and the HEPA filter when filtering through them NaCl aerosols with a particle size of 0.3 μm.

Figure 9 shows a graphical dependence of the air resistance for the inventive filters of nano alumina and the HEPA filter when examining their capacity for NaCl aerosols.

Figure 10 shows a graphical dependence of the effectiveness of the claimed filters of nano alumina, expressed as a percentage, on the size of aerosolized drops of KCl.

Figure 11 shows a graphical dependence of the antimicrobial action of the inventive filters of aluminum nanooxide impregnated with silver on the reproduction of bacteria from the exposure time.

12 schematically depicts a system used to test the inventive filters of aluminum nanooxide for the disposal of aerosols containing bacteria transmitted through water.

13 is a graphical diagram of the relationship between pressure drop and pore size versus fiber diameter.

Fig. 14 shows a comparison of the pressure drop of the inventive filter material from nano alumina and a pre-HEPA filter.

On Fig shows an electron micrograph in transmitted light of a fiber of nano alumina on a microglass coated with nanospheres of silicon dioxide.

On Fig shows a graphical dependence of the adsorption of dissolved iodine on the inventive nanofibers of aluminum oxide in comparison with adsorption on manufactured in the industry material containing activated carbon.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

In order to properly understand the disclosure of the claimed invention, the following paragraph defines the terms used in the description. In defining the following terms by the inventors of the invention, they in no way intended to deny the generally accepted and familiar meanings of these terms.

As used herein, the term "electrostatic" refers to any material having electrical charges, or to electrical charges.

As used herein, the term “aspect ratio” refers to the ratio of fiber length to fiber cross-sectional diameter.

As used herein, the term "nano alumina" refers to fibers with a size ratio of approximately greater than 5, where the smallest size is approximately less than 50 nm. The cross section of the fiber can be either round (cylindrical fiber) or rectangular (plate) in shape. The fibers are alumina with varying amounts of bound water, which as a result are primarily compositions of A1OOH with varying amounts of Al (OH) ₃ with possible impurities of gamma and alpha alumina.

As used herein, the term “lyosel” refers to fibrillated cellulose fiber precipitated from an organic solution in which hydroxyl groups are not replaced and chemical intermediates are not formed (Courtaulds, Ltd.).

The term "High Efficiency Particle Air" (HEPA) refers to a brand of filter material that is capable of retaining> 99.97% of 0.3 micron particles.

The term "Ultra Low Penetration Air" (ULPA) refers to a brand of filter material that is capable of retaining> 99.99% of particles of a particular size at a particular medium speed.

The term "Super ULPA" refers to a brand of filter material that is capable of retaining> 99.9999% of particles of a particular size at a particular medium speed.

As used herein, the term “adsorbent” means any material capable of adsorbing impurities on its surface mainly as a result of physical adsorption.

The term "absorbent" means any material capable of capturing a substance in its internal structure.

The term "reduction of pollution" means a decrease in the content of impurities in the fluid in which the impurity is trapped, removed or converted into a chemically or biologically inactive substance in order to increase the usefulness of the fluid, for example by converting the fluid into a safer for human use or more suitable for industrial applications.

The term "NanoCeram" refers to mixtures of alumina nanofibers and coarse fibers, in which coarse fibers serve as the basis for alumina nanofibers to create an asymmetric pore structure.

The term "fine powder" means a powder having an average particle size of significantly less than 100 mesh, and preferably less than 325 mesh (44 μm).

The term "ultrafine particle" means a particle having an average size of from 0.1 to 10 microns.

The term "nanoparticle" means a particle having an average size of less than 0.1 μm, including, but not limited to, nucleic acids (eg, DNA and RNA), proteins, poorly soluble or hardly volatile drugs, high molecular weight particles, functionalized polymers, ligands with introduced in them functionality and carbon tubes.

The term "microorganism" means a living organism that can be suspended in a fluid, including, but not limited to, bacteria, viruses, fungi, protozoa and their reproductive forms, including protective membranes and spores.

The term "paper" or "paper-like" usually means a flat, fibrous layer or rug of material obtained using the wet molding method.

The term "particle" means a solid or microencapsulated liquid having a size in the range from colloidal to macroscopic, regardless of shape.

The term "sorbent" means a particle of any powder that is capable of removing pollutants from a liquid or gas stream, including catalysts that are capable of converting pollutants into another less hazardous form. The term “sorbent” also includes a powdery catalyst or catalyst that is supported on a solid powdery or granular support, such as activated carbon.

The term "structure for medical use" means a non-woven material suitable for use in medicine, for example, to protect against infection, as a wound dressing and other similar applications.

Description of Embodiments

In one embodiment, the present invention provides filter media for removing particles, including liquid and especially water-aerosolized particles, from a fluid that is passed through the material to reduce its contaminant content. In the examples, the particles are pathogens such as bacteria, viruses, mold, fungi, mildew, organic matter, inorganic matter, microorganisms, carbon particles, mists from metalworking fluids, colorful mists, pesticides, ink mists or acid mists. In the examples, the liquid or gas stream has liquid aerosolized particles, such as water aerosolized particles. In one example, the filter material is a non-woven electrostatic material. The filter media includes alumina nanofibers mixed with second fibers. In one example, nano alumina is not spherical. The second fibers are placed in the matrix in order to create asymmetric pores. In one example, finely divided aluminum metal powder interacts with the second fibers to form an electrostatic material. The reaction is carried out by adding ammonia to a mixture of aluminum and a second fiber. The mixture is heated to the boiling point of water. In another example, aluminum trihydroxide is heated under conditions of high temperature and pressure in the presence of second fibers to form an electrostatic material. The reaction is carried out at a temperature of about 175 ° C. and a pressure of about 5 bar for about thirty minutes.

The second fibers can be any fiber that is sufficiently resistant to bending, including microglass, cellulose or fibrillated cellulose. In one example, the second fibers are smaller in size, which is larger than the smaller of the sizes of the alumina nanofibers by at least one order of magnitude. In the examples for an air or gas filter, the average pore size is in the range from 4 to about 48 microns. Preferably, the average pore size is greater than about 10 microns. More preferably, the average pore size is not more than about 20 microns. Typically, the pore size is related to the diameter of the second fibers. Therefore, a plurality of second fibers having a small diameter will create a plurality of asymmetric pores having a small size, while a plurality of second fibers having a larger diameter will create a plurality of asymmetric pores having a relatively larger size. See, for example, table 1 and FIG. 13. However, as the diameter of the second fiber increases, the ratio of surface area to unit volume decreases, and as a result, fewer alumina nanofibres disperse on the second fibers and / or in the pores. Therefore, in a preferred example, the plurality of second fibers is a combination of a plurality of large and a plurality of small fibers. The fine fibers can all have almost the same average diameter or some of the fine fibers can have different diameters. The introduction of small fibers leads to a corresponding reduction in pore size. See, for example, table 1 and FIG. 13.

The pore size determines the pressure drop across the filter medium. In a preferred example, the pressure drop is less than about 35 mmH ₂ O for a finished composite filter or filter unit at a flow rate of about 3.2 m / min.

In one example, the inventive filter material further includes sorbent particles, preferably colloidal particles, which are added to the filter material. In order to provide faster adsorption than in the case of larger granular coals, when absorbing volatile organic compounds, nerve agents or mustard gas, activated carbon is added in the form of a fine powder (for example, fine particles with a size of about 1 μm and an average size of about 28 μm).

In one example, the inventive filter material further includes a binder. The binder may have a fibrous form (Invista T104), or may be a resin such as Rhoplex HA-16 from Rohm and Haas. The introduction of a binder increases the strength and / or ability to bend the fibrous material, although a binder is not required to bind particles in the structure.

In one example, the filter material may further include an antimicrobial agent that is mixed with a plurality of nano alumina fibers and second fibers. In the production process, in order to use the filter material as an antimicrobial agent, after the suspension is prepared and before the mixture is sieved on a sieve, an antimicrobial agent is added and adsorbed onto alumina nanofibres. In one example, the antimicrobial agent is silver. In other examples, ions such as copper and zinc ions, or both, provide a synergistic effect with silver as an antimicrobial agent; in yet another example, ions such as copper and zinc ions act by themselves as an antimicrobial agent.

In one example of the present invention, the filter material is electrically charged, whereby alumina nanofibers trap particles such as pathogens and other substances. In one example, the filter material is a homogeneous non-woven filter.

In one example, the filter material is pretreated or preconditioned by passing a plurality of particles through it. Particles may have diameters in the range of 0.3 to about 1.5 microns. The introduction of these particles blocks at least part of the largest pores from the set of asymmetric pores in order to reduce the initial leakage through the filter material. In addition, preconditioning helps to create or obtain a HEPA or ULPA profile throughout the use of the filter. In one example, the plurality of particles is a plurality of latex spheres, although the plurality of particles can be made of any substance that is capable of blocking at least a portion of the largest pores.

In one example, the inventive filter material from nano alumina has a collection efficiency of at least the same as HEPA. In another example, the inventive filter material has a collection efficiency of at least as high as ULPA.

In another embodiment, the claimed invention is a method for producing a fluid filter from nano alumina. The production method includes the steps of forming an alumina nanofiber in the presence of a plurality of second fibers. The second fibers are disposed to form a plurality of asymmetric pores. In one example, nano alumina filter media is formed into a single homogeneous layer. In another example, nano alumina filter media is formed into more than one layer. In yet another example, the nano alumina filter media is pleated.

Filter media can be used in the filtration system. When used, a stream of air or gas is passed through the filter material and solid particles are removed from it as a result of trapping particles in the filter material. In one example, the fluid includes a suspension of drops of water. Examples of the use of the filter include, but are not limited to, use for indoor air purification, use in respirators or gas masks, use in automobile air filters, use in a room with a very clean atmosphere, use in an operating room or use in an industrial installation, for example, for removal paint or other specific substance contained in industrial fogs. In one example, filter media is used in an environment with a relative humidity of greater than about 75%.

In another embodiment, the present invention is widely used in nanotechnology and provides a fibrous structure for fixing particles that are very difficult to disperse and incorporate into fibrous tissues. In the examples, the dispersed particles are sorbents or catalysts that can remove contaminants from flows of liquids or gases. Examples of pollutants include organic compounds, such as halogenated organic compounds, pesticides and volatile organic compounds. In other examples, contaminants include bacteria and viruses, mold, fungi, mildew, organic matter, inorganic matter, microorganisms, carbon particles, metal mists, colorful mists, pesticides, ink mists or acid mists.

