Patent Application
20240075415
The present invention relates to modular graphene oxide-based microbial fluid filters, graphene oxide, graphene oxide filter scaffolds, filter spacer tools and methods of making and using such filters, graphene oxide, scaffolds and tools.
Current fluid filters do not filter out the microbial contaminants that cause biocontamination, biodeterioration, biodegradation, and biocorrosion in the fluid systems such as fuel systems. Current filters only remove coarse particulates and in some cases bulk water. Current filters rely on the use of small pore size membranes to trap particulates. Unfortunately, with current filters the filtration pressure is excessively high as such filters require very small pore sizes to filter fine particulates. For this reason, the minimal pore size for a typical dispenser filter such as a fuel dispenser filter is between 10 to 30 micrometers (μm) in diameter, and the very best filters may capture particles as small as 51 μm size with only 50% efficiency. In order to filter out microorganisms such as bacteria, a pore size of less than 0.22 μm in diameter is required. Such an extremely small pore size drastically affects fluid flow leading to large pressure drops that in turn decreases filtration rates to inefficient levels.
Applicants recognized that the solution to the problem associated with bacterial filtration did not lie primarily in the filter pores size but in the filter media. Such recognition lead to a reclamation and recycling process for graphene oxide, a scaffold comprising graphene oxide, a modular graphene oxide-based microbial fluid filter and a filter tool which allows the correct compression pressure of a modular filtration cartridge, and prevents internal leakage along the internal wall of the filter and thus provides correct sealing of the filter. Such modular graphene oxide-based microbial fluid filter does not require a sub-micrometer pore filtering medium, yet has a microbial filtration efficiency of up to 99.99% and the ability to filter particulates while still providing the filtration flow rates of current filters that do not employ a sub-micrometer pore filtering medium.
The present invention relates to a reclamation and recycling process for graphene oxide, a scaffold comprising graphene oxide, a modular graphene oxide-based microbial fluid filter and a filter tool that allows the correct compression pressure of a modular filtration cartridge, and prevents internal leakage along the internal wall of the filter and thus provides correct sealing of the filter. Such modular graphene oxide-based microbial fluid filter does not require a sub-micrometer pore filtering medium, yet has a microbial filtration efficiency of up to 99.99% and the ability to filter particulates while still providing the filtration flow rates of current filters that do not employ a sub-micrometer pore filtering medium.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.
Unless specifically stated otherwise, as used herein, the terms “a”, “an” and “the” mean “at least one”.
As used herein, the terms “include”, “includes” and “including” are meant to be non-limiting.
As used herein, the words “about,” “approximately,” or the like, when accompanying a numerical value, are to be construed as indicating a deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose.
As used herein, the words “and/or” means, when referring to embodiments (for example an embodiment having elements A and/or B) that the embodiment may have element A alone, element B alone, or elements A and B taken together.
As used herein, fuel encompasses fuels derived from crude oil, biofuels, synthetic fuels, and sustainable fuels.
As used herein, sustainable are fuels wherein the energy used to produce the fuel is less than the energy obtained from the fuel.
Unless otherwise noted, all component or composition levels are in reference to the active portion of that component or composition, and are exclusive of impurities, for example, residual solvents or by-products, which may be present in commercially available sources of such components or compositions.
All percentages and ratios are calculated by weight unless otherwise indicated. All percentages and ratios are calculated based on the total composition unless otherwise indicated.
It should be understood that every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
Modular Graphene Oxide-Based Microbial Fluid Filter and Filter Compression Spacer
For purposes of this specification, headings are not considered paragraphs. In this paragraph, Applicants disclose a fluid filter comprising walls that form a three dimensional housing, said housing comprising an interior chamber, at least one inlet passing through at least one of said walls to said interior chamber and at least one outlet passing through at least one of said walls to said interior chamber, said housing's chamber comprising a three dimensional structure comprising graphene oxide.