A fibrous structure is a woven product or fabric, or other material having the structure of individual fibers that are intertwined in an irregular manner. It is preferable that the fibrous structure is obtained by wet molding, but it can also be obtained by other methods well known in the art, including air molding, melt aerodynamic method, fiber forming method with ejection by high-speed air flow and carding. The fibrous structure includes alumina nanofibers mixed with and attached to second fibers as described above, and further including a variety of small, ultrafine, or nanoscale particles (described in more detail below) located on alumina nanofibers. The second fibers are arranged in a matrix to create asymmetric pores. As described above, a fine powder of aluminum metal interacts with the second fibers to form a fibrous structure. The reaction is carried out by adding ammonia to a mixture of aluminum and second fibers. The mixture is heated to the boiling point of water. Small, ultrafine or nanoparticles are added to the mixture either before the aluminum interacts with water, or during the reaction with boiling water, or after the mixture is cooled to room temperature. The resulting fibrous material (composition) is converted into a fibrous structure by sucking moisture from the grid side of the grid-shaped, as is done when casting a sheet of paper manually or on a paper machine, by methods that are well known for forming non-woven material using wet molding.

A lot of small, ultrafine or nanoparticles are placed on an alumina nanofiber. In the examples, the plurality of particles is a chemisorbent, a high surface area adsorbent, or a catalyst that converts a contaminant into a less hazardous compound. Examples of sorbents include activated carbon; silicon dioxide, silicates, aluminosilicates, titanium silicate, lead adsorbent and silica gel; zeolites; activated alumina; metal and metal oxides, including titanium dioxide; catalysts such as noble metals and transition metal catalysts including platinum, palladium, silver and silver oxide, iridium, rhodium and gold, and manganese dioxide-activated copper; bone coal; calcium hydroxyapatite; magnesium oxide; perlite; talc; polymer particles; clay; ion exchange resins; ceramics and their combinations.

In another example, the plurality of small, ultrafine or nanoparticles is RNA, a micro- or nanoscale polymer, a biologically active macromolecule, such as DNA, a functionalized macromolecule, or microencapsulants of substances that regulate the release of material contained within, such as microencapsulated dyes, drugs that can be released from a non-woven wound dressing, drugs that are able to evaporate in the flow of a dosage form for inhalation or a medicine that Some are capable of neutralizing toxic substances, such as chemical warfare agents.

In another example, the plurality of ultrafine or nanoparticles is activated carbon. The inventive fibrous structure, including powdered activated carbon, provides faster adsorption of pollutants than the material filled with commercial activated carbon. Examples of the inventive fibrous structure, including powdered activated carbon, can be used to protect military and civilian personnel from the effects of biological and chemical attacks, which are carried out in the form of an aerosol or through pollution of water resources.

In the example, the fibrous structure is used for medical purposes, for example, as a wound dressing or inhaler.

In another embodiment, the claimed invention is a method for producing a fibrous structure. The production method includes the steps of forming an alumina nanofiber in the presence of a plurality of second fibers. The second fibers are arranged to form a plurality of asymmetric pores. For application to nanofibers, a lot of small, ultrafine or nanosized particles are added to the mixture. In the example, water is removed from the mixture. In an example, the fibrous structure is formed into a single homogeneous layer. In another example, the fibrous structure is formed into more than one layer. In yet another example, the fibrous structure is corrugated.

In use, a stream of liquid or gas is passed through the fibrous structure, and contaminants are removed from it as a result of the retention of pollutants in the fibrous structure. Examples of the use of the inventive fibrous structure include, but are not limited to, the purification of drinking water or supplied air. Specific examples include the use of a fibrous structure in an indoor air filtration system, in respirators, in automobile air filters, in a room with a particularly clean atmosphere, in an operating room and in industrial installations, for example, to remove paint or other particulate matter contained in industrial fogs . In addition, the inventive fibrous structure can be used to remove biological warfare agents, such as anthrax or smallpox viruses, toxic substances, such as nerve gas, or radioactive substances, such as those from drinking water or air supply systems. can be delivered with a "radiation dirty" bomb. The ability to remove nuclear, biological and chemical substances (NBC) is necessary in personal respirators and protective structures, and in NFC protective suits that make it possible to protect a person from the action of these substances.

In another example of use, a layer of a composite of nano alumina and coarse fiber is placed in a stream immediately behind the inventive fibrous structure to trap any particles or contaminants that have slipped through the fibrous structure during use.

EXAMPLES OF THE PRESENT INVENTION

Examples - Filtering material for air purification

The following examples illustrate several embodiments of the present invention. These examples should not be construed as limiting. All percentages are mass percent. Calculations for determining pore size are provided in the section following the examples.

EXAMPLE 1

The purpose of the experiments described below was to develop a material of aluminum nanooxide having a pressure drop almost the same as that of the HEPA material, and the filtration efficiency is much higher than that of HEPA. The aim of the experiments was also to compare the characteristics of the filtering material of nano alumina for water adsorption with the same characteristic for the known filtering material HEPA (hereinafter, the "Donaldson HEPA filter") in order to optimize air filtration based on data on water adsorption.

Twenty-four suspensions of mixtures of nano alumina on microglass were obtained by reacting a powder of alumina with a diameter of 5 μm (Valimet Corp, # H-S) in water at 100 ° C in the presence of mulched wool of borosilicate glass fiber of various lengths (Lauscha). A nonwoven fibrous material containing aluminum nanooxide was formed on a 1 × 1 foot sheet casting mold and strengthened with 17-23% bicomponent fibers (Invista T104, diameter 20 μm, length 1/2 inch), which served as a binder. About 2% by weight of a binder grade Rhoplex in liquid form was also added. Sheets were labeled AF1-AF24.

The filters were tested as a single layer in an air stream having a flow rate in the range of 5.6 to about 23 m / min. The surface area available for filtration was about 8.2 cm ² . The filters were compared with a NanoCeram® water filter and a Donaldson HEPA filter in order to compare the filter characteristics of the invention for air or nano alumina gas with a water filter and a traditional HEPA filter.

Table 1 shows the composition, porosity, pressure drop and average pore size for each manually cast sheet and for NanoCeram and HEPA materials. 13 also shows the pore size and pressure drop for several filters of nano alumina that were tested. Each filter material shown in table 1 in FIG. 13 was tested as a single layer material. However, in use, performance can be improved by forming a structure containing more than one layer.

As shown in Table 1, the AF1-AF12 filters consisted of alumina nanofibers mixed with microglass with one average diameter of about 0.6 microns, or about 1.5 microns, or about 2.5 microns. AF13-AF24 filters consisted of alumina nanofibers mixed with the following combination of large and small micro-glass fibers: about 0.6 microns + about 1.5 microns; about 0.6 microns + about 2.5 microns; or about 1.5 microns + about 2.5 microns. The fiber content of each size included in this filter material of nano alumina is shown in table 1.

The relationship between the diameter of the microglass and the porosity of the material

From the data of table 1 it is seen that the material consisting of small diameter microglass fibers also has lower porosity and small pore size. These dependencies are further illustrated in FIG. 13. For example, a material consisting of 0.6 μm microglass fibers had a porosity of about 90% and a pore size in the range of 4.2 to 10 μm. A material consisting of 1.5 μm microglass fibers had a porosity of about 92.3% and a pore size in the range of 16 to 21 μm. And finally, a material consisting of 2.5 μm microglass fibers had a porosity of about 95.3% and a pore size in the range of 35 to 38 μm.

The data of Table 1 and FIG. 13 also show that the material having the largest pore size or the largest porosity also had the smallest pressure drops. For example, a material having a porosity of about 95% had a pressure drop of from about 3.4 to about 4.3 mm H ₂ O compared with a pressure drop of from about 125 to about 204 mm H ₂ O for a porosity of about 90%.

In the examples in which the filter material consisted of a combination of large and small fibers, the pore size did not increase as sharply as happened in the presence of only large fibers. See, for example, table 1 and FIG. 13. For example, 2.5 microns fibers combined with 1.5 microns fibers have a pore size in the range of 22-28 microns and a porosity of about 94%, with a corresponding pressure drop of about 5.7 to about 9.2 mm H ₂ O.

It should be noted that most AF1-AF24 samples had a pore size that was larger than the pore size in a Donaldson HEPA filter. For example, AF6 had a pore size that was more than six times larger than the pore size of a Donaldson HEPA filter.

Airflow Filtration Characteristics

Filters from the set of test filters AF1-AF24 were separated based on their characteristics in the air flow. Data for filters having a pressure drop of less than 10 mm H ₂ O at a flow rate of 3.2 m / min are shown in FIG. The solid line corresponds to a flow rate of 3.2 m / min. The results show that there are several variations in the compositions of the claimed material from alumina nanofibres that have a lower pressure drop than HEPA filters. These results are believed to be due to the larger pore size of the new filter media.

Evaluation of particulate filtration when tested with monodisperse latex

Typically, hydrocarbon-based aerosols such as DOP (dioctyl phthalate) are used to evaluate the air filter material for modeling liquid aerosols, and aerosols of sodium chloride (NaCl) or potassium chloride (KCl) are used to model particulate matter. The inventors compared the adsorption of ultrafine monodisperse latex spheres in water with HEPA filters and then based on test data for DOP and NaCl tried to establish the corresponding dependence. In particular, AF3 air filters (average pore size 16 microns, see table 1), AF6 (average pore size 38 microns, see table 1) and a Donaldson HEPA filter having a diameter of about 25 mm and an effective surface area of about 3.7 cm ³ was exposed to a stream of pure (RO) water containing 1 μm latex spheres at a constant flow rate of about 0.1 m / min. Although table 1 shows the filter material as a single layer, in this experiment sets of one to four layers were used to optimize the characteristics of the filter material in air and water purification applications. The turbidity of the incoming and outgoing water (in NTU units or units of nephelometric turbidity) was measured using a LaMotte Model 2020 nephelometer.

Figure 2 shows a graphical dependence of the turbidity of the stream exiting the filters consisting of aluminum nanooxide and microglass fibers, in comparison with the traditional HEPA filter. As can be seen, the filters of the invention, including nano alumina and fiberglass, were characterized by virtually undetectable turbidity in the effluent compared to the HEPA filter.

The results of this experiment were unexpected since the filters of the invention retained particles of 0.2 μm in size, even if the filters AF3 and AF16 had an average pore size of about 16 and 38 μm, respectively. It was expected that filters having such a large average pore size would not have to trap particles that were much smaller in size. Also surprising was the very low particle retention of the HEPA filter in an aqueous medium, which indicated that the HEPA filters are characterized by significantly lower particle retention in water than in air, and therefore behave differently in these two environments.

It was not found that there is a correlation between the data on the adsorption of water and the characteristic of air purification, and therefore, in subsequent experiments, test data for the air filter were obtained.

EXAMPLES 2-10

In Examples 2-10, nano alumina filter media labeled AF3, AF6, AF11, and AF16 were used to further characterize the nano alumina filter media of the invention compared to a Donaldson HEPA filter. As indicated in Table 1, AF3 consisted of 1.5 μm microglass fibers, AF6 and AF11 consisted of 2.5 μm microglass fibers, and AF16 consisted of a combination of 1.5 and 2.5 μm microglass.

EXAMPLE 2

The initial permeability of the particles of DOP and NaCl

Filters AF3 (average pore size 16 μm), AF6 (average pore size 38 μm), AF11 (average pore size 37 μm) and AF16 (average pore size 28 μm) prepared in Example 1, and the HEPA filter were sent to Nelson Laboratories located in Salt Lake City, Utah, USA, for testing with a DOP aerosol and a neutralized monodisperse NaCl aerosol. The concentration during the test was 1.5 · 10 ⁶ particles / cm ³ at a flow rate of 32 l / min through filters with an area of 100 cm ² . Aerosols had an average particle size of the order of 0.3 μm, which was considered the most penetrating size. Test samples were prepared in the form of 10 × 10 cm squares or discs with a diameter of about 4-5 inches. Three layers or three-layer flat sheets were fixed in a test device and subjected to an air stream at a speed of 32 l / min. The data are presented in table 2.

table 2 The initial permeability of the particles of DOP and NaCl Sample # layers DOP / NaCl Initial airflow resistance (mm H ₂ O) Permeability of particles,% HEPA one DOF 32.8 0.02 NaCl 32.8 0,025 AF16 3 DOF 29.1 0.513 NaCl 32.1 0.323 AF6 four DOF 23,4 1.27 NaCl 23.6 0.755 AF11 four DOF 19.5 2.72 NaCl 19,4 1,60 AF3 one DOF 21,2 4.12 NaCl 21.3 2.61

The AF16 filter had the lowest initial permeability of NaCl and DOP aerosols, although even this permeability was not comparable with that of the HEPA filter. This sample consists of a mixture of microglasses of 1.5 and 2.5 microns in size and contains only 7.7% aluminum nanooxide. It has a pore size of about 28 microns. The results show that many of the nano alumina compositions had a permeability higher than that of HEPA.

EXAMPLE 3

Determination of aerosol capacity NaCl

Filters AF3, AF6, AF11, AF16 and the HEPA filter (test area 100 cm ² ) were each subjected to NaCl aerosols at a flow rate of 32 liters / min for approximately 3 hours. About 0.0067 mg / min / cm ² NaCl was supplied to each filter, which is equivalent to about 40 mg / hour. As described above, usually three layers of AF16 (1.2 mm each, a total of 3.6 mm) were necessary to achieve the same pressure drop as for HEPA, therefore, for comparison with HEPA, the test was carried out with three layers.

Figure 3 shows a graphical dependence of permeability for each filter tested with NaCl aerosols on time. As shown, the AF16 filter had the lowest initial NaCl aerosol permeability, but it was still significantly higher than for HEPA. AF16 had the lowest permeability and was therefore used for further research.

Capacity

Figure 4 shows a graphical dependence of the air resistance on the filters from time to time. The capacity (or filter life) in this example is defined as the time (in minutes) required to achieve a pressure drop (ΔP) of the order of 50 mmH ₂ O. As shown in FIG. 4, all the tested nano alumina filters of the invention had a capacity , which was at least ten times larger than the capacity of the HEPA filter. AF6 and AF11 filters had capacities that exceeded the HEPA capacity by about 30 times. This data is important because the “service life” of the filter is usually determined according to the selected maximum pressure drop across the filter. The pressure build-up on the filter determines the life at a given level for a given application or design. Since pressure build-up is the result of a load, for systems with equal efficiency, a longer service life is usually directly related to a higher capacity. Efficiency is the tendency of a material to retain rather than let particles pass. Generally, the more effective the filter material when removing particles from the gas stream, the more quickly in most cases the filter material will reach a pressure difference that defines the “service life”, assuming other variables are kept constant.

A filter having an increased capacity has a significant advantage since it reduces the cost of frequent filter replacement. In addition, many filters, including those that trap bacteria and viruses or nuclear materials, must be disposed of as hazardous waste. Therefore, reducing the frequency with which hazardous waste filters must be replaced and disposed of is an additional economic benefit.

Table 3 presents the test results with NaCl aerosol at an air flow rate of 3.2 m / min for the filters disclosed in U.S. Patent Document. Patent No. 6872431 to Kohlbaugh, and fibers of the invention, including aluminum nanooxide and microglass, for 0.3 μm particles at a "pre-HEPA" level, where "pre-HEPA" is defined as material efficiency, ranging from about 98.9% to 99 , 6%. Table 3 also presents the test results of one of the filters of the invention (one filter layer AF16) for the most penetrating particles of neutralized KCl with a size of 0.33-0.40 microns at a flow rate of about 4.6 m / min.

Table 3 Aerosol permeability of NaCl (0.3 μm) through test samples at "pre-HEPA" ^b Material The initial permeability of the particles,% Number of layers The effectiveness of one layer,% Thickness mm Time to reach 125 mm H ₂ O, min The time to reach 50 mm H ₂ O, min US 6872431 0.6 ^a 10 40 0.5 ^b <170 ^C <80 ^C US 6872431 0.4 ^d fourteen 28 0.75 ^b <230 ^C <125 ^C US 6872431 0.4 ^a 25 twenty 1.4 ^{b, c} <260 ^C <170 ^C AF6 0.76 four 80 ^f 1.8 320 ^f 160 AF16 1.19 one 98.9 ^g 1,2 170 ^f 100 ^f

Notes: (a) this is an estimated value based on the equations given in U.S. Patent Document. Patent No. 6872431 on pages 23-24; (b) these are estimated values based on data provided in U.S. Patent Document. Patent No. 6872431 on page 35, lines 1-10; (c) these are estimated values based on data provided in U.S. Patent Document. Patent No. 6872431 on page 43; (d) this is an estimated value based on data provided in U.S. Patent Document. Patent No. 6872431 on page 39; (e) the estimated thickness exceeds the limit for a device made of filter material (see Claim 14 of Patent Document U.S. Patent No. 6872431); (f) these are estimated values; (g) this filter was tested with the most penetrating neutralized KCl particles with a size of 0.33-0.40 μm at a flow velocity of about 4.6 m / min.

The results shown in table 3 indicate that at the level of "pre-HEPA":

1. The AF6 material, which can be corrugated, has a higher capacity until a pressure drop of about 125 mm H ₂ O and about 50 mm H ₂ O is achieved compared to the material disclosed in US Patent No. 6872431, including either 10, or 14, or 25 layers. The expected life at 125 and 50 mm H ₂ O is increased by about 40%, 28% and 20%, respectively.

2. One layer of AF16 material has the expected life and removal efficiency of the most penetrating particles (KCl, 0.33-0.4 μm) that exceed these figures for the filters disclosed in U.S. Patent Document. Patent No. 6872431, of 10 and 14 layers of composites.

These data are important because they show that the fibrous material of nano alumina has an increased expected life compared to the filter of the patent document U.S. Patent No. 6872431, since their particle removal efficiency exceeds the particle removal efficiency for the filter of patent document U.S. Patent No. 6872431. Thus, the inventive filters of nano alumina are not only more economical, but they also work better. In addition, it is much cheaper to produce a single-layer material than a material with 10-14 different layers, and in the latter case, the material may have a tendency to delamination.

Table 4 shows the results of aerosol NaCl tests at an air flow rate of 3.2 m / min for the filters disclosed in U.S. Patent Document. Patent No. 6872431, and fibers of the invention, including aluminum nanooxide and microglass, to remove particles of 0.3 microns in size at the level of HEPA.

Table 4 Test results with NaCl aerosol at HEPA level Material Effective
composite nost% Number of layers The effectiveness of one layer,% Thickness mm Time to reach 125 mm H ₂ O, min The time to reach 50 mm H ₂ O, min US 6872431 99,97 ^a 16 40 0.89 ^b <170 ^C <80 ^C US 6872431 99,97 ^a 25 28 1.4 ^b <230 ^C <125 ^C AF6 99.97 ^d 5 80 ^d 1.8 300C ^d 140 ^d AF11 99.976 ^b 6 75 ^d 2.5 310 ^d 120 ^d Donaldson hepa 99,975 one 99,975 0.2 24 3,5

Notes: (a) these are estimated values based on the equations given in U.S. Patent Document. Patent No. 6872431 on pages 23-24; (b) these are estimated values based on data provided in U.S. Patent Document. Patent No. 6872431 on page 35, lines 1-10 (it should be noted that the estimated thickness exceeds the limit for the filter material structure for claim 14 of U.S. Patent No. 6872431); (c) this is an estimated value based on the data disclosed in U.S. Patent Document. Patent No. 6872431 on page 39, lines 39-45; (d) This is an estimated value.

The data shown in table 4 indicate that the materials AF6 and AF11 have large capacitance values to achieve a differential pressure of 125 or 50 mm H ₂ About in comparison with the material disclosed in patent document US Patent No. 6872431, which has 16 or 25 layers. The material of the invention increases the expected filter life by at least 80% to a final pressure of 125 mmH ₂ O compared with the material of US Patent No. 6872431, although the material of patent document US Patent No. 6872431, having 25 layers, has a comparable expected life in the event of a pressure drop of 50 mm H ₂ O.

EXAMPLE 4

Preconditioning

The purpose of this example was to prevent the initial slip through the HEPA protocol. It was suggested that the largest pores in the filter material (which contains pores with a wide range of sizes due to the asymmetric arrangement of the fibers) were responsible for the initial breakthrough. In addition, it was suggested that the introduction of a foreign particle into the filter in order to condition the filter before use will lead to its entry into the largest pores, blocking them and, as a result, reduce this slip and increase the efficiency of the filter.