Applicants disclose a fluid filter according to the previous paragraph wherein said three dimensional structure comprising graphene oxide is selected from the group consisting of:
Applicants disclose a fluid filter according to the two previous paragraphs comprising a filter compression spacer located between said inlet and said three dimensional structure comprising graphene oxide or between said outlet and said three dimensional structure comprising graphene oxide, preferably said filter compression spacer is located between said inlet and said three dimensional structure comprising graphene oxide, more preferably said filter comprises a first filter compression spacer located between said inlet and said three dimensional structure comprising graphene oxide and a second filter compression spacer located between said outlet and said three dimensional structure comprising graphene oxide. In one aspect, said filter comprises three or more filter compression spacers, at least one filter compression spacer being located between said inlet and said three dimensional structure comprising graphene oxide and at least one filter compression spacer located between said outlet and said three dimensional structure comprising graphene oxide and the remaining filter compression spacer being located within said three dimensional structure comprising graphene oxide.
Applicants disclose a fluid filter according to the previous paragraph each said spacer is independently selected from the group consisting of a spring, a ring, or a filter compression spacer, preferably each said spacer is a filter compression spacer, more preferably each said filter compression spacer is independently selected from the group consisting of the filter compression spacers of the “Spacer Tool and Process of Making and Using Same” section of the present specification, most preferably each said filter compression spacer is a filter compression spacer according to the filter compression spacers of the “Spacer Tool and Process of Making and Using Same” section of the present specification wherein said filter compression spacer comprises a first group of stems and a second group of stems, said first group of stems being longer than said second group of stems, each group of stems comprising at least three stems. This configuration is preferred as it results in the least pressure drop.
Applicants disclose a fluid filter according to the previous four paragraphs, said fluid filter capable of removing at a pressure drop of 7 psi or less, preferably at a pressure drop of 5 psi or less, more preferably at a pressure drop of 3 psi or less, most preferably at a pressure drop of 1 psi or less. In one aspect, said pressure drop is from 7 psi to about 0.01 psi or said pressure drop is from 7 psi to about 0.1 psi
Applicants disclose a fluid filter according to the previous paragraph wherein:
Applicants disclose the fluid filter of the previous two paragraphs wherein said fluid is selected from the group consisting of fuel, oil paints, coatings, additives, lubricants, hydraulic fluids, oils and mixtures there of preferably said fluid is selected from the group consisting of hydrocarbons, non-polar solvents, amphipathic solvents and mixtures thereof; more preferably said fluid is selected from the group consisting of metal working fluids, turbine oil, engine oil, hydraulic oil, brake fluid, power steering fluids, vegetable oils, fatty acid methyl esters, jet fuel, diesel fuel, gasoline, aviation gasoline, kerosene and mixtures thereof; most preferably said fluid is selected from the group consisting of j et fuel, diesel fuel, gasoline, aviation gasoline, kerosene and mixtures thereof. In one aspect, mixtures of fluids may be filtered using Applicants' fluid filter.
Applicants disclose a scaffold comprising graphene oxide, in one aspect said scaffold comprises a three dimensional structure comprising graphene oxide, said three dimensional structure comprising graphene oxide can comprise a support scaffold comprising an exterior surface and optionally pores having walls said pores passing through said support scaffold, said graphene oxide being attached to at least a portion of said three dimensional structure comprising graphene oxide, preferably said support scaffold comprises pores having walls said pores passing through said support scaffold, more preferably said graphene oxide is attached to the walls of said pores and said support scaffold's exterior surface, in one aspect, said support scaffold comprises a graphene oxide mesh, a bead, a fiber, a tube, a nanotube, nanoparticle all having a graphene oxide attached thereto. Such structure can be made by 3D printing said structure or coating graphene oxide on a support structure. Such scaffold comprising graphene oxide can be used in a filter or other areas wherein a scaffold is beneficial.
Applicants disclose a process of making a three dimensional structure comprising graphene oxide said process comprising:
Applicants disclose a graphene oxide recycling process, said process comprising:
Applicants disclose a filter compression spacer, said filter compression spacer comprising:
Applicants disclose the filter compression spacer of the previous paragraph, said filter compression spacer comprising a first group of stems and a second group of stems, said first group of stems being longer than said second group of stems, each group of stems comprising at least three stems. This configuration is preferred as it results in the least pressure drop.
Applicants disclose the filter compression spacer of the initial paragraph of this section titled “Spacer Tool and Process of Making and Using Same”, comprising at least six stems said stems having equal lengths or essentially equal lengths.
Applicants disclose the filter compression spacer of the previous three paragraphs, wherein said stems are branched.