In order to verify this assumption, the filters were preloaded with a conditioning agent to clog the pores before use. Sample AF16 (25 mm diameter filter) was used in this test. Monodispersed latex spheres (from Duke Scientific) were used to condition the filters, since these spheres are stable in air and are not affected by humidity in the air stream. The experiments were carried out with latex spheres of diameters of 0.2, 0.5 or 1 μm. The spheres were loaded with a filter, and air resistance was measured.

Airflow resistance was measured as described above. Preloading with 0.2 μm spheres had virtually no effect on the pressure drop across the filters of the invention (data not shown), and after a few preloads, the turbidity of the effluent was measured.

Figure 5 shows a graphical dependence of air velocity and pressure change after pre-loading the filters of the invention with latex spheres of 0.5 or 1 μm in size. During pre-loading, it was noted that the turbidity of the effluent was below the detection limit of 0.01 NTU, which meant the quantitative adsorption of these larger particles by filter material. The data suggest that latex spheres 0.5 and 1 μm in size are suitable for preconditioning filters with spheres.

In conclusion, the results of example 4 show that:

1. Foreign particles, such as monodisperse particles, can be used to condition the filter material of nano alumina.

2. Turbidity measurement during preload is an effective way to monitor and control the preload process.

3. Samples can be loaded with latex balls of 0.5 and 1 μm in size, which affects the pressure drop (ΔP) that occurs when testing with NaCl aerosol.

4. The latex particle size of 0.2 μm is too small to achieve the desired ΔP.

As an alternative to expensive latex particles, less expensive and preferably submicron particles can be used to precondition the filters, including, for example, ultrafine granular carbon, colloidal silicon dioxide agglomerates (Cab-O-Sil) or metal oxides.

EXAMPLE 5

Testing NaCl Permeability and Capacity of Preloaded AF16 Samples

Test samples were prepared by preloading latex spheres with a size of 0.5 μm on one surface of the filter, consisting of 3 layers of material AF16. The material was prepared in the form of round disks with an area of 175 cm ² . Samples (test area 100 cm ² ) were subjected (at Nelson Laboratories) to NaCl aerosol at a flow rate of 32 liters / min for about 3 hours each. The approximate mass of NaCl that was delivered to the filter was 0.0067 mg / min / cm ² , or 40 mg / hour, or 0.5% / hour of the weight of the exposed filter. At a flow rate of 32 liters / min, the linear velocity was 3.2 m / min. The filter thickness of the three AF16 layers was about 0.36 cm, resulting in a calculated residence time of about 0.07 s.

Figure 6 shows a graphical dependence of air resistance for filters of nano alumina, pre-conditioned latex spheres, during tests with NaCl. As can be seen, during the 3 hours of testing, the air resistance for all tested samples of nano alumina was much less than for HEPA. In the case of the HEPA filter, ΔP reached a value of 50 mmH ₂ O after about 4 minutes, while for nano alumina samples it took about 40 minutes to achieve the same ΔP (one filter made of nano alumina, which contained 9 wt.% Latex, reached ΔP 50 mm H ₂ O after approximately 30 minutes). This increase in filter life, which was 7-10 times longer than for HEPA, is an advantage in applications that use highly efficient filters, including filters for hospitals, for military collective protective equipment, for local safety, for automobiles and respirators.

Figure 7 shows a graphical dependence of NaCl permeability for filters of nano alumina, pre-conditioned using latex balls. Although the initial permeability did not decrease below 0.03%, particle capture increased with constant particle loading of NaCl. All preconditioned AF 16 samples had a lower NaCl permeability than the permeability of the untreated AF 16 sample. There is a tendency towards improved performance with increased preloading with 0.5 μm latex beads, at the lowest permeability value of 0.047% for 9 wt. .% latex compared with 0.03% permeability, which is determined by HEPA.

EXAMPLE 6

The filter material was tested for trapping NaCl aerosol in the laboratories of Nelson Laboratories, as in example 2. Figure 8 shows a graphical dependence of the permeability of NaCl aerosol of 0.3 μm through the test material. In this example, the following samples were compared: HEPA; one AF16 layer without pre-loading, which was used as a pre-filter before the HEPA filter; and three layers of AF16 preconditioned with latex particles. As you can see, only the HEPA filter could not be classified by efficiency as ULPA. In contrast, the AF16 preconditioned filter had an initial and long-term recovery of the order of> 99.99%, which is why it was qualified as an ULPA filter by its efficiency. In addition, as shown in FIG. 8, the addition of one AF16 layer (not preconditioned) as a pre-filter to the HEPA filter also led to ULPA qualification. These data show that the inventive nano alumina filter media has a capture that exceeds that of traditional HEPA filters, such as a Donaldson HEPA filter, and that the use of nano alumina as a pre-filter increases the qualification of HEPA to ULPA qualification.

Figure 9 shows a graphical dependence of the air resistance for the tested filters during the test for capacity by NaCl aerosol for the samples described above. Adding one AF16 layer that was not preconditioned extended the life of the HEPA filter by about 700% to achieve ΔP 50 mm, which could lead to significant savings if applied in practice.

Thus, the inventive filters are more effective at capturing particles and have a longer expected life than traditional HEPA filters, and therefore, these inventive filter materials of nano alumina are more cost-effective.

EXAMPLE 7

Samples of AF16 were tested at LMS Technologies, Inc. (Edina, MN) in accordance with Method 319 of the United States Environmental Protection Agency (EPA Method 319 regulations), which relates to the measurement of filter systems for trapping overspray paint in the aerospace industry. During finishing operations in the US industry, 30% of the spray paint, which is 90 million gallons, is sprayed excessively, most of which is dispersed in the atmosphere.

One layer of AF 16 material was tested at a flow rate of 15 ft / min. The initial pressure drop was 22 mm H ₂ O. Figure 10 shows a graphical dependence of the capture or expressed as a percentage of the efficiency of the test filter on the particle size. The same data are presented in table 5.

The filter was also compared with a commercial sub-HEPA filter (Trinitex K903-70, Ahlstrom). FIG. 14 compares the differential pressure across the Trinitex filter with the differential pressure across the AF16 filter. It is shown that the pressure drop across the two filters is almost the same. Importantly, AF16 capture was much better than EPA specification, as well as Ahlstrom material, for all particle sizes in the comparison intervals. The data show that the new material can significantly improve the performance of sub-HEPA material without the need for pre-conditioning.

Table 5 KCl aerosol capture based on particle size Particle Size Interval (μm) Initial capture with a single layer of filter material of nano alumina AF16 (%) EPA 319 Specification Ahlstrom trinitex 0.33-0.40 98,923 52% 0.40-0.50 99,365 > 75% 59% 0.50-0.60 99,743 63% 0.60-0.80 99,989 > 85% 68% 0.80-1.00 99,955 74% 1.00-1.50 99,983 90% 1,50-2,00 99,995 > 95% 95%

EXAMPLE 8

At the same time, the patent application under consideration is devoted to the use of silver to control the growth of bacteria. Therefore, an experiment was conducted here to incorporate silver into the material for air filtration. Three aluminum nanooxide sheets were prepared manually from aluminum powder, as described for sample HF0404 in Example 1, except that silver nitrate (0.1%, 0.3%, and 1% by weight, based on silver by weight) was added to the suspension dry suspension). Samples (25 mm in diameter) were fixed in the filter holder, and 10 ml of a suspension containing 8 × 10 ⁷ CFU / ml of Klebsiella terrigena bacteria in a buffered aqueous solution was loaded. Bacteria eluted from the filters in the opposite direction using a 3 ml solution containing 3% beef extract and 0.35% glycine solution, at pH 7.5 immediately after loading and then after 1, 5 and 18 hours of exposure.

Figure 11 shows a graphical dependence of the antimicrobial effect of the introduction of silver ions on nanofibres of aluminum oxide on the exposure time for the filter. As shown, silver impregnated nano alumina filters control the growth of bacteria, while control improves with increasing silver nitrate content.

Tests also showed that 1% silver had no tangible effect on the filtration of the MS2 virus, thereby demonstrating that the viral effectiveness of the filter material did not change after adsorption of 1% silver.

These results show that the addition of silver nitrate to the filter minimizes any secondary ablation of bacteria or virus from the filter, since it acts as an antimicrobial agent. The yield of silver from the filters that were impregnated with it was about 30 μg / L, well below the 100 μg / L required by EPA for drinking water. After use, the filter can be disposed of as household waste rather than hazardous waste requiring expensive processing.

EXAMPLE 9

Testing samples of material with aerosolized E. coli bacteria (E. Coil)

The setup, originally developed by Henderson [1], was assembled and used in a test with E. coli bacteria. In the setup shown in FIG. 12, 5 ml of a suspension of E. coli 1.4 · 10 ⁹ CFU / ml in a buffer solution was sprayed using a DeVilbiss PulmoMate Nebulizer aerosol apparatus (Model SR4650D). The second aerosol apparatus worked with an equal amount of buffer solution. The generated aerosols were injected into a tube with a diameter of 5 cm and a length of 90 cm. The relative humidity was adjusted by mixing the air, which was passed through the humidification and drying sections of the air conditioning unit before being fed into the spray tube. Relative humidity and air temperature near the end of the tube were measured using a moisture meter. Approximately 1/3 of the flow from the outlet of the aerosol pipe was passed through the AG1-30 impinger. The remaining stream was passed through a system of pipes with an internal diameter of 12 mm and then combined with air leaving the impinger. Air flow was passed through a HEPA filter (Whatman, PolyVent-1000 Cat # 6713-1075).

The total flow was 38 liters of air per minute. Two aerosol devices produced a flow of 12 l / min (6 l / min each), and 26 l / min of air flow was supplied using an air compressor. The air flow through the impinger was 12 l / min.

The filter efficiency was calculated as:

where the concentration of E. coli upstream of the filter was determined before entering the filter with an air stream containing E. Coli, and the concentration of E. coli downstream of the filter was determined after filtering the air stream containing E. Coli at approximately 100% relative humidity.

In the first experiment, three layers of filter material AF16 were installed in a filter holder with a diameter of 90 mm (without preconditioning with particles). In a second experiment, one layer of Donaldson HEPA was installed in the same filter holder. As shown in Table 6, the AF16 filter media showed bacterial capture, which was approximately 50 times greater than that of the HEPA filter.

Table 6 The percentage efficiency of the filter made of aluminum nanooxide against aerosolized bacteria of E. coli (E. Coli) (Conditions - 32 liters per minute, relative humidity 100%, temperature 23.9 ° C) Filter material Thickness, mm, (number of layers × thickness) The average pore size, * microns Filter / No filter The number of E. coli bacteria identified in AGI-30 buffer solution, CFU The capture efficiency of E. coli,% AF16 3.6 28 Filter <1 > 99,9998 (= 3 × 1.2) Without a filter 5.910 ⁵ AF6 7.2 38 Filter <4 > 99,9992 (= 4 × 1.8) Without a filter 5.210 ⁵ AF3 0.9 16 Filter <4 > 99,9992 (= 1 × 0.9) Without a filter 5.210 ⁵ AF11 1.3 37 Filter four 99,994 (= 1 × 1.3) Without a filter 6.7 · 10 ⁴ Donaldson HEPA 0.4 6 Filter 40 99,992 (= 1 × 0.4) Without a filter 5 · 10 ⁵ * Data from table 1

Each AF sample has a pore size that is significantly larger than the pore size of a conventional HEPA air filter. It is known that when filtering, the larger pore size of the material is less prone to clogging. This clogging resistance can also be transferred to the ability of the filters of the invention to be less resistant to flooding by water drops.

The demonstrated ability of alumina nanofibers to remove high concentrations of bacteria was an unexpected result and is an important advantage, especially when the filter is used for collective protection in a hospital where AIDS patients are treated, or for protection during the use of biological weapons. Such a material would also be beneficial in improving the capture of bacteria using a respiratory filter. An additional advantage is the lower pressure drop for the filter of the invention compared to the HEPA filter, especially as the filter is loaded. And finally, another advantage is that the pore size of the filter material of aluminum nanooxide is quite large, which gives a significantly more porous filter that allows you to capture much more water, as a result of which it can be exposed to prolonged loading with drops of water or fogs.

EXAMPLE 10

Two experiments were performed as described in Example 9, except that the aerosol contained MS2 virus (25 nm in size) and the test was carried out at two different relative humidity values. In this case, the test samples had a small pore size (~ 2 μm) and a thickness of 0.4 mm.

Table 7 shows that the filter had a high degree of purification for the aerosolized virus. These results are important because viruses, which are usually one or two orders of magnitude smaller than bacteria, are very difficult to capture due to the thickness of the filter material. The capture of the virus using HEPA is also problematic, since many pathogenic viruses are smaller than 0.1 μm, which is significantly smaller than test particles of 0.3 μm in size used to establish the characteristics of HEPA. Effective filtration of a monodisperse virus would be very ineffective. If the virus is enveloped in an aqueous aerosol, then HEPA filters, which are usually hydrophobic, lose their effectiveness as water accumulates in the filter. The inventive filter material of nano alumina provides higher efficiency and capacity and therefore could be used in filter gas masks and collective protection systems, for example in hospitals, and for protection against biological weapons.

Example 11. Hand-formed sheets of "lyosel / NC" and "cellulose / NC"

Eighty grams of purified fiber lyosel (20% solids) from Fiber Innovation Technology was dispersed in 0.75 L of purified reverse osmosis water using a household blender (12-speed Osterizer blender) in the “ice crushing” mode for 2 minutes. The amount of aluminum powder added to the mixture (1 g) was such that after the reaction, the solids consisted of 12 parts AlOOH and 88 parts lyocell fibers (sample AF34 in table 16a). Similarly, the amounts of aluminum powder added to the mixture (2 g) and 1 g of dry colloidal silica powders before the aluminum-water reactions were such that after the reaction, the solids consisted of 20 parts AlOOH, 5% colloidal silicon dioxide and 7, 5 parts of lyocell fibers (sample AF35 in table 8). As a control, manually formed sheets of pure lyosel (AF33), cellulose (AF28) and a mixture of 72% cellulose and 28% AlOOH (AF32) were prepared.

Table 8 Composition and properties of manually molded sheets containing lyocell / cellulose and MS2 capture results Sample # Structure The density of sheets, g / m ² Breaking length, m Porosity, in shares The average pore size, microns Number of layers Capture ^a MS2,% AF28 100% Cellulose 166 460 ± 28 0.82 8 3 0% AF32 72% Cellulose + 28% NC ^b 229 <10 0.89 13 3 twenty% AF33 100% Liocel 166 1022 ± 136 0.50 1.8 one 0% 2 10% 3 twenty% AF34 88% L + 12% NC ^b 188 1013 ± 119 0.50 2.0 one 99,9994 2 > 99,9997 3 > 99,9997 AF35 75% Liocel + 5% Cab-O-Sil + 20% NC ^b 183 906 ± 44 0.50 1/8 one > 99,9997 2 > 99,9997 3 > 99,9997 Notes: a) for the study, a solution of MS2 2.0 · 10 ⁷ PFU / ml was prepared. Aliquots of 10 ml of MS2 suspension were filtered through 25 mm diameter disks at a flow rate of 40 ml / min; b) NanoCeram.

Disks (25 mm) were excised from the samples described above and tested with MS2 viruses at an initial concentration of 2.0 · 10 ⁷ PFU / ml and a flow rate of 40 ml / min. Table 8 shows that manually formed sheets made from pure cellulose, microfibrillated cellulose (lyocell) or a mixture of 72% cellulose / 28% NC did not have efficiency or had a very low efficiency in removing MS2 virus. Mixtures of 88% lyocell / 12% NC and 75% lyocell / 5% Cab-O-Sil / 20% NC had an efficiency even greater than one NC layer (99.5%, see table 16), thereby indicating that lyosel is an excellent fibrous carrier for nano alumina.

Examples. Fiber structure

The following examples illustrate the incorporation of fine, ultrafine or nanoscale particles into a non-woven filter structure. Examples include sorbent, catalyst, powdered activated carbon, nanosized carbon, RNA, TiO ₂ particles (50 nm) and colloidal silicon dioxide (initial particle size of about 15 nm, as the agglomeration is several hundred nanometers). In each case, the molding time is much shorter than when aluminum nanooxide is used, which makes it expedient to produce new material using wet forming methods (paper production methods).

Examples are also given in which the claimed fibrous structure containing powdered activated carbon is compared with an activated carbon material manufactured in industry by comparing the leakage of soluble iodine through the corresponding material. The slip through one layer of industrial-produced material with approximately the same density occurs almost instantly, while the inventive filter material has a service life of approximately 800 times longer.

EXAMPLE 12. Starting materials

Suspensions of nano alumina on large fibers, such as microglass or lyocell, were prepared from aluminum powder. In a few words, two grams of microglass fibers (Lauscha Fiber International, borosilicate glass, grade B-06-F, diameter 0.6 μm) were dispersed in 0.75 L of the filtrate obtained from the reverse osmosis generator using a household blender ( 12-speed blender Osterizer) in the regime of "incomplete grinding" for 2 minutes. Amounts of 1.36 g and 0.61 g, respectively, of aluminum powder (Atlantic Equipment Engineers, brand AL-100, 1-5 μm) were added to the microglass so that after the reaction they would give 60 parts AlOOH / 40 parts of microglass, respectively and 40 parts AlOOH / 60 parts microglass.

Ammonium hydroxide (8 ml 36% per 750 ml mulch) was added to initiate the reaction of aluminum with water to form AlOOH and hydrogen. The mixture was heated to a boil and kept at a boiling point for 10 minutes until the color of the mixture turned white (if the added particles are black), and then cooled and neutralized to a pH of about 7 with hydrochloric acid. The result is nano alumina formed on a larger fiber (hereinafter, “NC” mixture), such as microglass or lyocell, as described in the following examples.

Then, the sorbent particles were added in the form of a dry powder or in the form of a suspension of powders (for example, TiO ₂ ) in water to a suspension of nanofibers and large fibers either before or after the aluminum-water reaction. Then the suspensions were mixed manually.

The following examples illustrate the inventive fibrous structure containing nanoscale particles, which includes amorphous colloidal silicon dioxide (average particle size (RMS) ~ 15 nm, firms Cabot Corp., Cab-O-Sil, brand M5), TiO ₂ powders with RMS ~ 50 nm, which are produced in Russia and supplied by Argonide Corp, and ribonucleic acid (RNA), the smallest size of which is approximately less than 1 nanometer. Other examples are given in which the particle is a sorbent (PAH) supplied by Calgon Carbon (WPH brand, 99% -100 mesh, 95% -200 mesh and 90% -325 mesh, RMS ~ 28 μm), and carbon nanopowders of size 30 nanometers supplied by Aldrich (Cat. # 633100).

In other examples, Arizona desert dusts, mainly consisting of silicon dioxide, were added to NC mixtures. Two different brands of Arizona desert dusts (Arizona test dusts), 0-3 μm (RMS ~ 1.13 μm) and 0-5 μm (RMS ~ 2 μm), both supplied by PT1 Powder Technology Inc., were used.

The example also shows Carulite-400 (type C) catalyst added to the NC mixture, which is copper activated with manganese dioxide powder (such as hopcalite), with a particle size of 3-8 μm, supplied by Cams Chemical Company.

The ratio of particles to a nano alumina / coarse fiber ("NC") network depends on the required performance of the material. For example, it is necessary to find a compromise between the ability of the PAH-NC composite to remove organic substances and the ability to remove pollutants in the form of particles that are affected by the selected PAH content. The PAH-NC composite, which contains a reduced amount of PAHs, increases the ability of the fibrous structure to remove bacteria, viruses and other contaminants from a liquid or gas stream, thereby allowing, for example, drinking water to be obtained, which is practically disinfected from microbes, as well as removing soluble contaminants substances, including chlorine, halogenated hydrocarbons and toxic soluble metals.

Other fibers, such as cellulose or polyester bicomponent fiber, may be added to strengthen the fibrous structure and make it more elastic.