The properties of synthesized graphene oxide and recovered graphene oxide should be verified using Fourier Transform Infrared Radiation Spectroscopy and Raman Spectroscopy. After preparing the graphene oxide filters, validation of their performance is determined by:
[(Cellcbf−Cellcaf)/Cellcbf]×100%=Low microbial cell concentration efficiency
[(Cellcbf−Cellcaf)/Cellcbf]×100%=High microbial cell concentration efficiency
The following examples illustrate particular properties and advantages of some of the embodiments of the present invention. Furthermore, these are examples of reduction to practice of the present invention and confirmation that the principles described in the present invention are therefore valid but should not be construed as in any way limiting the scope of the invention.
Example 1: Making and Using the Graphene Oxide Filter. In Order to accommodate the increasing flow rate required for multiple fuel systems and an acceptable pressure drop (<7 psi) while retaining the graphene oxide filtration efficiency (>90% microbial filtration efficiency), the fuel filters were designed as a modular filter cartridge design using graphene oxide coated metal meshes (graphene oxide scaffold) instead of 100% graphene oxide flakes. In addition to improved physical properties of the filters, the use of graphene oxide coated scaffold reduced the graphene oxide flake amount needed as the filter medium. Testing has showed that filters made out of graphene oxide coated scaffolds can retain an efficiency >90% with the retention time at 4 seconds. This was further enhanced by adding a graphene oxide flake bed at the inlet and outlet region of the filter cartridge. Testing with two different concentration of a microbe as shown in Table 1A and 1B show a retention time of 4 seconds could effectively remove the microbes from fuel with larger retention times increasing the removal efficiency to >99%. Similar observations have been made with other types of microbes as well. The use of the graphene oxide scaffold (graphene oxide coated mesh) is considered to have increased the contact by providing multiple paths for the fuel to mix and flow. Testing up to a 2 cm/s face velocity has shown that the graphene oxide coated scaffold is stable as evidenced by the microbial removal efficiency and fuel specification testing (filter did not affect any of the fuel specification properties). Testing at microbial concentrations of >2.5E+03 CFU/L has shown that a retention time of 4 seconds will allow removal of >90% of the microbes. Adjusting the retention time by changing the number of coated mesh or size, (such as pore size and/or mesh area) allows controlling the removal efficiency at different microbial concentrations to further improve filtration efficiency.
The filter shown in
The filter shown in
Example 2. Making and using the graphene oxide scaffold. Application of a graphene oxide coating onto a metal mesh to develop a graphene oxide scaffold for filtration required a method that provided a good adhesion to the metal and be able to achieve the required mass loading to provide the required filtration efficiency and withstand erosion from the fuel flow through the mesh. An approach that could support a commercial operation for coating the mesh that was independent of the mesh size was of interest. Different concentrations of the graphene oxide solution were applied to various mesh sizes used during the filter development showed that the surface tension in the graphene oxide solution be sufficient to attach to the mesh without forming a film that would flake and detach. Graphene oxide coating may be achieved by multiple processes including dipping, spraying, additive manufacturing, others.
Testing with graphene oxide flakes as a method to retain >90% of the microbes from fuel showed a retention time of >4 seconds is required and that the graphene oxide flakes require a high level of compaction. Increasing the packing density by compaction increased the pressure drop across the graphene oxide flake bed. For larger fuel flow rates (above 5 gpm) in field fuel systems, the amount of graphene oxide required in a flake bed to meet the targeted retention time increases and is underutilized due to the restricted ability of the fuel to move through a compacted bed. Therefore, a method that has an acceptable pressure drop (<7 psi), allows sufficient retention time for the microbes in the fuel to attach and increase the contact with the graphene oxide while reducing the amount of graphene oxide required was of interest.
Testing showed that by adjusting the concentration of the graphene oxide solution according to the metal mesh size and drying at a low temperature to avoid altering the graphene oxide characteristics allows forming a graphene oxide coating that adheres to the metal mesh. Testing also showed that applications of multiple coatings by repeating the coating process allows increasing the graphene oxide mass loading on the metal mesh. Specifically, a concentration of 1 mg/ml of graphene oxide solution applied to 0.87″ and 3.84″ diameter metal mesh as shown in
Example 3. Making and using the filter tool. Testing showed that the inlet and outlet require space with the graphene oxide coated scaffold (mesh) stack to minimize the pressure loss and to maximize the use of the scaffold stack by distributing the flow. In addition, the scaffold stacked in the filter cartridge requires them to be tightly packed and slight differences or imperfections could allow the fluid to escape filtration along the walls if a tight seal is not achieved by applying equal forces to seal the modular filter cartridge. Therefore, a method that prevents flow along the walls, distributes the flow to maximize the use of the scaffold (mesh) stack without increasing the pressure loss, and applies a distributed compressive force to the scaffold stack led to the development of the spacer.