EXAMPLE 13. The formation of fibrous materials

In this example, two grams or 1.3 grams of the particles described in Example 12 (i.e., amorphous colloidal silicon dioxide, RNA, Carulite, fine test dust, nanocarbon and PAHs and TiO ₂ ) were added to 60/40 or 40/60 NC suspensions. prepared as described in example 12, to obtain NC-suspensions containing 28 wt.% particle powders. Suspensions were mixed manually. Similarly, 5 g and 3.33 g of the above powders were added to suspensions 60/40 and 40/60 to obtain a 50 wt.% Load of particle powders. With the exception of the NC structure loaded with TiO ₂ (see below), the powder was added after the reaction started. In all examples, to evaluate the optimal time point for adding particles to the mixture, experiments were carried out by adding particles before and after the reaction began. However, when the particles include fine dust (Table 9), Carulite (Table 11), or RNA (Table 13), the particles are added after the start of the reaction in order to prevent a change in the natural properties of the particles. In the case of PAHs (Tables 14, 15), particles were added either before or after the start of the reaction.

The mixture was then diluted with purified using reverse osmosis water in a ratio of 2000: 1. An aliquot of the 500 ml suspension was poured into a holder for a vacuum filter with a diameter of 47 mm. The fibrous material was filtered through a filter disk with a diameter of 47 mm cut from Teflon fabric material (size 70 mesh), placed on the filter holder. A vacuum was created in the reservoir for collecting water using a rotary pump and the time from the beginning of the filtration stage to the moment when all the liquid passed through the moldable disk was recorded as the molding time. The finished discs were then dried in an oven, weighed after cooling and after equilibration with the laboratory air. In some cases, in order to estimate the yield of particles on a substrate from NC, the last mass was recorded, and the total mass was compared with the mass of the starting components.

EXAMPLE 14. Fibrous structures of nano TiO ₂ / nano alumina / microglass

Five (5) g _of a 50 nm TiO ₂ nanopowder was dispersed in a glass beaker filled with 1 L of purified reverse osmosis water and then mixed with an ultrasonic generator (Fisher Scientific, Model F20) for 30 minutes. After settling for 24 hours, the upper part (~ 0.6 L) of the supernatant was slowly decanted to separate suspended particles from any precipitated agglomerates.

Aliquots of the above 100 ml TiO ₂ suspension were added to 0.75 L of NanoCeram 60/40, which were formed previously in Example 12. Two control mixtures were used, one containing TiO ₂ in 0.85 L of water (for the measured mass), and the second containing microglass (in the absence of aluminum nanooxide) in 0.85 liters of water. The concentration of TiO ₂ nanopowders was determined by evaporating water and weighing the residue. Similarly, aliquots of the above 200 ml TiO ₂ suspension were added to 0.75 L of 60/40 fibrous material prior to the start of the aluminum-water reaction. Control mixtures of TiO ₂ in 0.95 L of water (for mass measurement) and a second containing microglass (in the absence of nano alumina) in 0.95 L of water. The concentration of TiO ₂ nanopowders in the control samples was also determined by evaporating water and weighing the residue.

Table 9 shows the composition of the fibrous materials, the time of their formation and the turbidity of the collected effluent.

Table 9 Molding a Nonwoven Fabric Containing Nano TiO ₂ Sample # Nano alumina ^a ,% Fiberglass ^a ,% Particles of TiO ₂ ,% Forming time, min Outflow Turbidity, NTU 628 56 38 7 ^b 0.7 ± 0.2 twenty 629 0 94 7 ^b 2.2 ± 0.6 114 643 53 35 12 ^c 1.0 ± 0.2 40 644 0 88 12 ^c 23 ± 6 132 Notes: a) the ratio of nano alumina / microglass is 60% / 40%; b) TiO ₂ powders were added to the fibrous material 60/40, which was previously formed; c) TiO ₂ powders were added before the aluminum-water reaction was initiated.

Samples 628 and 643, which included aluminum nanooxide in the mixture, had significantly shorter molding times than samples 629 and 644, which did not contain aluminum nanooxide added to the mixture. Comparison of the turbidity of the respective effluents shows that when aluminum nanooxide is present, a large amount of nanoparticle retention in the fibrous structure is observed.

Based on the measurements of the water flow given in Examples 1-10 above, the average size of the fibrous structure containing titanium dioxide was estimated to be about 3 μm. In addition, the fibrous structure is capable of containing about 7-12% of its dry weight particle, which is almost two orders of magnitude smaller than the pore size of the finished material. Without delving into the theory, however, it can be argued that the molding time is reduced due to the fact that the nanoparticles are firmly bound to the NC structure and do not constrict the flow, while in the absence of aluminum nanoxide, the nanoparticles freely form agglomerates inside the porous structure, thickening the mixture and blocking the flow.

Other nano oxides and refractory compounds, such as carbides, nitrides or nanodiamonds, could similarly be retained in such a structure. For example, pigment oxides and photosensitive nanomaterials could be incorporated into such a fibrous structure, and a fibrous structure containing nanodiamonds or tungsten nanocarbide could be used as a polishing cloth for high-precision surface treatment. The structure can serve not only to distribute and suspend the abrasive material, but it could also serve as a collector of waste generated during polishing.

EXAMPLE 15. The filtering fibrous structure of silicon dioxide / NC / microglass

Silica containing a fibrous structure (Table 10) was prepared as described in Example 13. In two samples (samples 630 and 642), colloidal silicon dioxide was added to the fibrous material. Colloidal silicon dioxide is known to form colloidal suspensions that are very difficult to filter out. It is widely used as a thickener.

In sample 630, colloidal silicon dioxide was added prior to the start of the reaction. Of the original solids equivalent to about 200 gm / m ² , only 63 g / m ^{2 was} retained on the filter. This represents approximately 90% of the added starting alumina and colloidal silicon dioxide, allowing only micro-glass fibers to be retained on the 70 mesh filter. The authors suggest that the addition of colloidal silicon dioxide at the beginning leads to its combination with aluminum nanooxide as it forms, resulting in poor adhesion or completely no adhesion of nano alumina to microglass, leading to the loss of both silicon dioxide and nano alumina , with an exit stream.

In sample 642, colloidal silicon dioxide was added after the aluminum-water reaction. In this case, the molding time was very short, and there was no loss of mass. This demonstrates a method for retaining colloidal silicon dioxide with a very high surface area (200 ± 25 m ² / g) in the fibrous structure.

On Fig shows an electron micrograph in transmitted light of this sample 642. From this and other micrographs it was estimated that nanofibres in the form of whiskers have a diameter of 2-3 nanometers and a length of several hundred nanometers. The spheres of silicon nanodioxide appear along the axis, completely enveloping the composite of aluminum nanooxide / microglass.

In sample 631, a control sample without alumina, colloidal silicon dioxide formed a colloid that clogged holes, significantly increasing the molding time to over 100 minutes.

Samples 632-636 represent material obtained by adding test dusts that are widely used in filter design, and which consist mainly of micron-sized silica. Test dust was added before the aluminum reaction. When dust was not added to the mixture, the loss of particles with an effluent was almost complete, and when dust having a size of 0.3 or 0.5 μm was added to the mixture, the loss of particles with an effluent was almost zero. In addition, the molding time was 35 and 22 times longer, respectively, for dusts of 0.3 and 0.5 μm in size without aluminum nanooxide than when it was present in the fibrous material.

The attached colloidal silicon dioxide can act as a sorbent, or it can be chemically treated using an appropriate reaction to attach organic ligands to it.

EXAMPLE 16. The catalyst

The test of sample 634 in Example 15 above was repeated in this example, except that Carulite, a copper catalyst activated with MnO ₂ , was used instead of silica. The molding time shown in table 11 shows that the addition of Carulite catalyst to the NC fibrous material results in a molding time that is part of the molding time of the fibrous material without nano alumina. The short molding time is associated with the rate of dehydration and is extremely important for the continuous production of nonwoven material by the wet molding method.

The resulting catalyst would have to be more efficient than granular forms, which would allow the oxidation of carbon monoxide or ozone in a layer of smaller thickness, since a larger surface area of the catalyst compared to the area of a large granule leads to a higher reaction rate, for example, of components in gas phase.

The catalyst could also be a noble metal, such as nano-sized platinum attached to nano alumina. The substrates of both nano alumina and microglass are stable at about 150 ° C and above, so that the NC / platinum catalyst structure is also stable. At temperatures ranging from about 150 ° C, nano-sized platinum is able to oxidize pollutants such as carbon monoxide and unburned hydrocarbons from gases, including automobile exhaust.

Table 11 NC Nonwoven Molding with Catalyst Particle Main
particle size, microns Sample # Nano alumina ^a ,% Fiberglass ^a ,% Particles Carulite, wt.% Forming time, min Carulite 400 Type C 3-8 624 43 29th 28 ^b 1.1 ± 0.4 625 0 72 28 4 ± 1 Notes: a) the ratio of MS / microglass is 60% / 40%; b) powders were added prior to the start of the aluminum-water reaction.

EXAMPLE 17. Nanocarbon

The test of sample 634 in Example 15 above was repeated in this example, except that nanocarbon particles were used instead of silica. Table 12 shows that the NC fibrous material loaded with nanocarbon has a spinning time that is part of the spinning time of the fibrous material without nano alumina. There was no difference in molding time when nanocarbon was added either before or after NC molding.

Such forms of carbon suspended in a nonwoven material would have to have sorption properties that exceed the sorption properties of HAC, and possibly also the sorption properties of PAHs.

Table 12 Nanocarbon Forming NC Particle The main particle size, microns Sample # Nano alumina ^a ,% Fiberglass ^a ,% Nanocarbon, wt.% Forming time, min Nanocarbon 0.3 645 43 29th 28 ^b 0.45 ± 0.10 646 0 72 28 2.0 ± 0.5 647 43 29th 28 ^c 0.5 ± 0.1 Notes: a) the ratio NC / microglass is 60% / 40%; b) powders were added before molding NC; c) powders were added after molding NC

EXAMPLE 18. RNA. The test of sample 634 in Example 15 above was repeated in this example, except that instead of silica, RNA (Torulo yeast ribonucleic acid supplied by Sigma, Cat # R6625) was used. As shown in table 13, the NC fibrous material loaded with RNA has a spinning time that is 8% of the spinning time of the fibrous material without nano alumina.

Table 13
Molded engineered bio-nanostructure Particle The main particle size, microns Sample # Nano oxide
aluminum ^a ,% Fiberglass
on ^a RNA, wt.% Forming time, min Rna 0.001 ^s 648 43 29th 28 ^b 0.45 ± 0.10 649 0 72 28 5.5 ± 0.5 Comments: a) the ratio NC / microglass is 60% / 40%; b) powders were added after the aluminum-water reaction; c) minimum RNA size.