Initially, a ring shim with an outer diameter equal to the inner diameter of the filter-housing placed on the mesh stack and compression springs placed on the top and bottom of the mesh stack prevented flow along the walls and provided the necessary compression of the mesh stack. While such a configuration is acceptable for a smaller diameter filter, where selecting the spring with the appropriate spring constant will provide the compression, assembly of a larger diameter mesh stack requiring several springs to provide a distributed load proved to be challenging.
The spacer configuration shows an approach to provide a distributed compression force. Its thickness/height is based on the level of the targeted compressed height of the mesh stack and the minimum space needed to allow flow distribution at the inlet and outlet without increasing the pressure loss through the mesh stack in the filter. A spacer is shown in
Example 4. Using the graphene oxide reclamation and recycling process. A method to recover and recycle graphene oxide for use in filters was developed. Recycling of used graphene oxide is a versatile method to reduce the cost of producing graphene oxide. Subsequently, it helps to reduce the cost of making graphene oxide fuel filters. Graphene oxide contains microorganisms and some left over fuel, which is absorbed to graphene oxide during fuel filtration.
In the process of recycle of graphene oxide, the used graphene oxide samples recovered from the filter beds of the syringe filters were washed as shown in
Briefly, used graphene oxide sample was washed with hexane thoroughly to remove the diesel fuel from graphene oxide. Then the sample was washed with acetone and dried by passing nitrogen gas over the sample. The graphene oxide sample was further washed with 100% ethanol to destroy the microorganisms that attached onto the graphene oxide surface. graphene oxide sample after washing with ethanol was sonicated in a bath sonicator for an hour to destroy any remaining microorganisms. In addition, the sonication process in water helps to extract dead microorganisms to an aqueous phase. Upon completing sonication, the sample kept standing for an overnight to separate graphene oxide and water layers. The water layer was carefully discarded and the precipitated graphene oxide sample was washed with acetone few times. The recovered graphene oxide sample was dried in an oven at 60° C. for few hours and analyzed using FTIR and Raman spectroscopy, as shown in
FTIR studies showed, no significant difference between as-synthesized graphene oxide and recovered graphene oxide. The two —CH2 stretching peaks appeared around 2925 cm−1 and 2848 cm−1 of graphene oxide-fuel sample is completely disappeared after graphene oxide-fuel sample was cleaned using the recycle procedure. All three samples were characterized by Raman spectroscopy. As shown in
Example 5: Making and using graphene oxide. Graphene oxide samples were prepared using a Hummers method with modifications to improve the quality and purity of graphene oxide samples. In a typical graphene oxide synthesis using Hummers method, first the graphite powder was expanded and slightly oxidized using H2SO4, NH4(S2O8) and P2O5. The product is further oxidized by manganese heptoxide (Mn2O7) as an oxidizer. Mn2O7 is formed by the reaction between potassium permanganate (KMNO4) and sulfuric acid (H2SO4) in the temperatures below 10° C. Mn2O7 is a greenish viscous solution and it is formed due to the dehydration of two HMnO4 molecules by H2SO4. Mn2O7 shows a highest reactivity between 35-55° C. and it reduces to MnO2 violently above 55° C. Mn2O7 oxidizes the graphite surface to form oxygen functional groups, such as carboxylic, carbonyl, hydroxyl and ether. In the presence of water, these oxygen functional groups on the surface graphite sheets produce hydrogen bonds with water molecules and increase the inter layer distance between graphene layers to convert graphite oxide to graphene oxide.
Example 6. Scale-up preparation of graphene oxides to 1 gram. Concentrated H2SO4 (10 mL) in a 500 mL flask was heated to 80° C., to which (NH4)2S2O8 (0.9 g) and P2O5 (0.9 g) were added. The mixture was stirred until the reagents were completely dissolved. The graphite powder (1 g) was added, and the resulting mixture was heated at 80° C. for 4.5 h. Upon being cooled to room temperature, the reaction mixture was diluted with water (250 mL) and kept for ˜12 h. It was then filtrated and washed repeatedly with water, followed by drying in a vacuum oven. The solid sample was added to concentrated H2SO4 (40 mL) in a 500 mL flask cooled in an ice bath. The mixture was added slowly to KMnO4 (5 g over 40 min), during which the temperature was kept at <10° C. The reaction mixture, with a change in color from black to greenish brown, was heated at 35° C. for 2 h, followed by dilution with water (85 mL—Caution: the temperature must be kept at <35° C. throughout) and further stirring for 2 h. The reaction mixture was poured into a large beaker, to which water (250 mL) and then aqueous H2O2 (30%, 10 mL) were added. Bubbles from the aqueous mixture along with a color change to brilliant yellow were observed. After the mixture was allowed to settle for ˜12 h, the clear supernatant was decanted, and the sediment was washed repeatedly with aqueous H2SO4 (5 wt %)-H2O2 (0.5 wt %) and HCl solution (10 wt %), followed by washing repeatedly with water until no layer separation was observed after centrifugation. The sample was then dialyzed against water for 7 days to yield a clean aqueous dispersion of GOs. The water was removed using rotary evaporation and graphene oxide was recovered as a black flaky powder.
Example 7. Scale-up preparation of graphene oxides to 8 grams. Concentrated H2SO4 (50 mL) in a 500 mL flask was heated to 80° C., to which (NH4)2S2O8 (4.5 g) and P2O5 (4.5 g) were added. The mixture was stirred until the reagents were completely dissolved. The graphite powder (5 g) was added, and the resulting mixture was heated at 80° C. for 4.5 h. Upon being cooled to room temperature, the reaction mixture was diluted with water (1250 mL) and kept for −12 h. It was then filtrated and washed repeatedly with water, followed by drying in a vacuum oven. The solid sample (5 g) was added to concentrated H2SO4 (200 mL) in a 500 mL flask cooled in an ice bath. The mixture was added slowly to KMnO4 (15 g over 40 min), during which the temperature was kept at <10° C. The reaction mixture, with a change in color from black to greenish brown, was heated at 35° C. for 2 h, followed by dilution with water (400 mL—Caution: the temperature must be kept at <35° C. throughout) and further stirring for 2 h. The reaction mixture was poured into a large beaker, to which water (1250 mL) and then aqueous H2O2 (30%, 50 mL) were added. Bubbles from the aqueous mixture along with a color change to brilliant yellow were observed. After the mixture was allowed to settle for ˜12 h, the clear supernatant was decanted, and the sediment was washed repeatedly with aqueous H2SO4 (5 wt %)-H2O2 (0.5 wt %) and HCl solution (10 wt %), followed by washing repeatedly with water until no layer separation was observed after centrifugation. The sample was then dialyzed against water for 7 days to yield a clean aqueous dispersion of GOs. The water was removed using rotary evaporation and graphene oxide was recovered as a black flaky powder.
Example 6: Sizing the filter for larger flow rates. The configuration used in the filter for the 2.5 GPM flow rate (this is a single modular filter cartridge) could be scaled up for larger flow rates using two methods. One method involves a modular filter configuration using a manifold that provides equal flow to several filters as shown in
When much larger flow rates are required, it will typically be necessary to scale up a filter module. The 2.5 GPM filter is a scaled up filter of the 0.3 LPM filter. A similar simple approach to scaling up will further scale up the 2.5 GPM filter module. When scaling up, an alternative scaffold configuration as shown in
Example 7. Graphene oxide filter connected to a gas station fuel dispenser pump as shown in
Example 8: Graphene oxide filter connected to an electric power generator as shown in
Example 9: Filter Configuration for Further Reduction of Pressure Loss. Filter configurations can be developed for increased flow rate and reduced pressure loss by addition of spacer elements such as springs (
Every document cited herein, including any cross-referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While the present invention has been illustrated by a description of one or more embodiments thereof and while these embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and process, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.
The present application claims priority to U.S. Provisional Application Ser. No. 63/404,107 filed Sep. 6, 2022, the contents of such provisional application hereby being incorporated by reference in its entry.
The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
| Number | Date | Country | |
|---|---|---|---|
| 63404107 | Sep 2022 | US |