This example demonstrates that alumina nanofibers can attach elementary biological particles that could be incorporated into a fibrous structure for biological action. In one example, biologically active components, such as growth factors, are introduced into structures for medical use, such as non-woven wound dressings, to accelerate the healing process. In a further example, silver nanoparticles are added to these dressings to give them an antimicrobial effect. In another example, the fibrous structure is used to deliver nutrients and drugs for penetration through the epidermis. In a number of other examples, the fibrous structure could be used as a sensor when a particular nucleic acid or protein attached to a nonwoven material can interact with a specific biological or chemical reagent.

In a number of other examples, artificial macromolecular particles are also distributed and fixed on a non-woven form, including, for example, polymer particles having specific functional groups. In the examples for use as a biocatalyst, bacteria are attached. Bacteria suspended in a nonwoven fabric remain viable due to the ease of perfusion of oxygen, carbon dioxide and waste products through the material.

EXAMPLE 19. Powdered activated carbon

The test of sample 634 in Example 15 above was repeated in this example, except that instead of silica, powdered activated carbon (PAH) was used. As shown in table 12, the fibrous structure, including PAHs, has a molding time that is less than 5% of the molding time of the fibrous material without nano alumina.

Table 14 Forming PAH mixtures Particle Sample # Nano alumina,% Micro glass fiber,% Initially evaluated particles,% Forming time, min The density of the material, g / m ² Calgon 650 43 ^a 29 ^a 28 0.6 198 ^b PAH 651 0 72 28 13 200 ^b Notes: a) the ratio NC / microglass is 60% / 40%; b) the required density of the material is 200 g / m ² .

EXAMPLE 20. Fiber lyosel

Two grams of purified lyosel fibers, supplied by Fiber Innovation Technology, were dispersed in 0.75 L of reverse osmosis purified water using the blender described in Example 12 under the “ice crushing” mode for 2 minutes. The amount of aluminum powder added to the mixture (0.61 g) was such that after the reaction, the solids consisted of 40 parts of AlOOH and 60 parts of lyocell fibers. Dry PAH powders were added before the start of the aluminum-water reaction, and the suspensions were then manually mixed in a 1 L beaker, and the aluminum-water reaction was carried out as in Example 12.

Table 15 shows the composition of the fibrous material containing PAHs and the fibrous material containing PAHs without nano alumina. The formation time of a material variant with PAHs is 16% of the variant when it contains aluminum nanooxide. The turbidity of the incoming flow into PAH-NC fibrous material was 10 compared to the turbidity of the incoming flow of 360 NTU without nano alumina, apparently as a result of the rapid integration of PAHs with other fibers. The formation of macro-fibrous agglomerates in the initial solution was observed when aluminum nanooxide was present. It was noted that sedimentation was very fast when half a liter of the PAH-NC stock solution was mixed in a 750 ml beaker and settling took place in the beaker for 30-40 seconds, ultimately leading to clarification of about 80% of the supernatant volume to a turbidity of less than 10 NTU, while the PAH / lyocell mixture (without aluminum nanooxide) did not settle for several hours. It was also noted that the turbidity of the effluent in the case of PAH-NC was approximately 12 times less than in the case when aluminum nanooxide was absent due to the breakthrough of most of the activated carbon particles. Apparently, these were the smallest particles, and it is very likely that they contribute to a fast adsorption rate. The ability of NCs to aggregate with PAHs, leading to a high yield of composite formation, has been clearly demonstrated when microglass is replaced by lyosel.

Table 15 Formation of mixtures of PAHs with lyocell fibers Particle Sample # Nano alumina,% Fiber lyocell,% PAH,% Forming time, min Input Turbidity, NTU Outflow Turbidity, NTU Calgon 652 29th 43 ^a 28 0.8 ± 0.1 10 ± 2 1.1 ± 0.2 PAH 653 0 72 28 5.0 ± 1.4 360 ± 40 13 ± 2

EXAMPLE 21. Hand-formed PAH sheets

In this example, various manually formed sheets were prepared from fibrous materials, as in Example 20, except that large amounts of components were used to produce test samples with a larger area. In addition, in this example, bicomponent fiber (Invista T105) and cellulose were added to increase elasticity and strength. Cellulose was added before the aluminum-water reaction was initiated, and the bicomponent fiber was added after the fibrous material was cooled and neutralized to about pH 7. And finally, in this example, the fibrous material was diluted to 500: 1 and not to 2000: one.

Hand-formed sheets of 12 × 12 inches were prepared using a headbox with a suction of water through a mesh to form a paper-like sheet. The manually formed sheet was air dried at room temperature. In samples using a polymer fiber such as a bicomponent fiber, manually formed sheets were dried in an oven and cured at 160 ° C. for twenty minutes.

Similarly, a manually formed sheet with pure NanoCeram material without coal was obtained, designated as NC in Table 16.

Pore size was determined as described above in examples 1-10. The pore size of all test samples was larger than the pore size of the filters made of nano alumina / microglass, which led to a lower pressure drop and the ability to withstand a higher flow rate.

EXAMPLE 22

The purpose of these experiments was to measure the capture of microbes by the fibrous structure and to compare it with filters including only nano alumina / microglass. A disk with a diameter of 25 mm was cut from sample No. 617 described above in Example 21 and Table 16. Another disk with a diameter of 25 mm was cut from NC material. The disks were exposed to a solution of the Brevundimonas diminuta bacterium (supplied by ATCC, Cat. No. 11568). B. diminuta are the smallest cultivated bacteria, having the smallest size of the order of only 0.3 microns. Both types of samples were examined with an aliquot of 10 ml bacteria at a rate of 40 ml / min, collected in sterile tubes and then analyzed for B. diminuta. While PAH-NC was able to provide 99% capture (Table 17), NC without PAH was superior to this result. A decrease in PAHs from its initial level (57%) increased the capture of bacteria. Both types of filters were also tested with MS2 viruses (supplied by ATCC, Cat. No. 1S597-B1), which were 25 nanometers in size. Table 18 shows that PAH-NC is characterized by almost the same virus capture as NC.

Table 17 Trapping B. Diminuta bacteria using NC material and PAH / NC material Material Thickness mm The density of sheets, g / m ² Initial concentration, CFU ^a / ml Removing ^b B. Diminuta,% 617 ^c 1,2 269 1 · 10 ⁴ 99 NC 0.8 220 7 · 10 ⁵ 99.95 Notes: a) colony forming units (CFU); b) 10 ml aliquots were passed through 25 mm diameter disks at a rate of 40 ml / min and collected in sterile tubes; c) 57 wt.% PAHs (see table 16).

Table 18 MS2 capture using NC material and PAH / NC material Material Thickness mm The density of sheets, g / m ² Initial concentration of MS2, CFU ^a / ml Removing ^b MS2,% 616 ^e 1,2 276 6 · 10 ⁶ 99 617 ^e 1,2 269 1.810 ⁶ 99 NC 0.8 220 6 · 10 ⁵ 99.5 Notes: a) plaque forming units (PFU); b) 10 ml aliquots were passed through 25 mm diameter disks at a rate of 40 ml / min and collected in sterile tubes; c) see table 16.

EXAMPLE 23

The purpose of these experiments was to measure the effectiveness of the dynamic adsorption of dissolved pollutant from a water stream. Iodine was used as a pollutant simulator, since the activated carbon capacity is estimated by the manufacturers of GAU and PAHs by the iodine number. Iodine is also a convenient substitute for chlorine, which is specially added as a disinfectant to water flows, but it gives drinking water a bad taste and smell. Activated carbons are used to remove chlorine in drinking water filters.

In this example, solutions with an iodine concentration of 20 ppm (ppm) were passed through one layer of disks with a diameter of 25 mm from various PAH-NC fibrous materials at a flow rate of 50 ml / min. Aliquots of 2 ml were collected in cuvettes (1 cm thick). The optical densities of both the initial solution and the effluent were measured at a wavelength of 290 nm using a Genesys-10 spectrophotometer for the ultraviolet and visible regions. The method had a detection limit of about 0.3 ppm.

The data in table 19 show that the volume of the effluent reaches 0.5 ppm (above 0.5 ppm, the taste of iodine is detected by an ordinary person) and 10 ppm (50% of the content of 20 ppm in the inlet stream).

The efficiency of the PAH / NC structure to capture iodine under such dynamic conditions is compared with the efficiency of materials from three manufacturers (A, B, and C). Material (2.5 inches in diameter and 10 inches long) was cut out from industrial cartridges.

The breakthrough was almost instantaneous in the case of industrial filtering material, while the PAH-NC structure retained its iodine capacity for a long time. On Fig shows a breakdown curve for sample 617 in comparison with the material of the three manufacturers. The semi-logarithmic dependence is used for a more detailed image of the breakthrough curves, in particular for filter material produced in industry.

The data also show that the use of a single layer of material produced in industry would lead to the immediate ingress of iodine into the effluent, which would be determined by taste and smell. In contrast, the new PAH-NC structure was able to pass about 800 ml of a solution containing 20 ppm of iodine until the iodine content in the effluent reached 0.5 ppm. Such an extraordinary dynamic capacity at such a high adsorption rate compared to commercially available material (more than 800 to 1) was a surprise. Without delving into the theory of this issue, however, it can be argued that, apparently, small particles of powdered activated carbon are retained in the structure and are not washed out of it.

Table 19 shows the volume of solution purified from iodine to a concentration of 0.5 and 10 ppm. The amount of iodine adsorbed up to 10 ppm is given, along with the calculated value of the iodine capacity, comparing the mass of iodine removed under dynamic conditions with the static adsorption capacity calculated from the values of iodine numbers reported by the manufacturers. All PAH / NC samples had similar slip curves, each holding about 55% -72% of the static iodine capacity until iodine leakage was detected, while the capacity provided by the industrial material was only 3.4%. These data highlight the benefits of using extremely fine particulate matter that is held within the structure for physical adsorption or chemisorption of contaminants from a fluid stream.

Table 19 Adsorption 20 ppm I ₂ with a single layer of material Material The density of the material, g / m ² The coal content in the material,% Volume (ml) I ₂ to 0.5 ppm Volume (ml) I ₂ to 10 ppm The amount of adsorbed I ₂ to reduce by 50% its content in the input stream, mg (I ₂ ) / g of coal % of the static sorption capacity PAH / NC, # 617 269 57 850 1700 443 55 ^a PAH / NC, # 618 287 46 750 1850 533 67 ^a PAH / NC, # 619 356 44 600 1760 553 67 ^a PAH / NC, # 620 297 55 850 2110 517 65 ^a PAH / NC, # 621 322 44 850 2050 579 72 ^a Manufacturer "A" 350 50 ^b <1 ^d 10 ^d 2 ^b 0.4 ^{b, c} Manufacturer "B" 242 20-30 ^b <1 ^d 20 ^d 11-17 ^b 2.2-3.4 ^{b, s} Manufacturer "C" 237 20-30 ^b <1 ^d 5 ^d 3-4 ^b 0.6-0.9 ^{b, s} Notes: a) the iodine number for Calgon WPH PAH is> 800 mg / g. In this example, it is taken equal to 800 mg / g; b) estimated value; c) an iodine value of 500 mg / g was assumed for the estimated mass of coal for material A, B and C; d) three series of measurements reproduced within each series. To exclude any possibility of bypass due to the lack of wetting, each sample was soaked for 2 hours and then washed as usual with a stream of purified water using reverse osmosis.

EXAMPLE 24

The test samples, the same as in example 23, was repeated in this example, except that the input stream contained 500 ppm compared to 20 ppm. Two different wavelengths were used to increase the detection limit: 290 nm for outflows with a low concentration and 450 nm for higher concentrations, where the detection limit was also about 3 ppm. A higher used capacity was achieved (from 76% to 147%) (table 20), approaching and exceeding the lower value of the static limit determined using the iodine number. A higher degree of capacity utilization for higher studied concentrations can be explained using the Langmuir or Freindlich adsorption isotherms, which retell a higher capture of the sorbed substance at higher concentrations [C. Tien, Adsorption Calculations and Modeling, Butterworth-Heinemann, Boston, 2001] . Values of static capacity greater than 100% are explained by the fact that the iodine number determined by Calgon Carbon, i.e. the manufacturer, is more than 800 mg / g. In the calculation, this value was taken equal to 800 mg / g.

Table 20 Adsorption of iodine at its concentration in the inlet stream of 500 ppm using one layer of PAH material Material The density of the material, g / m ² The coal content in the material,% Volume (ml) of the solution in which 250 ppm (50%) remained after iodine adsorption The amount of adsorbed I ₂ to reduce by 50% its content in the incoming current, mg (I ₂ ) / g of coal % of the static sorption capacity PAH / NC, # 617 269 57 180 1170 147 ^a PAH / NC, # 618 287 46 94 712 89 ^a PAH / NC, # 619 356 44 95 607 76 ^a PAH / NC, # 620 297 55 103 630 79 ^a PAH / NC, # 621 322 44 150 1060 133 ³

The high adsorption capacity of PAH-NC for dissolved pollutants can also be directly attributed to the air filter, on which volatile organic molecules can adsorb using PAHs, which are introduced into the air filter.

In addition, PAH-NC material, used either in air or in water, is able to remove chlorine and bromine as quickly as it removes iodine. This filter material could be used in chemical technology in which chlorine is used as a reagent. It should be noted that the capture of chlorine in order to prevent its leakage into the atmosphere, for example through the exhaust gas, is very important, since it is detected by a person by smell when it contains about 0.3 ppm and higher and has an irritation threshold of about 0.5 parts per million. In addition, the inventive material PAH-NC is used to prevent leakage of chlorine during transportation.

EXAMPLE 25. Dirt capacity

The dirt capacity of the PAH-NC sample (sample 621) for A2 fine test dust (PTI, Inc.) was measured and compared (Table 21) with NC material. The test involved treating disks with a diameter of 25 mm with a suspension of A2 fine dust in reverse osmosis-purified water with a turbidity of 250 NTU until the pressure drop reached 40 psi. inch. In the test, the turbidity of the effluent in each case was less than the detection threshold of 0.01 NTU, thereby indicating that the release of powder into the effluent was minimal. When removing such dust, the material filled with new coal was as effective as the NC material. This was an unexpected result, as PAHs had previously been suggested to reduce the ability of the NC material to adsorb particles.

Table 21 Dirt absorbance at an injected concentration of 250 NTU ^a Material Capacity, mg / cm ³ PA C / NC # 621 118 NC 110 Notes: a) corresponds to the loading A2 of fine dust ~ 350 ppm.

CALCULATIONS

From the data shown in table 1, the air permeability B (m ² ) for the samples was determined as:

Where:

v is the flow velocity m / s for a given ΔP,

µ is the viscosity of air. For air - µ = 18.6 · 10 ^-6 Pa · s,

z is the thickness of the material,

ΔР - pressure drop across the material, Pa.

Equation 2 assumes that the flow through the filter is characterized by a viscous flow regime. In addition, in the case of gas flow measurements, two additional conditions are required [2]: (i) pore diameters greater than 1 micron; (ii) the absolute pressure at the inlet to the filter is not more than 1.1 times the absolute pressure at the outlet of the filter, that is, the overpressure at the inlet to the filter should be no more than 40 inches of H ₂ O when the overpressure the outlet stream of the filter is zero (i.e., an absolute pressure of 400 inches of H ₂ O). When these two conditions are met, equation 2 can be used to estimate permeability.

From equation [2] and the data shown in figure 1, the permeability of the filter material was determined. From the values of permeability and porosity, the average flow diameter d was determined as follows:

where ε is the porosity.

The diameters of the flow d are shown in table 1. The average pore size of the material from nano alumina varied from 4.2 to 38 microns.

From Fig. 1, as well as from similar graphical dependences for other samples, the dependence of the linear air velocity through the material on the applied pressure drop was determined, and it is shown in Table 1. From these equations, ΔР of air (in mm of water, excess) at linear velocity a flow of 3.2 m / min is compared with ΔP of air for HEPA.

Although a very detailed description has been given above, it should be borne in mind that the examples and detailed embodiments are presented for clarification and not limitation. Design changes may be made, especially with regard to shape, size and layout, but within the spirit of the invention. For specialists in this field it is obvious that such changes or modifications of the invention, or combinations of elements, options, equivalents, or improvements in it fall within the scope of the invention, which is defined by the attached claims, and that the present invention can be easily carried out in the absence of any restrictions not expressly described in this document.

Claims (29)

1. A filter for the fluid containing:
but. alumina nanofibers; and
b. second fibers mixed with alumina nanofibers, the second fibers being arranged to create asymmetric pores having an average size of about 5 to 48 microns. 2. The filter according to claim 1, in which these second fibers are a combination of large and small fibers. 3. The filter according to claim 1, wherein said second fibers are selected from the group consisting of microglass fibers, cellulose fibers, fibrillated cellulose fibers and lyocell fibers. 4. The fibrous structure, including:
but. alumina nanofibers;
b. second fibers mixed with alumina nanofibers, the second fibers being arranged so as to create asymmetric pores; and
from. many particles located on nanofibers of aluminum oxide, and these particles are selected from the group consisting of ion exchange resin, catalyst, metal oxide. 5. The fibrous structure according to claim 4, wherein said alumina nanofibers have an aspect ratio, i.e. the ratio of fiber length to fiber cross-sectional diameter that is greater than about 5 and have the smallest size that is less than about 50 nm. 6. The fibrous structure according to claim 4, in which the second fibers are selected from the group consisting of microglass fibers, cellulose fibers, fibrillated cellulose fibers and lyocell fibers. 7. The fibrous structure according to claim 4, in which each of these second fibers has a diameter in the range from about 0.3 to 5 microns. 8. The fibrous structure according to claim 4, in which each of these particles has a diameter between about 0.001-50 microns. 9. The fibrous structure according to claim 4, in which these particles are selected from the group consisting of small particles having an average size between about 10 - 44 microns, ultrafine particles having an average size between 0.1-10 microns and nanoscale particles having size that is less than 0.1 microns. 10. The fibrous structure according to claim 4, in which these particles are a sorbent. 11. The fibrous structure of claim 10, wherein said sorbent particles are selected from the group consisting of powdered activated carbon, a noble metal, a macromolecular organic substance, a biological compound, and an antimicrobial agent. 12. The fibrous structure according to claim 4, in which these particles of metal oxide are selected from the group consisting of colloidal silicon dioxide, colloidal alumina, zinc nanooxide and titanium nanooxide. 13. The fibrous structure of claim 10, wherein said particles are powdered activated carbon. 14. The fibrous structure according to item 13, in which the specified powdered activated carbon is impregnated. 15. The fibrous structure according to 14, in which the specified impregnating substance is a catalyst. 16. The fibrous structure according to claim 4, in which the specified catalyst is an oxidation catalyst. 17. The fibrous structure according to claim 4, in which the specified metal oxide has a submicron size. 18. The fibrous structure according to claim 4, which is used to remove contaminants from a liquid, gas or air environment. 19. The fibrous structure of claim 18, wherein said contaminants include at least one particulate matter. 20. The fibrous structure according to claim 19, in which said at least one solid particles include submicron particles. 21. A method for producing a fibrous structure, comprising the steps of:
but. form nanofibres of aluminum oxide;
b. mixing a plurality of second fibers with said alumina nanofibers in the presence of said second fibers to form a plurality of asymmetric pores;
from. add a lot of particles to the specified mixture. 22. The method according to item 21, comprising the step of removing water from said mixture to form a non-woven structure. 23. A method of using a fibrous structure in which said structure includes a plurality of alumina nanofibers mixed with a plurality of second fibers, creating asymmetric pores between them having an average size of about 5 to 48 microns and having a plurality of particles located on said oxide nanofibres aluminum, including stages in which:
but. passing fluid through said fibrous structure; and
b. remove the contaminant from the specified current environment. 24. The method of use according to claim 23, wherein said contaminant is selected from the group consisting of halogen and at least one microbial pathogen. 25. Structure for medical use, including:
but. alumina nanofibers;
b. second fibers mixed with said alumina nanofibers, wherein said second fibers are arranged to create asymmetric pores; and
from. a plurality of particles supported on said alumina nanofibres. 26. The structure for medical use according A.25, in which these particles are selected from the group consisting of fine particles, ultrafine particles and nanosized particles. 27. The structure for medical use according A.25, in which these particles are selected from the group consisting of sorbent, drugs and antimicrobial agents. 28. The structure for medical use according A.25, in which these particles include powdered activated carbon. 29. The structure for medical use according A.25, which is a wound dressing.

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